SITE INFORMATION AND CORRESPONDENCE

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AWff� September 16, 1991s �� ARCO Service Station No. 2076, Lodi, California Stockpiled Soil Soil excavated from the tank cavities and product-Kne trenches will be stockpiled onsite and sampled according to SJCPHS-EHD guidelines. With their authorization, we will backfill the former tank cavity with stockpiled soil. If residual hydrocarbons remain in the soil, the hydrocarbons will be removed by vapor extraction when the VES is completed. If soil remains after backfilling the former tank cavity, soil will be disposal of at an appropriate disposal facility such as a Class III or Class II facility. 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# e cavity will be prepared by RESNA and submitted by ARCO to SJCPHS-EHD approximately 90 days after the project is completed. On the basis of the laboratory and field data, the SJCPHS-EHD will evaluate whether additional investigation at the site is required. Construction of Vapor-Extraction System If residual hydrocarbons remain in the soil, a 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, abatement equipment used to destroy or remove hydrocarbons from the vapor, and piping and valves connecting the wells and other equipment. During operation, a vacuum is created in the vapor-extraction wells which 1 induces soil vapor to flow through the soil and into the wells. Gasoline adhering to soil particles is volatilized and entrained in the soil vapor. The soil vapor and volatilized gasoline are removed from the wells and transported through the subgrade piping to the abatement equipment. Gasoline hydrocarbons are destroyed or removed from the soil vapor by the abatement equipment; the treated vapor is then discharged to the atmosphere. RESNA will obtain appropriate permits to construct and operate the VES before the system is completely installed. 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. The flow rate of vapor from of each well will be adjusted to maximize the amount of hydrocarbons being removed from the soil. The length of time the system operates will depend on the flow rate of vapor, the vertical and horizontal extent of the hydrocarbons, and the concentration of hydrocarbons remaining in the soil. When vapor sample results I 34008-3w lv a