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b <br /> i <br /> SCM <br /> Source — Former USTs and piping <br /> • Source removed 1992, secondary sources, impacted soil removed <br /> • Groundwater monitoring data show stability of localized impacts <br /> • Proposed geoprobe assessment to verify localized impacts and <br /> evaluatewater table and <br /> at depth consistent with lower portion of <br /> screens 15-20 ft and 46-50 ft samples <br /> • Stable groundwater impact, absence of sensitive receptors <br /> Exposure Pathways — not complete <br /> • Groundwater ingestion not complete - No sensitive receptors to <br /> Groundwater—well survey completed <br /> • Dermal contact not complete — soil excavation <br /> Vapor pathway — current groundwater concentrations below ESLs and <br /> suggest not a'risk-Table E-1 <br /> o Benzene ESL commercial 1.8E3 ug/L — conc 0.81 ug/L April 08 <br /> o 1,2-DCA ESL commercial 6.9E2 ug/L— conc 0.92.ug/L April 08 <br /> o If remaining soil impacts that are submerged, no exposure route for _ <br /> VI and do not appear 99 quality ear to be affecting w ualit based on well <br /> samples, assessment,to verify <br /> NFA for Cases Exceeding Water Quality Objectives <br /> 1) Plume stability / decreasing concentration trends <br /> 2) Estimation of when water quality objectives will be reached <br /> 3) Verification of no anticipated impaired groundwater uses <br /> Appendix A NFA Documentation Gaps <br /> Missing soils data — item 9 <br /> Estimation of time to reach WQ Goals for 1,2 DCA— limited data set, doesn't <br /> show decline in MW-4 — likely due to few samples at low concentrations <br /> Groundwater assessment to verify localized extent and absence of water <br /> table impacts <br /> i <br /> r ' <br /> i <br /> i <br />