This article was written by Derek Lacey for ENR Southeast.
BEST PROJECT: Nelson Street Pedestrian Bridge
Replacing the century-old Nelson Street Pedestrian Bridge required close collaboration among project team members who had to successfully traverse five of the busiest railroad tracks in Georgia, all in close proximity to busy pedestrian areas like the State Farm and Mercedes-Benz arenas.
New South Construction and Norfolk Southern had to piece together a construction schedule around the varying train schedules that saw trains passing underneath the bridge as many as 29 times every day.
The roughly 500-ft bridge required crews to place 12 precast concrete beams weighing 110,000 lb each and spanning up to 116 ft in length with a 900-ton crane, ultimately completing the bridge within budget and ahead of schedule in November 2022. Placing the beams at the tricky site required several onsite coordination meetings, practice lifts and multiple rigging and setting crews to install each beam.
Located in Atlanta’s Gulch area, now known as Centennial Yards, the Nelson Street Pedestrian Bridge connects two historic buildings and connects the Castleberry Hills neighborhood to downtown Atlanta with a vibrant mosaic of colors. The span features metal fencing, seating and a synthetic turf play area.
Design and pricing ultimately led to a hybrid cast-in-place concrete and precast concrete construction to minimize costs and facilitate speed of construction over the active train tracks. New South’s preconstruction efforts resulted in a design modified at one of the bridge abutments from deep foundation caissons to a large spread shallow mat footing due to high profile communication utilities known to exist but which couldn’t be located by the utility owner.
Other challenges included the unknown potential impact of the railroad traffic as well as the impact Norfolk Southern’s review and approval of construction methods might have had on the project construction schedule. Sometimes nearly 30 daily trains passed underneath at intervals as low as 15 minutes, leading to uneven work days that sometimes were as short as two hours.
Early on, coordination began with thorough and comprehensive shop drawings and submittal reviews detailing every aspect of the construction scope within Norfolk Southern’s right-of-way boundaries. Work couldn’t commence until several submittals were reviewed and approved by the company’s special provisions for the protection of railway interests.
Part of efforts to bring Atlanta’s rail hub to new life, the bridge is also part of a 50-acre reurbanization effort in the heart of Atlanta. Its array of eight bright blue and green sections separate it from others in the city, forming a mosaic pattern along the length of the bridge that ensures its identification from above. Tall decorative metal fencing and other pedestrian-facing elements contribute to an aesthetically pleasing design that helps create a major location for future development of retail, businesses and apartments with the aim of creating a diverse, collaborative and inclusive community. The pedestrian bridge also has the capability to support a fully loaded fire truck with its outriggers extended in case of emergencies and to support those future mixed-use structures.