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6 0 Discussion <br /> 6.1 Conclusions <br /> 6 1 1 MW-4 <br /> MW-4 was installed down gradient (at the time) from MW-2 to detect possible movement of <br /> used motor oil in the groundwater from the contamination source (former waste oil USTs at <br /> MW-2) No oil has been detected in the groundwater at MW-4, indicating that used oil <br /> contamination has not spread down gradient from MW-2 as far as MW4 <br /> Groundwater from MW4 continued to show contamination from TPH-gasoline, oxygenates + lI D i <br /> (except MTBE) and BETX The TPH-gasoline contamination increased slightly this quarter <br /> The source of the gasoline contamination remains unknown at this time Figure 10 shows how <br /> the groundwater elevation affects the TPH-gasoline concentration As the groundwater <br /> elevations rise,the contamination levels also rises I lyn 5` <br /> MW-4 has remained free from TPH-diesel contamination since second quarter 2002 <br /> 6 1 2 WASTE OIL LISTS <br /> The former waste oil USTs caused significant contamination of the soil and groundwater <br /> immediately adjacent to the tanks Substantial quantities of oil have been removed from MW- <br /> 2,however,contamination remains The used oil appears to move very slowly through the soil <br /> and in relatively close proximity to the former USTs location <br /> Analysis of MW-2 continued to show contamination from TPH-diesel and TPH-motor oils <br /> Oxygenates appeared at decreased concentrations than previous quarter MW-2 showed <br /> contamination from motor oils as reflected in the amount of floating oil removed during the <br /> past quarter and the analytical results The level of oil contamination has dropped continuously <br /> from 2001 MW-1, MW-3 and MW-4 continue to remain free of motor oils contamination, <br /> indicating that they have not been affected by contamination from the former used oil USTs <br /> 6 1 3 DIESEL USTs <br /> MW-1 (site of the former diesel USTs) continues to show contamination from diesel The <br /> TPH-diesel contamination level,as shown in Figure 6,continues to decrease <br /> The former diesel USTs caused moderate contamination of the soil and groundwater adjacent to <br /> the tanks Diesel contamination was detected in MW-2 (northeast of MW-1) and MW-3 <br /> (southeast of MW-1)in April 2000 This was not evident in later samples until December 2001 <br /> (MW-1, MW-2 and MW-4) and March 2001 (MW-3)when contamination was detected again <br /> Since that time, the diesel contamination in MW-3 and MW-4 has disappeared The <br /> contamination in MW-2 remains although it is decreasing overall <br /> 6/60 <br />