State pollution regulators have asked a judge to order an upper riverfront scrapyard in Minneapolis to stop violating air quality standards, even if that means reducing or ending operations, and to pay for permit violations.

The Minnesota Pollution Control Agency filed with Ramsey County District Court its first public explanation of why it has focused on Northern Metal in its investigation of exceedances of air quality standards.

The agency said that monitors on either side of the Northern Metal yard at 2800 N. Pacific St. have recorded eight times when air in the area exceed state standards.  It said it is focusing on Northern Metal because monitors found that the violations occurred downwind from the yard, and because monitoring filters contained significantly more metal particles than other monitors in Minneapolis.

The company’s yard receives scrap metal, and pulverizes some of it in a shredder inside an enclosed building that is equipped with what the company has described as the best available technology to control emissions. Installation of the shredder was controversial among some area residents.

Attorney Daniel White, representing Northern Metal, responded: "Simply put: MPCA's response is a desperate attempt to excuse its judicially-recognized non-compliance with the air emissions rules and protocols."

The monitoring was begun by the agency after its board voted in 2012 to relax the permit for the shredder without further environmental studies sought by three legislators, some area residents, and environmental advocates. That was done after the shredder failed to meet standards set in its original permit after it began operating in 2009.

The agency said when it revamped the permit that its studies found that the air-quality standards for fine particles would be exceeded by area firms but that the shredder contributed only 2 percent of that load. The violations resulting from the agency’s monitoring generally involve larger particles.

The agency also said that both its staff and a camera added to one of the monitoring sites have observed dust escaping from the shredder building.

Northern Metal went to court last month, arguing that the agency has unfairly singled out its facility in investigating the violations. The filing this week responded to an order by Ramsey County District Judge John Guthmann that the agency shut down the monitors or explain why not.

The agency asked the judge to assess a civil penalty of up to $10,000 per day of violation. It denied the firm's contention that it was not complying with state and federal procedures governing air monitors.