R98-39 AUTHORIZING THE AMENDMENT OF AN AGREEMENT

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�0�• fc�� c v �s '/[LINO\S March 24, 1998 PUBLIC WORKS MEMORANDUM NO. 98 - 19 MEMORANDLJM TO: Honorable Mayor and City Council FROM: James L. Williams, Jr., City Manager V Bruce A. McNabb, P.E., Director of Public Works� Stephen P. Swanson, P.E., City Enginee�,'� SUBJECT: DeWitt County and Cisco Well Field Study City Project 9717 The City Council at its meetin� of October 1, 1997, approved an agreement with Layne GeoSciences Inc. ("Layne"), to perform a capacity study of the DeWitt and Cisco Well Fields. The approved fee for the original scope of work is $98,000. Layne has completed their preliminary research and review of existing records and documents relating to the well fields. They have advised staff that the pumping tests included in the current scope of work for the DeWitt Well Field would not provide much additional information to what already exists and would essentially duplicate previous tests done at the well field. The pumping test included in the original scope of work was a seven-day test of one of the wells. This test period was selected based on the limited information available to staff at the time the scope of work was prepared. It was estimated to represent a reasonable pumping time to obtain sufficient data for use in evaluating the impacts to the Mahomet Aquifer and estimating the expected yield from the well field. The decision for the limited testing time was also done to control project costs. The control related to the City not committing to the more e�ended pumping tests in the event the data from the shorter duration tests provided conclusive information about the well field. The information Layne obtained and reviewed in their preliminary work has enabled it to deternune that the existing data or data obtained from a short duration testing will not provide sufficient information to make any conclusive determinations about the well field.