East Link construction mitigation is a high priority for the City of Bellevue and Sound Transit (the agency building the light rail project.) Several measures to ensure the design and construction impacts of the project were lessened. This is called mitigation. Several mitigation measures are in place for Mercer Slough Nature Park.
The 2015 Amended Memorandum of Understanding (Amended MOU) between the City and Sound Transit identifies many efforts to ensure noise, traffic and environmental impacts are lessened due to the design and construction of the East Link light rail project.
What vegetation/tree removal is occurring at Mercer Slough Nature Park?
In mid-July 2017, Sound Transit’s contractor began to clear and grub the area just north of the South Bellevue and south of the Blueberry Farm. This activity has occurred along 112th east side from south of SE 8th to north of SE 15th
As early as the week of Oct. 30, 2017, tree and understory vegetation removal will begin from the South Bellevue station site to 112th Ave SE. Construction Alert (10.18.17) This removal is necessary to build the guideway.
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What mitigation plans are in place for the vegetation/tree removal occurring within Mercer Slough Nature Park?
There are extensive replanting plans to mitigate for the loss of vegetation within the areas where the guideway will be built. The city has worked collaboratively with Sound Transit to minimize to the greatest extent possible impacts to critical areas and their buffers as well as provide visual relief from the light rail facility. The city-issued Design and Mitigation (D&M) Permit for the South Bellevue segment ensures that vegetation be retained to the extent possible, that critical areas mitigation planting and landscape buffers comply with the city land use codes, and that landscape development be installed and maintained per the Environmental Best Practices and Design Standards (Bellevue Parks Department 2006).
More specifically, the East Link South Bellevue D&M Permit identifies the type and number of trees to be removed and replanted within the project limits. (Go to next question)
Will the trees removed near Mercer Slough Nature Park be replaced/replanted?
Yes, but not necessarily in the same place that they were removed. For purposes of the East Link project, an area is cleared of vegetation to build something, such as the guideway. It would not be possible to replant trees where the guideway would be constructed.
Over 2,500 coniferous and deciduous trees were identified within the Light Rail Overlay areas, critical areas and critical areas buffer within the South Bellevue project corridor; around 1,460 were identified to be removed (including hazard trees).
An estimated 995 trees were identified to be mitigated and more than 9,500 will be replanted within the Sweyolocken mitigation site, the light rail station and adjacent park, Winters House, Surrey Downs Park and as part of corridor plantings.
In addition to the Design and Mitigation Permit for South Bellevue (D&M Permit) conditions of approval to build East Link, the city-issued Clearing and Grading permits also condition the project for landscaping requirements related to tree preservation and replanting consistent with the D&M Permit. The Development Services Department is responsible for reviewing and approving the permit; the Parks & Community Services Department is responsible for oversight of the replanting efforts.
What other environmental mitigation measures are in place for Mercer Slough Nature Park?
Enhancements and mitigation to Mercer Slough Nature Park include over six acres of wetland and wetland buffer restoration within the park and planting more than 2,800 trees to offset the 691 being removed for the project. Additionally, six acres were added to the park through acquisition of private property just south of the Mercer Slough Environmental Education Center. The six acres that were added offset East Link's permanent use of approximately three acres of parkland adjacent to Bellevue Way SE.
Following construction of East Link, a new building and parking area will be opened near the Winters House providing park restrooms and u-pick blueberry and seasonal farm-fresh produce sales. These will be connected to 700 linear feet of new boardwalk trail.
Other construction mitigation includes:
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Temporary parking lot for Mercer Slough Nature Park users due to the closure of the lots at Winters House and Blueberry Farm.
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Relocate pedestrian and vehicle access points to west side of Mercer Slough Nature Park via temporary parking lot.
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Maintain non-motorized trail access via the Park’s interior and eastern boundary trails.
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Maintain access to Sweyolocken Boat Launch during construction (with the exception of intermittent closures when necessary)
What other landscaping will occur near the South Bellevue light rail station?
The Design and Mitigation Permit for South Bellevue conditions landscaping requirements to comply with city land use code.
The Light Rail Permitting Citizen Advisory Committee (Light Rail CAC) was formed to review the context and design components of East Link light rail facilities and provide recommendations on compliance with development standards, design guidelines and other considerations. Many of the CAC’s recommendations regarding landscape standards and critical areas protection were included in the D&M PermitHow is water quality being protected during East Link construction occurring near Mercer Slough and other waterways?
Water quality protection is addressed through the Clearing and Grading permit, specifically the Construction Stormwater Pollution Prevention Plan (CWSPPP). The purpose of the CWSPPP is to identify potential sources of pollution that could affect the quality of stormwater discharges from the construction site and describe best management practices on erosion control, soil stabilization, dust control, water quality protection and other controls.
A common best management practice for erosion and sediment control is to install a silt fence. A silt fence is made of durable material and is intended to retain soil on an area where soil is being disturbedwhile allowing filtered stormwater to continue draining from the site. The fence remains in place until the activities disturbing the land are sufficiently completed to allow revegetation and permanent soil stabilization to begin.
In addition to the CWSPPP, the city required a Spill Prevention Control and Countermeasure Plan to quickly address any unexpected spills or releases, and a Turbidity and pH Monitoring Plan to verity that sediment is not being released to the storm system or water bodies.
City inspectors are responsible for ensuring all erosion control and response plans are properly implemented by the contractor.
Why is the large magnolia tree by Winters House being relocated?
Light rail construction work is occurring close to the existing tree and its root system. To minimize potential damage to the tree, the Heritage Magnolia tree will be relocated approximately 50 feet west of its current location within the Winters House parcel in late March 2020. A new magnolia tree will be planted in its place. A specialty tree relocation contractor will perform the relocation with oversight by the City.
Will the Park and trails be open during East Link construction?
Access to Mercer Slough Park, the trail system and the Sweyolocken Boat Launch will remain open during East Link construction. A new temporary parking lot, located on the east side of Bellevue Way SE between 112th Avenue Southeast and 113th Avenue Southeast, is available for park users only. Both the boat launch and temporary parking lot will be open for the duration of the project with intermittent closures as needed.
Is the Sweyolocken boat launch open during East Link construction?
Access to Mercer Slough Park, the trail system and the Sweyolocken Boat Launch will remain open during East Link construction. A new temporary parking lot, located on the east side of Bellevue Way SE between 112th Avenue Southeast and 113th Avenue Southeast, is available for park users only. Both the boat launch and temporary parking lot will be open for the duration of the project with intermittent closures as needed.