Oregon Guidance on Biofilters for Storm Water Discharge Pollution Removal

In 2003, the Oregon Department of Environmental Quality (DEQ) published guidance on the use of “biofilters” to remove pollution from stormwater. Biofilters include a variety of green infrastructure techniques installed along roadways to filter pollution from stormwater runoff such as constructed wetlands and bioswales (vegetated swales or ditches), among others. The guidance details the design best management practices (BMPs) that have been proven to work well in constructing biofilters, and argues that biofilters may be the “most economical” way to remove sediment and other pollutants from runoff. While the report does not specifically mention climate change, the considerations involved in choosing the right design for biofilters become even more important in areas that will experience heavier precipitation due to climate change.

The Oregon DEQ evaluated many test sites to determine the best design, construction, implementation, and maintenance of biofilters.  The guidance aims to directly address some of the challenges that have been problematic for biofilter installation in the past, and provides advice as to how to avoid challenges. For example, the section on bioswales discusses how to assess the desired soil pH, soil compaction, proper mix of bacteria to break down pollutants, type of vegetation to plant, and how to maintain the vegetation and bioswale itself. Additionally, multiple examples of successful biofilter projects with pictures and construction details are provided.

By detailing how to design, construct, and maintain successful green infrastructure techniques, the guidance helps to ensure that any funds expended will be effective at improving water quality and preventing runoff from overflowing onto roadways. This guidance provides specific information for how green infrastructure techniques could be designed, constructed, and maintained in any jurisdiction facing increases in heavy precipitation from climate change.


This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on June 11, 2015.


Publication Date: January 2003

Related Organizations:

  • Oregon Department of Environmental Quality


Resource Category:

Resource Types:

  • Agency guidance/policy
  • Best practice

States Affected:


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