Asarco has reached an agreement with the US Environmental Protection Agency (EPA) and the US Department of Justice to fund up to $150m in pollution improvements and modernise its Hayden smelter in Arizona.
According to EPA, the plant violated Clean Air Act standards by failing to control emissions of dangerous air pollutants, such as arsenic and lead from the smelter.
As part of the settlement, Asarco will install new and upgraded ventilation hoods to capture hot flue gases from its furnaces and replace an old electrostatic precipitator with a new baghouse and inject high performance lime to reduce sulfur dioxide (SO2) emissions.
In addition, Asarco will fund local environmental projects valued at $8m, place a cleaner model for $1m, and pay a civil penalty of $4.5m.
EPA said that the federal enforcement action targeted dangerous air pollutants, including lead and arsenic, particulate matter (PM).
Following the smelter upgrades, the pollutants are expected to be reduced by at least 8.5t a year, and PM emissions are set to minimised by 3,500t per annum.
EPA estimates that the facility's SO2 emissions would be slashed by 19,000t per year due to the installation of the new equipment and controls.
US Justice Department Environment and Natural Resources Division assistant attorney general John Cruden said: "This settlement will bring tremendous benefits to public health and the environment in Arizona for generations to come through dramatic cuts to harmful air emissions."
"The requirements of this consent decree will not only bring Asarco into compliance with the nation's clean air law, but will also result in testing for lead contamination in area homes, and improvements to nearby roads to further improve air quality."
The company will implement an improved dust control plan in order to minimise wind-blown dust from the facility and also operate five ambient air monitors in and around the Hayden and Winkelman communities to track pollution levels.
Under the settlement, Asarco is required to spend $8m to fund two environmental mitigation projects and will also invest $1m in a cleaner diesel-electric switch locomotive.
Hayden Smelter technical services manager Jack Garrity said: "Asarco is committed to ensuring that the environment in Hayden is clean and safe, and we are thrilled that we've reached an agreement with EPA to move forward with the modifications to the smelter."
The agency took action against the smelter in 2011 for releasing illegal amounts of lead, arsenic and eight other dangerous compounds, following which discussions have been going on between the company and the agency on an agreement to resolve the issue.
Asarco's Hayden site was built in 1912 and is a copper ore processing, concentrating and smelter facility located adjacent to Hayden and Winkelman.