Methane: A Risk to Water System Operators

We have all heard of the West Virginia coal mining tragedy, and our thoughts and prayers go out to the families of the victims. And we continue to hope for the rescue of the missing miners.
What caused this tragedy? Methane gas. Methane is the simplest of all the hydrocarbons. Its molecule has a single carbon atom at its center, surrounded by four hydrogen atoms. It is the same “natural gas” piped into many homes for stoves, ovens, and space and water heating. It is odorless and colorless. I assume it also has no taste; it makes no noise, and has no special feel to it. In short, the five senses on which we depend to detect dangers in our environment are completely inadequate in guarding against this risk! Fortunately, an odorant is added in utility systems, so that a leak can be detected readily.
Methane is lighter than air, so it dissipates quickly if adequate ventilation is available. This is the first line of defense for the miners, and it is one that we frequently use in the water industry, too. Methane is a risk to us, particularly in excavation work in water distribution systems. This is because the natural gas utilities place their service lines in the streets alongside of our water service lines. Their facilities are subject to mechanical failures, corrosion, and damage during excavations, just like our facilities are. When water systems are damaged, we see leaks and even flooding; when natural gas systems are damaged, things can get much more dangerous. Between concentrations of 5 and 15 percent in air, methane mixtures are combustible – and even explosive.
Our best protection against the hazards posed by natural gas is to use the Underground Service Alert system. We notify USA at least 48 hours prior to excavation, so that the gas folks – and all the other buried utilities – can tell us where their facilities are located, so we can avoid damaging those other utilities during the course of our work. We get similar notices from USA when the other utilities need to do work around our pipes.
Our second layer of protection is our noses. Thanks to the odorant, even small natural gas leaks are usually pretty obvious. Unfortunately for the miners, they do not have this luxury. They use gas monitoring instruments instead. We do the same as a further means of personnel protection.
What should we do if a gas leak is encountered? “RLH!” (That’s “run like heck!”) Dilution is the solution. Since natural gas is lighter than air, it will dissipate on its own, given enough time and distance.
What we need to avoid most of all is a flame or spark of any kind. Remember the “Ignition Triangle.” With a gas leak underway, we have two of the three ingredients for a combustion disaster – no spark means no disaster. So stop work immediately, turn off all vehicles, compressors, etc. And don’t go have a cigarette while you’re waiting!
Once we’re out of harm’s way, contact the gas company to have them address the leak – they’re the experts, and they have the training to deal with the situation swiftly and safely. Don’t try to resolve the problem on your own – we wouldn’t want them to try to fix a water leak (and they wouldn’t get blown up if they made a mistake doing that!)
If the leak appears to you to be even slightly more than a minor annoyance, contact the local fire department, too. They can determine if evacuations or other precautions are appropriate.
As always, safety first!

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