557 IL6of ^ 1991-12 gfM "j r, 10«* HYDROGEOLOGY OF SHALLOW GROUNDWATER RESOURCES, AURORA AND VICINITY, KANE COUNTY, ILLINOIS Timothy H. Larson Stephen S. McFadden Robert H. Gilkeson Open File Series 1991-12 ILLINOIS STATE GEOLOGICAL SURVEY Morris W. Leighton, Chief Natural Resources Building 615 East Peabody Drive Champaign, Illinois 61820 LIBRARY. % OFS 1111-13. C 2. era * %»! ionl HYDROGEOLOGY OF SHALLOW GROUNDWATER RESOURCES, AURORA AND VICINITY, KANE COUNTY, ILLINOIS Timothy H. Larson Stephen S. McFadden Robert H. Gilkeson Open File Series 1991-12 ILLINOIS STATE GEOLOGICAL SURVEY Morris W. Leighton, Chief Natural Resources Building 615 East Peabody Drive Champaign, Illinois 61820 11 CONTENTS ABSTRACT 1 INTRODUCTION 1 METHODOLOGY 1 Well Records 1 Surficial Geophysical Surveys 3 Test Drilling 3 GEOLOGIC FRAMEWORK 4 Stratigraphy 4 Bedrock Surface Topography 9 Drift Thickness 9 HYDROGEOLOGY 9 Upper Bedrock Aquigroup 1 Prairie Aquigroup 1 St. Charles aquifer 12 Marengo aquitard 12 Kaneville member, Elburn aquiformation 12 Pingree Grove aquiformation 15 SUMMARY 15 ACKNOWLEDGMENTS 17 REFERENCES 17 FIGURES 1 Location of the study area in Kane County 2 2 Stratigraphy of rocks underlying Aurora area 5 3 Areal geology of the bedrock surface 6 4a Stratigraphy of glacial drift (Prairie Aquigroup) underlying the Aurora area 7 4b Surficial drift map of Aurora area 8 5 Elevation of the bedrock surface 10 6a St. Charles aquifer, Prairie Aquigroup, a major aquifer in the Aurora area 13 6b Kaneville aquifer member, Prairie Aquigroup, a major aquifer 14 in the Aurora area 7a Cross section of the St. Charles bedrock valley in northwest Sugar 15 Grove Township 7b Cross section of the glacial materials east of Aurora 16 7c East-west cross section of the Aurora bedrock valley southwest of Sugar Grove 16 Releasedbyauthority ofthe State of Illinois/ 1991 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/hydrogeologyofs9112lars ABSTRACT The St. Charles aquifer, a highly productive sand and gravel aquifer, is present in the Aurora and St. Charles bedrock valleys, buried about 100 to 150 feet deep beneath ground surface. Within the St. Charles bedrock valley, the aquifer is locally more than 100 feet thick in the northwestern part of the study area. A shallower sand and gravel aquifer, the Kaneville aquifer member of the Elburn aquiformation, is present above the Aurora and St. Charles bedrock valleys and other parts of the area. The Kaneville aquifer member is generally less than 30 feet thick. Areas of aquifer interconnection, known for high yields, occur south of Sugar Grove. Declining water levels and high concentrations of radium and chloride in the present source of water, the deep (400 to 2,000 ft) sandstone aquifers in the Basal and Midwest Aquigroup, have made it necessary for the City of Aurora to explore other water sources. To support their investigation, the Illinois State Geological Survey has mapped the shallow aquifers of the area using a combination of existing records, surficial geophysical surveys, and test-hole drilling. Maps prepared forthis report can be used to explore further and test other areas for aquifer interconnection. INTRODUCTION Sandstone aquifers of the Basal Bedrock and Midwest Bedrock Aquigroups have supplied most of the water for northeastern Illinois. The City of Aurora in Kane County (fig. 1) has relied almost exclusively on this water source. However, declining water levels due to overpumping (Sasman et al. 1982) and high concentrations of naturally occurring radium and chlorides in these aquifers (Gilkeson et al. 1984) have made it advisable for the City to evaluate alternative water sources. Other possible sources of water include sand and gravel aquifers in the glacial deposits (Prairie Aquigroup), aquifers in the shallow fractured bedrock (Upper Bedrock Aquigroup), and the Fox River. This study identified the shallow groundwater resources (Upper Bedrock Aquigroup and Prairie Aquigroup) in the Aurora area, specifically in Aurora and Sugar Grove Townships (T38N, R8 and 7E) Kane County. The Illinois State Geological Survey (ISGS) has mapped the distribution of shallow aquifers. In a separate study, the Illinois State Water Survey is evaluating the hydraulic properties of the shallow aquifers. Aquifer pump tests will determine well yield, well spacing, potential aquifer yield, and shallow groundwater chemistry. Two other studies in Kane County provided additional information on the shallow groundwater hydrology of the study area. Kane County and many communities funded a regional study of the county's shallow groundwater resources. The results of this study conducted by the ISGS were reported in Curry and Seaber (1990). The Kane County area was also part of an extensive geotechnical study for siting the proposed Superconducting Super Collider (SSC). Graese et al. (1988) summarized the SSC-related investigations. METHODOLOGY Well records, surficial geophysical surveys, test borings, and existing reports and maps provided information on the glacial drift, drift thickness, bedrock surface and lithology, aquifer properties, and groundwater quality. The maps and general conclusions of this report are derived from Graese et al. (1988) and Curry and Seaber (1990). We have included specrfic information relevant to Aurora and Sugar Grove Townships and revised the maps accordingly. Well Records Well records on file at the Illinois State Geological and Water Surveys were used in the study. (Well locations are shown on fig. 1.) Well logs, recorded at the time of drilling, document the locations of wells and the geologic materials encountered during drilling. Well records included those from privately drilled wells, municipal and industrial wells, and test wells. Commonly, well ' 7 ,J 1 — r ^ icnm r / '1 CM ! _— 1 CO / (C0M • CiOn c3 O O \ - 1 <CD - co , o m CCMM CM jr UJ r* » t£ \ 3 Ol <o oo s 8- CO a> / i ' s 1 - r ! , | / » r>> CM en CCMO >. >/ * -4' '• 1* 1 p.. o r-. CO C7> CO 3 r '1 ii. ^-Sz locations described in the logs from private wells are inaccurate or very general. Private well locations were verified at the Kane County Permit Office. In most cases, descriptions of glacial drift were adequate to poor, but data on the depth to bedrock were generally considered reliable. Records of wells with unverified locations were used in areas of sparse data coverage and provided general information on geologic trends. Records of public water-supply wells for the municipalities in Kane County provided detailed and reliable data of the lithologic units. Published sources of well records in Kane County include Lund (1965), Reed (1975), Woller and Sanderson (1978), Kempton et al. (1985, 1987a, 1987b), Curry et al. (1988), and Vaiden et al. (1988). These records provided information on the depth and lithology of bedrock, and on the thickness and lithology of glacial drift. Surflclal Geophysical Surveys Seismic refraction, a surficial geophysical method, was used for detailed mapping of the bedrock topography and glacial drift thickness. (Locations are shown on fig. 1.) Seismic energy traveling through the ground is refracted back to ground surface from the interface between the glacial sediments and the bedrock. A buried explosive charge or weight-drop system was used as an energy source to produce seismic waves. Reversed profile seismic data were gathered using a 24-channel signal-enhancement seismograph. Field data were automatically processed with a modified version of a ray-tracing program (SIPT-1) written by the U.S. Bureau of Mines (Scott et al. 1972). The SIPT-1 program corrects for irregular surface terrain along the seismic profile and also calculates the depth to bedrock beneath each geophone. Geophones were spaced 50 feet apart along lines 650 feet long, or 100 feet apart along lines 1,300 feet long, depending upon the thickness of the glacial drift and seismic velocities of the materials. Anomalously great depths to bedrock are calculated from the seismic refraction method in areas where thick sand and gravel deposits are overlain by thick, clay-rich glacial till (Zohdy et al. 1974). This occurs because the sand and gravel layer has a lower seismic velocity than both the overlying till and underlying bedrock. The error in calculated depth is proportional to the thickness of the sand layer and always results in greater calculated depths to bedrock than actually exist. Because the anomalies are caused by buried sand and gravel, the anomalies are potential targets for further groundwater resource evaluation. A second surficial geophysical method, electrical earth resistivity, was used as a qualitative tool to determine-the texture of the geologic materials present in the glacial drift (fig. 1). A Schlum- berger electrode configuration was used (Zohdy et al. 1974), and the data were inverted to layering parameters using the Zohdy method (1973). In freshwater environments, sand and gravel units have a higher resistivity than finer grained deposits with greater clay content and can be easily identified by this method. Identification is difficult where the sand and gravel deposits are thin or deeply buried (McGinnis and Kempton 1961). Thickness determinations are not possible where the bedrock and overlying glacial deposits have similar resistivities, such as a fine-grained glacial till overlying shale, or coarse sand and gravel overlying dolomite. Therefore, electrical earth resistivity data were primarily used in conjunction with seismic refraction to identify sand and gravel deposits within the glacial drift. Test Drilling Test holes for new public supply sources were drilled in favorable areas identified by the geophysical surveys conducted as part of this and related local studies. Test holes were geophysically logged with a natural gamma-ray probe to identify aquifer materials and to assist in making stratigraphic correlations. Test drilling also provided the specific information required for the design of an aquifer test and production well. Favorable results from test drilling have resulted in several aquifer tests for Aurora to date. Gilkeson et al. (1987) reported on two tests and several others are summarized in Curry and Seaber (1990). A final report on the test drilling will be prepared by the Illinois State Water Survey. Test drilling in Kane County was also conducted for siting of the proposed SSC. Continuous cores of the bedrock sequence and discontinuous cores of glacial drift were collected and suites of geophysical logs were run. Results of this drilling are reported in Kempton et al. (1987a, 1987b), Curry et al. (1988), and Vaiden et al.(1988). GEOLOGIC FRAMEWORK Stratigraphy The geology of the area includes Precambrian crystalline basement rocks, Paleozoic sedimentary rocks, and Quaternary uncemented sediments. In northern Illinois, the Paleozoic history from 600 million to 245 million years ago is represented by rocks of marine origin (fig. 2) with a maximum thickness of 4,000 feet (Kempton et al. 1985). The Paleozoic rocks are overlain by Quaternary sediments as much as 150 feet thick. Bedrock The Paleozoic rocks most significant to the shallow groundwater resources in the area are the Ordovician Maquoketa Group and the Silurian Kankakee and Elwood Formations (Willman et al. 1975) (fig. 3). (The deeper aquifers are beyond the scope of this study, but are discussed in Visocky et al. [1985].) The Maquoketa Group is composed of shale, argillaceous dolomite and limestone, and interbeds of shale and dolomite; it is present at the bedrock surface in buried bedrock valleys beneath the study area. The regionally important formations of the Maquoketa include, in ascending order, the Scales Shale, Ft. Atkinson Limestone, Brainard Formation, and Neda Formation (Kolata and Graese 1983); but these cannot be readily differentiated in Kane County (Graese et al. 1988). Here, the Maquoketa consists of two sequences of basal shales that become increasingly carbonate rich. The Elwood and Kankakee Formations are composed of thin to medium-thick beds of dolomite; the Kankakee also contains abundant nodules and interbeds of chert. Because the lithology of these units is similar (Curry and Seaber 1990), they are not differentiated in this report. The distribution of Silurian dolomite (fig. 3) is determined chiefly by the buried bedrock topography. The shallow carbonate rocks are thickest where Silurian dolomite overlies the limestone and dolomite units of the upper Maquoketa Group. In the study area, this occurs on the north and east sides of Aurora, where the combined thickness of these carbonate units is generally more than 100 feet and locally exceeds 150 feet. Quaternary deposits Local stratigraphic classification of Quaternary deposits is illustrated on figure 4a; the sediments consist of glacial till, glacial outwash, glacial lakebed materials, windlblown sediments (loess), and recent deposits along steep slopes and floodplains (Curry and Seaber 1990). Distribution of the surficial drift units is shown on figure 4b. These deposits were produced in a variety of depositional environments associated with major glacial advances and retreats approximately 1.6 million to 14,000 years ago. Successive glacial advances modified the sediments deposited during earlier events and further complicated the geometry of the various units. Finally, since the retreat of the most recent glaciers, glacial deposits have been modified by erosion, predominantly in fluvial environments such as the Fox River valley. The oldest glacial sediments identified in Kane County are lllinoian and may correlate to the Glasford Formation near Rockford in Boone and Winnebago Counties (Berg et al. 1985). This includes the Herbert Till Member, which occurs as valley fill within the Aurora bedrock valley, lllinoian deposits are covered by Sangamonian and early to middle Wisconsman colluvium composed of organic carbon-rich silty deposits that have been modified by soil formation; these include the Berry Clay and Robein Silt (fig. 4). These sediments may be as much as 25 feet thick in Kane County, but more commonly, they are thin or absent (Curry and Seaber 1990).