Twenty-five manholes costing $1.3 million to replace mark the start of the huge repair bills ratepayers face in bringing the botched Marsden City development up to spec.

While Whangarei District Council is in court trying to recoup about $8 million from the companies it says are responsible for signing off the faulty infrastructure, it had also let the first major contracts to repair the development's slumping pipe network. Two contracts totalling $1.3 million would cover the replacement of the 25 manholes at risk of imminent failure, WDC waste and drainage manager Andrew Carvell said.

"These manholes looked like they were going to have immediate issues, so that's what we decided, to fix them first," he said.

All up, there were "130-odd" manholes across the 83-ha site, Mr Carvell said.


The story behind the once-hyped Marsden City development, which promised 2200 homes alongside new businesses and industry, soured in April 2014 when it was revealed that sections of the waste and stormwater systems vested to the council had failed and would cost ratepayers millions to repair.

The unforeseen effects of acid sulphate soils were to blame, the council said, and it now had a new process for assessing the risk from this type of soil.

The 83-hectare Marsden City development has been on the market since late last year. Photo / Michael Cunningham
The 83-hectare Marsden City development has been on the market since late last year. Photo / Michael Cunningham

"We suspect this occurs elsewhere, so we now have a process in place ... to avoid this happening again," Mr Carvell said.

The council was also reviewing its engineering standards, which in future would likely include commentary around acid soils.

An original estimate of $5.4 million to bring at-risk networks up to standard may have been overkill. More cost-effective solutions were being investigated.

"That $5.4 million was when we were looking at doing pipe repairs as well," Mr Carvell said. Now, some sections would be "dammed" to help hold up the water table and reduce pressure on the outside of the pipe. But Mr Carvell said the council would inevitably have to spend more money over time.

"The idea is to get the existing pipes to last as long as possible. When we cut these first ones out we'll get a better idea," he said.

WDC last year downgraded the value of the infrastructure "gift", thought to be worth $11.2 million, to $2.5 million. The original lifespan of the network was at least 80 years, since reduced to 18 years, which reflects the decrease in value.

Court action against the firms responsible for designing and signing off the work, Cook Costello, HEB Smithbridge, Kennedy and Associates Ltd and Hynds Environmental, was expected to take at least another year.

Meanwhile, the 83-ha site was still on the market after the companies of the developer behind the scheme, Oliver Scott, were put into receivership in May 2015.