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February 14, 1992 ZJ W ARCO Service Station No 2134, Stockton, California authorization to install subgrade components in the product-line trenches to later be used in a vapor-extraction system At this time remediation by soil vapor extraction appears feasible New tanks, product lines and subgrade components will not be installed until authorization is obtained from the SJCPHS-EHD Stockpiled Soil Results of analyses of samples of stockpiled soil will be submitted to the SJCPHS-EHD If laboratory analyses indicate hydrocarbons are present at concentrations that are not acceptable for disposal in a Class III landfill, the soil will be aerated onsite according to conditions stated in the aeration permit issued by the San Joaquin County Aar Pollution Control District dated June 28, 1991 The disposal of the soil is ARCO's responsibility Report Preparation A report containing information about the tank removal process and the results of the laboratory analyses of the samples collected from the cavity will be prepared by RESNA and submitted by ARCO to SJCPHS-EHD approximately 90 days after the project is completed Our plans for ongoing work will also be included in this document Construction of Vapor-Extraction System For residual hydrocarbons that exist in soil, a vapor-extraction system (VES) will be constructed after the vertical and horizontal extent of hydrocarbons in soil are defined A VES generally consists of vapor-extraction wells, a blower or vacuum pump to extract hydrocarbons from soil, abatement equipment used to treat hydrocarbons extracted from soil, and piping and valves connecting the wells and other equipment During operation, a vacuum is created in the vapor-extraction wells which induces soil gas to flow through the soil and into the wells Gasoline adhering to soil particles is volatilized and entrained in the soil gas The soil gas and volatilized gasoline are removed from the wells and transported through the subgrade piping to aboveground treatment equipment RESNA will obtain appropriate permits to construct and operate the vapor-extraction system A RESNA staff engineer will periodically monitor the system to ensure that the system is functioning properly, adjust the system to provide peak performance, and collect vapor samples for laboratory analyses to ensure compliance with permit conditions When system data indicates residual hydrocarbons have been removed, we will observe the drilling of soil borings and collect soil samples for hydrocarbon analyses If results of soil samples indicate an adequate level of remediation has been achieved, we will request site closure and destroy all wells onsite Otherwise, we will continue operating the vapor- extraction system and drill additional borings to reevaluate the soil at a later date 30003-4W 1V