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i i r i 5 0 CONCLUSIONS AND RECOMMENDATIONS . 5.1 Conclusions This work was undertaken to provide additional data regarding the vertical and lateral extent of contammation from the used oil USTs and the diesel USTs removed from this site in 1990 and r1998 respectively Previous investigations show high levels of contamination from used oil in the immediate vicinity of the former used oil USTs (MW-2), and moderate to light levels of ! contamination from diesel in the vicinity of the former diesel USTs (MW-1) The prior studies . did not detect lateral movement of contamination from the former used oil USTs, but did show . that diesel contamination moved laterally from the former diesel USTs (MW-1) northeasterly to B-5 and southeasterly to MW-3 . This investigation involved two new bore holes, B-6 located near the former used oil USTs . (between B-5 and MW-2) and B-7 located south of the former diesel USTs In addition, a new monitoring well, MW-4, was located down gradient form the former used oil USTs Soil analyses from B-6 showed moderate to light contamination from gasoline and diesel at 30 and 35 feet below grade, and no contamination above or below these levels This is generally consistent with expectations from results from B-5 in February 2000, which show soil contamination from diesel at elevations generally influenced by groundwater (30 and 35 feet bg) Again, there was • no contamination from used oil, indicating that oil tends to move vertically rather than laterally • (and slowly, as shown by groundwater analyses taken in 1997 that did not detect oil seven years after the used oil USTs were removed Floating oil was detected in MW-2 in 1998) . Bore hole B-7 showed no contamination in any samples, showing that contamination has not . spread laterally from either source (former used oil USTs or former diesel USTs) to this point MW-4 is highly contaminated from gasoline at all levels from 30 feet below grade to 50 feet . below grade The source of this contamination is unknown at this time Obviously, neither the • former used oil USTs or the former diesel USTs on the Cal Tk site if the source of this • contamination • Groundwater samples were secured from all four monitoring wells on 21 November 2000 as part of the Quarterly Monitoring Program Results are given in the Quarterly Monitoring Report Sol? dated 19 January 2001 The groundwater from MW-4 was contaminated by gasoline (76 ppm), • Environeering,Inc Project No 00-01108 18 • •