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Project overview

Map of the Green
<p>River Knotweed Control Project
Started in 2004, this project has systematically reduced knotweed on the middle and upper Green River and its tributaries.  Beginning at the headwaters on Tacoma Public Utilities Property, infestations were relatively light until the confluence with Soos Creek, right above the Auburn City limits.  All knotweed sites on the Green River have been treated for several years and the project is mostly in a maintenance phase at this point to avoid re-infestation from the surviving patches. Initial treatment of lower Soos Creek was begun in 2010. All known sites in the project area are being treated every year and have been reduced significantly in size and impact. This project was supported by primarily by grant funding from 2004 to 2014. Starting in 2015, funding will come primarily from King County Noxious Weed Program funds.


Project area (download map file)

The project area on the Green River extends from the uppermost infestation at Flaming Geyser State Park down to the City of Auburn city limits, and the project area on Soos Creek extends up to the wetland complex under SE 272nd St (Hwy 516). 

Specifically, this area covers RM 21 to 49 on the Green River (as well as some discontinuous sites in the upper watershed), and RM 0 to 5 on Soos Creek. This area includes Kanaskat Palmer, Flaming Geyser State Park, O’Grady, Auburn Narrows and Soos Creek Hatchery/ Hatchery Park. The project ends at the Auburn City limits.

Tributaries covered in the project area include Soos Creek (Big and Little), Jenkins Creek, Suzette Creek, and Newaukum Creek.

News and updates

From 2012 to 2014, the Noxious Weed Control Program began working on this project from a more interdisciplinary perspective including water quality monitoring and increased habitat restoration by partnering with other county groups, made possible in large part by a grant from Washington Department of Ecology and the Environmental Protection Agency. Project results from 2012 to 2014 are summarized in the following table:


Area Surveyed

Gross Area Treated

Net Area Treated

Crew Hours

Staff Hours


165.0 acres

10.42 acres

2.25 acres




257.4 acres

8.35 acres

1.37 acres





11.59 acres

1.51 acres



(*Gross infested area is defined as the smallest area that can be created around any two plants within 50 linear feet of each other. Net acreage is the total number of square feet occupied by plants within that gross acreage.)

Other accomplishments from 2012-2014 included:

  • Knotweed surveys along 25 river miles of shoreline, covering approximately 810 acres
  • Closer partnerships between all stakeholders as the gaps between complementary project areas diminish
  • Training for 60 crew members who worked on the project over the years

Need more information or want to get your property included? Contact us at

Photos - click thumbnail for larger image



  • U.S. Fish and Wildlife Service
  • National Fish and Wildlife Foundation
  • Environmental Protection Agency
  • Washington Department of Ecology