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0 0 <br /> ig6ETTLER - RYAN INC. <br /> March 7, 2000 <br /> C� :1� <br /> MAR 0 8 2000 <br /> Mr. Edward C.Ralston AL <br /> Tosco Marketing Company ENVIRONMENT <br /> 1 SERVICES T <br /> 1380 Lead Hill Road PERMIT <br /> Roseville,California 95661 <br /> Subject: Work Plan For Soil Sampling Following Underground Storage Tank (UST), <br /> Product Piping, and Product Dispenser Removal At Tosco (Former Unocal) <br /> Service Station#6981,4707 Pacific Avenue,Stockton,California. <br /> Mr. Ralston: <br /> At the request of Tosco Marketing Company(Tosco),Gettler-Ryan Inc. (GR)has prepared this Work <br /> Plan for soil sampling following removal of USTs,product piping,and product dispensers at the subject <br /> site (Figure 1). This work is being performed as part station demolition activities at the site. The <br /> existing USTs, piping, and product dispensers will be removed by Tosco's contractor,who will obtain <br /> the necessary permits from the San Joaquin County Public Health Services-Environmental Health <br /> Division(SJCPHS-EHD)and other agencies,as required. GR will collect compliance samples from the <br /> UST pit,product piping trenches,and from beneath the removed product dispensers as required by the <br /> State of California Water Resources Control Board's Leaking Underground Fuel Tanks(LUF7)Manual, <br /> the California Regional Water Quality Control Board's (RWQCB) Tri-Regional Board Staff <br /> Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites, and <br /> SJCPHS-EHD guidelines. <br /> The site is currently an active Tosco facility branded as a 76 Station, with a kiosk, three dispenser <br /> islands,and two 12,000-gallon underground storage tanks. Pertinent site features are shown on Figure 2. <br /> PREVIOUS ENVIRONMENTAL ACTIVITIES <br /> In May and June 1988,RESNA Industries collected soil samples during replacement of the USTs and <br /> from test pits excavated adjacent to the product dispenser islands. Petroleum hydrocarbons were <br /> detected in soil samples collected from the UST pit,product lines,and test pits. Approximately 1,600 <br /> cubic yards(yd')of hydrocarbon-impacted soils were excavated and removed from the site. Due to the <br /> proximity ofroads and structures,over-excavation was terminated before all hydrocarbon-impacted soils <br /> could be removed. A soil vapor survey was performed to assess the extent of residual hydrocarbons in <br /> the soil beneath the site. <br /> Thirteen groundwater monitoring wells,four vapor extraction wells,and one groundwater extraction well <br /> were installed at or near the subject site. These wells were installed between January 1990 and August <br /> 1992. A vapor extraction test(VET)was performed in March 1992 to evaluate the feasibility of vapor <br /> extraction as a remedial option for soil beneath the site. An aquifer pumping test was performed in <br /> Stockton,to N6981.WP1 <br /> 6747 Sierra Court , Suite J • Dublin , California 94568 ( 925 ) 551 - 7555 <br />