2>2>3. 3\ Un22-r V.7 87th Congress, 2d Session House Document No. 522 DELAWARE RIVER BASIN, NEW YORK, NEW JERSEY, PENNSYLVANIA, AND DELAWARE LETTER FROM THE SECRETARY OF THE ARMY TRANSMITTING A LETTER FROM THE CHIEF OF ENGINEERS, DEPART¬ MENT OF THE ARMY, DATED APRIL 2, 1962, SUBMIT¬ TING A REPORT, TOGETHER WITH ACCOMPANYING PAPERS AND ILLUSTRATIONS, ON A REVIEW OF THE DELAWARE RIVER AND TRIBUTARIES, REQUESTED BY A RESOLUTION OF THE COMMITTEE ON PUBLIC WORKS, UNITED STATES SENATE, ADOPTED APRIL 13, 1950, AND OTHER RESOLUTIONS OF THAT COMMITTEE AND OF THE COMMITTEE ON PUBLIC WORKS, HOUSE OF REPRE¬ SENTATIVES, LISTED IN THE REPORT IN ELEVEN VOLUMES Volume VII August 16, 1962.—Referred to the Committee on Public Works and ordered to be printed with illustrations mu «mgf *pri 6 tat 87th Congress, 2d Session House Document No. 522 DELAWARE RIVER BASIN, NEW YORK, NEW JERSEY, PENNSYLVANIA, AND DELAWARE LETTER FROM THE SECRETARY OF THE ARMY TRANSMITTING A LETTER FROM THE CHIEF OF ENGINEERS, DEPART¬ MENT OF THE ARMY, DATED APRIL 2, 1962, SUBMIT¬ TING A REPORT, TOGETHER WITH ACCOMPANYING PAPERS AND ILLUSTRATIONS, ON A REVIEW OF THE DELAWARE RIVER AND TRIBUTARIES, REQUESTED BY A RESOLUTION OF THE COMMITTEE ON PUBLIC WORKS, UNITED STATES SENATE, ADOPTED APRIL 13, 1950, AND OTHER RESOLUTIONS OF THAT COMMITTEE AND OF THE COMMITTEE ON PUBLIC WORKS, HOUSE OF REPRE¬ SENTATIVES, LISTED IN THE REPORT IN ELEVEN VOLUMES Volume VII August 16, 1962.—Referred to the Committee on Public Works and ordered to be printed with illustrations U.S. GOVERNMENT PRINTING OFFICE WASHINGTON : 1962 88197 0 REPORT ON THE COMPREHENSIVE SURVEY OF THE WATER RESOURCES OF THE DELAWARE RIVER BASIN APPENDIX N GENERAL GEOLOGY AND GROUND WATER PREPARED BY U. S. DEPARTMENT OF INTERIOR GEOLOGICAL SURVEY 1959 FOR U. S. ARMY ENGINEER DISTRICT, PHILADELPHIA CORPS OF ENGINEERS PHILADELPHIA,PA. . ■ • 333 , ? / V. 7 GROUND-WATER RESOURCES OF THE DELAWARE RIVER SERVICE AREA By F. H. Olmsted, Gerald G. Parker, and ty. B. Keighton, Jr. with special sections By N. M. Per Emitter and R. V. Cushman 1959 A report by the U. S. Geological Survey for and in cooperation with the Corps of Engineers, Philadelphia District, as a guide to the better understanding of the Delaware River service area. \ • i. CONTENTS Page Summary . 1 Introduction... 4 General ground-water hydrology of the basin . 7 Sources of ground water ......... 7 Occurrence and movement ...... 7 Discharge . ^ Types of aquifers ... ^ Hydrologic provinces . 11 The Coastal Plain ...12 General features . 12 Occurrence of ground water .. 16 Nonmarine sediments of Cretaceous age—the major group of aquifers . 18 Merchantville and Woodbury clays—a major aquiclude .21 Minor aquifers and aquicludes above the Merchantville and Woodbury clays . 22 EnglishtOwn sand .,.. 22 Marshalltown formation . 23 Wenonah and Mount Laurel sands .23 Navesink marl...... 25 Red Bank sand . 25 Horner stown marl . 26 Vincent own sand . 26 Manasquan and Shark River marls . 27 Piney Point formation . 28 Kirkwood formation—an important group of aquifers and aquicludes . 28 Cohansey sand—an aquifer of great potential..30 Beacon Hill gravel--a remnant cap ...32 Quaternary deposits—an important group of aquifers and a portal for ground-water recharge and discharge ..33 Bridgeton and Pensauken formations .33 Unclassified deposits of Pleistocene age . 34 Cape May and Talbot formations . 35 Basin-rim sand .36 Glacial outwash and alluvium. 36 Marsh and swamp deposits ..36 Beach and dune sand . 37 Recharge and discharge.37 Patterns of movement . 4 i ii. The Coastal Plain--Continued Ground-water storage .. ♦... . Use of storage..... Storage fluctuations ... Natural fluctuations .. Artificial fluctuations ... t ... Chemical character of ground-water supplies.. Pleistocene deposits .. Cohansey Sand ...... Sands of the Kirkwood formation ...... Vincentown sand ..... Wenonah and Mount Laurel sands .. Englishtown sand ...... Nonmarine sediments of Cretaceous age .. Salt-water encroachment .... Productivity of aquifers ..... The Appalachian Highlands ..... General features ..... Occurrence of ground water...... Crystalline rocks....... Gneiss of Precambrian age .... Ultramafic rocks..... Granitic to gabbroic rocks .... Glenarm series ...... :Quant‘zose rocks of Cambrian age ...' .. Basalt and diaibase of Triassie age ..... Hydrologic properties of the crystalline rocks ........ Carbonate rocks ..... Franklin limestone.... Cockeysville marble ... Carbonate rocks of Cambrian and Ordovician age ........ Carbonate rocks of Silurian and Devonian age ... Hydrologic properties of the carbonate rocks . ClaStiC rOCkS «o. 000..0..000. 009.000. #.oo. ......o Rocks of the Valley and Ridge province ...... Martinsburg shale o.oo.o9.o«ooooo.....«.e.......... Conglomerate and sandstone aquifers ... Interbedded sandstone and shale aquifers . Shale aquifers .... Rocks of the Appalachian Plateaus province . Rocks of the Triassie Lowland .. „... r .'. Stockton formation ..... Lockatong formation ....... Brunswick formation .. .... : . . Unconsolidated sediments of glacial origin ...... Unstratified sediments..... Stratified sediments .. Recharge and discharge .... Page ^3 ^3 44 45 45 b6 b6 48 49 49 49 49 50 50 62 63 63 65 - 66 67 68 68 69 70 '70 71 73 74 74 74 75 75 77 78 79 80 80 82 82 85 86 88 89 90 91 92 94 Ill Page The Appalachian Highlands - Continued Ground water storage . 97 Chemical character of ground water supplies . 98 Uncorasglidated.sediments of glacial origin . 99 Clastic rocks . 103 Martinsburg shale . 103 Catskill formation . 104 Stockton formation .. 105 Brunswick formation . t ... 106 Carbonate rocks .». 107 Crystalline rocks . 108 Wissahickon formation . 109 The service area outside the basin . 110 Fairfield County, Conn, by R. V. Cushman .. 110 Dutchess, Orange, Putnam, Rockland, Ulster, and Westchester Counties, N. Y. by N. M. Perlmutter . 115 Long Island, N. Y. by G. G. Parker ... 125 Introduction . 125 The water supply .-.. . 126 Geologic structure and materials .. 129 Pleistocene aquifers ... 130 The upper Pleistocene aquifers . 130 Jameco gravel . 131 Hydrology of the Pleistocene aquifers . 131 The upper Pleistocene aqyifers . 131 Jameco gravel . 132 Cretaceous aquifers . 132 Magothy (?) formation . 132 Lloyd sand member of the Raritan formation. 133 Hydrology of the Cretaceous aquifers . 134 Magothy (?) formation .„. 134 Lloyd sand member . 135 Aquifer-management practices .„. 136 Well and well-field design, development, and operation... 136 Well spacing . 136 Well development . 137 Well maintenance . 139 Protective barriers . 140 Retention of runoff . 141 Drainage . 141 Disposal of undesirable effluents ..*. 142 Artificial recharge . 142 Input wells . 142 Check dams and spreading basin . 143 Infiltration canals . 144 Sprinkling systems .i,.. 144 Induced recharge . 144 Aquifer storage and induced recharge . 146 Possibilities for future ground water development . 148 References . 151 iv ILLUSTRATIONS Following Plate Page 1 Groupings of counties in the Delaware River Service Area ... 6 2 Photographs of rock materials of contrasting hydrologic properties, Delaware River basin . 10 3 Map of region including Delaware River basin showing physiographic units ... In pocket 4 Configuration of bedrock beneath Coastal Plain of Delaware River basin and adjacent Delaware and New Jersey ...... 12 5 Fence dlagrnm of Coastal Plain in Delaware River basin and adjacent New Jersey . .. In pocket 6 Geologic map of south half of Delaware River basin and southern New Jersey showing unconsolidated sediments of Cretaceous and Tertiary age . In pocket 7 Geologic map of south half of Delaware River basin and southern New Jersey showing unconsolidated sediments of Quaternary age ..... In pocket 8 Idealized cross section illustrating "funnel effect" in recharge to Coastal Plain aquifers . 18 9 Map of Coastal Plain in Delaware River basin showing productivity of aquifers . ..... 28 10 Map showing theoretical flow pattern and location of interface between fresh water and salt water in nonmarine sediments of Cretaceous age under natural conditions .... 42 11 Geologic map of south half of Delaware River basin and southern New Jersey showing consolidated rocks of pre-Cretacapus age . .... . ... In pocket 12 Geologic map of north half of Delaware River basin and northern New Jersey showing consolidated rocks of pre-Cretaceous age .. In pocket 13 Generalized geologic cross sections of southern part of Appalachian Highlands ... 66 14 Geologic map of north half of Delaware River basin and northern New Jersey showing unconsolidated sediments of Quaternary age . In pocket 15 Geologic cross sections of major stream valleys in northern part of Delaware River basin . 92 16 Fluctuations of water levels in representative wells in unconsolidated sediments of glacial origin in northern part of Delaware River basin • o 98 Following Plate page 17 Map of Fairfield County, Conn., showing the coastal basins and expected yields of wells, by areas . .... .... 110 18 Map of metropolitan New York and adjacent part of New Jersey . 116 19 Water-bearing formations in central Long Island, N. Y. 126 20 Map showing occurrences of saline ground water in Long Island, Staten Island, and Manhattan, N. Y. 130 21 Graph showing pumpage and consumptive use from aquifers of Long Island, N. Y., 1950-57, pro¬ jected to 1960 . 132 vi TABLES Table Pa 8 e 1 Physical and hydrologic properties of the geo¬ logic formations and units in the Delaware River basin.....°. In pocket 2 Coefficients of transmissibility, permeability and storage in nonmarine sediments of Creta¬ ceous age ....... .. 20 3 Coefficients of transmissability, permeability and storage in Cohansey sand ......... <»..... 31 4 Water budget for Coastal Plain of Delaware River basin and New Jersey .. 38 5 Representative chemical analyses of ground water in Coastal Plain of Delaware River basin and New Jersey ..... follows 46 6 Inferred correlation of stratigraphic units of Paleozoic age in Delaware River basin and ad¬ jacent areas of New Jersey and New York . In pocket 7 Specific capacities of wells in crystalline rocks of northern Delaware .................. 73 8 Water budgets for Pomperaug River basin, Conn., and Appalachian Highlands part of Delaware River basin . .......... 95 9 Representative chemical analyses of water in un¬ consolidated sediments in Appalachian Highlands In pocket 10 Representative chemical analyses of water in con¬ solidated rocks in Appalachian Highlands .... In pocket 11 Summary of chemical analyses of 24 samples of ground water from valley fill ... 102 12 Summary of chemical analyses of ground water from glacial outwash ... 103 13 Summary of chemical analyses of 9 samples of ground water from the Martinsburg shale ..... 104 14 Summary of chemical analyses of 18 samples of ground water from the Catskill formation .... 105 15 Summary of chemical analyses of 54 samples of ground water from the Stockton formation .... 106 16 Summary of chemical analyses of 23 samples of ground water from the Brunswick formation ... 107 17 Summary of chemical analyses of 60 samples of ground water from carbonate rocks .. 108 18 Summary of chemical analyses of 18 samples of ground water from crystalline rocks .. 109 vii. Table Page 19 Summary of chemical analyses of 1 6 samples of ground water from the Wissahickon formation .... no 20 Summary of water-resources values by counties in New York and Connecticut part of Delaware River 114 - service area. 21 Summary of water-resources values, Long Island, N. Y. .... 127 . 1. SIMMARY The Delaware River basin service area, as considered in this report, occupies a total area of about 30,000 square miles, of which only 12,865 square miles are in the basin proper. The area includes parts of Connecticut, Delaware, Maryland, New Jersey, New York, and Pennsyl¬ vania. Use of water in this highly important region is increasing rapidly, and ground-water supplies constitute a small but locally very significant part of the total supplies. The Delaware River basin service area occupies parts of two major physiographic divisions, separated by the Fall Line, which extends north easterly across the region Wilmington, Del., Philadelphia, Pa., Trenton, N. J., and New York, N. Y. The Atlantic Plain division, or Coastal Plain as its emerged part is called, lies southeast of the Fall Line. The Coastal Plain is underlain by a thick wedge of seaward-dipping unconsolidated deposits of alternating permeable aquifers composed of sand and some gravel and relatively impermeable aquicludes composed of clay, silt, and marl. Northwest of the Fall Line is the, Appalachian Highlands division, characterized by ridges, valleys, uplands, and plateaus. The bedrock is consolidated, complex in composition and structure, and generally yields little water to wells, compared to the unconsolidated aquifers of the Coastal Plain. The northern half of the region described has been glaciated and in places contains glacial out- wash which constitutes an excellent aquifer. As a rough approximation, given only to indicate order of magni¬ tude, the potential ground-water supply in the Coastal Plain part of the Delaware River basin is considered equal to the ground-water discharge to streams—about 1,600 mgd in an area of 2,750 square miles. Because of practical limitations, chiefly."economic, it is estimated that only about half this total—or about 800 mgd—can be developed. Present use (1951-56 average) is about 210 mgd, but the net ground-water discharge is even less, because part of the water pumped is not consumed and re¬ turns to the aquifers. Aquifers in the nonmarine sediments of Cretaceous age—the lowest group of aquifers in the Coastal-Plain wedge of deposits—yield the largest proportion of the total ground-water pumpage at present (slightly more than half in 1951-5&), but the deposits of Quaternary age are becoming increasingly important, and the Cohansey sand offers perhaps the greatest potential for future development. As in the Coastal Plain, the potential ground-water supply in the Appalachian Highlands is considered equal to the ground-water discharge to streams— 4,100 ± 500 mgd. However, it is believed that only a small fraction of this potential supply can be developed feasibly. Instead, 2. development of surface-water supplies will continue to be dominant in the Highlands, although large ground-water supplies may be developed locally, as in the glacial outwash along some of the major streams. In many places, wells developed in permeable deposits near streams may induce recharge at rates far greater than the natural recharge rate, and individual sustained yields of about 500 - 1^000 gpm are not uncommon. Such developments of large ground-water supplies will be at the expense of streamflow, for ground water and surface water are each part of the same total resource. Ground water suitable for most uses may be developed, at least in small quantities, almost anywhere in the basin. In the Coastal Plain large quantities of fresh ground water can generally be developed ex¬ cept near the ocean and Delaware Bay, but even to this general rule there are exceptions. For instance, where thick impermeable aquicludes inter- - vene between the salt water of the ocean or bay and fresh water of deeper aquifers sizable supplies of good water can be developed—as in the "800-foot'* sand at Atlantic City, N. J. However, salty water extends inland to different and varying distances in each aquifer; for example, water in excess of 250 ppm as chloride is believed to underlie about half the entire State of New Jersey in the Cretaceous artesian aquifers. In the Coastal Plain of the area reported upon, numerous fresh¬ water well supplies have become salty. For the most part this repre¬ sents encroachment from the modern sea; however, some of the salty water originated in the geologic past as residual salinity never flushed out in later times. The encroachment is due in part to a slow world-wide rise of sea level (6 inches in this area since 1930 ) 3 but mostly it is due to pumping too near a body of salty ground or surface water. Some of the encroachment may be due largely, as it was at Lewes, Del., and Newark, N. J., to salt water being introduced to a former fresh-water domain through dredging operations. Extensive pump¬ ing of wells near the existing salt-water--fresh-water interfaces in aquifers, or deep dredging of river or canal channels that would, in effect, become inland arms of the s^a, would probably accelerate salt¬ water encroachment and either ruin or greatly depreciate the value of many existing ground-water supplies of the Coastal Plain. Although fresh ground water in the Coastal Plain aquifers is gen¬ erally good to excellent, there are some places where the ground water is hard and requires softening for many uses. The greatest quality prob¬ lem (apart from salt-water contamination) is the irregular and largely unpredictable presence of water high in iron and sometimes manganese. In the Appalachian Highlands most ground waters are of satisfactory chemical quality for most uses, although the carbonate rocks generally yield hard water, the sulfate content is high in some formations, par¬ ticularly in the anthracite coal regions, and objectionable quantities 3 . of iron occur locally in several types of rocks and deposits. Wells in very shallow aquifers, especially dug wells, sometimes become contamin¬ ated by surface sources. In Fairfield County, Conn., ground-water supplies are obtained from various crystalline bedrock formations and from unconsolidated glacial deposits. Average yield of wells in bedrock is about 8-10 gpm, but yields of wells in some of the coarse-grained stratified glacial depos¬ its commonly are several hundred gallons per minute. Of the average precipitation of about 48 inches, 26 inches is discharged as direct and base runoff in streams, and the remaining 22 inches is lost by evapo- transpiration. Encroachment of poor-quality, water has occurred in the glacial outwash in the coastal area of Bridgeport. In Dutchess, Orange, Putnam, Rockland, Ulster, and Westchester Counties, N. Y., ground water occurs in the same general rock types as those in the glaciated, northern half of the Delaware River basin. Highest yields are obtained from the glacial deposits; yields from sand¬ stone and shale aquifers in the Newark group (largely in Rockland County) commonly exceed 100 gpm per well; the lowest yields generally are from crystalline bedrock where average yield per well is less than 50 gpm. On Long Island, N. Y., large supplies of ground water are available from unconsolidated deposits comprising several aquifers of Pleistocene age and the Magothy formation and the Lloyd sand member of the Raritan formation, both of Cretaceous age. The total quantity of ground water available for perennial use is not known, although it is less than the average annual return flow to the ocean of 1,500 mgd. Present consump¬ tive use of ground water (estimated to be half the total withdrawal) is about 12 percent of the average annual return flow and about 19 percent of the return flow during the driest year to be expected. Although this suggests the possibility of considerable additional development, rational plans of development will be required to prevent excessive pimping near the shore which would result in salt-water encroachment. 88197 0-62-2 (Vol. VII) 4 . INTRODUCTION This report was prepared in response to a request from the Corps of Engineers for a report on the ground-water resources of the Delaware River service area„ The data herein summarized have been gathered chiefly as a result of many investigations by the U.S. Geological Survey in cooperation with the States of Delaware, New Jersey, New York, and Pennsylvania and with a large number of smaller politcal divisions and other agencies (including other Federal agencies) over many years. The work requested by the Corps of Engineers as a part of the Delaware River basin project was an important, but very small part of this total effort The report was written under the immediate supervision of Garald G. Parker, project hydrologist, and under the general supervision of Charles C. McDonald, chief. General Hydrology Branch. The Geological Survey field offices concerned with the Delaware River service area contributed data and made special studies. Ground-water data were fur¬ nished, and special hydrologic studies were made, for Delaware By William C. Rasmusen; for New Jersey by Henry C. Barksdale, Allen Sinnott Paul B. Seaber, Solomon M. Lang, and Leo A. Jablonski; for Pennsylvania by David W. Greeman, Donald R. Rima, Norman H. Blanchard, Jr., and William N. Lockwood; and for New York by Joseph E. Upson, George C. Taylor, Jr., Nathaniel M. Perlmutter, Edward H. Salvas, Julian Soren, and John Isbister. Quality-of-water data for Delaware, New Jersey, and Pennsylvania were supplied by Norman H. Beamer, and for New York by Felix H. Pauszek. Additional geologic information was furnished by Carlyle Gray, state geologist of Pennsylvania; Meredith E. Johnson, state geologist of New Jersey until 1958, and his successor, Kemble Widmer; Johan J. Groot, state geologist of Delaware; Horace G. Richards, Philadelphia Academy of Natural Sciences; Edward H. Watson and Lincoln Dryden of Bryn Mawr College; Bradford Willard of Lehigh University; Herbert P. Woodward of Rutgers University; and Paul MacClintock of Princeton Uni¬ versity. Horace G. Richards assisted in the study of the geology of the Coastal Plain, and interpretations of the stratigraphy of that important region are based largely on his work. Federal agencies that contributed data, maps, or file material in¬ clude the Corps of Engineers, Col. Allen F. Clark, district engineer to December 1, 1957, and his successor. Col. William F. Powers; the Soil Conservation Service, Fred H. Larson, head, Engineering Unit; the Public Health Service, Sylvan C. Martin, regional engineer; and the Weather Bureau, William E. Hiatt, chief, Hydrologic Services Division. Others, far too numerous to mention, including consulting engineers city, county, State, and other officials, contributed ideas and data. 5 . The writers have drawn freely on the data and conclusions of many re¬ ports by the Geological Survey and other agencies and individuals. No attempt is made to present ground-water and geologic information for all the Delaware River basin in the detail that some of these reports provide for parts of the area; instead the general subject matter in these re¬ ports is summarized briefly. Basic to the ideas and conclusions pre¬ sented in this report are the contributions of the several authors who wrote assigned parts of an unpublished 246-page report in 1957 that is a predecessor of this report. That report is largely the work of the fol¬ lowing authors listed alphabetically: James K. Culbertson, Garald G. Parker, Nathaniel M. Perlmutter, Donald R. Rima, William C. Rasmussen, and Edward H. Salvas. Also the present writers have drawn much information and important conclusions from a report, published in 195$ by the New Jersey Department of Conservation and Economic Development, entitled "Ground-Water Resources in the Tri-State Region Adjacent to the Lower Delaware River". That report, which contains the most comprehensive treatment of the ground-water resources of the lower part of the Delaware River basin, was prepared by Henry C. Barksdale, David W. Greenman, Solomon M. Lang, George S. Hilton, and Donald E. Outlaw. Most of the present report has been abstracted and somewhat modified from a longer and more inclusive report dealing with the broad aspects, of the hydrology of the Delaware River basin. As defined herein, the Delaware River service area covers about 30,000 square miles of which only 12,865 square miles are in the basin proper. Besides the basin itself, which includes parts of New York, Pennsylvania, New Jersey, Delaware, and a small tip of Maryland, the area comprises Fairfield County, Conn.; New York City and Long Island, and Dutchess, Orange, Putnam, Rockland, Ulster, and Westchester Counties, N. Y.; and all of New Jersey and Delaware. The service area and its sub¬ divisions, classified by the Corps of Engineers according to county groups, are shown on plate 1. Total population of the area in 1950 (last U. S. Census) was about 20 million; approximately 6 million people lived within the basin, and of these about 3*7 million lived in the Philadelphia metro¬ politan area. The population is growing rapidly, especially in the urban and suburban areas; water demands are growing even more rapidly and are creating problems that require comprehensive plans and programs for their solution. Ground-water sources now furnish a minor, but locally important part of the total water withdrawn in the Delaware River service area. Of a basinwide withdrawal of 6,100 mgd (million gallons per day) in 1955 (not including water for hydroelectric plants) ground-water sources supplied 340 mgd— 5*6 percent of the total (Kammerer, 1957 > P* 9 j revised 195$)♦ Ground water furnishes the largest proportion of total withdrawals for irrigation, rural, and small-scale municipal uses—types of uses where the demand is dispersed rather than concentrated in relatively small 6. areas. Also ground water is a more important source of supply in the Coastal Plain than in the Appalachian Highlands, northeast of the Fall Line; roughly two-thirds of the ground water pumped in the Delaware River basin is from the unconsolidated deposits of the Coastal Plain, which constitutes only one-fourth the area of the basin. Because ground-water supplies are but a part of the total it is em¬ phasized here that the magnitude of the potential ground-water supply of the Delaware River service area cannot be evaluated apart from the over¬ all total, as if ground water were a separate resource. Thus, it is axiomatic that heavy development of surface-water supplies tends to limit the amount of perennially recoverable ground water and conversely. In the final analysis, economic and other factors beyond the scope of this report determine the extent to which ground-water supplies are developed. This report attempts to indicate only the physical possibilities for ground-water development in the Delaware River service area. 7 . GENERAL GROUND-WATER HYDROLOGY OF THE BASIN SOURCES OF GROUND WATER In the Delaware River service area all ground water is derived from precipitation. Under the humid conditions prevailing in the region aquifers are usually full to overflowing and are so maintained by pre¬ cipitation. When the capacity of the soil to retain water against gravity (the field capacity of the soil) is exceeded, the excess water percolates to the water table to become ground water. Throughout most of their courses the streams of the service area usually act as drains rather than as sources of water. Seepage from streams therefore contributes recharge to ground water only where pumping of wells near streams reverses the natural direction of ground-water move¬ ment toward the streams. Under these circumstances substantial quantities of recharge may be induced from the streams. Near the ocean or other bodies of saline water such a reversal of movement may cause encroachment of the saline water. OCCURRENCE AND MOVEMENT Ground water may be considered as the water that is stored temporarily in saturated openings in earth material and that provides the water to wells, springs, and fair-weather flow of streams. A bed or zone of such materials that is capable of yielding usable quantities of water to wells is called an aquifer. Aquifers have two principal functions: they store water and they transmit water. Storage is perhaps the primary function of aquifers in which the water exists under unconfined, or water-table, conditions. Such con¬ ditions are most common near the land surface in permeable materials such as the coarse-grained deposits in large areas in the Coastal Plain and the thick mantle of weathered rock in many parts of the Piedmont physiographic province. Such aquifers obtain recharge di¬ rectly from rain or snow in their storage areas. 8. On the other hand, aquifers that contain water under confined, or artesian, conditions serve principally as conduits to transmit water from intake (recharge) areas to discharge areas. Artesian aquifers are enclosed by beds or zones of relatively impermeable materials (aquicludes) which, though they may be saturated, yield little water and act as barriers to water movement. The best examples of aqui¬ cludes and artesian aquifers in the basin are the extensive, alter¬ nating layers of clay and sand in the Coastal Plain province. Aquifers in the basin range widely in their capacity to store, transmit, and yield water. Their most significant hydrologic pro¬ perties are theiar coefficients of storage> permeability, and trans- missibility. Porosity is not so important, because not all, and in some materials such as clay very little, of the water stored in the' openings of a material will drain by gravity; hence some of this total storage capacity is not usable. Coefficient of storage is the volume of, water released from or taken into storage by an aquifer per unit surface area per unit change in the component of head (water pressure) perpendicular to that sur¬ face . In artesian aquifers, where the withdrawn water comes from elastic adjustment to head changes rather than from drainage of the pores, the storage coefficient is very small, commonly 0,00001 to 0.001, whereas in water-table aquifers, where the material is actually drained, the coefficient of storage commonly ranges from 0.05, and sometimes less, to 0.30. The coefficient of permeability of a material as used by the U. S. Geological Survey is the rate of flow of water in gallons per day through a cross-sectional area of 1 square foot under a hydraulic gradient of 1 foot per foot, at a temperature of 60°P. The field co¬ efficient of permeability is the same except that it is measured at the prevailing water temperature rather than at 60°P. Some of the deposits of coarse sand and gravel have permeability coefficients ex¬ ceeding 3,000 gpd per square foot, whereas most beds of clay have per¬ meability coefficients of a very small fraction of 1 gpd per square foot. The coefficient of transmissibility may be regarded as the pro¬ duct of the average field permeability of an aquifer and its thickness; it is expressed in gallons per day per foot. It indicates the capacity of the aquifer, as a unit, to transmit water at the prevailing temper¬ ature, under any given hydraulic gradient. Transmissibility coeffic¬ ients greater than 100,000 gpd per foot have been measured for sand aquifers in the Coastal Plain, but coefficients less than 1 gpd per foot have been estimated for adjacent clay aquicludes. 9 . Ground water, like surface water, moves in the direction of de¬ creasing hydraulic head. In water-table aquifers the water moves in fairly direct paths from higher to lower areas in the outcrop, but in artesian aquifers the water may follow long and sometimes rather circuitous paths. In the Delaware River service area distances trav¬ eled from intake points to discharge points in water-table aquifers range from only a few feet to thousands of feet. In artesian aqui¬ fers, such as those of the Coastal Plain, distances traveled by some of the water from the recharge at the outcrop to discharge points range from a few miles to tens of miles; however, some artesian re¬ charge is obtained from leakage through confining beds; therefore, recharge from such sources may be in the order of a few tens to sev¬ eral hundreds of feet. Times of transit also range widely from a few hours or days to tens and even hundreds of thousands of years. DISCHARGE Natural discharge of ground water takes place where the top of the saturated zone--the water table, or the overlying capillary fringe--is at or near the land surface. Some of this water returns to the atmosphere by the processes of evapotranspiration and thus may be considered as part of the natural loss. The remainder enters streams or other bodies of surface water and becomes a part of the water crop. In addition to natural discharge, considerable quantities of water are in places discharged artificially by pumped wells, mines, and quarries. New patterns of ground-water movement toward the pumped areas become established, and discharge at natural outlets may diminish or cease. In the basin most natural ground-water discharge occurs at rela¬ tively low parts of the outcrop of aquifers--along streams, in wet or swampy areas, and into the bays, estuaries, or ocean. The total amount of such natural discharge, including evapotranspiration, is not accurately known; however, it is estimated that about half the average annual streamflow in the basin is supplied from ground-water discharge. The total pumpage from basin aquifers is estimated to be about 340 mgd and the total ground-water discharge to streams is estimated to be about 6,000 mgd; in addition, an unknown quantity bypasses the streams and leaves the basin mainly in the Coastal Plain aquifers. Therefore, the ground-water pumpage is probably 5 percent or less of the total; certainly it is less than 10 percent. TYPES OF AQUIFERS Based on the nature of their water-bearing openings, two major types of aquifers exist within the Delaware River service area, those consisting of unconsolidated sediments and those consisting of con¬ solidated rocks, (pi. 2). 10 . Unconsolidated sediments consist of loose granular materials, deposited by water, wind, or ice, in which essentially all the water¬ bearing openings are pores between the grains„ Laboratory-determined porosities of sand samples from the Coastal Plain in New Jersey range from about 25 to 45 percent (Barksdale, Greenman, Lang, and others, 1958), and some clays have even higher porosities. Not all the water stored in the pores will drain by gravity, however. The term specific yield is therefore used to indicate the ratio of the volume of water that can drain by gravity from a satu¬ rated material to the volume of the material. This ratio, like por¬ osity, usually is expressed as a percentage. Where free drainage occurs, as under water-table (unconfined) conditions, the specific yield is practically equal to the coefficient of storage. In many parts of the Delaware River service area the specific yield of sand and gravel exceeds 25 percent. However, in clay and silt most of the water is retained in the tiny pores by molecular forces (capillary attraction), and the specific yield may approach zero. Consolidated rocks are dense, coherent materials which, in their fresh, unweathered state, have little or no intergranular porosity. Instead, the water-bearing openings consist largely of fractures, some of which are solutionally enlarged. Where weathered, such rocks may resemble unconsolidated sediments in having intergranular pores, and the distinction between the two types is not sharp. In the service area the consolidated rocks comprise three principal categories, each having distinct water-bearing properties: clastic rocks; carbonate rocks; and crystalline rocks. Clastic rocks include shale, sandstone, conglomerate, and re¬ lated rocks, all of which were deposited originally as unconsolidated sedimentso These materials have been hardened by cementation or com¬ paction so that little remains of their original intergranular por¬ osity, and most of their water occurs in fractures. However, some sandstone and conglomerate contain significant amounts of water in their intergranular pores where the cementing material has been dis¬ solved . Carbonate rocks, also of sedimentary origin, include limestone, (calcium carbonate), dolomite (calcium and magnesium carbonate), dolomitic limestone, and rocks gradational between the pure carbonate rocks and the clastic rocks in which the carbonate content is sub¬ stantial. Carbonate, rocks differ from other categories chiefly in having solution channels or cavities in addition to the other types of openings. Although the aggregate volume of the solution openings usually is but a small percentage of the total volume of rock, their 10a 2A Outcrop of black shale (Marcellus shale of Devonian age) at Wallace St. and Fulmer Ave., Strouds¬ burg, Pa. Here the "shale" is more nearly a claystone. Although numerous fractures occur in the claystone, the fractures are tight and water can move through them only very slowly. Wells developed in such bedrock would have very low yields■ 2B Kame-terrace deposit at Hawley, Pa. Such sandy and gravelly materials of glacial melt¬ water origin are highly permeable and where satur¬ ated, yield large quanti¬ ties of water to wells. Plate 2. —Photographs of geologic \ rock materials of contrasting hydrologic properties, Delaware River basin area ' relatively large size permits rapid movement of water, and the per¬ meability of some carbonate rocks in the basin area compares favor¬ ably with that of the coarse-grained unconsolidated sediments. Crystalline rocks, which are composed of interlocking mineral grains (crystals) have virtually no intergranular porosity, except where altered by weathering. Fractures in these rocks commonly contain small but significant quantities of water; however, in the area of this report few such openings extend deeper than about 300 feet, and most of the water is contained at much shallower depths. Considerable quantities of water occur in thick zones of weathered crystalline rocks such as are found in the Piedmont upland (pi.3). The consolidated-rock aquifers, as a group, are markedly in¬ ferior in their capacity to store and transmit and yield water. Probably few consolidated rocks have a specific yield as great as 2 percent, in contrast to the specific yields of 20 percent or more common in sand and gravel. Coefficients of transmissibility of 50,000 - 150,000 gpd per foot have been measured in several uncon¬ solidated granular aquifers (tables 3 and 4), but, with the excep¬ tion of some of the carbonate-rock aquifers and possibly some of the coarse-grained sandstone and conglomerate aquifers, probably few consolidated-rock aquifers have coefficients of transmissabil- ity higher than 5,000 gpd per foot. HYDROLOGIC PROVINCES The Delaware River basin comprises 2 greatly different hydrologic provinces which correspond to the 2 major physiographic units in the region: the Atlantic Plain occupying approximately the southern fourth of the basin; and the Appalachian Highlands constituting the northern three-fourths of the basin (pi. 3). The 2 provinces are separated by the Fall Line, which extends northeasterly across the southern part of the basin and lies along the northwest side of the Delaware River between Wilmington, Del., and Trenton, N. J. The Atlantic Plain, or Coastal Plain as its emerged part is designated, is underlain by a wedge of unconsolidated sediments having its northwestern edge along the Fall Line. This great wedge thick¬ ens seaward, reaching a maximum thickness of about 6,000 feet beneath the mouth of Delaware Bay (pi.4). It consists of an alternating sequence of sheet-like layers of sand, clay, and some gravel. Enor¬ mous quantities of water are stored in this great mass of deposits, and its aquifers transmit water much more readily than most of the consolidated-rock aquifers of the Appalachian Highlands. 12 . In contrast, the Appalachian Highlands are underla i n predominant- ly by consolidated rocks. In general, the consolidated-rock aqui¬ fers store and transmit much less -water than the unconsolidated gran¬ ular aquifers of the Coastal Plain. Unconsolidated deposits of glac¬ ial origin discontinuously mantle the northern part of the Highlands and occur also as tongue-shaped valley fills of glacial putwash throughout both northern and southern parts. Although the aggregate amount of water stored in the outwash is small compared with that in the consolidated rocks, the supplies from these deposits are readily available to wells and, under favorable conditions, may be augmented considerably by recharge induced from hydraulically connected streams and lakes. The Appalachian Highlands include k physiographic provinces, each of which has distinctive landforms resulting from the types and struc¬ ture of the underlying rocks and the geologic history of the region. From the Fall Line northward these physiographic provinces, as class¬ ified by Fenneman ( 1938 ), comprise the Piedmont, New England, Valley and Ridge, and Appalachian Plateaus provinces (pi. 3 ). The charac¬ teristics of each province and its subdivisions are described briefly farther on in the discussioh of the Appalachian Highlands part of the basin.. THE COASTAL PLAIN GENERAL FEATURES The Coastal Plain physiographic province is the emerged part of the Atlantic Plain (pi. 3 )> a gently sloping surface that extends 125-175 miles southeasterly from the Fall Line beyond the present coastline to the edge of the continental shelf. A net rise of sea level in the last 10,000 years since the shrinkage and disappearance of the continental glaciers of the most recent ice age (Wisconsin age) has inundated the outer part of the Atlantic Plain and has "drowned” the lower reaches of the streams, forming bays, estuaries, and tidal marshes near their mouths. Delaware Bay and the estuary of the Delaware River, which extends inland 133 miles from the mouth of the Bay to the Fall Line at Trenton, N. J., has been formed by this sea-level rise, which has amounted to about 150 feet (Flint, 1957* p. 262 ). The Co»«tal Plain occupies the south half of New Jersey, most of Delaware, and a narrow strip in southeastern Pennsylvania along the northwest side of the Delaware River. Excluding tidal marshes and bays, it includes an area of about 2,750 square miles within the basin and about 2,150 square miles in coastal New Jersey,outside the basin. In width it decreases toward the northeast from abput 70 miles in-. Delaware to less than 20 miles at Rax4tan Bay in New Jersey. Long Island, N. Y., averaging about 1 6 miles in width, is the continuation of the Coastal Plain in that State. U S GFOLOGICAL SURVEY PLATE 4 * k OO' - 40 * 00 ’ 40 - 30 ' - 39 * 00 ' L_ 6*W / ' > / ' II 1 ! / 4 / / / / / / Boundory of Delowore River bosln 0 10 20 Miles Compiled by F H Olmsted ond H G Richards,using data from the following sources • (I) Ewing, W M„ Wool lord, G P , ond Vine, A .C , 1939, Geophysicol investigations in the emerged ond submerged Atlantic Coostal Ploin; port IE, Bornegot Boy, N. J. t section: Geol. Soc Americo Bull.,v 50, p. 257-296 <2).1940, Geophysicol investigations in the emerged ond submerged Atlantic Coastal Plain , port 1ST. Cope Moy, N J., section. Geol. Soc. Americo Bull. 51 p. I82M840 Q (3)Morme, I.W , ond Rasmussen,W C , 1955, Preliminary report on the geoiogy ond ground-water resources of Delaware Del Geol Survey Bull 4 pi 5 14)Rasmussen,W C , Sloughter,T H , Hulme,A E .ond Murphy, J J ,1957, The water resources of Caroline, Dorchester, ond Talbot Counties . Md Dept Geol. Mines,and Water Res.,Bull. 18, pi.2 30 ' 75 * 00 ' 0 - 7900 (estimated) 30 ' 74 * 00 ’ CONFIGURATION OF BEDROCK BENEATH COASTAL PLAIN OF DELAWARE RIVER BASIN AND ADJACENT DELAWARE AND NEW JERSEY ■I ' ■ 13 . Throughout most of New Jersey the Coastal Plain consists of an inner part which slopes gently northwest toward the Delaware and Raritan Rivers and an outer part which slopes even more gently south¬ east toward the ocean, or, in the southern end of the State, south and southwest toward the Delaware Bay. In Delaware, the plain slopes east toward the Delaware River and Bay. The land surface is nearly flat over wide areas but is moderately hilly in places, particularly toward the northeast, in the vicinity of Raritan Bay. In that area a few hilltops rise to nearly 400 feet above sea level, but in general altitudes greater than 200 feet are rare, and more than half of the plain is below an altitude of 100 feet t The inner, northwestern part of the Coastal Plain in New Jersey is crossed by a sequence of approximately parallel belts, which are the beveled edges or outcrops of the geologic formations that dip to¬ ward the ocean (pis. 5 and 6). Where outcrops are not mantled by younger deposits of sand and gravel, each belt has a distinctive landform resulting from the relative resistance to erosion of the un¬ derlying materials. Unusually resistant beds such as sandstone or conglomerate (cemented sand or gravel) form steep-sided hills and ridges; beds of clay tend to form broad interstream sufaces but steep stream banks; and loose sand beds form gentle valley sides, or where wind action is strong and the sand is not held in place by veg¬ etation, dunes and "blowouts" may be formed. In plan view, some of the outcrop belts are deeply frayed or indented where they are crossed by the small streams flowing toward the Delaware or Raritan Rivers (pi. 6). Below the bend at Trenton, N.J., the Delaware River follows the innermost belt--the largely concealed beveled edge--of the basal unit consisting of nonmarine sediments of Cretaceous age. The rela¬ tive weakness of these materials and the resistance to erosion of the hard crystalline rocks immediately to the northwest across the Fall Line have evidently determined the course of this part of the river. The outer margin of the Coastal Plain in New Jersey has very low reflief and slopes gently toward the ocean on the east and southeast, and toward the bay on the south. In Delaware the topgraphy is simi¬ lar, except that the prevailing slope and drainage is toward the east. These areas are immediately underlain for the most part by permeable sand and gravel and are traversed by perennial streams of low gradient In their shoreward reaches most of the streams are tidal and are bor¬ dered by marshes. The coast in central and southern New Jersey is characterized by a line of offshore sand bars, formed by longshore currents and wave action, behind which lie shallow bays and marshes. Atlantic City is built on one of these bars. 88197 0-62- 3 (Vol.VII) 14 . The deposits underlying the Coastal Plain form a wedge which consists of an alternating sequence of relatively permeable coarse¬ grained beds of sand and gravel and relatively impermeable fine¬ grained layers of clay and silt. The coarse-grained beds and the fine-grained beds constitute, respectively, aquifers and aquicludes of variable thickness and extent. These aquifers and aquicludes correspond in a general way to the geologic formations that have been established on the basis of both physical character and age as deter¬ mined from fossils. However, the boundaries of the aquifers and aqui¬ cludes are not everywhere the same as those of the formations, because the formations change in character from place to place-■‘■a formation may be predominantly coarse-grained and classed as an aquifer at one place, and predominantly fine-grained and classed as an aquiclude at another--, and because some of the formations comprise several aqui¬ fers and aquicludes, and because aquifers in two adjacent formations may join to form a single hydrologic unit. The geologic formations that comprise the unconsolidated sediments of the Coastal Plain are listed in the order of their age on pages 15, 16, and are described briefly in table 1; The sequence lies on a platform of the consolidated rocks of the same type as are exposed northwest of the Fall Line. This platform, which had been eroded to a surface of very low to moderate relief by the beginning of the Cretaceous period, about 125 million years ago (table 1), now slopes southeastward from the Fall Line, where it is slightly above sea level, toward the ocean, where it is about 6,000 feet below sea level at the mouth of Delaware Bay--an average slope of about 83 feet per mile. Plate 4 shows the configuration of this surface in a very general way; not enough deep-well information and geophysical data are avail¬ able to determine the buried topography in detail. Nearly all the formations in the overlying wedge of deposits thicken seaward. Dips of the formations therefore decrease upward in the sequence from about 75 to 80 feet per mile in the Cretaceous formations near the base to perhaps only slightly more than the slope of the outer part of the Coastal Plain--about 10 feet per mile in the Cohansey sand--near the top of the sequence. Besides thickening seaward, most of the formations become finer grained and more difficult to identify in that direction. Oscilla¬ tions of the ancient shoreline caused the deposition of materials in alternating layers of different character that allows classifica¬ tion of the deposits into formations toward the northwest in and near their outcrop. However, because the ocean lay to the east throughout the time that all the deposits were accumulating, just as it does at present, all the formations probably grade eastward and southeastward into fine-grained silt and clay of deep-water origin, and it is be¬ lieved unlikely that many beds of sand extend as far as the edge of the continental shelf, some 100 miles east of the present shoreline. 15 . Nevertheless, some of the sandy aquifers probably extend at least several miles beyond the present shoreline. Some of these aquifers were deposited in the ocean and therefore were originally saturated with salt water. Now, however, they contain fresh water, which in¬ dicates that infiltrating precipitation has filled the inland re¬ charge areas of the aquifers, moved through them to the sea and in doing so has flushed the salt water out. This implies, of course, a connection between sea and land through the aquifers and has an important bearing on problems of salt-water encroachment along the coast o Bearing in mind that most of the formations change in character from place to place and may be missing altogether at some localities, a generalized picture of the sequence of aquifers and aquicludes is provided by the following list. The age increases toward the bottom of the list; hence in general, the units are in the order they would be penetrated in a well. Beach and dune sand . .. Marsh and swamp deposits ........ Alluvium and glacial outwash. Basin-rim sand . Tablot and Cape May formations... Unlassified deposits) Pensauken formation )... Bridgeton formation ) Beacon Hill gravel... Cohansey sand . Kirkwood formation . Piney Point formation . Shark River marl) Manasquan marl ) Vincentown sand . Hornerstown marl . . „ „ „ . . . . „ <> « . . » <» Red Bank sand o.o....ooo.oo.o..oo Neve sink marl «„ ... .. Mount Laurel sand) Wenonah sand )" A minor aquifer A portal for rechard and discharge An aquifer, more important in Appa¬ lachian Highlands than elsewhere. A portal for rechard and discharge An aquifer and portal for recharge and discharge. A portal for recharge and locally a minor aquifer An entry for recharge A major water-table aquifer A significant group of aquifers and aquicludes An entirely confined aquifer in southern part of basin A minore imperfect aquiclude A minor aquifer Together with Naves ink marl, an imperfect aquiclude An aquifer in northeastern part of area, largely outside basin Together with Hornerstown marl, an imperfect aquiclude An extensive minor aquifer. In Delaware, Mount Laurel sand not distinguished from Navesink marl 16, Marshalltown formation.An imperfect aquiclude; not known in Delaware Englishtown sand...A highly variable minor aquifer; not present in Delaware Woodbury clay 1 .An extensive major aquiclude Merchantville clay) Nonmarine sediments: .A complex group of aquifers and aqui- Magothy formation eludes. Aquifers constitute most Raritan formation important present source of ground Patapsco formation water in basin Patuxent formation OCCURREHCE OP GROUND WATER Very large quantities of fresh water occur in the great wedge of unconsolidated sediments underlying the Coastal Plain. Nearly all the usable water—that is, the water that can be withdrawn by wells— is in sheetlike layers of sand and lenslike beds of sand and gravel. These layers of sand and gravel—the aquifers—are interbedded with aquicludes composed of silt and clay which restrict the movement of water and confine the water in same of the aquifers under artesian pressure. The aquicludes generally increase in thickness and relative abundance toward the coast, reflecting the seaward change to a deeper water origin of the deposits. Presh water occurs, or occurred under native conditions, in all the near-surface materials in the Coastal Plain; however, salt water is contained in the lower, seaward part of the wedge in accordance with the Ghyben-Herzberg principle (p. 5^ ). The inland extent of the salty ground water is different in each aquifer. In general, the salt water extends farthest inland in the lowest aquifers. The aquifers in the nonmarine sediments of Cretac¬ eous age contain salt water as far inland as 50 miles. At Atlantic City, N. J., the ”800-foot" sand aquifer in the Kirkwood formation still contains fresh water, despite pumping which has lowered the fresh-water head in the aquifer by more than 100 feet (Barksdale, Greenman, Lang, and others, 195^)> but the aquifers below the Kirk¬ wood formation in this area contain only salty water. Salty water occurs in shallow aquifers of both the Cohansey sand and the Quaternary deposits at places along the coast, but this probably has resulted largely from pumping and to a lesser extent from dredging and drain¬ ing activities; it is not a natural condition. 17 . The outcrops or intake areas of the aquifers in the Coastal Plain are shown on plates 6 and 7. The Quaternary deposits (pi. 7), which blanket large areas of the older aquifers, covering practically all of Delaware and much of southern New Jersey, contain unconfined to semiconfined water and function somewhat as a sponge to receive infiltration from precipitation and transmit it to the underlying aquifers. Plate 8 is an idealized cross section showing geologic and hydrologic conditions in a Coastal Plain setting similar to that of New Jersey and Delaware. A capping layer of permeable sand and gravel lies unconformably over the seaward-dipping pre-Quaternary deposits that constitute a system of aquifers and aquicludes. The Quaternary capping layer itself is largely an unconfined aquifer. Its water table is a subdued replica of the land surface and water flows from high to low areas. The recharge that does not escape locally to streams--some of it soon enough to be considered a part of the di¬ rect runoff, but most of it as base flow--direct runoff, or to the atmosphere through evapotranspiration is available to underlying aquifers (designated A, B, and C in the diagram) through the so- called "funnel effect". This is a system by means of which precip¬ itation collected over a fairly extensive area of land surface is made available as recharge to smaller underlying permeable zones--the sub¬ surface intake areas of the older aquifers. Plate 8 illustrates also how parts of an aquifer can be both artesian and nonartesian, although the case is necessarily greatly oversimplified. The older aquifers (pi. 6) also contain unconfined water in much of their outcrop or where covered by the Quaternary deposits, al¬ though semiconfinement occurs where lenses of silt and clay inhibit the movement of water between the water table and deeper parts of the aquifers. As may be inferred from subsurface data on the character of the materials and from the results of pumping tests, complete lack of confinement, or true water-table conditions, probably are rather uncommon even in the shallower aquifers of the Coastal Plain, and conditions approaching true confinement exist in most of the nonmarine sediments of Cretaceous age which contain numerous lenticu¬ lar bodies of clay and silt that greatly restrict vertical movement of water. Nevertheless, during extensive periods of withdrawal and recharge of water, essentially unconfined conditions exist in the outcrop areas of most of the Coastal Plain aquifers. Down the dip, toward the coast, water in the aquifers below the Cohansey sand is confined by the intervening aquicludes. Under nat¬ ural conditions interchange of water through the aquicludes is ex¬ tremely slow and probably minor in amount. However, significant 18 . quantities of water may move through an aquiclude where a large differ¬ ence in hydraulic head between the adjacent aquifers is created by pumping from one aquifer. For example, assume the following condi¬ tions: thickness of aquiclude is 100 feet; average coefficient of permeability of aquiclude is 0.01 gpd per square foot; and difference in head between adjacent aquifers is 50 feet. Then, the quantity of water moving through a square-mile area of the aquiclude would be about 140,000 gpd--an amount sufficient to supply a town of 1,000 people at an average rate of consumption of 140 gpd per person. The physical and hydrologic properties of the aquifers and aqui- cludes of the Coastal Plain are described briefly in order from oldest to youngest in the following pages; and a more abbreviated description is provided in table 1. Later sections summarize the movement of ground water through the Coastal Plain deposits, the importance of storage, the chemical character of the ground-water supplies, the prob¬ lems of present and potential salt-water encroachment, and the pro¬ ductivity of the aquifers. Nonmarine Sediments of Cretaceous Age--The Major Group of Aquifers The nonmarine sediments of Cretaceous age include in ascending order the Patuxent, Patapsco, Raritan, and Magothy formations (table 1). These formations are not separated herein, because together they con¬ stitute a major hydrologic unit whose individual aquifers and aqui- cludes are comparatively inextensive and therefore susceptible of classification only in restricted areas. The nonmarine sediments--the lowermost part of the unconsolidated sediments in the Coastal Plain--form a seaward thicknening wedge that lies on a surface of low relief cut on consolidated rocks similar to those which crop out northwest of the Fall Line (pis. 4 and 5). The wedge thickens southeastward from zero along the Fall Line to more than 3,500 feet beneath the mouth of Delaware Bay and more than 5,000 feet beneath the southeastern corner of Delaware. The beveled northwestern edge of the nonmarine sediments, most of which is not an outcrop but is largely covered with Quaternary deposits (compare pis. 6 and 7) forms a lowland that extends from northern Delaware 100 miles to the lower Raritan River and Raritan Bay in northeastern New Jersey. Much of the Delaware River estuary lies along this belt, as does the Raritan River and its southwestern tributaries. Largely because of their location near the Fall Line where the large centers of population and industry are concentrated, the aquifers in the nonmarine sediments are more completely developed and provide more water supplies than any of the other aquifers in the basin. . S.GEOLOGICAL SURVEY PLATE 8 Ld CD cr < X o Ld QlL o Ld U_ Lu Ld -I Ld ID Ll. o i— < or f— CO ID z o I— u Ld CO CO CO o cr u Q Ld M _l < Ld O TO COASTAL-PLAIN AQUIFERS ' ■ 19 . The sediments represent several nonmarine environments--stream, marsh, lagoonal, and estuarine--and, in the upper part, there are thin tongues of marine deposits. The individual beds or layers, which are much less extensive than the beds in the overlying forma¬ tions of marine origin, consist of sand, clay, silt, and a little Varicolored tough clay and light, cross-bedded, fine- to coarse-grained sand are typical. Lignite (a brown low-grade coal) and pyrite (an iron-sulfide mineral) are prominent in some places. A few thin limy beds containing shells occur in the seaward part of the sequence. The hydrologic properties of the nonmarine sediments vary greatly. Some of the layers of coarse-grained sand are highly perme¬ able, but many of the intervening layers of clay are nearly imperme¬ able. Laboratory coefficients of permeability for samples from the Raritan formation in Middlesex County, N.J. ranged from 25 to 3,500 gpd per square foot and gave a weighted average of about 1,300 gpd per square foot; the average coefficient for sands in the Magothy formation was about 400 gpd per square foot (Barksdale, and others 1943). Pumping tests in New Jersey gave permeability coefficients ranging from 240 to 2,500 gpd per square foot and averaging about 1,200 gpd per square foot, although the results of 2 tests in northern Delaware indicated lower permeabilities there (table 2). Coefficients of transmissibility from 14 pumping tests in New Jersey, Delaware, and Pennsylvania (table 2) ranged from 5,000 to 150,000 gpd per foot and averaged 60,000 gpd per foot. None of these values is based on a pentration of the entire thickness of the non-marine sediments; the thickness of aquifers tapped ranged from 10 to 100 feet, and even the 100-foot thickness represented only partial penetration of the unit. In contrast to the moderate to high permeability and trans¬ missibility of the aquifers in the nonmarine sediments, the clay aquicludes probably have permeability coefficients of less than 0.1 gpd per square foot. One aquiclude in the vicnity of Camden, N.J., has an estimated coefficient of transmissibility of about 0.4 gpd per foot (Barksdale, Greenman, Lang, and others, 1958). Specific yields, determined by the Geological Survey's Hydrologic Laboratory, of samples of sand from Middlesex County, N. J., aver¬ aged about 35 percent for the Raritan formation and about 40 percent for the Magothy formation. Coefficients of storage determined from the pumping tests listed in table 4 ranged from .000062 to .0016 -- indicative of confined conditions--and the median was about .0003. 2a. 21 . In New Jersey, most wells in the nonmarine sediments that are de¬ signed for large capacity, yield in the range of 300 to 1,000 gpm, and yields exceeding 1,000 gpm are not uncommon. In Delaware, yields are considerably less, as a rule. Rasmussen and others (1957, table 15) reported an average specific capacity (discharge of a pumping well divided by the drawdown of water level) of only about 2 gpm per foot of drawdown for 66 wells in northern Delaware. This value indicates an average coefficient of transmissibility in the order of only 4,000 or 5,000 gpd per foot which is comparable with the 2,500-8,000 gpd per foot values derived from pumping tests at two sites in that area (table 2). Although individual beds of sand and clay in the nonmarine sedi¬ ments are quite lenticular, water yielding zones have been recognized in the most intensively studied areas. These zones appear to be separated by layers of clay that are more extensive than those separ- ating the individual sandy layers within each zone, and definite differences in artesian pressure and also in the chemical character of the contained water exist between the zones. In Northern Delaware Rasmussen and others (1957) defined 3 zones which were called the lower, middle, and upper aquifers; in the Philadelphia-Caraden area, 2 principal zones appear to be present. Graham (1950, p. 214-16, fig. 3) has given a lucid and concise description of the ground-water occurrence in the Philadelphia-Camden area, and his geologic cross section illustrates the nature of the 2 zones mentioned above. Merchantviile and Woodbury Clays - a Major Aquiclude The Merchantviile clay and the overlying Woodbury clay together form a widespread major aquiclude confining the water in the nonmarine sediments. The combined unit crops out or is covered by Quaternary deposits in a belt 1 to 4 miles wide lying immediately southeast of the intake area of the nonmarine sediments. Southeast of its outcrop the unit underlies all the Coastal Plain. The Woodbury clay has not been recognized in northern Delaware, but the Merchantviile clay there probably is equivalent to the combined Merchantviile and Woodbury clays, and possibly also to the Marshalltown formation of New Jersey (Rasmussen and others, 1957, p. 116). Near the outcrop the Merchant¬ viile and Woodbury clays together range in thickness from about 100 to 140 feet, but they thicken downdip and attain a maximum known thickness of more than 250 feet in the seaward part of Ocean County N. J. The Merchantviile clay is a black or greenish-black glauconitic, micaceous clay. Glauconite is a greenish to black amorphous mineral of the iron-potassium-silicate family and has pronounced cation ex¬ change properties; it is commercially mined in parts of New Jersey for use as a water-softening agent. The Merchantviile clay is generally greasy and massive, although the upper part is somewhat sandy and in places is distinctly laminated, particularly in Delaware. 22 . The Woodbury clay, on the other hand, is not glauconitic, and consists of a black or bluish-black, somewhat micaceous, tough clay. It weathers to light brown and breaks into distinctive blocks having curved or shell-shaped fractures. The Merchantville and Woodbury clays, which form the most ex¬ tensive and impermeable aquiclude in the Coastal Plain, are important chiefly in protecting the underlying aquifers in the nonmarine sedi¬ ments from contamination or encroachment of salt water from above and in restricting the loss of water from those aquifers by upward leakage. However, even though their permeability is very low, the Merchantville and Woodbury clays are capable of transmitting signifi¬ cant quantities of water where sizable differences in head exist be¬ tween the overlying and underlying aquifers. A few wells tap the sandy phases of the Merchantville clay, but the T'oodbury clay is everywhere too impermeable to be a source of supply. Minor Aquifers and Aquicludes Above the Merchantville and Woodbury Clays / Between the aquiclude formed by the Merchantville and Woodbury clays and the Kirkwood formation is a sequence of aquifers and aquicludes ranging in thickness from about 400 feet in its northwestern part to about 1,000 feet beneath the coast at Atlantic City, N. J. None of the aquifers in this sequence is an important source of water supply within the Delaware River basin, although 2 of them—the Englishtown sand and the Red Bank sand—are important outside the basin in the northeastern part of the Coastal Plain. However, all are capable of being used to a considerably greater extent than at present, should the need arise and economic factors be favorable. Englishtown Sand i Overlying the aquiclude formed by the Merchantville and Woodbury clays in the central and northern parts of the Coastal Plain is the Englishtown sand, a minpr aquifer in the basin but a fairly important source of water supply northeast of the basin in Monmouth and Ocean Counties, N. J. The Englishtown consists of fine-grained to pebbly quartz sand and a few lnextenslve layers of silt and clay. The sand contains s m all amounts of mica and glauconite, and in places, some lignite. Locally it is cemented by iron oxide. In outcrop the sand Is white, yellow, or brown, but in subsurface it is light gray. Clay and silt, which are not generally abundant, occur mostly in the upper part of the formation. 23 . The Englishtown sand becomes finer grained toward the south and east and thins southward. Its maximum thickness is about 160 feet in Ocean County, N„ J., but it wedges out and is missing southwest of Swedesboro, N„ J. The sand beds probably are moderately to highly permeable, where¬ as the few layers of silt and clay are relatively impermeable. No data on any of the hydraulic coefficients are available, nor have de¬ tailed data on productivity of wells been assembled. However, because of the wide range in thickness of the aquifer, its productivity var¬ ies greatly from place to place. Within the basin the maximum re¬ ported yield per well is 200 gpm, but more probably could be obtained in some places,particularly in the northeastern part of the Coastal Plain, outside the basin. Marshalltown Formation The Marshalltown formation is an imperfect aquiclude. It over- lies the Englishtown sand in most of the Coastal Plain in New Jersey but overlies the Woodbury clay in Salem County, N. J. In Delaware the Marshalltown has not been recognized, but possibly equivalent beds there have been assigned to the Merchantville clay (Rasmussen and others, 1957, p. 117). The Marshalltown formation consists of greenish-black to black sandy clay and lenticular beds of glauconitic sand. Downdip to the southeast where the beds of sand become more abundant, the Marshall¬ town resembles the Englishtown sand and the Wenonah sand. The maxi¬ mum thickness of the Marshalltown in New Jersey is about 125 feet. Because it is thin and contains some slightly to moderately per¬ meable beds, the Marshalltown formation constitutes a "leaky" or im¬ perfect aquiclude. Down the dip, where it becomes more sandy, it functions even less effectively as an aquiclude and water moves be¬ tween the underlying Englishtown sand and the overlying Wenonah sand where the required hydraulic gradients exist (Barksdale, Greenman, Lang, and others, 1958). Domestic supplies of water may be obtained from the Marshalltown at many places, and the sandy parts yield as much as 40 gpm to drilled wells. Wenonah and Mount Laurel Sands Throughout most of the Coastal Plain the Wenonah sand and the overlying Mount Laurel sand together form a minor aquifer. In northern Delaware, however, the Mount Laurel sand has been grouped, instead, with the overlying Naves ink marl which it resembles there (Rasmussen and others, 1957, p. 118). 24 . The Wenonah sand is a slightly glauconitic, micaceous quartz sand containing local thin layers of silt and clay,, The sand is mostly fine- to medium-grained and gray or black where unweathered, although in outcrop it is generally white, yellow, brown, or red. In northern Delaware it grades downward into the Merchantville clay. The overlying Mount Laurel sand contains more glauconite than does the Wenonah sand, is salt-and-pepper-colored, and is mostly medium to coarse-grained, though in northern Delaware it is finer grained and contains considerable amounts of silt and clay. In places the Mount Laurel is cemented by iron oxide to form a brown sandstone. The outcrop of the Wenonah and Mount Laurel sands forms an ir¬ regular belt 1/2 mile to 3 miles wide across the northeast part of the Coastal Plain about 8 miles southeast of the Delaware River, Like the other formations of the Coastal Plain wedge the unit dips southeast, and its top is about 2,140 feet below sea level at Atlantic City, N, J„ Near the outcrop the combined thickness of the Wenonah and Mount Laurel sands ranges from 35 to 100 feet and is greatest in southwestern New Jersey. Downdip toward the coast, the thickness may exceed 110 feet. For the most part, the beds of sand in the unit are moderately permeable. Thompson (1930) reported laboratory coefficients of permeability of about 570 and 890 gpd per square foot for sand samples from the upper and lower parts of the aquifer, respectively. An average coefficient of permeability for the aquifer in New Jersey might be in the range of 500-700 gpd per square foot (Barksdale, Greenman, Lang, and others, 1958); hence the coefficient of trans- miss ibility of an average section 70 feet thick would be about 35,000-50,000 gpd per foot. However, one pumping test at Bradley Beach, Monmouth County, N. J., gave a transmissibility coefficient of only about 7,000 gpd per foot (Lang, S.M. , written communica¬ tion). The storage coefficient for this test was 0.0001, which is indicative of confined conditions. Few data are available on the productivity of wells in the Wenonah and Mount Laurel sands. From the known properties of the aquifer it may be inferred that properly constructed wells of large diameter penetrating the entire aquifer should yield about 40 or 50 to 200 gpm. 25 . Naves ink Marl Within the basin the Navesink marl and the overlying formations, the Red Bank sand and especially the Hornerstown marl, form an imper¬ fect or leaky aquiclude overlying the aquifer formed by the Wenonah and Mount Laurel sands„ The Red Bank sand supplies only small amounts of water to wells within the basin and is missing in much of central and southern New Jersey; so in that area the Nevesink and Hornerstown marls form one aquiclude having generally similar char¬ acteristics. In Delaware the Nevesink marl is similar to the under- lying Mount Laurel sand and together with that formation forms a poor aquifer south of the Chesapeake and Delaware Canal and an imperfect aquiclude north of the canal. The Nevesink marl consists of a green glauconitic limey clay and sand and a basal bed of shells. Clay is most abundant in the upper part of the formation. Its maximum thickness within the basin is about 40 feet, diminishing toward the south to 25 feet or less. The combined thickness of the Nevesink and Hornerstown marl ranges from 35 to 70 feet. Red Bank Sand The Red Bank sand is fairly coarse grained, and contains clay and some glauconite in the lower part. In outcrop the sand is typi¬ cally yellow or reddish-brown owing to oxidation of the iron-hearing minerals, but in subsurface the color is commonly dark gray. White micaceous sand and dark clay occur locally as do some beds cemented by iron oxide. In Monmouth County, N. J., an upper member--the Tinton sand member--consists of somewhat cemented glauconitic, clayey sand. The Red Bank sand attains a thickness of 185 feet in the north¬ eastern part of the Coastal Plain, outside the basin, but thins southward and is missing altogether in central and southern New Jersey. It occurs again in Delaware where it is less than 20 feet thick. Few hydrologic data are available on the Red Bank sand, but it is believed to be similar in physical properties to the Englishtown sand (Barksdale, Greenman, Lang, and others, 1958). Within the basin it is not thick enough to be developed for more than domestic supplies, but outside the basin it yields considerable quantities of water to wells in Monmouth and northwestern Ocean Counties, N. J. 26 . Hornerstown Marl The Hornerstown marl, lowest formation of Tertiary age in the Coastal Plain (table 1), is scarcely distinguishable from the Nave- sink marl, which underlies it in much of the area. In the north¬ eastern part of the Coastal Plain in New Jersey and in Delaware the 2 formations are separated by the Red Bank sand, but in central and southern New Jersey the Hornerstown and Navesink marls together form an aquiclude 35-70 feet thick. The maximum thickness of the Hornerstown is about 55 feet, in Monmouth County, N„ J„, where it confines the water in the Red Bank sand--an aquifer of some import¬ ance in that area. The Hornerstown marl is not a true marl--an unconsolidated sedi¬ ment containing a considerable amount of carbonate as the term is define geologically-but actually is a dark-green to greenish-black glauconite or greensand mixed with some glauconitic clay and non- glauconitic sand. Toward the southwest, sand and clay become more abundant, and in Delaware it is difficult to distinguish the Horner¬ stown marl from the overlying Vincentown sand. At some places the sandy phases of the Hornerstown yield small supplies of water for domestic use. Vincentown Sand The Vincentown sand gradationally overlies the Hornerstown marl and underlies nearly all the Coastal Plain southeast of the outcrop of the Hornerstown marl. However, the outcrop of the Vincentown itself, is missing in eastern Salem County, Gloucester County, and Camden County, N 0 J„, where it is overlapped by the Kirkwood forma¬ tion (pi. 6). The Vincentown sand consists of a fossiliferous and somewhat consolidated limey sand and a sparsely glauconitic quartz sand. The limy sand is more abundant within the basin, whereas the quartz sand is more abundant in the upper part of the formation, especially northeast of the basin in Monmouth County, N. J„ Down the dip the sand beds pinch out and are replaced by beds richer in clay and glauconite. This change, which occurs within about 5-7 miles of the outcrop, greatly restricts the area in which the Vincentown is useful as an aquifer. The formation also thickens downdip toward the southeast from 25-100 feet in outcrop to about 460 feet at Atlantic City, N. J., (pi. 5). 27 . No data are available on the coefficients of permeability, trans- missibility, and storage of the Vincentown sand. However, the quartz sand is at least moderately permeable, as may be inferred from its medium to coarse grain size and from well-yield information. The limy sand probably is less permeable because of its cementation and somewhat smaller average size of grains. Yields of wells in the Vincentown sand range rather widely owing in part to the variability in thickness and permeability of the for¬ mation from place to place. Well yields as much as 300 gpm are re¬ ported from the thicker parts of the aquifer in Monmouth County, N. J., and in the vicinity of Salem, N. J 0 , but elsewhere, yields of 50-100 gpm are more common (Barksdale, Greenman, Lang, and others, 1958). Properly constructed wells might beexpected to yield 40 or 50 to 400 gpm at most places in the aquifer (pi. 9). Manasquan and Shark River Marls The Manasquan marl crops out in a discontinuous belt generally less than a mile wide from Clemonton in eastern Camden County, N„ J„, to the vicinity of Long Branch in Monmouth County, N 0 J 0 (pi. 6). Overlap by the Kirkwood formation creates the long gaps in this belt, and parts of the beveled edge of the Manasquan marl are covered by Quaternary deposits. Beneath the surface the Manasquan is present in most of that part of New Jersey east of a line from Cape May to the outcrop at Clementon. The Shark River marl overlies the Manasquan and is known only in Monmouth County, N. J 0 In outcrop the maximum thickness of the Shark River marl is about 11 feet, and of the Manasquan marl, about 25 feet. In subsurface the combined unit thickens southeastward to about 200 feet at Atlantic City, N. J. The lower part of the Manasquan marl is composed chiefly of glauconite (greensand), whereas the upper part is composed of an ashy mixture of very fine-grained sand and greenish-white clay. The Shark River marl consists of a mixture of greensand and light silty clay in which the uppermost 2-3 feet is cemented. The Manasquan and Shark River marls form an aquiclude confining water in the Vincentown sand. Where the Vincentown is productive, the aquiclude is not more than 25 feet thick and contains beds having noderate permeability; therefore it probably is not very effective as an aquiclude. 88197 0-62-4 (Vol. VII) 28 . Piney Point Formation The Piney Point formation does not crop out within the basin and was not recognized as a distinct aquifer in the area until Marine and Rasmussen (1955) described the formation in Delaware. The Piney Point occurs only beneath the southern part of the Coastal Plain--beneath Kent and Sussex Counties, Delo, and in the southern parts of Cumberland, Cape May, and Atlantic Counties, No Jo It rests on a surface eroded across the Manasquan marl, Vincentown sand, and Hornerstown marl; in turn it is overlain un- conformably by the Kirkwood formation. In thickness the Piney Point formation ranges from nearly nothing along its northern edge where it wedges out between the overlying and underlying formations to about 290 feet at Atlantic City, N 0 J. As determined entirely from well samples, the Piney Point formation consists of beds of coarse- to fine-grained glauconite, salt-and-pepper-colored sand and greenish-gray clay. All water in the formation is confined and is subject to re¬ charge only from adjacent beds, especially where they are relatively permeable. No data on its water-yielding character are available, because the formation has been developed only slightly for water supplies. Kirkwood Formation, an Important Group of Aquifers and Aquicludes The Kirkwood formation, which contains several important aquifers in the Coastal Plain of New Jersey and Delaware, underlies practically all the Cohansey sand in New Jersey and crops out in a northeast¬ trending belt inland from the outcrop of the Cohansey (pi. 6). The Kirkwood does not crop out in Delaware, but it underlies the Quater¬ nary deposits in approximately the southern two-thirds of the State (compare pis. 6 and 7). It extends seaward beneath the Cohansey sand and, where sea-water encroachment has not resulted from pumping of wells, contains fresh water beyond the present shoreline. The Kirkwood also underlies most of Delaware Bay. The Kirkwood formation lies on a buried surface of very low re¬ lief cut on formations ranging down in the sequence from the Piney Point formation to the Navesink marl (table 1). Throughout most of its extent, however, it overlies the Manasquan marl or the Vincentown sand. The lower part of the formation dips about 25 feet per mile to the southeast, whereas the upper part dips a little more than 10 feet per mile. The thickness ranges from nearly zero along its northwest edge to probably more than 700 feet beneath the mouth of Delaware Bay. U S. GEOLOGICAL SURVEY PLATE 9 MAPOFCOASTAL PLAIN IN DELAWARE RIVER BASIN SHOWING PRODUCTIVITY OF AQUIFERS . 29 . In outcrop the Kirkwood formation consists chiefly of fine¬ grained micaceous, quartzose sand alternating with layers of silt and clay of variable thickness. Locally, beds of llgnitic black clay are prominent. The Shiloh marl member, a highly fossilferous clayey or silty sand, occurs at the top of the formation in southern New ' Jersey. In subsurface the proportion of silt and clay increases down the .dip toward the coast, but the beds of sand become coarser grained and more permeable. Silt and clay are estimated to constitute at least four-fifths of the total thickness of the Kirkwood formation at Atlantic City (Barksdale, Greenman, Lang, and others, 1958). Several prominent sandy zones in the Kirkwood have been designated as aquifers: The Cheswold aquifer in Delaware, and its possible equivalent, the "800-foot" sand, at Atlantic City, N. J.; the F!*ederica aquifer in Delaware, separated from the underlying Cheswold aquifer by about 100 feet of silt and clay; and some aquifers above the "800-foot" sand in coastal New Jersey, the highest of which may be equivalent to the Shiloh marl member or to the Frederica aquifer. Because of the absence of deep wells through much of the extent of the Kirkwood formation, particularly in southern New Jersey between the coast and the area of putcrop, probably not all the aquifers in the Kirkwood formation are known. Field and laboratory tests to date have indicated only moderate permeabilities for the aquifers in the Kirkwood formation, Laboratory- ietermined coefficients of permeability for several samples of the "800-foot" sand at Atlantic City averaged about 860 mgd per foot (Thompson, 1928). A pumping test made in 1952 in the same area gave a closely comparable average coefficient of about 880 gpd per square foot for an 80-foot thickness of aquifer. Elsewhere, pumping tests and estimates based on yields of individual wells have yielded small¬ er values--in the order of 100-500 gpd per square foot. Coefficients of transmissibility derived in pumping tests range from 9,00Cto 70,000 gpd per foot, and coefficients of storage determined 30 far are all about 0.0003, except in one test at Ancora, N. J. rhich gave a value of 0.0004. The remarkably consistent values of stor¬ age coefficient may be just an accident because of the small statis¬ tical sample. These coefficients are representative of confined :onditions. 30 .. Cohansey Sand, an Aquifer of Great Potential The Cohansey sand, perhaps the most promising future source of ground-water supplies in the Coastal. Plain of New Jersey and Delaware occurs at or near the land surface throughout most of the outer part of the Coastal Plain in New Jersey—an area of about 2,500 square miles, of which about 1,000 square miles is within the basin (pi. 6). The Cohansey may be present also in southern Delaware, but owing to the difficulty of distinguishing it from the overlying Quaternary deposits, its presence there has not been confirmed. In New Jersey much of the Cohansey sand is blanketed by the Quaternary deposits— chiefly the Bridgeton and Cape May formations—which are generally thin but attain a thickness of about 200 feet in buried valleys and in places along the coast. The outcrop of the Cohansey is a gently seaward-sloping plain of low relief characterized by extensive m arshes along most of the streams. The Cohansey sand lies on a buried surface of low relief eroded on the Kirkwood and older formations. The dip of beds in the Cohansey averages about 10 feet per mile to the southeast, and the formation extends seaward beyond the coast, beneath the Quaternary deposits (pi. 5 - ) • The thickness of the formation ranges from nearly zero where beveled by erosion along its northwestern margin to about 265 feet at Atlantic City on the coast. The Cohansey consists largely of typically light-colored quartzose, somewhat micaceous sand, but it also contains lenses of silt and clay as much as 25 feet thick, and some gravel. The sediments probably were deposited in estuaries and deltas except toward the southeast where they may have been deposited in the ocean. The average grain size of the materials decreases southeastward \ and beds of silt and clay become thicker and more abundant near the coast. On the whole, the Cohansey sand is a highly permeable formation. The coefficient of permeability of the well-sorted medium- to coarse¬ grained sand probably is exceeded only by some of the sand and gravel in the glacial-outwash and channel-fill deposits of Pleistocene age. Coefficients of permeability for the Cohansey, determined from pump¬ ing tests made in Cumberland, Atlantic, and Cape May Counties, N. J., range from about 500 to more than 5 >000 gpd per square foot and aver¬ aged more than 1,000 gpd per square foot (table 3) • The tr ansmit sibility ranges from moderate to high, depending in part on the thickness of the aquifer * Coefficients o* transmissibil- ity determined from the pumping tests cited in table 3 range from about 40,000 to more than 20b,000 gpd per foot. All these values are based on less than complete penetration Of the Cohansey and hence are too Table 3 .--Coefficients of transmissibility, permeability, and storage In Cohansey sand Source of data USGS unpubl. data do do do do Coefficient of storage (dimensionless) Midpoint between extremes ~0.0016 i .0005 § • i Range no 8 • O 1 • o CVi O O • 1 8 • LT\ O 8 • l IA • .0002- .0004 i Coefficient of permeability (gpd per sq ft) Midpoint between extremes 8 •n H o 8 pH 1 -4 1,000 1/ Average of tests in west part of area 2/ Average of tests in east part of area 2/ Average of tests in all the area Range 8 ’• G\ •v pH 1 8 CM •v pH o o CM •\ pH 1 3 o\ 1 o t*- c— 8 ir\ ir\ 1 •s pH rH 1 8 LA Thickness of aquifer (ft) a -H lf\ -3“ -H u~v 120 -H O -J- -H O r— , >> -P ■P -H a © o 3 ^ u u -p o •s t*- X) 1 •V Lf\ LT\ •v vO tr\ i o 8 •N pH ■4- " •\ 1 i OJ On 8 OJ 1 •V t- LT\ « Location • i ha K c? Er\ s* 6 ► o £ a • ha • m ^ C\J O (A f 9 H • 0 -p « h» * 35 r- 1 • h> • A * M w W •% a 1 ^ 31 . 32 . low to be representative of the full thickness. Even so, they are comparable to transmissibility coefficients determined for the aqui¬ fers that at present are most productive—those in the nonmarine sediments of Cretaceous age (table 2). The coefficients of storage from the tests listed in table 3 range from 0.0008 to. 0.002 --values representative of confined to semiconfined conditions rather than of unconfined conditions. Such storage coefficients are not representative of the specific yield, which as determined by laboratory tests, is about 0.25* If pumping of the confined sands shohld proceed at any place to the point where the piezometric surface falls below the confining layers, then values of the coefficient of storage would approach or equal the specific yield. Modern drilled wells in the Cohansey sand may reasonably be ex¬ pected to yield between 100-eLnd 1,000 gpm and even higher yields may be obtained without excessive drawdown in places where the thickness of the aquifer exceeds 100 feet. Beacon Hill Gravel - a Remnant Cap The Beacon Hill gravel, or Bryn Mawr gravel as its probable equiv¬ alent is called in the Piedmont province (Richards, 195&), occurs at widely scattered places where it -caps broad hills and ridges. The Beacon Hill occurs at only 2 places in the portion of the Coastal Plain within the basin but caps about 25 hills outside the basin in Monmouth, Ocean, and Burlington Counties, N. J. (pi. 6 In the Piedmont in southeastern Pennsylvania and northern Delaware the Bryn Mawr gravel caps several broad interstream areas at altitudes of about 300 feet. The Beacon Hill gravel consists of highly weathered deposits of sand, gravel, silt, and some clay which are in places cemented by iron oxide. Some of the pebbles are so weathered that they crumble to tripoli--a friable or dustlike silica. The Pliocene(?) age listed in table 1 is uncertain, because no fossils have been found in the formation. Because of its position on hilltops above the water table, wells in the outcrop pass through the Beacon Hill gravel into saturated materials below. Therefore its hydrologic significance lies in its function as a moderately tr highly permeable intake area for the underlying formations (pi. 0 ). 33 . Quaternary Deposits—an Important Group of Aquifers and a Portal for Groundwater Recharge and Discharge In the Coastal Plain the unconsolidated sediments of Quaternary age comprise several geologic formations and units that overlie the older formations as valley fills, thin blanketlike masses, and scat¬ tered caps on ridges and hills. With the exception of relatively thin deposits of Recent age along streams, marshes, and beaches, these deposits were laid down during the Pleistocene epoch, or Ice Age, as it is often called. All tbs deposits therefore are less than about a million years old and are much younger than the underlying Cretaceous and Tertiary formations (table l). The Quaternary deposits are shown on a separate geologic map (pi. 7j) because they mask the Cretaceous and Tertiary formations fcp extensively in some areas that the relations of those formations cquld not be shown on the same map with the Quaternary formations. The extent of some of the Quaternary formations has not been defined acqurately in much of the region, partly because of the lack of detailed geologic study but at many places also because of the difficulty of distinguishing these formations from the underlying formations of Cretaceous and Tertiary age. Bridgeton and Pensauken Formations The Bridgeton formation and younger Pensauken formation are blanketlike deposits of quartzose gravel, sand, and silt in broad inter- stream areas in the Coastal Plain (pi. 7 )• The Bridgeton Is generally somewhat more highly weathered them the Pensauken but the two forma¬ tions are very similar. In places it is difficult to distinguish the Bridgeton from the coarser phases of the underlying Cohansey sand. The Bridgeton lies at altitudes more than 150 feet above sea level in central New Jersey and above 1.00 feet in southern New Jersey, where¬ as the altitude of the base of the Pensauken declines southward from about 100 feet in the area between South Amboy Camden, N. J., to 30 feet south of Salem, N. J. The Pensauken occurs also northwest of the Fall Line in Pennsylvania where it lies at altitudes of as much as 170 feet above sea level (Bascom, Clark, Darton, and others, 1909, p. 12). Both the formations were deposited in broad valleys by the ancestral Delaware River and its tributaries. The Bridgeton formation is as much as 70 feet thick, but the Pensauken generally does not exceed about 20 feet in thickness (Campbell and Bascom, 1933). 34. Although these formations are extensive in many parts of the Coastal Plain (pi. 7), they are scarcely thick enough to provide large supplies of water to wells. Nonetheless, they act as per¬ meable entry areas for ground-water recharge, and where they over- lie permeable formations such as the Cohansey sand and permeable beds in the non-marine Cretaceous sediments, they constitute water- table aquifers in conjunction with those formations, as shown in the schematic diagram, (pi. 8). Where they overlie aquicludes or less permeable beds the Bridgeton and Pensauken probably are capable of yielding only small supplies sufficient for domestic or small-farm uses. In such situations the water they contain discharges naturally along a line of seeps or small springs near their base. Unclassified Deposits of Pleistocene Age The unclassified deposits of Pleistocene age include a variety of materials that do not belong to the Bridgeton, Pensauken, Cape May or Talbot formation and whose proper assignment awaits the find¬ ings of future field investigations„ In Delaware these deposits were assigned to the Wicomico formation in the U. S. Geological Survey Geologic Atlas Folios (Miller, 1906; Bascom and Miller, 1920). In New Jersey the unclassified deposits were described in the U. S. Geological Survey Folios as a discontinuous mantle of surface mater¬ ial whose age, in many places, is not determinable. Owing to their thinness and uncertain extent the unclassified deposits in New Jersey are not shown on plate 7. The Wicomico formation in Delaware is described as a broad blanket like deposit of loam, sand, gravel, and scattered boulders which lies topographically above the adjacent younger Talbot form¬ ation (Miller, 1906). The Wicomico, which is as much as 50 feet thick, is reported to be somewhat fine grained toward the top. In New Jersey the unclassified deposits include a variety of materials ranging from silt and clay to coarse-grained sand and gravel. The deposits generally are only a few feet thick and at many places they closely resemble the weathered parts of the underlying forma¬ tions of Cretaceous and Tertiary age. The hydrologic properties of the unclassified deposits are not well known. Probably they serve primarily as a moderately to highly permeable blanket through which recharge enters the underlying aqui¬ fers or through which ground water discharges. In Delaware, buried valleys or channels filled by deposits provide large yields to favor¬ ably situated wells. 35 . Cape May and Talbot Formations The Cape May formation and its probable equivalent in Delaware, the Talbot formation, form a roughly wedge-shaped mass thinning in¬ land and having tonguelike extensions up the larger stream valleys. The Cape May includes broad, blanketlike deposits and channel-fill or valley-fill deposits which may be more than 100 feet thick in northern Delaware. The exact relations of the Cape May formation to the glacial outwash to the north are not known, but the coarse-grained gravelly deposits in the broad valley adjacent to the Delaware River near Trenton, N. J., have been described both as outwash and as Cape May formation in earlier reports (compare Greenman, 1955, and Bascom, Darton, Kuramel, and others, 1909). Richards (1956, p. 89) believes that no sharp lines exists between the Cape May formation and the glacial outwash. Parts of the Cape May formation near the coast are of marine origin, and the upper part of the formation includes estuar¬ ine deposits of clay and silt. Much of the 'Cape May and Talbot formations consists of stream- deposited sand and gravel that are much less weathered than the depos¬ its of the Bridgeton and Pensauken formation. Where such deposits lie in buried valleys more than 100 feet deep, large yields may be obtained from drilled wells. Rasmussen and others (1957, p. 124) reported yields of as much as 1,000 gpm from drilled wells in these buried val¬ leys in Delaware. At present, however, the location of the buried chan¬ nels and valleys is known only in a general way in northern Delaware and in Cape May County, N. J. Toward the coast the estuarine deposits of clay and silt in the upper part of the Cape May formation confine the water in the under¬ lying deposits of sand and gravel. The top of this silt-clay aquiclude is as much as 30 feet above sea level, but the underlying sand and gravel extend below sea level; therefore the ground water of these de¬ posits is hydraulically continuous with sea water. Such conditions make it possible for salt-water encroachment to take place where pump¬ ing has lowered water levels below sea level. In some places encroach¬ ment already has occurred. Together with the glacial outwash the Cape May.and Thibet forma¬ tions constitute one of the most promising sources of ground-water supplies in the southern part of the Delaware River basin. Yields of several thousand gallons per minute to individual wells are possible in places, especially where recharge may be induced from/adjacent streams and other fresh-water bodies. 36 . Basin-Rim Sand Throughout parts of the Coastal Plain are small, generally ellip¬ tical basins, the rims of which, and in places the interiors, are formed by deposits called basin-rim sand (Rasmussen, 1953)* The upper part consists of fine-grained sand and silt, whereas the lower part is a deposit of reddish-brown poorly sorted coarse-grained sand and gravel. The basins collect runoff, allowing it to infiltrate to the ground-water body, or'where the underlying materials are saturated, the basin centers are sites for large evapotranspiration losses. Thus the basins function as portals for recharge or discharge of ground water, or for both at different times of the year. Glacial Outwash and Alluvium The glacial outwash was deposited by streams flowing from the continental glaciers that occupied the northern part of the basin. The most extensive and permeable outwash deposits in the Coastal Plain are those of the Wisconsin glacial stage that occupy the broad valley adjacent to the Delaware River near Trenton. Older outwash deposits are herein grouped with the Pensauken formation and possibly the Bridgeton formation. Thin alluvium of Recent age is grouped with the underlying outwash of Wisconsin age because of the difficulty in dif¬ ferentiating the 2 deposits and because they are hydraulically con¬ nected. The glacial outwash appears to be mixed with similar de¬ posits of the Cape May formation downstream from Trenton, N. J., (pi. 7). The glacial-outwash deposits which are largely relatively un¬ weathered sand and gravel, are highly permeable and yield as much as 1,050 gpm to wells in southeastern Bucks County, Pa., (Greenman, 1955 > P* 39)* The outwash is quite similar in hydrologic properties to the coarse-grained part of the Cape May formation. Marsh and Swamp Deposits The marsh and swamp deposits occur along the streams and tidal estuaries and consist of dark silt and clay mixed with organic matter. They are all or partly covered by water most of the time and generally are in such a loose, flocculent state that appreciable recharge and discharge may pass through them. Along bays and estuaries the marsh deposits may serve as portals for salt-water encroachment into under¬ lying shallow aquifers in which the hydraulic head has been lowered below sea level by pumping or by drainage operations that reduce fresh¬ water head above sea level. Under natural conditions the fresh-water marshes and swamps are probably the sites of great quantities of ground-water discharge. 37 - Beach and Dune Sands The beach and dune sands consist of loose well-sorted sands along the beaches and offshore bars. The total thickness of these deposits probably does not exceed 30 feet, except near Lewes, Del., where dunes are as much as 80 feet high. The beach and dune sands act as a per¬ meable collector for recharge which in places may be transmitted to the underlying Cape May formation. Also, they locally provide small supplies of fresh water for domestic use along the shore. RECHARGE AND DISCHARGE Under natural conditions the aquifers of the Coastal Plain are recharged largely by infiltration of precipitation on their intake areas, which consist either of the outcrops themselves, or the over- lying blanket of Quaternary deposits (pi. 8 ). Seepage from the head¬ water reaches of streams may contribute a small amount of additional recharge. Some buried aquifers receive recharge from adjacent aquifers across the intervening aquicludes, but such recharge does not con¬ stitute a net gain of water in the system. The average rate of natural recharge to the Coastal Plain aqui¬ fers has not been determined directly. However, a 2-year water budget was made by Rasmussen and Andreasen ( 1958 ) for the drainage basin of Beaverdam Creek, an area of 19»5 square miles in the Coastal Plain of Maryland about 50 miles southwest of the mouth qf Delaware Bay. The physical and climatic conditions at Beaverdam Creek are believed to be similar to those in the aquifer intake areas in most of the Coastal Plain in New Jersey and Delaware. Rasmussen and Andreasen found that the average rate of infiltration or recharge was a little more than 1 mgd per square mile, which amounted to slightly more than half the average annual rate of precipitation. A semi-independent check of the results of the Beaverdam Creek study is provided by an analysis of precipitation and runoff data in the Coastal Plain of New Jersey and Delaware. Table b summarizes the data derived from maps prepared by the U. S. Geological Survey and the U. S. Weather Bureau showing precipitation, water loss, and run¬ off, and from base-flow recession curves and streamflow hydrographs developed by the Geological Survey. The values of precipitation, water loss, and runoff are averages for a 30-year period (1921-50) and thus are virtually unaffected by any change in the quantity of water in storage during the period. The last item—base-flow, chiefly ground-water runoff—indicates the lower limit of the ground-water discharge, and also the lower limit of ground- water recharge, because not all ground-water recharge eventually is 38. discharged into streams; a large part is discharged as evapotranspir¬ ation, and some ground water in the Coastal Plain is discharged di¬ rectly to the estuaries, bays, and ocean as unmeasured outflow. Total ground-water discharge, then, includes a part of the water loss in table 4 as well as all the base flow (ground-water runoff). Total ground-water recharge—or discharge—may be calculated as the sum of the base flow of streams, the discharge of ground water by evapotranspiration, and the unmeasured ground-water outflow beneath and between streams. Two methods of calculating the recharge or discharge are used in the following example. In both methods the base flow is estimated to average about 0.6 mgd per square mile (table 4); and on the basis of the Beaverdam Creek study (Rasmussen and Andreasen, 1958 )y ground-water discharge by evapotranspiration is estimated to be about 40 percent of the total evapotranspiration loss. In the first method, unmeasured ground-water outflow is assumed to be negligible; hence all the water loss in table 4 is assumed to re¬ present evapotranspiration. Thus, base flow (0.6 mgd per sq mi) + ground-water discharge by evapotranspiration (0.4 x 1.2 = 0.5 mgd per sq mi) = total ground-water recharge or discharge (l.l mgd per sq mi). Table 4. —Water budget for Coastal Plain of Delaware River basin and New Jersey Approximate Average Average per- Average Item range (mgd (mgd per cent of pre- percent per sq mi) sq mi) cipitation of runoff Precipitation Water loss I.9 ** 2.3 1.1 - 1.4 2.1 1.2 100 57 - Runoff .65- 1.2 •9 43 100 Direct runoff - • 3 14 33 , Base flow _ .6 29 672/ (chiefly ground- water runoff) 1/ Largely evapotranspiration, but includes some unmeasured ground- water outflow. 2/ Estimated value based on an interpretation of base-flow recession curves and streamflow hydrographs for Coastal Plain streams in the Delaware River basin and New Jersey. The value for Beaverdam Creek basin, Md., was nearly 72 percent (Rasmussen and Andreasen, 195'$), or, allowing for change in storage during the budget period, perhaps 74 percent. 39 . In the second method, unmeasured ground-water outflow is assumed to be 0.2 mgd per square mile (probably a maximum, rather than a likely value); hence, the total evapotranspiration loss is reduced from 1.2 mgd per square mile (table 4) to 1.0 mgd per square mile. Thus, base flow (0.6 mgd per sq mi) + ground-water discharge by evapotranspiration (0.5 x 1.0 = 0.4 mgd per sq mi) + unmeasured ground-water outflow (0.2 mgd per sq mi) = total ground-water recharge or discharge (1.2 mgd per sq mi). These values are approximate averages for the entire Coastal Plain in the Delaware River basin and New Jersey and are in approximate agreement with unpublished U. S. Geological Survey data obtained from hydrologic studies at Brookhaven, Long Island, N. Y. Rather large deviations from the averages might be expected in parts of the area, as indicated by the ranges in values of precipitation, water loss, and runoff shown in table 4. The average values also apply approximately to the part of the Coastal Plain entirely within the Delaware River basin. The estimated recharge is in close agreement with, though a little greater than, the 1 mgd per square mile estimated for the Beaverdam Creek basin. The slightly higher recharge estimated for the Coastal Plain of New Jersey and Delaware may reflect its somewhat greater aver¬ age precipitation—2.1 mgd per square mile—as compared with I.97 mgd per square mile for the budget period at Beaverdam Creek. In any case, an estimated average recharge of 1.1 mgd per square mile for the Dela¬ ware River basin and adjacent Coastal Plain is assumed, and is believed to be conservative. The area of the Coastal Plain in the Delaware River basin, exclud¬ ing salt-water marshes, bays, and estuaries, is about 2,750 square miles. Thus, if the average recharge for this area i£ 1.1 mgd per sq mi, the average recharge to ground water in the Coastal Plain in the Delaware River basin is about 3,000 mgd. By comparison, this is equivalent to about 40 percent of the flow of the Delaware River at Trenton, N. J., which is about 7,600 mgd, and which represents the runoff from that part of the basin above Trenton, about 6,780 square miles. As another compar¬ ison, discharge from pumped wells in the Coastal Plain of the basin was estimated to average about 210 mgd for 1956-57, which is 7 percent of the estimated total natural ground-water discharge of 3,000 mgd. But part of the water pumped returns to the aquifers; hence, the net dis¬ charge of ground water by pumping is even less than 7 percent of the natural discharge. Aquifers in the nonmarine sediments of Cretaceous age—the lowest in this wedge of deposits in the Coastal Plain — yield the largest proportion of the total ground-water pumpage at present (slightly more than half in 1956-57), but the deposits of Quaternary age are becoming increasingly important, and the Cohansey sand offers perhaps the greatest potential for future development. bo. As a rough approximation, given only to indicate order of magnitude, the potentially available ground-water supply in the Coastal Plain part of the Delaware River basin is assumed to equal the average discharge of ground water as base flow in streams—0.6 mgd per square mile (table 4). This assumption is conservative, because part of the natural discharge of ground water by evapotranspiration also may be recovered for use as water levels are lowered by increased pumping. Hence, the potentially available ground-water supply within the Coastal Plain of the basin is estimated to be 0.6 mgd per square mile x 2,750 square miles = about 1,600 mgd. Therefore, present use (1956-5?) is about one-eighth of this potential, but because part of the water pumped is not consumed and returns to the aquifers, the net discharge of ground water by pumping is less than one-eighth of the potential.. However, because of practical limitations, chiefly economic, it is estimated that only about one-half of the potential ground-water supply, or about 800 mgd, can be developed. It should be emphasized, moreover, that the ground-water supply is merely a part of the total water supply, includ¬ ing water from surface sources. Should it prove more feasible to develop most of the supplies from surface sources rather than from ground water, the ground-water supply that could feasibly be developed in the Coastal Plain might be substantially less than 800 mgd. Pumping of ground water has induced recharge from streams and other bodies of surface water where pumping has reversed the natural hydraulic gradients toward the surface-water bodies. Where the surface-water bodies are fresh, the induced recharge augments the ground-water supply; but where the surface-water bodies are salty, the saline water replaces the pumped fresh water in the aquifers. The largest amount of induced recharge occurs along the Delaware River estuary below Trenton, N. J., where several well fields on both sides of the estuary are withdrawing large amounts of water from the' nonmarine sediments of Cretaceous age. The present amount of induced recharge is not known, but the potential amount under a planned system of development may exceed 100 mgd (Barksdale, Greenman, Lang, and others, 1958). Over a long enough period of time changes in storage can be ignored because recharge approximately equals discharge. By far the greater proportion of total discharge occurs at natural- outlets—stream channels, estuaries, bays, the ocean, springs and seeps, lakes and ponds—and in marshes, and other low-lying lands where the water table is’ sufficiently near the land surface to allow discharge by evapotranspiration. Deter¬ mination of the magnitude of the discharge through these outlets would require detailed water-budget studies which are costly in terms of time, efforts,'and money. As a consequence such studies have only been at- temped in a few places in this part of the country. However, the approx¬ imate magnitude of discharge to streams and as evapotranspiration was indicated in the preceding discussion (p. 38? 39 ), and is believed to be sufficiently accurate that, except in unusual circumstances of local importance, such costly water-budget studies need not be made. 41. PATTERNS OF MOVEMENT Where not affected by pumping, most ground water in the Coastal Plain moves from high parts to low parts of the intake areas or to the outcrops of the aquifers (pis. 6 and 7) ; the quantity moving through the aquifers and aquicludes downdip from the intake areas is relatively small (Barksdale, Greenman, Land, and others, 1958), even through the quantity in storage is very large. In the intake areas the water either is unconfined or is semiconfined by inextensive lay¬ ers of silt and clay, and the configuration of the water table is somewhat like that of the land surface except that it is more subdued and regular. Hydraulic gradients are relatively steep and they slope toward the areas of discharge: (1) Near the base of the aquifers, or (2) along stream channels and marshes. The gradients are much gentler in the confined or artesian parts of the aquifers, which accounts for the smaller quantities of water movement in the artesian systems. Unfortunately, comprehensive, regional water-level data are lack¬ ing for nearly all the aquifers in the Coastal Plain of New Jersey and Delaware. Almost all water-level data are for small areas in and near well fields, where the native pattern of ground-water movement has been altered radically by pumping, and it would be impossible now to reconstruct the original water tables and piezometric surfaces. Some useful information is available, however, on the native pattern of movement of water in the nonmarine sediments of Cretaceous age. Plate 10 shows the theoretical flow pattern in the nonmarine sediments under natural conditions, as postulated by Barksdale, Greenman, Lang, and others (1958, fig. 18). The theoretical flow pattern is based on several simplified assumptions and does not, therefore, indicate the actual conditions in detail. For example, the interface between salt water and fresh water is not a sharp vertical line as shown in plate 10; rather, it probably is a zone of some thickness and is more nearly horizontal than verti¬ cal. Thus, the inland extent of salt water is considerably greater in the lower part of the unit than in the upper part. However, the map is believed to show adequately the general pattern of ground-water movement and the extent of fresh water in the nonmarine sediments before their development. In part, the validity of the theoretical flow pattern is confirmed by the earliest water- level data for wells penetrating the nonmarine sediments, and the position of the interface between salt water and fresh water is sub¬ stantiated in a general way at a few places where deep wells either have been drilled on both sides of the interface or have penetrated it (Barksdale, Greenman, Lang, and others, 1958). 88197 0-62- 5 (Vol. VII) 42 0 The map shows that most of the water that moves through the bur¬ ied, artesian portion of the nonmarine sediments travels circuitous paths from two relatively high intake areas—one northeast of Trenton, N. J., the other in northern Delaware--to discharge areas along the Delaware River estuary below Trenton and along Raritan Bay. Bear in mind, however, that a greater quantity of water moves in much shorter and more direct paths from high to low parts of the in¬ take area and discharges into the Delaware and Raritan Rivers and their tributary streams. Less is known about native patterns of movement in the other aqui¬ fers having intake areas along the innir northwest part of the Coastal Plain. In some respects, the patterns of movement probably were sim¬ ilar to those in the nonmarine sediments, although because high-level and low-level intake areas are not as distinct as in the nonmarine sediments and because the aquicludes are more permeable, more water moved downdip toward the ocean and bays and discharged by slow upward movement across overlying aquicludes and aquifers. As in the non¬ marine sediments, the greatest quantities of water moved relatively short distances to discharge points in the outcrops or intake areas. The predominant movement in the Cohansey sand and overlying Quaternary deposits in the outer part of the Coastal Plain was, and for the most part still is, along relatively short paths from intake points in the broad, flat interstream areas to discharge points along the adjacent streams and marshes. Longer and more devious paths are followed where there are layers of silt and clay, but such layers are not extensive or thick except near the coast or the shores of Delaware Bay. Artificial discharge through pumped wells has changed the pattern of ground-water movement considerably in parts of the Coastal Plain. Water now is diverted from natural outlets and moves toward the pumped areas, generally from all directions within the influence of the cone of depression that surrounds pumped wells. The greatest changes have occurred in the most heavily pumped areas, principally along the Delaware River estuary from Trenton, N. J., to northern Delaware, in the vicinity of Raritan Bay, and along the coast of New Jersey. Large-scale pumping of ground water from wells in the nonmarine sediments along the Delaware River estuary in places has diverted water from its former paths leading to discharge points in the chan¬ nel and has induced movement from the river into the aquifers at those places. Also, hydraulic gradients from the intake areas have been increased, and the loss of natural discharge to the river in U S GEOLOGICAL SURVEY PLATE 10 MAP SHOWING THEORETICAL FLOW PATTERN AND LOCATION OF THE INTERFACE BETWEEN FRESH WATER AND SALT WATER IN THE NONMARINE SEDIMENTS OF CRETACEOUS AGE UNDER NATURAL CONDITIONS 1 ‘ ■ 43 . some cases has been exceeded by the gain in artificial discharge in the pumped areas. Some ground water has been withdrawn from storage, and recharge to the aquifers probably has increased. Northeast of the basin, concentrated pumping in the intake area of nonmarine sediments along the Raritan and South Rivers has induced large quantities of recharge—some of it of very poor qual- ity--from those streams (Barksdale, Greenman, Lang, and others, 1958) o Along parts of the coast in New Jersey, heavy pumping of water from artesian aquifers, particularly from the "800-foot"sand in the Kirkwood formation at Atlantic City, has greatly lowered the artesian pressure. There, over an area of 20 or 30 miles along the shore, where prepumping water levels were about 25 feet above sea level, pumping has lowered the head to more than 75 feet be¬ low sea level. Thus, this represents a total head loss of more than 100 feet (Barksdale, 1945, p. 565), and has caused movement of large quantities of water downdip toward the centers of withdrawal. Almost certainly, some of the recharge to the Kirkwood formation within the Delaware River basin moves toward the major center of pumping near Atlantic City; the convergence of ground-water flow lines on the Atlantic City area has been likened to the paths of tourists in the summer. Although much of the water moves into the area from the seaward side, only slight signs of salt-water en¬ croachment have yet been detected. The flow pattern in the Kirkwood formation has been changed also in Kent and Sussex Counties, Del., where withdrawals from the Cheswold and Frederica aquifers have caused declines in artesian head of more than 80 feet in places (Rasmussen and others, 1957). GROUND-WATER STORAGE Use of Storage The aquifers underlying the Coastal Plain constitute large ground-water reservoirs which, because of the scarcity of sites suitable for surface reservoirs, are potentially very important in the management of water supplies. The storage capacity of these reservoirs is enormous; however, the calculation of this quantity is of little consequence other than to indicate that it is very many times the annual recharge. To use more than a small part of this capacity, therefore, the average rate of withdrawal from the reser¬ voirs would have to exceed the average rate of recharge for a long period--an overdraft procedure. kk. Ground-water overdraft, commonly known as "mining", is a practice common in the semiarid and arid parts of the country, hut is not like¬ ly to become a widespread practice in the Coastal Plain. Such a con¬ tinued overdraft of ground-water supplies would lead to salt-water encroachment, which results from lower ground-water levels near the coast. The ground-water reservoirs of the Coastal Plain are much more likely to be used on a sustained-yield basis wherein the storage de¬ pleted during periods of excess discharge, both natural and artific¬ ial, is replenished completely either naturally or artificially dur¬ ing periods of excess recharge. The long-term yield of the reserv¬ oirs, then, is equal to the long-term average recharge and the stor¬ age used is that required to level out the fluctuations in recharge and discharge. In the Coastal Plain of New Jersey and Delaware, water supplies are relatively abundant and uniformly distributed in time; drought periods seldom are sufficiently long or severe to require large drafts on ground-water storage. Peak consumptive use of ground- water supplies is for supplemental irrigation of crops in the summer, at a time when natural recharge is at a minimum. Such seasonal de¬ mands can be readily met with the available ground-water storage in the shallow aquifers. Rasmussen (1955) estimated that the usable reservoir capacity of the Coastal Plain aquifers in Delaware was sufficient to store more than a year's recharge, considering the recharge as 1 mgd per square mile of aquifer intake area. No such estimate has been made for New Jersey; however, because of the similar hydrologic and geologic con¬ ditions there, Rasmussen's estimate probably indicates the order of magnitude of usable reservoir capacity for all the Coastal Plain of this area. The capacity appears to be more than adequate to meet maximum fluctuations in ground-water storage that would occur on a sustained-yield method of operation. Storage Fluctuations The fluctuations in storage in an aquifer are reflected by fluctu¬ ations in the water table or piezometric surface; the ratio of the volume represented by the zone of fluctuation of the water table or piezometric surface is determined by the storage coefficient of the aquifer. For example, in a water-table aquifer having an average coefficient of storage of 0.1, a 10-foot decline in water table over a specified area represents a decline in storage equal to a 1-foot depth of water over the area. In an artesian aquifer having a co¬ efficient of storage of 0.0001, a 10-foot lowering of the piezometric surface represents a decline in storage of only 0.001 foot of water. In a water-table aquifer where part of the material actually is drained as the water table declines, the coefficient of storage is 45 . practically equal to the specific yield, but in an artesian aquifer none of the material is drained, and the water released from storage is derived principally from a slight expansion of the water itself and a slight decrease in the volume of the aquifer. However, an artesian aquifer becomes a water-table aquifer when the water level is lowered beyond its upper confining layer; the storage coefficient within the area of unwatering then becomes practically equal to the specific yield. Sustained-yield operation of artesian aquifers in the Coastal Plain probably would involve little dewatering, however; only in the shallower water-table aquifers, or the recharge-outcrops of the artesian aquifers where water-table conditions exist, would the upper part actually be dewatered seasonally. Natural Fluctuations The natural fluctuations in storage in most Coastal-Plain aqui¬ fers are small compared to the total storage capacity of those aqui¬ fers 0 For example, base-flow recession data for Coastal Plain streams indicate that in an average year the maximum range of fluctuation in ground-water storage supplying base or fair-weather flow to the streams amounts to less than a 3-inch depth of water over their drain¬ age area. Fluctuations in storage caused by changing rates of evapo- transpiration might amount to an additional 2-inch depth of water; hence, the total natural storage fluctuation ordinarily might be in the order of 5 inches of water. Assuming an average coefficient of storage of 0.1--a conservative estimate for the water-table aquifers of the Coastal Plain--the 5-inch change in storage would be reflected in an average water-table fluctuation of 50 inches--a small fraction of the saturated thickness of most water-table aquifers of the coastal Plain. Artificial Fluctuations Man is able to provide additional ground-water storage by pump¬ ing water from the aquifers. In most places in areas of humid climate pumping increases the recharge to the aquifers by: (1) Lowering the water table and thus providing additional storage space for infiltra¬ tion of precipitation that otherwise would have been rejected; and (2) by inducing infiltration from streams, lakes, or swamps where the normal hydraulic gradient toward these discharge areas is reversed. Pumping increases the total discharge, although it may reduce the evapotranspiration of ground water by lowering the water table and capillary fringe below the reach of plant roots and the capillary zone below easy reach of evaporation opportunity; additionally, pumping eventually reduces the discharge at other natural outlets by decreas¬ ing the hydraulic gradients toward those outlets. The local rate of recharge and discharge might then exceed by a substantial amount the estimated average rate of natural recharge and discharge of about 1.1 mgd per square mile of aquifer intake area. U-6-o Aquifer storage also could be used by recharging unfilled aqui¬ fers artificially with imported surface supplies. These supplies would augment the recharge induced from streams within the area. However, except for heavily pumped industrial and municipal well fields in which large withdrawals are concentrated in s m all areas, it is unlikely that imported supplies would be required. CHEMICAL CHARACTER OF GROUND-WATER SUPPLIES The waters of the Coastal Plain aquifers, except where contamin¬ ated by salt water, are generally of good quality and suitable for most uses. Usually they are of the calcium bicarbonate type, soft or only moderately hard, and are not highly mineralized. Many wells yield water free from objectionable quantities of iron, but in every aquifer localized objectionable concentrations of iron are found with an apparent random distribution, both areally and with depth. Treaianent, if required, is usually limited to softening or the re¬ moval of iron. Aquifers may be contaminated locally from surface sources, the disposal of wastes through recharge wells, leakage through corroded well casings, or from encroachment of salt water. In general, the waters from the several aquifers of the Coastal Plain do not differ greatly; they are described in'the following sections and representa¬ tive chemical analyses are given in table 5« Pleistocene Deposits Some of the best ground water in the Coastal Plain is obtained from the aquifers of the Pleistocene series, which comprise the shallowest (or uppermost) aquifers. The water is, for the most part, soft or only moderately hard. It contains relatively low concentra¬ tions of calcium and magnesium, and is only moderately mineralized. The dissolved-solids concentration is usually less than 200 ppm. The average hardness, as CaCOo, determined by kl analyses of water from the Pleistocene sediments in Delaware, was 51 ppm and it ranged from 7 to 2 UQ ppm (Marine and Rasmussen, 1955 > P» 85)* The water from the Pleistocene sediments often contains excessive concentrations of iron. Occasional samples with high concentrations of nitrate, sulfate, hardness, or total dissolved solids (table 5) usually repre¬ sent contamination from surface sources. The native water is generally satisfactory for most uses without further treatment except where the removal of iron is required. The principal discharge of ground water to the streams of Delaware and of a large part of coastal New Jersey is from the Pleistocene series; this is largely responsible for the good quality of water in m any of the streams of the Coastal Plain. a and Nev Jersey TABLE 5 Anal 4 y»i« I County and state no. 1 lor- de 1) Fluor¬ ide (F) Ni¬ trate (iro 3 ) Dis- itardnei CaCO; is as L solved solids Total fton- car- fconats pH _ __ ^ ___ r , .. 1 L 3 4 5 6 Sussex, Del. Nev Castle, Del. 8alem. N. J. Burlington, N. J. Cape May, N. J. Bucks, Pa. 5 - 7 4 4.2 6 8 mm am mm am 0.5 .0 .1 .1 0.0 15 .8 1.3 8.7 4.1 "204 146 244 85 106 l 4 o - BT “ 61 44 51 42 89 45 4 i 0 18 17 45 ■570 6.5 7.2 7-4 7.4 7 8 9 10 11 ax-Lan-cic uity, w. j. Salem, N. J. Gloucester, N. J. Burlington, N. J. Burlington, N. J. 276 3.0 4.2 2.9 2.8 — n — .2 .0 0 .0 — nr - 1.2 5.0 .1 .2 20 6 l 25 13 22 3 9 8 3.6 2 0 0 4 0 0 ^3 6.0 6.4 6.7 6.5 T5 — IX 13 14 Sussex, Del. Kent, Del. BurliaatQn. N. J. 3.4 2.8 3.1 .1 .2 .0 .6 .1 .1 219 202 49 l 4 B " 104 6 U 0 5 7.9 7.8 4.7 15 16 *7 Kent, Del. Salem, N. J. Salem, N. J. 2.5 3.0 5.6 .2 .3 .4 2.2 .0 .7 177 200 254 155 139 186 24 0 12 7.9 8.0 7.6 TT5 - lo 19 20 21 22 Nev Castle, Del. Salem. N. J. Salem, N. J. Gloucester,N. J. Burlington, N. J. 0 4 4.0 5.9 2.0 .1 .2 .3 .5 .1 .3 .0 1.2 .2 .0 152 250 155 133 115 107 191 59 90 78 31 68 0 22 0 7.9 7.6 8.2 7.6 8.1 1 23 24 25 26 27 28 Monmouth, N. J. Burlington,N. J. Monmouth, N. J. Monmouth, N. J. Ocean, N. J. Ocean, N. J. 4.5 2.6 2.7 4.0 1.6 2.2 .1 .4 .1 .1 .2 .1 .2 .3 .2 .4 1.0 1.6 iW 166 143 113 163 210 1^3 124 108 86 73 17 31 2 0 6 0 0 7.6 8.2 8.4 7.6 7.8 8.6 xz — i 59 *30 31 '32 33 lii ] Nev Castle, Del. Salem, N. J. Camden, N. J. Burlington, N. J. Burlington, N. J. Hercer, N. J. | 3.0 7.5 1.8 2 2.1 2.4 .1 .2 .4 .0 .2 .1 .1 .8 1.2 13 .3 .1 — 55 - 107 124 145 86 _ 23 50 47 71 61 10 34 0 43 9 4 TT 7.2 7.8 6.9 7.1 5.6 oajy/ 0-02 ( VoJ. ’Vll) (Face p. 4 ( 5 ) Table 5>--Representative chemical analyses of ground water in Coastal Plain of Delaware River basin and New Jersey TABLE 5 (Concentration* In part# per million) Magne- Sodium Potas- Bicar- Sulfate Chlor- Fluor- Ni- Dis- Hardness as CaCO^ slum (Mg) (Ha) sium (K) bonate (hco 3 ) (S0 4 ) ide (Cl) ide (F) trate (no 3 ) solved solids Total Non- car- pH bonate Quaternary (Pleistocene) depoaita , .... ^ 1 Sussex, Del. 131;ice 9.23-44 mm mm f25 _ 17 |—575— m 37 3.3 23 o - -55— 0.0 rm — — 85 ^5 57cT c. New Castle, Del. 24-25 4-23-31 .. 14 .03 nmarine Cretaceous sediments i ^0 31 *32 33 Ik New Castle, Del. Salem, N. J. Camden, N. J. Burlington, N. J. Burlington, N. J. Mercer, N. J. | 322 387 57 120-140 205 7 —2—56 4 - 26-56 5 - 1-51 7 - 3-53 5-22-51 9 - 26-49 54 61 mm mm 57 i 4 8.3 10 9-4 14 .01 .11 .11 .00 9-3 4.1 • 05 .00 • 19 .00 ^•t 11 14 12 16 2.2 2.7 5.4 t 2.9 i 10 ! 5.2 ; 1,2 -7 11 21 10 2.7 _ r .2 -- 1.9 6.3 3.6 4.3 1.0 21 20 103 34 64 8 T 5 - 44 15 4 o 16 6.2 3.0 7.5 1.8 12 2.1 | 2.4 .1 .2 .4 .0 • 2 .1 .1 .8 1.2 13 .3 .1 —55— 107 124 145 86 ■ ?7 23 50 47 71 6l — 10 l r- 17 ? 34 0 43 TT 7.2 7.8 6.9 7.1 5.6 Source and description of samples referred to by number in table 5 1. Rehoboth Beach, Sussex County, Del., Composite of 2 municipal wells. 2. New Castle, New Castle County, Del., Composite of 3 shallow muni¬ cipal wells, New Castle Board of Water and Light Commission. 3 • P enn svllle, Salem County, N. J., Lower Penns Neck Water Department well, phosphate 0.4 ppm. 4. Beverly, Burlington County, N. J., Delaware River Water Co. well 2; aluminum 0.0 ppm, cooper 0.00 ppm, zinc 0.00 ppm, phosphate 0.0 ppm, 5. Rio Grande, Cape May County, N. J., Wildwood Pumping Station; color 2, 6. I^vittown, Bucks County, Pa., Lower Bucks County Joint Municipal Authority; color 4o 7‘ Folsom, Atlantic County, N. J., P. Jacob well. 8. Parvin State Park, Salem County, N. J., State of New Jersey well; color 30, lithium 0.5 ppm e 9. Newfield, Gloucester County, N. J., Newfield Water Department . well 2; phosphate 0.0 ppm, nitrite 0.00 ppm, color 5<> 10. Lebanon State Forest, Burlington County, N. J., Pakin Pond Well, State of New Jersey; color 2, barium 0.0 ppm, fl-inm-imm 0.4 ppm, phosphate 0.0 ppm, nitrite 0.0 ppm 0 11. Chatsworth, Burlington County, N. J., A. DeMarco well; color 3, aluminum 1.5 ppm, cooper 0.0, zinc 5*0 ppm, phosphate 0.0. 12. Milford, Sussex County, Del., Milford Water Department well, Frederica aquifer; color 2, zinc 0.0 ppm, phosphate 0.2 ppm, copper 0.0 ppm, turbidity 2.3 ppm 13. Dover Air Base, Kent County, Del., U. S. Air Force well, Cheswold aquifer; color 2 14. Harrisville, Burlington County, N. J., well. 15. Clayton, Kent County, Del., Clayton city well; color 8 0 16. Alloway, Salem County, N. J., Williams General Store well; color 10, lithium 0.8 ppm. 17. Quinton, Salem County, N. J., Salem Water Co. well; color 6, phosphate 0.2 ppm, nitrite 0.00 ppm. 18. Odessa, New Castle County, Del., H. Davis well; Wenonah sand. 19• Woodstown, Salem County, N. J., Woodstown Restaurant well; color 20, lithium 0.2 ppm 20. Dikes Mills, Salem County, N. J., Warren Cobb well; color 25, lithium 0.6 ppm 21. :,Sewell, GloucebterJCouhty,-N.J., James Ledan well; color 5, phosphate 0.1 ppm, nitrite 0.00 ppm, 22. Vincentown, Burlington County, N. J., Vincentown Water Co. well; color 8, aluminum 0.0 ppm, phosphate 0.0 ppm, nitrite 0.0 ppm 0 23. Freehold, Monmouth County, N. J., Freehold Water Department, composite of 9 wells. he. Source description of samples referred to by number in table 5—• Continued 24. Marlton, Burlington County, N. J., Marlton Water Co. well; color 0, phosphate 0.3 PE®> nitrite 0.0 ppm. 25. Fazuingdale, Monmonth County, H. J., Farmingdale Water Depart¬ ment well 1. 26. Belmsr, Camp Evans, Monmouth County, N. J., U. S. Army Building o£ 27. Point Pleasant, Ocean County, N. J., Point Pleasant Water Depart¬ ment well 1. 2B. Lavmlette, Ocean County, N. J., Lavalette Borough Water Depart¬ ment well 2. 29* Near Summit Bridge, New Castle County, Del., Near Chesapeake and Delaware Canal; Magothy, 30. Salem, Salem County, N. J., Salem Ice and Cold Storage well; color 10, lithium 0.2 ppm. 31. Blackwood, Camden County, N. J., Blackwood Water Co. well; Color 2, aluminum 0.0 ppm, nitrite 0.0 ppm, phosphate 0.2 ppm. 32. Beverly, Burlington County, N. J., Delaware River Water Co. well 3; color 3, lithium 0.2 ppm, copper 0.00 ppm, zinc 0.00 ppm, phosphate 0.1 ppm. 33• Maple Shade, Burlington County, N. J., Maple Shade Township well; color 3, aluminum 0.0 ppm, phosphate 0.2 ppm, nitrite 0.0 ppm* 34. Higfctstown, Mercer County, N. J., Hightstown Water Department well 1; color 12. Cohansey Sand The water from the Cohansey sand is generally the best obtained from the Coastal Plain aquifers (table ?). It is not highly mineral¬ ized and is soft. Some samples are moderately high in iron, and the water is generally slightly acid and corrosive to iron pipes and fix* tures. Soluble materials in or near the surface may be dissolved by precipitation and (or) irrigation water,.and affect the composition of the ground water locally. In this way the leaching of chemical and organic fertilizers yields above normal nitrate concentrations. Salt water has encroached into the Cohansey sand in a few places where ex¬ tensive cones of depression have formed near salt-water bodies. There are few industries in the area that are underlain by Cohansey sand, therefore, at present the industrial use of water from the Cohansey sand is not great; the water is chiefly used on a large-scale basis for municipal applies and for irrigation. The Cohansey sand is po¬ tentially the most productive aquifer in the New Jersey part of the Coastal Plain, but must be protected from contamination and salt¬ water encroachment if it is to continue to produce the high quality water it now yields. 49 . Sands of the Kirkwood Formation The Kirkwood formation yields soft water, generally of good qual¬ ity, with a dissolved-solids concentration usually less than 250 ppm (table 5). The iron concentration is usually less than 0.3 ppm, but occasionally it is higher; commonly the silica concentration is 30 to 50 ppm. The water from some parts of the Kirkwood formation is slightly acid. The water is usually used without treatment; some- times it is softened or the pH adjusted before use. Salt water has encroached in the aquifer in a few places near the seacoast. Yincentown Sand The Vincentown sand yields water that is hard and moderately high in dissolved solids (table y ). It is mildly alkaline on the pH scale and in places contains objectionable concentrations of iron. Near the Delaware River there is a possibility of salt-water encroach¬ ment, but a considerable thickness of silt and clay in the river chan¬ nel at the outcrop area probably retards the interchange of water be¬ tween the Yincentown sand and the river (Barksdale, Greenmaa, Lang, and others, 1958, p. 1^9). Water from the Yincentown sand is used for farm and domestic supplies and as a supplementary municipal supply for Salem, N. J. Wenonah and Mount Laurel Sands Water of good quality is obtained from the Wenonah and Mount lAurel sands (table ’5). It is soft to moderately hard, with less than 150 ppm of dissolved solids, and is fairly uniform in chemical composition. It Is suitable for most uses without treatment, al¬ though excessive amounts of iron occur in some parts of the aquifer and water from such parts must be treated to remove the iron. Englishtown Sand The Englishtown sand, like the Wenonah and Mount Laurel sands, yields water that is moderately hard (table *~j ). Normally the water Is slightly alkaline and contains less than 200 ppm of dissolved min¬ erals. It is suitable for most uses without treatment, although oc¬ casionally softening or the removal of iron is required. The English¬ town sand is less subject to salt-water encroachment than are the other Coastal Plain aquifers. 50. Nonmarine Sediments of Cretaceous Age The uncontaminated waters from the nonmarine sediments of Cretaceous age are relatively low in dissolved-solids concentration (3-200 ppm), soft, and in general of high quality (table 5)« Near the intake areas where the recharge consists chiefly of rainwater, the water is soft, slightly mineralized, slightly acid, and somewhat corrosive. As the water flows downgradient in the formation it becomes more min¬ eralized, slightly alkaline, and noncorrosive and generally contains more iron, sometimes in objectionable quantities. The fluoride con¬ centration is usually 0 to 0.1 ppm but in the vicinity of Woodstown and Glassboro, N. J,, exceeds 1 ppm. In several places the native waters are contaminated. The loca¬ tion of the interface between fresh and salt water is described on pages 16, 57, 59. Where withdrawals of water near the interface are large, the encroachment of salt water may occur. This is true in the vicinity of Salem and Woodstam, N. J. In the vicinity of Camden and Philadelphia, the Delaware River flows over the outcrop of the Raritan and Magothy formations. Here, where large quantities of water are withdrawn, the aquifers are recharged with river water, and the quality of the well water approaches that of river water. . Above Camden the river wateb is no more mineralized than the native ground water, and river recharge has no adverse effects on, or may' even im¬ prove, the quality of the well water. Dowstream from Camden, however, the river water is more highly mineralized and (or) polluted, and wells near the river have been, and more of them may be, adversely affected by induced recharge of such water. The highest concentrations of dissolved solids in the lower aquifer of the Raritan formation are found within the city of Phila¬ delphia. This arises from 3 principal sources: (l) The disposal of wastes on dumps on the intake area of the aquifer; (2) seepage from leaky sewers; and ( 3 ) wastes discarded into "sanitary” or "dry" wells. SALT-WATER ENCROACHMENT Salt-water encroachment has been defined in many ways. Here we shall define it as the encroachment on fresh-water domains of any saline water in concentrations and volumes large enough to be de¬ leterious. In parts of the United States salt-water encroachment may have as its source brines from oil wells; salty waste liquors (bitterns) left after refinement of table salt; bitterns developed in the production of magnesium and by-products from brines; mineralized waste waters from some mines; salt that has accumulated in improperly designed or 51 . operated irrigation systems; "salt banks"—outcrops of salt deposits along stream courses; salt springs; salt domes; \juvanile water; con¬ nate water; water from modern seas; and residual saline water left by the high-level Pleistocene seas. In the Delaware River service area, fortunately, the sources of saline water are few and readily identifiable. Of the sources named above we need only concern ourselves with the last two, namely, modern sea water and residual salines. The residual salines are, or may be, similar to connate water- water that was entrapped with sediments as they were being deposited in the sea—but the residual salines are of late marine origin and they gained entrance into aquifers and aquicludes during the inter¬ glacial ages when the land was flooded by high-level Ice Age seas. Most of the residual salines are now greatly modified from their orig¬ inal chemical condition; usually they have been diluted and have under¬ gone ion exchange. This is a process by means of which calcium or magnesium in the water is exchanged for sodium, and to a lesser extent for potassium, in the enclosing rocks, or vice versa, depending upon local conditions. With respect to location, residual saline bodies inland from the shore area most commonly occur in aquicludes where they are found in the least permeable parts. This is because Ice Age salt water has been flushed out of the permeable aquifers and the more permeable parts of the aquicludes in the time since the last high-level Ice age sea; but not enough time has elapsed for the slow, normal circulation through the deeper or less permeable sediments for flushing to take place. Thus, where salt-water encroachment occurs in an area of the Coastal Plain it makes considerable difference if the source is a residual saline body or comes from the modern sea. In the latter case, the supply of salty water is unlimited and the maximum salinity is about 19,000 to 20,000 ppm in chloride content; in the former case the supply may be small—though not necessarily so; it all depends upon the volume of residual water being tapped—but in the Coastal Plain sediments in this area the salinity will never be as high as that of the ocean. It is highly important, therefore, that the source and kind of salty water causing the encroachment be identified early, for each of the two kinds of sources requires that a different devel¬ opmental plan be used to prevent the ruin of the fresh-water aquifer being developed. UNIVERSITY Of ILLINOIS LIBRARY 52. The density of water increases as the salinity increases. Pure water, which contains no dissolved solids, is a standard for measur¬ ing the specific gravity of liquids and is assigned a value of unity. Average ocean water contains approximately 35>000 ppm of dissolved solids (including about 19,000 ppm Cl) and has a specific gravity of 1.025. Thus fresh water is bo/kl as heavy as ocean water. Average ocean water (Sverdrup, Johnson, and Fleming, 19^6) con¬ tains the following principal constituents in parts per million: Calcium (Ca) kOO; magnesium (Mg) 1,270; sodium (Na) 10,600; potassium (K) 380; bicarbonate (HCO,) 140; sulfate (SO4) 2,650; chloride (Cl) 19,000; total dissolved solids 3^->500. Inasmuch as ocean water is heavier and denser than fresh water, the 2 liquids tend to remain separate. Thus, where the 2 liquids are in contact, fresh water occupies a position above salt water and tends to remain there except as turbulence causes mixing. In tidal reaches of streams and canals where salt water from the ocean has full access to the channels and where fresh-water flow is not sufficient to sweep the ocean water out, salty water commonly occupies the lower parts of the channels and extends inland as a blunt-nosed wedge. The seaward end of the wedge remains relatively unchanged at the ocean end of the channel, but the inland end of the wedge moves to and fro with the tides, and advances and retreats seasonally, as ocean level rises and falls and as streamflow responds to changes in rate of runoff. In major tidal estuaries, such as the Delaware, the salt-water wedge commonly is ill-defined. River currents, tidal currents, waves, propeller wash from large ocean-going vessels, and rough and uneven channel bottom and banks—all tend to mix salt and fresh water. If we may characterize the relationships in the Delaware Estuary, about all we can say is that as a rule the saltiest water is at the bottom of the channel; that the deeper depressions in the river bottom gen¬ erally contain ’’pockets" of water of higher salinity than adjacent higher parts of the channel floor; that horizontally across the chan¬ nel the salinity generally is about the same at the same depth below ' the water surface; and that the freshest water is at and just below the surface. "Salinity intrusion in the Delaware Estuary does not occur as a well-defined salt-water wedge such as is found in many estuaries. In most parts of the estuary within the limits of salinity intrusion, salinities from surface to bottom are essentially the same." (Waterways Experiment Station, 1956). Under conditions of low fresh¬ water discharge the salinity increases sharply downstream from the 53o Delaware Memorial Bridge, although under flood conditions the chlor¬ ide concentration at this point is as low as 30 ppm. Upstream from the Delaware Memorial Bridge the stream is usually well mixed and there is little change in concentration with depth. In 1950-55 the chloride concentration was less than 40 ppm for at least two-thirds of the time at Marcus Hook, Pa y ., and nine-tenths of the time at Camden, N. J. Only for 5 percent of the time did the chloride con¬ centration exceed 1,000 ppm at Marcus Hook; it was greater than 100 ppm only 1 percent of the time at Camden (Cohen, 1957). The extent of salt-water intrusion in the estuary depends upon fresh-water dis¬ charge, which is now regulated, and sea level, which has been rising slowly for centuries but has risen more than 6 inches since 1930. other tidal streams in permeable materials that carry salt water in their channels, the Delaware River has an elongate prism of saline water under and along that part of its course where salt water occupies the channel much of the time. Salt water from the channel, because of its greater density than fresh water, sinks down to the bottom of the permeable sediments (to the base of the aquifers be¬ neath the stream) and fills them from bottom to top. If fresh-water discharge takes place from aquifer to river, as it does in most of the length of the estuary, the fresh water flows toward the salt-water prism that underlies the cha nne l and moves upward over the prism to c seep into the stream along its sides and shoreward bottom. Where ground-water pumping begins in such an area and is great enough, or near enough the river's edge so that even shir] 1 pump age is effective, salt water from the prism beneath the stream migrates toward the wells, and the prism widens accordingly. Eventually the salt water reaches the wells. Restoring the fresh-water—salt-water contact to its original position may be a long and difficult task, or even Impossible. At Lewes, Del., where salt water was drawn into the municipal well field from the Lewes-Rehoboth canal when pumping was greatly stepped up during World War II, the orig inal well field had to be abandoned (Marine and Rasmussen, 1955, p. 138). New well supplies were quickly developed distant from the salt water of the canal and are being used to this day• In the meantime ground water in the old well field is freshening as recharge from precipitation flushes the salty water out of the aquifer. But the old well field is not safe for continued large-scale pumping again—if it were to be used heavily again salt water would encroach upon it. The encroachment problem in the aquifers of the Delaware Estuary area has never been studied in detail as it has been in parts of Florida (Parker, 1955, p. 617-619) and Maryland (Bennett and Meyer, 1952, p. 15^—157),7 although unpublished, local "spot studies" at end near certain well fields have been made, chiefly by consultants. Nonetheless, the principles involved are well known and apply to the Delaware River as well as to the Miami River and Canal, or to the Patapsco River estuary. Many miles of coastline in Delaware, New Jersey, New York, and Connecticut, in the area of this report, are hounded by the ocean, or bays connected with the ocean. Generally, throughout this region, the shores are in areas of permeable materials such as unconsolidated sand and gravel of the Cretaceous and Tertiary periods, or glacial materials of the Pleistocene epoch. In materials such as these where salt water and fresh water come into contact, their relationship is largely governed by the Ghyben-Herzberg principle. This is the famil¬ iar rule that, since fresh water is 4o/4l as heavy as salt water, it will take a body of fresh water 4l feet high to weigh as much as a similar body of salt water kO feet high. Or, stating the rule another way, given 1 foot of fresh water above sea level, the salt water will be found 40 feet below sea level; given 2 feet of fresh water, the salt water would be 80 feet below sea level, and so on. On a freely permeable island surrounded by ocean water, the "lens" of fresh water in the island's rocks floats upon the surrounding and underlying ocean water much as an ice cube floats in a bowl of water, with most of its mass submerged. However, the relationship between fresh water of the aquifers and salt water of the ocean or bay is not the simple static relationship of the ice cube to the bowl of water. The aquifer-ocean relationship is a dynamic situation and forces not considered in the Ghyben- Herzberg principle, which is simply that of the U-tube, operate. These forces have not been adequately defined to date but are the subject of a considerably amount of research, notably, in the United States, by the U. S. Geological Survey and the University of California. They are: 1. Molecular diffusion in the interface zone tends to dissipate the encroaching salt-water wedge. 2. Alternating tidal thrust and pull in and near the shore zone is a powerful mixing force in the aquifer, and it widens and thickens the zone between the fresh water and the salt water. 3. Fresh-water flow over the salt wedge exerts a slight downward pressure but its chief effect is an "eroding" force (Parker and others, 1935 > p. 612) which sweeps seaward the tidally mixed and diffused salt water; this action is especially ef¬ fective during the falling stage of the tidal cycle when the main body of the salt-water wedge not only moves seaward but also loses height throughout the area from which it withdraws. Thus we cannot apply the Ghyben-Herzberg principle to salt-water encroachment problems without making due allowance for these named factors. However, it is certain that the l-to-40 ratio of the Ghyben- Herzberg principle is a "safe" factor to apply in the development or conservation of water supplies in coastal aquifers, for seldom will equilibrium ever be reached, even close to the sea, at this limited 55. ratio. Rather, the depth to salt water will usually be greater than that predicted on a l-to-40 ratio, and, likewise, the amount of in¬ land encroachment of an intruding wedge of salt water will be some¬ what less. But even with this information, our control of salt-water en¬ croachment demands rather complete knowledge of all the factors in¬ volved. These factors are the most important: (1) The geology of the aquifers and associated aquicludes; (2) the hydrologic constants of the aquifers, including the coefficients of transmissibility and storage; (3) the changing hydrologic factors, such as changes in storage, head, and migration of the salt-water--fresh water interface. Thus to evaluate and conserve the water resources we must be well informed of the local conditions under which the salt-water--fresh water system operates. It is essential that an accounting system of input and outgo" be maintained so that changes in storage can be known and, under given expected conditions of rainfall, runoff, re¬ charge, evapotranpiration, pumping, and other related factors, pre¬ dictions can be made of future availability of water. Such an evalu¬ ation and accounting are important anywhere in the basin and its service area, but in seacoast areas, or inland areas where saline sources exist that are potential sources of encroachment, every pre¬ caution must be taken to safeguard our water supplies. On the basis of past experience, one might think that there is little to wdrry about for problems of salt-water encroachment have been faced before and have been solved, generally without excessive cost or irreparable damage. However, it would be most unwise to con¬ clude that conditions will always be so easily handled, hence this note of warning so that precautionary measures may be taken in ade¬ quate time. This logically leads to such pertinent questions as: "What is the salt-water encroachment situation in the basin and its service area today?"; "Where are the danger spots?"; and "What may we do to protect our fresh-water supplies against salt-water encroachment?". General answers can be given to each of these questions, and for certain localities such as Atlantic City, Asbury Park, Philadelphia, Camden, Newark, and a few others, specific answers can be given. But, for the most of the rest of the basin, generalizations must suffice for now. This is because the essential data needed to supply specific answers for local areas generally are not available. De¬ filed local information, such as David G. Thompson and subsequent workers (Thompson, 1928; Barksdale and others, 1936) gathered for the Atlantic City area, N. J., are needed now all along the shores and inland as far as tidal streams carry salty water; and such detailed 88197 0-62-6 (Vol. VII) 56 . data will he needed urgently over all the Coastal Plain of Delaware and New Jersey in the foreseeable future. Our understanding of the salt-water encroachment situation over a large reach in the area of the report probably is best developed at present on Long Island, N. Y., but even on Long Island there is still much detailed local information needed. Within the Delaware River basin and the adjacent Coastal Plain parts of New Jersey and Delaware, salt-water encroachment is a most serious threat to shallow aquifers along the shores and the tidal reaches of streams that at times cany salty water. Thus the entire eastern shore of Delaware and that part of New Castle County that is bisected by the Chesapeake and Delaware Canal are potentially threat¬ ened by salt-water encroachment. Salty water at times extends up the Delaware River to Philadelphia, thus New Jersey is surrounded by salty-water boundaries from Philadelphia to Cape May and northward along the Atlantic Ocean to and somewhat beyond Newark. Because all the Coastal Plain is underlain by aquifers and aquicludes of varying permeability and hydraulic head, the opportunity for encroachment to spread inland varies accordingly. Under the general operation of the Ghyben-Herzberg principle, with modifications imposed by dynamic conditions (p, 54 ), Nature has established interface zones in the several aquifers at different places with respect to the modern shoreline. . Thus, in the nonmarlne Cretaceous sediments, the salt-water—fresh-water interface (using 250 ppm as the bounding isochlor for the interface at depth in the aquifer) is along a gfently curved line that crosses New Jersey diag¬ onally from the ocean beach near Manasquan to a point on Delaware Bay about 8 miles south of Salem. Salt water containing more than 250 ppm of chloride therefore underlies about half of the Coastal Plain in New Jersey in the nonmarine Cretaceous sediments, and pumping from deep wells, tapping this aquifkr group anywhere south and east of this line would yield only high-chloride water. Pumping from deep wells north and west of this line, and close to it—as in central Salem, Gloucester, Burlington, and Ocean Counties—would be likely to pull salt water inward—that is, to cause encroachment. No large-scale ground-water pumping would be safe in this region without careful pre- checking to ascertain the status of the supply and the potential ef¬ fects of the pumping on existing supplies. The next major aquifer above the nonmarine Cretaceous sediments in New Jersey is the Kirkwood formation. This is the formation in which the "800-foot sand", utilized along the shore at Atlantic City and elsewhere, occurs. So far, there are only 2 areas of the Kirk¬ wood along the ocean that yield water containing more than 250 ppm of chloride. The southernmost is the tip of Cape May peninsula, includ¬ ing all the area south of the Cape May Canal and northward to a line extending about from North Cape May through Bennett to Wildwood. North of this line the hydraulic head in the Kirkwood generally has been sufficient to hold sea water some distance seaward from the present shore. Thompson (1928, p. 70-74) calculated that this salt¬ water—fresh-water interface in the Kirkwood was at least 7 miles offshore at Atlantic City at the time of his report. The northern high-chloride zone in the Kirkwood formation is in the vicinity of Manas quan-Point Pleasant and extends in lan d only a couple of miles. The westernmost high-chloride zone in the Kirkwood formation ex¬ tends from Salem to Canton and southwestvard almost to the mouth of the Cohansey River. Its average width, measured inland from Delaware Bay shore, is about 2 miles. Pumping within any of these 3 zones in the Kirkwood formation would result in obtaining water containing more than 250 ppm of chloride; and pumping inland from these areas, especially near the salt-water boundaries, would induce encroachment. The next important aquifer, or aquifer group, above the Kirkwood formation is the Coheuisey sand. This is the fomation that, in the Atlantic City area, contains the "100-foot" and the "200-foot" sands (Barksdale and others, 1936 , p. 52-91). For the sake of convenience, 1 aquifers in the overlying Pleistocene deposits are here grouped with the Cohansey. Chloride in excess of 250 ppm occurs in the Cohansey sand along most of the New Jersey and Delaware coastline, beginning about at Point Pleasant Beach, in northeastern Ocean County, and continuing southward beneath the offshore bars and islands; and on the beginning about at Toms River and continuing southward beyond Stone Harbor. In general, the i n la n d margin of this salty zone follows fairly closely the line of U. S. Highway 9j the salt aj water boundary bends in l an d in large curves around Great Bay and Great Egg Harbor*, and between these places probably averages about 5 miles from the ocean shore. A tiny tip of the zone of water containing chloride exceeding 250 ppm exists in the Cohansey on Cape May, and a narrow strip borders Delaware Bay in New Jersey, usually less than a mile vide, as far as the mouth of the Cohansey River. In Delaware, on the opposite shore of Delaware Bay, a similar but generally wider strip extends almost to Cape Henlopen, including Lewes. South of Lewes the next area of high chloride (i. e. greater than 250 ppm) is at Rehoboth Beach; the southernmost areas surround Rehoboth Bay, Indian River Bay, and Assawoman Bay—the latter chiefly in Maryland. 58. Wells developed sin the Cohansey sand—or in the permeable sends overlying it—in the areas described would thus yield, only water con¬ taining more than 250 ppm cl* .If pumping were on a very large fickle the salinity would undoubtedly increase as water of higher salinity was drawn into the aquifer. Inland from the zones described, wells should be developed with caution, not only because of danger to the new wells but also because existing supplies might be ruined by ad¬ ditional pumping. Inland, from each of the zones of high chloride described above for the 3 principal aquifers or aquifer groups of the Coastal Plain, there is a zone of ground water containing chloride ranging from 250 ppm down to "normal”. The word "normal” is put in quotes because not enough is known about the salt-water situation in this region to be certain of how much chloride should be considered "normal". Most ground-water hydrologists in New Jersey use 10 ppm for the norm, but Delaware ground-water hydrologists use 25 ppm in that State. Thus, mapping of chlorides in these ranges of values does not correlate from State to State. If one uses 10 ppm as the "normal", then wide areas in western Salem and Gloucester Counties, N. J., are underlain by the intermediate belt of 10-250 ppm chloride in the nonmarine Cretaceous sediments. Ptram this wide strip in Gloucester County a narrow band £ mile to 3 miles wide, averaging perhaps 1 mile, extends all the way up the river as far as the head of tidewater, below'Trenton; and a similar but wider strip occurs on the Pennsylvania side of the river. Much of this chloride in the strip up either side of the Delaware River is, however, not derived from sea-water contamination. Most of it north of the Schuylkill River stems from Industrial and muni¬ cipal wastes derived from leaky sewers, so-called "sanitary" land fill, wastes disposed of through wells or septic tanks, and other human causes. As a matter of fact, the shallow aquifer in South Philadelphia, especially in the vicinity of the U. S. Navy Yard, and reaching under the river across to Camden, is rapidly becoming useless for most purposes except cooling. But to get back to naturally occurring waters of salinity in the range from 10-250 ppm in the nonmarine Cretaceous sediments: there is a narrow ribbon of such water about a mile wide, extending from the very wide zone in Gloucester County, described above, northeast about to Manasquan. In Delaware, along the Christina River and Brandywine Creek and underlying most of Wilmington, a zone of such saline water occurs; another, much smaller, underlies Newark; and a third, about the size of that at Wilmington, underlies Delaware City. 59 . In the Kirkwood formation most of Cape May County is underlain by water in the 10-250 ppm range. The southern boundary is, of course, the high-chloride zone previously described. The inland boundary of this 10 r 250 ppm zone extends northeastward about from Reeds Beach to Strathmore. In Delaware a fairly large area containing water.of this quality extends from Delaware Bay at Liston Point downstream about 20 miles to Pickering Beach, and curves inland a maximum of about 10 miles to include Smyrna, Cheswold, and Dover. i In the Cohansey sand and hydraulically connected overlying Pleistocene deposits, practically all of Cape May County is included in this 10-250 ppm zone—excluding only those parts previously des¬ cribed where higher chloride exists, and a part of the northern end of the county where chloride is less than 10 ppm. Narrow strips a mile ot so wide, usually a little less, border the higher chloride zone previously described, and extend generally northward along the route of U. S. Highway 9 as far as Toms River and northwestward in Cumberland County about to the Cohansey River. On the Delaware State side of the estuary this zone, about a mile or a little more wide, begins at the north near Wilmington; it borders the river about as far as Woodland Beach (east of Smyrna) and from this point south lies in¬ land from the zone of high chloride preciously described. A,few miles north of Lewes this zone widens greatly to almost parallel the shore in the reach from Cape Henlopen to the Maryland line. In this reach the inland margin of the 10-250 ppm zone averages abopt 10 miles west of the Atlantic Ocean. This about sums up our present knowledge of the status of salt water in the Coastal Plain. Perhaps a few remarks about the situation in the vicinity of Newark, N. J., would not be amiss at this point. Newark is in the Passaic River valley, lying just west of Newark Bay, a salt-water body that is connected both to New York Bay and to Raritan Bay by channels at the north and south ends of Staten Island. The area is a part of the Triassic Lowland and is underlain by bedrock of the Newark group (p. 85-90. ) chiefly dense red shale and sandstone of the Brunswick formation of Triassic age. Prior to Pleistocene tinea major valley developed, trending northeast with depths as great as 100 feet under Newark and dipping to 300 feet or more under Harrison. In Pleistocene time this valley and its tributaries were filled with glacial deposits of sand, gravel, silt, and clpy. Modem streams developed after the Wisconsin ice sheet withdrew. Recent alluvium, chiefly silt, clay, and very fine sand, has accumulated over the glacial deposits, chiefly in and near present river beds. Thus in this part of New Jersey, the typical thick wedge of Cretaceous and Tertiary deposits, present in the Coastal Plain farther south, is entirely missing. 6o. Water occurs in the Brunswick formation chiefly in its cracks and crevices. Herpers and Barksdale (1951, p. 27) estimated the specific yield of the upper 300 feet of these rocks to he about 1 or 2 percent. Water moves most readily through the more vertical cracks and especial¬ ly through those trending northeasterly—apparently the joint pattern that produced the widest cracks. The Pleistocene gravels and sands that overlie the Brunswick formation in the river valleys of the Newark area are relatively high in permeability and both transmit .and store comparatively large quanti¬ ties of water. The alluvium has a low or very low permeability, and where thick and compact is relatively impermeable; however, the alluvium is not everywhere thick and compact, therefore it acts as an imperfect aquiclude. In the early days fresh water was obtainable from wells almost anywhere in the Newark area, except very near the river and bay, but heavy pumping in areas close to Newark Bay and the Passaic River, to¬ gether with dredging of ship channels in these bodies, has caused salt¬ water encroachment to take place. The dredging was no doubt a prime contributor to encroachment by breaching the imperfect seal of Recent and, in some places, Pleistocene silt and clay (Herpers and Barksdale, 1951, P* 50), thus exposing the permeable sands and gravels directly to salt water throughout the entire length and depth of the excavations. This is a case that should be given careful consideration in regard to the proposed deepening of the ship channel in the Delaware Bay and River. Salt-water encroachment "trouble spots" now exist in those coastal parts of the service area where large-scale pumping exists adjacent to salt-water bodies. Included are places that have already experienced the loss of once usable wells or well fields; others are potentially threatened with encroachment. Among them are Newark, ^erth Amboy, South Amboy, Sayreville, Asbury Park, Atlantic City, Cape May, Penns Grove—all in New Jersey, and in Delaware the most threatened spots probably are Lewes and Rehoboth Beach. But, as mentioned earlier in this section, wherever new large-scale pumping is developed in an aqui¬ fer near the salt-water--fresh-water interface—as in the nonmarine sediments of Cretaceous aquifer in eastern Camden County, 60 miles or so inland from the ocean—-salt-water encroachment could be induced and a new "trouble spot" could develop. How may the fresh-water supplies be best protected against dam¬ age or ruin by salt-water encroachment? The answer is not a simple one because the problems themselves are complex. In general we must first of all develop a better understanding of local conditions in all aquifers and related surface-water bodies that have a bearing on the salt-water problem. We need comprehensive information for the whole Coastal Plain similar to, but even more detailed than, that now 61. available for the Atlantic City area--details on the local geology and hydrology such as depth, thickness, and effectiveness of aqui¬ fers and aquicludes; the hydraulic heads and water-table or piezo¬ metric maps depicting these hydraulic heads; the variation of chloride in the aquifers, with isochlor maps currently constructed at reason¬ able time-intervals, perhaps semiannually in some areas and annually in others; and other similar or related data, including changes of chloride and of stage and flow of surface-water bodies. Given such essential background data consisting of permanent (geologic, chiefly) and changing (hydrologic and chemical quality) data, local or State authorities would be in a position to enact and put into effect the immediate controls required. With respect to streams carrying salt water, the most effective way to keep salt water out is to utilize dams, tidal gates, or other barriers as far downstream as possible. Where water traffic is im¬ portant, as it is on the Delaware and Passaic Rivers, such structures may be considered impractical because of navigational needs. If they are impractical, then the only alternative means of keeping salt water out of the streams is to maintain such high flows of fresh water that salt water cannot encroach in the face of it. Salt-water encroachment may be hastened, or even initiated, by construction of a tidal canal or canal system designed to do no more than drain low-lying marshes. This was the prime cause of the serious salt-water encroachment problem in southeastern Florida (Parker and others, 1955, p. 584-591). Or the encroachment may stem from the breaching of a relatively impermeable blanket of silt and clay on the bed of a river when ship-channel dredging takes place (Herpers and Barksdale, 1951, p. 40). Thus, there is a real possibility of such encroachment in the lower basin, owing to the proposed addi¬ tional deepening and widening of the ship channel from below Phila¬ delphia to head of tidewater at Trenton. Such dredging would undoubtedly facilitate the movement of water from the river into the aquifers, or vice versa, according to the relative hydraulic heads. No harmful results could accrue--in fact benefits would result--from such dredging if the quality of the river water were to be maintained in a satisfactory condition. But if the deepened and widened channel becomes an inland extension of the sea, or if pollutants are allowed to spoil the river water, the deepened channel would provide easy avenues of entrance to the aqui¬ fers, and the ground-water supplies would be endangered, if not ruined, for most uses. 62 . One other effect to be expected from widening and deepening the cut through the aquifers in the Philadelphia-Trenton area is con¬ cerned with discharge from the aquifers. Removal of silt and mud on the river bottom would increase the discharge for any given head that exists in the aquifers above river level. This would result not only in reducing hydraulic head close to the river, but also in making it that much easier for salty or polluted water to move into the aquifer against the lowered fresh-water head in the aquifers. No easy solution to this problem presents itself. It would be extremely costly and difficult to "pave" the deepened channel either by over-dredging and then allowing Nature to replace the removed silt-clay blanket, or to use cement grout or other known impermeable materials. The only practical ways are those mentioned earlier: (1) Construction and operation of a salt-water barrier or; (2) increased fresh-water flow in the river. PRODUCTIVITY OF AQUIFERS The productivity of an aquifer depends on several factors among which are the extent, thickness, average permeability, recharge poten¬ tial, storage capacity, and susceptibility to salt-water encroachment of the aquifer. An approximate measure of the productivity of the aquifers in the Coastal Plain is provided by the expected yields of properly constructed drilled wells tapping the entire thickness of the aquifers. The location, spacing, and size of such wells depend on the factors mentioned above, and also on the economics of water demand. As discussed in the section on ground-water storage, the average rate of consumptive withdrawal--the net discharge from the aquifers--cannot exceed the average rate of recharge without depleting the storage and ultimately ruining the coastal portions of the aquifers by causing encroachment of salt water. The hydraulic coefficients of, and yields of wells in, the aqui¬ fers of the Coastal Plain have been cited in a previous section. Plate 9 shows: (1) The areas in which it is known or believed that adequate wells can be developed in each aquifer; and (2) the produc¬ tivity that may be expected from properly constructed modern wells penetrating the entire aquifer. The map is generalized and is based partly on interpolation and extrapolation of field data. Because the available data are not sufficiently comprehensive, the map (pi. 9) can only approximately represent the entire picture. For example, wells may not everywhere produce as much as the map indicates,espec¬ ially on the fringes of the several areas; or highly productive zones may well extend beyond the boundaries shown, especially in a seaward direction. 63 '. THE APPALACHIAN HIGHLANDS GENERAL FEATURES The extensive region north of the Fall Line is a part of the Appalachian Highlands--a major physiographic subdivision of the United States (Fenneman, 1938). The region comprises parts of four physiographic provinces, each having distinctive landforms which are related to the types and structure of the rocks and to the geo¬ logic history of the province. From the Fall Line northward these include the Piedmont, New England, Valley and Ridge, and Appalachian Plateaus provinces (pi. 3) • Each province is further subdivided into sections or subprovinces. The Piedmont province contains 2 very distinct subprovinces: the Piedmont Upland, a considerably eroded low plateau formed primar¬ ily by weathered crystalline rocks such as granite, gneiss, and schist; and the Piedmont or Triassic Lowland, a lower and less rugged area formed largely by relatively soft shale and sandstone but in¬ cluding also ridges, hills, and small plateau-like surfaces formed by harder rocks—principally diabase, basalt, and argillite. Another, much smaller, area is Chester Valley (pi. 3), a narrow lowland trend¬ ing westward across the center of the Piedmont Upland. Chester Valley is underlain by limestone and dolomite (carbonate rocks on pi. n) which are soluble and therefore less resistant to erosion than the surrounding rocks. The New England province extends into the basin from the north¬ east as a long tongue terminating near Reading, Pa. Within the basin it consists entirely of the Reading prong of the New England Upland subprovince which is called the Highlands in New Jersey. The area is moderately rugged and, especially in its northeastern part, it is char¬ acterized by approximately parallel, somewhat irregular ridges and intervening valleys all trending northeast. The ridges, which rise about 500-1,000 feet above the valleys, are formed largely by gneiss and related hard crystalline rocks; the valleys are underlain by weaker rocks--principally carbonate rocks and shale. Most of the New England province has been glaciated. In the northeastern part, in New Jersey, the ridges are blanketed by extensive deposits of glacial till, and the valleys contain thicker deposits--largely out- vash—which completely mask the bedrock in most places. The Valley and Ridge province is divided by a ridge known in Penn¬ sylvania as Blue Mountain, into two main parts: (l)The Great Valley to the south; and (2) a sequence of narrow valleys and ridges to the north. Known also in New Jersey ss Kittatinny Mountains, and in New York as Shawangunk Mountains, this ridge for convenience will herein¬ after generally be designated as the Blue Mountain ridge. 64 . The Great Valley, a relatively broad feature 8-20 miles wide in the basin, actually consists of 2 belts of contrasting 3 a n d forms. The southern, and narrower, belt is a gentle lowland formed by rela¬ tively weak carbonate rocks. The northern belt, formed by more re¬ sistant shale, slate, and sandstone, is a deeply eroded surface ris¬ ing abruptly several hundred feet above the lowland to the south. As in the New England province, the northeastern part of the Great Valley has been glaciated, and parts of this area are covered by gla¬ cial deposits of varying thickness and permeability. North of the Blue Mountain ridge, the Valley and Ridge province is characterized by alternating ridges and valleys which trend gener¬ ally northeast, parallel to the regional "grain" of the topography but which, at many places curve, bend abruptly, reverse direction, or zig-zag. The highest and steepest ridges, which have rather uniform summit altitudes of 1,500-2,000 feet, are formed by the hardest mater¬ ials—chiefly thick-bedded quartzose sandstone and conglomerate. Lesser ridges are formed by more thinly layered sandstone and hard shale. The valleys are underlain by rocks less resistant to erosion, such as soft shale and carbonate rocks. The most extensive development of these valleys and ridges is west of the Lehigh River; the belt narrows between the Lehigh River and the Delaware Water Gap near Stroudsburg, Pa. Northeast of Stroudsburg the belt narrows still further and consists principally of the Kittatinny-Shawangunk Mountains ridge and the valley of the Delaware River. The area northeast of Stroudsburg has been glaciated, and the valleys of the Delaware River and its major tributaries are filled with glacial outwash. The Appalachian Plateaus province, which occupies approximately the northern third of the basin, is an upland formed by flat-lying to very gently folded beds of sandstone, shale, and conglomerate. The gentle to flat structure of the beds contrasts with the strongly folded and faulted structure of the similar beds in the adjoining Valley and Ridge province and accounts for the difference in landform between the 2 provinces. The relation of rock structure to topography is well shown by the gradational change from one province to the other near the Lehigh River; there the folds in the Valley and Ridge province flatten toward the northeast gradually rather than abruptly. The 2 sections or subprovinces of the Appalachian Plateaus pro¬ vince in the basin—the southern New York section (which includes the Pocono Mountain^ and. the Cat skill Mountains—differ chiefly in relief; the boundary between them shown on plate 3 is vague and arbitrary. In both areas the layers of rock are nearly flat; the greater alti¬ tude and relief of the Catskills, which attain an altitude of 4,200 feet at Slide Mountain on the eastern border of the basin, is due to 65 . the superior resistance to erosion of the conglomerate and coarse¬ grained sandstone, which are more abundant there. Few summits ex¬ ceed 2,000 feet in altitude in the southern New York section of the plateaus, and most of the area is between altitudes of 1,000 and 1,500 feet. The Delaware River and its major tributaries have carved deep, narrow valleys across the plateaus in both subprovinces. Probably all the plateau region has been glaciated, although the most recent glaciation--that of the Wisconsin stage (table l)--did not extend into the southermost part of the region (pl.3) 0 Glacial till mantles most of the area, and the drainage pattern has been modified greatly by the effects of the ice sheets. Marshes and lakes dot the flatter parts of the plateaus in Pennsylvania. The large valleys are filled with thick outwash. OCCURRENCE OF GROUND WATER In the Appalachian Highlands, ground water occurs in both con¬ solidated rocks and unconsolidated sediments, but although the glacial outwash supplies the most productive wells, by far the most water is in the consolidated rocks because of their greater extent. The glaciated northern half of the area is blanketed discontin- uously by unconsolidated sediments. Thin unbedded deposits of glacial till lie on the interstream areas; bedded deposits of glacial outwash lie along tne major stream valleys, both in the glaciated area and in the unglaciated area to the south. The glacial outwash is the most permeable and productive aquifer in the Highlands, but its total vol¬ ume is small; nonetheless, if large local supplies of ground water are to be developed, the best sites for such developments would be where the larger bodies of glacial outwash are to be found in hydraul¬ ic connection with perennial streams, as is commonly the case in the larger stream valleys. Though much more extensive than the outwash, the glacial till is less permeable and usually is too thin to yield large perennial supplies of ground water. The consolidated rocks underlie all the unconsolidated sediments and are exposed at or near the land surface throughout most of the southern, unglaciated, part of the Appalachian Highlands. The capaci¬ ty of the consolidated rocks to store and transmit water ordinarily is much less than that of the unconsolidated sediments, but their great thickness and extent make the consolidated rocks the princi¬ pal aquifers in the Appalachian Highlands. The consolidated rocks are herein divided into 3 major categories based on the nature and distribution of their water-bearing openings; (1) Crystalline rocks; (2) carbonate rocks; and (3) clastic rocks. The general characteristics of each of these categories are described 66 . briefly, and the geologic formations that compose each type are listed in the sections following. The individual formations are described very briefly in table 1 which shows also their relative ages and strat igraphic sequence. Because it is impossible to show in one table all the consolidated-rock formations in so large and diverse an area as the Appalachian Highlands portion of the Delaware River basin, table 6 lists the formations in each of the physiographic subdivision of the Appalachian Highlands and indicates their approximate age relation. The outcrops of the consolidated-rock formations are shown on plates 11 and 12 and stratigraphic and structural relations of the rocks are in part shown diagrammatically on plate 13. The unconsolidated sediments are described in a later section. Their extent is shown on plate 14 and their thickness and distribu¬ tion in and adjacent to the major stream valleys are shown on plate 15. CRYSTALLINE ROCKS Crystalline rocks are composed of interlocking mineral grains-- crystals--which formed either: (1) by cooling of molten material (to form igneous rocks) or; (2) by crystallization of previously ex¬ isting rocks either through tremendous pressure as the earth's crust folded and was squeezed, or (and) by deep-seated emanations of hot liquids or gases to form metaraorphic rocks. The crystals may range in size from microscopic grains to giants several inches in diameter. The common igneous rocks in the basin are granite, gabbro, dia¬ base, and basalt. Of these, the granitic to gabbroic rocks cooled slowly at considerable depth in the earth's crust and are relatively coarse grained. Many of these rocks appear to be of igneous origin but are now believed to be actually of metamorphic origin. Diabase, a dark rock generally having smaller crystals than granite or gabbro, forms intrusive sheets (sills) and dikes in sedimentary rocks, whereas basalt, a still finer grained rock, originated as lava flows that be¬ came interbedded with sedimentary rocks. The metamorphic rocks of the Appalachian Highlands include gneiss schist, phyllite, slate, quartzite, and probably some of the granitic- rock types mentioned above. These rocks derive their type name from the fact that they have been metamorphosed (changed) by heat hnd (or) pressure from rocks of sedimentary or igneous origin. They commonly have a pronounced banding, layering, or alinement of mineral. U. S. GEOL E RC (Fo exp Baked zone (horntels) Conglomerate PLATE 13 Feet 500 Seo l«v«t 500 W,, 1936 Geology and mineral ond Phoenixville Quodranglet, Bull. 691, PI. I . *N PART These cross sections are presented only to show the general nature of the geologic structure. In some cases the structural interpretations differ from those shown on the geologic maps (pis M ond 12). The cross sections are preliminary ond subject to review, and hove not been reviewed for conformance with stratigraphic nomenclature of the U. S. Geological Survey. U.S. GEOLOGICAL SURVEY EXPLANATION OF ROCK SYMBOLS (Formational symbols explained on plate 12 Baked zone (horntels) Sandstone Shale and slate Gneiss and schist MmSSSSSS Conglomerate Carbonate rocks Granitic to gabbroic rocks R V. D 5 Feet 1,000 - :s * 500- £ See level - 500- 1.000 - a> Feet 1,000 i 500 Sea level - From Greenman.D.W , 1955, Ground Water Resources of Bucks County, Pa. Geol. Sur. Bull. W-l I, PI. I. PLATE 13 LOCATION MAP Feet r1,000 -500 Sea level From Greenman, D. W., 1955, Ground Water Resources of Bucks County, Pa. Geol. Sur. Bull. W-l I, pi. I . 1 J Precambrian Gneiss Gneiss of Precambrian Age The oldest rocks in the Delaware River basin are various types of gneiss and similar crystalline rocks of Precambrian age. They occur in both the major areas of crystalline rocks—the Piedmont Upland and the New England Upland—but are most extensive in the New England Upland. The gneiss and related rocks are of diverse origin; they include highly metamorphosed sedimentary and igneous rocks, unmetamorphosed igneous rocks, and complex mixtures of these types. In the Piedmont 68 . Upland many of the igneous or igneous-appearing rocks have been dif¬ ferent iatied froir the known metamorphic rocks and are shown on the geologic map (pi. 11) as ultrsmafic rocks and granitic to-gabbroic rocks, but in the New England Upland all the rocks are grouped as gneiss and related crystalline rocks (pis. 11 and 12)» In the Piedmont Upland the gneiss of known Precambrian age has been called the Baltimore gneiss and the Pickering gneiss. In the Hew England Upland the named formations include the Byram granite gneiss, the Lossee diorite gneiss, and idle Pochuck gabbro gneiss, but there are also several kinds of unnamed ^leiss believed to be largely of metasedimentary origin (Smith, 1957, p. 71-76). Because of their similar water-bearing properties, their uncertain correlation, and their complex associations, all these rocks" are herein grouped in one hydrologic unit. Most of the gneiss is medium to coarse grained and has a more or less prominent banding or layering of the minerals. In composition, the types range from light-colored rocks having abundant quartz and feldspar to dark rocks containing abundant iron- and magnesium-bearing minerals. Gneiss or schist containing graphite occurs at scattered localities in the Piedmont Upland. lELtramaflc Hocks The ultramafic rocks (rocks high in magnesium end iron-bearing minerals) which consist; of more or less altered or metamorphosed igneous rocks—chiefly serpentine, metapyroxenite, and metaperiodot- ite—occur as small masses at scattered localities in the Piedmont Upland. The outcrops form low hills and ridges that are distinct¬ ively barren of vegetation and are characterized by very thin soils. The small amount of water that occurs in these rocks generally has a high content of magnesium bicarbonate, owing to the abundance of magnesium in the rock-forming ’ minerals. Granitic to Gabbroic Rocks The granitic to gabbroic rocks comprise granite, quartz monzonite, granodiorii^, quartz diorite, syenite, diorite, anorthosite, gabbro, and related rocks. At many places these rocks' inter gp?ade with gneiss of Precambrian age or with schist and gneiss of the Glenarm series, so that it is difficult to portray the boundaries of the units on a geo¬ logic map. Only the larger masses of relatively unmixed granitic to gabbroic rocks in the Piedmont Upland are shown on the geologic map (pi. 11) j in the Hew England Upland these rocks are grouped with the gneiss of Precambrian age. 69 . Gabbro is the most abundant type in the southern part of the Pied¬ mont Upland, whereas quartz monzonite, granodiorite, quartz diorite and anorthosite predominate in the northern part of the Upland, north of Chester Valley. Most of these rocks are medium to coarse grained and are not as strongly banded or layered as the gneiss and schist. Fractures (joints) are relatively far apart, are regularly spaced, and commonly form a set of three mutually perpendicular planes. A set of curved fractures (sheeting) approximately parallel to the land sur¬ face is developed in some of the sparsely jointed rocks. L ike the other crystalline rocks, the granitic to gabbroic rocks contain dikes of pegmatite and metadiabase and veins of quartz. Many th^ QSe Ve ^ S ^ ? lkeS are highly ^actured and yield more water than the surrounding rocks. Glenarm Series Most of the Piedmont Upland south of Chester Valley is underlain y a sequence of schistose and gneissose rocks of predominantly meta- f^ m +? ta2T ?oAn in aS the Glenarm series (Bascom, Clark, Darton, co ?^ erS i. + 9 ° 9 I J: In order of decreasing age the Glenarm series consists of the Setters formation, the Cockeysville marble, the Vissahickon formation, and the Peters Creek schist. The age of these rocks, formerly thought to be Precambrian, is now considered probably early Paleozoic. Increasing evidence indicates that the Glenarm series consists of more highly metamorphosed equivalents of rocks of known ST? 811(1 Ordovician fa ^ther north (Watson, 1957), as shown in The Setters formation consists largely of quartzite and mica- quartz schist and is similar to the Chickies quartzite of Cambrian age T.n t.ho ° The^Wissahickon formation, which constitutes the bulk of the Glen- ann series in the Delaware River basin, includes a variety of rocks ranging from gneiss in the southern part of the area to fine-grained schist and phyllite in the northern part. Micas (muscovite and biotite) are the most abundant minerals; other important minerals include ieldspar, quartz, chlorite, and garnet. The Peters Creek schist, which lies in the northern part of the outcrop of the Glenarm series, is generally similar to the fine- gained mica schist and phyllite in the Wissahickon formation immed¬ iately south. 79 . Spacing and orientation of fractures in the rocks of the Glen- arm series are dependent on the texture of the rocks and the direc¬ tion of application of deformational forces in the earth's crust. Where mica or chlorite are abundant the rocks tend to split readily, parallel to the layering of these minerals, but fractures are farther apart and more evenly spaced in the more massive rocks, where a con¬ siderable amount of admixed granitic or gabbroic rock is present. Quartzonse Rocks of Cambrian Age The quartzose rocks of Cambrian age include the Chickies quart¬ zite, the Harpers schist, and the Antietam sandstone in the Piedmont Upland, and their approximate equivalent. The Hardyston quartzite in the New England Upland (tables 1 and 6). These rocks actually are intermediate in character between the crystalline rocks and the clastic rocks; they consist of quartzose sandstone and some conglom¬ erate and shale that have been metamorphosed slightly to moderately. However, because of their almost total lack of intergranular porosity, they resemble in hydrologic properties the crystalline rocks more closely than the clastic rocks. Because of their brittleness the quartzose rocks are highly fractured at many places, particularly in the vicinity of faults or contacts with older rocks. In parts of the Piedmont Upland the quartzose rocks attain a thickness of more than 1,000 feet, and because of their hardness and resistance to weathering they form conspicuous ridges and hills. In the New England Upland, where these rocks generally are only a few tens of feet thick, they form inconspicuous low ridges or abrupt slopes at valley margins. Basalt and Diabase of Triassic Age In the Delaware River service area the youngest crystalline rocks are basalt and diabase--commonly called trap rock--of Triassic age. Both are dense dark rocks of igneous origin and consist mostly of ap¬ proximately equal amounts of plagioclase and augite. The basalt is fine-grained and occurs as lava flows interbedded with the shale and sandstone of the Newark group; the diabase is coarser grained and forms sills intruded between the beds of sedimentary rock of the Newark group or as dikes cutting across those beds. Both the basalt and the diabase are much more resistant to erosion than the surround¬ ing sedimentary rocks and form prominent ridges and hills several hundred feet high in the Triassic Lowland. The basalt forms a series of concentric arcuate ridges--the Watchung Mountains--in northern New Jersey, outside the Delaware River basin; the diabase forms many scattered hills and ridges across the basin and forms the well-known Palisades along the west bank of the Hudson River (pi. 12). 71 . Hydrologic Properties of the Crystalline Rocks In spite of their diverse origin, all the crystalline rocks have generally similar hydrologic properties: they have little or no in¬ tergranular porosity except in the weathered zone near the land sur¬ face; solution openings such as those in the carbonate rocks are scarce or absent; and practically all water in the fresh rock occurs in fracture openings. Porosity decreases with depth more rapidly than in any of the other rock types in the basin, and, except locally, little water is obtainable below a depth of about 300 feet. As a general rule the following zones are encountered in down¬ ward succession in the crystalline rocks: (1) Soil and decomposed rock consisting of granular material--largely a mixture of clay, silt, and some sand; (2) disintegrated rock which downward contains more and more residual masses of fresher rock; (3) relatively fresh frac¬ tured rock; (4) fresh rock in which the fractures are closed by the weight of the overlying rock. Usually these zones are gradational, and local exceptions to the sequence are common. At some places where erosion has been very active or the rocks are unusually resistant, fresh rock extends to the land surface, and in much of the glaciated part of the New England Upland, glacial deposits directly overlie fresh rock. The thickness and character of the zones are related to numerous factors, among which are the landform, the type of rock, and the geologic history of the area. Other factors being equal, the weather¬ ed zone also varies considerably with rock type. The hardest and chemically most stable rocks, such as quartzite, tend to form the thinnest weathered zones, whereas the weak and chemically unstable rocks, such as much of the gneiss and schist of the Glenarm series, tend to form thick weathered zones. The thickness of weathered material in the outcirop of the Glenarm series of the Piedmont Upland commonly exceeds 23 feet and in places exceeds 50 feet. The character of the weathered material is closely related to that of the parent rock; rocks high in quartz tend to form sand, whereas rocks such as gabbro which have little or no quartz form much less permeable clay and silt. Most of the crystalline rocks in the basin weather to an unsorted assemblage of clay, silt, and sand, hav¬ ing moderate to low permeability. Weathering is most active in the zone above the lowest level of the water table. The principal weathering agents in this area con¬ sist of dissolved carbon dioxide and oxygen and organic acids. Al¬ though some geologists believe that the lowest level of the water table is the lower limit of normal weathering processes (Penck, 1953, p. 61), much evidence exists to the contrary; in most crystalline-rock 88197 0-62-7 (Vol. VII) 72 . areas in the Delaware River basin the zone of fluctuation of the modern water table is well above the base of the weathered zone. Ruxton and Berry (1957, p. 1275) list 3 reasons for such a seemingly anomalous condition: (l) Deep weathering may have taken place be¬ fore an integrated circulation of water was established in the rock; (2) local deepening of the weathered profile may occur along promin¬ ent fractured zones; and (3) the level of the water table may be higher now than at the time the lower part of the weathered zone waa established. In any case, considerable quantities of water now are stored in the weathered crystalline rocks in many parts of the Pied¬ mont Upland, and New England Upland, and water released from grounds water storage sustains the high base flow of the streams in those areas . Fractures are caused by stresses of various origins. Deformation of the rocks during folding and faulting probably caused most frac¬ tures in the crystalline rocks of the basin, but shrinkage resulting from cooling of igneous rocks caused many fractures, particularly in the basalt and diabase. Depths to which open fractures extend are related to the strength and brittleness of the rock type an well as to the degree of deformation it has undergone. As a rule open frac¬ tures extend to greater depths in the hard quartzitic rocks than in the softer, less brittle rocks, such a3 phyllite qnd highly micaceous schist. Records of drilled wells indicate that open fractures do not ordinarily extend beyond a depth of about 300 feet, and that yields of wells are not increased appreciably by drilling below that depth. However, a few wells have obtained water from greater depths, prob¬ ably from fractures along faults or in shattered pegmatite dikes and quartz veins. The porosity of the fractured fresh crystalline rock is consider¬ ably less than that of the weathered zone, but the larger size of many of the fracture openings permits more rapid movement of water through them. The occurrence of water in fractured rock is much more irregular than in the highly weathered rock, owing to the unequal distribution of fractures. Adjacent wells commonly tap fracture sys¬ tems that lack nearby hydraulic connection, so that pumping of one well may not affect the water level in the other, at least Immediately. In the granular material, in the weathered zone the water table may be the usual subdued replica of the topography, hut in a fracture sys¬ tem, especially one in which the fractures are far apart and not inter¬ connected freely, a true water table commonly is absent, and water will stand at different levels in each fracture or set of fractures. At ' some localities water-bearing fractures may be separated from the water-bearing weathered zone by a zone of dry unfractured rock; at other places, ledges of hard, massive rock separate water-bearing zones in the weathered material (Ward, 1956 ). Much study remains to be done before the occurrence of water in the crystalline rocks in the Delaware River basin is well understood. 73 . As indicated by the rather limited data available, the coefficient of storage of the cryst allin e rocks probably ranges from about 0.009 to about 0.02—in the lov range of values for unconfined conditions (Greenman, 1955, p. 6). The higher values probably are representative of the unconsolidated granular material in the weathered zone, where¬ as the lower values are representative of the fractured fresh rock. The transmissibility and average permeability of these rocks also are moderately low to very low, as indicated by the reported specific capacities of wells. In the Piedmont Upland of northern Delaware, Rasmussen and others (1957, p. 99) reported the following specific capacities of wells tapping several types of crystalline rocks: Table 7* ~ Specific capacities of wells in crystalline rocks of northern Delaware Type of rock Specific capacity in gpm per foot of drawdown Number of Maximum Minimum Average wells (Sranodiorite (igneous) Weathered material 3.2 0.005 •m — 2 Hard rock 1.0 .07 0.3 10 Sabbro (igneous) 15 .003 1.6 33 ftssahickon formation . 13 .01 .7 74 Prom these hydraulic characteristics it is apparent that a typ¬ ical well tapping the crystalline rocks will exhibit considerable drawdown at any pumping rate, but substantial lowering of the water table will not extend far from the well, probably no more than a few hundred feet ordinarily, unless the rate of pumping is high. Reported yields of 202 wells tapping crystalline rocks in the basin range from less than 1 gpm to more than 300 gpm and average about 50 gpm. Except for the basalt and diabase, which are perhaps the poorest water-producers in the basin and seldom yield more than a few g all ons per minute to wells, differences in productivity among the many types of crystal lin e rocks seem to be outweighed by local differences within each type. Detailed studies should be made to de¬ termine the factors that affect the productivity of the crystalline rocks. CARBONATE ROCKS The carbonate rocks, as herein defined, consist of: (l) Lime¬ stone (calcium carbonate); ( 2 ) dolomite (calcium-magnesium carbonate; (3) rocks intermediate in composition between limestone and dolomite, sometimes called magnesian limestones; and ( 4 ) rocks intermediate be¬ tween limestone or dolomite and other types, in which the carbonate 7b. content is substantial. Included also is marble, a crystalline car¬ bonate rock which resembles the noncrystalline carbonate rocks in its water-bearing properties. The carbonate rocks comprise all or parts of several geologic or hydrologic units shown on plates 11 and 12 and listed in tables 1 and 6. In order of decreasing age these units include: Franklin limestone (Precambrian), Cockeysville marble of the Glenarm series of early Paleozoic (?) age, carbonate rocks of Cambrian and Ordovician age, and carbonate rocks of Silurian and Devonian age. These units are des¬ cribed briefly in the following pages. Franklin Limestone The Franklin limestone, one of the oldest rocks in the region (table l), typically is a white or gray corase-grained to locally fine-grained marble or dolomitic marble which in places contains con¬ siderable amounts of graphite and many other minerals. The Franklin limestone is most abundant just east of the Delaware River basin in the New Jersey Highland of the New England province, but it occurs also at scattered localities throughout the New England province in the basin and in small areas in the Piedmont (pis. 11 and 12), The marble is associated with various types of gneiss and related crys¬ talline rocks of Precambrian age. Cockeysville Marble The Cockeysville marble is a massive medium- to coarse-grained sugary marble which in places grades into impure schistose marble and limy mica schist. It underlies several small valleys in the southwestern part of the Piedmont Upland where it characteristically is covered by a thick residual deposit of clay. The Cockeysville marble overlies the Setters formation and is overlain by the Wissahickon formation. All three formations are part of the Glenarm series. Carbonate Rocks of Cambrian and Ordovician Age The thickest and most extensive unit composed of carbonate rocks comprises several formations of Cambrian and Ordovician age which are grouped herein because of their general hydrologic similarity and be¬ cause of the uncertainty of their correlation from one area to an¬ other. The formations are listed in tables 1 and 6 and are described briefly in table 1. 75 . The Cambrian and Ordovician carbonate rocks crop out chiefly in the southern, lowland, belt of the Great Valley, but they occur also in Chester Valley in the Piedmont Upland, in small areas in the Triassic Lowland, and in several long, narrow valleys in the New England Upland (pis. 3, 11, and 12). Typically, the Cambrian and Ordovician carbonate rocks consist of a thick sequence of limestone, shale, and slate, and, in the southern part of the Piedmont, some mica schist and phyllite. The limestone and dolomite weather to a thick residual deposit of clay and silt and form lowlands having only a few outcrops, whereas the zones containing noncarbonate rock types form low ridges and hills. The total thickness of the carbonate rocks of Cambrian and Ordovi¬ cian age ranges widely throughout the basin, but it is difficult to ascertain precise thicknesses, owing to the intense folding and fault¬ ing of the beds. The total stratigraphic thickness of the unit at any one locality may not exceed 2,500 feet, but because of folding and faulting the beds may extend to depths of 6,000 feet or more. Carbonate Rocks of Silurian and Devonian Age The carbonate rocks of Silurian and Devonian age comprise several relatively thin formations which are described briefly in table 1. In ascending order they are the Bossardsville, Decker, Rondout, Manlius, Coeymans, New Scotland, Becraft, and Port Ewen limestones. These for¬ mations .crop out in a narrow belt across the Valley and Ridge province a few miles north of the Blue Mountain ridge. !J3ie beds dip steeply to the north and are within reach of wells in only a rnnai 1 area in and near the outcrop. Pbr the most part, the sequence consists of light-gray to nearly black limestone and dolomitic limestone, and smaller amounts of limy sandstone and shale. The total thickness of the beds probably does not exceed 800 feet within the basin, and in places the thickness is much less. Hydrologic Properties of the Carbonate Rocks The carbonate rocks differ from the other consolidated rocks in having a significant quantity of solutionally enlarged openings. Water percolating downward from the soil contains small amounts of dissolved carbon dioxide and organic acids which make a weak acid solution that is capable of dissolving carbonate rocks. Solution generally starts along pre-existing fractures or root cavities and enlarges them to form a network of more or less interconnected chan¬ nels. Some such channels are enlarged to considerable size to form caverns, and in time a limestone may become honeycombed with caverns 76 . and. the land surface pitted with sink holes; part of the drainage is on the land surface and the rest takes place through these underground solution channels. The distribution of solution openings in most carbonate rocks is extremely irregular and is difficult to predict in advance of drilling. In some of these rocks, particularly those that are sandy or shaly and:- contain less calcium carbonate, solution openings may be virtually ab¬ sent, and all the water may occur in ordinary fracture openings simi¬ lar to those in unweathered crystalline rocks. Where the fractures are tightly closed, as in some of the Jacksonburg limestone of Middle Ordovician age, little or no water may be yielded to wells. In the Delaware River basin the most abundant fracture and solution openings are between depths of about 50 to 300 feet, although some wells have encountered large openings at depths of more than 1,000 feet. Openings also seem to be more abundant in the vicinity of surface streams. - Overlying the fresh carbonate rocks at most places is a weathered zone commonly as much as 50 feet thick, composed of residual clay, silt, and some sand. Owing to its considerable clay content, this material generally has rather low permeability and specific yield, and it does not ordinarily yield much water to wells. However, at some localities, such as in the outcrop of the Cockeysville marble in the Piedmont where the weathered zone averages more than 80 feet in thickness, the few available data suggests that the yields from the weathered material may exceed those from the underlying fresh rock where the fresh rock contains relatively few solution openings (Rasmussen and others, 1957 > p. 102). Ground water in the carbonate rocks occurs under unconfined to rather completely confined conditions. Unconfined or semiconfined conditions prevail in the weathered zone and in the immediately under¬ lying fractured rock. The deeper fractures and solution channels contain semiconfined to confined water and may, in some places, transmit water many miles from intake areas to discharge areas. Solution channels usually are more abundant near streams, and at many places surface drainage is controlled by the distribution of the subsurface openings. Stream valleys and other relatively low areas are therefore favorable sites for wells. Streamflow in areas underlain by carbonate rocks is unusually steady and includes a high proportion of base flow—chiefly ground- water discharge. Water budgets are particularly difficult to esti¬ mate for drainage basins in carbonate-rock terrane, because much of the water that moves through the networks of solution channels may enter drainage basins underground from adjacent basins or may leave the basins as unmeasured ground-water outflow. 77 . Detailed data on hydraulic coefficients of carbonate-rock aqui¬ fers of this region are lacking. However, from observed behavior of pumped wells tapping the artesian zone, and the effects of the pump¬ ing on adjacent wells, it may be concluded that a decline of artesian pressure as an effect of pumping generally is transmitted rapidly to some distant points but seldom is transmitted equally in all direc¬ tions. In fact, nearby wells may tap different systems of rock openings, in which case the pumping of one well will not appreciably affect the water level in the adjacent well, at least immediately. The transmissibility and average permeability of many carbonate- rock aquifers appears to be high, as indicated by reported yields of several hundred gallons per minute with pumping drawdowns of less than 20 feet. Small yields with large drawdowns are not uncommon, however, which suggests great variability in the aquifers. In the fresh rock, coefficients of storage probably are in the order of 0.0001 to 0.001 (Barksdale, Greenman, Lang, and others, 1958); in the weathered zone near the land surface, where water-table conditions prevail, the storage coefficients may be in the order of 0.01 to 0.10. Although successful wells in the carbonate rocks yield larger supplies than wells in any other type of consolidated-rock aquifers, unsuccessful wells or wells having disappointingly low yields are not uncommon. In some areas, particularly where noncarbonate rock types are abundant among the carbonate rocks, yields of wells average less than 25 gpm, and the drilling of two or more test wells may be required to obtain a successful supply well. At other localities, especially in the stream valleys, although test wells may still be needed, well yields exceeding 500 gpm have been obtained, and yields of as much as 1,500 gpm are reported. In the Pennsylvania part of the Delaware River basin, reported yields of 127 wells in carbonate rocks range from 4 to about 1,500 gpm and average nearly 200 gpm. Modern drilled wells 300-500 feet deep in the relatively pure carbonate rocks may be expected to yield about 50-500 gpm, but wells in formations, such as the Jacksonburg limestone, that contain considerable amounts of noncarbonate rocks are generally incapable of producing more than domestic or small- scale farm supplies. CLASTIC ROCKS Consolidated clastic rocks consist chiefly of fragments of rocks or minerals which have been derived from the disintegration of older rocks, transported to the site of deposition, and cemented or otherwise consolidated there. In the Delaware River basin area these rocks represent both marine and nonmarine depositional anvironments, but with a few local exceptions all the rocks 78 . now contain fresh water at depths ordinarily penetrated by wells. The clastic rocks are the most extensive aquifers in the Appalachian High¬ lands; they underlie most of the Valley and Ridge province and the Triassic Lowland, and all the Appalachian Plateaus. All the principal types of clastic rocks, ranging in texture from fine-grained shale in which the grains are microscopic in size to conglomerate containing boulders as much as several feet in diameter, are represented in the basin. On the basis of both their age, as de¬ termined from fossil content and.less direct lines of evidence, and their physical character, or lithology, the clastic rocks have been subdivided into numerous geologic formations. These are described briefly in table 1 and listed also in table 6. The general character¬ istics of these rocks in each of the three major areas where they oc¬ cur are discussed in the following pages. More detailed descriptions of the individual formations are given by Hall ( 193*0 and Lohman (1937)* Rocks of the Valley and Ridge Province Except for parts of the Great Valley and a narrow belt several miles north of Blue Mountain which are underlain by carbonate rocks, all the Valley and Ridge province is underlain by clastic rocks. The Oldest clastic formation exposed in the Valley and Ridge province is the Martinsburg shale of Ordovician age. Lying on the eroded surface of the Martinsburg shale is the Shawangunk conglomer¬ ate of Silurian age, which dips moderately to steeply northward and forms the Blue Mountain ridge. From the Shawangunk conglomerate upward, the formations of Silur¬ ian to Pennsylvanian age are folded into a series of anticlines and synclines and are cut by numerous faults. A large volume of the originally deposited material has been removed by erosion since the end of the Paleozoic era (table l), so that only the "roots'' of the anticlines and synclines remain. The harder beds of sandstone and conglomerate form ridges rising to altitudes of as much as 2,000 feet above sea level; the softer beds of shale and some limestone form the intervening valleys. The clastic rocks of the Valley and Ridge province include con¬ glomerate, sandstone, siltstone, claystone, shale, and slate which occur in alternating bed or zones of variable thickness and extent. Most of the thicker beds or sequences of beds can be 79 * identified over large areas and form mappable units, or geologic for¬ mations. Some formations have a distinctive character are com¬ posed predominantly of one rock type. However, most of the thicker formations are more or less heterogeneous and contain numerous alter¬ nating layers of different rock types, each having distinctive hydro- logic properties. The formations are described briefly in table 1. Martinsburg Shale The most extensive formation in the Valley and Bidge province is the Martinsburg shale, which underlies the northern part of the Great Valley in a belt 6-13 miles wide extending east-northeasterly across the basin. It occurs also farther south in several long, narrow belts bounded by the carbonate rocks of Cambrian and Ordovician age. The Martinsburg consists largely of gray shale which in many places is metamorphosed slightly to form slate, but it also includes sandstone, particularly in the upper part, and some conglomerate. In an extensive area between the Delaware and Schuylkill Rivers thick zones of slate of commercial quality are min ed for roofing material and other uses. In the slate the bedding of the original shale has been obscured by metamorphism, and instead, a prominent cleavage, usually at a considerable angle to the bedding, is de¬ veloped . The most widely accepted value for the maximum thickness of the Martinsburg shale in the basin is about 4,000 feet; however, Behre (1933), using a different interpretation of the geologic structure, estimated a maximum thickness of nearly 12,000 feet. Although the shale and slate have little or no effective inter¬ granular porosity, small but dependable supplies of water are yielded from fractures in these fine-grained rocks. The sandstone beds in the weathered zone contain some water in the intergranular pores where the cementing material has been leached out, and these beds generally are more permeable than the shale and slate. Most water yielded to wells in the Martinsburg shale is from depths of less than 200 feet, and it is seldom profitable to prospect beyond that depth. Most drilled wells yield less than 50 gpm, but a few yield 50-250 gpm. The outcrop of the Martinsburg shale is a dissected upland in which the bottoms of the narrow, steep-sided stream valleys lie as much as 500 feet below the broad interstream areas. The soils com¬ monly are less than a foot thick and have relatively low infiltration capacity and storage capacity; in the underlying rock is small; hence, 80 . a relatively large proportion of the precipitation runs off as over¬ land flow. In the glaciated area to the northeast, however, a mantle of glacial deposits acts as a more permeable intake, and streamflow probably is less flashy there. Conglomerate and Sandstone Aquifers The beds of conglomerate and coarse-grained sandstone are more resistant to erosion than the adjacent shale and thein-bedded sand¬ stone, therefore they form prominent rocky ridges. The thickest and coarsest beds are those in the Shawangunk conglomerate, the Oriskany sandstone, the Pocono formation, and the Pottsville formation (table 1)„ Although these formations are not tapped by many wells, they very likely are the most permeable bedrock aquifers in the Valley and Ridge province. Water occurs both in the fairly abundant fractures in the brittle quartzitic sandstone and conglomerate, and in the intergranular voids in the rocks of the weathered zone where the cementing material has been dissolved. Less permeable beds of sandstone or shale locally confine water, and flowing wells have been developed at several local¬ ities „ Data on hydraulic coefficients of the conglomerate and sandstone aquifers are not available; however, the physical characteristics of these rocks and the behavior of wells tapping them indicate that modern drilled wells more than 100 feet deep might be expected to yield about 50-300 gpm. Lohman (1937) reported that in Schuylkill County, Pa., several public-supply wells ranging in depth from 350 to 1,000 feet in the Pottsville formation yielded 65 to more than 125 gpm. However, he reported also that several deep wells had been unsuccessful in that area, owing to the absence of fradtures in the rock penetrated. Because of their firmly cemented character and very high content of quartz, the fresh conglomerate and sandstone are difficult and costly to drill. Moreover, the yields of wells in these rocks do not always increase with depth. There is always a risk involved in drill¬ ing for water in these rocks, and the deeper the drilling proceeds the less chance of getting large supplies becomes. Interbedded Sandstone and Shale Aquifers Several formations in the Valley and Ridge province consist not predominantly of one rock type, but, instead, of alternating layers of coarse- to fine-grained sandstone, shale, silt-stone, claystone, and some conglomerate. In order of decreasing age these formations in¬ clude (1) the Bloomsburg red beds -- a sequence of 8l* red and green shale, sandstone, and some conglomerate which, is largely of nonmarine origin; (2) the Mahantango formation of Willard (1935)_ mostly beds of gray flaggy sandstone and shale of marine origin; (3) the Portage group, as used in Pennsylvania,--several formations consist¬ ing of thin-bedded to thick-bedded sandstone and sandy shale of marine origin which form broad ridges having moderate relief; (4) the Catskill formation a thick sequence of red, brown, gray, and green somewhat lenticular beds of sandstone, shale, and conglomerate of nonmarine or¬ igin which also underlies nearly all the Appalachian Plateaus province; (5) the Mauch Chunk formation consisting of red and green shale and sandstone with some conglomerate in the upper part; (6) the Allegheny formation—the coal-bearing sequence containing irregular beds that range from shale and fire clay to coarse-grained sandstone and con¬ glomerate . It is difficult to generalize about the hydrologic properties of such a heterogeneous class of rocks. However, the beds of sandstone generally seem to be somewhat more permeable than the beds of shale. In weathered sandstone some water occurs in intergranular pores as well as in fractures, but water in the shale is contained almost en¬ tirely in fractures, many of which are along the bedding planes. Artesian conditions, which are common, are caused by the dipping beds of quite different permeability. Water-table conditions gener¬ ally occur in the weathered rock near the land surface. Reported yields of wells in the interbedded sandstone and con¬ glomerate aquifers have a great range. Some beds of shale yield only a few gallons per minute to wells, whereas wells tapping some beds of coarse-grained sandstone yield more than 150 gpm, and several deep veils are reported to yield more than 300 gpm. Because it underlies valleys that contain important centers of population, the Mauch Chunk formation is a particularly important source of water supplies, even thoiigh much of the formation is com¬ posed of shale. It receives ample recharge from adjacent ridges, ow¬ ing to its low topographic position. Reported yields of 100 wells in the Mauch Chunk range from less than 1 to 375 gpm and average about 50 gpm. However, the average yield, which is affected by the values for many small domestic wells, is toe low to be presentative of yields that might be expected from deep drilled wells used for municipal and industrial supply. In Schuylkill and Carbon Counties, Pa., where the Mauch Chunk formation is the most important source of ground-water supply, Lohman (1937) reported that many municipal and industrial wells yielded more than 100 gpm, and that a well in Schuylkill County, 452 feet deep, yielded 350 gpm with a drawdown of 217 feet—a specific capacity of l.o gpm per foot of drawdown. Assuming that the drawdown caused by entrance losses in the well was small and that the aquifer is artesian. the coefficient of transmissibility probably is in the order of 3,000-4,000 gpd per foot. Because of its location in the coal basins, the Allegheny forma¬ tion offers a special case. Coal-mining operations have expensively dewatered parts of the formation, and in many places the mining oper¬ ations have resulted in the formation of acid waters high in sulfate content, thus making the water at or near the mines unsuitable for most uses. Usable supplies of ground water may be obtained in the Allegheny formation in areas remote from mines, however. Shale Aquifers Three formations in the Valley and Ridge province, the Wills Creek shale, the Esopus shale, and the Marcellus shale, are composed of shale, siltstone, or claystone. The Wills Creek shale, which generally is given the local name Poxono Island shale (of White, 1882), occurs in a narrow band just north of Blue Mountain where it is largely covered by glacial deposits and is not tapped by many wells. Little is known about its water¬ bearing characteristics. The Marcellus shale and the Esopus shale, which are separated by the Onondaga limestone, are largely dark sandy shale or siltstone (pi. 2) and both contain hard slaty beds. These rocks are relatively impermeable, and the small amount of water they contain occurs almost entirely in fractures. In many localities the fractures are so tightly closed or so scarce that little or no water is yielded to wells. How¬ ever, some wells in the more highly fractured rock yield as much as 25 gpm. Rocks of the Appalachian Plateaus Province The Appalachian Plateaus province, which occupies a third of the total area of the Delaware River basin, is underlain almost entirely by a sequence of sandstone, shale, and some conglomerate predominantly of nonmarine origin. This sequence, which in places is more than 6,000 feet thick, has been called the Catskill formation. The Catskill formation has been divided into several smaller units which are listed in table 6. Toward the west and southwest the nonmarine beds inter¬ tongue with marine formations of the Portage group (as used in Pennsyl¬ vania) and the upper part of the Hamilton group. The younger Pocono formation crops out on the west and southwest flanks of the plateaus and when detailed mapping is completed may be found to cover a larger part of the plateaus themselves than the area shown on plate 12. How¬ ever, the question as to the presence or absence of the Pocono forma¬ tion on the plateau is of little or no hydrologic importance because of the similarity of the Pocono to the immediately underlying part of the Catskill formation. In contrast to the folded beds in the Valley and Ridge province, the beds underlying most of the Appalachian Plateaus province are either nearly flat lying or very gently folded. They consist largely of red, brown, gray, and green sandstone, shale and some conglomerate. Beds of homogeneous material range in thickness frc® a fraction of. an inch to several tens of feet. The following log of a test boring typifies the character of the beds: Well SvH4, New York City Board of Water Supply, test boring for shaft on line of East Delaware Tunnel, near Heversink Biver, about 4 miles scitheast of Willowemoc, Sullivan County. Altitude of land . thickness (feet) Depth (feet) Till 13 13 Shale, red 5 18 Sandstone, red 2 20 Sandstone, gray. 25 45 Conglomerate, gray, white quartz pebble* 5 50 Sandstone, gray 15 65 Shale, gray 1 66 Sandstone, gray 4 70 Shale, red and gray 2 72 Sandstone, gray 62 134 Shale, red and gray 3 137 Sandstone, gray 27 164 Shale, sandy, gray 8 172 Sandstone, gray 9 181 Shale, gray 2 183 Sandstone, gray 13 196 Shale, red 22 218 Sandstone, gray, trace of coal at 237' 29 247 Shale, red, gray, some sandy shale 6 l 308 Sandstone, gray, and red, shale streaks 23 331 Shale, sandy, red 12 343 Sandstone, gray 20 • 363 Conglomerate, gray, some sandstone and 6 l 424 shale Sandstone, gray, some shale,in thicstxat* 162 586 Shale, sandy, red 7 593 Sandstone, gray, some shade 73 666 Shale, sandy, red 29 695 Sandstone, gray, vein of calcite, 0.4 foot thick, at 731 feet " 43 738 Shale, sandy, red and green 5 743 Most of the beds are cut by comparatively smooth, regular planes of fracture (joints) which commonly consist of three mutually per¬ pendicular sets, one of which is parallel to the bedding. Joints at oblique angles to the bedding are not uncommon, however. These joints greatly facilitated "quarrying" of the rock by the glacial ice that scoured most of the area several times during the Pleistocene epoch. Tablelike surfaces, bounded by nearly vertical cliff's as much as several tens of feet in height, have resulted from such quarrying action at many places. Most of the consolidated rocks in the plateaus are covered by glacial deposits of varying thickness. These consist largely of till but include scattered bodies of outwash, some of which are of con¬ siderable size (pi. 14). Where permeable, these deposits, especially the outwash, absorb much of the precipitation and transmit some of it to the underlying bedrock; however, a large part of the till is rel¬ atively impermeable and does not allow much recharge to the underlying hard-rock aquifers. The exposures of bedrock, which probably cover less than 10 percent of the area of the plateaus, are characterized by numerous outcrops of rock and generally thin stony soils; these conditions result in rather low infiltration capacity. The beds In the Cat skill formation underlying the plateaus are moderately good to poor aquifers. Large variations in yield of wells occur within short distances, both vertically and horizontally. For example, dry holes as much as 400 feet deep have been reported in areas where successful wells are typical. Also, much deeper wells have been abandoned owing to, great depths to water, to insufficient yields, or to poor chemical quality of water. In general, the beds of sandstone are more permeable than the beds of shale; however, some of the sand¬ stone is so completely cemented and lacking in fractures that it yields little or no water. Exceptionai yields are obtainable in scattered large fracture systems, generally along faults or unusually large joints. Fluhr (1953) reported that flows of as much as 60O gpm were encountered in such zones at depths of as much as 1,700 feet below the land surface during the construction of water-supply tunnels. The tunnels were almost completely dry elsewhere, however. Records of 371 wells in the Appalachian Plateaus in the Delaware River basin show ranges in depth from 5 to 960 feet, most wells being 100-300 feet deep. Reported water levels range from 11 feet above the land surface—flowing artesian wells are-not uncommon—to 540 feet below. Yields of wells range from 0 to 600 gpm and average more than 25 gpm; specific capacities range from less than 0.2 to about 4 gpm per foot of drawdown- Springs are numerous and are used as sources of supply at many places. 85 - Rocks of the Triassic Lowland The Triassic Lowland, a broad belt 9-32 miles wide extending across the southern part of the Appalachian Highlands, is underlain chl ® f } y classic rocks that belong to the Newark group of Trlassic age (table l). Tne clastic rocks are in¬ truded by sills and dikes of diabase, and east of the basin in New Jersey they contain also several flows of basalt. The basalt and diabase are discussed in the section on crystalline rocks. Most of the sedimentary rocks are of nonmarine origin and are believed to have been deposited under semiarid conditions in a northeast-trending basin having a somewhat greater extent than the present Triassic Lowland (Johnson and McLaughlin, 1957, p. 36). The rocks are a thick sequence of shale, sandstone, argillite, nwfl conglomerate which lies on the eroded surface of the much older rocks of Precambrian and Paleozoic age (pi. 13 ) from which the materials were in large part derived. The beds are tilted to the northwest in most of the region, although locally they dip in other directions where they are warped into broad folds, particularly in the vicinity of the masses of diabase. At most places the dips are less than 20 degrees, although ’ adjacent to some of the large faults along the northwest border of the Lowland, dips are as much as 50 degrees. The maximum thickness of the Newark group in the Delaware River basin is about 12,000 feet along the Delaware River (Johnson and McLaughlin, 1957, p. 32). The Newark group has been divided into three formations, each having more or less distinctive types of rock (Kummel, 1897 ). From oldest to youngest, they are the Stockton formation, which is char¬ acterized by prominent beds of light sandstone high in feldspar con¬ tent (arkose); the Lockatong formation, which is chiefly argillite and hard shale, and the Brunswick formation, which is a thick, mo¬ notonous sequence of red shale and sandstone. A fourth unit, commonly grouped with the Brunswick formation, consists of lenticular beds of conglomerate and coarse-grained sandstone. Unlike most of the forma¬ tions of the Delaware River basin these formations are not clearly defined time units but instead are units representing changing con¬ ditions of deposition both in place and in time. In general, however, the Stockton formation is the oldest unit and the Brunswick is the youngest. The Lockatong formation represents a swamp and lake de¬ posit near the center of the ancient Triassic basin, and inter¬ tongues with the lower part of the Brunswick formation in a wide area, largely in Bucks County, Pa. The extent of the formations is shown on plates 11 and 12 and - their relations In cross section are shown on plate 13 . Their physical and hydrologic properties are described briefly in table 1 and in somewhat more detail in the following sections. 86 Stockton Formation The Stockton formation crops out in two principal belts, one in the southern and one in the central part of the Triassic Lowland, and also in two smaller areas—one mostly outside the Delaware River basin and between the two principal belts, the other along the Hud¬ son River at the eastern margin of the Triassic lowland, in north¬ eastern New Jersey (pis. 11 and 12). The Stockton overlies the eroded edges of rocks of Precambrian to Ordovician age and is in turn overlain by the Lockatong formation or by the Brunswick formation where the Lockatong is absent. The thickness of the Stockton ranges from about 1,000 to 3,000 feet in the southern belt and reaches a maximum of about 5,000 feet in the central belt. The most distinctive rock in the Stockton formation is a light gray or light yellow medium- to coarse-grained sandstone (an arkose) that contains much feldspar and some mica. Other types include con¬ glomerate, fine-grained red or brown sandstone, and soft red shale. Sandstone and conglomerate generally are more abundant in the lower part of the formation than in the upper part. Individual beds are not extensive, although some of the thicker zones or sequences of beds extend for many miles. The rock materials appear to have been derived in large part from the crystalline rocks to the south and apparently were deposited in a nonmarine environment. The beds of arkose and conglomerate foim low ridges; the softer beds of red shale and sandstone form the intervening valleys. The soils formed on these rocks are nearly as variable as the rocks them¬ selves; in general the soils are thickest and most permeable on the coarse-grained arkose and conglomerate and thinnest on the red shale where in places they are only a few inches •thick. The Stockton formation is one of the most productive of the con¬ solidated aquifers in the Delaware River basin and adjacent New Jersey and has perhaps the highest average permeability of any of the clastic rock formations. Most of the water in the Stockton occurs under confined or semiconfined conditions in the weathered and frac- i tured rock within about 500 feet of the land surface. The most per¬ meable beds are composed of coarse-grained arkose and conglomerate which contain water in fractures and also in openings between grains where the cementing material has been removed by weathering. Most of the intervening beds of shale are much less permeable and act as aquicludes confining water in the arkose and conglomerate aquifers. Recharge to the aquifers in the Stockton formation percolates downward in their outcrop areas. Joins the ground-water body, and moves in the direction of the hydraulic gradient to points of dis¬ charge . Preliminary pumping tests have given coefficients of storage of about 0.00001 or 0.00002, indicative of artesian conditions; prob ably nowhere does the coefficient exceed about 0.001 (Greenman, 1955 p. 28). Laboratory-determined specific yields of a dozen samples of arkose, conglomerate, sandstone, and sandy siltstone from outcrops of the Stockton formation (U. S. Geological Survey Water Resources Laboratory, Denver,unpublished data) ranged from nearly 0 to 19 per¬ cent and averaged about 8 percent. Porosities in these samples ranged from 7 to 30 percent and averaged about 15 percent. Coefficients of permeability for movement of water parallel to the bedding determined in 10 of the 12 laboratory samples ranged from 0.001 to 0.3 gpd per square foot and averaged only O.Oh gpd. Permeability coefficients for movement perpendicular to the bedding |from 0.001 to 0.2 and averaged about 0.03 gpd per square foot—somewhat less than the average permeability for movement par¬ allel to the bedding. Both these average values are much less than the average permeability of arkose and conglomerate aquifers sug¬ gested by well-yield data, which indicates that the most of the water probably moves toward pumped wells through the fractures in the rock rather than through the intergranular pores. However, the surprisingly high specific yields for the laboratory samples of weathered rocks suggest that most of the ground-water storage capacity in the aquifers of the Stockton formation is in the pore spaces between grains in the weathered zone near the land surface rather than in the fractures, even though the water moves much more readily through the fractures. As a result, wells may have rela¬ tively high initial yields, owing to the high permeability of the fractured zones, but the ultimate or long-term yields may be sub¬ stantially less, because they are governed by the much lower perme¬ ability of the weathered granular materials that supply most of the water withdrawn from storage. A more favorable aspect is that the low permeability of the granular materials allows them to retain water in storage for considerable periods. Reported yields of 180 wells tapping the Stockton formation in the Delaware River basin range from 2 to 800 gpm and average about 100 gpm. Specific-capacity tests for 23 wells in Bucks County, Pa., showed a range in values from 0.35 to M* gpm per foot of drawdown and on an average of about 6.0 gpm per foot (Greenman, 1955, p. 28). From all these data it may be concluded that most deep drilled wells of modem design in the Stockton formation should obtain yields in the range of 30 to 300 gpm, but that the long-term yields under continuous pumping would be substantially less than the initial yield. Because of the low coefficients of storage and the relatively high coefficients of permeability of the artesian aquifers, drawdown effects of pumping would extend considerable distances, so that proper spacing of wells to minimize interference is particularly im- portan + . 88197 0-62-8 (Vol. VII) 88 Runoff from the outcrop of the Stockton formation probably is less flashy than that from the other formations in the Triassic Low¬ land, owing to the greater permeability of many of the beds and the thicker soils. Lockatong Formation The Lockatong formation overlies the Stockton formation and v crops out in three principal belts lying north or northwest of the outcrops of the Stockton in the central and south-central parts of the Triassic Lowland (pi. ll). The Lockatong is absent in most of the Lowland northeast of the Delaware River basin and is missing also in the western part of the basin. It attains a maximum thickness of more than 3 .>800 feet in the outcrop along Tohickon Creek and the Delaware River (pis. 11 and 13). The most abundant and distinctive rock type is a thick-bedded dark-gray to black argillite (hard claystone or siltstone). Other types include thin-bedded dark shale, impure limestone, and limy ar¬ gillite. The upper part of the Lockatong, which grades into the Brunswick formation, includes tonguelike beds of dark-red argillite and red shale of the type occurring in the Brunswick formation. A thin zone at the base of the Lockatong contains coarse-grained beds like those in the underlying Stockton formation. The argillite is a dense, hard rock and forms prominent ridges where it is interbedded with softer shale, or broad plateaus where the soft rocks are absent. Most of the formation weathers to thin soil composed of yellowish-brown clay loam. The Lockatong formation contains some of the least permeable rocks in the basin. The fresh argillite has very little intergran¬ ular porosity, and fracture openings in this rock are neither large nor abundant. Most of the water occurs under unconfined or semicon- fined conditions in the weathered zone near the land surface. Yields reported for 205 wells in the basin and adjacent New Jersey range from 0.2 to 55 gpm and average about 10 gpm; specific capacities reported for 65 wells range from 0.02 to 2.0 gpm per foot of drawdown and average about 0.6 gpm per foot (Barksdale, Greenman, Lang, and others, 1958). Runoff from the outcrop areas of the Lockatong formation prob¬ ably is extremely flashy because of the low infiltration capacity of the thin impermeable soils and the small ground-water storage capacity available to sustain base flow. 89 . Brunswick Formation The Brunswick formation is the thickest and most extensive for¬ mation in the Triassic Lowland (pis. 11, 12, and 13). In the Dela - I ware River basin its outcrop is about equal in area to the combined outcrops of the Stockton and Lockatong formations; in New Jersey out¬ side the basin it underlies most of the Triassic Lowland. Its maxi¬ mum thickness within the basin probably is about 7,000 feet; outside the basin in New Jersey, where the Brunswick includes beds that are probably equivalent to the Lockatong formation and possibly to part of the Stockton formation as well, the total thickness may be greater The Brunswick formation typically consists of soft red shale [ interbed ded with smaller amounts of brownish-red siltstone and fine¬ grained sandstone, and green, yellow, gray, and purple shale and argillite. East of the basin, sandstone is more abundant, and beds of conglomerate occur in places. Along the northern border of the Triassic Lowland the fine-grained materials grade into conglomerate and coarse-grained sandstone (pis. 11 and 12) that probably represent I alluvial-fan deposits laid down by torrential streams near the end of Triassic time (Johnson and McLaughlin, 1957). In the vicinity of the Delaware River and to the west in Bucks County, the lower part of the Brunswick is gradational with the upper part of the Lockatong formation and includes beds of dark argillite interbedded with the typical red shale. Near the intrusive masses of diabase, the soft red shale of the Brunswick formation is altered to a hard dark finely crystalline rock (hornfels) that closely resembles argillite (pi.13). Because of its great extent and its relatively high average per¬ meability, the Brunswick formation is one of the most important source of ground-water supplies in the Appalachian Highlands. The weathered part of the formation above a depth of about 250 feet contains uncon- fined water and may be regarded as a water-table aquifer. Between ; depths of about 250 and 600 feet semiconfined water occurs in rela- ( tively permeable zones which rarely are more than 20 feet thick. The upper, water-table aquifer receives recharge directly from precipitation; the underlying semiartesian aquifers are in turn re¬ charged by drainage from the water-table aquifer. In the semiarte¬ sian aquifers the water-bearing openings are fractures, many of which have been enlarged slightly by the solution of limy material by cir¬ culating ground water. In the water-table aquifer, fractures are jj more abundant, and additional drainable water may be stored in the intergranular pores in the coarser materials. Herpers and Barksdale | (1951, p. 27) reported a specific yield of 1 to 2 percent for the zone within 300 feet of the land surface; a decline in water table of a foot over an area of a square mile therefore would represent a release from storage of approximately 2 to 4 million gallons. 90 . Most wells in the Brunswick formation tap both water-table and semiartesianaquifers. The ultimate yield of a well is related to the storage capacity of the water-table aquifer it penetrates and the rate at which that aquifer can supply recharge to the underly¬ ing semiartesian aquifers tapped by the well. As in the Stockton formation the long-term yield of a heavily pumped well may be only a fraction of the initial yield. Reported yields of 164 wells in the basin range from 2 to about 400 gpm and average about 90 gpm. East of the basin where the Bruns wick formation contains a higher proportion of coarse-grained beds the average yield of wells is higher; at Ridgewood in Bergen County, No Jo, well yields up to 750 gpm are reported. Most of the soils on the Brunswick formation are thin and not very permeable, hence their infiltration capacity is rather low. Moreover, the ground-water storage available to accept recharge com¬ monly is small. The runoff from the outcrop therefore probably is very flashy. UNCONSOLIDATED SEDIMENTS OF GLACIAL ORIGIN * Continental glaciers covered all the northern part of the Dela¬ ware River basin at least three, and. possibly four times during the last million years. The last ice sheet--that of the Wisconsin gla¬ cial stage (table 1)--retreated from the region about 10,000 years ago (Flint 1957) . The Wisconsin ice sheet and its predecessors-- those of the Illinoian and Kansan stages (pi. 14) --removed the soil and loose weathered material, quarried and scraped the underlying fresh rock, modified the pre-existing drainage pattern, deepened some of the stream valleys and filled others with deposits, and left a mantle of unsorted deposits as till or ground moraine over most of the area. Ridges composed of unsorted debris were deposited at the margins of the ice as terminal and recessional moraines, and lateral moraines accumulated along the margins of some of the ice tongues in the valleys. Glacial outwash and other stratified deposits were laid down in the valleys along the margins of the ice masses by melt water streams, and fine-grained sediments were deposited in lakes and marshes. Southward-flowing meltwater streams deposited outwash in the major valley far south of the ice margin. On the basis of their hydrologic properties the glacial sedi¬ ments of the basin are herein divided into two main categories, unstratified glacial sediments and stratified glacial sediments, which are described briefly in the sections following. Unstratified Sediments The unstratified sediments, which were deposited directly by the ice, consist of unsorted materials ranging from clay to boulders and having relatively low permeability. The most extensive of these deposits is till, which blankets perhaps 90 percent of the glaciated Larea. Other unstratified sediments are the morainal deposits of var¬ ious types, which differ from the till chiefly in their greater thick¬ ness and their distinctive landforra expression as curved or sinuous ridges, and their somewhat greater content of permeable bodies of sand and gravel. The oldest glacial deposits--those of Kansan 1 / age--consist largely of scattered boulders south of the Illinoian border (pi. 14). Scattered thin deposits of Illinoian age occur south of the Wisconsin border, but only a few of the thicker masses, such as the terminal morains near Allentown, Pa., are shown as early glacial drift on the geologic map (pi. 14). North of the Wisconsin border the till and moraines are almost entirely of the Wisconsin glacial age; the earlier deposits of Kansan and Illinoian age were largely worked by the Wis¬ consin ice and incorporated into the younger deposits. The till consists of an unsorted mixture of particles ranging in size from clay to boulders many feet in diameter. The character of the materials varies from place to place, depending on the nature of the parent rocks. Sand and gravel are abundant where the materials are derived largely from sandstone but clay predominates where the parent rocks are mostly shale. Limestone is not an abundant consti¬ tuent of till at most places in the Delaware River basin. In the broad upland areas the till generally is less than 30 feet thick, but in buried valleys the thickness is greater; Fluhr (1953) reported a thickness of as much as 350 feet in Delaware County, N. Y. In many of the present stream valleys fairly thick masses of till are interbedded with glacial outwash (pi. 15). The overall permeability of till is very low, owing to the usual moderate to large content of clay and silt, and the fact that smaller particles commonly fill spaces between larger ones. Direct runoff from most till-covered areas is large because of the low infiltration capacity of the materials. At many places till forms an aquiclude confining water in permeable outwash deposits, with which it is inter¬ bedded, or in the underlying bedrock. Much till in the upland area contains bodies of perched water laying above zones rich in clay or dense, relatively impermeable bedrock. L/ Deposits of Kansan age are sometimes referred to locally as Jerseyan drift. 92 . Yields of most wells in till are only a few gallons per minute. Rates of inflow into the wells commonly are even less, so that dug wells having large storage capacity are used. Such wells can be pumped for short periods at considerably greater rates than they could be pumped continuously. Most dug wells extend only a short distance below the water-table and depend on frequent precipitation for rechargeo Seasonal water-table fluctuations in till may be large (pi. 16), and many wells are reported to go dry after several weeks, others require months of drought. The moraines are believed to be similar to the till in hydrologic characteristics, except that they are thicker than most of the up¬ land till, and probably are more reliable as sources of perennial water supplies. The older morainal deposits south of the Wisconsin border, (pi. 14) such as those in the vicinity of Allentown, Pa., are generally more highly weathered and less permeable than the moraines of Wisconsin age. Stratified Sediments In the Appalachian Highlands the stratified sediments were de¬ posited: (1) in the open valley bottoms by meltwater streams as glacial outwash; (2) in depressions on the ice as kames; (3) in long, sinuous ridges beneath the ice as eskers; (4) along the val¬ ley sides at the margines of the ice tongues as kame terraces; and (5) in glacial lakes and marshes as deltaic, marsh, and lake- bottom deposits. Alluvium of postglacial (Recent) age occurs as thin stream and marsh deposits which are difficult to distinguish from the underlying deposits of Pleistocene age. Although these deposits are as heterogeneous as the till and morainal deposits, they differ in having definite bedding as a re¬ sult of being sorted by water. The most evenly bedded, and also the most fine-grained, sediments are the lenses and layers of clay, silt, and fine sand that were deposited in lakes and marshes dammed either by the ice or by moraines and rock walls beyond the ice mar¬ gin. Such deposits are most widespread in the area of the ancient Lake Passaic in northern New Jersey, near the cities of Morristown and Madison (pi. 14);smaller masses of similar deposits occur at many other localities. Outwash is fairly well bedded, but the in¬ dividual beds are exceedingly lenticular. The ice-contact deposits-- those in kames, kame terraces, and eskers--commonly are chaotically or crudely bedded (pi. 2) and locally contain bodies of till de¬ rived from the adjacent ice. The outwash, which is the most abundant and important of the stratified sediments, forms elongate masses partly filling the pre¬ glacial stream valleys. Tongues of outwash extend along the major U.S.GEOLOGICAL SURVEY PLATE 15 NW SE A 1 EXPLANATION Outwosh and alluvium (Sand, gravel,and some silt) Till and lake deposits (Boulders, sand, silt,and cloy) r- v' v A < f' , A V a <. A •>» -l -J A v r Consolidated bedrock Well or test boring IOOO 2000 —i-1-1 i i i 3000 Fe Horizontal scale Sections C-C', D-D 1 , E-E', ond F-F* modified otter T. W. Fluhr, Senior Geologist, New York City Board of Water Supply,1953. Sections G~G' ond H~H' modified after data fro U.S. Corps of Engineers, 1957 Locations of cross-sections shown on plate 30 GEOLOGIC CROSS SECTIONS OF MAJOR STREAM VALLEYS IN NORTHERN PART OF DELAWARE RIVER BASIN , valleys far beyond the borders of the glaciated areas into the Coastal Plain province. The Cape May formation in the Coastal Plain may be in part equivalent to the outvash of Wisconsin age, and the Pensauken and Bridgeton formations may be in part equivalent to the older outvash. . .Cross sections of the outvash in the Appalachian Highlands (pi. 15) are /pically U—shaped in basal outline as a result of quarrying and scour of the bedrock by the ice that occupied the valleys before the outvash vas deposited. At many places the locations of the pres¬ ent streams do not coincide vith the centers of the old valleys cut in the bedrock surface, and ridges of bedrock extend to the land surface at numerous places in the present valleys. The outvash 1 generally ranges in thickness from about 50 to 200 feet, although locally it is thicker. Stratified deposits as much as 500 feet thick occur, however; such thick deposits generally fonn kame ter¬ races along valley margins and only the lover part is saturated. Water occurs in the stratified glacial sediments under uncon¬ fined to semiconfined or confined conditions. Under natural con¬ ditions the deposits are recharged largely by infiltration of precipitation on their outcrop; the outvash in the valleys also receives some recharge from adjacent and underlying bedrock and from till along the valley sides. Under conditions of development, vhere the normal hydraulic gradients tovard streams and lakes are reversed by pumping, recharge may be induced from surface-water bodies and these may also include leakage from septic tanks, cess¬ pools^ and from sevrers or other underground pipes. Most natural discharge of ground-vater is into streams and lakes and into the atmosphere as evapotranspiration. Artificial discharge is chiefly through pumped veils; although leaky severs below the water table naay drain away some water in places, they may yield water in other places where the head in the sever is above the water table. Some of the .coarser and thicker deposits of outvash constitute Jthe most productive aquifers in the entire Delaware River basin area, although in some localities where silt and clay predominate, yields of wells are disappointingly; low. Reported yields of 55 vails tapping outvash in the basin range from 2 to pOO gpm. ■median yield of 28 large-diameter drilled wells used for industrial or public supply is 215 gpm. Sustained-yields of as jnuch as several thousand gallons per minute doubtlesss could be obtained largely from induced recharge to deposits of cparse-grained sand and gravel that are hydraulically connected vith perennial streams. The ad- ' vantages and disadvantages of pumping from wells versus pumping or diverting the water directly from the stream would, :of course, have to be appraised locally. As often as not the quality and tempera¬ ture of the water would be as important as the quantity. 9 ^. RECHARGE AMD DISCHARGE The aquifers of the Appalachian Highlands are recharged largely by infiltration of precipitation on their outcrops or on the over- lying blanket of glacial sediments. Seepage from the headwater reaches of some streams probably contributes a small amount of ad¬ ditional recharge, and some of the aquifers in the valleys are re¬ charged in part from the adjacent ridges. The infiltration capacity of the outcrops is a function of several variable factors, among which are the permeability of the soil and underlying weathered rock and the topography. The infil¬ tration capacity ranges from very high in the sandy and gravelly glacial outwash to low in the thin, poorly permeable soils on the shale of Triassic age and in the outcrops of dense, massive rocks. The average rate of natural recharge to the aquifers of the Appa¬ lachian Highlands ranges more widely and is more difficult to esti¬ mate than the recharge to the aquifers of the Coastal Plain. However, the average recharge in the Highlands may be estimated very approxi¬ mately by comparison with a nearby area of similar climatic, hydro¬ logic, and geologic conditions where a detailed water budget was worked out—the basin of the Pomperaug River, Conn., reported by MeInzer and Stearns (1929). „ The Pomperaug River basin, an area of 89 square miles in west- central Connecticut, is underlain largely by crystalline rocks except for the south-central part, which is underlain by diabase and sedimentary rocks of Triassic age; these consolidated rocks are covered by a discontinuous mantle of glacial deposit* (Meinzer and Stearns, 1929 , P* 76 - 77 )• Water budgets for the Pomperaug River basin and the Appalachian Highlands part of the Delaware River basin are compared In table 8. The data from the Pomperaug River basin have been modified slightly to allow for change in storage during the budget period, 1913-16. 95 . Table 8.-- Water budgets for Pomperaug River basin. Conn,, and Appalachian Highlands part of Delaware River basin Item Pomperaug River basin 1/ Mgd. per Sq.Mi. Percent of precipita- t ion Percent of Runoff Appalachian Highlands in Delaware R. basin Mgd. per .Mi Percent of precipita- t ion Precipitation Water loss Runoff Direct runoff Base flow (ground- water runoff) 2.12 1.132/ .98 .55 2/ .43 2/ 100 53 2/ 47 26 2/ 21 2 / 100 56 2/ 44 2/ 2.10 1.04 1.07 100 49 51 Ground-water recharge .74 .35 1/ Data modified from Meinzer and Stearns (1929) -J Figures adjusted to allow for change in storage during budget period. The similarity of the values of precipitation, water loss, and runoff in the two areas is at once apparent. Streamflow data for the Delaware River basin are not sufficiently detailed to permit estimates of direct and base, or ground-water, runoff. However, the value of 44 percent for the base-flow portion of total runoff determined in the Pomperaug River basin study is believed to be somewhat lower than the average value in the Appalachian Highlands of the Delaware River basin. The Pomperaug basin is entirely glaciated and has relatively thin soils of low permeability, whereas only the northern part of the Highlands in the Delaware River basin is glaciated, and in the southern part many of the soils and zones of weathered rock are relatively thick and per¬ meable. Likewise, the value of about 3/4 mgd per square mile for ground- water recharge in the Pomperaug River basin probably is somewhat lower than the average for the Highlands in the Delaware River basin; in any case, an estimated average rate of recharge of 3/4 mgd per square mile for the highlands appears to be conservative. A similar¬ ly conservative estimate for the recharge to the aquifers of the Coastal Plain, which generally have more permeable intake areas than those of the consolidated-rock aquifers, gave a value of 1.1 mgd square mile (p. 37-39). 96 % Because of the relatively low productivity and small storage capac¬ ity of most of the aquifers, and also because of many practical limita¬ tions, chiefly economic, only a small part of the ground-water discharge at natural outlets in, the Appalachian Highlands ban be diverted for man s use. However, pumpage substantially in excess of the 1955 rate of 130 mgd doubtless could be maintained with increased ground-water develop¬ ment, especially in the glacial outwash deposits in the major valleys, where induced recharge from streams is a significant factor. The estimated recharge rate of 3 A mgd per square mile is, of course, an average for the entire Appalachian Highlands; rather large variations from the average are to be ejected. Data developed by the U. S. Geolog¬ ical Survey and the U. S. Weather Bureau indicate that precipitation in the area ranges from about k 2 to 60 inches per year <2.0 - 2.9 mgd per sq mi); water loss ranges from about IT to more than 28 inches per year (0.8 - 1.3 mgd per sq mi); and runoff ranges from 15 to about' b 2 inches per year (0.7 - 2.0 mgd per sq mi). The area of the Appalachian Highlands in the Delaware River basin is about 9,700 square miles; thus, at an average rate of 3A mgd. per square mile, the total ground-water recharge or discharge averages about 7^300 mgd. Most of this water moves relatively short distances through the weathered and fractured rocks within a few hundred feet of the land sur¬ face to discharge outlets in stream channels, springs, seeps, lakes, ponds, marshes, and low-lying areas where the saturated zone is suffic¬ iently near the land surface to allow discharge by evapotranspiration. As in the Coastal Plain, the potential ground-water supply is assumed to equal the ground-water discharge to streams--an estimated 4,400 ± 500 mgd However, because of the low permeability and small storage capacity of most of the hard-rock aquifers, and also because of other practical lim¬ itations, chiefly economic, the writers believe that only a small fractioi of the potential supply can be developed feasibly and that development of surface supplies will continue to be dominant in the Highlands. However, large ground-water supplies may be developed locally, as in the glacial outwash along major streams in the glaciated part of the region. Discharge through pumped wells is only a small fraction of the total ground-water discharge; about 130 mgd is being withdrawn at present. This discharge does not include pumpage from mines and quarries, whose unknown total may equal or exceed all withdrawals from wells for direct u 97 . GROUND-WATER STORAGE T e aquifers in the Appalachian Highlands range -widely in their capacity to store water. As ground-water reservoirs, the deposits of glacial outwash in the major stream valleys compare favorably with the coarsest-grained aquifers in the Coastal Plain, whereas most of the consolidated-rock aquifers, which make up the bulk of the water-bearing materials m the Highlands, have relatively little storage capacity. In the outwash, some of the beds of gravel and sand probably have specific yields exceeding 30 percent. However, in consolidated-rock aquifers specific yields of more than 2 percent probably are uncommon, except in the upper part of the weathered zone. In most consolidated rocks the specific yield decreases markedly with depth, and most of the usable storage capacity is in the weathered and highly fractured material near the land surface. Therefore, although the storage capac lty of the consolidated rocks is much less than that of the unconsoli¬ dated sediments, the storage in some of the shallow, weathered and fractured rocks that provides the base, or fair-weather, flow of streams is comparable to that in many of the unconsolidated sediments. Lack of adequate.storage capacity is most likely to be an import¬ ant limiting factor in ground-water development in moderately perme¬ able aquifers having relatively low specific yields, such as the aqui fers in the Brunswick formation of Triassic age. 98 . Some of the larger masses of glacial outwash store considerable volumes of water. One of the largest masses is that along the Delaware River from below Milford, Pa., to Port Jervis, N. Y„, thence along the Neversink River and Basher Kill to Summitville, N. Y. From Milford to Summitville the length of the outwash body is 28 miles, its width averages a little less than a mile, and its aver¬ age thickness is between 100 and 150 feet. The total volume of the saturated materials, then, is estimated to be 150,000 feet x 5>000 feet x 100 feet = 75 billion cubic feet. If the specific yield of the outwash is estimated conservatively to be 15 percent, its stor¬ age capacity is about 11 billion cubic feet, oi* about 80 billion gallons. Only by diverting all or nearly all the streamflow from the valley during periods of pumping could a sizable portion of this ground-water storage capacity be used, however. So long as the streamflow is sufficient to supply, by induced recharge, a large part of the water pumped by wells in the valley, the greater part of the outwash will remain saturated. The character of fluctuations in ground-water storage in glacial deposits is shown in the hydrographs of three unused shallow wells' . (pi. 16). The fluctuations in all three wells are believed to be entirely the result of changing rates of.natural recharge and dis¬ charge. The peak water levels in the spring reflect high rates of recharge from rain and melting snow; the low water levels in the summer and autumn result from high evapotranspiration losses and hence lack of infiltration to the ground-water body. The average yearly water-table fluctuations in the three wells are from about 5 to 10 feet; because of the lack of specific-yield data for the materials penetrated by the wells, the changes in ground-water storage indicated by the fluctuations are not known. CHEMICAL CHARACTER OF GROUND-WATER SUPPLIES The formations of the Appalachian Highlands yield wa,ter with a wide variety of chemical characteristics. The concentrations of dis¬ solved solids in ihdividual samples analyzed ranged from 11 to 1,500 parts per million, and hardness from b- to 660 ppm ; measured as CaCO^. The pH of individual s^rapl^s ranged, from k.k to 8.9. . The fonnations of the Appalachian Highlands that contain water of highest quality are the glacial outwash in the New York part of the Ipasin, the Cats- kill formation in northeastern Pennsylvania, and the Wissahickon formation in southeastern Pennsylvania. A few representative chem¬ ical analyses of ground water are given in tables 9 and 10. ujnjop ftOOjjnt.puOf *0|§q jaaj ui'ioa^i j»|Om . 99 . Unconsolidated Sediments of Glacial Origin Water from glacial deposits in the Delaware River basin -ic c ^ o moderately hard and in general is not highly minimized L Shanow^U ^ U T Uy l0 “ tUt ln SOme P 1 “es : is object“nabl^high b hallow wells may be contaminated from surface som-r^c uu Y 8 ’ lndu r rechar ^ f-m adjLe^r^reLr: c P oT' the water ^“sL^Jy^r^ter^lUylharth^^^ 6 8tre “ 8 ' Rima fnrith . ^ rity than the native ground water Kima (written communication, 1957) has toil if r - 24 analvcpc nf not- c , /ns prepared table 11 summarizing part of the n , the valley £iU deposits in the central part of the Delaware River basin Tn hauin ii . i balanced V analyses^ ee Water e from 0 the"valle^fil^general ly 11 ^ “^“' Uy acid. A few samples had excessive concentrations of iron and had very high concentrations of nitrate and chloride l d to contamination from barnyards or cesspools ’ PerhaPS ° Wlng Source and description of samples referred to by number in table 9- Unconsolidated sediments of Appalachian Highlands 1. Near Pocono Lake Preserve, Monroe County, Pa., Pocono Lake Calculated ln8S * S ° dlUm pluS P o£as sium and dissolved solids Newfoundland, Wayne County, Pa., Dairymen's League well- Sodium pius potassium and dissolved solids calculated. Port Jervis, Orange County, N.Y., Diamond Dairy well- nalysis by New York State Department of Health Narrowsburg, Sullivan County, N.Y., Narrowsburg Water Department well; analysis by New York State Department of HealtfC Hancock, Delaware County, N. Y., Hancock Water Co. well- nalysis by New York State Department of Health. °?6? ware County> N - Y - McIntosh Slau * hcer *»>“ Source and description of samples referred to by number in table 10: Martinsburg shale L. Near Newside, Lehigh County, Pa., P. J. Cerman well. Near Laurys, Lehigh County, Pa., H. Moyer well Catskill formation '• „ ear Clamtown, Schuylkill County, Pa., K. Shellhamer well- color 3 • Honesdale, Wayne County, Pa., Dairymen's League well. 2 . 6 . 100. Source and description of samples referred to by number in table 10 Continued Lockatong formation 5. Plumstead Township, Bucks County, Pa., Camp Ockanickon, Boy Scouts of America well; color 3. 6 Lower Makefield Township, Bucks County, Pa., G. K. Balderston - H. R. Bradley well; color 1 Stockton formation 7. Phoenixville, Chester County, Pa. Phoenix Iron and Steel Co. well; color 2. 8. Norristown, Montgomery County, Pa., Handway and Gordon Dairy well; color 2. 9. Doylestown, Bucks County, Pa., Doylestown Borough well 8, color 2 10. Doylestown, Bucks County, Pa. Doylestown Ice Co. well 2, color 3 11. Newton, Bucks County, Pa., Newtown Artesian Water Co. well 3; color^3 12. Trenton, Mercer County, N, J. color 4. 13 0 Skippack, Montgomery County, Pa., Walter Dinse well; color 3. 14 o Near Quakertown, Bucks County, Pa., Quakertown Borough well 9; color 3 15. Near Perkasie, Bucks County, Pa. Perkasie Water Supply Co. well 5, color 3 16. New Hope, Bucks County, Pa., Universal Paper Bag Co., well; color 3 New Jersey State Hospital well 8; Carbonate rocks 18. Near Lancaster, Lancaster County, Pa., J. P. Brenneman well; Conestoga limestone 19. Buckingham, Bucks County, Pa., General Greene Inn well; Conococheague limestone 20. Near Colesville, Lehigh County, Pa., R. C. Eveland well; Beekmantown group. 21. Center Valley, Lehigh County, Pa. M. DeFiore well; Tomstown dolomite. 22. Near Fogelsville, Lehigh County, Pa., Lehigh Portland Cement Co. well; Jacksonburg limestone Diabase 23. Green Lane, Montgomery County, Pa., Montgomery County Park well; color 4 24. Near Sellersville, Bucks County, Pa., Sellersville Borough well 1; color 3 25. Milford Square, Bucks County, Pa., Milford Square Pants Co. well; color 2 101 . Source and description of samples referred to by number in table 10-- Continued Gneiss 26. Near Kennett Square, Chester County, Pa., E. Fahey well; Baltimore gneiss. 27. Lanhorne Manor, Bucks County, Pa., Langhorne Spring Water Co. well 2; color 3, Baltimore gneiss 28. Near Yardley, Bucks County, Pa., Yardley Water and Power Co. well 5; Baltimore gneiss, color 2 29. Near Shimersville, Lehigh County, Pa., Kings Highway Elementary School well; Byram granite gneiss 30. Near Center Valley, Lehigh County, Pa., K. A. Beers well; Pochuck gabbro gneiss. Chickies quartzite 31o Elverson, Chester County, Pa. Dolfinger Creamery well. 32. Langhorne Manor, Bucks County, Pa., Langhorne Spring Water Co. well 4; color 3 Wissahickon formation 33. Centerville, New Castle County, Del., Winterthur Farm well. 34 0 Lincoln University, Chester County, Pa., Lincoln University well. 35. Brandywine Summit, Delaware County, Pa., W. C. Walton well. 36. Hulmeville, Bucks County, Pa., O.K.O. Plush Co. well; color 3 37. Eddington, Bucks County, Pa., Publicker Industries well. 88197 0-62-9 (Vol. VII) 102 . Table 11.--Summary of chemical analyses of 24 samples of ground water from valley fill. (Parts per million) Maximum Average Minimum Silica (SiC> 2 ) 20 . 11 . 5.1 Iron (Fe) 7.2 1.3 .01 Calcium (Ca) 57. 22 . 4.1 Magnesium (Mg) 43. 13. 3.4 SodiumfPotassium (Na + K)(5 analyses) 7.0 4.3 1.2 Sodium (Na)(19 analyses) 76. 16. 3.1 Potassium (K)(19 analyses) 12 . 3.1 .9 Bicarbonate (HCO 3 ) 123. 38. 7.0 Sulfate (SO 4 ) 189. 50. 4.9 Chloride (Cl) 122 . 17. 3.0 Fluoride (F) .4 .2 .1 Nitrate (NO 3 ) 107. 18. .5 Dissolved solids 716. 202 . 63. Hardness as CaCO^ 319. 92. 18. Non-carbonate hardness as CaCOo 276. 62. 12 . Specific conductance (microhms at 25 C) 1,090 267. 82. pH 6.7 - 5.2 Temperature (°F) 60. 55. 47. Glacial outwash in the northern part of the basin contains water of much better quality than that of the valley fill. More than half the samples were soft and the remainder moderately hard. Iron is present locally, unpredictably distributed in the aquifers, but con¬ centration is not excessive in most of the samples. Table 12, sum¬ marizing analyses of water from glacial outwash in the northern part of the basin, was prepared from data furnished by N. M. Perlmutter and E. H. Salvas (written communication, 1957). Water from the glacial outwash in the northern part of the basin is less mineralized and softer than water in the valley fill .of the central part of the basin. So also is the quality of the stream water in the northern part of the basin better than that in the central part. 103 . Table 12.-- Summary of chemical analyses of ground water from glacial outwash (Parts per million) Maximum Median Minimum Number of Sflmnl 0 c Iron (Fe) 4.5 0.19 0.03 20 Manganese (Mn) .28 .01 .01 12 Bicarbonate (HCOo) 117 33.5 15 1 ft Sulfate (SO^) 27 9.3 4 -L O 11 Chloride (Cl) 20 4.4 .4 1 9 Nitrate (NO ) 2.0 1.4 . 1 A Dissolved solids 145 94 33 H 13 Hardness as CaCO 124 50.5 22 20 pH 3 7.9 6.8 5.8 19 Clastic Rocks Of the clastic formations in the Delaware River basin the Catskill, Stockton, and Brunswick are best known for the generally good quality of water yielded, and of these three, the best water i is obtained from the Catskill formation. Its water is uniformly as good as, or better than, that obtained from the glacial outwash or . rom the crystalline rocks. Only a limited number of analyses are are available for the remaining clastic aquifers, but from the available analyses it appears that the shale of the Mauch Chunk formation generally yields water that is soft and not highly miner¬ alized. The Martinsburg shale, the Bloomsburg red beds, and the I Middle and Upper Devonian marine beds contain water that is not highly mineralized but that ranges from soft to moderately hard. iThe waters of the Allegheny and Conemaugh formations are commonly polluted with acid mine drainage and even at some distance from |mines have large concentrations of iron and sulfate resulting from the oxidation of pyrite. In 5 samples of water, for example, the iron concentration ranged from 2.0 to 0.8 ppm. The chemical char¬ acter of the water contained in the Lockatong formation appears to be about the same as that in the Stockton and Brunswick formations. Martinsburg Shale I Wat er from the Martinsburg shale is soft to moderately hard, - e hardness being mostly of the noncarbonate type. A summary of - e analyses of water from 9 wells and springs in Lehigh County, Pa., is presented in table 13 (Rima, D. R., written communication, 1957) ind two representative analyses are given in table 10 . Table 13 .— Summary of chemical analyses of 9 samples of ground water from the Martinsburg shale /Parts per million/ Maximum Minimum Sodium + potassium (Na + K) 5-3 0.9 Bicarbonate (HCO3) 62 16 Sulfate (S 04 ) 6 l 8.3 Uhloride (Cl) 10 5.0 Nitrate (NO3) 33 7.8 Hardness as CaC03 124 43 Non-carbonate hardness, as CaC 03 89 29 Specific conductance (micromhos at 25 °C) 320 121 Temperature (°F) 55 51 pH 7.7 6.3 Catskill Formation The Catskill formation yields water of excellent quality, which is used for domestic, industrial and municipal supplies, generally without treatment. The water ranges from very soft to moderately hard and is commonly low in iron. A few deep wells in Wayne County give water containing small quantities of hydrogen sulfide. Table l 4 , prepared by D. R. Rima (written communication 1957 )> summarizes 18 chemical analyses of ground water from the Catskill formation; additionally two representative analyses are given in table 10.■ 105 . Table 14.--Summary of chemical analyses of 18 samples of ground water from the Catskill formation (Parts per million) —-- : - -- --- Maximum Average Minimum Silica (Si0 2 ) 13 7.3 4.0 Calcium (Ca) 28 11.2 2.0 Magnesium (Mg) 7.2 3.5 1 0 Sodium (Na) 20 6.7 1.0 Potassium (K) 2.4 1.4 .5 Bicarbonate (HC0„) 117 51.2 8 0 Sulfate (SO^) 23 6.4 1 0 Chloride (Cl) 22 5.0 1 0 Nitrate (N03) 6.0 2.4 .1 Dissolved solids 176 74 22 Hardness as CaCO^ 97 44 9.0 Non-carbonate hardness, as CaCO 22 9.0 1 0 Specific conductance (micromhos at 25°C) 100 60 34 pH 7.4 6.2 Temperature (°F) 57 50 48 Stockton Formation Water from the Stockton formation varies widely in its chemical characteristics. The water commonly has low to moderate concentra¬ tions of dissolved solids, generally less than 400 ppm. In the more highly mineralized samples sulfate constitutes a large proportion of the anions. This probably results from leaching local deposits of glauberite, a mineral with the chemical formula Na 2 S0/CaS0,. Most of the samples tested range from moderately hard to hard. The very hard waters have a relatively large proportion of noncarbonate hardness; rarely is the concentration of iron objectionable. Table 15 compiled by D. R. Rima (written communication, 1957) summarizes a group of chemical analyses of ground water from the Stockton forma¬ tion; six additional analyses regarded as typical are also given in table 10. I 06 o Table Ip. — Summary of chemical analyses of ^4 samples of ground water from the Stockton formation /Parts per million/ Maximum Average Minimum Silica(Si02) 33 22 8.4 Iron (Fe) 2.3 •3 .04 Calcium (Ca) 233 4 l 2.5 Magnesium (Mg) 27 12 1.6 Sodium + potassium (Na + K) (42 analyses) 46 18 .7 Sodium (Na) (12 analyses) 37 16 8.1 Potassium (K) (12 analyses) 3-5 1.6 • 5 Bicarbonate (HCO3) 258 no 7.0 Sulfate (SO^) 603 82 9.4 Chloride (Cl) 54 12 1.2 Fluoride (F) 1.1 .1 .1 Nitrate (NO3) 48 11 .4 Dissolved solids l, 04 o 261 45 Hardness as CaC03 660 161 18 Non-carbonate hardness as CaC03 562 8q 4 Specific conductance (micromhos at 25 °C) 1,230 385 69 pH 8.5 — 6.0 Temperature (°F) 58 56 53 Brunswick Formation The Brunswick formation produces water that is moderately miner¬ alized and may range from soft to very hard. In samples the hardness is mostly of the non-carbonate type. The water is suitable for do¬ mestic, industrial and municipal use although softening or treatment to remove iron is often required. Water from the Brunswick formation was alkaline (‘pH 7*1 to 8.9) in all 23 samples, perhaps because of the calcareous sandstone and conglomerate associated with this aquifer. Table 16 was prepared by D. R. Rima (written communication, 1957 ) to summarize a number of .chemical analyses of ground water in the Brunswick formation; also, four typical analyses are given in table 10 .. 107. Table 16.--Summary of chemic al analyses of 23 samples of ground water from the Brunswick formation (Parts per million) Silica (S10 2 ) Iron (Fe) Calcium (Ca) Magnesium (Mg) Sodium + potassium (Na + K )(6 analyses) Sodium (Na )(11 analyses) ! Potassium (K )(11 analyses) Bicarbonate (HCCL) Sulfate (SO^) Chloride (Cl) Fluoride (F) Nitrate (NO 3 ) Dissolved solids Hardness as CaCO^ Non-carbonate hardness as CaC 03 Specific conductance (microhms at 25°C) \ PH Temperature (°F) Maximum 25 1.8 190 112 14 76 1.8 242 144 22 .4 21 386 284 158 594 8.9 56 Average 19 67 32 4.9 18 1.0 134 61 8.3 .2 7.2 297 171 54 406 53 Minimum 10 .03 15 3.8 .6 2 .2 26 7.0 1.0 .1 .4 217 46 10 172 7.1 51 Carbonate Rocks Rainwater containing dissolved carbon dioxide is slightly acid and an excellent solvent for limestone and other carbonate rocks. Consequently the ground water from the limestone formations in the Delaware River basin characteristically is moderately mineralized and hard. The chief mineral constituents are calcium and magnesium bicarbonates. Ground water from carbonate rocks in the Delaware River basin usually is slightly alkaline, low in iron, and of excel- ent quality except for its hardness. Table 17 summarizes 60 analyses of water from carbonate rocks in Pennsylvania. These include many of the 41 analyses for southeastern Pennsylvania discussed by Hall (1934, p. 42) and lead to much the same conclusions. Hall found also that only I of his 41 samples contained more than 1 ppm of iron and more than half contained less than 0.1 ppm of iron. Additional information is presented in table 10 giving analyses from 6 samples regarded as typical. 108 . The ratio of calcium to magnesium in water from the Conestoga limestone is significantly greater than in waters from the Conoco- cheague, Cockeysville, and other limestone formations. Water from the Cockeysville marble (4 samples) appears to be less mineralized than water from other limestone formations. Table 17.-- Summary of chemical analyses of 60 sampl es of ground water from carbonate rocks (Parts per million) Maximum Medium Average Minimum Number of Analyses Silica (SiO^) 33 13 13 4.7 53 Calcium (CA) 107 57 56 5.6 34 Magnesium (Mg) 52 18 20 2.4 35 Sodium+Potassium (Na+K) 29 6.0 8.2 . 9 30 Sodium (Na) 38 5.7 7.8 1.3 24 Potassium (K) 7.7 1.9 2.5 . 6 24 Bicarbonate (HC0„) 388 186 194 41 56 Sulfate (SO 4 ) 120 26 35 2.3 61 Chloride (Cl) 58 7.5 13 1.0 58 Nitrate (NO 3 ) 73 12 16 .0 60 Dissolved solids 609 245 280 75 35 Hardness as CaC0 3 508 201 208 24 56 Specific conductance (microhms at 25°C) 633 356 369 138 27 pH 8.3 7.6 6.0 28 Crystalline Rocks The crystalline rocks of Precambrian and early Paleozoic age in the Delaware River basin yield excellent water that is low in dis¬ solved solids and hardness. See table 10 for typical sample analyses. With the exception of iron, which is locally present in excessive con¬ centrations (more than 3 ppm in some samples), the water contains no objectionable mineral impurities. Water samples from 4 wells in diabase, all near Quakertown, Pa., had from 66 to 398 ppm of dissolved solids, 32 to 272 ppm of hardness as CaC0 3 , and 0.18 to 1.4 ppm of total iron. These are calcium and magnesium bicarbonate waters. ~ SfJf le T S ° f ^ ater /i°m 4 wells and 1 s Pring in gneiss, in Bucks, elaware, Lehigh, and Northampton Counties, Pa., had from 51 to 26l ppm of dissolved solids, 13 to 174 ppm of hardness as CaCOo,‘and 0.03 to 0.74 ppm of iron. The samples with large concentrations of dissolved solids have large concentrations of nitrate or chlor¬ ide also. This is probably indicative of contamination from barn¬ yards or cesspools /Parts per million/ Silica (Si 02 ) Iron (Fe) Calcium (Ca) Vlagnesium (Mg) Sodium (Na) Potassium (k), Bicarbonate (HCO 3 ) Sulfate (S 04 ) hloride (Cl) Pluoride (F) Nitrate (NO^) Dissolved solids Hardness as CaCC >3 Non-carbonate hardness as CaCC >3 Specific conductance (micromhos at 25°C) pH ' Temperature (°F) Maximum Average Minimum 35 18 8.7 3-4 .67 .02 22 12 2.9 9.9 5.3 1.3 21 8.6 2.2 4.4 2.2 .4 106 35 8.0 -f 48 20 • 3 4o 10 1.0 .2 .1 0 34 12 .3 246 118 51 108 55 13 71 27 0 384 167 64 7.9 — 5.2 58 54 52 Wissahickon Formation Good water is obtained from the Wissahickon formation in Penn¬ sylvania and Delaware. The water is not highly mineralized, unless contaminated; 10 or 12 samples contained less than 100 ppm of dis- S un d J SOlidS ' ^ water is soft or onl y moderately hard, with low c onde concentration. Three samples from Delaware County, Pa. , and 1 from Bucks County, Pa., contained excessive concentrations of iron, but 7 of the 12 samples contained less than 0.3 ppm of iron. The harder waters generally have the higher concentrations of sulfate. According to Hall (1934, p. 27) excessive hardness is sometimes due to pegmatite dikes which contain large percentages lime-soda feldspar.. On the whole, however, the water contained 110 . in the Wissahickon formation is uniformly of good quality. Springs in the Wissahickon formation on occasion become polluted, as in the fall of 1957 when (Philadelphia Inquirer, 10/10/57) 75 springs issu¬ ing from the Wissahickon formation in Fairmount Park, Philadelphia, Pa,, were posted (closed for use). Pollution of these springs in a highly residential neighborhood probably stems largely from leaky sewers. In table 19 are summarized 16 analyses of water from the Wissahickon formation, and in table 10 are 6 analyses that are re¬ garded as representative of the formation. Table 19, - Summary of chemical analyses of 16 samples of ground water from the Wissahickon formation /Parts per million/ Maximum Median Average Minimum Number of samples Silica (Si02) 36 20 20 7.3 12 Iron (Fe) 8.7 .22 1.8 .04 12 Calcium (Ca) 14 6.1 7.9 3.4 12 Magnesium (Mg) 8.3 3 0 6 3.9 1.7 12 Sodium (Na) 8.3 5.6 5.1 2.8 11 Potassium (K) 2.8 1.6 1.6 .7 11 Bicarbonate (HCO 3 ) 70 31 35 8.5 16 Sulfate (SO 4 ) 60 10 19 2.7 16 Chloride (Cl) 16 5.3 5.6 1.8 16 Nitrate (NO 3 ) 34 6 . 6 8.7 .3 12 Dissolved solids 154 73 80 40 12 Hardness as CaC 03 102 44 47 17 15 pH 6.9 6.3 -- 5.9 7 IN THE SERVICE AREA OUTSIDE THE BASIN FAIRFIELD COUNTY, CONNECTICUT by R. V. Cushman Introduc tion Fairfield County occupies an area of about 633 square miles in southwestern Connecticut that is bounded chiefly by Long Island Sound, the Housatonic River and the New York State border (pi. 17) The estimated 1957 population of 597,900 for the county is largely U. S. GEOLOGICAL SURVEY PLATE 17 . 111 . urban and suburban and is engaged in industrial and commercial activities. Bridgeport, Stamford, Danbury, and Norwalk are the largest cities. The increasing demands for water by the growing population and expanding industry of Fairfield County are respon¬ sible f6r its being placed within the service area of the Delaware River basin. It is estimated in a report of the Connecticut fater Resources Commission (1957) that the county will have a demand for 152.2 million gallons of water daily by the year 2000. Principal sources of published information on the water re¬ sources, especially on the ground water of Fairfield County, are given by Gregory and Ellis (1916); Palmer (1920); Leggette and others (1938); Rodgers, Gate, Cameron and Ross (1956); New England- New York Interagency Commission (195*0; and Connecticut Water Re¬ sources Commission (.1957). Considerable unpublished information is available from the U. S. Geological Survey and the Connecticut Geological and Natural History Survey. Physical Features The surface of Fairfield County is generally a low rolling plain sloping gradually southward to Long Island Sound. iThe ter¬ rain is typically flat within a narrow coastal strip along Long Island Sound but is rolling and deeply dissected; by major streams for the remaining area. The northeastern third of the county is within the drainage basin of the Housatonic River. Most of the remainder of the county is drained by coastal streams of which the most important are the Byram, Mianus, Norwalk, Pequonnock, and Saugatuck Rivers. The largest of these is the Saugatuck. General Geology The area is underlain by a wide variety of consolidated rocks consisting chiefly of gneiss, granite gneiss, schist, and dolomitic marble, all of pre-Carboniferous age. The distribution of the several bedrock units is shown on the preliminary geologic map of Connecticut (Rodgers and others, 1956). The bedrock, though consisting of rocks di ^ ferent kinds, is generally dense, compact, and has a low poros¬ ity; however, it is broken by joint openings which provide the avail- aole space for ground-water storage and transmission. The bedrock is exposed at numerous places, but elsewhere it is overlain by glacial deposits of the Pleistocene epoch. These un¬ consolidated glacial materials consist of unstratified till and stratified drift or outwash. The till consists of a mixture of boulders, sand, silt, and clay lacking sorting and bedding. It 112 . lies directly on the bedrock and ranges in thickness from a few inches to as much as 50 or 60 feet. It usually has a low permea¬ bility owing to its unsorted character, the small rock particles filling spaces between larger ones. The stratified drift consists of irregularly bedded deposits of gravel and sand and minor amounts of silt and clay; the entire sequence was deposited by melt water from glacial ice sheets. Be¬ cause of the sorting action of flowing waters, stratified drift generally transmits water readily and is the most permeable of the aquifers in the county. The stratified drift occurs chiefly in valleys where it may have a thickness exceeding 100 feet, but it occurs also as a thin patchy veneer over many of the coastal flats bordering Long Island Sound. Generally the areas underlain by stratified drift are essentially the same as those shown by hori¬ zontal ruling on the map (pi. 17). The most extensive deposits are those bordering Long Island Sound and the Housatonic River in the vicinity of Bridgeport, and those underlying the Still River valley in the Danbury-New Milford area. Ground-Water Sources The principal sources of ground water in Fairfield County are the bedrock formations and the unconsolidated glacial deposits. Because the bedrock is dense and compact, ground water is stored in, and moves mostly along, joint cracks and other similar fracture openings. Therefore, the success of a well drilled in bedrock depends upon whether it taps open fractures filled with water, and whether such openings are interconnected in a sizable volume of rock. These openings are distributed in such a haphaz¬ ard manner that it is generally not possible to predict in advance of drilling where the greatest yield of water can be obtained. Information on the yields of drilled wells in bedrock in Fairfield County is available from the published data and from a large num¬ ber of well-completion reports filed with the State Water Resources Commission by well drillers in the area. The reported yields of individual wells range from less than 1 gpm (1,440 gpd) to a maxi¬ mum of 100 gpm (144,000 gpd); however, if a well yielding 100 gpm initially were pumped over a considerable length of time the yield quite likely would decrease. The average yield is about 8-10 gpm, which is sufficient for most domestic supplies. Little difference is noted in the water-bearing capacity of the several bedrock units, even the dolomitic marble shows about the same yields as other crys¬ talline rocks. Thus, although the crystalline bedrock is widely used as a source of domestic water supply because of its widespread occurrence in the county, it may be expected to yield quantities of ground water sufficient only for small municipal, industrial, and 113 . ' supplies. A number of Industrial plants in Bridgeport and tamford augment water purchased from municipal supplies with ground water from drilled wells in bedrock. Heavy pumping from a number of these wells located close to tidewater has resulted in a local increase in the chloride content of the ground water. The quality of natural ground water from bedrock is adequate fi > th^° S ^ pu f pos ® s ' The water generally is only moderately hard, ' . although water from the dolomitic marble may be hard to very hard. 1 ”* U V n th£ Social till in Fairfield County generally yield ess an gpm. Because of its widespread occurrence in upland Sr dT S/ S lmpo , rtan£ Potential source of small water supplies for domestic and stock uses. These supplies are commonly obtained •from dug wells. Throughout much of the area, however, the till is :thin, of small storage capacity, and of low permeability; therefore rurnishes rather undependable supplies. Consequently the general STwat^r C ° drU1 thr ° Ugh tHfe tlU lnt ° the underlying bedrock The deposits of stratified drift, where they consist of sand in Fairfield 3 ? 6 b r f3r j he mOSl: imporl:ant water-bearing formations in Fairfield County, and are potential sources for additional water supplies for agriculture, industries, and small municipal- ities The sand and gravel are quite permeable and readily absorb and store a large percentage of the local precipitation. The ex¬ pectable yield of modern large-diameter drilled wells, within the Sh ° Wn in Plate 17 is 8 enera lly between 100 d 500 gpm, although yields either greater or smaller than the limits indicated have been measured. These areas have not been tested sufficiently to permit an accurate areal evaluation of well yields, and particularly of sustained yields. Where finer grained 11s may yield less than the limits given, but where the deposits are composed of coarse- grained sand and gravel, properly constructed wells may yield a Billion gallons a day or more. Where the wells are favorably lo- Mn! t- Wlth u eS u eCt t0 Sources of recharge such as perennial streams, g term, high, sustained yields may be expected. For example severai wells of the Bridgeport Hydraulic Co., that penetrate sand gravel deposits adjacent to the Housatonic River in Shelton ire reported to have been pumped at rates exceeding 700 gpm (1 mgd) >er well for long periods. These wells are used to augment the ixtensive surface-water supply system for the Bridgeport area. In- •otar as is known, ground water in stratified drift in most of the 'alleys is in hydraulic continuity with adjacent streams. Ordinari- ■y, o course, ground water in these deposits moves toward and sus- lns e ow of the streams, but where heavy pumping occurs in quifers near the streams the hydraulic gradient may be reversed • the river water flows from the streams toward the wells. * Table 20=—Summary of water-r esources values by counties j in_New York and Corine cticut~part of Delaware River service area f -p PJ *\ \ r<> Q |c -3- OJ r 5 c t - O c ; (t t h O N 3 ) 0 3 O r 0 5 H o o VO 1 —1 r-J O d -H P -P d d a a CO -H P, 0) 10 bp a •H CT 1 co 'd' tu) 6 O • i—1 r H • H H C H 3 • H r H C • H o o o • H o t —i a 3*- a al -P > o < Ri CO i> o 'd bQ ri o ir\ vo 3 3 Jn 3 Ov ON i M 3 M o ON ON o o LTN o o LTN . a •rH OJ OJ d" OJ d* C\J OJ OJ •o CVJ H 0J OJ OJ OJ Average annual runoff, R 6 p o 00 CM o LTN OJ o On OJ LON On OJ t- o 8 8 OJ o o co •N 1-1 mgd/sq mi OJ • rH oo • o On • O rH • rH o • 1—1 -d- • rH OJ • rH rH • i—1 bD 6 o t- t- o G\ no o ON c- o NO OJ 8 OJ 8 vo •\ rH o ON LTN o o ON -d- • •H vo OJ 3 o OJ -d" OJ rH OJ o oo vo OJ OJ Average annual Tvrpc*’! rn tat ion. P o OJ U"N s LT\ o oo =o O 3 o LTN rH o vo ON o 2 8 •N oo e a CO d bf b p Pj- OJ OJ vo On • rH LT\ o OJ oo rH OJ LTN o OJ -d" OJ OJ -d - OJ 8 OJ rH OJ ! w s o o 3 -d- *\ rH 8 vO •S 1—1 8 p- rH o o LTN 8 -d- O O VO *\ OJ O o f —1 rH o o oo •N ON £ •r 2 OJ -H" vO ■d- -d- -d- 2 2 vo Area •r~ s c & on co * ^ n> rH CO 2 CO ION OO OJ 1—1 8 OJ d •N 1—1 CO Ss oo -d- -P . Q a d + p a o o «J + o v d H ) bO • a 5 d S a o H I • d z p> £ d Ph d rH • M z o o cc Hj a > CO ♦ 0) -H xi > o • -p 23 CO o \ ^ . • H CO rH • d a -P O 6L- Million gallons a day over entire county Billion gallons a year Il5» Heavy pumping from wells adjacent to streams that are polluted or close to tidewater may, therefore, induce water of undesirable quality to move into fresh ground-water bodies and adversely affect their use for most purposes. This has taken place where wells pene- heavily. ln the coa3tal area ° f Bridgeport have been pumped Th^ quality of natural ground water from stratified drift or ttt'heV'’ mOSt uses; however > the iron concentration may be somewhat high in some localities. Magnitude of Water Supply Ground water of Fairfield County is practically all derived Hrf°ni and _ s "°™ elt of local precipiation. About 1*8 inches of precipitation falls annually in the county, amounting to an average of about l,hOO mgd or 0. 5 20 tgy. Of this, 26 inches, or the rest 7 P? disahar S ed a ® direct and ground-water runoff in streams: Men eS ’ 0r a 0Ut °' 24 ° tgy is lost evapotranspira- ion. mis assumes, of course, no storage changes of consequence hal^rd/T 1- °J 6011 mois * ure - Of the 0.280 tgy runoff, about half is discharged as storm (direct) runoff and the remainder ap- pears as base flow in the streams (table 20). Public Water-Supply Systems Using Ground Water t 1 th ® P f eS ^ t time ' a number of smaller community systems in the Housatonic River basin part of Fairfield County are supplied entirely from ground water. These systems generally furnish less than 35 gpm to their consumers, although the State Hospital at Newtown is reported to pump about 350 gpm. Several of the large public water-supply systems pump ground water to augment surface- waier sources during periods of peak demand and low flow. The largest of these is the Bridgeport Hydraulic Co., which has a number of wells located throughout its franchise area. DUTCHESS, ORANGE, PUTNAM, ROCKLAND, ULSTER, AND WESTCHESTER COUNTIES, NEW YORK by N. M. Perlmutter Introduction -- - III I ■ __—— , h ltCh f 68 ’ Orange, Putnam, Rockland, Ulster, and Westchester -ounties together comprise on area of about 3,760 square miles in southeastern HewYbrk (pi. 18 and tab* 20). 'with the exception f small parts of Ulster and Orange Counties, which lie in the ' telaware River basin, the area is entirely in the adjoining Hudson ivei basin. Some of the counties are relatively densely populated ad use substantial quantities of ground water. Owing to their 88197 0-62-10 (Vol. VII) potentialities for increase in population and corresponding in¬ crease in water use, these counties are considered to be within the service area of the Delaware River basin. Accordingly, a brief summary of ground-water conditions and of the total water resources within these counties is pertinent to the overall investigation of the water resources of the Delaware River basin. Table 20, which summarizes water-resources values for this part of the service area (including Fairfield County, Conn.) shews that on an average annual basis approximately 46 inches of rain, and snow equivalent to rain, falls on nearly 4,4-00 square miles of these counties in New York and Connecticut. This is about equal to 9,300 mgd, or 3.4 tgy. However, about 22 inches is lost by evapotranspiration. This amounts to about 1.6 tgy. The rest of the precipitation, about 24 inches, or about 1.8 tgy runs off in the streams. Asselstine and Grossman (1955) nud Grossman (1957) have pre¬ pared published reports for two of the counties in New York, Westchester and Putnam. Reports are in preparation by the U. S. Geological Survey for Dutchess and Rockland Counties, but no investigations have been started in Orange and Ulster Counties. A considerable amount of unpublished ground-water and geologic data on these counties is in files of the U. S. Geological Survey either at Albany or at Mineola, N. Y« The following descriptions of the general geology and water-bearing characteristics of the aquifers in each county are based partly on examination of mis¬ cellaneous unpublished data of the Geological Survey, published bulletins of the New York State Water Power and Control Commission, and of the New York State Museum, the geological map of New York State (Merrill, 1901), and field observations of the writer, particularly in Rockland and Orange Counties. Dutchess Covinty Dutchess County contains approximately 8 l 6 square miles. The permanent population was 137>000 in 1950 and about 158,000 in 1955* The land surface in most of the county is a gently rolling plain ranging in altitude from about sea level along the Hudson River to about 500 feet in the interior. The southern border of the county is formed by the Hudson Highlands, a part of the New England Upland (pi. 3 ), which reaches an altitude of more than 1,600 feet. General Geology Dutchess County is underlain by igneous, metamor- phic, and sedimentary rocks ranging in age from PreCambrian to Ordovician. The rocks are closely folded and have a northeasterly strike. 117 . The main bedrock unite are: (l) undifferentiated granite, gneiss, and dionte of Precambrian age which crop out mainly along the southern border of the county; ( 2 ) an argillaceous (clayey) unit his- torically known as the Hudson River formation (now abandoned) which, as defined (Vanuxem, 1842) in this county, includes shale, slate, phyllite, and schist of the Nassau and Schodack formations of Early Cambrian age, and the Deepkill and Normanskill formations of Ordovic- ian age; and ( 3 ) scattered elongate belts of the Cheshire quartzite of Early Cambrian age, and the Stockbridge limestone, a metamorphosed ^p° n ?"l. r ° Ck fo ™ at;Lon of Cambrian and Ordovician age. The Hudson River formation of former usage is the most widely distributed bed- “^ n WklCh S „ in the Va;LLe y Ridge province as a north- ra ^(,' rtlon of the Great /alley in Pennsylvania (pi. 3 ). Uncon- solidatea deposits of till and outwash of Pleistocene age cover most of valleys"' 0 '* Surface ’ bein S thinner on the uplands and deeper in the Water-bearing Characteristics of the Deposits Ground water occurs in the till, outwash, and bedrock. Deposits 0 till range in thickness from less than a foot to 100 feet or more. Yields of wells in till average only a few gallons per minute. De¬ posits of outwash composed of sand and gravel yield the largest quanti- vi 1 ^ 1 if 05 * ° f th6Ee de I ,osits restricted to major valleys. Yields ox 34 wells screened in outwash range from 10 to 600 gpm and .■average about 100 gpm. Where in hydraulic continuity with the valley streams, the outwash deposits are capable of sustained high yields. About 90 percent of the existing wells tap the Hudson River forma¬ tion ox former usage or the Stockbridge limestone. Yields of 439 ^Is tapping the Hudson River formation of former usage range from ° ' t °J !30 average about 19 gpm. Yields of 153 veils tapping the Stockbridge limestone range from 0 to 220 gpm and average about 22 gpm. Yields from the other bedrock units average about 12 gpm. • Public-supply systems serve approximately one-half the popula- lon of Dutchess County. Most of the water used is taken directly • rom surface-water sources. Sixteen public-supply systems tap 5round-water sources wholly or in part, but some of the yield from rells is derived from streams as induced recharge where well-pumping .nfluences (cones of depression) reach stream courses. Magnitude of Water Supply Dearly all the ground water is derived from precipitation within e .county. One inch of rain, or of snow having a water content quivalent to 1 inch of rain, falling on 1 square mile yields about ( million gallons of water. Thus, with an average precipitation of out +2 inches falling on the 8 l 6 square miles of Dutchess County, 118. a total of 1,600 mgd or about 580,000 million gallons of water is received, eacb year. Of this, 18 mcnes, or about 0.250 tgy becomes runoff; and. 24 inches, or about 8.348 tgy is lost as evapotranspira- tion. In the above estimates it is assumed that changes of water storage in the area are negligible. This is reasonable because, over a long enough period of time (base period for these estimates is 40 years), changes in storage balance out at or near zero. Orange County Orange County contains an area of about 846 square miles. The permanent population in 195*8 was about 152,000 and in 1955 "wen about 168,000. The land surface in Orange County consists of four main types: (l) a broad, gently rolling plain in the central part of the county generally ranging in altitude from a few feet above sea level along the Hudson River to about 1,000 feet; (2) a dissected*highlands area to the southeast where land surface reaches an altitude of more than 1,580 feet; (3) a narrow northeasterly trending belt of. ridges and valleys bordering the plain on the northwest; and (4) a small plateau area in the extreme northwestern corner of the comity. General Geology Orange County is underlain by consolidated igneous, metamorphic, and sedimentary rocks ranging in age from Precamorian to Devonian. The rocks are folded and. strike northeasterly. Dips are gentle to steep. Major faults occur in some areas. The central two-thirds of the county is underlain by gray slaty shale and sand¬ stone comprising the Normanskill shale and the Snake Hill formation of Middle Ordovician age. To the southeast the rocks of the Normans¬ kill. shale are in contact with elongate belts of infolded and faulted beds of limestone of Precamorian, Cambrian, and Ordovician age, and sandstone, conglomerate, and shale of Devonian age. These rocks in turn lie on and against the complex crystalline rocks of the Highlands area which consist mainly of granite and gneiss. The beds of the Normanskill and Snake Hill are overlain unconformably to the northwest by the northwesterly dipping rocks of the Shawangunk conglomerate and High Falls shale of Silurian age which form Shawangunk Mountain. The prominent valley which parallels the northwest flank of Shawangunk Mountain is underlain by northwesterly dipping beds of limestone, shale, and sandstone comprising a number of formations ranging in age from Late Silurian to Middle Devonian. The plateau area to the north¬ west is underlain by sandstone and shake of Middle to Late Devonian age. The bedrock in most-of the county is covered-by a mantle of un¬ consolidated deposits of Pleistocene age composed of till and outwash. Water-Bearing Characteristics of the Deposits 200 Wells s P rin S s in Orange'County are , . . e b lbes °f the U. S. Geological Survey. Most of the data were obtained in the extreme northwestern part of the county . with some scattered data from other parts. Thus a detailed airorais al - the ^ water conditions requires considerably more field vork than has been accomplished to date. Lll ^^^ 8 ^ 508 ^ 6 are tU1) outwash > “ d b <^ock. The till covers the upland areas throughout most of the county and ! !r 11 r quantities suff idient for domestic ise to °f WaSh sand “ d emvel as much as several are^ Se l^est^T r ° f the strea ” valleys and lowland ; , . ® lar S est b °<*Y of outwash occurs in the Port Jervis trough +v^ a C ?v efl ? in the Valleys of Neversink River and Basher Kill) i^ ^ A° rthVeStei T Part ° f ^ ccmnty * ^ gavels and sands of this a vLvT a thickn ess of more than 200 feet and constitute » { large underground natural storage reservoir. Other deposits of outwash are relatively untapped and generally are potential su ^ stantial quantities of water. Where such deposits h ^raulic continuity with perennial streams their yields and s ^ st ai n ed, for water pumped from wells in these de- Tron thTlt replaced in the aquifer by induced recharge mnlT ^ 2 1elds of 13 wells screened in outwash 3 ° 38 ° *** avera S e about 85 gpm. Larger yields doubtless are available in many places. . M ° S * 0f 1 the vells in county are drilled into bedrock. The mam bedrock aquifer is the Nonnanskill shale. Yields of 16 wells penetrating the Nonnanskill range from about 2 to 80 gpm and average ibout 30 gpm. Yields of 21, wells in sandstone and shSe “ Devonian dwells G tannine^l 1 + gPm ^ 851,1 aai average about 20 SP®- Yields he htehe^ovaestone of Cambrian and Ordovician age are among , hlghest for bedrock aquifers. In.11 wells, the yields ranpe rom about 20 to 150 gpm and average about 80 gpm. Wells in granite nd gneiss have the lowest yields. In 10 wellsf the yields rfn^ ro ” about 1 to 25 gpm and average about 10 gpm. * 55 2 Xlmtedy 90 percent °f the water pumped in the county is rom surface-water sources. Thirty public-supply systems ranging rom small real estate developments to municipalities, pump water holly or in part from wells and springs. Ground water is also used or domestic, agricultural, and some industrial purposes. 120. Magnitude of Water Supply Ground water within the county is derived almost entirely from precipitation falling on its 846 square miles of the area. Receiv¬ ing an average of about 44 inches of precipitation a year, the total rainfall amounts to about 1 ? 700 mgd or O. 63 O tgy. Of this, 20 inches or about 0.290 tgy becomes runoff and the rest, 24 inches or about 0.340 tgy, assuming no essential water-storage change in the aquifers and soil, is lost by evapotranspiration. Putnam County From a report by Grossman (1957) on the ground-water resources of Putnam County most of the following data are summarized. Putnman County contains an area of 235 square miles. The perma¬ nent population in 1953 was about 20,000 and in 1955 was about 28 , 0 Q 0 . The county is in the Hudson Highlands, a dissected belt of low moun¬ tains which rise from about sea level along the Hudson River to as much as 1,400 feet in the upland areas. Valleys in the Highlands generally are narrow and straight. General Geology The bedrock underlying Putnam County consists of folded and faulted consolidated igneous and metamorphic rocks ranging in age from Precambrian to Ordovician. More than 90 percent of the bed¬ rock is composed of undifferentiated granite and gneiss of Pre¬ cambrian age. The remainder consists of: (l) scattered diorite bodies of the Pochuck gabbro gneiss of Precamtbian age, (b) the Stockbridge limestone of Cambrian and Ordovician age, and (c) the argillaceous and schistose beds of Ordovician age. The consoli¬ dated rocks are overlain by an irregular mantle of unconsolidated glacial deposits of outwash and till of Pleistocene age, which have an irregular distribution and thickness. In the upland areas the till generally is less than 30 feet thick but in some valleys may be as much as 200 feet thick. Outwash, consisting chiefly of sand and gravel, underlies large stream valleys. In some places the glacial deposits largely consist of silt and clay. Water-Bearing Characteristics of the Deposits Ground water occurs in the till, outwash, and bedrock. Records of a few wells in till indicate an average yield of about 2 gpm, which is an indication of the low permeability of these deposits. Many wells in till go dry during periods of low rainfall owing to 121. (Jeeline ° f the water table. Yields of 50 wells tapping outwash 30 n pgT 8r range fr ° m ab ° Ut 1 t0 450 8pm and aver age about 0 to IL^n dS ° f ab a Ut 370 " ellS P enetratin 8 bedrock range from 0 to about 120 gpra and average about 12 gpm. Most of the wells tan grand e and gneiss. There is little difference in the average yieLs of wells tapping the principal bedrock units. 8 Y d About one third of the total estimated pumpage of 1.5 mgd was w!ter 8 Zn' Wate : SOUrCeS ' El6Ven P ubl i c - a PPly systems use ground er wholly or in part. Ground water also is used for domestic agricultural and some industrial purposes. Magnitude of the Water Supply Annually, over the 235 square miles of Putnam County there is med^r^^ftn^ 0115111 ^ 1011 ° f ab ° Ut 46 inches equivalent to about 500 g 0.180 tgy. However, 24 inches, or about 0.095 tgy is avail- able as runoff. The rest, about 22 inches, or about 0.085 tgy is lost as evapotranspiration. These values are based on about 40 years of record, a long enough period of time so that changes of water storage in aquifers and in the soil can be neglected^ Rockland County Rockland County contains approximately 201 square miles. The inft m nnn nt pop “ lati ° n in 1950 was about 89,000 and 1955 was about the’Hudson R surfac ® ranges in altitude from about sea level along the Hudson River in the eastern part to about 1,200 feet in the isTvenM S n °“ hwestarn P art ' T he eastern two-thirds of the county g tly rolling plain which is bordered on its eastern margin by narrow curving ridge that rises as much as 700 feet above the plain. The plain terminates against the rugged highland area of the Ramapo Mountains in the northwestern part of the country. General Geolo gy mnrn , R 0 Ckla J d C ° Unt y is underlain by igneous, sedimentary, and meta- phic rocks ranging in age from Precambrian to Ordovician and lriassic. The eastern two-thirds of the county is underlain by beds of conglomerate, sandstone, and shale, and associated igneous rocks of Trlassie age. The sedimentary rocks are part of the Newark group The largest differentiated unit of igneous rocks is the Palisade diabase, a sill, intruded in the eastern part of the country in Triassic time. The rocks of Triassic age dip north¬ westerly and terminate along a major fault marking the southeastern border of a belt of crystalline rocks of Precambrian age. The crystalline rocks consist mostly of granite and gneiss. A small 122. area in the northeastern part of the county is underlain by an in¬ folded and faulted body of rocks of Cambrian and Ordovician age consisting of beds of quartzite, limestone, and phyllite. Glacial till and outwash of Pleistocene age cover the bedrock in most of the county. In some places the total thickness of these deposits is more than 300 feet. Water-Bearing Characteristics of the Deposits Ground water occurs in the till, outwash, and bedrock. De¬ posits of till are tapped by some domestic wells which generally yield less than 5 gpm. Deposits of outwash composed of sand and gravel are restricted to major valleys and yeild about 55 to 1,200 gpm to individual wells. At some places the outwash is composed largely of fine-grained material which does not yield large supplies. Most of the wells in the county tap the bedrock. The main water-bearing rocks are sandstone and shale aquifers, part of the Newark group. Yields of 220 wells tapping these rocks range from about 4 to 1,500 gpm and average about 80 gpm. The average yield of 40 public-supply wells penetrating the Newark group is about 300 gpm. The water is moderately hard. Yields of 13 wells tapping the Palisade diabase average about 11 gpm. Yields of 37 wells penetrating granite and gneiss average about 15 gpm. Yields from the other minor bedrock units are small, commonly less than 10 gpm. Most of the water used in the county is from ground-water sources. An average of about 7 mgd was pumped in 1955, most of which was pumped for public-supply use. Some was pumped for self- supplied industrial use and the remainder was for domestic, agri¬ cultural, and other minor uses. Magnitude of the Water Supply The annual precipitation over Rockland County's 201 square miles is about 44 inches. This amounts to an average of about 410 mgd or 0.150 tgy. Of this about 0.072 tgy, or 21 inches, becomes runoff. Evapotranspiration accounts for approximately 23 inches of rainfall annually, or about 0 o 078 tgy. Ulster County Ulster County contains approximately 1,172 square miles. The permanent population in 1950 was 93,000 and in 1955 was 102,000. Land surface ranges in altitude from about sea level along the Hud¬ son River to over 4,000 feet in the northwestern part of the county. The eastern half of the county is a gently rolling dissected lowland Shawangunk Mountain and some minor ridges and valleys which trend northeasterly across the county separate the eastern lowland from the dissected plateau which forms the Catskill Mountains in the northwestern half of the county. 123. General Geology The bedrock underlying Ulster County is composed of fnlrW a imentary rocks ranging in age from Ordovician to Devonil £he l l strike 6 .'^heT ° f ^ C ° U " ty have 3 -thesst^™* northerly and sandstone which y iargely t compfise e the e Normfnfkili a shale la of Ordov• cran age. Unconformably overlying the rocks „ V °f,? rd ° v : Siluria northwe ® terl y dipping beds of the Shawangunk conglomerate ^ 6 Silurian age Minor ridges and valleys immediately west and north shale aW sandstone Unta H ln i are Underlain ^ fold ^ beds mainly of marine Late Silurian toddle CatsTiU ^ u« a™ 36 ° f horizontalbeds t "of n ^ ^ C ° Unty is under lain by relatively 3 of Middle to Late Devonian al7 S Thf S b°d 6 ’ ® hale ’ and con S lo ">erate ... o u vonian age. The bedrock is overlain in most of aee rL Y Unc ° nsolid f ted deposits of till and outwash of Pleistocene Zn 200 ^ ° f th6Se glacial da P°-bs is more Water-Bearing Characteristics of the Deposits posits i in 1 Uls i ter n rr t £ h he water-bear L n g Characteristics of the de- p its in Ulster County because few records of wells and snr-inac counties n the lleCted ‘"il 6 C ° Unty t0 date - As in other nearby rock Tin of " Watar - beari , n S “nits are outwash, till, and bed- A * . ° f irre 8 u l ar thickness covers most of the upland areas ^“^c^e^d^ ? ““ Pr ° bably are 3 S^o- Per"ini ute. Scattered outwash deposits of sand and gravel occur in maior valleys and may yield as much as several hundred gallons per minute to individual wells, and where in hydraulic continuity with per- dependabir^Thr^d T“ n0t ° nly be high but would be dependabie The bedrock ls the source of water for most of the oriiahl COUn 5 y • The y ields of wella tapping bedrock units probably are on the same order of magnitude as the yields given for the same units in Orange County (p. 119). The ground water is used mostly for public supply, domestic nd otheT a ^, purposes; a sma11 quantity is used for industrial nd other miscellaneous purposes. About 10 public-supply systems Jatefnu a T SOU ^ CeS wholl y or ln P a «. The combined ground- pumpage from these systems averages somewhat less than % mgd. Magnitude of the Water Supply livhMv CiPita in 0n Ulster Count >' s UU 2 square miles ranges from o 54 inch Y n n h6S ° Ver the hi 8 her parts of SUde Mountain o 54 inches in the Overlook Mountain area; it drops off to about 46 inches at the base of the Catskill Mountains scarp on the east and from there eastward gradually diminishes until, at the Hudson River, the amount is about 44 to 45 inches, the lowest pre¬ cipitation being in the southeastern part of the county. Average precipitation over the entire county is about 48 inches, which is an average of about 2,600 mgd or O. 96 O tgy. Runoff takes about 30 inches, or 0.600 tgy, and evapotranspiration losses amount to about 18 inches, or O. 36 O tgy. Westchester County Westchester County contains a total of about 487 square miles. The permanent population in 1950 was about 626,000 and in 1955 vas about 718,000. The altitude of the land surface ranges from about sea level along the Hudson River in the western part of the county, to about 700 feet in the Hudson Highlands in the northern part. Land surface consists mostly of a series of northeasterly-trending low ridges and valleys. General Geology Westchester County is underlain by northeasterly-trending belts of closely folded igneous and metamorphic rocks which range in age from Precambrian to Ordovician. The principal units are Pre- cambrian: (l) Fordham gneiss, (2) Inwood limestone, and ( 3 ) Manhattan schist. In addition, relatively small areas are under¬ lain by the Harrison diorite, Yonkers granite, infolded belts of Poughquag quartzite, of Early Cambrian age, Stockbridge limestone, and slate of Ordovician age, and miscellaneous igneous rocks such as granite, pegmatite, and undifferentiated basic in- trusives. The bedrock in most of the county is covered by uncon¬ solidated deposits of till and outwash of Pleistocene age which range in total thickness from a few feet to as much as 200 feet. Water-Bearing Characteristics of the Deposits Ground water occurs in the till, outwash, and bedrock. Depos¬ its of till having a wide range in thickness are extensively dis¬ tributed on the upland areas and in some valleys. The till has relatively low permeability and except where it contains large sandy lenses yields only a few gallons per minute to dug wells. Scattered sizable bodies of outwash occur in parts of the county, the largest and thickest of which are restricted to major valleys. The outwash consists mostly of sand and gravel but in places con¬ tains much silt and clay. Outwash deposits of sand and gravel yield the largest supplies in the county. Individual wells screened in these deposits range in yield from about 3 to 600 gpm. The aver¬ age yield is about 200 gpm. 125 . ysU^'.^S' : w.T^“S? 1 ‘g‘Ko*S.‘“IK S low 45 ° m 0ther bedrock units are relatively Public-supply systems serve about QO -percent of the Ihe water is punped mostly from lakes and^tre^s use ground-water sources wholly or in part w^ J"?" ? 1 Sy£ \ tems supply domestic, agricultural, and somf industri^ needs PriDgS ° Asselstine and Grossman (1955 Part t ) a 4 . a a »«»»n. u sssLtsi&r”- Magnitude of Water Supply kflv *““ mU y ? n the ave r?se, there falls on Westchester Countv’s s’srrjs s 1 :- isicis: s;-. rs * 0 t l80 P vt tl ?w O ir S aCC Sr^ f ° r "PProxinately £2 inches, "or"ct’ut gy, us leaving 26 inches, or about 0.220 tgy for runoff. LONG ISLAND, NEW YORK by Garald G. Parker Introduction Although not a part of the Delaware River basin. Long Island is important to this study because it is a part of L w y? a Y hich is in «« Delaware Wver basS sem=fa rea . in considering S *he dev surro ’ i ' lded b y salt water, an important fact _ f ™™8 '-he development and use of water in large auantl+i»<= ^erf C ° ntainS ln “ S huge ^cial and CoaSal“n aquifers very large quantities of fresh water. These could b7 a^Ia^f e thf°L emergea ° y USe “ the NeW Y ° rk Clty me tropolitan ' Tn = if t a Were struck b y severe radioactive fallout w£ter w^ldT aU S « faCS VatSr ’ ^ PSrhaps some shal l° w ground Z cl ;ablf of S ^ rlt f °r USe ' but the deeper aquifers woSl be SUPPlleS Deeded Unt11 SUrface s °“~es could 126. The Water Supply The total volume of water stored in Long Island's aquifers is very great, probably in the order of 50 trillion (5 X 10^" ) gallons. However, not all, or even very much, of the water is- available for use. This is because of the delicate balance that exists between this large body of fresh water on land and the still larger body of salt water of the ocean that surrounds it on all sides. In other words, the salt-water encroachment factor is the dominant limiting factor here. The total quantity of water available for perennial use, which has been called "safe yield", is therefore not known, although it is less than the average annual return flow to the ocean which it¬ self is not precisely known for all the island but is estimated in table 21 „ In an attempt to place the water-supply picture in proper per¬ spective, table 21 and pi. 19 were developed. The values given are based on published data of the U. S. Weather Bureau and on both published and unpublished data of the U. S. Geological Survey, but are intended only to give the order of magnitude of the hydrologic values involved. Of general interest is the conclusion that the values assigned to Long Island are of the same order of magnitude for other parts of the Coastal Plain covered in this report (p„ 37-39)° How¬ ever, the water budget for Long Island (table 21) differs m one respect from that for the Coastal Plain in New Jersey and Delaware (table 4). In the water budget for Long Island, R includes un¬ measured, but estimated, ground-water outflow beneath and between stream channels, as well as runoff, and is designated average,annual return flow to the ocean. In the budget for the Coastal Plain in the Delaware River basin and adjacent New Jersey and Delaware, R represents only runoff; unmeasured ground-water outflow, believed to be much smaller per unit area than that in Long Island, is in¬ cluded in water loss in table 4.- Table 21 indicates that Long Island receives an average annual precipitation of about 2.1 mgd per square mile, which, over the 1,373 square miles of the island's surface amounts annually to approximately 2,900 mgd of new water. However, water loss amounts to about 1 mgd per square mile for a total estimated average annual loss of 1,400 mgd over the whole island. This leaves only about 1.1 mgd per square mile ( 1,500 mgd) of discharge from aquifers to streams and to the ocean as underground outflow. U.S.GEOLOGICAL SURVEY % o o o o o ,« o li. kO <0 o in o •» n «» Table 21*— Summary of vater resources values. Long Island, (note: values are rounded to 2 significant figures and give only order of magnitude) -p w O rG G O f G G 4 | G rl cd 0 0 •H 'd O ft rH -p bO > d w cd G £ O 0 ft rH ft w ool 6 G rd G 0 cd bO 0 d • G ft 0 ft cd £ ft w rH > O O rd rj J oj] g -h § ri O P r —1 bO > G W - 4 " ir\ • C ft O O ft O Ctf 0 bO 7 h 1 6 £ G Mod 8 a) S ft w CO < G O rd cd O ^ , G G - 4-1 G ft cd O O O rd O P rH LTV O b!) > C w •\ 5 6 O 0 ft rH > 0 \ ft ml E rH rd G 1—1 ft bp 0 cd • g £ ft w rH G ft O rd 8 rH - Cjl fn -g 1 8 B a a vo LTV • | POO ft O 0 *d rH| E bO G O cd bO < ft O rd •N 4 ] G-h S O O G rd O P rH o\ O bO > G W •N •H -P £ O O ft OJ ft ft m) E O rd K 1-1 O bO or cd • G £ ft w OJ ft 1-1 O rd | o£) G ft § S O ft rH bp > G W H • P OOP rH bO (d G ft rH | E * -» O r-"} P O £ Mod fi rn w O O O bO bO tiD 2 g g < 1)0 0 > > > cd cd cd WWW •d o o o E A & a ^ o o o W -H ft •£ m y\ ro oj OJ OJ co cd o O o ft cd G G o > < ft ft ft cd ft 4 o w & g g Cd Cd ^5 r”! P o cd cd ^ l^'d -d cd cd cd cd w G O rH W G o rH w G o rH i—I cj cd cd cd bO bO bO bo w G O rH ^XVJ VO H VO VO O O O O H H H rH X X X X «H rH r-1 rH G G O G G O ft O O ft rH ft ft rH r—I 3d U B 3 B -P 127. 88197 0-62-11 (Vol. VII) 128. On Long Island there is a negligible amount of direct runoff. Nearly all the 1.1 mgd per square mile seeps into the ground, be¬ comes ground-water recharge and then, the aquifers being full (and by nature required to remain so to maintain salt water of the ocean and sound in its "normal" position) is discharged chiefly as ground- water outflow beneath and between streams and as baseflow in streams. Thus, the streams of Long Island, none of which are large, are fed almost exclusively by ground-water discharge. The topmost curve of pi. 21 indicates the total amounts of water withdrawn from all aquifers on Long Island and projects pos¬ sible 1958 quantities through 1960. It is estimated (Lusczynski, written communication) about one half of the withdrawals on the island is returned to the aquifers, therefore the other half is, in essence, consumptively used by: (1) being sewered into the ocean; (2) included in manufactured products; (3) lost by evapotranspira- tion; or (4) lost by other means (this consumptive use includes, of course, the water used for irrigation). To see how important these withdrawals and consumptive uses are let us compare the pumpage for 1957 (0.137 tgy) with the total annual average return flow (0.560 tgy) and then with the total average re¬ turn flow during an extremely dry year (0.365 tgy). Thus: 0.137/0.560 approximately 24 percent (normal year) 0.137/0.365 approximately 38 percent (probable driest year) If, however, half the withdrawals are returned to the aquifers, the actual quantities we have to deal with are those of consumptive use. Thus: 0.69/0.560 approximately 12\percent (normal year) 0.69/0.365 approximately 19 percent (probable driest year) We may conclude, therefore, that the present consumptive use on Long Island is about 12 percent of the average annual return flow and about 19 percent of the return flow during the driest year to be ex¬ pected. This indicates that a great deal of additional development and use of ground water can be made. However, if lasting harm is not to be suffered from such increased development, rational plans must be developed and adopted to prevent overly large concentration of development too near the shore zones with resultant salt-water en¬ croachment. Present studies underway by the U. S. Geological Survey in cooperation with the State, county, and city governments should lay the solid basis needed for future safe development. 129. . l J rr * 8a “ on on Lon S Island is increasing, and total water loss likewise increasing. Because irrigation water is largely used consumptive ly , about 90 to 95 percent being lost by evapotranspira- tion, it has an importance that most other uses of water, not being so highly consumptive, do not have. 8 . A ^ cordin 8 to the U. S. Census Bureau (1954, p. 44-49) total ir- r 8 ? 7 e o 7 ^ Crea8e ° n L ° ng Island ^creased from 11,945 acres in 1949 to 37,275 acres in 1954. Inasmuch as an estimated average of 6-7 5 inches of water are applied during the growing season, about 1,900 mgy ( -inch rate) or 2,400 mgy (7.5 inch rate) were used in 1949 compared with 6,000 mgy and 7,600 mgy, respectively, for 1954 By courses, the irrigation water use for 1954, at 6-7.5 inch applica- l n rates, is distributed as follows: Kings.County, 13-16 mgy Queens County, 30 - 37 mgy; Nassau, 190 - 240 mgy; Suffolk County, j ,oUO - 7,300 mgy. Previously (table 21) it was estimated that the total return flow from Long Island averages about 560,000,000 mgd and during an extremely dry year amounts to about 365,000,000 mgd. Thus, maximum use of water for irrigation, compared with worst expected dry-year conditions, is 7,500/365,000,000, or 0.002 percent of the return flow and can be seen to be a very minor item in the over-all water budget. owever, much depends upon where and in what quantities the water is removed from the aquifers. Should it be too close to the salt-water --fresh-water contact near the shore area, salt water would be drawn in. In any case, local studies would have to be made if additional arge-scale irrigation supplies were to be developed. Additional pumping would be feasible only to the extent that it would not in¬ duce serious salt-water encroachment. Geologic Structure and Materials Although Long Island is adjacent 'to rocky New England, and its bedrock is a continuation of the same rocks found on the mainland the island is a part of the Coastal Plain rather than of the New England province. As in New Jersey and Delaware, the bedrock sur¬ face under the mantle of sedimentary rocks slopes generally seaward; on Long Island, however, the direction of the prevailing slope is more southerly than it is in New Jersey and Delaware. The dipping bedrock surface slopes from depths of only a few tens of feet below sea level in northwestern Queens County to depths of more than 2,000 feet at and beyond the south shore of Suffolk County. In central Suffolk County bedrock is about 1,400 feet below sea level. The overlying huge wedge of sedimentary rocks constitutes the ground- water reservoir of Long Island, which contains several notable aquifers. 130. Pleistocene Aquifers The upper geologic layers on Long Island are of diverse Ice Age origin and are collectively called upper Pleistocene deposits . They underlie almost all of f Long Island and in some places attain a thickness of about 300 feet (pi. 19 ) 0 Lying stratigraphically below these deposits in the western part of 1&e island is the Jameco gravel of early or middle Pleistocene age. The Upper Pleistocene Aquifers On the basis of their origin and lithology the upper Pleistocene deposits are assigned to three categories, each of which may be con¬ sidered an aquifer: (l) Glacial moraines, foming two sub-parallel ridges, Harbor Hill on the north and Ronkonkoma on the south, ex¬ tending almost the length of the island; (2) glacial outwash, form¬ ing a stratified sheet plain on most of the south side of the island, south of the Ronkonkoma moraine; and (3) a complex depositional se¬ quence lying both between the Harbor Hill and.Ronkonkoma moraines and also to the north of the Harbor Hill moraine. Glacial moraines t The Harbor Hill moraine extends from Kings County out along the North Fork, and the Ronkonkoma moraine extends from western Nassau County out along the South Fork (pis. 19 and 20). In their western parts the deposits of these two moraines carry local bodies of perched ground water on clayey members, but to the east there is less clay, and the gravels and sands are quite permeable and appar¬ ently allow ready movement of water through their interstices. • l. Glacial outwash The outwash deposits lying between the south shore and the Ron¬ konkoma moraine are mostly sand and gravel and generally are very permeable. Near the shore, and beyond, there are intercalated layers or lenses of marine clay of relatively low permeability. Glacial complex The complex of glacial deposits in the northern part of Long Island consists mostly of stratified sand and gravel, partly of out¬ wash origin, but there are also included two units of clayey till, one in th;e middle of the sequence and the other'at the land surface. It will require a great deal of detailed field and laboratory study to separate those units, map them, and derive a satisfactory quan¬ titative understanding of their hydrologic significance. . I ■ 4 . Jaineco Gravel The Jameco gravel is the aquifer that lies stratigraphically be- lov the upper Pleistocene aquifers. It is chiefly a body of highly permeable sand and gravel but locally includes lenses of silt and clay. The formation occurs only in Kings County, the southern part of Queens .County, and the southwestern part of Nassau County. For the most part the Jameco gravel seems to fill a system of buried valleys, though in places it covers the interfluvial areas between. It ranges in thickness from a featheredge to about 150 feet and everywhere lies 80 feet or more below sea level. It was probably derived from debris carried by meltwater streams of a pre-Wiscon- •sln glacial sheet. Hydrology of the Pleistocene Aquifers The Upper Pleistocene Aquifers The upper Pleistocene deposits, which mantle the entire island, are recharged entirely by local precipitation. Lacking a connec¬ tion through permeable rock with the mainland of New York and Connecticut, fresh-water cannot be transmitted from the mainland to the island naturally beneath Long Island Sound. Salt water sur¬ rounds Long Island's ground-water body on all sides. Over the years a hydrologic balance has been established by Nature between fresh water of the island and salt water of the surrounding ocean and sound. Pumping has changed this balance in some places, resulting in salt¬ water encroachment (pi. 20). Because most of the deposits are very permeable, direct runoff is slight. Overlying other permeable aquifers, the upper Pleistocene aqui¬ fers serve as water-catchment and temporary storage units for the deeper aquifers. Recharge to the Jameco gravel, the Magothy(?) formation, and the Lloyd sand member of the Raritan formation passes through the upper Pleistocene deposits. The total recharge estimated to average about 1 mgd per square mile. The upper Pleistocene ground-water body is unconfined, though in local areas it may be semiconfined, and the water table meets the sea level at the shoreline; inland the water table rises in some places to about 250 feet above sea level. Fluctuation of the water table chiefly reflects changes in rate of recharge from pre¬ cipitation; however, in those areas where purfrping is heavy water- table fluctuations may be more the result of -changes in rate of pumping than of changes in rate of precipitation. 132 o In those areas on western Long Island where perched bodies of water occuir in the upper Pleistocene deposits, more than one "water table" may be encountered in drilling wells. - i Because of their bulk and permeability, the upper Pleistocene deposits comprise the most productive aquifer system on the island, probably now producing about half the gross pumpage, or nearly 0.06l tgy in 1955. Plate 21 which shows estimated gross withdrawals from aquifers on Long Island, and estimated consumptive use therefrom, gives an overall view of estimated withdrawals from 1950 to now, and projects use to i960. This graph indicates that in 1957 the gross withdrawal from the -upper Pleistocene aquifers amounted to about 0.068 tgy. If pumping should continue to increase at its present rate, we.should expect withdrawals from these aquifers to reach ' about 0.08l tgy in i960. ' 1 Jameco Gravel , 1 The Jameco. gravel was once an important source of water in Kings County, but salt-water encroachment in idle aquifer, induced by fair¬ ly large-scale, pumping, has caused abandonment of all public supplies formerly obtained from it (Lusczynski, 1952). The Jameco gravel still supplies substantial quantities of water in Queens County and in southwestern Nassau County. It probably yields on the order of 5 percent of the gross pumpage on the island, or about 0.006 tgy in 1955(pl• 2l)o Water in the Jameco gravel occurs tinder artesian or semiartesian conditions, beiriig confined in varying degrees by the overlying Gardiners clay, which separates the upper Pleistocene aquifers from the Jameco gravel. Locally tlje clay forms a leaky aquiclude but at most places it'is a fairly effective barrier to water movement a- cross its thickness of 10 to 150 feet. Some of the recharge occurs to the Jameco gravel through the more leaky and permeable parts of the Gardiners clay; the remainder of the recharge enters the Jameco where the Gardiners clay does not extend above it. Cretaceous Aquifers Magothy(?) Formation The Magothy(?) formation in Long Island, like the similar and presumably correlative formation in New Jersey, Delaware, and Mary¬ land, is a wedge-shaped deposit of nonmarine Cretaceous sediments having its thick segment seaward'(pic 19)° In Kings, Queens, and Nassau Counties the MagothyC?) formation is overlain by the upper Pleistocene deposits, except in the southern parts of those counties where it is overlain by the Gardiners clay extending beyond the GROSS USE, IN MILLION GALLONS A YEAR U.S. GEOLOGICAL SURVEY PLATE 21 170,000- 160 , 000 - 150,000 — 140,000 130,000 120,000 110,000 100,000 NOTE: PUMPAGE FROM THE DIFFERENT AQUIFERS PROPORTIONED ON BASIS OF 1955 ESTIMATES AS FOLLOWS JPPER PLEISTOCENE DEPOSITS 50 PERCENT JAMECO GRAVEL 5 PERCENT MAGOTHY (7) FORMATION 35 PERCENT LLOYD SAND MEMBER OF 10 PERCENT RARITAN FORMATION CONSUMPTIVE USE ESTIMATED AT 50 PERCENT OF WITHDRAWAL rf TOTAL,ALL , AQUIFERS - 80 - 75 example; IN 1955 GROSS WITHDRAWALS FROM ALL LONG ISLAND AQUIFERS WAS ABOUT 0.122 TGY AND CONSUMPTIVE USE WAS ABOUT 0.061 TGY. 70- 65 60- 55 -I -50 UPPER PLEISTOCENE DEPOSITS 1950 51 53 54 55 56 57 58 59 60 GRAPH SHOWING PUMPAGE AND CONSUMPTIVE USE FROM AQUIFERS OF LONG ISLAND N Y 1950-1957 PROJECTED TO I960 ’ ’’ ’ CONSUMPTIVE USE, TOTAL ALL AQUIFERS, IN TGY - r . - : V'~ formation is present under most of lon« Island, being missing only in the western and northwestern harts of Kings and Queens Counties. western parts The Magothy(?) foraation in Long Island is a complex, hetero¬ geneous assemblage of lenses and stringers of clay, silty clay silt tobe'dist’iw ? and ’ “ d SOme grave1 ' Generally these deposits seem t0 ^ be ^ d il t f ibuted uns y BteiQ atically except, perhaps, in the western end of tiie island where the lowest few tens of feet of the formation appear to be more gravelly and sandy, and thus more permeab“s a whole, than the rest of the formation. as The upper surface of the Magothy(?) has been eroded to a relief of several hundred feet; its maximum elevation is about 220 feet SonV e f iT 1 EOuthem *»■*■ County. The base of the torL- surface %us ^T’ 1 ^ ng ° Sarly P ara U*l to the deeper bedrock fWh a * ’ formation has a range in thickness from a featheredge to at l^ast 700 feet. . Lloyd Sand Member of the Raritan Formation The Lloyd sand member of the Raritan formation is the deepest flce^h, ° n ,^° ng Is ^ nd - Nowhere does it crop out at the land^ur- vaSM r er r ? S all tHe island and extends out¬ distances^ 11 Island Sound and the At lantic Ocean for unknown The Lloyd member consists mostly of sand and fine gravel with ™ lL Cl 7’ S “ dy Clay ' and flne -nd. The lensesT^dC by less -De^A-hT 5CC ^ prorjilnsntl y in several permeable zones separated by less penneable zones consisting chiefly of clay and silt. . ^ ‘4 0yd Sand 8l °P es southeastward nearly parallel to the sub- n C nnrtb °o k SUrfaCe ’ ^ingf rom about 100 ^eTbelow sea levei lLT£ e “ Sj eena and Nassau Counties po about 1,400 feet below sea k sifMtT 6 ! 1 ¥S “ and ' to ' about 1 ' 700 feet t>elow sea level east^ut^n m^ y ‘! increases Somewhat to the south- easu but in most places ib about 250 feet. Overlying the Lloyd sand member almost everywhere is thfe clav nember of the Raritan formation. The clay member consists of clay ° bay > apd some Included lenses of silty sand and sand, which collectively constitute an aquiclude. Hydrology of the Cretaceous Aquifers Magothy(?) Formation The Magothy(?) formation which is presumably correlative in part with the Magothy formation in New Jersey, Delaware, and Maryland, is recharged by ground-water seepage from the overlying permeable deposits, chiefly the upper Pleistocene aquifers and the Jameco gravel. Ground water in the Magothy(?) is generally confined, less in the upper parts of the formation in the central part of the is¬ land, and more in the deeper parts of the formation where the confining effects of the beds of low permeability are felt. Along the southern shore of Long Island most wells penetrating-the Magothy(?) flow under natural artesian pressure. In southwestern Nassau County artesian heads up to 5 feet above mean sea level are not uncommon; the head increases to the east and reaches 9 feet within a few miles of the Suffolk County line:; The artesian head probably continues to increase, farther east along,the shore to a somewhere in Suffolk County, beyond which it decreases. Fluctuations of the piezometric surface of the Magothy(?) for¬ mation are primarily those caused by pumping, in contrast to the water-table fluctuations of the upper Pleistocene aquifers which reflect the effects of precipitation. Withdrawal of water from the Magothy(?) formation is limited by the capacity of its geologic materials to receive water from the are’as of recharge and to trans¬ mit it to the points of withdrawal. The salt-water--fresh-water relationships in fhe Magothy(?) formation are now being explored. Although they are not completely understood, it is believed that, in general, hydraulic continuity exists between the landward portion of ,the aquifer and its extension under the ocean. The lower part of the Magothy(?) at Atlantic Beach, near the west end of the South Shore barrier beach, contains water with more than 1,600 ppm of chloride. Farther east the water is fresh, where the artesian head is sufficient to prevent the landward movement of salt water in the Magothy(?). Little is known at pres¬ ent of the Magothy(?) along the north shore; however, a field study is in progress. The Magothy(?) formation is the largest aquifer on Long Island and the second most important source of water; the upper Pleistocene aquifer, though smaller in total area, ranks first. In 1955 the Magothy(?) produced about 35 percent of the gross pumpage on the is¬ land, or about 0.C&3 tgy (pi. 2 l) 0 135. Lloyd Sand Member The Lloyd sand member, fourth and lowermost of the principal aquifers of Long Island, is capped by the clay member; hence, water in the aquifer occurs under artesian conditions.. In the central * f r l 0f T1 th ' l6i “ d the floW is downward from the overlying formations to the Lloyd. Thus, recharge can be effected by slow and devious percolation through and around the lenses of clay and slit or pos elbly through erosional gaps in the clay layer (De Laguna and Perl- mutter, 1949 ). Near the shores the water movement is upward from the Lloyd sand member to the overlying material, and wells drilled in the shore area will flow because of artesian pressure.: In some areas, as near the western end of the barrier beach, fresh water may be obtained from the Lloyd, whereas overlying beds contain only salt water. Along the north shore, reportedly one or two wells drilled years ago into the Lloyd encountered only salty water. The Lloyd member is not greatly used, yielding perhaps about 10 percent of the gross pumpage on the island; presumably it could sustain additional fairly large development away from the shores. A glance at the graph, plate 21 indicates that the Lloyd, in 1955 produced about 0.012 tgy and that it will produce about 0.016 tgy * lh I960, if the present rate of increase continues. 136. AQUIFER-MANAGEMENT PRACTICES Aquifer management includes all those practices that are designed to enable man to make the maximum permanent use of the natural under¬ ground reservoirs. The hydrologic characteristics and the present uses being made of the aquifers in the Delaware River service area have been described earlier. The purpose of this section is to discuss some of the aquifer-management practices that are of value in increasing and protecting the ground-water supply. Let us first consider the matter of wells, their development and operation; items largely paraphrased or quoted directly from W. C. Radmussen (written communication, 1957)* WELL AND WELL-FIELD DESIGN, DEVELOPMENT, AND OPERATION Great advances have been made in the last 30 years in the design and construction of water wells. These advances include: (i) The use of a wide variety of types of well casing; (2) a multiplicity of screen types from which to choose for use in specific cases; (3) the methods of determining the kind of screen to use; ( b ) the method of mechanical underreaming and gravel packing; ( 5 ) the processes of chemical and physical treatment of screens, casings, and even of the aquifer materials adjacent to the well screen to increase well yield; (6) the hydraulics of determining proper spacing of wells and the in¬ fluence that a pumping well will have on other wells; (7) greatly im¬ proved pumps to meet diverse needs; and (8) the use of horizontal collector-type wells in areas of induced recharge. The scientific and economic design of wells or of well fields to capture the optimum amount of water is the responsibility of ground- water consultants and other specialists outside the U. S. Geological Survey. It is appropriate here only to sketch selected aspects of optimum well-field design. Let us first consider well spacing. Well Spacing Spacing of most water wells has been a happens tancee process. Location of the first well in an area has often been dictated by convenience to other facilities or by limitations imposed by land ownership. Frequently, when a well field is developed, wells are placed in line, with direction and separation dictated by the geo¬ metry of the area available. Little thought, in general, has been given to whether the aquifer being developed is artesian or water- table, or to such hydrologic factors as: (l) The geometry of the 137- aquifer; ( 2 ) the direction of ground-water flow; or ( 3 ) induced recharge. In fact, most of these elements of the hydrology of well- field development were unknown and unappreciated a generation or two ago in most parts of the country; and in the Delaware River service area even now knowledge of these factors is generallv lacKing. J . Today the Vrohlem of proper spacing of wells can be approached scientifically if the aquifer constants (such as the coefficients of transmissibility and storage), the geometry of the aquifer, its relation to other aquifers and aquicludes, and other physical and economic factors are known. All too frequently, however, data needed for the best design of a well field are not available, possibly be¬ cause of a lack of awareness of the specific data required and their proper utilization. Developers of ground-water supplies may find some useful parallels in the petroleum industry, where the unit oper- ation of many large oil fields, which requires rational spacing of wells, has been in practice for more than 20 years. Competitors have cooperated willingly with the result that more oil is recovered at lower cost than could have been recovered by haphazard development. The formulas necessary to solve many reservoir problems have been defined (Muskat, 1937) on the assumption that the basic coefficients and geometry of the reservoir can be determined. Data have not yet accumulated in sufficient detail in any except localized parts of the Delaware River basin to permit applying, on an areal basis, hydraulic theory to a rational plan for spacing wells in the several aquifers, until such large-scale regional planning and coordination become ne¬ cessary, however, there is opportunity for steady improvement in the esign of individual multiple-well systems. But the success of a battery of wells is largely based upon the successful development of ■each Individual well. Let us next consider this important matter. W ell Development Well development is concerned with obtaining an adequate, as¬ sured supply of potable, clear water. This is done by means of mechanically, hydraulically, or chemically treating the well before 1 is placed in service. Modern development frequently takes as long as, and sometimes several times longer than, the time required to drill, case, and screen the well. Development might be considered to start with the- choice of the est aquifer, after a test hole or pre-existing information has re¬ vealed one or more water-bearing sands. Decisions must be made to 138. case off those parts of the aquifer that are too fine-grained, or are ■nolluted, if the development is to he successful. On expensive veils, these decisions should be made on the basis of: (l) Study of cuttings or cores; (2) electrical logging; and (3) bacteriological (in some cases) and chemical examination of water from succeeding depths. This is best accomplished by an experienced ground-water geologist working with the driller. On less costly wells the driller will frequently make the decision, using his drilling log and sample . cuttings as guides. In order to develop the desired well yield, in areas of thin or silty sand strata, it may be necessary to use mul- . tiple screens with blank sections of casing opposite fine-grained, layers. These can be quite accurately located by careful electric logging: in fact, these changes in lithology are often more accurate¬ ly determined by interpretation of an electric log by a competent geologist than by examination of the most carefully taken well samples. The screen is one of the most important components of a properly designed well. Choice of the correct slot size is critical, inas¬ much as a certain percentage of fine material must be denied passage into the well while the maximum rate of passage of water is encour¬ aged. Commonly a slot size is chosen that will allow a certain percentage of the smaller sand grains to pass into the well and be pumped to waste. Gradually an envelope of coarser material is^ developed around the well, and the water clears. This method' is called "natural” development. The expensiveness of good screens often influences the decision on how much screen to set, even though hydraulically it may be ad¬ visable to screen as much of the aquifer as possible. Exact posi¬ tioning and placing of a screen is necessary, if development time is to be held to a minimum. A screen set only 1 or 2 feet out of proper position may allow fine sediments to enter the well contmu- ously, and the water may never clear. As mentioned above, electrical logging has been found more reliable than other logging methods to locate formation boundaries and permit casing and screening with the necessary precision. Gravel packing is common today in many wells designed, for high yield. Even when a well is to be gravel packed, the choice of screen slot is important, because the texture of the aquifer deter¬ mines the proper size of the gravel, and the size of the gravel in turn determines the proper slot size of the screen. The method of development--whether by surging, overpumping, blowing with air, use of dry ice, backwashing, or bailing--may affect the ultimate yield and longevity of the well. The use of acid, in limy sand like the Vincentovn sand, is sometimes helpful* 139. The use of polyphosphate detergents may be helpful in veils devel¬ oped m slightly clayey or irony formations. The nev method of pressure-fracturing is being used in consolidated formations, but is not applicable to unconsolidated materials. Also, vith careful application of the method, use of explosives in some consolidated rock formations is a successful means of fracturing the rocks to open additional channels for flov of vater to the veil. The length of development period is important to insure that the veil vill not yield undue amounts of sand, silt, or other sedi¬ ment after it is placed in service. An 8-hour development period may be adequate for veils of small or moderate yield in unconsoli¬ dated aquifers, vhereas a day or several days may be required for a high-yieid veil in the same formation; in most consolidated rocks shorter periods of time are generally required for development of wells (after drilling is complete) than for unconsolidated materials. Bennison (19V7, p. 219-251) has given an excellent discussion of ’ the problems of developing vater veils. It is imrportant to recognize, hovever that even the best drillers, using the most modern equipment and techniques, and alloving adequate development time, are occasion- - ally unable to develop the quantity or clarity of vater desired. For 1 example, successful development of veils in the Magothy and Raritan . formations in northern Delaware has been particularly difficult. Competent drillers in this area have spent a month, or even more, rying to develop veils in parts of these formations and have faildd to obtain veil yields greater than 75 gpm of "milky” vater. Experi- •. ence in northern Delaware has shown that many strata which indicate 1 “J. • If-potential and high resistivity on the electric log, and 1 which yield medium- to coarse-grained sand in washed samples from the rotary-drilling mud (generally considered indications of perme- - able sands), are so silty that long development and low yield are ■typical. Only by coring these sands would the developer' be warned impending failure. That the foregoing experience has been costly ° f Severa:L fillers indicating as much as ?30,000 for a dry hole . Well Maintenance After a veil is in service, it usually requires periodic mainten¬ ance. Not only do the turbines and shafts of the pumping equipment ear out, but the veil casing may deteriorate, screens may become corroded.or encrusted, or both, and the aquifer itself may become in ttie vicini ty of the veil. The maintenance problems are ignificant because they determine, in part, the extent to which 1 ers and vater users vill attempt development of an aquifer. 88197 0-62-12 (Vol. VII) DISPOSAL OF UNDESIRABLE EFFLUENTS All too commonly, the -undesirable effluents of industries or municipalities have been discarded untreated, on the ground, in "disposal" veils, or in streams, although the State boards of water- pollution control are gradually abating this practice. But large tidal streams, like the lover Delaware and Christina Rivers, are almost open industrial severs for wastes that are untreated and per¬ haps considered untreatable. Possibilities of effecting water-re¬ sources development, outlined in the section on tidal area controls suggest a partial answer to this problem in an industrial drainage canal, developed on an aquiclude, to carry the undesirable efflu¬ ents farther down the estuary. ARTIFICIAL RECHARGE Artificial recharge has been practiced successfully in many areas, but usually where water is at a premium and the cost is justified, as in parts of the western United States. Barksdale and DeBuchananne (1946) have described the artificial recharge of productive aquifers in New Jersey, outside the Delaware River basin. It may be many years before artificial-recharge practices are widely needed or adopted, but there are places in the Delaware River basin where deep cones of depression in the piezometric surfaces warrant early con¬ sideration of recharge by artificial means. The cones of depression developed in the piezometric surfaces of the Magothy and Raritan for¬ mations in the Philadelphia-Camden area are one example; in Delaware the Patuxent formation in the Delaware City area, the Cheswold aqui¬ fer in the Dover area, and the Frederica aquifer in the Milford area, are other examples. The means for accomplishing artificial recharge require a depend¬ able water source and either input wells, check dams, infiltration canals, or spreading basins, according to local geology and economics. Input Wells The use of input wells, usually to restore cooling water to a formation, is the most common method of artificial recharge in the East. On Long Island, input wells are required for each air-con¬ ditioning well supplying more than 100,000 gpd. The water circulates in an airtight system and is returned to the ground unaltered except for a slight rise in temperature. - At Louisville, Ky., it was found that the ground-water level was declining at an alarming rate because of greatly expanded use of ground-water supplies to operate industrial plants during World War II . Quantitative studies of the aquifer indicated that the pumpage was about 20 mgd more than the recharge. Industries voluntarily effected many economies of water use, and at two plants cold surface water was artificially recharged into the aquifer during the winter then pumped out again in the summer when the surface water was too warm. Through knowledge of the industrial needs, the hydrology and geology of the aquifer, and teamwork among the users, the Louisville problem was solved and the total withdrawal from the aquifer is now adjusted to the recharge. Such practices may become fairly common in the Delaware River basin in the future. Input wells generally must be supplied with nonturbid and chem¬ ically stable water to prevent plugging. This and many related prob¬ lems of recharging aquifers through input wells, using surface water, is now undergoing research by the Geological Survey and other agencies in several places, notably in Arkansas, Texas, and California. Check Dams and Spreading Basins Perhaps one of the most practical means of artificial recharge is to build a low dam on each surface stream just below the outcrop or intake area of each aquifer so as to raise the head of the water in the aquifer and induce more water to move down the dip beneath the confining beds. Artificial recharge can be accomplished also by constructing spreading basins. These usually are shallow ponds or pits that receive excess runoff during storms. The stored water is allowed to seep into the underlying aquifer for later withdrawal. The basin bottom must be maintained in a permeable condition, and either a considerable hydraulic gradient or a zone of aeration must be maintained between the water in the spreading basin and the water in the formation. At any given place, the percolation rate will be greatest when the water table is well below the bottom of the recharge basin. Under these conditions percolation is vertically downward and proceeds at a maximum rate. The depth to the water able does not affect the rate of percolation, however. For more than 50 years Runyon pond at the Perth Amboy Water Works, ajout 26 miles northeast of the Delaware River basin, has been used effectively as a spreading basin to recharge the Old Bridge sand mem- ■^ ar ^^ an formation at a rate of 0.6 mgd per acre (Barksdale an DeBuchananne ; 19^6, p. 727); and such recharge basins are currently ing used successfully on Long Inland to receive the drainage from storm-water conduits. 144. Infiltration Canals Infiltration canals developed over permeable substrata offer a means of inducing waters, which otherwise would have gone to waste as flood runoff, to seep into, and be stored in, aquifers for later use. Such canals cost no more to construct than other canals or ditches of similar size, but because they tend to silt up they cost more to maintain. As an example of a situation where an infiltration canal might successfully be used as a factor in aquifer management Sprinkling Systems For several years, on farms at Seabrook, N. J», recharge has been applied by sprinkling. The water applied is waste water from a vegetable-processing plant. Barksdale and Remson (195&, P* 522) observe: "On the other hand, at Seabrook, N, J., where recharge water is applied by sprinkling, no soil management has been necessary. The organic matter in the water is removed by biochemical action in the soil. The accelerated soil-forming processes and plant growth that accompany the irrigation seem to maintain and may even increase the infiltration capacity of the forest floor. Some parts of the Sea¬ brook waste-water spreading area have received 4,000 inches of water during the last 4 years and have suffered no apparent diminution of infiltration capacity. Gradual changes In soil structure over a longer period may produce adverse effects, but present indications suggest improvement rather than deterioration of the infiltration capacity". Such a high rate of infiltration is possible only where the aquifer is very permeable. INDI3CED RECHARGE Induced recharge may be thought of as water seeping from streams, lakes or swamps, into aquifers as a result of the cone of depression around a pumping well or a well field spreading far enough to inter¬ sect a body of surface water. In a sense it is a form of artificial recharge. In the early development of wells in this area, induced re¬ charge was accidently begun. Now, it is possible to take advantage of our knowledge of the geologic and hydrologic factors concerned and either intentionally induce or prevent recharge from the stream—a form of conservation of water supply and a definite factor in aquifer management. 1 ^ 5 . Where drawdown in a well reverses the gradient from river to ■ W +v 1 ? r f d ^ entS Very mUch stee P er than exist in nature may become established, and under theee circumstances much larger quantities of water will move from the river into the aquifer than^revJously moved from aquifer to river, Barksdale, Greenman, Lang, and ^ I rte+ail 1 ? 58 ' ?' J: 0it " 108 ) discuss this situation in considerable report ^ m ° St ° f the followins discussion is condensed from their P ? ba “ bdal induced recharge, where an aquifer is in direct contact with the river, is directly proportional to the permeabil- • tabliSLd ° the aqUifer ^ t0 the hydraulic gradient es¬ tablished in it by pumping. This potential, however, will be de¬ creased by river-bottom mud, silt, or clay, or by limited area of “a™?! b f ween the river aquifer. If, for example, sands and PS, 0 ® average aquifer in the Baritan formation of the Camden- lOO^e?^ area f e directly exposed to river water, a strip about , mit On S +u Ul a °! ePt aS mU ° h Water as the a< l u i fer could trans- i ° n . the ° ther hand , where the aquifer in the river bottom is covered by clay, induced recharge would be negligible, for 1 foot of at Lr? eS as much head loss as 10,000 feet of aquifer material at any given rate of flow. ent 2\T~ S±Ta ^l ity ° f induclng recharge from a stream is depend- !m„ T h a qUallty of the strea ” water as well as the quantity avail- Bnnv' p Induce ^ rec barge by water from the Delaware River below Marcus ^ dSr Pf evallill g quality-of-water conditions, would gen- a^ a r f 9 ^ 6 becaPSe of the Probability of. contaminating, arge areas of the aquifer with water of poor quality. 'DelJ^neV 3 subst “ tial evidence that induced recharge from the Delaware River is already occurring in the Philadelphia-Camden aquifer test on the M °rro Phillips tract in Camden in¬ dicated that after 2 years of operation on a new well near the river would he delivering about 90 percent river water. e r id ?u t that the relation9hi P of water in the lower Dela- . R ?-y er to ^ he lifers in hydraulic contact with it must be nr ri ^ ¥ considered in the future development of these aquifers or of dredging and deepening of the river. ^ AQUIFER STORAGE AND INDUCED RECHARGE 1 k6. In the hard-rock region there are in some places thick, extensive, and permeable glacial deposits, chiefly in some of the larger river valleys (pis. I 1 * and 1?). Where connected hydraulically with a perma¬ nent body of water, such as a large lake or a perennial stream, these bodies, largely of sand and gravel, offer tremendous water-supply potential. Large supplies, 900 gpm from an individual well is re¬ ported, have been developed for perennial use in these aquifers. How¬ ever, by temporarily pumping from the aquifers at a rate greater than the recharge rate, storage space can be created in which part of the streamflow can be stored, thus preventing some wastage of the poten¬ tial water crop by runoff to the sea. Manipulation of aquifer storage does not, of course, increase the total water supply in the basin, unless by lowering 1 the Water table evapotranspiration from the aquifer is reduced; the total water-supply potential is determined by the relationship that exists between pre¬ cipitation, runoff, and water loss. However, such manipulation con¬ serves water, makes more water locally available over a longer period of the year, and thus may be highly important. Also such factors as lower temperature and relative freedom from contamination may make ground water more desirable than river water. As an example, let us consider the Delaware River valley between Port Jervis, N. Y., and Milford, Pa. Here the valley is filled with glacial outwash and some till consisting of sand, gravel, silt, and clay to an average depth of about 100 feet over a width of about a mile; the length of this stretch of valley fill is about 6 miles— the distance between Port Jervis and Milford--but the valley fill ex¬ tends both northeast and southwest. In this mass of material between Port Jervis and Milford, assuming that the specific yield is about. 15 percent (perhaps conservative) there would be about 18,000 million gallons of water in storage: Now suppose, by proper spacing and pump¬ ing of wells, that one-fourth of this stored water could be withdrawn from the aquifer except for a strip 1,000 feet wide beneath the river. Under these assumed conditions, there would be produced from storage alone, about 3,600 million gallons or enough to supply 200,000 people for 3 months at 200 gpcd. However, while this much water was being withdrawn from storage in the aquifer, which is connected hydraul¬ ically with the river, a somewhat greater amount would seep from the river, and to a minor extent from the adjacent rocks of the valley walls and floor, as induced recharge brought about by pumping of the wells. Moreover, when one-fourth of the deposits on both sides of the river became dewatered, the rate of induced recharge, chiefly from the river, would be an estimated 100-150 mgd. How might this affect low flows of the river? The minimum low ■flow in this stretch of the river, after completion of the Cannons- | ville dam (scheduled for i960), as set by the U. S. Supreme Court I decree, with respect to New York City diversions, is 1,750 cfs (i,130 mgd) at Montague, N. J. If these operations induced as much as 150 mgd to seep from the river at a time of minimum flow, the daily flow of the river would be reduced by about 13 percent. Clearly this would not be in keeping with provisions of the U. S Supreme Court's decree. .^? r ° bably n ° ° ne would that such water legally could be withdrawn and consumptively used, either within or without the basin* however, it seems likely that the argument would be advanced that within-basin uses--largely non-consumptive as for municipal or in¬ dustrial uses or both—might be legally made. If such pumping were one, iegal suits might develop over the water rights involved, and, as this is an interstate aquifer and stream, the rights of citizens ^f/T ^ erSSy ^ Penafi ylvHnia, an p. III-13 - III-16) Leggette, Brashears, and Graham recommend the emplacement of lines of wells in the Cohansey sand along the Mullica, Batsto, and Wading Rivers, to induce recharge and to derive the optimum quantity of ground water from that part of the Wharton Tract. The water derived from the Mullica-Batsto wells could be diverted to the Camden area by a proposed aqueduct. Water from wells along the Wading River could be diverted to the shore area. V Similar developments of wells in the Cohansey sand in the drainage basins of Great Egg Harbor River and Toms River would undoubtedly pro¬ vide important quantities of ground water. Some equitable division of these waters may be required eventually, in order to supply the needs of the local inhabitants, the nearby growing shore area, and the in¬ dustrialized communities of the Delaware River basin. Developments of water of this kind, and on the large scale envis¬ ioned above, would reduce streamflow from each stream basin so devel¬ oped. In some places induced recharge would take water from the streams and in others ground-water pumping, would reduce the discharge from the aquifers into the streams. Thus, riparian rights, or exist¬ ing ground-water rights (not on streams) might well be interfered with; also, reduced flow in coastal streams would result in salt-water en¬ croachment in their tidal reaches (unless salt-water barriers or other protective works were employed in the seaward ends of the streams). Such possible large-scale developments may, therefore, have far-reach¬ ing effects and would doubtless involve not only hydrologic and eco¬ nomic factors, but legal factors as well. 151 . REFERENCES Anderson, J L», and others, 1948, Cretaceous and Tertiary subsurface geology: Maryland Dept, of Geology, Mines, and Water Resources Bull. 2 , 456 p. Asselstine, E. S., and Grossman, I. G», 1955; The ground-water re¬ sources of Westchester County, N. Y., pt. I, Records of wells and test holes: New York Water Power and Control Comm. Bull. GW 35 . Barksdale, H. C., 1952, Ground water in New Jersey Pine Barrens area: Bartonia, Philadelphia, v. 26, Dec., p. 36 - 38 . Barksdale, H. C., and DeBuchananne, G. D., 1946, Artificial recharge of productive ground-water aquifers in New Jersey: Econ, Geol., v. 41, no. 7, p. 726-737. Barksdale, H. C., Greenman, D. W., Lang, S. M., and others, 1958 , Ground-water resources in the Tri-State region adjacent to the lower Delaware River: New Jersey Dept, of Conserv. and Econ. Devel. Spec. Rept. 13, 190 p. Barksdale, H. C., Johnson, M. E., Baker, R. C., Schaefer, E. J., and DeBuchananne, G. D., 1943, The ground-water supplies of Middlesex County, New Jersey: New Jersey Water Policy Comm. Spec. Rept. 8 , 160 p. Barksdale, H. C., and Remson, Irwin, 1956 , The effect of land-manage¬ ment practices on-ground water: Internet. Assoc, of Hydrology, Pub. 37, Assembled generale de Rome, tome II. Barksdale, H. C., Sundstrom, R. W., and Brunstein, M. S., 1936, Supplement report on the ground'-water supplies of the Atlantic City region: New Jersey Water Policy Comm. Spec. Rept. 6 , 139 p. Bascom, Florence, Clark, W. B., Darton, N. E., and others, 19 O 9 , Description of the Philadelphia district /Pennsylvania-New Jersey- Delaware__/: U. S. Geol. Survey Geol. Atlas, Folio 162. Bascom, Florence, Darton, N* H., Kummel, H. B., Clark, W. B., Miller, B. L., Salisbury, R. D., 1909, Description of the Trenton quadrangle/New Jersey-Penn 3 ylvania J: U. S, Geol. Survey Geol. Atlas, Folio I 67 . Bascom, Florence, and Miller, B. L., 1920, Description of the Elkton- Wilmington quadrangles ^Alary land-Delaware-New Jersey-Penn sylvan ia_7: U. S. Geol. Survey Geol. Atlas, Folio 211. 1932, Description of the Coatesville-West Chester quadrangles /Pennsylvania//: U. S. Geol. Survey Geol. Atlas, Folio 223. Bascom, Florence, Wherry, E, F., Stose, G. W., and Jonas, A. I., 1931, Geology and mineral resources of the Quakert own-Doylestown district /Pennsylvania and New Jersey_7: U. S. Geol. Survey Bull. 828, 62 p. Bascom, Florence, and Stose, G. W., 1938 , Geology and mineral resources of the Honeybrook and Phoenixviile quadrangles /Pennsylvania/^: U. S. Geol. Survey Bull. 891 , 145 p. 3 52 . Bayley, W. S., Kummel, H. B., and Salisbury, R. D., 1914, Description of the Raritan quadrangle /New Jersey/• U. S. Geol. Survey Geol. Atlas, Folio 191. Behre, C. H., Jr., 1933, Slate in Pennsylvania? Pennsylvania Geol. Survey, 4th ser., Bull. M 1 6 . Bennett, R. R., and Meyer, R. R., 1952, Geology and ground-water re¬ sources of the Baltimore area: Maryland Dept, of Geology, Mines, and Water Resources Bull. 4, 555 P« Bennison, E. W., 1947* Ground Water, its development, uses, and con¬ servation: St. Paul, Edward E. Johnson Co., 509 p° Campbell, M. R., and Bascom, Florence, 1933, Origin and structure of the Pensauken gravel: Am. Jour* Sci., 5th ser., v. 2 6 , p. 300-318. Chadwibk, G. H., 1932, Eastern States Oil and Gas Weekly, v. 1, no. 17,p. Cohen, Bernard, 1957,. Salinity of the Delaware Estuary: U. S. Geol. Survey open-file report, 86 p. Connecticut Geology and Natural History Survey, 1956, Preliminary geological map of Connecticut: Bull. 84. Connecticut Water Resources Commission, 1957, Water resources of Connecticut: Report to the General Assembly. Darton, N. H., Bayley, W. S., Salisbury, R. D.„ q,nd Kummel, H. B., 1908, Description of the Passaic quadrangle /New Jersey-New York/:< U. S. Geol. Survey Geol. Atlas, Folio 167 . DeLaguna, Wallace, and Perlmutter> N. M., 1949, in Suter, Russell, and others, Mapping geologic formations and aquifers on Long Island, N. Y.: New York Water Power and Control Comm. Bull. GW-l 8 . Ewing, W. M., Woollard, G. P., and Vine, A. C., 1939, Geophysical in¬ vestigations in the emerged and submerged Atlantic Coastal Plain: Pt. Ill, Barnegat Bay, N. J., section: Geol. Soc. Am. Bull, v. 50, P . 257 - 296 . _I 9 U 0 , Geophysical investigations in the emerged and submerged Atlantic Coastal Plain; Pt. IV, Cape May, N. J., section: Geol. Soc. Am. Bull, v. 51, p. 1821-1840. Fenneman, N. M., 1938, Physiography of eastern United States: New York, McGraw-Hill Book Co., 691 p. Flint, R. F., 1957, Glacial and Pleistocene geology: New York, John Wiley and Sons, 509 p. Fluhr, T. W., 1953, Geology of New York City’s water-supply system: Municip. Eng. Jour., v. 39, P» 125-245. Graham, J. B., 1950, Ground-water problems in the Philadelphia area: Econ. Geol., v. 45, no. 3, P° 210-221. Gray, Carlyle, and others, 1958, Geologic map of Pennsylvania: Penn¬ sylvania Geol. Survey, 4th ser. (in preparation). Greenman, D. W., 1955, Ground-water resources of Bucks County, Pa.: Pennsylvania Geol. Survey, 4th ser.. Bull. W 11, 66 p. Gregory, H. E., and Ellis, A. J., 1916 , Ground water in the Hartford, Stamford, Salisbury, Willimantic, and Saybrook areas. Conn.: U. S. Geol. Survey Water-Supply Paper 374, 150 p. 153 . Groot, J. J., Organist, D. M., and Richards, H. G., 195 U, Marine Upper Cretaceous formations of the Chesapeake & Delaware Canal: Delaware Geol, Survey Bull. 3 , 64 p. Grossman, I. G,, 1957, The ground-water resources of Putnam County N e Y.: New York Water Power and Control Comm. Bull. GW- 37 . Hall, G. M,, 1934. Ground water in southeastern Pennsylvania: Penn¬ sylvania Geol. Survey, 4th ser., Bull, W 2, 255 p. Herpers, Henry, and Barksdale, H. C,, 1951, Preliminary report on the geology and ground-water supply of the Newark, N. J., area: New Jersey Dept. Conserv. amd Econ. Devel., Div. Water Policy and Supply, Spec. Rept. 10, 52 p, Howell, B. F., Roberts, Henry, and Willard, Bradford, 1950 , Sub¬ division and dating of the Cambrian of eastern Pennsylvania: Geol Soc. Am. Bull., v. 6 l, p. 1335-1368. Johnson, M. E., and Mclaughlin, D, B., 1957, Triassic formations in the Delaware valley: Geol. Soc. Am, Guidebook, Atlantic City meeting. Kammerer, J. C., 1957, Records available to September 30, 1956 , on use of water in the Delaware Basin Project area: U. S. Geol/ Survey open-file report, 33 p D Kummel, H. B., 1897 , Annual Report of State Geologist for- 1896 : New Jersey Geol. Survey, p. 25-88. Leggette, R. M,, and others, 1938 , Records of wells, springs, and ground-water levels in the towns of Bridgeoort, Easton, Fairfield, Stratford, and Trumbull, Conn,- : Connecticut Ground-water Survev Bull., GW- 1 , 242 £. ' Lewis, J. V,, and Kummel, H. B*, 1910-12, revised by Kummel, 1931, and Johnson, M, E., 1950, Geologic map of New Jersey: New Jersey Dept. Conserv. and Econ, Devel. Atlas, sheet 40. 19"! 5. lev Jersey Geol. Survey Bull, l4, p. 56 Lohman, S. W., 1937, Ground water in northeastern Pennsylvania: Penn¬ sylvania Geol, Survey, 4th ser., Bull.. W 4, 300 p. Lusczynski, N. J., 1952 , The recovery of ground-water levels in Brooklyn, N. Y», from 1947 to 1950: U. S. Geol. Survey Circ. 167 , 29 p. Marine, I. W., and Rasmussen, W, C,, 1955, Preliminary report on the geology and ground-water resources of Delaware: Delaware Geol e Survev Bull. 4, 335 p. Meinzer, 0. E., and Stearns, N. D», 1929 , A study of ground water in the Pomperaug basin, Connecticut: U 0 S, Geol. Survey Water-Supply Paper 597-B, i46 p, Merrill, F. J. H,, 1901, Geologic map of New York: New York State Museum Bull. 56 , ( 1902 ). Merrill, F. J. H., Darton, N« H., Hollick, Arthur, Salisbury, R. D., Dodge, R. E., Willis, Bailey, and Pressey, H. A., 1902, Description of the New York City district /New York-New Jersey7: U, S. Geol. Survey Atlas, Folio 83 . Miller, B. L., 1906 , Description of the Dover quadrangle ^Delaware- ,Maryland-New Jersey^: U. S. Geol. Survey Geol. Atlas, Folio 137- Miller, B. L., Bradford, Willard, Fraser, D. M., and others, 1939, Northampton County, Pa., geology and geography: Pennsylvania Geol. Survey, 4th ser., Bull C 48, 495 P» Miller, B. L., Fraser, D. M,, Miller, R. L., and others, 1941, I^high County, Pa., geology and geography: Pennsylvania Geol. Survey, 4th ser.. Bull. C 39, 492 p. Muskat, Morris, 1937, The flow of homogenous fluids through porous media: New York, McGraw-Hill Book Co., 763 P» New England-New York Interagency Committee, 1954, Resources of the New England-New York Region, Part 2, Chapter 22, Housatonic River basin. Connecticut-Massachusetts-New York: Washington, D. C. 1954, Resources of the New England-New York Region, Part 2, Chapter 237 Connecticut Coastal basins, Conn.: Washington, D. c. New York Department of Conservation, 1956, Saline waters in New York State: Bull. GW 36 • Palmer, H. S., 1920, Ground water in the Norwalk, Suffield, and Glastonbury areas. Conn.: U. S. Geol. Survey Water-Supply Paper 470, 171 p. . _ ' , Parker, Garald G., 1955, The encroachment of salt water into fresh in Water, the Yearbook of Agriculture: U. S. Dept, of Agric., p. 615 - 635 , 723 . Love, S. K., Parker, Garald G., Ferguson, G. E.,/and others, 1955, Water resources of southeastern Florida: U. S. Geol. Survey Water-Supply Paper 1255, 9^5 p. . Penck, W., (translated by Czech and Boswell) 1953, Morphological analysis of landforms: London, MacMillan and Co., 429 p. Philadelphia Inquirer, 1957, Fairmount Park Springs contaminated and unsafe: Oct. 10. Rasmussen, W. C., 1953, Periglacial frost-thaw basins in New Jersey-- a discussion: Jour. Geol. v. 6 l, p. 473-474. _1955, Magnitude of the ground waters of Delaware: Maryland- Delaware Water and Sewage Assoc. Proc. 28th Ann. Conf., p. 53-66. Rasmussen, W. C., and Andreasen, C. E., 1958, Hydrologic budget of the Be'averdam Creek basin, Maryland: U. S. Geol. Survey Water- Supply Paper 1472 (in press). Rasmussen, W. C., and Beamer, N. H., 3-956, Wells for the observation of chloride and water levels in aquifers that cross the Chesapeake~-& Delaware Canal: U. S. Geol. Survey open-file rept., 42 p. Rasmussen, W. C., Groot, J. J., Martin, R. 0. R., McCarren, E. F., Behn, V. C., and others, 1957, Water resources of northern Delaware: Delaware Geol. Survey Bull. 6 , 222 p. Rasmussen, W. C., Slaughter, J. H., Hulme, A, E., and Murphy, J. J., 1957, The water resources of Caroline, Dorchester, and Talbot Counties: Mary land. Dept. of Geology, Mines, and Water Resources Bull. 18, 465 p. Richards, H. G., 1956, Geology of the Delaware valley: Pennsylvania Mineralog. Soc., Philadelphia, 106 p. 155 . Ruxton, B. P., and Berry, Leonard, 1957 , Weathering of granite and associated erosional features in Hong Kong: Geol. Soc. Am. Bull v. 68 , p. 1263 - 1292 . *' Smith, B. L., 1957, Summary of the Precambrian geology of the New Jersey Highlands: Geol. Soc. Am. Guidebook, Atlantic City meeting, p. 71-76. Spencer, A. C., Kumrael, H. B., Wolff, J. E ., Salisbury, R. D., and Palache, Charles, 1908 , Description of the Franklin Furnace quad¬ rangle /Pennsylvania/: Ih S. Geol. Survey Geol. Atlas, Folio l 6 l. Sverdrup, H. V., Johnson, M. W, , and Fleming, R. H., 19 46, The oceans; their physics, chemistry, and general biology; New York, Prentice-Hall, 1087 p, Swartz, C. K., and Swartz, F. M., 1931, Early Silurian formations of southeastern Pennsylvania: Geol. Soc. Am. Bull;, v. 42, p. 621-662. _19M, Early Devonian and Late Silurian formations in southeastern Pennsylvania: Geol. Soc. Am. Bull., v. 52, p. 1129-1191. Thompson, D. G., 1928, Ground-water supplies of the Atlantic City region: New Jersey Dept. Conserv. and Devel. Bull. 30 , 138 p. _1930, Ground-water supplies in the vicinity of Asbury Park, N. J.: New Jersey Dept, of Conserv. and Devel. Bull 35 . Tippetts-Abbett-McCarthy-Stratton (T-A-M-S), 1955, Survey of New Jersey water-resources development: New Jersey Legislative Comm, on Water Supply, 130 p. Todd, D. K., 1952, An abstract of the literature pertaining to sea¬ water intrusion and its control: Berkeley, Univ. of California, 72 p. Trexler, J. P., 1953, Geology of Godfrey Ridge, near Stroudsburg, Pa.: M. S. thesis, Lehigh Univ^ U. S. Bureau of the Census, 1954, Census of Agriculture, middle Atlantic States, counties, and economic areas: v. 1 , pt. 2 , p. 44-49. Ward, R. F., 1956, The geology of the Wissahickon formation in Delaware: U. S. Geol. Survey open-file rept., 59 p. Waterways Experiment Station, 1956, Delaware River Model Study report 1 , Hydraulic and salinity verification: U. S. Corps of Engineers, Water¬ ways Experiment Station Tech, memo 2-337, Vicksburg, Miss., 25 p. Watson, E. H., 1957 , Crystalline rocks of the Philadelphia area: Gieol. Soc. Am. Guidebook, Atlantic City meeting, p. 153-180. Weller, S., 1900, New Jersey Geol. Survey Ann. Rept. State Geologist 1899, p. 3-46. Wherry, E. T., 1909 , Science, n. s., v. 30 , r». 4l6. White, I. C., l 88 l, 2d. Penna, Geol. Survey Rept. White, I. C., 1882, 2d. Penna. Geol. Survey Rept. Willard, Bradford, 1935, Geol. Soc. America Bull., v. 46, p. 202, 205-223. __1936, New York State Mus. Bull. 307, p. 74. Willard, Bradford, Swartz, F. M., and Cleaves, A. B., 1939, The Devonian of Pennsylvania: Pennsylvania Geol. Survey, 4th ser., Bull. G 19 , 48l p. Wilmarth, M. G., 1938, Lexicon of geologic names: U. S. Geol. Survey Bull. 896 , 2396 p. Vanuxem, L., 1842, Geology of New York, pt. 3 : Natural History of New York, v. 3 , pt. 4. . ' u \ \ ware River basin t Pennsylvania, < by dashed lines lAbLE 1 tquir&lent formation, in oth.r areas are «hovn in are considered as single hydrologic units. Hydrologic properties chea and off- Accepts recharge readily and In places contains fresh water sufficient for development of aaall supplies. sad maps • Saturated and frequently covered with water which in estu¬ aries sad bays near the ocean is more or Less saline; permeability generally moderate to low. y to coarse glacial Water occurs under unconfirmed to locally eemiconfined or confined conditions and, at most plnces near surface- water bodies, le hydraulically connected with them. Potentially a highly productive aquifer, especially in major stream valleys such as the upper reaches and tribu¬ taries of the Delaware River and of the Delaware River near Trenton, I. J. Where relatively thick bodies of sand and gravel are available, well yields of several thousand gallons per minute may be obtained, derived in part from streams ss induced recharge. Quality of water is generally good, although concentration of dls- •olv'sd iron is high in places. Bank storage in these deposits may significantly affsct streamflow regimen. its, largely ▼allays that Ludes also glacial till iln size from Lne-grained L marshes. m strati- terraces, J These i* bed as Many springs Issua from these deposits, and substantial supplies of water may be obtained in the thicker masses from both springs and wells. ir- *t of the 1 to a few ; generally tded vlth ik of Generally not a dependable so urea of water supply because of limited thickness and low perms ability, in many areas springs are common at contact with underlying bedrock, vhloh suggests that much of the contained water is perched or scmiperched. RANG OCAS GROUP i • 2 dnojS qs T72- I 1 •09001 J»H01 MI9001 •TPPTM ^ ^ J F J 1 J * J-T-> •0*001 'X*UjQ •oooovpij •nasoTM •ooooVptO •OOOOTM 09-1^ Tirliory TABLE 1 (Cont'd. ) rer b asin--Continue - * . Hydrologic properties of brownish- green, Includes srate e area e re la¬ the north¬ ed to hora- ck. Un- lov ridges thin soils Contains unconfined water in weathered part above a depth of about 250 feet and semiconfined to confined water in comparatively permeable zones rarely more than 20 feet thick from 250 to about 600 feet. Long-term yields of wells commonly are no more than one-third of the initial yield. Yields of drilled wells 300-600 feet deep range from about 25 to 500 gpm and are generally greatest in the northeast part of the Triassic Lowland, outside the basin. Water is moderately mineralized and moderately hard but is satisfactory for most uses without treatment. Runoff from outcrop is very flashy because of thin, poorly permeable soils and relatively small available 1 ground- water storage capacity of the formation. te (hard zones of thin- Jrgillite, Lte and some salon, vlth atneat ridges 1 plateaus lin yellowish- An unimportant source of water supply because of its very low porosity and permeability. verage yield of wells is only about 5-15 gpm. Water is moderate)y- to highly* mineralized and hard but does not consnonly contain ob¬ jectionable concentrations of any constituent except hardness-forming minerals. Runoff from outcrop is ex¬ tremely flashy because of low permeability of thin soils and small ground-water storage capacity available to sustain base flow. irkose (sand- maaller ircrvn sand- lation is part. Beds and se- ■kose and con- shale form keat and most lerate. One of the most productive of the hard-rock formations. Most water occurs under confined or semiconfined condi¬ tions in weathered zone within about 500 feet of the land surface. Rocks having highest permeability are coarse¬ grained arkose and conglomerate which contain water in intergranular openings where original cementing material has been removed by weathering, as well as in fractures. Yields of modern drilled wells commonly exceed 50 gpm and may locally exceed 500 gpm. Water contains moderate concentrations of dissolved solids and hardness-forming minerals and is generally low in iron content; concentra¬ tion of sulfate is high in places. Runoff from outcrop probably is le6S flashy than that from other formations of the Triassic Lowland. In coal-mining areas, unirnnortant as r\+ haibKI. >8 OTTOJAOpJQ ns'popLopjo •XPPTH wpopLopao v////;myym////xA \ [TTK *n l«Og p«a o£*ro£i OiZ-Slt Ordovician Silurian TABLE 6 basin and adjacent areas of New Jersey and New Vor T EASTERN PENNSYLVAMIA :au5 province U—- T _ j.W'Ho^ViiSwiartt Cl«av«* S'Atarix. a*J ! Nle^ Vnfrose red shale of W hi te (I«d 0 3) i CL ita*/issa red* 2hadw'.«.k (.1^32.;) £ c — V Ttfel 5 Kale- of Chadwick ( 32 ) ii e #^4 5<3ndo+one vheora formation ILL Iboa formation ii o> cl 0 3 t 0 ater3lu>l -formation f tuillord ( | Rock 3ani*4one Lauren* ja«i5+»«< a+ base Ca+sLill -f ormah#r Upper Devonian marine ” ^Moscow shale • Ludlowvilte +ormo-»»ar, Ccn+er-rieli r**f Skan«*it«lcs -formation Marfella> shale ( iie. 0 A^ahan-ban /Vorf E'jsien Shal< Ori^kany group De vonijn Devonian Lower* €> e ^«ujn Upper Or»ck*nf*rr*««ViOA DKunne man* conglomerate Portae group Bellvflle tand^Hne I o4 Lewis a a sHa|< ; Orijkony sandstone. OriSkan^ Sandstone £ ( Ew^n 1 1 A\es 4-o a e I k_ Becraff limesfontl O' Storm* ilia sandatowc o4 Weller (l *4 00 / R?rt Fwen limestone Becraft limestone. ^ l New Scotland \irust©*t ^ New Scotland jQ ^ yCoc»jmanj Umeyf«Ae Manlius limts+o^t Decker limeston-e. I Rondout limest©** Decker limestone. S4or**wiUc Scnis+one- *\/«ller ( 1 100) ^Cot^mtfnj limestone Manlius limestone l^Ondout limestone I Decker limestone BoSSUrdsviHe Lmeston* WillsCre^k 5kale ^ f 3 oS$ardsv*U< limestone Nil's Creek sKale L-ongwood snaie felftMMbw* rtibe<>> | Hi»h F«H» fcrma+..« ‘ Sehebdrit £ 50pus Oriskany f, v \ Port Ewl Alien cl Becratt New Sctf kallcbC' yCoeyAAi Manlius I Roncieut l Decker W* Bloo^sour^ I 61 r*ne »jaTor {oJ ftrebau, High Fells si I (3 r«CA Pond Conglomerate. I SKa*>flngjnk COnglomeraT-* | Shawangunk conglomerate i ShawOngUAlc Martinsbur-g Shale | Martinsburg shale MarTTmburg shale Mart\nsburg shale beesport limestone Jatk^onbur^ lim«s+*n« Jackoonb^rg lime etone Coneetoga 2.) llrrvCSto a« BteSm^nVo^A 1 3cek*>ron4 r»m IlmcotaA* Jdcks©n»burg limestone I Jacksanourg limestone I 0 co*.rva»r\-tovvn L me stone limestone ConottfcWeaguc limestone Allentown limestone Allento a*a limestone of Wk«rry (wolj 3) Coeke^svtlle marble £lbr©o*. limestone kittatinny l\meston«. _ . . - - jtpn ot Wherry i iqo^) Ll’meport liMcsVone o4 H o we II ,Rob« r'ts, and Willard (l<< 50 ) 3) kittatiAny limestone I ledger dolomite iCinuers formation \imlage JoWmiTa. Tomsto-un 144 • m — - - 33 -- 7.8 1.8 ■» • — - - 15 9.9 .8 33 2.8 -5-7 --- 52 4.1 *.5 0.0 13 _2i_. ' er in consolidated rocks in Appalachian Highlands parts per million) Magne¬ sium (M«) Potas- sium (K) Bicar¬ bonate (hco 3 ) Dis¬ solved solids Jn <1 r v.7 Table Q —Banr.sents.tlva chemical analyses of water in unconsoli d ated sediments In Appalachian High , lan ds (Concentrations In rarts per million) TABLE 9-10 Anal¬ ysis no. County and state Depth (feet) Date of collection Temper¬ ature Oy Silica (Si0 2 ) Iron (F«) Man¬ ganese (Mn) Cal¬ cium (Ca) 1 Monroe, Pa. • • 9-22-30 48 — -- 2 2 Wayne, Pa. 28 9-20-30 6o -- • • • • 7 3 Orange, R. Y. 110 8-7-47 — — .18 0.01 — 4 Sullivan, 5. Y. 57 4-19-56 .10 — 5 Delaware, R. Y. l66 7-10-46 .15 .015 • • 6 Delaware, R. Y. 70 5-18-49 — 8.5 .15 — l6 Sodium (Na) Potas- Bicar- Sulfate Chlor- Fluor- Ni- Die- Hardness as CaC0 3 si van (Mg) slum 00 bonate (HC0 3 ) (S04) ide (Cl) ide (F) trate (ro 3 ) solved solids Total Ron car¬ bonate pH .. V 2.8 -1 7- 15- 25 133 33 15 _ < 2 14 10.1 8.9 4.1 1.0 4.0 2.4 7.8 .8 4.5 0.0 0.1 2.4 l.~8 13 lH 50 144 33 2it 14 40 88 58 28 51 7 - 7.9 6.0 6.8 UL Table 10. —Represent at ire chemical analyses of water in consolidated rocks in Appalachiaa Highlands iConcentrations in parts per million) Martinsburg 1 Lehigh, Pa. 75 11-18-54 54 — 1.4 -- 2 Lehigh, Pa. 129 11-4-54 54 — - -33 — -- Anal- ysis no. County and state Depth Date of collection Temper¬ ature °F Silica Iron Man- Cal¬ cium (c.) Magne¬ sium (Mg) Sodium Potas¬ sium (K) Bicar¬ bonate (HCO3) Sulfate Cfclor- Fluor- Ni- Dis- Hardness as CaCO-^ (feet) (SiOp) (Pe) ganese (mn) (Na) (so u ) ide (Cl) ide (F) trate (NO3) solved solids Total won- car- pH bonate shale 3 4 5 6 ~W 33 34 3? Schuylkill, Pa. Vayne, Pa. 30 I Chester, 31 Bucks, Pa. Rev Castle, Del. Chester, Pa. Delaware, Pa. Bucks, Pa. Bucks, Pa, 120 238 5-4-49 9-19-30 T9" 5L 7.5 AA .17 .01 504 110 184 48 300 22 1-19-56 9-21-25 9-26-25 4-28-53 1-21-54 Catskilf 5.0 28 Lockatong Stockton Carbonate 17 16 IQ Lancaster, Pa. Bucks, Pa. Lehigh, Pa. 105 175 100 34 9-24-25 4- 14-53 5- 15-53 5-12-53 1-6-55 54 58 52 50 7.9 7.2 9.8 6.0 .10 .08 .01 .02 .63 — 72 65 20 21 Lehigh, Pa. Lehigh, Pa. Diabase 22 Montgomery, Pa. 350 4-21-49 — 31 1.0 *— • 23 Bucks, Pa. 765 4-8-53 55 25 .4 94 24 Bucks. Pa. Z£ _ 18 1.4 — 48 Gneiss 25 Chester, Pa. 54 9-25-25 mm 31 .31 •» <■ rr?f- 26 Bucks, Pa. 226 9-7-53 53 8.7 .29 2.9 27 Bucks, Pa. 198 4-9-53 54 15 1.1 18 28 Lehigh, Pa. 250 12-2-54 53 .61 Lehigh, Pa. 90 12-7-54 £3 — .AJL. . — — Chickies _25 Wissahickon 51 18- • V*T -- 23 .11 • • 54 28 4.1 57 24 3.4 mm 58 20 >15 — - - 4.3 - -- 3.6 - 62 -2 l 61 Ji 7 L 7.8 15 formation 121 70 ■ 2*1 4 7 1TT 4.3 Tormation Bucks, Pa. 330 4-22-53 53 ~T5- —oU ■ __ "TB- Bucks, Pa. -- _ 13 — ? 2>. -- -5P 15 AL 7.0 15 TT 1.2 120 174 nr 54 7.0 16 0.0 .1 2.1 .1 formation 229 274 7 Chester, Pa. 752 — 2 & - .14 0.01 “T5-- 8 Montgomery, Pa. — 6-28-56 - - 30 .17 .00 59 9 Bucks, Pa. — 3-24-53 54 18 .66 29 10 Bucks, Pa. — 4-17-53 54 15 .04 30 11 Bucks, Pa. 227 4-9-53 53 20 .25 22 12 Mercer, R. J. 372 9-27-49 — 27 .03 «. «, 27 Brunswick 13 Montgomery, Pa. 100 4-21-49 54 20 .17 52 14 Bucks, Pa. 300 3-25-53 52 22 1.3 77 15 Bucks, Pa. 303 4-7-53 53 19 1.1 37 16 Bucks, Pa. 511 9-8-53 56 17 .04 .4?.,. formation 13 11 1.4 198 23 7.0 .0 12 18 13 1.0 164 144 7.0 .3 2.8 16 13 1.8 172 31 10 .1 1.8 14 26 .6 156 53 22 .1 21 rocks IT 36 11 18 “ 6.5 ~ 3.5 - 4.2 7.1 2.2 217 312 134 108 258 30 15 2.3 8.4 22 46 4.0 4.5 579 572“ “TT 5" 5-1 4.5 3.8 80 formation 4.6 3.7 1.6 22 4.2 5.8 1.4 43 1.7 8.3 2.4 26 8-3 Ui 2.8 26 5.0 4.3 9.1 18 4.0 5.2 5.4 16 - 125 .0 122 .1 .1 .3 132 186 33 44 1.0 290 219 40 22 397 310 55 7.0 • 3 -- 104 0 7.8 10 — 104 16 7.7 15_ -- 320 109 7.4 74 32 9 85 45 14 72 154 17 0 48 88197 0-62 (Vol. VII) (In pocket) No. 4 7.7 6.8 4*9 1 -7 TT ■' I 12 3.5 0 12 I 5 8 j 28 1 22 j 20 | 2.4 1 104 1 23 20 — 3«° 1 176 1 90 1 4 oTT 7T JA 24 - - 17 -- 127 123 9-5 .1 2.7 “Hr 211 107 "in 17 - - 17 - ~ — 154 47 28. .1 48 351 217 91 7.2 17 8.3 .8 154 19 8.5 .0 5.5 195 142 16 7.7 9.9 37 3-5 48 72 54 .0 16 304 116 76 6.0 6.7 12 1 72 34 10 .0 1.2 156 82 23 6.3 6 .8 12 1.7 88 20 11 .0 12 158 95 28 6.7 242 "W 21 7.5 381 266 132 7.7 217 158 17 7.4 180 52 JLJ 5.9 6 ^ UN 'VE(?S(JY IUlN 0IS UBHAfiY 333 . 3 ) Urv 2,2. v v.? r U. S. GEOLOGICAL SURVEY 15 ' 76 * 00 ' 45 EXPLANATION Fall line-major division boundary, dashed where vague or arbitrary Boundary of province, dashed where vague or arbitrary Boundary of section or sub-province, dashed where vague or arbitrary Southern limit of Wisconsin glaciation CLASSIFICATION OF UNITS Major division Atlantic Plain Province Coastal Plain Section or sub-province Appalachian Highlands Piedmont Piedmont Upland Piedmont or Triassic Lowland New England Reading prong of New England\Uplc i f Great Valiev PLATE 3 U. S. GEOLOGICAL SURVEY 74*00' 73*50' EXPLANATION Foil line-mojor division boundary, dashed where vague or arbitrary Boundary of province, dashed where vague or arbitrary Boundary of section or sub-province dashed where vague or arbitrary Southern limit of Wisconsin glaciation CLASSIFICATION OF UNITS Province Coastal Plain Section or sub-province division Piedmont Piedmont Piedmont or Triossic Lowland Reading prong of New England\Uplohd NewEngland Appalachian Highlands Great Volley Valley ond Ridge (Valleys and ridges north of Blue MountainI Southern New York section Appalachian Plateaus CatskiH Mountains StfANTC Mr . st a 9 NEWAtK ' IviNCrON, NEW YORK! Reading prong TltEKTON Camden ATLANTIC cm 20 Miles Refined by F. H.Olmsted on basis of topography from Fennemon,N.M., 1930 Physiography of eastern United States. 88197 0-62 (Vol. VII) (In pocket) No. 5 UNIVERSITY Of ILLINOIS LIBRARY 333.91 U*;w,r v -7 U S. GEOLOGICAL SURVEY PLATE 5 EXPLANATION ' t l u. S. GEOLOGICAL SURVEY PLATE 5 88197 0-62 (Vol. VII) (In pocket) No. 6 UNIVERSITY Of ILLINOIS LIBRARY PLATE 6 ong RfOfich 73 * 50 ' 40 ° 30 / 15 ' 333.0| On Y. 7 9JOMO/B(J L jaddp) < ui (snoa. sapn/ombi T N 'OJCh puo Ajn U.S. GEOL 76 ° 30 / PLATE 7 7 4° 00' RARITAN BAY Xeansburg SANDY MOO last Keansburg Atlantic Highlands nasquan i* Plecsant 7 3° 50' —-i 40°30' i l i I ^eutiT-r- ’eeum-'n' PLATE 11 15 PLATE 12 a'aa.Sl \Jr\ 7j2j r v. 7 u. 76°30' 42°30\—— PLATE 14 I 7T