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~ ~ III 1111111111111111 <br />STATE OF COLORADO <br />--~ ~,: <br />Roy Romer, Govei <br />DEPARTMENT OF NATURAL RESOURCES <br />MINED LAND RECLAMATION DIVISION <br />FRED R. BANTA, Director <br />May 25, 1989 <br />Mr. Mark Heifner <br />37 East Colorado Avenue <br />Denver, Colorado 80210 <br />RE: Review of Response on Hydrologic Aspects, <br />Snyder quarry, Amendment No. 2, <br />Castle Concrete Company, File No. M-77-210 <br />Dear hfr. Heifner: <br />I have reviewed the responses you provided on May 22, 1989 regarding the <br />hydrologic aspects of the above-referenced amendment application. Based on <br />this review, and our conversation on May 24, 1989, further hydrologic and <br />hydraulic analyses will be required to provide desiDns for the drainage and <br />sediment control structures. I have identified below the design parameters <br />the Division considers necessary to be used in developing the sizing of <br />structures used for runoff and sediment control during mining and reclamation. <br />Sediment Control Basin <br />The sediment control basin at the base of the Phase III/Phase IV <br />watershed area will be designed to contain the runoff and sediment <br />generated from a 10-year, 24-hour precipitation event. Because the <br />structure is permanent, a spillway will be included which can safely pass <br />the 100-year, 2G-hour flood event. Hydrologic calculations and <br />construction drawings should be submitted for Division review, As-built <br />drawings of the sediment pond prepared by a qualified professional <br />engineer should be provided to the Division within 60-days of the <br />completion of construction. <br />2t5 Cemennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866.3567 <br />