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flood plains, and the large sizes in the alluvium and colluvium. The natural stream channel , which is evident upstream of the waste rock piles, has a fairly regular cross-section and the longitudi- nal profile exhibits a step-pool appearance. The channel cross-section width is about 20 feet and bank heights are about 4 feet. The channel bed, banks and the alluvial flood plain are stable, as evidenced by the sediment size, lichen growth and tree sizes and appearance. The channel appears stable in the sense that, although long-term changes may occur, they would occur in response to high recurrence interval flood or geologic events and not to the normal stream flow. A photo- graph of the natural channel conditions is given in Appendix R-3. The longitudinal step-pool profile is caused by the accum- , mulation of large cobbles and boulders.. The accumulations, as estimated based upon survey information, average about 2.1 feet in height and 145 ,1 feet in spacing. This type of profile is common to mountain streams and occurs as the stream attempts to minimize its rate of energy expen- diture during high flow. The steps serve as energy dissipators, effec- tively reducing the steep energy gradient during the high discharges necessary to move the large particles and form the system. Roughness coefficients or "n" values for this stream must take into account these bed forms as well as the sediment sizes and veg- etation. Based on published "n" values for natural streams (WSP 1849) , as related to the photographs in Appendix B, a "n" value for the stream and overbanks of 0.050 has been chosen. 3.5 Waste Piles The two waste piles, located on both sides of Ralston Creek, have practically an identical character. Their material is a good qual- ity rockfill with sizes of fragments less than 1 foot and with only a - 14 -