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Portage Bay Bridge and Roanoke Lid Project: Environmental Online Open House – NEPA reevaluation

What is a NEPA reevaluation? Why are we doing a NEPA reevaluation?

Large highway projects typically require the completion of an environmental impact statement (EIS) and an approved Record of Decision (ROD) by the Federal Highway Administration. If notable refinements of the project’s design occur after those planning documents are completed, a reevaluation of the project under the National Environmental Policy Act (NEPA) may be required. A NEPA reevaluation will either find that the existing environmental documentation is valid or that the subsequent refinements require additional analysis of the project’s effects on the built and natural environment.

WSDOT is conducting a NEPA reevaluation of planned refinements in the Portage Bay project’s design since the 2011 Final EIS and ROD. Rather than looking at overall environmental effects of the project, the reevaluation analyzes how these design updates may alter the project’s effects compared to the findings of the 2011 Final EIS and ROD. In other words, have refinements resulted in a significant change in the project’s environmental effects as compared to the previously approved project design?

2011 Preferred Alternative Baseline Design
Overhead map of the SR 520 corridor in Seattle between Montlake Boulevard and I-5. The map points out key features of the Portage Bay Bridge reconstruction project as initially proposed in 2011, with a single bridge and no shared-use path over the bay.
2020 Refined Conceptual Design
Overhead map of the SR 520 corridor in Seattle between Montlake Boulevard and I-5. The map points out key features of the Portage Bay Bridge reconstruction project under an updated design in 2020, with two parallel bridges and a shared-use path over the bay.

Public involvement in project design refinements

2011-2012 Seattle Community Design Process

Portage Bay Bridge and Roanoke Lid Project design refinements arose from extensive coordination with community members, the city of Seattle and other stakeholders. In 2011, WSDOT launched the Seattle Community Design Process (SCDP), which consisted of public workshops, open houses, stakeholder briefings, and coordination with the city of Seattle and the Seattle Design Commission. The process focused on collecting public feedback to further refine the project design. That process resulted in the SCDP report (PDF 31 MB). This report recommended the following design refinements:  

  • Add a 14-foot-wide shared-use path on Portage Bay Bridge
  • Conduct further outreach to identify the optimal Portage Bay Bridge type
Image of the lime-green cover page of the Seattle Community Design Process Final Report, published in 2012. The cover has three illustrations of urban parks with trees, walkways and, in one, a lakeshore with kayakers.

2014-2015 Final Concept Design Report

In 2014-2015, WSDOT conducted additional outreach focused on the design of the Portage Bay Bridge. This outreach and resulting design refinements documented in the Final Concept Design Report (PDF 25 MB). This outreach effort resulted in the following recommendations:

  • A box-girder bridge type
  • Two parallel bridges with the SR 520 Trail on the south side of the south bridge
Cover page of the 2014-2015 SR 520 West Side Final Concept Design report. The cover has three illustrations: one with pedestrians on a paved path, another with two buses and a city corner, and a third with bicylists and walkers on a path.

2019 Design Outreach

In 2019, WSDOT conducted another stakeholder process, which included three workshops, two open houses and an online open house, to refine the conceptual design further. This outreach focused on the look and feel of the Roanoke lid, nonmotorized connections, and the Boyer Avenue East and Bill Dawson Trail under-bridge areas. Key outcomes of this process included:

  • Refining the nonmotorized trails on the lid and connections to the city nonmotorized network
  • Identifying the location and design concept for the lid viewpoints
  • Developing treatments to improve the user experience in the areas under the Portage Bay Bridge

A detailed list of project refinements is included in the draft Section 4(f) evaluation (PDF 8.4 MB).

Cover page of a report entitled "Summary of 2019 community and stakeholder engagement" for the SR 520 Portage Bay Bridge and Roanoke Lid Project. The cover has pictures of people sitting around tables talking and looking at papers on the tables.

Review of environmental effects

Water quality and sediment

Picture of a large crane atop a barge on a body of water. The crane is lifting a large metal object.

Preliminary review has not identified any substantial new or worsened effects related to water quality due to design refinements. The updated project concept includes a refined stormwater design that will collect and treat SR 520 stormwater runoff. Currently, SR 520 runoff flows untreated directly into Portage Bay.

2020 refined conceptual design – construction-related effects

  • WSDOT is evaluating whether there would be substantial differences in construction-related effects on water quality and sediment compared to the 2011 Final EIS.
    • WSDOT will require best management practices that were identified in the Final EIS to minimize sediment disturbances.
    • With fewer in-water columns, WSDOT expects the project's effects on water quality and sediment to be less than what was analyzed in 2011.
  • In 2012, WSDOT received a permit from the U.S. Army Corps of Engineers that requires WSDOT to remove existing bridge columns as well as any temporary structures using either vibratory extraction and/or saw-cutting methods.
  • In July 2016, WSDOT submitted a permit modification to the U.S. Army Corps of Engineers to further quantify the effects of removing and replacing soil when using the saw-cutting method. Saw cutting the columns/pilings instead of vibrating them out requires removal of soil around each column.
  • This permit does not allow WSDOT to leave construction debris in the lakebed.
  • In compliance with the updated permit, the contractor may:
    • Remove soil around each column or pier.
    • Sidecast the excavated soil.
    • Saw cut the bridge columns/piles.
    • Remove the columns/piles and any deposited concrete debris.
    • Backfill with either native or imported soil or material.
  • The proposed soil disturbance is a short-term, temporary effect, and the lakebed will be backfilled upon removal of each column. The Corps permit does not allow for explosive demolition of the bridge into the lake.

2020 refined conceptual design – long-term effects

  • The current design concept will collect stormwater runoff similarly to the 2011 design. However, there have been design changes to the Portage Bay project regarding stormwater runoff as a result of public involvement.
    • The inclusion of the SR 520 Trail will not cause additional stormwater contamination. The path is strictly for nonmotorized travel and therefore won't generate polluted runoff.
    • WSDOT has updated its original plan to use collection ponds for runoff. Instead, WSDOT is proposing underground vaults, equipped with water treatment mechanisms. The vaults will reduce potential effects on surrounding recreational opportunities.
    • The current project plans include a grass filter strip to treat stormwater runoff from new impermeable surfaces added at the NOAA parking area under the future SR 520 bridge.

2011 Final EIS – construction-related effects

  • The Final EIS identified potential construction-related water quality concerns related to sediment disturbance, turbidity and pollution. Construction activities that could cause turbidity issues include earth work, grading, retaining wall construction, installation and removal of piles or columns from the old bridge, the new bridge, and/or the temporary work bridge. There is also potential for pollution and contamination from accidental spills.
  • WSDOT also analyzed soil samples for contaminant levels to determine proper land-based disposal of sediments during construction. WSDOT requires the contractor to dispose of contaminated soils in accordance with regulatory standards. The contractor must adhere to best management practices, such as those identified in the Water Quality Management and Monitoring Plan to minimize sediment disturbance and associated turbidity.
  • WSDOT requires the project contractor to meet established best management practices for construction runoff, turbidity and pH, and to create and comply with a temporary erosion and sediment control plan.
  • WSDOT requires the contractor to complete prevention, control, and countermeasures for spills, and effective concrete containment and disposal protocols
  • The Final EIS calls for additional control and mitigation measures, including:
    • Containment measures surrounding in-water work activities to prevent construction materials from mixing with surface waters
    • Containment measures to limit extent of turbidity generated during construction.
    • Construction water treatment systems, such as storage tanks, filtration systems, transfer pumps, and an outlet to ensure contaminated water is clean before it enters Portage Bay.

2011 Final EIS – long-term effects

  • The Portage Bay Bridge and Roanoke Lid Project would reduce pollutants in Portage Bay and connecting water bodies due to the addition of a system for treating SR 520's stormwater runoff.
  • Upon completion of construction, Portage Bay Bridge stormwater runoff will be routed to a land-based treatment facility prior to discharge into Portage Bay/Lake Washington.

Wetlands and habitat

Aerial picture of undeveloped green space and small ponds next to a large body of water. A trail meanders through the green space.

WSDOT’s preliminary review has not identified substantial new or worsened impacts to wetlands and habitat associated with project design refinements. WSDOT will continue to evaluate effects compared to the 2011 Final EIS design concept. WSDOT has already completed a number of mitigation actions to offset impacts of the project construction and operation.

2020 refined conceptual design – construction-related effects

  • The refined design concept will likely have similar effects on vegetation clearing and temporary shading compared to what was outlined in the 2011 Final EIS.
  • Construction will affect the beaver lodge in Portage Bay. WSDOT is working with state agencies to ensure a safe relocation of the resident beavers. While regulations do not require WSDOT to work with state agencies to perform relocation, WSDOT understands the importance of the lodge to the local community and is committed to ensuring the beavers are relocated safely.
  • WSDOT will comply with King County weed management laws.

2020 refined conceptual design – long-term effects

  • WSDOT reassessed the current conditions of the shoreline wetlands in Portage Bay in 2016 pursuant to the latest (2014) Washington State Wetland Rating System developed by the Department of Ecology. The updated ratings of Portage Bay wetlands remain consistent with those evaluated in the 2011 Record of Decision.
  • WSDOT has also consulted with the U.S. Fish and Wildlife Service and National Marine Fisheries Service to evaluate potential increases in effects on endangered species in the project area, which resulted in a determination of no additional effects.
  • WSDOT will review how the current project design would increase shading due to the addition of the SR 520 Trail. WSDOT will also analyze how the higher elevation and the removal of the planted median would offset the increased shade caused by a wider bridge profile.
  • The current design, which features wider bridge spans and fewer in-water columns, will likely reduce the permanent impact area on aquatic habitat and species in Portage Bay. Additionally, the reduction in columns may afford greater space and aquatic recreation access for boaters, paddle boarders, and kayakers.

2011 Final EIS – construction-related effects

  • The Final EIS found that vegetation clearing and shading by temporary work bridges would be the primary effects on wetland and wildlife habitat in the south Portage Bay area during project construction.
  • All in-water construction, such as pile-driving, would occur during specific work windows approved by regulatory agencies. WSDOT coordinated with the regulatory agencies and tribes to establish site- and project-specific in-water work windows to minimize potential effects on juvenile or adult salmon.
  • WSDOT has conducted mitigation projects to compensate for the effects of SR 520 reconstruction on wetland and aquatic resources. These mitigation projects are greater in area than the areas affected by SR 520 construction, including Portage Bay.

2011 Final EIS – long-term effects

  • WSDOT identified a number of mitigation sites in the Final EIS to address the project's long-term effects.

Noise and vibration

Picture of a pile driver, with two construction workers standing nearby. A grove of trees are in the background.

WSDOT’s refined concept will include similar noise-reduction measures and best practices outlined in the Final EIS. Preliminary modeling shows a few isolated areas with small changes in noise levels in the refined design. Mitigation analysis will be reviewed in areas where noise levels are greater than the analysis included in the Final EIS. WSDOT will apply for a Major Public Project Construction Noise Variance from the city of Seattle.

2020 refined conceptual design – construction-related effects

  • WSDOT's planned means and methods related to construction noise and vibration have not changed since the Final EIS.
  • WSDOT will apply for a Major Public Project Construction Noise Variance from the city of Seattle. This variance will outline noise requirements under which WSDOT's contractor will work. The MPPCNV will have a public process and comment opportunity. WSDOT plans to begin the variance application process late this year or in early 2021.

2020 refined conceptual design – long-term effects

  • WSDOT is conducting noise analysis and modeling of the refined project design. Preliminary analysis shows small changes in noise in a few isolated locations (less than 3 dBA). Mitigation analysis included in the Final EIS will be reviewed in any areas where traffic noise levels would be greater than previously evaluated.

2011 Final EIS – construction-related effects

  • During construction, people living and working near construction areas would be affected by noise from a variety of activities and equipment. The loudest construction-related noise activities are pile-driving and demolition of existing structures.Typical construction equipment is expected to have a range of 62 to 105 dBA maximum noise level 50 feet from the source. Major non-impact noise-producing equipment would include concrete pumps, cranes, excavators, haul trucks, loaders, and tractor trailers. Maximum noise levels from this equipment could reach up to 92 dBA at the nearest residences (50 to 100 feet).
  • Major vibration-producing activities would primarily occur during pile driving and demolition.
  • WSDOT identified a number of noise- and vibration-reduction measures in the Final EIS.
    • Limit operations of construction vehicles within 500 feet of residences where possible
    • Mufflers on motorized equipment
    • Strategic timing for certain activities
    • Pile coating
    • Other potential measures (e.g., turning off idling equipment, spacing out activities, installing acoustic barriers)
  • All construction activities are subject to local noise regulations and limits. WSDOT anticipates applying for a Major Public Project Construction Noise Variance from the city of Seattle for the Portage Bay Bridge project.

2011 Final EIS - long-term effects

  • In general, WSDOT's Final EIS analysis found an overall reduction in noise in the Portage Bay Bridge and Roanoke Lid project area compared to the no-build option.
  • The Preferred Alternative design of the Portage Bay Bridge and Roanoke Lid Project includes the following noise-reduction features.
    • A four-foot-tall solid barrier along the edge of the bridge.
    • Reduced speed limit to 45 miles per hour, which will provide a "boulevard feel" and also help to reduce the effect of traffic noise to the surrounding community.
    • Encapsulated bridge joints, which help to reduce the "thump thump" noise of vehicles driving over bridge transition spans. The bridge joint will likely be similar to the encapsulated joint used on the West Approach Bridge North rather than on the floating bridge.
    • Quieter concrete pavement will be used throughout the SR 520 corridor, including on the Portage Bay Bridge.
    • The Roanoke lid, with noise absorptive material on the lid portals, will reduce highway noise for nearby residents.
  • In the Final EIS, WSDOT analyzed whether noise walls would be a feasible noise-abatement measure. Because of the design features outlined above, it was determined that noise walls would not provide enough additional reduction to be considered cost-effective.

Cultural Resources

Picture of a light gray house with bluish trim and a steep, brown shingled roof. Green fir trees are in front of the house.

In coordination with regulatory agencies and community stakeholders, WSDOT developed a Programmatic Agreement in 2011 to outline project effects on historic and cultural resources in the project area and appropriate mitigation for those effects. Since 2011, WSDOT has identified project refinements that produce some small changes in the effects on cultural resources. However, WSDOT’s analysis, with concurrence from the State Historic Preservation Officer, found that these project refinements have not resulted in an increase in adverse effects to cultural resources.

2020 refined conceptual design – construction-related effects

  • Temporary project activities in or adjacent to historic properties would include installation of subsurface tiebacks, or anchors supporting retaining walls, from the SR 520 right of way to locations beneath new historic properties, relocation of a waterline in the southeast corner of Roanoke Park, and creation of pedestrian/bike connections at the northeast corner of Montlake Playfield. However, these activities' short-term effects on historic properties from related vibration, noise, fugitive dust, or traffic would not be sufficient to be considered new adverse effects.
  • WSDOT has consulted with the Washington State Department of Archaeology and Historic Preservation (DAHP) regarding the change in effects on historic properties.

2020 Refined conceptual design – long-term effects

  • Permanent subsurface easements for retaining wall tiebacks, or anchors, would extend farther than originally planned and would be located beneath additional historic properties. The tiebacks, however, would be located deep below ground and the subsurface easements would not represent new adverse effects to historic properties.
  • New permanent effects would include installation of a vault cover at ground level within the southeast corner of Roanoke Park, which is part of the Roanoke Park Historic District. However, this change would not be substantial enough to represent a new adverse effect on the park or the Roanoke Park Historic District. 
  • The Montlake Playfield is a historic property within the Montlake Historic District. Construction of pedestrian/bike connections at the northeast corner of the playfield would be a new permanent effect. However, this project refinement would not be substantial enough to represent a new adverse effect on the playfield, the historic district, or nearby residential historic properties.
  • WSDOT has consulted with the Washington State Department of Archaeology and Historic Preservation (DAHP) regarding the change in effects on historic properties.

2011 Final EIS- construction-related effects

  • Under Section 106 of the National Historic Preservation Act, WSDOT worked with FHWA, the Department of Archaeology and Historic Preservation (DAHP) and a number of other interested stakeholders, called "consulting parties," to develop a Programmatic Agreement (PA) that addresses the SR 520 project's adverse effects to cultural and historic resources. That PA includes mitigation measures to reduce those effects. Mitigation commitments for short-term, construction-related effects include:
    • Minimizing effects from construction staging and haul routes
    • Minimizing visual effects
    • Managing lighting and glare
    • Vibration monitoring and management
    • Noise monitoring and management
    • Protecting historic properties from excessive excavation, emissions, fugitive dust, and traffic
  • The PA also stipulates that WSDOT's contractor will develop a Community Construction Management Plan (CCMP) for each project phase that details construction management practices to avoid, minimize and mitigate impacts to historic and cultural resources. The CCMP provides opportunities for consulting parties and members of the public to provide input on these practices.
  • The PA also stipulates that houseboats currently docked on the west shore of Portage Bay between University Bridge and the Queen City Yacht Club be evaluated for eligibility on the National Register of Historic Places as mitigation for the visual and noise effects of construction.

2011 Final EIS – long-term effects

  • The PA stipulates additional measures to resolve permanent adverse effects. WSDOT has incorporated some of these commitments into the project conceptual design based on consultation with the Section 106 concurring parties, other key stakeholders, and the broader public. Other project commitments will have additional consultation opportunities after the future project contractor is brought on board.
  • Commitments incorporated in the current conceptual design:
    • A context-sensitive design for the new Portage Bay Bridge that reflects the surrounding environment.
    • Retaining-wall treatments and lighting along the Bill Dawson Trail
    • A connection between the Bill Dawson Trail and the Ship Canal Waterside Trail via the Arboretum Waterfront Trail via Montlake Boulevard and an accessible path on the property transferred to WSDOT from the NOAA Northwest Fisheries Science Center.
    • Agreement with the National Oceanic and Atmospheric Administration for measures to avoid and resolve adverse effects to the Northwest Fisheries Science Center
    • Design for the 10th Avenue/Roanoke Street intersection as negotiated with SDOT and adjacent neighborhoods, and in consultation with DAHP
    • Consulting with the city of Seattle on including the marker rock and memorial bench currently located at the Bagley Viewpoint
    • Roanoke Park Historic District National Register digitization for the city of Seattle's historic property database
  • Commitments to be finalized through outreach and consultation with the project contractor
    • Landscape design plan for the Roanoke lid compatible with the historic character of Roanoke Park Historic District and adjacent historic properties
    • Collaborative design process to address tree and hill contour retention, curb planting bed design, Bagley Viewpoint design, and signage locations
    • Underground wiring on the Roanoke lid to the maximum extent practicable
    • Retaining as much mature vegetation as possible on all sides of the lid

Social and community

Picture of a wide, unpaved trail running through a grove of green trees. Three bicyclists are on the trail.

WSDOT’s 2011 Final EIS outlined a number of effects to project neighbors, parks and trails related to travel disruptions from short-term roadway closures and traffic shifts on local streets. The Final EIS also found that the 2011 project design would improve community cohesion over the long-term by improving transit/HOV reliability through the SR 520 corridor and providing a new community-connecting lid and paths for people walking and biking in the Portage Bay/Roanoke Park neighborhood. WSDOT anticipates that the 2020 refined design will have similar construction-related effects on the neighborhood, and provide added long-term social and recreational benefit by extending the regional SR 520 Trail west over Portage Bay and onto the new Roanoke lid.

2020 refined conceptual design – construction-related effects

  • WSDOT will evaluate whether the short-term and construction-related effects to recreation and neighborhoods outlined in the Final EIS will be the same or similar under the refined design. WSDOT's refined design will include more detailed information and guidelines on temporary lane closures, traffic shifts and pedestrian and bicycles detours, which will be outlined in the project's request for proposals and contract.
  • WSDOT anticipates that the short-term and construction-related effects to low-income, minority, and limited English proficiency households outlined in the Final EIS will be the same or similar under the refined design.

2020 refined conceptual design- long-term effects

  • The key social and recreational improvement in the refined concept is the extension of the SR 520 Trail over the Portage Bay Bridge to Delmar Drive East at the Roanoke lid. WSDOT anticipates that the trail will improve community cohesions by providing an important regional, nonmotorized connection from the Eastside into Seattle and connecting to the city of Seattle's local trail network.
  • The long-term effects to low-income, minority, and low English proficiency communities outlined in the Final EIS will be the same or similar under the refined design.

2011 Final EIS – construction-related effects

  • There will be a number of short-term, construction-related effects to connectivity and neighborhood cohesion.
    • Temporary lane closures and traffic shifts may result in increased cut-through traffic through neighborhood streets.
    • There may be temporary effects to the transit stop on 10th Avenue East. WSDOT will work with King County Metro to notify the public of any updates to transit service.
    • Access to some recreational facilities like parks and trails may also be reduced. The Bill Dawson Trail to the east of Montlake Playfield will be closed for most of the six-year duration of the Portage Bay Bridge and Roanoke Lid Project. The trail will be closed to build the new path connection to the SR 520 Trail and to provide construction access to the Portage Bay Bridge work trestles.
    • More information on effects on recreation are included in the next page and the Section 4(f) technical report (PDF 8.4 MB).
  • WSDOT will develop a Community Construction Management Plan (CCMP) and a Neighborhood Traffic Management Plan (NTMP) to help mitigate the effects of construction on the surrounding neighborhood.  The CCMP will help minimize construction effects on the community by establishing best practices and creating communication protocols.  The NTMP will further evaluate construction effects on people walking, biking, using transit and driving, and identify measures to reduce those effects.
  • WSDOT will coordinate with the Muckleshoot Indian Tribe to identify important access points to usual and accustomed fishing areas in areas where proposed structures would be built.

2011 Final EIS - long-term effects

  • The Final EIS concluded that the completed SR 520 project will improve community connections and cohesion when compared to a no-build alternative. The new Roanoke lid will reconnect neighborhoods north and south of SR 520, create new nonmotorized connections and provide new open space recreational opportunities. The addition of transit/HOV lanes between Montlake and I-5 will also improve transit reliability throughout the corridor.
  • No low-income, minority, or low English proficiency households would be relocated because of the project.
  • No disproportionately high and adverse effects on tribal members are anticipated in relation to cultural resources.
Next steps

After this online open house closes, WSDOT will prepare a draft NEPA reevaluation for submittal to FHWA. We would like to hear from you before finalizing the draft. Does this open house address the key environmental concerns you have? Are there key concerns or topics that we missed? Please provide your comments in the box below.


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