Auckland's being shafted but it's all in a good cause.
A temporary shaft to gain access underground to create the new Karangahape Rd railway station has been dug down a vast 17m on the former Mercury Plaza site and will next week reach the maximum depth of 20m.
Dale Burtenshaw, Link Alliance deputy project director for the $4.4 billion City Rail Link, said today good progress had been made on the 15m-diameter shaft beside Mercury Lane and the Mercury Theatre.
Above that shaft, a temporary noise shelter half the size of a rugby field is being built to enable tunnelling work to run 24 hours a day.
That enclosure, now clearly visible from the Southern Motorway or State Highway 1, is 45m by 30m, built directly above the temporary access shaft in steel, now being clad and roofed.
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The noise shed or shelter is part of a project-wide approach to minimising sound from the worksites. The structure resembles an aircraft hangar and will house a 50-tonne overhead gantry crane, ventilation units for the mined tunnels and generators.
Throughout the night, the gantry crane will bring excavated soil above ground for stockpiling inside the new shed. The next day, this material will be trucked for grading offsite.
Burtenshaw said soil from the shaft found to be suitable was being trucked to the former Three Kings Quarry in Mt Eden where Fletcher is developing residences. The spoil is partly filling that old quarry.
Cam Butcher, tunnel manager who works for Link Alliance member Soletanche Bachy, said from the Mercury site: "This shaft will be finished next week."
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Shaft construction began in March just before the alert level 4 lockdown so work was suspended for the weeks that lasted.
The first 6m of soil dug from the ground was the relatively soft East Coast Bays formation, then harder ground, he said.
"Twelve people are directly involved in building the shaft but many more are working behind the scenes - designers, engineering team, etc," Butcher said.
The first 11m of the shaft is lined with sheet piles and the rest sprayed shotcrete, pneumatically projected at high velocity on to the surface.
"From this temporary access shaft, we'll then begin building the mine tunnel and there will be 60 people involved in that."
That is essentially the start of creating the new station, which will be accessed from Beresford Square and Mercury. The station platform will be 250m long or a quarter of a kilometre.
The mine tunnel will run 16m beneath the George Courts Building on the Karangahape Rd/Mercury Lane corner. Monitoring stations around the site will ensure there is no disturbance from digging the tunnels.
About next April, tunnel boring machine Dame Whina Cooper will be launched from Mt Eden, dig underground to the new K Rd Station then advance to the Aotea Station. There, she will meet the cut-and-cover sections of the tunnel already built from the old Central Post Office, beneath the new $1b Commercial Bay and up Albert St.
The TBM will then be craned from beneath the new Aotea Station and trucked back across the city in sections to be reassembled once again at the Mt Eden portal.
From there, she will be launched a second time to dig the second parallel rail tunnel, boring in the same direction from Mt Eden to the CBD.
Butcher has been working on the Sydney Metro tunnel job but has also worked on major civil works projects in Indonesia, Doha, Singapore and Sydney.
"I flew back and forth from here but obviously I can't do that any longer," he said referring to travel restrictions.
Some of the 60 people who will descend the new shaft and begin building the mine tunnel have also worked on the same Sydney rail project, he said.
The CRL is due to be finished in 2024 and double the city's rail network capacity to enable up to 54,000 passengers an hour. The 250m-long underground platforms will cater for longer, nine-carriage trains.
Karangahape will be the CRL's deepest station at around 40m below ground.