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Stantec
<br /> Work Plan for Vapor Probe Destruction, Well Destruction, and Well Installation
<br /> ARCO Service Station No. 2186
<br /> October 14,2408
<br /> 1.0 INTRODUCTION AND SITE INFORMATION
<br /> This work plan has been prepared by Stantec Consulting Corporation(Stantec)on behalf of Atlantic
<br /> Richfield Company(ARC), a BP Affiliated Company, in response.to the letter from the San Joaquin
<br /> County Environmental Health Department(SJCEHD)dated August 22,2008. This document presents
<br /> a work plan to conduct vapor probe destruction,well destruction,and well installation at ARCO Service
<br /> Station No. 2186 (site). Remedial options will be evaluated after the.wells.have been installed..and.
<br /> data has been collected. This work plan presents a brief site description,a summary of previous—site
<br /> assessments, and a detailed scope of work proposed for.the soil vapor probe destruction, well
<br /> destruction!and well installation.
<br /> The site is currently an operating service station located an.-the corner of North California Street and
<br /> Alpine Street in Stockton,Califomia(Figure 1). The service station is currently comprised of a mini-
<br /> mart,two 20,000-gallon,double-walled,fiberglass underground storage tanks(USTs), associated
<br /> product lines, and two dispenser islands. The majority of the subject property is covered with an
<br /> asphalt-paved parking lot and common landscaping. The.Site is bound to the east and to the south
<br /> by residential properties, to the west by a commercial property,'and to the north by a city park.
<br /> According to the United States Geological Survey topographic map dated 1987,the elevation of the
<br /> site is approximately 15 feet(ft)above mean.sea level on relatively flat terrain. The closest open
<br /> body of water is the Calaveras River, located approximately 4,000 ft to the north of the site.
<br /> 1.1 Site History and Previous Investigations
<br /> From August to September of 1:995, EMCON of Sacramento, California(EMCON)supervised the
<br /> drilling of six vertical soil borings (B-1, B-3 through B-5, 8-7, and B-8) and two 45-degree angle
<br /> borings (B-2 and B-6). Three borings (B-1, B-4, and B-5) were converted into groundwater
<br /> monitoring wells (MW-1 through MW-3; respectively). Three borings (B-3, B-7, and B-8) were
<br /> converted into dual-completion vapor extraction wells (VW-1 through VW-3, respectively). In
<br /> October 1996, EMCON supervised the drilling of one vertical soil boring (B-9). B-9 was
<br /> subsequently converted into groundwater monitoring well:MW-4.
<br /> From June through July 1999, two 10,000-gallon and one 8,000-gallon, double-walled,fiberglass
<br /> gasoline USTs,associated dispensers,and piping were removed from the site.Two 20,000-gallon
<br /> USTs were installed in the same cavity as the former USTs. Pinnacle Environmental Consultants of
<br /> Sacramento, California conducted compliance soil sampling activities for the tank pull.Analysis of
<br /> compliance soil samples indicated that gasoline range organics (GRO), benzene, and methyl tert-
<br /> butyl ether(MTBE) contamination were present in the soil. The excavation areas were backfilled
<br /> with pea gravel.
<br /> In August 1999, IT Group of Roseville,California(IT)conducted a soil and groundwater assessment
<br /> that included two cone penetrometer test(CPT)borings(CPT-2 and CPT-3)on the eastern edge of
<br /> the site and one CPT boring (CPT-1) north of the site. Benzene.and MTBE were detected in
<br /> groundwater samples from CPT-2. No petroleum hydrocarbon compounds were detected in the
<br /> groundwater samples collected from CPT-1 or CPT-3.
<br /> In September 2000, Delta Environmental Consultants of Rancho Cordova, California (Delta)
<br /> conducted a soil vapor extraction (SVE) test at the site. Three separate four-hour tests were
<br /> conducted. Soil vapors were extracted from wells VW-1 A through VW-3A.The tests indicated that
<br /> 2186 Work Plan for Vapor Probe Destruction, Well Destruction, and Well Installation.doc 1
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