Cross-Bore

Cross-bores occur when a utility is installed using horizontal directional drilling (HDD), boring, or other trenchless methods and unknowingly passes through an existing utility, typically a sewer pipe. The most dangerous cross-bore scenario involves a natural gas line penetrating a sanitary sewer lateral, which can cause gas to migrate into buildings and create explosion risks when the sewer is later cleaned with a mechanical rooter.

The cross-bore problem gained national attention in the 2000s after several explosions and fatalities were linked to gas lines that had been bored through sewer laterals. In response, many gas utilities launched cross-bore inspection and remediation programs, using CCTV sewer inspection to identify locations where gas lines intersect sewer pipes. When a cross-bore is found, hydrovac excavation is typically used to expose the intersection point so that the gas line can be safely rerouted.

Preventing cross-bores requires accurate utility locating before trenchless installation, and hydrovac potholing is the most reliable method for verifying the position and depth of existing utilities along a proposed bore path. Many utilities now require potholing at regular intervals along HDD routes to prevent cross-bore incidents.