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.

Early indications in Oklahoma seem to show a big battle brewing.

The U.S. Supreme Court put a stay on the plan and a federal appeals court will hear arguments in the case later this year.

When the EPA determines a state’s plan for compliance with the rule isn’t good enough, it steps in with its own plan.

Lawsuits against the U.S. Environmental Protection Agency keep rolling out of Oklahoma Attorney General Scott Pruitt’s office.

Unit No. 3 is buzzing with construction workers who are installing environmental upgrades to make the coal-fired operation run cleaner.

President Obama’s Clean Power Plan enraged many top officials in Oklahoma, who argued the rules were an expensive, unnecessary overreach by the federal government. But the effort to reduce greenhouse gas emissions could create opportunities in Oklahoma, researchers and officials say.

This is actually the second time Pruitt has sued the EPA over the Clean Power Plan