Environmental Protection Agency (EPA) head Scott Pruitt on Wednesday proposed another way to weaken U.S. environmental regulations protecting the nation's waterways from pollution.

In a memo dated June 26 but released June 27, Pruitt asked the EPA's Office of Water and Regional Administrators to draft a proposal that would restrict the agency's ability to revoke permits issued by the U.S. Army Corps of Engineers (USACE) allowing projects to dispose of dredged or fill material in rivers, streams and other waterways, The Hill reported.

"Today, I am directing the Office of Water to take another step toward returning the agency to its core mission and providing regulatory certainty," Pruitt wrote in the full text of the memo.

If the new proposal becomes policy, it would be the biggest change to how the EPA handles the dredging and filling of streams and waterways under the Clean Water Act in 40 years, according to The Hill.

Specifically, the proposal would block the EPA from preemptively blocking a permit to discharge materials in waterways before the USACE has issued one or revoking a permit issued by the USACE after the fact. It would also require that regional administrators get approval from EPA headquarters before vetoing a permit and that they listen to comments from the public before doing so.

Once a formal draft is ready, the public will have a chance to comment on Pruitt's proposed change, and opponents can attempt to block it in court, according to The Hill.

Former EPA staffer of the nonprofit Public Employees for Environmental Responsibility Kyla Bennett told The Associated Press that the move would rob the EPA of one of its few means of protecting waterways from mining and other industry.

Instead of protecting waterways, Pruitt's policy change would help those "he's always concerned with: oil and gas and mining," Bennett said. "His buddies who make money."

Indeed, Pruitt justified the change as simplifying the permit process for businesses.

"This long-overdue update to the regulations has the promise of increasing certainty for landowners, investors, businesses and entrepreneurs to make investment decisions while preserving the EPA's authority to restrict discharges of dredge or fill material that will have an unacceptable adverse effect on water supplies, recreation, fisheries and wildlife," Pruitt wrote.

In practice, the EPA has rarely vetoed permits either retroactively or preemptively, though Republicans and industry have argued against their ability to do so. That ability was affirmed in a 2014 decision by the U.S. Court of Appeals for the District of Columbia Circuit.

Pruitt's memo cited a case in which the EPA suggested it would use its veto power, under Obama, to preemptively block a permit for the pending Pebble Mine in Alaska after concerns from conservationists and Native American groups that it would harm salmon fisheries and wetlands, according to The Associated Press.

Pruitt started a process to reverse that preemptive decision, but in a surprise move, kept it in place following public outcry.