PROJECT PARTNER(S)
City of Olympia, WA & the Washington State Department of Ecology

LOCATION
Olympia, WA
Decatur Street SW, form 9th to 11th Avenues


GREEN INFRASTRUCTURE ASSETS

Key GI assets:

Rain Garden
Porous Pavement

DESCRIPTION
In Olympia, WA the city completed a low impact development demonstration project on Decatur Street. Originally, stormwater runoff from two blocks of Decatur Street SW from 9th to 11th Avenues entered the traditional stormwater system that currently pipes the runoff to Schneider Creek and into Puget Sound. During 2007 and 2008, the city of Olympia re-constructed those two blocks for a low impact development (LID) demonstration site. The city will quantatively compare the three different innovative LID techniques that clean and allow the stormwater runoff to infiltrate next to and under the road.

Description by project engineer Craig Tosomeen: "The City of Olympia has built a demonstration low impact development (LID) roadway that uses traditional pavement materials and infiltrates runoff under the roadway. City transportation needs prompt extensive amounts of pavement with inadequate right-of-way area for onsite stormwater management. Current roadway designs conflict with the LID goal of dispersing and managing stormwater near its source. The Decatur Street LID Roadway Project is an innovative design that meets LID goals and manages its stormwater within the existing right-of-way. Under-pavement infiltration is advantageous because traditional water quality treatment and pavement construction materials can be used. This accommodates traditional maintenance and life cycle cost expectations for the above-ground roadway features. Utilizing the entire roadway area for infiltration provides designs suitable for poorly drained soils and for use with various roadway widths. This paper presents the design and construction aspects of the Decatur Street LID Roadway Project." (Link to presentation at American Society of Civil Engineers website).

PHOTOS AND DRAWINGS

Plans for the Decatur Street Project

LESSONS LEARNED
Stormwater can be infiltrated along roadways with limited rights-of-way area by focusing on "under-pavement infiltration," an approach that allows designers to work with traditional building materials, maintenance and life cycle expectations yet also infiltrate and treat runoff.


ADDITIONAL RESOURCES

City of Olympia "Science and Innovations" Page - Decatur Street Project details (scroll down)

Report: The Decatur Street LID Systems (Department of Ecology project summary)

Underpavement Infiltration Demonstration - Decatur Street Low Impact Development Roadway Project" Paper (PDF)