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Wallace H. Erickson <br />Division of Reclamation, Mining and Safety <br />Department of Natural Resources <br />December 16, 2013 <br />activity. (Report p.2) However, the focal point of the County's complaint is that the LTF <br />is being used as a storage facility for untreated waters. As such, we are unsure what is <br />intended by Mr. Perry's note "there is no spillway currently installed for the <br />embankment ". (Report p.3) A spillway connotes a means to release waters from the LTF <br />to some downgradient location, which is a result that is unacceptable to the County for <br />reasons set forth in its Complaint. Because the LTF is being used as a reservoir to store <br />untreated waters, at a minimum any analysis should first determine: a) that it was <br />designed and constructed for the purpose of permanent storage; b) that it can be used for <br />safe storage of untreated waters based upon current practices. However, in no <br />circumstance should the LTF be re- designed in a manner to allow untreated waters to <br />escape the area of confinement. If Battle Mountain intends to convert the LTF to a <br />permanent storage facility for untreated waters (which is unacceptable to the County <br />absent a convincing showing that it is safe practice to do so), it should only be permitted <br />to do so after a clear and convincing showing that the LTF was initially designed and <br />constructed for safe water storage of waters and that in 2013 and future years it <br />continues to be a vessel for safe storage of untreated waters. <br />Resoonse to Paragraph 4: <br />The current operation of the tailing facility with a small pool in a low -lying area located <br />approximately 600 feet upgradient from the dam does not present a dam safety concern. <br />Monitoring well data at the dam document that low pore pressures within the dam embankment <br />are maintained by the drainage blanket that underlies the dam. Thus, the drain system is <br />functioning properly to prevent buildup of pore water pressures within the body of the dam; <br />thereby ensuring dam stability with a high factor of safety. The Initial Detailed Dam Inspection <br />Report will further describe and document the dam stability. <br />For dam safety purposes, preventing an embankment from overtopping during a flood <br />event is typically accomplished by either: (a) providing an armored (non - erosive) spillway that <br />is designed to safely convey over the dam and/or a channel to carry around the dam storm water <br />discharges in excess of the quantity that can be safely stored in the "flood pool" portion of the <br />reservoir volume, or (b) providing adequate storage capacity (volume) within the impoundment <br />area to fully contain the entire inflow design flood volume without overtopping the dam. No <br />spillway is required for dam safety purposes as long as adequate storage for potential runoff is <br />maintained. <br />As recommended in the DRMS Report (page 3), the Initial Detailed Inspection Report <br />will reconfirm, based on recent topographic mapping, that the existing impoundment area behind <br />the dam has sufficient storage capacity to fully contain the estimated total volume of runoff from <br />4 <br />