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4. The Applicant states the spillways are in accordance with the best practices of the Urban <br />Drainage and Flood Control District guidelines. Please provide additional information <br />pertaining to the design and construction of the inflow and outflow structures. At <br />minimum, please include the following information: <br />a. Justification for the spillway locations <br />b. Spillway invert elevations <br />c. Cross - section details (both lateral and longitudinal) <br />d. Design parameters <br />The design parameters should include the expected flood flow elevations and peak flows, <br />frequency of the expected flood flows, the expected water elevation in the lake and if the <br />spillways are designed to control the lake surface elevation. Additionally, a copy of the <br />Weld County Drainage Report (draft or final version) would be helpful in the Division's <br />evaluation of the spillway design. <br />6.5 Geotechnical Stability Exhibit <br />5. The Applicant's revised slope stability analysis with stockpile and tower surcharge loads of <br />1,100 and 3,000 pounds per square foot respectively was duplicated for verification by the <br />Division using Galena. No potential failure surfaces with lower safety factors than the <br />Applicant's identified critical slip circle were located. The safety factor produced by Galena <br />is slightly higher than that produced by the Applicant's model. The accuracy of the <br />Applicant's analysis is confirmed. A copy of the Galena cross - section is attached for <br />reference. <br />Please be advised the Iverson Mine application may be deemed inadequate, and the application <br />may be denied on July 25, 2011, unless the above mentioned adequacy review items are addressed <br />to the satisfaction of the Division. If more time is needed to complete the reply, the Division can <br />grant an extension to the decision date. This will be done upon receipt of a written waiver of the <br />applicant's right to a decision by July 25, 2011 and request for additional time. This must be <br />received no later than the deadline date. <br />If you have any questions, please do not hesitate to call me at 303 - 866 -3567 Ext. 8124. <br />Peter S. H s <br />Environmental Protection Specialist <br />Enclosure: Communication Tower - Galena stability analysis <br />Cc: Tony Waldron; Division of Reclamation, Mining & Safety <br />Pam Hora; Tetra Tech <br />2 <br />Page 2 of 2 <br />