Federal agencies on Thursday finalized a new clean-water rule that supporters including U.S. Rep. Scott Tipton say provides much-needed regulatory certainty.

But opponents, including the administration of Colorado Gov. Jared Polis, say it will result in the weakest protections since the passage of the Clean Water Act nearly a half a century ago.

The EPA and Army released the Trump administration’s new rules after last fall repealing a 2015 measure adopted by the Obama administration that expanded waterway and wetlands protections. Th 2015 measure was supported by environmentalists but opposed as overreaching by agricultural and other industries, and by the West Slope’s Club 20, Tipton and U.S. Sen. Cory Gardner, both Colorado Republicans.

At issue is how “waters of the United States” are defined in implementing the Clean Water Act of 1972. The Trump administration says the new rule applies to territorial seas and traditional navigable waters, perennial and intermittent tributaries to those waters, wetlands adjacent to waters falling under the rule’s jurisdiction, and certain lakes, ponds and impoundments. Groundwater, ephemeral streams that flow only due to rainfall, many ditches and prior converted cropland would be among waters exempted from the rule.

The EPA and Army said in a news release that the rule “ends decades of uncertainty over where federal jurisdiction begins and ends.”

Tipton said in a statement that the previous uncertainty “left farmers, ranchers and private land owners unprotected from federal land and water grabs.” He said the clarification provided by the new rule “will restore long-standing states’ water rights and greater certainty for the Coloradans whose livelihoods depend on availability of water.”

But the Colorado Department of Public Health and Environment is criticizing the rollback, saying it could impact 70% of waters in the state.

“The EPA’s announcement today is alarming as it puts our precious waters at risk,” Jill Hunsaker Ryan, the department’s executive director, said in a CDPHE news release.

“In the absence of federal leadership, we are going to do everything possible to protect streams and wetlands in Colorado,” Patrick Pfaltzgraff, director of the Water Quality Control Division, said in the same release.

Polis released a statement saying in part, “Our administration will continue to reject attempts by the Trump administration to gut proven ways to protect our health and environment.”

The EPA released a statement from Agriculture Secretary Sonny Perdue saying, “President Trump is restoring the rule of law and empowering Americans by removing undue burdens and strangling regulations from the backs of our productive farmers, ranchers, and rural land-owners.”

U.S. Rep. Peter DeFazio, D-Oregon, chairman of the House Transportation and Infrastructure Committee, told reporters in a conference call Thursday that the Trump administration was unable to provide him with solid data, but it’s estimated that half of wetlands will lose protections and anywhere from 18 to 71% of stream miles will be impacted by the new rule, and some 16,000 industrial sites, sewage treatment plants and other facilities no longer will need to be permitted.

“This is an extraordinarily dark day for the waters of the United States and for our environment,” DeFazio said.

Collin O’Mara, president and chief executive officer of the National Wildlife Federation, told reporters that the Trump administration isn’t just undoing the Obama rule.

“This is going back to the lowest level of protections we’ve ever seen in the past 50 years. It’s a staggering rollback,” said O’Mara, who predicted it would be overturned in short order in the courts.

Last April, the Polis administration and Colorado Attorney General Phil Weiser submitted joint comments on the rule proposal that was finalized this week. Their letter said that as with many western states, the large majority of Colorado’s stream miles are intermittent or ephemeral. The state said the proposal would shrink federal jurisdiction far below guidance issued in 2008 by the George W. Bush administration “to a smaller number of Colorado waters” than what presidential administrations have required since the Clean Water Act’s passage. While many ephemeral waters aren’t jurisdictional under the 2008 guidance, the new rule categorically excludes them from jurisdiction, “regardless of their connection to downstream waters,” the state wrote.

It wrote that the proposed rule “shifts the burden onto Colorado to protect federally excluded wetlands and waters, thereby saddling Colorado with the burden of protecting the quality of water received by nineteen states that receive Colorado waters.”

However, the Polis administration and Weiser, in the letter, supported the rule’s continued exclusion of prior converted cropland and its “recognition of the importance of upholding state sovereignty to administer and allocate water.”

Recommended for you