accommodations to proceed through
roughly the first 325 ft of the alignment, which consisted mostly of wet
soil and rocks. To simulate hard rock
conditions, this initial section was frozen so that the TBMs could operate
properly. To this end, more than 240
steel pipes were installed to depths between 80 and 106 ft below the surface.
A cold brine solution was injected into
the pipes and continuously recirculated,
causing the ground to freeze after about
10 weeks. This frozen state was maintained for three months until TBM operations had concluded in the immediate area.
To provide the space needed to disassemble the TBMs after the tunneling
activities, “cover-and-cut construction”
was used, Wahl says. The work was carried out in a belowground section of the
bus terminal in which buses circulate.
A portion of this space was excavated
and then covered with a deck structure
so that bus operations could resume.
“Once that deck structure was put into
place, the rest of the excavation and construction below that deck structure continued,” Wahl says.
The existing A, C, and E subway
lines, running north–south at this point,
C, and E lines had to be reconfigured, and
several columns of the existing tracks for
these lines had to be underpinned. Fur-
thermore, to meet the alignment of the
extension, the invert of the tail track had
to be lowered and the surrounding tun-
nel structure had to be reconstructed.
The inclined elevators within the
34th Street–Hudson Yards station cost
$2.7 million to fabricate and install.
Traveling a length of 172 ft while descending a vertical distance of 82 ft, the
inclined elevators move at a speed of
100 ft per minute, making the journey
in approximately two minutes from start
to finish. Designed to hold 15 standing
passengers or 3 to 5 passengers in wheelchairs, the inclined elevators were included so that disabled passengers could
disembark closer to the platform when
descending from the lower mezzanine,
says Richard Mulieri, a senior director of
public affairs for MTA Capital Construction Company. Manufactured in Italy,
the inclined elevators were installed by
KONE, which has its North American
headquarters in Lisle, Illinois.
The overall project, which also in-
cluded the design and construction
of four facility buildings housing me-
chanical, electrical, and communica-
tions systems, was paid for by New
York City without any federal fund-
ing. Of note, the city was able to fi-
nance the project by means of what is
called value capture, Lucey says. Under
this method, the city paid for the proj-
ect by issuing bonds that are backed
by the increasing value of the real es-
tate of the Hudson Yards area. This 28-
acre, $20-billion commercial, retail,
and residential area is being developed
adjacent to the station. By rezoning the
area from industrial to commercial and
residential land uses, the city opened
the door to denser development, which
will lead to higher real estate values.
Because several project components
are located on privately owned land that
is part of Hudson Yards, certain elements of the project design had to account for the needs of the future development, Lucey says. “The project needed
to be designed in full concert with the
commercial-residential overbuilds,” he
notes. Therefore, project facilities were
constructed below street level to the
fullest extent possible to maximize the
aboveground space available for private
development. In some cases, project facilities were designed to support structures expected as part of the site’s future
development. —JAY LANDERS
Nation’s First Waste-to-Energy
Plant in 20 Years Opens in Florida
A NEW POWER PLANT in West Palm Beach, Flor- ida, that generates electricity by burning solid waste incorporates state-of-the-art features that
engineers say make it one of the most advanced plants in
the nation. Renewable Energy Facility 2 began commercial
operation in August and is the first waste-to-energy plant to
be built in the United States since 1995.
The $670-million plant is capable of incinerating 1 million tons of refuse each year and has a generating capacity of
95 MW, enough to power 55,000 homes. It was constructed to relieve pressure on an adjacent waste-to-energy plant (Renewable Energy Facility 1) and
landfill that have operated since the late 1980s.
In recent years the older plant has ramped up
production in response to population growth.
It processes as much as 900,000 tons of solid
 Civil Engineering november 2015
The new waste-to-energy plant in West Palm Beach, Florida,
will increase generating capacity and relieve pressure
on an adjacent waste-to-energy plant and landfill.