Connecticut DOT - Walk Bridge Replacement Project
The Connecticut Department of Transportation (CTDOT) is replacing the Norwalk River Railroad Bridge (Walk Bridge) to address the current structure’s vulnerability to climate hazards such as storm damage and heat. The 118-year old Walk Bridge already experiences frequent and costly service failures, including closure failures due to extreme heat. CTDOT expects that heat-related operational failures will increase as the number of high-heat days increase with climate change. The Walk Bridge is a “swing bridge” spanning the Norwalk River in the Southeast part of the state. Swing bridges allow marine traffic to pass using a mechanism where the bridge can swing open by rotating along a central pivot.
Heat events cause operational failures of the Walk Bridge by preventing proper closure. The Walk Bridge opens on average 20-30 times per month to accommodate the passage of tall barges, and rail service must halt until the bridge is closed. However, due to heat events the bridge fails to close approximately ten percent of the time it is opened. Bridge closures failures require an average of two hours to repair, and cause significant rail backup, as the Walk Bridge is used by 140 trains each day. CTDOT has attempted to mitigate heat-related failures by painting the bridge white, but such actions will not be sufficient to adapt to future climate conditions. CTDOT cites research showing that by 2050 the region will experience temperatures exceeding 90 degrees three times more frequently than current conditions.
Although the Walk Bridge did not suffer damage during Hurricanes Irene or Sandy, the structure is highly vulnerable to severe weather events. CTDOT projects the bridge would suffer significant damage from a 100-year storm surge or flying debris from hourly wind gusts of at least 75 miles per hour (levels consistent with a Category 1 hurricane). CTDOT estimates that even minor damage to the bridge from a severe weather event could cause a total loss of the structure, as the span has already exceeded its fatigue life.
The Walk Bridge is critical to rail service in the Northeast Corridor, and a significant failure of the Walk Bridge would block the only direct rail connection between Boston and New York City. The resulting rail line disruption along the Boston – New York City – Philadelphia – Washington corridor would exacerbate traffic congestion and air pollution on interstate I-95 and likely result in significant regional and national economic harm.
The Walk Bridge is the oldest swing bridge along the New Haven Line/Northeast Corridor rail line in Connecticut. The original swing span – constructed in 1889 – remains in operation. Deferred maintenance has caused additional damage to electrical and mechanical components of the bridge.
The current Walk Bridge structure provides no system redundancy – all four Northeast Corridor tracks run along a single span, and all would remain out of service if the bridge suffered damage. The proposed replacement bridge would split the four tracks between two separate spans, which would provide essential redundancy during climate events and increase the overall resilience of this vital transportation corridor. CTDOT originally planned a 25 year rehabilitation of the bridge, but altered the project scope in favor of a full replacement. The maintenance and operation problems with the Walk Bridge and the CTDOT rehabilitation project are included in the state of Connecticut’s Master Transportation Plan and State Rail Plan.
The Walk Bridge replacement is projected to have a total cost between $300-600 million. In September 2014, CTDOT received $161 million in federal competitive grant money from the Federal Transit Administration Emergency Relief Program to partially fund the bridge replacement project; the State of Connecticut will also provide funding for the project. The Walk Bridge replacement project is in the design phase as of spring 2016, and construction is expected to begin in mid-2018. CTDOT will utilize a Construction Manager/General Contractor for the project, which helps to optimize cost, schedule, quality, and risk by involving the contractor in early design processes. Bridge components will be constructed offsite and later assembled in place to minimize construction duration and travel impacts to the public. This project is part of a larger Walk Bridge Program consisting of a series of additional related projects that are necessary to maintain rail operations during the replacement of the Walk Bridge.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on March 30, 2016.
- Connecticut Department of Transportation (CTDOT)
- Federal Transit Administration (FTA)
- Case study