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404 WEST FREMONT STREET r WKA No 1628 08 ' April 30, 1997 Page 2 The submersible pump was cleaned with a solution of Liqui-nox and water prior to purging each well to minimize the potential for cross-contamination All water removed during sampling and purging operations was placed in sealed and labeled 55-gallon drums and stored on site Analysis of water samples MW2, SMW2, MW3 and MW6 revealed no detectable concentrations of TPH or BTEX Concentrations of petroleum hydrocarbons were detected in the water samples from wells MW 1, MW4 and MWS Review of histonc data reveals continued decreasing TPH as gasoline concentrations in MW i and MW4 However, both TPH and BTEX have increased dramatically in MW5, (a former perimeter well) MtBE was not detected in any of the monitonng wells A summary of analytical results for ground water samples obtained from the six on-site and one off- site monitoring wells are included as Tables l and 2 Complete analytical reports and chain-of- custody documentation are included in the appendix The previous groundwater measuring event (December, 1996) indicated a southeasterly flow direction representing a significant change from previous measurements In addition, the December samples revealed decreasing concentrations in wells NMI, MW4 and MW5 Pnor to this sampling event, a northeasterly trend had been recorded and TPH as gasoline concentrations had been steadily increasing in both MW4 and MW5 while decreasing in MW1 The latest groundwater measurements, however, seem to indicate a return to the previous trends With the flow direction returning to a northeasterly direction, TPH continued to decrease in well MW1 and MW4, while increasing significantly in MW5 This earlier trend still seems to indicate that the plume of contamination is moving off-site in a northwesterly direction even though the calculated groundwater flow direction has returned to a northeasterly direction In addition to the TPH/BTEX analyses, SJCPHS requested that we analyze the local groundwater for Alkalinity, Hardness, Nitrates and Dissolved Iron to establish a baseline of data related to naturally_occurring bioactivity which may-degrade the_plume_of contamination -Concentrations for each of these constituents appeared very consistent with a notable variation only in Nitrates While MW 1, MW 3, MW4 and MW5 revealed Nitrate as N concentrations ranging from <0 05 to 0 19 mg/L, SMW2, MW2 and MW6 reported Nitrate as N concentrations of 15 mg/L 9 2 mg/L and 28 mg/L, respectively WALLACE KUHL Recycled paper SrASSOCIATE5 INC