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2002 151 Quarter Groundwater Report • Frontier Transportation ' 0502-163 May 6,2002 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. In January 2000, the well cover for MW-3 was destroyed allowing oily surface water to infiltrate the well. BEII concludes that the damaged well cover caused the increase in TPH-m in MW-3 from November 1999 to May 2000. ' 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 X6,000 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. The groundwater level dropped in the well by approximately 0.5 feet between November 2001 and April 2002. April 2002 groundwater analysis results identified dissolved TPH-d exclusively from MW-3 as 14,200 ' µg/L. No other detectable concentrations of dissolved TPH-d were identified from laboratory analysis. Groundwater analysis for TPH-d will continue to be performed for 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 from the maximum. Dissolved TPH-g concentrations in MW-1 have attenuated from 1,800 µg/L in August 1996 and remained under 50 µg/L since January 2000. ' Groundwater collected in April 2002 from all eleven groundwater monitoring wells s identified dissolved TPH-g concentrations exclusively in MW-3 as 9,750 µg/L using EPA method 8015 modified, a significant increase from the previous episode (218 µg/L) performed in November 2001. However, dissolved TPH-g concentrations have attenuated by 77% from the maximum recorded concentration in March 1998. The change in groundwater level in the well may have influenced the increase in dissolved TPH-g. All other monitoring wells identified no detectable concentrations of dissolved TPH-g from the April 2002 sampling episode. Please see ' Figure 4 for recent dissolved TPH-g isoconcentration map. •