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6. River Protection <br /> As is seen by the river location near the pit,there is a sharp outside bend in the river very near the <br /> proposed pit. Although the pit will maintain a minimum 100' buffer from the toe of low water in the <br /> river to the edge of excavation, embankment protection for this area of the river is still warranted <br /> for long term stability. This will ensure that the river never erodes into the lake during a large flow <br /> event. <br /> Therefore, a minimum durable angular rock of minimum size D50=4.50 feet size is specified for a <br /> length of 225 feet and a slope length of 16 feet as shown in the diagram below. The landowner has <br /> in the past placed many large rock and concrete slabs of this approximate size in a portion of this <br /> area. This has provided good protection, and more material has been placed laterally and vertically. <br /> A professional engineer has determined that sufficient rock has been embedded in the bank to <br /> prevent scouring. The maximum slope of the embankment will be 2H:1 V. <br /> The rock will be either a well-cemented sandstone or igneous/metamorphic rock that is durable. It <br /> will be placed as shown on the diagram below and Map E-1 Mine Plan. The top elevation of the <br /> protection riprap is 5598.0 feet, which is approximately 1.5 feet below the elevation of the 100-year <br /> flood at this location in the river. This elevation was estimated by the US Army Corps of Results <br /> show that boulders are stable for the cases of the wall and the bottom. These boulders now in place <br /> have withstood the test of time. They protected this property during high water and large flood <br /> stage in the early 90's. Therefore,no additional work will be done on this slope, which has been <br /> looked at by a professional engineer licensed in Colorado and Montana and determined sufficient to <br /> protect the land in question. <br /> 21 <br /> North Fork Pit March 04 <br />