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Project 310-01.02 <br /> Page 3 <br /> a,i wells are constructed of 3-inch diameter PVC casing. These wells were <br /> sampled during the current sampling event. <br /> Findings <br /> Groundwater occurred at an approximate depth of 9 feet below ground surface on <br /> November 6, 1991,with a northerly flow direction at an average gradient of 0.004 <br /> (Table 1,Figure 3). This data is consistent with that observed during the previous <br /> { groundwater monitoring event,although groundwater elevations have decreased in <br /> all site wells by approximately one foot. <br /> r Groundwater samples collected from site monitoring wells on November 6, 1991, <br /> were analyzed for TPH-gasoline,TPH-diesel,and BTEX compounds. Detectable <br /> � TP <br /> H-gasoline.concentrations were observed only in Wells U-2,U-5,and U-6,at <br /> coizcentrations of 290 parts per,billion(ppb)and 1,400 ppb,acid 2$0 ppb, <br /> respectively (Fig!re 4). Detectable TPH-diesel concentrations were not present in <br /> any of the site wells on November 6, 1991 Benzene concentrations were obseived <br /> in Wells U-21 U-S, and.0-6,with a maximum concentration occurring in Well U-5 <br /> F <br /> at 66 ppb: <br /> The sampling and analytical procedures utilized during this monitoring event are <br /> described in Attachment A, and the certified analytical reports and field data <br /> f <br /> sheets are included in Attachment B. <br /> f <br /> Additional Investigation r <br /> f The extent of petroleum hydrocarbons in groundwater in the vicinity of the site is <br /> not currently defined. Recommendations to install one off-site groundwater <br /> monitoring well to the north of the site,and one off-site well to the west of the site <br /> I were included in a PACIFIC report dated August 5, 1991. An access agreement <br /> 4 has been obtained to install the proposed well to the west of the site. However, <br /> because of difficulties in obtaining an access agreement from the Southern Pacific <br /> Transportation Company(Southern Pacific) for the proposed monitoring well to <br /> j the north, PACIFIC currently proposes that a well be installed on-site, at the <br /> 3 northern boundary of the bulk plant property(Figure 5). These wells are currently <br /> scheduled to be installed during January 1992. UNOCAL will continue in <br /> attempts to obtain private property access agreementsfrom Southern Pacific to <br /> install the proposed off-site well to the north in the event that this additional well <br /> g is needed in the future. The neat quarterly groundwater sampling event is <br /> scheduled for February 1992. <br /> s � _ <br /> 3 <br /> 3100162/4091 <br />