Crosslake Connection: 50 Years in the Making

A view of a Link light railtest train on theHomer M. Hadley Memorial Bridge withMount Rainierin the background. (Bruce Englehardt / CC-BY-SA 4.0)

Sound Transit's 2 Line light rail service will carry it's first passengers across Lake Washington in just a few days. Puget Sound residents have long envisioned a passenger rail connection between Seattle and the Eastside. In 1968 and 1970, voters failed to approve Forward Thrust rapid transit propositions. Less than a decade later, work began on what would eventually be the Crosslake Connection opening on Saturday.

Essential Groundwork: 1976-1993

In December 1976, a Memorandum Agreement was signed that outlined the construction of an improved I-90 facility between I-405 and I-5". The agreement, signed by Seattle, Mercer Island, Bellevue, King County, Metro Transit, and the Washington State Highway Commission, outlined a new I-90 roadway that should include reversible lanes dedicated for buses, carpools, and Mercer Island residents. The document also stated the new facility shall be designed and constructed so that conversion of all or part of the transit roadway to fixed guideway is possible". This language was optimistic at the time, but vital a few decades later.

I-90 on the Homer M. Hadley Memorial Bridge (left/center) and Lacey V. Murrow Memorial Bridge (right). (Joe Wolf)

The new bridge outlined in the Memorandum opened in 1989 and carried bi-directional traffic. A few weeks after it opened, the existing, parallel Lacey V. Murrow Memorial Bridge closed for a scheduled 3-year renovation project (during which it partially sank). After the renovations were complete in 1993, eastbound traffic moved to the Lacey V. Murrow Memorial Bridge and westbound traffic stayed on the now dedicated Homer M. Hadley Memorial Bridge. The formerly eastbound lanes on the Hadley Bridge were converted to reversible lanes used by buses, carpools, and Mercer Island residents.

Sound Transit's Beginnings: 1993-2003

Just days after the Murrow Bridge re-opened, the board of directors for the new Central Puget Sound Regional Transit Authority met for the first time. This new transit agency's board was made up of elected officials from King, Pierce, and Snohomish counties as well as the Washington State Secretary of Transportation. Now commonly known as Sound Transit, this new agency was responsible for designing and building a regional transit network. After a failed ballot measure in 1995, voters approved the Sound Move proposal in 1996. Sound Move included a widespread network of express buses, commuter rail between Everett-Seattle and Lakewood-Seattle, and light rail in Tacoma and between the University of Washington in Seattle and Sea-Tac airport.

Thanks to existing highways and heavy rail tracks, Sound Transit's regional bus and Sounder commuter rail services launched a few years later in 1999 and 2000, respectively. The light rail system, however, required starting from scratch. After a series of cost overruns and less-than-expected federal funding (sound familiar?), the Central Link (now 1 Line) was shorted to run between downtown Seattle and Sea-Tac airport. The 1.6 mile Tacoma Link line opened in August 2003.

Political and Technical Feasibility: 2003-2005

Central Link began construction in October 2003 and was scheduled to open in 2009. Before the line opened, Sound Transit staff were planning for the next phase for system expansion. Along with extending the 1 Line north to Lynnwood and south Star Lake, the agency set its sights on the Eastside. In 2004, Sound Transit met with the original signers of the 1976 Memorandum Agreement to add an amendment:

...all parties agree that the ultimate configuration for I-90 between Bellevue, Mercer Island and Seattle should be defined as High Capacity Transit in the center roadway and HOV lanes in the outer roadways; and further agree that High Capacity Transit for this purpose is defined as a transit system operating in dedicated right-of-way such as light rail, monorail, or a substantially equivalent system;"

With the political agreement between the necessary cities and agencies on a future light rail line across Lake Washington, Sound Transit had one more hurdle before it could seriously consider building a light rail line in the I-90 right-of-way: could the floating bridge withstand the weight and motions of a light rail train?

On September 9-11, 2005, WSDOT closed the I-90 westbound and express lanes overnight to simulate train weight and movement with trucks. The agency placed sensors across the bridge deck, on the pontoons, and on supporting structures to measure how the bridge responded to various static and dynamic tests. Static tests were completed by placing fully loaded flatbed trucks at specific points on the bridge. Dynamic tests involved four fully loaded flatbed trucks crossing the bridge in close succession (to similar a 4-car Link train), and two four-truck consists passing each other in the middle and near the west end of the bridge. Each truck was loaded to 148,000 pounds, about the weight of a light rail vehicle. The findings of these real-world tests matched those of prior computer simulations. The bridge could support light rail infrastructure with a few retrofits and a seismic upgrade.

Two flatbed trucks on the Hadley Bridge during the static load tests. (Sound Transit)Voter Approval: 2007-2008

In November 2007, the Roads and Transit ballot measure was rejected by voters. The roads" part of the ballot measure would have invested in state highways, bridges, and local roads in an attempt to fix key chokepoints. The transit" part of the package would have extended Link north to 164th St/Ash Way, south to Tacoma Dome, and east to Overlake/Microsoft in Redmond. The plan would have also funded additional ST Express service, the First Hill Streetcar, and planning studies for potential transit extensions.

After the ballot measure failed, Sound Transit went back to the drawing board for their Sound Transit 2 (ST2) proposal. In July, Erica C. Barnett (then at The Stranger), shared a breakdown of the revised ST2 plan. This plan included:

• Link expansion north to Lynnwood (from UW), south to Star Lake (from Sea-Tac), and east to Redmond Technology
• Expanded ST Express service
• Improved Sounder service between Lakewood and Seattle and to use 8-car trains

This plan was sent to voters in King, Pierce, and Snohomish counties in November 2008. This time, voters approved ST2 (Prop 1). These projects were bold expansions for a light rail system that was not yet open to the public.

After some debate, the above East Link alignment was selected. (Sound Transit)First in the World

With the sign off from voters, Sound Transit could get to work designing the first ever light rail line on a floating bridge. The I-90 bridge section had many unique challenges that required new solutions. On other sections of the Link network, rails are embedded in concrete or drilled into an elevated span. These techniques were not feasible for the Crosslake section as drilling into the surface of the bridge could hurt its structural integrity. Additionally, Link trains are electric and stray current could cause corrosion on the bridge. To mitigate these two big issues, the team designed a new plinth structure.

Simplified drawing of the plinths used on the floating bridge. (Sound Transit)

The plinths used on the floating bridge have various elements to handle different potential issues. On the top of the plinth sit lightweight rails. Below the rail is a plastic drip cap that forces rain water to drip off of the side, ensuring there is no continuous flow between the rail and the bridge surface. The main plinth structure is a lightweight concrete block below the drip cap. To attach each of the 9,000 plinths to the bridge surface, a strong adhesive called Dex-G was used.

Another challenge faced by the team was how to safely connect rails on stable ground to rails on a floating bridge. While the bridge appears stationary to the casual observer, it is always slightly moving, rotating, or turning due to the water below. Rails are not very flexible, so applying the subtle movements at one point would cause the rail to break. Instead, the team designed a track bridge system to distribute the movements over a longer distance (43ft). The track bridge approach was tested at the Transportation Technology Center in Colorado and worked at 3x the usual bridge movement and at the full 55mph train speed.

Two of the track bridges installed on the I-90 bridge near Mercer Island. (Sound Transit)Lawsuits: 2009-2022Gas Tax Funds

Despite the incredible engineering work that went into the Crosslake Connection, a few powerful people were not excited to have high capacity transit in their neighborhood. In 2009, Bellevue developer and serial transit obstructionist Kemper Freeman filed a lawsuit against Washington to block the conversion of the I-90 express lanes to light rail. The lawsuit argued that the I-90 express lanes were partially funded by the gas tax and therefore cannot be used for transit. Two years later, the Washington State Supreme Court ruled 7-2 to allow light rail on the I-90 bridge. A few days later, Freeman filed he same lawsuit in Kittitas County, likely hoping to get a more friendly judge. Fortunately, the Superior Court of Kittitas County disagreed with the argument because the laws do not restrict the State from eventually declaring the highway surplus and then using it for non-highway purposes" (full judgement). Freeman appealed this decision to the Washington State Supreme Court who again voted 7-2 to allow light rail on the bridge.

Mercer Island

On February 1, 2017, WSDOT and Sound Transit informed the City of Mercer Island that their single occupancy vehicle (SOV) access to the express lanes on I-90 was coming to an end. As outlined in the 1976 Memorandum Agreement, SOVs from Mercer Island had access to the reversible center express lanes on I-90. With the upcoming Link construction on the center lanes, WSDOT planned to add an high occupancy vehicle (HOV) lane in each direction to the outer lanes. Following this change, Mercer Island residents would be subject to the federal HOV-2 standard. In response, the City of Mercer Island planned to sue Sound Transit and WSDOT to retain SOV access to the new HOV lanes. Mercer Island also suspended an East Link construction permit to prohibit all Sound Transit work within 200ft of the Island's shoreline, essentially holding the project hostage. The public has been asking for lawsuits. You're going to get them in spades." threatened Mercer Island Councilmember Dan Grausz.

The then-planned lane configuration changes on the I-90 bridges across Lake Washington. (Sound Transit)

Sound Transit responded to Mercer Island's lawsuit less than a week later with a lawsuit of their own. The countersuit challenged the validity of Mercer Island's lawsuit. A statement released by the agency reiterated that Sound Transit is not to blame for preventing Mercer Island SOV access in the new HOV lanes:

In 2005 Sound Transit joined with King County and the cities of Mercer Island, Bellevue and Seattle in sending WSDOT a letter voicing support for granting Mercer Island SOVs access to the new HOV lanes on I-90. However, last year the Federal Highway Administration notified WSDOT that federal law prohibits SOV access to HOV lanes."

These lawsuits resulted in a $10M settlement in June 2017. Sound Transit funded 200 additional Park & Ride spaces on Mercer Island, improvements related the reconstruction of several streets near the Link station, and several other concessions. Part of the agreement around street reconstruction limited where buses could stop and layover. On October 23, 2020, Sound Transit submitted a Right-of-Way Use Permit Application that included the design for bus layover space along North Mercer Way. The Mercer Island City Council argued the design violated the 2017 agreement, and voted unanimously to sue Sound Transit. Part of the Council's letter read:

The City fought hard in 2017 to achieve an agreement that facilitated the safe movement of pedestrians and bicycles and minimized traffic on the north side of North Mercer Way. This was to ensure that Mercer Island commuters accessing Westbound I-90 from Island Crest Way would not be negatively impacted by Sound Transit buses."

This lawsuit was dismissed by a judge in 2021, and Mercer Island's appeal failed. In 2022, Mercer Island and Sound Transit settled to end all litigation. In this settlement, Mercer Island agreed to pay Sound Transit $2.1M over a two year period.

Construction: 2017 - 2025

After WSDOT closed the center express lanes on June 4, 2017, Sound Transit could start construction. The agency had to first retrofit the bridge to ensure it can support the weight of the tracks, trains, and overhead catenary system. These changes also enabled the bridge to survive stronger winds and waves.

Worker inside a floating bridge pontoon, under the road surface. (Sound Transit)

The retrofit work was completed in 2018 and the focus shifted west to the Judkins Park area. The Rainier Freeway Station was closed in the September 2018 service change so construction on Judkins Park station could begin. East Link construction crossed the halfway mark in April 2019. That same month, the first track bridge was installed on the Hadley Bridge.

Crews prepare the I-90 floating bridge for rail installation in 2019. (Sound Transit)Connect 2020

Between 2017 - 2019, East Link construction was independent of the existing 1 Line. That changed at the start of the new decade when Sound Transit needed to connect the two lines just south of International District/Chinatown station. To connect the lines, crews installed switches to route trains between the 1 Line and 2 Line. This required removing and replacing some of the existing 1 Line track in each direction.

One of the switches installed during Connect 2020. (Sound Transit)

The agency branded this work Connect 2020. During the 10 week project, trains ran between Angle Lake - Pioneer Square and UW - Pioneer Square. All passengers had to transfer at Pioneer Square using a new center platform. As the center platform had no exits, north and southbound trains arrived at the same time, and would only depart when the platform was clear.

When the Connect 2020 work finished, most of Seattle were staying home due to pandemic. East Link construction was paused in the early days of the pandemic, but the project's 2023 opening timeline remained unaffected. Throughout 2020 and 2021, crews installed thousands of plinths on the Hadley Bridge to support the Link tracks. On the Eastside, the first trains started rolling to conduct clearance tests.

Delay After Delay

In 2019, Sound Transit identified quality issues with track construction on both sides of the I-90 bridge. The plinths were constructed of poorly consolidated concrete that led to gaps under the rail fasteners. To fix the issue, a repair mortar was added fill in the gaps. Unfortunately, the mortar started failing in Fall 2020. Further investigation found addition issues with concrete plinths that were caused by poor concrete workmanship". Throughout 2021, Sound Transit and its contractors worked to develop solutions for the faulty plinths. In some cases, entire plinths needed to be demolished and rebuilt. Due to these issues, Sound Transit projected a 42 day delay of the East Link project.

Repair mortar shown between the concrete plinth and rail fastener. (Sound Transit)

In November 2021, about 300 concrete workers went on strike against six cement suppliers. This strike disrupted construction projects throughout Puget Sound, including all four Link extensions (East Link, Lynnwood, Federal Way, and Downtown Redmond). Sound Transit noted the impact of the strike in their February 2022 Agency Progress Report on Capital Programs: Because of the delay in work caused by the lack of concrete, our contractors have had to lay off 266 workers so far."

The plinth repair work continued into 2022 as crews removed removed enough concrete from the plinths that the internal rebar was shown. At this point, Sound Transit identified further structural integrity and durability issues with the plinth's construction.

On top of the plinth issues on solid ground, Sound Transit uncovered quality issues with the plinths on the floating bridge in March 2022. As discussed in the First in the World section, lightweight concrete blocks were used as plinths on the bridge. Inspectors observed cracking, flaking, or spalling in about 1% of examined blocks. All impacted blocks needed to be replaced. Additional issues with the nylon rail fastener bolt inserts were observed, causing Sound Transit to replace all 19,500 inserts.

Cracks on the concrete blocks around the nylon rail fastener bolt inserts. (Sound Transit) Map of where quality issues were observed. (Sound Transit)

In light of these quality issues and resulting delays, Sound Transit Boardmember and then-King County Council Chair Claudia Balducci proposed opening the 2 Line on the Eastside before the connection to Seattle. After staff confirmed that opening East Link Starter Line (ELSL) would not delay other Link projects, the Sound Transit Board approved the ELSL in August 2023. At the time, the Crosslake Connection was projected to open in Spring 2025.

Trains Start Running!

The East Link Starter Line opened on April 27, 2024 between South Bellevue and Redmond Technology stations. In October 2024, test trains ventured west from South Bellevue to Mercer Island, validating the rebuilt section. The first part of Sound Transit 3, the 2 Line extension between Redmond Technology station and Downtown Redmond, opened on May 10, 2025. Eleven days later, the first Link train crossed Lake Washington in an unpowered tow test. In September 2025, Link trains began crossing the lake powered by the overhead wire. Sound Transit has continued testing in 2026. On Valentine's Day, the full 2 Line started running simulated service in preparation for opening on March 28.

First ever Link train crossing the I-90 floating bridge under its own power.Looking Ahead

A passenger rail connection between Seattle and the Eastside will transform the region. Passengers will be able to travel between downtown Seattle and downtown Bellevue in 25 minutes, regardless of traffic. Improved frequency between International District/ Chinatown and Lynnwood City Center stations has already delighted passengers during simulated service. King County Metro and Sound Transit are redesigning their bus networks to provide more frequent connections to the 2 Line. Some of these changes will start on March 28, but most will be implemented in the Fall.

ST Express 2026 restructure

East Link Connections