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• RECEIVED EXECUTIVE SUMMARY 0 C T 2 6 1992 FIRESTONE PROPERTY AT ENVIRONMENTAL HEALTH 400 N. EL DORADO, STOCKTON,_ CA PERMIT/SERVICES Parcel # 139-070-09-8 To Whom It May Concern: With regards to the site history and the current disposition of the assessment and remediation of the subject facility, please review the following; The subject site has been used as a retail oil and gasoline facility dating back to the 1920 ' s . Most recently it has been utilized as a Firestone retail tire and automotive store. On April 25th, 1991 , twelve underground storage tanks were removed under the auspices of the Public Health Services , and the Stockton Fire Department. Soil samples were taken at the time of the tank removals , and analyzed according to San Joaquin County Public Health Services guidelines . At two of the tank locations (tank 5 and tank 16 ) , analytical results from the initial soil samples showed the presence of Total Petroleum Hydrocarbons (TPH) to be above the County' s Recommended Action Levels (RAL ' s) , therefore additional assessment and remedial work was proposed and prosecuted. In the area of the previously existing tank #16 , analytical results found TPH in the concentration of 430 mg/kg, as motor oil . Since motor oil typically does not migrate with the same rapidity as gasoline , it was proposed to perform additional excavation on the order of another two or three feet vertically, to visually inspect the excavation, and to collect additional samples . The proposed overexcavation was carried out on , and was effective in removing all of the above action level soils . Analyses performed on samples collected from the excavation after the removal of the impacted soils confirmed this . In the area of the previously existing tank #5 , initial analytical results found TPH in the following concentrations; 2200 mg/kg as gasoline and 1000 mg/kg as motor oil . Additionally, BTXE (benzene/toluene/ethylbenzene/xylene ) , chemical breakdown constituents of gasoline were also found, with a high concentration of total xylenes of 16 mg/kg. Analyses for metals detected the following concentrations ; Cadmium - 1 . 5 mg/kg, Chromium - 22 . 5 mg/kg, Nickel -- 22. 2 mg/kg, Lead - 12 . 9 mg/kg, and Zinc - 43 . 4 mg/kg. Two soil borings to a maximum depth of 401 , in the area of the previously existing tank #5 were advanced on September 10 , 1991 . Soil samples were taken during the boring proceedings , and