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I <br /> Cleologwal Technics!nC Page 5 <br /> Groundwater Momtonng Report <br /> Project No 723 2 <br /> March 15,2002 <br /> • Figure 4 illustrates TPH-G and Benzene concentrations versus elevation in well MW-3, <br /> which lies near the core of the plume There appears to be a direct relationship between <br /> the water table and the TPH-G concentrations However, Benzene concentrations have <br /> stabilized in the well <br /> ' • Figure 5 illustrates TPH-G and Benzene concentrations versus elevation in well MW-4, <br /> which lies up gradient of the core of the plume The contaminant concentrations have <br /> stabilized in this well <br /> • Figure 6 illustrates TPH-G and Benzene concentrations versus elevation in deep well <br /> MW-101, which hes near the core of the plume The concentrations are approaching <br /> stability The steep decline in the initial concentrations suggests that the contaminants <br /> ' detected in the well were initially a drilling artifact The low benzene concentration now <br /> detected (1 9 µg/l) is probably representative of the lower extent of the groundwater <br /> plume <br /> • Figure 7 illustrates the TPH-G concentrations in the shallow wells The high <br /> concentration in well MW-3 creates a localized node Additional investigation is <br /> needed to gain a more accurate site conceptual model <br /> 3.0 CONCLUSIONS & RECOMMENDATIONS <br /> Conclusions <br /> 1 The groundwater contaminant plume is not defined vertically or laterally <br /> 2 Groundwater flow trends to the northeast to east The southerly flow direction recorded <br /> on December 4, 2000, appears to be anomalous <br /> ' 3 High levels of BTEX and TPH-G are present in the groundwater of all six water table <br /> monitoring wells It is noted that the groundwater elevation exceeded the level of the <br /> ' well screens Low concentrations of BTEX and TPH-G are present in both of the deeper <br /> wells <br /> 4 Oxidation-Reduction Potential measurement (Table 4) shows that all eight wells are <br /> screened in areas of the groundwater plume that are affected by the biodegradation <br /> reactions occurring within the plume Negative ORP values indicate that the wells are <br /> within the halo of reaction depleted water caused by biodegradation of the contaminants <br /> ' This corroborates well with the laboratory data <br />