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• ditches. Ditch designs (SEDCAD) are included in Attachment N. The location of each ditch can <br />be found on Exhibits 13-4. <br />Each ditch was designed and constructed in accordance with the applicable regulations in 4.05.3. <br />Diversions were designed, constructed, and maintained in a manner which prevents additional <br />conVibutions of suspended solids to streamflow and to runoff outside the permit area. <br />Appropriate sediment control measures for these diversions may include maintenance of <br />appropriate gradients, channel lining, revegetation, roughness sVUCtures, and detention basins. <br />When no longer needed, each diversion will be removed and the affected land regraded, <br />topsoiled, and revegetated in accordance with 4.06, 4.14, and 4.15. <br />In accordance with 4.05.2 and the approved NPDES permit, Peabody used sedimentation ponds <br />to prevent, to the extent possible, additional contributions of sediment to streamflow or runoff <br />outside the permit area due to mining disturbance (see Exhibits 13-4 and 13-5). <br />The sedimentation ponds and impoundments were designed, constructed, and maintained to: <br />a. Provide storage for the runoff or inflow entering the pond as a result of a 10-year, 24- <br />. hour precipitation event and to meet all applicable State and Federal regulations for all <br />effluent limitations before discharge from the permit area. The characteristics of the <br />mine site, reclamation procedures, and onsite sediment control practices were also <br />considered in the design. <br />b. All sedimentation ponds were designed to provide adequate sediment storage volume <br />in compliance with the CMLRD regulations. <br />c. An appropriate rwnclogging dewatering device was installed to maintain a 10-year, <br />24-hour storage volume. <br />d. Appropriate combinations of principal and emergency spillways to safely discharge the <br />runoff from a 25-year, 24-hour precipitation or larger event, as required by the <br />CMLRD's regulations, were installed in Pond 001 and Pond 006. However, no <br />emergency spillway was provided for Ponds 002, 004 and 005 since they were <br />equiped to hold a 25-year, 24-hour event, as per the approval of Office of Mined Land <br />Reclamation dated 12/9/92, technical revision no. 7. <br />• <br />13-3 <br />