2010-08-06_PERMIT FILE - C1980007A (2)

Home Browse Search

West Elk Mine • below. When the sediment level reaches the cleanout level in one cell, the runoff flows are closed to that cell and opened to the other pond cell. The pond cell that is full of sediment can then be completely drained and sufficiently dried for cleaning. Access for operation and maintenance of the pond will be via a single -span bridge from State Highway 133. The pond has been designed to store a three -year sediment volume. A 54 -inch riser pipe serves as the upper, maximum level (primary) outfall in each cell of pond MB -5E, and contains two 12 -inch gated drain pipes at different elevations in the riser pipe. To better manage the ponds for CDPS permit compliance, MCC typically does not allow the pond to fill and spill into the primary outfall riser pipe. Instead, after sufficient settling time, the top drain pipe (mid -pool level) is typically utilized first to discharge from the middle level of the pond, avoiding potential floating or settled debris. The bottom drain can then be opened to further lower the pond level to better empty the pond for cleaning. The emergency spillway is an open - channel, rock lined spillway. MB -5E is sized to contain the 100 -year, 24 -hour storm event, and /or MCC's water right for this pond. SG -1 Sediment pond SG -1 was constructed in 1997 to accommodate storm water runoff from the pads associated with ventilation shafts #1 and #2, located in Sylvester Gulch. The pond was used to treat water from the construction of the shafts. The pond was designed to contain the • 10 -year, 24 -hour runoff volume and hold three years of sediment. The pond is lined with HDPE. The principal spillway consists of a channel of filter rock that filters the sediment prior to entering a slotted HDPE pipe, which then becomes a solid pipe. The system is an effective means to treat the water and the discharge pipe has been designed to remain open. However, the valve is usually closed to control discharge from the pond. The emergency spillway is an open - channel, rock -lined spillway. RPE Ponds The RPE ponds were also constructed during 1997 to accommodate storm water runoff and possible leachate from the Refuse Pile Expansion (RPE). The RPE ponds are essentially one pond with two cells, similar to pond MB -1. Water from the sediment ditch enters Cell A (the eastern cell). Water can be treated in this cell and discharged directly to the river through piping that connects the cell to the primary discharge structure in Cell B, or the water can be transferred over to Cell B for further treatment if necessary. The primary discharge is through a gated pipe. The emergency spillway is a pipe that remains open. The pond has been designed to hold the runoff volume from a 100 -year storm event and was designed to hold three years of sediment that could be generated during a storm event. FW-1 Freshwater Pond -1 (FW -1) was originally designed to store and provide two months storage capacity for potable and domestic water uses at the initial planned coal production rate of 250,000 • tons per year. At the projected coal production rate of 8.2 million tons per year, approximately 3.0 days of water storage capacity is provided. This pond has a capacity of ten acre -feet, an 2.05 -35 Rev. 06/05, 01/06, 03/06, 04/06 & 05/06- PRIO; 01109 - MR350; 04/09- TR116;; 05109 - MR354; 08109- 7R119