As of August 2017
Phase: Pre-design. On hold pending Washington State Department of Ecology (Ecology) grant funding.

The project was selected by Ecology in 2015 to receive $250,000 in grant funding for pre-construction activities (generally for pre-design and design engineering consultant fees). However, a revenue shortfall for the State’s Model Toxics Control Act (MTCA), caused Ecology in April 2016 to indefinitely delay funding for many grants, including the pre-construction grant for this project. The City is placing this project on hold until the delayed Ecology funding is available, or until alternative funding can be secured (if it is later determined that funding from Ecology is effectively unavailable). Consultant selection was completed as of March 2016, so once funding is secured an initial task will be to execute the contract for the pre-design and design engineering consultant.


UPDATE: The City re-applied for Ecology funding in October 2016 as recommended by Ecology grant managers in order to enhance likelihood of obtaining funding. On January 20, 2017, Ecology published the SFY18 Draft Water Quality Funding Offer List and Intended Use Plan (Draft List), which lists projects offered funding based on the Governor’s proposed 2017-19 Biennial Budget. The draft funding list offered the full amount of grant funding previously delayed. In July 2017, the 2017 legislative session ended without passing a new 2017-19 capital budget, meaning that no grant funding is available for this project. The following excerpt from the Governor’s message provides some hope that the legislature will still come to agreement on a new capital budget.

“I hope once legislators return to their districts and hear from community leaders, school officials and constituents whose projects or programs are being disrupted, they’ll agree to return to Olympia to pass the capital budget.” – Governor Jay Inslee

  10th Ave NE project mapSM

A map of the project location

Overview and History

This project will improve water quality and drainage capacity along 10th Avenue NE between NE 165th Street and NE 175th Street, a headwater area for Little’s Creek. The project will consist of bioretention/infiltration retrofits and other stormwater system improvements.

The improvements will address a ditch-and-culvert and piped storm drain system which runs approximately one half mile along 10th Avenue NE between NE 175th Street and NE 165th Street. Average slope from 175th to 165th is flat (less than 1%), portions of the existing system are negatively sloped, and pipes are typically undersized. System capacity is regularly exceeded, leading to flooding of the 10th Avenue NE roadway, shoulder, driveways, and some downslope private properties to the east. This drainage system conveys runoff from 21 acres along 8th and 10th Avenues NE between NE 165th and NE 175th Streets, and also receives high flows from a heavily-developed 65-acre contributing area of the North City business district. There is no existing flow control or water quality treatment within this headwater area for Little's Creek, a tributary to 303d-listed Thornton Creek.

To address these drainage issues, the 2009 Thornton Creek Watershed Plan recommended larger-scale detention and conveyance improvements, which were not programmed for implementation due to expected high costs. In 2014, the City's on-call Surface Water engineering consultants surveyed the 10th Avenue NE corridor between NE 165th Street and NE 175th Street and made several recommendations to improve drainage, including resolving negative slope issues and adding infiltration and/or bioretention features.

10th Ave NE and NE 170thSM
A back-watered ditch along the west side of the 10th Avenue NE south of NE 170th Street

The project will seek to improve the stormwater system by converting up to 1,000 linear feet (LF) of existing conveyance into bioretention and other infiltration facilities. For reference, the City completed a nearby project in 2013 with several similar components: the North Fork Thornton Creek Headwaters LID Stormwater Retrofit Project, utilizing grant funding from Ecology to design and construct 17 bioretention cells (548 LF total) and 2 gravel galleries (248 LF total). 

The specific extent and configuration of stormwater system improvements will be determined during pre-design and design efforts, which will accommodate input from a wide array of stakeholders including grant sponsor(s), neighbors, general public, utilities, and other public and private entities.