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_22_ VII. Alluvial Valley Floors - Rules 2.06.8 and 4.29 She alluvial valley floor findings made previously by the Division for the ARCO M*_. Gunnison No. 1 mine are directly applicable to the Bear mine. The proposed Bear permit area and hydrologically adjacent areas were included in the ARCO AVF survey area. The only area in the proposed permit or hydrologically adjacent area identified as having alluvial deposits is the valley of the North Fork of the Gunnison River. Several small bodies of alluvium lie along the course of the river between the mouth of Sylvester Gulch, immediately upstream of the Bear No. 1 portal facilities area and the town of Somerset, a distance of approximately 1'd miles. The existing facilities area for the Bear No. 1 portal and the area proposed for facilities associated with the Bear No. 3 mine are both alluvial deposits. However, neither of these areas meet the size criteria of the OSM technical guideline (IO acres) and thus both were found not to be alluvial valley floors. Downstream from the town of Somerset, the valley opens up and the ARCO study identified a much larger body of alluvium. Areas within Sections 13 and 14 have been identified as currently supporting agriculture. On the basis of information provided, the North Fork of the Gunnison and its associated alluvium in Section 18 (T13S, R90w) and Sections 13 and 14 (T13S, R91W) have been found to meet the criteria of alluvial valley floors. The alluvial valley floor probably continues downstream, but no determination has been made for the North Fork Valley between Section I4, TI 3S, R9Iw and Section 29, T135, R91W. Pursuant to Rule 2.06.8, the Division is required to make specific written findings on the effect of mining upon any AVFs within the permit and adjacent area. The findings for the North Fork AVF are presented below. The AVF is not within the mine permit area, and will not be physically disturbed by the mining activities. No impacts to the AVF are anticipated. I. Pursuant to Rule 2.06.8(5)(a)(i), the Division finds that the proposed surface coal mining operations would not interrupt, discontinue, or preclude farming on the alluvial valley floor (Rule 2.06.8(5)). Although underground mining would occur in areas adjacent to the alluvial valley floor, all surface disturbances are located more than a mile upstream from the alluvial valley floor, and would not affect agricultural activities on the alluvial valley floor. The alluvial valley floor would not be undermined by the proposed operations. 2. Pursuant to Rule 2.06.8(5)(a)(ii), the Division finds that the proposed surface coal mining operations would not materially damage the quantity and quality of water in surface and ground water systems that supply those alluvial valley floors or portions of alluvial valley floors. All of the surface flow from the permit area drains to the North Fork of the Gunnison. The two largest drainages are Lone Pine Gulch, to the west, and Sylvester Gulch, to the east. ARCO has monitored both drainages. During the monitoring period, Lone Pine Gulch experienced ephemeral flow. The recorded yield of water from Sylvester Gulch was 208 acre-feet per year in 1978, and was less than le of the mean annual flow in the Nos•th Fork of the Gunnison River. In addition, mining during the permit term will be limited to the "C" seam, which is separated from the surface by several hundred to ovez• a thousand feet of bedrock throughout the permit and adjacent areas. Surface flow supplied to the alluvial valley floor along the North Fork comes primarily from areas upstream from the proposed permit area and this flow is regulated by