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HEI MICK+IINN II 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 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. F',,,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 2) w t dry ice they were removed from the excavations with a crane and 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 19 November the 500 -gallon gasoline tank excavation was backfilled with the soil excavated during tank removal. On 6 and 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 tank 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 bottom of the tank. The fourth corner was unable to be sampled due to the proximity of the excavation to the school building, which hindered the backhoe's access to that corner. Instead, 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-