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Changes in the quantity of water supplied to the AVF depend on the difference <br />between water used and water discharged to the North Fork of the Gunnison River. <br />Total water use is expected to be about 150 acre- feet per year during maximum <br />projected production. This represents less than 0.04 percent of the average annual <br />stream flow on the North Fork. Since less than 70 percent of [his use is deemed to be <br />consumptive use, the loss is actually less than 0.03 percent of the average stream flow. <br />In addition, water is withdrawn during higher flows when MCC's water rights are in <br />priority. During low flow periods when other calls for water exist, MCC would not <br />be withdrawing water. <br />Water quality changes resulting from discharge of waste water will not constitute <br />material damage because no measurable change in water quality is expected to occur. <br />Of the 200,000 gallons/day maximum projected use, 38,000 gallons/day <br />(28.5 acre-feet/year) would be required for potable water use. Consumptive use of <br />potable water would be minimal. Assuming no consumptive use, one would expect a <br />discharge of less than 0.06 cubic feet per second (cfs) during plant operation. This <br />use and return flow is insignificant compared to the Flows in the North Fork of the <br />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 [o sediment pond MB-1. 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 />56 <br />