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Project No. S8100-06-30 September 15, 1995 Page 5 CONCLUSIONS +r Utilizing the data acquired during the site investigation, a summary of the soil and groundwater conditions beneath the site as of July 1995 is presented below: �.. . TPHg, TPHd, TPHmo, TPHk and BTEX were not detected above the test method detection limits in soil collected from borings SBI through SB8 with the exception of one soil sample collected in boring SBI and in two soil samples collected in boring SB5. • Soil sample S135-2, collected beneath the former dispenser island at 3.4 meters (1I feet) bgs, contained 240 mg/kg TPHg and 11 mg/kg TPHd. The underlying soil samples collected between the depths of 6.4 and 9.3 meters (21.0.and 30.5 feet) bgs, tested below the laboratory test method detection limits for TPHg, TPHd, TPHmo, TPHk and BTEX. L. o Soil sample SBI-1, collected within the former UST excavation at 1.7 meters (5.5 feet) bgs, contained 8.3 mg/kg TPHmo. The underlying soil samples collected between the depths of 3.2 and 7.8 meters (10.5 and 25.5 feet) bgs tested below the laboratory test method detection limits for TPHg, TPHd, TPHmo, TPHk and BTEX. • The subsurface investigation was extended to a maximum depth of 14.0 meters (46 feet) v bgs. Groundwater was not encountered during the drilling activities, consequently, a groundwater investigation was not performed. Field screening of soil samples with the FID did not indicate the presence of significant organic vapors. Consequently, drilling beyond the depths investigated was not warranted. La • Analytical data for soil samples collected beneath and in the vicinity of the former USTs and the former dispenser island indicate that the former refueling operations have had �.• minimal impact on the surrounding vadose zone soil. o The minimal impact to vadose zone soil discussed above is evidenced by 1) the relatively low concentration of residual TPHg (240 mg/kg in soil sample SB5-2 collected at I I feet bgs) present in only one soil sample, 2) the absence of detectable benzene in all investigation soil samples to a depth of 45 feet bgs, 3) the existence of 34 feet of clean vadose zone soil beneath soil sample SB5-2 and 4) the absence of groundwater and groundwater impacts evidenced by the investigation. RECOMMENDATIONS Analytical data from native soil samples collected from borings SB1 through SB8 in the vicinity of the former USTs and the associated former dispenser island indicate that the former refueling operations have had limited impact on the surrounding vadose zone soil as discussed above. Geocon recommends that Caltrans submit a copy of this letter report to SJCEHD for review with L' a request for case closure.