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5.0 OBSERVATIONS & RECOMMENDATIONS <br /> Observations <br /> Ground Zero, taking into consideration the data obtained from the groundwater monitoring <br /> event, makes the following observations: <br /> ' • Groundwater flow at the WWTP is complex and is probably affected by pumping wells, <br /> the Stanislaus River, regional groundwater flow patterns and possibly the treatment <br /> ponds. Historical groundwater flow trends to the southwest but is typically variable. <br /> ' • The reported concentrations of each constituent of concern observed in the monitoring <br /> wells this quarter are all within historical ranges observed at the WWTP, with the <br /> ' exception of various constituents reported to be present in MW-7. <br /> • Background monitoring wells (MW-9 & MW-10) appear to show water chemistry similar <br /> to the other monitoring wells on-site. <br /> ' • The level of groundwater in MW-7 fluctuates greatly as compared to other monitoring <br /> wells at the Site and is almost always situated at the top of a water mound. The <br /> groundwater fluctuations are possibly a result of less recharge in neighboring areas or the <br /> ' fact that MW-7 is screened directly above a tight silt layer and may be monitoring <br /> perched groundwater. <br /> ' • VOCs were not reported above laboratory detection limits in all wells during September <br /> 2015 monitoring event, with the exception of chloroform. Chloroform was detected in <br /> monitoring wells MW-4, MW-6, MW-9 and MW-10. <br /> • No discernible trends are observed in the analytical data from the monitoring wells, i.e. <br /> none of wells show steadily increasing or decreasing concentrations. The concentrations <br /> of the various constituents appear to fluctuate seasonally. <br /> ' • Historically, the water chemistry in the Stanislaus River does not change appreciably <br /> between sampling stations R-I and R-2. <br /> ' Recommendations <br /> Ground Zero recommends that the quarterly groundwater and surface water monitoring <br /> ' program continue according to the WDR (Order No. 5-00-142) and corresponding MRP. <br /> 1 <br /> ' Ground Zero Analysis,Inc. 6 <br /> 894 3rd QMR 15 <br />