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Best Practices in Abandoned Mine Land Reclamation <br /> Best Management BMP#1 -DIVERSION DITCHES clean water will flow away from, and not come <br /> Practices Applicable situations: in contact with, the contaminated pile. <br /> waste rock piles <br /> mill tailings The size of the ditch generally depends on how <br /> draining mine openings much water is expected. The simplest ditches <br /> are dug either by hand, using a backhoe, or <br /> Description and purpose using the corner of a bulldozer blade to make a <br /> Diversion ditches are effective where the qual- triangular cut.Care should be taken to dig deep <br /> ity of rainwater, snowmelt or surface flow is enough to catch incoming shallow groundwater <br /> degraded by flowing over or through mine as well as water flowing on the surface when <br /> waste, tailings or into mine workings. using any of these methods. The side walls of <br /> Diversion ditches can also be used to intercept the ditch should be smoothed to a slope of 2:I <br /> shallow groundwater that may enter a mine (two feet horizontal to one foot vertical)or flat- <br /> waste or tailings pile. ter to maintain stability,as shown in Drawing i. <br /> Ideally, the slope or gradient of the bottom of <br /> How to do It the ditch should be designed to encourage <br /> A diversion ditch should be located upstream water to flow freely, while not ponding, but <br /> of the contaminated waste rock or tailings <br /> pile, and should capture and channel the <br /> clean water from uphill around the problem, <br /> as shown in Maps A&B. Because the only goal <br /> of the ditch is to keep clean water away from ore J1 <br /> ON <br /> contaminated rock or tailings, the length of <br /> the ditch depends on the size of the contami- <br /> nated pile and the topography of the site.The <br /> ends of the ditch should be in a place where JJJJJJ <br /> NC NTA INA+W N NTA�IN ED W <br /> Map A Map B <br /> DRAWING I (at top right)-Cross section of a diversion ditch showing side slopes at 2:1. To maintain stability,side slopes <br /> should be at 2:1 or flatter.MAPS A&B(above)-Simplified views of a tailings pile and the quality ofsurface water flow- <br /> ing into a nearby stream. (Also applies to waste rock piles.)Map A shows that uncontaminated surface water originating <br /> uphill of the tailings pile will become contaminated of ter flowing across or through the contaminated pile.Map B shows that <br /> a properly placed diversion ditch will channel the water originating uphill of the pile away from the pile to avoid becoming <br /> contaminated. The amount of contaminated flow downhill of the tailings pile entering the stream is then greatly reduced. <br /> 14 <br />