9 LIBRARY UNIVERSITY OF CALIFORNIA DAVIS y t- IVEF.L Lll 4 COPY 2 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING BULLETIN NO. 63 SEA-WATER INTRUSION IN CALIFORNIA GOODWIN J. KNIGHT Governor HARVEY O. BANKS Director of Water Resources November, 1958 fuNlVEFi JFORNIA FEB LIBRARY STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING BULLETIN NO. 63 SEA-WATER INTRUSION IN CALIFORNIA GOODWIN J. KNIGHl Pfr : { 3 G ^ \ HARVEY O. BANKS Governor \a\\ '& FitJffldi Director of Water Resources November, 1958 LIBRARY UNIVERSITY OF CALIFORNIA DAVIS TABLE OF CONTENTS I 'age LETTER OF TRANSMITTAL 5 ACKNOWLEDGMENT i iRCAXIZATION, STATF RESOURCES DEPARTMENT OP WATER ORGANIZATION, CALIFORNIA WATER COMMISSION 19 19 19 ORGANIZATIONAL CHANGES 8 (CHAPTER I. INTRODUCTION Authorization for Investigation !• Related Investigations and Reports !• Scope of Investigation and Report 1(1 Area Under Investigation 11 Definitions 11 Water Quality Criteria 13 CHAPTER II. PHYSICAL CHARACTERISTICS OF SEA WATER INTRUSION INTO AQUIFERS 15 Prerequisite Conditions 15 Geologic Conditions 15 Hydraulic Conditions 15 Fresh Water-Salt Water Relationships 15 The Sea-Water Wedge 16 Other Causes of Increased Ground Watei Salinity Hi Applicability to Existing Conditions 16 CHAPTER III. PRESENT STATUS OF SEA-WATER INTRUSION IN CALIFORNIA Areas of Known Sea-Water Intrusion Areas of Suspected Sea-Water Intrusion and Areas Where Chlorides Exceed 100 Parts Per Million Areas of No Apparent Sea-Water Intrusion Areas Where the Status of Sen-Water Intrusion Is Un- known Descriptions of Areas of Known Sea- Water Intrusion Petaluma Valley Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Napa-Sonoma Valley Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Santa Clara Valley Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Pajaro Valley Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Salinas Valley Pressure Area Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Oxnard Plain Basin Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion West Coast Basin Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion East Coastal Plain Pressure Area Occurrence and Movement of Ground Water Quality of Water Status of Sea-Water Intrusion Mission Basin Occurrence and Movement of Ground Water Quality of Water — Status of Sea-Water Intrusion 23 23 23 23 24 24 2.1 25 211 21 i 2(> 27 28 28 29 2! I 30 30 31 31 32 32 :;:•, 33 34 34 34 34 35 311 37 37 38 38 3!) 3! I 3! I 3! I i ■ , ■ CHAPTER IV. METHODS OF CONTROL OF SEA WATER INTRUSION 41 Raising of Ground Water Levels to or Above Sea Level by Reduction in Extractions and/or Rearrange nl of Area! Pattern of Pumping Draft 41 Costs 42 Direct Recharge of Overdrawn Aquifers to Maintain Ground Water Levels ai or Above Sea Level 12 Costs *'■> Maintenance of a Fresh-Water Ridge Above Sea Level Along the Coast 44 Costs 14 Construction of Artificial Subsurface Barriers - 44 Costs 45 Development of a Pumping Trough Adjacent to the Coast 16 Costs 46 Comparison of Costs 4li CHAPTER V. EXPERIMENTAL STUDIES PERTI- NENT T(> THE SEA-WATER INTRUSION PROB- LEM 49 Prior Experimental Studies 49 Parameters Governing Intrusion of Saline Waters . 4'.i European Studies 49 Degradation of Ground Water Quality at Nassau. Ba- hama Islands •'" Studies in Japan 50 Investigations in the Hawaiian and Other Pacific [s lands 50 Ground Water Quality Studies in Connecticut 50 Sea Water Encroachment ill Galveston-Houston Area, Texas 50 Degradation of Ground Water Quality Near l'arlin. New Jersey 50 Investigations Conducted in Florida. — oil investigations of the Occurrence and Movement of Sea- Water Intrusion in California 51 Recharge of Ground Water Through Injection Wells 51 Replenishment of Ground Water Supply at Long I> land. New York - 51 Injection Through a Brackish Water Well at Camp Peary. Virginia 52 Management of Ground Water Supplies at Louisville, Kentucky and Binghamton, New York 52 Deep Aquifer Replenishment at Canton, Ohio 53 Artificial Recharge Experiments tit El Paso, Texas— 5:: Injection Well Experiments by Los Angeles County Flood Control District in 1950 53 Injecting Reclaimed Sewage Into Ground Water Aquifers in West Coast Basin. California-- 54 Investigation of Travel of Pollution, University of California 54 Other Uses of Injection Wells 55 Recharge of Ground Water Thr.. ugh Surface Spreading- 55 Artificial Recharge Basins on Long Island, New York— 55 Los Angeles County Flood Control District Experiments Near Redondo Beach 55 Sewage Spreading Experiments by Los Angeles County Flood Control District at Whittier and Azusa 55 University id' California Sewage Reclamation Field Studies at Lodi 56 Artificial Subsurface Harriers by Grouting 56 Cement Slurries 56 Chemical Injection 56 Use of Silts and Clays 57 Asphalts 58 Artificial Subsurface Harrier Through Construction of Earthen Wall 58 Wilmington. California 59 Pasco, Washington 59 Kennewick. Washington 5!) Experimental Studies Under Chapter 1500, Statutes of 11151 ( 1 ) TABLE OF CONTENTS-Continued Page West Coast Basis Experimental Project, Los Angeles County 60 Experimental Objectives 00 Description of Field Site 00 Projecl Facilities (il Recharge Operations 62 Recharge Water Treatment 02 Occurrence and Movement of Saline Wedge OH Derivation of Equation for Fresh Water Waste to Ocean 63 Test Results 03 Costs 64 Applicability to Other Areas 64 Laboratory Experiments Performed by the University of California at Berkeley 65 Reduction of Aquifer Permeability 65 Model Aquifer .Studies 60 Laboratory Studies Performed by the University of California at Los Angeles 68 Project Faeilities 68 Test Procedures 68 Test Results 08 Sea-Water Intrusion Studies by the United States Geo- logical Survey 69 Test Procedures and Results 69 Other Experimental Studies 69 Recharge Tunnel Experiments in Honolulu Area 69 United States Geological Survey Studies in Florida TO Activities of the High Plains Underground Water Con- servation District No. 1, Texas 7(1 University of Arkansas Field Experiments in the Grand Prairie Region 7(1 Pit Injection at Peoria, Illinois . To Injection Through Wells at Kins Ranch, Texas 71 Studies by the United States Department of Agricul- ture. Agricultural Research Service. In San Joa- quin Valley 71 Los Angeles County Flood Control District Recharge Tests Near El Segundo Using Reclaimed Sewage— 71 CHAPTER VI. ECONOMIC AND LEGAL CONSID- ERATIONS 73 Economic Aspects of Sea-Water Intrusion 73 Some Consequences of Inaction 73 Protection of Safe Yield 73 Urban Development 74 Agricultural Development 74 Increase in Supply Through Utilization of Imports 74 Other Considerations 74 Economic Planning Required for Choice of Alternative Courses of Action 7r> Legal Aspects of Sea-Water Intrusion 75 Authority to Control Sea-Water Intrusion 7.1 Determination of Water Rights 77 CHAPTER VII. PLANS FOR PREVENTION AND CONTROL OF SEA-WATER INTRUSION 7!) Plans for Areas of Known Sea-Water Intrusion.. 79 Petaluma Valley 79 Napa-Sonoma Valley so Santa Clara Valley 80 Pajaro Valley _ 81 Salinas Valley Pressure Area 81 Oxnard Plain Rasin 81 West Coast Basin _ so East Coastal Plain Pressure Area ._ 82 Mission Basin _ S3 CHAPTER VIII. CONCLUSIONS AND RECOMMEN- DATIONS 86 ( '(inclusions S5 Recommendations st LIST OF REFERENCES 89 No 1. TABLES Page Status of Sea-Water Intrusion Into Ground Water Ba- sins Bordering the California Coast and Inland Rays 20 Possible Methods for Prevention and Control of Sea Water Intrusion in Areas Where Intrusion Is Known to Have Occurred T9 PLATES I Plates are bound at end if report 1 No. 1. Coastal (J lUllll Increased than Sea and Napa- and Napa Location of Area of Investigation 2. Diagrammatic Sections Through Water Basin 3. Schematic Diagram Showing Sources of Ground Water Salinity from Causes Other Water Intrusion 4. Status of Sea-Water Intrusion in California 5. Status of Sea-Water Intrusion, Petaluma Sonoma Valleys 6. Water Level Fluctuations in Wells, Petaluma Sonoma Valleys T. Status of Sea-Water Intrusion, Santa Clara Vallej S. Geologic Sections A-A' and B-B', Santa Clara Vallej '■>. Changes in Chloride Concentration and Water Level Fluctuations in Wells, Santa Clara Valley 10. Status of Sea-Water Intrusion. Pajaro Valley and Sa- linas Valley Pressure Area 11. Geologic Sections C-C and D-D', Pajaro Valley and Salinas Valley Pressure Area 12. Changes in Chloride Concentration and Water Level Fluctuations in Wells, Pajaro Valley and Salinas Val- ley Pressure Area 1.';. Status of Sea-Water Intrusion. Oxnard Plain Basin 14. Geologic Sections E-E' and F-F', Oxnard Plain Basin 15. Changes in Chloride Concentration and Water Level Fluctuations in Wells, Oxnard Plain Basin. West Coast Basin and East Coastal Plain Pressure Area 10. Status of Sea-Water Intrusion, West Coast Basin and East Coastal Plain Pressure Area IT. Geologic Sections H-H', J-J', and K-K', West Coast Basin 18. Geologic Sections L-L', M-M', East Coastal Plain Pres- sure Area 19. Status of Sea-Water Intrusion and Geologic Sections N-N', O-O', P-P\ and Q-Q', Mission Basin 20. Changes in Chloride Concentration and Water Level Fluctuations in Wells, Mission Basin 21. Location of Wells, West Coast Basin Experimental Project 22. Areal Geology, West Coast Basin Experimental Project 23. Geologic Sections I-P and G-G', West Coast Basin Ex- perimental Project 24. Lines of Equal Elevation of Ground Water, January. 1953, and June. 1954, West Coast Basin Experimental Project 25. Piezometric Profiles Along the Rechnrp Coast Basin Experimental Project 26. Piezometric Profiles Along the "G" Lin Basin Experimental Project 27. Lines of Equal Chloride Ion Concentration. January, 1953, and June, 1954. West Coast Basin Experimental Project 28. Chloride Ion Concentration Along the "G" lane Before and After Injection, West Coast Basin Experimental Project I'll. Chloride Ion Concentration at Selected Wells. West Coast Basin Experimental Project 30. Relationship of Minimum Height of Artificial Recharge Mound, Transmissihility of Aquifer, and Rate of Re- charge 31. Plan Under Investigation for Control of Sea-Water In- trusion in Los Angeles Coastal Plain Line. West West Coast (2) TABLE OF CONTENTS-Continued APPENDIXES (Appendixes A and I! are bound separately; Appendixes (', 1>, and E are combined in one volume i A. STATUS OF SEA-WATER INTRUSION. B. REPORT BY LOS ANGELES COUNT! FLOOD CONTROL DISTRICT ON INVEST- IGATIONAL WORK FOR PREVENTION AM) CONTROL OF SEA-WATER INTRUSION, WEST COAST BASIN EXPERIMENTAL PROJECT, LOS ANGELES COUNTY. ('. LABORATORY AND MODEL STUDIES OF SEA-WATER INTRUSION, and AN ABSTRACT OF LITERATURE PERTAINING TO SKA WATER INTRUSION AM> ITS CONTROL, and REVIEW OF FORMULAS AND DERIVATIONS FOR THE EQUILIBRIUM HAT!) OF SEAWARD FLOW IN A COASTAL AQUIFER WITH SEA-WATER IN TRUSION. I). AN INVESTIGATION OF SOME PROBLEMS IX PREVENTING SEA-WATER INTRUSION P.Y CREATING A FRESH-WATER BARRIER. K PRELIMINARY CHEMICAL QUALITY STUDY IX THE MANHATTAN BEACH AREA. CALIFORNIA. (3 ) LETTER OF TRANSMITTAL GOODWIN J. KNIGHT HARVEY O. BANKS GOVERNOR ADDRESS REPLY TO Director P. O. box 388 Sacramento 2 1120 N STREET HICKORY 8-4711 STATE OF CALIFORNIA Skjrarttttfttt at Water !?Bxwro0 SACRAMENTO November 10, 195H Honorable Goodwin J. Knight, Governor, and Members of the Legislature of the State of California Water Pollution Control Boards Gentlemen : I have the honor to transmit herewith Bulletin No. <>•:> of the State Depart- ment of Water Resources, entitled "Sea- Water Intrusion in California," au- thorized by Chapter 1500, Statutes of 1951, and by Section 229 of the Water Code. Chapter 1500 directed that an investigation be made to develop design criteria for the correction or prevention of damage to underground waters of the State by sea-water intrusion. Extensive field and laboratory experimental activities were undertaken as a part of this investigation. Intrusion of sea water, resulting from severe overdraft, has already damaged some of the State's most important ground water basins. Unless effective meas- ures to correct this condition in these basins and to prevent intrusion into other coastal basins are commenced immediately, extensive and irreparable damage will inevitably result. As part of the investigation for this report, a large-scale field experimental project w'as constructed and operated at Manhattan Beach, Los Angeles County, by the Los Angeles County Flood Control District, under a cooperative contract. The object of this project was to determine the feasibility of correcting and preventing sea-water intrusion by creating a pressure ridge by injecting fresh water into the affected aquifers through wells. The University of California, both at Berkeley and Los Angeles, and the United States Geological Survey, under contract, conducted extensive laboratory studies of various aspects of the overall problem. The Department of Water Resources studied all known coastal ground water basins to determine the extent of the problem and develop plans for correction. This bulletin discusses the present status of sea-water intrusion into coastal ground water basins in California, describes methods of control, summarizes prior and current experimental studies applicable to the determination of design criteria for the prevention or control of sea-water intrusion, and presents pre liminary plans for prevention and control of sea-water intrusion into ground water basins. Very truly yours, ^ Haevei O. Banks Director ACKNOWLEDGMENT Tin* data presented in this publication come from many sources. Because of space limitations, it is virtually impossible to give individual recognition to the numerous contributors to this investigation. However, specific mention is made of the assistance furnished by the following: Atchison, Topeka and Santa Fe Railway Company Baroid Sales Division of the National Lead Company California State Department of Natural Resources, Division of Mines City of Los Angeles, Department of Water and Power City of Manhattan Beach City of Oceanside Cronese Products, Inc. Los Angeles County Flood Control District Macco Corporation Richfield Oil Corporation Shell Development Company Standard Oil Company of California The Metropolitan Water District of Southern California United States Department of the Army, Corps of Engineers United States Department of the Interior, Geological Survey, Ground Water Branch, Quality of Water Branch, and Engineering Geology Branch United States Department of the Navy University of California at Berkeley, Richmond Sanitary Engineering Re- search Field Station University of California at Los Angeles, Department of Engineering The Department gratefully acknowledges their help and cooperation, in toto. i 6 i ORGANIZATION STATE DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING HARVEY O. BANKS Director of Water Resources M. J. SHELTON Deputy Director of Water Resources WILLIAM L. BERRY ._. Chief, Division of Resources Planning CARL B. MEYER Principal Hydraulic Engineer Chief, Special Activities Branch The water qualify activity under which this report was prepared is directed by MEYER KRAMSKY * Principal Hydraulic Engineer assisted by WILLARD R. SLATER Supervising Hydraulic Engineer In the Southern California District this investigation was conducted under the direction of MAX BOOKMAN District Engineer assisted by DAVID B. WILLETS Supervising Hydraulic Engineer The report was prepared by LAURENCE B. JAMES Chief Geologist RAYMOND C. RICHTER ...Supervising Engineering Geologist JACK J. COE Senior Hydraulic Engineer ROBERT G. THOMAS Senior Engineering Geologist E. PHILLIP WARREN Associate Statistician RUSSELL R. KLETZING Associate Attorney assisted by PHILIP J. LORENS Senior Engineering Geologist COLE R. McCLURE Senior Engineering Geologist ALAN L. O'NEILL ...... Senior Engineering Geologist ROBERT C. FOX Associate Engineering Geologist WALTER L. TERRY Associate Hydraulic Engineer JACK H. WYATT - _ Associate Public Health Chemist ROBERT FORD Assistant Engineering Geologist DONALD McCANN Assistant Engineering Geologist DAVID LEVE Assistant Hydraulic Engineer TOM NAGEL — Junior Engineering Aid P. A. TOWNER, Chief Counsel PAUL L. BARNES, Chief, Division of Administration ISABEL C. NESSLER, Coordinator of Reports * Prior to March 18, 1957, P. J. Coffey was in charge of this activity and prior to June 30, 1956, Carl B Meyer was in charge. ( 7 I CALIFORNIA WATER COMMISSION CLAIR A. HILL, Chairman, Redding ARNOLD FREW, Vice Chairman, King City JOHN P. BUNKER, Gustine RICHARD H. FUIDGE, Marysville EVERETT L. GRUBB, Elsinore WILLIAM H. JENNINGS, La Mesa KENNETH Q. VOLK, Los Angeles GEORGE B. GLEASON, Chief Engineer WILLIAM M. CARAH, Executive Secretary ORGANIZATIONAL CHANGES On July 5, 1956, pursuant to the provisions of Chapter 52, Statutes of 1956, First Extra Session, the Department of Water Resources was created and placed under the control of a director appointed by the Governor. The department succeeded to, and is vested with, all the powers, duties, purposes, responsibilities, and jurisdiction vested in the former Division of Water Resources and the State Engineer, with the exception of certain powers pertaining to water rights which were vested in the State Water Rights Board. (S) CHAPTER I INTRODUCTION Prior to 1900, utilization of "round water supplies was relatively limited in California. However, rapid development in the use of ground water since the turn of the century lias created many serious prob- lems, including overdraft and sea-water intrusion. Sea-water intrusion was first noted in California about 1906 along the bayward margin of Mission Val- ley in San Diego County. Since 1940, long continued ground water draft, a protracted period of dry years, and increasing agricultural, municipal and industrial demands have lowered ground water elevations below sea level along the seaward margins of many ground water basins. In many instances the natural seaward hydraulic gradient has been reversed. Thus, as a re- sult of this ground water overdevelopment, extensive damage caused by sea-water intrusion has already occurred in numerous ground water basins adjacent to the coast and saline inland bays of California, with resultant large economic losses. Unless means of pre- vention and control of this source of degradation are undertaken now, further and more widespread de- terioration of ground water supplies will occur in the areas already affected ; and a large number of other ground water basins, in which geologic and hydrologic conditions are conducive to sea-w 7 ater intrusion, will also suffer from this source of degradation. AUTHORIZATION FOR INVESTIGATION The California State Legislature, by Chapter 1500, statutes of 1951, appropriated $750,000 to the State Water Resources Board for an experimental program to determine criteria for the prevention and control of sea-water intrusion into ground water basins border- ing the California coast and inland bays. The legisla- tion is quoted as follows: "The sum of seven hundred fifty thousand dollars ($750, 000) is hereby appropriated out of any money not otherwise appropriated in the Postwar Unem- ployment and Construction Fund, or, in the event that such amount of money is not available there- from then to the extent not so available out of any money not otherwise appropriated in the General Fund to the State Water Resources Board for in- vestigational work and design criteria for correc- tion or prevention of damage to underground waters of the State by sea-water intrusion in the West Coast Basin of Los Angeles County and other criti- cal areas. The cost of such investigation and study shall include the cost of providing water, water in- jection wells, observations wells, water spreading grounds, pipe lines, equipment, rights of way. and other facilities necessary to introduce water into the water-bearing aquifers. The board is authorized to cooperate and contract with the Los Angeles County Flood Control District, the Wesl Basin Mu- nicipal Water District, and any other public or pri vate corporation or agency to the purpose of this act." The former State Water Resources Board, in order to implement the intent of this legislation, contracted with the Los Angeles County Flood Control District, University of California, and United States Geological Survey, Quality of Water Branch, for certain basic portions of this investigational program. The Califor- nia Department ( then Division i of Water Resources, acting as the engineering staff for the State Water Resources Board, coordinated and supervised the in- vestigational program. At the same time, the Depart- ment of Water Resources augmented this experimental program under authority of Section 229 of the Water Code, which directs that the Department shall: "... investigate conditions of the quality of all waters within the State, including saline waters, coastal and inland, as related to all sources of polltl tion of whatever nature ..." This augmentation consisted primarily of geologic and hydrologic studies of coastal ground water basins. RELATED INVESTIGATIONS AND REPORTS Numerous studies and investigations pertaining to sea-water intrusion in California and in other critical areas throughout the United States have been made in the past. A bibliography of these projects is given in Appendix A of this report entitled, "Status of Sea- Water Intrusion" and in Appendix ('. Part III. en- titled "An Abstract of Literature Pertaining to Sea- Water Intrusion and its Control." Numerous reports of prior investigations containing information pertinent to the evaluation of the status of sea-water intrusion in California, and to determina- tion of plans and design criteria for correction or pre- vention of damage to underground waters by sea water intrusion were referred to in connection with the current investigation. Prominent among these are State Water Resources Board Bulletins No. 5 "Santa Cruz-Monterey Counties Invest igat ion *' ; No. 7, "Santa Clara Valley Investigation"; No. 12 "Ven- tura County Investigation"; No. 13 "Alameda County Investigation"; and No. 19 "Salinas River (0) 1(1 SEA-WATER INTRUSION IX CALIFORNIA Basin Investigation." The investigation directed by i In court in the ease of California Water Service Com- pany vs. City of Compton, results of which were pub- lished as "West ("oast Basin Reference — Report of Referee," by the California Department of Public Works also provided valuable data. Reports by the I nited States Geological Survey on Petaluma Valley. Napa-Sonoma Valley, and the coastal plain areas of Los Angeles and Orange Counties were also utilized. References utilized in this investigation are desig- nated in the text by superscripts and are listed at the end of this report. SCOPE OF INVESTIGATION AND REPORT In order to carry out the legislative intent, the State Water Resources Board on July (i, 1951, requested that the Division of Water Resources investigate and submit recommendations for an experimental program for the prevention and control of sea-water intrusion. These recommendations, contained in a report en- titled "Proposed Investigational "Work for Control and Prevention of Sea- Water Intrusion into Ground Water Basins," dated August, 1951. were as follows: 1. An allocation of $30,000 should be made from funds presently available, for laboratory research and investigations of certain basic factors involved in sea- water intrusion and means for its prevention. Such research program should be undertaken by one of the large universities having adequate hydraulic labora- tory facilities. Work should be started immediately and run concurrently with field experimentation, with results and data interchanged as quickly as they he- come available. 2. The sum of $450,000 should be allocated, fi-om funds presently available, for installation and one year's operation of a field experimental project to investigate the hydraulic feasibility of creating a pres- sure ridge in confined aquifers by means of injection wells and the effectiveness of such a ridge in prevent- ing sea-water intrusion. This project should be under- taken in the vicinity of Manhattan Beach in West Coast Basin, Los Angeles County. The initial installa- tion should comprise five injection wells and sufficient observation wells to yield the observational data nec- essary for complete and conclusive interpretation of the results. Capital cost for feeder and distribution pipe lines should be kept to a minimum and emphasis placed upon experimental techniques and collection of pertinent data so that the results and conclusions will be applicable on a state-wide basis. :!. Additional funds should be allocated to tin- Man- hattan Peach field experiment if results of the first six months operation, analyzed in conjunction with laboratory research studies, indicate that the initial installation of five injection wells is not extensive enough to vield conclusive results. 4. If the pressure ridge is found to be hydraulic-ally feasible and effective in the prevention of sea-water intrusion and if funds are then available, a field ex- perimental project should be undertaken to deter- mine tile feasibility of maintain", such a ridge with reclaimed water. The experiment could be conducted near the Hyperion sewage treatment plant of the Citj of Los Angeles or at other suitable locations using the effluent therefrom; estimated cost— $300,000. 5. No field experimental work using injected mate- rials or other techniques to reduce the permeability of aquifers as a means of preventing sea-water intrusion should be undertaken until results of the laboratory research recommended in paragraph 1 above are avail- able and the possible application of the various methods and materials can be judged therefrom. 6. The State Water Resources Board and its stall should further investigate and study the techniques of construction and results achieved in actual installa- tions of the puddled clay and similar types of cutoff walls, before a decision is made as to the desirability or necessity for a field experimental project using sub- surface barriers of this type. If such a field experi- mental project is found advisable, it should be done either at tin- mouth of San Luis Rev Valley or along the coast in Orange County. 7. The State Water Resources Board should care- fully supervise the planning and execution of all ex- perimental work, in order to assure that the results obtained therefrom are interpretable and usable on a. state-wide basis. 8. Upon conclusion of the experimental program. the Stale Water Resources Board and its staff should study and report upon the economic factors and con- siderations involved in prevention of sea-water in- trusion. In order to implement this comprehensive investi- gational program the State Water Resources Board contracted with various agencies, as previously men- tioned, for certain basic portions thereof. At the same time a comprehensive study was initiated of the cur- rent status of sea-water intrusion in some 260 ground wtiter basins bordering the coast of California, and of the geologic and hydrologic characteristics of these basins. The State Water Resources Board allocated $642,- 000 to the Los Angeles County Flood Control District to study the hydraulic feasibility of creating a pies sure ridge in confined aquifers by means of injection wells, and the effectiveness of such a ridge in pre- venting sea-water intrusion. The District constructed and operated large scale experimental recharge fa cilities in the Manhattan Beach-Hermosa Peach area as part of this study. State funds were exhausted in December, 195:!; and the District has since continued operation on a reduced scale, using its own and local fluids. SEA-WATER INTRUSION IX CALIFORNIA 11 Funds for laboratory studies were also made avail- able to the University of California to supplemenl this field experiment. Model .studies of basic param- eters of sea-water intrusion and studies of methods of reduction of aquifer permeability were conducted by the University of California at the Sanitary Engi- neering Research Field Station, Richmond, California. A comprehensive survey and abstract of literature pertaining to sea-water intrusion was completed by the University. Laboratory studies were also conducted at the De- partment of Engineering of the University of Cali- fornia at Los Angeles, to determine the compatibility of Colorado River water purchased from the Metro- politan Water District of Southern California with ground waters in the Silverado water-bearing zone of the West Coast Basin. Chemical analyses of numerous samples of ground water at the site of the West Coast Basin field test were made by the United State Geological Survey at Sacramento, California, to study the geochemistry of the ground water and to determine whether salt-water intrusion in the test area was due to ingress of sea water, oil field brines, connate water, or a combina- tion thereof. Results of this investigation are presented in this report in the seven ensuing chapters. Chapter II, "Physical Characteristics of Sea-Water Intrusion Into Aquifers," discusses fresh water-salt water den- sity relationships, including the Ghyben-Herzberg principle and sea-water wedge, as well as the geologic and hydrologic conditions in coastal ground water basins under which sea-water intrusion may occur Chapter III, "Present Status of Sea-Water Intrusion in California," evaluates the status of sea-water in- trusion in California and discusses increased ground water salinity from causes other than sea-water in- trusion. It also includes a detailed description of critical areas throughout the State. Chapter IV, "Methods of Control of Sea- Water Intrusion," de- scribes five major methods of control and prevention of intrusion and presents basic cost data. Chapter V, "Experimental Studies Pertinent to the Sea-Water Intrusion Problem," evaluates prior and current studies pertaining to injection wells, surface spread- ing, subsurface barriers, and other techniques which might be utilized in preventing and controlling sea- water intrusion. It also includes a detailed study and evaluation of the experimental studies which were performed by the Los Angeles County Flood Control District, University of California, and United States Geological Survey. Economic and legal aspects are discussed in Chapter VI, "Economic and Legal Con- siderations." Chapter VII, "Plans for Prevention and Control of Sea-Water Intrusion," describes plans for control of sea-water intrusion. Chapter VIII, "Conclusions and Recommendations," includes the conclusions and recommendations resulting from the investigation and studies. This report is augmented by live appendixes. Ap- pendix A contains detailed tabulations of the status of sea-water intrusion into coastal ground water basins, including geology and typical analyses "I' sur- face and ground waters; Appendix I! presents the report of the Los Angeles County Flood Control Dis- trict; Appendixes C and I) present the reports of the University of California and University of California at Los Angeles, respectively; and Appendix E is the report of the United States Geological Survey, Qual ity of W T ater Branch. AREA UNDER INVESTIGATION The area under investigation encompasses all ground water basins in California bordering Hie coast and saline inland bays. Particularly intensive field experiments were conducted in a portion of West Coast Basin, Los Angeles County, in connection with an investigation of the feasibility of establishing a pressure ridge in- a confined aquifer. Locations of these areas are delineated on Plate 1. "Area of Investigation." DEFINITIONS In this report, certain terminology and concepts relating to geology, hydrology, and water quality are utilized with specific connotations. In order to facili- tate the reader's understanding of the material con- tained herein, and avoid ambiguities and misconcep- tions regarding interpretation of these terms, the following definitions are presented : Alluvium — A general term for stream deposited sedimentary materials, usually of recent geologic age. Aquifer — A formation sufficiently permeable to yield water to wells or springs. Fault — A fracture or fracture zone alone- which there has been relative displacement of the two sides parallel to the fracture. Geologic Formation — Any assemblage of rocks which have some character in common, whether of origin, age, or composition. Artesian Will — A well tapping a confined or arte- sian aquifer i.e.. one in which the static water level rises above the top of the water-bearing body. Confined Ground Water — A body of ground water overlain by material sufficiently impervious to sever free hydraulic connection with overlying water. Confined water moves under pressure due to difference in head between the intake or fore- 12 SEA-WATER IXTRI'SInX IX CALIFORNIA bay area and the discharge area of the confined water body. Connah Water — Fresh, brackish, or saline water entrapped in the interstices of a sedimentary rock at the time of deposition. Fret <•' ran nil Water — Ground water in the zone of saturation that is not confined beneath an im- pervious formation. Ground Water Overdraft — The rate of net extrac- tion of water from a ground water basin in excess of safe ground water yield. Ground Water Pressure Surface or Level — An im- aginary surface connecting points to which eon- fined ground water will rise in non-pumping wells which pierce an artesian or confined aquifer (synonymous with piezometrie surface). Perched Ground Water — Groundwater occurring in a saturated upper zone separated from the main body of ground water by impervious material. Permeability Coefficient — The rate of How of water in gallons per day and at 60° F. through a cross section of an aquifer one square foot in area under a unit (100 per cent) hydraulic gradient. Piezometrie Surface — Synonymous with ground water pressure surface. Safe Ground Water Yield — The maximum rate of net extraction of water from a ground water basin which can be continued over an indefinitely long period without eventually bringing about undesirable results. Commonly, safe ground water yield is determined by one or more of the following criteria : 1. Mean annual extraction of water from the ground water basin does not exceed mean annual replenishment to the basin. 2. Water levels are not so lowered as to cause harmful impairment of the quality of the ground water by intrusion of other water of undesirable quality, or by accumulation and concentration of degradants or pollutants. 'A. Water levels are not so lowered as to imperil the economy of "round water users by exces- sive costs of pumping from the ground water basin, or by exclusion of users from a supply therefrom. 4. Prior rights of others in adjacent ground water basins are not interfered with. Transmissibility Coefficient — The rate of flow of water through an aquifer, in gallons per day, at the prevailing water temperature, through a vertical strip of the aquifer one foot wide having a height equal to the thickness of the aquifer and under a unit (100 per cent) hydraulic gradient. Water Tattle -The upper surface of a free ground water body. Chemical Classification of Waters — Waters are classified, with respect to mineral composition, in terms of the predominant ions. Specifically, the name of an ion is used where it constitutes at least half of its ionic group, expressed in equiva- lent weights. Where no one ion fulfills this re- quirement, a hyphenated combination of the two most abundant constituents is used. Thus a cal- cium bicarbonate water denotes that calcium constitutes at least half of the cations and bi- carbonate represents at least half of the anions. Where calcium, though predominant, is less than half, and sodium next in abundance, the name is modified to calcium-sodium bicarbonate. Contamination — As defined in Section 13005 of the Water Code "Contamination means an impair- ment of the quality of the waters of the State by sewage or industrial waste to a degree which creates an actual hazard to public health through poisoning or through the spread of di- sease ..." Jurisdiction over matters regarding contamination rests with the State Department of Public Health and local health officers. Degradation — Impairment in the quality of water due to causes other than disposal of sewage and industrial waste, such as sea-water intrusion, ad- verse salt balance, lateral and/or vertical diffu- sion of connate brines, etc. No direct, definite means of prevention and control are available under present law ; but one of the basic statutory responsibilities of the Department of Water Re- sources is to investigate these problems and re- port thereon with recommendations to the Legis- lature and Regional Water Pollution Control Boards (Sec. 229 Water Code). Pollution — As defined in Section 13005 of the Water Code, "Pollution means an impairment of the quality of the waters of the State by sewage or industrial waste to a degree which does not create an actual hazard to the public health but which does adversely and unreasonably affect such waters for domestic, industrial, agricultural, navigational, recreational or other beneficial use, ..." Regional Water Pollution Control Boards are responsible for prevention and abatement of pollution as defined in this section. However, the Attorney General has stated that the term "pollution" as used in Section 229 of the Water Code, which relates to investigations of water quality by the Department of Water Re- sources, is general in nature. Thus, with respect to this study, it encompasses all types of water quality deterioration, including sea-water intru- sion and other types of degradation. SEA-WATER [NTRUSION IX CALIFORNIA 13 Quality of Water — Those physical, chemical, and biological characteristics of water that affect its suitability for beneficial use. Salt Balanci — Relationship of salt input to salt out- put in a hydrologic unit. A favorable balance ex- ists when salt output equals or exceeds input. Where the total quantity of salts entering the unit exceeds the quantity leaving the unit, an accumulation of salts occurs within the unit, and an adverse salt balance exists. WATER QUALITY CRITERIA The suitability of waters for beneficial use, and the effect thereon of sea-water intrusion, can best be de- termined by consideration of water quality require- LIMITING CONCENTRATIONS OF MINERAL CONSTITUENTS FOR DRINKING WATER U. S. Public Health Service Drinking Water Standards, 1946 in parts per million Constituent Mandatory limits Fluoride (F) Lead (Pb) Selenium (Se) Hexavalent chromium (Cr +6 ) Arsenic (As) Nonmandatory but recommended limits Iron (Fe) and Manganese (Mn) together Magneisum (Mg) Chloride (CI) Sulfate (SOi) Copper (Cu) Zinc (Zn) Phenolic compounds in terms of phenols- Total solids Desirable Permitted.- Limit 1.5 0.1 0.05 0.05 0.05 0.3 125 250 250 3.0 15 0.001 500 1,000 ments. Presented herein are general criteria and Limiting values presently used by the Department of Water Resources in evaluating and classifying water quality. In general, these values should be considered only as guides and indicators, and not as absolute limitations. The standards promulgated by the United States Public Health Service, listed on the left, have been widely adopted as definitive criteria for domestic wa- ter supplies. In addition to these constituents, other organic or mineral compounds must be considered if their pres ence in the water renders it unsatisfactory for use Hardness of water is of importance in domestic ami industrial use. The United States Geological Survey has suggested the following four classes of degree of hardness: HARDNESS CLASSIFICATION OF WATERS U. S. Geological Survey in parts per million Class Range of hardness Degree 1-. 2_. 3 0- 55 56-100 101-200 201-500 Soft Slightly hard 4_ Very hard The suitability of water for irrigation use varies throughout the State, because of the great diversity of climatic conditions, crops, soils, and irrigation prac- tices encountered in California. A suggested classi- fication of irrigation waters, which must of necessity be general in nature, follows: QUALITATIVE CLASSIFICATION OF IRI LIGATION WATERS Class 1 Class 2 Class 3 Chemical properties (Suitable for most plants under any conditions of soil and climate) Excellent to good (Possibly harmful for some crops under certain conditions) Good to injurious (Harmful to most crops and unsatisfactory for all but the [i ii ist tolerant) Injurious to unsatisfactory Total dissolved solids Less than 700 Less than 1,000 Less than 5 Less than 17.5 Less than GO Less tlian 0.5 700-2.000 1,000-3,000 5-10 175-350 60-75 0.5-2.0 Mure than 2,000 In conductance EC X 10 6 ... . __ ... More than 3.000 Chloride ion concentration Sodium in per cent of base constituents Mure tiian 75 More than 2.0 (Adapted from the report by Wilcox, L. V. and Magistad, 0. C, "Interpretation of Analyses of Irrigation Waters ami the Relative Tolerance of Crop Plants.' 1 United State Department of Agriculture, Bureau of Plant Industry. Soils and Agricultural Engineering. May 1943.) 14 SEA-WATER INTRUSION IN CALIFORNIA Water quality requirements for industrial use range from the exacting demands of boiler make-up water to the relatively high tolerances of water used for washdown and metallurgical processing. The follow- ing tabulation shows general quality requirements for various industrial uses, as suggested in "Progress Report of the Committee on Quality Tolerance of "Water for Industrial Uses, ' ' Journal of the New Eng- land Water Works Association, 1940. WATER QUALITY TOLERANCE FOR INDUSTRIAL USES ; Allowable limits in ports per m llion Tur- bidity Color Hard- ness :i> CaCOa Iron as Fe Man- ganese as Mn Total solids Alkalinity as CaC03 Odor, taste Hydro- gen sulfide Miscellaneous requirements I >•■ Health Other 0.5 0.2 0.1 0.1 0.2 0.2 0.2 0.2 0.5 0.2 0.2 0.2 0.02 1.0 0.2 0.1 0.1 0.05 0.0 0.2 0.25 0.25 1.0 0.2 0.5 0.2 0.1 0.1 0.2 0.2 0.2 0.2 0.5 0.2 0.2 0.2 0.02 0.5 0.1 0.05 0.05 0.03 0.0 0.2 0.25 0.25 1.0 0.2 Low Low Low Low Low Low Low Low 1 0.2 0.2 0.2 1 1 0.2 0.2 5 No corrosiveness, slime forma- 10 10 10 10 10 2 10 Potable h Potable b Potable h Potable >> Potable ln Potable >■ Potable b tion Brewing 500 1,000 75 150 NaCl less than 275 ppm (pi! 6 5- 7.0). NaCl less than 275 ppm (pll 7 ( 'aiining Legumes-- 25-72 or more) ( 'arbonated beverages - 10 250 850 100 50-100 Organic color plus oxygen con- sumed less than 10 ppm. pH above 7.0 for hard candy- Food - . General- .._. 50 10 5 50 No corrosiveness, slime forma- Low Low Potable' 1 Potable 1 - tion. 5 50 50 180 100 100 50 8 55 50-135 SiO? less than ppm. Plastics, dear uncolored Paper and pulp : Groundwood 2 50 25 15 ,5 5 0.3 20 5 5 2 20 15 10 5 5 10-100 20 5-20 70 5 200 No grit, corrosiveness. 300 200 200 100 Soda and sulfide High-grade light papers. Rayon (viscose): Pulp production Manufacture total 50; hydroxide 8 AI2O3 less than 8 ppm. SiOj less than 25 ppm. Cu less than 5 ppm. pH7.8 to 8.3 total 135; hydroxide 8 Textiles: General 200 Constant composition. Residual alumina less than 0.5 ppm. t lotton bandage-.. — 5 Low ■' Moure. E, \\\. Progress Report of 271. 1940. '■ Potable water, conforming to U. ■ Limit given applies to both iron the Committee on Quality Tolerances of Water for Industrial Uses: .1 ml of New England Water Works Association. Volume 54. page S. P. H. S. standards, is necessary. alone and the sum of iron and manganese. CHAPTER II PHYSICAL CHARACTERISTICS OF SEA-WATER INTRUSION INTO AQUIFERS Intrusion of sea water into aquifers is governed by physical laws which are relatively simple in theory but difficult to apply because of the inherent com- plexities of ground water basins. Conditions prerequi- site to sea-water intrusion and the laws governing its occurrence and behavior are presented herein. PREREQUISITE CONDITIONS From a practical standpoint, there are two funda- mental conditions which must exist before a ground water basin can be intruded by sea water. First, the water-bearing materials comprising the basin must be in hydraulic continuity with the ocean; and second, the normal seaward ground water gradient must be reversed, or at least be too flat to counteract the greater density of sea water. Geologic Conditions Ground water supplies in coastal basins in Califor- nia are stored mainly in the larger alluvium-filled valleys. These valley fill areas, which are of variable depth, are composed of unconsolidated alluvial fan, flood plain, and shallow marine deposits. Extensive sand and gravel deposits occur in the large coastal plain areas in Orange, Los Angeles, Ventura, Mon- terey. Santa Clara, Napa, and .Sonoma Counties. These deposits extend to many hundreds of feet below sea level along the coast, and may extend for some distance beneath the floor of the Pacific Ocean and under San Francisco Bay. In addition to the extensive ground water supplies in these large coastal plain areas, limited quantities of ground water occur in numerous shallow alluvium- filled valleys along the coast. These small valleys, and the several known buried channels filled with sand and gravel, represent buried coarse-grained deposits in ancestral channels of Pleistocene streams. The base of these old buried stream channels adjacent to the coast is quite shallow, generally 150-200 feet below sea level. In a few isolated areas, however, the base approaches 300 feet below sea level. Geologic evidence indicates that the water-bearing deposits along the seaward and bayward margins of these coastal ground water basins either may be in direct contact with the ocean or bay floor at the shore- line, or may extend beneath the floor as confined pressure aquifers in contact with sea water at some distance offshore. Numerous submarine canyons are incised into the continental shelf, resulting in rela- tively close-in exposure of the fresh-water-bearing sediments to sea water. Hydraulic Conditions Sea-water intrusion can occur only when the pressure head of sea water exceeds that of the fresh ground water, a condition which usually results when ground water levels are lowered to or below sea level by excessive pumping of wells. "When the hydraulic gradient within a coastal basin slopes seaward, ground water is moving toward the ocean; and conversely when the slope is reversed, sea water is moving land- ward. It should be noted that under extremely small seaward gradients of the fresh water, both conditions can exist simultaneous^'. In practice, the slope of the hydraulic gradient is established from measurements of depth to water in observation wells. FRESH WATER-SALT WATER RELATIONSHIPS Fresh water weighs less than sea water. Therefore, when the two come in contact within a permeable formation, there is a tendency for the lighter fresh water to float on the heavier sea water. This phe- nomenon can be demonstrated by a simple laboratory apparatus in which a tube containing loose sand is partially immersed in ocean water and then filled from the top with fresh w r ater. Under these idealized condi- tions, the fresh water displaces ocean water from the sand and floats upon it much as a solid buoyant object floats on water. The presence of the sand greatly impedes diffusion of the two liquids which would otherwise occur almost instantaneously. The floating body of fresh water in this example conforms to Archimedes law of buoyancy which states that any floating object will displace its own weight of the medium in which it floats. This principle, as applied to relationships between fresh and sea water, is com- monly known as the Ghyben-Herzberg Principle. It was described by Badon Ghyben in 1880, and applied to water supply problems by Bairat Herzberg in 1901. Since sea water weighs 1.025 times as much as fresh water, the relationship between water table elevation above sea level (T) and depth to sea-water interface ( 7/ ) may be developed by simple algebra as follows : {II + T) = 1.025/7 T = 1.0257/— 7/ T =7/(1.025—1) T =0.025// (1) T '-To H (15) 16 SEA-WATER INTRUSION IX CALIFORNIA Equation (1) indicates that a body of fresh water floating upon sea water within a porous medium ad- justs in elevation until the depth of its lower surface, measured below sea level datum, is 40 times the heighl of its upper surface above this datum. Tims the float- ing body assumes a shape such that its depth below sea level is everywhere 40 times its surface elevation above sea level. THE SEA-WATER WEDGE The theoretical sea-water front assumes the shape of an inclined surface which always slopes landward. and which advances or recedes in response to changes in the hydraulic gradient. Because of its shape, this prism of ocean water has been called the sea-water wedge. Plate 2 depicts a diagrammatic section through a coastal basin for both confined and uncon- fined aquifers. Condition I depicts a seaward sloping hydraulic gradient, whereas Condition II represents a landward sloping hydraulic gradient. It follows from elementary hydraulics that under these condi- tions the hydraulic gradient must meet sea level at the point where the aquifer attains hydraulic conti- nuity with the ocean, and consequently both H and T of equation (1) become zero at this point. In an im- confined aquifer under Condition I, the sea-water in- terface must therefore intersect ground water surface at the shore line. Advance and retreat of the wedge commences at the toe, the position of the upper end of the interface remaining fixed at the shore line until all fresh water near the coast is depleted to sea level, at which time the upper end of the interface commences its advance and the entire wedge moves as a body. If on its land- ward advance, the toe of the wedge extends into a water table depression, an upwelling of sea water occurs. The configuration of this upwelling conforms to the dictates of equation (1). Where the depression is conical, as in the case created by a pumping well, the upwelling assumes the shape of an image cone, the surface of which theoretically becomes 40 times as steep as the sides of the overlying pumping depres- sion. The sea-water wedge also forms in pressure aqui- fers, as indicated in the schematic illustrations of Plate 2. By reasoning similar to that developed in the preceding paragraphs, it can be demonstrated that the relationship H = 40T also holds true for pressure conditions; however, in this case, the corollary that the interface intersects land surface at the shore line is not necessarily valid. Parameters governing intrusion characteristics of a sea-water wedge were developed at the University of California from construction, operation, and study of a scale model. Results of this investigation are pre- sented at length in Appendix C to this report, and are briefly summarized in Chapter V. OTHER CAUSES OF INCREASED GROUND WATER SALINITY An increase in the salinity of ground water within a. coastal basin does not necessarily establish the exist- ence of sea-water intrusion. Such increases may be attributable entirely or in part to other factors. Some of the more significant causes of ground water degra- dation other than sea-water intrusion, illustrated schematically on Plate 3, include the following : 1. Degradation of ground water through its use and re-use. Without sufficient outflow, this may result in adverse salt balance. 2. Degradation through lateral or upward migra- tion of brines or degraded waters contained in the formations flanking or underlying the ground water basin. •'!. Degradation through downward seepage of sew- age or industrial waste. 4. Degradation through downward seepage of min- eralized surface waters from streams, lakes and lagoons. 5. Degradation through the migration of saline water from one water-bearing zone to another either through natural breaks in impermeable layers or through defective, improperly con- structed, or abandoned wells. It is sometimes difficult to fix the true causes for rises in salinity of ground water. Before sea-water in- trusion can be definitely established as the cause, it must be shown that there is evidence of hydraulic con- tinuity with the ocean, a landward sloping hydraulic gradient has prevailed, and progressive degradation of ground water quality has occurred adjacent to the ocean or bay. Even in the presence of these conditions, it is possible under certain circumstances that the salinity rise may be due to some other cause, as pre- viously mentioned. In such instances, chemical anal- yses and the ratios of certain constituent ions may prove helpful in identifying sea water. However, it is to be noted that with present knowledge, it is exceed- ingly difficult, if not impossible, to distinguish sea water from certain oil field brines or connate waters by means of chemical analyses. A need for additional research in this field is clearly indicated. APPLICABILITY TO EXISTING CONDITIONS In California, the deep aquifers of many ground water basins extend offshore, in some instances for several miles. Many of these extensions are overlain by materials of low permeability, and are in contact with the ocean only at their seaward extremities. 1'n- der conditions of surplus ground water supply and seaward sloping hydraulic gradients, these extensions transmit fresh water to the ocean under artesian pres- sure. The quantity of fresh water stored offshore within the extensions is often considerable. The effect SEA-WATER IXTRrsiON IN CALIFORNIA 17 of this offshore storage is to postpone the arrival of sea water into the basin proper until Long after Land- ward sloping hydraulic gradients arc established, tn eei-tain instances, ground water levels in confined aquifers have been lowered and maintained below sea Level for Lengthy periods without chemical evidence of sea-water intrusion becoming apparent. At West Coast Basin near Wilmington and at Goleta Basin near Santa Barbara, fresh-water levels have dropped to 104 and 70 feet below sea level respectively and have remained below sea level for many years with no chemical evidence of intrusion. In these and other similar instances, it is exceedingly difficult to deter- mine whether sea-water intrusion is being delayed due to the effects of offshore storage or whether hydraulic connection between the aquifers and ocean is poor or non-existent. Obviously, the transmissibilities and storage capacities of the seaward extensions of pres- sure aquifers are not amenable to accurate determina- tion. Because of such complexities, the application of theoretical equations to the estimation of rate of intrusion, or to the prediction of the time of arrival of the sea-water interface, is generally difficult and uncertain. The sediments comprising free ground water aqui- fers generally occur as interfingering lenses of fine and coarse sediments. Sea water advances more rapidly through the coarser, more permeable members, and less rapidly through the finer deposits. Thus, sea- water intrusion ordinarily does not advance as a uni- form sloping front as assumed in most theoretical discussions. Generally, the ocean floor slopes gently along the shore. Consequently, deep gravel beds arc exposed at greater distance offshore than are shallow beds, and the paths traversed by sea water through the beds, from point of exposure on the ocean floor to shore line, are shorter for the shallower beds. Because of this condition, intrusion may first become evident at shallow depth, contrary to the dictates of the then retical laws governing the sea-water wedge. Often, shallow sediments for some distance inland are saturated with sea water by percolation of tidal waters from sloughs. In these instances the theoreti cal sea-water wedge does not develop. In regard to changes in configuration of the sea water interface in response to water table fluctua- tions, it is reiterated that these responses are general!} slow. When wells are pumped, the water table is gen- erally quickly depressed. However, equilibrium in the fresh-salt water interface may be attained only if these pumping depressions are maintained for long periods. Because of this time lag, the depth to the interface can rarely be determined through applica- tion of equation (1). In brief, theoretical concepts assist in comprehen- sion of the mechanics of sea-water intrusion. However, due to inherent complexities of ground water condi- tions, an academic approach to problems in this field is applicable only in those rare instances in which conditions are relatively simple and straightforward. CHAPTER III PRESENT STATUS OF SEA-WATER INTRUSION IN CALIFORNIA This chapter summarizes the eurrenl status of sea- water intrusion into ground water basins bordering the California coast and inland bays. Along the coast, "Jli'J ground water basins have been identified in which water-bearing deposits are apparently open to the ocean or to saline inland bays. All of these basins must be considered as potential areas for intrusion of sea water. These 262 ground water basins are grouped into the following four categories with respect to the present status of sea-water intrustion therein, as de- termined from data available: (1 ) Areas of known sea-water intrusion (2) Areas of suspected sea-water intrusion and areas where chlorides in the ground waters ex- ceed 100 parts per million ( 3 i Areas of no apparent sea-water intrusion i 4 ) Areas where the status of sea-water intrusion is unknown The status of sea-water intrusion into ground water basins bordering the California coast is shown in Table 1 and Plate 4. Comprehensive descriptions of all coastal ground water basins are presented in Appen- dix A. AREAS OF KNOWN SEA-WATER INTRUSION Existence of all of the following characteristics and conditions is presumed to constitute positive evidence of the intrusion of ,sea water : (1 ) Water-bearing deposits at the coast line extend to considerable depths below sea level ; ( 2 1 Water-bearing deposits are either in direct contact with the ocean or bay floor, or they ex- tend beneath the floor as confined pressure aquifers and at some distance offshore may be in contact with sea water; ! '■'< I There is moderate to extensive development of ground water ; (4) Ground water levels in the coastal areas have been below sea level for considerable periods of time, and the normal seaward hydraulic gradi- ent has been reversed so that ground water moves inland from the coast ; [51 Coastal ground waters now contain chlorides in excess of 100 parts per million and these high chloride waters are moving landward in the direction of the reversed hydraulic gra- dient. As of 1957, sea-water intrusion was a critical water quality problem in nine coastal ground water basins (see Plate 4 and Table 1 i. The most serious invasion has occurred in the overdrawn West Coast Basin in Los Angeles County, when' intrusion was first noted in lllll'. and in the adjacent Hast Coastal Plain PreS sure Area in Orange County, Draft on ground water supplies exceeds replell ishniellt ill those basins; Water levels are and have been for some years, below sea level; tin- ground water gradients slope inland to pumping troughs; and there are no continuous bar riers in the aquifers to landward movement of saline water. Other critical areas in which sea water has en- croached include: (1) Petaluma Valley in Sonoma County; (2) Napa-Sonoma Valley in Napa and So- noma Counties; (3) Santa Clara Valley in the San Francisco Bay Area; (4) Pajaro Valley in Monterey and Santa Cruz Counties; (5) Salinas Vallej Pressure Area in Monterey County; (6) Oxnard Plain Basin in Ventura County; and (7) Mission Basin in San Diego County. Draft on ground water supplies in these basins exceeds replenishment, especially during the critical summer months. Continued pumping at present rates will allow fur- ther encroachment of sea water into these basins. In addition to direct encroachment of sea water into fresh water-bearing deposits, intrusion may now be occurring, or may occur in the future, in these areas due to percolation of saline or brackish perched or tidal waters through natural or man-made breaks in the clay layers overlying pressure aquifers. The nine areas where sea-water intrusion is known to have occurred arc discussed in detail later in this chapter, and plans for correction and prevention of intrusion are presented in Chapter VII. AREAS OF SUSPECTED SEA-WATER INTRUSION AND AREAS WHERE CHLORIDES EXCEED 100 PARTS PER MILLION Sea-water intrusion is thought to account for the observed deterioration in quality of the coastal ground waters, in most instances, where the following condi- tions exist. Although other causes may also be opera- tive, the available data an- inadequate for a positive determination as to cause (1) Water-bearing deposits at the coast line appar ently extend below sea level and are open to the ocean ; ( 10 , 20 SEA-WATER INTRUSION IN CALIFORNIA TABLE 1 STATUS OF SEA-WATER INTRUSION INTO GROUND WATER BASINS BORDERING THE CALIFORNIA COAST AND INLAND BAYS o rround irate] basin No. 2-1 2-2 2-9 3-2 3 4.01 4-4.01 4-11.02 8-1.01 1-8 1-9 1-10 -5, 2-6 3-lfi 3-18 4-3 9-1 9-3 Ground water basin or valley Areas of known sea-water intrusion Petaluma Valley Napa-Sonoma Valley . Santa Clara Valley Pajaro Valley. Salinas Valley Pressure Area Oxnard Plain Basin — West Coast Basin — ._. East Coastal Plain Pressure Area___ Mission Basin - _ -- Areas of suspected sea-water intrusion and areas of over 100 ppm chloride Redwood Creek Basin — Mad River Valley Eureka Plain - Eel River Valley Russian River Basin _ Bodega Bay Basin Frank Creek Basin — — San Rafael Basin.. Novato Valley Basin Southampton Bay Basin__ __ Benicia Basin . Suisun- Fairfield Valley. _. Sacramento-San Joaquin Delta Clay ton- Ygnacio Valley Market Street Basin Sharp Park Terrace Half Moon Bay Terrace San Gregorio Creek Basin Scott Creek Basin Monterey Area Arroyo del Corral Basin Villa Basin Cayucos Point Basin Cayucos Basin Little Cayucos Basin Toro Basin Morro Basin Chorro Basin Pismo Basin Schumann Canyon Basin Lompoc Plain Cojo Basin Gaviota Basin Cementario Basin Tajiguas Basin Canada del Refugio Basin Canada del Corral Basin Las Varas Basin Bell Canyon Basin Campbell Creek Basin Goleta Basin Hope Basin Carpinteria Basin Ventura River Valley Big Sycamore Basin Zuma Canyon Basin Ramera Basin _ M alii m Ba;-in Las Flores Basin West Coastal Plain-North Laguna Canyon Basin Aliso Basin San Juan Valley San Onofre Valley Santa Margarita Coastal Basin Loma Alta Basin Buena Vista Creek Basin Agua Hedionda Basin Encinaa Basin v San Marcos Basin. _ _. San EH jo Basin San Dieguitu Valley County and Sonoma and Marin Napa and Sonoma Alameda, Santa ( llara and San Mateo Santa Cruz Monterey Monterey Ventura Los Angeles Orange San Diego Humboldt Humboldt Humboldt Humboldt Sonoma Sonoma Marin Marin Marin Solano Solano Solano Solano, Sacramento, San Joaquin and Contra Costa Contra Costa San Francisco San Mateo San Mateo San Mateo Santa Cruz Monterey San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Ventura Ventura Los Angeles Los Angeles Los Angeles Los Angeles Los Angeles Orange Orange San Diego San Diego San Diego San Diego San Diego San Diego San Diego San Diego San Diego San Diego *Index No. 251 253 25 1 255 256 259 260 261 262 1 4 7 22 49 64 65 67 70 74 76 79 81 82 85 112 114 115 122 141 145 151 152 154 157 160 161 162 168 173 17-4 176 177 189 198 199 203 205 207 213 217 220 221 222 226 230 236 240 fGround w a>ter basin No. 9-17 9-18 9-19 3-1 3-7 3-12 3-17 4-4 . 03 Ground water basin or valley Areas of suspected sea-water intrusion and areas of over 100 ppm chloride — continued Soledad Basin Rose Canyon Basin Tecolote Creek Basin Mission Valley Basin Las Chollas Basin. Paradise Basin- _ __. Sweetwater Valley Otay Valley Tia J nana Basin Areas of no apparent sea-water intrusion Smith River Plain Lower Klamath River Basin .. McDonald Creek Basin Cottoneva Creek Basin Garcia River Basin Walker Creek Basin Tomalea Bay Basin . Point Reyes Sand Dunes Area Drakes Estero Basin Laguna Ranch Basin Bolinas Lagoon Basin Rodeo Lagoon Basin Richardson Bay Basin Ross Valley Basin San Pedro Point Basin Merced Valley Basin Calera Basin San Pedro Basin Pescadero Basin San Lorenzo River Basin Soquel Valley Carmel Valley San Jose Creek Basin Big Sur River Basin Arroyo de la Cruz Basin Pico Creek Basin. _ San Simeon Basin Santa Rosa Creek Basin Old Creek Basin Los Osos Basin San Luis Obispo Basin Arroyo Grande Basin Santa Maria River Valley . San August] n Basin Arroyo Hondo Basin Arroyo Quemado Basin Capitan Basin Dos Pueblos Basin Tecolote Basin Santa Barbara Basin Mound Basin Little Sycamore Basin Arroyo Sequit Basin Trancas Basin Solstice Basin Topanga Basin Sand Canyon Basin San Mateo Valley Areas where the status of sea- water intrusion is unknown Wilson Creek Basin Cedar Mill Basin Prairie Creek Area Maple Creek Basin Little River Basin Dows Prairie Area Fleener Creek Basin Bear River Basin Singley Creek Terrace Davis Creek Terrace Mattole River Basin Big Flat Creek Basin Jackass Creek Basin ( 'ounty San San San San San San San San San Dii o I >iego Diego I >iego I tiego I tiegO I I iega I )iego Die^o Del Norte Del Norte " ■ uholdt Me Ijeino uj.endocmo Marin Mai in Marin Marin Marin Marin Marin Marin Marin Marin San Mateo and San Francisco San Mateo San Mateo San Mateo Santa Cruz Santa Cruz Monterey Monterey Monterey San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo and Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Ventura Ventura Los Angeles Los Angeles Los Angeles Los Angeles Orange San Diego Del Norte Del Norte Hlllilbnlilt HumbuMi Humboldt Humboldt Humboldt Humboldt Humboldt Humboldt Humboldt Humboldt Mendocino SEA-WATER [NTRTJSION IX CALIFORNIA 21 TABLE 1 -Continued STATUS OF SEA-WATER INTRUSION INTO GROUND WATER BASINS BORDERING THE CALIFORNIA COAST AND INLAND BAYS tG round water basin No. ( Ground water basin or valley Areas where the status of sea-water intrusion is unknown — continued Tsui ( reek Basin Harda ''reek Basin.. Juan (reek Basin Howard Creek Basin De Haven Creek Basin.- Wages ( Ireek Basin ._ Abalobadiah Creek Basin.- Seaside Creek Basin Ten Mile River Basin Little Valley Area.. Mill Creek Basin Pudding Creek Basin . Noyo River Basin Hair Creek Basin Jug Handle Creek Basin Caspar I Ireek Basin Russian Gulcb Basin Bit; River Basin Little River Basin Albion River Basin Salmon Creek Basin Navarro River Basin Greenwood Creek Basin Elk Creek Basin Alder Creek Basin Staramella Ranch Basin Brush Creek Basin Point Arena Creek Basin Mate Creek Basin Ross Creek Basin Gallaway Creek Basin Schooner Gulch Basin Gualala River Basin Russian Gulch Basin Scotty Creek Basin Salmon Creek Valley Basin Estero Americano Basin Estero de San Antonio Basin Sand Point Area Kehoe Creek Basin Drakes Bay Basin Point Reyes Basin Estero de Limantour Basin Glenbrook Creek Basin Muddy Hollow Basin Bear Valley Basin Elk Valley Basin Horseshoe Bay Basin Marin Island Basin Sulphur Springs Basin Arroyo del Hambre Basin Little Bull Basin Bi« Bull Basin Crockett Basin Canada del Cierbo Basin Oleum Basin Rodeo Basin Refugio Basin Pinole Basin Sobrante Basin Guadalupe Basin County Mendocino 107 Mendocino Mendocino 108 Mi-lnlur-ilio lO'.l Mendocino 111 Mendocino 116 Mendocino 117 Mendocino 119 Mendocino 121 Mendocino 123 MeliiliiriiK. 124 Mendocino 125 Mendocino 126 Mendocino 128 Mendocino 129 Mendocino 130 Mendocino 131 Mendocino 132 Mendocino 133 Mendocino 131 Mendocino 135 Mendocino 136 Mendocino 137 Mendocino 138 Mendocino 139 Mendocino 140 Mendocino 142 Mendocino 143 Mendocino 144 Mendocino 146 Mendocino 148 Mendocino 153 Mendocino 155 Sonoma 156 Sonoma 159 Sonoma 164 Sonoma and Marin 169 Marin 179 Marin 181 Marin 182 Marin 183 Marin 184 Marin 186 Marin 187 Marin 188 Marin 190 Marin 191 Marin 192 Marin 193 Solano 194 Contra Costa 197 Contra Costa 206 Contra Costa 212 Contra Costa 214 Contra Costa 225 Contra Costa 227 Contra Costa 231 Contra Costa 232 Contra Costa 252 Contra Costa 257 San Mateo 258 * Index No. tG round water basin No. 3-14 Ground water basin or valley Areas where the status of sea-water intrusion is unknown continued Visitation Basin Potrero Basin [elaie Basin Fort Masmi Basin. Montara Terrace Montara Point Basin Tunitas * .reek Basin. Poraponio Basin . . Los Krijoles Basin Whitehouse < !reek Basin Ano Nuevo Terrace Wadell Basin Mni i mm ( Ireek Basin I >a ■■■ enporl Landing Basin ___. _ San Vicente Creek Basin . Liddell Creek Basin Respinj Creek Basin Laguna Creek Basin _ Majors Creek Basin Baldwin Creek Basin - Needle Rock Basin Bandy Flat Basin. Meder Creek Basin Terrace Basin Moore Creek Basin Arana Gulch Basin.. Sch wans Lagoon Basin Doyle Basin Valencia Creek Basin Elkhorn Slough Area Little Sur River Basin Sycamore Canyon Basin San Carpoforo Basin Arroyo Laguna Basin Geronimo Basin Willow Creek Basin San Antonio Creek Valley Bear Creek Basin Spring Canyon Basin Canada Honda Basin Jalama Basin Damsite Canyon Basin Canada del Co jo Basin Gato Basin Agujaa Basin Bulito Basin Canada de la Brea Basin Canada de Santa Anita Basin. . Alegria Basin Canada San Onof re Basin Eagle Canyon Basin San Roque Basin Oriegas Basin Escondido Canyon Basin Corral Canyon Basin Santa Ynez Canyon Basin Santa Monica Canyon Basin La .Julia Basin South Las Chollas Basin La Paleta Basin | ' i i I I F I 1 ' Ban Mate i and San Francisco San Francisco Sa 'i i rancisco Ban l ranci - - San Mate i San Mateo San Mateo San Mateo San Mateo San Mateo Ban Mateo Santa Cruz Santa Cruz Santa Cruz Santa Cruz Santa Cruz Santa < !rUZ Santa Cruz Santa ( 'ruz Santa < Iruz Santa Cruz Santa ( Iruz Santa Cruz Santa Cruz Santa Cruz Santa Cruz Santa Cruz Santa Cruz Santa Cruz Monterey Monterey Monterey San Luis Obispo San Luis Obispo San Luis Obispo San Luis Obispo Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Santa Barbara Los Angeles Los AriL'clrs Los Angeles Los Angeles San Dimo San Diego San I >i< * Numbers assigned to ground water basins Identified in Appendix A and shown on Plate 4 of this report. r Numbers assigned to ground water basins identified in Division of Water Resources publication, "Ground Water No. 3, 1952." Basins In California. Water Quality Investigations, Report (2) The ground water lias been developed in vary- ing degree, as a source of water supply ; (3) Where water level data are available, a land- ward hydraulic gradient is indicated; however, information is not generally available as to direction of the hydraulic gradient in all of these areas; (4) Chlorides in excess of 100 parts per million occur in the ground waters of localized areas within the coastal segment of the basin. There are 71 ground water basins in which chlorides in the coastal segments exceed 100 parts per million (see Plate 4 and Table 1 i. For purposes of this report. a chloride content of 100 parts per million is arbi- 22 SEA-WATER INTRUSION IX CALIFORNIA trarily considered as the criterion for saline degrada- tion in the coastal segment of the ground water basin, since under natural conditions few if any coastal ground waters contain chlorides to that extent. It is believed that degradation in many of these basins is due to direct lateral movement of sea water. How- ever, degradation could be due, at least in part, to ot her factors including : il ' Mired infiltration of saline or brackish tidal waters through natural breaks in silt or clay layers, or through improperly constructed, de- fective, or abandoned wells; (2) Upward or lateral movement of saline or brackish connate waters into fresh water-bear- ing deposits from adjacent and underlying older geologic formations; (•'i i Interchange between aquifers, of waters of dif- fering mineral quality through natural breaks in silt and clay layers, or through improperly constructed, defective, or abandoned wells ; ( 4 ) Downward movement of perched waters of poor quality ; i 5 ) Percolation of water from highly mineralized springs, streams, or both; ( 6 1 Downward seepage of industrial wastes and sewage ; ( 7 ) Adverse salt balance. In general, most of the basins in this category are small, narrow, alluvium-tilled valleys, in which there is now only limited development of ground water. His- torical data pertaining to water quality, water level measurements, hydraulic gradients, and fluctuations of piezometric surfaces or of the free ground water table, are usually not available, other than field meas- urements and analyses made during the course of this investigation. A positive determination that sea-water intrusion is the cause of degradation of water quality in these coastal areas cannot be made until additional water level measurements and water quality data arc obtained through continuing basic data collection pro- grams. There has been moderate to extensive development of ground water in a number of the basins identified in this category. Among these are: ( 1 I Mad River Valley in Humboldt County : (2 i Eel River Valley in Humboldt County; (3) Snisnn-Fairfield Valley in Solano County; ( 4 i Lompoc Plain in Santa Barbara County ; (5) Goleta Basin in Santa Barbara County; (lii Carpinteria Basin in Santa Barbara County; and. i 7 I Tia Juana Basin in San Diego County. Dral't on ground water supplies in these basins is generally fairly extensive in comparison to the re- sources of the basin. In some instances ground water levels in the coastal areas have been below sea level for varying periods of time, and a landward hydraulic gradient exists at least during the heavy pumping season. Unfortunately, the available long time hydro- logic and water quality data for most of these basins are not adequate to positively identify sea water as the source of observed ground water quality degrada- tion. Because of the importance of these basins, a con- tinuing program of measurement of water levels, determination of hydraulic gradients, and analysis of ground waters should be conducted. Detailed geologic, hydrologic, and water quality studies should be under- taken immediately to positively establish the causes of ground water quality degradation. Only after the causes have been delineated can plans for prevention and control be formulated and put into effect, includ- ing the provision of supplemental water supplies where necessary. AREAS OF NO APPARENT SEAA/VATER INTRUSION There is no reason to believe that ground water basins in which the following conditions now prevail are presently affected by sea- water intrusion, even though the water-bearing deposits at the coast line apparently extend below sea level and are open to the ocean : (1) Development of the ground water for benefi- cial use has so far been moderate in comparison with the resources available ; (2) Where adequate information is available, a gen- erally prevailing seaward hydraulic gradient is indicated. However, information is generally insufficient to determine position of the ground water surface or direction of hydraulic gra- dient ; (3) From the limited information available, there is no present evidence of high chlorides in the ground waters of the coastal segments of the basins. There are 48 ground water basins in this category (see Table 1). In general, the great percentage of these basins are small, narrow, alluvium-filled valleys in which there has been only limited development of ground water. In these areas, also, there is limited his- torical data on water quality and hydrology except such as could be obtained during this investigation. There are 5 basins of the 4S identified in this cate- gory which are important sources of water supply. and in winch there is moderate development of ground water, namely ; (1) Smith River Plain in Del Norte County (2) Carmel Valley in Monterey County (3) Arroyo Grande Basin in San Luis Obispo County SEA-WATER INTRUSION' IN CALIFORNIA 23 (4) Santa Maria River Valley in San Luis Obispo County (5) Santa Barbara Basin in Santa Barbara County Draft on ground water supplies in these basins does not now appear to be extensive in comparison with the resources of the basin. Water levels are generally above sea level in the coastal segment, and a seaward hydraulic gradient exists over the entire basin, except during short periods of time. As far as can be determined, ground waters of these basins have not as yet been affected by intrusion of sea water. However, any appreciable increase in pumping in the coastal segment of these basins could induce sea-water intrusion by lowering water levels and reversing the existing seaward hydraulic gra- dient. To obviate the possibility of future widespread degradation, effective controls and safeguards should be instituted if ground water development reaches the point where sea-water intrusion is threatened. Hydrologic and geologic studies should be made to determine ground water safe yield and optimum pumping pattern. A ground water monitoring pro- gram should be established and maintained to con- tinually observe water levels and check water qual- ity. Long range studies of future water requirements should be conducted, so that plans for supplemental supplies could be formulated and facilities developed in time to meet all prospective demands. AREAS WHERE THE STATUS OF SEA-WATER INTRUSION IS UNKNOWN This category encompasses 134 ground water basins in which there is little or no development of ground water, and no information could be obtained during this investigation to determine geologic, hydrologic, or water quality conditions in coastal segments. In each of these basins it may be assumed that, with little or no development, encroachment of sea water is restrained for the present due to ground water levels in the coastal area being at or above sea level. However, there is danger that sea-water intrusion would occur if ground water supplies were overde- veloped. All of these basins are limited in extent. In most instances, particularly in northern California, they are located in remote reaches of the coast line and are not readily accessible. It is probable, however, that in the future many of these areas will develop, as the population of the State increases, and will eventually draw upon their ground water resources. Thus, ground water conditions in these basins should be continually observed and carefully evaluated at the appropriate time to determine the extent to which they can be safely developed. DESCRIPTIONS OF AREAS OF KNOWN SEA-WATER INTRUSION There are presented herewith descriptions of the areas of known sea-water intrusion, including details of geologic, hydrologic, and water quality aspects. Petaluma Valley Petaluma Valley is the westernmost of a series of valleys adjacent to San Pablo Bay at the north end of San Francisco Bay, in Sonoma and Marin Coun- ties. The valley extends north from San Pablo Bay a distance of about Hi miles, and occupies an area of about 45 square miles. About 10 square miles of the bayward portion is unreclaimed tidal marshland which is at or below sea level. Reclaimed portions of the tidal marshland are utilized for pasture and dry farming. The inland portion of the valley, north of Petaluma, is a rural area devoted largely to the poul- try and dairying industries. This area is shown on Plate 5. Surface and ground waters are used for a variety of purposes including domestic, irrigation, industrial, and stock-watering. Ground water is used to supple- ment the surface water supply for the City of Peta- luma, which in 1951 obtained almost half of its sup- ply from ground water. In years of deficient rainfall and runoff, ground water becomes the principal source of supply for Petaluma Valley. In 1949, an estimated 1,800 acre-feet of water were pumped for all uses. ( )f this total, approximately 760 aere-feet were for public supply, 250 acre-feet for irrigation, and the remainder for various domestic and industrial needs.' 11 Occurrence and Movement of Ground Water. Petaluma Valley is an alluvium-filled, structurally controlled depression, similar to Napa and Sonoma Valleys to the east. The valley floor is underlain by a thick series of water-bearing sediments including allu- vium, the Merced and Petaluma formations, and vol- canic rocks known as the Sonoma volcanics. Nonwater- bearing basement rocks underlie the central portion of the basin at depths ranging from about S0(l feel to well over 2,000 feet. The principal sources of ground water are the alluvium and the Merced for- mation, which are described in more detail herein. Alluvium of Quaternary age is divided into younger and older alluvium. The younger alluvium is made up chiefly of fine-grained silt, sandy clay, and thin gravel beds, with silts and clays predominating near the bay. Its thickness has not been definitely ascer- tained, but is believed to range from about 200 feel in the upper portion of the valley to as much as 300 feet in the bayward portion. There are no continuous confining beds which would impede the downward movement of waters from the surface. In general, permeability is low and yields to wells are small to moderate, older alluvium underlying the younger •24 SEA-WATER INTRUSION IN CALIFORNIA alluvium in the valley floor is a somewhat more per- meable unit, consisting of sand and gravel, and inter- bedded silt and silty clay. Its thickness is not defi- nitely known but may approximate 200 feet. These alluvial deposits probably extend out beneath San Pablo Bay. It seems likely, however, that these water- bearing deposits are capped by relatively imperme- able bay muds and thus not in direct hydraulic con- tinuity with bay waters. The Merced formation underlies the older alluvium beneath most of the valley floor and is exposed in the hills northwest of Petaluma. This formation is a ma- rine deposit of Pliocene and Pleistocene age, consist- ing of massive beds of fine sand and sandstone with interbeds of clay, silty clay, and lenses of gravel. It is the principal source of ground water in the upland area northwest of Petaluma, and is tapped by deeper wells near the center of the valley and near the bay. Available information indicates that this formation may extend beneath the bay below the alluvium. Ground water in both the younger and older allu- vium north of Petaluma is generally unconfined, ex- cept in the bay ward portion where confinement occurs in the older alluvium and to a lesser extent in the younger alluvium. In the Merced formation, water is known to be confined in the northern part of the valley where several wells flow in the spring. Near the bay, water in this formation may be confined by materials of low permeability in the overlying alluvium. The Tolay fault passes through the northeastern portion of the basin. It is not known to cut deposits younger than the Merced formation, and therefore appears to have no effect on movement of ground water in the alluvium. No information is available to determine whether this fault may form an effective barrier to movement of ground water in the Merced formation. Ground water in the area north of Petaluma is recharged largely by deep infiltration of rainfall and runoff. Ground water moves generally toward Pet- aluma Creek and thence downstream, discharging to both Petaluma Creek and into the tidal sloughs. In the tidal flats south of Petaluma, however, the fresh ground water body appears to be partially confined and overlain by lenses of brackish and saline water. In recent years, overdevelopment of ground water supplies in the vicinity of Petaluma has caused local- ized overdraft conditions, but it does not appear that this overdraft problem is basin-wide 1 as yet. Quality of Water. Surface waters of Petaluma Valley above the area of tidal influence are of good mineral quality. Analyses of water in Petaluma Creek at Petaluma indicate that it is calcium bicarbonate in character, with a concentration of 390 ppm total solids. 80 ppm chlorides, and 0.16 ppm boron. Brack- ish to salty waters occur in the tidal reach of Petaluma Creek between the Citv of Petaluma and the bav. Water in Adobe Creek, two miles east of Petaluma, is calcium bicarbonate in character, containing 187 ppm total solids, 14 ppm chlorides, and no boron. Water in San Antonio Creek, three miles south of Petaluma. is magnesium bicarbonate in character, with a total solids content of 177 ppm, 26 ppm chlorides, and 0.07 ppm boron. Ground water in the unconsolidated alluvium in the upper portion of the valley ranges from calcium- magnesium bicarbonate to sodium bicarbonate in char- acter, with total solids ranging from 200 to 500 ppm and chlorides from 20 to 60 ppm. Analysis of water from a well in the vicinity of Petaluma, where intru- sion of brackish water has occurred, indicates that in 1954 the degraded ground water there had a total solids concentration of as much as 885 ppm, and a chloride concentration of 362 ppm. Another well. approximately one mile to the east in an area un- affected by intrusion of brackish water, had a total solids concentration of 423 ppm and chloride concen- tration of 47 ppm. In the southern portion of the valley, in the area of tidal influence, ground water near Petaluma Creek and tidal sloughs is commonly brackish. Analyses of samples from two wells in this area in 1954 indicated total solids concentrations of 772 and 1,700 ppm. and chlorides of 146 and 835 ppm. Representative analyses of surface and ground waters are presented in Appendix A. Status of Sea-Water Intrusion. Little data are available to determine when degradation of ground waters by intrusion of brackish bay water first began in the vicinity of Petaluma. Since 1850, when settle- ment of the area started, development of ground water has progressed slowly. The major development has occurred since 1945 and it is possible that deteri- oration of water quality due to sea-water intrusion began then or was rapidly accelerated at that time. Since 1945. intensive ground water pumpage in summer months has been concentrated in an area east and northeast of Petaluma, which is only slightly above sea level. This heavy draft has caused water levels to be seasonally lowered below sea level, thereby inducing downward and lateral movement of brackish tidal waters into the pumping depression. The seasonal lowering of ground water levels below sea level is illustrated by the well hydrograph shown on Plate li During the winter months when pumpage is reduced, the depression disappears and a partial flushing bj fresh water takes place. Despite this flushing action. quality of ground waters in this area of the valley has been progressively deteriorating. The chloride concen- tration of a well located 0.7 mile north of Petaluma Creek in the vicinity of Petaluma increased from 216 ppm in August. 1950, to 325 ppm in February, 1954. As of the summer of 1954, an area of approxi- mately | square miles was underlain by degraded water, as shown on Plate 5. In the fall of 1954. ground SEA-WATER INTRUSION IN CALIFORNIA 25 water levels in an area of approximately two square miles were below sea level. In the tidal flat area, from Petaluma south to San Pablo Bay, there are few wells and little ground water pumpage. Little is known concerning the extent of ground water degradation. However, a large por- tion of this area is underlain by poor quality brackish water, particularly near the bay, Petaluma Creek, and the tidal sloughs. With the exception of areas adjacent to the hills, ground water is at or below sea level during the summer and fall months. Therefore, ground waters at shallow depths in the younger al- luvium are subject to degradation by seepage of tidal waters into pumping depressions surrounding shallow wells. Analyses of samples from some shallow wells show chlorides in excess of 1,000 ppm. There are in- dications that ground water from depths of several hundred feet or more in the alluvium or Merced for- mation may have lower chloride concentrations than the shallow waters, but still in excess of 100 ppm.' 11 However, extraction of water from these deeper zones is very limited. It appears that sea-water intrusion in Petaluma Valley is not occurring directly from the bay by sub- surface inflow, but rather through the downward and lateral movement of surface and near-surface brackish and saline waters. Napa-Sonoma Valley Napa-Sonoma Valley, shown on Plate 5, consists of two parallel, elongated valleys in Napa and Sonoma Counties, the bayward portions of which are merged at San Pablo Bay. Sonoma Valley, the westernmost unit, extends northward from the bay a distance of 15 miles and occupies an area of approximately 35 square miles. Napa Valley extends northward from the bay a distance of 40 miles and occupies an area of approximately 85 square miles. The merged bayward portion of these valleys is largely undeveloped tidal marshland, but some areas have been reclaimed and are utilized for pasture and dry farming. The inland portions of both valleys are developed by small diversified farms devoted to the raising of grapes, orchard crops, pasture, dairying- anil poultry. Numerous wineries are scattered throughout both valleys. The principal population centers are Napa, St. Helena, and Calistoga in Napa Valley, and Sonoma in Sonoma Valley. Ground water is the principal source of water sup- ply in Sonoma Valley. In Napa Valley, ground water is an important source of supply, but surface water is being increasingly utilized by towns and ranches, since the supply from wells in parts of the valley is not adequate to meet the increasing demand. Napa, St. Helena, and numerous ranches now obtain water from Lake Ilennessy, a reservoir impounded behind Conn Dam on Conn Creek. Estimated ground water pumpage for the year ending March 31, 1050, was approximately 8,000 acre-feet, of which about 5,5(1(1 acre-feet were pumped in Napa Valley and 2,500 acre-feet in Sonoma Valley. 1 - 1 Occurrence and Movement of Ground Water. Napa-Sonoma Valley is a structurally controlled de- pression underlain by water-bearing alluvial deposits of Recent and Pleistocene age, and by Sonoma vol- canics of Pliocene age. The alluvial deposits include the younger alluvium of Recent age, the older al- luvium and the Huichica formation of Pleistocene age. and the Glen Ellen formation of Plio-Pleistocene age. The principal sources of ground water are the younger and older alluvium. The younger alluvium is mainly silt and clay with discontinuous lenses of sand and gravel. These de- posits underlie the flood plains of Napa River and Sonoma Creek and the tidal marsh lands adjacent to the bay. Throughout a large part of the area, the younger alluvium is only a thin veneer covering the older alluvium. The older alluvium is composed of lenticular deposits of unconsolidated silt, clay, sand. and gravel ; and there are no continuous impermeable beds which would restrict the downward movement of water from the surface. The older alluvium generally overlies the Huichica and/or the Glen Ellen forma- tions and underlies the younger alluvium. The older alluvium probably exceeds 300 feet in thickness near the bay and extends beneath the bay for an unknown distance, where it is overlain by relatively impervious bay muds. The Huichica and Glen Ellen formations occur be- neath the older alluvium. These two formations con- sist chiefly of poorly sorted mixtures of silt and clay with lenses of sand and gravel. Permeability of both formations is low, and consequently yields to wells are often insufficient even for domestic needs. These for- mations may also extend beneath the bay under the alluvium. The Sonoma volcanics generally underlie the Huichica and Glen Ellen formations beneath Napa- Sonoma Valley and are exposed in the adjacent hills. The Sonoma volcanics consist of a thick and highly variable series of volcanic rocks including basalt, andesite. rhyolite, tuffs and pumice. Small to mod erate and locally large yields can generally be ob- tained from the tuffs and pumice, but the andesite and basalt flows are generally impermeable. Ground water in the younger alluvium and in most of the older alluvium is unconfined; however, there are some localized areas of confinement in the older alluvium. Water in the Huichica and Glen Ellen for- mations is partially confined, and silt and clay in these formations confines water locally in the under- lying Sonoma volcanics. Ground water in the unconfi 1 water body in the younger and older alluvium is replenished by infiltra- tion of rainfall and seepage from streams. The source 26 SEA-WATER INTRUSION JX CALIFORNIA of water in the Huichica and Glen Ellen formations and the Sonoma volcanics is from infiltration of rain- fall and stream seepage in the outcrop areas in the adjacent hills, and by downward seepage of water from the overlying alluvium where confinement is not complete and the pressure head is low. Under natural conditions, ground water moves in a bayward direc- tion and discharges into the tidal marshlands and into Napa and Sonoma Rivers. Deep waters in the confined zones may discharge directly into San Pablo Bay further south. Although overpumping of ground waters in the vi- cinity of Schellville in Sonoma Valley and between the City of Napa and Suscol Creek in Napa Valley has caused local overdraft, it does not appear that there is a basin-wide overdraft problem. Quality of Water. Surface waters of Napa-So- noma Valley above the area of tidal influence are gen- erally of good mineral quality. Water from Schell Creek in Sonoma Valley is calcium bicarbonate in character with a concentration of 143 ppm total solids. 16 ppm chlorides and 0.14 ppm boron. Water in Sonoma Creek in Sonoma Valley is magnesium bicar- bonate in character, containing 142 ppm of total solids, 14 ppm chloride and zero boron. In Napa Valley, water in Suscol Creek just above the area of tidal influence is calcium bicarbonate in character, with 136 ppm total solids, 10 ppm chlorides and zero boron. Water from streams and sloughs within the area of tidal influence is brackish to saline in charac- ter, with chlorides ranging from 7,400 to 10,800 ppm. Ground water in the alluvial deposits in the central and northern portion of the area is generally calcium bicarbonate in character, with low total solids, chlo- ride and boron. Analyses of samples from several wells in this area indicates total solids ranging from 166 to 225 ppm, chloride from 9 to 16 ppm, and boron from 0.1 to 0.2 ppm. Ground waters from the Sonoma volcanics are often of poor quality, but still usable for irrigation and domestic purposes. In some limited areas, however, boron concentration is over 10 ppm, rendering those waters unfit for irrigation use. Chlo- rides are generally less than 40 ppm, except in very localized areas. Ground water from shallow wells in the bayward portion is generally sodium chloride or sodium bicar- bonate in character. Analyses of samples from several wells in this area indicate a range in chloride concen- tration from 100 to over 1,000 ppm. Representative analyses of surface and ground waters are presented in Appendix A. Status of Sea-Water Intrusion. Little historic data are available to determine when degradation of ground waters in Napa-Sonoma Valley first began. Prior to 1930, wells belonging to the City of Napa, located near the south city limits, were abandoned and destroyed because the water became too brackish to use.'- 1 An area of degraded water also occurs in the vicinity of Schellville, but it is not known when degradation first occurred. In the vicinity of Schellville and Napa, ground water levels in the younger and older alluvium have been seasonally lowered to or below sea level in several isolated areas which are only slightly above sea level (see Plate (ii. These depressions are caused by pump- ing of ground water from the several aquifers.'-' This condition of depressed water levels has induced down- ward and lateral seepage of brackish waters from the sloughs and tidal reaches of Napa River and Sonoma Creek into the pumping depressions. During the win- ter and spring months, there is some recovery of water levels, brackish waters are partially flushed out, and chloride concentrations drop considerably. As of the summer of 1954, several isolated areas adjacent to the tidal portion of the Napa River and Sonoma Creek were underlain by brackish waters with chlo- ride concentrations in excess of 1,000 ppm, as shown on Plate 5. Brackish waters are largely restricted in occurrence to the unconfined water body in the younger and older alluvium. The Sonoma volcanics, occurring at depths of 300 feet or more beneath the alluvium, is generally protected from the overlying brackish water by impervious materials. However, in the vicinity of Napa, there has been some movement of brackish water into the Sonoma volcanics through deep wells which are perforated in both the alluvium and the Sonoma volcanics, or through wells which are otherwise improperly constructed or defective. A large portion of the tidal flat area is underlain by poor quality water. The younger alluvium and perhaps portions of the older alluvium were deposited in tidewater and, therefore, these brackish waters appear to be connates, at least in part. Fresh ground water, which occurs in the lower portions of the older alluvium, is subject to degradation by seepage of tin- upper brackish waters into pumping depressions. However, the extent to which this degradation may have occurred is not known. As of about 1950, many shallow wells yielded brackish water with chloride concentrations of as much as 1,000 ppm. Brackish water is apparently restricted to approximately the upper 100 feet of sediments, and deep wells draw bet- ter quality water from zones below 200 feet, which are probably confined or partially confined. In general, sea-water intrusion in Napa-Sonoma Valley occurs through the downward and lateral movement of brackish surface and shallow ground waters and it appears that sea-water intrusion is not occurring directly from the bay by subsurface inflow. Santa Clara Valley Santa Clara Valley occupies the alluviated area adjacent to the southern portion of San Francisco Bay in Alameda, Santa Clara, and San Mateo Counties. The valley is generally bounded by the Santa Cruz SEA-WATEK IXTRISIOX IX CALIFORNIA 27 Mountains on the west and the Diablo range on the east, and extends southward to a drainage divide at Morgan Hill in Santa Clara Comity. The west bay area from Palo Alto to South San Francisco in San Mateo County, and the east bay area from San Lean- dro to Richmond, largely in Alameda County, are heavily populated urban and suburban regions with considerable industrial development. Ground water use and development in both these areas is extremely limited. Surface water from the Heteh Iletchy Aque- duct of the City of San Francisco supplies the entire west bay area except for a small amount of ground water pumpage by private individuals and industries. In the east bay, the metropolitan and industrial areas are supplied almost exclusively by surface water, of which the greatest portion is furnished from the East Bay Municipal Utility District's Mokelumne Aque- duct. There is extensive ground water use and develop- ment in the area south of San Leandro in southern Alameda County and north of San Jose in northern Santa Clara County. This portion of the valley is de- voted largely to irrigated and dry farming, and to a Lesser extent to urban, suburban, and industrial devel- opment. The principal centers of population are the Cities of Ilayward, San Leandro, San Lorenzo, San -lose, and Palo Alto. The bayward portion is composed of tidelands, much of which is being or already has been reclaimed for industrial sites. A large portion of the tideland area of southern Alameda County is de- voted to evaporation ponds. This study is confined largely to those portions of the valley in southern Alameda County and northern Santa Clara County that constitute the principal area of ground water development, and where, as a conse- quence, intrusion of sea water has occurred. This area is shown on Plate 7. Occurrence and Movement of Ground Water. Water-bearing formations in the area include alluvial, tideland, and shallow marine deposits of Quaternary age, and the Santa Clara formation of Plio-Pleistocene age. 1 ' 141 Lying beneath the Santa Clara formation are nonwater-bearing sediments and crystalline rocks of Tertiary and older ages. Alluvium in the area consists of unconsolidated mixtures of sand, gravel, silt, and clay ; and occurs as alluvial fans and cones, and flood plain deposits. The alluvial fan deposits inter-finger with the tideland and flood plain deposits, and extend beneath the bay where they are overlain by bay mud. Three prominent allu- vial cones, located on San Lorenzo, San Leandro. and Alameda Creeks, have been formed at the apexes of the alluvial fans. These cones, composed of sand and gravel, represent the coarse phases of the fan deposits. The Santa Clara formation is exposed in the foothill areas to the east and west of San Jose, and extends beneath the Quaternary alluvium on the valley floor. This formation is similar in composition to the allu- vium, but the sediments are more consolidated. Ground water in the area occurs principally in an upper aquifer and a scries of lower aquifers, as shown on Plate 8. The aquifers consist of a series of perme- able sand and gravel beds which occur in both the alluvium and the Santa Clara formation. The upper aquifer is separated from the lower aquifer's by exten- sive clay beds of low permeability. These aquifers merge in the areas adjacent to the foothills on the east and west sides of San Francisco Bay and in the area south of San Jose, forming the forebay. The upper aquifer occurs within the upper 100 to 150 feet of sediments. (8) It is generally overlain by silts, clays, and bay muds in the bayward portions of the valley floor and beneath the bay. Under natural conditions, ground water in the bayward portions of the upper aquifer v>as under artesian pressure; but in much of the area water levels have been lowered below the upper confining layers, and in effect a free ground water table now exists. The top of the series of lower aquifers occurs at 120 to 250 feet beneath the surface. (1 round water in the lower aquifers is confined. As of 1953, although water levels were drawn below sea level, the lower- confined aquifers supplied the bulk of ground water to the area. Both the upper and lower aquifers extend beneath the bay. The upper- aquifer is exposed to saline bay waters and has been extensively affected by sea-water intrusion. The lower aquifers, however, are generally well protected by several confining clay layers; and as yet no direct inflow of sea water from the bay has been detected. These aquifers are recharged by subsurface inflow from the forebay area adjoining the foothills and ex- tending south of San Jose. Infiltration of rainfall, stream flow, drainage from adjacent hills, and the un- consumed portion of water applied for irrigation are the principal sources of natural ground water replen- ishment to the forebay area. Ground water is also re- plenished by artificial means through the activities of the Santa Clara Valley Water Conservation District and the Alameda County Water District. As of 1957, the Santa Clara Valley Water Conservation District operated 21 artificial recharge projects located along streams south of San Jose; and the Alameda County Water District operated 3 projects in the Niles coin- area adjacent to Alameda Creek. Lateral migration of ground water is impeded by the Ilayward fault. 1 ' 1 ' This fault extends along the foothills of the Diablo Range except where it crosses the Niles cone between Niles and Irvington, ( Plate 7 I. In 1950, ground water levels in the Niles cone aver- aged about 30 feet higher on the east side of the fault than on the west side. It is unlikely that sea water could intrude beyond this barrier. South of the Niles cone, where the Santa Clara formation outcrops at 28 SEA-WATER INTRUSION IN CALIFORNIA the base of the Diablo Range, the fault probably re- stricts lateral movement of ground water from the Santa Clara formation into the valley alluvium. The Mission fault is located about one mile east of the Ilayward fault on the Xiles cone, but is not consid- ered an effective barrier to ground water movement. Coyote Hills also forms a partial barrier to the move- ment of ground water along the east side of the bay. Prior to 1916, artesian conditions existed through- out much of the area 1 "' 01 ; but in subsequent years there has been a steady decline in water levels. Hydro- graphs of wells presented on Plate 9 show the down- ward trend of water levels since the 1920 's. All hydro- graphs for wells in the area show a temporary raising of levels between 1937 and 1945 due to a period of above-normal precipitation; however, levels again de- clined after 1945 until 1950, when the lowest of all levels were recorded. Since 1950 there has been a slight rise in the average water levels, due in part to another period of above-normal precipitation. The natural gradient for ground water in Santa Clara Valley is from the direction of the mountains or higher portions of the valley toward the bay. How- ever, landward gradients have been established in the upper aquifer since the 1,920 's or before, resulting in subsurface inflow from the bay through breaks in the upper confining beds. This has resulted in intrusion of saline water throughout bayward portions of the upper aquifer, and has- caused virtual cessation of ground water pumpage therein. Heavy pumping draft has in recent years caused the formation of pumping troughs in the lower confined aquifers, resulting in a landward hydraulic gradient and subsurface inflow of fresh ground water from beneath San Francisco Bay. The confining clays capping the Lower aquifers and extending beneath the bay apparently are con- tinuous and are sufficiently impermeable that waters in these aquifers have not as yet been degraded by direct intrusion of saline water. Subsurface inflow to the area from sediments beneath the bay has been estimated at about 25,000 acre-feet per year, for the period 1947-48 through 1951-52. '»•••' In 1953, several pumping troughs were formed in the lower aquifers, as shown on Plate 7. The axis of one trough was located about 4 miles inland from the bay and extended about 10 miles westward from the Santa Clara-Alameda County line. The axis of an- other trough passed through Palo Alto and could be traced for a distance of about 5 miles. These two troughs are probably connected during certain periods of the pumping season. In southern Alameda County, a pumping trough existed in 1953 which extended from San Leandro Creek about 21 miles to the south. The axis of that trough roughly paralleled the bay shore and extended a maximum of 31 miles inland near Ilayward. Quality of Water. Surface inflow into the area is generally of good mineral quality. Water from streams emanating from the Santa Cruz Mountains on the west side of the valley generally contains higher concentrations of total dissolved solids than that from the Diablo Range on the east side. Total dissolved solids concentration of surface water in the area is generally less than 500 ppm while chloride concentra- tion averages less than 100 ppm.' 3,4 ' Representative analyses of waters from Coyote, Stevens, Belmont, Alameda and San Leandro Creeks are presented in Appendix A. Ground water is generally of good mineral quality where unaffected by sea-water intrusion, although there are local areas of poor quality water along fault zones. Analyses of samples from wells in the upper aquifer and in the forebay area indicate that concen- trations of total dissolved solids range from about 225 to 850 ppm, chlorides from 11 to 150 ppm, and boron ranges from zero to 5 ppm. Mineral quality of water in the lower aquifers is similar to that of the upper aquifer. Concentrations of total dissolved solids range from about 300 to 1,000 ppm, chlorides vary from 23 to 100 ppm, and boron ranges from zero to 1 ppm. Since the 1920 's, numerous wells extracting water from the upper aquifer and portions of the lower aquifers have shown a steady increase of chloride concentration to over 1,000 ppm, indicating the effect of sea-water intrusion. Changes in chloride concentra- tion for various years are shown graphically on Plate 9. Appendix A presents representative mineral analy- ses of ground waters in Santa Clara Valley. Status of Sea-Water Intrusion. Salt-water inva- sion of the upper aquifer was recognized as early as 1920 in wells located near the bay, in the areas east of Palo Alto and west of Centerville. By 1925. steadily increasing irrigation drafts had resulted in lowering of ground water levels far below sea level. This con- dition of depressed water levels induced saline intru- sion into the upper aquifer and forced abandonment of many irrigation wells. Indications are that sea water may have seeped into the upper aquifer near the bay through natural breaks in the overlying clay layers, through abandoned wells, or through openings in the surface clay and mud created by earlier dredg- ing operations near the shore. By 1928, the situation had become so serious that a line of abandoned wells, which had been dug in 1904 within the tidelands of the bay near Palo Alto, were filled and sealed/ 8 ' The wells had been left uncapped, and the casings had rusted and become defective; consequently, saline water from the bay was entering aquifers through these wells. Intrusion into the upper aquifer has progressed inland at a rate varying with the ground water draft and recharge from surface streams. In 1939, a survey of saline ground water conditions was conducted by SEA-WATER INTRUSION IN CALIFORNIA 29 Poland and Tolman. (8) It was found that salt-water encroachment into the upper aquifer had reached a maximum of li miles inland from the bay near Palo Alto and Moffett Field. During a water quality sam- pling program conducted in 1949-50, s4.- 000 acre-feet of Colorado River water has been pur- chased for direct municipal use and ground water recharge. Despite these imports, ground water levels remain below sea level throughout most of the East Coastal Plain Pressure Area. Occurrence and Movement of Ground Water. The water-bearing deposits underlying the East Coastal Plain Pressure Area include sediments of Recent, Pleistocene and Pliocene ages. In general, the sediments occur as interfingering lenses of gravel, sand, silt, and (day. Two water-bearing zones have been differentiated within the Recenl sediments, three in the Pleistocene deposits, and one in the Pliocene deposits. These aquifers are depicted by geologic sec- tions on Plate 18. The Recent alluvial deposits are divided into an upper and lower portion. The upper portion is com- posed of silt, sand, and gravel of fluvial origin with interbedded lenses of fine sand, silt, and (day of la- goonal origin near the coast. The lower portion of the Recent deposits contains the coarse grained Talberl water-bearing zone and the "80-foot gravel." The Talbert water-bearing zone is composed of a tongue of coarse sand and gravel extending from the coast through Santa Ana cap into the forebay area. This aquifer varies in thickness from 40 to 100 feet ; and its base is approximately 160 feet below sea level at the coast. The "80-foot gravel" extending from the coast through the Bolsa gap, is composed chiefly of coarse sand and gravel varying from 5 to 20 feet in thickness. Inland from the gap, it merges with the Talbert zone. Its base is encountered from 60 to 90 feet below sea level. Unnamed upper Pleistocene deposits comprise the surface of the mesas and underlie the Recent materials in the East Coastal Plain Pressure Area. These de- posits are composed of fine sand and silt with lesser quantities of coarse sand and gravel; and are gen- erally considered to be of fluvial, lagooual, and shallow marine origin. The upper Pleistocene deposits are de- formed along the Newport-Inglewood uplift, dipping generally inland and oceanward from the uplift. The lower Pleistocene San Pedro formation under- lies the entire East Coastal Plain Pressure Area with the exception of the southeastern portion of Newport Mesa. These deposits are of marine orie-in and are composed of relatively thick extensive beds of coarse sand and gravel, silt, and lesser quantities of clay. The San Pedro formation has been deformed almost every- where along the Newport-Inglewood uplift and dips from the uplift inland into the basin. Underlying the San Pedro formation is the upper portion of the Pico formation of Pliocene age, which contains numerous zones of fine to medium-grained sand separated by thin beds of siltstone. The Pico con- tains some fresh water and is tapped by a few wells of low yield. Recharge of the aquifers of the East Coastal Plain Pressure Area occurs chiefly in an intake or forebay 38 SEA-WATER INTRUSION IN CALIFORNIA area near Anaheim, where recharge is effected by in- filtration from the Santa Ana River channel. Perco- lating water enters the Talbert zone and, in part, passes; into the underlying Pleistocene and Pliocene aquifers. Under natural conditions, ground water moved in a southerly direction through the several aquifers, discharging ultimately to the ocean. The Newport-Inglewood uplift is the only signifi- cant ground water barrier within the region. This geologic structure comprises a group of en-echelon faults and folds extending in a northwesterly direc- tion. The uplift has little effect upon the movement of ground water within the Recent deposits but does act as a partial barrier to subsurface flow within the Pleistocene and older sediments. Movement of ground water is retarded by zones of cementation and gouge located along the fault planes, and by lithologic dis- continuities. Heavy pumping has depressed ground water levels below sea level throughout most of the East Coastal Plain Pressure Area. The resulting piezometric sur- face forms a trough, the axis of which parallels the coast about five and one-half miles inland. The posi- tion of this trough axis and the line delimiting the extent of the area beneath which ground water levels were below sea level in 1955 are shown on Plate 16. The trough axis is significant inasmuch as it marks the limit to which sea water would intrude were these pumping conditions maintained. However, this limit is in no way fixed, as a change in the pattern of pumping could shift the position of the axis and con- sequently establish a new theoretical limit for sea- water intrusion. Quality of Water. There is little surface flow in the East Coastal Plain Pressure Area; and conse- quently no attempt is made herein to discuss its qual- ity. The character of ground waters in and adjacent to the forebay area is generally calcium bicarbonate. These waters are suitable for domestic use and are considered to be Class 1 for irrigation use. Total dis- solved solids content ranges from about 200 to 600 ppm and the chloride concentrations are usually less than 50 ppm. Hardness ranges from about 130 to 350 ppm and boron content is less than 0.2 ppm. Seaward of the Newport-Inglewood uplift, ground waters are generally of a sodium to calcium chloride character and approach sea water in quality. They are unsuitable for domestic or irrigation use. Where not impaired by oil field brines or sea-water intrusion, ground waters within the Pleistocene deposits inland of the uplift are dramatically different in character and quality, generally exhibiting a calcium or sodium bicarbonate character. These waters are generally suitable for domestic and irrigation use, although they range from soft to very hard in character. The total dissolved solids content of these waters is usually less than 400 ppm, the chloride concentration generally less than 50 ppm and hardness less than 350 ppm. The boron content does not exceed 0.2 ppm. Waters inland of the fault zone in the areas of Huntington Beach Mesa and Santa Ana gap, however, have been impaired by the percolation of oil field brines, intrusion of sea water, and the migration of connate waters. Within these areas, the waters are calcium chloride to sodium chloride in character and extremely variable in quality. These waters contain excessive chloride and total dissolved solids concen- trations which generally render them unsuitable for domestic and irrigation uses. There are other areas along the uplift, notably Alamitos gap and Bolsa Chiea Mesa, where deterioration of water quality has occurred, but data are not sufficient to determine the cause or causes. Representative mineral analyses of ground water are shown in Appendix A. Status of Sea-Water Intrusion. Sea-water intru- sion is a major cause of degradation of ground waters in the East Coastal Plain Pressure Area. In addition, increased salinity also appears to be a consequence of the disposal of industrial waste, oil field brines, exten- sive re-use of ground water, migration of connate water, and deterioration in the quality of inflow to the basin. These factors are mentioned because their effects are sometimes erroneously attributed to sea- water intrusion. With the exception of connate waters and industrial wastes, however, the effects of these factors are insignificant in comparison to the rapid salinity rises caused by sea-water intrusion. The salinity of ground waters underlying portions of Newport Mesa and adjacent areas and underlying the strip between the coast line and the Newport- Inglewood uplift is attributed chiefly to the presence of connate brines. In these areas, ground water of poor quality existed before landward hydraulic gra- dients were established and before significant quan- tities of oil had been produced. Therefore, this degra- dation could not have been due to the disposal of brines or to sea-water intrusion, although subsequent deterioration of water quality in these areas has prob- ably been influenced by both of these factors. Long time residents of Huntington Beach Mesa report that ground water beneath the mesa became saline as early as 1925, five years after discovery of the Huntington Beach Oil Field and 22 years before a continuous landward hydraulic gradient was estab- lished. Furthermore, there are localized areas of high ground water salinity beneath the mesa or beneath areas immediately adjacent to the mesa, which are indicative of improper disposal of oil field brines. Such observations indicate that the initial manifestations of ground water degradation in this locality were prob- ably the result of the disposal of oil field brines mi the surface of the ground, possibly augmented by interconnection of aquifers by improperly constructed oil wells. SEA-WATER INTRUSION IN CALIFORNIA 39 The Ground Water Branch of the United States Geological Survey has, in cooperation with the Orange County Flood Control District and Orange County Sanitary District, made studies of the status of salt-water intrusion in Orange County. In then- reports, they noted that sea-water encroachment began as early as 1942 in Alamitos gap and that in Santa Ana gap 275 acres were underlain by sea water in 1944. The Talbert zone underlying Santa Ana gap has been seriously affected by the intrusion of sea water, and many wells have been abandoned because of excess salinity. By 1955, the saline front extended inland more than two miles, as shown on Plate 16, and is steadily advancing. Changes in chloride ion concen- tration and water level fluctuations in wells are illus- trated graphically on Plate 15. Mission Basin Mission Basin, delineated on Plate 19, is the west- ernmost and largest of several elongated basins that lie along the San Luis Rey River in the northern por- tion of San Diego County. It is a shallow alluvium- filled valley extending about eight miles inland from the Pacific Ocean. The valley floor ranges in elevation from sea level to about 100 feet at its eastern limit. San Luis Rey Canyon, located at the extreme western end of the basin, is a narrow, steep-walled gorge ex- tending inland from the coast about two miles where it enlarges to a width of approximately one mile. The canyon constitutes the only outlet for surface drain- age from the basin. Ground waters of Mission Basin are presently uti- lized for domestic and agricultural purposes on over- lying lands. Both the City of Oceanside and the Carls- bad Mutual Water Company pump and export ground water from this basin for municipal and agricultural purposes. The continued draft on this relatively small ground water basin, during the period of subnormal rainfall and runoff which started in 1945, has lowered ground water levels throughout most of the basin. In January, 1956, ground water levels were below sea level approximately five miles inland from the coast, as shown on Plate 19. Because of lowering ground water levels and depre- ciation in quality, both the City of Oceanside and the Carlsbad Mutual Water Company import Colorado River water through facilities of the San Diego County Water Authority to supplement the local sup- ply. The total import by both agencies was 14,900 acre-feet during the period from 1950 to June 30, 1957. On July 2, 1957, voters in the City of Oceanside passed a bond issue to finance construction of a sewage reclamation project. Water reclaimed from sewage is used for industrial purposes and also to recharge ground waters of Mission Basin. Occurrence and Movement of Ground Water. Recent alluvium in Mission Uasin was deposited in an ancestral channel of the San Luis Rey River carved in the geologic past, when sea level was about 300 feet below its present elevation. The logs of wells reveal a zone of fine sand, silt or clay generally extending from the surface to depths of about 100 feet, in all but the eastern end of the basin. Underlying these fine-grained materials are about 100 feet of highly permeable gravels and coarse sands which constitute the principal pumping zone. The walls and floor of the basin are older sedimen- tary formations, which are much less permeable than the alluvium. San Luis Rey Canyon is cut in resistant, firmly cemented conglomerate, the San Onofre breccia. The La Jolla formation flanks and generally underlies the recent alluvium throughout the remainder of the ground water basin. This formation consists of sedi- mentary materials deposited in a marine environment and subsequently elevated to their present position. The formation is slightly permeable, and contains brackish or saline ground water, possibly due to the presence of sea water as yet not entirely flushed from the formation. Under natural conditions, ground water flowed west- ward through the basin and discharged to the ocean through the gravels in San Luis Rey Canyon. At present, heavy pumping has lowered ground water levels below sea level and a landward gradient has been established. A comparison of historic water levels at wells indicates that a pumping trough has existed continuously near the center of the basin since 1948. The axis of the pumping trough is shown on Plate 19. Quality of Water. Surface runoff in Mission Basin is sodium chloride in character and of good mineral quality. Representative analyses are shown in Appendix A. Ground waters of Mission Basin are subject to marked degradation from saline connate waters in underlying and surrounding formations, and sea water. Degradation from both of these sources is in- fluenced by ground water levels. As levels are lowered, mineral concentrations increase; and the predominant anion changes from bicarbonate to chloride. Careful evaluation of quality changes and water level changes indicates that quality deterioration in the lower por- tion of Mission Basin near San Luis Rey Canyon is caused by sea-water intrusion. Deterioration of ground water in the remainder of the basin is caused prima- rily by connate water from adjacent and underlying formations and in part by use and re-use of water. Mineral analyses of typical ground waters in Mission Basin are shown in Appendix A. Status of Sea- Water Intrusion. A 7,000 ppm rise in the chloride ion concentration in ground water al 40 SEA-WATER INTRUSION IN CALIFORNIA well No. 11S/5W-23E1 during the period 1951-52 through 1954-55 is interpreted to indicate the arrival of sea water in the immediate vicinity. This well, located in San Luis Rev Canyon approximately 4.000 feel from the ocean, supplies wash water for a sand and gravel plant. These wash waters are discharged to tailings ponds in the alluvium located upstream of the supply well and only about 700 feet from well No. 11S/5W-14Q1. Chloride increases at this latter well could be caused by sea-water intrusion or gravel plant operations, or both. The gravel plant operation, whereby diluted ocean water is finally discharged as wash water further inland, affects the hydraulic gradi- ent and rate of sea-water intrusion into the western end of Mission Basin. Salinity increases and ground water level fluctuations in wells Nos. 11S/5W-14Q1 and 11!S 5W-23E1 arc shown on Plate 20. Low water levels further inland have also been an important factor in causing sea-water intrusion. As shown on Plate 20, the bydrograph of well No. US 5W-13N1, located about 11,000 feet from the ocean, indicates that the water level at that point first receded below sea level in August, 10411, and has re- mained below sea level since that date, with the ex- ception of brief periods in December, 194!) ; January, 1950; and March, April, and May of 11)52. These observations indicate that sea-water intrusion could have commenced as early as August, 1949. Extent of the 100 ppm isochlor in January, 1956, is shown on Plate 19. CHAPTER IV METHODS OF CONTROL OF SEA-WATER INTRUSION In the light of present knowledge an rec l uired for direct distribution in con- ditch would be kept full of bentonite slurry to retain junction with the pumping trough, would probably be the vertical walls. more costly than reclaimed waste water that could be 5. The excavated material would be mixed with 30 utilized for the P^ssure ridge. Other adjustments per cent of bentonitic slurry from the trench by pug- of lesser magnitude, such as a deduction from pres- mill, and would then serve as backfill, thus creating sure ridge charges of the cost of chlorinating injection an impermeable barrier. water, which would not be needed for the pumping From the foregoing, it appears that construction of trough, might also be required, a puddled clay cutoff wall to depths of 200 feet, more less, may be physically feasible. COMPARISON OF COSTS Aquifer permeability has been reduced through _ . , grouting with cement, chemicals, silts, and asphalts, For comparison purposes, the general orders of but cost data for such projects are either not available magnitude of costs of the five methods of control have or are not considered applicable to sea-water intrusion been estimated for a one-mile reach of coast. It was barriers. However, it has been reported that, in gen- assumed that the depth of the base of the aquifer to eral, costs of grouting with chemicals are approxi- be protected averaged about 225 feet, similar to the mately two to three times the costs of cement grouting. Silverado water-bearing zone in the West Coast Basin. It has been further reported, as later mentioned, that Although such depths are at or above the upper limit costs of materials and placement for grouting at considered within the limits of subsurface barrier con- Great Falls Reservoir, Tennessee, averaged $1.19 per struction, for purposes of comparison, it was assumed cubic foot and $1.35 per cubic foot for cement and that barriers could be constructed to the aforemen- asphalt, respectively. tioned depths It was a i so assumed tnat the safe yield of the basin to be protected was 30,000 acre-feet per DEVELOPMENT OF A PUMPING TROUGH ye ar, if water levels could be safely maintained below ADJACENT TO THE COAST sea level; but was decreased to 15,000 acre-feet if This method would require the continuous mainte- water levels must be raised to sea level or above as nance of a pumping trough along the coast in order part of the plan for protection. This assumption is not to create a seaward hydraulic gradient over most of applicable to the West Coast Basin, where safe yield SEA-WATER INTRUSION IN CALIFORNIA 47 would probably be negligible if water levels were maintained at sea level. However, in principle it more closely typifies general conditions in the areas of known sea-water intrusion. Assumed water costs reflect conditions in the West Coast Basin. Softened Colorado River water at $23 per acre-foot was utilized for direct distribution ; untreated Colorado River water at $12 per acre-foot was assumed for direct recharge of aquifers ; and cost of the fresh-water barrier was based on reclaimed waste water at $10 per acre-foot. Estimated capital and annual operation and maintenance costs for a total usable supply of 80,000 acre-feet per year are presented in the following tabulation: Estimated coats for one-mile reach of coast Method of control Capital Reduction or rearrangement of pattern of pumping draft** Direct recharge of overdrawn aquifers" $246,000 Fresh-water harrier 210,00(1 Artificial subsurface bar- riers bc 2,420,000 Pumping trough bc 400,000 » Full utilization of ground water basin not possible. yield 15,000 acre-feet per year. b Assumes all major ground water producers have already which they may obtain Imported water. c Assumed safe ground water yield 30,000 acre-feet per .1 niiiuil operation and in" in i> mi nee, including water costs $130,000 110,000 86,000 105,000 290,000 Assumed safe ground water connected to facilities from year. CHAPTER V EXPERIMENTAL STUDIES PERTINENT TO THE SEA-WATER INTRUSION PROBLEM The more important prior experimental studies ap- plicable to sea-water intrusion are discussed first in this chapter. Following this discussion, there is pre- sented a summary of investigations conducted under Chapter 1500, Statutes of 1951, and other recent ex- perimental studies. Part III of Appendix C to this report contains an abstract of literature concerning experimental studies directly concerned with sea- water intrusion. PRIOR EXPERIMENTAL STUDIES Many agencies have conducted experimental studies. varying in nature and scope, which are applicable to certain of the methods for control of sea-water intru- sion set forth in the preceding chapter. Such studies have dealt principally with direct recharge of over- drawn aquifers through use of injection wells or through surface spreading, determination of pa- rameters of sea-water intrusion, and reduction in aquifer permeability. Information of actual field ex- periments relating to the pumping trough method of preventing sea-water intrusion has not been found. Although much of the early work described in the literature consisted of individual studies or projects designed to correct some specific conditions and did not reflect a true experimental approach, it did pro- vide valuable data to serve as the basis for succeeding studies. Prior experimental studies discussed herein are grouped in five categories: 1. Parameters Governing Intrusion of Saline Water ; 2. Recharge of Ground Water Through Injection Wells ; .'1. Recharge of Ground Water Through Surface Spreading ; 4. Artificial Subsurface Barriers Through Grout- ing; and 5. Artificial Subsurface Barriers Through Con- struction of Earthen Walls. Paramefers Governing Intrusion of Saline Waters A multitude of studies has been conducted to deter- mine the nature and occurrence of sea-water intru- sion, particularly with reference to the shape and rate of movement of the interface between the ad- vancing sea water and the displaced fresh water. Such investigations have provided much valuable data needed for the development or application of the methods of sea-water intrusion control outlined previ- ously . European Studies. Sea-water intrusion into coastal ground water basins in England, France, Bel- gium, Germany, and the Netherlands has been ob- served anil studied for many years. One of the first references In sea-water intrusion in 1 lie literature con cerns infiltration of salt water into wells at London and Liverpool in England in 1855. Later literature describes high salinity concentrations in water from wells located along the coast of Hampshire, England in 1910. It was concluded at that time that heavy pumping was the cause of the observed intrusion. In 1916, Whitaker discussed, at some length, mixtures of native ground water and sea w y ater found near Essex, England. < 14 > d'Andrimont completed extensive studies on the availability, movement, and quality of ground water in the dune area along the Belgian coast in the earlv 1900's.( 15 ' 1G ' 17 ' 18 » Both Dubois and Pennink investigated sea-water intrusion in the lowlands of Holland in 1905, noting that salinity of ground water appeared to increase witli depth and pumping effected an increase in salinity.* 19 ' 201 Both investigators corroborated the Ghyben-IIerzberg principle previously discussed. Reportedly, the fresh water content of the fresh ground water lenses in the Netherlands dunes is de- creasing rapidly through overdevelopment. Thiele re- ported in 1953 that sea-water intrusion existed from Calais, France to Denmark, and added that the most carefully studied dune water lenses in the world were those at Amsterdam in the Netherlands.' 21 ' The dune water lense at Leyden is being replenished through artificial recharge. The Government Institute for Water Supply at the Hague has estimated water re- quirements up to the year 2000 and the percentage of supply from dune water lenses, ground water from inland areas, ami surface water sources. It is proposed that surface sources will be further developed and will provide a much greater percentage of the total water supply in the future. In the western portion of the Netherlands, 44 per cent of the total supply was ob- tained from dune water lenses in 1953, and it is esti- mated that in the year 2000 this value will have decreased to 13 per cent of the total supply. (40) 50 SEA-WATER INTRUSION IN CALIFORNIA Degradation of Ground Water Quality at Nassau, Bahama Islands. In 1933, Riddel reported on pres- ence of saline waters in aquifers at Nassau on New Providence Island, Bahama Islands. (22) It was noted that salt water cones formed in aquifers below pump- ing- wells ; and that a series of wells of small capacities were more desirable than fewer wells of large capa- cities and drawdowns for the skimming of fresh water off the underlying salt water. This condition is similar to that found on many other islands. Studies in Japan. Toyohara reported on a field experiment at Tottori, Japan, in 1935, which corrobo- rated prior model sea-water intrusion studies, al- though some deviation from the theoretical was ob- served regarding diffusion along the salt water-fresh water interface. <23) A report published in 1939 by K. Kitagawa pre- sented derivations for the parabolic equations defining the fresh water-salt water interface and demonstrated that these equations compared favorably with results of model studies. <24) The report also described a field experiment utilizing observation wells and dyes to verify the shape of the interface. A major earthquake occurring in Japan on Decem- ber 21, 1947, resulted in substantial land subsidence and inundation of coastal areas. Salt-water infiltra- tion into ground water supplies occurred, and the rate of advance and shape of the interface along the coast of the Island of Shikoku was observed. In 1951, Ha- yami reported on the field studies and developed a mathematical theory for the process of infiltration. (25) Investigations in the Hawaiian and Other Pacific Islands. The United States Geological Survey stud- ied sea-water intrusion in the Hawaiian Islands in the 1900 's.« 261 Studies in these islands in the 1930 's confirmed the Ghyben-Herzberg principle and in- cluded determinations of depths to sea water by re- sistivity measurements using the Lee partitioning method. (27) "Wentworth, in 1939, utilized the Ghyben- Herzberg principle to determine effects of various ground water and sea water specific gravities on the interface. He also reported on the relations between water temperatures and specific gravities. (28) Application of the Ghyben-Herzberg principle to ground water conditions in the Hawaiian and Mari- anas Islands was reported by Ohrt in 1947. (2! " Ohrt concluded that water supplies of the Pacific Islands were very limited and could best be utilized through use of skimming tunnels. Ground Water Quality Studies in Connecticut. Shape of the salt water-fresh water interface was observed by the United States Geological Survey in Connecticut in the 1920 's by sampling ground water at varying depths and distances from the shoreline. (30> The zone of diffusion at the interface was reportedly 60 to 100 feet in width. Relationships between pump- ing and ground water salinity, and yearly temper- ature and salinity were established. Sea-Water Encroachment in Galveston-Houston Area, Texas. Studies conducted in the 1930's in the Galveston-Houston area, Texas, indicated that sea- water intrusion had occurred about 20 miles in- Land. (31) Abandonment of wells in Galveston in 1896 indicates that intrusion may have existed at that time. Ground water levels are now reported to be as much as 220 feet below sea level in Houston, and land sub- sidence in excess of three feet has been observed in this area. Degradation of Ground Water Quality Near Par- lin, New Jersey. In 1940, Barksdale reported that sea water in the pressure aquifer near Parlin, New Jersey, was advancing inland at a rate of approxi- mately one mile in six years. l32) Observations in moni- toring wells revealed that sea water advanced in waves of high salinity followed by waves of lower salinity, with each successive crest being higher than the pre- vious crest. Investigations Conducted in Florida. Sea-water intrusion has been a paramount problem in certain areas in Florida for the past 30 years. It has been determined that drainage canals have lowered the fresh ground water level in coastal aquifers, permit- ting intrusion of sea water in certain areas. Sea water has also entered these canals during dry periods, per- colating into fresh water aquifers. The diffusion zone at the fresh water-salt water interface is about 60 feet wide. Special investigations sponsored by the United States Geological Survey and the Florida State Geo- logical Survey were begun at several locations about 1930. Alarming increases, iu 1939, in chloride ion concentration of ground water at the well field serv- ing the City of Miami, led to the initiation of intensive investigations into the occurrence and movement of sea-water intrusion in the area. It was found that in- trusion had taken place over a 47-year period, with a rate of encroachment until about 1943 of approxi- mately 235 feet per year. l33) During the drought of 1943-46, the rate increased to about 890 feet per year. As a remedial measure, low-level removable dams were installed in many of the numerous drainage cauals. These dams, together with increased precipita- tion during the period 1946 to 1951, caused a seaward movement of the salt water front. Members of the staff of the University of Florida prepared a report in 1953 for the Division of Water Survey and Research, State Board of Conservation, State of Florida, in connection with sea-water intru- sion.' 3 " It was concluded from this iuvestigation that the chloride ion is the most reliable indicator of sea- water intrusion, since this ion is not commonly subject to oxidation, reduction, or base exchange. Further- SEA-WATER INTRUSION IX CALIFORNIA 51 more, although connate brines are also high in chlo- ride ion concentration, sea water may usually be assumed to be the cause of degradation if a landward hydraulic gradient exists. In reporting on the results of his studies in the Miami area. Love of the United States Geological Survey stated that when cation exchange occurred as a result of the movement of sea water through aqui- fers containing exchangeable materials, active colloids in the formation gave up calcium ions in exchange for the magnesium and sodium ions in the sea water. (3B) In this regard, Revelle has indicated three types of modification which sea water may undergo in flowing through porous media; base exchange, changes in pro- portion of negatively charged ions as a result of sulfate reduction and substitution of acid radicals, and changes in both cations and anions through proc- esses of solution and precipitation. (36) Love and Revelle agree that the chloride ion is the best indicator of sea-water intrusion, although Revelle recommends that a ratio of chloride to bicarbonate be used to eliminate the effect of a temporary increase in total dissolved solids. Investigations of the Occurrence and Movement of Sea-Water Intrusion in California. In 1940, it was reported that degradation of ground waters was oceur- ing in the Santa Clara Valley bordering the southern tip of San Francisco Bay ; and it was found that sea water entering the aquifers through abandoned wells in tidal areas was the paramount cause of degrada- tion.' 37 ' Studies by the State Division of "Water Resources in the Salinas area revealed that in October, 1945, there were approximately 6,000 acres underlain with sea water, extending up to one and three-quarters miles inland from the coast. (3S) The advance of the saline front was estimated at 600 feet from August, 1944, to August, 1945. Since a pumping trough existed in this basin, the advance of the saline front would be a maxi- mum at the trough ; and, at this point, would underlie approximately 9,200 acres. The State Division of Water Resources, as Referee in an action to adjudicate water rights in the West Coast Basin, Los Angeles County, conducted an in- vestigation from the fall of 1946 through the winter of 1950-51, including determination of areas under- lain with saline water and the source of this water. (39) Sea-water intrusion in this area has been previously discussed in this report in some detail. Starting in 1949, the United States Geological Sur- vey, in cooperation with the Orange County Flood Control District and the Orange County Water Dis- trict, undertook a field investigation of sea-water in- trusion in Orange County. (40) The study included col- lection of water samples at various depths in key observation wells, making conductivity traverses within wells, determination of depths to ground water, collection of well logs, mid ascertaining the transmis- sibility of underlying aquifers. Ground water samples were analyzed for chloride ion concentration, hard- ness and conductivity. This program included observa- tion of the advance or recession of the sea-water front and the determination of the shape, rate of movement, and salinity changes in the front. The State Division of Water Resources, in coopera- tion with Ventura County, conducted a water re- sources investigation in Ventura County in 1951-1953, which included determination of extent and source of high chloride concentrations near Port Eueneme.' 41 ' A detailed discussion of this problem has already been presented in this report. Recharge of Ground Water Through Injection Wells The main water-bearing sediments within the major ground water basins along tin' coast of California are overlain with impervious deposits. This physical con- dition, coupled with high costs of rights of way, makes it generally infeasible to employ surface spreading techniques to raise piezometric surfaces above sea level in many overdrawn basins, and has led to experiments involving the use of recharge or injection wells to replenish ground water supplies. The disposal of oil field brines through use of injec- tion wells has been practiced in the petroleum indus- try for many years. Injection wells have also been extensively used to recharge ground water aquifers with cool water during winter months; and, during summer months, to return used cooling water to the aquifer from which it was withdrawn. Conservation and disposal of runoff and waste waters have also been important uses of injection wells. Replenishment of Ground Water Supply at Long Island, New York. For many years, overdevelop- ment of ground water resources in the heavily urban- ized and industrialized areas of western Long Island, New York, resulted in a gradual lowering of ground water levels; and in 1933 it was found that levels underlying more than 40 square miles in Brooklyn were below sea level. (42) Ground water levels report- edly reached their lowest stage in 1941, and in 1947 the last municipal well field in Brooklyn was aban- doned as a result of sea-water intrusion. Since then, levels have recovered slowly, although they are still below sea level in many places. Declining ground water levels prompted the passage of state legislation which provides that no well having a capacity in excess of 45 gallons per minute shall be drilled without prior approval of the State Water, Power, and Control Commission. (43) Since enactment of this legislation, the Commission has required that water pumped from new wells and used for cooling and air-conditioning he returned to the aquifer from which it was withdrawn in an unpolluted condition. :,■■ SEA-WATER INTRUSION IN CALIFORNIA In 1954, approximately 715 recharge wells were used to return over 40 million gallons per day to aqui- fers underlying Lorn? Island. Some recharee wells on Long Island, with capacities of i "e than 1,000 gal- lons per minute, have been successfully operated for as long as ten years without rehabilitation. Approximately 75 per cent of the injection wells (•(instructed on Long- Island are screened below the phreatic line; and this type of well, when gravel- packed, appears to be the most suitable for this area. Although more expensive, due to greater depth, this type of construction, known as the "wet" type, mini- mizes clogging of the well screen by gases released from solution or air mixed with recharging water in the zone of aeration. Furthermore, standard methods (if well redevelopement, such as surging, bailing, and chemical treatment, are not as applicable to the "dry" type injection wells which are screened above the zone of saturation. According to Sanford, the most suitable type of injection well on Long Island is a 30-inch diameter pit with an 8-inch to 12-inch diameter inner casing equipped with an acid-resistant well screen.' 44 ' San- ford also reports that the use of dry ice for well re- habilitation has proved both successful and economi- cal. Hydrochloric and sulphuric acids may have to be used, in some eases, for loosening encrustations. The temperature of water returned to the ground water supply through injection wells on Long Island ranges from 2 to 20 degrees higher than the temper- ature of water pumped from supply wells, depending on the type of industrial cooling apparatus. Although, at some installations, the temperature of the ground water lias risen as a result of the return of warm water, the problem may be remedied by proper spac- ing of injection wells. Also it has been observed that the temperature of the ground water drops rapidly upon cessation of warm Avater injection. It has also been demonstrated on Long Island, that properly treated industrial waste water, sanitary sewage, and storm runoff can be used for recharging. Storm runoff recharge wells in Nassau County, Long Island, usually consist of reinforced concrete slotted pipe sections 7i feet or 10 feet in diameter. The larger sections have 7-inch thick walls for depths down to 60 feet and 10-inch walls for greater depths. Sections are fastened together in six places through the slotted openings with vertical steel straps. Double straps are used for depths exceeding 60 feet. The end of the bottom section is open to aid recharge and is equipped with a steel cutting edge to facilitate sinking the well by the open caisson method of excavation. Tests indicate that well infiltration rates as high as 440 gallons per square foot of seepage area per day can be expected with this type of well. It is reported that the most effective wells are those which extend more than six feet below the highest ground water level. Water from storm drains passes through special catch basins before discharging into the recharge wells, permitting the heavier sediments to settle and deposit in the basin. Periodic removal of silt from catch ba.sins and from the wells themselves is neces- sary to maintain satisfactory recharge rates. Injection Through a Brackish Water Well at Camp Perry, Virginia. Injection and pumping experi- ments were performed in 1946 at Camp Perry near Williamsburg, Virginia, in a well which originally produced water with a chloride ion concentration of 340 parts per million. 14 "" Fresh water from the mu- nicipal distribution system was injected through the well for about 43 days, commencing at a rate of 250,- 000 gallons per day and terminating at a rate of 200,000 gallons per day. When it became evident that the well was partially clogged, it was pumped and the discharge water analyzed. These experiments indicated: (1) about 50 per cent of the amount of water recharged was not degraded when pumped from the aquifer; (2) some (dogging of the recharge well could be expected, except where the water-bearing formation is coarse grained and the well highly developed when constructed; (3) foreign matter should be removed from the recharge water; (4) restoration of recharge rates is difficult; and (5) an observation well located near the injection well is desirable to indicate shape and extent of re- charge mound. Management of Ground Water Supplies at Louis- ville, Kentucky and Binghamton, New York. In- dustrial use of ground water in excess of replenish- ment occasioned an alarming lowering of ground water levels underlying Louisville, Kentucky, and re- sulted in one of the first planned operations of a ground water reservoir. (4CI During the winter of 1944, industries united to carry out a program of using the municipal water supply consisting of filtered river water, rather than ground water, while injecting cold filtered river water through wells. The objectives of the operation were to raise groimcl water levels and keep the ground water temperature below 60° F dur- ing the ensuing summer. Recharge was continued for three months in the spring of 1944, using three wells at an average total recharge rate of 1,000 gallons per minute. Reports indicate that the project Avas suc- cessful. A similar problem involving rapidly declining ground water levels in an industrial area in Bingham- ton, New York, was remedied by winter injection of cold water, pumped from wells near the Susquehanna River, through wells located at the cone of pumping depression. (42) SEA-WATER IXTRUSIOX IX CALIFORXIA 53 Deep Aquifer Replenishment at Canton, Ohio. In many coastal ground water basins, waters of only one of several producing aquifers may be degraded by sea- water intrusion. Injection wells can be utilized to con- vey water of good quality from one aquifer to a deeper aquifer into which sea water has intruded. The phe- nomenon of inter-aquifer How using injection wells has been demonstrated in the Canton, Ohio, region, where a relatively thin aquifer overlies an aquifer of considerable storage capacity, the two being separated by an impervious member. (42) Three horizontal col- lector wells were sunk alone' streams which cross the area and recharge the upper aquifer. These collectors have continuity with both aquifers and allow water to flow continuously from the upper to the lower aqui- fer, the combined rate of recharge of the three col- lectors being about eight million gallons per day. One of the collectors is used as a source of supply; and about ten million gallons per day are pumped from the lower aquifer. Artificial Recharge Experiments at El Paso, Texas. Excessive withdrawals from the ground water supplies underlying El Paso, Texas, resulted in an alarming drop in ground water levels, followed by the intrusion of saline waters. Recognizing the need for corrective measures, the City of El Paso, in 1947. requested the United States Geological Survey to study the feasibil- ity of storing treated surface water from the Rio Grande in the ground water reservoir underlying the City.' 471 During the winter months from 1947 through 1951-52, with the exception of the winter of 1949-50, water diverted from the Rio Grande and treated at the City's treatment plant was injected through a municipal well. Treatment consisted of screening, grit removal, prechlorination, aeration with forced air, primary settling, coagulation with alum or ferric sul- fate, softening with lime, activated carbon treatment for taste and odor, settling, refloceulation, recarbona- tion, chlorination, and rapid sand filtration. The in- jection well was a city supply well drilled in 1924, and was in intermittent operation until injection was commenced. At first, recharging was accomplished through the pump conductor pipe; but later, after the pump was removed, injection was carried on through an injection pipe with gate valve. Bottoms of both pipes were about 100 feet below static ground water level. It was concluded from this field investigation that intrusion of salt water could probably be retarded, and in some places even halted by injection of treated surface water at a rate of about six million gallons per day, utilizing three or four wells spaced 1,500 feet apart. Injection Well Experiments by Los Angeles County Flood Control District in 1950. Prom May 16, 1950 through October 13, 1950. the Los Angeles County Flood Control District injected 325 acre-feet of water through a single well at Manhattan Beach, California, at rates varying from 0.5 second-fool to 2.3 second-feet. Water injected was a mixture of treated < 'olorado [liver water and native ground water from inland of the area of sea-water encroachment. The District's final report describing the experiment included the following conclusions:* 48 ' 1. "The abandoned well used for recharge purposes in a pressure aquifer of limited thickness was able to convey flow to the ground water body for a 5-month period at rates between 1 and 2 cfs. Since this re- charge was not chlorinated during the major part of this period, it sinus conservative to assume that thoroughly developed new recharge wells can absorb at least 2 cfs of chlorinated water initially and 1 cfs over a considerable period of months without rede- velopment." 2. "Bacterial slimes will form and clog the aquifers being recharged unless the flow is sterilized." 3. "With conditions as they exist at Manhattan Beach, it appears reasonable to expect that bacterial slimes can be controlled by dosing the recharge flow with chlorine at an initial dosage of 15 ppm." 4. "Chlorine dosages should be commenced imme- diately upon rechareine- in order to sterilize potential bacterial growth sources in the ground water around the well and prevent any build-up of bacterial slimes." 5. "The threat of clogging the aquifer by incrusta- tions of insoluble carbonates did uot occur to a notice- able degree during the duration of this test." 6. "It is desirable to exclude air from the recharge flow." 7. "The recharge flow displaced the existing saline water up to a radius of over 500 feet from the injec- tion well. Pumping tests indicated that little or no mixing had taken place between the injected fresh water body and the displaced saline water." The Los Angeles < 'ounty Flood Control District con- ducted basin recharge experiments in the City of Los Angeles, north of the City of El Segundo, concur- rently with the previously mentioned injection well studies at Manhattan Beach. (48> Initial basin recharg- ing rates were quite low at the El Segundo test site due to the presence of relatively impervious, iron- cemented sand layers at depths of 12 to 20 feet below ground surface. To penetrate these semi-impervious sediments, 25 pit-type injection wells, 30 inches in diameter, and varying in depth from 23 to 46 feet, were drilled in the recharge basin at intervals of 40 feet and filled with pea gravel. The average injection rate per well after nine days of operation was 0.11 second-foot. It was found advisable to maintain a mound of gravel at the top of each well to serve as a filter. These mounds were sterilized intermittently with copper sulfate or calcium hypochlorite to prevent clogging of the well with algae and bacterial slimes. 54 SEA-WATER INTRUSION IN CALIFORNIA Injecting Reclaimed Sewage into Ground Water Aquifers in West Coast Basin, California. In July, 1946, Harold Conkling, Consulting Engineer, pro- posed that reclaimed sewage from the City of Los Angeles' sewerage system be injected into the ground water reservoir underlying the West Coast Basin in Los Angeles County. (49) Sewage would be aerated, filtered, and chlorinated prior to injection through 400-foot deep, 16-inch diameter cased wells, spaced not less than 2,000 feet apart. Injection wells would be so located as to maintain a minimum distance of 1,000 feet from pumping wells. Although injection rates over an extended period of time were estimated at about two second-feet, it was assumed that due to intermittent use a continuous recharge rate in the order of one second-foot per well would be more practicable. With injection wells in operation at this design rate, approximately 80,000 acre-feet of water per year would be added to the overdrawn aquifer. This proposed replenishment program using injec- tion wells and treated sewage has not been put iuto effect as yet, except on a field experimental basis as discussed later herein. Most of the area in the West Coast Basin has acquired rights to the use of imported Colorado River water by annexation to The Metro- politan Water District of Southern California. Investigation of Travel of Pollution, University of California. From April, 1951, through 1954, the University of California at Berkeley, under contract with the State Water Pollution Control Board, in- vestigated the travel of pollution in ground water within a shallow pressure aquifer at the University's Richmond Sanitary Engineering Research Field Sta- tion. <50) A portion of these studies was conducted concurrently with experimental investigations author- ized by the State Legislature under Chapter 1500, Statutes of 1951, which are discussed hereinafter. The field facilities consisted of one 12-inch injection well and eighteen 6-inch observation wells located at distances from 10 to 500 feet from the injection well. Diluted sewage containing coliform organisms in the order of 10 e per 100 milliliters, suspended solids of 3.3 parts per million, and a BOD of 4 parts per million was injected at the rate of 31.6 gallons per minute. It was concluded from the University's studies that colifonn bacteria quickly reached an apparent maxi- mum distance of travel with no increase in concentra- tion residting from additional injection. Coliform or- ganisms decreased in number from 10 6 to less than 38 organisms per 100 milliliters while traveling 100 feet in 33 hours. It was found that injection wells should be gravel- paeked to obtain desirable injection rates. In addition, grouting was required above the aquifer to prevent injected water moving upward along the outside of the casing and eroding the overlying formation, caus- ing subsidence around the well. These findings were corroborated by the injection well studies in the West Coast Basin, which are discussed at length in suc- ceeding portions of this report. As a result of the University's studies, it was also concluded that : 1. Serious clogging can result from the dispersion of the clay fraction of an aquifer, or of clay in the boundary layers of the aquifer, if excess sodium is introduced. 2. Clogging of an aquifer is directly proportional to the amount of solids injected in any period of time. With 20 and 27 per cent sewage, clogging produced an average rate of pressure increase in the recharge well of 5.5 feet of water per day. 3. Particulate organic matter does not penetrate the aquifer to any important extent. With the excep- tion of bacteria and similar small particles, it tends to remain in a filter mat at or near the aquifer face. 4. The buildup of clogging during sewage injection produces a pressure pattern in the recharge well which shows conclusively that biological decomposi- tion of organic solids takes place underground and acts to lower the rate of clogging. A sharp break in the pressure curve takes place after two or three days, indicating that a biological equilibrium has been established. 5. Pumping at moderate discharge rates is inade- quate to remove clogging to a satisfactory degree. 6. Gas binding of the aquifer occurred when the temperature of the recharge water was lower than the temperature of the ground water. 7. The recharge well can be successfully developed by injecting heavy doses of chlorine to break up the organic mat built up in the aquifer, allowing a contact period, then pumping at approximately 80 gallons per minute for periods up to four hours. 8. It was found that in general the chlorine should extend to the 13-foot observation wells, remain in contact for about half a day, and be sufficient in amount to show a slight residual in the well discharge at the beginning of pumping. 9. Loss of fine material during redevelopment does not seem to endanger the aquifer at the discharge rates (up to 80 gallons per minute) used in the inves- tigation. 10. It was necessary to develop the recharge well once a week in order to make possible continued in- jection of 20 or 27 per cent sewage at 37 gallons per minute. 11. Redevelopment of the recharge well involved a maximum discharge of from four to five per cent of the volume of the injected water. 12. The problems of recharge well operation rather than the danger of pollution travel seem to be the critical factors in sewage reclamation by direct re- charge. SEA-WATER INTRUSION IN CALIFORNIA 55 Other Uses of Injection Wells. Use of injection wells to dispose of storm runoff or to circulate cooling waters is common practice in California. Injection wells in southern Alameda County, parts of Orange County, and in the City of Fresno, have been used for storm runoff disposal for many years. Injection wells are used to return cooling waters to underlying aqui- fers in portions of the Sacramento and San Joaquin Valleys, and in the Los Angeles area. Although the disposal of waste waters by wells is known to have been practiced in California, there is a paucity of available data concerning such disposal, with the exception of the University of California's field experiment at Richmond. It is known that more than 175 wells have been used in the Orlando, Florida, area for sewage disposal and drainage. (r,1) Reportedly, a deep well current meter was used successfully in certain of these wells to determine the horizons at which these surface waters entered the underlying limestone formation. Although most of the uses just described cannot be considered controlled experiments, nevertheless such long term operation does indicate that using injection wells to raise ground water levels above sea level along the margins of coastal ground water basins may be a feasible method for preventing sea-water encroach- ment. Recharge of Ground Water Through Surface Spreading Direct recharge of overdrawn aquifers to maintain ground water levels at or above sea level may also be achieved through surface spreading. Spreading of storm runoff and sewage effluent has been successfully practiced for decades in California, and in other loca- tions. Mitchelson reports that the first recorded at- tempt at conservation of water by spreading was carried out by the Denver Union "Water Company in 1889. {r>2> He further reports that spreading on the Santiago Creek and Santa Ana River cones in Orange and San Bernardino Counties, respectively, was first undertaken in 1896 and 1900, respectively. In 1895, the conservation of floodwaters of San Antonio Creek by spreading was first attempted near the mouth of San Antonio Canyon in Los Angeles and San Bernar- dino Counties, an activity which has been continued to the present time. Over one and three quarter million acre-feet of water were reported to have been spread in California since the turn of the century. The forebay areas of most coastal ground water basins afford an excellent natural facility for the direct recharge of depleted aquifers by surface spread- ing, due to the absence of overlying impermeable sediments and the availability, in most eases, of runoff from mountain and foothill areas. Spreading in the forebays may not be sufficient to raise ground water or pressure levels above sea level in the coastal seg- ments, however, due to inadequate aquifer transmis- sion capacities. As previously discussed in Chapter IV, it may be necessary to utilize several methods of control to stem sea-water intrusion in any particular area. Surface spreading in the forebay areas, coupled with the use of injection wells nearer the coast line, may be required. Artificial Recharge Basins on Long Island, New York. Overdevelopment of ground water supplies and ensuing sea-water intrusion at Long Island, New York, have occasioned construction and opera- tion of over 300 artificial recharge basins by Nassau County.' 43 ' This program of spreading storm run- off was initiated in 1935, and is conducted in an area approximately 100 square miles in extent. Average infiltration rates of about three feet per day have been observed. Harrowing and weed removal in basins is performed semiannually. Staff of the United States Geological Survey com- menced intensive studies of infiltration and evapora- tion in the project area in May, 1949. Preliminary results of controlled recharge in a 40-foot by 50-foot test basin indicate infiltration rates equal to, or greater than rates experienced at larger basins operated by the County. Los Angeles County Flood Control District Exper- iments Near Redondo Beach. In conjunction with their previously described single well injection test at Manhattan Beach and injection pit test north of El Segundo, the Los Angeles County Flood Control District performed a surface spreading experiment in the sand dune deposits along the coast at Redondo Beach in 1950. ,4S ' Major project facilities consisted of a one-acre basin and 23 observation wells. It was found that for the deposits in the area, percolation rates of from 2 to 3 second-feet per wetted acre could be maintained if the recharge water was chlorinated with dosage of about 3 parts per million to prevent growth of soil clogging micro-organisms. Sewage Spreading Experiments by Los Angeles County Flood Control District at Whittier and Azusa. The Los Angeles County Flood Control Dis- trict, in exploring the possibilities of large-scale rec- lamation of sewage, established and operated experi- mental spreading plots at the Whittier and Azusa sewage treatment plants.' 53 ' Experiments were con- ducted with the effluents from these plants, under various degrees of treatment, to determine their per- colation characteristics and the influence thereon of physical, chemical, and biological factors. It was found that effluents from these plants, both of which use the trickling filter process, can be utilized to replenish ground waters by surface spreading. Sus- tained percolation rates ranging from 0.2 cfs per acre to 0.6 efs per acre were obtained. The maintenance of aerobic environment in the spreading plot was 56 SEA-WATER INTRUSION IN CALIFORNIA essential. Satisfactory sanitary conditions resulted if the dissolved oxygen content of the percolating fluid was at least 0.5 ppm, and the biochemical oxygen demand less than 0.5 ppm. Comparison of sewage efflu- ent with the originating water supply showed that the use cycle resulted in an increase of 172 ppm in dis- solved solids content. University of California Sewage Reclamation Field Studies at Lodi. In 1050, the Sanitary Engi- neering Research Laboratory, University of Califor- nia, initiated a field investigation of sewage reclama- tion by surface spreading at Lodi, California, under the sponsorship of the California State Health De- partment, and later, the California State Water Pol- lution Control Board. l54) During the 28-month study, extensive chemical and bacteriological determinations were made which indicated that sewage could be re- claimed by spreading on Hanford fine sandy loam soil, at rates of about 0.5 foot per day, producing bacteriologically safe water if the liquid percolated through at least four feet of soil. It was further con- cluded that high infiltration rates are possible if a highly treated effluent is used. Studies of sewage recharge were resumed at the University's Richmond Sanitary Engineering Re- search Field Station in 1952, with one of the objec- tives being the determination, using lysimeters, of infiltration rates of five typical pervious California soils. Application of settled sewage produced abrupt decreases in infiltration rates for the more permeable Oakley and Yolo soils, while little or no change was noted for the less permeable Hanford, Hesperia, and Columbia soils. After 48 hours of application, infil- tration rates for Oakley and Yolo soils dropped from 30 feet per day and 15 feet per day, respectively, to 0.5 foot per day and 2.0 feet per day, respectively. Infiltration rates for Hanford, Hesperia, and Colum- bia soils remained fairly constant at 0.8, 0.6, and 0.6 foot per day, respectively. The marked decline in rates for the more permeable soils was attributed to clog- ging of the soil surface by particulate matter. Artificial Subsurface Barriers by Grouting As previously discussed, reduction of aquifer per- meability may be the most feasible method of control- linn: sea-water intrusion into certain coastal basins. Reduction in permeability may be accomplished in various ways depending upon physical conditions, such as depth of aquifer below ground surface and particle .size of sediments. Artificial subsurface bar- riers have been constructed by grouting with cement, chemicals, silts and clays, or asphalts, or installation of an earthen cutoff wall. Cement Slurries. Laboratory studies to develop suitable grouting materials have been myriad in num- ber, especially those dealing with cement. Cement slurries have been used in oil well drilling and to seal rock fractures and porous materials underlying struc- tures, notably dams, for many years. Techniques re- garding- grouting mixes, additives, and operating pressures have been developed to a high degree. Al- though cement grouting has proven successful in seal- ing coarse-grained materials, cement particle size pro- hibits effective sealing in materials finer than fine sand. Intrusion-Prepakt, Incorporated, reports they have achieved complete water shut-off at depths up to 60 feet by use of a process called mixed-in-place intru- sion grouting. This process consists of injecting cement grout through a hollow shaft to a rotating mixing head, which mixes the slurry with the soil in place. 150 ' The result is a pile-like column which, in combination with adjacent columns, provides a cutoff wall. Chemical Injection. In recent years, considera- tion has been given to injection of chemicals for re- duction of sediment permeability. Beiitonite, chrome- lignin, calcium acrylate, and a silica gel combination of sodium silicate and calcium chloride have been particularly studied as grouting media. Aniline fur- fural used with vibrators, sodium and calcium ion exchange, dissolution of silica with acid, and pore water freezing by use of carbon dioxide are other techniques considered. Of all the chemicals, a mixture of sodium silicate and calcium chloride has probably been the most commonly used, being successfully employed to stop seepage and prevent movement of quicksand. The first use of sodium silicate and calcium chloride was re- ported in Europe, and it is known that many tech- nical papers have been written, especially in France, Germany, and Russia, concerning studies of its use. In 1929, a modification of this method was utilized in rendering watertight the cutoff wall for Alexander Dam at Eauai Island, Hawaiian Islands, by use of a mixture of soda ash, or crude sodium carbonate, and clay soil containing silica. <50) Charles Langer, a French engineer, has reportedly developed a technique for controlling reaction time between sodium silicate and calcium chloride by low- ering the pll of ground water through addition of acid to the mixture. 1571 By delaying the time of set, greater penetrating distances can be realized. Laboratory studies by Polivka at University of Cali- fornia at Berkeley indicated that, due to the low vis- cosity of the silicates, a mixture of sodium silicate and calcium carbonate could be injected into formations where other materials, such as cement, bitumen or beiitonite, might fail to penetrate. (5SI However, in this regard, it has been reported that for chemicals with the viscosity of water, injection into clay soils is for all practical purposes impossible, and injection into silts is possible only with high pressures. (59) SEA-WATER INTRUSION IX CALIFORNIA 57 The United States Bureau of Reclamation reports that solutions of sodium silicate, in combination with calcium chloride, sodium bicarbonate, or aluminum sulfate, penetrated tight rock seams better than did eenieiit grout. (eo) This was attributed to the fact that these chemicals formed a colloid. The Bureau of Rec- lamation has employed two methods of chemical grouting: (1) single injection method in which the chemicals are mixed before being pumped; and (2) double injection method in which the individual chemicals are pumped separately into the formation. Riedel has described a chemical process which solidified sediments and improved the foundation under a bridge pier near Kuttawa, Kentucky. 11 -' 11 Loose soft rock, sand boils, and artesian water were encountered during construction of the bridge pier. Sodium silicate and calcium chloride were pumped alternately into the formation through pipes until water and sand boils were sealed satisfactorily. Sub- sequent tests indicated that the chemicals had formed a soft sandstone which was impervious to water and exhibited bearing strengths up to 50 tons per square foot. Also, it was found that this pi-ocess is not ap- plicable to strata containing more than 25 per cent clay, silt, or sand passing a 125 mesh sieve. Sodium silicate and calcium chloride solutions were also used to successfully seal leaks at an underpass at La Grande, Oregon. (02) Solidification of strata to depths of approximately one foot beneath the concrete base of the underpass was achieved by pumping the solutions at 400 pounds per square inch pressure through a series of one and one-half inch holes. According to some recent research by T. W. Lambe, calcium acrylate is the best soil solidifier.' 03 ' These tests included determinations of volume change, strength, and flexibility. Solutions of stabilizer AM-955, acrylamid methyl- enebisacrylamide, either alone, or mixed with calcium acrylate with suitable catalysts, have been used to stabilize and reduce the permeability of cohesionless sands. (S9) Compressive strength of one type of sand, after polymerization of AM-955, was about 20 pounds per square inch, permitting vertical cut excavation in the treated sand. Intrusion-Prepakt, Incorporated, in cooperation with Hough Soils Engineering Laboratories, con- ducted a grouting experiment near Wyoming, New York, using chrome-lignin. ,04) Conclusions drawn from the experiment are as follows : 1. Chemical grout, like cement grout, follows the paths of least resistance through the soil ; 2. Underground chemical flow rates can be imme- diately altered by varying the slurry viscosity; 3. Chemical grout can be pumped with approxi- mately one-sixth the pressure required to pump ce- ment grout, under like conditions; 4. Chemical grout can be pumped through any ma- terial through which water can be primped ; 5. Surface "break-outs" are more prevalent with chemical grout than with cement grout. Plastics have also been used to reduce aquifer per- meability. In oil well drilling in Texas, nearly 83 per cent (if the sealing attempts using plastics resulted in over 50 per cenl shut-off; and about 65 per cent of the attempts resulted in 100 per cent shut-of Liquid plastics proven to be suitable for oil well seal- ing are unpolymerized styrene, vinylidene chloride, partially condensed phenolformaldehyde, vinyl esters and ester of maleie acid with dietliylene glycol. These plastics are all clear liquids, contain no suspended matter, and undergo polymerization, condensation, or association reactions until the whole liquid becomes an insoluble, strong, solid plastic when subject to tem- peratures encountered in oil wells. Use of Silts and Clays. Silt and clay, especially bentonite, have been used for many years to reduce aquifer permeability. In 1920, Warren reported that bentonite does not absorb saturated salt solutions, and no volume change occurs when bentonite is in the presence of such solutions.' 001 This finding, of course, is very pertinent as far as reducing ground water movement by grouting with bentonite which may come in contact with intruding saline waters. Warren fur- ther reports that bentonite in contact with pure water swells to several times its original volume. Davis performed further work in connection with the swelling of bentonite in the presence of different liquids. <07) These studies indicated that lubricating oil. kerosene, and gasoline prevent bentonite swelling and leave a hard, granular residue. Saturated solu- tions of salts also prevent bentonite from swelling, although dilute solutions of salts merely retard swell- ing. While it was found that increasing the tempera- ture accelerated the rate of swelling, an increase of acidity or akalinity decreased the swelling rate. Experiments with bentonite by the United States Army. Corps of Engineers, in 1938, 1939, and 1940 were concerned with methods of mixing bentonite with water to form grout, stability of slag treated with various concentrations of bentonite grout, and the ratio of bentonite grain size to the grain size of the soil to be treated. (^s • 0,l • 7 " , In 1952, Johnson described a field project in Ne- braska in which a slurry of graded loess, a yellowish clay or loam, was injected under pressures ranging from 80 to 270 pounds per square inch, into wells spaced 50 feet apart, to stop seepage from unlined canals.' 71 ' The wells consisted of 6-inch diameter holes. 150 feet deep, equipped with 2-inch diameter pipes 40-feet long centered within the holes and sur- rounded by gravel envelopes. It was found that seep- age could be halted for a distance of 80 feet from the well at a cost of about one dollar per cubic yard of injected slurry. ;,s SEA-WATER INTRUSION IN CALIFORNIA Asphalts. The use of cement, chemical, and clay grouts is often unsatisfactory in reducing aquifer permeability in areas of relatively high ground water velocities. In many such cases, desired results have been achieved by grouting- with hot asphalt. For ex- ample, the United States Bureau of Reclamation has used asphalt to seal cavities or joints underlying and adjacent to hydraulic structures, where use of con- ventional grouting materials has proven unsuccess- ful. |C0) The United States Army, Corps of Engineers, in a report released in 1950, discussed an experimental field investigation at Mansfield Hollow, Connecticut, where pervious soils were grouted with asphalt emul- sion." 2 ' Stratified sand and gravel deposits, a portion of which were below the phreatic line, were sealed to a depth of 35 feet through use of 10 injection holes spaced equally distant along the circumference of a 10-foot diameter circle and one hole at the center of the circle. The degree of sediment permeability was ascertained subsequent to grouting by pumping tests, sample borings, and open trench excavation ; and it was found that seepage was markedly reduced where asphalt emulsion had penetrated. It was concluded, however, that the method of injection used did not result in a uniform distribution of asphalt due to the stratified formation. Leakage of more than 450 second-feet from Great Falls Reservoir, Tennessee, was reduced to two per cent of this flow by injecting either cement or hot asphalt into 608 holes along a cutoff line almost a mile long. 173 ' Where leakage occurred at all reservoir eleva- tions, asphalt was used ; while cement grout was used where leakage occurred at high reservoir stages only. Five hundred-gallon capacity heaters and double- acting reciprocating pumps were employed for melt- ing and placing the oxidized petroleum asphalt. With asphalt temperatures varying from 300° to 350° F., average pumping rates from 40 to 80 cubic feet per hour were attained at an average cost of $1.35 per cubic foot of asphalt, including materials and place- ment. Total cost of cement and placement was $1.19 per cubic foot of cement. Packers were used for both asphalt and cement grouting, with greatest penetra- tion being achieved when packers were placed as close as possible to the cavities or pervious sediments. Shell Development Company has evolved the "Slicllperm" process in which Shellperm, a patented asphaltic emulsion, is pumped through pipes, placed at appropriate spacing and depth, into sediments to be solidified. Chemicals in the asphalt emulsion cause the asphalt to separate, coagulate, and form an im- permeable plastic mass within the interstices of the deposits. Shellperm was originally developed to improve foundation soils. It has been employed at numerous locations in the United States, as well as in Egypt, Belgium, Holland, and England. In 1948, Shell De- velopment Company reported on a series of experi- ments to determine distribution of Shellperm in saturated, damp, and dry sands. (74) Results indicated that an emulsion containing 30 per cent by weight of asphalt could be successfully injected into the afore- mentioned types of sand if one per cent of casein stabilizer were added, pressures controlled to avoid channelization of asphalt flow, and ethyl formate, which is added to the emulsion to produce hardening, was first mixed with the diluting water to avoid lumps forming in the mixture. The first large scale field test in the United States using Shellperm was undertaken in 1948 on the Santa Ana River, in Orange County, California, where a ver- tical cutoff wall was installed to prevent leakage at a diversion dam. Asphalt was injected in the amount of 10 gallons per vertical foot in holes spaced four feet apart along a 350-foot reach, and 20 gallons per verti- cal foot into a second line of holes, offset 14, feet from the first line and staggered in relation thereto. (75> Depths of holes varied from 5 to 30 feet and pressures varied from 20 to 30 pounds per square inch. A total of 32,400 gallons of emulsion were used at this site, resulting in the conservation of approximately 0.88 acre-feet of water per day which ordinarily would pass beneath the diversion dam as underflow. (76) It was noted, however, that irregularities in the distribution of emulsion near ground surface resulted in incom- plete impermeabilization. (77) Shellperm was used to reduce ground water seepage 70 to 80 per cent at the Witherby Street Undercross- ing in San Diego. (T8) An emulsion containing 60 per cent by weight of asphalt was necessary. It has been generally concluded from field experi- ments performed to date that grouting with asphalt, emulsions effects appreciable reductions in soil per- meability where uniform distribution of injected as- phalt has been achieved. Although this condition is seldom realized, further development of asphalts and injecting techniques may increase the degree of im- permeabilization. Artificial Subsurface Barrier Through Construction of Earthen Wail Other artificial subsurface barriers to ground water flow may take the form of earthen cutoff walls, which may be defined as artificial subsurface structures hav- ing definite physical boundaries and formed primarily of earthen materials which are relatively impermeable. Earthern core or cutoff walls have been constructed at hydraulic structures, principally dams, for many years, their construction consisting primarily of ex- cavation of overburden and placement of imported, relatively impermeable fill. This excavated material itself may be backfilled and compacted after proper mixing with suitable sealing agents. SEA-WATER INTRUSION IN CALIFORNIA 59 ('(instruction techniques employed in the installation of cutoff walls vary with depth and degree of consoli- dation of formations encountered. In unconsolidated materials, a slurry similar to the mud used in oil well drilling is often used to: (1) support walls of the trench during construction; and (2) mix with, and thus decrease the permeability of the backfill. Wilmington, California. One of the major earthen cutoff wall installations on the "West Coast is located at Wilmington, California, where it became necessary to increase the width and height of levees surrounding the properties of the Union Pacific Railroad Company, Southern California Edison Company, and General Petroleum Corporation because of land subsidence. To prevent movement of sea water through and under the levees, over 18,000 lineal feet of three-foot wide, clay cutoff wall, ranging from 15 to 45 feet in depth below land surface, was installed by the Macco Corporation in 1950 on Union Pacific Railroad Company land.' 711 ' S01 The trench for the cutoff wall was excavated with a rebuilt. Buckeye C-20, ladder-type, positive action ditching machine. Rotary drilling mud, containing bentonite, was pumped into the trench during con- struction. The slurry was displaced with dry, im- ported, selected clay, which was backfilled and tamped into the trench. This type of wall is termed a "puddled clay ' ' cutoff wall. The trencher, trucks containing mud, desander, and backfilling unit operated at specified distances apart along- the ditch, and an average of 400 lineal feet of cutoff wall were installed per eight-hour day at an approximate cost of $2.50 per square foot of wall. Core samples were taken at 25-foot intervals, and it was found that the wall was free from sand lenses and voids. To demonstrate the effectiveness of the installation in eliminating seepage, piezometer tubes were placed on the seaward and landward sides of the wall, and the landward side was dewatered using well points. Water levels observed regularly on the seaward side reflected tidal fluctuations, while water levels on the landward side showed no such fluctuations, indicating that a seal had been formed. The contractor contended that, although the equip- ment used on that particular project could not go deeper than 45 feet, much greater depths could be attained if the volume of work was sufficient to justify the expense of developing and altering equipment. Pasco, Washington. To prevent the flow of water from the reservoir formed by McNary Dam under the levees along the Columbia River, impervious cutoff walls were installed in the levees, with the walls ex- tending down 30 to 60 feet to an underlying imper- meable formation. IMl A clam shell was used to exca- vate the material from the 6-foot wide open trench, excavated material then being placed in windrows where it was blended with imported materials. Sub- sequent to mixing, a bulldozer pushed the material into the open ditch. The results of core drilling indi- cate that a greater impermeability was obtained than was required by the specifications. The work was conducted by Peter Kiewit Sons Com- pany of Longview, Washington, under the supervision of the United States Army, Corps of Engineers. Kennewick, Washington. Approximately 10,580 lineal feet of cutoff wall, three times that installed at Pasco, were constructed at Kennewick, Washington, across the Columbia River from Pasco. ' *-• B3) Unsup- ported open trench excavation was attempted first, but proved difficult due to the unconsolidated nature of the subsurface materials and excessive ground wa- ter flows, which resulted in excessive amounts of ex- cavation. The contractor, M. H. Hasler Construction Company and D. and H. Construction Company, then employed the Wyatt method, which utilizes a ben- tonite and water slurry to stabilize the ditch walls without caving. Slurry in the ditch was maintained at a sufficient level to balance the ground water head ; and the viscosity of the slurry, plus a "filter cake" formed on the walls, prevented the slurry from flow- ing through the trench walls. The presence of four- foot boulders made it inadvisable to use a trencher, necessitating the use of Manitowoc 4500 and Lima 1201 draglines. EXPERIMENTAL STUDIES UNDER CHAPTER 1500, STATUTES OF 1951 As previously mentioned, by enactment of Chapter 1500, Statutes of 1951, the State Legislature directed that an experimental program be undertaken to de- termine design criteria for the prevention and control of sea-water intrusion into ground water basins ; and appropriated $750,000 to the State Water Resources Board for its implementation. To carry out the intent of this legislation, the State Water Resources Board requested the Division of Water Resources to outline such an experimental program, which was subse- quently set forth in the Division's report entitled "Proposed Investigational Work for Control and Prevention of Sea-Water Intrusion Into Ground Water Basins," dated August, 1951. The following: four sea-water intrusion investiga- tions were performed with the funds indicated and are discussed hereinafter : 60 SEA-WATER INTRUSION IN CALIFORNIA To1 "' purpose of the field experiment was to determine, if Inrvshiiiiliiiii Contractor aUoculion ., , ,, „ ,. ' , . , _, . ™ , possible, the iollowmg: 1. West Coast Basin Los Angeles County Hood Experimental Project Control District __$642,126.30 * 1. Feasible rates of injection through wells as re- ■2. Model studies, reduc- University of California lated to thickness, permeability, and other prop- ti„n in ai -„..if..r 1..-I- at Berkeley.. $25,000.00 erties of the aquifers and var iation in rates of meabiltty and ab- . . 1 ' stract of literature inject Km with pressure head built up m the well 3. Permeability studies University of California and with time ; at Los Angeles- $10,000.00 2 IIe ight and shape of pres sure ridge that can be 4. Water quality inves- United States Geological built up as related to thickness and permeability tigations Survey, Quality of £vcjji_jtj- Water Branch- . .$10,000.00 ot aquifer and hydraulic gradient ; _ . . . . -„„„ .. „.. „„ 3. Required height of pressure ridge and amounts Subtotal $68(, 126.30 ' ° r . . ... ^ ot water necessary to inject to control intrusion Supervision, inspec- State Department of „ . , , , , ,-. „ .„ tion, coastal surveys. Water Resources (for- of sea water as related to depth of aquifer; ■""' n 'i""' ls ?^J? , D, -partmeut . of 4. Required spacing of injection wells to control Public W orks, Division ^ . r , , ... „ of Water Resources)- $62,873.70 sea-water intrusion as related to thickness ot aquifer, permeability, and hydraulic gradient ; Total $750,000.00 . „ . „ . .. , . o. Gradient of the pre-recharge piezometric surface * See following section for itemized breakdown. . ' . . m the water-bearing deposits and its effect on West Coast Basin Experimental the quantity of water injected and the shape of Pro/erf, Los Angeles County the Pressure mound ; To implement the approved experimental program, 6 - Rates and amounts of displacement of saline wa- the State Water Resources Board entered into a con- ters and / or de S ree of dilution of saline waters; tract with the Los Angeles County Flood Control Dis- 7. Effect of ground water extractions in the inland triet on October 1, 1951, for prosecution of certain areas on the rate of injection necessary to control phases of the work. The Board made an initial alio- sea-water intrusion ; cation of $450,000 to the District for installation and 8. Degree of chlorination or other treatment neces- one year's operation of a field experimental project sary f or continued injection of water at feasible in the vicinity of Manhattan Beach, Los Angeles rates- County, to investigate the hydraulic feasibility of „ , T . , „ „ n ,. -, , ,. . . . „ , .. , 9. Maintenance of wells, including procedures such creating a pressure ridge m confined aquifers by , , .,. . , ,- , , ,. . . ■ .. „ . j, , , , ,, as sand bailing, surging, deaeration, and studies means ot injection wells, using fresh water, and the „ „ ,. „ . -, ., a c ~, . . i. i • i • j.- or formation ot microorganisms and the effect ot effectiveness ot such a ridge m preventing sea-water , . . ,. ., ,, -, „ , . . „ .. ...»-, - . . J , , chlorination or other methods ot disinfection on intrusion. Amendments to this agreement extended ,,. ,-, n -,. £ , , ,, . , , T „„ 5„ r . , . , , , their growth, and studies ot base-exchange reae- the contract period to June JO, 19o4, and included , ■■ j VJ -, , ,... , ., ,. ... . . . ., tions and suspended solids deposition. additional allocations, resulting m a total state allo- cation to the District of $642,126.30, which was ex- Description of Field Site. The site of the experi- pended as follows: mental field project is located within the boundaries Item Cost of the Cities of Manhattan Beach and Hermosa Beach, Capital . $333,870.14 as s hown on Plate 21, and its selection was based on Operating and maintenance .. __ !>S.833.fi. - S * ., ,. , -. , , Engineering, investigation and testing— 109,705.33 considerations enumerated below: MSatous-::::::::::::::::::::::::: K™ *■ Sea ™ ter had hitraded iiito the mai » a( i uifer underlying the area ; Total _ $042,126.30 2 The Atch i son Topeka and Santa Fe Railway •Includes $32, 967. SO for cost of recharge water. „ , . , , . , ... . Company, which has a single track line approxi- These funds were exhausted in December, 1953, but mately paralleling the coast line at a suitable the District has continued operation on a reduced distance inland, provided free right of way for scale, using its own and local funds. In 1954, project project facilities - facilities were sold to the District except for certain 3 A som . ce of sui ^ hle injection water was avail- engineering equipment which was retained by the able hl the vk , initVi lianielv> filteml aiul so f te ned Board. The Los Angeles County Flood Control Dis- Colorado River water through facilities of the trict s final report describing the field experiment ap- Metropolitan Water District of Southern Cali- pears as Appendix B to this report, fornia- Experimental Objectives. Under terms of the 4. The underlying Silverado water-bearing zone is contract between the State Water Resources Board a confined pressure aquifer suitable for the de- and Los Angeles County Flood Control District, the sired experiments utilizing injection wells; SEA-WATER IXTKI'SloX IX ( 'AM K< >RXI A 61 5. Existing piezometric surface and the Silverado water-bearing zone are comparatively close to ground surface in the area ; 6. Local interests were desirous of reclaiming as much of the aquifer underlying the test site as possible. Areal geologic features of the test site are depicted on Plate 22. As mentioned, this site is underlain at relatively shallow depths by the confined merged Sil- verado water-bearing zone in the San Pedro formation of Pleistocene age, as shown on Plate 23. This zone contains two phases; an upper brown phase and a lower gray phase. The upper brown phase is primarily a continental and littoral deposit, consisting of yel- lowish-brown gravel, sand, and silt. This phase grades into the lower gray phase, which is a shallow marine deposit, consisting of fine to very fine silty sand and clay. A study of the rock fragments indicates only minor differences between the two phases. The larger rock fragments are granitic types, with some meta- inorphics, volcanics and sedimentary types. Quartz and feldspar make up the major portion of the sedi- ments in both phases. Mineral content of the upper phase ranges from about 1 to 15 per cent, and in- cludes magnetite, ilmenite, pyroxenes, amphiboles, micas, and a number of other minerals. In the lower gray phase, the range of heavy minerals, consisting largely of biotite, is from about 2 to 8 per cent. Thick- ness of this formation is about 110 feet at the northern portion of the test area, increasing to over 150 feet at the southern end. The top of the zone is a few feet below sea level near the coast and dips landward so that near the recharge line it is approximately 30 feet below sea level. There appears to be a continuous clay cap overlying this formation, varying in thick- ness from about 20 feet near the inland boundary of the test area to mere traces at the beach. The lower limits of the Silverado water-bearing zone are bounded by relatively impermeable silts and clays of the San Pedro formation. As previously discussed, the produc- tive Silverado zone is the coarse basal member of the San Pedro formation and is a distinct body of highly permeable sand and gravel with scattered discontin- uous layers of relatively impermeable sandy silt, silt, and clay. Transmissibility of this zone, as determined by the Los Angeles County Flood Control District by field pumping tests along the recharge line varied from 32,300 to 161,600 gallons per day per foot (0.05- 0.25 efs/ft) and averaged about 106,600 gpd/ft (0.165 cfs/ft) prior to recharge. Pressure levels, which were above sea level through- nut the West Coast Basin in the early 1900 's, had dropped below sea level at individual wells by 1920 ; and by 1932, levels were below sea level throughout most of the area. Since that time, the decline in pres- sure levels has continued with only minor interrup- tions, with the greatest lowering occurring northeast of Wilmington where a pumping trough has 1 n formed. Pressure levels in this area were as much as 105 feet below sea level prior to the curtailment of pumping of ground water which commenced -lime 1, 1955, under agreement among the major water users. Pressure levels along the recharge line varied IV about 5 to 12 I'eet below sea level prior to initiation of the experiment. Concurrent with declining pressure levels has been the degradation of ground water quality along the coastal margin of the West ('oast P.asin. Chloride ion concentrations along the recharge line immediately prior to injection varied from l(),70(l parts per million to 18,300 parts per million. Throughout the general area of the test site, within 6,5011 feet of the coasl line, the chloride ion concentration of the ground water exceeded the United States Public Health Service per- missible maximum of 250 parts per million for do- mestic water. Project Facilities. Construction commenced in January, 1952 with the initiation of well drilling, and was completed one year later. Nine 12-inch injection wells, one of which was gravel-packed, were drilled at 500-foot intervals along the Atchison, Topeka and Santa Fe Railway Company right of way. lying approximately parallel to, and some 2,000 feet inland from the coast line. Thirty-six 8-inch observation wells were drilled at selected locations surrounding the re- charge line. The cable tool method of well drilling was employed since it was felt that this technique would result in more accurate logs, more suitable perforation locations, and more satisfactorily developed wells free of drilling mud. All of the aforementioned 45 wells were perforated in place using a Mills Knife, with the exception of the gravel-packed recharge well, which was perforated in place using a Moss Hydraulic Per- forator. Double, hard red steel casing was installed throughout. All wells were very carefully logged : and samples and cores of formation material were taken for further study. Construction of a steel pipe line and appurtenances, to convey treated and softened Colorado River water from the supply line of the Metropolitan Water Dis- trict of Southern California to, and along the recharge line was started in the fall of 1952 and completed in February, 1953, when injection was initiated. The pipe line consists of approximately 10,000 feet of 20- inch, 10 gage pipe and approximately 2.000 feet of 14-inch and 16-inch, 12 gage pipe, all asphalt dipped. Installation of ehlorination equipment completed the initial facilities. As the field experiment proceeded, it became neces- sary to add eighteen 2-inch and four 4-inch observa- tion wells and to replace two nongravel-packed re- charge wells with gravel-packed wells. It also became necessary to cement grout several of the recharge wells when formation subsidence or leakage above the eon- 62 SEA-WATER INTRUSION IN CALIFORNIA fining clay member became evident. Locations of project wells and pipe line are shown on Plate 21. Project facilities included extensive instrumentation and metering- in order to measure and record total and individual flow rates to injection wells, chlorine dos- age, chlorine residual, fluctuations of pressure levels in 10 key observation wells, and conductivity of ground water in four strategic wells. Specially fabri- cated well header assemblies and back pressure valves prevented air entrainment during recharge operation. Extensive tests and studies were conducted prior to initiation of recharge to determine hydraulic charac- teristics of injection wells, and hydraulic and geologic characteristics of the aquifer. Recharge Operations. The first phase of the re- charging program involved five of the recharge wells spaced 1,000 feet apart, with injection commencing in Well G, the center well. Artificial recharge was com- menced in February, 1953, with injection through Well G at a rate of 0.5 second-foot. Pressure levels were affected in observation wells approximately 1,200 feet inland almost immediately ; and under a constant recharge rate, stabilization was attained in approxi- mately five days. As the injection rate was increased in this well, the two adjacent injection wells, located 1,000 feet distant north and south, were put into oper- ation, with the injection rate in these wells being in- creased at planned intervals. It was planned to con- tinue this operation with additional wells north and south of Well G being put into operation progres- sively. It was hoped that an injection rate of approxi- mately one second-foot per well would be attained eight weeks after injection was initiated in Well G. Unfortunately, formation subsidence at Wells G and I and leakage of recharge water upward around the cas- ing of Well C into the strata above the clay cap pre- vented the completion of this program. The necessity of decreasing well spacing, reducing individual well injection rates, and reducing injection heads within the injection wells was manifested by these difficulties. Injection was subsequently initiated in a total of eight recharge wells spaced 500 feet apart. Recharging in the ninth recharge well, Well C, was discontinued in May, 1953, due to the aforementioned upward leakage and was not resumed until June, 1955, after cement grouting. Initial injection rate at all eight injection wells was approximately 0.5 second-foot ; however, it soon be- came evident that an unbalanced pressure ridge de- veloped under this uniform rate due to lateral flow at the ends of the injection line and variations in aquifer t lansmissibility. It was, therefore, decided to vary the individual well injection rates in such a manner as to obtain a ridge with pressure level elevations of about 2 to 3 feet above sea level at the internodal points midway between injection wells. These elevations were determined to be sufficient to halt the inland flow of sea water, in accordance with the Ghyben-Herzberg principle. Pressure levels along the recharge line be- tween Well D and Well K were equal to, or above, 2.5 feet above sea level for the first time in January, 1954, with eight wells operating at a spacing of 500 feet. These levels have been maintained equal to, or above, the required elevation of 2 to 3 feet above sea level since that time, except for short periods during maintenance operations on wells or pipe line. It was found that a total recharge rate of about 4.5 second-feet was required to maintain the ridge along the 4,000-foot test reach, or about 6 second-feet per mile. Injection rates along the recharge line varied from about 0.3 second-foot to 1.1 second-feet per well. With the view of determining the maximum accept- ance rate of gravel-packed Well E, the injection rate through this well was increased in small increments until a maximum rate of 1.86 second-feet was attained on May 12, 1954. Injection heads required to maintain desired pres- sure-level elevations at the internodal points varied from 35 to 75 feet in June, 1954. Injection rates of over 1.0 second-foot were maintained with injection heads of from 27 to 50 feet in gravel-packed wells, while approximately the same heads were required to maintain one-half of this rate in nongravel-packed wells. Average recharge rate per foot of injection head was approximately 60 per cent of the average dis- charge rate per foot of drawdown observed when the recharge wells were pumped during development. Lines of equal elevation of ground water before commencement of injection operations and after sta- bilization of the pressure ridge are shown on Plate 24. Pressure level profiles along and normal to the re- charge line are shown on Plates 25 and 26, respec- tively. Recharge Water Treatment. Concurrent with re- charging operations, experiments were conducted to determine the minimum chlorine dosage for the re- charge water, which had already been filtered and softened, to maintain suitable well acceptance rates. Recharge water was chlorinated at 20 parts per mil- lion at the commencement of injection in Februai'y, 1953. This dosage was subsequently reduced in small increments until the dosage was 1.5 parts per million in April, 1954. The district concluded that a chlorina- tion rate of less than 10 parts per million and more than five parts per million was required at the test site to control the growth of slime-forming bacteria which tend to accumulate at the well perforations and at the face of the aquifer. In addition, a "shock" treat- ment of 20 or more parts per million of chlorine was occasionally required. No redevelopment of injection wells was required during the test period except as a result of inadequate well construction. Hence, little knowledge was gained relative to the ultimate useful life of the wells and SEA-WATER INTRUSION IN CALIFORNIA 63 redevelopment needed to maintain effective well oper- ation. Occurrence and Movement of Saline Wedge. As previously mentioned, the chloride ion concentration of the ground water underlying the recharge line varied from 10,700 to 18,300 parts per million prior to initiation of recharge operations. The concentration decreased greatly with inci*eased distance from Santa Monica Bay, with the 250 parts per million isochlor being approximately 4,200 feet inland from the re- charge line and 6,500 feet from the coast. An inten- sive ground water sampling program was undertaken in the test area before and during operations, using " thief s" and portable pumping equipment. Analyses of water samples collected at various depths in the observation wells indicated that salt water was in- truding under the fresher native ground water in the form of a wedge. The toe of this wedge was lo- cated approximately 3,000 feet inland from the re- charge line prior to injection, and a wedge of rela- tively fresh native ground water existed near the top of the Silverado water-bearing zone, overlying the saline wedge, in the region of the recharge line. Injection of fresh water along the recharge line resulted in a •'splitting" of this wedge and a flow of injected water and sea water both seaward and land- ward from the recharge line. Injected water tended to override and displace the intruded saline water with very little commingling exhibited. As recharging op- erations proceeded, injected fresh water completely displaced the saline water directly beneath the injec- tion well line. During a 21-month period of recharge the "amputated" toe of the previous saline wedge moved inland approximately 2,000 feet while the re- mainder of the wedge moved seaward about 500 feet. Chloride ion concentration in "Well MB-8, located approximately 2,850 feet inland from the recharge line, increased from 1,500 parts per million in Janu- ary, 1953, to over 5,400 parts per million in February, 1955. The chloride ion concentration in Well M-18, situated approximately 4,900 feet inland from the recharge line, increased from 390 parts per million in January, 1953, to 1,280 parts per million in August, 1955. The chloride ion concentrations of ground water at these two wells subsequently decreased with the passing inland of the saline wave and the arrival of the fresher injected water. It is of particular interest that, although there was apparently little commin- gling between the intruded sea water and injected fresh water, the highly saline water originally under- lying the recharge line was never detected in inland observation wells. Conductivity traverses in wells along the recharge line indicated that a considerable period of recharg- ing is required to freshen the entire thickness of aquifer at the internodal points. This is primarily due to the existence of a stagnation point, or area of 3—86952 no ground water movement, in the flow net near the internodal point, produced as a result of the super- imposition of the radial flow pattern from injection wells on the pre-recharge piezometric surface. Lines of equal chloride ion concentration of ground water before recharging in June, 1955, are shown on Plate 27. The inland movement of the saline wave is illustrated on Plate 28, and changes iu chloride ion concentrations in key wells are shown on Plate 29. Computations by Mr. J. A. Harder of the Univer- sity of California, Berkeley, indicated that there were about 80,000 tons of chloride ion inland from the recharge line within the West Coast Basin prior to injection, assuming an aquifer thickness of 100 feet and a porosity of 30 per cent.' 84 ' This chloride content- would degrade the quality of 240,000 acre-feet of ground water to a concentration of 250 parts per mil- lion, the generally accepted recommended maximum concentration for domestic use. Due to the unpredictable effects of the inland ad- vance of the saline wave, waivers were obtained from four ground water pumpers located inland from the test site prior to recharge operations. These waivers stipulated that State agencies connected with the proj- ect, and the Los Angeles County Flood Control Dis- trict, would not be held responsible or liable for dam- age resulting from test operations. Derivation of Equation for Fresh Water Waste to Ocean. The Los Angeles County Flood Control Dis- trict derived an equation for fresh water waste to the ocean from a pressure ridge created to prevent sea- water intrusion. The derivation is based on a combina- tion of the Dupuit-Forchheimer theory and Kozeny's basic parabola solution and appears in Appendix B to this report. The equation is as follows: q = nKM 2 (S—l ) 2L Where : , q = seaward fresh water flow per foot of ocean front S = specific gravity of sea water M = thickness of aquifer, down to the lowest depth which must be protected K = aquifer permeability for a 100 per cent hy- draulic gradient L = length of sea water wedge, from ocean outlet to the toe n = coefficient which is less than 1 and depends upon the ratio M. L Test Results. Results of the pressure ridge field experiment indicated that for coastal ground water basins in the State with geologic, hydrologic, and topographic conditions similar to those found at the test site in the West Coast Basin : 64 SEA-WATER INTRUSION IN CALIFORNIA 1. It is physically possible to raise the piezometrie level for a confined aquifer above sea level by injection of suitable water through wells, and thus prevent further intrusion of sea water; 2. It is engineeringly feasible to maintain a pres- sure ridge above sea level to the extent necessary to prevent sea-water intrusion for long periods of time if the quality of injection water meets certain standards and properly designed injec- tion wells are installed and subsequently rehabili- tated by bailing and surging as necessary when injection rates decline. Although injection water may have undergone .standard treatment, it must contain sufficient free chlorine at the time of in- jection to control bacterial activity within the well and adjacent portions of the aquifer. A gravel-packed recharge well, properly sealed with cement grout above the confining clay member to prevent formation subsidence, was found to be the most feasible type of well construction ; 3. The rate of recharge required to maintain piezo- metrie levels sufficiently high to halt sea-water inflow along a coastal reach equals the sum of the pre-recharge inflow from the ocean, the amount of recharge water which necessarily wastes to the ocean, lateral flow at each end of the reach, and any small amount entering stor- age. If a pressure ridge extends along the coast entirely across a completely confined aquifer, the required recharge rate will essentially equal the sum of the first two items, because of the small magnitude of the other two factors. If a pumping trough exists in such a completely confined aqui- fer, the pre-recharge inland flow equals ground water production seaward of the trough ; 4. An aquifer containing water already degraded by sea-water intrusion can be reclaimed for future use. If sea water has advanced inland from the recharge line, certain hazards attend reclamation of the aquifer. Recharging opera- tions will temporarily accelerate the landward sea-water movement immediately inland of the recharge line. If inland ground water producers are located within this area, they might pump water of high mineral concentration sooner than would occur under natural conditions. Although the concentration is probably less than that which would have eventually occurred naturally, the parties responsible for recharge operations might be subject to legal action. In areas where ground water is produced by persons or agencies other than the organization conducting the injection operations, it is recommended that written waivers of possible damage be obtained prior to injection. Costs. Much less self-evident than the engineer- ing feasibility of creating a pressure ridge by injec- tion through wells to prevent sea-water intrusion is the economic feasibility of such a method. In 195"), the Los Angeles County Flood Control District esti- mated annual costs of capital recovery and of opera- tion and maintenance of any future project in the West Coast Basin to be $14,900 and $32,000, respec- tively, per mile. Costs of right of way, pipe line con- necting the project with a source of recharge water, and recharge water were not included in these cost estimates. Until such time as more definite plans are evolved as to route of recharge line and source of recharge water, the aforementioned three items of cost will remain uncertain, as will the economic feasibility of such a project. With regard to the possible sources of recharge Mater for any future pressure ridge project in the West Coast Basin, the Los Angeles County Flood Con- trol District is presently investigating the feasibility of treating sewage effluent from the City of Los An- geles' Hyperion sewage treatment plant by percola- tion through slow sand filter beds constructed in the natural sand dune material in the area. This experi- ment is discussed hereinafter. The Los Angeles County Flood Control District is also studying two other al- ternative sources: (1) untreated Colorado River water; and (2) treated sewage effluent from a water treatment plant that could be installed adjacent to the Hyperion plant. Applicability to Other Areas. It was the intent of the Legislature that the results obtained from the pressure ridge field experiment in the West Coast Basin be analyzed and interpreted so as to be usable in the design of similar works for other coastal areas in the State. To carry out this intent, data obtained from the field experiment pertaining to aquifer transmissibility, recharge rate, and height of pressure ridge above the initial piezometrie surface, have been analyzed. Inter-relationships between these factors are presented on Plate 30. If aquifer transmissibility, elevation and slope of the initial piezometrie surface, and elevation of the bottom of the confined aquifer in a coastal basin are known, then by use of the curves on Plate 30, the gen- eral order of magnitude of the recharge rate necessary to prevent sea-water intrusion can be estimated. The recharge rate obtained through use of these curves is applicable to an initial landward hydraulic gradient and length of sea-water wedge equal to those which existed at the West Coast Basin field experiment. This rate must be multiplied by the ratio of the gradient in the basin under study to the gradient at the experi- ment, which averaged about 0.004, to ascertain the approximate rate required. Correcting for differences in length of sea-water wedge is not necessary in most cases, since this affects only the amount of injected SEA-WATER INTRUSION IN CALIFORNIA 65 fresh water wasting to the ocean, which is usually small compared to the rate of injected fresh water movement inland. If individual well injection rates can be ascertained, possibly from well discharge rate data, approximate number of injection wells required to prevent intru- sion can be determined. With these data, it would be possible to complete a preliminary estimate of annual costs of water, capital recovery, and operation and maintenance for a proposed project. Well spacing and well construction costs are primarily dependent upon aquifer transmissibility and type of construction, re- spectively. Annual recharge water requirement could, of course, also be obtained if aquifer thickness and permeability and underflow from the ocean, or the ground water production between the proposed recharge line and the pumping trough, were known. Laboratory Experiments Performed by the University of California at Berkeley In response to a recommendation in the August, 1951 report of the Division of Water Resources to the State Water Resources Board on proposed sea-water intrusion studies, portions of the investigational pro- cram were assigned to the University of California at Berkeley. This agency undertook certain laboratory studies and completed an abstract of technical litera- ture pertaining to sea-water intrusion under terms of State Standard Agreement No. 3SA-423, dated Jan- uary 1, 1952, and amended December 10, 1952. Funds in the amount of $25,000 were allocated to the Uni- versity from the appropriation provided under Chap- ter 1500, Statutes of 1951. Principal objectives of the laboratory research pro- gram were : 1. Determination of shapes and rates of travel of the interface between intruding saline water and displaced fresh water ; 2. Study of hydraulic phenomena in connection with the operation of injection wells, including shape and height of pressure mounds or ridges produced thereby ; 3. Determination of effect of partial penetration of injection wells into aquifers; 4. Study of types of injection wells and methods of construction thereof ; 5. Investigation of phenomena related to the raising of the piezometric surface by rearrangement of pumping pattern ; 6. Study of materials and methods related to reduc- tion of aquifer permeability. In preparing the abstract of literature, all readily available references containing information concerned directly with sea-water intrusion were summarized. Abstracts were divided into the following five cate- gories: (1) reduction of aquifer permeability; (2) sea-water intrusion; (3) injection and recharge of aquifers; (4) laboratory and model studies; and (5) ground water How. The University's laboratory research was performed concurrently with the pressure ridge field experiment in the West Coast Basin, previously described. Labora- tory ami field experiments supplemented each other, including the exchange of basic data and test results, with the work coordinated by representatives of the Slate Division of Water Resources. In addition, lab- oratory studies of reduction in aquifer permeability supplemented investigations by the State Water Re- sources Board and its staff on this subject. The University's final report on sea-water intrusion laboratory studies and the abstract of literature ap- pear as Appendix C to this report. Reduction of Aquifer Permeability. The Univer- sity's laboratory studies were initiated by studying the use of various admixtures to obtain reduction in aquifer permeability. The main item of laboratory equipment developed for these experiments consisted of a permeameter with center and annular screens. Back pressures were regulated to eliminate sidewall leakage around the central core being tested. A con- stant head reservoir supplied water to the permea- meter under a hydraulic gradient of 1,000 per cent. Water was circulated through the samples for periods of up to two weeks; and flow rates were measured by noting the rate of travel of the meniscus in a cali- brated narrow-core glass tube. The first phase of the permeability reduction experi- ments consisted of adding a thin bentonitc slurry hav- ing an absolute viscosity of 15 centipoises, similar to the slurry used in oil well drilling, to three different types of material consisting of various proportions of clay, silt, fine sand, and medium sand. The second portion of the permeability studies was devoted to increasing the viscosity of various slurries by the addition of bentonite in an attempt to further reduce the permeability of the aforementioned three samples. Although a backfill mixture containing only sufficient slurry to fill its voids exhibited a low per- meability, it was unworkable. For practicable con- siderations, emphasis was placed on securing a back- fill material which was both workable and suitably impermeable. The use of cement in decreasing aquifer permea- bility was investigated by adding 5 and 71 per cenl of cement to a sample containing about 111 per cent silt. Sufficient 15 centipoise bentonite slurry was added to provide a workable mix having a 3 to 4 inch slump. Asphalt emulsion, 20 per cent by weight, was an- other material added to 15 centipoise slurry and mixed with a sample containing about 10 per cent silt. 66 SEA- WATER INTRUSION IN CALIFORNIA The University's report on their laboratory studies, appearing as Appendix C to this report, presents the following data on unit costs of admixtures, excluding labor costs and costs of gravel, sand, and silt: 1. Assuming a sf>10 per ton cost for hauling clay, a puddled clay admixture would cost approxi- mately $12 per cubic yard of backfill. 2. Chrome-lignin is estimated by the patent holder to cost from approximately $4 to $11 per cubic yard of backfill. 3. The University estimates that an admixture of one-third clay by weight to equal parts of sand and gravel would cost approximately $4 per cubic yard of backfill, as would a thin bentonite slurry containing 20 per cent asphalt emulsion. 4. For about $0.75 per cubic yard of backfill, seven per cent Wyoming bentonite slurry mixed with an aggregate containing from 10 to 15 per cent silt and 30 to 50 per cent sand, could be provided. The permeability of this mixture would be on the order of 0.001 gallons per day per square foot under a 100 per cent hydraulic gradient, the lowest attained by any of the admixtures dis- cussed. However, this permeability is increased ten-fold in the presence of sea water. From the results of the University 's laboratory tests it was concluded that : 1. Bentonite slurry of a consistency ordinarily used in drilling operations does not produce satisfac- tory reductions in permeability when added to backfill mixtures containing up to 30 per cent silt. 2. Stiffer slurries, containing from 7 to 8 per cent dry bentonite, promote a satisfactorily low per- meability coefficient in well-graded backfill mix- tures containing from 15 to 30 per cent silt. 3. It is unlikely that excavation equipment can op- erate in these thick slurries ; even tetra-sodium pyrophosphate was unable to reduce their vis- cosity appreciably. Unless some material is found that will act in conjunction with the thinner trench slurry to form a satisfactory additive, a separate source of slurry must be used with the backfill mixture. 4. Only enough slurry should be added to the back- fill mixture to obtain minimum workability; any additional amount raises its permeability and contributes to the danger of piping. For this reason a method of backfilling should be selected which will allow a minimum amount of water or trench slurry to be incorporated in the mix during placement. Extreme care should also be exercised during backfilling operations to avoid "bridging" of backfill across the cutoff trench. 5. Preliminary data indicate that the permeability to sea water of a mixture incorporating bentonite slurry is roughly ten times its permeability to fresh water. 6. No mixture was found which provided a com- plete seal. The residual leakage and possible degradation of fresh water inland of the bar- rier may be determined from the permeability value for the barrier and from a knowledge of ground water level elevations on each side of the barrier. Model Aquifer Studies. In order to confirm cer- tain theories relating to sea-water intrusion phenom- ena, a model typifying a pressure aquifer pierced by injection wells was constructed and operated inter- mittently for about two and one-half years. Para- mount objectives were determination of shapes and rates of travel of the interface between intruding sa- line water and displaced fresh water, amounts of fresh water wasting to the ocean from a pressure ridge, and effect of partial penetration of injection wells into aquifers on creation of a pressure ridge. The model measured 6 inches high, 3 inches wide, and 4 feet long and was constructed of Lueite. It was packed with a washed quartz sand, Del Monte No. 1, 30 mesh, with an effective grain size of 0.22 milli- meters, a uniformity coefficient of 1.3, and a permea- bility of 0.032 centimeters per second. Chambers were attached at each end of the model and served as con- stant head sea water and fresh water reservoirs. Pie- zometer tubes were used to permit measurement of the piezometric surface. Two model injection wells, one- fourth inch in diameter, represented prototype wells approximately 40 feet in diameter. The University believed that this obvious scale distortion would not hinder the model experiments since the flow within a 20-foot radius of prototype wells would for all prac- tical purposes be radial. The horizontal and vertical scale factors were taken as 1 : 2,000 and 1 : 200, respectively, thus representing a section of confined aquifer 100 feet thick and 8,000 feet long. One of the 6-inch by 4-foot vertical rec- tangular sections of the model represented a section at the internodal point between injection wells, assum- ing a well spacing of 1,000 feet. The other vertical section represented a section through an injection well. Using the ratios for horizontal and vertical scale, specific gravity, and permeability, and the equa- tion for fresh water flow to the ocean, a time-scale relationship of one minute to 26.7 days was obtained. Both calcium chloride and sodium chloride solu- tions with specific gravity of 1.10, were used to simu- late sea water in the model. Normal sea water has a specific gravity of 1.025. To distinguish salt water from fresh water within the model aquifer, Rhadamine B was added to the saline water and Fluorosal was added to the fresh water. Use of these fluorescent dyes resulted in a distinctive red sea water and blue fresh water in the presence of ultraviolet light. SEA-WATER INTRUSION IN CALIFORNIA 67 The University recorded on motion picture film the salient features of the phenomena illustrated by the model. A 16 millimeter Kodak Cine Special camera with a lapse-time attachment was employed. Prints of this film accompany the University's final report to the State Water Resources Board. The equation for fresh water leakage to the ocean, which the University derived mathematically using Muskat's approximate potential theory, was checked experimentally by use of the model. The theoretical equation was substantially verified, as shown on Fig- ure 7 of Appendix C. The equation is as follows: MT Q = l(S— 1)-£- where : Q = seaward fresh water flow per foot of ocean front. 6' = specific gravity of sea water. .1/ = thickness of aquifer, down to the lowest. depth which must be protected. T = aquifer transmissibility for 100 per cent hy- draulic gradient. L = length of sea-water wedge, from ocean out- let to the toe. Since "K" in the previously discussed Los Angeles Flood Control District's equation equals — — in the University's formula, the two equations are identical except that the District's equation contains an addi- tional factor of "n." This coefficient "n" depends "M" upon the ratio —y , and since for most conditions "n" is practically equal to "1," the equation may usually be considered identical. However, since the derivations of the two equations varied widely, the State Division of Water Resources retained Dr. Nor- man H. Brooks, Assistant Professor of Civil Engineer- ing at the California Institute of Technology, as a consultant to review and report on the derivations. Dr. Brooks' report, appearing in Appendix C to this report, presents three independent derivations based on: (1) Kozeny basic parabola solution; (2) Muskat's approximate potential theory; and (3) Dupuit-Forch- lieimer theory, all of which corroborated the Univer- sity of California equation. The "pumping trough" method of preventing intru- sion of sea water was also investigated by use of the model. Water was pumped from the model wells and the rate of movement and shape of the interlace were observed, as were the amounts of ocean and fresh water pumped. Results of the University's experimental model studies indicated the following: 1. In accordance with the Ghyben-Herzberg prin- ciple, the fresh water piezometric surface must be maintained above sea level a distance equal tO (S — 1) times the distance below sea level of the lowest point within the aquifer which must be protected from sea-water intrusion, where S is the specific gravity of sea water; l\ When a pressure ridge is maintained above sea level, the fresh water flow seaward is inversely proportional to length of the sea-water wedge from the ocean outlet determined by the formula previously presented. Fresh water waste to the ocean is independent of the elevation of the aquifer; 3. The total injection rate along the recharge line must be equal to the sum of the fresh water waste to the ocean necessary to maintain the position of the sea-water wedge and the over- draft of the basin originally being satisfied by landward flow of sea water. This relationship may be expressed as follows : Q = l(S—l)^-T + iT where : Q = total injection rate i = landward hydraulic gradient prior to in- jection S = specific gravity of sea water .¥ = thickness of aquifer, down to the lowest depth which must be protected L = length of sea-water wedge, from ocean out- let to the toe T = aquifer transmissibility for 100 percent hy- draulic gradient This relationship is independent of well spacing, location of perforations vertically in the aquifer, individual well injection rates, and well size or type ; 4. When conditions are such that the saline wedge moves inland, the wedge tends to flatten out and the toe moves somewhat faster than the remain- ing interface. In a prototype aquifer, it is be- lieved that nonuniformity of material, with accompanying varying transmissibility. may greatly distort the shape of the interface since the intruding saline water will tend to follow the path of least resistance ; ."). Diffusion along the interface is apparently slighl as a sharp line of distinction was observed be- tween the sea water and fresh water. It can be expected that some mixing will take place in the immediate vicinity of pumping wells; 6. In areas where the saline wedge has intrude, I past the recharge line, the wedge will be divided as a result of injection and saline water will be displaced seaward and landward. Injected fresh liS SEA-WATER INTRUSION IN CALIFORNIA water tends to override the severed toe, which becomes (latter as it continues to move inland; 7. Injection well spacing is of little importance, excepl that the toe of the intruded wedge should be held at least half a well spacing seaward from the injection line, ruder this condition, seaward flowing fresh water from the injection wells will have merged to nearly uniform How as it reaches the toe ; 8. Saline-water intrusion can he controlled by es- tablishment of a pumping trough, created by a line of pumping: wells parallel to the coast line. Model studies indicate that a saline wedge is created immediately inland from the line of pumping wells similar to the wedge that forms at the ocean outlet, although the wedge inland from the wells is longer for the same fresh water flow seaward. This method of controlling sea- water intrusion would provide no replenishment to a coastal basin, but the loss of fresh water need be no greater than that which would occur with a pressure ridge established through the use of injection wells. Relative to economic justification for the use of a pressure ridge to control sea-water intrusion, the University recommends that prior to initiation of a field project, the sum of the costs of treating water to be injected, injection, and pumping at a later date be compared with the cost of treating water to an extent necessary to permit its direct use for industrial purposes and some forms of agriculture, plus the cost of surface distribution. Laboratory Studies Performed by the University of California at Los Angeles A portion of the investigational program was con- ducted by the University of California at Los Angeles under State Standard Agreement No. 3SA-430, dated February 1, 1952, and State Standard Agreement No. 53-SA-55, dated January 31, 1953, as amended and reamended on December 17, 1953. The State Water Resources Board allocated $10,000 from funds pro- vided by Chapter 1500, Statutes of 1951, to the Uni- versity for performance of the experiments. Objectives of the laboratory studies comprised the following : 1. Determination of the compatibility of treated ( 'olorado River water used as recharge water at the pressure-ridge field experiment in the West Coast Basin, and the native ground water in the vicinity; 2. Treatment of recharge water necessary to main- tain suitable permeabilities of core samples se- cured from the same field project. Laboratory investigations and the field experiment conducted by the Los Angeles County Flood Control District were coordinated by the State Division of Water Resources. The University's final report of their experiments appears as Appendix D to this report. Project Facilities. In addition to standard lab- oratory equipment, Lucite permeameters having an in- side diameter of 2' inches, were provided. These per- meameters were fabricated to accommodate 6-inch long cores obtained from the Silverado water-bearing zone during test well drilling at the pressure ridge ex- perimental site. Screens at each end of the permea- meters and "O" rings prevented movement of sample particles and "piping" along the periphery of the sample. The core sampler contained a series of 2-i-inch outside diameter brass rings, 1 inch wide, to facilitate cutting the sample to any desired length. Test Procedures. Rings and cores were removed from the core barrel and placed in tin cans, labeled, and sealed in paraffin immediately after coring in the field. Selected cores were then forwarded to the Uni- versity where cores and rings were inserted into per- meameters. Colorado River water from the Metropoli- tan Water District of Southern California, similar in quality to the recharge water used at the pressure ridge field experiment, was then circulated, untreated and after various types of treatment, through the un- disturbed samples. Treatment consisted of the follow- ing: (1) ehlorination; (2) addition of hydrochloric acid; (3) ehlorination plus addition of acid; and (4) deaeration and filtration. Except for a few cores which contained impermeable clay lenses, circulation periods varied from 500 to 5,000 hours. Changes in permea- bility were noted. Test Results. The effect of percolating water treated by ehlorination plus acidification was to in- crease permeabilities of cores, even those previously tested with waters which had been treated with acid or chlorine alone. When water treated with acid plus chlorine was percolated through cores previously tested with untreated water, the average permeability increased to 1.4 times the average initial permeability, with one core showing a gain of 30 times its initial permeability. Long-term operation with chlorine-acid treated water might conceivably cause corrosion prob- lems. Therefore, it might be desirable to employ short- term shock treatment using high concentrations of acid and chlorine to maintain satisfactory aquifer per- meability without corrosion. All tests using untreated water and using water treatments other than chlorine plus acid showed sig- nificant reductions in permeability. Expressed as per- centages of initial permeability, permeabilities after extended percolation (1,000 to 1,200 hours) were 1 per cent using filtered deaerated water, 4 per cent using untreated water, and 15 to 20 per cent using waters treated with chlorine or acid alone. It was also found, with untreated water, that reversing direction of flow had the effect of temporarily restoring a portion of the lost permeability on two samples. SEA-WATER INTRUSION IN CALIFORNIA 69 For locations where it is desirable to increase flows of water into injection wells, the report recommends that the effect of treating the water with chlorine and acid be investigated. The report also suggests further experimental work toward creation of a dynamic bar- rier using air-entrained water as a means of decreas- ing the quantity of injection water required. Additional laboratory experiments indicated that the treated Colorado River water used for injection in the West Coast Basin was compatible with ground water in the area. Furthermore, bacteria found in the Silverado water-bearing formation at depths of 150 feet appeared to be aerobic or facultative and in the dormant state. The native environment in the aquifer was found to be anaerobic, however. Sea-woter Intrusion Studies by the United States Geological Survey The State Water Resources Board allocated $10,000 to the United States Geological Survey, Quality of Water Branch, from funds provided by Chapter 1500, Statutes of 1951, to prosecute water quality laboratory studies pertaining to the chemical aspects of sea-water intrusion. This work was conducted under terms of State Standard Agreement No. 53-CA-3, dated July 1, 1952. The final report describing- this investigation appears as Appendix E to this report. Since ground water underlying portions of the West Coast Basin was thought to be degraded by sea-water intrusion and polluted through improper disposal of oil field brines, and since an intensive ground water sampling program was being conducted in the Man- hattan Beaeh-Hermosa Beach portion of the basin as part of the pressure ridge field experiment, the West Coast Basin was selected for investigation. The labora- tory studies were also facilitated by the preponderance of historic water quality data available for the area. Test Procedures and Results. Approximately 170 ground water samples were collected from various depths, at test wells drilled as part of the pressure ridge experiment. Representatives of the State Divi- sion of Water Resources and the Los Angeles County Flood Control District collected the samples by use of portable pumping equipment. Ground water was pumped at each depth until no further change in con- ductivity of the discharge water was observed, in order to secure a representative sample at the desired aqui- fer elevation. These samples were analyzed by the United States Geological Survey in Sacramento. Other nearby wells, including several located in the Rose- crans and Torrance oil fields, were also sampled. All sampling was completed prior to initiation of injec- tion at the pressure ridge experiment. Trilinear plots of selected mineral analyses of ground water from the Manhattan Beach area indi- cated that ground water in the region was not a simple mixture of ocean water and native ground water. Analyses indicated that ground water in the test area contai 1 more calcium and less sodium than calcu- lated mixtures of native ground water with either ocean water or oil field brines. It was, therefore, as- sumed that native ground water was either degraded by a highly concentrated calcium and magnesium chloride water, or that the intruding sea water was being altered during intrusion. Connate waters from the Rosecrans and Torrance oil Gelds did not contain high concentrations of calcium and magnesium chlo- ride. Therefore, the possibility of alteration of sea water was investigated. ( lore samples from the Silverado water-bearing /.one collected (luring the drilling of the aforementioned test wells, located approximately one mile inland from the coast, were examined for the presence of exchangeable materials. These wells were located in- land from the area of high chloride ion concentration, and it was felt that exchange materials within the aquifer at this location would be largely unaltered. Sea water was circulated through these cores and then analyzed. The concentration of magnesium ions was greater in the effluent than in the sea water, indicat- ing that the cores contained exchangeable materials. The gain in calcium and magnesium equivalents was not as great as the loss of sodium and potassium equivalents. This can be partially explained by pre cipitation from solution of a portion of the calcium, either as calcium sulfate or carbonate, subsequent to the base exchange process. It was also determined that in the highly degraded areas near the coast line little base exchange was oc- curring at the time, since the exchange capacity of the deposits had been largely depleted. This decrease in base exchange activity was also noted at greater depths where waters of higher sodium concentrations had previously traversed. Sulfate concentrations in the affected ground water were similar to sulfate concentrations in sea water, indicating further that intruding sea water was the source of degradation. Oil field brines contain much less sulfate than does ocean water. Since degradation of ground water quality did not increase with decreased distance to the Torrance and Rosecrans oil fields, but did increase with decreased distance to the ocean, it was further concluded that encroachment of ocean water had occurred. Also, de- gradation increased with depth of aquifer, which would be expected in the presence of an intruding saline wedge. OTHER EXPERIMENTAL STUDIES Recharge Tunnel Experiments in Honolulu Area In 1951, Wentworth proposed that the Board of Water Supply. City and County of Honolulu. Hawaii. undertake certain construction and research projects, including recharge tunnels in Palolo, Manoa. Nuuann, 70 SEA-WATER INTRUSION IN CALIFORNIA and Kalihi Valleys. 185 ' Due to the paucity of data re- garding construction and operation of recharge tun- nels in formations comparable to those found in the Hawaiian Islands, it was proposed that the initial step be construction of an experimental recharge tunnel to provide data upon which to base future construc- tion plans. Determination of the proportion of re- charge water that could be recovered by supply wells was to be a main objective of the experiments. Construction of a pilot recharge tunnel in Nuuanu Valley was commenced in 1955. The tunnel is pres- ently in operation. (8G) The facilities consist of diver- sion works on a stream below an existing regulatory reservoir, a diversion ditch to the recharge tunnel, and the tunnel itself through which recharge water percolates into the porous lava formation to the water table, where it becomes available for future use. United States Geological Survey Studies in Florida The United States Geological Survey is currently engaged in a study of the characteristics of sea-wat^r intrusion along the Florida coast, particularly in the Miami area where the City 's well field has been threat- ened by encroachment. Large swampy areas inland from Miami are being drained as part of land devel- ojmient programs and flood control projects. It is ex- pected that construction of these drainage canals will further aggravate the intrusion problem, both by low- ering levels of the underlying fresh ground water to about sea level, and permitting sea water to enter the canals and diffuse downward and laterally into fresh- water aquifers. The limestone aquifer in this area has a thickness of about 100 feet and permeability of about 70,000 gallons per day per square foot. The Geological Survey reports that a fresh water head of 2.5 feet above sea level is theoretically neces- sary to prevent intrusion under conditions that exist in the Miami area. Investigators are perplexed as to why intrusion has ceased in recent years with fresh- water levels less than 2.5 feet. Special attention is being given this phenomenon of underground hydro- dynamics. Activities of the High Plains Underground Water Conservation District No. 1 , Texas Decline of ground water levels in portions of Texas as a result of increased use of ground water for irriga- tion led, in 1950, to enactment of state legislation authorizing the creation of districts "for the conserva- tion, preservation, protection, and recharging and prevention of waste of the underground water of an underground reservoir or subdivision thereof." s Angeles County Flood Control Dis- Chlorinated fresh water was injected through the well 72 SEA- WATER INTRUSION IN CALIFORNIA initially, but since July, 1956, sewage effluent from the drains has been injected at a rate of about 0.3 second-foot. During one 127-day test period, with an injection head not exceeding 46 feet, the biochemical oxygen demand of the injected water averaged 1.5 pai-ts per million and the suspended solids content averaged 13 parts per million. Chlorination to a re- sidual of 0.1 part per million has been effective in limiting the coliform bacteria count in the recharge water to meet United States Public Health Service drinking water standards. About every five weeks, the recharge well is reactivated by bailing, surging, and adding aggregate to the gravel envelope. Due to the difficulties and costs associated with ac- quiring necessary lands along the coast of the Wes1 Coast Basin for use as natural filtering basins, the Los Angeles County Flood Control District installed a pilot "polishing" treatment plant adjacent to the Hyperion sewage treatment plant. Objective of the studies was to determine what "polishing" treatment of the effluent from Hyperion would be required to provide water of suitable quality for injecting through wells. These experiments consisted of use of trickling niters with subsequent sedimentation, rapid sand filters, and intermittent high-rate spreading. Field work had been completed and test results were being analyzed at the time of preparation of this report. CHAPTER VI ECONOMIC AND LEGAL CONSIDERATIONS ECONOMIC ASPECTS OF SEA-WATER INTRUSION The principal economic effect of sea-water intrusion is believed to lie in the impairment of the intruded ground water basin as an underground storage reser- voir and as a source of water supply. It is this effect which is treated in the following discussion. Other consequences, such as damages resulting from exces- sive salinization of soils, are usually of lesser signifi- cance. Such losses, where applicable, would be added to those resulting from curtailment of the ground water supply in the economic evaluation of any spe- cific sea-water intrusion problem. From an economic standpoint, there are three alter- natives available to an area faced with a present or potential sea-water intrusion problem. First, it can be decided that no action be taken, in which case eco- nomic activity and expansion would probably be sup- plied largely by mining of accumulated ground water reserves. Exhaustion of that accumulation would eventually require drastic curtailment of activity. The second choice is to limit agricultural or industrial activity to a level that is within the capabilities of the basin safe yield. It should be noted that the safe yield of the basin can vary considerably, depending on whether measures are taken to prevent or control sea- water intrusion. The third alternative is to take posi- tive action to insure continued growth by timely pro- vision of additional supplies. To determine the most desirable action from an economic standpoint, the benefits and costs of each proposed alternative should be assessed, and the program which would maximize the use of land, labor, and capital be ascertained. Some Consequences of Inaction In most ground water basins in California con- fronted with sea-water intrusion problems, develop- ment of the economy has been based on exploitation or "mining" of ground water supplies accumulated over untold centuries of time. In such cases, the eco- nomic structure is larger than can be supported by the safe yield of the basin. As the accumulated supply becomes depleted and the basin becomes degraded by the advancing sea water, more and more water wells will have to be abandoned. Unless an alternative sup- ply is found, the farms dependent on those wells must revert to dry-farm status. Likewise, if an urban econ- omy finds itself in these straits, and nothing is done to alleviate the situation, the activities dependent upon the wells in question would have to In- discon- tii 1. Ultimately, if no corrective action were taken, a once flourishing community could become little more than a ghost town. If a decision is made that a plan of protection or importation is infeasible, advance planning can insure that disinvestment will be orderly, whereas unplanned inaction would result not only in larger economic losses occurring but also in the social losses of disloca- tion. Neither situation appears to have occured in California to date. However, in several instances, sup- plemental water supplies have been imported from great distances at heavy cost. It becomes less possible to avoid the consequences of inaction as the size of the community, rural or urban, decreases, as the isolation of the area increases, and as the distance to water sources increases. Protection of Safe Yield The second general course of action involves the protection of the safe yield of the ground water basin. Tins implies the stabilization of economic activity at a level consistent with the safe yield. As was previ- ously stated, the safe yield of a coastal ground water basin can depend upon whether or not measures are taken to protect the basin from sea-water intrusion. A decision as to whether to undertake such a plan of protection would require an evaluation of its costs and benefits. This evaluation would involve at least two major phases. One consists of assessing the economic consequences of a reduction in the water supply re- sulting from sea-water intrusion. The second phase involves determination of the cost of construction of protective works and comparison of the two amounts to determine the economic justification. A third phase might be a separate analysis to determine whether sufficient financial resources are available to carry out the project. There might be alternative methods of providing an annual supply equivalent to that pro- vided by the proposed plan of protection, such as a system for importation or for re-use of water. In this case, a direct comparison of costs would reveal the most economical project. Factors which bear on the evaluation of alternative courses of action include present and potential land- use patterns, water requirements, the safe yield of the basin under various conditions and the costs of pro- duction of these yields, the cost of protective works, and cost of imported water. A significant considera- (73) 74 SEA-WATER INTRUSION IN CALIFORNIA tion in determining- any course of action is the possible use of the ground water basin as a storage reservoir, regardless of the source of water. The relative stages of development of the urban and agricultural portions of an area overlying a ground water basin would de- termine to a great extent the types and quantity of losses which would occur. Urban Development. In urban areas, the ideal evaluation of losses would consist of a determination, unique for each community, of its income structure, characteristic activities, and those activities most sen- sitive to a decrease in water supply. These losses would be difficult to evaluate, consisting as they would in the decrease in net income to business abandoned and in equivalent rental value of dwellings lost through the decrease in water supply. Indirect or secondary losses would also accompany a curtailment of urban activi- ties. These losses are even more difficult to assess. It is believed that in most cases the losses involved in a curtailment of urban activities would be far greater than the cost of providing an alternative water supply. If a combination of works for the im- portation and /or re-use of water produced a supply less costly than that of an equivalent plan of basin protection, the protected safe yield of the basin avouIc! not be significant from an economic point of view until such time as the community expanded to the extent that the imported supply was completely used. Agricultural Development. The course of action to be followed in an agricultural area would involve a determination of the reduction in irrigated acreage caused by sea-water intrusion, and the difference in net income and farm investment values between a dry-farm and an irrigation economy on that acreage. The annual loss could be evaluated in the following steps: (1) determination of the difference in acreages capable of irrigation under conditions of basin pro- tection and of no protection; (2) estimation of the probable annual net farm incomes and farm invest- ment values on the differential acreage, assuming the best combinations of crops under irrigation and under dry farming; and (3) determination of the capital equivalent or present worth of the difference in net income estimated from (2), assuming a suitable rate of interest. The present worth of the losses, as com- puted in step (3), would lie compared with the cost of the plan of protection, to determine the economic desirability of the plan. As indicated previously in the section on urban development, it is possible that a scheme of importation could lie less costly, in which case this plan would be tested against the losses to determine its feasibility. Regardless of the method of providing the incremental water suply, the margin of profit to irrigators from that supply should be sufficient to warrant taking the risks involved. Increase in Supply Through Utilization of Imports The third alternative course of action is the timely provision of imported supplies to sustain the growth of an economy that was developed by "mining" of a ground water basin. Until ground water extractions have proceeded to the point at which the basin would be jeopardized by further withdrawals, there nor- mally would be no reason why the "mining" should not continue. A problem exists, of course, in determin- ing when the critical point is reached. Another prob- lem concerns the rate of "mining" as it affects pos- sible over-capitalization. In the case of agriculture. more acreage might be brought under irrigation than could be sustained by the safe yield of the basin under conditions of basin protection. This high level of irri- gation could ultimately be sustained only if the necessary import Avorks could be financed. An urban area developed on the basis of "mining" might be brought to such an economic level that expensive works for the importation of water could be financed, thus not only maintaining but further expanding the economy. In some cases, preservation of safe yield is a sec- ondary consideration in the provision of works de- signed to protect a basin from sea-water intrusion. Where the ground water basin is largely a pressure aquifer, there is little or no storage available for con- servation of local runoff. The main purpose of such protective works might then be the complete exploita- tion of the accumulated ground water supply and, where appropriate, the efficient distribution of an imported supply or of reclaimed sewage. The cost of the protection works would have to be balanced pri- marily against the value of reclaimed sewage as a water supply and against the cost of the works re- quired to achieve surface distribution of the required imports — and only to a minor degree against the actual loss of local safe yield. Other Considerations In some areas, continued expansion of an urban economy will require the importation of large quan- tities of water and provision of facilities for regula- tion and distribution of these imports. Under such circumstances, the utility of a ground water basin for "peaking" and regulatory storage could represent additional justification for basin protection. The eco- nomic evaluation of the protection works for peaking purposes would involve comparison of the costs of two surface systems — one having the larger capacities re- quired in the absence of supplemental peaking facili- ties, and the other a smaller system made possible by use of the ground water basin. Another possibility in some basins, which would also have to be evaluated in terms of costs and bene- fits, is the mixture of partially degraded water from the basin with a fresh imported supply providing SEA-WATER INTRUSION FN CALIFORNIA water of sufficiently high quality for specified pur- poses. In this ease, the cost of protection works would be balanced against the losses resulting from the net level of degradation anticipated in the absence of such works. The maintenance of a ground water supply by the construction of basin protection works might not be wholly subject to explicit economic evaluation. An important function of such a supply mighl be to sup port a population during time of war if surface sys- tems were disrupted or contaminated by enemy at- tacks. Surface water supplies are vulnerable to dis- ruption by high explosives and sabotage. They are also subject to the hazards of contamination by radio- active fallout and by bacteriological warfare. As a standby source, the ground water basins, which are relatively immune to such perils, would then be in- valuable. Also, a protected ground water basin would be insurance against unforseen periods of drought, when other supplies might be curtailed or unavailable. Economic Planning Required for Choice of Alternative Courses of Action It has been stated that a decision whether or not to undertake a particular project depends upon: (1) a comparison of the benefits and costs of the project, and (2) a comparison of the cost of the project with costs of other means for accomplishing the same ends. In terms of the three major alternatives previously set forth, those responsible for making water policy in a coastal ground water basin must essentially carry out this type of analysis. Each possible course of action has its costs and benefits, and if these can be defined with sufficient clarity, the various plans can be compared to determine the one best plan. The ex- tent to which "mining" of accumulated ground water supplies should be carried, the timing of con- struction for basin protective works, the provision of facilities for re-use of water or reclamation of sewage. and the decision as to size and timing of import works are all subject to the kind of analysis herein indicated. It is possible that some combination of plans can turn out to be the most advantageous. It could also he that the cost of importation works would be prohibitively expensive. In this case, the best course would consist of completely exploiting the local sup- ply and subsequently relocating those activities which could no longer be supported. In a given area, the larger the economic and social grouping involved in a decision, the more alternatives there are from which to choose. This being the case, there is more opportunity to find the course of action which will be most advantageous. For instance, with reference to import of supplemental supplies, it be- hooves local interests to cooperate to the fullest extent, to the end that the most economically advantageous supply be obtained. LEGAL ASPECTS OF SEA-WATER INTRUSION The feasibility of any proposal for prevention of sea- water intrusion may well hinge upon legal considers lions. Effective and economical prevention or elimina tion of sea-water intrusion must necessarily involve planned use and management of the threatened ground water basins. An effective method of controlling extractions in these basins is essential to any such program. Also, in many cases, it is necessary lo modify the pattern of pumping. Such planned utilization of the coastal ground water basins is necessary, not only to control sea-water intrusion, but also lo bring about their maximum utilization to meet the needs of the water users. In any effective, long-range program for the pre vention of sea-water intrusion, it may be necessarj to determine the water rights of those using water from the basin. Information as to these rights is of greal assistance in making an equitable division of the costs of mutual protection. Where, through planned utilization of a ground water basin, its regimen is materially changed, it will also be necessary to have information as to the rights of the water users in order to furnish them with the quantity of water to which they are entitled, or, in some cases, to properly com pensate them for interference with their rights. The prevention of sea-water intrusion is but one phase of the required program for planned manage- ment of ground water basins that is necessary to effectuate The California Water Plan. The legal prob- lems that are involved in such planned utilization of ground water basins are discussed in Department of Water Resources Bulletin No. 3, "The California Water Plan," Way, 1957, and those considerations will not be reviewed here. Consideration will be given, however, to the adequacy of present laws to authorize measures necessary for the prevention of sea-water intrusion, including planned management of ground water basins; and to the adequacy of present pro- cedures for the determination of rights to the use of ground water. Authority to Control Sea-Water Intrusion Under present law, no administrative agency of the State is empowered to take all necessary actions to prevent and control sea-water intrusion. The Attorney General's office, in a letter to the State Water Pollu- tion Control Board dated November 2, 1950, stated that the enforcement responsibility and authority of the State and Regional Water Pollution Control Boards extends only to impairment of water quality caitsed by discharge of sewage and industrial waste. Under Section 229 of the Water Code, the Department of Water Resources is directed to investigate and report upon the quality of all waters within the State, including saline waters, coastal and inland, as related 76 SEA-WATER INTRUSION IN CALIFORNIA to all sources of pollution of whatever nature. This provision lias been broadly interpreted to encompass all types of water quality problems, including sea- water intrusion. The Department is directed to report to the Legislature and to the appropriate Regional Water Pollution Control Board; ami its reports may recommend any steps which might be taken to improve or protect the quality of waters of the State. However, as related to the jurisdiction of the Water Pollution Control Boards, pollution is narrowly defined in Sec- tion 13005 of the Water Code to mean ". . . impair- ment of the quality of waters of the State by sewage or industrial waste . . . ." The methods of preventing sea-water intrusion that have been set forth in Chapter IV of this study are: ( 1 ) Reduction of pumping or rearrangement of pumping patterns. (2) Recharge of the basin (ordinarily with im- ported water) to bring ground water levels up to or above sea level. (3) The creation of a coastal fresh-water ridge through spreading or injection. (4) The construction of an artificial subsurface physical barrier. (5) The creation of a pumping trough along the coast. Under present statutes, there is no district or state agency which has authority to require a reduction of pumping or rearrangement of the pumping pattern except under a voluntary agreement among the parties to be affected. In the absence of such agree- ment, either of these objectives could be accomplished only in a court proceeding. The Raymond Basin case (to be discussed subsequently) is a precedent for the authority of the courts to order necessary reductions in pumping from ground water basins. The logical extension of this principle, combined with the well established authority of courts to impose a physical solution in water rights cases, would indicate author- ity to require a rearrangement of the pumping pat- tern. As yet, however, this has not actually been done. Since rearrangement of the pumping pattern would probably require the construction of physical works to supply water to the area of diminished pumping, it would probably have to be accomplished by the court with the cooperation of a proper district or state agency. In this connection, it should be noted that the State Water Rights Board can, after filing of its report in a court reference proceeding, seek an injunc- tion under Water Code Section 2020 to have pumping restricted in order to curtail sea-water intrusion in the five southern California coastal counties (Santa Barbara, Ventura, Los Angeles, Orange and San Diego). A number of districts have the authority to recharge ground water basins. Of special interest are the Water Replenishment Districts which can be established under Division 18 of the Water Code in the Counties of Santa Barbara, Ventura, Los Angeles, San Diego, Riverside and San Bernardino; and that portion of Orange County not included within the Orange County Water District. These districts are specifically de- signed for ground water replenishment. The Orange County Water District is also authorized to engage in ground water replenishment activities. Water Replenishment Districts have the advantage of being authorized to levy assessments in proportion to ground water pumpage. This is particularly impor- tant in making equitable assessments on those holding appropriative and prescriptive rights to use water on non-overlying land, since these water users might not be adequately assessed on an ad valorem basis. Such districts also have the power (Water Code § 60221) to distribute water in exchange for ceasing or reducing ground water extractions for the purpose of replenish- ing the ground water supplies within the district. Thus, through voluntary arrangements, modifications of pumping patterns could be achieved. As yet, no Water Replenishment District has been organized, although one is in the process of organiza- tion in Los Angeles County. Because of the advan- tages of this type of district in effectively utilizing ground water basins and controlling saline intrusion, consideration should be given to extending the cover- age of the Water Replenishment District Act through- out the State. In 1953, The Orange County Water District Act [Cal. Gen. Laws 1954, Act 5683 (Deering)] was amended to give the District powers to assess on the basis of water pumped from the underground. The validity of these powers was sustained in Orant/c County Water District v. Farnsworth, 138 Cal. App. 2d. 518, 292 P. 2d. 927 (1956). This decision also con- stitutes a precedent for the validity of this type of assessment by Water Replenishment Districts. Although there is some question, which it might be well to resolve by appropriate legislation, a Water Replenishment District could probably maintain a fresh-water ridge, construct a subsurface barrier, or maintain a pumping trough to protect a ground water basin from intrusion of sea water. These doubts could be removed by expanding the powers of these districts to include specific authority for control of sea-water intrusion. A number of other districts could also ac- complish these deterrents to sea-water intrusion under their general authority to conserve water. Another essential ingredient of the program for pre- venting sea-water intrusion is the control of extrac- tions from the affected basins. The situation is partic- ularly acute in coastal basins because sea-water intru- sion may irreparably injure the basin as a source of water supply, or may cause damage that can only be corrected over a period of many years and at a great SEA- WATER INTRUSION IN CALIFORNIA 77 expense. Because of the great economic hardship that drastic limitations of pumping might cause, this remedy could well remain with the courts and not be exercised by governmental agencies. Since the limita- tion of extractions from a ground water basin must be preceded by an authoritative determination of the rights of the water users, it is logical that the court should have the final authority. In addition to the authority to carry out the spe- cific proposals for the prevention of sea-water intru- sion that have been discussed, statutory authority is needed for the planned management of ground water basins. As pointed out previously, only the courts now have such authority. Legislation to provide such authority to the State or to local agencies would make it possible to require rearrangement of pumping pat- terns. It would also make it possible to utilize coastal ground water basins to store water during wet periods for use during the ensuing dry years, as contemplated in The California Water Plan. Any such legislation must, of course, provide full protection for vested rights to the use of ground water. Because of the far- reaching changes that planned utilization of ground water basins would cause in relation to the thousands of individual water users, a constitutional amendment to authorize this practice may be desirable. A prin- cipal function of such an amendment would be to make sure that the injunctive process would not be used to delay or prevent such programs. Although this policy may already be established in California, any doubt could be allayed by specific provisions that the user of ground water must accept compensation either through the furnishing of water (a physical solution) or by way of monetary damages. At present, the procedures in the Water Code for appropriation of unappropriated water do not apply to ground water basins. Consideration should be given to legislation that would extend to percolating ground water the procedure for the filing of applications and the granting of permits and licenses to appropriate. Through this means, more accurate records could be obtained as to extractions, and conditions could be im- posed in the public interest that would provide for better management of basins. Determination of Water Rights Each owner of land overlying a ground water reser- voir has a paramount right to the reasonable beneficial use of the water underlying his tract [Miller v. Bay Cities Water Co., 157 Cal. 256, 107 P. 115 (1910) ]. This right is generally analogous to riparian rights to surface flow {Burr v. Maclay-Rancho Water Co., 154 Cal. 428, 98 P. 260 (1908)]. Furthermore, the underground supply must be shared by all, and the right of each owner is correlative to that of every other similar owner [Katz v. Walkinshaw, 141 Cal. 116, 70 P. 663, 74 P. 766 (1902)]. Overlying rights can be lost by laches or prescription. Appropriative rights to surplus ground water can now be acquired by taking the water. Unless they bave developed into prescriptive rights through adverse use, they must yield to the rights of overlying owners. As mentioned previously, there arc no statutory pro- visions for licensing of ground water appropriations, as is provided in the case of surface waters. Determinations of basic water rights would make possible a more equitable distribution of costs, no matter what type of sea-water intrusion control pro- gram is adopted; and would furnish a basis for a physical solution or the payment of damages. Present methods of determining water rights include: a. Voluntary agreement among water users ; b. Statutory adjudication procedure; c. Court reference procedure ; d. Civil suits without reference. It seems improbable that agreement could be reached on a voluntary basis for a basin supplying any eon siderable number of water users. The statutory adju- dication procedure is limited by present law to deter- mination of rights to surface streams and to subter- ranean streams flowing through known and definite channels. It is seldom that ground water basins fall definitely in the latter category. This procedure is therefore not generally available for the contemplated purpose. Under the court reference procedure, the court can refer the action to the State Water Rights Board for investigation and report upon any or all of the phys- ical facts involved. The report may include a recom- mended solution. This procedure is applicable to all types of water rights suits and has been frequently used in suits involving rights to surface streams. It has also been used in the several actions involving ground water, one of which has been carried to the Supreme Court of California and also the Supreme Court of the United States {Pasadena v. Alhambra, 33 Cal. 2d 908, 207 P. 2d 17 (1949) certiorari denied sub nom, California-Michigan Land and Water Co., v. Pasadena, 339 U. S. 937 (1950)]. The decree of the Superior Court in this action was affirmed as modified and the court reference procedure was approved. This ease is commonly referred to as the Raymond Basin case. It affords a firm precedent for recourse to the court reference procedure in suits involving the deter- mination of rights to the use of ground water consti- tuting a common source of supply, and for exercise by the court of power to impose adequate control of ground water extractions to prevent continued over- draft. The case also affords a firm precedent for the trial court in its decree to retain broad jurisdiction, to make changes in the decree from time to time as occasion may require, and to appoint the Department of Water Resources or another agency as watermaster to enforce the decree. 78 SEA-WATER INTRUSION IN CALIFORNIA In the Raymond Basin case, sea-water intrusion was not involved. However, it is considered that the hazard to the continued availability of ground water by sea-water intrusion, due to continued overdraft, establishes ample basis for invoking tbe power of the court to impose control over extractions as was done in the Raymond Basin case. In this connection, water rights actions in the West Coast Basin of Los Angeles County, and in Tia Juana Basin of San Diego County, have been referred to the State Water Rights Board for investigation. It is also possible to adjudicate rights to the use of water from a common ground water source by court procedure without reference. In the determination of rights for an entire ground water basin, such court procedure will generally be more expensive and time- consuming than the reference procedure, with less productive results. It follows that recourse to the court reference pro- cedure is the most practicable and feasible means available under existing law whereby the State may afford legal and technical assistance in the formula- tion and imposition of a physical solution adequate to remedy continued overdraft on a common supply of ground water which has resulted in intrusion of ocean water to such an extent as to threaten availability of such common supply for beneficial uses. Under this procedure, all possibilities of a feasible physical solu- tion can be fully explored, assistance of trained specialists in the field of ground water geology and hydrology can be made available to assist the court and the parties in the formulation of a just and equi- table solution to ground water problems, and such solution can be fully effectuated. However, in many cases, even the court reference procedure is lengthy and expensive, and could be materially improved in several respects. Consideration should be given to legislation that would improve the court reference and statutory adjudication procedures, and extend the latter to ground water basins.* For a discussion of many of the legislative proposals that have been suggested here, see statement of Henry Holsinger, then Principal Attorney, Division of Water Resources (now Chair- man, State Water Rights Board) to Joint Legislative Interim Committee on Water Problems, December 14, 1954. CHAPTER VII PLANS FOR PREVENTION AND CONTROL OF SEA-WATER INTRUSION Selecting a method, or methods, for prevention and control of sea-water intrusion involves considera- tion of many factors, as discussed in Chapter IV. These considerations should be carefully analyzed and evaluated prior to selection of control methods. This may involve an investigation of the following factors : 1. Depth, thickness, extent, and transmissibility of water-bearing formations; and barriers to ground water movement. 2. Occurrence, movement, and quality of ground water. 3. Amount and areal distribution of extractions from the basin. 4. Availability, cost, and quality of recharge water. 5. Availability and cost of right of way for arti- ficial recharge projects. 6. Availability and cost of an alternate water supply, if use of ground water is to be curtailed. 7. Benefits accruing from optimum utilization of underground storage. 8. Salt balance. 9. Organizational and management problems con- nected with basin or project operation. 10. Water rights. 11. Economic feasibility. 12. Financial feasibility. In many areas in the State where intrusion has occurred, federal, state, and local agencies have made comprehensive investigations of geologic and hydro logic conditions. In some instances, local agencies have constructed facilities to control, in part, farthei intrusion. I londitions within the nine areas where sea-water intrusion is known to have occurred have been studied to determine which method, or methods, of control might be utilized for prevention of further intrusion. Possible plans for each of these areas are discussed in tins chapter, and set forth in Table 2. PLANS FOR AREAS OF KNOWN SEA-WATER INTRUSION Petaluma Valley The several methods based on raising ground water levels above sea level appear to be most suitable for preventing sea-water intrusion in Petaluma Valley, Sonoma County. Among these are reduction of ex- tractions, basin-wide recharge of aquifers, or mainte- nance of a fresh-water ridge along the coast. Con- struction of an artificial subsurface barrier parallel tn the coast is not considered feasible, since the Qua- ternary alluvium is over 300 feet deep in the bayward portion of the valley. Furthermore, an unknown depth of older alluvium underlies these sediments. It is felt that rearrangement of the pumping pat- tern would not be effective in Petaluma Valley since ground w 7 ater withdrawals in the bayward portion of TABLE 2 POSSIBLE METHODS FOR PREVENTION AND CONTROL OF SEA-WATER INTRUSION IN AREAS WHERE INTRUSION IS KNOWN TO HAVE OCCURRED Raising of ground water levels above Direct recharge of sea level by reduction overdrawn aquifers Maintenance of a or rearrangement to maintain ground fresh water ridge Construction of Development of a of pattern water levels at or above sea level artificial subsurface pumping trough Area of pumping draft above sea level a along the coast* barriers adjacent to the coast X X X X Santa Clara Valley . . . . . . X X X Pajaro Valley _ X X X X X X X X X X X 1 ' x*> X X X X X X X X X x a Assumes recharge water available. b This method would be effective only if applied in the remaining portions of Coastal Plain. Los Angeles County. (79) 80 SEA-WATER INTRUSION IN CALIFORNIA the valley arc not significant. Most ground water devel- opment now occurs in the inland portions of the area. Unless an industrial demand should develop for brackish water, the use of a pumping trough adjacent to the coast to prevent sea-water intrusion does not appear to be feasible. There are at present no projects under way to con- trol sea-water intrusion into aquifers underlying Pet- aluma Valley. At present, imported water is not avail- able to supplement overdrawn ground water supplies, and it is doubtful whether it would be feasible to maintain ground water levels above sea level until such supplies become available. The North Bay Aqueduct, authorized for construc- tion by Chapter 2252, Statutes of 1957, as a unit of The California Water Plan, would provide a firm supplemental supply to Petaluma Valley. This facility would divert water from the Sacramento-San Joaquin Delta, about 15 miles east of the City of Fairfield, and terminate in Novato Reservoir about ten miles south- east of Petaluma. The aqueduct, which would supply the needs of Petaluma Valley until the year 2010, is described in Department of Water Resources Bulletin No. 60, "Interim Report to the California State Legis- lature on the Salinity Control Barrier Investigation," March 1957. When supplemental supplies are secured, it may be possible to raise ground water levels above sea level through spreading operations without the use of wells, due to the absence of confining clay strata. Final se- lection between raising ground water levels above sea level throughout the entire basin, or maintaining a fresh-water barrier parallel to the coast would re- quire extensive engineering, economic, and financial studies. Napa-Sonoma Valley Napa-Sonoma Valley is similar to Petaluma Valley in that the most feasible method of controlling sea- water intrusion appears to be importation of supple- mental water to be used, in part, to raise ground water levels above sea level throughout the entire basin or to operate a fresh-water barrier parallel to the coast. The aforementioned North Bay Aqueduct would provide such a supplemental supply. As in Petaluma Valley, it may be possible to maintain water levels above sea level through spreading operations without the use of wells. Selection of the best of these two methods would be based on economic and financial aspects, including the benefits obtained from fully utilizing the storage capacity of the ground water basin. Further hydrologic and geologic studies may be required. Due to the 300- to 500-foot depths of unconsoli- dated alluvium along the bayward margin of the Napa-Sonoma Valley, use of an artificial subsurface barrier to prevent further intrusion does not appear engineering!}' or economically feasible. Like Petaluma Valley, there is little ground water development in the bayward portions of the basin and, therefore, change in pumping pattern would not assist in controlling intrusion. Also, unless an indus- trial demand for brackish water should develop, the use of a pumping trough adjacent to the coast to pre- vent intrusion does not appear feasible. None of the methods of control of sea-water intru- sion, as outlined previously in this report, have as yet been attempted in this valley. Santa Clara Valley Importing supplemental water and raising ground water levels above sea level along the coast appears to offer the only permanent solution to the problem of sea-water intrusion in the Santa Clara Valley. This could be accomplished by maintaining a fresh-water ridge. However, a change in pumping pattern and re- duction of pumping draft, coupled with the use of supplemental water, would also halt encroachment of saline water, particularly in the Palo Alto-San Jose area. If ground water withdrawals adjacent to the coast were reduced and withdrawals further inland were comparably increased, the existing landward hydraulic gradient would be flattened, thus decreasing the rate of intrusion. There are presently 24 artificial recharge projects located in the Santa Clara Valley, 3 of which are operated by the Alameda County Water District and the rest by the Santa Clara Valley Water Conserva- tion District. These conservation programs have un- doubtedly reduced the rate of ground water level decline. Portions of the Santa Clara Valley are receiving an imported supply from the Tuolumne River through the Hetch Hetehy Aqueduct of the City of San Fran- cisco, and from the Mokelumne River system through facilities of the East Bay Municipal Utility District. The valley is in the area to be served by the proposed South Bay Aqueduct, a feature of the authorized Feather River Project. Existing and proposed water development facilities are described in State Water Resources Board Bulletin No. 7, "Santa Clara Valley Investigation," June, 1955. Depth of alluvium along the 80 miles of the Santa Clara Valley coast line which are open to San Fran- cisco Bay is as great as 1,000 feet. Thus it appears infeasible to construct artificial subsurface barriers to prevent further intrusion of saline water from San Francisco Bay. Unless a commercial need for brackish water should arise, the use of a pumping trough ad- jacent to the coast to prevent sea-water intrusion does not appear to be feasible. In areas where surficial clays are nonexistent or readily removed, it might be feasible to prevent fur- ther encroachment of sea water into the upper aquifer by creating a fresh-water ridge through a series of SEA-WATER INTRUSION IX CALIFORNIA 81 recharge basins parallel to the coast. However, the use of injection wells would be necessary to maintain a coastal pressure ridge in the pressure aquifers. Al- though there would be some waste of fresh water to San Francisco Bay attendant with maintenance of a fresh-water mound or pressure ridge, this method of control would permit better utilization of the vast Santa Clara Valley ground water basin and would increase the safe yield therefrom. Pajaro Valley A supplemental source of water to serve as a direct supply to coastal pumpers would be required to per- manently control sea-water intrusion in the Pajaro Valley. Supplemental supplies might also be used to maintain a pressure ridge adjacent to the coast. Since both water-bearing zones adjacent to the coast are confined, the use of injection wells to create a ridge would be necessary. However, some reduction in en- croachment of sea water could be achieved if ground water withdrawals in the area east and southeast of Watsonville were increased and ground water pump- ing southwest of Watsonville near the coast were de- creased accordingly. Furthermore, this change in pumping pattern would probably induce increased subsurface inflow to the coastal confined aquifers from the forebay area, and ground water safe yield might be increased. Since only three miles of the valley are open to Monterey Bay, it would seem, at first glance, that use of an artificial subsurface barrier would be the most desirable method of preventing further sea-water in- trusion. However, the base of the main pumping zone lies as much as 300 feet below land surface in certain areas ; and a deeper water-bearing zone underlies the main zone. In view of limitations of present construc- tion equipment and techniques, it is not considered feasible to construct subsurface barriers to these depths. Development of a pumping trough adjacent to the coast is not considered feasible in this valley. Supplemental water supplies could be secured by importation or further development of local supplies, such as would be afforded by the proposed Watsonville Project, described in State Water Resources Board Bulletin No. 5, "Santa Cruz-Monterey Counties In- vestigation," August, 1953. Preliminary studies un- dertaken in 1957 indicate that the Feather River Project would be the most feasible source of imported water, which could be diverted from the proposed San Luis Reservoir in the San Joaquin Valley and conveyed by tunnel beneath Paeheco Pass. Salinas Valley Pressure Area Planned operation of coastal and inland ground water basins for the benefit of overlying users, in conjunction with use of surface water supplied from upstream storage facilities appears in be the mosl feasible method of local water development and pre- vention of sea-water intrusion. The largest upstream storage facility is Nacimiento Dam on Nacimiento River in San Luis Obispo County, which was com- pleted in 1956 for the Monterey County Flood Cini- trol and Water Conservation District. The reservoir lias a storage capacity of 350. 0(10 acrc-fcet ; and re- leases percolate in the natural channels of the Nacimi- ento and Salinas Rivers, replenishing, in part, the ground water basins and thus retarding sea-water intrusion. Bulletin No. 19 of the Department of Water Resources, "Salinas River Basin Investigation, " cur- rently under preparation, describes plans for local water supply development and importation of waters from other areas. Rearrangement of pumping pattern by reducing ground water withdrawals in the area between Salinas and the coast would, of course, flatten the landward hydraulic gradient and decelerate the intrusion rate. Water-bearing sediments along the coastal peri- phery of Salinas Valley in which most of the wells are perforated, are up to 300 feet thick. Therefore, use of an artificial subsurface barrier to prevent sea- water intrusion is not considered feasible. Employ- ment of a pumping trough parallel to the coast is also not considered feasible in this area. Oxnard Plain Basin The most feasible method for halting sea-water in- trusion in the Oxnard Plain Basin would require reduction of ground water extractions to the safe yield of the basin, which could be increased to some extent by artificial recharge in forebay areas. Sup- plemental water requirements would be obtained from existing and proposed surface storage facilities in the Santa Clara River watershed. Artificial recharge in the forebay areas, combined with use of a surface distribution system on the Ox- nard Plain, could also be utilized in conjunction with a pressure ridge along the coast, or subsurface cutoff walls. Injection through wells would be required to create a pressure ridge. Under these conditions, pres- sure levels underlying the plain inland from the barriers could be lowered below sea level without inducing intrusion of sea water. The Oxnard Plain is bordered by about 17 miles of coast line and is underlain with Recent alluvium and Upper Pleistocene deposits 200 feet or more in thickness. Installation of artificial subsurface barriers to depths of 200 feet may be feasible. Since sea-water intrusion has been observed only in the Port Hueneme and Point Mugu areas, which coincide with the loca- tions of the Hueneme and Mugu submarine canyons. respectively, it may be that sea-water intrusion con- trols are only needed in these areas. It is likely that aquifers are not in hydraulic continuity with the 82 SEA-WATER INTRUSION IN CALIFORNIA ocean elsewhere along the coast. At any rate, if a subsurface barrier or a pressure ridge were employed in an attempt to protect the Oxnard Plain from fur- ther intrusion, they should first be constructed at the aforementioned two critical areas. Direct recharge of local, or future imported, sup- plies in the forebay areas supplying ground water to the Oxnard Plain Basin does not, in itself, appear to be a complete solution to the sea-water intrusion prob- lem, due principally to the inadequate transmissibility of the pressure aquifers. In other words, ground water Eorebay storage could be full, while pressure levels underlying the Oxnard Plain were below sea level. Development of a pumping trough parallel to the coast to prevent intrusion into the aquifers under- lying the Oxnard Plain does not appear to be feasible. In 1955, the United Water Conservation District completed construction of Santa Felicia Dam on Piru Creek, capable of impounding 100,000 acre-feet of water. This project is being operated in conjunction with an artificial recharge project in Piru Basin and two recharge projects in the Oxnard Forebay Basin. Water from this project is supplied to the Oxnard Plain through a distribution system, now partially completed. Water development projects are discussed in State Water Resources Board Bulletin No. 12, "Ventura County Investigation," October, 1053. West Coast Basin From data presently available, it appears that the most feasible plan for prevention of sea-water intru- sion in the West Coast Basin, Los Angeles County, consists of a combination of reduction of pumping draft and artificial recharge in forebay and coastal areas. In addition, a change in the pumping pattern, i.e., reducing ground water withdrawals along the coast in favor of increased pumping further inland. would tend to decrease the landward hydraulic gradi- ent and retard the intrusion rate. The base of the main water-bearing zone, the merged Silverado formation, is as much as 500 feet below sea level along the coast of Santa Monica Bay. This formation may also be in hydraulic continuity with San Pedro Bay, but its depth in this region is unknown. The depth of this formation along most of the coast line tends to preclude the use of an arti- ficial subsurface barrier to prevent further intrusion. Sea water is known to have intruded from San Pedro Bay into the Gaspur zone, which overlies a small por- tion of the Silverado formation, but production from this zone is relatively small compared to that from the Silverado formation, therefore large expenditures of funds for facilities to prevent intrusion into the Gaspur zone might not be justified. Unless an industrial demand for large quantities of brackish water should develop, the use of a pump- ing trough adjacent to the coast to prevent intrusion does not appear to be feasible. As discussed in Chapter V, the Los Angeles County Flood Control District has injected softened Colorado River water through wells in the Manhattan Beach- Ilermosa Beach area on an experimental basis since February, 1953. It has thereby demonstrated that it, is possible to maintain a pressure ridge above sea level along a one-mile reach of coast for lone periods of time. Economic feasibility of such a ridge depends largely on the cost of recharge water. Two sources oi water are presently being considered for this project. One possible supply is sewage effluent from the nearby City of Los Angeles' Hyperion treatment plant, which now discharges to the ocean through an outfall sewer The second source under consideration is untreated Colorado River water, which is available from the Metropolitan Water District of Southern California, though at a considerable distance from the project. The Los Angeles County Flood Control District has recently launched a geologic and hydrologic study of various plans for prevention of sea-water intru- sion. These plans could be incorporated into the opera- tions of a proposed replenishment district covering the West Coast Basin and portions of the Central Basin, to be formed under provisions of the Water Replenishment District Act, The replenishment dis- trict would obtain funds, through taxes or an assess ment on ground water pumping, to purchase imported or reclaimed waters for artificial recharge. In this manner, it is hoped to prevent further intrusion and permit continued utilization of the ground water basins. As stated heretofore, the plan for prevention of sea-water intrusion in the West Coast Basin which appears to be the most feasible incorporates a combi- nation of several methods of control. Features of the plan include extending the existing pressure ridge project to a total length of about 11 miles along Santa Monica Bay; installation of an injection well and/or spreading project near Alamitos Bay and near Wilmington to protect the Silverado formation and possibly the Gaspur zone; spreading of runoff, im- ported water, and possibly reclaimed water in the Montebello Forebay Area; reduction of ground water withdrawals in the West Coast Basin and in the Central Basin ; and additional use of imported sur- face supplies. A plan incorporating these features is depicted on Plate 31. The Los Angeles County Flood Control District has estimated from preliminary data that the cost of installing fresh-water ridges along Santa Monica Bay, near Wilmington, and near Ala- mitos Bay would be in the order of $7,600,000. East Coastal Plain Pressure Area The most feasible plan for preventing encroachment of sea water into the East Coastal Plain Pressure Area of Orange County appears to include the follow- ing elements : increased use of imported or other sources of supplemental supplies by surface distribu- SEA-WATER INTRUSION IN CALIFORNIA 83 tion, reduction of pumping draft in the coastal por- tion of the plain, rearrangement of pumping draft, and an expanded program of artificial recharge in forebay areas. The success of such an approach depends largely on the ability of aquifers to transmit water from forebay areas to points of use on the coastal plain. Like the West Coast Basin, there is an imported supply of -water available to most major ground water producers in the East Coastal Plain Pressure Area, provided through the Orange County and Coastal Municipal Water Districts from the Metropolitan Water District of Southern California. Thus, it is likely that a voluntary reduction of ground water withdrawals along the coastal margin of the coastal plain could be effected, especially when existing well installations and pumping equipment required re- placement. Although about three-fourths of the 16-mile coast line are open to the ocean, sea water has intruded to an appreciable degree only into the Talbert water- bearing zone in the Santa Ana gap. As previously mentioned, the Newport-Inglewood uplift impedes, wholly or in part, the landward intrusion of sea water into the deeper Pleistocene and Tertiary sedi- ments along the coast. The Talbert zone is exposed to the ocean along about three miles of coast, and its base is approxi- mately 190 feet below land surface. Construction of an artificial subsurface barrier across the Santa Ana gap to prevent further intrusion might prove feasible. Geologic- data available indicates that a fresh-water ridge across the Santa Ana gap might also prevent further intrusion into the Talbert zone. One possible source of water for such a project is the sewage effluent which now discharges to the ocean through the nearby Orange County Sanitation District's out- fall sewer. Unless an industrial demand for large quantities of brackish water develops, use of a pumping trough adjacent to the coast to prevent sea-water intrusion does not appear feasible. Spreading of storm runoff in the forebay areas of the coastal plain, which has been conducted since the early 1000 's, has been instrumental in slowing the rate of decline of ground water levels. In 1953, the Orange County "Water District was formed for the purpose of replenishing ground water supplies by artificial re- charge. Funds for purchase of water are obtained through assessments on ground water extractions. The jiresent assessment is $3.90 per acre-foot of water pumped. Up to July 31, 1958, the district has pur- chased a total of approximately 420,000 acre-feet of untreated Colorado River water from the Metropolitan Water District of Southern California. This water lias been allowed to percolate in the channel of the Santa Ana River and in off-channel artificial recharge basins in the Santa Ana Forebay Area. The Orange County Water District is currently constructing additional spreading basins and expand- ing conveyance facilities to supply its artificial re- charge projects, existing and proposed. The District also conducts annual studies to determine the amount of Colorado River water required to satisfy the un- balance between ground water discharge and recharge. The Talbert Water District, formed in 1954, is diverting approximately 2,200 acre-feet of primary effluent annually from the Orange County Sanitation District's outfall sewer. This effluent is being utilized for irrigation purposes on 2,250 acres of land in the Santa Ana gap. As of 1957, most of the area of the Water District was affected by sea-water intrusion and many wells had been abandoned. Utilization of this effluent has reduced pumping draft on the basin, and thus been instrumental in retarding the advance of sea-water intrusion. Mission Basin Mission Basin in San Diego County is considered one of the few ideal locations in the State for con- struction of an artificial subsurface barrier to pre- vent sea-water intrusion. Construction of a puddled clay cutoff wall at this site is considered physically feasible, since the base of the unconsolidated alluvium is about 200 feet below land surface and only about a thousand feet of basin are open to the ocean. A cut- off wall across the mouth of the San Luis Rev River would stop subsurface outflow and natural aquifer flushing in Mission Basin, the coastal poi-tion of the valley. Despite this lack of subsurface outflow, how- ever, favorable salt balance conditions would probably be maintained if present exportation of ground water continued. The use of a fresh-water mound across the mouth of the valley to prevent intrusion might also be suita- ble here, due to the short reach of coast involved. Sewage effluent from the City of Oceanside's treat- ment facilities or imported Colorado River water might serve, wholly or in part, as a water supply for such a water mound. Colorado River water is now delivered to the City of Oceanside, via San Luis Rev Valley, through the Fallbrook-Oceanside Branch of the San Diego Aqueduct. Construction of a second aqueduct to supply additional Colorado River water to San Diego County is in progress and will augment the present imported supply to San Luis Rev Valley. The development of a pumping trough across the mouth of the San Luis Rev River also appears possi- ble. Gravel washing operations in this area utilize saline ground waters at present, and could conceiva- bly use ground water extracted in connection with a pumping trough. This method of solution does offer the distinct advantage of contributing to maintenance 84 SEA-WATER INTRUSION IN CALIFORNIA of favorable salt balance, although this factor of itself does not justify its adoption. If imported water were used directly as a surface supply, in conjunction with reduction of ground water use and spreading to recharge the overdrawn coastal basin, ground water levels could probably be raised above sea level. Intrusion would thus be halted, al- though complete utilization of the ground water basin would not. be achieved, with resultant waste of local runoff. "With regard to decreasing ground water with- drawals, a suit has been filed to adjudicate the water rights of the valley. On June 2, 1957, voters of the City of Oeeanside authorized a bond issue to finance reclamation of sew- age effluent. As a result of this bond issue, the City has abandoned its outfall sewer to the Pacific Ocean, and constructed a line to carry treated sewage to Whalen Lake in Mission Basin. Effluent from the lake, which serves as an oxidation pond, is spread to re- charge ground waters of Mission Basin. The system was placed in operation on July 1, 1958; and the vol- ume of reclaimed sewage will vary from 1,600 acre- feet per year initially to -1,700 acre-feet annually by the year 2000. CHAPTER VIII CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS As a result of experiments and investigations au- thorized by Chapter 1500, Statutes of 1951, and Sec- tion 229 of the Water Code, it is concluded that : 1. Ground water reservoirs in California are of tre- mendous economic importance to the State as basic sources of water supply, as reservoirs for regulation of local runoff and imported supplemental supplies, and as sources of water in time of national emergency. 2. Geologic evidence indicates that water-bearing deposits within many coastal ground water basins are in direct contact with sea water or brackish tidal waters. 3. Sea-water intrusion into coastal ground water basins is a serious threat to ground water quality and the storage capacity of these ground water reservoirs. 4. Restoration of a ground water basin that has been damaged by sea-water intrusion is a slow, difficult, and expensive operation. Prevention is unquestionably the most logical and economical approach to the problem of sea-water intrusion. 5. There is definite evidence of sea-water intrusion in 9 coastal ground water basins of California. Sea water has advanced inland up to 4| miles in some areas. Continued pumping at present rates will allow further encroachment into these basins, resulting in further widespread deterioration of ground water supplies unless effective remedial measures are under- taken. Damage to the ground water resources of some of these basins is already severe. 6. There are 71 coastal ground water basins in which chloride content of ground waters exceeds 100 parts per million, but the source of degradation is not established. It is suspected that sea-water intrusion is occurring in some of these basins. 7. There are 48 coastal ground water basins in which there is now some development of ground water, and in which sea-water intrusion may become a prob- lem if development exceeds safe yield. There appar- ently is no sea-water intrusion at present. 8. There are 134 coastal ground water basins in which there is little or no present development of ground water, and little or no information is available regarding hydrologic or water quality conditions. The status of sea-water intrusion in these basins is un- known. 9. Prevention and/or abatment of sea-water intru- sion into coastal ground water basins may be accom- plished by various methods, depending upon geologic and hydrologic conditions. Five such methods are listed : a. Raising of ground water levels to or above sea level by reduction in extractions and or rear- rangement of areal pattern of pumping draft ; b. Direct recharge of overdrawn aquifers to main- tain ground water levels at or above sea level ; c. Maintenance of a fresh-water ridge above sea level along the coast; d. Construction of artificial subsurface barriers; e. Development of a. pumping trough along the coast. 10. Cost comparisons of control methods, based on a hypothetical situation, indicated that "raising of ground water levels to or above sea level by reduction in extractions and, or rearrangement of areal pattern of pumping draft" required minimum capital outlay; while lowest operation, maintenance, and water costs were associated with "maintenance of a fresh-water ridge above sea level along the coast." The cost and quality of available supplemental water supplies for direct distribution and/or ground water recharge may be the controlling factor in final determination of the optimum method of control of sea-water intrusion into a coastal ground water basin. 11. Decision as to the method of control to be used at any given location should be based upon thorough study of geologic, hydrologic, and water quality data, and an appraisal of pertinent engineering, legal, and economic aspects. 12. Any comprehensive program for abatement of sea-water intrusion should include establishment and enforcement of suitable standards of well construc- tion and abandonment to prevent degradation of ground waters by interconnection between water- bearing zones. 13. Principal conclusions drawn from laboratory model studies of sea-water intrusion into a confined aquifer, conducted by the Sanitary Engineering Re- search Laboratory, University of California, Berkeley, are as follows : a. In accordance with the Ghyben-Herzberg prin- ciple, the fresh-water piezometric surface must be maintained above sea level a distance equal to (S — 1) times the distance below sea level of the lowest point within the aquifer which must be protected from sea-water intrusion, where S is the specific gravity of sea water. (85) 86 SEA-WATER INTRUSION IN CALIFORNIA b. When a pressure ridge is maintained above sea level, the fresh-water flow seaward is inversely proportional to the length of the sea water wedge from the ocean outlet, as determined by the fol- lowing equation: MT Q = l(B — l)j± Where Q = seaward fresh-water flow per foot of ocean front. 8 = specific gravity of sea water. M = thickness of aquifer, down to the lowest depth which must be protected. T = aquifer transmissibility for 100 per cent hydraulic gradient. L = length of sea-water wedge, from ocean outlet to the toe. Fresh-water waste to the ocean is independent of the elevation of the aquifer. c. The total injection rate along the recharge line must equal the sum of fresh-water waste to the ocean necessary to maintain the position of the sea-water wedge and the overdraft of the basin originally being satisfied by landward flow of sea water d. When conditions are such that the saline wedge moves inland, the wedge tends to flatten out and the toe moves somewhat faster than the remain- ing interface. In a prototype aquifer, it is be- lieved that nonuniformity of material, with accompanying varying transmissibility, may greatly distort the shape of the interface since the intruding saline water will tend to follow the path of least resistance. e. Where a recharge line is located in an area where sea water has already intruded into an aquifer, the sea-water wedge will be divided as a result of injection and saline water will be displaced both seaward and landward. Injected fresh water tends to override the severed toe, which becomes flatter as it continues to move inland. f. Injection well spacing is of little importance, ex- cept that the toe of the intruded wedge should be held at least half a well spacing seaward from the injection line. g. Intruding sea water can be intercepted by estab- lishment of a pumping trough, created by a line of pumping wells parallel to the coast. This method would provide no replenishment to a coastal basin, but the loss of fresh water need be no greater than that which would occur with a pressure ridge established through the use of in- jection wells. 14. Laboratory studies by the University of Cali- fornia at Berkeley upon the effectiveness of admix- tures in reducing aquifer permeability may be sum- marized as follows: a. Bentonite slurry stiff enough to adequately re- duce the permeability of an aquifer would prob- ably be too stiff to use with ordinary excavation equipment. Stiffer slurries containing 7 to 8 per cent dry bentonite are effective in permeability reduction in well-graded backfill mixtures con- taining 25 to 30 per cent silt. b. Preliminary data indicate that the permeability to sea water of a mixture containing bentonite slurry is roughly ten times its permeability to fresh water. c. None of the admixtures tested, including benton- ite, bentonite with asphalt emulsion, bentonite with portland cement, and chrome-lignin, pro- vide a complete seal. 15. The West Coast Basin Experimental Project established conclusively that water can be successfully injected into a coastal confined aquifer on a contin- uous basis. The results of this research program, which are applicable to areas having similar geologic and hydrologic conditions, may be summarized as follows : a. Injection of water through wells can pressurize a confined aquifer continually along a coastal reach, thereby reversing any pre-existing land- ward gradient and preventing further sea-water intrusion. b. Loss of fresh water to the ocean will be small in relation to the total quantity of water injected. c. An aquifer containing water already degraded by sea-water intrusion can be made usable by injection of water through wells. d. Wells used for injection of water into a confined aquifer must be properly sealed at the confining member and carefully developed. Gravel-packed wells proved most successful on this project. e. A recharge rate of six second-feet per mile, effected by injection through wells spaced 500 feet apart, is adequate to establish a pressure ridge two to three feet above sea level. This is sufficient to halt the inland flow of sea water. f. Water for injection must be compatible chem- ically with native waters and must be treated to avoid clogging the aquifer. Chlorine dosages of between five and ten parts per million are neces- sary to prevent slime growth and maintain trans- missibility. 16. Laboratory tests conducted by the University of California at Los Angeles indicate that pretreat- ment of injection water (softened Colorado River water) with chlorine plus acid is most effective for SEA-WATER INTRUSION IN CALIFORNIA 87 maintaining permeability of the formation (Silverado water-bearing zone). 17. Water quality studies conducted by the United States Geological Survey, Quality of Water Branch, confirm the fact that salinity in the confined Silverado water-bearing zone of the West Coast Basin is caused by intruding sea water and not oil well brines. 18. Preliminary field tests by the Los Angeles County Flood Control District indicate that sewage effluent from the City of Los Angeles ' Hyperion treat- ment plant can be successfully injected through wells in the West Coast Basin, after treatment by further oxidation, settling, filtration, and chlorination. 19. Serious economic losses can accrue to urban and agricultural communities overlying ground water basins subject to or threatened by sea-water intrusion. These losses are largely associated with the impair- ment of the basin as an underground reservoir and as a source of water supply. Evaluation of these losses is essential in determining the feasibility of plans for protecting, replacing, or augmenting the required supply. 20. In order to effectively control or prevent sea- water intrusion, authority is required for the planned management of threatened ground water basins; and an efficient method for the determination of rights to the use of ground water is necessary. Existing laws are not fully adequate for these purposes. RECOMMENDATIONS In order to promptly detect sea-water intrusion, to better predict rates of intrusion, and to effectively control and prevent sea-water intrusion, it is recom- mended that the following measures be undertaken in all coastal ground water basins : 1. There should be a continuous program for collec- tion and intepretation of hydrologic, geologic, and water quality data, including drilling of test wells as required. 2. Improved methods of detecting sea-water intru- sion and accurately differentiating such intrusion from other possible sources of degradation should be de- veloped. 3. There should be continuing study and prepara- tion of plans for controlling or preventing intrusion in known areas of sea-water intrusion. 4. Communities confronted with the problem of sea- water intrusion should evaluate the economic and related impacts of available alternatives prior to adop- tion of a course of action. 5. After thorough study and consultation with in- terested parties throughout the State, legislation should be prepared to strengthen and clarify the authority for planned utilization of ground water basins, and to improve existing procedures for the determination of rights to the use of ground water. 6. It is essential that positive measures be initiated as soon as possible to halt and abate sea-water intru- sion in all basins known to be affected at present, and to prevent intrusion into threatened areas. Included in these measures should be early formulation and implementation of plans for furnishing additional or substitute water supplies, as required. Where public agencies with adequate powers to accomplish these tasks are not already in existence, formation of such agencies should be started immediately. LIST OF REFERENCES 111 United Stales Department of the Interior, Geological Survey. "Geology and Ground Water in the Santa Rosa and Petaluma Valley Areas, Sonoma County, California". Water Supply Paper 1427. 195S. '•' United Stales Department of the Interior, Geological Survey. "Geology and Ground Water in Napa and Sonoma Valleys, Napa and Sonoma Counties". Open file report. 1958. (3 ' California State Water Resources Board. "Alameda County Investigation". Bulletin No. 13. July, 1955. '" California State Water Resources Board. "Santa Clara Valley Investigation". Bulletin No. 7. June. 1955. °> United Stales Department of the Interior, Geological Survey. "Contributions to the Hydrology of the United States. Ground Water Resources of the Niles Cone and Adja- cent Areas". Water Supply Paper 345-11. 1914, w) United States Department of the Interior. Geological Survey. "Ground Water in Santa Clara Valley". Water Supply Paper 519. 1024. <7> West, Charles H., "Ground Water Resources of the Niles Cone. Alameda County, California". Federal Land Bank. Unpublished Report. November 1, 1937. Tolman, C. F. and Poland, J. F., "Ground Water, Salt-Water Infill ration, and Ground Surface Recession in Santa Clara Valley, Santa Clara County, California". Trans- actions American Geophysical Union, Pt. 1, 1940. ""Allen. John Elliot, "Geology of the San Juan Baulista Quadrangle. California". California Division of Mines Bulletin 133. March, 1046. <10) California State Water Resources Board. "Santa Cruz- Monterey Counties Investigation". Bulletin No. 5. Au- gust, 1053. "" California State Water Resources Board. "Salinas River Basin Investigation". Bulletin No. 10. March, 1055. Whitaker, W. "The Water Supply of Essex From Under- ground Sources". Memoirs of the Geological Survey, England and Wales, I'p. 24-34. 1016. 051 d'Andrimont, R. "Notes stir l'hydrologie du Littoral Beige" ("Notes on the Hydrology of the Belgium Coast"). Soc Geol. Belgiipie Annales, Vol. 20, Pp. M120-M144. 1002. d'Andrimont, R. "Note Complementaire a l'Etude Hydrolo- gique du Littoral Beige" ("Supplementary Note on the Hydrology of the Belgian Coast" I. Annales de la Societe Geologique de Belgique, Vol. 31, Pp. M167-183. 1004. d'Andrimont, R. "L'Allure des Nappes Aquiferes Contenues dans des Terrains Permeables en Petit, an Voisinage de la Mer" ("The Nature of Ground Water Contained in Freely Pervious Aquifers Adjacent to the Sea" ) . Annales de la Societe Geologique de Belgique, Vol. 32, Pp. M101- M114. 1005. <1 '° DuBois, E. "Etudes sur les Eaux Souterraines des Pays- Bas" ("Studies of the Ground Water of the Nether- lands"). Musee Teyler Archives, Second Ser., Vol. 9, Pp. 1-96. 1905. 1 Pennink, J. M. K. "Investigations for Ground Water Sup- plies". Trans. Amer. Sue. of Civil Engineers, Vol. 5 1-1'. Pp. 169-181. 1905. ' Thiele, II. J. "Ground Water Problems in Some European Countries", Summary Statement of Lecture, C. S. ion- logical Survey Fourth Guyton, W. F. "Depleted Wells at Louisville Recharged with City Water". Water Works Engineering, Vol. 9S, Pp. 18-20. 1945. (i7> Sundstrom, R. W. and Hood, J. W. "Results of Artificial Recharge of the Ground-Water Reservoir at El Paso, Texas". Texas Board of Water Engineers Bulletin 5206. July. 1951'. " 8> Los Angeles County Flood Control District. "Report on Tests for the Creation of Fresh Water Barriers to Prevent Salinity Intrusion. Performed in West Coastal Basin, Los Angeles County, California". March 10, 1951. < m Conkling, Harold. "Report to West Basin Water Associa- tion, an Imported Water Supply for West Basin, Los Angeles County, California". July, 1946. (50) California State Water Pollution Control Board, Publica- tion No. 11. "Report on the Investigation of Travel of Pollution". 1954. <61 » Unklesbay, A. G. and Cooper, H. H. "Artificial Recharge of Artesian Limestone at Orlando, Florida". Economic Geology, Vol. 41, No. 4, Pp. 293-307. 1946. <52) Mitchelson, A. T. "Underground Storage by Spreading Water". Am. Geophys. Union Trans., 15. Pt. 2, Pp. 522- 523. 1934. IM) Stone, Ralph and Garber, Wm. F. "Sewage Reclamation by Spreading Basin Infiltration". Trans. Amer. Soc. of Civil Engineers, Vol. 117, Pp. 1180-1217. 1952. ''" University of California, Sanitary Engineering Research Laboratory. "An Investigation of Sewage Spreading on Five California Soils". June, 1955. (K) Intrusion-Prepakt, Incorporated. "Prepakt Reporter". '*» Brown. W. A. "Underground Barriers". California State Department of Public Works. Division of Water Re- sources. September 129. 1948, Unpublished. Memorandum report. a ~' Lewin, J. D. "Grouting with Chemicals". Engineering Xews- Record, Vol. 123, No. 7, Pp. 221-222. 1939. m Polivka, M. "Soil Solidification By Means of Chemical In- jection". M. S. Thesis, University of California, Berkeley, 33 Pp. 1948. "> Gnaedinger, John P. "Soil Stabilization by Injection Tech- niques". Industrial and Engineering Chemistry, Vol. 47, No. 11, Pp. 2249-2253. November, 1955. "*» Simonds, A. \V., Lippold, F. II., and Keim, R. E. "Treat- ment of Foundations for Large Dams by Grouting Methods". Trans. Amer. Soc. of Civil Engineers, Vol. 116, Pp. 548-574. 1951. re "Rie(lel. C. M. "Chemicals Stop Cofferdam Leaks". Civil Engineering, Vol. 21, X... 4. Pp. 23-24. 1951. (0 -' Anonymous. "I'se of Silicates of Soda". Silicate P's and Q's, Philadelphia Quartz Co. of California, Berkeley, Vol. 30, Xo. 10. 105(1. < °" > Lambe, T. W. "Stabilization of Soils With Calcium Ac- rylate". Journal of the Boston Society of Civil Engineers, Vol. 38, No. 2. Pp. 127-154. 1051. '""Intrusion-Prepakt, Incorporated, "Chemical Clouting of Epstein Farm Pond". Unpublished. «» Hefly, D. G. and Cardwell, P. H. "Use of Plastics in Water Control". The Petroleum Engineer, Vol. 15, No. 3, Pp. 51-54. 1943. ' Warren, J. A. "Effect of Stilt Water on Bentonite". Mining and Metallurgy. Vol. 7, Xo. 236, P. 349. 1926. Anonymous. "The Shellperm Process for Controlling the Flow of Underground Water". Shell Oil Company, New York, 8 Pp. 1949. <77 > Endersby, V. A. "Construction Report on Shellperm Project at Diversion Dam of the Santa Ana Valley Irrigation Company". Report No. S-13023-R, Shell Development Company, Emeryville. California, 15 Pp. 1048. <7S> Endersby. V. A. "The Shellperm Process — Witherby Street Undercrossing, San Diego, California". Report Xo. S-13035-R, Shell Development Company. Emeryville, California. 4 Pp. 194s. I7 '" Rhodes, A. D. "Puddled-Clay Cutoff Walls Stop Sea-Water Intrusion". Civil Engineering, Vol. 21, No. 2. Pp. 21-23. 1051. 'Cox, E. L. "Levees Surrounding Union Pacific Railroad I >il Properly at Wilmington, California". February 12. 1051. (sl> Anonymous. "Digging a Trench to Keep Water Out Under Columbia River Levees". Western Construction. Vol. 27. No. 6, Pp. 107-108. June. 1952. '* 21 Anonymous. "Cutoff Walls Beneath Columbia River Levees Placed With Clay Slurry for Trench Support'". Western Construction. July, 1053. " ' M. II. Easier Construction Company and D. & H. Construc- tion Company. "Summary of Cutoff Trench Operations in the Construction of the Kennewick Levees and Pumping Plants Right Bank of the Columbia River Vicinity of Kennewick. Benton County. Washington. Utilizing the Wyatl Method". 7 Pp. Unpublished. SEA-WATER INTRUSION IN CALIFORNIA 91 University of Arkansas, Department of Agricultural Engi- neering; Agricultural Experiment Station. "Ground Water Recharge by .Means of Wells". September, 1954. tm Anonymous. "Recharge and Travel of Pollution". The John- son National Drillers' Journal, 1". 15. Jan. -Feb., 1954. van der Goot, H. A. and Hertel, R. M. "A Report Summariz- ing Progress on Hyperion Waste Water Reclamation Research Project". Los Angeles County Flood Control District, Hydraulic Division. March 30, 1956. 86952 11-58 1M printed in California state printing office PLATE STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA LOCATION OF AREA OF INVESTIGATION SCALE OF MILES 40 40 80 \ PLATE 1 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA LOCATION OF AREA OF INVESTIGATION SCALE OF MILES 40 BERNARDINO N WEST COAST BASIN EXPERIMENTAL PROJECT M M X I C DEPARTMENT OF WATER RESOURCES 1957 PLATE 2 LEGEND SEA-WATER INTRUSION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEArWATER INTRUSION IN CALIFORNIA DIAGRAMMATIC SECTIONS THROUGH A COASTAL GROUND WATER BASIN PLATE 2 LEGEND SEA-WATER INTRUSION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEArWATER INTRUSION IN CALIFORNIA DIAGRAMMATIC SECTIONS THROUGH A COASTAL GROUND WATER BASIN ZONE OF INTERMIXTURE /^ T= 40^ _MHVDHAJJUC_lRAD i ENT_iN_PJ.ESJURE_AQUJF_ER_. WATER TABLE, ZONE OF INTERMIXTURE - -SEA LEVEL HYDRAUUC GRAD.ENT-IN- p„TssuSr fc^ ~ - Condihon / (Seaward sloping hydraulic gradient) Replenishment to the ground water supply exceeds draft on the ground water basin, and as a consequence the water table and pressure gradient slope seaward and fresh water is discharged to the ocean through the aqui- fers in contact with the ocean floor. Wedges of salt water exist near the points of discharge. The length of these wedges is controlled by the quantity of seaward fresh woter flow and the thickness and transmissibility (permea- bility) of each aquifer. Parameters governing length of wedge ond relation- ship of fresh and sea-water pressure heads are developed in Appendix C. LEGEND SEA-WATER INTRUSION Condition II (Landward sloping hydraulic gradient) Draft on the ground water basin exceeds the supply to ground water resulting in a landward slope of the water table and pressure gradient and intrusion of sea water into the aquifers. Since the head of fresh water is less than that of the sea water a condition of instability exists. The prism of fresh water within the deep aquifer is "floating" on sea water. The sea-water wedge will move inland to axis of pumping trough. STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA DIAGRAMMATIC SECTIONS THROUGH A COASTAL GROUND WATER BASIN DEPARTMENT OF WATER RESOURCES 1957 PLATE 3 r ILLED GROUND WATER BASIN UNDERLAIN E SEDIMENTS OF MARINE ORIGIN E ND AND STRATA IRECTION OF ROUND WATER IOVEMENT through evaporation. The seepage, unconsumed by vegetation, re- ching salts from the soil. ligrafion of Saline Waters and were subsequently elevated to their present positions. Sea water o the alluvium under influence of the hydraulic gradient created by migration was generally negligible. of Sewage and Industrial Wastes permeable sumps ultimately migrates to the ground water supply. rface Waters From Streams, Lakes and Lagoons upply. iters the lower productive water-bearing zone through an opening improperly constructed or abandoned wells. :es of increased ground water han sea-water intrusion PLATE 3 HLLED GROUND WATER BASIN UNDERLAIN SEDIMENTS OF MARINE ORIGIN ND AND STRATA IRECTION OF ROUND WATER IOVEMENT through evaporation. The seepage, unconsumed by vegetation, re- ching salts from the soil. ligrafion of Saline Waters and were subsequently elevated to their present positions. Sea water D the alluvium under influence of the hydraulic gradient created by migration was generally negligible. of Sewage and Industrial Wastes jermeable sumps ultimately migrates to the ground water supply. rface Waters From Streams, Lakes and Lagoons upply. iters the lower productive water-bearing zone through an opening improperly constructed or abandoned wells. :es of increased ground water han sea-water intrusion IRRIGATED CROPS SCHEMATIC SECTION ACROSS AN ALLUVIUM-FILLED GROUNDWATER BASIN UNDERLAIN AND FLANKED BY LESS PERMEABLE SEDIMENTS OF MARINE ORIGIN ALLUVIUM CLAY SHALE LEGEND SAND STRATA DIRECTION OF GROUND WATER MOVEMENT Key to Illustration 1 Degradation of Ground Water Through Use and Re-wse Example: Irrigation water applied to crops is increosed in salinity through evaporation The seepage, union: turns to the ground water and is further degraded en route by leaching salts from the soil 2 Degradation of Ground Water Through lateral or Upward Migration of Saline Waters Example: The sand strata illuttraled were deposited in the ocean and were subsequently elevated to their pre eontoined within these sediments since their deposition migrates to the olluvium under influence of ihe hydrc pumping of the wells. Prior to exploitation of ground wafer such migration was generally negligible Sea water created by 3 Degradation of Ground Water Through Downward Seepage of Sewage and Industrial Wastes Example: Sewage ond industrial woste seeping (rom cesspools or permeable sumps ultimately migrates tc 4 Degradation Through Downward Seepage of Mineralized Surface Waters From Sit Example: Mineralized surface woler migrates to the ground water supply ground wale Lakes and Lagoons 5 Degradation Through Intenonaf Migration of Saline Waters Example Degraded water within Ihe upper water-bearing zone enters the lower productive water-bearing tor in the clay layer thot separates the two lonet or through defective, improperly constructed or abandoned wells. SCHEMATIC DIAGRAM SHOWING SOURCES OF INCREASED GROUND WATER SALINITY FROM CAUSES OTHER THAN SEA-WATER INTRUSION DEPARTMENT OF WATER RESOURCES 1957 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA -WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION IN CALIFORNIA SCALE OF MILES 20 PLATE 4 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA -WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION IN CALIFORNIA SCALE OF MILES 20 GROUND WATER BA5IHS AREAS OF KNOWN SEA-WATER INTRUSION Icie. No •a - Pn.lum, 88 Naf.a-Sonn ■ 10] sutidi 147 i'urn V.li., 10 talioaaVa i.. Preaaara HI C>.n>-J fl >a Baaia 84 ttai Co.. Baa is 23J EibCou al 11. i- Pro 14] IfiMiOC ft AREAS OF SUSPECTED SEA-WATER INTRUSION AND AREAS OF OVER 100 pnm CHLORIDE adei Red. ood Creek BtalB 201 Canada 1-1 Rn.,,,, B Hid H.,« VJIev (03 Canada del Canal Baa 12 Eurek. pjaia 204 U« VareaBa.in 13 Eri «,.e. Vallej IDS Bell Canjoa Baaia S7 R u ..,. n Ritci Baaia as ■ 60 Bodega Bar Baain 110 Goltra Baain Frual i real Baaia .Ml Hof.e Baain 83 Sac Rafael Bum ;■ 1 j Carpinieria Baain a Not.io vilk, B.«ii. 216 vtn.ur. RiraVallt) as Soarhaaipian B«t Batm 119 B.( V-ore Bat.t] m Benin. Baain W Zui Co, on &.,,„ So..«i)-F..rlitld Vallej :;* 93 s '«'»'«°-5» J"q»» D^i" m MalibaBa.in 54 CI., 1O0 -V, o «, o Valla, iv» La. Flore. Baain 110 Huta Sura Sana m ■>» Cc.nn] Pl.m-Na Sharp Patk Terrace ot Lmjoaa Caatoa. Baain 118 HaJInwa Bar Tatraee 138 Aliac. Baain 120 Saa Gretario Creak Baaia UoDieit, *re. J39 241 San Jyao Valle, Saou liarf arua C«aa IM am] Baaia 144 163 Villa Baaia Bueaa Vina Creel B. 165 Cikb Poin. »..,e Agua Hedionda Baain l« 247 Escinit Kaurj ISI Torn ».-.o ;!" Saa ElijD Baaia 171 Hone. Ba.ln San r .,-,„»(, Valle T '-' Ctmrro Baaia 251 Soledad Basin 17b ^buauaa Can,™ Buia »3 rccdntCreci Baaip UJ Million Valley Hli.O IS' LaaCbolla* Baain 19] Bnlon Baaia 219 PlMalM Baaia Cemeoiarig Baaia 260 Sneeiaairr Valley T>)II»a Baaia Z6i Oi) Valley Til luao. Bairn •Number refer, is .nde. number a Appeadii / Tabl 1. Depanmeni al lata Reaaurce. Pabl.caiioa No, 6). 'Sea-tain [ai raaia in California'. 0% r) PLATE 5 PLATE 5 DEPARTMENT OF WATER RESOURCES 195? y" 1 PLATE 6 Note: No Fall Measurements For 1954-56 Note: No Fall Measurements For 1953-56 1956 1957 PLATE 6 Note: No Fall Measurements For 1954-56 Note: No Fall Measurements For 1953-56 1956 1957 Nole; No Fall Measurements For 1954-56 ^ £ \ / o z / ---. / — y \ \ / -——_____ / ^ WELL 5N/7W-35KI 1953 WELL 5N/5W-28NI WATER LEVEL FLUCTUATIONS IN WELLS PETALUMA AND NAPA-SONOMA VALLEYS DEPARTMENT OF WATER RESOURCES 1957 PLATE 7 DEGRADED AREA IN LOWER AQUIFER (Chlorides exceed 350 ppm in Alomeda County and 100 ppm in Santo Clara County) Doto as of 1955-56 LINE OF EQUAL CHLORIDE CONCENTRATION _.— _ LINES OF ZERO GROUND WATER ELEVATION AXIS OF PUMPING TROUGH IN LOWER AOUIFER i LINE OF GEOLOGIC SECTION + WATER WELL SURFACE WATER SAMPLING POINT STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION SANTA CLARA VALLEY SCALE OF MILES PLATE 7 DEGRADED AREA IN LOWER AQUIFER {Chlorides exceed 350 ppm in Alomedo Counfy and 100 ppm in Santo Clcra County) Data as of 1955-56 LINE OF EOUAL CHLORIDE CONCENTRATION _..-_ _ LINES OF ZERO GROUND WATER ELEVATION — AXIS OF PUMPING TROUGH IN LOWER AOUIFER LINE OF GEOLOGIC SECTION + WATER WELL SURFACE WATER SAMPLING POINT SEE PLATE 8 FOR GEOLOGIC SECTIONS STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION SANTA CLARA VALLEY SCALE OF MILES jS ■i/ ALAMEDA SAN MATEO 7^k /\/ y m iX/>>< AW/k > * xtq / v Xg*I ^Ulx/' ( x /x J _Vrs )V v^T ~^' >'' ' x /' X / &'/ . / X.' .,«S4P\/ x? .' /X"^ V X.*u"3o^XXv.,iA»'iJ? s — - /""» ^"X /^7kT^ric!FTTtl!ri:^:^^^= s r* = * =s x"/ s X\ #1 XcjS >x^yl& ''A vS- 5 /A,\4/s /^/ / ,^x / aye^S^*/' yvS' — ■»< — r — ~ /' ,MENLO PAR!' «>^if\ /\ >c ;/x 7V >x /I- ; V >X ' X /\ ; r^C /mountain viewjcX-^^j^x / v x /^x 'x. // 7/ \ ^ '**•> / XV £>// N -AT /j>^9as^/ ''\X\'\ J/>\ / x/ / V K ,rf»V^- \ ^#*^ A^ ' X^n San'a Clato Coum Oa'o ai st 1955-56 -^-^ LINE Of COUSL C»LOHl0E CONCE ~__~ LIMES ■.■'■ EEROGR0UNI *'"'EB ElEvaiiON — -— fl»IS OF PUMPING TROUG" IN LOWER OOUrFEW i LINE Of GE0LOC 4 *ATEB WELL $ SURMCE WSTER S4MPLINC POIN X.* BURLINGAME X/ / ^ / 6 /v y / X / / Xy /*■ n / Vs * L 7S? 5 ** '' C V ^Y /^ / \\\ / w ^x 7\x y_ ^/ i/ ._>2>^ / x. / IK. / yc / . x/ \ A / x[^ ■S^LJ''^ 'ToX X^?"x<£s /^X: sV' -xy y/ / \; NOTE THE GEOLOGIC FORMiTiONS, INDICATED BY THE SYMBOLS Oal, ANO TO. APPEARING ON THIS PLATE, ARE SHOWN IN COLOR AND ARE EXPLAINEO IN APPENDIX A TO THIS STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION SANTA CLARA VALLEY SEE PLATE 8 FOR GEOLOGIC SECTIONS I SAN BRUNQ DEPARTMENT Of WATER RESOURCES 1957 - PLATE 8 A' SOUTH —.200 _-2|£- ? 19 23 SLIGHTLY PERMEABLE TO IMPERMEABLE MATERIALS MODERATELY PERMEABLE TO PERMEABLE MATERIALS LEGEND £r^-3CJ CLAY H-jZrr| SANDY CLAY L^ S — I CLAY, SAND AND GRAVEL SAND SANDY GRAVEL •VI GRAVEL PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE: LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 7 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS^ A-A' AND B-B' SANTA CLARA VALLEY PLATE 8 r jT^-;>^lfjH§_ ? 19 23 LEGEND SLIGHTLY PERMEABLE TO IMPERMEABLE MATERIALS MODERATELY PERMEABLE TO PERMEABLE MATERIALS ^£~^^| CLAY H-jZrr| SANDY CLAY £^r". S 7E:| CLAY, SAND ANO GRAVEL '.od SANDY GRAVEL ^31 GRAVEL [IZ] PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE; LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 7 STATE OF" CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTR USIO N IN CALIFORNIA GEOLOGIC SECTIoTJs" A-A' AND B-B' SANTA CLARA VALLEY II . i SAN JOSE SAM FfANCISCO BAT jK A ~--ri: «W - : Jpfgf Waan -3, Sao Lava/ ~^~ _i_L *: E r .-&'■■'' == ,,'-''" J^g" r ; ::EH----— -fHt^ as*-- r t *S5r-^~ --slf" SCALE OF MILES SECTION fl-fl' DUMBARTON 8RI0GE TO SAN JOSE SCALE OF MILES SECTION B-B' STANFORD UNIVERSITY TO NILES DEPARTMENT Of WATER RESOURCES 195 T r s I I ' E3> f GEOLOGIC SECTIONS IHlOBiOE CONCEN' *»TIOM DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INT RUSIO N IN CALIFORNIA GEOLOGIC SECTIONS A-A 1 AND B-B' SANTA CLARA VALLEY e\ 1 1 1 • 1- U S G.S ASIC OAT 1 «! \j WELL 6S/3W IB / WELL Nil NOT KNOWN 1 1 J WELL 6S/3W IBI • 6 WELL S/3W ICI / r 1 \ A * WELL 6S/3W IBI \ N VELL N2 pT KNOWN V 1 \w 1 \ T 6_ \- - .-* i i i 1 1 • N \ ) , . 1 \ \ \ T i 'V i/ \ \ 1 \ 1 \l M i 1 !\ )6 REPRODUCED 1 RESOURCES OF iMEDA COUNTY, \ X . i. \ \ is ' \ 1 i\, WEST, FEDER :fi 1,1937 1EDQ \L \ /- \ I / • -. i \ ^~ NO RCCORO — 1 ' 11 \i 1 PLATE 9 1935 1940 SOUTH BAY PALO ALTO [lower aciuifer] AREA STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS SANTA CLARA VALLEY PLATE 9 -WEST'S REPORT WELL 6S/3W IB O.W.R RECORDS Z WELL N« NOT KNOWN it WELL 6S/3W IBI WELL 6S/3W ICI W WELL N* NOT KNOWN I V J6 REPRODUCED I RESOURCES OF iMEDA COUNTY, WEST, FEDERAL :r 1,1937 4ED) / "v 1935 1940 SOUTH BAY PALO ALTO [lower aquifer] AREA STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS SANTA CLARA VALLEY ;.-:■. SKSvs&i^* : 3 4S/IW29MI / : : 4 T \ / - I / A '\ II /1 \ /- A ,", : f, <\ <\ . V Ja \ ' " i ' * \ iV V J \ 1 i> \ \ A /' 'v A 1 i ■■ - \ 1 - V t 1 \l 1 u V it ', '1 •■((»« *0» i»JC-.»5t •I"OCKK(0 V I. ^ 1/ :.■.£" ■,.,'.:'i,E_ ■■■ L v" '~ \ . '■ > „ .-:- 7 t MINI ■- 1 1 1 EAST BAY CENTERVILLE AREA [upper aquifer] EAST BAY russell city- alvarado area [lower aquifer] SOUTH BAY PALO ALTO AREA [lower aquifer] 3 ' 1 WELL 1 JJ\mmm' A .,, w an LL W9J. ■ 1. mJ6> 1 WELL • ',. 2W 9 n --^_1__ ■ulnliilu " ■• «■ \ ' ' mi '■' — . 1 \ \ 'l , "\ 1 A, * 1 '. \.\ '- rt , ,», 1 1 ' ' J 1 i V 11 1 1 M '» i 'l 6 w n LL 9' t 1 1 i i ( ... 1 i] < 1 1 \ i 1 1 1 i |! 1 ll ; i 1 [1 WELL 7§/ IW 3GI 7 /, ', '] I 1 1 I 1 . i »i 1 II 1 1 1 . CO- re i y I ' s 1 \ 1 'w 1 1 \\ 1 1 ' 1" t u 1 1 1/ i I w 1 1 1 s f\ h \ 1 ) 1 i J u V 1 ' II II WELL TS/IW26I ( i | 1 i \ » If 1 1 l l n ! i I i 1 i i l t n u i !l i i 1 1 1 SOUTH BAY SOUTH BAY SANTA CLARA AREA [lower aquifer] STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS SANTA CLARA VALLEY ITMENT OF WATEB RESOURCES I OGIC BY Ot i- ON M IN C D IN lEPOri l~ OGIC BY 01 IG ONj N IN C D IN ] SEPOfi R. k= note: the geologic formations, indicated by the symbols Ool. Oool .01 , Os, AND TO APPEARING ON THIS PLATE, ORE SHOWN IN COLOR AND ARE LOCATION MAP :. : AREA OF SEA- WATER OatO a> Ot 1954 _'Sr nt EQi'AL CHLORIDE -.-.■.■■ ■ LINE OF GEOLOG'C F«CF *Aitfl SAMPLING POIN STATE OF C DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION PAJARO VALLEY AND SALINAS VALLEY PRESSURE AREA SCALE OF MILES DEPARTMENT OF WATER RESOURCES 1957 o IfclHJj^ J ""' SCALE OF MILES SECTION D-D' MONTEREY BAY TO SALINAS SOUTHWEST NORTHEAST 40NTEBEV B t "„,--' !| Hsk4fc ®WM^'" t °" lt Aromas fled SCALE OF MILES SECTION C-C' PAJARO VALLEY E3- El- DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PL»NNrNG SEA -WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS C-C' AND 0-D' PAJARO VALLEY AND SALINAS VALLEY PRESSURE AREA OEF-ttBTMENT OF WATER r\ PLAT 1? A s Is- IE" 5 wellI I3S/2E-30H2 ■i P h E— WELL t r /2E-I2 Ji WELL ' / I I" A , "1 8* A IES/IE-ZSSI K- WELL _ I3S/2E-30BI |i3S/SE •I9fl|l OJ /\ WELL !5 ;e -ioa !■ 1 \ .,-- s u „-'' "S, x jl 1 —1- -w 1 -■* "'* .T>« r 1 1 -— >\ II 4 1 \ ■ r\ -■ ■"• ... '• L._ - -- ' / \ 1 1 1 V A l_ 1 WELL I4S/2E-I20I \ 4 / I 2 T ll -I r V '1 \ 4. I Li !'! 3ll : „ ■'"'•" "■"« ■ V 1 1 ( !! 4-1 1 ' ' 1. ! at - is" ' "*i ' w " ^ ' ^ ' ^1 ' ^ ' w ' ^» /' / ll II ' 1 I ^ ... y 1 11 l! 'i Ll 1 Hi 1 " ■\ 1 |g I 1 51 HI e5"° 3' ' well' I4S/2E-26PI w I3S/2 E 30" V --I-I- + -h -5 1 — ""'"■'" ' T | STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS PAJARO VALLEY AND SALINAS VALLEY PRESSURE AREA * — i \ ■- ', \ \ 1 1 <] , <\ * uj wellI 1 V \l V V V ( v.^ 1 \ 1 . S 1- 5 1 1 i '- V v 1 , Ii 1 r ! a EC-ZBJSJ 1 ji * » ERtjtfS! 11 1 ! 5 3 SALINAS VALLEY PRESSURE AREA OEPiSTUEN r F W WE ESQ URC ES j". r\ PLATE 13 TrrxK LOCATION MAP NOTE: SEE PLATE 14 FOR GEOLOGIC SECTIONS N NOTE: THE GEOLOGIC FORMATIONS INDICATED BY THE SYMBOLS Ool, TO, Ooal, Os, 01 AND TOvw ARE SHOWN IN COLOR AND ARE EXPLAINED IN APPENDIX A TO THIS REPORT STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA^WATER INTRUSION OXNARD PLAIN BASIN SCALE OF MILES PLATE 13 -Err*" LOCATION MAP NOTE: SEE PLATE 14 FOR GEOLOGIC SECTIONS N NOTE: THE GEOLOGIC FORMATIONS INDICATED BY THE SYMBOLS Qal, TO, Oool, OS, 01 AND TQvw ARE SHOWN IN COLOR AND ARE EXPLAINEO IN APPENDIX A TO THIS REPORT STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA^WATER INTRUSION OXNARD PLAIN BASIN J SCALE OF MILES PLATE 13 DEPARTMENT OF WATER RESOURCES 1957 PLATE 14 E OF MILES TION E-E - NEME TO SATICOY F' NORTH —I 200 °cen 6 Deposits J 1 :-■->,—. _-— — "%% fANy on AQU ifE" ?s 9 \o> LEGENO PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE: LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 13 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA- WATER INT RUSIO N IN CALIFORNIA GEOLOGIC SECTIONS E-E'.F-F' OXNARD PLAIN BASIN PLATE 14 E OF MILES TION E-E' NEME TO SATICOY F' NORTH —i 200 °cen ( Deposes d 1 3- LEGENO PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE: LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 13 ■1200 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES 1*00 DIVISION OF RESOURCES PLANNING SEA-WATER INT RUSIO N IN CALIFORNIA GEOLOGIC SECTIONS E-E'.F-F' OXNARD PLAIN BASIN T SOUTH Mi/CV LAGOON PLEASAN T SCALE OF MILES SECTION E-E' PORT HUENEME TO SATICOY VALLEY F' NORTH —i 200 PACIFIC OCEAN Deposits N YON ,oo.f eb y- PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLOR'OE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 13 SCALE OF MILES SECTION F-F' MUGU LAGOON TO CAMARILLO AIRPORT STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES 1*00 DIVISION OF RESOURCES PLANNING SEA- WATER INT RUSIO N IN CALIFORNIA GEOLOGIC SECTIONS E-E'.F-F 1 OXNARD PLAIN BASIN DEPARTMENT OF WATER RESOURCES 1957 PLATE 15 < I- < > 12 | 600 l 1400 \\ / a 1 / i 6S WELL /IIW-I Gl lT ^A / b tt \ 1 / 5 t T J 4 ----- .-- -~ -^ ^ V V t v i ^ \ T V •i / •N.V ">-- TOSECOf / / / — \ / / \ \ ■ ^^ -1 / -2 r i -i ^ \ -4 1941 1942 1943 1944 1945 1946 1947 1949 1949 1950 1951 1952 1953 1954 1955 EAST COASTAL PLAIN PRESSURE AREA LEGEND CHLORIOE CONCENTRATION WATER SURFACE ELEVATION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS OXNARD PLAIN BASIN, WEST COAST BASIN, AND EAST COASTAL PLAIN PRESSURE AREA PLATE 15 < < > 5 IT 1943 1944 1945 1946 1947 1948 1949 1950 195 954 1955 EAST COASTAL PLAIN PRESSURE AREA LEGENO CHLORIDE CONCENTRATION WATER SURFACE ELEVATION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS OXNARD PLAIN BASIN, WEST COAST BASIN, AND EAST COASTAL PLAIN PRESSURE AREA PORT HUENEME AREA - r~\ r~ \ V \ % s WELL r \ I | I 1 1 1 1 1 1 ■ \i 1 1 \. 1 ;; , 1 1 1 1 1 1 !!. M ['; w v 1 1 1 1 i i i / ,l/ ! 1 1 w II i 1 1 \ I ',! 1 \ 1 1 1 1 1 1 4 i i i II \l ! ii j i w ? i i WE 13/Z'V LL -SMI / II — - / 1 MUGU LAGUNA AREA NEAR OXNARD OXNARD PLAIN 8A5IN K t A / \ \ i\ i > \ WELL /ISW-ZJMS A / I \ \ i "^ / \ \ \ \ i ', • \ / V j ^ \ / 1 ' N / v ;s'i5w-jsci \ l V PLAYA DEL REY AREA ,/\ "*"■ ' \ \ I \ \ 1 \ 1 V \ \ . / / \y \ \ h 3S/HW-70IF \ / v MANHATTAN BEACH AREA r- rv 1 \ -' \ WELL 4S/I3W-35MI / \ \ \ \ k^^ / r DESTROYED -19- SB \ >'\ / * as/i3w-aeic ., LONG BEACH AREA WEST COAST BASIN / / SI WELL 1SPI r rt 1 -A / V '\l \ ^~ 7 \ --- *s V N, \ 6 wellI /IIW-ISAI 1 \ \ \ -- ., "~"~ — \ ,' \ A / "' J v' EAST COASTAL PLAIN PRESSURE AREA | \ / l\ 1 / WELL 6S/IIW- 161 _r -> / \ / f / __- — - .-- "" "* •k 1 t v V > 5 M V ql ,/ / — ^ ^ / / \ / """ Y EAST COASTAL PLAIN PRESSURE AREA SEA-WATER INTRUSION IN CALIFORNIA CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS OXNARD PLAIN BASIN, WEST COAST BASIN, AND EAST COASTAL PLAIN PRESSURE AREA DEPARTMENT OF WiTEH RESOURCES I95T PLATE 16 IER PROJECT RATION VATION 1 AQUIFER STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION WEST COAST BASIN AND EAST COASTAL PLAIN PRESSURE AREA SCALE OF MILES C SECTIONS PLATE 16 ER PROJECT RATION VATION 1 AQUIFER STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION WEST COAST BASIN AND EAST COASTAL PLAIN PRESSURE AREA SCALE OF MILES C SECTIONS 4.NTA \|ICA PLAYA DEL RAY BUCNA PARK BELLFLOWER —x^> \ \ range; W --"■V^-" \ * A' \ \/^\* -A* * «V * \ -'' \ \,'' \ VGARDEN *?r\ I ANA -V V \ &„ ( \'"'"«\\ \ -''\ ><\ V 5 V' \ ^C ^WESTMINSTER '« \ '■ " \>, ■■■'■■' ^ - _ 4 VJBSm. u "A,r T .-\ MANHATTAN BEAQ W REDONDO BEACH tTORRANCE^. ., . JOWUJ.CJ. W^? ii-J-V? '.*s.«".'?A jaV LEGEND I aBE» OF SEl-«0t£Q IHTB • A 5 * NEWPORT BEACH ' EOS ANGELES ~ ^5 AN PEDRO 5-^4", EZ3' E OF eOiUL CHI.0HIDE C SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION WEST COAST BASIN AND EAST COASTAL PLAIN PRESSURE AREA KP*BT«ENT OF WATER RESOURCES 1957 PLATE 17 H" SOUTH 200 NOTE: LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 21 NORTH COASTAL PLAIN Mean Sea Level ) e p o s i t s LEGEND PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION -800 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES " l00 ° DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS h-h: j-j: and k-k 1 west coast basin PLATE 17 H' SOUTH 200 NOTE: LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 21 K 1 NORTH COASTAL PLAIN Mean Sea Level deposits Z .°N, *£: . LEGEND PORTION OF PERMEABLE -DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION -800 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES ' l00 ° DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS h-h: j-j: AND K-K' WEST COAST BASIN H NORTH WEST COAST DOMINGUEZ GAP Pleistocene Deposits GASPUR WATER BEARING ZONE- Recent Alluvial Deposits Pico Formation J__ SCALE OF MILES SECTION H-H' BALLONA GAP TO DOMINGUEZ GAP NOTE LIMES Of GEOLOGIC SECTIONS SHOWN ON Pl»T£ 16 _L _L J_ SCALE OF MILES SECTION J-J' PACIFIC OCEAN TO CENTRAL COASTAL PLAIN SCALE OF MILES SECTION K-K' SAN PEDRO BAY TO CENTRAL COASTAL PLAIN PORTION OF PERMEABLE -DEPOSITS CONTAINING GROUND WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES ■1000 division OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA ,aoo GEOLOGIC SECTIONS H-H. J-J! AND K-K' WEST COAST BASIN DEPARTMENT OF WATER RESOURCES I9S? PLATE 18 M NORTH — llOO LEGEND PORTION OF PERMEABLE DEPOSITS CONTAINING GROUND WATER WITH CHLORIOE CONCENTRATION GREATER THAN lOO PARTS PER MILLION NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 „ STATE OF CALIFORNIA UU DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING , 00 SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS L-L*. M-M* EAST COASTAL PLAIN PRESSURE AREA PLATE 18 M NORTH — 1 100 LEGEND PORTION OF PERMEABLE OEPOSITS CONTAINING GROUNO WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 0Q STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING , 00 SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS L-L', M-M' EAST COASTAL PLAIN PRESSURE AREA 32,000 40,000 SCALE OF FEET SECTION L-L' LANDING HILL TO NEWPORT MESA 12,000 14.000 SCALE OF FEET SECTION M-M' ALONG AXIS OF SANTA ANA GAP PORTION OF PEflMESBLE DEPOSITS CONTAINING G«OUND WATER WITH CNLOfllOE CONCENTRATION jSt-'tR THAN 100 PARTS PES MILLION STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING D0 SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS L-L'.lvl-M' EAST COASTAL PLAIN PRESSURE AREA OEPARTMENT OF WATER RESOURCES 1957 PLATE 18 M NORTH — 1 100 LEGEND PORTION OF PERMEABLE DEPOSITS CONTAINING GROUNO WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 00 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING , 00 SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS L-L'.M-M' EAST COASTAL PLAIN PRESSURE AREA PLATE 18 M NORTH — 1 100 LEGEND PORTION OF PERMEABLE OEPOSITS CONTAINING GROUNO WATER WITH CHLORIDE CONCENTRATION GREATER THAN 100 PARTS PER MILLION NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 00 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING , 00 SEA-WATER INTRUSION IN CALIFORNIA GEOLOGIC SECTIONS L-L.', M-M' EAST COASTAL PLAIN PRESSURE AREA L 1 L ' NORTHWEST ^ * SOUTHEAST _ * NEWPORT MESA — , 100 - LANDING T«ffoce "JNTINCTON 8EACH (J •iMMVT RAP 60LSA Chica ROlSA GAP Deposit*- . SANTA ANA GAP fT 2 /T«rroce Oepoi.lt_ ^^ _- — ■ ^ — ■ — -J 5 i— — ^ '^ , - t -,,— -Alfji Jea Level 1 Deooi'ti^^ rfj " sC^ ^~~~ : T\l / ■ -100 ■ ^^yr-:-> "" ™"'" ^^^fe^^f ;--' -100 I 3 < Q -200 ^-i^oTr^^A-rER -BE»B_^L_ A^ ' /^^\^~— -— ' "^.-r--' -200 O 3 ' -300 / - ^""-"--^^ -300 *«? ^~~~~~~~=- E | z 2 -400 -400 O « E -soo -600 / - -600 -700 1 / 1 . 1 . 1 . 1 ■ 1 , I . 1 -700 SOOO 16,000 24,000 32,000 40,000 48,000 56.000 64 : SCALE OF FEET SECTION L-L' LANDING HILL TO NEWPORT MESA M m' SOUTH , j NORTH 100 -6 I - 100 2 3 -(00 £-200 " ! I ___— ■ -100 LEGEND §■■■■■■■ PORTION Of PEBMEASlE DEPOSITS CONTAINING -200 ■ GROUND WATER WITH CHLORIDE CONCENTRATION GREATER ThAV 100 PARTS PER MILLION 1Mb.. .*._**'.'.'*>' hi a t e a - REARING 01 »..''•* \ " ZONE *'.* " " ■*' » *'*.'*•,'/ Sea Ley*/ s a ^■Lb e r t \ ^ \ P., r ° F ' n \ ""~~^ 'V u -300 - San Pedro Formation \, ~V^ -300 z '_ \> - z 9-400 - 1 f \ " -400 NOTE LINES OF GEOLOGIC SECTIONS SHOWN ON PLATE 16 u ~ X* - -500 O ", \ - -SOO -600 _ '*', '» \ _ 600 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES " \ . ' \ J 1 1 1 ■ * ■ 1 ■ 1 1 ■ f . | | - DIVISION OF RESOURCES PLANNING -700 | 1 70O SEA-WATER INTRUSION IN CALIFORNIA a 4000 6000 BOOO 10 000 12,000 14,000 16,000 lfl.000 20,000 22,000 2 4.0 00 26.000 tm SCALE OF FEET GEOLOGIC SECTIONS L-L', M-M' SECTION M-M' EAST COASTAL PLAIN PRESSURE AREA along axis of santa ana gap ^E^siMcr DF WATER LEGEND ~T 1 ALLUVIUM AND LA600NAL DEPOSITS Qdl I UNCONSOLIDATED SAND, GRAVEL, AND CLAY Ts6:;i SAN ONOFRE BRECCIA WELL CEMENTED BOULDERS, COBBLES, PEBBLES, AND SAND ' ■-.. ' I LA JOLLA FORMATION ■ Hi I CONSOLIDATED SAND, CLAY, AND SHALE M EXTENT OF SEA WATER INTRUSION (Chlorides exceed lOOppm) Ooto os of Jonuory 1956 _„ VALLEY AREAS LINE OF GEOLOGIC SECTION — . LINE OF ZERO GROUND WATER ELEVATION AXIS OF PUMPING TROUGH -+- WATER WELL ffi SURFACE WATER SAMPLING POINT HIGHLY PERMEABLE INCLUDES UNCONSOLIDATED SANDS AND GRAVEL SLIGHTLY PERMEABLE INCLUDES SILT AND FINE SANDS IMPERMEABLE INCLUOES CLAY AND CEMENTED SANDSTONES STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION AND GEOLOGIC SECTIONS N-N', O-O', P-P,' AND Q-Q' MISSION BASIN PLATE 19 N' Qal AT AXIS OF BURIED CANYON Qal Ts6:;i LEGEND ALLUVIUM AND LAGOONAL DEPOSITS UNCONSOLIDATED SAND, GRAVEL, AND CLAY SAN ONOFRE BRECCIA WELL CEMENTED BOULDERS, COBBLES, PEBBLES, AND SAND LA JOLLA FORMATION CONSOLIDATED SAND, CLAY, AND SHALE EXTENT OF SEA WATER INTRUSION (Chlorides exceed lOOppm) Data as of January 1956 VALLEY AREAS LINE OF GEOLOGIC SECTION — ' L' NE OF ZERO GROUND WATER ELEVATION AXIS OF PUMPING TROUGH -+- WATER WELL ffl SURFACE WATER SAMPLING POINT HIGHLY PERMEABLE INCLUDES UNCONSOLIDATED SANDS AND GRAVEL SLIGHTLY PERMEABLE INCLUDES SILT AND FINE SANDS IMPERMEABLE INCLUDES CLAY AND CEMENTED SANDSTONES STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF HESOURCECS PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION AND GEOLOGIC SECTIONS N-N', 0-0', P-P,' AND Q-Q' MISSION BASIN ^ ,M€AN SEA LEVCL -GROUND SURFACE ^ WATER TABLE JANUAHt 1956 : Tlj Tlj 32,000 36,000 40,000 SCALE OF FEET SECTION N-N' THROUGH SAN LUIS REY RIVER CANYON AND MISSION BASIN r- — s ^/ 3 1 \OE«L°o°p fi ED»T i-{ Qal : : /' - \WELL IIS'SW-23£( ' ^w**-" z o \ '-^- Tso \ ■ > -200 ■ - 900 1 100 1500 1800 ZIQO 2400 2700 SCALE OF FEET SECTION 0-0' ACROSS SAN LUIS REY CANYON F 1 p 100 } J \ ' - = ZZ / \ ■- — / V Tlj \ % Q* 1 = /- ■ -100 ~: / / - \ ■ V \ - 200 300 400n 8000 SCALE OF FEET SECTION P-P' ACROSS MISSION BASIN \ — — / — - - \ = = zz / \ \ - Tlj i 1 Oal s ^J* /Tlj k_ ^_^- -" " ~~ ""*" - i 1 1 1 i I 12,000 SCALE OF FEET SECTION Q-Q' ACROSS MISSION BASIN LOCATION MAP DEPARTMENT OF WATER RESOURCES 1957 'Han' \ WATER WELL 8 SURFACE WATER SAMPLING POINT MISSION BASIN SCALE OF" FEET 30.00 60,00 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF HESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA STATUS OF SEA-WATER INTRUSION AND GEOLOGIC SECTIONS N-Nl 0-0', P-P,' AND 0-0' MISSION BASIN f • PLATE 20 DN AND WATER LEVEL FLUCTUATIONS 1947 1948 1949 1950 1951 1952 EN WELL IIS/5W-I3NI AND SHORELINE 1953 1954 1955 E CONCENTRATION 'UATIONS IN WELLS BASIN PLATE 20 DN AND WATER LEVEL FLUCTUATIONS 1947 1948 1949 1950 1951 1952 EN WELL IIS/5W-I3NI AND SHORELINE 1953 1954 1955 E CONCENTRATION 'UATIONS IN WELLS BASIN CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS SEAWARD SLOPE 1938 1939 1940 GROUND WATER SURFACE 952 1953 1954 1955 SLOPE OF GROUND WATER SURFACE BETWEEN WELL IIS/5W-I3NI AND SHORELINE CHANGES IN CHLORIDE CONCENTRATION AND WATER LEVEL FLUCTUATIONS IN WELLS MISSION BASIN DEPARTMENT OF WATER RESOURCES 1957 PLATE 21 Ul > < AVE ^7fOC UJ > < ©7I0A BEACH VAULT = EL SEGUNOO F BLVD. EOER LINE ■&73IA -&-72IG in UJ > < (/] 72IF ♦I UJ z < UJ > < 71 1 A-$- bl4 7 # ST. CD < 721 K-^ CURTIS AVE. 722C ■$■ o Q Z o Q UJ 722A © > < ©v> o -J m < > ^722 B fJM-18 LANE I2B ^■712 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT LOCATION OF WELLS JANUARY 1956 SCALE OF MILES 0.5 PLATE 21 Ul > < AVE ^-7fOC UJ > ®7I0A BEACH VAULT » EL SEGUNDO F BLVD. :eder LINE _& 72 IG •&73IA t/t UJ > < Ul 72IF UJ z OJ > < 7IIA-< 73l-<| ? 4 C ST. V) en UJ z *: cc < 721 K-0- CURTIS AVE. o UJ a. 722C ■$■ tr ui o Q z o a 722A © > < in o _i m < > ^-7228 dstjs LANE STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT LOCATION OF WELLS JANUARY 1956 SCALE OF MILES 0.5 III' DETAIL A SCBLE or fee DEPARTMENT OF IMTEB BESOUHCES 1957 PLATE 22 >- CE < Z EH < Z> o Qdsr Qds LEGEND DUNE SAND Qpu a. UNDIFFERENTIATED TERRACE DEPOSITS, PALOS VERDES SAND, UNNAMED DEPOSITS. -G LINE OF GEOLOGIC SECTION CONTACT Qds STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT AREAL GEOLOGY PLATE 22 < z < O Qdsr Qds LEGEND OUNE SAND UJ K Opu UNDIFFERENTIATED TERRACE DEPOSITS, PALOS VERDES SAND, UNNAMED DEPOSITS. LINE OF GEOLOGIC SECTION CONTACT Qds STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT AREAL GEOLOGY SC1LE IN FEET lOOO 2000 3000 4= Z Oo OIL RESERVOIRS CD. MARINE AVE. BEACH Qds GOULD LANE BLVO Qdsr Qds LEGEND DUNE SAND UNDIFFERENTIATED TERRACE OEPOSITS, PALOS VERDES SAND, UNNAMED DEPOSITS. -G LINE OF GEOLOGIC SECTION CONTACT DEPARTMENT OF WATER RESOURCES 1957 PLATE 23 EA LEVEL < 5 SOUTH «0m, STATE OF CALIFORNIA i 00 DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING 125 SEA-WATER INTRUSION IN CALIFORNIA 150 WEST COAST BASIN EXPERIMENTAL PROJECT --I75 GEOLOGIC SECTIONS G-G' AND l-l HORIZONTAL SCALE 500 PLATE 23 £a level --200 < s SOUTH «mm, MEAN SEA LEV EL 100 75 50 25 25 -50 -75 -100 -125 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA 50 WEST COAST BASIN EXPERIMENTAL PROJECT -175 GEOLOGIC SECTIONS G-G' AND l-l NOfllZONTAL SCALE 500 — — 1000 ^FEET PLATE 23 GEOLOGIC SECTION G-G' SANTA MONICA BAY TO SEPULVEDA BLVD. STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA --I50 WEST COAST BASIN EXPERIMENTAL PROJECT GEOLOGIC SECTIONS G-G' AND l-l GEOLOGIC SECTION l-l' ALONG RECHARGE LINE HORIZONTAL SCALE ,00 SCALE C5 DEPARTMENT OF WATER RESOURCES 1957 PLATE 24 Q > _J CD IE BLVD. > LANE )N OF 1953 )N OF 4 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT UNES OF EQUAL ELEVATION OF GROUND WATER JANUARY 1953 AND JUNE 1954 SCALE OF MtLES 4 PLATE 24 E*x! o > _i BLVD. z o I- < > < LANE &N OF 1953 H OF STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT UNES OF EQUAL ELEVATION OF GROUND WATER JANUARY 1953 AND JUNE 1954 SCALE OF MILES 4 PLATE 24 DEPARTMENT OF WATER RESOURCES 1957 PLATE 25 LOCATION MAP ATES IN CUBIC FEET PER SECOND WELLS H 1.05 I. 04 ) 39 ) 45 D.53 ). 58 63 0.37 59 45 75 0.54 1.05 39 64 91 0.74 0.47 0.70 0.60° l-A o° 36° 0.37° 1.03 1.13 1.00 88 0.51 78 55 26 0.43 48 74 0.74 0.30 45 0.46 TOTAL 0.75 2.43 4 84 4.4L 4.77 3 95 .4 26 PLATE 25 i LOCATION MAP ATES IN CUBIC FEET PER SECOND WELLS E F G H l-A J K TOTAL o» ) 0.75 oa 0.75 1.05 0.54 036° 48 243 i. 04 63 1.05 0.37° 0.51 74 4 84 3 39 0.37 39 0.47 1 03 78 0.74 4 41. ) 45 59 64 0.70 1.13 55 0.30 4.77 D.53 0.45 0.91 1.00 26 45 3 95 ). 58 0.74 0.60 b 88 0.43 0.46 .4 2 6 2000 '750 SOUTHWEST 250 250 500 DISTANCE IN FEET FROM WELL G 1750 2000 NORTHEAST V . ■--. - ->*^k * VLINEi \ \ \> »\ \ 1 ! \c LOCATION MAP INJECTION RATES IN CUBIC FEET PER SECOND DATE WELLS C D E F G H l-A J K TOTAL 2-12-53 o« 3-10-53 75 00 75 6-15-53 1 05 0.54 36* 48 2 43 10-11 -53 50 1.04 63 1 05 37" 51 74 4 84 12-3-53 24 39 37 39 47 1 03 78 074 4 41 6-24-54 41 4 5 59 64 70 1 13 55 30 4 77 5-17-55 35 53 45 091 1 00 26 45 3 95 3-1-56 29 28 58 74 60* 88 0.43 46 4 26 o WELL b WELL I WEST COAST BASIN EXPERIMENTAL PROJECT PIEZOMETRIC PROFILES ALONG THE "G" LINE DEPARTMENT OF . ' RESOURCES 1357 PLATE 26 LOCATION MAP INJECTION RATES IN CUBIC FEET PER SECOND E WELLS C D E F G H l-A J K TOTAL 53 00 -53 0.75 oa 0.75 ■53 1.05 0.54 036° 0.48 2.43 53 0.50 1. 04 0.63 1.05 0.37° 0.51 0.74 4.84 53 0.24 0.39 0.37 0.39 0.47 1.03 0.78 0.74 4.41 -54 0.41 0.45 0.59 0.64 0.70 1.13 55 0.30 4.77 55 0.35 0.53 0.45 0.91 1.00 0.26 0.45 3.95 56 0.29 0.28 0.58 0.74 0.60* 088 043 0.46 4.26 I H-A PLATE 26 LOCATION MAP INJECTION RATES IN CUBIC FEET PER SECOND E WELLS C D E F G H l-A J K TOTAL 53 00 -53 0.75 oa 0.75 ■53 1.05 0.54 036° 0.48 2.43 53 0.50 1. 04 0.63 1.05 0.37° 0.51 0.74 4.84 53 0.24 0.39 0.37 0.39 0.47 1.03 0.78 0.74 4.41 -54 0.41 0.45 0.59 0.64 0.70 1.13 55 0.30 4.77 55 0.35 0.53 0.45 0.91 1.00 0.26 0.45 3.95 56 0.29 0.28 0.58 0.74 0.60 fc 0.88 0.43 0.46 4.26 I H-A LINES OF EQUAL CHLORIDE ION CONCENTRATION IN PARTS PER MILLION FOR JUNE 1954 STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT LINES OF EQUAL CHLORIDE ON CONCENTRATION JANUARY 1953 AND JUNE 1954 DEPARTMENT OF WATER RESOURCES 1957 PLATE 27 LANE ION S PER 53 ION PER STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT LINES OF EQUAL CHLORIDE ION CONCENTRATION JANUARY 1953 AND JUNE 1954 SCALE OF MILES PLATE 27 LANE ION S PER 53 ION PER STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT LINES OF EQUAL CHLORIDE ION CONCENTRATION JANUARY 1953 AND JUNE 1954 SCALE OF MILES 4 20 000 18 000 _ 16 000 12 000 - 10 000 8 000 _ 6 000 4 000 2 000 3000 3500 4 000 4 500 5000 DISTANCE FROM OCEAN IN FEET 5500 6000 6500 7000 8000 WEST COAST BASIN EXPERIMENTAL PROJECT CHLORIDE ION CONCENTRATION ALONG THE "G" LINE BEFORE AND AFTER INJECTION DEPARTMENT OF WATER RESOURCES 1957 PLATE 28 LOCATION MAP LEGEND ESTIMATED CONCENTRATION WITHOUT INJECTION JANUARY, 1953 JULY, 1953 JUNE, 1954 JANUARY, 1955 AUGUST, 1955 OMMENCED FEBRUARY, 1953 6500 7000 7 500 8000 PLATE 28 LOCATION MAP LEGEND ESTIMATED CONCENTRATION WITHOUT INJECTION JANUARY, 1953 JULY, 1953 JUNE, 1954 JANUARY, 1955 AUGUST, 1955 OMMENCED FEBRUARY, 1953 6500 7000 7 500 8000 PLATE 29 ' 4000 1 1 ( I i 1 - to* dfe> ! <^WELL K-8 >^ t V \ J \ ^WELL H-4 \ \ ' \ LOCATION MAP low y— T :st HOLE 1 rTEST iOLE I r WELL M-18 „____- WELL K-B^ —— — — — " — — — - Si - — — ~ — — — •Z£2" "™."- '-JT- 'W- ■•.:.-" ■-£/- •-^;:" -JUiS" ■•-Si" 'ili" • Sii- — ■" '"- ; '■ : "' ~" *'* n (fe J ~" ■is=- '"■"■■■ '""-" •W Mis- ■ ™r- ■ - ' -:.' - ,... „ ...„ WEST COAST BASIN EXPERIMENTAL PROJECT CHLORIDE ION CONCENTRATION AT SELECTED WELLS DCPWfHUT 3( BATCH »E r^ PLATE 29 _£! LOCATION MAP 16 000 15 000 14 000 13 000 12 000 1 1 000 10 000 9 000 8 000 rooo 6 000 5 000 4 000 5 000 2 000 -> 1956 PLATE 29 16 000 15 000 14 000 13 000 12 000 1 1 000 10 000 9 000 8 000 7000 6 000 5 000 4 000 3 000 2 000 .TEST MOLE I .£• LOCATION MAP 1956 PLATE 30 ^ ? 5 \ s> \v » ^ Vj \ ^*«v \ • LEGEND ^—5^ RATE OF ARTIFICIAL RECHARGE OF AQUIFER IN CUBIC FEET PER SECOND PER MILE OF RECHARGE LINE TRANSMISSIBILITY OF AQUIFER IN CUBIC FEET PER SECOND PER FOOT OF WIDTH UNDER UNITY HYDRAULIC GRADIENT RELATIONSHIP OF MINIMUM HEIGHT OF ARTIFICIAL RECHARGE MOUND, TRANSMISSIBILITY OF AQUIFER, AND RATE OF RECHARGE DEPARTMENT OF WATER RESOURCES 1957 PLATE 30 LEGEND — 5—- RATE OF ARTIFICIAL RECHARGE OF AQUIFER IN CUBIC FEET PER SECOND PER MILE OF RECHARGE LINE PER SECOND PER FOOT OF WIDTH RflDIENT tTIFICIAL RECHARGE MOUND, RATE OF RECHARGE PLATE 30 LEGEND -5— RATE OF ARTIFICIAL RECHARGE OF AQUIFER IN CUBIC FEET PER SECONO PER MILE OF RECHARGE LINE PER SECOND PER FOOT OF WIDTH RAOIENT tTIFICIAL RECHARGE MOUND, RATE OF RECHARGE PLATE 31 INJECTION WELLS SUPPLY PIPE LINE I CONNATE WATER LEGEND i»— — —— COLORADO RIVER WATER DISTRIBUTION LINES I : A SAND I; •'.*•'•.•] GRAVEL | SILT, CLAY, AND SHALE I * > DIRECTION OF GROUND WATER MOVEMENT ^5$»*, INTERFACE BETWEEN SCA AND FRESH WATER P*> STATE OF CALIFORNIA DEPARTMENT OF WATER RESOURCES DIVISION OF RESOURCES PLANNING SEA-WATER INTRUSION IN CALIFORNIA WEST COAST BASIN EXPERIMENTAL PROJECT PLAN UNDER INVESTIGATION FOR CONTROL OF SEA-WATER INTRUSION IN LOS ANGELES COASTAL PLAIN DEPARTMENT OF WATER RESOURCES 1957 • / THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW BOOKS REQUESTED BY ANOTHER BORROWER ARE SUBJECT TO RECALL AFTER ONE WEEK. RENEWED BOOKS ARE SUBJECT TO IMMEDIATE RECALL JUH 5 1979 RECEIVED S£p SEPu-iVd90 0^5 PHYS SCI LIBRARY j&f;Uo dec 10 1996^ JUNl* 1982 RECEIVED JUIU? — c SEP 2? 199° 3CI MBRABY1 LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS Book Slip-Series 458 ?1iO>iP9 California. Dept. of water resources. T1..-1 T _x i «. W4 ( PHYSICAL SCIENCES LIBRARY Call Number: LIBRARY UNIVERSITY OF CALIFORNIA DAVIS 240489