Power producers must curb the tainted water they discharge into waterways under a proposal the Environmental Protection Agency issued Friday, the latest in a series of rules aimed at utilities that burn coal.

The EPA proposed four options for regulating the disposal of toxic waste from power plants, which are the top source of pollutants in streams, rivers and other waters. The final rules would have the most impact on coal-fired plants, which are the primary source of the pollutants, and would be phased in beginning in 2017.

The Sierra Club, which sued the EPA to issue these rules, urged the agency to adopt the strongest of the four proposals and said the announcement is an important step forward.