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1 I . 2004 Yd Quarter Groundwater Report I Frontier Transportation January 10,2005 Page 5 Iperformed in June 2004 also identified no detectable TPH-g(See Table 1) Historically no detectable to trace concentrations (<5.8 µg/L) of dissolved BTEX were identified in monitoring wells MW-4, MW-5, MW-6, MW-7, MW-8, MW-9, MW-10, MW-11, MW-12 and MW-14 since initial groundwater testing began in each well Monitoring wells MW-1 and MW-2 have remained at non detect to trace levels since at least July of 1999 Monitoring well MW-13 contained 62 gg/L dissolved total BTEX in June 2002 but has remained non-detect since then. Newly installed monitoring wells MW-15 through MW-18 identified no I detectable concentrations of dissolved total BTEX during the 2004 first and second quarter groundwater monitoring events Only monitoring wells MW-3 and its replacement MW-3R contained dissolved BTEX from every groundwater sampling episode Detectable concentrations of dissolved BTEX were identified exclusively in monitoring � � � wells MW-1 and MW-3R for the groundwater samples collected in September 2004 I Groundwater sample results from MW-1 identified dissolved-i My as 0.4 µg/L. No dissolved benzene, toluene, or ethylbenzene was identified above laboratory reporting limits(0.3 µg/L) See Figure 8 for dissolved benzene in MW-1 over time. Analytical results from MW-3R demo ted a significant decrease in total dissolved BTEX from 221 6 µg/L in December 2003 to f�g/L in September 2004 Dissolved benzene was detected above the MCL at 9 2 gg/L from MW-3R in September 2004, a decrease from the maximum of 494 pg/L identified in October 2 e Figure 9 for dissolved benzene over time in MW-3R). Grab samples were {� take fror.W9 and MW- prior to g the wells Total dissolved BTEX was identified �5 y p 5 4� 1.q 5V&MW-13 as r4' jiO and gg/L, respectively No detectable concentrations of 1 dissolved BTEX wag id tified in the groundwater samples collected in September 2004 from the remaining f urtee ) monitoring wells using EPA method 8020 See Figure 10 for the recent dissolved BTEX Isoconcentration Map. 1 p � - MTBE was identified in four groundwater wells and 9M grab sample using EPA method 8260 from the third quarter 2004 sampling episode. The current California Department of Health Services (CDHS)primary Maximum Contaminant Level (MCL) for MTBE in groundwater is 13 gg/L. Monitoring well MW-1 identified dissolved MTBE concentrations at 8,100 gg/L in September 2004, the maximum ever identified in MW-1. The previous maximum dissolved MTBE in MW-1 was identified in October 2002 at 5,800 µg/L (See Figure I 1 for MTBE in MW- 1 over time) Monitoring well MW-3 identified a maximum dissolved MTBE concentration of 29,400 µg/L in March 1998 This well was abandoned in May 2002 Groundwater analysis for replacement well MW-3R identified a maximum dissolved MTBE concentration of 6,000 µg/L I in December 2003 Dissolved MTBE for September 2004 has remained at the same level as the previous quarter, 1,000 gg/L (See Figure 12 for MTBE in MW-3R over time) The third quarter i,�l Q�p A0&�two��6r 1 kt ��`�