Our environment and sustainability experts assist in planning, permitting, and construction compliance of our system expansion projects. We do this to ensure project designs are permittable, environmental permits are obtained, and the project complies with all environmental rules and regulations during construction. Our team works with contractors to oversee how ecosystem restoration and mitigation projects are constructed.
After the ecosystem mitigation projects are constructed, we conduct post-construction monitoring and maintenance. This ensures all ecosystem restoration and mitigation projects comply with permit requirements.
Environmental review before construction
We conduct environmental review on projects in compliance with the State Environmental Policy Act (SEPA) and, when there is a federal approval or funding, the National Environmental Policy Act (NEPA).
Environmental review helps Sound Transit, partner agencies, the public, and decision-makers understand the potential detriments and benefits of a project. As part of our environmental review, we analyze potential impacts to the built and natural environments and transportation systems during construction and future operations of a project.
Topics we study include ecosystem resources, historic and archaeological resources, noise and vibration, visual, traffic, displacements, public services, and social resources, among others. The environmental review process also identifies measures Sound Transit will implement to mitigate negative effects of the project.
Tree impacts and mitigation
Constructing our Capital Projects involves removing some trees. However, we plant more trees than we remove on any given project, in some cases replanting new trees before construction begins.
The specific removal/replacement ratio varies depending on the jurisdiction and the number, maturity, and species of trees removed, as well as federal and state environmental regulations.
We recognize that our communities strongly value trees and the benefits they provide. That’s why Sound Transit works with stakeholders to save as many trees as possible while meeting project needs and allowing for the safe operation of transit. We’re also partnering with cities along our routes to create opportunities for early plantings and additional trees throughout neighborhoods, parks, and open spaces.
In some areas, Sound Transit has conducted plant salvage operations. These operations include notifying residents about opportunities to salvage plants in areas that will be cleared for the project footprint. Not all areas are conducive for plant salvage, but we strive to include neighbors in preserving vegetation when it’s safe and practical.
Wildlife protection and conservation
Protecting wildlife and conserving their habitat are essential for maintaining biodiversity and ecosystem health, especially as Sound Transit expands infrastructure to reach more communities. Sound Transit works closely with federal, state, and local agencies to identify the locations of protected wildlife and implement measures to protect and preserve habitats. For example, to protect migratory bird species during clearing or demolition actives, we monitor nesting birds and adjust construction schedules when feasible to prevent stress and allow young birds in nests to fledge.
Wetland and stream conservation is an important area for our team because these habitats provide for numerous species, including birds, fish, amphibians, reptiles, and mammals, while also providing valuable functions like carbon storage, water filtration, and flood regulation. Sound Transit’s conservation efforts focus on restoring and maintaining the ecological integrity of these special areas.
Mitigation sites aim to compensate for the loss or degradation of natural ecosystems. For Sound Transit, effective conservation strategies of these mitigation sites involve restoring native plant communities, improving species diversity, controlling invasive species, and enhancing habitat functions. We work to protect habitats from disturbances caused during construction and operations. Managing these areas is done in compliance with environmental regulations but also contributes to preserving the unique character of western Washington. By working closely with environmental groups, government agencies, and local communities, Sound Transit promotes sustainable growth while safeguarding important habitats for future generations. This important work aligns infrastructure development with environmental stewardship.
Ecosystem mitigation projects
Sound Transit is committed to avoiding and minimizing impacts to natural areas like wetlands, streams, and buffers where possible. When impacts to wetlands, streams, or buffers are unavoidable, Sound Transit provides compensatory mitigation by creating and restoring other wetlands; enhancing wetland and stream habitats; and/or by adding habitat features to existing wetlands, streams, and their buffers in the project vicinity.
When not practical or sustainable to create a mitigation site close to an affected wetland or stream, such as an area that is already developed, Sound Transit pays for mitigation “credits” from a nearby mitigation bank or in-lieu-fee organization. These organizations then use our funds to create, enhance, and/or preserve large wetland and stream systems in the same watershed where the impacts occur.
Examples of mitigation projects constructed with major funding contributions from Sound Transit include the King County Mitigation Reserves Program’s Chinook Wind Mitigation Project, Taylor Creek Mitigation Project, and Issaquah Creek Mitigation Project. Sound Transit has also contributed to the Keller Farms Mitigation Bank in Redmond, Washington, as part of our mitigation for the Downtown Redmond Link Extension project.
Cultural resources program
Sound Transit recognizes the importance of cultural resources including historic buildings, structures, and objects, as well as archaeological sites and traditional cultural places.
Such cultural resources may be important to Indigenous peoples who have called this region home since time immemorial, or they may be important to peoples who have moved to the region in the last 200 years.
Sound Transit’s projects and maintenance have potential to affect these cultural resources, and we work with the Tribes, descendant communities, and other parties throughout Washington state, as well as federal, state, and local agencies and the public, to identify and protect these resources through all phases of work to expand, maintain, and operate our transit system.
At Mercer Slough Nature Park, Sound Transit staff removed a commercial blueberry operation from a portion of the park to rehabilitate wetland, replacing non-native/invasive vegetation with diverse native plants and filling in agricultural ditches.
At Laurelwood Park in Federal Way, Sound Transit crews restored and improved Laurelwood Park's wetland and stream buffers to mitigate impacts from light rail construction elsewhere in the city.
Along the 2 Line in Bellevue, we reused some of the trees in the area that had to be removed to make way for the light rail tracks. Much of the materials from the tree clearing operations were reused elsewhere, including for hundreds of habitat structures, like standing snags and log piles.
An elliptical culvert that blocked fish passage was replaced with a box culvert at the edge of the Green River valley. The new culvert allows fish to pass, and coho salmon have been observed spawning upstream.
Crews walk the mitigation site near the Mercer Slough where wetlands were restored as part of the 2 Line light rail project.
