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. Mr Fred Cruz, SJVAPCD October 22,2003 Addendum to Authority to Construct Application(N-1031677) Page 2 October 1991 The concentration of petroleum hydrocarbons in the subsurface has likely decreased due to natural attenuation processes The proposed SVE systems have a provision for introducing atmospheric air for diluting the extracted soil vapor stream before entering the catalytic oxidizer Based on the concentration of influent and effluent samples (using a photo-ionization detector [PID]), Stratus technicians (on a bi-monthly basis) modulate the quantity of air being processed by the catalytic oxidizer in order to maintain the required operating temperature of 750T Based on operating instructions provided by the manufacturer, and on our experience with similar units at other sites, maintaining an operating temperature of 750°F results in a minimum of 95% destruction efficiency Our experience at similar gasoline service stations also indicates that the petroleum ` hydrocarbon concentrations influent to the SVE system generally decrease by 60 to 70 percent after the first three to four weeks of operation In addition, although the proposed blowers are rated at 200 cfm, due to inherent inefficiencies of blowers and motors, the maximum flow rates attainable is typically around 150 cfm Stratus proposes to conduct a source test, consisting of starting-up the SVE systems, collecting influent and effluent air samples, and shutting down the systems pending review of analytical results The analytical results of the air samples collected dunng the source testing will be representative of current subsurface conditions, and the results will be used to estimate the mass extraction rates, mass emission rates, and destruction efficiencies of the SVE systems Based on the results of the source test, flow rate for each system will be set such that annual mass emission rates for both of the SVE systems will be less than 20,000 pounds, or less than a daily mass emission rate of 54 8 pounds The air samples will be analyzed for total petroleum hydrocarbon as gasoline (TPHG) using United States Environmental Protection Agency (USEPA) method 8015, and for benzene, toluene, ethyl benzene and total xylenes (BTEX) and methyl tertiary butyl ether (MTBE) using USEPA method 8260 Stratus will forward to SJVAPCD a copy of the analytical results and the estimates for emission and extraction rates and destruction efficiencies If the mass emission rates estimated for air samples collected during the source testing operation are in compliance with SJVAPCD's ATC, Stratus will initiate the operation of the SVE systems on a continuous basis (24 hours a day, 7 days a week) To ensure compliance with SJVPAPCD emission offsets, Stratus proposes to the following • Operate each SVE system at approximately 100 cfm for approximately three months and monitor the system performance • Conduct weekly site visits to verify system compliance using PID measurements P 1Bp-Arco for URS16I001Correspondence\Arco 6100 ATC Addendum doe