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• • <br /> Mr. Maurice Benson - 2 - 12 October 2011 <br /> Defense Logistics Agency <br /> obtained historic aerial photographs and engineering drawings dating from 1955 through 1987, <br /> and a conceptual site model for the Site. <br /> Central Valley Water Board Staff Comments <br /> 1) Before implementing the EE/CA-recommended alternative, DLA should evaluate the <br /> following additional remedial alternative: Excavation of soil with concentrations of pesticides <br /> above a cumulative excess cancer risk to industrial workers of 1x10-6. <br /> 2) The EE/CA proposes a confirmation sampling plan that reduces the relative amount of <br /> samples as the surface area of the excavation floor and sidewalls increase. For example, if <br /> the total surface area of the floor was 500 square feet (ft2) the number of samples collected <br /> would be two; if the surface area was 10,000 ft2the number of samples would be nine. The <br /> sample density proposed in the Draft/Final EE/CA should be two for every <br /> 500 ft area. In the example above, 20 samples would be collected from an excavation <br /> floor area of 10,000 ft2, not nine. <br /> 3) There is a typographical error in Table 2-1 of the EE/CA: The US EPA Residential Soil <br /> Regional Screening Level (RSL) for dieldrin should read 0.03 milligrams per kilogram <br /> (mg/kg), not 0.3 mg/kg. <br /> 4) There is a typographical error in Table 3-1 of the EE/CA: The US EPA Residential and <br /> Industrial Soil RSLs for carbaryl appear to have been transposed. <br /> 5) Appendix D of the EE/CA presents historic engineering drawings and aerial photographs. <br /> There are discrepancies in the building numbers between Engineering Drawings 1 and 3, <br /> and Aerial Photographs 2, 4, 5, and 6. This creates confusion in the text of Section 3.3.2 of <br /> the EE/CA that describes Former Buildings 234 and 237. The text should be clarified. <br /> 6) On Figure 5-2 of the EE/CA, pink-shaded areas show the locations of former buildings. <br /> One of the areas shown in pink is actually an extension of the arc-shaped feature visible on <br /> the aerial photos shown in Appendix G. Figure 5-2 should be corrected. <br /> 7) In Section 3.3.2 of the EE/CA, the sixth sentence of the first bullet reads, "To the west of <br /> Building 236..." It should read, "To the east of Building 236"... <br /> If you have any questions, please contact me at (916) 464-4675, or by email at <br /> jbrownell@waterboards.ca.gov. <br /> - R <br /> JAMES R. BROWNELL, P.G. <br /> Engineering Geologist <br /> Federal Facilities Unit <br /> cc: Mr. Phillip Ramsey, USEPA Region 9, San Francisco <br /> Mr. Christopher Sherman, DTSC Region 1, Sacramento <br /> Mr. Harlin Knoll, San Joaquin County Health Department, Stockton <br /> Mr. John Hill, AFCEE, San Antonio, Texas <br /> Mr. David Hofmann, Booz Allen Hamilton Inc., San Antonio, Texas <br /> Mr. Charles O'Neill, HDR, Folsom <br />