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to be a reading of 500 on the PID. On January 14 , 1991 , the PID registered 250 , and a slight odor was noted from the exhaust of the charcoal. A bag sample was then obtained and brought back to Western Geo-Engineers portable laboratory in Woodland, California, late in the evening. The sample was immediately run the next morning and determined that breakthrough had occurred. The pilot test was then terminated that day, see Tables 1 , 2 , and 3. During the source test, bag samples were obtained from monitor well MW10 and showed a relatively stable vapor stream consisting of 119 to 164 mg/L (31 ,000-42,700 ppm gasoline vapor) of Total Fuel Hydrocarbons (TFH) in air along with 14% methane (Stockton area is a known basin for natural gas production and it is believed that this methane is produced from the underlying formations and not from a leak in the gas main) . At the completion of the test the extraction system was connected to the excavation wells so samples could be obtained from that source area. Steady state was probably not reached in the excavation during the short half hour duration of vapors being pulled from that area, but sample analyses indicates a similar vapor stream of 32,800 ppm TFH and 14% methane. All bag (tedlar) samples were analyzed for Total Fuel Hydrocarbons (TFH) as gasoline along with Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) using DHS headspace method with FID chromatograph Western Geo-Engineers (WEGE) . Also a methane analysis was run using a dedicated methane infrared analyzer with the FID chromatograph for confirmation. An influent sample to the charcoal was obtained prior to shutting the system off and disconnecting it from the wells (for analysis by Chemtech • Laboratories ) . This sample was analyzed using EPA modified 8015 and 602 for TPH and BTEX, respectively, and used to profile the charcoal drums for shipment for regeneration. 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, see Figure 6B. This source test will help evaluate the amount of fuel range hydrocarbons available and the supplemental fuel/oxygen needed to achieve incineration using the Hirtz Incenerator for emissions control during ground water and soil remediation for this site, see Figures 7 manifold for vapor extraction system and 8 schematic for vapor extraction system. If you have any questions, please call (916) 662-4541 . i Sincerely yours, George' L. Converse • Project Geologist cc: Mr. Dick Cunningham, R. J. Cunningham and Assoc.