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Process Waste Control Process waste will include solids from the wash plant operation. These solids will be deposited in 2 slurry disposal areas in the permit area. Estimated quantities of solids are included in Appendix 4-B. The accumulation of solids will be cleaned out of each disposal area at the projected rate of once every 1 to 2 months. These fines will be deposited on the refuse disposal pile. Potable water and wash plant requirements are met through mine dewatering. Discharge from the mine, at full production, is estimated to be 60,500 gallons per day. Of this, 8,000 gallons per day will be treated for potable water use while 45,000 gallons per day will be used in the wash plant operation. The excess 7,500 gallons per day will be treated by passing through underground sumps. Mine discharge water will not be mixed with surface drainage and surface drainage water will not mix with the process waste contained in the slurry disposal area. Surface Water Flow Regime n LJ The flow in North Thompson Creek will not be significantly affected by impound- ments, surface disturbances, or surface facilities. The 3 sediment-control structures and the ditch-life energy dissipators will retain some storm runoff volume, this volume is insignificant in relation to the entire drainage area. At the mouth of the Number 3 mine, North Thompson Creek has a drainage area of 32 square miles (20,480 acres). Referring to drawings D-4-5 and D-4-10, a total of 5.6 acre ft. will be retained in these structures. According to the USGS stream gauge data based on 16 years of records, the average annual discharge is 12,100 acre ft. per year for 26.8 square miles. As applied to the total drainage area of North Thompson Creek (37.9 square miles), this results in a mean annual flow of 17,100 acre ft. A water augmentation plan is being established to assure priority water rights will be met. • 4-109