A new report puts the cost of getting regional wastewater treatment up to national standards at between $330 million and $500m, says Horizons Regional Council strategy and regulation manager Dr Nic Peet.

The report is by environmental consultancy Boffa Miskell for the Department of Internal Affairs. It covers all of New Zealand and says small towns will be disproportionately affected - towns in the Horizons and Waikato regions especially so.

There are 46 wastewater treatment plants in the Horizons region. In June this year only 34 per cent were fully compliant, and 22 plants were significantly noncompliant.

A further 10 have been checked since, Peet said, and the majority of those were noncompliant as well - though sometimes for minor reasons.


In order to lower the incidence of E.coli and meet the objectives of the Government's national policy statement for freshwater management, 24 of the Horizons region's 46 plants would need an upgrade. The capital cost would be between $330m and $500m and about half of the region's ratepayers would be expected to pay it.

Some of that expense would be for minor improvement, but it all adds up.

It's a big ask for a region this size with a low population base, Peet said.

"It's not an excuse not to keep improving wastewater, but it's a useful piece of context around affordability - particularly as a lot of those plants were originally built with government support back in the 1950s and '60s."

Like farmers, people in towns are being expected to limit their effect on water quality - and that means rate increases to pay for wastewater upgrades.

Horizons works with councils as they improve wastewater treatment, giving priority to places where the environment is seriously affected. For example, fixing Whanganui's wastewater was urgent, when it was being discharged untreated into the sea.

In Rangitīkei the Hunterville and Taihape plants came first and now need minor adjustments. Marton and Rātana are the next priority and are underway. Bulls comes next.

Whanganu's new wastewater treatment plant is up for its first assessment early in 2019.