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7 � • <br /> Mr. Maurice Benson <br /> February 26, 2010 <br /> Page 3 <br /> The Contingency Plan should provide rationale why Public Health Goals (PHGs) <br /> were not considered as warning levels, regardless of whether promulgated, <br /> especially considering the realistic cumulative risk to human health if multiple COCs <br /> impact a potable water supply well. <br /> 3.) Page 3-2, section 3.2.1 and 3.3.1, Guard Monitoring Wells: The report should clearly <br /> identify the sampling frequencies proposed by each of the Guard Wells listed in <br /> Table 3-2. Section 3.3.1 of the sampling frequencies only states that "each year <br /> data from the groundwater monitoring program, which includes analytical results <br /> from guard well samples, will be evaluated..." DDJC-Sharpe's draft Off-Depot Water <br /> Potable Well Contingency Plan proposes semi-annual sampling of all guard wells <br /> and would expect that DDJC-Tracy's Water Supply Contingency Plan include similar <br /> sampling frequencies for consistency and protectiveness requirements. <br /> 4.) Page 4-1, section 4.1 and section 4.2: Similar to comment#1, the Report's warning <br /> levels for three COCs represent the same value as the MCLS, therefore sections 4.1 <br /> and 4.2 essentially state the same thing, although the decision logic and response <br /> actions are different for each. Similar to the DDJC-Sharpe meeting discussion and <br /> agreements made on January 28, 2010, the Warning Level should be renamed as <br /> the "Trigger Level" and represent a value of one-half the MCL. Contaminant <br /> concentrations at the MCL or higher will be stated as the "Action Level." <br /> Accordingly, for consistency, the laboratory turnaround times and agency notification <br /> timelines agreed to during the January 28, 2010, meeting should also be adopted as <br /> part of the Tracy Contingency Plan. <br /> 5.) Page 4-1, section 4.2.1, last bullet: According to the proposed Contingency Plan <br /> language, if an impacted potable water supply well's water is "...used for drinking or <br /> cooking, a sufficient supply of bottled water may be supplied." DTSC recommends <br /> the word "may" be removed, as this seems to assume some independent discretion <br /> by DESJC and whether this action is deemed necessary or protective. DTSC <br /> recommends a more transparent and protective process indicating that "...a <br /> sufficient quantity of bottled water will be supplied as deemed necessary by the <br /> regulatory agencies and DESJC. <br /> Conclusions <br /> The off-site potable well contingency plan proposes reductions in the sampling <br /> frequencies for off-site potable wells. The rationales for the reductions in the sampling <br /> frequencies are to help minimize the groundwater monitoring programs operational <br /> costs and to help reduce Defense Logistics Agency's liability due to regular sampling of <br />