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San Joaquin County Public Health Services August 16, 1991 Page Two FINDINGS: TPHg for sample 1 is 290 milligrams per kilogram (mg/kg), Benzene and toluene are non—detectable (ND), Ethelbenzene (1 .6 mg/kg), and Xylene 2.4 mg/kg). TPHg and BTEX for sample 2 are non—detectable (ND), EPA Methods 7420/7421 and 8240 are non—detectable (ND) for samples 1 and 2. TPHd for sample 3 is 6900 mg/kg, Benzene and Toluene are non—detectable (ND), Ethylbenzene (0.14 mg/kg) and Xylene (0.27 mg/kg). TPHd and BTEX for sample 4 are non—detectable. The documented soil contamination seems to be. confined under the tank fill tubes and pump islands. Due to the condition of the tanks upon removal, it is probable that the soil contamination is a result of product line disintegrity, or surface spillage around pumps or fill tubes. According to Mr. Brick Joseph, the tank system dispensed less than 500 gallons of fuel per month, a relatively small amount. Hence, the opportunity for large scale contamination by hydrocarbons would seem unlikely. This conclusion is corroborated by the fact that sample results 1, 2, and 4 on the east end of the excavation are non—detectable. The above facts lead us to believe that a re—excavation of the tank pit will be the most direct and economical remediation program. WORK PLAN: All work to be performed will be done by Cal West Concrete Cutting Inc. , the owner of the property. They hold a current State of California Contractors License (see attached "California Licensed Contractor Questionnaire"). 'The area to be excavated will be approximately 20' x 10' x 6' to a depth( of 18 to 22 feet.! The excavation shall begin at approximately 10' east of the current building and continue in a 20' wide pattern to approximately 20' east of the building (Figure 2). Soil samples 1 and 3 were collected from the center of the area to be excavated. Soil samples should be collected out of the excavator bucket at approximately 20' in depth and as close to the original sample locations as possible. For ease of identification, the sample under the former gas tank will be identified as 1 — 22. This sample will be analyzed for (TPHg) and (BTEX). The sample under the former diesel tank will be identified as 3 — 22 and will be analyzed for (TPHd) and (BTEX). Each sample will be collected in a brass tube, the ends covered with aluminum foil and plastic caps and sealed. Each sample will be placed on blue ice and transported under chain of custody to a state certified analytical laboratory by a lab employee. The excavated material, opproximatel,y 45 cubic yards of material', will be