Sewer Main Line

A sewer main line is the primary pipeline in a sewage. There are branching pipes from different locations that connects to the main sewer line. A sewer lateral line is the underground pipe that connects a residence or business to a main sewer line. Using traditional methods, pipeline installers have difficulty locating nonmetal sewer lines. As a result, lateral sewer lines go unlocated and unmarked prior to drilling which potentially leads to cross-bores being form.

What is cross bore?

A cross-bore is the unintentional drilling of a new pipeline through legacy pipelines using trenchless drilling technologies. Cross-bore compromises the integrity of underground infrastructure. It is not a danger on its own. But in time, sediment builds up and blocks the sewer line. The build-up contributes to even more damage to the pipeline. Cross bores create a pathway for bacteria and other contaminants to enter pipeline.


Cross bores pose a serious safety risk because it can allow gas or other hazardous materials to leak into the tunnel and becoming a risk to public safety. By planning and coordinating between utility companies and contractors, cross bores can be prevented. Once a cross bore is identified, utility companies should work together to avoid or mitigate the hazard. Utility companies and contractors can do regular inspections on their facilities for cross bores and take steps to mitigate any that are found.


There are several ways to detect cross bores. Visual inspection is typically the first step when locating cross bores by obtain an accurate and current underground utility drawing or map of the area. After obtaining drawings or a map of the area in question, inspect to see if there are any features that may indicate the presence of cross bores. Some features can be change in the surrounding soil, evidence of previous drilling activity and anomalies in the pipeline or duct. Ground Penetrating Radar (GPR) is an electromagnetic imaging technique used to detect the presence of a cross bore. GPR is used to detect what is not visible to the naked eye and to map the orientation and location of the bore.

Source:    What is a Cross bore?

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