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2005 1" Quarter Groundwater Report11 • Frontier Transportation April 28, 2005 p ��1 bj Page 5 ir No other wells identified TPH-g concentrations (y;6g/L) See Table 1 Historically no �etectable to trace concentrations (<5 8 µg/L) of dissolved BTEX were identified in monit n g wells MW-4, MW-5, MW-6, MW-7, MW-8, MW-9, MW-10, MW-11, y��✓ MW-12 and MW-14 since initial groundwater testing began I ea Xwell Monitoring wells MW-1 and MW-2 have remained at non detect to trace levels�smce at least July of 1999 Monitoring well MW-13 contained 62 µg/L dissolved total BTEX in June 2002 but has remained �r non-detect since then Newly installed monitoring wells MW-15 through MW-18 identified no detectable concentrations of dissolved total BTEX during the 2004 first and second quarter 4.3010\04t,f+^- groundwater monitoring events Only monitoring wells MW-3 and its replacement MW-3R contained dissolved BTEX from almost 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 March 2005 Groundwater sample results from MW-1 identified dissolved E and X only as 12 µg/L and 0 6 µg/L, r%p5ctiv e1 �No dissolved benzene or toluene was identified above laboratory reporting limits &M and µg/L) See Figure 8 for dissolved benzene in MW-1 overtime Analytical results from MW-3R demonstrated a significant decrease in total dissolved BTEX from 2216 µg/L in ' • December 2003 to 30 6 µg/l, in March 2005 'Dissolved benzene was detected above the MCL at 17 1 µg/L from MW-3R in March 2005, a decrease from the maximum of 494 µg/L identified in October 2002 (See Figure 9 for dissolved benzene over time in MW-3R No detectable ' concentrations of dissolved BTEX were identified in the groundwater samples collected in March 2005 from the remaining seven (7) monitoring wells See Figure 10 for the recent ' dissolved BTEX lsoconcentration Map MTBE was identified above MCL in four groundwater wells (MW-1, MW-3R, MW-9 ' and MW-17) using EPA method 8260 from the first quarter 2005 sampling episode The current California Department of Health Services (CDHS) primary Maximum Contaminant Level (MCL) for MTBE in groundwater is 13 µg/L Monitoring well MW-1 identified dissolved MTBE ' concentrations at 3,400 ug/L in March 2005, which is a decrease from the September 2004 concentration at 8,100 µg/L (See Figure 11 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 in December 2003 ' Dissolved MTBE for March 2005 was identified at 3,600 µg/L, an increase from the previous level at 1,000 µg/L (See Figure 12 for MTBE in MW-3R over time) The first quarter 2005 groundwater sampling also identified dissolved MTBE in MW-9 at 1A00 µg/l, and in MW-17 at ' 750 µg/L No dissolved MTBE was detected in the deeper monitoring wells The elevated 1 1