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Mr. Maurice Benson <br /> June 25, 2002 <br /> Page 2 <br /> treatment system, it would put the current target date at 2011 rather than the stated <br /> 2013. Please revise the section to reflect a period of 16 years, or provide rationale <br /> for the additional 2 years of groundwater treatment plant operation. <br /> 3.) Page 6, section 2.2.1.1, last sentence; the final sentence states that "Chromium <br /> concentration trends have not required action." A technical memorandum dated <br /> May 18, 2001 from Mr. Bob Pedlar to Mr. John Guzman and Mr. Jarel Starling titled <br /> "Recommended Government Position Regarding Chromium Contamination in <br /> Groundwater at the DDJC-Sharpe Site," discusses the fact that wells MW406A, <br /> MW418A and DW004 "have significantly increasing trends in total chromium <br /> concentrations..." in addition to their respective baselines. The Basewide Remedy <br /> Record of Decision (ROD) for DDJC-Sharpe states "that remediation of chromium <br /> and lead concentrations must be considered if concentrations of those metals <br /> exceed baseline values and have an increasing statistical trend." Based on the <br /> ROD rationale, remedial actions are warranted for chromium contamination at <br /> DDJC-Sharpe. <br /> Similarly, the technical memorandum from Mr. Pedlar encompasses several other <br /> issues with chromium contamination at DDJC-Sharpe: <br /> . It states "...an evaluation of background concentrations should be conducted for <br /> hexavalent chromium." To date there is no evaluation of background concentrations <br /> for hexavalent chromium even though it was discussed in the memorandum and <br /> requested in the past by the Central Valley Regional Water Quality Control Board, <br /> (CVRWQCB) <br /> . It discusses the replacement of test Method 7196 with a new Method 7199, which <br /> would allow for lower detection limits and fewer false positives developed for testing <br /> drinking water supplies. Unfortunately, test Method 7196 is still being used despite <br /> requests from the CVRWQCB to switch to test Method 7199 with the lower detection <br /> limits; and <br /> • It recommends the establishment of baseline concentrations for chromium VI. <br /> Currently, there are no baseline concentrations for chromium VI that can be used to <br /> make a determination on whether or not remedial actions may be warranted. <br /> Please address these comments in the specified section of the report or in a <br /> memorandum attached as an addendum to the report. Please discuss the rationale of <br /> evaluating background concentrations for chromium VI and the establishment of <br /> baseline concentrations for chromium VI. As per requests from the CVRWQCB, DTSC <br /> would like to see Method 7199 replace Method 7196. If not feasible, please provide an <br /> explanation as to why the change cannot be made. Lastly, please describe what <br />