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• Regulations for Coal Mining, Performance Standards, require that <br />all surface drainage from disturbed areas be passed through a <br />sedimentation pond or other treatment facility. The pond must be <br />designed to provide storage for flows resulting from a 10-year, <br />24-hour precipitation event. The pond must also provide for <br />sediment storage and removal operations. <br />.2.9.2 Design Criteria <br />The design criteria listed below are taken from the Mined <br />Land Reclamation Division regulations and generaly accepted <br />design criteria: <br />a) The principal spillway should consist of a <br />corrugated steel pipe drop inlet with the <br />overflow elevation located above the <br />estimated elevation of the stored sediment <br />volume; <br />b) The principal spillway outfall should be <br />located so as to minimize the effects of <br />concentrated flows; <br />c) The emergency spillway should be located such <br />that overflows will not impinge on the <br />adjacent fill areas; <br />d) Principal and emergency spillways should <br />safely pass the runoff resulting from a 25- <br />year, 24-hour storm; <br />e) The embankment design and construction shall <br />be certified by a qualified registered <br />Professional Engineer; <br />f) Adequate maintenance access for heavy <br />equipment should be provided; <br />2.9.3 Proposed Design <br />Based on preliminary design considerations, the sediment <br />pond will be designed to accept water and sediment runoff from <br />about 5.78 acres. About 258 (1.42 acres) of this total is from <br />undisturbed land above the portal bench and below the diversion <br />ditch. The remainder (9.36 acres) is comprised of the cut slope <br />and portal bench. <br />A preliminary design for the sediment pond has been <br />completed using the values slightly different than these due to <br />minor changes in the bench and fill design. This design is <br />described in another report (Golder, 1986). Construction <br />drawings showing the sediment pond final design will be prepared <br />and certified by a professional engineer. <br />10 <br />