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2000 STIMSON ROAD <br /> WKA No 2086 05 <br /> March 25, 1993 <br /> Page 2 <br /> The AASF is operated by the California State Military Department and has been operating at the <br /> Stockton Metropolitan Airport since the 1950s, the site was expanded to its present size in 1974 <br /> The site is located on relatively flat lying alluvium (silts and clays) at an elevation of 25 feet <br /> above sea level Depth to ground water beneath the site is expected to fluctuate between 20 and <br /> 50 feet below surface grade based on water level measurements of county well 01N/07E- <br /> 31L01M, located one-half mile south of the site (Historical Ground. Water Levels in San Joaquin <br /> County, Department of Water Resources, April 1990) The regional ground water flow direction <br /> is to the north, based on the Spring 1990 San Joaquin County Flood Control Map showing equal <br /> lines of ground water elevations <br /> Fuel storage for the AASF was located in three 5000-gallon underground steel tanks which were <br /> installed in the early 1950s The tanks were oriented east-west and rested on a six-inch thick <br /> concrete slab which still remains in the excavation at a depth estimated to be 11 feet below grade <br /> The fuel dispensers were originally located on the north side of the tanks During the 1974 <br /> expansion/modernization, the dispensers were moved 30 feet east Aviation gasoline was <br /> reportedly stored in the tanks until the early 1960s when turbine powered aircraft began replacing <br /> older piston powered planes From approximately 1962 until 1988, JP-4 was stored in the tanks <br /> No fuel loss from the tanks was observed based on inventory monitoring Inventory monitoring <br /> was accomplished by weekly sticking There is no record of any precision leak test having been <br /> performed on any of the three tanks There is no record of any tank repairs, however, as <br /> described previously, the dispensers were relocated 30 feet east during the 1974 expansion <br /> The tanks ceased operation in 1989 and were removed from the site in January 1990 The tanks <br /> appeared to be intact and not leaking at the time of removal Five soil samples (1 through 5) <br /> were collected from beneath the tanks at the time of removal by Blaine Tech Services, Inc (Plate <br /> 2) Samples 1 through 4 were collected along the edge of the concrete slab, sample 5 was <br /> collected after coring a hole through the slab All samples were reportedly collected from 2 75 <br /> feet below the concrete slab, approximately 13 to 14 feet below grade Test results revealed no <br /> detectable concentrations of fuel constituents from samples 2, 3, and 5 Test results of sample 1 <br /> revealed 1500 ppm total petroleum hydrocarbons (TPH) as diesel and 1600 ppm TPH as Jet fuel, <br /> 7510 <br /> WALLACE KHL <br /> Rec ded pa • Er ASsacwms lifl'C <br />