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t~ <br />Utn AHi \tt tJf OF rl41UI14t NE SOU11CEs <br />D. Monte I'asmt, E~~mm~ve Drtec mi • <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (3031 839-3567 <br />~cav~+vs. <br />Da7id C. Shelton <br />Director <br />M E M O RAN D U M <br />T0: €d--Bischoff ~-~tiw{ <br />FROM: Todd Gibson <br />DATE: August 27, 1980 <br />RE: Reply to Utah International's discussion of Culvert <br />Spacing Requirements <br />In brief, U[ah International's argument was that the culvert spacing regula- <br />tions do not materially aid in controlling sedimert from areas disturbed by <br />haul roads because: <br />The spacing requirements were developed in Pennsylvania, and are <br />arbitrary and capricious applied to Colorado. <br />2. Road design criteria serve no clear and definable objective in areas <br />already protected by sediment ponds, since effluent limitations of <br />runoff from these areas are the only definite criteria to judge ero- <br />sion by. <br />3. Drainage systems [hat discharge into natural drainages cause less <br />erosion than allowing discharges to occur over slopes. <br />Utah International's basic conclusion, [hat there should be variance allowed <br />from the culvert spacing requirements, is sound. Some discussion is in order <br />on their supporting facts, in order that specialists examining proposed cul- <br />vert spacing should be familiar with hydrologic principles as influenced by <br />road drainage: <br />The spacing requirements evidently were based on avoiding erosion of <br />haul road embankments and ditches only rather than including other <br />road-related erosion and hydrologic problmes, and therefore are rather <br />arbitrary. It is, nevertheless, important to culvert flow across the <br />road even when there is no natural drainage to receive the water, for <br />reasons to be discussed belorJ. <br />2. Road design criteria for purposes of erosion control need not apply to <br />disturbed nine areas .here the runoff enters a sediment pond (provided <br />the pond is near [he disturbance). Culver[ spacing in this case may <br />still have some bearing on road stability, however; water ponding against <br />haul road embankments could lead to problems. <br />