Mayors back contractors' plan to reopen Manawatu Gorge in two years

Thursday, 31 August 2017

A consortium of Manawatu civil contractors has come up with a plan that could potentially reopen the Manawatu Gorge in two years.

The group's idea to raise the gorge road by 15 metres and cut a 'safety zone' to contain most future slips, at a cost of between $165 million and $195m, has the backing of the region's mayors and Horizons Regional Council.

A group of civil contractors believes improving the maligned Manawatu Gorge road remains a better option than cutting a new route.

The route has been closed since April because of slips, with motorists forced to use the Saddle Rd and Pahiatua Track instead.

Consortium spokesman Les Fugle said the group worked on its plan for months, commissioning independent engineers and geologists to do a preliminary assessment on if it was possible, before sending it on to the NZ Transport Agency.

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He said the plan would be far quicker to complete, and far cheaper than the other alternatives on the table because it required fewer consents, worked with existing roading and didn't include using any privately owned land.

Four alternative routes were proposed in a 2012 report for the NZ Transport Agency, priced from $120m to $1.8 billion. Each carried formidable challenges, from moving wind turbines and excavation, to hefty land purchases and contending with major fault lines.

The mountains around the gorge had poor drainage, which made them particularly prone to slips, so any alternative route needed to be able to handle them.

'We're always going to get slips. It's just the makeup of the mountains in the area. We think this concept can manage that more easily and safely than the alternatives.'

Horizons Regional Council chairman Bruce Gordon said the regional council, along with mayors from Manawatu, Palmerston North, Tararua and Southern Hawke's Bay have lobbied the transport agency to get the proposal included in the options under consideration for a gorge fix.

The region could not afford to rely solely on the Pahiatua Track and Saddle Rd for more than a couple of years, he said.

'The cost of the closure to our region and to our business is just too great, especially in Woodville. We've already seen businesses that haven't survived or have had to move out of town.'

Palmerston North mayor Grant Smith said he helped push for the plan's inclusion because it was important not to give up on the gorge if there was a chance to reopen the route and build resilience against future slips.

Smith said he didn't have the expertise to judge if the consortium's plan would prove viable, but its local knowledge meant it was worth looking into.

'Collectively, they've been operating in the gorge for 60 years. They know that terrain like the back of their hand.'

Fugle said the continued widening of the road over time by chipping away at the foot of the slope had weakened it.

Past gorge core samples have shown a solid rock face lies about 15m under a skin of the looser rock and dirt that falls in the slips.

The consortium's plan was to take that loose material, and use it to raise the road up 15m and leave a 15-20m gap between it and the new cliff face. Drainage rods would be put into the hillside.

That would mean most future slips would involve less rock and dirt, have further to go before they blocked the road, and leave more space for workers to get in and clean up, Fugle said.

Transport agency regional transport systems manager Ross I'Anson said the agency had received the consortium's proposal, and it may be considered in the detailed business case.

A final decision on the gorge alternative was expected in December.