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SITE CONCEPTUAL MODEL AND REMEDIAL ACTION PLAN B <br /> 7-Eleven Store No 14117,2725 Country Club Blvd Stockton,CA June 20,2042 <br /> Depth to groundwater prior to Initiation of DPE testing ranged between about 7 37 and 7 70 feet bg At the <br /> end of the test (about 4 hours) depth to water ranged between 7 56 and 7 83 feet bg, Indicating up to 0 2 <br /> ' feet of drawdown in wells located up to 45 feet from the extraction point A total of 1,200 gallons of <br /> groundwater was removed from the site to a licensed disposal facility for oily-water recycling (DeMenno <br /> Kerdoon, Richmond, California) At an applied vacuum of 20 Inches of mercury and 1,200 gallons of <br /> groundwater withdrawn over a 4-hour period, the average groundwater extraction rate was at about 5 <br /> gallons per minute (gpm) <br /> ' Extracted vapor concentrations ranged up to 1,500 parts per million by volume (ppmlv]) during the test <br /> Given that well MW-2 is installed inside a conductor casing from 0 to 12 feet bg and, therefore, has <br /> virtually no access to the vadose zone within the tank pit, the observed extracted vapor levels are <br /> considered to be relatively high SVE within the tank pit pea gravel are likely to produce higher levels of <br /> hydrocarbonloxygenate vapors <br /> Evaluation of HPC counts Indicates that the microbial population in the groundwater Is expanding so <br /> ' rapidly an accurate colony count could not be established (Appendix B) Therefore, thriving indigenous <br /> populations have been documented to be present In the area of highest oxygenate concentrations, and <br /> are likely responsible for the observed shift in MTBE/TBA ratios <br /> so TREATMENT ALTERNATIVE COST COMPARISON <br /> 51 Capital Costs <br /> Capital costs include all in-situ and above-ground treatment equipment, including treatment equipment <br /> (pumps, panels, oxygen generators, infection blowers, air strippers, GAC systems, and vapor extraction <br /> units), monitoring hardware (I e , explosimeters, flowmeters, stripchart recorders, pressure gauges and <br /> ' regulators), and other materials such as piping and control valves <br /> Capital equipment costs depending on application are estimated to range between $70,000- $125,000 <br /> ' Mobile remediation (I e , trader-mounted SVE) results in little to no capital equipment costs based on the <br /> assumption that pre-purchased equipment Is used <br /> 1 <br /> 14117Scm2 doc <br />