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I I I2003 4"' Quarter Groundwater Report • Frontier Transportation - ' February 11, 2004 Page 4 � �C includes the third quarter 2003 sampling episode Groundwater analysis for TPH-d will continue ' to be performed for the site ' Historical groundwater monitoring results have identified TPH-g concentrations above to 15000 gg/L in MW-1andfW-3 only 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 Iast groundwater sample collected from MW-3 prior to abandonment detected dissolved TPH-g as 9,750 gg/L 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 Groundwater collected in December 2003 from fourteen groundwater monitoring wells ' identified dissolved TPH-g concentrations exclusively in MW-3R as 984 gg/L using EPA method 8015 modified The previous episode performed in October 2003 identified 431 gg/L as TPH-g in MW-3R All other monitoring wells identified no detectable concentrations (<50 ' gg/L) of dissolved TPH-g from the fourth quarter 2003 sampling episode Please see Figure 4 for recent dissolved TPH-g isoconcentration map Historically no de tabcentri��s`gf dissolved BTEX were identified in monitoring wells MW-5, W- , MW-7, MW-8, W-9, MW-10, and MW-11_since�nitial -1 groundwater testing began in each well Monitoring wells MW- , -2, and MW-4 have hev,er 5- ��,� remained non detect since at least July of 1999 Only monitoring well MW-3, which wasp, replaced by MW-3R, contained dissolved BTEX from every groundwater sampling episode Detectable concentrations of dissolved BTEX were identified exclusively in monitoring well MW-3R for the groundwater samples collected in December 2003 Analytical results for ' MW-3R demonstrated an increase in BTEX from 60 2 gg/L in October 2003 to 2216 gg/L in December 2003 No detectable concentrations of dissolved BTEX were identified in the groundwater samples collected in December 2003 from the remaining thirteen monitoring wells ' using EPA method 8020 See Figure 5 for the recent dissolved BTEX Iso concentration Map 3tC7 ytp ETBt �' t� l� 6tiir �Arn� 1y1fU. y}' rnVK, MTBE was the only oxygenate identified in groundwater using EPA method 8260 from l a the fourth quarter 2003 sampling episode Monitoring well MW-1 identified dissolved MTBE concentrations at 75 gg/L, a decrease from the maximum 5,800 gg/L identified in October 2002 Dissolved MTBE was also identified in June 2002 as 230 gg/L The depth to groundwater in ' MW-1 was recorded as its lowest level (10 75') in June and October 2002, which coincides with the observance of increasing dissolved MTBE concentrations between those episodes Monitoring well MW-3 identified a maximum dissolved MTBE concentration of 29,400 gg/L in 1 1