Clearances to Other Services
Separations, crossings and the alternatives where space is tight.
Sewers share the subsurface with water mains, stormwater, gas, electricity, telecommunications and other utilities. Minimum separations protect both assets and the people who work on them, and they are a standing requirement of every authority and utility owner.
Where separation cannot be achieved, a designed alternative is required: encasement, structural protection, relocation, or a departure agreed in writing with the affected asset owner.
Reference table
| Interface | Design consideration |
|---|---|
| Water main crossing | Vertical relationship and encasement requirement set by the water authority |
| Stormwater | Grade compatibility, crossing angle, and responsibility at the interface |
| Power and communications | Clearance, warning devices, and excavation restrictions near the asset |
| Gas | Clearance and the asset owner's excavation and notification requirements |
Key design considerations
- Minimum horizontal and vertical separation by service type, from the authority and each utility owner.
- Crossings are normally arranged at right angles, with the required vertical relationship and encasement where separation is tight.
- Locate all services by potholing before fixing levels; dial-before-you-dig plans are indicative only.
- Maintain clearances at maintenance holes, property connections and thrust or anchor blocks.
- Allow for future services and for access to other utilities for maintenance.
- For work on the property side, AS/NZS 3500.2 separation rules also apply.
Design checks
- Separation checked at every crossing on the long section.
- Asset owner approval obtained where separation is reduced.
- Services located by potholing before construction levels are fixed.
Standards and authority references
- WSA 02 Gravity Sewerage Code of Australia (current edition), Water Services Association of Australia
- Authority and utility owner clearance requirements
- AS/NZS 3500.2 Sanitary plumbing and drainage
Confirm the current edition, amendment and any local supplement before applying any of the above.
Limitations and assumptions
- Clearance dimensions are not reproduced here.
- Utility owner requirements can be more onerous than the water authority's.
This reference is general engineering information. Confirm requirements against WSA 02, the current Australian Standards and the local water authority's supplement before use in design, and obtain project-specific advice for the conditions at hand.