Laserfiche WebLink
Summary of BMPs <br />BMPs included in the design are silt fence, hydromulch, and gravel surfacing. Silt fence shall be installed <br />along the contour upstream from Pond 1. The silt fence will treat disturbed runoff from the intake shaft <br />installation before it enters Pond 1. Silt fence should be connected to steel fence posts spaced every 6 ft. <br />One 0.3 ft deep x 4 ft long weir shall be cut into the silt fence where it crosses the drainage that leads into <br />Pond 1 (Exhibit 6). After the intake shaft installation is complete, silt fence is no longer necessary. <br />Hydromulch will be the BMP employed to stabilize disturbed slopes. Hydromulch should be applied to <br />the shaft pad outslopes, and to the pond embankments. Hydromulch will protect these disturbed slopes <br />during the first growing season as vegetation begins to establish. It is anticipated that a reasonably high <br />vegetative cover will replace the hydromulch after the first growing season. <br />After the shaft pad is graded, it should be covered with coarse gravel. Because of the relatively large size <br />of the gravel particles, little sediment is expected to be produced from the pad during storm events. <br />Summary <br />The 18L intake shaft installation at Foidel Creek Mine has been analyzed for hydrology and <br />sedimentology given conditions that will occur both during construction and after the installation is <br />complete. A combination of silt fence and two sediment ponds in series have been designed to treat <br />stormwater runoff from the installation during construction of the shaft pad. After construction is <br />complete, the silt fence can be removed and perforations can be added to the riser pipe of the Pond 1 <br />principal spillway. Pond 1 will then operate as a treatment structure that automatically dewaters the 10- <br />y r, 24-hr runoff volume in 1.17 days. After it can be demonstrated that discharge from Pond 1 meets <br />NPDES requirements for discharge, the lower sediment pond can be reclaimed. <br />\_J <br />Twentytmile Coal Company 18L Shaft Pad 8 Water & Earth Technologies, Inc. <br />Drainage and Sediment Control System Design March 2, 2009