Clear Harbour Alliance represents a significant investment by Metrowater and Auckland City Council in improving drainage infrastructure and protecting the environment.
This project is part of Metrowater’s ongoing plan to separate Auckland’s remaining 300km of combined stormwater and wastewater drainage systems. This will remove a major source of pollution to our streams, beaches and harbours.
This is expected to significantly reduce the amount of wastewater pollution that enters the Waitemata Harbour around Westmere and remove 30 of the points where wastewater pollution overflows. However, it means that we need to undertake some work on private properties within the project area.
Approximately 15% of Auckland City is serviced by a combined drainage system, meaning both wastewater and stormwater flow through the same pipe (see Diagram 1 on the “How the Separation works” tab). This system was built over 70 years ago, when the population was a fifth of what it is now.
The combined drainage system is unable to properly cope during wet weather as the amount of stormwater entering the system increases dramatically. This results in the system overflowing wastewater pollution into the streams and waterways leading to the Waitemata Harbour. This is the reason why there are often signs warning against swimming at some Auckland beaches. Combined drainage areas are marked red on the project area map on the home page.
The remainder of the project area is serviced by a stormwater soakage system. This is in areas where the volcanic ground allows for the free draining of stormwater into soakholes or soakpits in the ground and wastewater flows through a separate pipe system (see Diagram 3 on the “How the Separation works” tab). Sometimes stormwater can make its way into the wastewater system in these areas and this contributes to the overflows of wastewater pollution. Stormwater soakage areas are marked green on the project area map on the home page.