| Trump's Tower
Digging
The Donald's Chicago Condominium by Craig
Barner The $750 million Trump International Hotel & Tower is already
an important project in Chicago even though it has yet to emerge from the ground.
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When it is finished in three years, the 92-story
tower will reach 1,360 ft., said Paul James, senior vice president in Chicago
of New York-based Bovis Lend Lease, the construction manager. As a result, it
will be the Second City's second-tallest building after only the 1,450-ft.-tall
Sears Tower.
Moreover, the Trump will probably be the 12th tallest building
in the world, assuming each announced project taller than it is constructed according
to plan. Ironically, Chicago-based Skidmore, Owings & Merrill LLC, the architect,
also configured the Burj Dubai tower under construction but not topped out in
the United Arab Emirates. Burj is expected to be the world's tallest building
even though its height remains a secret to prevent the announcement of a taller
project.
Back in Chicago, Trump will have a major impact on the city's
skyline due to its height and location on the Chicago River on the former site
of the Chicago Sun-Times. Last fall the newspaper departed the North Wabash Avenue
location it had called home for 50 years for the nearby Chicago Apparel Center
building, and demolition of its former barge-shaped office was completed in the
spring.
Thousands will see the Trump daily because of its location next
to the river and landmark Wrigley Building and due to its proximity to the Magnificent
Mile district. The celebrity of flamboyant developer Donald Trump is stirring
further interest.
The project will contribute greatly to the residential
flavor of the Michigan Avenue area, a street that is being increasingly compared
to New York's Park Avenue due to the large number of upscale high-rise residential
projects that have accelerated since Millennium Park opened in 2004.
Tere
Proctor, director of sales in Chicago for the New York-based The Trump Organization,
said the Trump will hold 758 units - 472 condominiums and 286 hotel-condominiums.
"Sales
are ahead of schedule," she added. Indeed, the tower is 70 percent sold even
though construction is expected to last through 2008.
A
Bedrock Project The building expected to make a splash on the Chicago skyline
is already having a big impact below grade.
Robert Schock, vice president
of Roselle-based foundation contractor Case Foundation Co., said the structure's
bearing pressure, 250 tons per sq. ft., is reportedly the highest ever in Chicago.
"The
city code normally allows only 200 tons per sq. ft. as the maximum value,"
he said. "They allow that to be increased with a full-scale load test, which
we did here."
Because of the structure's 2.6 million-sq.-ft. size,
the foundations are partly seated in bedrock to prevent the differential settlement
due to pressure from the huge building.
Schock said 57 rock caissons are
to be installed to support the tower's core area. In addition, about 160 of the
traditional belled caissons are to be set.
Seating the rock caissons requires
drilling shafts to a depth of about 110 ft. where the bedrock starts. About 12
ft. of the bedrock is augered to create sockets that hold the foundations' tips.
A
carefully choreographed drilling sequence was implemented to install the casings
that form the foundations.
After a drill penetrates the earth, 13-ft.-diameter,
20-ft.-long temporary casings are installed. The bit is inserted through each
of the temporary casing, and through them, 12-ft.-diameter, 40-ft.-long second
temporary casings are inserted.
The shaft is flooded with water and polymer
slurry for thickening.
"Once we penetrate below the hard pan layer
into the boulder area [atop the bedrock], that's water-bearing and under pressure,"
Schock said. "If we were to penetrate that in a dry shaft, it would blow
in a hurry." Danger would arise because adjacent structures supported on
belled caissons could be undermined by the sudden change in earth pressure.
As
a result, water stays in the shaft as the drill is inserted to lengthen the shaft
for the installation of the 10-ft.-diameter, 80-ft.-long permanent casings with
jagged-tooth bottoms.
Once reaching the bedrock, the down-hole hammers
use bits that operate like jackhammers, Schock said. They shatter the rock into
gravel-size pieces that are sucked to the surface and collected in canisters for
emptying.
"This new application of the down-hole hammer has saved
us a lot of time," he added.
Grout is inserted between the rock and casing
to eliminate voids and allowed to set and form a seal.
"Now we have
a tight, safe hole that's fully sealed," Schock said. "We take the water
out of the hold and drill the rock sockets."
The 9.5-ft.-diameter,
12-ft.-deep sockets are drilled, and high-strength, 10,000-pound-psi concrete
is poured the full length of the shafts.A 10-Ft.-Thick
Mat Once the foundations are complete, the remaining key sitework elements
include excavating about 35 ft. - where the tops of the caissons are - installing
earth retention and pouring a 10-ft.-thick concrete slab. The building's concrete
columns will rise from the mat.
"The mat is about 4,500 cu. yds of
concrete, so it is good-sized," Bovis' James added.
The building
will have a two-level partial basement, and earth retention in the form of sheeting
with raker beams will be installed to form it.
Once the sitework is done,
the building will start emerging, and two tower cranes will be used, James said.
Because of the building's size, about 185,000 cu. yds. of concrete will be poured
over the course of the project.
$28 Million Penthouses There
will be a range of prices and unit sizes in the building, and the asking prices
for the penthouses are an eye-popping $28 million.
The Trump Organization's
Proctor said there are 23 layouts that range from 580-sq.-ft. studios to 6,850-sq.-ft.
penthouses, and the units will be located on floors 29 through 89. The studios
are $500,000.
The hotel-condominium units on levels 16 through 27 range
from $815,000 for a studio to $3 million for a two-bedroom unit, she said. Seventeen
layouts range from 526 sq. ft. to 2,245 sq. ft. of space.
Parking will
hold 1,000 cars, and amenities include a 60,000-sq.-ft. health club, five-star
restaurant, ballroom, conference and meeting rooms, Proctor said. The building
base will have additional restaurants and retail spaces of an upscale nature.
A
1.2-acre park will be surround the building base, and the park's three tiers will
face a walkway on the river.Why a Viaduct? Another
key element in the project's early going has been the demolition and reconstruction
of the Wabash Avenue viaduct. The Wabash bridge was rebuilt during the reconstruction
of Wacker Drive in 2002.
Because the original viaduct dated to the 1930s,
the Chicago Department of Transportation had planned to demolish it within a decade,
said Bovis' James. The Trump Organization learned about the replacement while
it was planning the tower.
"To enhance their property and to ensure
the viaduct was replaced in time for their opening, [the Trump Organization] agreed
to replace the viaduct at Trump expense but to CDOT standards," he added.
About
400 ft. was demolished in January to avoid disrupting holiday shoppers the previous
month. A pedestrian bridge was erected between North Wabash Avenue and the IBM
Plaza.
James said 120 belled caissons and columns support the viaduct,
and the existing network of streets below will be maintained, including Lower
Wabash Avenue, Lower Kinzie Street and Lower East North Water Street.SIDEBAR
ONE The Trump's Timeframe The schedule might have
been among the biggest issues for the Trump International Hotel & Tower in
Chicago.
The foundation work started in February and was completed at the
end of August, said Robert Schock, vice president of foundation contractor Case
Foundation Co. of Roselle.
"We were signed to a pretty aggressive
completion schedule," he added.
Case is using three of its largest
drill rigs to accelerate the work, and normally the company would have used two
rigs. A crew of 25 people is on the project; and a typical employee count would
have been 15.
And, the newest drilling tools, such as down-hole hammers,
are being used also to keep work going.
Even with these measures, progress
is hampered a bit, said Paul James, senior vice president in Chicago of New York-based
Bovis Lend Lease, the construction manager. The site's location in the Loop means
it falls under noise reduction ordinances that restrict work from 8 a.m. to 8
p.m.
"There are some exceptions, but generally speaking we're working
long days," he added. "They often use Saturdays to service cranes and
make up a lost day to bad weather." SIDEBAR TWO Removing
Obstacles Below-grade obstructions "were pretty significant"
on the Trump International Hotel & Tower in Chicago, said Robert Schock, vice
president of the Roselle-based foundation contractor Case Foundation Co.
It
was necessary to remove them to clear paths for the drill rigs to install the
rock caissons.
The Chicago Sun-Times was the previous tenant, and "the
Sun-Times had a pretty heavy foundation because of the weight of the presses and
for paper storage," Schock said. "There were extremely thick slabs and
mats with piles underneath."
Chicago-based Brandenburg Industrial Service
Co. removed most near-grade obstructions. Hydraulic machinery was used to crunch
obstacles, and spoils were pulverized for quick removal.
The belled caissons
that had supported the Sun-Times had been dug and set by hand in a long-ago construction
era. They were about 6 ft. in diameter with flared bottoms up to 15 ft. in diameter.
Some were densely packed at about a depth of 80 ft. and could not be avoided during
drilling even though a goal in planning the Trump's columns had been to miss obstructions.
About
a dozen existing caissons were cored through to create the space for the caisson
shafts.
Another obstruction was the boulder layer at a depth of about 100
ft., and it was cleared with the drill rigs. Click
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