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Knickerbocker Floodplain

The Knickerbocker floodplain site is a section of the South Branch of Thornton Creek in Northeast Seattle.  This project will relocate several hundred feet of the creek and create a 1.5 acre vegetated floodplain. This increased storage capacity will provide benefits to downstream stream-side properties and improve the habitat for biological communities within the creek. A new pedestrian bridge over the creek will be built as well.

Project Updates

March 28, 2014 Update

The Knickerbocker project is in the advertisement phase and currently soliciting bids from prospective general contractors. SPU is requiring contractors to submit their bids no later than 2:00 p.m. on Wednesday, April 2, 2014. SPU has made a decision to include the north-end portion (north of NE 100th Street) of the project, as “additive work.” This decision was made strictly because of financial challenges to the project. It is SPU’s hope that the bids will come in lower than the engineer’s estimate. We are continuing to evaluate our options for retaining the north-end construction in the scope of work.

January 30, 2014 Update

A great deal of work has been going on to prepare for work at the Knickerbocker Floodplain site:

  • All permits have been obtained
  • Currently going through the City’s Department Circulation process to get signatures from other City Agencies (Seattle City Light, Seattle Dept. of Transportation, Parks)
  • Project Manual is being finalized in preparation for the upcoming Public Works process (ad, bid, award contract)
  • Finalizing the Memorandum Of Agreement (MOA) with Sound Transit
  • Contractor expected to be under contract with SPU by early May
  • Construction tentatively scheduled to start in early June (riparian, upland areas) and creek work will be done during the fish window (July1-Aug 30)
  • Two rounds of invasive removal was done last October and December; another round of noxious weed removal scheduled for next month (February)
  • Volunteer planting may be permitted after all construction activities have been completed, preferably in the Fall, and all work need to be coordinated with both SPU and Parks
  • The old pedestrian bridge will be removed and replaced with a new, longer pedestrian bridge

August 14, 2013 Update

Removal of invasive plant species is scheduled for August 28-30. The Seattle-based non-profit group EarthCorps will be performing this work. It will include both physical removal and treatment with an “eco-friendly” herbicide application, which will be reapplied in the spring. They will be targeting Japanese knotweed, nightshade and morning glory, English ivy, bamboo, blackberries and a variety of other non-natives.

Project Schedule

The project design work was completed in 2012, and reconstruction of the upland areas is scheduled to begin in early June of 2014. The work in the creek itself, the “floodplain reconnection” portion, can only be done during the “fish window” of July 1 – August 30, as determined by the Washington State Department of Fish & Wildlife.

Contact Us

For additional information, contact Arnel Valmonte, SPU Project Manager, at (206) 615-1438 or

Related Links

Lake Washington Watershed
Thornton Creek Alliance