After decades of planning, construction of Boston’s newest residential and office tower is proving to be one of the most challenging projects the city has seen. The $1.5 billion South Station tower is steadily rising into the skyline, and the construction crew, as of late January, has erected 36 of its 51 floors. It took years to line up approvals and financing for the 1 million square meter luxury office and apartment project, given its location adjacent to a major regional transportation hub, with several government entities involved in the process. verification
But as difficult as it was to get to the starting line, those early pains paled in comparison to the construction challenges of building on one of New England’s busiest rail hubs with little room to set up equipment and materials in a traffic jam. and a densely developed section of downtown Boston, project team members say.
Even Boston’s soil and bedrock proved more difficult to work with than other major cities, they note.
Yet despite all these challenges, and a temporary shutdown due to the COVID-19 pandemic shortly after work began, developer Texas Hines and the construction team, led by Suffolk Construction, are on track to deliver the tower in 2025.
The project was completed early purchases of critical materials such as structural steel that have long lead times as a hedge against rising construction prices post-Covid. Some of the construction work sequence was also rearranged to allow key parts of the project to move forward faster than originally planned.
When completed, the South Station tower will feature 166 luxury apartments, 685,000 square feet of office space and 520 parking spaces. The Ritz-Carlton brand will help oversee the units and related building amenities, while residential units will feature floor-to-ceiling windows.
“One of the big challenges is obviously building a project of this scale and complexity within a major transportation hub,” says Jim Gutmann, Hines’ vice president of construction. “Detailed logistical planning allowed the project to communicate all our movements to the station to be coordinated with all rail entities to limit disruption to the public and station operations.”
When completed next year, the tower will include 166 condominiums and 670,000 square feet of office space.
Representation courtesy of Hines
A six-story podium was built first, providing a base for the tower and a crucial staging area.
Image by Viatechnik, courtesy of Hines
Overcoming the first obstacles
Construction initially began in March 2020, only to be shut down for three months due to COVID-19 and the temporary shutdown of construction sites in Boston.
Despite this anticipated delay, the project team has been able to keep up with the original construction schedule. “We were scrambling and itching to get back to where we were,” says Ronald Thomson, Suffolk’s senior superintendent.
For the first two years, work focused on a 100,000-square-metre expansion of the South Station bus terminal, which the developer had to complete under its agreements with state officials before work could begin in the tower
“When five o’clock or six o’clock came, we couldn’t be at the [rail] platform with 120,000 people passing by”.
—Richard Pielli, vice president and project executive, Suffolk Construction
The expanded terminal, which will connect to the railway station, has been built on foundations that were installed between the tracks in the 1980s, when the expansion plans were started before being stopped.
Initially, work had to be done at night to keep rail passengers safe, with a scramble to finish in the early hours of the morning as the first wave of tens of thousands of commuters pass through the station south every day “It was a challenge with the schedule,” says Richard Pielli, Suffolk’s vice president and project executive. “When five o’clock or six o’clock came, we couldn’t be at the [rail] platform with 120,000 people passing by”.
As the project has progressed, construction has moved forward. According to Jeff Gouveia, president and CEO of Suffolk Northeast, who spoke with ENR earlier, logistics were a challenge given the various city, state and federal agencies that needed to be consulted, as well as the challenge of building in the middle of operation of a busy commuter train station. after the team could host an official opening in the fall of 2022.
At that point, the team was also able to focus on building the tower itself. An eight-level podium was the first to be built, raised directly over the railroad track. It provided a foundation for the tower, and for future expansion, while also serving as a crucial construction area.
Set to be a sky park when the project is complete, the 77,000 square meter podium roof provides a platform for temporary equipment storage and assembly, as well as structural steel trusses, reinforcing cages for steel and other materials before they are hoisted by cranes into the frame of the skyscraper. “It’s a balancing act,” says Thomson. “Weight is a limiting factor, and there’s only so much you can lift at one time.”
A structural steel podium above the active train yard extends the bus terminal, connects it to the train station, and will eventually serve as a landscaped roof garden for the tower’s residents.
Photo by Dave Desroches, courtesy of Hines
When completed, the sky park will feature a dining terrace, meeting spaces, pathways, contemplative gardens and activity lawns. The first 35 floors of the tower will include office space that will occupy 29,000 square feet of floor space. The tower then tapers for its final ascent, topped by 16 floors of condominiums on smaller floor plates.
Innovative structural steel work is also on display on the 35th floor. It marks the dividing line between the office space below and the condominiums above, with large steel trusses supporting the floors of the residential space.
“Technology really helped with the process and made everything fit into very tight spaces.”
—Ronald Thomson, Senior Superintendent, Suffolk Construction
Banker Steel Co., working with McNamara Salvia Structural Engineers, made use of rack trusses, which allow extremely heavy rebar to be placed in more manageable sections. The sections, in turn, allowed for more bolts and fewer welds, saving money and time.
The latest 3D modeling technology was also used to help plan each step of the steel erection. “Technology really helped with the process and made everything fit into very tight spaces,” says Thomson, adding that it has also been a useful tool in presentations detailing the project and its various phases.
In addition to using the podium for staging, Suffolk coordinated all deliveries with a software program. Drivers must register for a time slot and face being turned away if they arrive without one. Close coordination became more important as the tower began to go up, according to project officials, with five trucks a day delivering steel and another 15 delivering concrete.
Soil conditions at the Boston development site were also more challenging than those typically found in some other major cities. according to the team. In New York, crews could hit bedrock after 15 feet, but at the South Station site, the construction crew had to dig up to 150 feet. “It’s strong,” says Adam McCarthy, director of McNamara/Salvia, referring to the soil and bedrock. conditions in Boston, “but not like building in New York or Chicago.”
Crews build the tower beam base, which transfers the loads from the tower above to the deep foundation elements.
Photo by Dave Desroches, courtesy of Hines
Eight supercolumns, split between four solid 10-foot by 10-foot reinforced concrete columns and four built-up structural steel columns, support the tower’s core. These columns posed a challenge when it came to potential internal overheating given the depth of the structures.
“This is some of the strongest concrete ever seen in Boston,” says Thomson. However, he adds that “the more cement you have, the greater the resistance but also the more heat involved”.
Also posing a potential overheating problem was a 20-foot-deep massive beam, which distributes the tower’s loads to the deep foundation system, as well as the arched footing beneath the tower’s core.
The project team developed a plan to simulate the temperature distribution within high-strength concrete (12,000 psi) and found ways to mitigate it by controlling peak temperatures and thermal gradients within the concrete. Attention was also paid to the fine-tuning of the concrete mix.
