"I still question why it has taken EPA so long to only just start turning off the sludge faucet," said Radanovich, chairman of the House of Representatives National Parks subcommittee.

The lawmakers earlier this year accused federal agencies of failing to enforce laws to protect the endangered shortnose sturgeon, which scientists discovered six years ago in the Potomac 55 miles (90 km) downriver from a discharge point of a water treatment plant.

The agency had maintained that the 200,000 tons of sediment dumped by the Washington Acqueduct facility every year was not harmful to the river.

But in releasing a proposed permit renewal for the plant, which processes drinking water for 1 million people, it cited studies warning of potential effect on eggs and larvae.

Radanovich and other House members from Western states had also accused the EPA of uneven enforcement.

"In the West, the protection of the environment and wildlife comes above people, individual rights and prosperity," Resources Committee Chairman Rep. James Hansen, a Utah Republican, said in a statement. "But in the East, as the EPA has proven in this instance, mere lip service is paid to the quality of our environment and the welfare of our wildlife."