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• <br /> <br />iii iiiiiiiiniii iii <br />TR9PPBR MINING INC. Doc Date:1y11/2pp, <br />January 20, 1993 <br />Mr. Kent Gorham <br />Colorado Office of Mined Land Reclamation <br />215 Centennial Building <br />1313 Sherman Street <br />Denver, CO 80203 <br />Dear Kent: <br />Subject: Deer Dam No. 1 Sediment Control Pond <br />Trapper Mine, C-81-010 <br /> <br />JAN 2 51999 <br />M1~yFRq~S G~~`~, <br />In August of 1992, Trapper Mining Inc. constructed Deer Dam No. 1 as part of its <br />sedimentation control program. The dam design was originally permitted in a revision <br />dated February 13, 1987. The original design was based on watershed, sedimentology, <br />and hydrology parameters as approved by COMLR at that time. <br />In July, 1992, Trapper submitted, as part of its Permit Renewal Number 3, a new <br />hydrologic design model based on a revised watershed and projected disturbance and <br />the currently accepted values for the 10-year and 25-year storm events. These values <br />were revised from 1.7 to 1.4 inches and from 2.1 to 1.8 inches, respectively. The <br />projected watershed was increased from 25.25 to 31.60 acres to more accurately reflect <br />the current projections for disturbance. <br />During construction, two field modifications were made to the original approved design. <br />The original design incorporated asemi-circular metal flume for the principal spillway <br />which is no longer used by Trapper. Instead, aconcrete-lined, v-notch spillway was <br />constructed which is the currently approved method. Also, the overall embankment <br />design was increased one-half foot, from 8.5 feet to 9.0 feet. <br />On October 30, 1992, Trapper submitted the dam construction certification for Deer <br />Dam No. 1. The previously described changes were incorporated into the stage storage <br />relationships and modelled hydrologic performance submitted as part of the <br />certification. The modelled performance indicates that Deer No. 1 will adequately <br />provide the required hydrologic and sedimentation control for the Deer watershed. <br />Please contact Mark Wehmanen or me if you have any questions. This correspondence <br />should be placed in Appendix Q, Section XVI, of our Mining and Reclamation Permit. <br />Sincerely, <br />~~ ~~~ °~- <br />Larry ~enderson <br />Sr. Environmental Engineer <br />• LWH/mg/MLRt19 <br />c MW Wchmanen <br />F'W Luke <br />file (2) <br />P.0. Box 187 Cralg, Colorado 81626 (303) 624-4401 <br />