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STATE OF-CALIFORNIA - Environmental Prote0n Agency • PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION EFd1VfRQf� 'I 'Eh A HEALTH <br /> 7 s( <br /> 3443 Routier Road, Suite A M H <br /> Sacramento, CA 95827-3098 Pl_Rt:II SERVICE <br /> PHONE: (916) 255-3000 <br /> DOD FAX: (916) 255-3052 93 JUL -8 pH 2: 29 <br /> 2 July 1993 f <br /> Mr. Michael Work <br /> Federal Facilities Enforcement Branch <br /> Office of Superfund (H-9-1) <br /> Environmental Protection Agency, Region IX <br /> 75 Hawthorne Street <br /> San Francisco, CA 94105-3901 <br /> CONFERENCE CALL OF 18 JUNE 1993, SUMMARY OF AGREEMENTS FOR OPERABLE <br /> UNIT NO. I (OU-1) RECORD OF DECISION (ROD), DEFENSE DISTRIBUTION REGION <br /> WEST (DDRW), TRACY, SAN JOAQUIN COUNTY <br /> We have received your 21 June 1993 letter summarizing the agreements reached in the 18 June 1993 <br /> conference call regarding the OU-1 ROD. Three of the statements provided by the Environmental <br /> Protection Agency (EPA) do not accurately reflect the Board's position. Therefore, it is necessary <br /> to clarify our position on these issues. The EPA's comments from the 21 June 1993 letter are <br /> restated below followed by a statement clarifying the Board's position on these issues. <br /> 47. Section 5.3.1 <br /> The State believes that there is probably an off-Base source of dieldrin. EPA stated that an <br /> off-Base source is certainly possible. However, EPA stated that the more important point to <br /> be made is that the data also suggests an on-Base source. <br /> CLARIFICATION <br /> The Board believes that the source of dieldrin groundwater contamination may be on-Base <br /> and/or off-Base. Monitoring wells that are part of OU-1 monitoring program that have <br /> detected dieldrin and arsenic downgradient of selected solid waste management units <br /> (SWMUs) were not designed to be detection monitoring wells for these SWMUs. Until the <br /> comprehensive site-wide Remedial Investigation (RI) is completed, we believe it is premature <br /> to determine whether an on-Base source for dieldrin and metals exists. Monitoring wells <br /> specifically designed to detect contamination at the point of compliance at each SWMU will <br /> be installed as part of this RI effort. <br /> Section 5.3.1. must be clarified to state that concentrations of inorganics may be present at <br /> background concentrations. Many of the inorganic constituents in question are naturally <br /> occurring. Monitoring wells will be installed as part of the site-wide RI to establish <br /> background concentrations at appropriate upgradient locations. <br />