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' S E C O R ' Request for No Further Action Chevron station 9-2396 December 16,2004 Page 6 ' identified over 200 wells (Table 6) Unfortunately, 21 of the 223 total wells Identified were drilled prior to 1960 and the cross streets no longer exist Of the remaining 182 wells, most of them are domestic with a few being agricultural, commercial, or Industrial The field search confirmed that 45 out of 182 wells are operational and 9 out of 182 wells have been destroyed Despite the fact that the operational status of the rest of the wells was not ' verified, conversations with home and business owners led to the understanding that this region is not serviced by a public water system and that all locations most likely rely on individual wells for water San Joaquin County confirmed that there is no water purveyor for ' the Acampo area Therefore, it is probable that the remaining 128 unverified wells are in fact currently operational The only monitoring wells identified from this search are the three wells installed by SECOR on the Chevron service station premises The only ' domestic well sampled is the one on-site, which was sampled in June and July 1994, TPHg and BTEX were reported as below method detection limits ' 4.0 EXTENT OF PETROLEUM HYDROCARBON IMPACTS 41 Petroleum Hydrocarbons Adsorbed to Soil ' The highest detected concentrations of hydrocarbons in soil are located in the vicinity of the former UST pit between 3 feet and 16 feet bgs During UST, product line, and dispenser lie removal activities on August 25 and December 15 through 17, 1993, concentrations of TPHg were reported at several discrete locations (Figure 7) These include TX-7-16' (1 9 ppm), P-2-3' (110 ppm), OX-3-16' (8 ppm), OX-8-16' (410 ppm), SP-1A (6 ppm), 1 SPA D (41 ppm), SP-71D (2 ppm), and SP-10A-D (24 ppm) There Is one exception at the location of the remote fill piping from the former waste oil UST Here the sample WO-1-2 5', collected 2 5 feet bgs, had the highest concentration of TPH although its analysis did not match the typical patterns for either gasoline or diesel On April 26 and 27, 2001, three confirmation borings (SBA through SB-3) were drilled in ' the vicinity of the former UST pit and downgradient of the former UST pit No petroleum hydrocarbons were detected in soil samples collected from these borings On May 14 and 15, 2002, three soil borings (MW-1 through MW-3) were drilled in the vicinity of SBA through SB-3 No petroleum hydrocarbons were detected in soil samples collected during assessment activities The mass of TPHg in the soil at the site was calculated based on the results of confirmation ' sampling In the vicinity of the former UST pit The historical extent of hydrocarbons adsorbed to soil is presented in Figure 7 1 ' I IChevron1923961Reports\FINAL_NFAR_REPORT doc