Improving beach water quality
Project CARE is North Shore City Council’s commitment to improving beach water quality in our city by reducing wet weather wastewater (sewage) overflows and improving stormwater quality.
This 20 year programme will see our wastewater system progressively repaired and improved to reduce the number of wet weather overflows of sewage onto our city beaches.
Wet weather overflows happen when storm water flows into the sewage pipes during heavy rain through leaky manhole covers, leaky pipes and private drains, and directly from roofs and gully traps. This is called infiltration and increases the volume of sewage to be treated. When volumes become so great that our sewer pipes and pumping stations cannot cope, sewage can overflow onto our beaches.
Project Care aims to improve beach water quality by reducing the number of wet weather overflows to an average of two a year by:
- Repairing and replacing old pipes, to minimise the amount of storm water leakage into the system
- Increasing capacity by laying new larger pipes and increasing the flow capacity of our pumping stations
- Incorporating storage facilities such as tanks and enlarged pipes to ease peak loads on the system
- Improving the treatment plant’s capacity and efficiency
Since the project began in 1997 the council has spent $83m improving its wastewater system. That work, which means our city’s beaches are now better protected, has included:
- the new Kahika and Silverfield storage tanks,
- the re-commissioning of four old storage tanks,
- increasing the capacity of the network by replacing old sewers with new, larger ones eg Browns Bay
- repairing the network by re-lining pipes and resealing joints.
Project CARE infrastructure milestones
The
Kahika Storage tank
Kahiha Storage tank in Beach Haven was completed in 2002 and can hold 4500 cubic metres. In the four years since it was built the number of overflows into the Kaipatiki inlet has been reduced from five per year to about one every two years. The tank cost $4.5 million to build.
The Silverfield storage tank
The second of the new storage tanks built by the council, Silverfield significantly reduces overflows in the Wairau catchment and pollution at nearby Milford Beach. The $7.2 million, 6500 cubic metre capacity tank - equivalent to nearly four Olympic swimming pools - is beneath the car park at the North Shore Events Centre and was completed in 2004.
Enlarged sewers in Browns Bay
In Browns Bay enlarged sewers have been installed which have the extra capacity to provide temporary storage for increased flows during wet weather. The $12.6m waste water and storage project proved its worth on the first day it was brought into use by preventing sewage overflows onto the beach during the storm at the end of January. Up to a third of the 4000 cubic metre capacity they provide was used.
Water
introduction