Michigan Gov. Jennifer M. Granholm, a Democrat, is proposing a requirement that power plants operating within the state reduce mercury emissions by 90 percent by 2015.

"Michigan must take actions to protect its citizens and environment from mercury contamination, but we must do so in a way that balances energy, environment and the economy," Granholm said.

Under the new rule, Michigan power plants will have to reduce mercury emissions by 90 percent by 2015 based on a systemwide approach. The first phase would use the reduction in emissions authorized under the federal Clean Air Mercury Rule. However, the second phase would go beyond the federal requirements to achieve a 90 percent reduction.

The federal government has estimated its plan would eventually result in about a 70 percent reduction in mercury emissions.

The governor has asked the Department of Environmental Quality to draft the rule, taking into account both technological and cost-based considerations. Granholm wants utilities to be given extra time to comply if it installs and operates modern mercury reduction equipment, but its plants fail to achieve the required emissions reductions. In addition, utilities should receive an extension if a power plant demonstrates that the annualized incremental cost of mercury reduction technology exceeds a specified percentage of the gross revenue from electric generation.