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MRN - _ ` 13, 1990 and the test was shut down until the leak was fixed. The test resumed on December 27, 1990 and effluent bag sampling along with the PID screen commenced. Bag samples were obtained from the effluent of the pump, along with vacuum or pressure readings from the wells and pump. PID screening of the charcoal exhaust shoved _ breakthrough occurring on January 4, 1991. At this time an effluent sample was obtained from the charcoal tub scrub exhaust prior to shutting the system off and disconnecting it. from the wells. This sample was analyzed using the DHS headspace method for Total Fuel Hydrocarbons and BTEX. A sample of the influent to the charcoal was also obtained and chain of custody delivered to 02 Chemtech Laboratories for analysis using EPA modified 8015 and he for TPH and BTEX respectively. This sample was used for the the profile for shipment of the charcoal to be regenerated. Throughout the test vacuum readings were obtained from the ground water monitoring wells, to help establish the radius of influence of the vapor extraction system. PILOT TEST RESULTS Vacuum readings derived from the extraction wells (EN, P1 and P3) show a tight formation (high vacuum) . Also vacuum readings obtained from the ground water monitor wells show vacuum influence covering most of the site with the exception of MW-6, see Figure 9A. The bagsamples_ obtained from the exhaust of the blower indicate that 59 2 '.;pounds per., day of total: fuel . hydrocarbons can .be,. produced from the three extraction wells with an aver rate of 30 cubic:'feet .per minute from the formation. This vapor stream contains 0.92 pounds per day of Benzene, 2.04 pounds per day of Toluene, 0.74 pounds per day of Ethyl Benzene and 11.3 pounds per day petroleum product of Xylenes, indicating an aged contamination problem. VAPOR EXTRACTION CONTROL The site, prior to removal of the underground storage tanks and gasoline dispensing system, operated as a Regal service Station. The station was allotted a poundage rate that could be released from the dispenser nozzels and tank vents from its retail operations. With this in mind, that prior allotmf,'at should be allowed for the remediation of this site. Western Gen-Engineers has engineered—, installed-and-are- monitoring—_ - _-.__.-----_---_ _-- various ongoing vapor extraction systems throughout Northern California. A system that is economical and relatively maintenance free is emission rate control by the infrared (IR) �-� Total Petroleum Hydrocarbon analyzer with valve controls that page 9