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(160 gallons) in 17,030 fti of soil at the site The total mass of TPH as diesel in the soil <br /> Prior to treatment was 3,685 lbs (2,482 lbs + 1,203 lbs) <br /> Thus, approximately 67 percent of mass was treated at the site, only by excavating the <br /> heavily impacted material If intrinsic bioremediation is considered at the site, it is likely <br /> that the amount of treated mass will increase significantly. <br /> 11.0 Regulatory g tory Conditions <br /> The Califomna Regional Water Quality Control Board and local government agencies have <br /> strongly considered recommendations set forth in a study reported by Lawrence Livermore <br /> National Laboratories (LLNL) regarding California's leaking underground fuel tanks (LUFT) <br /> The study, conducted to improve and streamline the LUFT clean-up process, recommended <br /> closure for petroleum leak sites that pose a low-nsk to human health and the environment <br /> The Lipton site meets the conditions typical of a low-risk soil and groundwater site TPH as <br /> diesel does not have a primary maximum contaminant level The secondary action level for <br /> TPH as diesel is 100 pg/L, based on taste and odor. The average groundwater concentrations <br /> measured at the site and the predicted average groundwater concentrations do not exceed this <br /> secondary action level. There is no other contaminant of concern associated with this fuel <br /> release <br /> 12.0 Summary and Conclusion <br /> In May 1986, three USTs were removed from a common excavation Subsequent <br /> investigations and monitoring resulted in the determination that TPH as diesel was the only <br /> contaminant of concern at the site In May 1995, interim corrective action activities consisted <br /> of the excavation and disposal of approximately 330 cubic yards of TPH as diesel impacted <br /> soil from the source area, resulting m the reduction of at least 67 percent of the TPH as diesel <br /> mass at the site It is estimated that a maxunum residual mass 160 gallons of TPH as diesel <br /> could be present in the 70-foot thick vadose zone at the site The mathematical modeling of <br /> TPH as diesel at the site estimated that the maximum average (area-weighted) TPH as diesel <br /> concentration in groundwater from the leachate would be 44 pg/L 'Thos is consistent with the <br /> results from recent groundwater sampling events. Bioassessment tests results indicate that <br /> intrinsic bioremediation is likely taking place and contnbutmg to the observed decreasing soil <br /> and groundwater TPH as diesel concentrations <br /> M7/06-13-97/VDBF/97-0009 BK 8 <br />