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Working To Restore Nature Addendum One to Remedial Action Plan March 1, 1993 Coca-Cola Former Distribution Facility, Stockton, California 54006.01 of 5,287 mg/m3 (based on the laboratory results reported in Table A-5 in Appendix A), the initial TPHg extraction rate for VEW-3 for the first month of operation is estimated to be about 1068 lb TPHg/month, for a 24 hour per day operation. The calculations for mass extraction (removal) rate at startup are reported in Appendix B at the end of this report. During approximately the second month of operation, VEW-2 and VEW-7 will also be brought on line. During the second month, with all three vapor wells operating, the estimated removal rate is about 2,130 Is TPHg, assuming an approximately 33% decrease in the average TPHg vapor concentration since startup. The calculations for the mass extraction rates for month two are also reported in Appendix B. During the third or fourth month, based on RESNA's experience and on published data (Shell, 1990), the extracted ' TPHg concentration is predicted to drop to about 90%of the startup concentration. So that during the third or fourth month, about 10.7 lb/day (or 321 lb/month) can be removed from the soil. The mass extraction rate will continue to decrease with time. Based on the calculations in Appendix B, and assummg the USTEC value of 9,560 Ib of TPHg in soil, the estimated cleanup time is about 12 to 15 months, until about 90% of volatile vapors are removed from the soil and extracted vapor concentrations are less than the method detection limit (MDL). The MDL is typically 5 mg/m3 for TPHg. If the weight of the TPHg in the soil is less than estimated by USTEC, then the remediation time will be correspondingly reduced. The proposed soil vapor extraction system will be operated until ' the extracted vapor concentration is less than the MDL (nondetectable). Off-Gas Emissions Rate Calculations Emissions rate calculations for average system startup TPHg and benzene concentrations are attached in Appendix B. Extraction rates are the mass of TPHg removed from the soil; and emission rates are the mass of TPHg discharged to the atmosphere after the extracted petroleum hydrocarbon vapor has been treated. The approximate average startup mass extraction rates for TPHg and benzene during the first month of operation were previously ' estimated at 35.6 lb TPHg/day(1,068 lb TPHg/month)and 23 lb benzene/day, respectively. This assumes that only VEW-3 operates during the first month at about 75 cfim, on a 24- hour per day continuous operation. The TPHg and benzene mass emission rates at startup, after abatement by the thermal oxidizer, are estimated at 1.8 Ib TPHg/day and 012 lb benzene/day, respectively. These projected emissions rates are within the regulatory ' emissions rate limit of 15 lb TPHg/day and 1 lb benzene/day. During the second month of operation, TPHg and benzene extraction rates were previously estimated at 71 Ib TPHg/day (2,130 lb TPHg/month) and 4.6 Ib benzene/day, respectively. After abatement by the thermal oxidizer, the TPHg and benzene mass emission rates are 7 I