2018-09-04_REVISION - C1980007 (11)

Home Browse Search

64 A stipulation regarding the North Fork of the Gunnison AVF was included in the original permit approval requiring MCC to demonstrate that the mining operation's fresh water usage will not materially damage the quantity and quality of water supplying the alluvial valley floor. This stipulation was complied with on March 25, 1982, with the following response: Mining activities at the West Elk Mine will not affect the quantity and quality of water in the North Fork. The coal seam to be mined lies a significant distance above the North Fork and is not considered to be an aquifer. Surface facilities have been designed and located to prevent contamination of the river. Alluvial deposits in Sylvester Gulch and along the North Fork of the Gunnison River next to the mine are too small or irregular in shape to support agricultural activities, and therefore do not qualify as AVFs. High terraces along the North Fork of the Gunnison River are colluvial upland deposits and, therefore, do not qualify as AVFs. Changes in the quantity of water supplied to the North Fork AVF depend on the difference between water used by MCC and water discharged to the North Fork of the Gunnison River. MCC’s total water use is expected to be about 150 acre-feet per year during maximum projected production. This represents less than 0.04 percent of the average annual stream flow on the North Fork. Since less than 70 percent of this use is deemed to be consumptive use, the loss is actually less than 0.03 percent of the average stream flow. In addition, water is withdrawn during higher flows when MCC's water rights are in priority. During low flow periods when other calls for water exist, MCC would not be withdrawing water. Water quality changes resulting from MCC’s discharge of waste water will not constitute material damage because no measurable change in water quality is expected to occur. Of the 200,000 gallons/day maximum projected use, 38,000 gallons/day (28.5 acre-feet/year) would be required for potable water use. Consumptive use of potable water would be minimal. Assuming no consumptive use, one would expect a discharge of less than 0.06 cubic feet per second (cfs) during plant operation. This use and return flow is insignificant compared to the flows in the North Fork of the Gunnison. Even during the lowest flow on record (17 cfs) for the 1934 through 1979 period of record on the North Fork at Somerset, the potable water use would be less than 0.4 percent of the flow. The return water will be treated to meet NPDES effluent limits and should pose no problem for downstream irrigation use of AVFs. The remaining 162,000 gallons per day (gpd) of water use is for coal spraying and dust suppression activities. The estimate is conservative and includes a 15 percent contingency for leakage. Consumptive use is difficult to estimate, but should be less than 85 percent. The return flow along with any seepage water would be collected and routed to sediment pond MB-1. This water is then treated and either released to the North Fork or recycled. Assuming 138,000 gpd (0.2 cfs) is the consumptive use, only about one percent of the lowest flow on record would be consumed. The information provided above demonstrates that there is no risk of material damage to the quantity and quality of water supplying the AVF identified on the North Fork of the Gunnison River.