The San Juan Generating Station is a four-unit, 1,600-megawatt coal-fired power plant. It dumps about 14 million tons of carbon dioxide, 21,000 tons of sulfur dioxide, and 28,000 tons of nitrogen oxides and 751 pounds of mercury into the Four Corner's air shed every year. The nitrogen oxide pollution from San Juan is roughly equivalent to the emissions from 1.5 million cars. It is one of the largest polluters in the U.S.