July/August 2023 - 25

DFI 2023 Outstanding
Project Award Winner:
Climate Pledge Arena
D F I A C T I V I T I E S
OPA Winning Project by Thornton Tomasetti
Every year, DFI recognizes the superior
work performed by its members on project
aspects related to geotechnical work,
deep excavations and deep foundations.
This year's Outstanding Project Award is
the Climate Pledge Arena in Seattle, submitted
by Thornton Tomasetti.
A presentation on the project is
being delivered and the award is being
presented at DFI's 48th Annual
Conference on Deep Foundations in
Seattle, October 31-November 3.
The historic Key Arena has undergone
a major transformation, and is
now known as the Climate Pledge
Arena and the new home of the Seattle
Kraken NHL team. The $930 million
renovation and expansion project
required near-total demolition of the
old structure and construction of a new
one, all while keeping its landmarked
façade intact and 44 million lb
(20 million kg) roof supported above.
The steel and concrete structure was
constructed in 1961, and the Seattle
Landmarks Preservation Board classified
Key Arena as a local landmark in
2017. This distinction requires that the
roof, curtain wall and exterior concrete
elements be preserved as part of the
renovation with virtually zero impacts to
their aesthetics. The central challenge of
the renovation project became how to
support the existing roof while work
continued below it.
Its 65 ft (20 m) deep perimeter foundation
wall system presented many
challenges. Because of the need for an
open arena and numerous slab openings,
the interior floor slab diaphragm
could not be used to brace the new foundation
walls. Instead, the engineer
selected permanent tiebacks as the wall
support for the perimeter wall system
including a slurry wall, secant piles, soil
nails and a permanent soldier pile and
lagging system. And the design team had
to rely on virtual imaging to identify
and resolve potential conflicts in the
complex tangle of tiebacks required to
support the walls.
In all, the system included more
than 650 soldier piles, each of which
had to be installed in a predrilled 30 in
(760 mm) diameter borehole and
grouted in place. To support the walls
there were 2,400 tiebacks with a total
drilled and installed length of 130,000 lft
(40,000 m). Finally, an earth retention
wall allowed for
680,000 cu yd (520,000 m3) of soil.
This project ranks among the largest
Thornton Tomasetti has designed. Look
for a detailed feature article on the
Climate Pledge Arena in the September/
October issue of Deep Foundations
magazine.
OPA honorable mentions include
1&9T-New Road, Jersey City, New Jersey
(Menard USA); ALCOSAN North End
Expansion, Allegheny County, Pennsylvania
(Richard Goettle); East St. Louis
Deep Cutoff Wall, Illinois (Bauer Foundation);
Milken Center for Advancing the
American Dream, Washington, D.C.
(Berkel & Company Contractors).
DEEP FOUNDATIONS * JULY/AUG 2023 * 25
the excavation of
July/August 2023

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