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Surgically Eliminating Subsurface Surprises
Minimally Invasive Vacuum Excavation Is Fast and Cost-Effective
By Mike Twohig
Exposing underground utilities is like surgery. And there is an inherent risk in peeling back layers. Risk and healing time in the medical world have been reduced by endoscopy, a minimally invasive diagnostic procedure that involves inserting a tube into the body through a small incision in order to assess the interior surfaces of an organ. Non-destructive vacuum excavation is the endoscopy of the subsurface utility engineering (SUE) profession.
The opening is small (1 sq ft), the suctioning of earth usually swift (10 minutes or less) and the utility exposed in a safer manner than using a backhoe, excavator or even hand digging. Precise X, Y and Z locations can be captured, and in some cases, the utility can be assessed for repair or maintenance. If air vacuum excavation is used, as opposed to the hydro method, then the removed materials (if free of contaminants) can be put back in the hole — practically eliminating “healing time.”
There’s a key difference in this analogy, though. Surgeons know their way around a human body. Organs and arteries, bones, joints and muscles are pretty much in the same place from person to person, but we don’t always know what or exactly where utilities are located beneath the ground.
Out of Sight
There are millions of miles of utilities in the United States — communication, gas/propane, petroleum, water, sewer, storm, power and steam lines — weaving a spidery network of veins and arteries below the Earth’s surface. With advanced mapping technologies such as GPS and GIS, utility locators are getting better at knowing precise locations. But more often than not, they don’t know for sure, and not everyone knows how to properly read those maps.
Despite the best intentions, utilities are often mis-marked. One wrong move with an excavator, backhoe or even a hand shovel can be catastrophic for the workers, others in the vicinity, the property/utility owners and sometimes entire communities. Lives, liability and litigation have become buzzwords on the tongues of project owners, as well as the engineers and contractors hired to designate, expose, locate and perform work on utilities.
Case in point: Several years ago in Walnut Creek, Calif., workers digging a water main trench with a backhoe struck a petroleum pipeline, triggering an explosion. The costs were catastrophic: five dead, four seriously injured, property damage, project delays, criminal investigations, litigation, hundreds of thousands of dollars in fines and at least $6 million in settlements.
California safety investigators mainly blamed the pipeline owner for untrained employees who didn’t know how to read blueprints and failed to properly mark a bend in the high-pressure line. But the contractor and engineering companies were also fined, as was the water main owner.
After the Walnut Creek explosion, California enacted a law establishing tougher safety practices for excavation work conducted near high-risk utilities. Some of these practices include non-destructive excavation, as well as certified training for anyone whose job is to mark utility locations.
Other states have similar laws: the Underground Utility Damage Prevention Act (Virginia), the Underground Utility Facility Damage Prevention Act (Illinois) and the Underground Facility Damage Prevention and Safety Act (Florida), to name a few.
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