Whichever construction technique is used to install underground service utilities, the project is greatly improved by an understanding of the existing services and the ground in which they are to be installed before work commences. This is particularly important for trenchless projects, where the project design is based on a site investigation report. In open cut projects, the trench itself is often 'the investigation' and the plan usually involves solving problems as they occur. Advances in the design and use of CCTV have considerably reduced the cost of surveying water and sewage networks, and information on conditions below the water level can be obtained by the use of ground penetrating radar. A traditional rule for most underground projects is that cost usually rises in direct relationship to the depth of work below the surface. As a result, the first consideration has been to make any new installation as shallow as practical, and any access to an existing service as short and direct as possible.

For trenchless projects, experience has shown that there is little relationship between cost and depth. For work on existing services, the access points already provided could be used and work can be planned to reduce disruption.

For new projects, the nature of the ground and depth of the water table can influence the chosen technology and process to be used. By using Trenchless technologies, project designers can take advantage of the most favourable ground conditions, irrespective of depth, allowing for the installation of new services in areas where open cut methods were previously impossible.

The ability to install pipe at great depths can help to simplify designs by allowing longer pipe runs with shallow gradients, thus avoiding the need for pumping stations and sumps. This facilitates pipe installation below already congested underground areas close to the surface in towns and cities.