Laserfiche WebLink
• Adopt the requested format in future submittals. <br /> General Comments <br /> 7 . In correlating this round of analytical results with those <br /> obtained from earlier sampling events, a large decrease in <br /> TCE and PCE levels were noted in LM-17. The decrease in TCE <br /> and PCE concentrations were 706 percent and 179 percent, <br /> respectively. <br /> Both TCE and PCE are immiscible with and more dense than <br /> groundwater and should, therefore, continue to migrate <br /> downward. It would be expected that a deeper well screened <br /> in the same lithostratigraphic unit would be located <br /> hydraulically downgradient from LM-17 in order to intercept <br /> these contaminants and permit their tracking. Both, LM-87 <br /> and LM-92 are situated hydraulically downgradient of LM-17 , <br /> but are screened across different intervals. It is, <br /> therefore, unlikely that contaminants emanating from Area 4 <br /> and being detected in LM-17 could be adequately tracked and <br /> evaluated with the current monitoring well configuration in <br /> this area. <br /> While it is understood that some degree of retardation will <br /> take place as a result of sorption and dispersion, it is <br /> unlikely, given the geologic diversity and screened <br /> intervals that either LM-87 or LM-92 will intercept these <br /> contaminants. <br /> • DDRW-Tracy should take this information into account <br /> when locating new monitoring wells. <br /> 8 . As was shown above LM-35 exhibited a marked increase in PCE <br /> concentration since the last round of sampling and analysis. <br /> No wells exist hydraulically downgradient of LM-35 to <br /> monitor the same lithostratigraphic interval. Neither LM-36 <br /> nor LM-82 are in a position to detect contaminants that pass <br /> LM-35. It would, therefore, be recommended to place another <br /> groundwater monitoring well off-site of DDRW-Tracy and down- <br /> gradient to LM-35 to monitor the same interval. This well <br /> would provide information on migration pathways in this <br /> uppermost unit of the Upper Tulare Formation. <br /> • DDRW-Tracy should include this information into account <br /> when locating new monitoring wells. <br /> 9. The following wells exhibit high levels of TCE, PCE or both. <br /> These levels exceed the current and proposed maximum <br /> contaminant levels (MCLS) established as a water quality <br /> goal by EPA and the California Department of Health Services <br /> 4 <br />