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i <br />I].V ~.yuarr mild ]r,i`) above thi~ nnnr pr.r~u~rt~-, an~i <br />' ' approximately 18.1 miz at the downstream end of the property. <br />The watershed boundaries for Rito Seca in the vicinity of the <br />' San Luis Project are shown on figure G-4. <br />The headwaters of the Rito Seco watershed are located <br />at the crest of the Sangre de Cristo mountains at an <br />~ 1 approximate elevation of 12,000 ft mean sea level (msl). Rita <br />Seca flows generally southwest past the proposed mine to the <br />alluvial fan areas northeast of the town of San Luis. At the <br />I, ' mouth of the canyon, the stream channel e~'evation is <br />approximately 8,250 ft msl. <br />The channel of the Rito Seco exhibits a marked difference <br />across the proposed project. The upstream portions of the <br />channel just east of the East Pit are characteristic of a <br />typical mountain stream. The channel is relatively shallow and <br />stable with a rocky bottom, fairly straight pattern and <br />moderate gradient. The canyon in this area is narrow, not <br />allowing the channel much room to move across the valley <br />bottom. The rock into which the channel is downcutting is <br />highly resistant Precambrian rock. <br />' The valley begins to widen as the Rito Seco glows across <br />the proposed project. The stream channel becomes deeply incised <br />in the less resistant rock of the Santa Fe Conglomerate and <br />begins to meander. In some places the channel is incised as <br />deep as 15 to 20 ft. The gradient across the project area is <br />' shallower and the natural sediment load is most liF:ely higher. <br />In addition, beaver ponds, active and abandoned, dam the stream <br />channel along this reach. <br />At the mouth of the valley, the Rito Seco channel changes <br />again. The channel flows across alluvial fans toward the town <br />of San Luis becoming somewhat braided. <br />' <br /> G- 9 <br />1 <br />