The Confluence is the flat area in Meadowbrook along 35th Ave NE between NE 107th to 115th Streets. It is the site of convergence of the North and South Forks of Thornton Creek, and many smaller tributaries join in this area, as well. The creek system flows into Meadowbrook Pond at about NE 107th Street on the east side of 35th Ave NE. The Pond collects and filters the water before it flows down to Matthews Beach and out into Lake Washington.
The year 2014 is the final stage of a three-year effort to improve the creek and pond environments, increase capacity for water and thereby help prevent flooding in the surrounding areas. This year, beginning in May, the creekbed at about NE 107th Street on both sides of 35th Ave NE will be widened, deepened and improved for more capacity, thereby preventing flooding. Under 35th Ave NE, going across at about NE 107th Street, new, much larger culverts will be put in and this work will necessitate the closure of 35th Ave NE for some months. Buses will have to be rerouted over to Lake City Way NE and then back toward Wedgwood along NE 95th Street.
At a recent meeting of the Lake City Neighborhood Alliance, Confluence Project Engineer Jason Sharpley explained the work to be done. A very large number of trees will have to be removed because they have become too big and are choking and narrowing the creek channel. This includes the poplar trees along the creek on the west side of 35th Ave NE, going toward Nathan Hale High School; the willow tree in the empty lot on the east side at about NE 107th Street; and a few of the flame ash street trees at that point where new culverts will be put in underneath 35th Ave NE.
For years, the Confluence of the North and South branches of Thornton Creek has been prone to flooding. High waters have frequently inundated nearby homes on both sides of 35th Ave NE, as well as Nathan Hale High School and Meadowbrook Community Center. Water has sometimes flowed over 35th Ave NE.
To fix the problem, Seattle Public Utilities (SPU) will remove an undersized culvert under 35th Ave NE and realign the existing creek channel through a new two-acre flood plain. The wider channel and flood plain connection will help native fish habitat by spreading out and slowing the peak flows of Thornton Creek.
To perform the work, it will be necessary to close a section of 35th Ave NE, between Northeast 110th Street and Northeast 105th Street, for about six months. There will be only local access traffic, including access to the Meadowbrook Community Center and Swimming Pool just north of NE 105th Street.
Traffic will be detoured from 35th Ave NE to Lake City Way NE via NE 110th Street and NE 95th Street. Detour signs will be in place prior to the closure.
Southbound Metro buses (Route 64 and 65) will be detoured to Lake City Way NE via NE 110th Street and NE 95th Street. Northbound Metro buses will be diverted to Sandpoint Way NE via NE 95th Street and NE 110th Street. As the closure date approaches, more information will be found at http://metro.kingcounty.gov/alerts/.
Seattle Public Utilities is working with federal scientists (U.S. Fish and Wildlife Service and NOAA Fisheries Science Center) to measure project performance by comparing existing conditions with post-construction changes in flood plain storage, habitat conditions and biological response (abundance and diversity).
Along with the ecological benefits of restoring stream and flood plain processes to the Thornton Creek Confluence Reach, the project will reduce the City’s operating costs at nearby Meadowbrook Pond by reducing the frequency of dredging needed at the Pond (currently averaging every three to five years).
During the construction project, Annie’s Playground at Meadowbrook will be usable. The playground will be fenced off but can be entered from the side nearest to the Nathan Hale High School parking lot.
Learn more about Seattle Public Utilities’ Thornton Creek Confluence Project: www.seattle.gov/util/meadowbrookthorntoncreek. You can attend an informal drop-in session to learn more about the Confluence Project on Tuesday, May 13 from 5:30 to 7 PM at the Meadowbrook Community Center, 10517 35th Ave NE.