On the final day for public comment on a deal reached between TransAlta and the state Department of Ecology to limit pollution, 16 environmentalist and conservation groups filed a letter calling for tougher restrictions.

    It described the deal, reached behind closed doors, as “disappointingly weak.”

    TransAlta’s Centralia Steam-Electric plant is the only coal-fired facility of its kind in Washington. It has drawn the ire of environmentalists who say a deal reached with Ecology to reduce nitrogen oxide and mercury emissions falls short of encouraging real improvements.

    Ecology representatives have said it’s the best they can do under current law, and TransAlta officials have called it a voluntary effort to reduce its impact on the environment.

    The letter calls for a 90 percent reduction in mercury rather than the 50 percent agreed upon by the state. It includes the opinion of an air quality expert who disputes the effectiveness and parameters of the deal.

    The coal plant is the second worst haze-causing power plant in the country, according to a release from Earthjustice. The groups claim the pollution reduces air quality in 12 protected areas, including in Mount Rainier and Olympic National Parks. Pollution from the plant also impairs air quality in the North Cascades National Park, as well as the Alpine Lakes and Goat Rocks Wildernesses and many other forest, wilderness and recreational areas throughout the region, the groups claim.

    The groups have already filed a petition with the Environmental Protection Agency disputing a pollution permit granted to the plant.