??UL-60(28)/79 ??TIN 60-28 ?? OF ILLINOIS ILLINOIS INSTITUTE OF NATURAL RESOURCES Public Groundwater Supplies in Carroll County by Dorothy M. Woller and Ellis W. Sanderson ILLINOIS STATE WATER SURVEY URBANA 1979 PUBLIC GROUNDWATER SUPPLIES IN CARROLL COUNTY by Dorothy M. Woller and Ellis W. Sanderson Introduction This publication presents all available information on production wells used for public groundwater supplies in Carroll County. Bulletin 60, which is divided by county into separate publications, supersedes Bulletin 40 and its Supplements 1 and 2. The definition of public water supply as contained in the Environmental Protection Act of 1970 was used to determine those water systems and wells to be included. Systems and wells described furnish water for drinking or general domestic use in: 1) incorporated municipalities; 2) unincorporated communities where 10 or more separate lots or prop• erties are being served or are intended to be served; 3) state-owned parks and memorials; and 4) state-owned educational, charitable, or penal institutions. This report includes separate descriptions for groundwater supplies of 7 municipalities and 1 state park in Carroll County. These are preceded by brief summaries of the ground• water geology of the county and the development of groundwater sources for public use. An explanation of the format used in the descriptions is also given. Acknowledgments. This report was prepared under the general direction of Dr. William C. Ackermann, Chief of the Illinois State Water Survey, and Richard J. Schicht, Head of the Hydrology Section. Special thanks are given to R. T. Sasman, Hydrologist, who checked all of the data and reviewed the manuscript. Mrs. J. L. Ivens and Mrs. P. A. Motherway edited the manuscript, Mrs. Marilyn J. Innes typed the camera-copy, and John W. Brother, Jr., supervised the preparation of the illustrations. The chemical analy• ses, unless otherwise stated were made by personnel of the Water Survey Chemistry Sec• tion under the supervision of Laurel M. Henley. The analyses made by personnel of the Illinois Environmental Protection Agency were under the supervision of Ira M. Markwood. M. L. Sargent of the Illinois State Geological Survey prepared the generalized column of rock stratigraphic units and aquifers. R. D. Brower, Assistant Geologist, Illinois State Geological Survey, and M. L. Sargent reviewed the geological information in the manu• script. Grateful acknowledgment also is given to consulting engineers, well drillers, water superintendents, and municipal officials who have provided valuable information used in this report. Groundwater Geology The geology of Carroll County is described generally in meable deposits of sand and gravel 50 to 200 ft thick are Illinois State Geological Survey Circular 206, Groundwater associated with the Mississippi River valley along the western in Northwestern Illinois, and Circular 491, Plum River Fault edge of the county. These sands and gravels offer excellent Zone of Northwestern Illinois. The following brief discus• possibilities for developing large irrigation, municipal, and sion of geologic conditions in the county is taken largely industrial supplies. Sand and gravel outwash and alluvial from these publications. For a more detailed definition of deposits favorable for development of small to moderate sup• the geology in this portion of the state, the reader is referred plies may also be present in the valleys of the larger creeks. to the State Geological Survey which is located on the Uni• Glacial ice did not advance to the northwestern part of versity of Illinois campus, Urbana. Carroll County but in the rest of the county the uplands are Glacial drift deposits, loess, and alluvium materials form covered by less than 50 ft of glacial drift and loess with poor the present day land surface in Carroll County and vary possibilities for the presence of water-bearing sands and gravels. greatly in thickness and water-yielding character. Glacial Loess covers the entire upland to a depth of 25 ft at the outwash and alluvium consisting mostly of extensive, per• bluff and thins to 10 ft along the eastern side of the county. 1 Beneath the glacial deposits, the upper bedrock forma• County (see figure 2). The top of this dolomite lies at tions consist principally of beds of dolomite (a limestone• depths from less than 50 ft in the central and southeast areas like rock) and shale. The bedrock stratigraphy is compli• of the county to about 250 ft in the northeast and north• cated by the presence of the Plum River Fault Zone which west areas. It usually varies in thickness from about 200 ft extends from Leaf River (Ogle County), westward through in the southwest to about 350 ft in the northern and eastern Savanna, into Jackson County, Iowa. The bedrock forma• areas. Water from this dolomite is obtained from cracks and tions in Carroll County range in geologic age from Silurian crevices, and where it lies directly beneath permeable sand to Precambrian (see generalized stratigraphic sequence in and gravel deposits, its yield potential is enhanced. figure 1). The Glenwood-St. Peter Sandstone (Ancell Group of Silurian dolomite underlies the glacial drift in most of the Ordovician age) lies below the Galena-Platteville. This sand• northern tier of townships and in the south-central area of stone aquifer is encountered at depths from about 300 ft in the county (see figure 2). These rocks, known as the Silurian the southeast to about 600 ft beneath the bluffs in the western aquifer, are part of the geohydrologic unit referred to as the part of the county, and ranges in thickness from about 90 to shallow dolomite aquifer system. They are encountered from 150 ft. The Glenwood-St. Peter is one of the principal water- near land surface to depths of about 100 ft, and have a yielding units of the Cambrian-Ordovician aquifer. maximum thickness of about 225 ft tapering to a feather- The Glenwood-St. Peter overlies various units in different edge where they have been thinned by erosion. Where the parts of the county that include the Prairie du Chien Group, Silurian has been removed by erosion, the underlying Ma- the Eminence-Potosi Dolomite, and the Franconia Formation quoketa Group is exposed. The yield capability of the that consists of interbedded sandstones, shales, and dolomites. Silurian rocks depends primarily upon the number, size, The Prairie du Chien Group (Ordovician age) is present only and degree of interconnection of water-filled cracks and along the western and southern edges of the county. It con• crevices within the rock that are penetrated by a well tains three formations; the Shakopee Dolomite, the New bore. In some areas the Silurian rocks directly underlie Richmond Sandstone, and the Oneota Dolomite. These units permeable deposits of water-bearing sand and gravel. Under have a combined thickness up to 330 ft, but thin rapidly to such geohydrologic conditions formation of solution cracks zero toward the north. In most of Carroll County the Glen• and crevices and free exchange of water from the glacial wood-St. Peter overlies the Eminence-Potosi Dolomite (Cam• drift to the bedrock is possible, thereby enhancing the brian age) and the Franconia Formation (Cambrian age). yield capability of the Silurian aquifer. These units are encountered at depths from about 800 ft The Maquoketa Group (Ordovician age) underlies the in the southwest on the Mississippi River floodplain to about glacial drift in a portion of the southeastern and south• 1100 ft on the topographic high a few miles to the east and western areas and is present beneath the glacial drift and occur within this range in most of the county. They have alluvial deposits in the bottoms of deeply eroded stream total thicknesses varying from about 130 ft at Mt. Carroll valleys in the northern tier of townships north of the Plum to about 550 ft at Savanna and Milledgeville. The shales and River Fault Zone. The Maquoketa consists primarily of dolomites yield small quantities of water, but the sandy parts nonwater-bearing shales that separate the Silurian aquifer of these formations may contribute moderate quantities of from deeper water-bearing units. These shales lie at depths water to wells where they are not cased off by liners. of 20 ft (in the lowlands) near Savanna (Well No. 5) to as The Ironton-Galesville Sandstone (Cambrian age) is the much as 260 ft beneath the bluff at Mississippi Palisades most consistently permeable and productive unit of the State Park. The Maquoketa rocks are absent in a large Cambrian-Ordovician aquifer system in northern Illinois. part of central and eastern Carroll County where they have In Carroll County it lies at depths from 1000 ft south of been eroded away exposing the underlying Galena and Platte- Shannon to as much as 1400 ft beneath the bluffs in the ville Dolomite Groups, but are about 150 ft thick at Shannon western part of the county and varies in thickness from and as much as 200 ft thick at Mississippi Palisades State about 100 to 150 ft. The Ironton-Galesville is the principal Park. The Maquoketa Group generally is not considered as water-yielding unit of the Cambrian-Ordovician aquifer. a source for water supplies. The Eau Claire Formation lies below the Ironton-Gales• Below the Maquoketa Group there is a thick sequence of ville Sandstone. The upper and middle parts of the Eau Claire hydrologically connected rocks that is referred to as the contain many nonwater-bearing shales that separate the Cambrian-Ordovician aquifer system. This aquifer system Cambrian-Ordovician aquifer from deeper water-bearing consists in downward order of the Galena and Platteville units. The Elmhurst Sandstone Member at the base of the Dolomite Groups, Glenwood-St. Peter Sandstone, Prairie du Eau Claire Formation and the underlying Mt.