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1.2 Chronology of UST-Related Events i ' Kllpatrick's operated one 1,000-gallon gasoline UST system The UST was located beneath the sidewalk along South Center Street An associated fuel dispenser was located within the building The UST, the dispenser, and the portion of product piping from the UST to the building were removed in December 1990 The remaining product piping, from the edge of the building to the former dispenser, was properly abandoned on April 17, 1998 ' On April 16, 1998, two 1-inch diameter direct-push probeholes were driven beneath the former UST to collect soil and groundwater samples for laboratory analysis Analytical results, summarized in the June 2, 1998 Preliminary Subsurface Site Investigation Results and Product Piping Abandonment Completion Report, indicated benzene, toluene, ethylbenzene, Iand xylenes (BTEX) impact to subsurface soil and groundwater The soil and groundwater samples did not contain detectable oxygenate compounds ' In July 1999, Ground Zero Analysis, Inc (GZA) of Escalon, California, performed a subsequent subsurface investigation GZA drilled three soil borings, completed them as groundwater-monitoring wells (MW-1, MW-2, ' and MW-3), and collected soil and groundwater samples for laboratory analysis GZA's investigation, summarized in their July 28, 1999 Groundwater Monitoring Well Installation Report, detected BTEX and total petroleum hydrocarbon as gasoline (TPH-g) impact in soil and groundwater samples collected at the MW-2 Samples collected from MW-1 and MW-3, placed in hydraulically upgradient positions relative to the former UST, did not contain detectable petroleum hydrocarbons The SJCEHD required quarterly groundwater-monitonng be performed to ' assess contaminant trends, which included the oxygenate analytes tert-butanol (TBA), methyl-tert-butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl-tert- butyl ether (ETBE), and tert-amylmethyl ether (TAME) After several quarterly events, the laboratory analytical data indicated that higher concentrations of petroleum hydrocarbons were detected in samples collected from well MW-2 and non-detectable or lower concentrations were measured ' at the upgradxent locations SJCEHD requested that additional investigation be performed to assess the extent of petroleum impact PSC submitted a September 24, 2001 Subsurface Site Investigation Workplan to SJCEHD, which proposed further assessment SJCEHD approved this work plan in a letter dated October 16, 2001 ' PSC performed an investigation in March 2002 Six probeholes (PH-3 through PH-8) were advanced, one groundwater-monitoring well (MW-4) was installed, one air-sparging well (SP-1) was constructed, one soil-vapor- extraction well (VW-1) was constructed, and samples of soil and groundwater ' 2 Quarterly Groundwater Monitoring Report 4th Quarter-November 2005 Prepared for SARA LEE BAKERY GRoup,INc Prepared by PSC Environmental Services Invegugauve and Quarterly Report 14th Quarterly Report 11_2005 doe February 24 2006