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r7 i{ Ms Vicky McCartney May 23, 2005 • Page 5 of 6 • No field evidence of hydrocarbon contamination (hydrocarbon odor, discoloration) was observed in any soil boring Slightly elevated PID readings, lacking any accompanying odor, were present within the saturated zone soil in boring SBA • No analytes of concern were detected in any of the soil samples collected from the borings Samples were analyzed from depths ranging from 5 feet to 50 feet below grade • Benzene was detected in the discrete groundwater sample collected from SBF MTBE was reported in the discrete groundwater sample collected from SBC The MTBE result is not believed to be representative of actual groundwater conditions • Groundwater levels in the site monitoring wells rose since last monitored in July 2004 The average groundwater gradient across the site was 0 01 ft/ft (apprx 50 ft/mile) Groundwater flowed in a northeasterly direction, which is consistent with previous measurements • TPHg, toluene, ethylbenzene and xylenes were not detected in any of the monitoring well samples Benzene was not detected in well MW2 YV5 • • Benzene was present in the water samples from wells MW1 and MW3 1,2-DCA was detected in the groundwater sample from upgradient well MW2 CONCLUSIONS AND RECOMMENDATIONS Data from the current investigation along with that from previous phases of investigation have completely defined the lateral extent of groundwater contamination Figure 4 qualitatively depicts the extent of dissolved benzene in groundwater utilizing data from all discrete groundwater samples and the most current results from the site monitoring wells Previous phases of investigation determined that residual soil contamination is negligible Dissolved benzene levels have continued to decrease with time in wells MW 1 and MW2 The concentration of benzene in MW 1 is approaching the MCL of 1 ppb and benzene has not been detected in well MW2 for one year Benzene levels in downgradient well MW3 were on an overall trend of increase from the inception of monitoring until 2001 Since that time, Ievels have risen and fallen from sampling event to event but the pace of overall increase has slowed substantially '?,a- The presence of 1,2-DCA has been confirmed in the vicinity of upgradient well MW2 However, the current concentration is only marginally above the MCL for this compound • We recommend continuing with the current semi-annual groundwater sampling program to verify the behavior of the contaminant plume No additional monitoring wells are warranted at this time G 1GROUNDZEIW MSAR1200511 SAR05bornngreport doe