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Quik Stop No 121 Closure Report • CCI Project No 12118 Page 13 On April 18,2006, after four additional quarters of groundwater monitoring, the Quik Stop site remained free of detectable petroleum hydrocarbons 7. SUMMARY & CONCLUSION 1 Groundwater contamination discovered during the replacement of the fuel tanks in March 1998 was investigated at both on and offsite locations during several field investigations conducted between November 1998 and August 2001, 2 The results of these investigations and continuous quarterly monitoring showed the groundwater contamination remained on site, in the A-aquifer, mainly in the vicinity of monitoring wells MW-3 and RW-1 The lack of migration of contaminants from the site was most likely due to a relatively flat groundwater gradient at the site Minor concentrations of MTBE were detected in two of the three B-aquifer wells over the last five years of groundwater monitoring Most of the B-aquifer contamination was detected in well MW-6 Since July 2005, the MTBE detected in MW-6 has been below 1 ug/L and the latest sample collected on April 18, 2006 shows the well to be free of detectable contamination Minor concentrations of MTBE were detected in B-aquifer well MW-9 in 2002, but the well has been free of detectable contaminants • since April 2003, 3 There was virtually no soil contamination detected above the capillary fringe of the fuel tank area or in the soil borings and monitoring wells installed around the site All detectable soil contamination was found between 10 and 20 feet, with the majority of the compounds being detected at 15 feet, which was at or below the site water table This soil contamination was most likely due to a smear effect from a rising and lowing water table It is CCI's opinion that any soil contamination which was found above the water table was remediated during the 9 MTS events conducted at the site in 2001 Further, operation of the KVA C-sparge system for over 2 5 years, would remediate any soil contamination found within 2 to 3 feet of the capillary fringe, 4 From February 2001 to December 2001, a series of 8-hour dual-phase treatment events were conducted at the site The vapor extraction events were conducted mainly on wells MW-3 and RW-1 A total of 9 MTS events were conducted at the site During that time, a total of 47 29 gallons of equivalent product were removed from the site, 5 During interim remediation activities of the site and including the 20-hour pump test, a total of approximately 8,296 gallons of water were extracted from the site All the extracted groundwater was transported to Seaport Environmental, located in Redwood City, California for proper disposal,