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1 2002 2nd Quarter Groundwater Report Frontier Transportation ' 0902-182 September 3, 2002 Page 4 ' identified dissolved TPH-g concentrations exclusively in MW-3R as 3,310 pg/L using EPA method 8015 modified. The previous episode performed in April 2002 identified 9,750 pg/L as ' TPH-g in the former MW-3. Monitoring well MW-13 identified dissolved TPH-g as 704 pg/L in June 2002. All other monitoring wells identified no detectable concentrations of dissolved TPH-g from the June 2002 sampling episode except MW-11, which was not sampled. Please see ' Figure 4 for recent dissolved TPH-g isoconcentration map. Historically no detectable concentrations of dissolved BTEX were identified in ' monitoring wells MW-5, MW-6, MW-7, MW-8, MW-9, MW-10, and MW-11 since initial groundwater testing began in each well. Monitoring wells MW-1, MW-2, and MW-4 have remained non detect since at least July of 1999. Only monitoring well MW-3, which was ' replaced by MW-3R, contained dissolved BTEX from every groundwater sampling episode. No detectable concentrations of dissolved BTEX were identified in groundwater samples ' collected in June 2002 from monitoring wells MW-2, MW-4, MW-5, MW-6, MW-7,MW-8, and MW-10 using EPA method 8020. Trace dissolved BTEX concentrations were identified in monitoring wells MW-1 as 0.7 pg/L, MW-9 as 5.2 pg/L, and MW-12 as 5.8 µg/L. Monitoring well MW-13 contained dissolved BTEX as 62 µg/L. Groundwater collected from replacement well MW-3R identified dissolved BTEX as 792.6 pg/L. See Figure 5 for the recent dissolved BTEX Isoconcentration Map. MTBE was the only oxygenate identified in groundwater using EPA method 8260 from ' the June 2002 sampling episode. Monitoring well MW-1 identified dissolved MTBE concentrations at 230 µg/L, an increase from <5 pg/L during the previous seven monitoring episodes. However, MTBE concentrations have attenuated by 82% from the maximum ' concentration of 1,300 µg/L identified in MW-I during August 1996. Replacement well MW-3R identified dissolved MTBE as 2,600 pg/L and as 46 µg/L in MW-13. No detectable concentrations of other oxygenates were identified from groundwater sample analysis of the ' monitoring wells sampled using EPA method 8260 (See Appendix B). See Figure 6 for the recent MTBE Isoconcentration Map. ' 5.0) CONCLUSIONS AND RECOMMENDATIONS Based on groundwater sample analysis results, the dissolved TPH-g, BTEX, and MTBE - plumes appear to be localized near the former UST locations. No detectable concentrations of T dissolved TPH-d, TPH-g, BTEX, and MTBE were identified in eight of the thirteen monitoring wells dedicated to the site. However, the identification of dissolved MTBE in MW-1 may be an ' indicator that lateral migration of MTBE may be occurring.