District-wide wastewater network inflow and infiltration
We are working to reduce the amount of rainwater and groundwater getting into wastewater networks across the Far North. This work will help reduce pressure on wastewater pipes and treatment plants, lower the risk of overflows and make our wastewater networks more reliable and resilient.
What is inflow and infiltration?
Inflow and infiltration (I/I) happens when water that should not be in the wastewater network gets into it. This can happen when rainwater enters the wastewater system through things such as incorrect stormwater connections. Groundwater can also get into the network through damaged or ageing pipes, faulty joints and maintenance holes.
Extra water in the wastewater network can put a lot of pressure on pipes, pumps and treatment plants, particularly during heavy rain. It can increase the risk of wastewater overflows, damage to infrastructure and higher operating costs.
What is FNDC doing?
FNDC is taking a district-wide approach by pinpointing where extra water is entering the wastewater network and how much is getting in.
The project will help us identify the areas where improvements are most needed, so investment can be targeted where it will have the greatest benefit.
The work includes:
- monitoring wastewater flows and how they change during rainfall
- using hydraulic modelling to better understand how wastewater moves through the network
- analysing rainfall-related inflow and infiltration
- investigating individual catchments to find sources of excess water
- inspecting wastewater pipes using CCTV
- inspecting maintenance holes
- carrying out smoke testing where needed (to identify unwanted connections that are discharging into pipes)
- investigating wastewater laterals and private connections
- identifying opportunities to repair, renew or rehabilitate parts of the network.
The information gathered will help FNDC plan future improvements and make better decisions about where investment is needed.
Where is the work happening?
The initial work will focus on:
- Paihia
- Russell
- Opononi and Ōmāpere
- Hihi
- Whatuwhiwhi
Other communities will be included as the programme progresses, and investment is staged across the district.
Why is this work needed?
Reducing the amount of rainwater and groundwater entering the wastewater network can help the system cope better during wet weather.
The project aims to:
- reduce the risk of wastewater overflows
- reduce pressure on wastewater treatment plants and networks
- improve the reliability and resilience of wastewater services
- reduce unnecessary pumping and treatment costs
- improve the performance and life of wastewater infrastructure
- help protect rivers, estuaries and coastal environments
- support public health by reducing the risk of wastewater discharges and service disruptions.
The information from this work will also help FNDC plan for future growth and meet wastewater consent and regulatory requirements from 2028 onwards.
Planning for the future
The work will help FNDC build a clearer picture of the condition and performance of wastewater networks across the district.
This information will be used alongside existing Long Term Plan budgets and future capital investment planning to decide where upgrades and renewals are needed.
By identifying and addressing sources of inflow and infiltration, we can make better use of existing infrastructure while planning for the future needs of Far North communities.
The long-term goal is to provide wastewater networks that are more reliable, resilient and better able to cope with wet weather and future growth.