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Hydrogeologic Evaluation of Sand and Gravel Aquifers for Municipal Groundwater Supplies in East-Central Illinois

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Title: Hydrogeologic Evaluation of Sand and Gravel Aquifers for Municipal Groundwater Supplies in East-Central Illinois
Author(s): Kempton, John P.; Morse, Walter J.; Visocky, Adrian P.
Subject(s): Sand and Gravel Aquifers Municipal Groundwater Supplies
Abstract: Glacial sand and gravel aquifers have been identified stratigraphically and mapped in a 50- by 80-mile rectangular area of east-central Illinois. Located within the area are several water-short communities as well as the cities of Danville, Champaign, Urbana, Decatur, Shelbyville, Mattoon, Charleston, and Paris. An evaluation of all existing subsurface data, including data from 14 test holes and 7 test wells drilled for this study, indicates that only slightly more than half this region is underlain by aquifers with a potential for yielding municipal groundwater supplies. The principal aquifer is the Mahomet Sand, a basal pre- Illinoian Banner Formation aquifer partially filling the buried Mahomet Bedrock Valley located generally west of Champaign. The Mahomet Sand is more than 100 feet thick in many locations and averages just under 10 miles wide over its approximately 30-mile length within east-central Illinois. Yields of individual wells from the aquifer are as high as 3500 gpm. Elsewhere in the region, small, thin aquifers occur within the Banner Formation. The Glasford Formation (Illinoian) overlies the Banner and contains extensive sand and gravel aquifers, mainly at its base, throughout the western and northern parts of the region. Although Glasford aquifers are second in significance to the Mahomet Sand, primarily because they are thinner and cover less area, the largest of these may still yield up to 1000 gpm in local situations. A basal Wedron Formation (Wisconsinan) aquifer has been mapped in numerous, small scattered areas; wells at some of these locations yield up to 500 gpm. Similar yields are also obtained from some areas of the surficial Henry Formation, which is present as narrow fills of the principal river valleys and a narrow, discontinuous plain just outside the margin of the Wedron Formation. Scattered aquifers have been documented throughout the region; however, there are probably no widespread, highly productive aquifers remaining to be identified. Hydraulic conductivities are highly variable in the shallower deposits, even within well fields, but become uniformly greater with depth. Storage coefficients reflect artesian conditions in the Mahomet Sand as well as other Banner Formation aquifers; in the shallower units, conditions range from artesian to water table. Water quality does not differ substantially from formation to formation and is generally of good quality for municipal use. Aquifers in east-central Illinois are unevenly distributed. All major aquifers, including the Mahomet Sand, are concentrated in the western half of the region. In the eastern half, the limited size and thickness of the aquifers restrict current and future development of public groundwater supplies. Communities with insufficient or marginal water supplies must assess the costs of prospecting for local sources in relation to the costs of acquiring access to the nearest dependable, productive aquifer. Cooperation between communities would contribute to the economical, efficient exploration for and development of available resources. Finally, further study and evaluation of the principal aquifers, particularly of the underdeveloped Mahomet Sand, is necessary to determine their maximum potential and promote responsible development and management.
Issue Date: 1982
Publisher: Illinois State Water Survey and the Illinois State Geological Survey
Series/Report: Cooperative Resources Report 08
Genre: Technical Report
Type: Text
URI: http://hdl.handle.net/2142/35243
Date Available in IDEALS: 2012-11-21
 

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