KEY POINTS:
Hundreds of Mt Albert residents are discovering that motorway route investigations are being extended under their properties.
Transit NZ, which previously limited investigations for its $1 billion-plus "Waterview connection" project to a 5km corridor of largely green belts, has sent leaflets to homes in about 25 streets east of its main study corridor announcing plans to drill boreholes nearby.
But the aim is to find out whether underground conditions are suitable for deep-bore tunnels, as an alternative to "cut-and-cover" excavations in sensitive environmental areas such as Oakley Creek, a development welcomed last night by Eden-Albert Community Board chair Lindsey Rea.
She said she had received several phone calls and emails from residents who found the leaflets in their letterboxes late last week, but these appeared not to be causing any great alarm because she believed most were keen for Transit to tunnel through as much of the route as possible.
"The less they see of the motorway the happier they will be."
One resident said it had come as a "rude surprise" to learn that her home was now within the investigation zone, but she indicated a preference for tunnelling rather than disruption to green spaces such as the Phyllis St Reserve, where Transit initially planned to build a traffic interchange.
Transit contractors began operating two drilling rigs in that area about a week ago, and are expected to complete 39 test bores through the study zone by mid to late-January, to depths varying from 10m to 50m.
Residents have been told in the leaflets that more investigations, building on work conducted from 2000 to 2003, are needed for a better understanding of "complex geological ground conditions".
The widened study area suggests Transit will consider a more direct route if it is able to go underground for a large part of the distance between Maioro Rd in New Windsor, where the Roskill motorway extension will end, and a connection with the Northwestern Motorway at Waterview.
But Waterview residents' spokesman Bill McKay said a tunnel would still have to surface at Waterview, where Transit faced a major challenge squeezing elaborate motorway-to-motorway links through a very narrow corridor.
Transit's Waterview project manager, Clive Fuhr, said it was too soon to speculate over a final route, but he hoped results of the new geological investigations could be reported to his agency's board by about February to reduce the uncertainty facing residents.
He said the testing was to gain a better understanding of the underground conditions, which varied in places from volcanic basalt to Waitemata sandstone and alluvial layers.
"This information will be of great assistance in establishing more robust construction cost estimates and will assist in determining the feasibility of constructing a bored tunnel option," Mr Fuhr said.
The owner of Harcourts' Mt Albert property agency, Brendan Ryan, said uncertainly caused by the proposed motorway had made it very difficult in recent years trying to sell any homes around the Hendon Ave part of Owairaka, but he hoped the extended investigations would end up with a tunnel along as much of the route as possible.
