Can easements or utility infrastructure prevent a dual occupancy?

Yes, they can affect a dual occupancy. Easements, sewer or stormwater pipes, electricity infrastructure and other utility services can restrict where buildings can be located on the block.

You may need to keep certain areas clear so utility providers can access and maintain their infrastructure. In some circumstances, building within an easement or utility protection area may require written approval from the relevant utility provider.

This does not necessarily mean you cannot build a dual occupancy, but the easement or infrastructure may affect the location, size and layout of the dwellings.

Reference: ACT Easements - https://www.planning.act.gov.au/community/get-to-know-your-block/surveying-a-boundary/easements