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Remediation Report - 152 East 11th Street, Tracy, California Page 19 Then interpolating in Table A6 on Page A-6 of Reference 20, for a confidence level of 99% 0 e a = 0 01) at a power of 0 80 (1 e a = 0 20), yields an estimate of 11 6 for the number of samples required Rounding the above estimate up to the nearest whole number of samples provides a conservative estimate of 12 for the number of samples required to demonstrate, with 99% percent confidence, that the treated soil met the cleanup criteria Spreading Soil for Treatment After the stockpiled soil was sampled and analyzed and the SJVUAPCD confirmed that it could be treated by aeration without obtaining a permit from that agency, a Case 821 loader with a 4-cubic-yard bucket and a Case 850D bulldozer were used to spread the material to a uniform thickness of approximately 12 in over a 450 ft by 81 ft area of fallow land at the treatment site The arrangement of the spread soil as it was laid down in the treatment shown to on Figure 8 DISPOSA.L OF ACCUMULATED PURGE WATER ■■ Purge water generated by groundwater-quality monitoring conducted at the 152 East I l th Street site had been stored on the property in a closed-top, 1000-gallon tank After the contaminated soil excavated from the site had been spread for treatment at the soil aeration site, the purge water tank was opened and its contents inspected The volume of stored «ater was less than 250 gallons No visual or olfactory indicators of gasoline were detected in it This is attributed to the initial low concentrations of components of gasoline in the purge water and volatization from the large surface area of the stored liquid the total \olume of which amounted to was less than 25 percent of the total volume of the large-diameter tank The purge water holding tank was transported to the soil aeration site where its contents were sprayed in a fine mist into the air above the spread soil This was done to remove traces of components of gasoline from the water by volatization The sprayed water fell onto the spread of contaminated soil so that if any residual hydrocarbons remained they would be eliminated by the soil treatment process TREATMENT OF HYDROCARBON AFFECTED SOIL To treat the hydrocarbon-affected soil that had been spread at the treatment site it was thoroughly rototilled throughout its thickness by a heavy-duty, tractor-powered agricultural rototiller immediately after it was laid down It was then left to aerate and was periodically inspected for visual or olfactory signs of remaining traces of components of gasoline As judged necessary from time to time, the rototilling operation was occasionally repeated to accelerate volatization of components of gasoline On one occasion, to break up soil that had become compacted, the bulldozer was used to rip the spread prior to rototillinu r