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<br /> <br />Recommendation 2. Provide DIMP or TCLEE in concentrations exceeding drinking water <br />standards occurs in any of the wells cited in Recorrunendation 1, the operator should determine <br />whether such contaminants will be collected via the mine pump system, and how such <br />contaminants will be handled prior to discharge. <br />• Please see response to Tom Schreiner Comment 23 and Attachment N and Attachment P. <br />Although concentrations of DIMP located cross-gradient and off the proposed Tanabe <br />site exceed drinking water standards, concentrations of DIMP in dewatering flows will be <br />relatively low compared to standard values. Dewatering flows will be discharged to the <br />South Platte River as described in the response to Tom Schreiner Comment 24. It is <br />anticipated that impacts to the river from these dewatering flows will be negligible since <br />the aquifer has historically discharged, and continues to discharge, to the same river reach <br />(see Attachment K) with few documented affects. <br />Recommendation 3. Provided DIMP or TCLEE in concentrations exceeding drinking water <br />standards occurs in any wells cited in Recommendation 1, it is recommended that the operator <br />report the health risks associated with withdrawal of such contaminants. At a minimum, the <br />operator should furnish to the Division an MSDS report on each of the contaminants found in the <br />ground water contaminant evaluation cited in Recommendation 1 above. <br />• According to the agencies consulted, health risks associated with dewatering flows <br />containing the estimated concentrations of constituents are not expected. Concentrations <br />of constituents in dewatering flows are well below applicable State water quality <br />standards (Attachment N) and RMA Ground Water Containment System Remediation <br />Goals. The RMA remediation goals are based on the human health risk due to <br />concentration and exposure pathway. The major exposure pathway for DIMP and most <br />other identified constituents near the proposed Tanabe site is through oral ingestion. <br />Drinking water or other domestic uses are not anticipated for dewatering flows. <br />Additionally, the Phase I Environmental Assessment Addendum Report (Attachment I) <br />states that the ground water standard of 8 µg/L for DIMP is extremely conservative. <br />Toxicological testing has indicated that no adverse human health affects are observed at <br />exposure concentrations of 600 µg/L. It is anticipated that the U.S. Army and Shell Oil <br />Company will petition the Colorado Water Quality Commission next year to raise the <br />Basic Standard for Ground Water value to 600 µg2. <br />An MSDS sheet for tetrachloroethene is presented in Attachment Q. Since DIMP is not a <br />"product", an MSDS sheet was not available. <br />Page 10 <br />