Stratus’Ground Disturbance Defined Practice details many types of controls that can be put in place (blind sweep, line location, potholing, etc.) to reduce the probability of striking underground utilities.

The following is an example of a Stop Work event that was required because a line was discovered – even with all the controls in place.

Scope and Preparation: The contractor was onsite to oversee the in-place abandonment of underground storage tanks (USTs). Prior to the ground disturbance activities, both public and private utility locating service activities had been completed  for the required sweep zone of the excavation areas (30-feet minimum).

Stop Work: During excavation, a ½” copper water line was encountered within the UST pit that had not been identified by either of the utility locate services. When the line was identified, Contractor personnel onsite called a Stop Work and the project manager (PM) was notified.

Assessing Risk: The line appeared to be abandoned and associated with the USTs, given its location (crossing the pit between fill ports). The Stop Work remained in effect until the private utility service could conduct additional locating for this line, which was carried out the next morning. The utility locate determined that the line was no longer connected to any above or below ground structures and was in fact, abandoned.

Resume Work: Once confirmed, the Stop Work was ended, and the excavation resumed onsite without further incident.

Learnings: It was determined by the utility locating service that the copper line was not identified by either of the previous locates due to the line’s location over the USTs. The public locate did not identify it because it did not terminate at the surface and the private locate (which had been conducted with a ground penetrating radar and EM) did not identify it because it had been masked by the signals received from the USTs.

Remember: Good planning and communication up-front is key to safe work but it doesn’t always end there. Be prepared to reassess and update communications as conditions warrant.