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' 30 January 1998 • AGE-NC Project No 95-0104 ' Page 3 of 4 ' 32 ANALYTICAL RESULTS OF GROUND WATER SAMPLES During the December 1997 sampling event, TPH-g was detected in water samples collected from MW-1, MW-5, MW-6 and VW-1 at concentrations ranging up to 50,000 parts per billion (ppb, reported as micrograms per liter) ' BTE&X were detected in samples collected from each well at concentrations i anging up to 10,000 ppb(xylenes,V W-1) Benzene was detected from each well at concentrations ranging up to 270 ppb (VW-1) MTBE was not detected utilizing EPA methods 8020 and 8260 in samples collected from MW-1, MW-5, MW-6 and VW-i TBA was detected from MW-6 and VW-1 at concentrations ranging up to 25 ppb DIPE, TAME and ' ETBE were not detected in any ground water samples during this quarterly sampling event Analytical results of selected ground water samples are summarized in Table 2 The laboratory reports (Alpha Analytical Batch Number 97-1216-16 and KIFF Analytical Report Number l 0864) and chain-of-custody forms are presented in Appendix B • 4.0. DISCUSSION AND CONCLUSIONS Based upon data collected during the December 1997 monitoring, AGE has the following conclusions • In December 1997, the gradient was approximately 0 006 ft/ft, or approximately 34 feet per mile • Ground water flow direction on the site was estimated to be toward the northeast in the area Iof wells MW-2, MW-4 and MW-6 and toward the southeast in the area containing MW-1, MW-3 and MW-5 • The ground water surface elevation at the site continues to remain above the slotted screened intervals in wells MW-2 through MW-4 Therefore,ground water samples were not collected from these wells because ground water samples collected from submerged wells may not be representative of shallow ground water dissolved petroleum hydrocarbon concentrations • From August to November 1997, the dissolved petroleum hydrocarbon-plume substantially I • increased in concentration near VW-1 The approximate distribution of dissolved total petroleum hydrocarbons in wells MW-1, MW-5, MW-6 and VW-1 is depicted in Figure 4 • Concentrations of benzene detected in MW-6 and VW-1 exceeded the State of California Maximum Contaminant Levels(MCLs) for drinking water of 1 0 ppb, respectively, and was • detected above laboratory reporting limits in wells MW-1 and MW-5 The approximate Advanced GeoEniironmental,Inc