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2 � a <br /> Project 310-01.04 <br /> Page 2 <br /> Findings <br /> Groundwater occurred at an approximate depth of 8 to 9 feet.below ground <br /> surface onFebruary 19, 1992;with a northerly flow direction at an average <br /> gradient of 0.005 (Table 1, Figure 3). This data is consistent with that observed <br /> during the previous groundwater monitoring event, although groundwater <br /> elevations have increased in all site wells by approximately one foot. <br /> Groundwater samples collected from site monitoring wells on February 19, 1992, <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 U6, ate <br /> concentrations of 320 parts per billion (ppb),4,700 ppb, and 4,000 ppb, <br /> respectively(Figure 4). Only Well U-3 contained a detectable concentration of <br /> .TPH-diesel on,February 19, 1992, at a concentration of 3,700 ppb. Benzene <br /> concentrations were observed in Wells U-2, U-5, and U-6,with the maximum' <br /> concentration occurring in Well U-5 at 340 ppb.'k <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 /> t 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. PACIFIC proposed the installation of four additional <br /> groundwater monitoring wells. These wells were installed in March 1992. Two of <br /> the proposed wells are to be installed on the bulk plant property(Figure 5). The <br /> proposed well located in the northwestern corner of the property is intended to <br /> provide information on the groundwater quality in the downgradient direction <br /> from potential on-site sources; and the proposed well located in the north-central <br /> portion of the site is intended to delineate the extent of hydrocarbons in <br /> groundwater to the east. The proposed off-site wells are intended to define the <br /> lateral extent of hydrocarbons in groundwater to the west of the site. The next <br /> groundwater sampling event is scheduled for March, 1992, and a report <br /> documenting this phase of the investigation should be available by May 15, 1992. <br /> 3100104/1Q92 <br />