BY LOUIS LA PLANTE
Milan has long been synonymous with high fashion, big business and smog.
Since 2003—when a study by Milan's Macedonio Melloni hospital suggested that breathing the city's air was the equivalent of smoking 15 cigarettes a day—the jam-packed Italian metropolis has been considered one of Europe's most polluted cities. Last December, schools were closed for two days because of dangerous air conditions, and some pedestrians have even begun wearing respiratory facemasks.
Given that backdrop, a US$83 million construction project from Milan-based investment firm Hines Italia isn't just another mixed-development unit. It could prove to be just the breath of fresh air the city needs.
As conceived by Milan-based architecture firm Stefano Boeri Architetti, the project entails constructing twin towers with nearly 500 balconies filled with more than 600 trees and 4,000 shrubs. Known as Bosco Verticale (Vertical Forest), the virtual microclimate of trees and plants will filter dust particles and carbon dioxide, produce humidity and oxygen, and protect the building from dust and noise pollution. That same amount of plant life would require 50,000 square meters (538,195 square feet) of horizontal land.
Not surprisingly, a project this novel presents several irregularities.
“The project can be thought of as neither normal nor simple,” says Ferdinand Platter, the project's technical manager, who works for ZH General Construction Company AG/SPA in Milan.
Almost all of the unusual characteristics stem from one crucial element: the balconies. The team couldn't rely on the traditional approach of extending the building's concrete floor slab over the edge to form the balcony. Instead, the towers had to incorporate oddly positioned balconies cantilevered to a length of 3.35 meters (11 feet), allowing the structures to support the weight of both humans and lush plant life. The project team also had to construct the balconies so that weight loads could be transferred over the height of several floors, especially at the corners.
The 18-month schedule was ambitious, especially given the project's unusual features. Mr. Platter allotted extra time at the start, slating 14 days to complete each of the first 10 floors of each tower. Comparatively speaking, each floor of the 104-story Freedom Tower in New York, New York, USA, took one week to finish.
Once the Bosco Verticale team was beyond the 10th floor, Mr. Platter leveraged lessons learned to fast-track construction, condensing the schedule to just 10 days for each floor.
Despite the innovative nature of the project, he relies on tried-and-true scheduling basics. A look-ahead plan identifies what was accomplished on each day of the previous week, as well as what would be accomplished in the current week and the following one.
Daily meetings help keep scope creep under control and address potential structural changes early. Mr. Platter contends that the ramped-up schedule actually increased morale by boosting team member confidence as they delivered on the ambitious goals.
HIGH TOWERS, HIGH RISK
Mr. Platter knew the unusual arrangement of the balconies and the height of the towers—110 and 76 meters (360.9 and 249 feet)—would bring risk. So he proactively created mitigation plans two months prior to the scheduled start date.
The most serious risk seemed obvious: The higher the structure, the higher the risk of falls. Based on the project requirements, engineers developed a custom formwork and scaffolding solution that could not only transport heavy loads of concrete up each floor, but also serve as a secure enclosure for team members.
Mr. Platter had to wait until the custom-built solution was on site to train team members firsthand. But because the risk assessment had been conducted early, training time could be built into the original schedule. And given that only a small fraction of the 180-person team would use the equipment daily, just one full day of training was needed. Mr. Platter also sought out equipment operators familiar with some of the technologies used in the custom solution.
This attention to talent management paid off: To date, there have been no fall-related accidents, and team members are working more efficiently than anticipated. They built an entire floor of 18 units in half a day, which provided additional time to build the shaft platforms and the next vertical sections.
As Mr. Platter and the team move to the next phase, using cranes to raise plants onto the balconies, the project remains on budget and schedule. By year's end, Bosco Verticale will be finished, and Mr. Platter—and Milan's denizens—may breathe a little easier. PM
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