November/December 2022 - 73

A regular column showcasing successful
best practices for sustainable foundations
FOUNDATIONS FOR A SUSTAINABLE FUTURE
Foundation Reuse Reduces CO2 Emissions in Chicago
the existing caissons. Problems during
foundation construction required
remediation of two caissons, whereby
one was supplemented with micropiles,
while the other was abandoned and
replaced with a straight-shaft rock
socketed caisson.
The Solution
Apart from reusing the caissons,
construction cost savings were also
realized through reusing the existing
concrete basement walls for the new
underground parking garage and
loading dock for the redevelopment.
The project demonstrated that reuse
Credit: Goettsch Partners
The Challenge
Between 2003 and 2005, a 51-story
c omme r c i a l o f f i c e t owe r wa s
constructed on the site of the former US
Gypsum (USG) building in Chicago. That
building had been founded on a forest of
belled caissons bearing at elevation -56
Chicago City Datum (CCD). The ground
surface at the site is approximately
elevation +20 CCD.
To reduce the foundation cost, the
design of the new building envisaged 26
new bel led caissons that were
supplemented by the reuse of 25
caissons from the USG foundation. The
new caissons were designed to bear on
hardpan approximately 10 ft (3 m) below
of existing foundation caissons to
supplement new caissons can be a
practical solution for redevelopment of
project sites that might otherwise be
restricted by extensive obstructions. In
addition to the cost savings in the
construction of the new building, the
reuse of the existing foundation and the
below grade wal ls enabled the
developer for 111 South Wacker to
qualify for green building credits under
the Leade r shi p in Ene r gy and
Environmental Design (LEED) program,
becoming the first building ever to be
certified LEED-CS Gold. The LEED
program, administered by the US Green
Building Council, seeks to promote
buildings that are environmentally
responsible, profitable and healthy
places to live and work.
The Results
From a sustainability point of view,
reuse of the caissons eliminated the
need to remove some 1,265cu yd (970 cu
m) of spoil, and subsequent placement
of the same quantity of concrete. This
eliminated the need for around 140
AUTHORS Darren Diehm, Nancy Straub and Bernard Hertlein, GEI Consultants
DEEP FOUNDATIONS * NOV/DEC 2022 * 73
This is equivalent to CO2 emissions from:
157,533
1,548,973
176
7.7
57,169
0.004
137,525
18.5
272
3,241
0.0004
170,299,705
gallons of gasoline
consumed
pounds of coal burned
homes' energy use
for one year
railcars' worth of
coal burned
propane cylinders used
for home barbeques
natural gas-fired power
plants in one year
gallons of diesel
consumed
tanker trucks'
worth of gasoline
homes' electricity use
for one year
barrels of oil consumed
coal-fired power plants
in one year
number of smart phones
charged
round- t r ips for t rucks haul ing
excavated spoil through downtown
Chicago, and a similar number of roundtrips
for concrete deliveries. The
DFI/EFFC Carbon Calculator estimates
that this resulted in an emission
reduction of some 540 tons (490 tonnes)
CO2 equivalent, which equals the CO2
emissions from consuming 12,378 gal
(56,300 L) of gasoline, or the annual
energy use of 14 homes. In reality the
emission reduction was even higher,
given the reuse of the concrete
basement walls.
November/December 2022

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