BOZEMAN (AP) -- A proposal to burn tires and slag at a cement plant near Three Forks poses no additional health or environmental risks, as long as certain restrictions are followed, a state review of the plan concludes.

The comprehensive environmental study of Holcim Inc.'s proposal was released Monday by the state Department of Environmental Quality. The agency also has issued a draft air quality permit which would allow the company to burn more than 1.1 million used tires a year in its cement kiln, but sets limits on how many tires can be burned at any given time.

Holcim first proposed using old tires as a source of fuel in 2001 when it sought a state air quality permit. Environmentalists opposed the idea and were joined by a number of local lawmakers when it was revealed in 2005 that the plant was also getting slag from a Superfund site in East Helena.

Slag, the byproduct left from the smelting process, is used as a substitute for iron ore, with iron being one ingredient in making cement.

The DEQ's environmental impact statement looked at the cumulative effects of burning both the tires as fuel and the slag and concluded that, under the limits set by the draft permit, ''the total risk for burning tires and adding slag are essentially identical to the risks associated with the present operation without tires.''

The DEQ is giving the public until Sept. 28 to comment on the adequacy and accuracy of both the EIS and the draft air quality permit.

''We distributed (the report) to some professional experts for review,'' said Kris Thomas of Montanans Against Toxic Burning.

Nicole Prokop, Holcim's manager for alternative materials, said the company will also submit comments on the state agency's findings.

''We're excited it's out,'' she said about the EIS, which has been more than a year-and-a-half in the making.

The study, which is more than 400 pages long, did find that the plant's carbon monoxide emissions would increase slightly under Holcim's proposal, but still fall well within state and federal limits.

The company already is permitted to burn coal, petroleum coke and natural gas to heat its kiln. The draft permit would allow it to add tires to that mix, although tires could only account for 15 percent of the heat source at any given time, the report said.

Information from: Bozeman Daily Chronicle, http://www.bozemandailychronicle.com