Environmental groups plan to challenge the decision in court.

In testimony at meetings in recent years and documents filed in support of its application to the EPA, Oklahoma environmental officials and utility industry representatives argue strongly for more state authority over coal ash.

The crippling five-year drought Oklahoma finally broke out of in 2015 is still fresh in the memory of the state’s water regulators, which is looking for ways the state can better withstand future dry spells.

Oklahoma’s environmental agency made a private contractor pay just under $1 million earlier this year for improperly treating water in a small southern Oklahoma town. But the state’s budget shortfall swallowed up the money before the city of Hugo had a chance to use it.

Coal is the king of modern electricity generation in the United States. It’s also responsible for one of the nation’s largest streams of industrial waste. About 130 million tons of coal ash containing arsenic, cadmium and mercury are produced every year. The waste can be disposed of — or recycled. But critics and residents in southeastern Oklahoma question whether federal rules and state regulations are enough to keep the public safe.

Cities like Wichita Falls, Texas, and San Diego, California have already embraced the idea.

Just east of Chouteau, in Mayes County, there’s a massive coal-fired power plant. And just east of that is the Grand River.