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Mr. Marshall Cloud <br /> February 6, 2008 <br /> Page 3 <br /> water contamination. Based on the 2007 CPT fieldwork Phase I results, the <br /> report should identify that a persistent source is likely responsible for the <br /> steadily increasing TCE concentrations found in MW418 series. The <br /> DESJC-Sharpe conceptual site model should be updated to include the 2007 <br /> CPT fieldwork results. <br /> 8. Page 3-6, Section 3.3.4.7, See comment#6. <br /> 9. Page 3-7, Section 3.3.4.13, MW445C's highest PCE concentration was <br /> recorded as 45.2 pg/L during the 1Q07 sampling event, rather than 43.2 pg/L. <br /> Please revise statement in the report to identify the highest PCE <br /> concentration measured during 2007 sampling events was 45.2 pg/L. <br /> 10.Page 4-5, Section 4.3.2, last sentence; As previously stated, with TCE <br /> concentration increases observed in EWCC3 and the constant levels of TCE <br /> found in MW510C, the statement "...the plumes are not migrating." is not <br /> supported by analytical data. Conversely, the TCE detections observed in <br /> MW510C indicate that TCE toe-of-plume to the west of the base is migrating <br /> and has escaped capture from EWCC3. Please amend the statement to <br /> accurately reflect the ground water conditions, especially with respect to the <br /> Central Area TCE and SB PCE plumes. <br /> 11.Page 4-12, Section 4.6.10; The 2007 CPT fieldwork results will determine the <br /> actual ground water conditions north of EWCC3 and should not be speculated <br /> on until the analytical results are presented. Please include the most recent <br /> 2007 CPT results in the report or refrain from interpretation until the analytical <br /> data are reported and formally presented to the regulatory agencies. <br /> 12.Page 5-7, Table 5.3-1, 2008 Proposed Well Sampling Frequencies; The table <br /> provides proposed changes to the current DESJC-Sharpe well monitoring <br /> frequencies for the 2008 calendar year and into the future. DTSC has <br /> reviewed the proposed changes to the monitoring well network at <br /> DESJC-Sharpe and cannot agree to the proposed decision logic or well <br /> monitoring frequencies at this time. Ongoing CPT fieldwork is being <br /> conducted at DESJC-Sharpe to define the TCE and PCE plumes and is not <br /> expected to be completed until late February 2008. The fieldwork is <br /> anticipated to help define both the lateral and vertical extents of on-site and <br /> off-site TCE/PCE plumes for the North Balloon, Central Area, and South <br /> Balloon, and will help refine DESJC-Sharpe's conceptual site model. The <br /> 2007 CPT fieldwork has already identified two persistent source areas and is <br />