KEY POINTS:
The North Shore's $100 million investment in cleaner streets and beaches goes on show next Saturday.
Once an embarrassment for the city after rain storms, the Rosedale Wastewater Treatment Plant is now a key aid to reducing the times when raw sewage oozes from popped manholes and coastal and suburban pumping stations.
The plant opened in 1962 in Albany to serve the Shore's 60,000 residents. But the city's growth to more than 220,000 meant it had to be upgraded to cope with wet weather flows and to treat sewage to a high quality.
Since 1993, the council has spent more than $104 million on upgrading the plant's capacity and efficiency.
Mayor Andrew Williams will open stage 5 of the upgrade on Saturday and from 11am to 2pm the public can have guided tours of the plant.
Manager Paul Bickers said benefits from the recent improvements include a 40 per cent increase in capacity, a further reduction in smells from processing, and a boost to energy efficiency.
About 60 per cent of the plant's power needs are generated from waste, resulting in a $45,000-a-month saving in the power bill.
The plant's former oxidation ponds, visible from the motorway, work more as a storage lake rather than for removing pollutants.
Only treated effluent goes into the lake.
Although the sun works as a natural disinfectant, there is also an ultra violet system to kill bugs.
Pond storage has been boosted to cope with a one-in-50-year storm event and to balance the limited capacity of the plant's outfall pipe, which discharges only 600 metres off coastal Kennedy Park.
Work started in January on a replacement - a $116 million tunnel that will pass under city streets, parks and homes for 2.6km from the plant to a point offshore and discharge it 2.8km out to sea in a pipe buried in the sea bed.
North Shore City Council operates its own wastewater collection system and treatment plant, unlike other cities in the region, which are linked to Watercare Services' plant at Mangere, on the Manukau Harbour.
North Shore councillors yesterday told the Royal Commission of Inquiry on Auckland Governance that it started a 20-year programme of improvement to wastewater collection and treatment in 2001.
It aims for a 65 per cent improvement in beach water quality by cutting wet weather overflow events from an average of 12 a year to two.
Mayor Williams noted there was a move to have a single integrated entity providing all water and wastewater utility services for the Greater Auckland area.
He told the Herald: "There would be equity issues [if that happened].
"North Shore ratepayers have spent a fortune in the last decade to get the plant to a point where it has capacity for the next 50 year and the outfall pipe project to be completed in the next two years will give 100 years' future-proofing for that plant.
"I have been told that to build that plant again and with the land it's on, you'd need $1 billion. So our ratepayers should not have to start paying again when so many areas, such as Auckland City, have not spent the same level on their wastewater issues."
North Shore's average household rates now include an annual waste water charge of $396.48 and it is proposed to raise this to $417 in 2008-09. About 23 cents of each rates dollar is spent on waste water services.
The council has deferred a proposal to charge by volume for wastewater this year.
