During design or planning, cost savings can be achieved by reducing utility conflicts and identifying unknown utilities before construction begins. This can result in better bid documents and lower bids.
Before construction begins, it is a best practice to locate the utilities and to reduce risk. Damaging or disruption of critical utility services such as fiber optic cabling, communication and electrical lines, or gas piping during construction is costly (change orders, time delays, and repairs) and potentially dangerous. Something as simple as digging a hole to plant a tree has the potential for damage.
The earlier in the project that the utilities are known the more opportunities there are for cost savings.