Fixing the problems
We began the Project CARE city wide strategic planning work in 1998 by looking at how our sewer network performs. The work identified that there is no simple solution to improving that performance and, in turn, the beach water quality.
It is a fact that city living has flow-on effects for the environment. There is no perfect solution to the problem of beach and stream water pollution. Our aim is to minimise the impact on beaches by fixing the problems of the past and planning better for the future.
After extensive investigations and at the same time fixing immediate problems, such as the Devonport leaky sewers, the Project CARE team identified a range of projects to improve beach water quality across the city. There is no simple solution to improve the performance of our sewer network, but a solution that includes a range of projects:
- repairing or replacing old pipes
- increasing the capacity and reliability of some pipes and pumping stations
- providing extra storage.
We used a sewer-modelling computer programme (SEWCOM) to identify the most efficient and cost-effective mix of works across the city.
We looked at numerous options and drew from experience in Australia, Britain and Europe. The risk to public health is greatest from the sewer network and to improve our beach water we must reduce the number of wet weather overflows. The reality is that whatever technology we choose to upgrade the performance of our sewers, the network needs to be fixed first as a priority.
Fixing the Devonport sewers
The old leaky sewers in Devonport were considered a priority for improvement. As one of the oldest parts of the city, infiltration into Devonport sewers was a significant problem. The long distance between Devonport and the wastewater treatment plant at Rosedale meant that a large amount of energy was required to pump the increased sewage flows that result from infiltration. By repairing the old and leaky sewers, large savings could be made in other areas. Sewer inspections began in Devonport in 1998 and work began in 1999.
Stormwater
Stormwater is also part of the problem and we are starting to address stormwater pollution through projects such as the WaiCare stream monitoring programme, the installation of Enviropod filters and stormwater-friendly practices. To find out more about stormwater click here.
The network improvement programme is designed to cater for the city’s needs to 2050 and the complexity of the problems means that implementing solutions will take time. Works will also require detailed planning and resource consents from the Auckland Regional Council. As a part of Project CARE, this process is called the Kokopu Connection. To send us your feedback click here. We will progress with the improvement programme as fast as we can and there are likely to be many works happening all over the city.
There is no perfect wastewater pipe network - pipes do leak! We have no choice but to fix pipes. We plan to spend a total of $96 million on the pipe network, pumping stations and sewage storage tanks in the next ten years. This is part of the 20-year work programme investing $210 million in the sewerage network. We have a number of activities and projects under way or planned for the future:
Repairing and replacing old pipes
Repairing and replacing old pipes reduces leakage of stormwater into and sewage out of the pipes. It also reduces the total amount of sewage to be treated and prevents pumping stations overflowing into our streams and onto our beaches.
Increasing capacity
Increasing the capacity of the sewer network is achieved by laying new larger sewer pipes and increasing the flow capacity of the pumping stations; for example, a larger pump and rising main (discharge pipe) allows a pumping station to cater for increased flows.
Improving reliability
Pumping station reliability is improved by installing new pumps and electric switchgear and duplicating rising mains. Duplication provides a backup to keep the system working when there are equipment or power failures.
Increasing storage
Storage facilities and large tunnels ease the peak loads on the sewer network by storing increased sewage flows, especially following wet weather when rain can leak into the pipes and increase the amount of sewage to be treated. A sewage storage tank has been built at Beach Haven and we are planning storage for Browns Bay and Wairau to further reduce sewage overflows following wet weather.
Treatment plant improvements
A number of major improvements have been completed at our Rosedale treatment plant – all of them designed to either improve the capacity, standard of treatment and efficiency of the plant, or reduce odours. Extensions planned over the next 15 years are designed to alter the plant to ultimately cope with a population of up to 300,000 by 2050.
Development checks
We have looked closely at the effect on the sewerage system of infill housing and development. We would still have a problem with our ageing sewer network without any growth in the city. We check the ability of the local network to cope with new homes before building consents are issued. We’re also looking at fairer ways of charging developers for growth-related sewerage network costs.
What about alternative technology?
The priority for Project CARE is to reduce sewage overflows and pollution on our beaches as soon as possible. Whether we choose to stay with established methods or to incorporate alternative technologies, the sewer network must be fixed.
We asked ourselves the question "what is the role of alternative technologies in improving the performance of the existing sewer system?" Cost and time are the important factors. We are convinced that to achieve an improvement in beach water quality in the shortest time, the existing network must be upgraded first. Longer-term planning can take a more holistic approach. It can consider new environmentally friendly technologies such as composting toilets, satellite sewage treatment plants, water conservation and rainwater harvesting.
Water
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