Page 16 - AL811 2022 issue 4

Cross Bores: A Dangerous Intersection
By Tre Hayes and Jason Smith Colliers Engineering & Design
According to the U.S. Department of Transportation (DoT) Pipeline and
Hazardous Materials Safety Administration (PHMSA), there is
over 2.5 million miles of pipeline underground. Over 300 companies operate the pipes long enough to wrap around the Earth 100 times. So, what happens when utilities are fighting for underground space?
What is a Cross Bore?
A cross bore is defined as the intersecting of an existing utility or underground structure by a second- party utility, resulting in the direct contact of the different utilities and compromising of either or both structures. The most common cross bores seen today are between natural gas pipelines and sewer systems.
Despite the high amount of danger cross bores can have on contractors, homeowners and the community, The Cross Bore Safety Association (CBSA) states that they were recognized as a high-level risk to utility workers only a few decades ago. In 1976 the U.S. DoT concluded that two fatalities and four injuries that year were due to a cross bore of a gas distribution line and a sanitary sewer. Contractors brought cross bores back into the conversation in the late 1990s when two major natural gas installation contractors began recognizing what caused cross bore gas explosions, with their utility installed in sewers.
Cross bores are not just dangerous for contractors and utility workers; they are also a hazard for homeowners. The CBSA reports that the primary reason cross bores were previously detected was due to back up in a home’s sewer system. Homeowners or contractors would use drainage tools to break
the blockage and sometimes, would break the crossing utility’s system in
the process. These often resulted in catastrophic explosions, fires, injury and sometimes death.
Engineers at Collier’s Engineering & Design (CED) have experienced the effects of cross bores firsthand and are
Illustration of what a cross bore looks like underground
working to expand education on the dangers they possess.
SUE Saves the Day!
Experts and associations agree that a full and thorough subsurface utility engineering (SUE) investigation can help contractors avoid catastrophic damage. With new advancements in technology, engineers can not only prevent cross bores from being created but assist in safely identifying possible cross bore locations for homeowners, contractors and utility companies.
“We need to make SUE investigations more available to workers across the state to make sure the job is done right,” said Tre Hayes, Senior Subsurface Utility Engineering Manager at CED’s Dallas office. “Finding qualified people to do the investigation and having it mandated rather than a suggestion will not only protect the lives of the workers but will help protect the community surrounding the area.”
Currently, Colorado is the only state
to mandate a SUE survey for an installation of a new utility in the pre-construction stage. Mr. Hayes believes all 50 states should adopt laws requiring this as well, stressing the importance of how being a few feet off in boring could have catastrophic effects.
“There are ways we can do these important surveys without leaving a trace. We have technology available to
us that will greatly benefit the current and future utility workers. It doesn’t take much to prevent a disaster,” Mr. Hayes added.
So, Can We Prevent Cross Bores?
The good news is cross bores are completely avoidable when it comes to the installation of a new utility. Jason Smith, Subsurface Utility Engineering Manager at CED’s Nashville office says that the prevention of cross bores starts with educating the public and utility contractors on the dangers they can cause.
“It is so important to get in front
of these projects and help the contract workers and utility staff identify potential crossings prior to construction,” Mr. Smith said. “A full SUE investigation can prevent cross bores from being created. Homes and buildings need these utilities, but we need them to be installed safely and correctly.”
If a cross bore was installed, SUE technicians would also be able to identify them during their after- construction inspection. Some of the ways SUE field staff investigate a site include sewer tunnel equipment, GIS mapping and cameras. All investigations progress through four quality levels from D to A, ranging from collecting previous as-builts and other records
for the location to drilling holes to
test the investigation’s accuracy. All data collected can also be adjusted and shared as needed, sharing the wealth for future projects. Deliverables vary depending on the project but often include field data, test hole data, and designation data digitally saved in a CAD file or GIS map.
Overall, cross bores are a serious threat to service workers, homeowners and the communities they surround. The inclusion of a SUE investigation can not only prevent the creation of a new dangerous intersection but identify the risks before it’s too late.
Tre Hayes is the Senior SUE Manager for Colliers Engineering & Design | Dallas Jason Smith is the SUE Manager for Colliers Engineering & Design | Nashville
14 • Alabama 811 2022, Issue 4