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��,4oer4V UNITED STATES ENVIRONMENTAL PROTECTION AGENCY `' <br /> Region 9 <br /> 75 Hawthorne Street <br /> San Francisco CA 94105-3901 <br /> December 22, 1993 <br /> Marshall Cloud <br /> Environmental Protection Office <br /> DDRW-Tracy <br /> P.O. Box 960001 <br /> Stockton, CA 95296-0250 <br /> RE: EPA Review of Well Redevelopment Report (NOV 93) <br /> Dear Marshall, <br /> Following are EPA's comments on Montgomery Watson's (MW) Well Monitoring Program <br /> Well Redevelopment Report for DDRW-Tracy dated November 1993. EPA generally agrees with the <br /> methods used and the recommendations by MW. However, we would like to provide the following <br /> comments. <br /> 1. MW states in Section 3.2.0.1 that "wells LM1A through LM43A may be sampled using a <br /> submersible pump and bailer" and further, in Section 3.2.0.3, that "elevated turbidities may be <br /> anticipated from wells LM1A, LM11A, LM14A, LM20A, LM22A, LM23A, LM25A, LM26A, <br /> LM29B, and LM31A." Please know that Chapter Six, page 6-48, of RCRA Ground-Water <br /> Monitoring: Draft Technical Guidance (EPA/530/R-93-001) dated November 1992 states in <br /> part that "a well that cannot be developed to the point of producing low turbidity water (e.g., <br /> <5 NTUs) may be considered by the Agency to have been improperly completed (e.g., <br /> mismatched formation materials/filter pack/screen slot size) depending on the geologic <br /> materials in which the well is screened." Further, Chapter Seven of RCRA Ground-Water <br /> Monitoring: Draft Technical Guidance (EPA/530/R-93-001) dated November 1992, <br /> recommends the use of a bladder pump for sampling of all analytes, including inorganics and <br /> volatile organic compounds (VOCs), to obtain representative groundwater samples of low <br /> turbidity. Therefore, it is not clear to EPA why the use of the bladder pump is not the <br /> recommended procedure for the wells which are anticipated to have "elevated turbidities." <br /> 2. RCRA Interim Status groundwater monitoring requirements, as stated in 40 Code of Federal <br /> Regulations (CFR) Part 265 and in this guidance document, may be considered requirements <br /> under the CERCLA process for wells that monitor solid waste management units (SWMUs). <br /> This would include monitoring wells LM3A, LM15A (SWMU No. 3), LM16A (SWMU No. <br /> 5), LM17A (SWMU No. 6), LM18A, LM19A (SWMU No. 8), and others. EPA therefore <br /> believes that those particular monitoring wells (with the exception of wells LM22A and <br /> i <br />