The Hidden Dangers of Cross Bores: What You Need to Know
A cross bore occurs when a newly drilled underground utility pipeline intersects with an existing underground utility pipeline, such as a sewer, septic line, or fiber optic duct. This “intersection” can cause potential hazards, such as damage to the existing pipeline or accidental release of hazardous materials if utility companies and contractors do not take proper precautions during drilling and excavation. To mitigate the risks associated with cross bores, all contractors must accurately locate and mark all existing underground utilities before starting any excavation work and follow all relevant safety regulations and industry best practices.
One example occurs when a contractor installs a new natural gas line using trenchless methods. Another frequent cause of cross bores happens when information about the locations of pre-existing underground utilities is missing or incorrect.
According to the Cross Bore Safety Association (CBSA), gas distribution pipelines are sometimes the highest utility risk category from cross bores. The ratio of gas lines intersecting lateral sewers compared to intersecting mainline sewers ranges from 4:1 in some systems and, in others, 1:1. Intersections in mainline sanitary sewers are less frequent due to the depth of collection sewers and the frequent higher elevation of gas pipeline installation.
Cross bores happen more often than you might think. According to CBSA, the average rate of a cross bore is 1 in 0.4 miles of mainline sewer.
Mario Chavez, an Area Manager at Equix Integrity, explained that while the frequency of how many cross bores his team finds while on the job can vary, he estimates they see an average of one cross bore per week.
“We have experienced very high rates of finding a cross bore in as much as one in twenty inspections and rates as low as one to two per year in tens of thousands of inspections,” said Andrew Undicelli, General Manager at Equix Integrity. “How often you find a cross bore is fully dependent on the cross bore program put in place by the utility.”
The discovery of cross bores may seem like a small problem, but they can have extremely dangerous consequences. Our experts attested that if a cross bore is present but is not detected, it can cause backups in the sewer lateral or damage the structural integrity of a pipe.
“If a drain cleaner or wastewater professional is unaware of the intersecting gas line and attempts to drill through one of these blockages, they can cause severe, even deadly, explosions,” said Chavez. “Anyone near the blast is at serious risk of injury or even death, costly claims, lengthy litigation, and damage to the reputation of the entities involved. Further, cross boring into a sewer line could result in groundwater contamination.”
Efforts toward cross bore risk reduction began in the mid to late 90s, according to the CBSA. Since then, mitigation efforts have grown to include improved processes and technologies. Therefore, it is crucial that underground utility contractors band together to stay up to date on knowledge of best practices and these new technologies.
Equix Integrity does just that with our cross bore inspection services, which allow our clients to mitigate the risk of causing a cross bore during construction and identify any cross bores in existing utility systems. Our experts use closed-circuit television (CCTV) inspection trucks and remotely controlled cameras to document utility lines. In addition, our integrated sonde locating device provides industry-leading accuracy.
Performing inspections takes skill, perseverance, and a detailed eye. Our team never knows what awaits them in their search, but they work hard to prepare for any challenge they may face.
“Inspections can be challenging to locate because the contractor is identifying them in an underground utility that may not have been maintained for decades,” said Undicelli. “The sewer main or lateral may need cleaning or repairs to gain access.”
According to Chavez, the biggest challenge we face while performing a cross bore inspection is being able to traverse the sewer main.
“We often run into heavy debris or collapsed lines, so we either must clean the lines with our Jet/Vac trucks to get through or set up on the opposite side of the line and attempt to televise through that direction,” said Chavez. “If we can’t traverse through the sewer main, then our crews must go door to door and inspect the laterals through the cleanouts.”
Once our team locates a cross bore, we immediately notify the utility owner, capture videos and pictures, and then find it on the surface.
“This ensures the utility can mobilize a crew to repair the cross bore and eliminate the risk immediately,” explained Undicelli.
Unfortunately, as our team works to find and report cross bores, more are being created. So, how do we fix this? What do we do to prevent these dangerous accidents from happening?
Mario and Andrew shared their expert advice with us.
A robust cross bore program that utilizes pre- and post-construction inspections is considered the best practice to prevent cross bores. In addition, establishing clear communication between the inspecting contractor, the drilling contractor, and the utility owner is essential. Equix achieves collaboration and team communication by utilizing online dashboards populated with real-time locates and inspections. As a result, all stakeholders can access information in real-time and ensure information is available upon construction.
“Communication is key. A lot of the cross bores we’ve encountered resulted from information not being interpreted or relayed properly,” Andrew explained. “Understanding the importance of this service and the potential consequences starting from senior management down to the field technician is paramount.”
“Avoiding cross bores can be as simple as conducting a sewer lateral inspection before and after a new gas line is installed,” said Mario. “Taking steps to ensure you know where laterals are and performing post-drilling inspections is key.”
These are great tips we can share with others and work to do ourselves. We implore each of you to support cross bore work and prevention in your community, and we’d love to help you do that! Visit our Contact Us page to get started today.