When a new utility line—such as a line for gas, electric, telephone, or cable television—needs to be installed in an urban area, it’s very common for utility providers to dig horizontally underground, also called directional boring. Since this installation method does not involve digging a trench, it avoids damage to sidewalks, patios, and landscaping, as well as existing utility lines marked by Underground Service Alert (www.call811.com
). PG&E uses this trenchless method.
However, the sewer pipes that connect private homes and businesses to the sewer main, called "laterals," are not typically marked by Underground Service Alert, so it’s possible for laterals to go undetected during directional boring. The unintentional result is that the borehole for a utility line can cross directly through a sewer lateral, creating what is known as a "crossbore."