Next time that you get stuck in traffic, think about the traffic jam that is below you. There are over 35 million miles of in use and abandoned utility lines that are causing a huge traffic jam underground. Between the labyrinth of pipes, conduits and cables, it is difficult to tell what is dead or alive, because most utilities that are no longer in use remain underground.
Traditional digging can yield unwanted surprises and deadly consequences — especially in older parts of the cities where old utility lines (such as water and sewer) are still in use and undocumented. When coming across these undocumented lines, all work must stop until workers know exactly if the line is live and if it is safe to dig. This delay costs time and thus costs money. While newer plastic pipes are often color-coded to indicate their function, older pipes were often made of similar materials, making them difficult to differentiate, adding even more to the confusion to the underground maze of utilities.
There are so many chances to get it wrong, to dig near unmarked (or incorrectly marked) lines: About 400,000 utility excavations occur every day across the United States, making it incredibly difficult to put something new underground without having some sort of conflict with other utilities underground.
The 811 “call before you dig” free service, is in place throughout all 50 states to help identify and locate underground utilities to prevent damage, injury and death; but industry experts say the system isn’t faultless.
The latest utility locating technology such as electromagnetic locating devices and ground-penetrating radar, have their limitations. Buried steel railroad, streetcar tracks, old brick or stones can all interfere with the locating devices making it difficult to know for sure if there is or is not an underground utility.
Records of what is underground and what is live are many times incomplete or nonexistent. In the past, recording what was underground was not as effective as it is today. Today, utility companies take their responsibilities very seriously when it comes to marking and protecting their utilities from strikes, but the utilities that were not marked in the past, are still present. No matter how accurate lines are marked going forward, the lines of the past will most likely always be there due to the high cost of removal.
It’s common to assume hand digging with a shovel is the safest way to dig when digging around known utilities, but this notion is not entirely true. Almost 20% of utility line hits are caused by shovels. Vacuum Excavation, whether using water or air, is the ONLY safe way to dig. The high pressure water or air is at a psi that will cut the soil with razor like precision, but is not strong enough to damage utilities. Each year, millions of miles of new utilities are put underground, joining a mix of old and new pipes that snake through the ground at varying configurations and depths, increasing the amount of utilities and likeliness to hit something using traditional excavation methods.
Works Cited: http://goo.gl/pcU57J http://goo.gl/l0AOUo