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2.0 <br /> SITE BACKGROUND <br /> The following section provides a description of the site history, land use, and climatology <br /> of the site and the surrounding area. Information presented in this section was used to , <br /> help evaluate potential chemical exposures and corresponding potential health risk in <br /> subsequent sections. <br /> 2.1 SITE DESCRIPTION AND HISTORICAL USE <br /> —r <br /> YFS operated a motor freight distribution terminal from 1973 to 1990 at 4520 South <br /> Highway 99 Frontage Road in Stockton, California. The site covers 12.3 acres and <br /> consists of 50 docking-bays, truck and trailer parking, a fire protection pond, a drainage <br /> retention pond, and a truck fueling and weighing area. The majority of the site is <br /> overlain with 6 to 10 inches of concrete and asphalt. The fire protection pond and <br /> drainage retention pond,which are located at the eastern section of the site, are overlain <br /> with native or imported fill soil. <br /> Two 10,000 gallon underground storage tanks were removed October 1994. The tanks <br /> had contained gasoline from 1973 to 1979 and diesel from 1979 to 1990. Holes were <br /> observed in the fill pipes of both tanks and in the bottom of one tank. The other tank `^ <br /> appeared to be in good condition. The tank bottoms were approximately 11-feet below <br /> ground surface (bgs). Following the detection of petroleum contaminants, soil was -- <br /> excavated down to a depth of approximately 30 feet at the center of the excavation. <br /> Following excavation, soil samples were taken and petroleum hydrocarbon constituents Y <br /> were detected. Additional excavation was conducted down to approximately 32 feet bgs. <br /> The excavation was backfilled with drain rock fill and pea gravel and was paved over. <br /> Additional borings down to groundwater were taken. <br /> The results of the soil samples indicate that residual petroleum hydrocarbons exist from <br /> 34 feet bgs to approximately 55 feet bgs in an area that is approximately 15 feet wide. <br /> Petroleum hydrocarbons appear not to have impacted groundwater at the site based on r <br /> a groundwater sample that was taken approximately 15 feet from the former tank area <br /> SALDMYELLO.RPT May 4,1995 2-1 <br />