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Posted 7/16/2018

Release no. 18-037

Sarah P. Bennett

Portland, Ore. – This summer, the U.S. Army Corps of Engineers and Washington Department of Ecology will battle an infestation of Eurasian watermilfoil, an invasive plant, in Rock Creek with an herbicide treatment. The treatment is part of a larger restoration effort, with the goal of increasing the prevalence of native vegetation in Rock Creek to improve both salmon habitat and access for recreation and wildlife viewing.

As part of a cooperative agreement with the Klickitat County Noxious Weed Board, contractors will treat the watermilfoil with an herbicide on two days between July 15 and August 31, and the Corps will temporarily close the recreation area. 

“We treat the watermilfoil at this time of year before it flowers, after which plant fragments break off and establish new plants,” says Erin Stockdale, natural resource specialist and park ranger at John Day Lock & Dam. “Our goal is to stop the proliferation of this aggressive invasive in the Rock Creek watershed, where it threatens native salmonids and restricts recreational use.”  

 Eurasian watermilfoil is an invasive aquatic plant species included on Washington’s list of noxious species that poses a significant threat to the ecological, cultural and recreational integrity of the Rock Creek watershed. The well-established infestation at the mouth of Rock Creek forms dense submerged mats of vegetation that impedes passage and impairs habitat conditions for migratory native salmonids, degrades water quality, hampers traditional uses of the watershed by the Yakima Nation, and restricts access for recreational users. 

The treatment will involve deploying Renovate Max G aquatic herbicide in granule form into the affected waters. Following state safety recommendations, the Corps will close Rock Creek Recreation Area and the waters at the mouth of Rock Creek for 48 hours starting at 8 a.m. on each day of treatment to allow for complete herbicide absorption by invasive aquatic weeds. Entry is not permitted in Rock Creek Recreation Area during these periods.

Specific closure dates will be posted on signs at the recreation area and online at www.nwp.usace.army.mil/john-day. Information is also available by calling the John Day Ranger Office (541-739-1135) or the Washington Department of Ecology (360-407-6600).

The work is being undertaken in partnership with the, Klickitat County Noxious Weed Control Board, the Central Klickitat Conservation District, the Eastern Klickitat Conservation District and the U.S Fish and Wildlife Service, and is being conducted in accordance with Klickitat County’s Integrated Aquatic Vegetation Management Plan for Rock Creek.

John Day Lock & Dam is a multipurpose project operated by the Corps for hydropower, navigation, irrigation, flood risk mitigation, recreation, environmental stewardship and fish passage. As at its other projects, Portland District focuses on restoring, enhancing and maintaining ecosystems while meeting other missions. The District works to improve significant ecosystem function, structure, and dynamic processes that have been degraded. Various recreation opportunities, including the Rock Creek area, are provided along the Columbia River.