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Mr. Stephen P. Swanson <br /> August 28, 1997 , <br /> Page 3 I <br /> Mahomet Va11e Water Authori , the N'ixon S ecial Draina e District, and the United III <br /> Y tY P 8 <br /> States Geological Survey(USGS). We will also discuss the project with the Illinois State ' <br /> Water Survey to incorporate their comments and suggestions to improve the results of the I <br /> tests. �' <br /> To accomplish these objectives, Layne proposes the following scope of services: ' <br /> Task 1) Compile Ezisting Data �I <br /> At the start of the project, we will compile all the existing data we can find for the <br /> wellfields and surrounding aquifers. This data will come from the City's files, our office <br /> files, reports and files from the Illinois State Water Swvey and USGS, geophysical <br /> investigations in the aquifer, well logs from the surrounding area, plans and specification <br /> for the wellfield, pernuts for the wellfield, and previous reports and pumping tests for the <br /> wellfield or other wellfields in the aquifer. This information will be reviewed to form a <br /> conceptual model of the aquifer and refine the workplan to obtain optimal information <br /> from the study. <br /> Task 2)Evaluate Condition of Well fields <br /> Both wellfields are only operated on an intermittent basis and sit idle most of the time. As � <br /> a result, the condition of the wells and pumps is not known with certainty. We believe <br /> that it is necessary to determine the condition of the wells and pumps before proceeding ' <br /> with the rest of the investigation. To accomplish this, we will have an experienced pump ' <br /> service crew conduct step drawdown tests on the well chosen for the constant rate test. ' <br /> The purpose of the test will be to deternune the efficiency of the wells, the optimum ', <br /> pumping rate for the well, and the condition of the pump. The step test will consist of ' <br /> four pumping steps of 90 minutes duration each with a recovery period of approxirriately � <br /> 18 hours. Past experience has shown that this testing schedule is likely to produce much � <br /> more reliable results than the three hour step test suggested in the RFP. Water levels will <br /> be recorded with an electric water level indicator or downhole pressure transducer during <br /> the step test and with a transducer and data logger during the recovery period. The flow ' <br /> rate will be measured with a temporary 10 inch water meter installed into the piping. As <br /> an option, we will look into the accuracy and cost of completing the installation of the <br /> flow meters that have been partially installed in the DeWitt County wells. The data from <br /> the step tests will be analyzed using the Bierschenk Method to determine the laminar and , <br /> turbulent well loss coefficients. ' <br />