Maintenance-Free Concrete Sewer Encasements | Protecting Sydney Water Assets
Encasing sewer pipes in concrete for long-term strength, stability, and compliance

Upgrading and protecting aging sewer mains and pipelines in Sydney is crucial for ensuring efficient wastewater management. Many of the existing sewer mains and pipelines around Sydney are constructed from materials like clay or cast iron, which are prone to deterioration over time. To enhance durability and longevity, Sydney Water generally recommend replacing these older pipes with modern PVC alternatives.

The PVC pipe material offers superior resistance to corrosion and wear. Surrounding the PVC pipe with a layer of concrete further fortifies the structure, providing added strength and safeguarding against external pressures and ground movements.

Concrete sewer encasements not only reduce maintenance costs but also enhances the overall resilience of the sewer system, promoting environmental sustainability, public health, and long-term infrastructure stability.

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What is a concrete sewer encasement?

A maintenance-free concrete sewer encasement is the process of removing the earth around a sewer main and surrounding the pipe in concrete. This process makes the pipe ‘maintenance free', thus allowing structures to be built over or in close proximity to the Sydney Water sewer main.

This technique is essential when construction activities, such as building foundations, roads, or heavy structures, are planned near or over existing sewer infrastructure.

Concrete sewer encasements usually form part of the Sydney Water approval works and can only be undertaken by Sydney Water accredited minor and major works constructors to ensure compliance with industry standards. This guarantees that the encasement meets structural requirements and protects Sydney's essential wastewater network.

All Line Plumbing are fully accredited and insured to be able to execute a wide range of concrete sewer encasement projects in Sydney and surrounding areas.

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Works that may require a concrete sewer encasement

Permanent or temporary building works that may adversely impact the sewer main and usually require a concrete encasement include residential, commercial, and industrial works such:

• Domestic swimming pool installations and water tanks
  Preventing pipe damage due to excavation and added weight.
• Carports, verandahs, pergolas, and sheds
  Ensuring structural stability when building near sewer mains.
• Decks and retaining walls
  Protecting underground sewer lines from pressure and soil movement.
• Driveway or pavement constructions
  Preventing pipe collapse due to heavy vehicle loads.
• Planting trees and landscaping
  Avoiding root intrusion and ground shifting near sewer pipes.
• Residential subdivisions and housing estate developments
  Ensuring long-term infrastructure protection.
• Duplex or townhouse developments
  Meeting Sydney Water's building plan approval requirements.
• Granny flat constructions
  Safeguarding sewer infrastructure when extending residential properties.
• Demolition and excavation
  Preventing accidental sewer pipe damage during site clearing.
• School campus expansions or new educational facilities
  Maintaining sewer integrity in high-traffic areas.
• Road construction projects
  Strengthening sewer mains beneath highways, streets, and pathways.
• Civil infrastructure projects
  Supporting long-term urban planning and public utility networks.
• Public parks, sporting facilities, and recreation areas
  Preventing disruption to essential wastewater services.

By encasing sewer mains in concrete, these projects can proceed without compromising essential wastewater systems, ensuring long-term durability and compliance with Sydney Water regulations.

Process of a concrete sewer encasement

Before you can receive a Section 73 Compliance Certificate or Building Plan Approval, you will need to adhere to the Sydney Water Notice of Requirements, and these may include the need for a sewer encasement.

The most common process and steps for a maintenance-free concrete sewer encasement are:

1. Approval
   Before any concrete sewer encasement works can commence, the works will need to be approved by a Water Servicing Coordinator (WSC) who is accredited by Sydney Water. This approval will usually form part of your Building Plan Approval works but sometimes can fall under Section 73 works also. Once the project has been approved by an accredited Water Servicing Coordinator, the concrete sewer encasement works may commence on site.
2. Excavation
   The first step of the construction works is to excavate the existing sewer main. Depending on the depth of the sewer main and ground conditions, sometimes the trench will need to be supported by trench shoring or will have to be benched out to ensure the trench is stable and safe to work in.
3. Pipe Preparation
   Once the excavation is completed the sewer main must be prepared for the placement of concrete. Often the sewer mains which are old clay pipe will be removed and replaced with new PVC piping at this stage. The sewer main will have to be supported and fixed so that it is straight and on percent of fall to ensure it does not move when the concrete is being poured.
4. Inspection
   An inspection of the sewer encasement will need to be undertaken by the Water Servicing Coordinator (WSC) once concrete is ready to be poured. As the constructor, All Line Plumbing will liaise with your project WSC to schedule this inspection for the correct time.
5. Pouring of Concrete
   Once the works have passed inspection, concrete will be able to be poured around the sewer main. The concrete will fully encapsulate the sewer main making the pipeline structurally sound and "maintenance free".
6. Backfilling
   After the concrete has adequately cured, the trench can be backfilled back up to the existing ground level and site will be tidied. This is the last step for the on-site construction works.
7. Work as Constructed Documentation
   The last step of the concrete sewer encasement construction process is submission of the Work As Constructed information to the project's Water Servicing Coordinator. This will provide Sydney Water with the information of the works complete and enable them to update their records accordingly.

Cost factors for Concrete Sewer Encasements

Some of the factors which will need to be considered when calculating the cost or your concrete sewer encasement are:

• Length of the sewer encasement
  The longer the section of sewer main that is required to be concrete encased, the more material and labour will be involved with carrying out the works.
• Depth of the sewer main
  The depth of the sewer main can drastically affect the cost of the works. For deeper excavations, the trench may need to wider or supported with trench shoring and this is a major factor to consider when calculating the cost of your works.
• Access for excavation equipment to the area
  On many projects the concrete sewer encasement works may be required to be carried out at the back of a property, with existing structures in the way which prevent the works from being carried out with large excavation plant. All Line Plumbing have a wide range of specialised mini excavation equipment to fit in narrow access areas. In these instances, we also have the facilities of a concrete pump, which can be utilised where a concrete truck is not able to reach the work area.
• The ground conditions
  The ground conditions are a very important factor to consider when planning your concrete sewer encasement. Sand is very easy and quick to dig, however may become unstable when trenching at depths, and may require trench shoring or widening of the trench for stability. Clay grounds may not be as easy to dig as sand but are usually much more stable and can be benched out when trenching at deep depths.
• Surrounding structures which may limit room
  Sometimes there will be existing structures such as fences, trees, buildings and other structures on site, which limit work area where the concrete encasement will be needed. This may see the need for the excavated material to be removed from site temporarily while the works are undertaken or the works to be performed in stages to minimise the amount of material that is present in the work area.

While several factors influence the cost of your concrete sewer encasement, All Line Plumbing offers expert solutions at the best possible price, ensuring high-quality, maintenance-free concrete sewer encasements backed by industry-leading expertise.

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