Transportation
Big Dig Snafu Delays Boston Greenway Projects
(archrecord.construction.com - 10/09/2006)
By Ted
Smalley Bowen
Engineering and safety concerns threaten
to slow the surface development that will cap Boston's 15-year,
$15 billion Central Artery/Third Harbor Tunnel project.
The Rose Fitzgerald Kennedy Greenway,
the 27-acre crescent freed by the Big Dig with the removal
of the elevated portion of Interstate 93, is zoned for parks,
civic structures, and private development. But the complex
engineering required to build over the tunnel is a major hurdle,
particularly in the aftermath of July’s ceiling collapse
in the Interstate 90 connector tunnel. Repair work, an engineering
review of the Big Dig tunnels, and a reassessment of the Greenway
could lead to further changes and delays.
Safety concerns, and politics, delayed
the development agreement for the first major Greenway project,
the Daniel Libeskind–designed New Center for Arts and
Culture.
With the development agreement in hand,
the developer would need six months to assess “all the
things necessary to construct our building on that site,”
says New Center chairman, developer Ronald Druker. “We
don’t know what we're building on.”
Building on top of such extensive and
varied underground structures will test designers and puts
the onus on Big Dig officials to relay mountains of engineering
data to developers.
To support aboveground structures, tunnels
need an additional load capacity of about 150 pounds per square
foot per floor, plus bracing for wind and seismic loads, according
to James Lambrechts, professor of civil engineering at Wentworth
Institute of Technology in Boston. As-built drawings, concrete
core samples, and ultrasonic readings can provide critical
information like the spacing and size of rebar, he adds.
"We've never built over anything
that complex," says architect Moshe Safdie, whose firm
is handling the $90 million Boston Museum project tentatively
slated to open in 2012. "The existing [tunnel] structure
has been designed to take certain loads and there are two
major exits right under our building."
The $4.5 million Harbor Islands Gateway
Pavilion, which is expected to open in 2009, has a proposed
grade just three feet above the Central Artery tunnel, according
to designer Stephen Yablon. "We proposed a lightweight
glass box for an even distribution of the load and explored
a waffle slab," he says. "We're going to do some
as-built probes. We have all the construction documents, but
was it actually built at that height?"
This summer, Governor Mitt Romney appointed
a new chairman of the Massachusetts Turnpike Authority, which
oversees the Big Dig and controls the Greenway real estate.
The move effectively realigned the agency with the Massachusetts
Highway Department, which as of press time, was still grappling
with tunnel closures and repairs and had yet to full address
the engineering of aboveground projects, according to spokesman
Jon Carlisle. Government officials and developers estimate
that it will be another 15 years or more before the reconfiguration
of the waterfront district is complete.
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