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LLEEDSHILL•HERKENHOFF. INC. <br /> Task 3: Groundwater Investigation <br /> Installation of "cluster wells" during the Phase I investigation is prema- <br /> ture, especially given the lack of available site specific geologic data. <br /> To better define the site-specific geologic conditions, the proposed direct <br /> rotary construction method for installation of the monitoring wells will be <br /> modified at the first monitoring well location to include "punch coring" to <br /> full depth. Soil samples obtained from this sampling technique will provide <br /> detailed information concerning vertical geologic stratification. If deemed <br /> necessary by LH's onsite hydrogeologist or geologist, selected intervals may <br /> also be punch cored at other monitoring well locations. In either case, <br /> cutting samples will be continuously logged by the onsite hydrogeologist or <br /> geologist. <br /> As discussed in LH's original Workplan, the completed monitoring well depths <br /> and screen locations will be based on evaluation of available information <br /> obtained during Task 2 and the site-specific geologic conditions encountered <br /> during drilling. <br /> To confirm the presence of TCE and/or PCE contamination, a shallow groundwa- <br /> ter monitoring well is proposed for construction within approximately 50 <br /> feet of LV Well #1. This monitoring well will either be one of the three <br /> originally proposed monitoring wells relocated because of the availability <br /> of data from Chevron, or an additional monitoring well . <br /> Task 4: Off-Site Investigation (New) <br /> To locate and sample all supply wells within a 1-mile radius of the site, <br /> prior to documentation of offsite contaminant migration is premature. <br /> However, in the event that offsite migration of TCE and/or PCE is occurring, <br /> then downgradient wells within a half mile of the Lincoln Village Center <br /> will be located, sampled and analyzed for TCE and PCE using EPA method 601 . <br /> Conversely, if water samples from the monitoring wells show no offsite <br /> migration, then no further work will be conducted in Phase I, and a Workplan <br /> for the Phase II investigation focusing on further delineation of source <br /> and/or mitigative alternatives will be prepared. <br /> TIME SCHEDULE <br /> It is estimated that completion of the Phase I Workplan Tasks and submittal <br /> of LH's technical report will require approximately four months after RWQCB <br /> approval of LH's Phase I Workplan. <br /> ( I F78703.wpl/263 <br /> l -3- <br />