Three large drainage basins (M Street, Littlerock & Linwood) combine to discharge untreated stormwater runoff to the Deschutes River. These basins are primarily commercial and public roadways; however some residential stormwater makes its way to Tumwater Valley. Impervious surfaces in these areas generate increased runoff velocities and pollutants commonly associated with stormwater, including oils, metals, sediments and nutrients. During heavy rain events, stormwater has been known to “jump its bank” and head east down M Street, impacting downstream residents and businesses. Water quality in the Deschutes River is impaired, currently listed for temperature, dissolved oxygen, fecal coliform bacteria, pH and fine sediments.
The contributing area of this large drainage basin is approximately 195 acres, of which just over 50% contributes runoff directly from roadways and other hard, impervious surfaces. The stormwater runoff currently receives no treatment for sediments and other common stormwater pollutants before discharging to the river. The increased velocity at the outfall continues to erode the channel, contributing additional sediments to the River, degrading downstream habitat and adding to nutrient loading issues in Capitol Lake and Budd Inlet.
The proposed project will construct a treatment wetland, preceded by a stilling basin. Stormwater velocities will be slowed, sediments will have time to settle out and natural, vegetative processes will help treat the stormwater before it enters the Deschutes River. In addition, a walking trail will be placed around the wetland, with educational signage describing how the facility works and why stormwater treatment is important.
This project is partially grant-funded through support from the WA Department of Ecology, $50,000. Total project is estimated to cost $1.6 million.
The project is currently under design and awaiting final permits.
- Design completion – Fall 2015
- Final Permit Approval – Estimated, July 2017
- Solicitation of grant funding - Fall 2017
- Solicitation of bids – Spring 2018
- Construction – Summer 2018
- Stormwater runoff treatment added to existing outfall; improved surface water quality
- Enhanced wetland construction, eliminating non-native noxious plants
- Neighborhood beautification, including walking trail and educational signage for stormwater treatment, habitat restoration and water quality
- Reduced potential for stormwater-related flooding