Directional drilling is a fast and efficient way to install underground pipe and conduit, but when a gas line is bored through a sewer line, disaster can ensue.
Cross Bores – when a line bores through a sewer line – have been the cause of catastrophic events in the past. To combat this issue, municipalities, utilities, contractors, and the trenchless industry must join forces to ensure proper pre- and post-inspections are conducted and avoid disaster.
There are almost always more connections than what surface observation suggests. The reality is that subsurface most likely there are more connections than marked after an 811 call. Municipal utilities must learn to spatially map out subsurface infrastructure during routine maintenance to improve accuracy for 811 locator requests.
Auditory systems with GPS capabilities (SL-Rat) and CCTV Camera systems have made an incredible positive impact on finding the missing conditions. By using an auditory inspection system like the SL-Rat (OMAG has several to loan to municipalities) a municipality can map their sewer system. Then they can use a CCTV camera (OMAG has grants available for these) through sewer mains. In this way, line taps can be identified and recorded to inform utilities or system owners, and potential hazards can be addressed prior to drilling. Equally important is to make post-drill inspections to confirm lines have not been breached during installation of a utility.
While gas or communication lines are typically what we think of when we hear the term cross bore, directional drilling of other utilities can negatively impact the integrity of our sewer systems as well.
Developing a partnership between utility owners and municipalities is critical if cross boring events are to be identified and addressed to keep communities safe. Developing a comprehensive prevention program between the municipality and utility owners where they share the costs and get cross bore inspection work done economically and responsibly is a win-win for the municipality, utility, and the customers.
NASSCO, whose mission it is to set standards for the assessment, maintenance, and rehabilitation of underground infrastructure, identified the need to set standards for proper cross bore prevention and detection. The worst thing that can happen is if an operator finds a cross bore and does nothing about it. Standard assessment and cleaning of mainlines could also potentially uncover cross bores masked by roots. If a cross bore is hiding behind roots that have infiltrated a pipe and the roots are cut, disaster could occur. A significant benefit of a regular chemical root control maintenance program is the ability to kill the roots without cutting or damaging pipes (OMAG has a root control grant with Duke’s Roots).
In addition to municipalities and utilities working closely together, the relationship between utilities and contractors is extremely important for the implementation of a successful cross bore program. Developing a relationship with contractors laying pipe or conduits and working with them to identify hazards or challenges and working to develop unique solutions, provides better quality data and a higher level of confidence that we are keeping our communities, homes and businesses protected.
The most common question pertaining to cross bore inspection and remediation is always “Who is responsible?” The answer: “When is comes to keeping our community safe, we all are.”
For more information about the SL-Rat, CCTV camera, or Duke’s Roots grants contact William Sheppard, OMAG Risk Management Specialist at wsheppard@omag.org.
