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I I <br /> I x M I <br /> i <br /> Project No 58080-06-02 <br /> May 5, 1995 <br />' 1 3 Previous Environmental Studies } <br /> Initial subsurface investigation was performed at the site in March 1991 by Uriah Inc of Livermore, <br /> California The initial environmental work performed by Uriah consisted of the drilling of three soil <br /> borings (SB-1 through SB-3) and the collection of soil samples for chemical analysis Total <br /> petroleum hydrocarbons as gasoline (TPHg) was detected in soil at concentrations ranging from <br />' 1,200 to 1,400 mg/kg at the depths of 15 and 20 feet bgs Total petroleum hydrocarbons as diesel <br /> fuel (TPHd) was detected in soil at concentrations ranging from 54 to 75 mg/kg <br /> Between December 1991 and June 1992, Uriah performed additional subsurface investigation <br /> consisting of the drilling of eight additional soil borings (EB-4 through EB-1 1), the construction of <br /> Sthree groundwater monitoring wells(MW-1 through MW-3) and the collection and chemical analysis <br /> of soil and groundwater samples beneath the site The results of these additional studies indicated <br /> that TPHg and TPHd existed in soil beneath the site at concentrations up to 11,000 and 2,200 <br /> mg/kg, respectively The maximum depth of detectable TPHg in soil at that time was approximately <br /> 43 feet bgs beneath the southern portion of the site <br /> Groundwater beneath the site was reported to be impacted with total petroleum hydrocarbons as <br /> gasoline (TPHg), 1,2-Dichloroethane (DCA), 1,2-Dichloroethene (I)CE), Trichloroethene (TCE), <br /> Tetrachloroethene (PCE) and Methyl Tert-Butyl Ether (MTBE) <br /> The depth to groundwater beneath the site (approximately 55 feet bgs) and the maximum depth of <br /> detectable petroleum hydrocarbons in soil (approximately 43 feet bgs) suggest that the chemical <br /> ' compounds in groundwater have migrated to beneath the subject site from offsite locations This <br /> is further supported by the fact that MTBE was detected in groundwater beneath the site MTBE <br /> is used as a motor vehicle fuel additive and was not introduced into Northern California until the <br /> early 1980's after the former USTs were removed from the subject site <br /> -6- <br />