Contractors watch concrete being poured into a structure
beneath the ocean as construction of the Tahuna sewage
outfall pipe continues. Photo by Craig Baxter.
It sounds impossible: Take enough concrete to pour the
bases of eight family homes, pump it 250m and fill a large hole
9m below the surface of the Pacific Ocean.
But contractors working on the Dunedin City Council Tahuna
sewage outfall pipe did just that successfully yesterday.
Specialist staff from AAA Concrete Pumping were brought in
from Marlborough and Queenstown to pump 190 cubic metres of
concrete along the length of the construction pier and into
an underwater steel structure.
The resulting concrete block will securely hold in place two
outfall pipes - an underground pipe laid from the Tahuna
sewage treatment works and a 1km long marine pipe - to enable
a short joiner pipe to be placed between them.
It was important to "hold things together", council project
manager Brian Turner said yesterday.
"The pipes will join approximately 9m below the surface and
5m below the seabed, so this is the most critical area to get
right."
Pumping began at 7am and was finished by 2pm.
The job was the most challenging AAA Concrete Pumping had
attempted, administration manager Paula O'Donnell said
yesterday.
"The distance was the farthest we have ever done . . . What
the guys did takes a lot of skill, but it all went very
smoothly."
The $37 million pipe project has been delayed by rough
weather, but Mr Turner said pressure testing was expected to
take place next month, with the pipe expected to be
commissioned in December.
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