North Shore City Council confirms sewer improvement programme

North Shore City Council will this week consider a major report updating progress on Project CARE, council's 20-year programme of work to improve beach water quality.

Works and environment committee chairperson, Joel Cayford says that the council's sewer improvement programme is on track and there is a reduced overall cost to meet the overflow reduction target for 2020, from approximately 12 to two events a year.

"Approximately $210 million is now expected to be invested in the wastewater system to meet the target in 2021. Recent investigations have identified $40 million expenditure, to cater for growth and deterioration of the network, that may now be deferred until after 2020. This is a reduction on the original Project CARE estimate in 2000 of $250 million.

"This deferral represents options for council to either complete the work earlier or reduce the cost over 20 years.

"We need to ensure that sewer maintenance money is very efficiently and carefully spent, and find the balance between 'throwing money too fast down the drain', and too slow where we never catch up.

"Ensuring that costs are fairly apportioned is also a concern and costs for new wastewater infrastructure will be funded through developer contribution levies where possible, rather than rates," Councillor Cayford says.

Project CARE began in 1998 following a public outcry over the frequent sewage overflows contaminating the city's streams and beaches.

Initial investigations highlighted the poor performance of the wastewater (sewage) network and the harmful effects of stormwater pollution on beach water quality.

General manager of water services, Geoff Mason, says the complexity of the problems in the network meant that a range of solutions needed to be considered.

"We needed to find ways of cost-effectively reducing the number of sewage overflow events that occur when stormwater leaks into the pipe system after heavy rain.

"The priority has always been to ensure that the lowest cost combination of work is selected, to deliver the earliest possible improvement in beach water quality," Mr Mason says.

Computer models were set up to determine the most cost-effective solutions for different parts of the city and the public was consulted in February 2000.

As a result of public feedback the target was set to reduce wet weather sewage overflow events from approximately 12 to two a year by 2020.

Average overflow volumes in North Shore City are expected to reduce from 227,000 cubic metres in 2001, to 64,000 cubic metres in 2021, a 72 per cent improvement.

By 2050 further improvements should reduce to 57,000 cubic metres, an improvement of nearly 75 per cent.

As changes to the network are interdependent it is recommended that a five-year monitoring and review process be followed. Improvements in one area may mean that the scope and timing of work in other areas will change.

While rainfall over the last two years has been below average, there has been a significant improvement in wet weather sewage overflows as a result of the early works and improved operation and maintenance of the wastewater network.

Work completed to achieve this level of improvement includes: · Birkley tunnel, 2001, $1.2m · Northboro storage tank/tunnel, 2002, $500,000 · Kahika storage tank, 2002, $4.5m · Tonar Street trunk sewer, 2002, $700,000 · Kahika pumping station upgrade, 2002, $200,000 · Sulphur Beach storage tank, 2002, $300,000

Work underway now includes: · Oteha Valley trunk sewer upgrade, 2002, $1.8m · Mairangi Bay trunk sewer inlet improvements, 2002, $300,000 · Hauraki tunnel storage, 2002, $300,000 · Alma pumping station upgrade, 2003, $300,000

Planning is underway to undertake the following work in the near future: · Mairangi Bay pumping station upgrade, 2002, $200,000 · Beach Haven sewer upgrade, 2002, $800,000 · Shakespeare Road trunk sewer upgrade, 2003, $400,000 · Silverfield storage tank, 2003, $6m · Browns Bay sewer upgrade and storage facility, 2004, $9m · Link drive/Wairau Road sewer improvements, 2004, $4.5m

Work is also underway to reduce stormwater leaking into the wastewater network from private property, in conjunction with our sewer repair programme. As part of Project CARE, priority parts of the city are being tested and owners required to fix the problems. Approximately $20 million has been invested since 1998 to repair old, leaky public sewers and investigate the private sewers in the Devonport and Narrow Neck area. Work has now begun in the Hauraki/Belmont and older parts of Northcote.

An ongoing citywide inspection programme is also in place as part of our maintenance and operations. Other projects are targeting specific areas of concern e.g. schools which have large impervious areas that may result in stormwater flowing into the sewers.

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