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F)� <br /> March 16, 2017 <br /> Michael Cunningham <br /> Colorado Division of Reclamation, Mining and Safety <br /> 1313 Sherman Street, Room 215 <br /> Denver, CO 80203 <br /> RE: Lyons Quarry; DRMS File No. M-1 977-141; Technical Revision No. 2, <br /> Responses to DRMS Comments in Adequacy Review No. 3, <br /> Dear Michael, <br /> This letter documents responses to the Division's comments in their Adequacy <br /> Review No.3, dated January 4, 2017, for Lyons Quarry Technical Revision No. 2. <br /> For your convenience and completeness, the following paragraphs include the <br /> original DRMS comment numbers and comments, followed by responses in italics. <br /> 6.4.5 Exhibit E — Reclamation Plan <br /> 1. The revised HDR Report states under Item 6.0 — Fill Slope Scour <br /> Protection, that the scour berm will be designed to withstand a <br /> minimum 100 year flood event. Pursuant to Rule 3.1.5, all grading <br /> shall be done in a manner to control erosion and siltation of the <br /> affected lands, to protect areas outside of the affected from slides and <br /> other damage. Please provide the Division with the results of the <br /> hydrologic analysis used to determine the proposed design of the <br /> scour berm is adequate to withstand a 100 year flood event. <br /> Response: <br /> The results of the hydrologic and scour analysis are summarized below <br /> and provided in Attachment A of this letter. The hydrology used for the <br /> design is based on the flow rates recently developed for the Preliminary <br /> Basis of Design Report for South St. Wain Creek Restoration at Hall <br /> Ranch, prepared by Matrix Design Group for Boulder County, dated <br /> September 2016. The flows used are considered conservative and are <br /> greater than the established Federal Emergency Management Agency <br /> (FEMA) Flood Insurance Study (FIS) flow rates. The flow rate for the <br /> 100 year design storm event is 7,234 cubic feet per second. <br /> Scour analysis assumes a worst case scour caused by migration of St. <br /> Vrain Creek to the toe of the scour berm. Long term scour and general <br /> hdrinc.com <br /> 1670 Broadway, Suite 3400, Denver,CO 80202-4824 <br /> (303)764-1520 <br /> 1 <br />