The right drain for rain – looking after our sewerage network

Did you know there are two separate systems that manage the water from your home?

One is the sewerage system and the other is the stormwater system. Each has a different design to make it suitable for a specific task, but both play an important role in safely managing the water from your home. It is vital that we understand what should go into each system.

The sewerage system is the network responsible for removing and safely treating the wastewater from your home. It collects the wastewater from your toilets and the drains in your kitchen, laundry, and bathroom. A series of pipes and pumping stations transfer the wastewater from your home to a treatment facility. This infrastructure is designed for continuous but lower volumes of water and all water that passes through this system must be treated before it is returned to the environment.

The stormwater system is responsible for managing rainwater that is collected by your roof, gutters, hard surfaces such as driveway or patio, and surrounding lawn. The stormwater system has been designed to manage sudden large volumes of water that fall during a rain event. It has larger pipes connected to other flow management infrastructure such as retention or detention basins and importantly, the water that flows through the stormwater system is relatively clean and does not need to be treated before being returned to the environment.

Hear directly from our stormwater engineer, Mark Edenborough to find out more about stormwater design, management and maintenance in our local region in this informative video. See local examples of recent infrastructure and learn how we can all help protect our stormwater system.

An issue that can impact the sewerage system is the inflow and infiltration of stormwater into the sewerage network. This water, which should drain into the ground or be directed to storm drains, can overload the sewerage system causing sewage overflows to creeks, surcharges at manholes and impact operations at the treatment plants. One cause of stormwater infiltrating the sewerage system is the illegal connection of stormwater to the wastewater network. Others include landscaping that diverts stormwater into the sewerage system through manholes, overflow relief gullies or damaged vertical inspection shafts. Council is continually working to ensure that the sewerage system is working effectively, but we can all do our bit to help.

What is Council doing?

PMHC collect and treat 7400 megalitres of wastewater every year. In order to maintain the system and reduce sewer issues, Council:

  • Conducts routine repairs and maintenance of the more than 655km of sewer pipelines, 13000 manholes and 167 sewage pump stations
  • Is designing & constructing a new treatment plant at Thrumster
  • Conducts CCTV camera investigations of sewer pipelines
  • Engages with contractors to complete inflow and infiltration testing to identify defects – including smoke testing and manhole inspections
  • Is completing a Sewer Catchment Management Plan to aid in the prioritisation of maintenance and upgrade works
  • Runs modelling of the sewer network – including current infrastructure and proposed additions/alterations

What can you do to help?

There are some simple things that we can all do to help manage this important system, including:

  • Ensure that downpipes and rainwater tank overflows are not directed into the sewerage system
  • Avoid planting trees and shrubs over sewer lines – roots can enter and block pipes, and allow groundwater to seep into pipes
  • Make sure your visual inspection shaft* (VIS) has a sealed and unbroken lid
  • When landscaping, ensure that stormwater and groundwater is not directed to your overflow relief gully* (ORG), which should sit higher than the surrounding ground
  • Don’t pour Fats, Oils or Grease (FOG) down the drain. As these cool they harden and block pipes which can cause sewage to back up

*To find out what these terms mean, issues to look for around your home and how you can help, visit “troubleshooting sewer issues”.

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