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vegetative areas. This ditch will be seeded and lined with a mulch may [t will be constructed <br />(including seeding) prior [o any placement of developmen[ waste on [he pile. <br />2) a silt fence below [he pile. This fence will be constructed prior to any placement of developmen[ <br />waste on the pile. <br />3) circumvential ditches (ditches DWP-W and DWP-E) around the upper portions of the pile. <br />Runoff from the upper half of the pile would be divided and Oow around the toeof-slopes in <br />these ditches. These ditches would also capture runoff from small watersheds located between <br />the interceptor ditch and the circumvential ditches. These circumvential ditches will be feathered <br />out inside (uphill) of the perimeter silt fence to discribu[e discharge along pottions of the lower <br />silt fence (and thence into vegetative debris filters). These ditches will be constructed prior to <br />any placemen[ of waste on the pile. During construction, en[renchmen[ of [hese ditches will be <br />arrested by the exposure and accumulation of the cobble sized fraction of the si[e soils. After <br />construction (no more development waste to be placed on the pile), these circumven[ial ditches <br />will be seeded and protected with mulch mats. These circumvential ditches are designed to <br />accommodate 100-year, 3~1-hour storm events. <br />4) after construction is complete, a midslope silt Cence will be placed on the downhill slopes of the <br />pile. <br />5) after construction is complete, the pile and disturbed areas about [he site will be stabilized with <br />vegetation (seeding and mulched). <br />6) natural vegetation and vegetative debris ground litter (equated to a grass flier). Runoff from the <br />downhill slopes of the pile and discharge from the circumvential ditches would flow through the <br />lower sill fence and into [he vegetative debris filler. The filter will provide final fillration of all <br />the runoff from the pile. <br />This analysis addresses a 'worst rase" scenario, i.e., the site is protected by an interceptor ditch, the <br />circumvential ditches have not been vegetated, [he entire pile is considered as constructed wi[h no ground <br />cover, and only a lower perimeter silt fence is considered as ins[alled. No credi[ is given to silt fences or straw <br />bales with regard to sedimen[ con[rol or mi[iga[ion of allects on the quality of storm runoff. Partial <br />implementation of all [he best management prac[ices iden[ified will reduce [he po[ential for erosion and <br />provide a degree of impact somewhat less than the 'worst case' scenario. <br />1.3 Criteria <br />To qualify as a Small Area Exemption (SAE), runoff• from disturbed ground must not exceed effluent <br />limi[ations during a 10-year 24-hour storm event of 0.5 millilitersAiter (ml/I) of peak settleable concentration <br />(SSp) of sediment (reference Rule 4.0.2. Division of Minerals and Geolo4ry}. Titus water quality analyses are <br />based on this storm event. <br />The development waste pile is to be protected from 100-year, 2~3-hour, storm evens (Rules 4.10.3(2) and <br />4.09.2(7)]. The interceptor and circumvential ditches are designed to provide this level of protection. <br />A 0.3 foot of freeboard for diversion ditches is required by the Division of Minerals and Geology [Rule <br />4.05.3(7)]. A OS foot of freeboard is used for to design Cor all the ditches, however, to add an extra measure <br />of protection. <br />(West Elk SAE. Lone Pine Gulch Development Waste Pile. Page : oC 8) <br />