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crowned final configurations, with drainage directed from the top of pile toward 4:1 <br />outslopes with uninterrupted runs of up to 100 vertical feet. During active refuse operations, <br />there aze no pazticulaz provisions for preventing drainage over the outslope. Please amend <br />applicable permit sections to address how compliance with Rule 4.09.2(5) will be <br />achieved. Typically, operators address this requirement by providing for terrace benches <br />which break up long outslopes, safely direct runoff from the top of pile to a perimeter <br />diversion, and allow for contemporaneous reclamation of bench outslopes below the current <br />working bench. <br />14. Based on pernut review and field inspection, we have identified a number of discrepancies <br />and concerns with respect to permanent perimeter ditch design and installation for Refuse <br />sub-areas RP-SA and RP-1, and interim "in-pit" perimeter ditch design and installation for <br />sub-azea RP-2-314 combined. <br />RP-SA permanent perimeter ditch designs <br />a) Map 80A includes a ditch cross section labeled "Diversion Ditch Detail", which shows <br />a "V" ditch with 2:1 side slopes, and notes specifying 3.77' max. depth (disturbed <br />areas) Segment 6; 1.92' Min depth (Disturbed Areas) Segment 1; and 3.85' Minimum <br />depth (Undisturbed Areas). With 2:1 side slopes, a 3.85' deep ditch would have a 15.4' <br />top width. Dimensions listed for the specified segments do not appeaz to correspond to <br />the dimensions listed in the ditch design section of Permit Illustration 6A. Please <br />amend Map 80A, as appropriate. <br />b) The Map 80A detail contains the further note that ditches will be seeded and energy <br />dissipation devices, such as cobble dams, utilized on slopes where velocities are <br />expected to exceed S %sec. and may cause erosion problems. For head over check dams, <br />H=(Q/CL)2/3, where C=3 and L=4 for a 1 ' ck dam. This seems to conflict with permit <br />narrative on page IV-2Q which states simply that ..."the ditches will be designed to <br />carry the design flow depth and 0.3 feet of freeboard in all azeas including the riprap <br />and checkdam sections. " Please address this appazent discrepancy. For practical <br />implementation and field evaluation, required depth over check dams should be <br />specified within the detailed design section of Illustration 6A, if the required depth at <br />check dam locations differs from immediately adjacent channel segments. Please <br />amend Illustration 6A design information as appropriate to include the required <br />depth at check dam locations, and include reference to Illustration 6A within the <br />Map 80A notes. <br />c) Illustration 6A includes a table and associated sketch that break the RP-SA perimeter <br />ditches into 12 sepazate segments, with specified slope and velocity control (either <br />riprap or rock check dam with design spacing) for each segment. Check dam spacing <br />varies from 1 check dam every 30 feet to 1 check dam every 175 feet. Following is a <br />segment specific comparison of velocity control design specifications versus <br />Deserado Mine Apri130, 2002 <br />