LEAD, S.D. (AP) — The operator of the only large-scale, active gold mine in the Black Hills will be conducting exploratory drilling.

Wharf Resources has notified South Dakota regulators it will drill 125 holes near the Richmond Hill Mine in search of gold. The mine was closed 26 years ago because of environmental pollution caused by acid-rock drainage.

The company produced nearly 77,000 ounces of gold and more than 50,000 ounces of silver last year at its Wharf Mine near Lead. Sales of the gold and silver generated $96.5 million in 2018. The Rapid City Journal says the remaining life of the Wharf mine is estimated to be seven years.