Firm adept at solving complex problems

Firm adept at solving complex problems
The Pyramid Bridge project involved stretching a wire rope cable across the river using a ‘dead-man’ anchor comprising steel bridge piles buried six metres into the ground at each end

Reinstating a crucial water supply lost during a flood which also destroyed a road bridge required out-of-the-box thinking on the part of Fulton Hogan Southland’s team.
On February 2 2018 Pyramid Bridge spanning the Mataura River in rural Northern Southland collapsed late morning after a 50m section broke away during the flood, taking with it a pipeline which supplied 253 connections to a scheme for stock and household water
.Fulton Hogan Southland civil construction divisional manager Phil Fahey recalls getting a telephone call from the Gore District Council early the same evening asking for assistance.
“Without the water supply from the pipeline the water scheme only had six to seven days storage.”Restoration of the supply would require the pipe-line to be re-established along a 120 metre span over the river which was still in flood with nothing left to support it.
Phil’s suggested solution involved stretching a wire rope cable across the river using a ‘dead-man’ anchor comprising steel bridge piles buried six metres into the ground at each end.The cable would become the new support for 180mm diameter polyethylene pipe welded into a continuous length.
“Off-the-shelf” clamps would be used to support the piping on the cable.The concept was put to Gore District Council’s engineer who engaged Opus to develop it into a working solution during the weekend.
“We had all that set up with the clamps on with the cable attached and the pipe fixed to it in one big string 130 metres long, fixed to an excavator and then we got a helicopter and it lifted it across the river and attached it to another digger on the other side.”
The engineer’s design of the cable and pipe needed to determine how much tension the cable could safely handle and how much it would sag over the 130 metres, “We started the project pretty much on the Monday and we had the water supply reinstated the following Saturday morning in about five-and-a-half days.”
Fulton Hogan’s skills and resources were tested in different way in a major Southland project which had the benefit of considerable forward planning, the State Highway One realignment at Edendale.

Firm adept at solving complex problems
The 130 metre-long cable was lifted across the Mataura River by helicopter.

The $13.5 million, two year project halfway between Invercargill and Gore was designed to increase safety, with traffic diverted away from the local primary school and residential properties while eliminating two railway crossings and a 45km/h corner around the adjacent Fonterra site.
“It’s the biggest roading project in Southland of all time.”A key challenge was reinstalling an extensive piping system through a new 30 metre long concrete box culvert under the highway from Fonterra to its wastewater treatment plant.
The piping work could only be done over a two and a half month period during Fonterra’s winter shutdown, a task other industry insiders said could not be achieved and that would require a second winter to complete.
“That was a big part of the job. We got all the pipe work done in one winter and finished the job about six months early because of it.“Every other tenderer of the project said it was impossible.”
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