Klondex Mines has started construction work on the Midas tailings expansion after receiving permits for the project in north-central Nevada.
The final permit for expansion of the Midas tailings impoundment has been received from the Nevada Division of Environmental Protection, Division of Water Resources.
Following receipt of the permit, Klondex began construction of phase VI of raising the tailings impoundment to a maximum height of 5,680ft above mean sea level.
The expansion is expected to add approximately 400,000t of tailings capacity.
NewFields Engineering and Remington Construction has been contracted to build the engineered, reinforced concrete wall.
When coupled with the existing tailings, the wall will provide Klondex with approximately 900,000t of tailings capacity at the Midas mine.
Construction of the expansion, according to the company, is slated for completion in the fourth quarter of 2015.
Klondex Mines COO Brent Kristof said: "The tailings expansion permit is an important milestone in our long-term planning for Midas and Fire Creek.
"The expansion will provide Klondex with a timeline to be able to build a second tails dam at the Midas property. Studies to design, permit and construct a new, long-term tailings facility have been initiated.
"The water pollution control permit at Fire Creek, and tailings expansion permit at Midas are key to supporting our long-term growth plan."