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r 1.0 Summary of Site Investigation, Cleanup and Monitoring Two underground"fuel storage tanks (one 350-gallon diesel and one 500-gallon gasoline) were removed by a City contractor in 1985 from a location that later became a portion of Sixth Street. Soil samples collected at the west end of the excavation at that time showed 18,000 parts per million (ppm) of Total Petroleum Hydrocarbons as Diesel (TPHD). There is no information regarding any soil being removed during this work in the 'street: As a result of the tanks removal information, SJC/EHD requested additional site assessment. Wright Environmental .Services, Inc. (Wright) was retained by the City to drill and sample three exploratory borings at the reported former underground tank pits in Sixth Street in February 2003. Soil boring samples collected in February 2003 showed that contaminants contained TPHG and TPHD in soil samples near the capillary fringe, with the highest values in B-2. Groundwater samples from these borings showed TPHG and TPHD in Borings B-2 and B-3. These samples together with the inferred northerly groundwater flow direction indicate that a dissolved plume has migrated across Sixth Street and toward the Delta Disposal property line. Three groundwater monitoring wells were installed as required by EHD following a review of Wright's 2003 study. The main objective of the 2008 assessment was to evaluate the current groundwater conditions and monitoring of groundwater. Wright presented this information to the EHD, who has concurred with this conclusion and that the site qualifies for site closure/NFAR in their letter dated September 24, 2009. The following sections summarize the information collected by Wright on this site to support the request for Closure Summary Report to support No Further Action Required (NFAR). Each documentation item is summarized in the following sections using the RWQCB NFAR outline to present the information. Selected figures and maps to illustrate the discussion are abstracted from the original reports (see Appendices A and B). 2.0 Site Closure Summary for NFAR Documentation 2.1 Site History and Current Site Conditions Summary The property is located at-99 Sixth Street in Tracy, California. The property is located in the right-of-way of Sixth Street. The property immediately north of the where the underground storage tanks were located in Delta Disposal. Residential development is located to the east and west of Delta Disposal and Southern Pacific Railroad property occurs on the south side of Sixth Street(see Appendix A Figures 1, 2, 3 and 4). 2.2 Site Geology and Hydrogeology Summary A total of three GeoProbe exploratory borings were drilled and three groundwater monitoring wells installed at the locations shown on Figures in Appendix A. Page 3 of 17