Laserfiche WebLink
4 Firestone Service Center 400 North El Dorado, Stockton, California <br /> February 2, 1494 Soil Remediation Plan — 2072.01 Page 2 of 6 <br /> 2.0 PURPOSE AND SCOPE <br /> Based upon the findings reported, several remedial options have been evaluated, including <br /> overexcavation and leaving the remaining soil contamination in place (no further action) <br /> Overexcavation of the tank pit, completed November 12, 1991 , was limited due to the <br /> adjacent structure and a heavily trafficked public roadway Thus, overexcavation did not <br /> completely remove the contaminated soil Due to the site constraints, further <br /> overexcavation is not feasible The San Joaquin Public Health Department has indicated <br /> that closure of the site with no further action is not an option, predicated on field <br /> observation and PID monitoring from the October 1993 assessment activities and the <br /> analytical results from the UST removal and overexcavation sampling events <br /> Since overexcavation and leave-in-place are not acceptable options, this Soil Remediation <br /> Plan proposes implementation of a soil vapor extraction system (VES) to provide insitu <br /> extraction of the remaining volatile hydrocarbons. This plan supercedes the original Tank <br /> 5 Area Remediation Work Plan submitted October 1992. The following provides details <br /> of the proposed VES, including a description of the well system and equipment, the <br /> monitoring program, and the proposed site closure criteria. <br /> 3.0 APPROACH <br /> • 3.1 Basis for Design <br /> Based on the available laboratory analytical results described herein, it appears that <br /> the remaining volatile hydrocarbons present in the native silt layer are confined to <br /> a thin band of soil adjacent to the previously excavated pit walls and floor The <br /> analytical data indicates this band of impacted soil varies in thickness from 0- to <br /> a possible maximum of 6-feet laterally and vertically <br /> This impacted area, surrounding the backfilled pit area, will be addressed by <br /> creating a vacuum within the pea gravel backfill of the pit to induce flow through <br /> the silty soil of the pit walls and floor A vapor extraction well WE 2) with a 10- <br /> to 15-foot screened interval will be advanced into the pea gravel backfill of the pit <br /> to provide the vacuum <br /> PID results indicate the presence of volatile hydrocarbons as soil vapors in the <br /> substrata below the backfilled pit (described above) This layer is comprised <br /> primarily of sand or silty sand. The previously completed vapor extraction well WE <br /> 1), with an 18- to 28-foot screened interval, will be utilized to remediate the soil <br /> vapors in this layer The well locations are shown on Figure 2 <br /> RYAN-INURPHY, INQORPORA'IM Deaver <br /> F�virodnedal Condructkm M Meement Los Angeles <br />