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that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southeast with a slight mounding effect noted in the vicinity of well MW-2 The average hydraulic gradient on January 27, 1997 was calculated to be 0 012 ft/ft or approximately 63 ft/mile A summary of groundwater momtonng data is presented in Table 1 CONCLUSIONS Petroleum hydrocarbon constituents remained detectable in the groundwater samples collected from wells MW-3 and MW-6 Concentrations of petroleum hydrocarbon constituents decreased in well MW-3 since the last monitoring episode in October 1996, up to two orders of magnitude, to generally the lowest concentrations detected in MW-3 since monitoring and sampling of the well began in August 1993 In well MW-6, concentrations of petroleum hydrocarbon constituents were similar to the last quarter results The direction of groundwater flow and the magnitude of hydraulic gradient are consistent with the previous quarter Groundwater elevations have increased due to seasonal conditions As per a request from the PHS/EHD, Smith Technology has evaluated the concentrations of petroleum hydrocarbons detected in groundwater in monitoring wells MW-3 and MW-6 for this quarter and last quarter to determine if soil vapor extraction is necessary to remediate the residual petroleum hydrocarbons in the soil under the site The analytical results are ambiguous Concentrations of petroleum hydrocarbons in groundwater are similar to last quarter in monitoring well MW-6, and have decreased dramatically in MW-3 This dramatic decrease in concentrations in MW-3 may have been due to the increase of groundwater levels observed in each well on-site The top of the water column in well MW-3 may have been in soil which does not have concentrations of petroleum hydrocarbons, and thus, the concentrations in groundwater decreased However, the concentrations of petroleum hydrocarbons in well MW-6 appear to be unaffected by the increase in groundwater The groundwater level was below the top of the screen in MW-3 and MW-6 (at 20 feet bgs) RECOMMENDATIONS Based on the results of the first quarter 1997 monitoring episode, we recommend the following o Conduct the Second Quarter 1997 groundwater monitoring and sampling of wells MW-1 through MW-6, and collect a split sample from monitoring well MW-3 Send a split of the sample collected from MW-3 to another State Certified laboratory for confirmation of the analytical results for TPHg and BTEX o Evaluate the petroleum hydrocarbon concentrations in groundwater per the need for vapor extraction at the site after the Second Quarter groundwater monitoring and sampling is completed w 1943731quart1yl1gr-1997 d= 3 • sNrrN