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-12- VII. Alluvial Valley Floors (2.06.8, 4.29) Identification of Alluvial Valley floors In the original permit application the applicant identified four areas within or adjacent to the mine plan area which may meet the geomorphic criteria of alluvial valley floors. Alluvial deposits were identified along Minnesota Creek, Dry Fork Minnesota Creek, Sylvester Gulch, and the North Fork of the Gunnison River (Exhibit 2.8.4.B). Two of these areas, Minnesota Creek and Dry Fork Minnesota Creek, although geographically adjacent to the permit area, are not hydrologically adjacent to the activities approved in the permit. Both a surface water divide and a ground water divide (Exhibit 2.8.2.A) separate these areas from mining activities. Agricultural areas currently exist along Minnesota Creek, and the area is probably an alluvial valley floor. However, a formal determination for either of these two areas will not be made at this time. When the applicant submits an application that proposes mining activities within either the surface watershed or ground water system for these areas, the Division will make the required alluvial valley floor determinations. A third area is located along Sylvester Gulch. The proposed area of disturbance for the permanent lower waste pile would occur in a portion of this area. Specifically, the pile would be constructed west of the mouth of Sylvester Gulch. As identified in the Mt. Gunnison application, this area is approximately 20 acres in size. Examination of the Division's aerial photography suggests that the area of possible fill may be considerably smaller. The applicant notes (2-34a) that the "alluvial origin of the valley deposits at this location is doubtful". The non-alluvial origin of this fill is confirmed by geologic mapping by the Colorado Geological Survey (lunge, 1978, see attached map) which identifies the fill material as colluvial-wedge deposits formed by gravity-dominated processes (Qcw). On the basis of this information, this area is found not to meet the geomorphic criteria for an alluvial valley flooc. The fourth area identified as having alluvial deposits is located along the North Fork of the Gunnison River. Deposits located upstream of the operation are not a part of the hydrologic system that could be affected, and no determination will be made at this time. The first area of unconsolidated streamlaid deposits adjacent to the permit area is found at the mouth of Sylvester Gulch. This area is identified incorrectly by the applicant as being an alluvial fan and excluded by the applicant from alluvial valley floor consideration because it is an upland area by definition (page 2-343d). The Division rejects this argument. The definition of upland areas (Rule 1.04 (147)) only excludes landforms, such as alluvial fans, when they are located outside the flood plain and terrace complex. The area in question is clearly located within the valley bottom landform. However, this area