PROVO — Federal prosecutors have charged two managers of an iron pipe manufacturer — and the company itself — with trying to skirt environmental regulations at the company's Provo foundry.

A six-count indictment was returned Thursday in U.S. District Court in Salt Lake City charging Pacific States Cast Iron Pipe Co. and the vice presidents, Charles Matlock and Charles "Barry" Robison, with conspiracy to violate federal laws.

Matlock, a Pacific States general manager and a vice president of its parent company, McWane Inc., was charged additionally with violating the Clean Air Act by allegedly tampering with a monitoring device.

Robison, McWane's vice president of environmental affairs, also was charged with making a false statement by submitting an emissions report for the foundry he knew was inaccurate, according to court papers.

The indictment is not Robison's first. He is awaiting sentencing for a June conviction in Birmingham, Ala., of submitting a false statement to the Environmental Protection Agency.

According to court papers, federal investigators believe a furnace running at the Provo foundry was equipped with an air-pollution control device that was insufficient to remove all pollutants required by law.

Employees melted pig iron — which is clean and essentially free from impurities, according to court documents — rather than the normal shredded scrap automobiles on days when they tested equipment for environmental compliance to avoid the cost of upgrading equipment necessary to reduce emissions, court papers said.

Emissions reports submitted to the state intentionally misrepresented the amount of an air pollutant that can become embedded in human lung tissue, cause respiratory problems and exacerbate other cardiovascular diseases, documents said.

The pollutant also reduces visibility and increases the rate of deterioration in buildings, court papers state.

McWane officials denied the allegations in a statement Thursday: "We are disappointed that the (Department of Justice) has chosen to take this action, and we will demonstrate the innocence of both the company and our employees."

Evidence will show that nothing was improper on compliance test days, and that before the investigation began, McWane had installed a $6 million state-of-the-art emission-control system at Pacific States, the statement said.

If convicted, the conspiracy charge carries a maximum penalty of five years in prison and a $250,000 fine. If the company were convicted, it would be fined $500,000. Matlock's and Robison's additional charges each carry maximum sentences of five years, court papers state.

A U.S. Department of Justice statement called McWane one of the largest manufactures in the world of ductile iron pipe. Thirteen plants in the United States and Canada make pipes used in municipal and commercial water and sewers.