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i T` Quarterly Groundwater Report Frontier Transportation ' 1201-Oso December 20, 2001 Page 3 ' gasoline, 8020 for BTEX, and 8260 for MTBE, respectively. Laboratory analysis results for all monitoring episodes are presented in Table 1. Recent analytical reports are included as ' Appendix B. Historical groundwater data has identified dissolved TPH-m in monitoring well MW-3 ' exclusively. Maximum concentrations of dissolved TPH-m were identified in MW-3 as 33,000 pg/L in January 2000 using EPA method 8015 modified. BEII concludes that the damaged well cover caused the increase in TPH-m in MW-3 from November 1999 to May 2000. The casing of MW-3 allowed oily surface water to infiltrate the well. Dissolved TPH-m concentrations have remained non-detect at the site since September 2000, when the well cover was repaired. BEII, therefore, has discontinued groundwater sample analysis for TPH-m at the site. ' Laboratory analysis identified dissolved TPH-d in monitoring well MW-3 at a maximum concentration of 33,000 µg/L, however it was reported as TPH-d and TPH-m combined. Since then, dissolved TPH-d concentrations in MW-3 have attenuated from >6,000 µg/L in December 2000 to non-detect in April, August, and November of 2001. None of the remaining ten monitoring wells identified detectable concentrations of TPH-d either. Should dissolved TPH-d Nremain non-detect for one more additional monitoring episode, then BEII will recommend that groundwater sample analysis for TPH-d be discontinued at the site. ' Historical groundwater monitoring results have identified TPH-g concentrations above 1,000 µg/L in MW-1 and MW-3 only. Maximum dissolved TPH-g concentrations were ' identified in March 1998 as 42,000 µg/L in MW-3, which was the shallowest recorded groundwater depth in that well. Since then, dissolved TPH-g concentrations have attenuated. Dissolved TPH-g concentrations in MW-1 have attenuated and remained under 50 µg/L since ' January 2000. Groundwater collected in November 2001 from all eleven groundwater monitoring wells ' identified dissolved TPH-g concentrations exclusively in MW-3 as 218 µg/L using EPA method 8015 modified, a significant decrease from the previous episode (5,980 µg/L) performed in August 2001. Dissolved TPH-g concentrations have attenuated by 99% from the maximum ' recorded concentration in March 1998. All other monitoring wells identified no detectable concentrations of dissolved TPH-g. Please see Figure 4 for recent dissolved TPH-g isoconcentration map. No detectable concentrations of dissolved BTEX were identified in groundwater samples collected in November 2001 from monitoring wells MW-1, MW-2, MW-4, MW-5, MW-6, MW- 7, MW-8, MW-9, MW-10, and MW-1 I using EPA method 8020. Monitoring well MW-3 exclusively identified total dissolved BTEX at a concentration of 53.3 pg/L, a decrease from i 1