Whangarei flood detention dam draws closer

Moves are underway on behalf of ratepayers to compulsorily acquire the handful of remaining Raumanga properties needed to allow construction of an $8 million detention dam designed to better protect central Whangarei from flooding.

Eight months after signalling its intention to use the Public Works Act to acquire the eight properties (including two with homes on them), the Northland Regional Council has recently formally served notices to that effect.

Bruce Howse, the council’s Land/Rivers Senior Programme Manager, says all going well construction of the dam – to be sited at the ends of Raumanga Valley Road and Kotuku Street – is due to begin late next year.

When completed mid-2015, it will hold up to 1.27 million cubic metres of floodwater during heavy rain, about two-thirds of the Whau Valley dam’s capacity. The detention dam would then slowly release the trapped water over the next couple of days, reducing river swelling and downstream flooding that would otherwise threaten Whangarei’s CBD.

Mr Howse says the dam will be one of the largest engineering projects the regional council has embarked on and involves securing 20 private properties worth about $4m collectively and covering about 25 hectares on behalf of ratepayers. Another 7ha of Whangarei District Council road and reserve land is also needed.

He says initial discussions to secure all the land required began about two years ago but moved up a notch in February this year.

“The regional council has now secured 12 of the 20 properties needed for an as yet- undisclosed sum. Eight of these were homes and the remainder involved bare land or easements over land.”

Mr Howse says the council’s attempts to secure the remaining eight properties (including two with homes on them) are ongoing.

“We remain hopeful of a positive outcome with several of these owners, but in order to keep to a reasonably tight construction timeframe which is largely dictated by weather, council has now formally issued notices to take land and/or easements under the Public Works Act.”

Mr Howse says the act provides a formal mechanism to secure the land needed for public benefit, but also ensures both parties’ legal rights are recognised and that fair compensation is made.
The act’s provisions are more commonly used by officials for large scale roading projects like the Kamo bypass extension.

All going well – and dependant on any possible appeals – the regional council hopes to have secured all the land required for the detention dam within the next six to 12 months.

The dam is part of a multi-phase project to reduce the impact of flooding in Whangarei’s CBD, which also involves river clearance to remove blockages and current upgrading of the Rust Avenue Bridge to improve stream flows beneath it.

Mr Howse says while its current estimated $8 million price tag does represent a big upfront investment, the proposed dam should significantly reduce the cost of flood damage in the Whangarei CBD and effectively pay for itself in just a few years.

The council will pay for the dam via a targeted rate on 23,000 properties in the CBD and contributing catchment areas.

ENDS

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