Fencing and safety

Land development reference 5.3.5

Fencing requirements

For public safety the need for fencing of all structures should be considered. For example, all inlet and outlet structures in the proposed system will require fencing.

A fence should also be included in the design for any other structures which have a vertical drop exceeding 750mm and are accessible to the public.

Conventional fencing shouldn't be used to cross floodways as debris will tend to build up against them. This may worsen flooding upstream and could create a potential downstream flood wave if sudden failure was to occur. In some unique situations (subject to our approval) floodway panels may be used to cross floodways where security is required. Floodway panels are designed to break away at their base under pressure and fall back as the flow reduces.


If entry to an existing underground drain is required, it's necessary to contact us to arrange inspection. Entry into any underground drain must only be undertaken by persons appropriately qualified in Confined Space entry.

Various other safety hazards exist in underground drains. These include:

  • drops

  • silt traps

  • ventilation

Grates should be provided to inlets to deter entry, but grates shouldn't be used on outlets.

Fencing should be used to provide security to outlets.

Designers should consider the safety of the public during flooding. If persons could be washed into a drain then they should be able to be washed out.

Depending on the situation, it may be appropriate to design for the invert of the outlet to be permanently drowned out to deter public access.


A safety bar should be installed across the drain immediately upstream of a drop structure. Step irons should be built into the make up sections for hand-holds at drops and transitions.

Silt traps

A potential hazard exists if silt traps are designed to be included within the underground drain. These can be difficult to clean and dangerous gases will emit from the build up of organic silt. This problem can be avoided by designing silt traps that are included in the outlet structures where they can be more easily cleaned.

Dangerous gases

To minimise the possibility of a build up of dangerous gases in underground drains, Gatic Type BV (or similar) covers must be used on all drains to be vested in us. These covers are a vented version of a Type B cover.


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