Imagine you’re engaged in a high-stakes game of connect-the-dots. On spotted paper, you and a partner alternate drawing lines in an attempt to create a picture. You can’t just draw a line anywhere and expect it to turn out. You have to start at a dot and stop when you reach another, and intersecting lines are a serious no-no for the players.
Such is the case with the many sewage and other utility pipelines and cables running underneath our feet---except lines that intersect can cause major damage and put all kinds of stakeholders at risk.
Millions of miles of such lines exist, and though the area they cover is wider than a sheet of dotted paper, ensuring they don’t intersect and cause catastrophic damage is a major subsurface utility infrastructure challenge. The real world of buried utility infrastructure is no game.
As utility workers in the trenches know all too well, accurate “as-built” maps showing them where to bury their pipes and dig for other buried utility lines oftentimes simply do not exist. The work they do is underground, and they often have to rely on imprecise locating technology to get an image of the area beneath their feet.
Because of this, it’s not uncommon for workers to inadvertently drill a hole for one type of a utility line (such as fiber-optic line or gas pipe) through another (such as water or sewer pipe).
The origin of the problem
Up until the 1970s this wasn’t much of a problem. At that time most digging occurred in open trenches where visibility was high. “Daylight”, or being able to see the utility in the ditch, is a very good thing.
But as cities and utilities began installing lines on citizens’ private properties, there developed a need for a faster and more discreet method (who wants a huge trench in their front yard?), so utility workers began using the method now known as “horizontal boring.”
They would drill a horizontal hole or tunnel through the soil and rock, trying not to hit any other utilities getting from point “A” to point “B”. In the interest of saving time, the old practice of “daylighting” with a hole on each side of a potential utility intersection (still a very good idea) is not always done.
This horizontal boring method, though practical and efficient, can also be quite dangerous. When drilling is confined to such a restricted area (a narrow hole or tunnel rather than an entire open trench) visibility decreases significantly.
When tunneling subsurface paths for gas lines, utility workers can never be entirely certain of what other underground assets are hidden in the area. Often, private and unmapped sewage or other utility lines may be nearby. Unaware of their proximity, utility workers can accidently drill into them.
The dangers of non-daylight horizontal boring
And what happens then? Cross-boring—the technical term for intersecting pipe and sewage lines—can have devastating consequences. When horizontal boring machinery hits a sewage pipe, the collision can cause damage to the pipeline. The slightest nick on these utilities can cause a leak, not to mention the damage that can result from a gash or hole.
This is precisely what happened three years ago in Minnesota. In February of 2010 a sewer-cleaning contractor accidentally struck a natural gas pipeline that had been mistakenly installed through a sewer service lateral. As a result of the impact, gas leaked out and ignited, setting fire to and destroying a nearby home.
The accident is just one of 155 incidents of cross-boring on record in that state. And Minnesota isn’t the only state where these problems occur. In the past eleven years incidences have been reported in eleven different states. How many more accidents like these are still waiting to happen? Time will tell.
Increasing damages from this practice are demanding national attention, and several states, including Minnesota, have released new guidelines for installation. One practice the state is recommending (and which has proven to be both safe and efficient) is the “map and record” method.
Under this method, all underground assets are electronically marked so they can be easily identified on an “as-built” GIS / GPS map. Then, given the proper technology, utility workers can pinpoint the exact location of these assets and ensure they avoid them when drilling.
Accurately marking buried utility assets points and asset intersection points with fail-safe Magnetic-RFID is an idea that’s time has come. One tool that will enable this exact location and identification is Berntsen’s InfraMarker.
Simply (1) get within a few yards with GPS, (2) get within an inch or so with a magnetic locator, and (3) interrogate the Magnetic-RFID marker with an easy to use RFID reader. It’s a great way to accurately locate and identify underground assets marked with RFID tags.
Once a GPS map has shown utility workers the approximate locations of assets in their area, this tool will enable them to pinpoint exactly where they are and verify precisely what the assets are.
Utility installation may never be as simple as connect the dots, but tools such as the InfraMarker move it one step closer.
Get a closer look at the InfraMarker by visiting its product page or ordering a catalog.
Image courtesy of crossboresafety.org