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Mr. Ken Price - 3 - 3 July 2003 Background Concentration Comment Table, con't Constituent Range of RWQCB RWQCB Response Background Back round Bromacil <1 to 0.3J ug/L <1 ug/L Since 0.3J represents a value below the laboratory quantitation limit of 1 ug/L,the range of bromacil concentration in background remains less than 1 u Diuron <1 to 1 ug/L <1 ug/L Diuron was detected at 1 ug/L only one time in 17 monitoring events. Background is more aptly characterized by<1 u Simazine <0.5 to 0.8 ug/L <0.5 ug/L Simazine has not been detected in the 11 monitoring events since July 1999. Background for simazine is <0.5 ug/L. If an upgradient release occurs that is unrelated to historical activities at the site and introduces pollutants into upgradient monitoring well MW-16, MSRM will not be held responsible to clean it up. Analytical Detection Limits The Groundwater Cleanup Criteria Table also included a value for the Analytical Quantitation Limit for each constituent. hi its comment letter, Geomatrix refers to its 1996 Sampling and Analysis Plan for this site that Board staff approved and incorporated into Monitoring and Reporting Program (MRP)No. 96-817. The Executive Officer rescinded MRP No. 96-817 and issued MRP No. R5-2002-0831 on 30 August 2002. This new MRP contained maximum quantitation limits applicable to constituents of concern. The quantitation limits listed in MRP No. R5-2002-0831 for 1,2,3-TCP, 2,4,5-T, dicamba, dinoseb, and nitrate are higher than those listed on the Groundwater Cleanup Criteria Table. This is in error, and the MRP will be corrected when it is next revised. In its comment letter, Geomatrix also states that MSRM's contracting laboratory cannot achieve all of the analytical quantitation limits listed in the Groundwater Cleanup Criteria Table. If MSRM's contract laboratory is unable to meet a specified detection limit, MSRM should authorize that laboratory to subcontract the analysis to another laboratory that is able to do so. The following table identifies Geomatrix' comments about specific analytical detection limits and Board staff responses. Analytical Quantitation Limit Comment Table Constituent Geomatrix RWQCB RWQCB Response Practical Analytical Quantitation Quantitation Limits Limit Dichlorodi- 1 ug/L 0.5 ug/L Geomatrix is correct. The 0.5 ug/L quantitation limit fluoromethane is not achievable for all of the constituents in the volatile organic compound scan,including dichlorofluoromethane,bromomethane,and methylene chloride. This is corrected in the attached Revised Groundwater Cleanup Criteria Table. 1,2,3-TCP 0.01 ug/L 0.005 ug/L There are laboratories that can achieve the 0.005 ug/L uantitation limit.