The National Marine Fisheries Service has blocked a drainage district from replacing a failing tidegate that keeps saltwater from flooding about 400 acres of farmland in Skagit County, Wash.

NMFS West Coast administrator Jennifer Quan said in a letter to the Army Corps of Engineers repairing the gate would jeopardize the existence of Puget Sound chinook salmon and killer whales, which eat the salmon.

Repairs will extend the tidegate’s use by 50 years and prevent Skagit Delta farmland from becoming fish habitat, according NMFS. The agency said the district’s concerns about losing farmland was “not relevant.”

Skagit County Dike, Drainage and Irrigation District 12 has sued NMFS in U.S. District Court for Western Washington to challenge the decision. The suit alleges NMFS overstated the project’s impact.

“I just don’t think they did any site-specific analysis,” Skagit County Drainage and Irrigation Districts Consortium executive director Jenna Friebel said Thursday. “I think they just wanted to oppose the project.”

The consortium represents a dozen dike and drainage districts that protect the low-lying and fertile delta about 60 miles north of Seattle. Tide gates open to let out water and close to keep out salty Puget Sound tides.

District 12 protects about 10,000 acres of farmland. A gate that Friebel said protects about 400 acres was damaged in 2019. The tide gate is now “on the verge of total collapse,” district operations manager Stephen Lefeber said in a court declaration.

Because Puget Sound chinook salmon and killer whales are protected by the Endangered Species Act, the corps, which must issue the district a permit, consulted with NMFS.

NMFS issued a biological opinion in April finding the repaired tidegate would jeopardize the survival of chinook salmon and killer whales throughout Puget Sound.

Repairing the tide gate would allow “habitat” to continue to be “managed for agriculture” and “appreciably reduce” the likelihood of recovery and survival of chinook salmon and killer whales, according to NMFS.

In response to comments from the drainage district, NMFS said the land’s current agricultural use was not relevant to its analysis.

“In terms of farmland being relevant, the point is simply that the ESA maintains a level playing field and holds different land uses to consistent standards,” NMFS spokesman Michael Milstein said in an email.

As required, NMFS offered “renewable and prudent alternatives.” To make up for repairing the tidegate, the district could turn 8.6 acres somewhere in the area into fish habitat or fund a restoration project.

“This biological opinion outlined reasonable and prudent alternatives that would reduce the impacts of replacing the tidegate to the point where the remaining impacts would be exempted as incidental take,” Milstein said.

The drainage district estimates the alternatives would cost $3 million to $5 million. The district, which also maintains dikes for flood protection, has a drainage budget of $100,000 a year, Friebel said.

Other Skagit County drainage districts would be in the same position if required to undertake multi-million dollar restoration programs to maintain tidegates, she said.

“It’s the end of them,” Friebel said. “They can’t mitigate at that level.”