$1.8b road in Auckland poses safety risk to power station

The proposed East-west Link on the northern edge of the Mangere Inlet. Image / NZ Transport Agency

Plans for a $1.8 billion road through Auckland's industrial belt could trigger explosions and other safety issues at the Southdown power station, says Mercury Energy.

The safety risks were today outlined by Mercury's legal counsel, Rachel Devine, to a board of inquiry hearing submissions on the East-west Link, which will connect State Highway 1 at Sylvia Park with SH20 at Onehunga.

The mammoth roading project, costed at between $1.25b and $1.85b, also received strong backing today from the National Road Carriers, which represents 6000 truckies who use the route each day.

Devine said there were a number of safety risks from locating the road close to the power station, including disc failure and rotor end cap ruptures that could result in explosions and fast moving projectiles.

With diligent maintenance, she said there was a low, but not negligible, risk of this occurring during the generation of electricity. The risk increased if large numbers of road users, including pedestrians and cyclists, were near the station, she said.

Other risks included drivers being distracted by noise from the start-up of the power station and objects or vehicles falling from the elevated road on to the electricity and gas infrastructure at Southdown, Devine said.

"That's a nice hand grenade to throw around," board of inquiry chair Dr John Priestley said, "but what do you want us to do?"

She called for the project to be stopped for the NZ Transport Agency to understand the effects on Southdown and consider alternative routes.

Priestley asked Devine if there anywhere else on Mercury's Southdown site where the plant could be relocated safely.

"No," said Devine.

Devine said Mercury has told NZTA at senior levels that it wants to retain the option of restarting the decommissioned Southdown power station to support security of electricity supply for New Zealand.

Restarting the power station, including reconnecting to the gas network, would take three to four months. The construction of the East-west Link would add at least four months to the time with a negative impact on security of electricity supply, Devine said.

Alan Bickers, a member of the board of the inquiry, said the dilemma was balancing the nationally significant issues of transport and benefits arising from the East-west Link and the issue of the national grid and electricity supply.

NZTA Auckland highways manager Brett Gliddon said the agency has been working constructively with Mercury Energy since 2014 to ensure the design of the East-west Link responds to any potential impact on the decommissioned Mercury infrastructure.

"Earlier this year they raised new safety concerns. We are continuing to work with Mercury to gather information and evidence to ensure we provide a design that addresses their concerns and provides a safe and reliable new transport route," he said.

National Road Carriers (NRC) chief executive Grant Turner strongly supported NZTA's solution to traffic congestion in the Onehunga-Penrose area, saying it currently took 20 to 30 minutes to travel between Southdown and the motorway network when it should take less than 10 minutes.

The NRC is seeking a strategic road to allow the efficient and safe movement of 6000 trucks a day that currently use local roads and to keep pace with growth, saying freight in Auckland is forecast to increase about 6 per cent a year.

Earlier, Transpower, which operates the country's national grid, told the board of inquiry that it is "neutral" on the merits of the East-west Link.

It is one of the biggest roading projects in Auckland, costing between $1.25b and $1.85b.

Transpower's interest in the project was to ensure the national grid is not compromised, its counsel James Gardner-Hopkins said.

Some power lines will need to be relocated, towers will need to be replaced and some towers will be raised with possible visual effects, he said.

Gardner-Hopkins said Transport was confident that effects on the national grid will be minimised, saying the costs of any works will be met by NZTA.

Among the lines affected are the Henderson-Otahuhu line, which supplies 70 per cent of the transmission capacity across Auckland.

"Without this line, the existing peak load in Auckland and North Auckland could not be supplied," Gardner-Hopkins sad.

The project will also affect the Penrose-Mt Roskill line, which supplies one of three substations supplying power to central Auckland, and the Mangere-Roskill line, which supplies another substation that supplies part of the central city load and acts as a back-up to the CBD network.

Transpower's substation at Southdown, which supplies Auckland's electric rail network, is also affected.

Spark is also affected by the huge road project along the northern edge of the Mangere Inlet, telling the board of inquiry its Hamlin Hill and Otahuhu cellular sites need to be substantially reconfigured and relocated respectively.

Spark is not opposed to the project, its counsel Daniel Minhinnick said, provided there are appropriate reconfiguration and relocation of its assets, saying it was currently in negotiations with NZTA.

"These negotiations have not progressed to the point where Spark is comfortable that it can withdraw from the hearing process, which is disappointing from Spark's perspective," Minhinnick said.

The board of inquiry, chaired by retired High Court Judge Dr John Priestley, is set to run until August 25.

The board will release a draft decision on October 9. Following comments from submitters on minor or technical matters, the board is due to make a final decision on November 22.

Construction is expected to begin late next year and be completed by 2025.