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• All ponds will be examined on a quarterly basis at a minimum for <br />structural weakness, erosion and other hazardous conditions. Consistent <br />with applicable regulations, the CMLRD will be notified of any hazardous <br />conditions, remedial measures will be initiated and appropriate <br />modifications will be completed in a timely manner. <br />4.05.7 DISCHARGE STRUCTURES <br />Flow rates and velocities for temporary diversion ditches and discharge <br />calculations for sedimentation pond outlets are presented in Exhibit 19, <br />Drainage and Sediment Control Plan. As documented by these flow <br />parameters, design flows will generally be low, on the order of five (5) <br />cubic feet per second or less. Where specific constraints imposed by the <br />natural terrain result in steeper gradients, flows may exceed five (5) <br />feet per second and placement of riprap and bedding material may be <br />necessary to limit flow velocities, assure channel stability, and prevent <br />any significant erosion. <br />• Generally, discharge structures have been designed and installed at <br />minimum gradients to limit discharge flow energy. Any potential for <br />erosion at the outflow of discharge structures will be effectively <br />controlled by placement of riprap and bedding materials in an apron <br />configuration at the outflow. Generally, once the initial discharge <br />energy is dissipated in these apron areas, erosion from the discharge flow <br />will not be a problem since most receiving drainages have established a <br />stable bed configuration and most drainages are effectively armored by <br />exposed cobble and gravel materials. Hydraulic calculations do not <br />indicated the need for fabricated energy dissipators, stilling basins, or <br />other artificial flow control structures. Selective use and placement of <br />riprap and bedding materials should provide adequate channel protection <br />and erosion control. <br />4.05.8 ACID FORMING AND TOXIC FORMING SPOIL <br />• No acid or toxic forming materials have been identified as occurring <br />within the mine or loadout areas as a result of chemical analyses of <br />soils, coal, roof and floor materials, or coal refuse. Comprehensive <br />4.05-20 <br />