Lafarge North America, a building materials company that consistently ranks among the state's worst mercury polluters, agreed Thursday to spend $170 million to cut air pollution at its sprawling Harleyville cement plant and 12 others around the country.
It also will pay a $5.1 million fine.
The deal followed an investigation by the Environmental Protection Agency that found the company modified factories without proper permits and failed to install pollution control equipment required under the Clean Air Act.
Thirteen states, including South Carolina, joined the EPA in the settlement.
Under the settlement's terms, Lafarge said it would reduce emissions of nitrogen oxides by more than 9,000 tons a year and sulfur dioxide by more than 26,000 tons a year at its 13 cement plants.
Both chemicals are key ingredients of ground-level ozone, which can trigger respiratory problems.
Officials at the Harleyville plant referred questions to their headquarters in Herndon, Va. In a statement, Sylvain Garnaud, Lafarge's cement division president, said the company "remains firm in its belief that it has operated its plants in an environmentally responsible manner and in compliance with the requirements of the Clean Air Act."
He added that the agreement demonstrates "we want our plants to continue to minimize emissions to the atmosphere as much as possible."
Cement plants, which typically burn coal, are the nation's third-largest source of industrial pollution, generating 500,000 tons per year of sulfur dioxide, nitrogen oxide, and carbon monoxide, the EPA says.
The plants also are among the biggest emitters of mercury, a neurotoxin known to cause birth defects, and carbon dioxide, a greenhouse gas.
In past years, Lafarge's large plant near I-26 consistently was one of the state top mercury polluters, according to a (Charleston) Post and Courier analysis of data collected by the EPA.
In 2008, the state Department of Health and Environmental Control fined the company $90,000 for air pollution problems at the factory, one of the agency's largest fines that year.
According to Thursday's deal, Lafarge will pay $3.4 million to the U.S. government and split the rest among 13 states. DHEC's share is $55,250.
Thursday's settlement is part of a larger effort by the EPA to clamp down on industries that generate significant amounts of air pollution, "not just in the coal fired power plant industry, but also in industries like cement and glass manufacturing," said Ignacia Moreno, a Justice Department attorney involved in the agreement.
Conservation groups hailed the agreement, saying the deal should make residents downwind of the plants "breath a little easier," said Keri Powell, an attorney with Earthjustice, a nonprofit group that's fought to reduce air pollution from cement kilns.
"Cement plants are among the worst air polluters in this country."