Diversion wall in Lake Rotoiti focus of meeting
For immediate release:
Thursday 31 March 2005
Diversion wall in Lake Rotoiti focus of public meeting
A multi-million dollar diversion wall that should considerably improve Lake Rotoiti’s water quality is the focus of public meetings in Rotorua next week.
Environment Bay of Plenty and Rotorua District Council are running a public information session in the Rotorua District Council chambers on Tuesday 5 April between 6pm and 9pm. A meeting will be held earlier in the day for stakeholders and interest groups, with another for iwi and hapu of Lakes Rotorua and Rotoiti the following week.
Rotorua lakes project coordinator Paul Dell says staff, scientists and engineering experts will be discussing options for a diversion structure in Lake Rotoiti to reduce the nutrients entering it from Lake Rotorua.
Mr Dell says different options vary in how they look from the surface of the lake and where they are placed on the lake. “Because of this, we really want to know what people think and are seeking their feedback,” he says. “We want to select the option that is both effective and publicly acceptable.” He hopes to lodge a resource consent application for the preferred structure by the end of April.
One possibility for the structure is to build a long wall by fitting concrete panels between steel piles. An advantage of this would be its relatively long life and low impact during construction. However, more of the structure would be visible when lake levels fell, Mr Dell says.
A second option involves a flexible synthetic curtain attached at the water’s surface to a float or pontoon and to the lakebed by a dead weight and anchors. The curtain would be flexible enough to move with the wind and waves and adapt to changes in lake water levels, but would be less durable and would require ongoing maintenance.
Mr Dell says there are three possible routes for a diversion structure, though all start at the Ohau Channel and extend across the entrance to the Okere Arm, which leads into the Kaituna River. In all options, the proposed structure would stop about 60 metres offshore to allow boats to access the main body of Lake Rotoiti and to allow outflow from the lake.
More than 70% of Lake Rotoiti’s nutrients come from Lake Rotorua through the Ohau Channel. A diversion structure would stop water from Lake Rotorua flowing into the main body of Lake Rotoiti, redirecting the outflow so it runs through the Okere Arm of Lake Rotoiti and into the Kaituna River.
While this will cause a small increase in the level of nutrients entering the Kaituna River, the river’s turbulence and flow naturally limits algal growth. The diversion is expected to reduce algal blooms in Lake Rotoiti within three to five years.
In June last year, the Government pledged up to $4 million towards urgent works in Lake Rotoiti. Environment Bay of Plenty will fund the remainder of the cost. The project is expected to cost at least $10 million.
For more information on the diversion structure please contact Paul Dell at Environment Bay of Plenty on 0800 ENV BOP (368 267) or Peter Dine, Rotorua District Council, on 07 348 4199.