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Ms Laurie Cotulla April 29, 1992 Page 7 • During the pilot test, vapor samples were collected m Tedlar Bags at groundwater wells E-5, E-10, and E-11 Vapors were extracted from each well for at least 30 minutes pnor to sample collection The vapor samples collected from wells E-10 and E-11 were analyzed for BETX and TPH-G using Modified EPA Methods 8020 and 8015 for halogenated solvents (chlorinated compounds) using the CARB 410A/422 method In addition, charcoal tube samples collected from wells E-5 and E-10 (the wells with the highest hydrocarbon concentrations based on field measurements) were analyzed for organic lead, using a method developed jointly by ARCO and BCC, to determine the lead content in the subsurface soils The results of the BETX,TPH-G, and lead analysis are presented in Table 1 The concentrations of the constituents that were identified above laboratory detection limits from the CARB 410A/422 analysis are also presented m Table 1 Laboratory reports and chain-of-custody documentation for all of the vapor analysis is included m Appendix B The analytical results from air samples collected during the test indicate that hydrocarbons are present in the vapors from the three tested wells with the highest concentration occurring near the UST area (E-11) Lead was identified in very minor concentrations in the air samples collected from wells E-5 and E-10 Of the ten parameters tested for (m samples from E-10 and E-11) using the CARB 410A/422, only two (dichloromethane and 1-2-dichloroethane) were identified CONCEPTUAL DESIGN OF SOIL REMEDIATION SYSTEM This section presents a conceptual design of the soil remediation system proposed for ARCO Station 2133 The conceptual design is based on the series of vapor extraction pilot tests performed by BCC and described above The results of the vapor extraction pilot tests indicate that vapor extraction would be a viable remediation alternative for this ARCO Station 2133 Several remediation technologies are available to treat volatile hydrocarbons in the extracted soil vapor These technologies include. 1 Activated carbon adsorption (GAC) 2 Thermal Oxidation 3 Catalytic oxidation 1. Vapor Phase GAC At the completion of the pilot testing, measurable concentrations of hydrocarbons were identified at the exit of the two 55-gallon carbon canisters The rapid breakthrough of the GAC is the result of high hydrocarbon concentrations in the extracted soil vapor At these levels, GAC treatment is not cost-effective Brown and Caldwell 6747gUP0RrsZ747-04.LTR Consultants