PDCA STEEL MEMBER – STEEL PROJECT
station. The cofferdam design required an excavation depth of
35 feet, with dimensions of 55 by 73 feet. In addition to maintaining
the open excavation, the cofferdam was to remain in
place and act as the exterior form for the lift station.
The project inside of the refinery posed many challenges
throughout the course of planning, mobilization and execution.
The cofferdam’s proposed footprint conflicted with the intersection
of three plant roads, a tank dike wall, elevated pipe racks,
underground storm drainage and difficult driving conditions
due to the extremely dry dense sand with some clay. Rainfall
totals in the months of April and May were measured at just
over an inch, making the soils even harder and drier than usual.
The scope of work for Cajun Industries included engineering,
design and construction of the permanent cofferdam shoring
system. As this project was schedule-driven, engineering was
called in early, during the proposal stage, to ensure that everything
would work as it should. However, construction could not
begin until specific permits were issued in late March 2018.
The planning stages of the cofferdam were as critical as the
actual construction. The proposed shoring structure had to
coincide with the lift station design and construction sequence.
Open lines of communication with all the parties involved
was the only way to achieve a successful project conclusion.
The excavation depth and large size of the cofferdam meant
the shoring system was subject to larger than average loads.
Traditionally, this would have been equalized by utilizing a system
of multiple waler and strut tiers with cross sections within
the cofferdam design. However, the project team suggested a
king pile system that utilized a heavy sheet pile profile coupled
with a large beam design. This design effort would reduce labor
and material costs, expedite scheduling and eliminate the
need for a multiple tier bracing system. The waler system was
designed by Cajun Engineering, however, Cajun reached out to
Nucor Skyline for their help with the engineering phase of the
king pile wall. Nucor Skyline has an in-house engineering and
Left: Start of cofferdam installation
Above: Completion of cofferdam shoring
drafting team and is able to assist customers with design needs,
taking into consideration cost, load and schedule/product
availability when implementing their designs.
After analyzing all constructability concerns and project
risks, the team decided that Nucor Skyline’s HZ 1080A beams
and AZ 28-700 sheet were the right choice for this cofferdam
project. The chosen material also aided in the constructability
of the civil aspect of this project by eliminating concrete
construction joints that require a multiple tier bracing system.
Nucor Skyline has a partnership with ArcelorMittal, the
only manufacturer of the HZ beam used in this configuration.
Because the material originated overseas, planning and communication
were the key to the success of this project. The
material was shipped from Europe to the Port of Mobile, Ala.,
where it was transported to a coating facility. The coated piles
then made their way to Texas City, Texas where they were delivered
in a specific order to keep the project flowing smoothly,
without taking up unnecessary space at the job site. This also
allowed the construction crew size on site to be kept to a minimum.
The single waler and strut tier was designed and fabricated
offsite to allow for speedy onsite assembly.
With a six-week lead time, the schedule was dependent upon
uninterrupted global shipping delivery. Nucor Skyline provided
the partners with real time updates on the material location
and delivery progress. Utilizing MarineTraffic.com satellite
tracking, the cargo ship’s actual location was shared with the
project team twice per week.
Traditional vibratory installation methods were chosen to
install the sheet pile and beams. Nucor Skyline worked with
Cajun Industries and International Construction Equipment
(ICE®) to oversee proper and frequent quality control checks
to prevent any tolerance issues. After one such check, Nucor
Skyline suggested that with the hard, dry clay soil conditions
at the site, the initial ICE 44 vibratory hammer was less
successful in driving the pile to depth. Instead, an ICE 66
80 | EDITION 5 2019 www.piledrivers.org
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