Feature

Wasps and other challenges

The Midland Line dodged a bullet from New Zealand’s biggest-ever earthquake – the South Island Main Trunk didn’t – but copped a beating from other natural hazards. Hugh de Lacy with the story.

THERE WAS NO BIRDSONG in what was left of the beech forest after the fire that damaged five KiwiRail bridges on the Midland Line, but the wasps survived in their droves.

Indeed, so bad was the plague of wasps during the reconstruction of the bridges between Cass and Springfield in February this year that insect traps had to be sited at either end of each bridge to provide some protection for the workers.

Even so, none of them escaped without wasp stings during the six weeks it took to reopen the line across the centre of the South Island after a huge fire destroyed 300 hectares of the surrounding bush.

No one knows what started the fire that broke out on February 3 and took three days to put out, but by the time exhausted fire crews had got it under control, it had damaged six of the Midland Line’s bridges.

The biggest problem both for the firefighters and the KiwiRail and contracting staff trying to effect repairs was the difficulty of access.

At Springfield the railway line diverges from SH73, heading north and hugging the south bank of the Waimakariri River while the road goes west, and the two don’t meet up again until Cass, 60-odd road kilometres west.

That meant firefighters and bridge repairers alike had to get across the Craigieburn State Forest Park and farmland to reach the centre of the blaze and the worst-damaged bridge, Number 25, known as Truscotts Bridge.

“A track was there but all the corners had to be widened to get the machinery around,” KiwiRail South Island networks manager Jeanine Benson tells Contractor.

“That would get us into Broken River, then to get to Truscotts we had to open up a four kilometre track, and that took seven days.”

A crane loaded on to a rail wagon for transport to the site.

The five-span Bridge 25 over Truscotts Stream was the worst damaged, but to get access to it for cranes on rolling stock, Bridge 26 over Rocky Stream had first to be temporarily repaired, having suffered major damage to sleepers, outriggers and footwalks.

Truscotts Bridge was built in 1905 and re-built in 1963, but the fire left two of the piles on pier one, four on pier two and six on pier three so badly burned that the bridge was actually sagging.

The fire had spared the intermediate bridges 21, 23 and 24, and Christchurch company Smith Crane and Construction was engaged to rail in three cranes – a 150, a 90 and a 16-tonner – for the reconstruction.

Southern Lakes Scaffold, which has bases in Central Otago and Christchurch, was brought in to handle the scaffolding, while KiwiRail staff were assembled from Tauranga, Invercargill, Christchurch and Greymouth.

The KiwiRail team was led by Aucklander Richard Hattaway as project manager, with the help of Brodie Neville and Phil McVicar.

Bridge 27 at Broken River suffered less damage from the fire fanned by fierce nor-west winds, but some sleepers and a windbreak had to be replaced.

Bridge 22 was just a low bridge but required the replacement of 30 sleepers.

The eastern-most Bridge 19 is a viaduct known as The Staircase, a formidable structure often photographed from the Waimakariri River by jetboat tourists, and major damage occurred there requiring the replacement of a fifth of the sleepers, as well as repairs to windbreaks, footwalks and inspection walkways.

To create a site office from which the repairs could be directed, KiwiRail opened up a previously disused signalling shed at Springfield, stocked it with desks and computers, and had the local Springfield Cafe supply lunches for staff whose numbers at times exceeded 60.

The old depot also became a conference room for the daily safety briefings before everyone moved out to the work-sites.

It further served as the place where staff compared wasp-stings. Despite the traps at either end of the bridges, everyone got stung at some stage, heightening their awareness of the damage German wasps are doing – by gobbling up the honey dew on the beech trees – to the bird population.

“The critical path was to get to Bridge 25 and replace the 15 burned piles there, so we could move on to 26 and 27,” Jeanine Benson says.

The cranes had to be loaded onto the rail wagons at Bridge 27 near Broken River, which is why Bridge 26 had to be temporarily repaired to give the cranes access to Bridge 25.

Getting the cranes onto the rail wagons was a major task in itself, involving hoisting them up onto chocks high enough for the wagons to be rolled in underneath.

But for three days staff had to sit twiddling their thumbs while they waited for the Fire Service to bring the blaze under control.

Whatever caused the fire – and that’s still under investigation – it could scarcely have come at a more damaging time for KiwiRail.

While miraculously the entire Midland Line emerged unscathed from the 7.8 magnitude Kaikoura earthquake in November which closed the Main Trunk between Kaikoura and Picton (it remains closed but could be functional again by Christmas). The fire occurred when a huge slip near Otira on the western side of the Southern Alps had only just been cleared.

The slip occurred in January and took a week to clear at a time when coal, milk and the TranzAlpine tourist traffic on the line was at its busiest.

To try and salvage some of the damage from the lost tourist trade, KiwiRail meanwhile ran a shortened version of its highly popular tourist trip, going from Christchurch to Arthur’s Pass and back.

The line had been open again for just 10 days before the fire closed it for a further six weeks, until March 20, lumping KiwiRail with a massive hit from the lost tourist trade alone, which is worth $15 million annually to the region.

Milk and coal had, in the meantime, to be transported by road.

Jeanine says the three-day wait to get started proved useful because “a lot of heavy thinking was required on how to tackle the situation”, and the decision to target Bridge 25 first proved the correct one.

She declines to reveal how much the fire cost KiwiRail in repairs and lost business, but says the company was grateful to state-owned collier Solid Energy and the Hokitika-based dairy co-operative Westland Milk, which supply the bulk of the freight carried on the Midland Line, for their understanding and patience.

Nobody, however, is thanking the wasps for their contribution.

Southern Lakes Scaffold, which has bases in Central Otago and Christchurch, was brought in to handle the scaffolding, while KiwiRail staff were assembled from Tauranga, Invercargill, Christchurch and Greymouth. 
This article first appeared in Contractor July 2017.

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