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1433 North Market Boulevard • Sacramento California 95834-1943 • (916)928-3300 • Fax(916)928-3341 <br /> 'ENVIRONME At I1EAL1H DIVISION <br /> 304 E Weber;Ave Toird Floor <br /> P O Box 388, Stockto A 95201-0388 <br /> Approved O <br /> Denied [� <br /> Conditions October 9, 1997 <br /> Project 0805-147 04 <br /> Date_/,o <br /> Mr Steve Sasson <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, California 95201-0388 <br /> Re- Workplan to Conduct an Additional Subsurface Investigation at ARCO Service <br /> Station No 2186, Located at 3212 No California Street, Stockton, California <br /> Dear Mr Sasson <br /> At the request of ARCO Products Company (ARCO), EMCON has prepared this <br /> workplan to conduct an additional subsurface investigation at the subject site (see <br /> Figure 1) The purpose of this investigation is to delineate dissolved hydrocarbons <br /> downgradient from the underground storage tanks (USTs) Work will include the drilling <br /> and sampling of one soil boring and installing one groundwater monitoring well <br /> BACKGROUND <br /> The site is located at the southeast corner of the intersection of Alpine Avenue and North <br /> California Street in Stockton, California (see Figure 1) Based on information provided by <br /> ARCO and data collected during a previous investigation, there are three UST's at the site <br /> (one 8,000-gallon tank storing super unleaded gasoline and two 10,000-gallon tanks <br /> storing regular unleaded and rrud-grade gasoline) The approximate tank locations relative <br /> to site structures are shown on Figure 2 <br /> In August and September 1995, EMCON observed the drilling of six vertical soil borings <br /> (B-1, B-3 through B-5, B-7, and B-8) and two 45-degree-angle borings (B-2 and B-6) <br /> Three of the borings (B-1, B-4, and B-5) were converted to groundwater monitoring wells <br /> (MW-1 through MW-3), and three of the borings (B-3, B-7, and B-8) were converted to <br /> duel-completion vapor extraction wells (VW-1 through VW-3) Total petroleum <br /> hydrocarbons as gasoline (TPHG) were detected in borings B-1, B-3, and B-7 at <br /> concentrations ranging from 1 1 parts per million (ppm) in B-1 (56 5 feet) and B-3 <br /> (56 5 feet) to 3 3 ppm in B-3 (41 5 feet) Benzene was detected in borings B-1 (56 5 feet) <br /> and B-3 (56 5 feet) at concentrations of 0 019 ppm and 0 015 ppm, respectively TPHG <br /> and benzene, toluene, ethylbenzene, and total xylenes (BTEX) concentrations were below <br /> laboratory detection limits for all other soil samples analyzed <br /> SAC\N TW805\08051470 4$S-97\pa 1 <br />