Parua Bay Wastewater Scheme
- Project typeWastewater system improvements
We are working on short-, medium- and long-term solutions to improve the Whangārei Heads and Parua Bay wastewater systems.
Short term
We are working to keep the area as clean and spill-free as possible while we determine where stormwater is getting into the wastewater system and working out next steps for increasing the capacity of the wastewater scheme.
The sucker trucks
Sucker trucks are removing wastewater from the wastewater storage tank at Parua Bay to free up storage capacity and taking it to the wastewater treatment plant at Kioreroa Road.
The smell
Opening the cover at the pump station when we began emptying it caused an odour problem, so we have modified the lids and will not need to fully open them as often in future.
Why is there wastewater in the storage tank?
Wastewater drains into the pump station / storage tank from surrounding household connections. When it reaches the right level in the wet well, a pump is activated to convey wastewater to the next pump station along the line.
It does not empty the tank fully. It sends a manageable amount of wastewater to the next pump station to deal with. The wastewater system along Whangārei Heads operates in a daisy-chain configuration. Wastewater conveyance is dependent on the full operation of each pump station.
When more wastewater flows into the storage tank, this is added to the amount already in storage and the level rises again.
This cycle works well when wastewater is coming into the system steadily, i.e. dry weather flow scenario.
It fails when stormwater gets into the system and overloads the pump stations and wastewater network.
The wastewater system is for wastewater, not stormwater
The wastewater system is designed to take the wastewater that comes from showers or baths, washing machines, toilets and other household or business sources. It is not designed to manage stormwater.
Stormwater
Rainwater runoff should only drain into stormwater drains that discharge into streams and then into ponds or the sea.
Stormwater in wastewater
During storms, stormwater and ground water is getting into the Whangārei Heads wastewater system, faster than it can be pumped out. That causes it to overflow.
Keeping the tanks empty
While we are finding out where the stormwater is getting into the wastewater pipes and how to stop that from happening, we will be emptying out the storage tank(s) by sucker truck, so they can contain the maximum amount of wastewater volume, to minimise the potential for overflows. Our aim is to keep the system as empty as possible while we address the next part of the problem.
Medium term
Finding out where the stormwater is getting into the system
Our aim is to direct as much stormwater into the stormwater system as possible and to keep it away from the wastewater system.
To do this we need to know where it is getting into the system, so we will be carrying out catchment studies on groups of properties (about 30 at a time) that are connected to the wastewater system.
Inflow
To find out where stormwater is flowing into the system from above ground, we will be looking for things like:
- places where downpipes are draining into gully traps
- gully traps that are underneath leaking spouting / guttering
- damaged gully traps or gully traps that are set low that enable stormwater to drain into them
- non-compliant connections, stormwater connections to the wastewater pipelines
- places where stormwater forms ponds that are higher than the gully trap, letting water flow in.
Infiltration
Groundwater can also get into old, broken, gappy or bad connections in pipes below ground.
We will be looking for any indications that this is happening too.
Monitoring
At the same time, we will be looking for any places where stormwater and ground water could be getting into the system on Council property and fixing any problems we find.
Mapping
This information will be mapped, so we can see where the 'hotspots' are. From there, if improvements are required, we will be going from group to group to show people what needs to be done on their property.
Long term
At that stage we should be seeing a marked decrease in the flow of stormwater into the wastewater system and we will know what needs to be done to increase the capacity of the pump station at Parua Bay.
Planning, design and construction of that work will be the final stage.