What is Environmental Mitigation?
As Sound Transit plans its projects, every effort is made to avoid impacts to the environment. At times, however, it is impossible to completely avoid influencing an environmental resource such as a wetland or a bird’s nest.
When a potential environmental impact is identified, our team investigates the most ecologically and culturally sensible approach to making up for the functions and values of the altered resource. This process is called environmental mitigation.
In order to ensure that the agency is adequately addressing environmental impacts, Sound Transit has identified environmental mitigation as a key principle of its environmental policy. And, once an environmental mitigation project begins, Sound Transit’s team of environmental planners and scientists make sure that the agency follows through on its commitment to restoring and enhancing the environment.
Osprey Nest, Tukwila
In order to construct the elevated Link light rail trackway along East Marginal Way, Sound Transit moved
Seattle City Light electrical lines near South 112th Street and East Marginal Way in late 2004. For several years before this work occurred, a pair of osprey (Pandion haliaetus) had been nesting on one of the City Light towers attached to the lines. In order to minimize construction-related disturbances to the osprey during the nesting season, April to October, Sound Transit designed and built a replacement nesting platform.
The nest replacement platform was constructed nearby in Cecil Moses Memorial Park, a King County park along the western shore of the Duwamish River. The wooden platform is 60 feet high atop a telephone pole. Remnants of the old nest, made of matted grass and sticks, were saved and placed in the new platform to encourage the birds to relocate. The new nesting location is distanced appropriately from the construction activity and provides excellent access to the river where the ospreys hunt for fish, their primary food source.
During the first nesting season following relocation, the osprey pair successfully built a new nest on the platform and raised two fledglings. We anticipate that a pair of osprey will continue to return each April from their winter migration to nest in their new home.
Additional information about other successful osprey nest relocation projects can be found here: Ospreys in Oregon and the Pacific Northwest.
Beer Sheva Park Wetland Restoration, Seattle
Sound Transit has made up for impacts of Link light rail construction to a small wetland located at South Trenton Street. Mitigation includes restoration of an existing wetland at Beer Sheva Park, owned by Seattle Parks and Recreation. Prior to restoration, the site consisted of an abandoned vehicle turnaround and boat ramp paved in the 1960s.
In partnership with Seattle Parks, Sound Transit restored the existing wetland that had been degraded by invasive plant species, trash, and asphalt paving, and turned the site into a scrub-shrub and forested wetland with a vegetated buffer.
During the initial five-year monitoring period after construction, Sound Transit is coordinating with Seattle Parks to maintain the mitigation area and control the presence of seasonal mosquito larvae in the ponded areas. The site already has become better habitat for many animal species, such as turtles, amphibians and birds. It also provides natural treatment for stormwater runoff before it drains to Lake Washington.
Future plans at Beer Sheva Park include installing a sign illustrating the history of Beer Sheva Park and including information about wetlands.
