WATERFORD, Conn. (AP) – The Nuclear Regulatory Commission gave Millstone nuclear power plant a passing grade in an environmental review Friday, a key piece of the plant’s application to receive a 20-year extention on its license.

A final ruling on Millstone’s application is not expected for another year.

Millstone’s Unit 2 and Unit 3 reactors still must clear other reviews to win the extention, including a safety evaluation and a final approval from a five-member panel. The current licenses expire in 2015 and 2025.

Connecticut Coalition Against Millstone leader Nancy Burton and David Locbaum, a nuclear safety engineer, have been critical of how the plant handles air and water pollutants. Burton claims the facility has driven winter flounder fish to near extinction.

Peter Hyde, spokesman for Dominion Nuclear of Connecticut, Inc., said there is no evidence to back those claims.