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NflMI�X�-lfBIYfB LW Mr. Charles Leubner 25 March 1991 Page 2 a hole to the proper depth. After the samples were collected they were labelled and prepared for shipment to the analyzing laboratory using the protocol described above. During the sampling the soil was monitored for the presence of hydrocarbons using a portable organic vapor analyzer (OVA) equipped with a flame ionization detector (FID). �,.. This field monitoring was conducted by filling a glass jar to approximately one-third capacity with soil and sealing the container with an airtight screwtop lid. The container was then placed in the sun to promote volatilization of hydrocarbon constituents in the soil sample. After approximately 15 minutes a hole was punched in the lid of the container and a probe attached to the OVA was inserted in the container headspace. The concentration of organic vapor in parts per million by volume was then read and noted. Field screening +-- also included visual observation of samples to note changes in color or appearance which might suggest the presence or absence of contamination. REMOVAL OF UNDERGROUND TANKS Both the 10,000-gallon diesel tank (Tank No. 1) and the 500-gallon gasoline tank (Tank No. 2) were removed on 20 December 1990. The 10,000-gallon diesel tank was resting on a concrete slab. No slab was present beneath the 500-gallon gasoline tank. After the tanks were inerted with dry ice they were removed from the excavations, placed on a flatbed truck, and inspected for holes. No holes were evident in either tank. The tanks and associated piping were transported by Erickson, Inc. to their facility in Richmond. On 20 `r December the 500-gallon gasoline tank excavation was backfilled with the soil excavated during tank removal. On 21 December 1990 the 10,000-gallon diesel tank was backfilled with imported pea gravel and the soil excavated during tank removal. Lo EXCAVATION SAMPLING Letitia Resch of the San Joaquin County Public Health Services, Environmental Health Division, was on site during the collection of the soil samples submitted for analyses. Samples were collected on 20 and 21 December 1990. Five soil samples were collected from the 10,000-gallon diesel tank excavation. One sample was collected from each of the four corners of the excavation, immediately adjacent to the edge of the concrete slab. Each of these samples was collected at a depth of approximately one to two feet into the native soils beneath the level of the bottom of the tank. One sample was collected from �., beneath the concrete slab after a hole was punched in the center of the concrete slab using a jackhammer mounted on the backhoe arm. This sample was collected at a depth of one to two feet beneath the bottom of the slab by driving the core sampler directly into the +.• native soil beneath the bottom of the concrete slab. r.. LW