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i <br /> PROBLEM ASSESSMENT REPORT <br /> ' Moore Petrotem, Inc. <br /> 5941 F Street, Banta, CA <br /> NCA Project No. 10-90.481 <br /> Page 11 <br /> n <br /> 5.2 Ground mater <br /> ,4 Because of the limited areal extent of dissolved hydrocarbons <br /> # ground aster at the site, in <br /> the fact that free product has not been <br /> detected on the ground-water surface, and the relatively high <br /> Permeability of water-bearing sediments, practical ground-water <br /> remediation alternatives are <br /> probably <br /> treating ground water at the site. Acost-effective pumping and <br /> treating system for ground-water remediation at t pumping and <br /> wv accomplish the following goals, he site should <br /> • Capture the dissolved plume of hydrocarbons in order to <br /> M, prevent off-site migration. <br /> '" • Quickly remove ground-water containing dissolved <br /> hydrocarbons from the aquifer. <br /> Rapidly lower concentrations. of dissolved hydrocarbons <br /> in re^overed ground water to level <br /> disposal. s suitable for <br /> in order to meat the <br /> computer. goals of ground-water remediation, the <br /> model program DREAM. (Lewis Publishers; 1989) was utilized to <br /> ground-water flow to determine the most efficient arrangement <br /> n . <br /> of extractioand/or injection wells to quickly capture and remove <br /> the dissolved plume of hydrocarbons. The computer program was also <br /> used in estimating the time needed for ground-water remediation <br /> at the site. <br /> DREAM is an analytical (as opposed to numericalground-water <br /> model that uses the Theis equation to calculatedrawdowns and water <br /> level elevations due to Pumping and/or injection wells. The <br /> following assumptions are inherent in the Theis equation. <br /> • The aquifer is homogeneous, . isotropic, confined, of <br /> uniform thickness, and infinite areal extent. <br /> • Flow to wells is horizontal and laminar, s <br /> ® well diameter is infinitesimal so that storage within . <br /> the well can be neglected, <br /> • water removed from storage is discharged instantaneously <br /> with decline in head. <br /> - - --- -- <br /> - <br /> - while all-of_the-above--assumptions-are rarely satisfied in nature, <br /> use of the Theis equation should provide reasonable a <br /> to declines in water levels produced b pproximations <br /> injection at the site, y ground-water pumping or <br /> j. <br /> t� <br />