Knickerbocker Restoration Would be “First In The Nation”

Mike “Rocky” Mrachovec of SPU outlined the Knickerbocker Floodplain project Thursday.

The Knickerbocker Floodplain Project on Thornton Creek will include innovative subsurface restoration techniques that would be the first of its kind in the nation and part of a studied, living laboratory, according to Mike Hrachovec of Seattle Public Utilities (SPU).  Mike, known to everyone as “Rocky,” is a SPU engineer who has been designing the floodplain restoration on and off for seven years as funding came in leaps and starts. He gave an enthusiastic talk Thursday night at Sacawajea Elementary School as part of SPU presentation for local residents about the project which is planned to begin construction next summer.

Nearly two dozen members of the public attended including the original Knickerbocker family the site is named after (they sold the first parcel to SPU and the Parks Department including their house just south of NE 100th which has since been demolished). Cheryl Eastberg with the Parks Department began the meeting by describing the history of the project and acquisitions of property around Thornton Creek including the Rossi property on the south side of Thornton Creek that was accessed via the wooden bridge at the end of NE 100th Street (which will be replaced by a rock ford once the project is done).

Katherine Lynch then talked about the funding that made the project happen. Although the city has been interested in creating the floodplain for the past seven years, funding had all but dried up two years ago just as plans had finally been developed. A grant from the King County Conservation District helped move the project forward, while the Thornton Creek Watershed Oversight Committee sought out further funding which finally came from the Washington State Department of Ecology, the EPA, and most importantly Sound Transit which kicked in for floodplain mitigation as part of its Northgate Light Rail station project.

The main goals of the Knickerbocker project are 1) improve instream and riparian habitat, 2) optimize floodplain storage and slow peak flows, and 3) serve as a demonstration project. “Rocky” then began describing the process of engineering which he called, “an incredibly complex design.” Using the area of the creek just west of NE 102nd as a model for what the Knickerbocker site should look like (though with more large wood), he said the city needed to correct what been engineering dogma throughout the 50s and 60s, namely taking out any large trees and installing retaining walls.  “We shattered the habitat in the process,” he said. The Knickerbocker project will rip out the rockeries and retaining walls, remove 9,000 yards of dirt and replace it with logs (mainly under the surface) and create a floodplain.  Restoration will not only occur on the surface (with indigenous plants and rerouting and widening the creek), but under the surface as well by rebuilding the entire subsurface, a first-in-the-nation effort.  He admitted it would be “a radical experiment in stream ecology,” and “we’re just making educated guesses,” but as part of an ongoing plan the area would be monitored and studied extensively with adjustments made where needed. If you would like to see an extensive 30-page technical drawing of the project, check out this pdf from the city.

Project manager Arnel Valmonte talked about scheduling. Right now the project is at “90% design.” If any changes are to be made, now is the time. They hope to finish the design work by May 2013 and have all the permitting done. The earliest they could begin is June 2013 and wrapped up by the end of October.  They need to work around the fish window giving them between July 1st and August 30th as the creek is diverted into pipes while the construction goes on. An 80 foot bridge will replace the current one over Thornton Creek (part of the 20th Ave NE walkway), and they are timing it not to interfere with the school year as many students use it to access Sacawajea from Victory Heights.

Contractors in theory work from 8 AM to 5 PM Monday through Friday but have the discretion to work past those hours and on weekends. Neighbors will be kept informed of activity if it impacts them. There will be noise and vibrations associated with the work, and the city will attempt to deal with problems with nearby residents.

Finally, Deb Hayden talked about the future of the site after construction is completed. “Our intention is to let the site grow naturally,” she said, but other than noxious weeds and invasive species being managed they want to remain hands-off. Sound Transit would assume responsibility for managing and maintaining the site (i.e. be paying the bills) for the first five years, after which it would be the domain of the Parks Department. “We’re open to feedback,” was the message.

Visit the City’s official Knickerbocker Floodplain website.

The Seattle That Wasn’t: Freeways Through Victory Heights

In 1960, city planners proposed three north-south freeways through Seattle, one of which would have crossed Victory Heights right over Thornton Creek!

Long-time residents might recall the proposed R.H. Thomson Freeway or at least seen the “off ramps to nowhere” on the west side of the Evergreen Point floating bridge that would have connected with it. It would have been the eastern of three parallel north-south freeways cutting through Seattle that appear on a 1966 planning map that is available from the Central Library.

The big map shows the entire city, the thickest black lines denote freeways. The Northwest Freeway followed Highway 99, cut over to Fremont, headed north to Holman road, then back to following 99. What is now Interstate 5 would have been called the Central Freeway, and the R.H. Thomson freeway would have run through the Arboretum (!), intersected 520 (the off ramps that still exist), tunneled under the ship canal, and then run up 25th Ave NE, Ravenna Ave and then Lake City Way out to Bothell. An east-west connector between the Northwest Freeway and the Thomson would have run along N. 110th Street (Northgate Way). If you click the blown up section, at Roosevelt Way, the crosstown freeway would have turned southeast and traveled down Thornton Creek to connect with the R. H. Thomson Freeway at NE 98th Street.

It’s unimaginable now to think how our city (and our neighborhood) would been impacted by all these freeways. We would have been no better than Los Angeles. Fortunately, public protests at putting a freeway through the Arboretum in 1969 led to a vote in 1972 that canceled the projects forever.