PROJECT PARTNER(S)
City of Seattle Department of Public Utilities

LOCATION
Seattle WA, USA

GREEN INFRASTRUCTURE ASSETS
See assets identified in the 5 completed projected identified below.

DESCRIPTION
SEA (Street Edge Alternatives) Streets projects are designed to provide storm drainage that more closely mimics drainage in the undisturbed natural landscape than do traditional piped systems. General methods employed to achieve this goal include reduction of impervious surfaces in the public rights-of-way, provision of surface detention in swales, additional planting in the public rights-of-way.

There are a number of completed projects in Seattle that conform to and significantly expand upon the above mentioned general principles and goals. These projects are as follows:

1. Pilot Project (2001)
Returning design of drainage and vegetation in the street right-of-way to a natural systems approach is an important goal of the pilot project which is located in the 117th – 120th Street blocks of 2nd Avenue NW.

The following link provides further, detailed information including access to: a virtual tour of the project, a description of approaches to the design of landscape elements / drainage improvements, a discussion of costs and benefits to the community as well as construction documents: http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/GreenStormwaterInfrastructure/NaturalDrainageProjects/StreetEdgeAlternatives/index.htm

2. 110th Cascade Project (2003)
Street rights-of way in the four blocks of NW 110th St, (between Greenwood Ave N and 3rd Ave NW) are treated with a “Cascade” drainage system. This system is composed of a series of stair-stepped natural pools that slow damaging storm water flows, reduce flooding, and trap pollutants before they reach downstream locations.

The following link provides further, detailed information including access to: a virtual tour of the project, a descriptive brochure as well as construction documents: http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/GreenStormwaterInfrastructure/NaturalDrainageProjects/110thCascadeProject/index.htm

3. Broadview Green Grid (2005)
The Broadview Green Grid, involves 15 city blocks, manages stormwater flow from approximately 32 acres, and addresses almost an entire sub-basin. Goals of the project include reducing quantities and speeds of runoff, increasing stormwater infiltration, and improvement of water quality. To achieve these ends, natural drainage features such as swales, stormwater cascades, small wetland ponds, larger landscaped areas and smaller paved areas were included.

Additionally, Seattle Public Utilities partnered with the Seattle Department of Transportation to integrate improvements such as landscaping, traffic-calming devices, and sidewalks within the project.

The following link provides further, detailed information including access to: a virtual tour of the project, a descriptive brochure, a typical right-of-way section, a plant list, as well as construction documents: http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/GreenStormwaterInfrastructure/NaturalDrainageProjects/BroadviewGreenGrid/index.htm

4. High Point Natural Drainage System (2005 and 2009)
The High Point Natural Drainage System is a response to a unique opportunity to implement a large scale natural drainage system within a 34 block urban environment. It represents the largest natural drainage project the City of Seattle has undertaken and the first time a natural drainage strategy of this scale has been used in such a high density urban setting.

The High Point Natural Drainage System mimics nature by using features such as swales to capture and naturally filter storm water and open, landscaped ponds or small wetland ponds to hold an overflow of storm water. When completed, the High Point Natural Drainage System will process storm water in a manner similar to a forest meadow.

The following link provides further, detailed information including access to: a descriptive brochure, overviews of LID practices and stormwater flow paths, typical street sections, typical details for roadways, drainage solutions and sidewalks as well as specifications addressing construction of swales and pervious pavements: http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/GreenStormwaterInfrastructure/NaturalDrainageProjects/HighPointNaturalDrainageSystem/index.htm

5. Pinehurst Green Grid (2006)
The Pinehurst Green Grid addresses enhanced drainage within a 12 block area of Seattle. Goals of the project include: elimination of spot flooding, improvements to drainage conveyance service, management of stormwater runoff volumes. The project also incorporates new sidewalks, roadways, and landscaping with native and non-native plants to enhance the pedestrian experience while benefiting wildlife habitat.

The following link provides further, detailed information including access to: background descriptions of project planning, background vegetation studies, construction plans, and technical specifications:
http://www.seattle.gov/util/About_SPU/Drainage_&_Sewer_System/GreenStormwaterInfrastructure/NaturalDrainageProjects/PinehurstGreenGrid/index.htm

PHOTOS AND DRAWINGS




LESSONS LEARNED
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ADDITIONAL RESOURCES
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