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• <br /> Review of the Draft FFA Annual Progress Report <br /> October 2004 - September 2005 <br /> DDJC-Sharpe Site <br /> Lathrop, California <br /> November 2005 <br /> SPECIFIC COMMENTS <br /> 1. Section 3.4; Baseline Concentration for Chromium, Page 3-2: It would be helpful if <br /> the chromium results in Table 3.2-1,Mann Kendall Statistical Trend Analysis Results for <br /> Monitoring and Potable Wells with Significant Trends, DDJC Sharpe, were discussed in <br /> this section of the Report. If statistical chromium analysis has been performed on wells <br /> at DDJC Sharpe then a more detailed discussion of the Mann-Kendall results, including <br /> what they are and what they mean, should be discussed in this section of the Report. <br /> Also, there is no indication in the text that chromium results are available from the past <br /> year, nor is Table 3.2-1 cited in the text. In the next version of this document please <br /> provide a more detailed discussion of the chromium results included in Table 3.2-1, or <br /> reference the section of the text where they are discussed. <br /> 2. Section 4.3.4,Extent of VOC Contamination in Potable Water Wells, Page 4-7: The <br /> text states that "PW051 is 2,600 feet north of the depot boundary, and the current <br /> hydraulic gradient is southerly toward the depot," but no figure was developed showing <br /> potentiometric surface contours for the potable wells because there are not enough <br /> D Zone wells. Please explain the basis for the statement that the hydraulic gradient is <br /> southerly in the vicinity of PW051. <br /> 3. Figures 4.3-4,4.3-5,4.3-6, and 4.3-8: All these figures use a light blue color to denote <br /> concentrations of tetrachloroethene(PCE) above 0.5 micrograms per liter(ug/L), which <br /> is the aquifer cleanup level (ACL) of PCE, but this is potentially confusing because the <br /> same color is used to show trichloroethene (TCE) above 0.5 ug/L, which does not exceed <br /> its ACL or maximum contaminant level (MCL). A darker blue color is used to denote <br /> TCE and PCE above 5 ug/L, which is the MCL for both compounds and is the ACL for <br /> TCE. As a result,readers unfamiliar with the Sharpe facility may assume that the light <br /> blue color on the PCE figures indicates groundwater that is not contaminated above any <br /> regulatory action level, particularly as the figures do not specify the ACL or MCL. <br /> Please consider using different colors for the PCE figures, adding a note that the ACL for <br /> PCE is 0.5 ug/L to the figures, or using some other method to clarify the plume extent on <br /> the PCE figures in the Report. <br /> 1 <br />