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,. <br />a <br />s~ <br />thi:a annual deposition bf sand and gravel that Sandco, <br />Inc. proposes to remove from the river channel by <br />sel=ctively restricting the mining operation to the most <br />elevated deposits, This method of controlled mining will <br />contribute to the stability of the river system by <br />preventing the accumulation of sediment within the channel <br />with a coexistent decrease in channel capacity, and an <br />increased probability of flooding due to aggradation of the <br />streambed. Maintenance of the natural channel capacity in <br />this manner reduces the flood stage that would otherwise be <br />created by aggradation. The extraction of sediment from <br />the most elevated sand and gravel deposits will coincide <br />with the seasonal periods of low water flow that typically <br />occur during late fall, winter and early spring months in <br />the Animas River. Because the low water cycles vary due to <br />weather variation, mining operations must vary <br />accordingly. Excavations will not extend below the water <br />level of the river, and the volume of material rert~oved is <br />th~.s limited to that annually deposited above the level of <br />low water flow, <br />Ber:ause this controlled mining of the sand and gravel <br />deposits does not increase the existing channel bank <br />heights, accelerated erosion thereto will not occur. <br />Further, since the streambed will not be excavated below <br />the low water level of the river, streambed degradation due <br />to induced headcutting will not occur and no detrimental <br />2 <br />