SR 520 Construction Corner

The go-to source for information on SR 520 construction

Click on any topic below to learn more about potential effects. For each topic, learn:

  • What to expect during construction. What might you see, where, and when?
  • Construction commitments. What have we agreed to do to manage these effects?
  • Construction practices to minimize the effects. What will we do to reduce effects?
  • More information. We offer some sources to learn more.

During the Montlake Project, the current phase of SR 520 construction, work will occur at several locations in the Montlake and Madison Park areas. Check our Construction Map for information about what’s happening now or in the coming weeks.

Our community construction management plans, linked at the bottom of this webpage, detail the actions our contractor crews follow to limit the effects of construction on nearby neighborhoods and travelers within the highway corridor.


Heavy construction equipment

What to expect during construction

The contractor will perform many construction activities during the Montlake Project. Each activity uses different types of equipment and results in different levels and kinds of noise. Each week, we post the latest report of data and nighttime noise complaints.


  • Crews may work 24 hours a day, seven days a week throughout construction.
  • Typical work hours for the loudest (impact) work:
    • 7 a.m. to 10 p.m. weekdays
    • 9 a.m. to 10 p.m. weekends and holidays

Working at night and on weekends limits weekday traffic congestion on Montlake Boulevard and local streets. We’re always looking for opportunities to reduce nighttime effects on the neighborhood, and we’ll schedule noisy activities during the day when possible.

  • Most nighttime construction activities will be monitored and controlled under a Major Public Projects Construction Noise Variance granted to WSDOT by the city of Seattle. The variance addresses nighttime construction noise that could be higher than levels normally allowed by city ordinance.
  • Variances for nighttime work require specific notifications and restrict certain types of noisy activities.
  • Nighttime noise monitoring is performed throughout Montlake Project construction. Electronic noise meters are used to verify that noise from nighttime work remains within the approved limits set in the variance.
  • An independent noise specialist oversees noise monitoring and reports on compliance directly to the city. If noise exceedances occur, WSDOT will work with its contractor and the city to determine the best course of action to mitigate the construction activity.

Construction commitments:

  • WSDOT and the contractor will meet all WSDOT, federal, local and statewide regulatory requirements, and any contract and permit requirements.
  • WSDOT prepared a Construction Noise and Vibration Mitigation and Monitoring Plan that identifies:
    • Expected noise levels at many locations.
    • The risk of exceeding allowable noise levels.
    • Measures for the contractor to implement if noise levels are higher than allowable levels.

Construction practices to minimize noise:

  • The contractor will follow best management practices, WSDOT standard specifications, and local ordinances to minimize noise.
  • Examples of best practices include:
    • Noise monitoring of all nighttime work.
    • Prohibiting use of impact tools such as auger shaking, jack hammering, hoe rams, and impact pile driving at night, and using vibratory pile driving methods whenever feasible.
    • Using lower-noise compressors at night.
    • Using less intrusive back-up warning devices or using back-up observers for some vehicles.

More information


A pile driver in Lake Washington

What to expect during construction

WSDOT is committed to minimizing activities that would result in noticeable vibrations, but some activities necessary for construction are likely to cause vibrations. Construction activities that may cause noticeable vibrations include pile driving, constructing drilled shaft foundations and demolishing existing structures.

Construction commitments:

  • WSDOT and the contractor will meet all WSDOT, federal, local and statewide regulatory requirements, and any contract and permit requirements. The Montlake Project contract specifies threshold limits for vibration levels, which the contractor will be obligated to follow.
  • For historic properties, any vibration damages will be repaired based on the Standards for the Treatment of Historic Properties (pdf 17.9 mb). For more information about WSDOT’s commitments related to historic properties, see the SR 520 I-5 to Medina Section 106 Programmatic Agreement (pdf 3.9 mb).

Construction practices to minimize vibration:

  • WSDOT will monitor vibration levels near Montlake Project construction sites before beginning construction and will conduct preconstruction inspections to set a baseline during the construction period.
  • During construction, vibration monitors will be used to ensure that the contractor stays within the limits outlined in the Montlake Project contract.
  • Read the Montlake Project Vibration Monitoring Plan (pdf 6 mb) to learn how the contractor will track the level of ground vibration from SR 520 pile driving and other work.

Air quality and dust

Worker spraying a building with water as it is demolished.

What to expect during construction

Certain construction activities may affect air quality in the vicinity of the construction site. Some of these activities include truck traffic, asphalt paving, earthmoving, and demolition.

Construction commitments:

  • WSDOT and the contractor will meet all WSDOT, federal, local and statewide regulatory requirements, and any contract and permit requirements.
  • A Fugitive Dust Prevention and Control Plan will be prepared by the contractor that provides additional details on activities to mitigate air-quality impacts during construction.
  • The contractor's Concrete Containment and Disposal Plan will identify methods for controlling concrete dust, including dust from saw-cutting.

Construction practices to minimize air-quality effects and dust:

  • Applying water to active, dust-generating construction areas, as needed, and if applicable, to other areas of the work site to keep the soil damp and minimize fugitive dust without creating unnecessary muddy areas.
  • During the demolition of concrete structures as well as loading of construction trucks with demolition debris, using a water spray to minimize fugitive dust.
  • When appropriate, installing tarps on trucks to cover their loads prior to leaving the site to control loss of material while the trucks are in transit.

Views, glare, and lighting

Road construction under bright lights.

What to expect during construction

Montlake Project construction activities will affect views of and the visual context of the Montlake area. The construction of the West Approach Bridge South will likely require the use of a temporary work bridge, barges and/or floating derricks that will alter views of Lake Washington. While the contractor will conduct most construction activities during the daytime, some construction work will occur during the night and will require lighting to work safely.

Construction commitments

  • WSDOT and the contractor will adhere to all WSDOT, federal, local, and statewide regulatory requirements and/or as required by the contract documents. This includes WSDOT standard specifications.
  • Per the Section 106 Programmatic Agreement, the contractor is required to limit the use of construction lighting as much as possible and keep necessary lighting shielded, directed downward, and pointed away from residences and other sensitive areas to the maximum extent practicable.

Construction practices to minimize visual quality effects

  • Use directional lights instead of floodlights; direct light to the work zones and away from residents in order to minimize light pollution beyond the construction limits to the greatest degree practicable.

Traffic and transportation

A road closed off with sign saying 'ramp closed'

What to expect during construction

Montlake Project construction activities will cause traffic and transportation disruptions due to adjustments in existing roadways, temporary closures, detours, and changes to pedestrian and bicycle access through the area.

Conditions on the SR 520 mainline will remain similar to previous conditions, with two general-purpose lanes in each direction between Montlake and the floating bridge. Some short-term closures will be required. Construction activities on major city arterials like Montlake Boulevard and Lake Washington Boulevard will require lane shifts on those streets.

Construction commitments

  • WSDOT will require the contractor to adhere to all WSDOT, federal, local, and statewide regulatory requirements and/or other regulations as required by the contract. This includes WSDOT standard specifications and coordination with the city of Seattle.

Construction practices to minimize traffic and transportation effects

  • The Montlake Project contractor will typically open new lanes before closing existing traffic lanes during construction in order to maintain vehicle capacity on existing streets.
  • The contractor will minimize short-term closures and limit necessary closures to non-peak traffic periods.

More information

  • The SR 520 Montlake Project Neighborhood Traffic Management Plan (pdf 4 mb) includes more information about traffic-related concerns, traffic management during the construction period, and traffic-calming measures planned by WSDOT and the city of Seattle to minimize traffic impacts during SR 520 construction.

Utilities and services

A worker passes another worker some equipment.

What to expect during construction

Montlake Project construction will require the relocation of some sewer lines and other utility lines in the Montlake area. WSDOT and the contractor will notify potentially affected residents of work that may result in service interruptions or closures. One notable project will be replacement of a 54-inch-diameter city water line that runs under SR 520 just east of Montlake Boulevard.

Construction commitments

  • WSDOT and the contractor will adhere to all WSDOT, federal, local, and statewide regulatory requirements and/or as required by the contract documents.
  • WSDOT and the contractor will coordinate with the city of Seattle prior to any service interruption.

Construction practices to minimize effects on utilities and services

  • Advance notification will be provided to potentially affected residents and other stakeholders before conducting work that may affect utilities or services. Notifications will include contact information for comments or questions.

Vegetation management and erosion control

A tree with a sign attached entitled 'Public Notice Protect Tree'.

What to expect during construction

Some trees and vegetation will be removed near the Montlake Project area due to a number of activities, including building the work bridges for the West Approach Bridge South and preparing staging areas for construction activities. The contractor has developed a Tree and Vegetation Management and Protection Plan (pdf 4.8 mb) that identifies specifics areas where trees may be removed or disturbed. The contractor will also prepare a Temporary Erosion and Sediment Control Plan to reduce water quality impacts of construction.

Construction commitments

  • WSDOT and the contractor will adhere to all WSDOT, federal, local, and statewide regulatory requirements and/or as required by the contract.

Construction practices to minimize vegetation effects and control erosion

The Temporary Erosion and Sediment Control Plan will include the following practices to reduce impacts on soil and vegetation in the project area:

  • Marking sensitive and vegetation-protection areas with high-visibility fencing.
  • Installing silt fencing where needed to reduce sediment from entering nearby water bodies.
  • Temporary and permanent seeding, plastic covering, and erosion-control fabrics and matting to protect vegetation and reduce erosion.

Over-water and in-water work (boating restrictions)

A crane operating over water.

What to expect during construction

Construction of the new eastbound bridge (the West Approach Bridge South) will require an extensive amount of in- and over-water work. Temporary work bridges and barges will be used to complete removal of the old bridge and install the drilled shaft foundations, bridge columns and bridge deck in and over Lake Washington.

Construction commitments

WSDOT and the contractor will adhere to all WSDOT, federal, local, and statewide permits and approvals, including, but not limited to:

  • Section 401 and 404 of the Clean Water Act
  • Hydraulic permit approval
  • Coast Guard permit requirements
  • Seattle shoreline permit

Construction practices to minimize effects when working over or in the water

In addition to requirements of the permits listed above, the design-builder will prepare a Water Quality Monitoring and Protection Plan which outlines a number of best management practices, including:

  • Having spill-response kits and containment booms onboard barges and vessels.
  • Providing containment and/or covering for fuels, concrete, concrete process water, stormwater runoff, construction materials and debris.

Boating restrictions - ensuring the safety of watercraft users on Lake Washington.

To receive updates about boating activities and navigation restrictions on Lake Washington, email us at and ask to be added to the boater-notification list. Notification emails will be on an as-needed basis.

To stay safe around over-water work trestles, barge-mounted cranes and other heavy equipment, boaters, canoeists and kayakers should stay at least 100 feet away from all in-water construction equipment and structures.

Kayak/canoe access during construction

Kayak and canoe route during construction.

This map shows the off-limits areas for watercraft during construction of the SR 520 Montlake Project.

During Montlake Project construction, one navigation channel under the SR 520 bridge may be blocked periodically for critical construction work. During these blockages, marine vessels should plan to navigate through the unaffected channel (see below for navigational height restrictions). At least one branch of the navigation channel at the west end of the floating bridge will always be open and accessible to boaters. The navigation channel at the east end of the floating bridge will not be affected by the Montlake Project.

Navigation changes on Lake Washington along SR 520

Update: Both navigation channels open to boaters

Graphics showing the navigation channels immediately east and west of the 520 floating bridge. The clearance on the west side is shown as 47 feet. To the east, it's 65-70 feet.

For more information, visit:

The locations and clearance heights of the SR 520 floating bridge navigation channels.

Construction staging and haul routes

A truck hauling an oversized load.

What to expect during construction

The contractor will stage equipment and materials both on land and on barges near the construction areas. Staging areas will vary in size and function, but will be available for use by the contractor 24 hours per day, 7 days per week. In order to build the new eastbound bridge, the contractor will also build a temporary work bridge. The “WSDOT Peninsula,” next to the Washington Park Arboretum, will be a primary staging area during Montlake project construction, though other staging areas also will likely be used (see map below).

The contractor will use I-5, SR 520 and city arterials as haul routes for construction vehicles during the Montlake Project (see map below).

Construction commitments

  • WSDOT and the contractor will adhere to all WSDOT, federal, local, and statewide regulatory requirements and/or as required by the contract.
  • Additional Section 106 coordination for the Montlake Historic District will be required if the contractor proposes the use of haul routes outside of those previously identified in the Section 106 Programmatic Agreement (pdf 3.9 mb) coordination process.

Construction practices to minimize the effects of staging and haul routes

The Montlake Project contractor will work to limit the community effects of hauling and staging construction materials with actions such as:

  • Locating construction sheds, barricades and materials storage, where practicable, away from historic properties, and avoid obscuring the views of and from historic properties.
  • Where practicable, installing temporary construction screens/barriers, such as plantings or fencing, around construction areas so that visual impacts of construction activities on historic properties are minimized. The location and type of screens/barriers will be determined in consultation with adjacent property owners.
  • Where practicable, avoiding placement of temporary work bridges and other short-term construction features where they would require permanent removal of mature trees or would damage them.

Map showing construction staging areas in the Montlake area

Key construction-related management plans

Our community construction management plans (CCMPs) outline how the public can provide ongoing input into construction decisions that help to avoid, reduce or mitigate the effects of construction activities on historic properties and other neighborhood residences and businesses. The plans also guide the actions of our hired construction contractors, describe best management practices they are to follow, and provide opportunities for WSDOT to keep the public informed and gather input that improves our construction practices.

Click on the links below to read key SR 520 construction management plans and agreements: