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' INTERIM WORK PLAN: LIMITED GROUNDWATER EXTRACTION Western Lift 3430 South El Dorado Street Stockton, California 1 October 1994 1.0 INTRODUCTION 9 In accordance with the request of the Bank of Stockton, Geological Audit Services, Inc. (GeoAudit) has prepared this Interim Work Plan for Limited Groundwater Extraction at ' 3430 South El Dorado Street in Stockton, California (the site). The location of the site illustrated on Figure 1. A plan of the site is illustrated on Figure 2. 2.0 BACKGROUND Between 1992 and 1993, five 2-inch diameter groundwater monitoring wells were installed at the site. The wells were installed to assess the extent of hydrocarbon impacted groundwater at the site. Groundwater monitoring has performed erformed on seven occasions at the site since June 1992. The depth-to-groundwater at the site is approximately 41 feet.The flow direction has ranged ' from north to east. Low concentrations of petroleum hydrocarbons continue to be detected in samples from ' MW-1, MW-4 and MW-5, which are down or cross gradient of the former UST excavation. During the most recent sampling (September 1994) TPH as gasoline was detected in MW-1 at a concentration of 170 ppm. Benzene was detected in MW-1 and MW-4 above the State ' of California Maximum Contaminant Level (MCL) for drinking water; toluene was detected in MW-1, MW-4 and MW-5 below the state MCL. A complete site history and background tis outlined in the Quarterly Report prepared by GeoAudit in October 1994. 3.0 SCOPE OF WORK As stated in the Quarterly Report for September 1994, remediation of low concentrations ' of hydrocarbons in groundwater is often ineffective and impractical. GeoAudit concluded that it is unlikely that traditional methods (i.e. pump and treat, air sparging) could cost- effectively reduce hydrocarbon concentrations at the site successfully. Therefore, we ' Owlo�.xf A.&S.M.N. 1 Wp4:h.aySJ•L140a 1994