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LFR Inc. 7.0 EVALUATION OF GROUNDWATER QUALITY Based on quarterly groundwater sampling results from wells MW-1 through MW-5 during the second quarter of 2003 through the second quarter of 2005, the tire fire did not appear to affect groundwater quality within the site boundary. Concentrations of general minerals and metals in the collected groundwater samples appear to reflect background conditions. Pyrolytic oil constituents (TPH, VOCs, and SVOCs) were not detected in groundwater samples collected from the five on-site wells during the eight quarterly groundwater sampling events. However, during July 2005, pyrolytic oil was encountered in soil during excavation activities in the north-northwestern corner of the Site (the "source area"). The pyrolytic oil was observed floating on the groundwater table and was detected in groundwater samples collected from sampling locations (soil borings SB-1 and SB-2 and well MW-6) located approximately 50 feet downgradient from the source area. The CIWMB approved additional funding so the embankment overburden could be excavated to accommodate removal of the pyrolytic oil-affected soil that extended beneath the embankment. Embankment and pyrolytic oil-affected soil excavation activities, conducted by SCI, began on March 27 and were completed on April 21, 2006. Due to the location of groundwater monitoring well MW-6, the well was destroyed (with County approval) during the excavation activities. To further assess the extent of affected groundwater, well MW-8 was installed approximately 200 feet downgradient from the northwestern boundary of the Site and groundwater monitoring well MW-9 was installed approximately 250 feet downgradient from well MW-8. The following concentrations of diesel-range organics were detected in groundwater samples collected from well MW-8 during 2006: • February 14: 2,500 µg/1 • June 1: 200 µg/l • June 23: 1,100 µg/l • August 8: 110 µg/l • September 19: 240 µg/1 The following concentrations of diesel-range organics were detected in groundwater samples collected from well MW-9 during 2006: • July 14: 970 µg/l • August 8: 140 µg/l • September 19: 150 µg/l The concentrations of diesel-range organics detected in the most recent groundwater samples were lower than the concentrations detected in the first samples collected from the two downgradient wells. The source of the pyrolytic oil has been removed from the Page 36 rpt-RA_Sunun-Nov06-final-09025:FNC