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' Quarterly Groundwater Report ! Frontier Transportation ' 0801-052 August 27, 2001 Page 3 ' methods 8015 modified for diesel, 8015 modified for gasoline, 8015 modified for motor oil, 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. t Groundwater collected from all eleven monitoring wells identified no detectable dissolved TPH-m concentrations in all eleven monitoring wells. 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, will discontinue 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 2000 to non-detect in April and August 2001. None of the remaining ten monitoring wells identified detectable concentrations of TPH-d either. Should dissolved TPH-d remain non-detect for one ' more additional monitoring episode, then BEII will recommend that groundwater sample analysis for TPH-d be discontinued at the site. ' In addition, laboratory analysis of groundwater samples identified no detectable (<50 µg/L) concentrations of dissolved TPH-g in ten of the eleven wells sampled this episode. 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 August 2001 from all monitoring wells identified dissolved TPH-g concentrations exclusively in MW-3 as 5,980 pg/L using EPA method 8015 modified, an increase from the previous episode (809 µg/L) performed in April 2001. The fluctuation of the ' potentiometric groundwater level in MW-3 may be dissolving adsorbed petroleum hydrocarbons and causing the TPH-g concentrations to also fluctuate. All other monitoring wells identified no detectable concentrations of dissolved TPH-g. Please see Figure 4 for recent dissolved TPH-g ' isoconcentration map.