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Environmental Stewardship at WSDOT


SR 530 unnamed tributary to NF Stillaguamish River after correction in 2014


What does WSDOT do for the environment?

WSDOT is responsible for more than 20,000 lane-miles of roadway, nearly 3,000 vehicular bridges and 524 other structures. As part of that responsibility we protect:

Technical Information

Looking for technical information? Links to major topics can be found on the left hand side of this page. If you know of a specific subject you are looking for use the alpha index listed under Site Index .

Protecting air and water quality

Air Quality  - Climate Change

Water near roadway

In Washington, transportation accounts for nearly half (47%) of the total greenhouse gas emissions, including emissions from cars, trucks, planes, and ships.

WSDOT is developing effective, measurable and balanced emission reduction strategies. View  Sustainable Transportation  for details.

Wetlands  - Since 1988, WSDOT has built 250 replacement wetland sites totaling more than 1,400 acres, including 15 new sites on 260 acres in 2014.  WSDOT has also built 3 mitigation banks totaling 370 acres since 2001.  These replacement wetland sites can take several years to become self-sustaining, so WSDOT monitors and manages them for up to ten years to ensure their success. 

Stormwater management – Statewide, WSDOT has approximately 40,000 acres of paved surfaces, which include roadway surfaces, park and ride lots, ferry terminals, safety rest areas and maintenance yards. Stormwater running off these surfaces, if left untreated, may pick up pollutants such as oil, fertilizers, pesticides, soil, trash and animal waste and carry them to rivers and streams. WSDOT uses a variety of methods to manage stormwater.

WSDOT staff assessing conditions

Erosion control during construction – When construction of transportation facilities disturbs soils, crews prevent erosion at these sites by spreading straw, planting grass, building ponds and other measures. Construction areas that have a high potential for erosion control due to the project area’s size, steepness, soil type or proximity to waterways are inspected by WSDOT weekly.

Our ferry system is currently working on a variety of projects designed to reduce pollution and improve the environment.

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38 foot bottomless arch

Protecting communities

Fish passage - WSDOT began a program to remove barriers to fish, such as highway culverts, in 1991. Since then, we have evaluated all the culverts on the 7,056 miles of the highway system in order to identify which ones are barriers, and to prioritize the corrections that have the most benefit to fish.

Elk crossing roadway

Wildlife migration  – Wildlife need to move across the landscape and highway corridors for seasonal migration, access to food and to establish new territories as the young mature. WSDOT works with the Department of Fish and Wildlife to identify wildlife corridors where there is significant wildlife movement. These corridors are considered during transportation planning, project development and maintenance operations.

Reducing animal kill - Approximately 3,000 collisions occur yearly with deer and elk on state highways. These collisions can result in serious injuries and fatalities to motorists. One of the ways we are protecting wildlife from highway collisions is through the use of Wildlife fencing and testing.

Historic and cultural preservation - WSDOT works to protect the cultural and historic resources. When impacts cannot be avoided, we consult with tribes and other state and federal agencies to minimize disturbance and mitigate effects. Cultural resources include:

  • archaeological sites,
  • historic structures (such as buildings and bridges) and
  • areas of traditional cultural importance to tribes or other communities.

Social and community effects - Transportation projects often affect local communities. WSDOT looks at how transportation projects affect the social elements of an area including how neighborhoods are affected.

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Protecting roadsides

Vegetation Management - WSDOT manages vegetation over approximately 100,000 acres of non-paved roadsides using an Integrated Pest Management (IPM) process with a goal of establishing more naturally self-sustaining roadside plant communities over time. To accomplish this, each of the agency's 24 maintenance areas has developed an annually updated Integrated Roadside Vegetation Management (IRVM) Plan that provides basis for all vegetation maintenance actions mile by mile, year by year along all WSDOT managed highway corridors.

Control methods include a prescribed multi-year combination of actions which may include: mechanical mowing and trimming, hand pulling and cutting, herbicide application, introduction of beneficial biological organisms, and the planting and encouragement of desirable roadside vegetation to outcompete weeds and unwanted trees.

When using herbicides, WSDOT exercises precautionary measures above and beyond labeled restrictions, and state and federal regulations to further minimize potential risk to the environment and human health. With the implementation of the Area IRVM Plans in 2004, WSDOT’s annual herbicide use decreased by 60% in the first four years and has remained relatively stable each year since then.

Litter control – WSDOT coordinates a volunteer army of 1,100 groups involved in its Adopt-A-Highway program. These volunteers pick up trash from sections of state highway several times each year. In 2007-2009, Adopt-A-Highway, Department of Ecology Youth Corps, and others picked up 6,075 tons of litter from state highways, which WSDOT disposed of at a cost of $3 million annually. 

Roadside Restoration – If a transportation project disturbs the roadside areas, WSDOT restores the landscape according to the characteristics of the surrounding area. For example, in an urban setting, we may restore the roadside to blend with a city’s street tree program, whereas in a forested area, we would plant native vegetation to blend in with the natural growth. Using native plants in roadside restoration will over the long term reduce maintenance requirements and costs and retain the natural character of the Evergreen State.

Native plant communities, once established survive in our climate reduce soil erosion; intercept, treat, and store rainwater; provide pollinator habitat; and will out-compete many weeds and undesirable plants that would otherwise be mowed or sprayed. See the Roadside Policy Manual for restoration requirements and the Roadside Manual for how to accomplish those requirements.


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