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3 Xylenes up to 270 mg/kg were found at the same location Benzene. ethylbenzene, and toluene (BETX) were not detected in soil samples collected from the Site Soil contamination will be remediated by extraction of vapors from existing monitoring wells ATR-2, ATR-4, ATR-5, and TEX-1, which are screened across the capillary fringe Well locations are shown on Figure 2 Soil Vapor Extraction On December 16, 1991, Brown and Caldwell Consultants (BCC) performed a series of pilot tests using existing monitoring wells ATR-2, ATR-3, ATR-4, and ATR-5 The results o1 this test indicate that vapor extraction is a feasible alternative and volumetric flow rates between 20 and 40 cubic feet per minute (ctm) can be obtained from each well A wide range of TPH concentration can be expected in the extracted vapor from 23,000 micrograms per later (pg/1) in ATR-3 (near the UST) to 640 pg/1 in ATR-2 Data generated dunng the pilot test are provided in Appendix A Wells ATR-2, ATR-4, and ATR-5 are approximately 25 feet deep and constructed ot 4-inch- diameter Schedule 40 polyvinyl chloride (PVC) casing with 20 feet of 0 02-inch slotted well screen The well screen extends from approximately 5 feet below ground surface (bgs) to 25 feet bgs Well TEX-1 is approximately 40 feet deep and constructed of 6-inch-diameter PVC casing with 30 feet of 0 02-inch slotted well screen The well screen extends from 5 feet bgs to 35 bgs • Vapors will be extracted at a rate of 0 to 30 cfm from wells ATR-2 ATR-3 ATR-4 ATR-5, and TEX-1 using a vacuum blower located at the treatment area Each well will be connected to an extraction and treatment system by below ground PVC piping Figure 2 shows the layout of the piping system and treatment area. Soil Vapor Treatment A vapor extraction and treatment system (VETS) has been designed based on the pilot test results In the VETS, the extracted soil vapor will be treated by a King Buck and Associates catalytic oxidizer, or equivalent unit The unit will have a nominal capacity of 100 cfm and consists of a vacuum/compression unit, electrical preheater, catalytic oxidizer, and operating controls The system will be powered solely by electricity and designed for continuous services The unit will rest on a concrete pad located in the treatment area as shown on Figure 2. The unit can be shut down four ways (1) a thermal cutoff switch in the catalytic oxidizer which is triggered if temperatures exceed 1300' F, (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 AMIPM building, and. (4) an emergency shutoff switch located in the condensation drum which is triggered when 40 gallons have collected The treatment unit will be surrounded by an 8-foot-high fence • 7403gZEP0RTS\RSMEDATN PLN