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GRANITE CONSTRUCTION — FRENCH CAMP Page 5 WKA No. 2088 . 09 October 10, 2005 From September 1993 through January 1995 five additional monitoring wells (MW4 through MW 8) were installed to depths of 40 feet bgs at the site to further evaluate the extent of groundwater contamination beneath the site. The two-inch diameter monitoring wells were constructed using 0. 024nch screen from 20 to 40 feet bgs. A licensed California surveyor surveyed the location and casing elevation of the wells. On September 28, 1993 approximately 700 cubic yards of diesel-contaminated soil was excavated from beneath the former dispenser island and stockpiled and aerated onsite. Results of laboratory analysis of soil samples obtained from the excavation revealed low but detectable concentrations of TPH as diesel. San Joaquin County Environmental Health Department did not require additional excavation of soil. The UST excavations were lined with plastic and backfilled with clean fill upon authorization from SJCEHD . The stockpiled soil remains on site and is currently located in the southwest comer of the property. Quarterly groundwater monitoring and sampling was performed at the site from 1993 until 2004. Predominate groundwater flow direction beneath the site has been to the northwest. The estimated hydraulic gradient beneath the site has ranged from 0.001 feet/foot to 0.0073 feet/foot, with an average hydraulic gradient of 0.003 feet/foot. Depth to groundwater beneath the site has ranged from 15 to 30 feet bgs. Groundwater has been impacted primarily with gasoline and benzene. There has been a significant decreasing trend in concentrations of gasoline and benzene. Concentrations of TPH as gasoline have decreased by an order of magnitude (from 3 ,200 µg/I to 220 µg/1) and benzene has decreased by two orders of magnitude (from 510 µg/1 to 1 .2 µg/1). During the latest sampling event (October 2004) TPH as gasoline was only reported in well MW I at a concentration of 220 µg/1. MTBE has been analyzed in the wells from 1998 through 2004. MTBE has never been detected in any of the monitoring wells, with the exception of a trace concentration reported in MW8 (0.56 µg/1) during the October 2004 sampling event. Results of the latest laboratory analysis shows concentrations of TPH as diesel reported in wells MWI , MW2, MW3 , MW6 and MW7 at concentrations ranging from 87 to 180 µg/1. NK WALLACE . KUK Fi AF')SOU ETES INC.