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2003 2"d Quarter Groundwater Report Frontier Transportation August 6, 2003 IPage 4 identified in March 1998 as 42,000 µg/L in MW-3, which was the shallowest recorded groundwater depth in that well f Since then, dissolved TPH-g concentrations attenuated to a low of 100 µg/L The last groundwater sample collected from MW-3 prior to abandonment detected dissolved TPH-g as 9,750 µg/L-'�Dissolved TPH-g concentrations in MW-1 have attenuated from 1,800 pg/L in August 1996 and remained under 50 µg/L since January 2000 — Groundwater collected in June 2003 from thirteen groundwater monitoring wells identified dissolved TPH-g concentrations exclusively in MW-3R as 668 µg/L using EPA method 8015 modified The previous episode performed in March 2003 identified 798 µg/L as TPH-g in MW-3R All other monitoring wells identified no detectable concentrations (<50 µg/L) of dissolved TPH-g from the second quarter 2003 sampling episode Please see Figure 4 for recent dissolved TPH-g isoconcentration map Historically no d ec`t'�bl�c ncentrations o issolved BTEX were identified in monitoring wells MW- 5, V�-6, MW-7, MW-8,M -9, M10 land MW-11 since initial groundwater testing began in each well 'Monitoring wells - , -2, and YA MW-4 have ' 3 remained non detect sig�n,,�a at le July of 1999 Only monitoring well MW-3, which was `5� replaced by MW-3ROLon ii�eAssolved BTEX from every groundwater sampling episode , n rhg Detectable concentrations of dissolved BTEX were identified exclusively in monitoring well MW-3R for the groundwater samples collected in June 2003'Analytical results for MW-3R rdemonstrated a decrease in BTEX from 150 6 pg/L in March 2003 to 94 8 µg/L in June 2003 BTEX concentrations in monitoring wells MW-1 and MW-9 respectively decreased from 0 9 ' µg/L(exclusively ethylbenzene) and 0 8 gg/L (as toluene and xylene combined) in March 2003 to non-detect in June 2003 No detectable concentrations of dissolved BTEX were identified in the groundwater samples collected in June 2003 from the remaining monitoring wells using EPA ' method 8020 See Figure 5 for the recent dissolved BTEX Isoconcentration Map -- MTBE was the only oxygenate identified in groundwater using EPA method 8260 from the second quarter 2003 sampling episode Monitoring well MW-1 identified dissolved MTBE concentrations at 450 µg/L, a decrease from the maximum 5,800 µg/L identified in October �/ 2002 Dissolved MTBE was also identified in June 2002 as 230 pg/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 pg/L in ' March 1998'/Replacement well MW-3R identified a maximum dissolved MTBE concentration as 5,500 pg/L in January 2003 Second quarter 2003 groundwater analysis from MW-3R ' identified dissolved MTBE at 3,100 µg/L—Monitoring well MW-9 identified a maximum I