Businesses and states say the US Environmental Protection Agency didn't properly account for the cost of implementing rules to limit mercury and other pollutants from power plants.
A coalition of environmental groups say the federal government granted Shell conditional approval to drill in the Arctic illegally by overlooking a regulation for protecting walruses.
A coalition of environmentalists and native Alaskans are suing the federal government in an effort to block Shell's plans to drill in the Arctic this summer.
Environmental groups are suing the state, claiming it is allowing the industry to pump fracking wastewater into below ground drinking water supplies.
Nearly all of the coal ash that leaked from a Duke Energy-owned coal ash impoundment remains at the bottom of the Dan River in North Carolina.