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i EDB and organic lead were none detected for each of the eight soil samples. . . The second sampling was completed on October 4,1989. Groundwater monitoring wells were developed and initially sampled approximately two weeks after completion. Ground water samples were sent to a State certified laboratory for analyses. Ground water samples from the two up-gradient wells (MW-2 and MW-3)were none detected for total hydrocarbons and BTX. However, analyses of the ground water samples from the down-gradient monitoring well (MW-1) detected total hydrocarbons at 4,300 ugrl benzene at 250 ugll, ethyl benzene 30 ugrl and xylenes at 280 u9A from the first sampling (June 1989). and benzene at 882 ugll, xylenes at 151 ugl and total hydrocarbons at 574 ugll from the second sampling (October 1989). EBMUD removed the two remaining underground fuel storage tanks in September 1989. Kleinfelder understands that laboratory data from the sol samples collected from the removed tanks indicated that the soils did not contain hydrocarbons above analytical method detection levels. On-site observations and tank tests did not indicate past fuel leakage from these two tanks. 1.2 Present Investigation -WESTON In February 1991, at the direction of EBMUD, WESTON submitted a Work Plan to the EHD for an additional soil'and groundwater investigation at the EBMUD site. The investigation plan consisted of`lhe iristalla6h'and development of four additional groundwater monitoring wells on the site, soil sampling from the four well borings and sampling and analysis of groundwater from all seven (the three previously installed and the four new) monitoring wells. The Work Plan was approved and the well permits were issued by the EHD. Field work took place in February and March 1991. 1.3 ,Rite Desaition EBMUD maintains an operations and maintenance yard at 1804 West Main Street in Stockton, California (Figure 2). The site is occupied by buildings used as offices,mainte- nance garages, and supply and equipment storage areas. Vehicles are currently refueled In the yard from new, above ground storage tanks. The yard is essentially flat and is situated In an area of mixed residential and industrial use. The Port of Stockton and the Stockton deep water channel are located approximately 1000 feet north of the yard. 2.0 1991 INVESTIGATION 2.1 Monitoring WeLkmlabfian In February 1991, four monitoring wells(MW-d, MW-5, MW-6 and MW 7)were installed In addition to the three wells already on the site. The purpose of the four new wells was to establish additional groundwater monitoring points,three in the downgradient direction (MW-4, 5 and 6)and one in the sidegradlent or upgradient direction (MW-7)by providing both groundwater quality data and groundwater flow gradient information. - 3