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• Alluvial sediments of an appreciable extent are <br />developed at only a few locations within the proposed lease <br />area; tl~e Stevens Gulch alluvium, where the C+.I well field <br />leas been developed, the Terror Creek alluvium in the <br />vicinity of t}~e Morrell Cow Camp and East Roatcap Creek, <br />where there is a potential of alluvial sediments as well. <br />All these areas are limited in extent but may be important <br />from a ground water point of view. <br />Stevens Gulch is an ephemeral stream with major flows <br />only during spring snowmelt runoff and after rainstorm <br />events. A major occurrence of alluvial deposits is <br />approximately at the center of Section 13 where the alluvium <br />is about 90 feet thick. Ground water investigation performed <br />by C6JI in 1977 proved an aquifer of good quality capable of <br />providing approximately 40,000 gpd. A well was later <br />developed at this location and has served as a source of <br />potable water for both underground and surface operations <br />at the Orchard Valley Mine. <br />A similar occurrence of alluvial deposits is close to <br />the northern area boundary at the center of Section 1. The <br />alluvial deposits are in the drainage area of West Fork <br />Terror Creek close to the Morrell Cow Camp. Although no data <br />are available on this alluvium, it is probable that it could <br />be developed for water supply purposes. <br />• colluvial soils cover most of the proposed lease area. <br />Included in them are numerous landslide deposits that have <br />been identified by Junge (1978). <br />Ground water was identified in colluvial soils in <br />several of the test holes drilled by CWI(DH 62, 64, 66). <br />Tlie origin of this water is from snowmelt and surface <br />runoff. Water percolates through the soil cover until it <br />reaches an impermeable layer. This layer may be a layer of <br />impermeable soil within the colluvium or the bedrock surface <br />if it is formed by shales or impermeable siltstones. Local <br />occurrence of ground water can result under such conditions. <br />Old mass movements, such as landslides, significantly <br />contributed to the occurrence of ground water. <br />It is believed that colluvial and alluvial soils are <br />the source of all springs that have been documented within <br />the lease area. <br />Springs in the lease area have been documented in <br />detail by Dames & Moore (1981) and Brooks (1983). In <br />addition, CP+I is performing a detailed monitoring program of <br />the quanti*_y and quality of selected springs. <br />• <br />- 17 - <br />