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Mr. Maurice Benson <br /> May 1, 2003 <br /> Page 2 <br /> EWCC3 and EWCC4. If the recommendations by WES are implemented by <br /> DDJC, it will take more than 20 years before the boundary of the plume is <br /> pulled back to the property line of the base. This means the residents living <br /> west of DDJC-Sharpe will have a TCE plume underneath their residential <br /> development for over a decade before the boundary of the TCE plume begins <br /> to recede back towards the base. Currently, with areas of the TCE plume <br /> directly under the residential development, as well as the central portion of <br /> the base, there exists a question with regards to the protectiveness of the <br /> remedy. DTSC's position is that the assumptions used to develop the remedy <br /> were based on specific exposure pathways that did not account for indoor air <br /> pollution. In order for DTSC to approve the five-year report, DTSC requests <br /> that Defense Logistics Agency (DLA) and DDJC show the regulatory team, <br /> through modeling, that indoor air pollution will not pose a threat to humans <br /> living in the residential development west of DDJC-Sharpe or on the base <br /> itself. <br /> Lowering of PHGs for Hexavalent Chromium Total Chromium and TCE <br /> 2.) Recent guidance from the United States Environmental Protection Agency <br /> (U.S. EPA) Region IX proposes lowering the Preliminary Remediation Goals <br /> (PRGs) for hexavalent chromium, .total chromium and TCE. The proposed <br /> PRGs for TCE are directly related to the lowering of the cancer slope factor. <br /> Lower PRG's for the respective contaminants could propagate to the lowering <br /> of Federal and California Maximum Contaminant Levels (MCLs)'for these <br /> constituents. If lower MCLS are established for these contaminants, then the <br /> validity of the Remedial Action Objectives (RAOs) and the overall <br /> protectiveness of the selected remedy for DDJC-Sharpe will need to be <br /> reevaluated and further action may be necessary to ensure protectiveness of <br /> human health and the environment. Please be prepared to account for any <br /> such changes in the MCLs, since there is a good likelihood of these changes <br /> to occur within the next five-year review period. <br /> Accepted Target Year to Achieve Remedial Action Cleanup Levels for OU1 <br /> 3.) Originally, the predicted cleanup time for the Operable Unit 1 (OU1) at DDJC- <br /> Sharpe was 16 years based on achievement of full operation of the treatment <br /> systems by 1998. This puts the current target year at 2014 in order to <br /> achieve remedial action cleanup levels. Conversely, according to the WES <br /> modelers, the predicted cleanup time is closer to 30 years from now with the <br /> current well configurations. In light of the new modeling results, the target <br />