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i ' D • 20052 d Quarter Groundwater Report ' Frontier Transportation, Inc. August 5, 2005 Page 6 ' never identified MTBE during previous sampling events The elevated dissolved MTBE concentrations are limited to the shallow monitoring wells only See Figure 13 for the recent shallow well MTBE Isoconcentration Map Beginning in March 2004, all groundwater samples collected were analyzed for v�-p` 1 oxygenates ETBE, TAME, TBA, DIPE, 1,2-DCA and EDB using EPA method 8260 No �'y 8 detectable concentrations of analyzed oxygenates were identified in June 2005 The reporting Iimit for DIPS, ETBE and TAME was 0 50 µg/L and for TBA it was 20 pg/L See Appendix B 1 J0 ' for laboratory analytical results 5.0) WASTE MANAGEMENT ' Any free product,purged groundwater, and decontamination water generated from the site dunng sampling activities will be stored in sealed 55-gallon drums for a period not to exceed ' 90 days Stored wastes will be profiled for hazardous constituents and characterized as Non- Hazardous, California Hazardous, or RCRA Hazardous, as appropriate Any transportation of waste will be under appropriate marufest 6.0 CONCLUSIONS AND RECOMMENDATIONS tBased on groundwater sample analysis results, the dissolved MTBE plume appears to be 0 Gam ' significantly expanding to the west as identified in MW-9 No detectable to low-level concentrations (below CDHS primary MCLs) of dissolved TPH-g and BTEX were identified in ' the 9 sampled monitoring wells at the site However, the id nhfific tion of elevated levels of CIIAO dissolved MTBE in MW-1, MW-3R, MW-9, and MW-174mlcates that lateral migration of ' MTBE is occurring beneath the site BEA recommends that specifications for soil vapor extraction and groundwater sparging ' and a cost-benefit analysis of alternative remediation be prepared as soon as possible based upon the significant expansion of MTBE to the west BEA further recommends that quarterly groundwater monitoring continue at the site until constant or decreasing dissolved MTBE ' concentrations are observed Further, migration of MTBE indicates that the source area may need to be re-excavated to prevent additional migration Groundwatcr samples will be analyzed for TPH-g using EPA method 8015m and for oxygenates and BTEX using EPA method 8260 in 1 all future monitoring episodes as directed by the PHS/EHD Should dissolved MTBE concentrations continue to be above EPA primary MCLs beneath the site, then groundwater ' remediation/treatment may be warranted i 1 i 1