In Phase I, half the total reductions were required by January 1, 1995, largely by requiring 110 electric power generating plants (261 units in 21 states) to cut sulfur dioxide emission rates to 2.5 lbs/million British thermal units (mmBtu).
In Phase II, all fossil-fired units over 75 MWe were required to limit emissions of sulfur dioxide to 1.2 lbs/mmBtu by January 1, 2000.