Transit tunnels to protect bush

By MATHEW DEARNALEY

Transit will add tunnels and a second "eco-viaduct" to its $300 million tolled motorway to Puhoi, but critics want it to do more.

It has confirmed plans to dig twin 240m tunnels rather than carve 60m out of bushclad Johnsons Hill, on the distinctive ridge between Waiwera and Puhoi, and to simplify an intersection with the existing highway north.

This is what residents and independent engineers have urged for years, although some are sceptical about the announcement's timing amid public hearings where Transit is struggling to find support for a toll road.

Rodney Economic Development Trust, representing 7741 businesses, said last week that it was not against tolls generally but believed it unfair to charge motorists on 7.5km of road for which a resource consent was gained to build a free highway.

Another surprise addition to Transit's project is a 210m viaduct across an arm of the Nukumea Stream above Orewa, instead of an embankment with culverts.

This will allow rare fernbirds and other wildlife to pass below, as with a 240m viaduct previously proposed for one of three branches of the Otanerua Stream behind Hatfields Beach.

Transit chief Rick van Barneveld said the viaducts would keep the streams intact and provide corridors between ecologically significant areas which would otherwise be severed by the road.

He denied the enhancements were a kneejerk appeasement of critics, saying they followed months of investigations by Transit and its design and build partners, although they did not want to raise expectations before board approval last week.

But Dr Wendy Pond of the Manu Waiata waterway group said both Nukumea branches should be bridged, as the motorway would cross just above their confluence and a large wetland breeding ground for rare native fish and eels.

There was little point building a viaduct across one arm if the other was to be channelled through a culvert from which rushing water would wreck the breeding ground.

Mr van Barneveld said Dr Pond apparently wanted a viaduct more than 1km long but Transit's scheme provided a valuable connection across the motorway and "a reasonable balance between cost and achieving a result".

The tunnels would allow a lower and less obtrusive bridge than earlier planned across the Waiwera River, and avoid scarring an escarpment of significance to the Auckland region.

Motorists would gain a safer route with less climb.



Mr van Barneveld said that although the tunnels and their 500m approach bridge would cost $50 million, and the second viaduct $15 million, they remained within the road's $300 million budget.

Tolling the road subject to satisfying the Government of strong local support would allow these environmental enhancements in line with the new Land Transport Management Act.

Mr van Barneveld assured local people, many impatient for the new road although irked at having to pay $1.80 to use it, that the tunnels would not add delays to a project Transit hopes to complete by 2009.


There will be two southbound lanes through one of the tunnels, but just one northbound through the other for "traffic-calming" purposes, although with room for a second lane whenever the motorway is extended further north.

An emergency passage will link the tunnels half-way, and other safety features will include closed-circuit television and a water deluge system for fires.

But Mr van Barneveld would not choose between environmental or engineering concerns when asked which were the main reasons for the tunnels.

"The Land Transport Management Act doesn't identify a priority - this is a winning result environmentally and from engineering and safety perspectives. It provides a superior result for the users who will pay this premium of a toll."

Dr Pond said the extra net cost of a viaduct was far less than $15 million. She had seen figures showing the entire 1.2km-wide Nukumea valley could be bridged for just $5 million more than filling it in with a destructive embankment.

Engineer Peter Riley, a rock mechanics expert who at hearings five years ago proposed twin tunnels through a shorter route from a narrower part of the Waiwera River, is thrilled the bush corridor connecting Johnsons Hill to Wenderholm Regional Park will be spared.

It includes a notable kauri beside the main road on the Puhoi side of the hill, which he has kept an eye on since he began travelling from his family's Matakana farm as a boy more than 50 years ago.

Hill resident Armie Armstrong also welcomed the tunnels, but wondered whether Transit would still have "pulled them out of a hat" had the toll road not faced so much opposition at the hearings, which resume in Orewa tomorrow.