ARCHIVED REPORTS XR0009319 - Laserfiche WebLink

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with accurate determination of depth to water 5.0 CONCLUSIONS AND RECOMMENDATIONS 5.1 Conclusions • The former used 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, but significant contamination remains The used oil appears to move very slowly through the soil so that the area of contamination appears to be in relatively close proximity to the former r USTs location r . The former diesel USTs caused moderate contamination of the soil and groundwater adjacent to the tanks Diesel contamination was detected in N4W-2 (northeast of MW-1) and MW-3 r (southeast of MWA) in April 2000 This was not evident in later samples (July and November 2000), and the diesel contamination in MW-1 dropped significantly over this same period (330 r ppm to 9 3 ppm), indicating that diesel contamination is dissipating and poses little or no threat r . to groundwater quality (Figure 5) MW-4 was installed down gradient form MW-2 to detect possible movement of used oil in the groundwater from the contamination source (former used oil USTs at MW-2) No oil was . detected in the groundwater at MW-4, indicating that used oil contamination has not spread r down gradient from MW-2 as far as MW-4 MW-4 groundwater was also free of diesel . contamination MW-4 is contaminated by gasoline, oxygenates and BTEX, at relatively high levels The source r of this contanvnation is not known at this time The adjacent site (south of the Cal Tk site) is a ! former key-lock gasoline service station The USTs from that site were removed two to three r years ago r 5.2 Recommendations r r EI recommends • 1 Continued removal of floating oil from MW-2 every two to four weeks, depending upon r Environeenng,Inc Project No 01-00109 Page 10 r r r