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Geological Techacs lne Page 4 Groundwater Monitoring Report Project No 662 2 October 3, 2002 i • Figure 4 MTBE vs Groundwater Elevation - MW-3 illustrates a fairly direct ' relationship between the concentration of MTBE in groundwater and the elevation of groundwater in well MW-3 • Neither BTEX nor TPH-G was present in any of the groundwater samples above the ' laboratory reporting limits • Oxidation-Reduction Potential measurements (Table 3) show that the values for all four wells are positive, suggesting that there is a limited amount of biodegradation of the ' contaminant plume occurring This is to be expected, since the primary contaminant is MTBE, which is resistant to biodegradation The lateral extent of the groundwater contamination plume is only defined upgradient to the northwest by MW-2 The vertical extent is currently defined by well MW-104 ' GTI makes the following recommendations • Perform plume definition and evaluate the mass of,contaminants present by installing ' additional monitoring wells GTI has submitted to the SJC PHS/EHD a "Soil & Groundwater Investigation Work Plan" dated October S, 2001 The work plan was approved with conditions in the SJC PHS/EHD's October 26, 2001 correspondence The first phase of the work, advancing a continuous core boring to determine site lithology, was completed on May 30, 2002 A monitoring well (MW-104) was placed in this boring with a five foot screened interval starting at 24 feet below the water table ' Additional wells will be installed pending concurrence from the SJC PHS/EHD 3.0 LIMITATIONS This report was prepared in accordance with the accepted standards and practices of the field of environmental geology, groundwater hydrology and good business practices It should be recognized that definition and evaluation of environmental conditions is a difficult and an inexact science Judgments leading to conclusions and recommendations are generally made with an incomplete knowledge of the site-specific conditions present The tasks proposed and completed during this project were reviewed and approved by the local regulatory agency for compliance with the law No warranty, expressed or implied, is made