Four utilities that own a massive coal-fired power plant in Nevada that has been accused of polluting the Grand Canyon and blocking its views have agreed to spend $300 million to install scrubbers to reduce sulfur-dioxide pollution. The agreement, expected to be announced today, comes as a settlement in a lawsuit brought by enviro groups in 1998. The plant emits as much as 40,000 tons of sulfur dioxide a year, making it one of the largest sources of the pollutant in the West. Meanwhile, another coal-fired power plant in Arizona announced yesterday that it has completed a $420 million cleanup that is also expected to help clear the air in the Grand Canyon.