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2.8.2 Design Criteria <br />The following criteria are recommended for use in the design <br />and construction of the diversion ditch. There are several <br />alternative methods of diversion ditch design which are to be <br />evaluated during final design and used as required. <br />a) The ditch should be designed for the 10-year, <br />24-hour discharge of 0.65 cfs described in <br />Section 2.3.2 of this report. <br />b) The ditch should be designed at such a grade <br />so as to minimize eroding or depositing of <br />sediment, depending on the nature of the <br />material through which the ditch is <br />constructed. <br />c) Steep grades should be controlled by <br />constructing riprap drop structures and check <br />dams. <br />• <br />d) Channels with steep grades which may produce <br />erosive velocities and which cannot be <br />controlled with grade control structures <br />should be controlled by use of a graded <br />riprap lining and filter material, if <br />required. <br />e) An alternative method if properly sized <br />riprap materials are not economically <br />available may be channel stabilization using <br />a gunite lining. <br />f) An alternative method <br />in steep reaches is <br />corrugated steel pipe <br />channel section with <br />outlet structure. <br />to lining the channel <br />the installation of <br />culvert or 1/2 pipe <br />a riprap inlet and <br />2.8.3 Proposed Design <br />The proposed ditch design would use the existing road as a <br />base for constructing the ditch. The inside edge of the road <br />will be graded, using heavy equipment, to a triangular ditch <br />shape about 1 1/2 feet deep. This depth is more than adequate for <br />the low flows from these small areas of low runoff potential. <br />The ditch slope will approximately match the road grade. Steep <br />reaches will be evaluated and erosion control measures as <br />described under design criteria constructed, as required. <br />2.9 Sediment Pond <br />• <br />2.9.1 General Description <br />The State of Colorado Mined Land Reclamation Division <br />9 <br />