What is a Cross Bore?
Trenchless technology, such as Horizontal Directional Drilling (HDD), has revolutionized how utilities are installed in Colorado. It allows contractors to lay miles of new fiber optic, gas, and power lines without tearing up roads, sidewalks, or beautiful landscaping.
However, drilling underground blindly comes with a massive, hidden risk known as a cross bore.
A cross bore occurs when a trenchless drilling machine accidentally bores directly through an existing underground utility. The most common—and most deadly—type of cross bore happens when a natural gas line is drilled straight through a private sewer lateral.
The Ticking Time Bomb
When a gas line intersects a sewer pipe, it usually goes unnoticed. The drilling machine pushes the gas line right through the PVC or clay sewer pipe, effectively plugging the hole it just created. The gas line works fine, and for a while, the sewer line might even continue to drain.
The disaster strikes months or even years later when the sewer line inevitably backs up. A plumber or homeowner will rent a mechanical drain snake or rooter to clear the clog. The sharp, spinning blades of the auger will tear right through the plastic gas line blocking the pipe.
Suddenly, high-pressure natural gas floods the sewer line, travels up the pipes, and fills the home or business. A single spark from a water heater or light switch can cause a catastrophic explosion.
How to Prevent Cross Bores Before Drilling
The only way to prevent a cross bore is to know exactly where every intersecting utility is before the directional drill is put into the ground.
1. Don’t Rely Solely on 811
While calling 811 is required by law, it is not enough to prevent cross bores. 811 marks public utilities, but the vast majority of sewer laterals (the pipe running from the building to the municipal main in the street) are considered private property. 811 will not mark them, leaving trenchless contractors totally blind to their location.
2. Comprehensive Private Utility Locating
Before any trenchless excavation begins, a private utility locating firm like JLP Tech must be brought in to scan the bore path.
- Electromagnetic (EM) Locating: We can use traceable rodders inserted into the sewer cleanout to send an EM signal directly from the underground sewer pipe, allowing us to map its exact depth and trajectory on the surface.
- Ground Penetrating Radar (GPR): For complex intersections, GPR can detect non-metallic pipes and provide a clear 3D image of the subsurface, ensuring the drill path is completely clear of obstacles.
3. Potholing (Daylighting)
Once the utilities are marked, contractors must physically expose the existing utilities (often using non-destructive vacuum excavation) at the exact point where the drill path crosses them. This allows the drill operator to visually verify that the drill head passes safely above or below the existing pipe.
Protecting Colorado Communities
Cross bores are an entirely preventable disaster. Whether you are a telecom company installing new fiber optics in Boulder or a plumbing contractor replacing a water main in Denver, skipping the private locating phase is a risk you cannot afford to take.
Contact JLP Tech today to ensure your next trenchless drilling project is completely safe, compliant, and free of hidden hazards.