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i I3.1.3 Groundwater Analytical. Results—December 2000 Laboratory analytical results of the December 2000 groundwater sampling event, which Included two ' sample groups (the middle "B" casing and lower casing samples), plus two samples from monitor wells MW-3A and MW-5A, revealed variable results between sample groups Compared with previous ' analytical results (September 2000), the results were relatively consistent A summary of analytical results for the December 2000 sampling event is presented in Table 2 A copy of the corresponding Ilaboratory analytical report and chain-of-custody documentation Is provided in Appendix C ' Groundwater samples were recovered from only two of the upper "A" casings wells (MW-3A and MW-5A) due to the lack of water in the other upper "A" casings wells Results of these samples Indicated hydrocarbons In groundwater at concentrations similar to those of water from the corresponding middle"B"casings Analytical results of groundwater samples collected from the well casings screened across the yt g p groundwater Interface (middle `B" casings) revealed the highest concentrations of hydrocarbons in groundwater from wells MW-3B, MW-4B, MW-2B, and MW-6B The concentrations of hydrocarbons in groundwater from MW-3A (140,000 TPHg and 31,000 benzene suggested that the source area of hydrocarbons was near MW-3B The elevated concentrations of hydrocarbons in water from MW-2B, MW-4B, and MW-6B suggests that the hydrocarbon plume spread across the site between the eastern and western property boundaries Lower level detections of benzene in groundwater from monitor wells MW-5B, MW-8A, and MW-9B suggested that the boundary of the hydrocarbon plume was near the northern and southern property boundaries The extent of hydrocarbons in groundwater associated with the middle "B"casings is shown on Figure 4 Analytical results of groundwater samples collected from the lower casing wells, screened between Iapproximately 60 and 100 feet bgs, revealed the highest concentrations of hydrocarbons in groundwater from wells MW-6 and MW-4 The concentrations of hydrocarbons in groundwater from MW-6 (2,900 pg/L TPHg and 1,300 pg/L benzene) Indicated a shift in the hydrocarbon concentration pattern compared ' with data from the anIddle `B" casings Rather than the hydrocarbon plume circling the building with a "bulls-eye"pattern, the plume was confined to the southern portion of the site along the eastern (MW-4) and western (MW-6) property boundaries Samples from monitor wells MW-1, MW-2, MW-3, MW-5, ' and MW-8 did not contain TPHg or benzene above method detection limits 07/10/01 1 Blaes Project#002-70950-02 bjm C 1BLAESIU-Hau1170950170950r141 doc I