Pier repairs not for fainthearted
Imagine a job that requires working at heights, in a tiny space, under the sea, where you can only escape by being reeled out by someone else.
That’s the kind of work required to fix the columns beneath the 300 metre-long New Brighton Pier, which were damaged in the 2010 and 2011 earthquakes.
The Christchurch City Council has commissioned Fulton Hogan to repair the pier by strengthening the columns underneath at a cost of $10 million.
But how do you repair the columns while waves are crashing around them?
Fulton Hogan is building 4m-wide casings, then burying them metres in the sand by using water jets to blast the sand on the seafloor away and lowering the casings as the sand resettles.
Project manager Hayden Sturzaker said it took time to work out.
‘‘The biggest challenge with that is, of course, access. To obtain access we’re required to install casings around each individual column. They’re assembled from the pier deck. Once they hit the seabed we fluidise the sand with high-pressure jets.
‘‘Imagine standing in the sand and sort of moving your feet and you settle – we’re just doing that with water under pressure. That’s what creates that turbulence and allows the casings to settle.’’
The casing is braced against the column with ‘‘spiders’’, or steel fixings, to keep the casing centred while being buried. The biggest casing, on the last column of the pier, is 12m long and will be buried 6m in the sand.
The workers then climb down into the casings and repair the damage. The columns will be designed to be rigid to a point and then flexible to enable them to shift during an earthquake.
‘‘We’re breaking out that damaged concrete, exposing the reinforcing, priming it and installing the 5m-long pile jacket,’’ Sturzaker said.
Workers who climb into the casings are trained to work in confined spaces and at heights. They also have access to a modern ‘‘canary in the mine’’.
‘‘We’re one of the first sites I believe in New Zealand to use bluetooth gas detectors, which means that the likes of us in the side office here can be alerted in the event that there is an issue with gas or an emergency down there – or they can push the panic button and alert us straight away.
‘‘This job should be no different from any other. Provided the controls are in place ... this should be no more dangerous than working on the road out there,’’ he said.
The pier project is expected to be completed by April next year.