SITE INFORMATION AND CORRESPONDENCE_2004-2014

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Mr. Marshall Cloud March 22, 2007 Page 5 20.) Page 4-4, section 4.3.2; It should be identified in this section that the interpretation of 2006 data only occurred from one quarter (3Q06). Typically, the Annual report compares four quarters of analytical data to the previous years data in order to make interpretations and conclusions. DTSC is skeptical in making conclusions about the remedial progress in 2006 based only on one quarters worth of analytical data. 21.) Page 4-9, section 4.6.2, first bullet; The sentence states the purpose of the focused extraction at MW418C and MW437C was to accelerate mass removal from the areas of highest concentrations. According to page 4-6, section 4.3.8, focused extraction from MW437C removed less than half the TCE mass in 2006 compared to when EWCC1 was operating in 2005. Please describe in the final report how the extraction/treatment system is being optimized to accelerate mass removal when the interim measure is only half as effective in mass removal. 22.) Table 4.3-1; DTSC notes from the report that increases in TCE plume areas were identified in the B-zone Central Area and all-zones in the North Balloon. Additionally, the areal extent of PCE plumes increased for the C-zone in the South Balloon and all-zones in the North Balloon. 23.) Page 4-25, table 4.5-7; The table shows the Air:Water Ratio for both the South Balloon and North Balloon treatment plants are operating outside of the required design ratios of 25-40 cubic feet/cubic feet. Please describe in the final report whether the Air:Water Ratio at the treatment plants is planned to be adjusted so the treatment plants can operate within the design specifications. If you have any questions or comments regarding this letter, please feel free to contact me at (916) 255-3713, or e-mail me at pmacnichCcDdtsc cagov. Sincerely, f Peter MacNicholl, P.E. Remedial Project Manager Federal Facilities Unit cc: See DDJC-Sharpe Distribution List.