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5 " i.:k'F=.0 Vii•- � -" `�', �_ p �.-y. .s�' ,T �- _ —'� <br /> k <br /> PHASEI IIYDROGEOLOGIC 1NVFSTIGA7ION <br /> 4491 West Durham Fury Road,Tracy.California <br /> Delta Project No.40-91-732 <br /> Page 3 <br /> 2.2 Sife,$tickground <br /> Ms. Stella Ruiz purchased the property fmm Mr. Eugene Heitt in May 1936. In February 1988, Petro <br /> J. <br /> Check removed two 1,000-gatlOn Underground storage tanks which had contained leaded and unleaded <br /> gasoline. Chemical analysis of soil samples collected from the tank excavation indicated that further <br /> investigation was required. <br /> On May 27, 1988, monitoring well MW-1 was installed north of the.t=*.l0mdons by Water Works. A <br /> ground water sample was collected on June 13, 1388, from m0aitar'in well MW-1 anJ analyzed for <br /> w petroleum constituents. The results of the cbemicai analysis lndcated roncentratiaas of 1.6, I6.11-, and <br /> 247 parts per billion(ppb)for benzene,toluene,and total yetroleum hydrocarbons, respectively. "Fur her <br /> investigation was requested by the County of San Joaquin in a letter dated June 11, 1991. <br /> On July 26, 1991, Delta submitted a Phase I Hydrogeologic Investigation Work Plan to Ms.Eleanor Ratliff <br /> -' of the County of San Joaquin(the County)to characterize the presence of petroleum hydrocarbons at the site. <br /> 2,3 RgOcnal HydMC01 av <br /> A regional map showing the.ground water elevation contours for the uncoAned aquifer for spring 1989, <br /> prepared by the San Joaquin County Flood Control and Water Conservation District, shows the direction <br /> of ground water flow is towards the north or northeast. Depth to ground water is expected to be <br /> approximately 15 to 20 feet below the ground surface. <br /> 3,0 MULTS <br /> 3.1 Site i and.GzAir <br /> On August 28, 1991, two soil borings were drilled on site to deplhs of 25 feet below the ground surface and <br /> were completed as monitoring wells (MW-2 and MW-3; monitoring well MW-1 had previously been <br /> -- installed). The monitoring well locations are shown in Figure:2,and the soil boring logs are pr=nted in <br /> Appendix A. Generally, the lithology was comprised of dark to light brownsalty clay and sandy silt with <br /> medium to fine grained sand lenses. The sand lenses were approximately 2 feet thick at a depth of <br /> -.-----------approximately 3feet.--Sampling procedures are presented in Appendix B. <br /> � � , P11too1.8P <br /> i� <br />