January/February 2023 - 80

the project in design
build, design assist,
value engineering and
or other necessary
preconstruction activities.
In 2018, Malcolm
Drilling Co., was
approved by the SFPUC
and brought on board as
the foundation core
trade partner.
The founda t i on
partner participated in
weekly meetings with
the CMGC, SFPUC and
the SFPUC's design
team to provide value engineering on
several major scopes of work. It
proposed continuous flight auger (CFA)
piles at certain structures, in lieu of the
more traditional drilled shafts, which
brought immediate schedule and cost
savings to the project. In order to verify
the capacities of the CFA piles and
drilled shafts, the team performed an
early-work onsite load test program,
which gave the SFPUC design team
confidence in the pile foundation
selection.
Malcolm also provided guidance on
the selection of temporary shoring
systems to be utilized at the two major
excavations (Facility 610 and Facility
600). Several cutter soil mix (CSM)
shoring wall options utilizing deep soil
mixing or even jet grouting plugs, as well
as deeper secant pile walls, were
considered. Initially, a 70 ft (21 m) deep
CSM shoring wall was envisioned for
both excavations, however after
reviewing the available geotechnical
information it was uncertain if the wall
would be deep enough at the Facility 610
to provide effective groundwater cut-off.
As part of another early-work onsite test
program, the foundation team installed
and performed a pump test program to
provide the design team with more
information about the groundwater
conditions. It was discovered that two
underground aquifers (one at 40-60 ft
[12-18 m] below grade and another at
80-100 ft [24-30 m] below grade) were
80 * DEEP FOUNDATIONS * JAN/FEB 2023
Shoring system with the excavation at full depth at Facility 610
Due to the close
p r o x imi t y o f t wo
nearby active railroad
lines, the project could
not utilize a shoring
system that might
allow uncontrollable
drawdown outside the
shored excavat ion.
Options for a drilled
secant shoring wall
a n d a t emp o r a r y
diaphragm shoring
wall were evaluated
since they could both
reach greater depths
connected and that a 70 ft (21m) deep
CSM wall would not provide an effective
cutoff to control groundwater drawdown
outside the excavation.
than the CSM wall option. Ultimately, a
temporary diaphragm shoring wall was
selected for the shoring system at
Facility 610 due to the faster install
Level three tieback drilling

January/February 2023

Table of Contents for the Digital Edition of January/February 2023

TOC
January/February 2023 - Intro
January/February 2023 - 1
January/February 2023 - 2
January/February 2023 - TOC
January/February 2023 - 4
January/February 2023 - 5
January/February 2023 - 6
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