The two installations options currently available for access to underground utility services are Open Cut and Trenchless.

For access by open cut there are four stages:

• Excavation of the trench, removal of spoil and temporary support of other services.
• Laying and jointing the product pipe.
• Refilling the trench and compacting the selected spoil or filling material
• Restoring above ground infrastructure

All four stages are characterised by the amount of physical work to be undertaken. Typically, 50 times the amount of spoil to be occupied by the product pipe has to be moved once during the excavation and again in refilling.

Much of the work in all four stages is labour intensive, involving different skills that require co-ordination between several companies and authorities. A large project can extend over a long period and be very disruptive in social, economic and environmental terms. Access using trenchless techniques also requires surface work, but not on the scale needed for an open cut approach.

Trenchless Technology projects require careful consideration of the existing condition of the underground pipes and ground conditions in order to select the most appropriate technique. The technology and approach must be determined and the surface work must be conducted using an existing access or by digging access pits.

The determination of the technique, location of the access pits and the route for a new pipe requires an initial survey. This is often viewed as an additional expense in comparison to open cut techniques. However, the cost of the initial survey stage of a trenchless project is usually offset by a shorter time on site.

Trenchless technologies present a number of unique advantages. With new installations, engineers can install pipe in the most favourable stratum, irrespective of depth. For gravity sewers, significant savings can be realised by retaining gravity flow and avoiding pumping stations.