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I lie Vacuum Extraction Systeo Workplan October, 1992 Firestone Store, 400, N. El Dorado, Stockton, Q Page 4 of 8 Ihorizontal extent because of N. E1 Dorado St. , and utilities to the crest of the tank site. Additionally, vertical depth was limited to about 14 feet because of the sideslope limitations and the potential for sloughing of soils that could undermine the structural stability of soils beneath the building foundation and the utilities beneath the sidewalk on N. E1 Dorado Street. Based on the results of the over-excavation work, hydrocarbons primarily in the volatile hydrocarbon range (gasoline and BTEX) remain in soils at the site. During all soil sampling activities, a representative from the Public Health Services, San Joaquin County, was on-site to record, inspect, and assist in the location of each soil sample retrieved for laboratory analysis. IAfter evaluating several remediation options, it is determined that vacuum extraction (VES) technology is appropriate for the removal of the remaining volatile hydrocarbons from the near surface soils at the site. The following section describes a pilot study approach to determine the effectiveness of VES at the site. YES PILOT STUDY This section describes the clean-up goals for the site, VES installation and operation, permitting, confirmation soil sampling, and well closure. Cleanup Goals At the request of the PHS, the cleanup goals for the site are established using the State Water Resources Control Board LUFT I manual risk evaluation Table 2-1 (Leaking Underground Fuel Tank Manual Guidelines f or Site Assessment, Cleanup, and Underground Storage Tank Closure) . This table, located on page 29 of the I October 18, 1989 edition of the LOFT manual, was ". . . designed to permit estimating the concentrations of TPH and BTEX that can be left in place without threatening ground water" . A copy of Table 2-1, completed for the site features at the Firestone site, is included in Attachment A. The assumptions and values assigned to each site feature in Table 2-1 are: Minimum Dept to Ground Water. Assumed groundwater to be 60 feet below site ground surface. Depth to soil sample is 13 feet (sample 5-38, November 12, 1991 over-excavation sample) . Therefore, dept to groundwater from soil sample is approximately 47 feet. Score 5 paints for this feature. I Ryan-Murphy, Incorporated I 'The Good Earth Company"