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Report identifies areas for wastewater wetlands

GISBORNE District Council has identified possible sites for small "polishing" wetlands close to Gisborne City, but spokesmen stress the council has no firm intention to focus on any area at this stage.

The review of possible sites was a desktop exercise, said community lifelines director David Wilson.

They will be part of a much broader set of options that will be presented to the council at its August meeting, at which it will have to make some major decisions on the multimillion dollar upgrade of the city’s wastewater system.

A report to the Wastewater Management Committee showed a number of areas within 2.5 kilometres of the city shaded green, including the land occupied by Gisborne Park Golf Club and other land close to the Poverty Bay Golf Club and Gisborne Airport.

But Mr Wilson said there was no intention to take the golf club land or any other.

“We drew a line on the map where 2.5 kilometres would take us and that included the golf course,” he said.

“No one is taking the golf course, it was purely a desktop exercise. We did not highlight any land in particular. We highlighted lots of land.”

He said what they had done was rudimentary and there was a lot of land within the 2.5 km radius.

“If you go further out you end up going past potential sites to other potential sites and it is too long a distance. You start to have technical issues if you pumped over that distance.”

"To pump the water further than 2.5km would mean constructing additional pumps and pipes, which would add unnecessary costs to the project, especially if there are suitable sites closer to the city,” said project manager Wolfgang Kanz.

“The pumps alone are about $1 million and the cost of pipes would be about $650,000 a kilometre.”

High level”It's all high level at this stage," Mr Wilson said.

"We have deliberately not gone down the road of proposing any specific piece of land because we want the community to say what they want us to do first.

“We want to make sure the technology is right and the price is right before we start identifying specific locations. We have based the costing of the project on the physical constraints and limitations of the land within this 2.5km, being careful not to underestimate costs.”

Present estimates were conservative with adequate contingencies. It was difficult to settle on costs until you knew the general area where you were going and the type of land.

The wetland did not have to be in one place, and could cover multiple areas of land. It could look part of the natural landscape from overhead.

A number of options will be presented to the council in August. The common denominator is an upgrade of the current Banks Street site to clean the water.

The wetlands are seen as a final "polisher" and a reservoir for the water to be stored and then taken for alternative use such as irrigation.

A range of options will be presented to the council, from small polishing wetlands to more complex wetlands. The $50 million option was still a possibility but the council will decide in August whether to include it in consultation. It would be up to the community to decide on which option it prefers.

“We are after the best option for our community and it is not necessarily about cost alone. The council want the best outcome for our community and this is what we want."

After the August meeting the council would be giving the community options on where it wanted to go.

There would be two rounds: a pre-consultation phase of meetings followed by consultation as part of the 10-year long-term annual plan in December, by which time they will be considering the preferred option.

POSSIBLE WETLAND LOCATIONS: This image from a report to the waste management committee shows areas of land within 2.5 kilometres of the Banks Street wastewater plant where “polishing wetlands” could be established. They are shaded blue, and include Gisborne Park golf course and land around the airport.