January/February 2023 - 84

Rebar cage installation in tandem with slurry wall excavation
Quality control of the concrete mix
design is a critical factor for the slurry
diaphragm wall system. An extensive
preproduction trial batch program was
implemented prior to mobilization for
this project to develop a mix with local
suppliers that met the required design
strengths and workability parameters.
During construction, continuous testing
of the delivered concrete for flow, flow
retention and segregation following the
EFFC-DFI Guide for Tremie Concrete
was implemented prior to the concrete
going in the ground.
Conclusions
The early involvement of a core trade
subcontractor proves successful to the
design and construction of mega
infrastructures that are complex and
require intensive coordination between
owner, CMGC, design team and
contractors to overcome the many
challenges a project like this presents.
In 2018 and 2019, the foundation
partner spent many hours traveling to,
and attending, in-person meetings with
the design team and the CMGC, which
84 * DEEP FOUNDATIONS * JAN/FEB 2023
were indeed necessary. With online
meetings so commonplace now, this
collaboration process only became
more efficient as the project progressed.
For this megaproject, not only did the
foundation team deploy nearly every
type of drilling method in its arsenal, but
also undertook many scopes that
normally the general contractor
handles. In addition, the foundation
partner had to meet a local small
business hiring goal for the project,
which essentially meant that any
subcontractor hired had to be a small
business based in San Francisco.
Through community outreach meetings,
and partnering with local companies,
the team successfully found and managed
multiple local subcontractors for
the following scopes of work: excavation,
spoil off-haul/disposal, rebar
cage fabrication, surveying, site security
and dust control.
Many valuable lessons were learned
on this project and while they don't
come around often, Malcolm and
Brierley are well suited to take on the
next future challenging megaproject.
Acknowledgements
The authors would like to acknowledge
the following organizations who
were involved with the project and
whose collaboration was valuable
throughout design and construction:
SFPUC, the SFPUC design team and the
MWH/Webcor JV
Robert Small, P.E., served as the lead project
manager for Malcolm Drilling on this
megaproject. He has been with Malcolm for
more than 14 years and is currently the
assistant district manager in Malcolm's
Northern California office.
Ihab Allam, P.E., is the director of slurry
wall operations for Malcolm Drilling. He has
mo re than 23 years of expe ri ence
constructing diaphragm walls and deep
foundations across the U.S. and worldwide.
Amshu Chappa, P.E., is a geostructural
engineer at Brierley Associates. She has more
than 10 years of experience in the heavy civil
industry, which includes design of excavation
shoring, deep foundations and various
contractor support functions.
January/February 2023

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