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BUR <br /> Sample Location Approx. Depth' Date(s) PCE Concen. In Total Haz <br /> (ft-bgs) g.w.(Pg/L) Subst.' <br /> (approx.pg/L) <br /> CPT-014 79 5/14/97 29,000 31,000 <br /> CPT-040 75 9/03/97 27,000 30,700 <br /> CPT-100-65 65 11/08/96 25,000 26,200 <br /> CPT-100-75 75 11/08/96 9,100 10,460 <br /> CPT-241A-54 54 11/26/97 28,000 30,000 <br /> CPT-241A-66 66 11/26/97 13,000 14,000 <br /> CHMW-003A 48 -68 1999-2005 6,000- 15,000 6,400- 15,400 <br /> MW-108A 40-60 1997 -2005 4,000- 5,800 4,100-5,900 <br /> CPT sample depth or screened-depth interval for monitoring wells, in feet below ground surface <br /> (ft-bgs) <br /> z One-half the reporting limit used to estimate the concentration of"non-detect" hazardous substances <br /> As can be seen on this table, PCE concentrations observed in groundwater in the Eastern Hot Spot <br /> are of similar magnitude to those observed in the "Historical Source Area." Over time, the high <br /> VOC concentrations in the Eastern Hot Spot have diffused into the large volume of silts and clays <br /> present in the A-zone sediments. These fine-grained sediments provide for long-term sequestered <br /> storage of VOCs, making remediation more difficult. Simply relying on the existing groundwater <br /> pump-and-treat system to remediate these highly contaminated fine-grained sediments is likely to <br /> be insufficient. For these reasons, remedial action alternatives must be evaluated for groundwater <br /> in the Eastern Hot Spot, as well as the "Historical Source Area." <br /> Response to Comment 1: <br /> The Trust appreciates FA's acknowledgement of the efforts put forward to assess effective <br /> remedial technologies within the Historical Source Area (HSA). <br /> In summary, FA's Comment 1 states that "the existing site data are sufficient to conclude that <br /> persistently high PCE concentrations have been observed in the Eastern Hot Spot" and then <br /> concludes that the area east of the HSA poses a similar remedial issue as the HSA. Such a view is <br /> at odds with the SCM developed for the Lincoln Center Site and LFR disagrees with FA's <br /> comment for the following reasons. <br /> First, the lateral and vertical extent of the "source" area has been adequately characterized and <br /> documented. As first discussed in LFR's Revised Draft Feasibility Study (FS) Report dated August <br /> 5, 2002, from 1996 through 2000 the regional groundwater elevation has risen by approximately <br /> Itr-Farr-FS-respon -G6750.dm:1fr 2 <br />