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54. Section 6.3.7 <br /> With regard to dieldrin at the Base the text states "DDRW-Tracy is probably not the <br /> only source of dieldrin in the study area." Also, the text states, "it is unlikely that <br /> the risk attributable to dieldrin usage at DDRW-Tracy constitutes a significant risk <br /> when potential use of pesticides and herbicides in the study area is considered." <br /> However, it is not clear which study is referenced. EPA does not recall the citing of <br /> such a study in the risk assessment for OU #1. Further, the groundwater data <br /> reviewed by EPA, to date, do not appear to support the assertion of a source other <br /> than DDRW-Tracy. <br /> Corrective Action: Omit references to a study unless it has been referenced and <br /> incorporated in the risk assessment. <br /> 55. Figure 6.2-1, Exposure Point Locations <br /> The figure includes an arc of dots adjacent to the NE boundary of the Base. <br /> However, the meaning of these symbols is not clear. <br /> Corrective Action: Please either provide an explanation of how these dots are <br /> meaningful to the Exposure Point Locations or delete the dots from the figure. <br /> 56. Section 7.0.1 <br /> In section 7.0.1, the sentence stating: "The selection was based on the criteria <br /> described above" should be modified since no criteria are described above. <br /> Corrective Action: Edited the text to state "criteria described bei. <br /> 57. Section 7.0.3 <br /> The nine criteria for evaluation of the alternatives needs to include more complete <br /> descriptions of each. More complete descriptions of the nine criteria will assist in <br /> understanding subsequent sections of the ROD and help to explain some of the <br /> following comments. <br /> Corrective Action: Employ more complete descriptions, as can be found in the NCP. <br /> 58. Section 7.1.1.3 <br /> It is not clear why monitoring will be focused on only the outer fringe of the plume. <br /> Further, it is not recommended that future monitoring options be limited by <br /> including the level of detail that is presented in this section (e.g., references to <br /> horizons, sampling frequency, and duration). Specific monitoring requirements can <br /> be stated in subsequent FFA primary documents. <br /> Corrective Action: Delete the details and state instead that DDRW-Tracy commits to <br /> EPA/R9 June 7, 1993 14/40 <br />