Wellington Water is looking for public feedback on a consent they wish to renew, which would allow them to discharge overflows of wastewater at Bluff Point when storm events overload the wastewater system.
To provide an easy means for the public to provide online feedback on this consultation, New Zealand Underwater Association (NZUA) has set up an online survey, the results of which will be forwarded to Wellington Water. All project information has been provided by Wellington Water.
Wellington Water operates wastewater networks around the Wellington metropolitan area, including the wastewater system that serves the Hutt Valley and Wainuiomata. This system receives wastewater from Upper Hutt, Lower Hutt, Wainuiomata and the Eastern Bays. This consent renewal application relates to the Eastern Bays network.
Wastewater is pumped through the Eastern Bays wastewater main to the Seaview Wastewater Treatment Plant. There is an outfall pipe which conveys treated wastewater from the plant to Bluff Point (near Pencarrow Head) where it is discharged into Cook Strait.
During very heavy rain, the capacity of the Eastern Bays sewer can be exceeded due to inflow and infiltration of stormwater to the wastewater system. When this happens, any wastewater that cannot be pumped to the Seaview Wastewater Treatment Plant (overflow) is automatically diverted from the Point Arthur Pump Station. It mixes with the treated wastewater in the main outfall pipeline, and discharges at Bluff Point.
This has been monitored since 2004, and has occurred, on average, 2.1 times per year, and never more than 5 times in a single year.
According to the 'consent renewal' (February 2018) brochure sent by Wellington Water to NZUA, Wellington Water diverts overflows of wastewater to Bluff Point to avoid excess wastewater being discharged from the Eastern Bays wastewater system into Wellington Harbour.
They express that by diverting the excess wastewater to the Bluff Point Outfall significantly reduces the potential public health risk posed by discharge of wastewater to the Harbour.
Stormwater (rain water), is not meant to enter the wastewater system. Rainfall during storms can be much more than the volume of wastewater that people normally produce from bathing, washing, and using the toilet. Stormwater systems have more capacity to cope with heavy rain.
When stormwater does enter the wastewater system, it can put wastewater pipelines and wastewater treatment plants over capacity.
Inflow of stormwater happens when drains or inlets that collect stormwater are incorrectly connected to wastewater pipes.
Infiltration happens when there are cracks, broken pipes or loose joints in the wastewater system. When there is heavy rain, these small defects can allow stormwater in the soil to seep into the wastewater system.
Wellington Water wishes to renew the consent they currently have, allowing the existing Bluff Point Wet Weather Discharge system. If this consent is granted, overflow discharge would continue to occur on an infrequent basis, for short periods of time. When they do need to divert overflow wastewater, during storm events, there will continue to be temporary, localised effects in the area close to the outfall at Bluff Pt.
This is not the consent application consultation, but the feedback from this will form part of the application for consent renewal process.
Wellington Water's brochure assures that they have been working to reduce wastewater overflows which sometimes cannot be avoided, but they want to avoid the environmental effects as much as possible. Since 2003 they have undertaken work aimed at reducing the impact of overflow discharges.
In 2004, Wellington Water upgraded the pumps at Point Arthur, so that the station could operate at higher pressure. This work was designed to increase the volume of wastewater that could be pumped to the Seaview Wastewater Treatment Plant.
They have conducted an inflow survey of the Eastern Bays wastewater network, and identified a range of areas that require rehabilitation work to reduce the volume of stormwater that can enter the wastewater system during heavy rain. If they succeed in reducing inflow and infiltration of stormwater to the Eastern Bays wastewater system, it will reduce the likelihood of overflows during storms.
Wellington Water are undertaking technical investigations on the effects that overflow discharges cause, and beginning consultation with stakeholders and the community about our plan to apply to renew the consent.
This work will include environmental investigations such as the pattern of dispersion of the discharge, study of the quality of the discharge and its effect on the water quality in the area.
They will consult with Eastern Bays residents, and representatives of local iwi and hapu, including the Wellington Tenths Trust and Port Nicholson Block Settlement Trust. They also seek views from recreational users of the area – such as local yacht clubs and recreational fishing organisations.
Feedback from everybody consulted and technical information from investigations will become a part of the application to renew the consent. Feedback on the proposal from all sources is welcomed.
NZ Underwater will keep the website updated and keep you informed about developments in the consent renewal process.