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Hall Pacific Rebuilds Borrow Pits Left from WWII; Aid Project Wins Award

Hall Contracted used its cutter suction dredge Amity for an aid project, through the New Zealand government, at Tuvalu, a small Pacific Island country.

Hall Contracted used its cutter suction dredge Amity for an aid project, through the New Zealand government, at Tuvalu, a small Pacific Island country.

The aid project rebuilt borrow pits left from WWII, when U.S. Marines built an airstrip and Navy base, leaving huge plots of excavated land.

Hall Pacific won an award for the 2016 Innovate Awards of Excellence, held in New Zealand in September. The dredging and civil construction company, wholly owned by Hall Contracting of Australia, worked in conjunction with New Zealand’s Calibre Consulting on an aid project in Tuvalu, a small island country, located approximately halfway between Australia and Hawaii.

The awards recognize excellence in engineering and consulting, and Hall Pacific’s winning project involved removing more than 250,000 cubic meters of sand from a local lagoon and used it to fill man-man pits in the porous coral atoll.

The atoll is a thin strip of land, no wider than 300 feet in most places, with a large natural la-goon on one side and deep ocean on the other. It is home to some 10,000 people. During World War II, U.S. Marine Corps landed at Funafuti atoll and constructed an airstrip and navy base. This was used to stop the advance of Japanese forces, which had made it to Tarawa a couple hundred miles north.

The land excavated to provide fill for the air-strip left open area some 150-feet wide and many more than 1,000 feet long, which filled and emptied with the tide.

“This took away much of the usable land on Funafuti and many residents built pole houses over the borrow pits. With stagnant water, pig and human waste in the pits, they became a source of disease and infection,” said Cameron Hall, managing director, Hall Pacific.

With a densely populated area, the local community could desperately use additional land, and the project increased the land space on the island by six percent.

In 2014, the New Zealand government aid program put out an international tender for early contractor involvement in the design and construction of the remediation of these borrow pits. 

“Hall Contracting won this tender and worked with Calibre Consulting Engineers from Wellington, New Zealand, to come up with a solution to dredge sand from the lagoon and fill these pits back to their natural state,” Hall said.

The pig and human waste collecting in the pits was infiltrating through the floor of the borrow pits and into the lagoon, creating algae blooms, which killed the coral. Fish that feed off the corals were also disappearing as a result.

To dredge the lagoon and fill the borrow pits, Hall Pacific used its 24-inch cutter suction dredge Amity to dredge clean sand from up to 15-meter depth in the lagoon and pump it to the pits ashore. “Tailwater from the dredging was disposed of on the ocean side of the atoll, though in most cases the water simply infiltrated through the floor of the borrow pits,” Hall said.

A 180-foot barge, three excavators, a Poritrack mini loader, a wheel loader and three trucks accompanied the dredge Amity on the project. The company worked six months on the $7 million aid project.

During a tropical cyclone a number of years ago, a breach in the northern part of the atoll had also occurred. The Pacific Ocean swells breached the island and threatened the cut off the northern part of the atoll from the main population center. Hall Contracting also worked to repair this breach.

Tuvalu is also one of the lowest lying nations, making it particularly vulnerable to rising sea levels, severe storm systems and coastal erosion.

“As there is no rock on the atoll and very little in the way of coral boulders, the wall was constructed using 5-tonne Elcorock sand bags, a product made in Australia. Hundreds of these bags were stacked to reconstruct the ‘storm ridge’ slope,” Hall said.

Late last year, Hall Pacific also completed the design and construction of a seawall on Tuvalu’s Nukufetau atoll, helping to further protect the island from the impacts of climate change. Nukufetau is 60 nautical miles north of Funafuti and in only accessible by boat. Tropical Cyclone Pam in 2015 devastated the area. Again, Hall used an Elcorock sand bag wall to rebuild the area. 

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