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k r � ` 2.4 Discussion �J Groundwater flow direction is northerly at a flow gradient that is consistent with historically observed northerly flow trends (see Figure 1). A groundwater mound appears present in the vicinity of MW-3R and MW-91Z that is attributed to the recent soil excavation and placement of somewhat more porous fill. The water level measurement at MW-31Z appears to low for the contoured data and was not used in the groundwater contour plot,however the water level is presented on the map. Wright will check the survey information on the resurvey of the well casing MW-3R. TPHG concentrations declined markedly in MW-3R and in MW-9R (see Figures 2 and 3). Benzene concentrations declined in Well MW-3 none detected and decreased slightly in MW-91Z. Well MW-4 showed that contaminants were not detected. MTBE and related oxygenates were not detected in any well. Separate phase product was not observed in MW-3R and MW-9R during this sampling event a change from the sheen to tenths of inches of product observed at irregular intervals over about the previous year. Selected combined Time vs. Contaminant Graphs, (combined data of MW-3 and MW-3R, and combined data of MW-9 and MW-91Z) were prepared to show historic dissolved trends that are attached to this report. Wright is adding the data from MW-3R and 9R since these wells were installed only about 5 feet from the previous locations. While the locations have changed slightly, it is Wright's opinion that the combining the historic data to the new wells data will enable ease in continued contaminant trend tracking in the areas of historically most elevated TPHG and Benzene. Soil excavation activities removed residual contaminant in the vadose zone and upper aquifer in the area around MW-3R and 9R. While some residual is known to remain, the dissolved TPHG and Benzene concentrations have decreased. The interpreted location of the dissolved plume based on the historic groundwater flow and interpreted contour information continues to generally show no net plume movement beyond the area immediately around Wells MW-3R and MW-9R. 2.5 Conclusions and Recommendations Groundwater flow direction was northerly under a low calculated gradient and water levels in monitoring wells had changed slightly since the previous quarter. A groundwater mound appears near MW-3R and MW-9R that is attributed to the soil excavation backfill that has somewhat more porosity than the native soil and may retain more water. In-our opinion, the mapped contaminant dissolved plume continues to occur near the center of the sfte, similar to historic site observations and previous investigation reports submitted to SJC/EHD. The TPHG and Benzene levels show a decrease in monitoring wells MW-3R and MW-9R. Soil excavation activity in this area has removed residual contaminant in the vadose and upper aquifer soil and sediment and in our opinion accounts for the dissolved contaminant decrease. Flucuations of TPHG and Benzene may occur from desorption since some residual sources under the large utility pipelines could not be removed during the soil excavation. The water level measurement from MW-3R appears anomalous and was not used in the data plot of the groundwater elevation contour map this quarter. Wright will check the casing survey information on the resurvey of elevation data on the well casing MW-3R. The site is scheduled for continued quarterly monitoring at this time. Page 4 of 5