Mercer Island Transit Interchange

As part of the Environmental Impact Study and Record of Decision for the East Link Light Rail project, Sound Transit will make traffic mitigation efforts around the Mercer Island station. The improvements primarily consist of improved traffic signals, pavement, and markings at three intersections nearest the station. The scope of these improvements includes replacing existing hanging traffic signals with traffic light poles, installing new curbs and sidewalks for improved pedestrian experience, enhancing crosswalk markings, completing final landscaping improvements, replacing an existing catch basin on the SE corner for better stormwater management, and installing new curbs and sidewalks for improved pedestrian experience.

Work is expected to start in mid-August 2024, with utility location, surveys, necessary demolition, and installation of erosion control measures. The public should anticipate some temporary traffic and pedestrian impacts. The City of Mercer Island and the Washington State Department of Transportation reviewed and approved the traffic detour plans. Additionally, trucks with drilling equipment may be used for "potholing" to investigate subsurface conditions. This project is anticipated to be completed in January of 2025.

More project information can be found here.

As of April 2023, all of the main construction at the project area is complete, and the new roundabout is operational. Both station plazas are also complete, with only minor curbing and fence removal to wrap up. Lanscaping is installed and will be monitored as the summer arrives.

Other remaining construction in the area is related to the ongoing King County Sewerline work.

Sound Transit crews continue to work down at track level to correct some concrete issues that are leading to a delay in full opening for East Link on Merer Island (currently expected to be Spring 2025)

For the next 6 weeks, Sound Transit will implement a minor pedestrian detour (starting Jan. 26) that redirects foot traffic from the southern sidewalk of North Mercer Way between 77th Ave SE and 80th Ave SE.

Pedestrians will instead need to make use of the detour depicted in the map on the north side of the street.

In addition, the King County Metro bus stop located at N Mercer Way and 80th Ave SE will be temporarily moved west of its current location.

Contact eastlink@soundtransit.org with questions.

As of early January, Sound Transit has completed all major construction at the 80th Ave station entrance, and does not expect any additional lane or sidewalk closures. Planting has begun and will continue through the spring (see photo).

Meanwhile, minor work continues along North Mercer Way at the bus layover area next to the Park & Ride.

Construction at the roundabout on 77th Ave is expected to last several more months.

On December 8, Sound Transit officially confirmed that East Link's opening will be delayed up to two more years due to construction challenges along the I-90 bridge approaches, a regional concrete strike, Covid-19 impacts, and other factors. Exact dates are still to be determined and are slated to be approved by the Sound Transit Board in January 2023, The prior published opening was mid-late 2023.

One current placeholder alternative involves opening a shorter segment of East Link on the Eastside from South Bellevue to the Redmond Tech Station in the spring of 2024. This line would not be connected to existing rail service in Seattle, and would stop short of Mercer Island's station.

Learn more about this new delay and possible scheduling adjustments from Sound Transit's blog.

The City of Mercer Island and Sound Transit announced that both agencies reached an agreement to end current litigation pertaining to the Mercer Island Transit Integration project. This is after several years of legal dispute. The agreement allows both agencies to avoid costly ongoing legal proceedings, including a trial set for early next year.

This agreement resolves litigation first filed after disagreements emerged regarding an earlier settlement between the two parties. That earlier settlement resolved impacts on Mercer Island from increased vehicle and pedestrian infrastructure needs brought on by East Link and King County Metro station use, and Sound Transit agreed to reimburse the City for $10,050,000 in infrastructure projects and improvements. This new agreement does not change those terms.

Under the new agreement, the City of Mercer Island will pay Sound Transit a total of $2.1 million over two years and end all current legal disputes between the City and Sound Transit.

City Council unanimously approved the new agreement on behalf of the City at the December 6, 2022 Regular Council Meeting, citing the benefits of ending a dispute between two public entities, which frees up resources to focus on transportation and infrastructure projects and improve collaboration as regional partners. Three members of City Council participated in the settlement negotiations along with City staff and legal team representatives.

The terms of the agreement can be found in the CR 2A Agreement.

In October, construction work on the roundabout shifted to the southern half on the site. The northern half is now being used for two-way traffic, and temporary lanes guide traffic and buses (see photo) entering/exiting 77th Ave SE. No traffic can yet circulate all the way around the roundabout. At this time, roundabout construction is still expected to continue until early 2023.

Good news, In early October, the I-90 (aka "Mountains-to-Sound") trail will reopen to bicycle and pedestrian traffic (see photo). But note that ongoing King County sewer work may still affect other parts of that trail.

In the work location, the cut-through trail from SE 24th Street to North Mercer Way will also reopen, but the southern sidewalk along North Mercer Way will be closed, requiring a short pedestrian detour.

Sound Transit has announced that road work will soon be shifting from the north side of North Mercer Way to the southern side of the construction site at 77th Ave. This lane shift keeps cars flowing by using the new (northern) half of the roundabout while crews complete the rest of the intersection. At this time, roundabout construction is expected to continue until approximately the end of 2022.

The City has coordinated with Sound Transit's East Link outreach staff to offer office hours every other Tuesday (11:00am-1:00pm), starting July 12 through at least the end of 2022. Look for ST staff in the lobby of the community center (MICEC, 8236 SE 24th Street) where they will host an outreach table, offer flyers and materials, and answer general questions about light rail and the construction of the transit interchange (i.e the roundabout and other features).

In order to safely construct the roundabout at North Mercer Way and 77th Ave SE, Sound Transit has implemented several trail detours that will be in place untll approximately the end of 2022.Various portions of the Mountains-to-Sound (aka I-90 Trail) and some neighboring sidewalks are closed to all users. Click here to view detour map. The green lines in the detour map are the suggested alternative routes; note that the dotted green route connects but does not have sidewalks. Detour routes are signed at key intersections and locations.