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the newly-installed wells surveyed. The top of casing elevations for all of the wells was presented in Table 3 of the Site Investigation Report. The survey only included elevation measurements of the top of the well casing and top of the well vault box. A survey map of the site features was not requested and therefore was not provided by the surveyor. The surveyor provided a letter with tabulated survey results, which has been included as an attachment to this letter. Forwarding Report Copies to Off-site Property Owners: As mentioned in Cambria's January 27, 1998 letter to SJCPHS, copies of the November 11, 1997 Site Investigation Report have been mailed to the two off-site property owners. Additionally, future correspondences regarding the investigation at this site will be copied to the off-site property owners as requested by SJCPHS. Site Description and Background The subject site is located on the southoa" corner of the intersection of Pacific Avenue and Porter Avenue in Stockton, California (Plates 1 and 2). The service station layout consists of three underground gasoline storage tanks, two product islands, and a station kiosk. In 1990, the former underground fuel storage tanks (USTs) were removed. A total of fourteen soil borings (B-1 through B-14) were drilled and sampled. Total Petroleum Hydrocarbons calculated as Gasoline (TPH-G) concentrations ranged from non detect (ND) to 17,000 parts per million (ppm) in selected soil samples. Benzene concentrations ranged from ND to 400 ppm. Borings TS-1 through TS-6 were drilled through the former UST complex to a depth of 16 feet below grade (fbg). Borings TR-I through TR-6 were drilled along product lines and near dispenser islands. TPH-G concentrations were detected in soil samples ranging from ND to 19,000 ppm. Benzene concentrations were detected in soils ranging from ND to 280 ppm. Monitoring wells MW-1 through MW-3 were installed to evaluate ground water quality. Soils from these well borings contained TPH-G ranging from ND to 28 ppm and benzene ranging from ND to 0.38 ppm. Vapor extraction well VEW-2 soils contained TPH-G ranging from 2,800 to 12,000 ppm and benzene ranging from 18 to 110 ppm. Soil analytical results are summarized in Table 1. In late 1991 and 5V early 1992, a 75-day vapor extraction feasibility test was performed at the subject site using wells VEW-1, VEW-2, and MW-3. Wells VEW-1 and VEW-2 were tested to evaluate their feasibility in addressing petroleum hydrocarbons detected below the former USTs location. Well MW-3 was selected based on previously detected separate-phase hydrocarbons (SPH) in this well. However, SPH has not been detected in well MW-3 since August 1993. In September 1995, four Geoprobes (GEO1 through GEO4), were driven to depths up to 56 fbg and sampled. Soil samples obtained from these probes contained TPH-G ranging from ND to 7,000 ppm and benzene ranging from ND to 10 ppm. These soil data were obtained from samples collected from depths ranging from 16 to 49 fbg. 240-0854 2