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GeoStrateg ies <br /> FIRST QUARTER 1995 STATUS REPORT <br /> at <br /> Unocal Station No. 6981 <br /> 4707 Pacific Avenue <br /> Stockton, California <br /> Report No 4855 02-3 <br /> INTRODUCTION <br /> This report summarizes field activities performed at the subject site between April and <br /> June, 1995 Field activities included quarterly monitoring and sampling of the groundwater <br /> monitoring wells, modification of the abatement device from thermal to catalytic mode, and <br /> startup of vapor-extraction system Location of the subject site is shown on the Vicinity <br /> Map (Figure 1) <br /> BACKGROUND <br /> The subject site is an active Unocal Service Station situated on the northwest corner of the <br /> intersection of Pacific Avenue and March Lane in Stockton, California Underground <br /> storage tanks (USTs) were replaced in May and June, 1988 Approximately 1,600 cubic <br /> yards (yd') of hydrocarbon-impacted soils were excavated and treated onsite during UST <br /> replacement A soil vapor survey was performed to assess the extent of residual <br /> hydrocarbons in the soil beneath the site Thirteen groundwater monitoring wells, six <br /> vapor extraction wells, and one groundwater extraction well have been installed at or near <br /> the subject site between January 1990 and August 1992 A vapor extraction test (VET) <br /> was performed in March 1992 to evaluate the feasibility of vapor extraction as a remedial <br /> option for soil beneath the site An aquifer pumping test was performed in August 1992 <br /> to evaluate the feasibility of utilizing groundwater extraction to remediate <br /> hydrocarbon-impacted groundwater A VES was installed at the site and operation initiated <br /> in September 1994 Locations of the pertinent site features are shown the Site Plan <br /> (Figure 2) <br /> The VES was brought online September 22, 1994 The VES consists of six vapor wells <br /> (VW-1 through VW-6) manifolded into a single vapor stream connected to a Baker Furnace <br /> thermal/catalytic oxidizer system After destruction of the extracted petroleum <br /> 485502-4 <br /> 3035 Prospect Park Drive, Suite 110 • Rancho Cordova, CA 95670 • (916) 631-1314 • Fax (916) 631-1317 <br />