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February 14 1997 Page 4 • EPA Method 8015/8020 Certified analytical i epos is are not contained within Chevron files, and therefore the results have not been included in Table 2 November 1988. EA drilled six borings on site to depths between 4I and 50 feet bgs and converted the borings into 4-inch diameter monitoring wells (MW-1 through MW-6) The maximum concentration of petroleum hydrocarbons (3,300 ppm total purgeable petroleum hydrocarbons calculated as gasoline [TPPH-g] and 9 6 ppm benzene) detected in soil was reported from the samples collected from Well NDAI-4, located proximal to the northeast corner of the former UST complex (Table 2) While installing Well MW-5, an abandoned 550-gallon steel UST was encountered and accidentally punctured (Figure 2) The liquid inside the tank was sampled and character- ized as weathered gasoline Soil around the UST was later excavated to expose the tank During tank excavation, product piping was uncovered leading to two additional , steel USTs (3,000- and 4,000-gallon) that had been abandoned-in place and filled with soil December 1988. The three additional steel USTs were removed and documented by Blaine Tech Services, Inc (Blaine) Prior to excavation the liquid inside of the 550-gallon UST was pumped, and soil inside the 3,000- and 4,000-gallon tanks was removed Upon excavation, no holes,in the tanks were observed One soil sample was collected below each end,of the 4,000-gallon tank (Samples EF#1 and EOP44), and below each end of the 3,000-gallon tank (Samples FOP92 and FF#3), and one soil sample was obtained from below the middle of the 550-gallon tank (DM#5) No petro- leum hydrocarbons, ethylene dibromide, or organic Iead was detected in any sample ' analyzed (Table 2) January 1989 EA drilled seven borings and completed them as five soil vapor extrac- tion (SVE) wells (V-1 through V-5), and two groundwater monitoring wells (MW-7 and MW-8) r The maximum concentration of petroleum hydrocarbons were reported at 26 5 feet bgs in the sample collected from Boring V-3 (16,000 ppm TPPH-g and 160 ppm benzene),, drilled through the center of the former 10,000-gallon gasoline tank complex (Figure 2) April 1989. EA conducted a pilot-scale test utilizing SVE Wells V-2 through V-5 to determine the design parameters for a vapor extraction system to remediate areas of hydrocarbon-impacted soil on site Vapor samples from Wells V-2 and V-5 contained concentrations of TPPH-g up to 4,500 and 16,000 ppm, respectively, and a radius of influence of at least 22 feet was calculated indicating that SVE was a practical approach 320133713ICLOSURE3 L