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ORN <br /> October 15, 1991 <br /> Project 310-01.02 <br /> Page 2 <br /> r� <br /> Findings <br /> Groundwater occurred at an approximate depth of 8 feet below ground surface on <br /> August 30, 1991,with a northwesterly flow direction at an average gradient of <br /> 0.004 (Table 1,Figure 3). This data is consistent with that observed during the <br /> previous groundwater monitoring event,although groundwater elevations have <br /> decreased in all site wells by 0.03 foot to 0.25 foot. <br /> Groundwater samples collected from site wells on August 30, 1991,were analyzed <br /> for total petroleum hydrocarbons calculated as gasoline(TPH-gasoline), total <br /> petroleum hydrocarbons calculated as diesel(TPH-diesel), and benzene,toluene, <br /> ethylbenzene, and xylenes(BTEX compounds). Detectable TPH-gasoline <br /> concentrations were observed only in Wells U-2 and U-5, at concentrations <br /> 1,700 parts per billion(ppb)and 2,200 ppb respectively. A single Occurrence of <br /> detectable TPH-diesel was present in Well U-5 on August 30, 1991 at a <br /> concentration of 380 ppb. Beniene concentrations were observed in Wells U-1, <br /> U-2, U-5,and U-b,with a maximum concentration occurring in U-5 at 100 ppb. <br /> Dissolved hydrocarbon concentrations are presented on Figure 4. The certified <br /> analytical reports and field data sheets are included in Attachment B. <br /> Additional Investtgataon <br /> The extent of petroleum hydrocarbons in the soil and groundwater underlying the <br /> site is not currently defined. PACIFIC submitted a technical report dated <br /> August 5, 1991, documenting the results of the soil and groundwater investigation <br /> conducied at the site. That report included recommendations to install one off-site <br /> groundwater monitoring well to the north of the site,and one off-site well to the <br /> west of the site(Figur:, 5), PACIFIC is currently in the process of obtaining <br /> private property access agreements to install these monitoring wells. The next <br /> quarterly groundwater sampling event is scheduled for November 1991. <br /> f <br /> Jl0olU2(3(?91 <br /> i <br />