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-1z- A third area is located along 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 criterion for an alluvial valley floor. The fourth area identified as having alluvial deposits is located along the North Fork of the Gunnison River. Deposits located upstream of the proposed operations are not apart 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 by the applicant as being an alluvial fan and is 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 is found not to be an alluvial valley floor. The Colorado Department of Highways is in the process of relocating State Highway 133 to cross the site under consideration. As a result, any determination that the site is an alluvial valley floor is pointless. Between Sylvester Gulch and the town of Somerset, several smaller bodies of alluvium lie along the course of the river. Two of these areas are occupied by the Bear Mine Portal and Bear loadout. None of these areas meet the size criteria of the OSM Technical guideline (10 acres), and these areas are found not be alluvial valley floors. Downstream from the town of Somerset, the valley opens up and the applicant has identified a much larger body of alluvium. Areas within Sections 13 and 14 have been identified as currently supporting agriculture. No specific information has been provided concerning flood irrigation (existing or potential) or subirrigation. On the basis of the information provided, the North Fork of the Gunnison and its associated alluvium in Section 18 (T135, R90W), and Sections 13 and 14 (T13S, R90W) are found to meet the criteria of alluvial valley floors. The alluvial valley floor probably continues downstream, but for those areas no determination will be made at this time due to limited impacts predicted. Alluvial Valley floors - Findings 1. The proposed surface coal mining operations would not interrupt, discontinue, or preclude farming on an alluvial valley floor (Rule 2.06.8(5)).