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F 6.0 Dicussion 6.9 Conclusions 6.1 1 MW-4 MW-4 was installed down gradient (at the tune) from MW-2 to detect possible movement of used motor oil in the groundwater from the contamination source (former waste oil USTs at MW-2) No oil has been detected in the groundwater at MW-4, indicating that used oil contamination has not spread down gradient from MW-2 as far as MW-4 ! Groundwater from MW-4 continued to show contamination from TPH-gasoline, oxygenates (except MTBE) and BETX The TPH-gasolme contamination increased this quarter but still continues to decrease throughout the years The source of the gasoline contamination remains unknown at this time Figure 10 shows how the groundwater elevation affects the TPH- gasoline concentration As the groundwater elevations nse,the contamination levels also rise MW4 has remained free from TPH-diesel contamination since June 2002 6 1.2 WASTE OIL USTS ! The former waste oil USTs caused significant contamination of the soil and groundwater immediately adjacent to the tanks Substantial quantities of oil have been removed from MW- 2, however, contamination retrains The used oil appears to move very slowly through the soil and in relatively close proximity to the former USTs location Analysis of MW-2 sampled on 03/11/05 continued to show contamination from TPH-diesel, and TPH-motor oils BTEX appeared at an increased concentration than previous quarter s MW-2 showed contamination from motor oils as reflected in the amount of floating oil removed during the past quarter and the analytical results The level of oil contamination has I dropped continuously from 2001 MW-1, MW-3 and MW4 continue to remain free of motor oils contamination, indicating that they have not been affected by contamination from the former used oil USTs r ! 6 1.3 DIESEL USTs � 5 MW-1 (site of the former diesel USTs) continues to how contamination from diesel The TPH-diesel contamination level, as shown in Figure , dropped below the reporting limit in June 2001, peeked at 72000 ppb in June 2002, decreased through Sept 2003, increased in March 2004,and,after a slight decrease since March 2004, increased this quarter ! ' The former diesel USTs caused moderate contamination of the soil and groundwater adjacent to ` the tanks Diesel contamination was detected in MW-2 (northeast of MW-1) and MW-3 (southeast of MW-1) in April 2000 Thns was not evident in later samples until December 2001 (MW-1, MW-2 and MW4)and March 2001 (MW-3)when contamination was detected again Since that time, the diesel contamination in MW-3 and MW4 has disappeared The contamination in MW-2 remains although it is decreasing overall The presence of diesel contamination in MW-2, indicates that diesel contamination is still affecting groundwater quality(Figure 6) __ k 4