Major Roading Plans - Transmission Gully Motorway Project

Building the Transmission Gully Motorway will create damage to the upper part of Cannons Creek Valley, especially the streams.  Inevitably there will be problems caused by construction.  Afterwards, we expect drainage from the motorway to bring toxins into the stream, traffic to create fumes and rubbish, and the natural supply of water to some parts of the bush to be disturbed, causing dieback and more erosion.

The actual area if the land required is not finalised (as at mid-2010), nor when it will be definite.  Funding for it was pledged by the Government on the 15th of December, 2009.  A formal hearing of the applications for designation and resource consent for the whole project is expected in early 2011.  See Porirua City Council for more and up-to-date details.

The original route called for a 300-metre long viaduct over Cannons Creek gorge, and an impression exists on the NZTA website - Transmission Gully fly-through video.  However, a revised route shifts the bridge some 50 metres further upstream to a site where it will be shorter (and thus cheaper to build).  The new "cut and fill" area will be right in front of the Takapu Park Entrance.  It still cuts across the 30ha Takapu Conservation Covenant (protected bush) over a narrow part of the gorge, which is 70 metres deep at that point.

Route of new motorway

Route of Transmission Gully - Feb 2010.

[Larger image]

The earlier plans would have involved greater roadworks, probably destroying a precious stand of nikau palms in the gorge; and a proposed Link Road from eastern Porirua would have cut across the seepage slopes just above the Cannons Creek Conservation Covenant, diminishing the groundwater on which that bush depends.  Fortunately, the revised plan removes the Link Road 2km towards Whitby, avoiding that risk.

Increased silting in Cannons Creek itself - already prone to erosion and flooding - is still going to be a danger, requiring serious mitigation work even before construction begins.  With no details yet available, it is not known what NZ Transport Agency plans to do about this area, nor in Duck Creek, nor in the northern Horokiri catchment.

A secondary effect on the restoration work, and even on park track development, also comes from the constant delays in finalising the Transmission Gully Motorway alignment.  Until the formal hearing of the applications for designation and resource consent for the whole project, expected in early 2011, new Park track plans cannot be finalised either.

These tracks are the only means of access for the public, for Greater Wellington staff, and for farming operations in this area.  Underpasses must be constructed, but where? and how many?  How can a 100ha farm be managed, with the headquarters and 10% of the farm on one side of such a Motorway, and 90% of the farm land on the other side?

How indeed will this Park not be split in two?  These issues are still being wrestled with by Greater Wellington and the Regional Council, who now own the farmland (having purchased it from Landcorp NZ in 2005).  No easy matter: for it is NZ Transport Agency who will then own the alignment, and every access point must be negotiated.

For the Friends of Maara Roa, this means not only that two of the new tracks in our own 2001 Plan have been impossible to build, but also the two we have now will both have to be re-thought.  And as for the fate of the bush with such a roadway above it, as for the birds and other creatures, who knows?

And as for the boundaries for our present restoration, and the future "Maara Roa Scenic Reserve" with its "long protected garden" (maara roa) all the way to the top of the Belmont Hills, well, we can only plead the cause, and hope the negotiations between Greater Wellington and the NZ Transport Agency will be for the best.  Till then, our work will need to go on – and the more supporters and Friends we have as these decisions are being made, the better the outcome will be.


See also our News item about an Information Day attended on Transmission Gully Motorway Plans - 9 October 2010.