2019-05-29_REVISION - C1981018 (11)

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27 The Division has granted a number of small area exemptions (SAEs) from the use of sediment ponds and treatment facilities, due to the limited size of the areas in question and due to the fact that ponds and treatment facilities are not necessary for the drainage from these sites to meet the effluent limitations of Rule 4.05.2 and applicable State and Federal water quality standards for receiving streams; and also due to the fact that no mixing of surface drainage from these areas with a discharge from underground workings will occur. The small areas to be exempted are listed in Section IV.J.5 of the application. Sedimentation demonstrations for the SAE’s are provided in Illustration 44, of Volume 12, and the locations are shown on Map 147 (4.05.2(3)(b)(i)). B. Diversions and Conveyance of Overland Flow l. The Division approved the diversion of an ephemeral stream draining at least one square mile. Scullion Gulch has been diverted with a large diameter pipe culvert such that it passes beneath the D Portal facilities area. The decision to approve this diversion is based on a finding that the diversion meets the requirements of 4.05.l8 and 4.05.4, applicable local, State, and Federal statutes and regulations and is designed to safeguard public safety and to minimize adverse impacts to the hydrologic balance (4.05.4(1) and (4)). C. Sedimentation Ponds Sediment ponds are discussed under Section IV.J.1 Volume IV of the permit application. The applicant uses sedimentation ponds in all disturbed drainages to control the increased sediment loads within the ephemeral drainages on the mine site. All sediment ponds are designed to contain or treat the 10-year, 24-hour even and safely pass the 25-year, 24-hour event, at a minimum. An alluvial well field near the confluence of Scullion Gulch and the White River was originally developed to supply water for mine operations. The 1984 completion of Kenney Reservoir east of Rangely, Colorado inundated much of the alluvial well field. Because the alluvial surface is almost completely submerged by the reservoir, recharge to the alluvium is now instantaneous. Due to inundation of the well field by the reservoir, and due to high salinity of the alluvial well water, the operator pumps water directly from the White River into an adjacent lagoon formed by the Kenney Reservoir. Approval to pump directly from the raw water lagoon to the raw water system was affirmed in Permit Renewal No. 2 in 1994. Only one alluvial well, Qal-5, located at the mouth of Scullion Gulch, Remains in use as monitoring well. The raw water lagoon is a semi-in situ impoundment that collects water from the White River. The Division approved (MR-55) the construction of a dike that separates Scullion Gulch drainage from the lagoon area. The location of the dike