Either you're on an industrial site or walking the streets of your neighborhood, there's a hidden language beneath our feet, communiques only a handful of people have learned to read. To the untrained eye, they're random lines of colored graffiti on public sidewalks or tiny flags swaying in the grass. But those simple hidden messages literally save our lives every day. So, what do they are mean, and where did they come from?
The next time you're walking around your neighborhood, look for a series of signals sticking up out of the ground. They could be short stakes, or mini-flags flapping in the wind. Their color will be white. These are messages placed by "the sender" to indicate a simple question:
"What you got down under here?"
The sender of that message—maybe a homeowner, probably a contractor—stuck these signals into the ground because they want to dig below the ground in that spot. Maybe they want to add a deck to their suburban two-story, install a new mailbox, or just plant a tree.
Digging holes is risky: Kick that shovel into the ground without planning or asking any questions and you never know what you could hit. If you accidentally hit some wiring—and you're lucky—then you'll be answering some angry calls from neighbors who are suddenly out of power. If you hit something and you're unlucky, then you'll soon need the services of a lawyer—or undertaker. So, would-be excavators identify where they want to dig with those white flags or stakes or paint and then call for help, either by calling 811.
Within a week, crews wearing logo-ed uniforms and baseball caps, armed with spray paint cans and pockets of flags, will enter the area in question and answer the query set forth. At their disposal are agreed-upon symbols and semaphores. For example, a straight mark between 18 and 24 inches long and two inches wide indicates an underground utility line. A mark that runs into a half-box, looking as though a capital T had a few too many and toppled over, means that underground lines have come to an end. On lawns, where paint won't be clear or might wash away, flags can stand in for paint.
These crews also use a whole slew of abbreviations to tell you what's happening beneath your feet. "HP" means "high pressure," "EM" means "electronic marker." But the letter's aren't nearly as important is the color scheme. Blue, that's potable water. Red, electricity-related cables. Orange means communications-related wires, like those laid down by AT&T or Comcast. Yellow is gas, purple is reclaimed water, and green is sewage. Don't go anywhere near that last one.
Here's an easy-to-read chart for anyone wanting a pocket-sized sheet to consult:
While "call before you dig" systems have been in place in parts of the country for decades, it wasn't until a horrific explosion in 1976 that they truly were unified into one easy-to-understand group of symbols.
On June 16, 1976, construction workers attempting to widen a Los Angeles street punctured a gas line on the 9500 block of Venice Boulevard in Culver City. As the Los Angeles Times put it at the time, "The gasoline, under 600 pounds of pressure per square inch, shot up like a fountain and then formed a mist that seemed to hang in the air for about 90 seconds." The resulting "wall of fire" destroyed half a dozen cars, demolished seven buildings, and left nine people dead.
It was clear the explosion was caused by a failure of communication regarding what utilities were underground, and where. It may seem odd today, when a spray-paint SWAT team shows up at your home to map out the subterranean landscape, but this level of planning was not the rule for utilities back then. It was first-come, first-serve, with privatized industries like home telephone service competing for limited space with public works like sewage and water.
James E. Attebery, the uniform color code's developer, laid it out in a 2008 interview published by the APWA Press: "[A utility] would start digging a trench. They might encounter some sort of obstruction, so they would offset a bit. The end result sometimes was that after digging for two miles, the telephone company had literally taken up half of the right-of-way under that street, so there was no room for other major utilities." It was a mess, and a dangerous one. "Most [accidents] happened because people doing the excavation just don't know where the utilities are buried."
In an attempt to contain the mess, the APWA started the Utility Location Coordination Council and installed Attebery as its chairperson. He traveled the country for ideas. In Detroit, a city engineer mentioned his "one-call" plan; a similar one was succeeding in Pittsburgh. Around the same time, telephone companies approached Arizona legislature for a fix after realizing how much money was being wasted because someone cut the wrong cord.
The final piece was a phone call: "[An engineer] called and told me they couldn't find any standard for color marking the utilities," Attebery said. "I told him I'd find out the standards. The problem was, I couldn't find any." So he brainstormed with David Punches, ULCC markings committee chairman, and their code is still being used today throughout the world—with one notable holdout, says Murv Morehead, former chair of the Utilities and Public Right-of-Way Committee: "Australia. They use about twice as many shades of colors, and their color codes are reversed. If we [went there and dug], we'd be dead."
Once the colors were standardized, the last step was knowing who to call. Assigning every area its own 800 number proved unwieldy, but a non-profit organization called the Underground Service Alert stuck upon the answer when it used the phone number 811 number for excavators in their region to call. In 2002, Congress passed the Pipeline Safety Improvement Act, mandating the institution of a "one-call notification process," and in 2005 the FCC cleared 811 numbers around the country. (At that time, 811 was used mostly to reach the business offices of local telephone companies, something mobile technology made unnecessary).
Today, if you don't call 811 before you dig, well, you're probably breaking a state law. More than that, you're risking one hell of a fiery demise. "Unfortunately, people think they have a lay of the land and dig without calling," said Ryan White, Board Liaison of WSA North. "But there's less than a one percent chance of accident if you use 811."
So, it is absolutely worth the time it takes to input three numbers into your phone (811). And now that you know about the language of the subterranean, I promise that you'll starting noticing these markings everywhere. It's like having momentary X-ray vision to understand what utility infrastructure lurks beneath our feet. Just try not to bore too many of your friends with your knowledge about this hidden world.