Protecting pipelines

Here you will find information about protecting our pipelines during construction works, including clearance distances, soil cover, backfilling and reinstatement.

You will need to follow these guidelines when working near our pipelines:

Maintain clearance distance

Maintaining adequate clearance distances to other services is essential to:

  • ensure adequate access for future maintenance, repairs or replacement
  • reduce the risk of pipelines being impacted by other assets or works located nearby
  • reduce the risk of impacts on other parties’ infrastructure our pipelines or associated works.
Overhead clearance, or headroom, of at least 15m from ground level over pipelines is required to enable access for lifting equipment.

For pipelines with a diameter of less than 300mm, the minimum vertical clearance must be at least 150mm. For pipelines with a diameter of more than 300mm, the minimum vertical crossing must be at least 300mm.

Greater clearances are required when:

  • services run parallel to our mains
  • greater protection or access to a main is required.

Provide adequate soil cover

The soil cover over pipelines provides support and protects them from excessive loads and damage.

The actual depth of cover may vary over time if the ground levels change. The following is a guide, depths may differ from these values:

Trunk, water distribution or drainage pressure mains – 300mm diameter or greater
  • If located in the verge, requires a minimum cover of 750mm and a maximum of 2m.
  • If located under the road a minimum cover of 900mm and a maximum cover of 2m is required.
Water reticulation mains – smaller than 300mm in diameter
  • If located in the verge, the minimum cover required in 600mm and the maximum is 900mm.
  • If located under the road the minimum cover is 600mm and the maximum cover is 750mm.
Sewer pressure mains – any size
  • Sewer pressure mains located in the verge need a minimum cover of 900mm and a maximum cover of 2m.
  • If located under the road a minimum cover of 1m and a maximum cover of 2m is required.

The depth of cover as found on site cannot be altered either by removal or placement of material, without prior approval by us.

All damage must be reported on our 24-hour Faults, Emergencies and Security line on 13 13 75.

Uncovering pipelines

Pipelines should not be exposed and at least 500mm cover must be maintained at all times, including during road box-out, unless approved otherwise.

Minimal exposure is acceptable, such as for service crossings and if only the top of the pipeline is exposed.

You must contact us on  13 13 75 if:

  • a sewer pressure main needs to be exposed, other than at a customer service crossing
  • greater than 1 pipe length needs to be exposed, this could be 2.4m to 12m depending on the type of pipe
  • you need to expose a main for a number of days
  • you need to expose a main to  below the spring line height (i.e. mid height) of the pipeline
  • you are digging, or tunnelling is required, underneath a pipeline
  • you are digging, or tunnelling is required, parallel to a pipeline.

Our  plans indicate pipeline material type.

Asbestos cement (AC) pipes are brittle and can be easily damaged if they’re exposed or the supporting soil is disturbed.

Asbestos cement and vitreous clay (VC) pipes are assembled from short pipe lengths. Any differential soil movement can damage these joints causing a leak or burst.

Some pipelines have a protective wrap which contains asbestos. This asbestos only poses a health risk when the protective cover is damaged or disturbed.

It is essential to follow these guidelines if you need to expose a pipeline:

  • Excavators and other equipment working nearby must not travel across or strike the exposed main.
  • Loads cannot be placed on the pipeline including side loads from adjacent work.
  • The pipeline bedding or side support cannot be excavated.
  • The pipeline cannot be exposed to chemicals or excessive heat.
  • The pipeline cannot be left exposed any longer than necessary.
  • Barricades, pipe support or ground support may be required.
Unsaturated soil

If the soil is not saturated the existing soil, free of any road base, rocks greater than 50mm or other foreign matter can be returned to the excavation to 200mm cover above the pipe. This must be compacted by tamping to ensure no voids exist around the pipe. The remaining volume must be filled in 300mm lifts with 4 - 6 passes with a small plate compactor (e.g. 300mm plate compactor) on each lift.

Saturated soil

Excavation should be dewatered, so that backfilling and compaction can be done using unsaturated soil. Cement stabilisation will only be permitted when there is no alternative.

If the soil surrounding the pipe is saturated, cement stabilised sand (sand:cement ratio no stronger than 20:1 by volume) must be used to 200mm above the pipe. This is to be compacted by tamping to ensure there are no voids around the pipe. The remaining volume is to be filled in 300mm lifts with 4 - 6 passes with a small plate compactor on each lift.

Reinstate the surface as required by the local authority. Please refer to the Main Roads Restoration and Reinstatement Specifications for Local Governments for more information.

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