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feet bgs were submitted for analyses TPH gasoline, VOCs, and the five fuel oxygenates were not detected above laboratory reporting limits in the three soil samples Seven groundwater monitoring events have been performed between June 2000 and January 2005 During the first monitoring event, TPH gasoline, BTEX, MTBE, and TAME were detected in downgradient well MW-1,benzene,total xylenes, and MTBE were detected in MW-2, and MTBE was detected in MW-3 During the second monitoring event performed In October 2000 (approximately five months after removing the UST),petroleum hydrocarbon concentrations in the groundwater significantly decreased,most significantly in downgrad>ent well MW-1 MTBE was the only constituent detected in MW-1 and MW-2 Petroleum hydrocarbons were not detected above laboratory reporting limits in MW-3 Groundwater monitoring did not occur again until April 2004 Four consecutive quarterly monitoring events were performed between April 2004 and January 2005 Beyond a single detection of total xylenes at 1 1 ug/L in MW-2 during the April 2004 sampling event,MTBE was the only constituent detected in the groundwater samples since June 2000 NO FURTHER ACTION REQUIRED REQUEST Ina letter dated December 20,2004,Ms Margaret Lagono of San Joaquin County Environmental Health Department requested that following the January 2005 monitoring event, a NFAR report be prepared As requested, Kleinfelder prepared this report according to the Central Valley Regional Water Quality Control Board (CVRWQCB), Appendix A, dated April 16, 2004 Appendix A contains a checklist used to sun nanze the required information The completed checklist is included in Attachment A of this report CONCLUSIONS • The source of contamination was mitigated with the May 18, 2000 removal of the 12,000- gallon gasoline UST and 118 cubic yards of soil around the UST c • Based on analytical results from soil and groundwater investigations performed in the vicinity of the former UST,the soil i npact appears to be limited and groundwater impacted with MTBE has been the primary concern at the site Four consecutive quarterly groundwater monitoring events were performed between April 2004 and January 2005 Results of the monitoring events show that groundwater gradients have been consistently in a northern direction and MTBE concentrations have been consistently below the water quality objective established at 5 ug/L Therefore, the contaminant plume appears to be stable and does not appear to be migrating The lateral extent appears to be limited to the near vicinity ' of the former UST • Well MW-4 is screened in a deeper groundwater zone than the shallow groundwater zone in which MW-1 through MW-3 are screened The shallow groundwater gradient indicates that MW-4 is downgradient of the former UST Petroleum hydrocarbons were not detected above laboratory reporting limits in MW-4 during the four quarterly monitoring events Additionally, petroleum hydrocarbons were not detected in soil samples from MW-4, collected at depths below the shallow groundwater zone Therefore, the vertical extent of groundwater impact appears to be limited to the shallow groundwater zone ' • According to the City of Tracy, Public Works, Water Resources coordinator, the City of Tracy supplies treated water to the site and surrounding areas from a municipal well located . approximately 700 feet southwest (upgradient)of the site The City of Tracy also indicated that according to their best knowledge, domestic and irrigation wells within a 2,000-foot radius of the site have been destroyed or abandoned 49014-1/SAC5R423 Page 2 of 3 June 30,2005 CoppC 2005 Klemfefder,Inc �� KLEINFELDyn R 3077 Fite Circle, Sacramento, CA 95827-1815 (916) 366 1701 1916} 366-7013 fax