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i Mr Martin Harris Page 2 of 7 • ethylbenzene and total xylenes at levels exceeding the respective laboratory detection limits Soil analytical results are summarized in Table 1 ! Sensitive Receptor Survey At the request of the San Joaquin County Environmental Health Department (EHD), the property owner and Ground Zero conducted a survey of production and/or domestic wells within 2000 feet of the site Approximately fifteen wells (domestic and irrigation) are Iocated within 2000 feet of the site The nearest water supply wells are the former facility well located approximately 220 feet northwest (downgradient) of the former UST and a neighboring domestic well located approximately 125 feet southeast (upgradient) of the former UST The former facility well is no longer used by the facility, but is maintained as an emergency fire suppression well The facility currently utilizes a newer well at the northern boundary of the property approximately 500 feet north of the former UST All three of the wells mentioned above were sampled for gasoline constituents on September 26, 2003 No gasoline constituents, including benzene or MTBE, were detected in these water supply wells Subsurface Investigations i • Ground Zero supervised the drilling of three soil borings on December 17, 1999 to investigate the extent of soil and groundwater contamination in the vicinity of the former UST Results of ! the investigation indicated that soil and groundwater had been impacted from an unauthorized release of gasoline Residual soil contamination appeared to be limited vertically to a depth of less than 15 feet below ground surface (bgs), but monitoring wells were necessary to evaluate the extent of groundwater contamination Ground Zero installed and sampled four groundwater monitoring wells in January 2001 and initiated quarterly groundwater monitoring and sampling to investigate the lateral extent of groundwater contamination at the site Based upon the analytical results of soil and groundwater samples collected at the site through March 2002, Ground Zero submitted a formal request for site closure as a low risk groundwater case in correspondence dated June 18, 2002 EHD disagreed with Ground Zero's recommendation and requested additional investigation, including additional shallow monitoring wells and an investigation of the vertical extent of soil and _ groundwater contamination Pursuant to a directive from EHD three additional groundwater monitoring wells were installed, and one deep soil boring was advanced in January 2004 to further investigate the vertical and lateral extent of contamination Based upon this additional investigation, Ground Zero concluded that the vertical extent of groundwater contamination had been defined and the downgradient extent of contamination in the shallow aquifer had been essentially defined • G 1Gt20UNDZF%Tuttl3oy1Rcporls\Qh1R120051IQM2005 doc