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Wanstedt <br />Page 2 <br />April 19, 2001 <br />After reviewing the revised designs, we have the following recommendations: <br />Sub-watershed 1 A (undisturbed uplandl. 2A and 3A -Please remove the silt fence from the <br />design and provide for two rock-riprapped channels across sub-watershed 2A for conveying <br />water from lA to Scullion Gulch stream bed. Modification of the channel gradient and <br />contouring of the surrounding disturbed area could be utilized to prevent disturbed area <br />runoff from entering the channels. Additional sediment control may include straw bales or <br />silt fence along the channels for the short distance across the disturbed area. Please provide <br />a design demonstrating that the channel can safely carry 10-year, 24-hr. runoff and will not <br />receive inflow from disturbed land in subwatershed 2A. <br />2. Sub-watersheds 4A 1B. 2B, and 3B -These locations have berms with filter fabric outlets <br />and are adequate as submitted. No response necessary. <br />Reclaimed road segments outside subwatersheds listed above -Please confirm in amended <br />permit text or on Map 89 that a rock-riprapped channel will be constructed to convey water <br />to Scullion Gulch from the smaller ephemeral drainage that exists on the road east of azea A <br />(refer to BME's response to comment 7d dated February 8, 2001). <br />4. For all other reclaimed road segments outside sub-watersheds listed above, please prepare a <br />SEDCAD model demonstrating that effiuent limitations will be met by 10-yr., 24-hr. runoff <br />from the reclaimed areas, accompanied by a map showing locations of any expected <br />concentrated flow on the reclaim or uplands. If there are no areas of concentrated flow (sheet <br />flow only), the SIDCAD model could be for a hypothetical parcel of one or two acres in size <br />using composite input values (acreage-weighted for the upland undisturbed azea and the <br />reclaimed road). <br />Please contact me or Mike Boulay if you have any questions. <br />Sincere , <br />Dan T. Mathe s <br />Environmental Protection Specialist <br />cc: Denver File <br />Mike Boulay <br />