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Gunnison. Even during the lowest flow on record (17 cfs) for the 1934 through 1979 <br /> period of record on the North Fork at Somerset, the potable water use would be less <br /> than 0.4 percent of the flow. The return water will be treated to meet NPDES effluent <br /> limits and should pose no problem for downstream irrigation use of AVFs. <br /> The remaining 162,000 gallons per day (gpd) of water use is for coal spraying and <br /> dust suppression activities. The estimate is conservative and includes a 15 percent <br /> contingency for leakage. Consumptive use is difficult to estimate, but should be less <br /> than 85 percent. The return flow along with any seepage water would be collected <br /> and routed to sediment pond MB-I. This water is then treated and either released to <br /> the North Fork or recycled. Assuming 138,000 gpd (0.2 cfs) is the consumptive use, <br /> only about one percent of the lowest flow on record would be consumed. The <br /> information provided above demonstrates that there is no risk of material damage to <br /> the quantity and quality of water supplying the AVF identified on the North Fork of <br /> the Gunnison River. <br /> The applicant has met the requirements of Rules 2.06.6 and 2.06.8. <br /> Based on the above information, for the North Fork and Sylvester Gulch AVF <br /> determination, the Division makes the following findings: <br /> 1. The surface coal mining operations would not interrupt, discontinue, or preclude <br /> farming on an alluvial valley floor (Rule 2.06.8(5)). <br /> Although underground mining would occur in areas adjacent to the alluvial valley <br /> floor, all surface disturbances are located more than a mile upstream from the <br /> alluvial valley floor. The alluvial valley floor will not be undermined by the <br /> operations, nor will it be significantly affected by surface and groundwater <br /> impacts from the surface operations. <br /> 2. The surface coal mining operations would not materially damage the quantity and <br /> quality of water in surface and undergroundwater systems that supply those <br /> alluvial valley floors or portions of alluvial valley floors (Rule 2.06.8(5)). <br /> All of the surface flow from the permit area drains to the North Fork of the <br /> Gunnison. The applicant has monitored the largest two drainages crossing the <br /> permit area. During this period, Lone Pine Gulch has experienced no flow. <br /> Sylvester Gulch has experienced ephemeral stream flow. The record yield of 208 <br /> acre-ft/yr in 1978 is less than one percent of the mean annual flow in the North <br /> Fork of the Gunnison River. Surface flow supplied to the alluvial valley floor <br /> along the North Fork comes primarily from areas upstream from the permit area <br /> and this flow is regulated by Paonia Reservoir which is located approximately six <br /> miles upstream of the alluvial valley floor. Mining operations require <br /> approximately 150 acre-feet of fresh water per year for sanitary and drinking <br /> water. This water is withdrawn from the North Fork during spring runoff when <br /> water rights are available and used throughout the year. The wastewater is then <br /> 59 <br />