2008-04-22_PERMIT FILE - C1981017 (15)

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Chapter II • c. Diversions. A number of diversion ditches have been designed and constructed, and are maintained, to control surface runoff and to minimize water quality degredation. The ditches have been located so as to divert water away from disturbed areas, or to convey water flowing out of disturbed areas to treatment facilities. All diversion ditches which drain disturbed areas lead to sediment ponds. The diversion ditches were designed according to CMLRB regulations. Temporary diversion ditches (such as one at the base of the old coal refuse disposal area) were designed to convey a minimum peak flow from the 10-year/24-hour storm event, and with a minimum freeboard design of 0.3 feet. The ditches have been installed as approved by the Board on the inside of all cuts and fills so that the flow velocities will not cause adverse erosion. The ditches are also located away from the toe of the fills to prevent undercutting during periods of high flow. Where necessary, rip/rap and/or vegetative control measures are also employed. A permanent diversion ditch has been constructed in the south fork of Dutch Creek. It was designed to convey the peak flow runoff event from the 100-year/24-hour • storm, and using the best technology currently available to minimize the contribution of sediment to Dutch Creek. In construction, the culverts were sized and placed in the stream channel using dozers and a crane. The fill material was placed using a backhoe and compacted with a vibrator compactor. The outstopes were stabilized as necessary with rip rap, or were revegetated. A 100-foot buffer zone has been left below the toe of the spoil, landfill and refuse disposal area adjacent to the South Fork of Dutch Creek. Diversion ditches have also been constructed around the preparation plant. Perimeter ditches and berms have also been constructed around the refuse, landfill and Adit/Rock Tunnel spoil disposal areas. An extensive drainage control plan/system was developed in accordance with CMLRB rules and regulations, section 4.03.0 -Performance Standards for Haul Roads. The road drainage system has been designed to handle a 10 year/24 hour rainfall event. See Vol. 3, App. II-B-7, Att. 2. These roads bisect three major drainages: Coal Creek, Dutch Creek and Bear Creek. Eleven miles of the total 13.7 miles are within the Dutch Creek drainage. Natural drainage channels were neither altered nor relocated for construction of the haul road system, and where the roads cross perennial streams, culverts have been • 31