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S E C ® R Atlantic Richfield Company ARCO Service Station 4932 . September 22, 2003 Page 4 additional GW E (EW-3 through EW-7) wells and one SVE (SVE-2) well San Joaquin County approved the remedial recommendations in their letter dated November 7, 2002 SCOPE OF WORK On November 13, 2002, SECOR field staff observed West Hazmat Drilling, of Rancho Cordova, California, drill and install onsite well EW-6 On August 5-7, 2003, SECOR field staff observed Cascade Drilling, of Rancho Cordova, California, drill and install onsite well SVE-2 and offsite wells EW-3, EW-4, EW-5 and EW-7 Wells EW-3 through EW-7 are 6-Inch diameter groundwater extraction wells that were installed to depth ranging from 35 to 41 feet bgs Well SVE-2 1s a 2-inch diameter soli vapor extraction well Installed to a depth of 30 feet bgs The completed scope of work is discussed below • Permitting Prior to the commencement of field activities, SECOR obtained a well construction permit from the San Joaquin County Environmental Health Department (SJC EHD) for the Installation of the wells SECOR obtained an encroachment permit from the City of Stockton to install extraction wells EW-3, EW-4, EW-5 and EW-7 In the sidewalk Copies of the well construction permits and encroachment permits are Included In Attachment 2 • Well Installation SECOR observed the drilling of exploratory borings to a maximum depth of 43 feet below ground surface (bgs) using a hollow-stem auger, and convert the borings to groundwater extraction (EW-3 through EW-7) and soil vapor extraction (SVE-2) wells Groundwater extraction wells were constructed with 6-Inch diameter Schedule 40 PVC casing with 20 feet of 0 020-inch wire wrap steel screen The sod vapor extraction well was constructed with 2-inch diameter Schedule 40 PVC casing with 25 feet of 0 020-Inch slotted casing Well construction details are Included In Table 1 Work was conducted in accordance with well construction permit requirements and SECOR's field and laboratory procedures (Attachment 3) Boring logs and well construction details are presented in Attachment 4 • Sod Analytical Results Where possible, SECOR collected soil samples at 5-foot intervals14 from the borings Samples were analyzed for the presence of Total Petroleum Hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and fuel oxygenates (MtBE, TBA, D1PE, ETBE, TAME, 1,2-DCA, EDB, and ethanol) using EPA 8260 Analytical results for soil samples are summarized in Table 2 The certified laboratory analytical reports and chain-of-custody documentation are provided In Attachment 5 5 • Groundwater Analytical Results. Groundwater extraction wells were developed and sampled on September 3 and 4, 2003 Groundwater samples collected from the wells were analyzed for the presence TPHg by EPA 8015 and BTEX and fuel oxygenates (MtBE, TBA, DIPS, ETBE, TAME, 1,2-DCA, EDB, and ethanol) by EPA Method 82608 Analytical results for groundwater samples are summarized in Table 3 and shown on Figure 2 Well development and sampling sheets, the certified laboratory analytical report, and chain-of- = custody documentation are provided in Attachment 6 • Stockpiled Soil Analytical Results SECOR collected one composite soil sample (4 brass sleeves) from the stockpiled sod for laboratory analyses for use in evaluating disposal options The stockpile sample was analyzed for the presence of TPHg and BTEX by EPA Methods 8260, and total lead by EPA Method 6010B Analytical results for the stockpile sample are summarized in Table 4 The certified laboratory analytical report and chain-of- custody documentation are provided In Attachment 4 1 1ARCO\49321Reportslremedial well start up doc