“Cocoon” wraps construction sites in safety

With the Prudential Center and John Hancock building on the horizon, 90 to 100 construction workers briskly built the superstructure for the 21st floor of the luxury tower that is filling the former crater at Boston’s famed Filene’s site. The crew installed reinforcing steel, formwork and raised heavy materials as an air-horn’s sporadic blast warned workers to look out for a giant crane hoisting loads overhead.

Despite being a hair-raising 280 feet above ground, the team worked as confidently and efficiently as if they were on the ground. Their sense of safety is provided by a series of steel mesh screens wrapping the Millennium Tower Boston like a Christmas present. The giant yellow apparatus bordering their workspace is the ultimate safety tool for high-rise construction projects.

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Nicknamed the “cocoon” and manufactured by Peri-USA, the Lightweight Protection System, or LPS, is slotted into a rail system that allows the panels to rise with the building — protecting construction crews as well as their materials and tools from falling overboard. Its mesh design allows natural light to illuminate work areas while protecting workers from the elements.

Peace of mind

A byproduct of the state-of-the-art safety system is that it gives workers the peace of mind they need to work more productively on a condominium tower that will ultimately soar 685 feet above Boston’s bustling Downtown Crossing shopping district.

“Our production is a rapid pace, we are doing a floor-and-a-half to two floors every week right now,” S&F Concrete’s Carpenter Foreman Joel Hagan said while leaning on the “cocoon” as casually as an athlete leaning against a locker. “This helps the production because everyone who stands behind the system is 100 percent sure nothing is going to happen to them and nothing is going to happen to the material they are handling — whether it be high winds, rain, snow; it doesn’t matter, they feel protected.”

The LPS — which has never been utilized on a project of this magnitude in Boston — also helps Millennium Tower’s owner rest a bit easier.

“I don’t sleep well at night because there’s a million other things to think about,” joked Millennium Partners Principal Kathleen MacNeil, who also used the “cocoon” on another luxury residential building in Downtown Crossing called Millennium Place, “but at least that one is off the list.”

The Millennium Tower project includes rehabilitating the original Beaux Arts-style Filene’s building. The historic building, which was renowned architect Daniel Burnham’s last major work in 1912, will house a much-anticipated 25,000-square-foot flagship Roche Brothers gourmet grocery slated to open April 29. When the 1.4-million-square-foot complex tops out at 54 floors in September it will be the third tallest building in Boston behind the Hancock Tower and Prudential Center.

In the meantime, crews feel much more surefooted working at the edges of the tower knowing the “cocoon” prevents them from kicking a hammer over the side of the building that could smash a windshield or worse.

“In a developer’s eyes they are trying to build a high-rise on a postage stamp where pedestrians are 10 feet away,” New England Sales Engineer for Peri-USA Chris Wells said. “In a city like Boston — with how close the traffic is and how close the pedestrians are — I think safety is a huge element of it.”

Wells said the LPS is typically used on high-rises 10 to 12 stories or higher, but it is also used on shorter buildings where extra protection is needed such as buildings next to schools or playgrounds. Wells also said some “cocoons” are adorned with advertisements that offset the system’s overhead. In fact, he said a project situated near intersecting highways in Toronto paid for itself with ads.

While costs associated with the system vary depending on the size of the project and how many man-hours it takes to erect, MacNeil said you cannot put a price on safety. She invoked the memory of a 20,000-pound platform collapse that killed three people in 2006 on Boston’s busy Boylston Street.

“Stuff does happen,” MacNeil said. “I think people tend to forget how dangerous construction is. I don’t know what the stats are, but it’s still a dangerous proposition and it continues to be and anything we can do as developers and owners to mitigate that is important.”

Wrapping Up

After three months of engineering and design work on the 38-panel LPS, it took only five nights for subcontractor, S&F Concrete, to install it this past August.

The 7,000-pound prefabricated steel panels were shipped in 11-foot-by-6-foot installments and expanded to 17-by-11 on the building. The Millennium’s panels are about twice as tall as panels on most projects and cover a total surface area of approximately 24,550 square feet.

Once installed on a building there are some adjustments that have to be made to make the “cocoon” rise smoothly. Rails that work similar to an extension ladder allow it to be jacked up the building every time a new concrete floor needs to be poured. The Millennium project also has a five-man crew dedicated to monitoring the system. They enlist another three to five guys when they come in at 5 a.m. to lift the LPS.

Before systems such as the “cocoon” were adopted about a decade ago, high-rise towers used wooden two-by-fours or aluminum guardrails. Sheets of plywood had to be lifted in place with cranes when a floor needed to be enclosed completely and that made for a dark and less productive work environment.

“In the old days we used to put up a wooden guardrail and if something heavy fell off the building the guardrail wasn’t going to stop it,” Hagan said.

Up to speed

The first generation of Peri’s “cocoon” system was used in Europe before it was installed on a tower in Chicago in 2007. Made of lumber, that first system was about 20 percent heavier than the current generation. It was first used in Boston in 2008 on a 34-story Back Bay condo called the Clarendon.

Suffolk Construction General Superintendent, Rich Michaels, worked on the Clarendon before joining Suffolk and is currently managing construction on the Millennium Tower.

Michaels — who along with Wells of Peri-USA is trying to make the “cocoon” feasible for a steel structure — said Peri’s first-generation LPS worked well at the Clarendon.

“In the winter it’s a good way to hold in the heat and keep construction moving forward,” Michaels said.

Although Michaels did note that Clarendon construction was halted one day by the city’s Inspectional Service Department. ISD was nervous about the LPS since they had never seen one before. Michaels said ISD asked them to submit their engineering designs to prove the LPS wouldn’t fall.

Ever since that project, Michaels has been lobbying city officials to include safety systems such as the “cocoon” in Boston’s building code the way it is embedded into New York City’s code.

“Concrete buildings built in an urban environment should use this system,” Michaels said. “The city should dictate to all contractors that they should use it to protect the public.”

This post was a collaboration between Justin Rice and Suffolk National Safety Director Gary Cunningham. If you have questions, Justin Rice can be reached at jrice@suffolk.com or follow him on Twitter at @JustinAlanRice. Gary Cunningham can be reached at gcunningham@suffolk.com

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