By Bernard Orsman
Changes to the Britomart project will allow thousands of tonnes of polluted stormwater to be treated on land before being flushed into the Waitemata Harbour.
The environmental spinoff will see a large settling tank built underground to recover much of the central city's stormwater solids before the water is
discharged beside Captain Cook Wharf.
The Auckland City Council has approved a $7 million plan to divert stormwater around Britomart and through the settling tank into the harbour.
Councillor Jon Olsen said the tank was a big environmental plus, but he was unconvinced it was the best method of removing toxic sediments, including heavy metals, PCBs and organochlorines, which can spread through the food chain.
Mr Olsen said he would look at other methods which might improve on claims the tank would recover 65 per cent of stormwater solids before discharge into the harbour.
"It sounds good but it still means 35 per cent of solids are going into the harbour."
Ngati Whatua is appealing against the passing of resource consent from the Auckland Regional Council to the city council to concentrate most of the central city's stormwater into one 3m-wide pipe at Captain Cook Wharf.
It has cautiously welcomed the tank but at this stage has no plans to drop its appeal to the Environment Court.
Moving the bus terminal from the second underground floor to the first floor has created space under the Quay St east underpass to build the settling tank.
The tank will be 110m long, 20m wide and 3m deep and provide capacity for 6600 cu m of water.
After recovering 65 per cent of stormwater solids on land by dredging or vacuuming the tanks, the council will dredge the seabed every 20 years to recover a further 20 per cent of toxic sediments.
