557 IL6of 1997-3 (W-^^i ORANGEVILLE POTENTIAL WETLAND COMPENSATION SITE: FINAL HYDROGEOLOGIC CHARACTERIZATION REPORT Illinois Route 26, near Orangeville Stephenson County, Illinois (Federal Aid Project 316) James J. Miner Christine S. Fucciolo Coastal and Wetlands Geology Unit Illinois State Geological Survey 615 East Peabody Drive Champaign, IL 61820-6964 Submitted Under Contract No. AE89005 to Illinois Department of Transportation Bureau of Design and Environment, Wetlands Unit 2300 South Dirksen Parkway Springfield, IL 62764 March 3, 1997 Illinois State Geological Survey Open File Series 1997-3 JUL 1 7 1998 IL GftOL iohvtr ORANGEVILLE POTENTIAL WETLAND COMPENSATION SITE: FINAL HYDROGEOLOGIC CHARACTERIZATION REPORT Illinois Route 26, near Orangeville Stephenson County, Illinois (Federal Aid Project 316) James J. Miner Christine S. Fucciolo Coastal and Wetlands Geology Unit Illinois State Geological Survey 615 East Peabody Drive Champaign, IL 61820-6964 Submitted Under Contract No. AE89005 to Illinois Department of Transportation Bureau of Design and Environment, Wetlands Unit 2300 South Dirksen Parkway Springfield, IL 62764 March 3, 1997 Illinois State Geological Survey Open File Series 1997-3 • \ h\ J r4|-I 'C-T J \~jT \ At^t I -i J > yA- :' j, Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/orangevillepoten19973mine EXECUTIVE SUMMARY The hydrogeology of a potential wetland compensation site on the Richtemeyer farm near Orangeville, Illinois (FAP 316), was studied between February 1994 and December 1996. The study area is located in the floodplain of Richland Creek adjacent to the western wall of the creek valley. Bedrock is exposed in the valley wall, but is covered by thin glacial sediments in the upland west of the study area and by thicker alluvial sediments in the floodplain where the compensation site is located. Alluvial sediments underlying the site are composed of 3 m of clayey silt (unit C) overlying greater than 2 m of sandy gravel (unit B). No surface-water inputs such as ditches or streams were seen, although some overland sheet flow from neighboring parcels is likely. In addition, Richland Creek floods the site, but not every year. Precipitation infiltrates through glacial sediments on the upland to the west of the study area into the underlying bedrock, then flows toward the valley of Richland Creek. At the face of the valley walls, ground water discharges from the bedrock into unit B, where it flows eastward. In the study area, upward ground-water flow is present throughout the year and suggests that ground water flows from unit B upward into unit C. This upwelling occurs to within about 1 m or less of land surface throughout the year at most wells. Ground water in unit C flows through the study area from southeast to the northwest, but is likely altered by artificial drainage because land surface slopes downward to the southeast. Wetland hydrology is not regularly present, and given that no hydric soils are mapped, it is not likely that wetland hydrology was present immediately prior to drainage. Therefore, removal of artificial drainage alone should not cause wetland hydrology to occur. Because ground-water upwelling is likely the primary source of water for the planned compensation site, it would be necessary to excavate in order to intercept the upwelling ground water for a sufficient duration to cause wetland hydrology. Monitoring well measurements and a simplified ground-water model of the parcel suggest that excavation on the order of 75 cm is recommended between wells 2, 3, and 5 in the acreage required for compensation. This depth of excavation is expected to cause saturation to land surface, but no permanent inundation. A spillway that prevents standing water greater than 50 cm in depth should be installed in case more water is available than predicted. All available land outside the main area of excavation should be graded inward at about 50:1 so that additional runoff of precipitation will be available to support the wetland compensation site. Additional recommendations include routing all roadway drainage away from or around the compensation site to reduce road salt input, and removing of all field tile in the study area. It should be noted that farms to the north may drain into Richland Creek through the tile system in the parcel, so that rerouting drainage into or around the excavation may be necessary to prevent unintended offsite saturation. The text and illustrations in this document have received only limited scientific and editorial review. CONTENTS EXECUTIVE SUMMARY ii INTRODUCTION 1 METHODS 2 GEOLOGY 3 Regional Setting 3 Site Characterization 3 Regional Geologic History 4 HYDROLOGY 4 Regional Setting 4 Climate 4 Site Characterization 5 COMPENSATION POTENTIAL OF THE PARCEL 13 RECOMMENDATIONS 14 SUMMARY 14 ACKNOWLEDGMENTS 15 REFERENCES 16 APPENDIX A Geologic Cross Sections and Logs of Borings 17 Part 1 Index of Geologic Symbols 17 Part 2 Geologic Cross Sections 18 Part 3 Geologic Logs of Borings 19 APPENDIX B Water-Level Elevations and Depths to Water Below Land Surface 28 APPENDIX C Well Construction Information 30 APPENDIX D Description of the Ground-Water Model 31 FIGURES 1 Location map showing the Richtemeyer parcel 1 2 Site map showing the Richtemeyer parcel and locations of borings, monitoring wells, stage gauge A, and the line of cross section 2 3 Precipitation data for the region 5 4 Water-level elevations recorded in upper (U) monitoring wells and at stage gauge A 7 5 Depth to water below land surface in upper (U) monitoring wells 8 6 Ground-water flow directions 9 7 Water-level elevations recorded in lower (L) monitoring wells 10 8 Depth to water below land surface measured in lower (L) monitoring wells 1 1 9 Potential for flow between units B and C 12 TABLES B1 Water-level elevations 28 B2 Depths to water in wells 29 C1 Construction information for monitoring wells 30 IV INTRODUCTION This report was prepared by the Illinois State Geological Survey (ISGS) to provide the Illinois Department of Transportation (IDOT) with final conclusions regarding the hydrogeologic conditions in a portion of the Dean Richtemeyer farm near Orangeville, Illinois (fig. 1). The parcel (fig. 2) described below contains the proposed compensation site for wetland impacts projected for the construction of the Illinois Route 26 by-pass around Orangeville (FAP 316). The purpose of this report is to identify the hydrogeologic conditions within the parcel and to make recommendations regarding the design of the proposed wetland compensation site. This report includes ground- and surface-water level data collected between February 1994 and December 1996. Monitoring has been discontinued until post-construction monitoring is required. The majority of the parcel is located in the SE%, SWJ4, SW%, Section 36, T29N, R7E, approximately 0.5 kilometers (km) west of Illinois Route 26 on the north side of St. James Road, about 0.5 km southwest of Orangeville. The southeasternmost portion of the parcel is located in SW14, SW!4, SE 1 /4, Section 36. The study area is located in the valley of Richland Creek, and is bounded on the east by an abandoned railroad track embankment and on the west by the wall of the Richland Creek valley. Figure 1 Location map showing the Richtemeyer parcel (shaded) on the Orangeville, IL, 7.5-minute topographic map (U.S. Geological Survey 1971). Contour interval is 10 ft (3 m). • geologic boring and monitoring well(s) ■ stage gauge ■ farm building Figure 2 Site map showing the Richtemeyer parcel (shaded) and locations of borings, monitoring wells, stage gauge A, and the line of cross section. Map based on USGS (1971). METHODS The geology of the parcel was characterized by drilling five borings (1 through 5) (fig. 2) using a Mobile B-57 drilling rig. Split-spoon samples 0.45-meter (m) long were collected every 0.75 m in depth. Geologic logs for each boring were prepared, and are shown in Appendix A. The hydrology of the parcel was characterized by measuring ground-water levels in monitoring wells (fig. 2) installed at various depths in each geologic boring. Upper (U) and lower (L) monitoring wells were installed in each boring except 4, which has only a lower (L) well. Monitoring wells were installed in open boreholes after auger withdrawal; nested monitoring wells were installed in the same borehole. Surface-water levels in Richland Creek were measured at stage gauge A (fig. 2). Water-level elevations and depths to water in wells and at the stage gauge are reported in Appendix B, and are rounded to the nearest 0.01 m. Measurements were made monthly. Well casing and screen consisted of 2.5-centimeter (cm) diameter PVC pipe. Well screens were 0.76 m in length, and contained slots 0.25-millimeter (mm) wide. Well screens were packed with quartz sand 0.25 to 0.50 mm in diameter. Borings were backfilled to 0.5 m below land surface with bentonite, then were sealed to land surface with concrete. Wells were developed by pumping the wells with a peristaltic pump until clear water was obtained or until dry; well 1 L was not pumped due to its greater depth. Appendix C lists all well-construction measurements. The elevations of the stage gauge and wells were determined by leveling to third-order accuracy using a Sokkia B-1 automatic level and a fiberglass extending rod. Elevations given in this report are referenced to the National Geodetic Vertical Datum (1929) and were surveyed to a benchmark established on site by IDOT. GEOLOGY Regional Setting Topography The study area is located in the valley of Richland Creek. Total relief from the top of the valley walls west of the study area to the bottom of Richland Creek is about 40 m (fig. 1) (U.S. Geological Survey 1971). However, the compensation site and most of the study area lies on the floodplain of Richland Creek and has total relief of less than 1 m. Richland Creek slopes from north to south about 0.75 m/km (U.S. Geological Survey 1971). Bedrock Bedrock crops out in the valley walls that mark the western boundary of the study area, but is buried by sediment within the study area and on top of the valley walls west of the study area. Exposed bedrock is composed of shaly to cherty limestone and dolomite of the Ordovician Galena and Platteville Groups, as described in a quarry located about 1 km to the south (Willman and Kolata 1978). Sediments In the floodplain of Richland Creek, bedrock is overlain by unlithified Quaternary sediments up to approximately 8 m thick (Piskin and Bergstrom 1975), consisting of sand, silt, and clay of the Wisconsinan to Holocene Cahokia Alluvium (Willman and Frye 1970, Berg and Kempton 1988). On the uplands west of the study area, sediments are less than 8 m thick (Piskin and Bergstrom 1975) and are mapped as less than 6 m of Wisconsinan Stage Roxanna Silt overlying less than 6 m of Glasford Formation silty and clayey diamictons of the lllinoian Stage (Berg and Kempton 1988). Diamicton is a term used to describe all very poorly sorted sediments, such as glacial tills and debris flows, without implying an origin of the deposit. Soils Soil in the majority of the parcel is mapped as somewhat poorly to moderately well-drained Dorchester silt loam, with a small body of well-drained Downs silt loam present along the valley wall on the west edge of the parcel (U.S. Department of Agriculture 1976). The soils mapped in the parcel are not listed as hydric (U.S. Department of Agriculture 1991). Site Characterization A cross section showing site geology is presented in Appendix A. The line of cross section is shown in figure 2. The lowermost geologic unit found at the study area consists of dolomite bedrock (unit A). About 2 m of unit A was penetrated in boring 1 , located near the valley walls. The top of the bedrock was degraded and broken into gravel. This unit was not encountered in other borings, and is presumed to slope downward sharply to the east into the center of the valley of Richland Creek. Bedrock is exposed in places along the valley walls, and is similar to that encountered in boring 1 . This unit is Ordovician in age, and is likely part of the Platteville Group, possibly the Quimby's Mill Formation (Willman and Kolata 1978). Overlying the bedrock in the study area is unit B, which is dominantly a sandy gravel. This unit is found in all borings, but was fully penetrated only in boring 1 , where it was about 2.5 m thick. This unit has a variable texture, including sand, gravel, and sandy silt. The base of this unit dips to the east, where it thickens toward the center of the river valley. This unit is mapped as Cahokia Alluvium (Berg and Kempton 1988), but the coarse gravel content of site deposits is inconsistent with normal descriptions of the Cahokia Alluvium. Given this inconsistency, it is difficult to assign this unit to a formation, but this unit was likely deposited during the major erosional episodes that formed the main river valleys in the area, and therefore may be late Wisconsinan in age or older. Therefore, the unit may instead belong to the Henry Formation. Overlying unit B in all borings is a clayey silt (unit C). Unit C ranged in thickness between 3 and 3.5 m. The lower portion of this unit was generally gleyed in color and contained plant material, shells, and wood fragments, indicating slow deposition in a wetland or frequently anaerobic environment; upper portions appear to be more oxidized. Fine sandy laminae in the unit indicate regular input of flood waters. Given the origins suggested by these sedimentary structures, unit C was likely formed by aggradation on the low-gradient floodplain of Richland Creek; poorly drained portions of the floodplain contained wetlands that preserved organic material and received intermittent silt and sand from floods and wind deposition. In parts of the floodplain, the sediment package built up beyond the reach of regular flooding, causing the soils including those in the parcel to be nonhydric. Also, anthropogenic entrenchment of the stream may have reduced regular flooding of the site. Unit C is likely classified as Cahokia Alluvium, and was formed in the Late Wisconsinan Subage and the Holocene Age. Regional Geologic History lllinoian glaciers advanced over this region and deposited diamicton and glacially derived sediments. These sediments have been preserved at land surface in upland areas. Afterward, major rivers eroded through the glacial deposits and into the bedrock, forming bedrock-walled valleys. This erosion may have been enhanced by permafrost action caused by nearby Wisconsinan glaciers that did not override this area. Some aggradation in river valleys later occurred, likely during the Late Wisconsinan Subage and Holocene Age, forming the alluvial deposits found in the floodplains. HYDROLOGY Regional Setting Water-well records for this area indicate that water for most private homes is withdrawn from the St. Peter Sandstone encountered at a depth between 15 and 30 m. Surface water flows eastward into the creek valley from the upland area that extends from 0.4 to 0.8 km to the west of the study area. Within the Richland Creek valley and the study area, land surface slopes downward to the south. No obvious ditches or streams flow into the parcel, so that surface drainage may take the form of overland sheet flow. Landowner Dean Richtemeyer stated that Richland Creek floods the parcel every few years. The floodplain of Richland Creek has an extensive drainage network, including drainage tiles and ditches. Mr. Richtemeyer stated that drainage tiles and tile mains run through the parcel. Climate Total average annual precipitation in the region is approximately 86 cm. Precipitation is highest in May through September, when more than about 8 cm per month falls on average (U.S. Department of Agriculture 1976). Most ground-water recharge in Illinois is estimated to occur during spring, fall and winter when evapotranspiration is low (Hensel 1992). The growing season is defined as the period of time when soil temperatures exceed 5°C at a depth of 0.5 m (U.S. Army Corps of Engineers 1987). Where soil-temperature data are unavailable, the growing season can be approximated as the period between the last killing frost of the spring and the first killing frost of the fall. A killing frost occurs at an air temperature of -2.2°C (U.S. Department of Agriculture undated, U.S. Department of Agriculture 1994). In Stephenson County, the average dates for this period are April 24th and October 15th, giving a growing season of 174 days (U.S. Department of Agriculture 1976). I lAverage 1961-1990 —♦—1994 -■-1995 -A- 1996 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 3 Precipitation data for the region, including average monthly precipitation between 1961 and 1990 and monthly precipitation recorded during the monitoring period at Freeport, Illinois (Midwestern Climate Information Center). Monthly precipitation during the monitoring period is presented as a two-month running average [e.g. June=(May+June)/2]. During the monitoring period, climatic conditions were quite variable. Figure 3 shows precipitation recorded about 15 km south of the study area at the Freeport Sewage Treatment Station, obtained from the Illinois State Water Survey's Midwest Climate Center in January 1 997. Average monthly precipitation is shown from the 1961 through 1990 period. Precipitation recorded during the monitoring period is presented as a running two-month average [e.g. June = (May + June)/2]. This type of averaging smooths the data and shows the long-term trends more clearly. Monthly precipitation ranged between much below average and well above average. In 1 994, precipitation was below average in March through June, and above average in July through December. In 1995, precipitation was above average in May and in October through December, but below average in March and in June through September. In 1996, precipitation was below average in March, April, and September, then above average in May, June, and July. For the entire year, precipitation was 99% of average in 1 994, 1 04% of average in 1995, and 110% of average in 1996. Site Characterization Ground Water The purpose of the hydrogeologic investigation was to identify aquifers, aquitards, and flow paths in the study area, and to identify sources of water available to sustain wetlands in the proposed compensation area. Monitoring wells were installed in various geologic units throughout the study area to 1 ) identify water levels within each unit, 2) determine ground-water gradients, 3) estimate ground-water flow directions, 4) estimate source areas for ground-water input, and 5) determine the extent of wetland hydrology at the study area. Water levels measured during the monitoring period are presented in Appendix B. Water-level measurement began in February 1994 and ended when characterization was completed in December 1996. Ground-water conditions in unit C Unit C underlies the entire study area at land surface. Ground-water conditions in this unit will indicate whether wetland hydrology is already present onsite. Because understanding the horizontal and vertical ground-water flow directions in unit C helps show how water moves through the study area and indicates potential water sources to be used in the design of the compensation site, the upper monitoring wells (U) were installed in this unit. Water-level elevations and depths to water below land surface recorded in these wells are shown in figures 4 and 5, respectively. Surface-water elevations in Richland Creek, measured at stage gauge A, are also shown in figure 4. As stated in the 1987 Wetlands Delineation Manual (U.S. Army Corps of Engineers 1987), the existence of wetland hydrology depends on the period of time sediments are saturated to within 0.3 m of the land surface. If that saturation level is exceeded for 12.5% of the growing season then wetland hydrology is shown to exist, if between 5% and 1 2.5% then wetland hydrology may exist, and if less than 5% then wetland hydrology does not exist. Given that the study area has a growing season estimated to be 174 days, 12.5% of the growing season is 22 days, and 5% is 9 days. During the growing season, no water levels were recorded within 0.3 m of land surface for any significant length of time except for well 5U, which is located in a 0.2-hectare (ha) area near the valley wall where cattail and bulrush are present. No hydric soils are mapped and no obvious seepage or springs were observed in this area, although a "wet spot" is shown on the soil survey map at this location, and the soil unit is known to contain hydric inclusions (U.S. Department of Agriculture 1993). Wetland hydrology at well 5U was positively indicated by measurements made in spring 1994 and in summer 1996, when record amounts of rainfall occurred in northern Illinois. Given that most wetlands in Illinois show wetland hydrology in the spring then dry up in summer, the higher water levels recorded in summer 1996 are probably abnormal and should not be expected to occur regularly. Therefore, wetland hydrology occurred in only one out of the three monitoring years. Because wetland hydrology should occur in one out of every two years on average (National Research Council 1995, U.S. Army Corps of Engineers 1987, U.S. Department of Agriculture undated), and because average precipitation was received in each of the three monitoring years, this area is not likely wetland or is only wetland in a small portion of this 0.2-ha area where ground-water discharge may be more concentrated. In any case, conditions near well 5U are probably affected by ground-water discharge at the base of the bluff and are not indicative of the rest of the parcel. Ground-water flow directions in unit C change in relation to precipitation conditions. Ground water in unit C most often flows to the north or northwest, but during times of heavy precipitation events or snow melt, ground water flows to the east or southeast. Figure 6 shows the direction of ground-water flow in April 1995 and June 1996, which were periods of average and above average precipitation, respectively. Given that land surface slopes downward to the southeast, the expected flow direction in unit C would be to the southeast toward Richland Creek. The field tiles that artificially lower water levels in unit C may be causing altered ground-water flow paths except when the volume of water input exceeds output through the tile. Ground-water conditions in unit B Unit B is a sand and gravel aquifer that underlies the entire study area at a depth of 3 to 3.5 m. Figure 7 shows water levels in unit B, which was saturated during drilling. Wells 2L through 5L were installed in this unit to determine horizontal and vertical ground-water flow directions through unit B. Well 1L, which likely reflects water levels in the carbonate bedrock of unit A as discussed below, is also shown on this figure. Water levels in unit B showed significantly less fluctuation than the wells in unit C, indicating that the unit likely receives steady input from a regional aquifer such as unit A. Ground water flows => 3 3 3 m i- c\i co in g, CD 0) Q) Q) HH! 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CD O CO t 3 co c I CD .Q ._ CD *- CO o w .C C S2 o in -° (lu u|) s||9m jeddn uj aoejjns puei M0|eq jaje/v\ oj ijidaQ CO £ to 3. ® u> > 17 CD • geologic boring and monitoring well(s) ■ stage gauge ■ farm building Figure 6 Ground-water flow directions during normal precipitation (April 1995) and during heavy precipitation (June 1996), inferred from water levels recorded on each respective date (June 1996 levels shown in italics, April 1995 in normal typeface). generally eastward from the valley walls toward Richland Creek, but may vary to the southeast or northeast given changing climatic conditions. No obvious correlation of flow direction to precipitation conditions was observed. Figure 8 shows the depth to water measured in wells 1 L through 5L. Water levels in unit B (wells 2L through 5L) are within about 1 m of land surface throughout the year, indicating that unit B is confined and has potential for flow upward into unit C. Figure 9 shows the potential for flow between units B and C by comparing levels observed in upper and lower wells at each well location. Upper wells are installed in unit C, and lower wells are installed in unit B. The upward potential observed at most wells indicates that ground water flows upward from unit B to unit C throughout much of the year with the exception of well 2L, which only has an upward gradient during periods of high precipitation. Ground-water conditions in unit A Unit A is composed of carbonate bedrock. It was only encountered in boring 1 near the valley wall, and is likely present at depth throughout the study area. The bedrock is exposed in the valley walls at the western boundary of the study area, but is covered by sediment in the valley floor to the east and in the adjacent upland to the west. Well 1 L was installed above the natural collapse of borehole 1 after penetration to bedrock. Upward flow through the collapsed portion of the borehole likely causes water levels in well 1 L to reflect levels present in unit A. Figure 7 shows that water levels noted in this well are much higher than in all other wells. Water in this unit is capable of discharging upward into units B and C and up to land surface throughout the year. (D q Q) Q) Q) 5 5 § § § + + H + Z6uer 96 aon 96 das 96inr 96 Aeiftj 96JBIAI 96 uer 96 aon S6des S6inr 96Abiaj 96JBIAJ 96 uer fr6AON fr6dss fr6 inr WAbim ^JBIAI CO .a E O Q -o c CO ■*■ CD O) ^ CO 3 -Q u_ c I O) c c o E o "2 o CJ w c g 1 o ID O in 8 3 5! 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Q 12 Given that bedrock is present in the uplands to the west of the study area, it is likely that precipitation infiltrates to the bedrock in the uplands, then flows through the bedrock along fractures and bedding planes toward the Richland Creek valley, where it discharges into units B and C. Some ground-water discharge to land surface at the base of the valley wall is evident from wetter conditions observed when the rest of the parcel is dry (e.g. near boring 5), but no springs or seeps were observed. Surface Water Surface waters near the parcel include Richland Creek, located to the east. Stage gauge A was installed in Richland Creek. Water levels recorded at that gauge are shown in figure 4. Water levels in the creek have been relatively constant, and have not been recorded as high enough to flood the study area. However, given that the creek floods the parcel occasionally as noted by the landowner, and that local history notes flooding problems in Orangeville (Barrett 1972), monthly measurements may not adequately characterize the highest flood peaks. The raised railroad bed along the east side of the parcel likely does not prevent flooding by Richland Creek due to a farm-implement underpass just north of St. James Road. No other ditches or streams are present that flow into the parcel. Some sheet flow from adjacent parcels to the north and west likely occurs. COMPENSATION POTENTIAL OF THE PARCEL Wetland hydrology was not observed regularly at any wells in the study area during the monitoring period. Because hydric soils were not mapped in this area, it is not likely that wetland hydrology was present in this area prior to artificial drainage caused by the placement of field tiles. Therefore, removal of field tiles alone will not likely produce wetlands, so that the establishment of wetlands in the compensation area is not restoration, but creation. Wetland creation is not a preferable compensation alternative because it is difficult to measure accurately all the hydrogeologic factors involved, and the balance between the factors may be altered unpredictably by construction. To create wetland in nonwetland locations, it is necessary to either increase the amount of surface water available to the site or to excavate so that the water table would more closely approach the land surface for longer periods during the growing season. There is no surface- water source to divert or retain on site; Richland Creek is too deeply incised to flood the site annually. Therefore, the only option would involve excavation of the land surface. Ground water in the compensation area flows upward from unit B to within about 1 m of land surface or closer throughout the monitoring period. Excavation of land surface to intercept that upwelling may create wetland hydrology. Field tiles in the parcel should also be removed, but any drainage coming into the site through the interconnected tile system from farms to the north should not be interrupted. The amount of excavation necessary to create a wetland in the parcel is difficult to predict. Based on the depths to water measured in unit B (fig. 5), the minimum amount of excavation that would be required to create wetland hydrology near wells 2, 3, and 5 is about 60 cm. This does not account for the additional evapotranspiration (ET) that would occur after excavation, so that additional excavation is likely needed. It is difficult to predict the amount of additional excavation, because the ground-water system will adjust to the new situation by altering flow paths. However, a simplified ground-water model was created for the site and suggests that an additional 15 cm of drawdown may occur due to increased ET, so that a total of 75 cm of excavation is needed to create saturation to land surface. A description of the ground-water model is found in Appendix D. This model was made using an average of conditions 13 experienced throughout the year, so that in the summer the wetland is expected to dry out, and be inundated for some portion of the fall, winter, and spring. RECOMMENDATIONS Excavation of the proposed compensation site in the area between borings 2, 3, and 5 to a depth of 75 cm is recommended to create and sustain wetland hydrology. Excavation to this depth should be made in the acreage required to meet the needs of the construction project. Side slopes of about 50:1 should be added outside of the main excavation using all available land. The additional area of sloping sides would increase the amount of surface-water runoff into the excavation. A spillway leading to a drainageway should be constructed on the south end of the excavation so that water depths in the excavation will not exceed 50 cm, above which vegetation establishment may be inhibited. This spillway would be active during times of heavy precipitation or if more water is available at this site than predicted by the model. This spillway and drainageway should be protected from erosion by riprap or concrete, then vegetated. Additionally, drainage from the roadway should not be diverted into or through the compensation site. High concentrations of road salt can be extremely detrimental to wetland creation projects, causing plant mortality and/or an invasion of undesirable plant species. In order to minimize compaction and siltation, excavation should only be performed in dry or frozen conditions using excavators equipped with tread specifically designed to minimize compaction. Field tiles that drain the compensation area must be removed so that water levels in unit C are allowed to rise. It should be noted that field tiles that run through the compensation area are believed to carry water drained from fields north of the study area to Richland Creek to the south, so that unintentional saturation of offsite areas may result if tile mains are removed. These tile mains may be left undisturbed if the laterals in the field tile system that drains the compensation site are removed. Although diversion of the tile main discharge into the compensation site may provide an additional margin of safety by increasing water available to the mitigation site, agricultural chemicals may be contained in tile discharge. SUMMARY The hydrogeology of the Orangeville potential wetland compensation site was described and monitored between February 1994 and December 1996. The parcel is located in the Richland Creek valley located about 0.5 km southwest of Orangeville and is located in the floodplain of Richland Creek adjacent to the valley wall on the west. Total relief in the compensation area is less than about 0.5 m, but land surface rises abruptly about 40 m to the top of the upland west of the study area. Bedrock is exposed in the walls of the river valley, but is overlain by thin glacial sediments in the upland to the west and by thicker floodplain sediments in the valley of Richland Creek to the east. Ground water infiltrates through the upland sediment into the bedrock, where it flows toward the river valley and discharges into sediments of units B and C. A small amount of discharge to land surface at the base of the valley walls also occurs, but no seeps are present. Water levels in monitoring wells show that no areas of wetland hydrology regularly occur. Near well 5U, some wetland vegetation occurs and wetland hydrology was present during spring in 14 one of the three monitoring years. Water levels in unit C are likely lowered artificially by drainage tiles, but because hydric soils are not mapped in the parcel, it is not likely that tile removal alone will restore wetland hydrology over any significant portion of the site. Ground- water flow in unit C is most often from southeast to northwest, and is likely altered by drainage. Monitoring wells screened in unit B show artesian conditions throughout the monitoring period. Water levels indicate the potential for upward ground-water flow to within about 1 m of land surface or closer throughout the monitoring period. Ground-water flow through unit B is generally eastward. There are no streams or ditches that supply water to the parcel, although some overland flow may occur from the field to the north or from the valley walls to the west. Richland Creek does not flood the parcel annually. Therefore, no obvious source of surface water is available to regularly supply the compensation site. The primary source of water in the proposed compensation site is expected to be ground-water discharge. Excavation would be required so that land surface would intercept upward flow and cause saturation sufficient to satisfy wetland-hydrology criteria. This excavation is expected to be on the order of 75 cm in the area between borings 2, 3, and 5. A spillway on the south end of the excavation is recommended to prevent inundation greater than 50 cm in depth, which could inhibit plant establishment. This would also allow discharge from the excavation if more water is available than predicted. All available area outside the acreage required for compensation should be graded inward at a slope of about 50:1 to increase surface-water input. Field tile in the parcel should be removed in the construction process, but saturation of offsite areas is a possibility given that areas to the north are believed to drain southward through the field tile in the parcel. Discharge from these tile mains should be rerouted so that drainage of offsite areas is not affected. No drainage from the roadway should be allowed to flow into the compensation area. Road-salt use increases chloride levels above general use standards in many roadside compensation sites, which is detrimental to successful wetland establishment. ACKNOWLEDGMENTS Funding for this study was provided primarily by the Illinois Department of Transportation under contract number AE89005. Additional funding was provided by ISGS. David Larson, Steven Benton, and Nancy Rorick of ISGS reviewed this report. Philip DeMaris and Alison Meanor of ISGS monitored wells at the site. 15 REFERENCES Barrett, J. W., 1972, A History of Stephenson County, 1970: County of Stephenson, Freeport, Illinois, 679 p. Berg, R. C, and J. P. Kempton, 1988, Stack unit mapping of geologic materials in Illinois to a depth of 15 meters: Illinois State Geological Survey Circular 542, Champaign, Illinois, 23 p. Freeze, R. A., and J. A. Cherry, 1979, Groundwater: Prentice-Hall, Inc., Englewood Cliffs, NJ, 604 p. Hensel, B., 1992, Natural Recharge of Groundwater in Illinois: Illinois State Geological Survey Environmental Geology 143, Champaign, Illinois, 33 p. Midwestern Climate Information Center, January 1997, Illinois State Water Survey, Champaign, Illinois, available on line at www.mcc.sws.uiuc.edu. National Research Council, 1995, Wetlands Characteristics and Boundaries: Committee on Characterization of Wetlands, National Academy Press, Washington, D.C., 308 p. Piskin, K., and R. Bergstrom, 1975, Thickness of Glacial Drift in Illinois: Illinois State Geological Survey Circular 490, Champaign, Illinois, 34 p. U.S. Army Corps of Engineers, 1987, Corps of Engineers Wetlands Delineation Manual: U. S. Army Corps of Engineers Technical Report Y-87-1, Washington, D.C., 100 p. U.S. Department of Agriculture, undated, Natural Resources Conservation Service, undated, ECS Hydrology Tools for Wetland Determination: National Employee Development Center, 268 p. U.S. Department of Agriculture, Soil Conservation Service, 1976, Soil Survey, Stephenson County, Illinois: Washington, D.C., 133 p. U.S. Department of Agriculture, Soil Conservation Service, 1991, Hydric soils of Illinois (rev. January 31, 1992), in Hydric Soils of the United States: Miscellaneous Publication No. 1491, Washington, D.C. Also, the list revised December 15, 1995 is available on line at www. statlab.iastate.edu:80/soils-info/hydric/il. html. U.S. Department of Agriculture, 1993, unpublished data base of soils with hydric inclusions in Stephenson County, Illinois: National Resources Conservation Service, Champaign, Illinois. U.S. Department of Agriculture, Soil Conservation Service, 1 994, 1 80-V-NFSAM (National Food Security Act Manual) Glossary, Part 525, Third Edition. U.S. Geological Survey, 1 971 , Orangeville Quadrangle, Illinois, 7.5-Minute Series (Topographic): U.S. Department of the Interior, Geological Survey, Reston Virginia, map scale 1:24,000, 1 sheet. Willman, H., and J. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, Champaign, Illinois, 204 p. Willman, H. B., and D. R. Kolata, 1978, The Platteville and Galena Groups in Northern Illinois: Illinois State Geological Survey Circular 502, Champaign, Illinois, 75 p. 16 APPENDIX A Geologic Cross Sections and Logs of Borings at the Orangeville Site Part 1 Index of Geologic Symbols "B 7, o B n o 1 n a ° n n Sandy gravel Gravelly sand Sand _-_-_-. Silty sand Clayey sand Sandy silt Silt Clayey silt Sandy clay Silty clay A A A A A A . A A A A A A A A A A A Diamicton Peat V//// I / / / I^Ta Muck Organic material Dolomite (bedrock) No recovery Clay 17 APPENDIX A continued Part 2 Geologic Cross Section (line of cross section shown on figure 2) < i < z g i- o LU CO CO CO o o CO LU T ~ < - T3 c o £ £ o r-iT) ♦2 2 X o D5 CJ> co x a> o '■E a) > CM CO CM IT) ■<* CM •«* co cm rr •* ^ S: S C\J CM CM