March/April 2024 - 17

They were drilled anywhere between 35-60 ft (11-18 m) into
the ground, depending on the subsurface conditions, each
bearing a design load of 253 kip (1,125 kN). Due to the weight
of the bars and access at the top of the mountain, all
reinforcing bars were lowered into the drill hole by helicopter.
To construct the top station, more than 500 cu yd (380 m3) of
Concrete pours by helicopter
This critical step paved the way for subsequent
construction phases, breaking up the rock to allow for easier
handling of the material.
Top Terminal Construction:
Helicopter Ballet in Concrete
The top terminal's foundation comprises 17 micropiles for
axial support of the station and 6 tiebacks to resist
overturning. All the tiebacks and micropiles were constructed
with 6 in (150 mm) diameter holes and reinforced with
Williams Form 2.25 in (57 mm) Gr. 150 galvanized center bars.
concrete, poured via helicopter, formed the robust foundation.
All concrete for the project was flown to the top of the mountain
in 0.5-0.75 cu yd (0.4-0.6 m3) buckets. Due to this limitation, all
concrete pours had to be broken down into smaller sections
and completed during clear weather windows. The maximum
amount of concrete poured in a single day was 80 cu yd (60 m3).
Any pour that was over a volume of 40 cu yd (30 m3) typically
required the work of two helicopters - usually consisting of a
Bell UH-1 " Huey " and a UH-60 Blackhawk. Concrete trucks
were staged further down the mountain, and the turn-around
time per trip during a concrete pour was around five minutes.
Complex formwork added an extra layer of intricacy to this
high-altitude ballet of construction.
Tower Footing Construction:
Anchoring the Heights
The lone tower on the span, standing tall at 100 ft (30 m), was
located about 600 vertical ft (182 m) below the top terminal
location. While this does not sound very substantial, it
required a rope descent down the mountain and ended with a
vertical repel down into the tower footing location. A rigorous
hike up and down the mountain, paired with the intense
elevation, tested the crew members' cardio.
Tower worksite
DEEP FOUNDATIONS * MAR/APR 2024 * 17

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Table of Contents for the Digital Edition of March/April 2024

TOC
March/April 2024 - Intro
March/April 2024 - 1
March/April 2024 - 2
March/April 2024 - TOC
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