Underwater lake wall okayed

The Ohau Channel wall will feed pollution into the Kaituna River and out to sea. Picture / Alan Gibson

A pioneering, multimillion-dollar underwater wall designed to cut pollution in one of the country's most beautiful lakes, Lake Rotoiti, has been given the green light.

Despite opposition, the Environment Court has approved the Ohau Channel diversion, a major engineering project never before attempted in this country, and dismissed the formal objections.

"This is the first project of its type in the world to deal with pollution of a major waterway and this decision is a vindication of our science people," said John Cronin, chairman of the Environment Bay of Plenty regional council.

"This will be a visual statement to the community that the lakes are being cleaned up."

Now the project had consent, he hoped work could begin within three months.

He doubted the Environment Court decision would be challenged.

The regional council claims the diversion, expected to come with a price tag of between $12 million and $16 million, could reduce toxic algal blooms in Lake Rotoiti by up to 40 per cent over four years.

Rotoiti is one of the lakes worst-affected by the smelly, dangerous cyanobacteria linked to blooms.

Under the plans, the wall will start below the Ohau Channel, which links lakes Rotorua and Rotoiti, and extend for about 1km to Te Akau Pt.

It will be about 75m offshore, running parallel to State Highway 33. It will stand on the lake floor and rise to just above the waterline.

It will channel nutrient-rich water from farm run-off and other pollution from Lake Rotorua down the Kaituna River and out to sea through the Maketu Estuary, avoiding Lake Rotoiti.

Some Maori groups opposed the plan, saying it would affect the mauri or spirit of the Kaituna River by creating adverse health effects through the increase of nutrients in the water.

Another opponent argued the ocean should not have to take pollution from the lakes.

Rotorua Mayor Kevin Winters said the strategic partners in the project would talk to the Government about the shared funding for the entire lakes programme

Several measures are planned to clean up Rotorua's lakes including a major sewerage scheme by the Rotorua District Council.