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f t • ults Mr. Robert McClellon February 28, 2006 Page 3 VW-5D,VW-6S,VW-6D,EW-1, and EW-2 were 0.5%, 3.1%, 6.5%, 2.2%, 8.4%, 5.7%, and 6.4%, respectively. The oxygen concentration in all probes ranged from 0% to 22.9%.The carbon dioxide concentration in all probes ranged from 0.1% to 21.8%. The results for each probe and extraction well are summarized in Table 1. Laboratory Results On December 7, 2005, influent and effluent vapor samples were collected from the first portion of the pilot test where extraction well EW-1 was connected to the vapor extraction system. The methane concentration of the influent and effluent samples for EW-1 was 8.9% and 0.00032%,respectively. The oxygen concentration of the influent and effluent samples for EW-1 was 3.1% and 18%,respectively.The carbon dioxide concentration of the influent and effluent samples for EW-1 was 25% and 3.4%, respectively. The nitrogen concentration of the influent and effluent samples for EW-1 was 63% and 79%, respectively. The total VOC result of the influent and effluent samples for EW-I was 1,274 parts per billion volume(ppbv or 1.274 parts per million volume [ppmv]) and 38.39 ppbv (or 0.03839 ppmv), respectively. Based on the total VOC results for the influent and effluent samples,the destruction rate for the thermal oxidizer was 97%. The permit requires that the effluent VOC concentration level after the control device shall not exceed 1,000 ppmv and that either the VOC control efficiency shall not be less than 98% or the total VOC emission rate shall not exceed 2 pounds per day were met during the pilot test. On December 9, 2005, an influent vapor sample was collected during the second portion of the pilot test where extraction well EW-2 was connected to the vapor extraction system. The methane concentration of the influent sample for EW-2 was 5.3%. The oxygen concentration of the influent sample for EW-2 was 3.8%.The carbon dioxide concentration of the influent sample for EW-2 was 17%. The nitrogen concentration of the influent sample for EW-2 was 74%. The total VOC result of the influent sample for EW-2 was 4,852 ppbv (or 4.852 ppmv). The analytical results are summarized in Table 2 for natural gas analysis and Table 3 for VOC analysis. The analytical reports are provided as Attachment A. CONCLUSIONS AND RECOMMENDATIONS Following the pilot test activities,methane was measured above 5.0% in VW-5D,VW-6D,EW-1, and EW-2. Based on comparing the before and after the pilot test results, it appears that the potential hazards to the public from methane along the border of the site have been reduced as a result of the pilot test. Although the methane concentrations above 5% were detected in VW-5D and VW-6D for the most recent measurement, the methane concentrations measured in the probes(shallow) screened above these deep probes were less than 5%.For methane to present any hazard to the public, the methane would need to migrate to the surface from the screened depth of the deep probes. Prior to reaching the surface, the methane would migrate through the soil layer where the shallow probes are screened. Since the methane concentrations in the shallow probes were less than 5%, the need to prevent any potential methane hazards at this time can be addressed at a later date. We recommend that before any remedial alternative activities are implemented at the site, we shall continue to monitor the methane concentration in the probes along the border of the site and continue to evaluate potential remedial alternatives for the site and when the methane concentration in the shallow probes or in the single completion probes are greater than 5%, a work plan shall be transmitted to SJCEHD for review and approval. The monitoring information shall be used to estimate rate methane is K:\Wprocess\25532\WorldEnterprise\V apExtPi lotTest\Report\LtrRpt.doc