GPRS has done a lot of great work for The Detroit Zoo over the years, so it was no surprise when they contacted us to locate underground utilities this spring.
Most people think of using ground penetrating radar (GPR) to avoid hitting a gas main or an electrical conduit before excavating for construction or demolition. However, one of the many ways GPR can be of service for large facilities, municipalities, or campus sites is locating vulnerable utilities near mature trees. Tree roots can extend to 2-4 times the circumference of the crown and to depths of up to 20 feet as the tree matures, so when you need to relocate or remove older trees, utilities can be compromised.
As GPRS Project Manager Trey Merrell shared at the zoo, “They want to take out some trees, grind down the stumps, and pull them out. They didn’t think there was much here, but we found a few utilities.”
The “few” utilities Merrell located on that particular day included electrical lines, a gas main, and a water main. Hitting any of those lines while digging up tree roots could cause a dangerous and costly accident for the City of Detroit, so it was vital that they knew their locations and could avoid a utility strike.
In fact, the average cost of a campus or facility utility strike, according to the 2021 Finch Report, is $56,000 in repairs, delays, and downtime. In a public venue like the Detroit Zoo, that cost could skyrocket due to the nature of the facility and the safety of the animals and people who could be impacted, both short and long-term.
Another way in which tree roots and utilities are intertwined is that when a root system encounters nutrient-rich and hydrated soil, like the kind that can be found near a leaking water pipe, the roots will speed up their division process to take full advantage of the “optimal” conditions.
As reported in The Arborist Network’s Tree Root Damage to Pipes report, “Tree roots are opportunistic, and they are stimulated, elongate and divide more rapidly as moisture levels and the surrounding temperature approaches optimal levels for the particular species.”
That’s how a simple pipe fracture can turn into a full-blown root blockage in a water or sewer line. The problem, of course, is that until the water pressure drops, standing water develops above ground, or the water stops flowing, there are no visible signs of a compromised utility. That’s where an annual water loss survey or a full NASSCO-certified Video Pipe Inspection report can save the day. The GPRS VPI report details every pipe defect and obstruction in your system, provides photos and video, and ranks pipe defects by severity, so you can tackle the most serious problems first to get the water flowing.
Once a root obstruction has been located, any number of actions can be taken to remove the tree roots and repair the pipe. One way to clear a pipe is to utilize hydro jetting, where high-pressure water is forced through the pipe to sweep away debris. Another option is to use a “root killing” solution that is flushed down the pipe, and a third option is to simply excavate the whole pipe, clear the roots, and hope that’s solved the problem. Regardless of the way you clear the pipe or drain of roots, once the blockage is cleared, the affected pipe can usually be excavated and repaired with minimal additional damage.
Back in Detroit, Merrell also showed Palko how the zoo uses camouflage to hide utility infrastructure from zoo visitors.
“A lot of facilities like this, they have public-facing areas and then private-facing areas. They try to disguise their utilities from their guests.” He went on to explain that the stockade fencing used by the zoo to hide unsightly utility infrastructure can make his job more challenging because it obscures the aboveground evidence of buried utility lines. That’s one of many reasons why hiring an experienced professional utility locating service with decades of experience can make facility, municipal, and campus construction, renovation, and O&M a lot easier.
GPRS has achieved and maintains a 99.8% accuracy rate on utility locates and concrete scanning on over 400,000 jobs nationwide. We Intelligently Visualize The Built World™ for our clients above and below ground, every day.
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