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RECOMMENDATION <br /> Evaluate this site as a low risk groundwater site, for closure based on the following. <br /> I. Source removal has been accomplished and documented in the soils beneath this site with <br /> documentation borings SB4, SB5, S136 and SB7. <br /> 2. The lateral and vertical extent of the groundwater plume has been delineated and is shown to be <br /> reducing and stable with evidence that bio-attenuation is occurring. <br /> 3. This site has been shown to contain only occasional trace amounts of MTBE in offsite wells. <br /> The source of the MTBE maybe from an offsite source. <br /> 4. The Lawrence Livermore Study has shown that gasoline range hydrocarbon plumes do not <br /> migrate very far laterally and reach stabilization and degradation with time. <br /> 5. With the exception of MW2, which is situated in a low transmissivity area and monitor wells <br /> MW8, MW12 and MW13 the BTEX's have met the primary MCL's for drinking water <br /> standards. <br /> 6. Tier 2 RBCA results found on page 15 of this report show that the only exposure possible would <br /> be from groundwater ingestion. It is highly unlikely that a drinking water supply well would be <br /> installed and developed at this shallow depth near MW2 and used as the source for drinking <br /> water. <br /> REQUEST FOR CLOSURE REVIEW <br /> APPENDIX B, TRI-REGIONAL BOARD STAFF RECOMMENDATIONS, MARCH 1,1994 <br /> CLOSURE DOCUMENTATION <br /> RWQCB APPENDIX B, CLOSURE DOCUMENTATION <br /> Location of the Minimum information needed for the following as stated in the CVRWQCB <br /> Recommendations of Closure Request Appendix B, see Appendix I of this report. <br /> 1. Distance to wells, see Appendix E. <br /> 2. Site maps, see Figure 3 <br /> 3. High and low, water levels see Figure 5. <br /> 4. Tabulated results sampling and Analyses see tables 1,2, 3 and 4. <br /> 5. Contamination Contours, see figures 6A-6C TPHg soil, 7A-7C Benzene Soil, SA-8C TPHg <br /> water, and 9A-9C Benzene in water <br /> 6. Mass Balance Calculation substances treated. <br /> The original estimated mass of soil contamination is taken from the results of the sampling of the <br /> base of the tank Pit excavation and the sampling of Soil Borings 1-3 and monitor wells MW1- <br /> MW10, see table 5 and the figures in item 5 above. <br /> 10 R603 Update#52/CLOSURE RV 7/98 <br />