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2004 3 Quarter Groundwater Report ' Frontier Transportation January 10,2005 Page 4 ' 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 gg/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. Therefore, groundwater sample analysis for TPH-m has been , discontinued at the site Laboratory analysis identified dissolved TPH-d in monitoring well MW-3 at a maximum ' concentration of 33,000 gg/L in January 2000 However, the groundwater results were reported as TPH-d and TPH-m combined Since then, dissolved TPH-d concentrations in MW-3 have attenuated to non-detect in April, August, and November of 2001 Groundwater analysis results from April 2002 identified dissolved TPH-d exclusively from MW-3 as 14,200 gg/ The groundwater level in MW-3 dropped to its lowest recorded depth(10 72') in April 2002 Monitoring well MW-3 was abandoned in May 2002 Replacement well MW-3R identified no detectable concentrations of dissolved TPH-d. No other detectable concentrations of dissolved TPH-d were identified from laboratory analysis Fn any of the wells sampled since then, which ' includes the second quarter 2004 sampling episode Gro coin ' Histoncal groundwater monitoring results have identified TPH-g concentrations above 1,000 gg/L were limited in MW-i only once at 1,800 gg/L, in MW-3 and in MW-3R Dissolved TPH-g concentrations in MW-1 have attenuated from 1,800 gg/L in August 1996 and remained under 50 gg/L since January 2000 (See Figure 6 for dissolved TPH-g over time in MW-1). Maximum dissolved TPH-g concentrations were identified in March 1998 as 42,000 gg/L in ' MW-3, which was the shallowest recorded groundwater depth in that well Since then, dissolved TPH-g concentrations attenuated to a low of 100 gg/L The last groundwater sample collected from MW-3 in April 2002 prior to abandonment detected dissolved TPH-g as 9,750 gg/L. The ' maximum dissolved TPH-g concentration in MW-3R was 3,790 gg/L in October 2002. Since then, the dissolved TPH-g levels have decreased over time to non-detect in 2004 (See Figure 71 tjo Ld Groundwater collected in September 2004 from all eighteen (18) groundwater monitoring wells identified only one well with dissolved TPH-g at 167 gg/L in MW-3R using EPA method t 8015 modified A grab sample from this well before purging also identified dissolved TPH-g at W° b 2,640 µg/L No other wells identified TPH-g concentrations (<50 Ag/L) The previous episode cowlfa 1 1