Wesdome initially leased then subsequently acquired the former Magnacon mill and tailings facilities in 1996. The mill is 17 km by road from the mine. The mill capacity was increased from 600 to 1,000 tpd in 1999. Even though the addition of the cone crusher expanded capacity to the permitted level of 1,200 tonnes per day on a crushing basis, required maintenance time means the practical limit is approximately 850 tonnes per day of Eagle River underground ore as it is configured to achieve targeted gold recoveries.
The mill employs the Merrill-Crowe process for the recovery of gold from Eagle River ore with about 40% of the gold recovered into a gravity concentrate using a recently installed Falcon gravity circuit concentrator. The Merrill-Crowe process involves cyanide solution and zinc precipitation. Precipitate is refined on site to produce doré bars containing approximately 80% - 92% gold. By-product silver is recovered at a rate of one part for every six to ten parts of gold. Overall mill recoveries for Eagle River is around 96.5 % and for Mishi ore around 83%.
The mill tailings commonly average grades of 0.25-0.50 g/t Au are deposited in the tailings pond. The tailings are processed through a drum filter in order to thicken them. Water from this process and the pond is reclaimed for use in the mill process as required to minimize the discharge of effluent. The mill operates 24 hours per day, seven days per week with two crews working 12-hour shifts on a seven days in, seven days out rotation.
The TMA consists of the Magnacon tailings pond located to the south side of the mill and the polishing pond located to the northeastern of the mill. Thickened tailings are transported using a conveyor to stockpiles on the west side of the TMA. When the stockpiles are large enough, the thickened tailings are re-distributed or pushed down into the TMA using a combination of haulage truck and a dozer. Thickened tailings have a moisture content of about 22% (dry weight basis) and contain about 32% fine sand, 60% silt and 8% clay size particles. The TMA facility has undergone various phases of modifications between 1995 and 2017. In 2019, the Company reinforced the existing TMA followed by the vertical raise extension (Stage 4) which provides additional storage capacity for the future. The TMA expansion was about 75% completed at the end of 2019 and will continue in 2020.
The Eagle River Mine is supported by two surface settling ponds by the portal while the Mishi Pit is supported by a settling pond to its north to manage water quality.