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Construction Safety

Underground Construction Risks—What's Underground Can Kill

TJ Lyons | September 1, 2011

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When I was 12, my dad decided to build a pond on the farm. We asked Bob Stickles (who truly had one eye) to dig it. This was 1973. Bob came running into the barn soon after starting, shaking, for he had struck the main gas line from New York City to Albany. Just scraped, but he was scared. My dad called the gas company, and they inspected the line. At dinner my dad chuckled, "Thank God Dick Ellers was busy this week. I had asked him to dynamite a pond!"

Following are some best practices and tips for the risk manager or safety professional on the hazards of the underground world of our construction sites—a hazard you truly cannot see. I refer to the underground world as the Underground Casino, for when you enter it without a plan, odds determine your luck.

I went through my notes and found that I've investigated more than 48 incidents of breaking functioning utilities. Not once did anyone get hurt or die. There were fires, but as the Casino knows, chance favors death. The odds of dying, you ask? I did the math for 20 years of utility strikes in the United States. When injury resulted, one in five people died. Those are good odds for the Underground Casino. In the simplistic world of Lyonetics, if you have hit a utility four times, you must not hit another.

Under our feet, across the United States and, yes, below our lakes, rivers, and oceans, run utility lines, tunnels, and structures. If you hit them, some can kill you, and all will cost you. You will encounter hidden hazards that kill the striker quickly—steam, gas, propane, and electricity—and those that may kill others—telephone and communications cables and national defense lines. Most people are unaware of and some do not respect this dangerous world.

Across the United States, utility owners recognize the threat from contractors. Not too long ago, each state had an organization that contractors called when they needed to dig, and the states would send specialists (called "locators") to determine and mark the location of buried utilities before digging began. With names like Dig-Safe in Massachusetts or Dig-Safely in New York, these organizations are now centralized in the United States in the form of the "811—Call before You Dig System," coordinated by the Common Ground Alliance. This is one of the greatest accomplishments for underground safety in the United States. Contact for more information.

811 - Know what's below. Call before you dig.

How the 811 System Works

Anyone anywhere in the United States can dial 811 or use the online service to notify utilities so they can "mark out" their underground facilities. Always remember, you must call for these utilities to get marked, whether you are constructing a subway or driving a steel post to tether your Labrador. It is free, it is easy, and it's the law. As New York State puts it:

You must call regardless of where the excavation is located. Even if it is on private property, out in the middle of a field, or on a street that has no name ... you must call....

You must call even if you are only excavating a few inches or just surface grading. If you move material ... you must call. (NYS Excavators Manual)

Each year, approximately 700,000 underground utility lines are struck during excavation work, according to the Common Ground Alliance, a group that provides training and education on underground hazards. The cost of one utility strike may rise to hundreds of thousands of dollars, and insurance will typically not cover that loss. Additional costs can be fines levied by the utility that can no longer provide service to its clients. These fees can range around $10,000 per hour for loss of service. If you shut down a hospital or stop work at a factory, you will likely pay for their losses too.

Figure 1: Street boring—properly marked (USA is Northern California's group)

Street boring—properly marked (USA is Northern California's group)

Tips—When to Call

Here are some guidelines to follow.

  • It doesn't matter what you are doing—if you scratch the ground, plant a tree, anything, you must call.
  • It doesn't matter where you are—in the middle of the woods, in a hayfield, or at Yosemite—you must call.
  • Driving those steel stakes for a party tent? You must call.
  • Even if you are confident that you know where something is buried (say, you installed the line), remember that many contractors dig up lines they have just buried. So be sure to call.
  • If the lines are on private land or lead to a missile silo in Kansas, you must call.
  • Don't mark out the area with wooden stakes. Wooden stakes have been driven through gas lines. That is the reason you must use white paint or "feathers."

Not calling is a violation of the law and plays into the odds of the Underground Casino.

Figure 2: Underground roulette—calling 811 after you're done digging

Underground roulette—calling 811 after you're done digging

Note that the post is buried between gas and electric lines.

An Example

A machine was used to remove and replace material along a country road in the Northeast. The investigation later found that the contractor assumed there was no gas in the area since it was in the country! As the machine graded the edge of the road, he did indeed find a gas line. Over the years, the road shoulder had been worked and scraped, and the once deeply buried line was soon too shallow. Striking the gas line cost the contractor not only the price of the machine but also the repairs to the overhead line that soon failed in the fire.

Figure 3: Contractor hits gas line while repairing country road

Contractor hits gas line while repairing country road

More Tips

When planning to dig, walk your site. If there is a building, always walk the basement and look at each foundation wall. If there is a pipe, cable, or anything coming into the basement, there is an underground hazard outside. The following are indicators that something may be buried.

  • Manholes. Steel covers can contain gas, electric, or sewer storm lines and plastic or composite (green or gray) communications.
  • Warning signs. Often orange or yellow for gas or communications. You may also see TILE DRAIN, which indicates underground drainage.
  • Overhead power lines. These are often on a right-of-way so underground utilities are often run down this "protected" corridor.
  • Candy cane steel pipes. These are mostly yellow and provide airflow for a sleeved gas line below.
  • Streetlights. Unless the power for these travels from post to post, they are buried between the posts.
  • Traffic signals. These will have multiple feeds from power to the sensors in road surfaces and buttons you push to cross.
  • Trees. Yes, when trees grow, they grow around buried utilities. When you remove the tree and the roots, the utilities will come up as well.
  • Hydrants. This seems obvious, but the lines may not run directly from one to the next.
  • Transformer pads. Typically, a 3' x 4' green or gray steel box sits on a concrete slab. The lines leading to and from almost always are hidden underground.
  • Meters—Outside of a house, with a pipe running into the ground, indicate gas or electric lines, likely from the street. 811 may or may not mark from the meter to the street, so hand digging is needed to confirm where the line is if you are digging in that area.
  • Lines running up overhead power poles. If they lead from the ground, they are buried in the area.
  • Lines or patches in pavement that don't match the balance of the surface. When you run a new buried utility across blacktop, the color change in material is a great way to spot a buried hazard.
  • Unknown markings. These often indicate something underground.

Figure 4: the color may vary (should be white), but it should get your interest.

The color may vary (should be white), but it should get your interest.

Case History

Early one morning, I traveled to a site, arriving before work started at 6:00. When I pulled up, a motor grader was working and removed some soil for a new road. I walked over and soon ran the rest of the way yelling and screaming for the operator to stop. He did; I finished my prayer and walked over. One concern in the identification of underground hazards is the danger of driving the warning signpost into the utility it is to protect. On rare occasions, a warning sign or a marking is installed away from the underground hazard and is labeled "OFFSET." Knowing this detail and why is critical for any operator to understand.

Hint: Always remember that, in the world of construction safety incidents, there are many contributing factors. And in this example, they were all important.

TJ: "Hey, sorry for the yelling, but I think you're cutting over a gas line."

Tony: "Nope, those lines runs over …" (points to the aged sign along the new road).

TJ: "Well, let's take a walk. I want to show you something. By the way, why are you starting so early?"

Tony: "I was laid off for a week, rehired today, and wanted to get back into it. I hoped to be working when the boss showed up. I started at 5:00 a.m. Yeah, it was kinda dark, but enough light to get started."

TJ: "But don't the guys need to use this road to get to the trailer?"

Tony: "Yeah, but I wanted to dress it up a bit for them too."

All understandable for a guy wanting to make a good impression on the boss, but his starting in the dark, the need to prove he was a self-starter as valuable as the rest of the team, almost killed a good guy. When the investigation was over, it was discovered that Tony had removed all but 7" of soil covering a major fuel line running to and under one of the prettiest harbors in the United States. The marker for this line was in fact an offset marker but, due to the darkness and the sun rising behind the warning sign (was in a shadow), he did not see that the sign was an offset warning. He thought it marked a buried line.

Of more importance, it was determined later during the interviews, was that the operator did not understand what an offset marker was, and neither did his supervisor. The contractor released Tony that morning, but in fact, this was an operational failure, not just Tony's fault. The investigation focused on the system failure, for it was soon apparent that the contractor, not just Tony's supervisor, did not understand the dangers of the Underground Casino.

Figure 5: Example of an offset marker

Example of an offset marker

Tips—Use the 811 System

In general, the "penetrating contractor" calls 811 and asks for a "mark-out." The excavator then outlines the exact work area in white paint or flags; some call them feathers. The utilities that have "facilities" in the buried area will come out and mark where their utilities are in their own specific color. If they do not have a buried utility, they note that as well, also in their specific color. Often it will look like "no gas CP+L 5/14/11." If you are instructed that seven utilities have buried lines where you intend to dig, and all seven respond after a period of 2–10 days, it's okay to start digging. If only six respond, you must call 811 again and coordinate with the last utility. If you take the chance in the hopes that they did not respond because they have nothing in the area, you are again gambling at the Underground Casino. The online e-ticket makes this process very easy, for they will identify exactly who will respond to mark out.

Always remember that the "penetrating contractor" contacts 811. General contractors can as well, but it's not their responsibility. This is often misunderstood in the field. The general contractor can help plan and coordinate marking out the affected area, but it is always the excavator's responsibility to call 811.

Case History—"I Thought You Called!"

When I visit a site, first I travel the border to see who the neighbors are and whether there is a fence to keep them out. One morning, a crew was driving steel posts to install the site fence. As I walked over, I noticed that the pneumatic hammer was not advancing the post as one expected—it seemed to bounce. I told the guys to stop and asked where their safety glasses were (I was young) and who had called 811. The answer started with "I think…." So, the work was stopped, and it was soon apparent that 811 had not been called. So we pulled out the steel pipe, now full of soil, and found little bits of yellow plastic at the end. The reason for the obstruction: a gas line to the adjacent hospital.

Due to the circumstances, the gas company was called immediately, and that commenced a bad day for the contractor. This was again an operational failure (note the trend), for the general contractor had not verified that 811 was called, and a training failure for the contractor who did not understand the 811 system and those responsibilities.

To give you an indication of why so many good contractors get killed from visits to the Underground Casino, take a look at the photo below: The marks for the gas line were in yellow, the post locations in white. They illustrate how the line was hit.

Figure 6: Poorly marked underground hazards

Poorly marked underground hazards

More Tips—Some Best Practices

To avoid construction accidents, it's important to follow construction best practices. Below are a few tips.

Install Temporary Warnings

It is very common for a contractor to install utilities on its new project and dig them up again when it plants that final tree or installs the sprinkler systems. Many contractors are now planting signs when new utilities are installed.

Figure 7: Temporary warning sign

Temporary warning sign

Eliminate the Threat Forever

When a project entails working over buried utilities, encourage the owner to have those lines rerouted before construction so site operation does not disrupt them. The added benefit is that if there are any further excavations on the site—from planting of replacement trees to installing the flagpole the president wanted—you know you have removed those underground hazards, thus protecting both your people and business continuity.

Free 811 Training

Take advantage of the free training that your local 811 provider gives. It is a great tool, for they will often travel to your firm to do the training, and most host a quarterly meeting of the local utility owners, those that do the markings, and excavators. Those presenting are truly experts, and they will do anything to help keep you from damaging their underground facilities.

Realize That Lines Aren't Always Linear

Quick tip—buried lines do not run in straight lines. That is why they are marked out well past both sides of where they may lie. If you are near a utility line or crossing one, take the time to dig by hand (that is the law) and expose them occasionally to make sure you know where they are. Also, when subcontractors install lines for a utility, they may be paid by the foot, so crafty contractors will loop the line as often as possible since additional footage equals additional profit.

Recognize the Danger: Propane versus Natural Gas

I have met the enemy, and it is indifference. "That's what insurance is for!" This was the reply of a superintendent who was asked why he strayed well outside his work area and dug along a gas line for a house. The Underground Casino had provided a favor, and the line had not separated from the meter (when then edge of the excavation failed) and filled the house with gas.

Note: Often, you will hear of a house "demolished" in the midst of a neighborhood and "the source of the explosion is suspected as natural gas." When natural gas escapes from its lines, it is lighter than air and will fill the house from the attic to the basement. When there is enough in the air to ignite, and the pilot light on the water heater meets it, a gas must expand, and a house cannot, so it is destroyed, often with no fire.

Figure 8: Unsupported gas line

Unsupported gas line

When a buried propane line is hit, the gas will travel downhill until it finds something to ignite it. This may be a town (Gilboa, New York, for example) or a campsite along the creek the pipe crossed. Does this happen often? Take a look at Wikipedia's list of pipeline accidents.

Everyone must understand, respect, and fear what is underground. Consider an example. A new underground propane system was installed on a Thursday in a summer home in Upstate New York. The occupant was not home, for he was what we call "a weekender." The investigation showed that when he did arrive later Friday afternoon, he entered the house, hit the lights for the kitchen, and the spark from that switch ignited the gas that had been accumulating from the leaking new line. This gas had traveled along the new trench line through the foundation into the cellar.

Remember, propane is heavier than air. It first filled the basement and then entered the first floor. When asked to investigate, I found that the house had been lifted and moved off the entire foundation. I found portions of the house a quarter of a mile away. The deceased occupant appeared uninjured, but every bone in his body had been broken.

Pay Close Attention to the Initial Call

The safety professional has a great tool when investigating a utility strike—the initial call.

"We just hit a gas line, but it's only low pressure."

"We hit a gas line, but it's blowing, not burning."

"We hit a gas line, but just bumped it; it's not leaking."

How the notification is made indicates at least the level of concern by the caller but also their level of understanding. In the case of a gas, steam, or electric strike, those involved should be scared to death. When any gas line is struck (plastic or steel), as the gas flows, it will create a static charge similar to rubbing a balloon. Just because the gas is flowing does not mean all is well. There is no indication of what will happen the next second.


In closing, I would like to add a personal note. During the many utility strikes I have investigated, the bills would come in, and I would complain about the $4,600 fee from the gas company to fix the leak. I would think to myself, "They get to rack up overtime; plus, they always have three guys doing the work."

One year, we had more than a dozen such hits and as many bills. The crew was always the same three guys in fire-retardant coveralls: one guy clamping the leak, one helping him, and one guy standing by with a fire extinguisher. No wonder it cost so much, I always thought. Then, one day, that crew of three guys was caught when the little gas line they were fixing flashed, and that second guy, the guy helping, burned to death. Since then, I have a new respect for things under the ground, the dangers presented to good people resulting from someone else's poor planning, and the lack of understanding of what gambling in that Underground Casino brings to the unknowing, uncaring, and unprepared.

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