Page 18 - AR811 2022 issue 4

HDD Brings
Challenges in
Damage
Prevention
By Michael Downes 811 Magazines
As more utilities and contractors embrace trenchless technologies for installing new underground facilities, the risk of deadly cross
bore incidents grows. Utilities and organizations like the Common Ground Alliance (CGA) are spreading the word of caution to stakeholders, including a group not commonly associated with damage prevention — plumbers.
A cross bore incident occurs when
a new facility is accidentally pulled through an existing buried line — most commonly sewer pipes — rather than crossing over or under the existing line. While every effort is made to locate all underground facilities, some parts of the sewer network are not mapped and take some extra effort on the part of field crews to avoid striking them.
Lance Andrews, director of operations for Atmos Energy in Dallas, Texas, spoke about the challenges of avoiding cross boring incidents during a recent presentation.
“Everyone in the industry wants to know what’s underground,” Lance said during a recent telephone interview. “We do things like calling 811 to get accurate locates, and “potholing” the facilities to ensure that we don’t damage them.
“What causes special challenges with sewer lines is that most laterals to
the sewer main are owned by the residential or commercial customer. Municipalities don’t locate the portion of the system between the house and the property line. Those present a more significant challenge than other utilities,” he said.
With the advent of horizontal directional drilling, pneumatic piercing tools and other devices that allow electric, gas and communication lines to be installed with minimal interruption to the surface, cross bore incidents have been on the rise. And typically, those cross bore incidents involve branches
of a sewer line that aren’t part of the locate request.
When an unmapped sewer line is expected — like in a residential or commercial utility right-of-way — workers should take extra care to
locate all buried obstacles. Lines can be located by inserting a metal fish tape into the plastic or terra cotta pipe at the house’s sewer clean-out access point and using sensing equipment at the surface to locate the approximate location
of the facility. Specialized ground- penetrating radar can also be used to locate plastic pipes without a tracer wire, Lance said.
No matter how the line is located, CGA considers “potholing,” or exposing the third-party facility, to be the best way to avoid the danger of a cross bore incident and other types of facility damage.
“If you expose the third-party utility, you can see it. You can see your bore
go across it without damaging it. You have a visual indication that no damage occurred. Exposing and potholing are considered best practices by CGA,” Lance said.
But when care isn’t taken and a sewer line is compromised by another utility, it creates a ticking time bomb scenario in someone’s backyard.
“There’s no immediate indication of damage to a sewer line,” Lance said. “If due diligence isn’t taken to locate the facility and someone bores through a sewer line and pulls their facilities back through, they might not know right away,” Lance said. “If you cut a water line, water flows immediately. If you
cut a gas line, gas blows. If you cut an electric line, someone’s power goes off. With a sewer line, it may take months or years for a clog to form where the lines cross, and eventually it clogs enough for someone to call a plumber.”
But an overflowing toilet, however inconvenient, isn’t the real hazard presented in cross bore incidents.
When a business or homeowner calls
a plumber to clear out their sewer,
they have no idea there’s a cross bore situation creating the clog under the ground. If the plumber doesn’t inspect the pipe with a camera before using a mechanized plumber’s snake, widely known as a Roto-Rooter, a deadly utility strike could occur, Lance said. The metal cutting surface of the snake is intended to cut through tree roots, but in several instances, they have sliced through gas lines and electrical conduit within the sewer line, resulting in explosions, fire, death and other injuries to workers and bystanders. The Common Ground Alliance and other groups are getting the word out to plumbers and other workers to make them aware of the possibility of cross bore situations.
Using CGA best practices and anticipating unmapped lateral sewer lines in the field, utility workers can avoid cross boring of utilities and ensure their safety — and the safety of others.
16 • Arkansas 811 Magazine 2022, Issue 4