Constructing a new tower at the site of the former Filene’s Basement retail store in the heart of Boston’s Downtown Crossing was bound to capture the attention and imagination of the city’s residents.

Indeed, at times, previous pushes to redevelop the site became a favorite soap opera for many Bostonians, as plans started and stalled and eventually came to a complete stop amidst a deepening recession in 2008. Then Millennium Partners stepped in as the new, sole developer of the project in 2012 – and things finally started to happen, including the signing up of major tenants and the launch of construction in 2013.

But there’s another aspect to the Millennium Tower Boston saga, beyond the rich and high-profile history of the site and the fact that an adjacent renovated building along Washington Street was designed by legendary architect Daniel Burnham in 1912: The residential Millennium Tower Boston would be 685 feet and 60 stories high, making it the third tallest skyscraper in Boston, behind the Hancock Tower (now known as 200 Clarendon and 790 feet tall) and the Prudential Tower (749 feet).

And Millennium Tower Boston was also facing the fact that not since 1976, when the Hancock/200 Clarendon tower was completed, had Boston seen anything like this tower project – in terms of building height, materials, new building technologies and the sheer number of contractors, subcontractors and workers involved, all confined within a dense neighborhood with more than 200,000 people living and working there every day.

The story behind the story – of how 65 subcontractors, 150 material suppliers, construction manager Suffolk Construction and Millennium Partners have worked together since 2013 – is one of intense pre-construction planning, precise execution and an unrelenting focus on safety, quality and hitting deadlines.

The team has taken a “vertical assembly line” approach toward the tower’s construction – in which the lower floors of the tower were finished by subcontractors even while crews above were still pouring concrete for the upper floors.

“It’s one of the most efficiently run projects I’ve seen in a while,” said John Cannistraro, president of Watertown-based J.C. Cannistraro LLC, one of dozens of subcontractors working on the $700 million project. “The job has been great, really lean with excellent execution among so many parties.”

The Millennium Tower Boston project is now about 80 percent done – its topping off ceremony was held in mid-September – and officials expect the residential tower of 442 luxury units (including a two-level club and lounge, dining, a health club and an indoor lap pool) to open its first phase this summer, on schedule.

But the project really started well before construction crews ever hit the site: during seemingly endless pre-construction meetings between officials from Millennium, Suffolk and subcontractors.

“It is the only way to get it done right and on time,” Rich Michaels, senior superintendent for Suffolk Construction, said of the multiple meetings to go over the fine points of building Boston’s third-largest tower. “Everything has to be very organized and coordinated.”

The project’s general statistics alone suggest the magnitude facing Suffolk Construction and all its subcontractors: 1.2 million square feet of horizontal construction; 61,000 cubic yards of concrete (including 6,000 cubic yards for its base mat, the largest continuous concrete placement in Boston’s history); 10,000 tons of reinforcing steel; 410 plate steel link beams (equating to 850 tons of steel); and 8,000 exterior curtain-wall panels.

On any given day, up to 500 workers have been on site – and, at times, trucks hauling materials and equipment through Boston’s narrow and curving streets arrived at the site every six minutes or so.

Careful choreographing of all the logistics on a daily, weekly and monthly basis – sometimes on days with 200 different activities going at the bustling site –is daunting, critical and simply a must, Michaels and many subcontractors said.

“You’re dealing with such heights and all the workers and materials being hauled up by crane or elevators,” said John D’Elia, vice president of Worcester-based Greenwood Industries, a roofing and sheet metal subcontractor that’s working on the roofing and balconies at Millennium Tower. “It’s all about the details. Luckily, many subcontractors were familiar with each other and have worked together in the past. And Suffolk has been great.”

Indeed, some subcontractors note that they worked together on a previous Millennium Partners project only a few years ago, Millennium Place at 580 Washington Street, just a few blocks away from the new tower. But that project was only 150 feet tall, or one-fifth the height of Millennium Tower.

Armies of Subs

There have been a number of challenges and unique features to the Millennium Tower project. Among them were having to excavate, refill and then re-excavate the cavernous hole for the building’s mammoth foundation. The re-excavation was necessary for construction design changes from the previous developer’s plan and to make the final product structurally sound and faster to build.

Once the foundation’s base was set, construction on the actual building got underway – and many subcontractors still marvel at how, as the tower rose with each truckload of concrete poured, small armies of workers would converge on the lower floors to perform their work.

In Cannistraro’s case, his team of workers installed fire protection and plumbing systems. Like other subcontractors, J.C. Cannistraro LLC pre-fabricated as much of its work as possible off site, to save time once workers began installing items within the actual tower itself.

Floor by floor, the concrete foundation rose higher – and floor by floor, and room by room, subcontractors were right below those higher up pouring the concrete, a process Suffolk Construction’s Michaels refers to as a “vertical assembly line.”

After each subcontractor finished a lower-floor job, others would take their place, including drywallers from Century Drywall and others. Every job was carefully inspected and reinspected before the next subcontractor started its own work.

“There was no float in this project,” said Cannistraro. “You have to get it right. There was no comeback work. When the topping off ceremony was held this fall, when the last bucket of concrete was poured, it was wonderful to look up knowing that interior finishes were already completed to the 15th floor.”

At all times, all safety measures were, and still are, strictly enforced. The exterior of the tower was wrapped by a stateof-the-are safety “cocoon,” or a series of steel mesh screens wrapping around the building. Designed to protect both workers and pedestrians below, the screens, which were built by Peri-USA, were slotted into a rail system that allowed panels to slowly rise with the building of the tower.

Every subcontractor team dispatched to upper floors was kept to strict schedules, if only because there’s only limited space on the project’s two cargo elevators.

“To get up that high has been a challenge in and of itself,” said Steve Guarracino, operations officer at JM Electrical, a Lynnfield subcontractor working on carbon-monoxide exhaust systems and the interlocks for fuel systems to the tower’s emergency power generators. JM Electrical is doing work for Canton’s Automated Logic-New England, itself working for E.M. Duggan.

Len Monfredo, executive vice president of E.M. Duggan Inc., said a number of innovative technologies and practices were used to ensure high quality, subcontractor coordination and faster construction, including extensive use of state-ofthe-art Revit software that allowed architects, engineers and subcontractors to review 3-D models of the tower before individual projects commenced.

E.M. Duggan also relied extensively on pre-fabrication of about 50 percent of its HVAC components at its shops in Canton. Entire panels with pre-attached piping and pumps were shipped by truck to the work site and “literally put together like Lego pieces,” said Monfredo.

But all the new technologies, materials and best construction practices alone weren’t, and aren’t, enough to guarantee high quality and timely construction. Ultimately, it’s taken scores of subcontractors collaborating closely with Suffolk and Millennium project managers, as well as among subcontractors themselves, to complete an incredibly ambitious project like Millennium Tower Boston, Monfredo said.

“It’s a partnership, rather than someone saying, ‘You have to do this and you have to do that,’” he said. “They let subcontractors have a say and input on schedules and other matters.”

The bottom line, Monfredo said, is that Millennium Tower Boston, when it opens its first phase this summer, will be a welcome new landmark for Bostonians.

“And it will be done on schedule, believe me,” he added.

Original Article The Professional Contractor