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v a <br /> A S S O C I A T .E S . 1 N C . <br /> •r Given the biodecay rates for TPHg (578 days) and benzene(408 days)the time <br /> requied to biodegrade TPHg presently in groundwater to 100 ppb (taste, odor <br /> j threshold) and benzene presently in groundwater to 1 ppb (MCL)has been <br /> { estimated to be.approximately.11.years. <br /> Although the upper sand strata`have been impacted by petroleum hydrocarbons <br /> L this upper water bearing zone is of poor quality and not utilized for as a source of <br /> .PP g P q tY <br /> water for irrigation or municipal proposes. Overlying clay strata(s) that would be <br /> expected to act as a physical protection barrier against migrating petroleum <br /> contaminants protects the underlying aquifers. <br /> -Human exposure to residual petroleum affected soil is unlikely unless excavation <br /> of the soil were to occur. The site is capped concrete and asphalt. <br /> 6_2. Appendix BICheck List <br /> Appendix B of theTri-Regional Board's recommendations checklist of required data for site <br /> closure of USTs has been completed, as appropriate. The checklist is included in this report as <br /> Appendix A. <br /> C � <br /> L 7.0 SUMMARY <br /> ' Intrinsic biodegradation is a viable method to remove the petroleum hydrocarbon=impacts in the <br /> �-` first water bearing zone at the Fayette Manufacturing site. <br /> Findings of our evaluation concluded that the project site. does not appear to represent a <br /> significant risk to human health and the environment. <br /> 8.0 CONCLUSIONS/RECOMMENDATIONS <br /> 8.1 Request for No Further Action <br /> Based on the available data, on behalf of Dr. Glover, ATC formally requests this case be reviewed <br /> for No Further Action. <br /> rrl <br /> L' <br /> wA95122\eports\Request for NFA&c 17 <br />