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,r Site Background Boyett Petroleum(419 S.Main St.,Manteca.) Page 4 of 5 One municipal water well, the City of Manteca Well #5, is located at 331 Jessie Avenue, approximately 1,500 feet west of the site; however, during the area reconnaissance, this well was observed at 323 Jessie Avenue. Mr. Eric Medeiros of CMPW described this well as installed in 1952 to a total depth of 125 feet bgs and was constructed using 100 feet of 18-inch casing with no screened intervals. Mr. Joe Wells of the City of Manteca Public Works (CMPW)indicated that a groundwater sample collected from this well in September 2002 tested negative for MTBE. A detailed description of the SRS was presented in Condor's Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003. L In the Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003, Condor recommended that quarterly monitoring of the site should continue. All of the monitor wells contained a high percentage of sediment and require redevelopment. In addition, Condor recommended that damaged wells MW-4 and MW-5 be properly destroyed and MW-4 be replaced with a new monitor well. Also, Condor recommended the installation of an additional well south of MW-9 in order to provide data between the USTs and the northwestern portion of the site, which has historically contained elevated levels of MTBE in groundwater samples collected from monitor wells MW-1 and MW-7. Data from this location should be useful in evaluating whether the UST area is the likely source of the elevated levels of MTBE in groundwater in the northwestern portion of the site. On December 27, 2002, a Condor representative was onsite to measure water levels in and collect groundwater samples from all nine monitor wells for the fourth quarter 2002 groundwater monitoring event. Monitor well MW-5 was dry, and MW-4 contained significant sediment and was purged dry during sampling and did not recharge; thus, groundwater samples were not collected from MW-4 and MW-5. No floating product, sheen, or odors associated with petroleum hydrocarbons were observed in any of the wells sampled during the fourth quarter 2002 monitoring event. All of the groundwater monitor wells sampled contained a significant amount of suspended sediment. Laboratory analytical results for the groundwater samples collected at the site on December 27, 2002, indicated that BTEX and TPH-G were not detected at or above the laboratory reported detection limits in any of the groundwater samples collected from the monitor wells. Selected gasoline oxygenates/additives were not detected at or above the laboratory reported detection limits in the groundwater sample collected from MW-6. MTBE was detected in the groundwater samples collected from MW-1 through MW-3 and MW-7 through MW-9. TAME was detected in the groundwater samples collected from MW-1 and MW-7. TBA was detected in the groundwater sample collected from MW-1. Static water level measurements collected on December 27, 2002, generally indicated a groundwater flow direction to the north/northeast, a reversal from that reported in the Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003. In the Fourth Quarter Groundwater Monitoring Report, December 2002, Condor restated the recommendations presented in the Groundwater Monitoring Report, Third Quarter 2002, dated January 16, 2003, with the additional recommendation that the water levels in the site's monitor wells be measured and groundwater samples collected for MTBE laboratory analyses on a monthly basis, for a consecutive six month period. The primary objective of this increase in monitoring frequency would be to garner additional information pertaining to the site's historically highly variable groundwater gradient, which may help explain the fluctuations in the MTBE levels recorded for MW-2 and MW-8 and the historically elevated levels of MTBE in groundwater samples collected from MW-1 and MW-7. V On March 21, 2003, a Condor representative was onsite to measure water levels in and collect groundwater samples from all nine monitor wells for the first quarter 2003 groundwater monitoring event. Monitor well MW-5 was dry, and MW-4 contained significant sediment and was purged dry during sampling and did not recharge; thus, groundwater samples were not collected from MW-4 and MW-5. v