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2005 V Quarter Groundwater Report Frontier Transportation April 28, 2005 Page 6 dissolved MTBE concentrations are limited to the shallow monitoring wells only See Figure 13 for the recent shallow well MTBE lsoconcentration Map Beginning in March 2004, all groundwater samples collected were analyzed for oxygenates ETBE, TAME, TBA, DIPE, 1,2-DCA or EDB using EPA method 8260 Detectable concentrations of dissolved ETBE were identified MW-9 and MW-17 for the groundwater samples collected in March 2005 Concentrations of ETBE in MW-9 and MW-17 were at 3 2 µg/L and 0 96 4g/L, respectively `Due to dilution factors, MW-1 and MW-3R identified ETBE at <10 µg/L All other sample results were <0 5 µg/ (non-detect) for ETBE Detectable ' concentrations of dissolved TAME were identified in monitoring wells MW-1, MW-3R, MW-9 and MW-17 as 13 µg/L, 11 4g/L, 18 µg/L and 0 88 4g/L, respectively All other sample results were <0 5 µg/L (non-detect) for TAME Groundwater samples collected from all 9 monitoring ' wells sampled identified no detectable concentrations of TBA, DIPE, - using EPA method 8260 V 5��1 a; ' 5.0) WASTE MANAGEMENT Any free product, purged groundwater, and decontamination water generated from the site during 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 manifest ' 6.0) CONCLUSIONS AND RECOMMENDATIONS Based on groundwater sample analysis results, the dissolved MTBE plume appears to be ' slowly expanding to the west No detectable to low-level concentrations (below CDHS pnmary MCLs) of dissolved TPH-g and BTEX were identified in the 9 sampled monitoring wells at the site However, the identification of elevated levels of dissolved MTBE in MW-1, MW-3R, MW- 9, and MW-17 indicates that lateral migration of MTBE is occurring beneath the site BEA 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-er x a ted to prevent additional migration _ roundwater samples will be analyzed for TPR-g using EPA method 8015m, for BTEX using EPA method 8020, and for oxygenates using EPA method 8260 in all future monitoring episodes as directed by the PHS/EHD Additional testing at the site has been ' proposed in a separate work plan Should dissolved MTBE concentrations continue to be above EPA primary MCLS beneath the site, then groundwater remediation/treatment may be warranted l