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ej,' ` 11L ��lYA f1 I1 Jill/ Mr. Charles Leubner 30 January 1991 Page 2 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 he 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 con amination. 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 19 November 1990. The 10,000-gallon diesel tank was resting on a ncrete cradle. slab was present beneath the 500-gallon gasoline tank. After the tanks we with dry ice they were removed f iom the excavations with a crane and placed % on a flatbed truck and inspected for holes. 4o holes werg vident in either tank. The Jg tanks and associated piping were transport d by Erickson,�Inc. to thWackfai�lled in�Rictond. On ovem er t e -ga on g so in can was wit excavated during tank removal. On 6 a d 7 December 1990 the 10,000-gallon diesel tank was backfilled with imported pea gravel And the soil excavated during tank removal. 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 19 and 21 November and 6 December 1990. Five soil samples were collected from the 10,000-gallon diesel t nk excavation. One sample was collected from three of the 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 foot into the native soils beneath the level of the bortorn of the tank. The fourth corner was unable to be sampled due to the proximity of t ie excavation to the school building, which hindered the backhoe's access to that corner. nstead, this sample (No. 017) was collected towards the center of the excavation wall. Sample No. 017 was collected by attaching the core sampler to lengths of auger extension rods and then driving it into the native soil with a slide-hammer. Once the core sampler was removed from the excavation the brass liner containing the sample was removed from the sampler and prepared for transport to the laboratory using the protocol outlined above. One sample (No. 025) 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 by driving the core sampler directly into the native soil beneath the bottom of the concrete slab. Seven samples were also collected along the length of the remote fill line of the 10,000-