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GROUND ZERO ANALYSIS, INC. '"f <br /> 3422 W. Hammer Lane, Suite C-294 <br /> Stockton, California 95219 <br /> Telephone: (209) 952-3481 <br /> Facsimile: (209) 952-9891 <br /> May 24, 995 S <br /> Mr. Mi a Infurna <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> PO Box 388 <br /> Stockton, CA 95201-0388 <br /> Subject: Report on Tank Removal Soil Sampling and Source Removal Overexcavation at Flag <br /> City (Bokides) Chevron, 6421 West Paddock Place, Lodi, California. <br /> Dear Mr. Infurna: <br /> As required, Ground Zero has prepared this report on tank and dispenser island removal and <br /> overexcavation activities performed at the subject site on March 31, and in April 1995. <br /> TANK REMOVAL <br /> On March 31, 1995 Ground Zero Analysis, Inc. (Ground Zero) observed Stockton Service Station <br /> Equipment (SSSE) remove five 12,000-gallon steel underground storage tanks (USTs) and dispensers <br /> from the site (Figure 1). The steel USTs were triple tar wrapped. Visual inspection of the tanks <br /> indicated at least two layers of tar wrapping were still intact. No holes, pitting, or corrosion were <br /> observed on the former USTs. Condition, capacities, and contents at the time of tank removal are <br /> described in the soil sampling report included in Attachment A. <br /> TANK PIT OVEREXCAVATION AND SAMPLING <br /> Ground Zero observed SSSE overexcavate the tank cavity laterally approximately 2 feet to the north, <br /> south, east, and west in order to remove discolored soil with petroleum hydrocarbon odor. Following <br /> lateral overexcavation a sheen was observed on groundwater, encountered at a depth of approximately <br /> 9 feet below ground surface (bgs), in the tank cavity. Under the supervision of San Joaquin County <br /> Public Health Services-Environmental Health Division (SJCPHS-EHD), Ground Zero collected soil <br /> samples from the sidewalls of the tank cavity at depths of approximately 8 to 9 feet bgs. Sidewall <br /> sample locations are shown on Figure 2. The sidewall soil samples were submitted to Argon Mobile <br /> Labs (Argon) of Ceres, California for analysis of total petroleum hydrocarbons as gasoline and diesel <br />