St Helena : St Helena: RESURFACING OF MIDDLE WHARF
Submitted by Saint Helena Herald (Public Relations Information Office) 19.05.2013 (Article Archived on 02.06.2013)
The Middle Wharf Resurfacing Project is now entering its final few weeks and on completion will provide a new, structurally sound, safe and well engineered improvement to the wharf infrastructure.
The Middle Wharf Resurfacing Project is now entering its final few weeks
and on completion will provide a new, structurally sound, safe and well
engineered improvement to the wharf infrastructure.
The levels for the new surface have been conditioned by the need to
preserve the wharf wall, which was found to be undermined by sea water and to
be in a poor structural condition. In
the past, concrete had been poured against the wharf wall to provide it with
extra stability, and so to remove this concrete would have been to risk a
serious structural failure of the wall necessitating its reconstruction. As a
result, the levels for new wharf surface were set out to create a fall of two
degrees from the wharf buildings to the wall, without removing the concrete.
The concrete slab poured for the new surface is a Continuous Reinforced
Concrete Slab (CRCP) which is specifically designed to carry the huge loads
that will bear on it from the Container Stacker and on occasion from the
cranes. The Container Stacker will
regularly role over the slab, imposing a load upon it of over 100 tonnes. This weight is distributed across two axles
creating the potential for huge point loads to be imposed on four different
concrete panels at once. It was therefore necessary to ensure that the slabs
could not act independently from one another. The type of joint between
concrete panels that enables this independent action is called an Isolation
Joint, and this kind of joint is being employed in the new concrete surface by
the Bastion, adjacent to the Customs Terminal Building. It is appropriate to use this structural
design for this part of the work, as the concrete is not required to carry huge
All of the
longitudinal and transverse joints will be filled with an expansion material
which will allow for shrinkage, expansion, contraction and curling of the
concrete slabs, thus minimising cracking and spalling of edges. These joints
will be sealed with a Dowcorning 888 joint sealant which will prevent water
getting into the joint and causing the rebar to rust, and will also prevent
water getting into the road structure which is the main contributor to
settlement, rutting or cracking of the concrete slabs.
The surface texture
of the middle wharf section has been made to retain a good level of grip to
vehicles, particularly when the surface is wet. This surface will wear down
considerably with time through regular use, and it is also in consideration of
this wear that the surface has been so textured. A smooth surfaced walkway will
provide safe foot access along the front of the wharf buildings, and this will
feature any necessary ground drainage to prevent the ingress of sea and rain
water into the buildings.
All of the exposed
services, including the water and electricity pipes and cables, have been
provided with ducts and access culverts enabling better maintenance and making
the wharf a much safer place for people to work in and enjoy leisure hours. The high voltage electricity cable currently
hanging across the front of the Yacht Club will be removed and placed in a new
The bio-hazard of
“black water” - otherwise known as raw-sewage - which has been passing into the
bay from the Yacht Club WC, will now pass into a two thousand litre septic
tank, thus making the bay a cleaner and safer place to dive and swim.
The wharf wall will
be provided with a new handrail to match the existing handrails and to provide
a guarded height of 1.1 metres from the finished road level. As a result, the
middle wharf will be the only part of the whole wharf with a handrail set at
the correct regulation height for public safety.
The works are
scheduled to be completed within the next four weeks and will be completed
ahead of schedule.
6 May 2013