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Wallace H. Erickson <br />Division of Reclamation, Mining and Safety <br />Department of Natural Resources <br />December 16, 2013 <br />larger floods ... "(Report p.2) Based upon the major flood events in Boulder, Weld and <br />other counties in 2013, catastrophic flood events obviously can and do occur; <br />Response to Paragraph 9: <br />BMRI concurs with the statement in Mr. Perry's Engineer's Inspection Report (page 1) <br />that the tailing impoundment is not subject to State Engineer regulation. <br />The dam safety evaluation that is currently in progress will include evaluation of the <br />capacity and performance of the runon diversion ditch system and the dam embankment during <br />major flood events. These analyses will be based on recent topographic data, recent surveys of <br />the runon diversion structures and modeled runoff during a PMF event. The potential need for <br />upstream slope protection on the dam face during large events is also being evaluated. The <br />results of these analyses will be presented in the Initial Detailed Inspection Report. <br />10) Mr. Perry's report mentions that under the Crest section "the owner recently had a <br />stage capacity and dam crest survey performed" (Report p.1) We would like to review <br />that document. Further, Mr. Perry's recommendation was that the dam crest elevation is <br />maintained for the original design criteria (Report p. 1). Once again, the Operator's <br />testimony is that the intended use of the L TF at the time it was built is different than its <br />current use as a permanent water storage facility. <br />Response to Paragraph 10: <br />The updated survey information (including an updated topographic map) will be included <br />in the Initial Detailed Inspection Report. That report will also evaluate the current dam crest <br />elevation in the context of the original design criteria. <br />11) From Mr. Perry's report, it is not clear if the Operator's intention is to use the LTF as <br />a permanent storage facility or its desire is to move water away from the free water pool. <br />For example, Mr. Perry mentions under the Outlet section that "During the normal <br />operations, the facility holds only a small amount of surface water" (Report p.2). It is not <br />clear if he is referring to the LTF. <br />Response to Paragraph 11: <br />As noted in the DRMS Report (page 2), the May 13, 2013 inspection focused on the main <br />embankment of the tailing impoundment. Consequently, it appears that the facility referenced on <br />page 2 of Mr. Perry's report is the lined tailing facility (LTF). BMRI concurs with Mr. Perry's <br />observation that only a small amount of water (estimated to be < 30 acre -feet compared to the <br />7 <br />