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The specific changes to the plan being requested through this Technical Revision <br />application are as follows: <br />Pit Inflow and Outflow - In the approved plan, berms would be placed around the top <br />of the pit at an elevation just above the 50 year flood event in order to keep this <br />magnitude of flood out of the pits. These berms will be instalied at the beginning of <br />active mining in each pit and would remain as a permanent feature of the reclamation <br />plan. Control sills would be placed at the downstream end of each active pit in order <br />to provide a controlled discharge point for flood and stormwater flows. The control <br />sills will be constructed during the commencement period far active mining for each <br />pit. 12iprap will be placed on the riverside, crest and pit side of the berms in order to <br />protect the berms from potential erosional flow damage. Riprap will also be placed <br />in a number of locations along the south bank of the active channel to further enhance <br />the project flood control measures. <br />There are two modifications proposed for the scenario outlined above. Based on the <br />request of the Army Corps, the berms placed along the river side of the pits to deflect <br />the 50 yeaz flood will be removed at the time each pit is reclaimed, This material <br />from the berms will be pushed into the pit to help form the sidewalls of the ponds. <br />The second modification related to the 404 permit is the installation of control sills at <br />the upstream end of each pond as part of the reclamation for that pond. These inflow <br />structures, along with the removal of the berms, are meant to allow normal high water <br />into the pond with the idea that the ponds will eventually be filled back up with the <br />solid materials carried by the river. The outflow structures currently designed for the <br />reclaimed pits wiil remain in place to allow a controlled outlet for the floods entering <br />the pits. Thus each reclaimed pit will now have both an inflow and outflow structure <br />in place to help manage future flood events. <br />The purpose of the inlet facility is to allow flow into the pond in a controlled manner <br />that will cause the stream to deposit some of the soil and gravel materials it carries. <br />The concept is that eventually the ponds will be reclaimed by nature back to some <br />semblance of the floodplain existing there today. The inlet elevations will be <br />designed for normal high water. The inlet structures will be two stage inlets, with the <br />first stage designed for the two year storm and the second for the 50 yeaz storm. The <br />design for the inlet structure is the same as for the outflow structure for each pit. A <br />copy of the design for these structures, prepared by project engineer High Country <br />Engineering, is attached to this cover letter. The Floodplain Study for the project <br />was submitted previously. <br />2. Reduction of Mining Area -Based on site visits conducted with the Army Corps of <br />Engineers and the U.S. Fish and Wildlife Service, more detailed field work was <br />completed regarding the location of the high water mark and top of bank along the <br />river. These agencies requested a more accurate starting point for the riverside <br />buffers in some areas. This resulted in a more significant buffer area between the <br />