General Design Category

Thornton Creek Water Quality Channel - HONOR AWARD
SvR Design Company

Project Description:
Carved out of an abandoned parking lot, the Thornton Creek Water Quality Channel is a storm water treatment facility and public open space in an urban center. The channel treats pollutants from urban runoff, enhances community connections, and offers a respite amidst lush plantings and flowing water. Once the site of a cranberry bog, the parking lot covered a 60-inch storm pipe that channeled untreated runoff from 680 adjacent acres.

Due to concerns about the health of Seattle's urban creeks, the buried pipe and site became a focal point for creek advocates' efforts to reveal the waters, improve water quality, and restore habitat. Following several years of dialogue between community stakeholders, the City, and the developers, a solution was reached that allowed the site to develop while obtaining environmental and urban center goals.

Working with Seattle Public Utilities, the Design Team developed a scheme to divert the water into a necklace of water elements. The experience of the space includes a sequence of waterfalls; pools and weir walls; flow spreaders; and a meandering base flow channel. Bridges and overlooks allow views to the water and plantings. Benches and walls provide places for visitors to stop and rest.

Mechanically stabilized earth walls accommodate topographic change and are filled with special soils to achieve required structural requirements and support plant life. The sinuous flexible nature of these walls allows for large sweeping and stepped curves.

Plantings are at the heart of this project; they provide a major component of the water quality treatment. The channel plantings are storm water filters with winter time biomass and summer drought tolerance. Their dense mass slows polluted water to allow sediments and particulates to settle out.

This project provided an opportunity for Seattle Public Utilities to offer educational interpretive signage. As part of their Restore Our Waters campaign they worked with the Design Team to create educational signage that explains the sources of pollution and how the channel is helping to mitigate pollution before it can reach vital habitat. The Design Team also collaborated with the Project Artist who worked with multiple water themes.

The Thornton Creek Water Quality Channel is a high performance facility that provides treatment and conveyance, as well as being a community catalyst for future projects to integrate the enhancement of our environment into new and old urban development.

Jury Comments:
"Daylighting" a piped and buried watercourse to improve water quality and restore habitat is always a significant event, but when daylighting occurs in a high-density urban context, it is truly a cause for celebration. The jurors were impressed by the landscape architects' involvement in this project, which turned an abandoned parking lot over a piped channel into an open channel that cleanses stormwater runoff from 680 acres of developed multi-use area, while providing a green, lushly planted neighborhood open space and abundant wildlife habitat. Reflecting Seattle's Restore Our Waters campaign, an educational exhibit teaches the public about the significance of stormwater in the urban environment. Finally, the channel's system of pools and weirs manages outflow to Thornton Creek downstream while cleansing the water that enters the stream. "This is the kind of work landscape architects should be doing," exclaimed one juror.