Flowering rush, an aquatic weed that clogs irrigation canals, has spread to multiple new sites near McNary Dam along the Columbia River since its discovery in the area last year.
Meanwhile, the federal government must again clear environmental regulatory hurdles before removing new patches of flowering rush found growing below the dam, which is under the jurisdiction of a different regional office of the U.S. Army Corps of Engineers.
“Because we’re part of the federal government, we have to follow federal laws and regulations,” said Diana Fredlund, spokesperson for the Army Corps’ Portland District.
Flowering rush was first found growing on the Oregon side of the Columbia River in August 2014, with surveys eventually locating 15 sites near McNary Dam.
That portion of the river is governed by the Walla Walla District of the U.S. Army Corps of Engineers, which had to obtain approval under the National Environmental Policy Act, the Endangered Species Act and the Archeological Resources Protection Act to remove the weed with diver-assisted suction hoses.
“This should be straightforward. We’re just going in and by hand removing some small sites,” said Tim Butler, Oregon Department of Agriculture’s noxious weed program manager.
By the time the agency cleared those hurdles and scheduled a dive team to yank the flowering rush patches in August 2015, the weed had expanded to 45 total sites in the area.
While divers were able to treat 39 of those sites, six of them were growing on the Columbia River below McNary Dam, which means they come under the purview of the Army Corps’ Portland District, said Mark Porter, an integrated weed management coordinator for ODA.
For that reason, the process of obtaining clearance under NEPA, ESA and ARPA must now be repeated by the agency’s Portland office, which is unlikely to occur in time for the patches to be removed before next year, he said.
The agency expects that the regulatory processes will be completed over winter, when the plants disappear below the water line, so they can be covered with mats or removed when they re-emerge next spring, said Fredlund.
“We do want it to keep it from becoming a bigger problem,” she said.
The Army Corps’ Walla Walla District can continue removing the weed without re-clearing regulatory barriers, and its experience is expected to speed up the Portland District’s compliance with those statutes, said Damian Walter, wildlife biologist for the agency.
Apart from sites on the Columbia River, there’s a large population of flowering rush upriver on the Yakima River in Washington, which state regulators are attempting to control, he said.
“There is a constant source currently in the system,” Walter said. “We’ve got to address the source of it.”
As part of long-term plans to battle flowering rush, Washington State University is studying predatory beetles in Central Europe that feed on the weed’s roots in that region, limiting its spread.
The weed poses a serious threat if it’s able to enter irrigation systems along the Columbia River or its tributaries, said Porter. Flowering rush grows so thickly that it greatly slows the movement of water and changes aquatic ecosystems.
“This plant seems to be a very aggressive aquatic invader. This isn’t just another weed,” he said. “it has the big potential to do some harm.”