Third container berth a major undertaking for Deltaport Constructors

  


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24 Oct 2010

conteiner_maersk1234_thumb.jpgTackling Deltaport’s third container berth, a $204 million project, involved meeting a number of major challenges head on. “The scope of the job was large, the quantities were large and the resources needed to complete the job were large,” said project manager Dave Basnett of Deltaport Constructors Ltd. (DCL), a joint-venture between Vancouver Pile Driving and Graham Construction.





The successful completion of the contract – a month before the original
deadline, which was thought unachievable – has earned DCL a VRCA Silver
Award in the projects over $40 million category.

The project consisted of three main elements. The contractor had to
install a third berth measuring 430m long to handle container ships,
create a 22-hectare dock space on the land side of the berth and
install a new tug harbor for the vessels stationed at Deltaport.

“When the contract was awarded in December 2006, we were in the middle
of a construction boom and everyone was going flat out. We thought the
biggest challenge would be putting together the people and equipment,”
said Basnett.

However, by working with the unions and making their needs known, the
two joint-venture partners handled the workload for the first two
years.

“We had up to nine floating cranes ranging from l00 tons to 350 tons on
the job and about half of them were working double shift and so getting
enough crews to operate these machines for long periods was a
challenge,” he said.

The underwater foundation for the new berth required a million tons of
crushed gravel to be compacted into a solid base. This took nine months
using large floating cranes equipped with poker vibrators called
vibroflots to achieve the densification required, said Basnett.

DCL’s operators made use of a GPS system to ensure the vibroflots
probed the gravel consistently. The GPS aerials were fixed to the crane
booms and the operators were able to monitor the precise probing
locations on computer screens mounted in their cabs.

“It was like playing a video game. It worked beautifully for the
densification and all the other underwater construction,” he said.

Confirming the foundation’s density was another challenge. Becker
Penetration Tests were used. Testing entailed driving a closed-ended
pipe into the gravel with a small pile hammer and recording the number
of blows to penetrate each foot.

The berth’s construction consisted of 10 caissons placed in line on the compacted mat of gravel.

Each concrete caisson, cast in North Vancouver, measured 15m (49 feet)
in width, 42m (137 feet in length) by 21m (68 feet) in height and
weighed 6,100 tons.

They were towed to the site and sank in a storage area on the seabed, ready for final placement later.

The caisson tops were visible at high-tide.

However, in November 2007, a severe storm hit with pounding waves
causing seven of the 10 caissons to dig themselves 18-20 feet into the
sand.

The caissons became only visible at low tide and all were tilted. Two
had bashed into one another causing damage that had to be repaired
using difficult under water techniques.

“Recovery of the caissons was a huge contract in itself,” recalled Basnett.

Once recovered, the caissons were moved into place and settled with a
falling tide onto the foundation. A survey confirmed their positions
and they were filled with water and later with gravel.

Maneuvering and sinking the 6,100-ton caissons accurately into position was described as part science and part art.

Exacting environmental requirements were in place throughout the project.

For example, the PH of the seawater was monitored at a depth of 60 feet, while concrete was poured underwater.

“This was to ensure we did not compromise the marine habitat and affect
fish. It was certainly the most environmentally sensitive project I
have worked on,” he said.

At the new dock area, silt curtains were deployed to prevent material
from entering the water. About 85 per cent of the project is now
underwater and out of sight.

The project’s success was credited to the strong VanPile/Graham management team.

“It was intentionally an integrated supervisory staff with people in
key positions from both companies. Co-operation between the two groups
was excellent,” he said.

Deltaport Constructors will wind down as the final paperwork is completed.



Source: Journal of Commerce

Sources:  www.Shipid.com

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