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August 28, 1997 <br /> Mr. Stephen P. Swanson,P.E. <br /> City Engineer <br /> City of Decatur <br /> 1 Gary K Anderson Plaza <br /> Decatur, Illinois 62523-1196 <br /> RE:PROPOSAL FOR PRODUCTION CAPACITY.4ND IMPACTS STUDY OF ' <br /> DEWITT COUNTYAND CISCO WELL FIELDS, CITYPROIECT ND. 9717 <br /> Dear Sir: <br /> Layne-Western, in conjunction with our hydrogeologic consulting goup, Layne <br /> GeoSciences, Inc., (Layne) is pleased to submit this proposal to conduct a production <br /> capacity and impacts study for the DeWitt County and Cisco well fields. This proposal is ; <br /> intended to address the issues presented in your Request For Proposals (RFP) dated � <br /> March 24, 1997 with modifications to the scope of worked based on our discussions in the '�, <br /> meeting of April 16. '', <br /> BACKGROUND ''I <br /> The City of Decatur owns two well fields which are operated periodically to supplement II <br /> the City's surface water supply which is drawn from the Sangamon River. The DeWitt I <br /> County wellfield consists of 8 wells completed in the Mahomet Sand aquifer in 1989 and <br /> 1990. The Cisco wellfield consists of two wells drilled into the Mahomet Sand aquifer in <br /> the 1950s. <br /> The DeWitt County wellfield has an assumed capacity of approximately 25 mgd for 90 <br /> days, though this capacity has never been verified. The pumps in each well are powered ' <br /> by diesel engines. The wellfield discharges to a stilling basin which discharges to a <br /> drainage ditch that flows into Friends Creek. The ditch easily accommodated a sustained <br /> discharge of 12 to 18 mgd in November of 1996, but no hydraulic analysis of this ditch has <br /> been performed to determine if it can actually handle the full discharge of the wellfield. <br /> The discharge capacity of the ditch is beyond the scope of this project. <br />