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t00 to '1000 time larger than that of the waste material. This indicates that the <br /> water will move much faster through the drain than through the pile. Because of <br /> this fact and the relative steep slope of the valley floor (drain slope) compared to <br /> the pile surtace, each zone drains approximately independently, in time, of the <br /> others. This is the routing effect and means that only a portion of the pile will be <br /> contributing flow to the drain during any given time interval of the design event. <br /> Physical PropaRios <br /> geometry valley slope = O.'1265 <br /> pile face slope= 0.4000 <br /> pile top slope =O.O'100 <br /> pile length = 1600 ft <br /> Average pile dimensions for flue equal length segments<ft) <br /> (bottom of pile upvalley to top of pile ->) <br /> length 320 320 320 320 320 <br /> width 320 500 420 380 200 <br /> thickness 44 t3'1 t02 66 27 <br /> hydraulic hydraulic wnductivity, K <br /> gravel (drain file material - <br /> range of Ku = O.00tO ft/s to O.'1024 ft/s <br /> average Ku = 0.0132 fLs _ <br /> waste rock material <br /> Kw= 'I.066 x '1 O�fVs <br /> hydrologic gross in£Hration rate =50%of long term precipitation <br /> p "pitaYo - mean ma month = 6 38 i (period of record) <br /> note: hydraulic conductivities and the infiltration era coarse estimates based on <br /> _reported teM book values for similar materials. <br /> After balancing the estimated inflow to the drain with the flow capacity of the <br /> drain and adding a safety factor a size was estimated. It is reasonable to assume <br /> that the drain size should decrease as you move upvalley and have less volume <br /> and surtace area contnbuting to it. <br /> The lower portion (approximately 400 ft.) will be serviced by the existing drain <br /> constructed for the original waste pile. The new drain was designed in three <br /> sections of 400 feet. <br /> Underdrain Size <br /> Reach Length (ft. bottom to top) Drain size Cwidth x depth in ft) <br /> '1 O to 400 existing 3x3, square <br /> 2 400 to 800 7x4, rectangular <br /> 3 800 to '1200 Sx4, rectangular <br /> 4 '1200 to '1600 3x3. rectangular <br /> The new portion of the drain should be connected to the existing drain at its <br /> terminus. Because the existing drain is not sized to handle all flow generated <br /> above it an 8' drain pipe (schedule 40 pvc in bedding) should be connected at <br /> .Tanuary 1998 <br />