Home' Infrastructure Australia : Infrastructure Australia 2011 Contents 44 INFRASTRUCTURE AUSTRALIA APRIL 2011
Remediating wharf tie rods
East Arm set to expand
The environmental impact assessment for the expan-
sion of the Northern Territory s major port facility
is expected to be released this month.
Darwin Port Corporation said there are increas-
ing demands on wharf infrastructure as well as identi ed
future requirements from major Darwin industries, including
the Department of Defence and the oil and gas industry.
e Northern Territory Department of Lands and Planning,
Darwin Port Corporation and the Department of the Chief
Minister are jointly managing plans for the staged expansion
of East Arm Wharf.
URS Australia has been engaged to develop the dra En-
vironmental Impact Statement and Supplement as part of the
environmental impact assessment process.
Darwin Port Corporation said: " e East Arm Wharf
Expansion project will deliver the infrastructure necessary
to manage increasing freight numbers -- including expanded
storage, berth and rail facilities.
" e project will also see the development of a speci c
marine supply base to service the growing o shore oil and
Speci cally, the East Arm Wharf expansion includes a ramp
and hardstand for the commercial barge operations and De-
fence logistics requirements; a marine supply base to service
o shore exploration, development and operations; extension
of the East Arm Wharf quay line and construction of tug
boat berths; and new rail infrastructure providing access to a
proposed new stockpile area.
Work is due to start on the
remediation of structural
tie bars on the Northern
Territory s major import/
export facility East Arm Wharf.
Located a short drive from Darwin s
CBD, the port caters for Panamax Class
and third generation container vessels,
and has a terminal with a capacity to
handle 250,000 containers (TEU) per
year. East Arm Port Stage 1 (EAP1) was
designed and constructed by a consortium
of Barclay Mowlem, iess and Westham
Dredging and handed over to Darwin Port
Corporation in December 1999.
e EAP1 structure consists of a sheet
piled wall tied back to concrete deadmen
with 201 pairs of lower level tie bars. e
lower tie bars are in the tidal zone -- 5m
below the wharf deck. Since June 2005, 16
of these lower bars have been discovered
to have failed. e ship mooring bollards
are anchored by 78 upper level tie bars
which also maintain the crane rail gauge.
e upper tie bars are just over 1m below
the wharf deck and one of these upper
bars has also failed.
Darwin Port Corporation said the bar
failures have occurred behind the concrete
capping beam where the seaward ends of
the bars have bent due to the settlement
of the ll over time.
"The tie rods are being remediated
because there is a risk that many more tie
rods may fail in the future as the wharf
ages," Darwin Port Corporation said. " e
corporation, advised by the Northern Ter-
ritory Department of Construction and
Infrastructure, is taking a conservative
approach to wharf safety since the rst
failed tie rod was discovered."
Late last year the Northern Territory
government nalised an agreement with
the Barclay Mowlem (now trading as
Laing O Rourke)/ iess joint venture to
replace all lower and upper tie bars of
East Arm Wharf Stage 1. e project was
deemed necessary to ensure the ongoing
safety and structural stability of the struc-
ture. e joint venture will now replace
all lower and upper tie bars at the joint
venture s own cost, with a contribution
by the territory government.
Before commencing the main remedial
works, the joint venture will conduct an
engineering trial to prove the e ective-
ness of the proposed excavation method
to access the tie bars for remedial works.
is will involve excavation down to
the level of the lower tie bars, which are
installed in pairs, cutting one bar, drilling
a new hole through the concrete capping
beam and inserting a new length of bar
which is then welded to the landward end
of the existing bar.
e bar is locked o with a nut on the
wharf face, and the procedure is repeated
with the second bar. As the upper bars
are closer to the surface, they will be
excavated by trenching back to a central
coupler and then, rather than welding, a
new section of bar will be attached to the
coupler. e excavations will be back lled
On completion of the works, new
stormwater drains will be installed to
collect water from the whole of the EAP1
pavement, and a new asphalt pavement
will be laid over the whole area that has
been excavated. The joint venture has
scheduled to work 10 days on and four
days o , with 24 hour work days. e main
work is expected to take 18 months with
completion expected in January 2013.
e Northern Territory Department of
Construction and Infrastructure will be
supervising the works.
The East Arm Wharf in Darwin is about to undergo rehabilitation to ensure wharf safety.
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