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WELLS FARGO BANK PROPERTY 49 SOUTH WILSON WAY STOCKTON, CALIFORNIA DECEMBER 28, 1998 Page 4 i one additional 80-foot deep soil boring, and the monitoring and sampling of the four existing groundwater monitoring wells. The following is a summary of the findings from the investigation and monitoring event • The groundwater flow direction was measured to be to the northeast with a hydraulic gradient of 0.0055; • TPH-g concentrations between 1.3 and 590 img/kg were reported in the soil samples collected from Boring B5 at depths between 35 and 61 feet bgs. The deepest sample, B5-78, collected at 78 feet bgs, Was reported to contain 2.8 mg/kg of TPH-g; • Only sample B5-50, collected at 50 feet bgs, was reported to contain benzene, at 0.006 mg/kg. • TPH-g and BTEX were not reported in groundwater samples collected from monitoring wells MW-1 or MW-3; It • TPH-g was reported in the groundwater samples collected from MW-2 and MW-4 at concentrations of up to 3.4 ppm; • Benzene was reported in the groundwater sampl s collected from MW-2 and MW- 4, at concentrations of 1.2 ppm and 11 ppm, respectively; • MTBE and other fuel oxygenates were not reported in the soil or groundwater _ samples collected; and • A review of a historical photograph of the site, historical Sanborn Fire Insurance Maps, and the current concentrations of TPH-g and benzene indicates that the most probable locations of the former USTs were east of the former pump island, near the corner of East Market Street and South Wilson Way, which is beneath the current bank building. Based on the above-mentioned observations, analytical results, and telephone conversations with the SJCEHD, Building Analytics has concluded that the TPH plume beneath the site has been sufficiently delineated, has notJsignificantly impacted the site and dose not pose a significant threat to human health. The fallowing is our formal request for no further action. 1 I Location of former USTs Subsequent to the Phase I ESA, Building Analytics further reviewed historical fire insurance maps as well as historical photographs to assess the location of the former USTs. A review of a historic photograph, circa 1950, supplied by the Bank of Stockton Archives _ and a 1950 Sanborn Fire Insurance Map, revealed that.the southeast corner of the subject property was occupied by a Golden Eagle gasoline service station. The gasoline service station consisted of a small building and one pump island. The pump island was located to the east of the small building and consisted of two pump dispensers. i ^I E