Building a new bridge, under a bridge, under a bridge in Brooklyn

The 5th Avenue Bridge in Bay Ridge, Brooklyn, is a vital infrastructure piece connecting various neighborhoods, while also facilitating the movement of people and goods. Over the years, the bridge has seen significant wear and tear, necessitating a comprehensive reconstruction project to ensure its safety and functionality.

Spanning over the Long Island Railroad (LIRR) and the Sea Beach (N) Line, the 5^th Avenue Bridge has been a crucial part of Brooklyn’s transportation network for over a century. Originally built in 1915 to accommodate the growing traffic demands of the early 20th century, the bridge has undergone several modifications and repairs over the years. The last major reconstruction took place in 1962. Since then, the increasing loads upon the bridge and its aging infrastructure have made a complete overhaul necessary.

The new bridge, a single-span integral abutment bridge, will span 170 feet across 10 active railroad tracks and replace the existing bridge where it currently stands. Above the bridge lies the Gowanus Expressway viaduct (I-278), which runs east-west and sits approximately 19-feet above the southern half of the 5^th Avenue Bridge.

The decision to reconstruct the 5th Avenue Bridge was driven by several factors, including structural integrity, safety concerns, and modernization:

1. Structural Integrity: Inspections revealed significant deterioration in the bridge’s structural components, including corrosion of steel elements and weakening of concrete supports 
2. Safety Concerns: The bridge’s condition posed safety risks to both vehicle and pedestrian traffic. Ensuring the safety of commuters was a primary concern for the New York City Department of Transportation (NYCDOT) 
3. Modernization: The bridge needed upgrades to meet current standards and accommodate modern traffic demands, including larger vehicles, increased pedestrian usage, and seismic regulations.

The reconstruction project, managed by the New York City Department of Transportation (NYCDOT), involves a comprehensive plan to rebuild the bridge from the ground up in the exact location of the previous bridge. NYCDOT hired John Civetta & Sons as the general contractor for the rebuild project. Underpinning and Foundations Skanska (Skanska) were then subcontracted for the foundation work needed on the job.

Once awarded the contract, Skanska considered various designs, means, and methods to overcome the confined conditions. These methods included underpinning the existing south abutment, utilizing a gravity wall to enable deeper excavation and create more headroom, installing piles from the existing bridge deck, and utilizing drilled piles instead of H-piles. However, after consideration, none of these alternatives were able to work and the final solution was to use a combination of micropiles, H-piles, and soldier piles. Skanska reached out to Nucor Skyline to manufacture the structural steel foundation elements needed on the bridge.

The north integral abutment will be constructed at street level. However, to maintain two-way traffic lanes and pedestrian sidewalks during construction of the new bridge, the south integral abutment will be constructed from the track level, with minimal headroom available. Skanska constructed and load-tested multiple types of deep foundational elements to see what would work best in the tight conditions provided at the south integral abutment. Nucor Skyline supplied hollow bar, micropiles, H-piles, and 24” steel pipe soldier piles for the foundation work.

Headroom ranged from 12 feet at the lowest level of the south integral abutment to 23 feet. Most of the hollow bar and micropiles were driven near the 12-ft height restriction. However, the soldier piles, H-piles, and the remaining micropiles were in an area with more headroom.

The hollow bar micropiles were produced in Nucor Skyline’s Camp Hill facility, the H-pile were produced at Nucor-Yamato Steel, and the 24” x 1.0” steel pipe piles that were used as soldier piles were produced in Nucor Skyline’s Longview, WA facility.  Working with Nucor Skyline gave Skanska access to all the products they needed for the deep foundation of the new bridge. Each product was trucked to the jobsite in Brooklyn to be available as needed.

The hollow bar system eliminated the need to extract temporary casings. They also allowed a smaller drill rig to be used in the minimum headroom and were able to get through cobbles and boulders without requiring retooling of the drill. Two nonproduction static load tests were completed, including a static compression load test and an uplift test.

Skanska used two dedicated Comacchio 8D drill rigs to streamline the micropile installation process. One was fitted for rotary drilling and installed the 12.75” steel casings to the tip elevation. The other rig had a drifter head for installing the 3” diameter hollow bars into the casings. Spoil containment systems were in place to manage the discharge, slurry, and debris and keep it from the active tracks. The second drill, used for the hollow bars, used grout as the drilling fluid and once the hollow bar reaches design bond tip zone, the grout mix is thickened to the approved permanent design parameters for adequate soil-bond grout stress and structural strength.

To keep the project moving, it was run in simultaneous phases. Therefore, Nucor Skyline’s steel products had to be on-hand early in the process. There was only one access point for all equipment and materials, located on 64^th Street and 4^th Avenue. This yard was one block from the south abutment site and across the wide array of railroad tracks. Products had to be individually brought to the site from that laydown yard.

To support the integral south abutment stem of the bridge, the Nucor Skyline HP16x183 piles were driven into the subsurface, which consisted of a mix of silty sand, with varying amounts of gravel and silt. The H-piles were driven in the 13-foot wide second level of the bridge foundation, between an existing bridge pier and an existing gravity wall, leaving very little room to maneuver in the minimum 23-foot headroom. The H-piles were driven to a depth of 50 feet, allowing for 10 feet to remain above the existing grade.

After much discussion, collaboration, and testing, Skanska concluded that the APE 8-3 low-headroom hydraulic impact hammer would be able to penetrate the dense sand they found at the site and would ultimately give them flexibility should they encounter a denser soil mix once drilling began. The impact hammer was mounted to the Kalmar DCE 150-6 Forklift, which provided the mobility and lifting power needed for the project.

Each pile had to be driven in 10-foot sections, requiring five complete-joint penetration welds, taking upwards of 3 hours for each weld, including ultrasonic testing. A logistics plan was developed to continue driving H-piles while other H-piles were being welded. The installation team hand-excavated 10-feet deep, sheeted pits, at each pile location. This allowed elimination of one welded splice from each pile location, as well as removed any obstructions that might cause the pile to deviate.

The drilled 12.75” diameter micropiles supported the abutment wingwalls and the drilled 24” x 1.0” soldier piles with lagging were used to retain the soil around the abutment piles. Soldier piles were located to clear the existing south abutment gravity walls, bridge piers, and the Gowanus Expressway viaduct column foundations, which consisted of battered timber pile groups.

The 5^th Avenue Bridge project utilized both permanent and temporary drilled-in soldier piles. Both types of soldier piles held lagging panels and were used to retain the soil around the south integral abutment foundation. The area had similar spacing constraints, and Skanska chose the CZM LR-40 drill rig because of the sloping terrain, limited headroom, and challenging terrain in this location. The soldier piles were 1” thick, 24” outer diameter, permanent steel casings from Nucor Skyline. These casings were then backfilled with reinforced concrete. Open-hole drilling was used to avoid splicing smaller casing lengths together. This was the most efficient and effective method to meet design requirements.

The reconstruction of the 5th Avenue Bridge is expected to bring several benefits to the Bay Ridge community:

1. Improved Safety: The new bridge will provide a safer environment for both vehicle and pedestrian traffic, reducing the risk of accidents and enhancing overall safety
2. Enhanced Connectivity: The bridge will improve connectivity between neighborhoods, facilitating easier movement of people and goods. This is expected to boost local businesses and contribute to the area’s economic vitality
3. Modern Infrastructure: The modern design and materials will ensure the bridge’s longevity, reducing the need for frequent repairs and maintenance 
4. Community Engagement: The project has fostered a sense of community engagement, with residents and businesses actively participating in the planning and implementation process

The reconstruction of the 5th Avenue Bridge in Bay Ridge, Brooklyn, is a significant undertaking that addresses critical infrastructure needs while enhancing the safety and connectivity of the area. Despite the challenges, the project promises to deliver a modern, sustainable, and resilient bridge that will serve the community for decades to come. The collaborative efforts of the NYCDOT, John Civetta, Underpinning and Foundation Skanska, Nucor Skyline products, local agencies, and the community highlight the importance of investing in infrastructure to support urban growth and development.

Using dedicated rigs, advanced planning, and precise material staging, the project team successfully managed the challenges of limited access, spoil removal, and continuous production. The result is an efficient and reliable installation process, supporting the structural needs of complex urban construction projects such as the 5^th Avenue Bridge.