Seattle, Washington

Venema Natural Drainage System

The award-winning Venema Natural Drainage System captures residential and road runoff from an 80-acre basin and conveys it to a cascading, linear system of 24 bioretention cells located in the City of Seattle right-of-way. Prior to the system being installed, polluted runoff was discharged during storm events into Venema Creek at the top of an eroding 80-foot sand cliff, which feeds into the fish-bearing Pipers Creek. Working with Seattle Public Utilities, the Osborn team designed a solution to improve stream habitat by mimicking natural stream hydrology through installation of bioretention cells and underground injection control (UIC) wells.


Seattle Public Utilities


The bioretention cells provide retention and water quality treatment of the runoff. The treated runoff is collected by underdrains and routed to one of three UIC wells, where it is infiltrated approximately 80-feet-deep to a point below the impermeable glacial till and into the permeable glacial outwash. The infiltrated and cleansed runoff then gradually moves laterally through the glacial outwash, where it is cooled and supports year-round base flows for Venema Creek.

Award Winning

In 2015, the project won the ASCE Seattle Chapter Local Outstanding Civil Engineering Achievement (LOCEA) award in the small project category.

In 2016, the project won the American Council of Engineering Companies (ACEC) Best in State: Gold Award for successfully fulfilling client needs.

Engaging the Community

Early and frequent engagement of local stakeholders was instrumental in gaining project acceptance by the community. To address resident concerns about impacts to their property and adjacent landscaping, as well as parking and construction impacts, Osborn Consulting supported SPU’s outreach team, which visited individual homeowners in the neighborhood to receive comments and answer questions.