An environmental group says the air pollution permit for a proposed $416-million clean coal plant should be yanked.

The West Virginia Highlands Conservancy claims developer Western Greenbrier Co-Generation has waited too long to begin construction. The conservancy filed a lawsuit Wednesday in Kanawha County Circuit Court seeking to force the state Department of Environmental Protection to revoke the permit.

Western Greenbrier Co-Generation is trying to build the 98-megawatt electric plant in Rainelle. The plant would serve as a demonstration project by using coal waste, or gob, for fuel.

The DEP issued the air pollution permit in April 2006. The lawsuit argues that state rules require the DEP to revoke the permit after 18 months, if the company doesn't submit written proof that it's made a good-faith effort to begin construction.

Western Greenbrier spokesman Wayne Brown says the developer is awaiting final approval from the U.S. Department of Energy before construction begins.