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Firestone Service Center 400 North El Dorado, Stockton, Cahfornia February 2, 1994 Soil Remediation Plan—2072.01 Page 2 of 6 2.0 PURPOSE AND SCOPE Based upon the findings reported, several remedial options have been evaluated, including overexcavation and leaving the remaining soil contamination in place (no further action) Overexcavation of the tank pit, completed November 12, 1991, was limited due to the adjacent structure and a heavily trafficked public roadway Thus, overexcavation did not completely remove the contaminated soil Due to the site constraints, further overexcavation is not feasible The San Joaquin Public Health Department has indicated that closure of the site with no further action is not an option, predicated on field observation and PID monitoring from the October 1993 assessment activities and the ' analytical results from the UST removal and overexcavation sampling events Since overexcavation and leave-in-place are not acceptable options, this Soil Remediation Plan proposes implementation of a soil vapor extraction system (VES) to provide insitu extraction of the remaining volatile hydrocarbons This plan supercedes the original Tank 5 Area Remediation Work Plan submitted October 1992 The following provides details of the proposed VES, including a description of the well system and equipment, the monitoring program, and the proposed site closure criteria 3.0 APPROACH 3.1 Basis for Design Based on the available laboratory analytical results described herein, it appears that the remaining volatile hydrocarbons present in the native silt layer are confined to a thin band of soil adjacent to the previously excavated pit walls and floor The analytical data indicates this band of impacted soil varies in thickness from 0- to a possible maximum of 6-feet laterally and vertically This impacted area, surrounding the backfilled pit area, will be addressed by creating a vacuum within the pea gravel backfill of the pit to induce flow through the silty soil of the pit walls and floor A vapor extraction well WE 2) with a 10- to 15-foot screened interval will be advanced into the pea gravel backfill of the pit to provide the vacuum PID results indicate theY resence of volatile hydrocarbons as soil vapors in the p substrata below the backfilled pit (described above). This layer is comprised primarily of sand or silty sand The previously completed vapor extraction well WE 1), with an 18- to 28-foot screened interval, will be utilized to remediate the soil vapors in this layer. The well locations are shown on Figure 2 RYAN-MURPHY, 1NCORPORAMM Denver Enwhvoo s tal Contraction Manageoeat Los Angeles