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P - 9 J 4 t Soil Vapor Extraction Wells i i 5 Eight soil vapor extraction wells were installed in the areas identified during the problem iation. The wells are completed in interbedded silt aid sand. assessment as requiring soil remed Each vapor well is approximately 55 feet deep and constructed of 4-inch diameter schedule 40 PVC casing with 45 feet of 0.04-inch slotted well screen. The well screen extends from approximately 10 feet below ground surface (bgs) to 55 feet bgs. t:<s The layout of the piping system connecting the vapor extraction wells to the treamient , system is shown on Figure 3. Vapor wells 1 and 2 are connected to one manifold,vapor wells M 4, 7, and 8 are connected to a second manifold and vapor wells 3, 5, and 6 to a third manifold. The piping consists of Mach and 6-inch diameter PVC buried approximately 3 feet deep. On June 27, 1990, Brown and Caldwell Consultants performed a series of pilot tests on the r' vapor extraction wells. The volumetric flow rates during the pilot tests varied from 40 to 150 cubic, feet per minute (cfiu) for each manifold line, or 10 to 80 efm for each vapor well. Data generated during the test indicate that at an extraction rate of 50 cftn, each soil vapor well will ' influence a minimum radial distance of 75 feet. Data generated during the pilot test are provided in Appendix A. e Soil Vapor Treatment From the pilot test results a vapor extraction and treatment system (VETS) was designed { and constructed. In the VETS the extracted soil vapor is treated by a King Buck and Associates model MMC-5A catalytic oxid ter. The unit has a nominal capacity of 1C0 cfm and consists of a vacuum/compression unit, electrical preheater,catalytic oxidizer, and operating controls. The system is powered solely by electricity and is designed for continuous service. The unit rests on a concrete pad located as shown in Figure 3, The unit can be shut down four ways: (1) a thermal cutoff switch in tate catalytic oxidizer which is triggered if temperatures exceed MOT- (2) 3 O ;(2)a pressure shutoff located in the influent piping which is triggered when process air flow falls below approximately 40 CFM: (3) emergency shut-off switches located on the unit and inside the ARCO AM/PM building, and: (4) an emergency shutoff switch located in the condensation drum which is triggered when 40 gallons have collected. The treatment unit is sum, unded by �- a 8-foot high fence with 3 strand barbed wire on top. Air emissions are regulated by San Joaquin Valley Unified Air Pollution Control District authority to construct permit number AP 91-2. The system began operating 24 hours per day starting June 3, 1991. The system is currently pulling a total of 100 cfm through all three manifolds. Brown and Caldwell estimates it is operating at 97.3% efficiency and removing 110 pounds of total hydrocarbons(measured as C-7 hydrocarbon)per day. The system is maintained on a weelkly basis by Brown and Caldwell Consultants. r