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16 Working To Restore Nature <br /> Report on Vapor Extraction Test January 29, 1993 <br /> Coca-Cola Former Distribution Facility, Stockton, California 54006.01 <br />' of subsurface gasoline is predicted to be cost-effectively removed from the soil by soil vapor <br /> extraction (Shell, 1990) <br />' With three vapor wells on line at an average of 75 cfm per well, the total flow rate will be <br /> 225 cfm At startup, it is recommended that during approximately the first month of <br /> operation that VEW-3 will be the only operating well, until some of the highest vapor <br /> concentrations beneath the tank pit are removed This method of operation will contain <br /> petroleum hydrocarbon vapors beneath the tank pit, and reduce lateral and vertical <br /> migration of the vapors During the second month of operation, VEW-2 and VEW-7 will <br /> also be brought on line At an average startup TPHg concentration of 5,287 mg/m3 (based <br /> on the laboratory results reported in Table 1), the initial TPHg extraction rate for VEW-3 <br /> for the first month of operation is estimated to be about 1068 lb TPHg/month During the <br /> second month, with all three vapor wells operating, the estimated removal rate is about <br /> 2,130 lbs TPHg, assuming some decrease in the average TPHg vapor concentration During <br />' the third or fourth month, based on RESNA's experience and on published data (Shell, <br /> 1990), the extracted TPHg concentration is predicted to drop about 90% So that during <br /> about the third or fourth month, about 10 7 lb/dav (or 321 lb/month) can be removed from <br /> the soil The mass extraction rate will continue to decrease with time to nondetectable <br /> levels This yields an estimated cleanup of about 12 to 15 months, until about 90% of <br /> volatile vapors are removed from the soil and extracted vapor concentrations reach <br />' nondetectable levels The planned Soil vapor extraction system will be operated until <br /> extracted vapor concentrations are nondetectable (<5 mg/m3) Detailed calculations for this <br /> data will be included in the San Joaquin Valley Unified Air Pollution Control District <br /> tPermit Application to Construct and to Operate <br /> 1 Projected Diesel Removal Rates <br /> TPHd in the soil is of concern if regulated constituents such as BTEX leach into the <br /> groundwater Due to the lower solubility of diesel compared to gasoline, and since the <br /> groundwater table is at a depth of about 70 feet (as seen in Appendix A, Table A-4), most <br /> of the BTEX in the groundwater is estimated to be due to TPHg, not TPHd, because <br /> gasoline is more soluble in water than diesel Because of diesel's high boiling point, it is <br /> estimated that less than about 30% of the TPHd in site soil can be removed in 12 to 15 <br /> months by vapor extraction After the soil vapor extraction system is shut off, groundwater <br />' will continue to be monitored on a quarterly basis Once the gasoline is removed from the <br /> soil, groundwater concentrations may come into compliance in about one year after soil <br /> treatment If so, no other soil or groundwater remediation may be required If <br /> groundwater does not come into compliance, groundwater treatment is expected to be more <br /> cost-effective than excavation and disposal of the soil This will be determined at a later <br /> ' 15 <br />