Cross bore is that the intersection of an existing underground utility or underground structure and a secondly installed utility by using trenchless technology. This leads to directly cross old utilities, compromising the integrity of either or both utility or underground structure. In the previous few decades, communities have grown rapidly. Also, demands on communication which rely on utility infrastructure have grown at a fair faster rate. Today, the society is fairly dependent on high speed communication in virtually all aspects of everyone’s life. All this data must have a robust physical infrastructure to support it. We still have not realized “wireless”. Wireless is not real wireless, just a remote connection to a physical network cable. Our need for advanced, improved infrastructure combined with the desire of protection and aesthetics results in moving these lines underground. This caused countless additional miles of new installations being conducted every day. What’s more, these installations pose a potential risk to existing lines. Especially sewer lines, which are often the foremost vulnerable. With such a high demand for utility upgrades and new installations in developed areas, traditional trenching would not be considered. Not to mention there is also a requirement to minimize disruption to homes and businesses within the scope of those projects. Traditional trenching undoubtedly minimizes the risk of an unknown utility strike. Because of the mess and disruption of using this method, it is often seen as an unacceptable solution. Though trenchless excavation or horizontal directional drilling may be a valuable and effective method for installing new utilities without the mess and disruption that can occur with traditional trenching. It may result in undetected utility strikes. Sewer lines are especially susceptible. Since, typically, there is no immediate loss of service nor visible feedback, like water spraying out, to the operators that a strike has occurred. This damage can remain undetected for days, months or even years, depending on the specific circumstances. In America, many cross-bores involve sewer laterals on private property, which are exempt from One-Call legislation in many states. These sewer lines are often not made of metal and are difficult for pipeline installers to locate using traditional methods. As a result, lateral sewer lines have not always been located and marked before drilling, which can potentially lead to cross-bores being created. Utilities have been making changes in their operating practices since the early 2000s, as they have come to understand this phenomenon. But because the trenchless drilling machine operator cannot actually see the head of the boring equipment during tunneling, they rely heavily on accurate "locates" to show them the location of other existing underground utilities. Unlike other types of underground utilities, sewers are traditionally difficult to locate. As mentioned, they are product of non- metallic materials and are installed without any other form of aid to permit them to be located from above ground. Sewers can also be very old. Records can be incomplete. Even "ownership" of the sewer infrastructure usually changes from the municipality to the property owner at some point between the sewer main and the building. Additionally, if for a few reasons either the gas line or the sewer line was installed at an unusual depth and the sewer line could not be accurately located, a conflict can occur. Dave Wisniewski, vice president of Underground Solutions for Vermeer, explains how there can be cross bores connections in two reasons. Firstly, it is hard to detect sewer laterals. Some pipes are nonmetallic, which makes them tougher to seek out and locate with locating systems. More often, they are made of clay or concrete, which can be hard to see in clay or soil. Secondly, sewer laterals often lie in areas of land where underground utility maps might not exist. They are usually on private property and technically fall within the jurisdiction of the property owner. But it is not realistic to expect the average homeowner themselves to locate and record their position. Meanwhile, municipalities usually own the mainline sewer pipes, and in many cases are exempt from state requirements for One Call locating services. This can make for poor utility location record keeping. “The biggest issue with cross bores could also be the ambiguity,” Wisniewski says. “There is no one specific person or entity who clearly has the responsibility and, therefore, incidents happen.” Risk Associated As cross-bores first being noticed by policy and public in 1976, a sewer drain cleaner hit a cross-bored gas line, causing an explosion that resulted in two deaths. While this tragic incident brought awareness of cross-bores, there are many cross bores connections remaining undetected underground for years. Now it is a known incontrovertible fact that natural gas cross bores through sewer laterals can blow up houses. Even telecommunications drilling has resulted in home explosions when crossing gas lines. Cross bores of sewer lines can result in unintended sewer blockages that may cause a backup of wastewater into buildings or homes creating dangerous consequences for residents. So as to clear these blockages, plumbers may favor to use a mechanical rotary tool, or root cutter, to clear a sewer line. But this may damage a natural gas line that has been unknowingly inserted into a sewer line. References 1. https://www.nassco.org/sites/default/files/NASSCO_TechTipsDec2017_Web.pdf 2. https://www.goecotech.net/what-is-a-cross-bore-and-how-does-it-occur/ 3. https://www.ncsl.org/research/energy/cross-bore-prevention.aspx 4. https://www.uniongas.com/about-us/safety/cross-bore-safety 5. https://www.navigatornation.com/blog/post/cross-bores-are-one-of-the-biggest-challenges-facingtrenchless-contractors 6. https://www.bhug.com/news/new-technologies-help-mitigate-cross-bore
