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• Definitions: <br />• <br />Permanent containment ditch: A ditch that is designed and constructed with the intent <br />to handle runoff from the disturbed azea following reclamation. <br />Final containment ditch: Synonymous with permanent perimeter ditch. <br />In-pit or interim containment ditch: A ditch that is constmcted to convey mnoff along <br />and/or away from the toe of a refuse pile. It is frequently formed by the V between the <br />refuse pile and opposite sloping terrain. <br />Rotary breaker reject: Refuse comprised of harder and coazser than normal material <br />that passed through the rotary breaker without reaching the size required to pass on to the <br />wash plant. <br />Ditch Specifications <br />In-pit or interim containment ditches: <br />Unless otherwise specified, the capacity of these ditches are to be maintained to that <br />reflected in the designs for the permanent ditches. <br />Stability is of concern from several perspectives. First, the ability to contain mnoff and <br />continue to direct such flow to a sediment pond. Second, reduce additional sediment <br />contributions resulting from the erosion of the ditch channel. Third, eliminate excessive <br />cutting into the refuse pile resulting in slope stability problems. <br />Conventional design models poorly predict the actual stability issues encountered on an <br />active refuse area. Their shortcomings typically originate from their focus on erosivity at <br />peak flows originating from large storm events. Little attention is paid to depositional <br />issues at lower flow rates or the quantity of sediment in the mnoff. Therefor, operational <br />experience provides the best measure for predicting problem areas and prescribing <br />corrective measures to address these issues. <br />Problems originating from deposition include the reduction in channel volume. <br />Deposition actually provides the greatest risk to the integrity of the mnoff containment <br />system than erosion. Excessive deposition and channel volume reduction can lead to the <br />escape of mnoff onto undisturbed areas. Erosion, on the other hand, rarely poses such <br />risks unless it is cutting into an outside berm of the containment s[mcture. In azeas where <br />deposition is expected ditch constmction should take this into consideration by providing <br />for additional sediment storage beyond design. <br />Conventional channel stability, erosion protection, is the main focus of designs. <br />Operationally, we can prescribe various measures to reduce erosion to acceptable levels <br />based on slope, expected flows, expected sediment load, channel geometry and size, and <br />