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M' _ <br /> -- Project 3I0-01.02 <br /> Paze <br /> all wells are constructed of 3-inch diameter PVC casing. These wells were <br /> sampled during the current sa,noling event. <br /> `T1 <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 /> Groundwater samples collected from site monitoring wells on November 6, 1991, <br /> were analyzed for TPH-gasoline,TPH-diesel,and BTEX compounds. Detectable <br /> TPH-gasoline:concentrations were observed only in Wells U-2, U-5,and U-6,at <br /> concentrations of 290 parts per biilion(ppb)and 1,400 ppb, and 280 ppb, <br /> respectively(Figure 4). Detectable TPH-diesel concentrations were not pres=t in <br /> any of the site wells on November 6, 1991. Benzene concentrations were observed <br /> in Wells U-2,U-S,and U-6,with a maximum concentration occurring in Well U-5 <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 /> sheets are included in Attachment B. <br /> Additional Investigation <br /> 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 /> were included in a PACIFIC report dated August 5, 1991. An access agreement <br /> 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 /> the north,PACIFIC currently proposes that a well be installed on-site, at the <br /> 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 agreements from Southern Pacific to <br /> install the proposed off-site well to the north in the event that this additional well <br /> is needed in the future. The next quarterly groundwater sampling event is <br /> scheduled for February 1992. <br /> noato2hQ9t <br /> l <br /> f <br />