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June 16, 1997 Page 3 • Groundwater was encountered and stabilized at a depth of approximately 30 to 32-1/2 feet bgs during drilling Groundwater elevation data, calculated from data collected on February 12, 1996, indicated that groundwater flow beneath the site was toward the southwest at an approximate gradient of 0 001 A northwest-southeast trending groundwater ridge was reported on the site The southwesterly groundwater flow direction observed in the southern portion of the site is consistent with groundwater flow at nearby sites Mr Matt Machado, Civil Engineer with the City of Ripon Public Works Department, stated in a telephone conservation on May 1, 1997 that the trend of groundwater flow beneath Ripon City limits is generally southwesterly Additionally, Mr Machado stated that the Stanislaus River was a losing river in the vicinity of the Ripon City limits February 1996 groundwater elevation data suggests that onsite groundwater flows to the southwest Nondetectable concentrations of hydrocarbons were reported in the onsite upgradient well Groundwater elevation, flow direction, and gradient data are shown on Figure 2 Previous Work An unauthorized release was reported during UST removal activities on September 27, 1995 An Underground Storage Tank Unauthorized Release (LEAK)/Contamination Report was prepared (Attachment E) Touchstone Developments (Touchstone) was • present during UST removal and conducted soil sampling activities Two soil samples were collected beneath the USTs at depths of 15 and 16 feet bgs Analytical results reported nondetectable concentrations of hydrocarbons, with the exception of concentrations of benzene at 0 0077 and 0 011 parts per million (ppm), respectively One soil sample was collected at the western dispenser island at approximately 3 feet bgs The analytical soil results reported 12 0 ppm TPH-g Additional soil excavation was performed beneath the western dispenser island Soil samples were collected from the excavation limits by Touchstone Results reported one soil sample from the NE side of the excavation(7 feet bgs) at 260 ppm TPH-g and one sample from the excavation bottom (8 feet bgs) at 14 ppm TPH-g Soil samples were also collected from the sidewalls of the new tank excavation Analytical results reported one sample from the SE wall (6 5 feet bgs) at 1 1 ppm TPH-d and one sample from the SE wall (9 feet bgs) at 0 03 ppm benzene and 0 1 ppm MtBE No other concentrations of hydrocarbons were reported UST and overexcavation sample locations and soil analytical results are presented as Attachment F (Touchstone) An estimated 315 cubic yards of soil were removed from the project site and transported to the BFI-Vasco Road Landfill in Livermore,California, on October 16, 1995 On January 10, 1996, PACIFIC installed four soil borings (B-1 through B-4) and four groundwater monitoring wells (MW-1 through MW-4) at the site The soil borings and wells were installed to investigate soil and groundwater conditions in the vicinity of the �F former USTs, product piping, and product islands 9201026A/CLosERPT