Mining of the Johnny Lee deposit requires only a small underground operation by modern standards. The upper zone ranges from 150 feet to 600 feet deep and is 3,000 feet long in a north south direction, and 1500 feet wide in an east west direction. The Johnny Lee lower zone lies 1500 feet below the bottom of the Sheep Creek Valley, and gently rises to a depth of 1100 feet on its western end and is 3,000 feet long in an east-west direction and up to 500 feet wide in a north south direction. The surface opening (portal) for the 5,000-foot long access tunnel for the Johnny Lee deposit will lay on the south side of Sawmill Hill, well outside the Sheep Creek Valley, and is about 200 feet above the water table. Though relatively small, the high-grade Johnny Lee deposit contains just under one billion pounds of copper.
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Located completely on private land, our underground mine will have an extremely small footprint above and below ground. The underground workings contain approximately 14.5 million tons of copper-enriched rock encompassed in an area of 3,000 feet by 2,000 feet. The surface disturbance of the mine workings is planned for a footprint of 310 acres, within an overall permit boundary of 1,888 acres. A four-wire fence will surround the surface facilities which include the 80 acre cemented tailings facility, 20 acre process water pond, roads, parking areas, plant facilities, and the temporary waste rock storage areas. A tall wildlife protection fence will surround each pond and the dry cemented tailings facility.
We are keen to improve all aspects of our community including opportunities for recreationists and tourists. We are working with our Meagher County Stewardship Council for recommended projects and activities embracing positive ways we can support recreation in our community as we develop Black Butte Copper.
Yes, we are looking forward to working with our conservation community to enhance the fisheries. This is an important area for cutthroat trout restoration, and we believe there are opportunities for us to assist in these important efforts. The Meagher County Stewardship Council will help guide us with the correct direction for local conservation enhancements.
The estimated average Winter base flow in Sheep Creek around the project is 15 cfs and at its confluence with the Smith River is 30 cfs. This is during the low flow periods of November through March. The average base flow in the Smith River during this same Winter period is approximately 90-100 cfs.
All of the water not consumed by the milling process at the mine will go through the reverse osmosis (RO) water treatment plant and then be returned back to the groundwater system through an underground infiltration system. The consumptive use rate of the mine is 210 gpm; any additional water pumped from the mine will return directly to the groundwater system with the maximum amount possibly reaching up to 290 gpm). Consumed water is completely mitigated with leased water rights being returned to Sheep Creek to keep flows in balance.
Estimated dewatering rates pumped from the mine range from 220 gpm to 50 gpm as the mine access is developed. The dewatering rate during full operation is estimated between 420 and 470 gpm. All but the 210 gpm of water needed for use in the milling process returns back to the groundwater system via the underground infiltration system after treatment by the reverse osmosis water treatment system.
The cone of depression over the mine area extends slightly into the Sheep Creek alluvium with the largest drawdown near the western and southwestern edge of the alluvium. The drawdown in the alluvium adjacent to Sheep Creek is one foot. This indicates that the drawdown in the alluvium has the potential to slightly deplete flows in Sheep Creek. The numerical model shows that the potential maximum depletion in Sheep Creek is approximately 0.45 cfs (~200 gpm). The base flow (lowest yearly flow) of Sheep Creek is 6700 gpm, so our maximum effect on Sheep Creek could be 3% of its flow. We will be replacing more than this with our mitigation plan.
Read MoreOur numeric hydrologic model shows that dewatering of the mine area will have an effect on the water table only in the area of the mine itself with noticeable drawdown only in the part of the bedrock hydrologic system containing the mine. Continuously backfilling the mine with cemented tailings reduces the extent of drawdown as mining advances. The water table will return to normal on completion of mining.
Sandfire has designed the BBCP to completely protect Sheep Creek and its fisheries, and in turn the Smith River and all the recreational uses and businesses supported by it. The operation will treat all water released from site to meet Montana’s strict non-degradation standards and return the treated water straight back into the ground water system through an underground infiltration system buried 6-8 feet in the ground.