Case Study: Controlling The Flow: Innovative Screening Device Solves Detention Maintenance Issues
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A nine-year, $5.29 million road improvement joint venture between the City of Beaverton, Ore. and Washington County widened 5,680 feet of a two-lane road. It also improved traffic flow and reduced the erosion of nearby Johnson Creek's banks during flooding. Since the joint project's completion in June 2004, the community enjoys planted medians, new curbs, sidewalks, bike lanes, a pedestrian bridge, as well as improved storm drains and treatment of stormwater runoff.
The Challenge
Rick Raetz, PE, principal engineer for the Washington County Department of Land Use and
Transportation, designed two underground detention tanks to address area flooding issues and
meet the project advisory committee's requirements
for urban runoff, wetlands
and stormwater. Each
tank had a small outlet to
attenuate the smaller, more
frequent storms eroding the
Johnson Creek banks.
Each tank captures and stores the entire volume of every storm and releases it through a 48 inch pipe several hundred feet long, at a pre-determined rate equal to the runoff rate of the pre-developed site. Controlling the rate at which the runoff leaves the detention tank:
- protects downstream channels from scouring
- reduces flooding
- provides settling of particulates (sediment and organic debris that transport pollutants or cover fish spawning beds)
Click here to download the entire case study in pdf format.
Source: Stormwater360