Pine Bend Refinery in Rosemount is one of two major petroleum refineries in Minnesota, along with the Marathon refinery in St. Paul Park. (Jim Gehrz, Star Tribune file/The Minnesota Star Tribune)

Minnesota's two petroleum refineries must hire more highly trained contract workers under a new law signed Tuesday by DFL Gov. Tim Walz.

The refinery safety bill, which passed the House and Senate with bipartisan support, was pushed by union workers who were worried about safety risks they faced on the job. An explosion at a refinery in neighboring Superior, Wis., in 2018 injured three dozen people, caused hundreds of millions of dollars in damage to the facility and forced thousands of residents to evacuate their homes.

"We're just damn lucky it hasn't happened more often," Walz said Tuesday at the office of a local pipefitters union before signing the bill. "If we don't have the training, if we don't have the safeguards, and if we don't have professional union folks in place, the chances increase greatly that we have an accident."

Under the law, a percentage of all third-party contracted employees working at oil refineries must be apprentices or graduates of a registered program. The new requirement for trained and skilled refinery workers will be phased in over time, hitting 60% of the contracted workforce by Jan. 1, 2026.

Enforcement will be handled through the Minnesota Department of Labor and Industry, which could respond to complaints or start their own investigations. Companies can face fines between $5,000 and $10,000 per violation.

"This bill came around because workers in refineries were seeing unsafe practices, they were seeing things that needed to be corrected," said freshman state Sen. Judy Seeberger, DFL-Afton, who sponsored the bill this session.

The proposal has been debated for several years at the Capitol. Many Republicans and Minnesota business groups opposed what they called burdensome requirements under the bill, which could risk the jobs of some contract workers.

Rep. Nolan West, R-Blaine, was one of the GOP legislators who joined Democrats to sponsor the measure, arguing accidents at oil refineries are not the same as accidents at other jobs.

"If there's a problem at the refinery, it's different than if there's an accident at the warehouse. This has global implications," said West. "It's a good idea to make sure the people working there have top-notch training."