2010-11-19_PERMIT FILE - C1980007 (30)

Home Browse Search

J Washwater and Stormwater Management The facility washwater and stormwater runoff from the paved containment area will be conveyed by gravity flow to a series of stormwater management structures. These management structures are shown on Drawing 1 in Appendix A and include a sediment trap, oil separator and stormwater retention pond. Sediment Trap The sediment trap is designed to remove sediment from facility washwater and stormwater runoff draining to the trap. The layout of the sediment trap and design details are shown on Drawings 1 and 3 in Appendix A. Washwater will be collected and piped to the sediment trap through a trench drain to be located below the loadout facility and south of the railroad track located adjacent to the facility. The washwater will be conveyed from the trench drain to the sediment trap through a buried pipe. (The trench drain and pipe layout are shown on Drawing 1 in Appendix A. The trench drain will also function as part of the hydraulic oil spill containment system discussed later in this report.) Stormwater runoff from the paved containment area upgradient of the sediment trap will be directed to the sediment trap through site grading. During facility W4shdown operations, washwater will discharge from the sediment trap to the oil separator through a pipe connecting these facilities. (The walls of the sediment trap have been configured to direct any oil that may be floating on the water surface toward the inlet pipe to the oil separator.) The sediment trap is designed to contain 20 cubic yards of sediment below the invert of the inlet pipe to the oil separator. (Sizing calculations for the sediment trap are included in Appendix C.) Approximately 20 cubic yards of sediment is currently removed quarterly from the existing sediment pond During larger storm events, water entering the sediment trap will also discharge through an emergency spillway. The emergency spillway will be located along the northwest wall of the West Elk Mine Train Loadout Environmental Improvements pA 11-407VeporAreport.doc Shepherd Miller, Inc. July 1997 (Revised April 1998)