Water Quality

FY2023

• WSDOT built 25 stormwater treatment and flow control facilities in FY2023
• WSDOT prevented 1,306 cubic yards of sediment from reaching water bodies in FY2023

WSDOT published its first required report to the Legislature on the stormwater proviso funding from Move Ahead Washington in September 2023. The stormwater retrofit report summarizes the efforts of WSDOT's stormwater retrofit program over the past year, how WSDOT is addressing 6PPD (a chemical from tires that can contaminate water systems), and funding needs for ramping up to meet the challenges of retrofitting the state transportation system to address new contaminants of concern.

FY2022

• WSDOT built 88 stormwater treatment and flow control facilities in FY2022
• WSDOT prevented 1,748 cubic yards of sediment from reaching water bodies in FY2022

Legislature authorizes funding for stormwater treatment

In 2022, the Washington State Legislature authorized $500 million as part of the Move Ahead Washington funding package to enhance stormwater treatment from existing roads and infrastructure, with an emphasis on green infrastructure retrofits (designed to improve water quality) over the next 16 years.

Six million dollars of the funding will be dedicated to the I-5 Ship Canal Bridge Pilot Project in Seattle. This is part of a collaboration with The Nature Conservancy, Department of Ecology, and local agencies in the Seattle area to develop a green infrastructure stormwater park to treat stormwater from Ship Canal Bridge and the surrounding area.

For the remaining $494 million of funding, WSDOT will be seeking input from partners including federal, state, local governments, tribes, and non-profit organizations to prioritize locations on WSDOT infrastructure that focus on benefits to salmon recovery and ecosystem health, reducing toxic pollution, addressing health disparities, and cost effectiveness.

Stormwater retrofit program helps address transportation impacts

WSDOT's stormwater retrofit program addresses impacts from existing transportation infrastructure using three approaches:

• Project-triggered retrofits add stormwater treatment for existing impervious surfaces as a part of transportation improvement projects and as required by regulations.
• Opportunity-based retrofits add treatment for existing impervious surfaces as a part of transportation projects when it makes sense and is cost-effective, even when not required by regulation. WSDOT specifically looks for these retrofit opportunities with every fish passage project so fish can return to higher quality habitat after a barrier is removed.
• Stand-alone retrofits add treatment for existing impervious surfaces at prioritized locations and are not part of a larger transportation project.

Newly-discovered contaminant leads to updated prioritization criteria

While WSDOT still has a lot of work to do to address the state's existing priorities for stormwater retrofit, the agency has begun efforts to add new prioritization criteria based on the requirements in the funding package as well as recent information learned about 6PPD-quinone. In particular, several streams have been verified to have 6PPD-quinone-related prespawn mortality (when adult salmon die after completing migration but prior to spawning) as well as several streams suspected of being vulnerable habitat for coho and/or steelhead exposed to road runoff. By cross-referencing these locations with WSDOT's existing prioritization for stormwater retrofits, the agency was able to identify several locations that are potential opportunities to address these emerging issues quickly as more is learned about this contaminant.

WSDOT will continue to work with partners in planning and research to ensure that combined efforts are aligned and that the agency is positioned to include emerging scientific knowledge to continually update policies and priority models for the best possible outcomes for improving ecosystem health.

FY2021

• WSDOT built 72 stormwater treatment and flow control facilities in FY2021
• WSDOT prevented 3,951 cubic yards of sediment from reaching water bodies in FY2021

FY2020

• WSDOT built 106 stormwater treatment and flow control facilities in FY2020
• WSDOT prevented 2,943 cubic yards of sediment from reaching water bodies in FY2020

FY2019

• WSDOT built 66 stormwater treatment and flow control facilities in FY2019
• WSDOT prevented 2,983 cubic yards of sediment from reaching water bodies in FY2019