MADISON, Wis. — The state Assembly is poised to lift Wisconsin’s nearly 20-year ban on gold and silver mining.

Legislators passed a bill in 1998 that requires sulfide mining applicants to prove a similar mine has operated in North America for a decade without polluting and a similar mine has been closed for 10 years without polluting.

Gov. Scott Walker voted for the measure as a member of the Assembly.

Rep. Rob Hutton and Sen. Tom Tiffany, both Republicans, are pushing a bill that would wipe out the requirements.

Supporters say mining could help northern Wisconsin’s economy. Opponents say lifting the prohibition will lead to devastating pollution.

The Assembly is set to vote on the bill during a floor session scheduled to begin Thursday afternoon. Approval would send the bill to the Senate.