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The applicant has made a demonstration, based on site specific precipitation rates, percent of grade, and soil properties, that use of alternative specifications for culvert and bridge sizing will not result in increased erosion. The Division therefore approved the use of the alternative specifications for the haul road culverts. The culverts were located such that drainage is routed to existing major drainageways which are incised to bedrock. (4.03.1(4)(e)(vi)). Access Roads Information regarding access roads will be incorporated into the permit application package with approval of the revision required by Stipulation 27. C. Light-Use Roads Information regarding light-use roads will be included in the permit application package with approval of the revision required by Stipulation 27. II. Support Facilities - Rule 4.04 Support facilities at the mine include administrative and production buildings, surface water runoff control structures, and water monitoring structures. Administrative and production related facilities locations are shown on Exhibits 12-1 and 12-2, of the permit application package. Locations of structures relating to surface and groundwater hydrology are shown on Exhibits 7-2 and 7-7 in the permit application package. III. Hydrologic Balance - Rule 4.05 Water Quality Standards and Effluent Limitations Surface Water Hydrology Information on surface water can be found in Volumes 4, 5 and 6, Tab 7, of the permit application package. The Seneca II Mine is located within two adjacent drainage basins: Grassy Creek and Fish Creek. Both of these Yampa River basin in northwestern Colorado. water quantity conditions at the Seneca II Probable Hydrologic Consequences discussion and sediment control features are described Grassy Creek are sub-basins of the upper A discussion of surface Mine is provided in the of this document. Drainage below for each drainage basin. A major portion of the Seneca II Mine is located within the Grassy Creek basin. Surface runoff originating in the western part of the permit area flows into Little Grassy Creek, a tributary of Grassy Creek. A large sediment pond, the Wadge Impoundment (NP DES 002), is located near the mouth of Little Grassy Creek and controls runoff and sediment from a 2100 acre area of which 860 acres are to be disturbed by mining. This pond has been designed with a large permanent pool of 2b7 acre-feet. Runoff from the 10 year, 24 hour design storm is 12 acre-feet. -13-