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6.0 Dicussion 6.1 Conclusions 1 ' i 6.1.1 MW-4 � MW-4 was installed down gradient (at the tine) 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 MW4 r� �.4 v1K Groundwater from MW4 continued to show contamination from TPH-gasoline, oxygenates (except MTBE)and BETX The TPH-gasolme contamination 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 f groundwater elevations rise,the contamination levels also rise Nat 4t6issAril MW4 has remained free from TPP-diesel contamination since June 2002 6.1.2 WASTE OIL USTs 1 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, W2, however, contamination remains The used oil appears to move very slowly through the soil and in relatively close proximity to the former USTs location 1 Analysis of MW-2 sampled on 09/22/04 continued to show contamination from DCA12,DIPE, -03-41 ) TPH-diesel, and TPH-motor oils BTEX reappeared at concentrations lower than previous quarters 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 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 r former used oil USTs 6.1 3 DIESEL USTs ' MW-1 (site of the former diesel USTs) continues to show contamination from diesel The TPH-diesel contamination level, as shown m Figure 5, dropped below the reporting limit in E June 2001, peeked at 72000 ppb m June 2002, decreased through Sept 2003,and increased to a reasonably consistent level since March 2004 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 'This was not evident in later samples until December 2001 (MW-1, MW-2 and MW-4) and March 2001 (MW-3)when contamination was detected again Since that time, the diesel contamination in MW-3 and MW-4 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) j � 4 - -