Shoreline's Green Street Project

by Janet Way, originally published in Of Paramount Importance

City Experiments with "Low Impact Development" Street Treatment Project

17th NE. Photo by Janet Way

On a small neighborhood street between NE 145th and NE 150th on 17th Ave NE, an extraordinary experiment is underway. This is the "Green Streets" project undertaken by Shoreline's Public Works and Surface Water and Environmental Services. 

Permeable Asphalt Pavement Medium 
creates new sidewalk
Photo by Janet Way

Green Streets is a Capital Improvement Project approved by the City Council in 2009, and implemented by the need to comply with the NPDES II (National Pollution Discharge Elimination  Standard) Permit required by the WA Department of Ecology.  

This permit allows municipalities to operate their drainage systems. The latest permit is providing a very high standard that now surpasses the stormwater requirements of DOE, because City Council approved this newest Stormwater Code in 2009.

It is partially inspired by the now well known SEA streets (Street Edge Alternative) project in Seattle's Greenwood Neighborhood. 

That original project was created in 2003, and has now achieved acclaim nationwide for its effectiveness in infiltrating stormwater, slowing traffic and providing an attractive neighborhood environment. 

These photos show 17th NE while the project was underway

Photos courtesy City of Shoreline

Now the Shoreline 17th Street Project is nearly completed. It features bioswales planted with native plantings in the Right of Way, "pervious" asphalt sidewalks and driveways, and an attractive "meandering" design which slows traffic. The pervious asphalt is underlain with a bed of prepared soil, as are the swales which absorb a large quantity of stormwater which would otherwise run quickly into the local stream. In this case it is Hamlin Creek, a tributary of Thornton Creek, which is already greatly stressed as an urban stream.  When the stormwater percolates into the ground in the bioswales or through the asphalt, it is cleaned naturally by the soils and plantings. 

Here are some before and after shots provided by the Surface Water Environmental Services.

17th NE before the project

Photo courtesy City of Shoreline

Street Edges shown before the project.

Photo courtesy City of Shoreline

Planted swale next to sidewalk section before permeable asphalt applied.  Photo courtesy City of Shoreline

One feature of the project was that some of the existing trees have been preserved, though some were too impacted to be saved. The City met frequently with the neighborhood to address their concerns. 

This huge Madrone tree was protected and reserved next to the sidewalk. It had previously had a circular bed surrounding it that covered part of the trunk. Hopefully now it has more breathing room .

Photo by Janet Way

One neighbor I spoke to said she was happy with the sidewalks and the fact that traffic is now lessened and slowed down, but she was surprised how much of the area she'd thought was her yard was impacted. She also said she felt the project came out much differently than she'd expected. But, she also said that the stormwater DOES seem to be infiltrating well into the pavement and swales

Section of 17th NE project adjacent to the VFW Hall. This sidewalk appears to be the typical concrete material.

Photo by Janet Way

Here's hoping that this magnificent Madrone which is watching over the project will thrive and the neighbors will as well! We look forward to the completion and the plantings growing into their true potential to do their "water quality work".

Giant Madrone on 17th NE

Photo by Janet Way