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Section 785.19 (c) Continued. <br />General <br />A field investigation and technical evaluation of all drainages <br />containing streams within and adjacent to the mine plan area has <br />been conducted in accordance with this Section and the draft OSM <br />Technical Guideline, "Technical Identification and Study of Alluvial <br />Valley Floors", dated revised August 15, 1978. In summary, the <br />investigation and evaluation resulted in no identification of <br />alluvial valley floors in or adjacent to the mine plan area based <br />on geomorphic and water availability criteria, and further that no <br />alluvial valley floors which may exist within the general area will <br />be adversely affected by mining operations. <br />Geomorphic Characteristics <br />General Area. The investigation was initiated by mapping unconsoli- <br />• dated deposits of more than 30 feet in width in the general area, <br />using published and unpublished geologic maps and ground recon- <br />naissance. These deposits and their associated stream channels are <br />shown on the Twentymile Park Hydrology (Map 6 ). Also shown are <br />delineations of the Middle, Foidel and Fish Creek watersheds and <br />the general topography of the flood plain areas. From field recon- <br />naissance, it was Eound that most of the mapped flood plains in the <br />general area are too narrow (less than 30 feet wide) or contain too <br />much topographic relief in the form of slope and terrace develop- <br />ment to be considered irrigable alluvial valley floors. The stream <br />deposits of Foidel and Middle Creeks are discontinuous, there is no <br />clear topographic expression of the flood plain, and the difference <br />between unconsolidated colluvial, windblown and alluvial deposits <br />is undiscernable at the surface. Much of the mapped flood plain <br />of Fish Creek in the general area does meet the geomorphic criteria <br />of AVF surface landforms, although it is not known at specific <br />locations if the flood plain is underlain by unconsolidated mate- <br />. rial or bedrock. However, field checks after the initial mapping <br />785-9 <br />