Rainwater tanks proposed

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The owners of new buildings might have to install rainwater tanks as part of their building project if proposed new regulations are adopted by the Gore District Council.

The proposed revision of the council’s subdivision and land development bylaw recommends mandatory installation of tanks at new buildings, including houses, Gore District Council general manager regulatory and planning Ian Davidson-Watts says in a report discussed by the council’s regulatory and planning committee on Tuesday night.

“This is an action under the water taskforce action plan which is a very proactive, short-term initiative by the council to address issues such as water shortages, given the changing climate,” Dr Davidson-Watts said.

“This really is the start of the conversation.”

It is envisaged rainwater be collected from a dwelling’s roof and directed into a tank.

Dr Davidson-Watts said heavier rainfall events were predicted for the Gore region but also longer dry periods in-between, so “the historic record of water restrictions in the Gore and Mataura urban areas [meant it would be] prudent for residents and businesses to adopt some self-help approaches .. particularly in relation to the outdoor use of water for washing of vehicles and windows, and watering of lawns and gardens.”

It is envisaged tanks would have a slow-release mechanism when not being used to reduce the peak flow impact of rainfall.

The water collected in the tanks would not be intended for human consumption or use within dwellings.

If any occupants decided to drink their tank water, treatment requirements would apply.

“Over the past 17 years, an average of 20 new dwellings and four commercial or industrial buildings have been built each year within the Gore and Mataura reticulated areas.”

While in the short term this would not impact significantly on the volumes of water the council needed to supply, it would provide an advantage to the property owners with tanks, he said.

Depending on the size of tanks, a rainwater tank would cost between $3000 and $5000 per installation.

The optimum size for a domestic dwelling tank is 3000 litres.

To cope with any overflow of rainwater from tanks, ideas including rain gardens, ponds, wetlands or soak holes – all known as green infra-structure – could be used to minimise impact on the council’s infrastructure.

“The other advantage of this is it looks good, it’s good for wildlife and it helps with climate change mitigation – the plants will effectively soak up some carbon dioxide.”

Gore District Council planner Keith Hovell said the bylaw revision document was technical and designed to target builders and developers.

Cr Doug Grant believed the revision of the document was “bang on” for timing.

Cr Ralph Beale asked whether there would be an opportunity for the owners of existing houses to install rainwater tanks.