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5.2 ALLUVIAL VALLEY FLOOR DETERMINATION <br />5.2.] Mine <br />Introduction <br />A reconnaissance level study of the North Thompson Creek mine area was conducted <br />to determine the extent and nature of possible alluvial valley floors. The area <br />of investigation includes a 2 mile radius around the "life of mine" boundary and <br />Thompson Creek to its confluence with the Crystal River. Features were plotted <br />on a 1:24000 scale topographic base map, see D-5-1. Low altitude black and <br />white, and color aerial photos ar an approximate scale of 1:24000 were used to <br />identify and evaluate many of the features, most of which were field checked at <br />a later date. <br />• General Topography <br />The area around North Thompson Creek mine is typical of many mountainous regions <br />were the topography is controlled by the lithology of the various formations. <br />In the areas of fairly resistant units, the topography is steep with narrow, <br />relatively straight streams, whereas the nonresistant units produce low-angled <br />slopes and wide valley bottoms. The Thompson Creek drainage is typical of high- <br />energy mountain streams; straight, narrow flood plains, coarse sediments, low <br />flows, except during snowmelt, and little, if any, permanent soil. <br />Description of Unconsolidated Sediments <br />Unconsolidated sediments throughout the reconnaissance study area were iden- <br />tified using the aerial photos and then checked on the ground. Drainages <br />included in this study area are North, Middle and South Thompson Creeks and <br />their major tributaries. The study resulted in four geomorphic categories for <br />these sediments. <br />5-3 <br />