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December 22 , 1988 Page 2 r Project 156-117 . 1 Flood Plain Deposits are flat-dipping and conformable, indicating a virtually continuous deposition. The sediments are generally fine-grained, consisting of clay, silt, fine sand, and occasional gravel . , Site Inspection On November 17 , 1988 , a site inspection was performed at the subject site to locate potential sources of contamination . No visual signs of contamination were observed on-site. Evidence of an underground storage tank was observed on the property bordering the east side of the subject site, immediately adjacent to the subject property line. According to San Joaquin Local Health District (SJLHD) records, the i underground diesel fuel storage tank was installed in 1987 and has a 10 , 000 gallon capacity. The tank and associated piping are double walled and continuously monitored, and the itank has an overfill protection device . In January of 1988 , the underground tank passed a precision integrity test, indicating the tank to be structurally intact . Numerous 55-gallon drums were observed in the rear of the concrete vault and box producing facility west of the subject site . The contents of the drums are unknown. Potential Sources of Contamination The main potential for contamination as a result of past site usage appears to be from pesticides or herbicides associated with possible past agricultural use, or with possible migration of contaminants from the steel yard to the north of the subject site or the barrel storage area observed at the concrete facility to the west of the subject site. The sample locations and the chemical analyses performed on soil and shallow ground water samples were selected to determine if contamination has occurred from previous site usage , or if contamination from the potential off-site sources has migrated to the subject site. Description of Field Investigation On November 28 , 1988 , the field investigation commenced at the subject site . Prior to any subsurface investigation, well construction permits were filed with the SJLHD and underground utilities were identified by a professional locator service . ' California Department of Water Resources , 1967 . "San Joaquin County Ground Water Investigation" , Bulletin 146 . Metac_ lssociates Anc.