2009-11-13_PERMIT FILE - C1982056A (7)

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Effective drainage and sediment control for the estimated 0.01 of of runoff (from a 10-year, 24-hour event) from this area is achieved through use of the following components: 1)Asphalt-surfacing of parking areas; 2) An established vegetative filter on the down-gradient outslope; and 3) Drainage ditches on both sides of the Brown Palace access road (connecting with Haulroad C), with a series of rock check-dams to reduce flow velocities and collect any contained sediment prior to discharge to Foidel Creek. The small area exemption is shown on Map 24. Asbestos abatement was completed in early 2005, and the building was later demolished during Summer-2005. During demolition, drainage and sediment control for the site was provided by the existing drainage control features and sediment fencing and/or straw wattles. Following demolition, the site was stabilized by grading and reseeding disturbed areas. Calculations documenting the adequacy of the design drainage features are presented in Exhibit 8Z, CYCC Office Building Drainage Design Documentation. Sandstones Power Substation -Sediment control for this area (less than one acre) will consist of a perimeter containment berm/temporary diversion ditch and gravel filter(s) sufficient to treat the estimated 0.06 acre-feet of runoff from the 10-year, 24-hour event. The location of this SAE is shown on Map 39 (Substation and Powerline Location). This SAE was expanded slightly in Fall 1993 to allow the drilling of a replacement borehole into the mine, which was in turn, used for drilling of a water supply/monitoring well underground (FCM No. 2). The expansion of the SAE entails extension of the berm to the west to encompass the very limited (approximately 50 x 50 feet) of additional disturbance. Any topsoil stripped will be windrowed/temporarily stockpiled adjacent to the pad. Following completion of the well work, a portion of the expanded area may be reclaimed, with remaining topsoil being added to the existing topsoil stockpile. The topsoil and reclaimed area will be seeded and stabilized using the pastureland see mixture. Railroad Spur Extension Area -This SAE covers 2.75 acres and is located west of Pinnacle Peak, adjacent to the railroad embankment. A portion of this SAE area is a seeded topsoil stockpile. All water drains to the south and is filtered through a silt fence located west of the rail spur extension. The area below the silt fence is vegetated and serves as a vegetative filter. Peak flow from this small area is approximately 4.4 cfs, as previously approved in the original submittal under the C-81-071 permit. Warehouse/Shop Area -This SAE covers approximately 5.88 acres and is located on anorth-facing slope below the shops. Water (approximately 0.15 acre-feet from the 10-year, 24-hour event) drains through established vegetation, gathers along the railroad track embankment and runs along Ditch F-2 toward the culvert under the light-use road adjacent to Pond F. The water collects in a natural depression on the upper end of the culvert before flowing through the culvert. Once through the culvert, drainage flows down the north side of Pond F and the light- use road/railroad embankment. The area is vegetated and serves as a vegetative filter to inhibit and filter flows. A rock check dam, previously established in this area, acts as a final filter and flow control for drainage before it leaves the area. Stoker Coal Loadout -The Stoker Coal Loadout, which covers 1.8 acres, is located north of the Old Equipment Parking Lot and adjacent to the railroad tracks. Sediment control in the area consists of a berm and rock filter located on the west side of the bench, and a rock filter on the north side of the railroad track. These control any potential surface runoff from the bench area. Stoker Coal Handling Modifications (TR08-65) -The stoker coal handling modifications involve extending the existing truck turn-around area to the north approximately 15 feet. Drainage from the truck-turn-around area and the associated Haulroad B-2 is controlled by a berm on the north side of the road with sediment traps and rock filters located at intervals along the berm. Drainage and sediment from construction activities for extension of the truck turn-around area, and drainage from the outer fill slope of the road will be controlled through placement of silt fence and/or straw or wood-fiber wattles on the edge of the expansion disturbance area. The road outslope will be seeded following completion of the extension, and sediment controls will be maintained until adequate vegetative cover is established to control erosion and sedimentation. Warehouse Area No. 2 -This SAE consists of approximately 1.5 acres located between the Stoker Pad and the Warehouse/Shop SAE's. There is little or no drainage from the flat, graveled area, and any flow from the area would be controlled and treated by either the Stoker Pad silt fence or the warehouse exemption rock check dam. TR09-66 2.05-84 04/11/09