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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 on February 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 saniples collected from site monitoring wells on February 19,1992, <br /> were analyzed for TPH-gasoline,TPH-diesel,and B T EX compounds. Detectable, <br /> TPHi-gasoline concentrations were observed only in Wells U-2,U-S,and U6 at <br /> concentrations of 320 parts per.billion.(ppb),4,700 ppb,and 4,000 ppb, <br /> respectivety;`(itq'are 4), Only Well U-3 contained a detectable concentration of <br /> TPH-diesel an F'ebru 19,1992,at a concentration of 3,700 ppb. Benzene <br /> concentmtiorz were observed in Wells U-2,U-5,and U-6,With the MaXimu.m <br /> concentration occurring in-Well U-5 at 340 ppb. <br /> The sampling and analytical procedures utilized during this monitoring event are <br /> i described in Attachment A,and the certified analytical reports and field data :< <br /> sheets are included in Attachment B. <br /> `J Additional Investigation <br /> 4 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 he installed on the bulk plant property(Figure 5). T}ae <br /> proposed well located in tut;northwestern corner <br /> of the property is intended to <br /> provide information on the groundwater quality in the downgr3dient 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 /> groundwaâ–ºPr to the east. The proposed off-site wells are intended to define the <br /> Iateral extent of hydrocarbons in groundwater to the west of the site. The next <br /> duled for March, 1992,and a report <br /> groundwater sampling event is sche <br /> documenting this phase of the investigation should be available by May 15, 1992. <br /> y <br /> i <br /> 310010411092 <br />