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ERI <br /> ENVIRONMENTAL RESOLUTIONS, INC. <br /> August 24, 1998 <br /> ERI 227904W01 <br /> Mr Bob Boust <br /> Unocal Diversified Business Group <br /> AMG - North Region <br /> 2121 N California Blvd #250 <br /> Walnut Creek, California 94596 <br /> Subject Work Plan for Hydrogeologic Investigation at Former Unocal Service Station #5098, <br /> 5606 Pacific Avenue, Stockton, California <br /> Mr Boust <br /> At the request of Unocal AMG (Unocal), Environmental Resolutions, Inc (ERI) is submitting this <br /> work plan to perform a hydrogeologic investigation at the subject site The purpose of the work is to <br /> evaluate the groundwater flow direction and gradient during pumping and non-pumping periods of the <br /> adjacent Delta College agricultural well and provide an estimate of the radius of the cone of depression <br /> caused by pumping of the well The work will include obtaining data related to the operational periods <br /> and flow rates of the existing agricultural well, installing pressure transducers in four existing wells, <br /> obtaining four days (96 hours) of groundwater elevation data utilizing the pressure transducers, <br /> removing the transducers and downloading the data, interpreting the data and preparing potentiometric <br /> maps depicting select pumping versus non-pumping periods, and preparing a letter documenting the <br /> work and providing the results and conclusions <br /> PROPOSED WORK <br /> ERI will perform the following tasks <br /> TASK I - AGRICULTURAL WELL DATA <br /> 1 1 Obtain data regarding the periods of operation to verify the operational periods of the <br /> agricultural well prior to installation of the transducers and obtain flow rates and volume of <br /> water to enable ERI to calculate the anticipated cone of depression <br /> TASK 2 - HYDROGEOLOGIC INVESTIGATION <br /> 2 1 Install single-channel pressure transducers/data loggers in monitoring wells MW3, MW4, <br /> MW11 and MW17, shown on Plate 1, at 12 00 PM on August 31, 1998, pending authorization <br /> for access to MW3 and MW4 on the Montgomery Ward property If ERI does not receive <br /> . access authorization, MW15 and MW16 will be used instead Depth-to-water measurements <br /> will be obtained prior to data acquisition The transducers/data loggers will collect and store <br /> water elevation data (i e feet of head above transducers) at a pre-determined interval of 1 to 5 <br /> 74 Digital Drive, Suite 6, Novato, California 94949 415-382-9105 (FAX 415-382-1855) <br /> Lake Forest • Novato • Seattle <br />