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iiiiiiiuiiiiiiiiii <br />TECHNICAL REVISION REQUEST FOR REST PIT POND <br />HYDROLOGYfSEDIMENTOLOGY AND POND DESIGN UPDATE <br />The enclosed SEDCAD Hydrology and Sedimentology modelling <br />run for the West Pit Pond is to demonstrate the adequacy of the <br />pond design during the period of initial topsoil stripping in the <br />watershed above the pond (a worst case scenario). <br />Enclosed, please find a revised cover page, certified <br />drawings, inlet and emergency spillway rip rap designs, supporting <br />calculations, copies of the SEDCAD runs for both the 10 year and 25 <br />year events, and modelling map. It is intended that this <br />information should replace the entire current West Pit Pond <br />information which can be found in the Colowyo Permit C-81-019, <br />Volume 3, Exhibit 7 Hydrology Information, Section 8 Design of <br />Surface Runoff Control Structures Permit Revision 1991. <br />The 125 acres of stripped area represents the maximum <br />area that Colowyo will be allowed to have completely stripped of <br />topsoil at any one time, if the West Pit Pond is the sole structure <br />for water runoff and sediment containment. Topsoil stripping will <br />only occur within the watershed above the West Pit Pond. <br />In accordance with Rule 4.05.9(2), the West Pit Pond will be <br />considered a temporary impoundment and shall be designed and <br />constructed in accordance with the requirements of Rules 4.05.6(2), <br />(3)(d), (3)(e), (5), (6), and (8) through (12). Upon completion of <br />the construction of the pond, a certified as built drawing will be <br />forwarded to the Division. The pond will be added to the quarterly <br />pond inspection list. <br />