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4 Z Mr.Paul Fry N WE Project 05-001500 July 31, 1998 Page 2 of 7 Joaquin County Public Health Services-Environmental Health Division (SJEHD), a 10,000-gallon gasoline underground storage tank (UST), a 7,500-gallon gasoline UST, a 5,000-gallon gasoline UST, and a 550-gallon waste oil UST were removed from the subject Property in May 1987. Analysis of soil samples collected during the UST removal indicated no detectable concentrations of petroleum constituents, lead, VOCs, and poly chlorinated biphenyls (PCBs). However, according to the SJEHD, an adequate number of samples were not collected from the excavation pit. In addition, the 1a..horatory detection limit for many of the chemical analytes apparently exceeded current standards. Therefore, the SJEHD requested additional investigation of the site. SUBSURFACE CHARACTERISTICS/HYDROGEOLOGY The Manteca area is considered to fall within the geographic boundaries of California's Great Central Valley, part of a large, northwest-southeast trending trough paralleling the junction of the North American and Pacific.. crustal tectonic plates. This situation is bounded locally to the west by the Sacramento/San Joaquin River Delta, and by the Sierra Nevada to the east. The subsurface features of the area are related to geoiog,ic events that shaped the nearby ridges and deposited erosional sedirnents in the vnlleys. The soil underlying the subject Properiy has been characterized as Hanford Sandy Loam, which consists of brown to light brown, recent alluvial deposits from granitic and similar quartz-bearing rnicac eons rock sources. They are neutral to slightly basic in reaction and medium to fine textured. In a typical soil profile, the subsoil begins at 10 to 15 inches, is slightly light brown, but otherwise has about the characteristics as the surface. Normally, the soil is six or more feet deep. Permeability is slow (Soil Survey of San Joaquin County, California, United States Department of Agriculture, Soil Conservation Service (USDA/SCS), 1952). SCOPE OF WORK Field work performed at the subject Property on July 16, 1998, was intended to assess the presence or absence of petroleum constituents and VOCs in soil and groundwater at selected locations beneath the site. This work included the following: • Acquisition of drilling permits and preparation of a work plan for the SJEHD. • Preparation of a site-specific Health and Safety Plan.