SITE INFORMATION AND CORRESPONDENCE

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Mr. Phillip Vallejo ... _ 2 _ `.. 8 April 2003 Mr. Tony Arnaiz Central Valley Construction In March 2002, five additional soil borings were drilled to further delineate the lateral extent of contamination. The lateral extent of soil contamination was delineated by these borings. Consultants for this site estimated that the mass of contamination left in soil is approximately 2.6 gallons of TPHd. Three groundwater monitoring wells (MW-1 through MW-3)were installed on 5 November 2001. Quarterly groundwater sampling revealed no detected TPHg or fuel oxygenates, and low levels of TPHd (100 µg/L). After four quarters of groundwater monitoring,TPHg, fuel oxygenates and TPHd were all non-detect at appropriate method detection limits. An onsite domestic well is located 40 feet north of the UST area. Groundwater from the onsite domestic well was tested 6 times from January 2001 to November 2002. No contaminants were reported in groundwater samples from the onsite domestic well. In September 2002, an off-site domestic well, located approximately 600' downgradient from the site at 124 Klo Road,was sampled. No chemicals of concern were detected in the 124 Klo Road domestic well. On 20 November 2002, Central Valley Construction, Inc. requested site closure. The closure report included a well receptor survey. The well receptor survey showed 23 domestic wells within a 2000-foot radius of the site. In a letter dated 27 November 2002,Regional Board staff concurred with the site closure request and asked for a work plan for monitoring well destruction. On 24 February 2003, Regional Board and San Joaquin County Environmental Health Department staff witnessed the decommissioning of the three monitoring wells. On 25 February 2003, Central Valley Construction, Inc. provided a monitoring well destruction report. Soils beneath the site consist of clay, silt, silty sand, and sand to 31 feet,the total depth of the investigations. Depth to first groundwater is approximately 18 feet below ground surface. As a result of the soil excavation and with the information of decreasing concentrations of petroleum hydrocarbons in groundwater, this site does not appear to pose a threat to water quality, human health and safety, or the environment. In light of the above, a No Further Action Required Letter should be issued and the Geotracker database be updated to reflect site closure.