Laserfiche WebLink
was only detected in the off-site Rose and Robertson wells <br /> is in error. Additionally, the statement that carbon <br /> tetrachloride "likely had an off-base source" is not <br /> substantiated. <br /> Delete the statement indicating that carbon <br /> tetrachloride has been detected only off-site or revise <br /> the text to include the on-site data. <br /> Delete the statement that carbon tetrachloride likely <br /> had an off-base source, or substantiate it with data. <br /> 16. Section 2 . 2 . 2 . 6, Page 2-4 <br /> Section 6 of the RI has established the organic chemicals of <br /> concern for OU-1; it is not appropriate to state that only <br /> TCE and PCE are the "targeted contaminants of concern. " <br /> Table 4 . 0-1 of the RI notes that MCLS have also been <br /> exceeded for: <br /> Conc. FED/CAL <br /> µg/L MCLs µg/L <br /> Carbon Tetrachloride 6. 8 0. 5 <br /> 1, 1, -Dichloroethane 83 0. 5 <br /> 1, 1, -Dichloroethene 11.9* 6 <br /> * Sampled in September 1991 <br /> The text should be modified to reflect that DDRW-Tracy <br /> intends to meet the above listed MCLS in this remedial <br /> action. As previously stated in EPA' s comments, the FS <br /> needs to explain that TCE and PCE are the most <br /> prevalent and mobile of the contaminants, but that this <br /> action will address all the organic contamination. <br /> This section of the FS is one of the logical sections <br /> for including this explanation. <br /> 17 . Section 2 . 2 . 4 . 2 , Page 2-4 <br /> Either the text or Table 2 . 2-1 is in error because the text <br /> states that the recommended public health levels (RPHLs) for <br /> TCE and PCE are 2 . 5 and 0.7 µg/L, respectively, while the <br /> table states the opposite correspondence. <br /> • Please correct whichever is in error. <br /> 18. Section 2 . 2 . 4 . 3 , Page 2-5 <br /> The combined cancer risk for the reasonable maximum exposure <br /> (RME) conditions as shown in Table 2 . 2-2 is 1. 4 x 10-6 which <br /> 6 <br />