$3m cost to protect flood-prone houses

John Mackie
John Mackie
The Dunedin City Council has run up against a problem of economics in its bid to protect houses in Somerville St, Andersons Bay, from flooding.

The scheme it has been investigating would cost more to build than the value of the houses it is designed to protect.

Water and waste services manager John Mackie told yesterday's meeting of the council's infrastructure services committee that building a pipeline beneath Somerville St to carry water away from a flood-prone nameless stream would cost more than $3 million.

He told the Otago Daily Times later that the stream, which runs through private property, severely affected ‘‘four to six'' houses when it flooded.

The stream, which empties into the Andersons Bay Inlet, flooded twice in 2005.

Mr Mackie reported yesterday the pipeline investigations revealed ‘‘space limitations'' in the road reserve, which would require other services to be shifted, and this had a significant impact on the cost.

The committee recommended an alternative ‘‘green engineering solution'' be investigated that would see the bed of the stream widened to be capable of carrying more flood water. The change would mean work would not be done in the 2007-08 year.

It would take nine-12 months to obtain resource consent from the Otago Regional Council, Mr Mackie said.

Cr Dave Cull was concerned the solution might ‘‘trigger'' the need to install safety barriers along the stream.

Cr Bill Acklin asked if the council was obliged to do the flood protection work.

Mr Mackie replied that it was not but it had previously ‘‘made a commitment''.

Stormwater run-off from houses in new subdivisions further up the valley had exacerbated the flooding problem, he said.

Cr Richard Walls asked if those stormwater discharges were legal.

Mr Mackie replied that they were and were marked on building consents issued by the council.

Cr Michael Guest suggested the committee should be careful when discussing its own liability in open meeting.

‘‘Four councillors have effectively said we are liable.''

Cr Fliss Butcher suggested part of the new investigation should include ideas on water collection.

Mr Mackie said in Waitakere where there were similar issues with small streams, new houses must have ‘‘soak holes'' so they did not add to the volume of stormwater leaving a property.

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