Tackling Deltaport’s third container berth, a $204 million project, involved meeting a number of major challenges head on.
FEATURE | VRCA Awards
Tackling 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.
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