The 250-megawatt Highwood Generating Station is being built by the Southern Montana Electric Generation and Transmission Cooperative. It has encountered numerous delays tied to problems raising money for the project, and to lawsuits by some environmental groups and residents of the Great Falls area.
The plant risked losing its air permit first issued in May 2007 if construction was not well under way by the end of November.
Southern Montana Electric scrambled to meet the deadline, starting construction in late October with only a small portion of the necessary funding in hand.
Charles Homer, DEQ permitting manager, wrote Southern Montana Electric on that the co-op had succeeded in deadline compliance.
Keeping the air permit helps the co-op make its case to potential investors that the power plant will be built, said Tim Gregori, general manager of Southern Montana Electric.
"Validating the air permit and showing we're under construction shows we have a valid project moving forward and there's a reasonable expectation the project will be completed," Gregori said.
Under the project's construction timeline, the plant could be operating by 2013.