Digging up gas lines

gerard · May 2, 2002

One thing I learned during a "public safety" type meeting is that for natural gas the odorant is not added until the gas reaches a distribution facility. Prior to that, when in the in the high pressure transportation pipes that run state to state there is no "smell" if you get a rupture. Of course in those lines the PSI is around 800 so what you will see is a geyser of dirt blowing up from the ground! On those lines even if you detect the leak and close the pipe at the two nearest shutoffs it will still take a long time for the pressure to bleed off to 0. Anything you can smell is coming from the smaller feeder lines (which still doesn't mean I want to be close to one when it's leaking!)

MChalkley · May 2, 2002

Thanks, guys, for the excellent info, as always. A few responses:

Usually its best to hand expose all lines when doing hoe work. They can be located and marked. The line I hit had been marked, but the marks had been obliterated by traffic. We did hand-dig the ones we thought were close, and in fact hand-dug the correct one, but upon not finding any evidence of a line, and since we thought it was about 5 feet over, I finished it with the backhoe - big mistake...

The plastic lines have metal tracers with them. I've now invested in a <A target="_blank" HREF=http://www.pollardwater.com/emarket/Pages/P881%208840%20&%208850%20Locators.asp>pipe and cable locator</A> from Pollard Water, so that should help reduce the possibility of the exact same thing recurring.

Diesel equipement working around hydrocarbons should be equiped with a positive air shutoff so the engine can't run away or ignite the leak. In many places this is a requirement when using diesel engines. I did not realize this, and am glad to know it. Any ideas for sources of positive air shutoffs, and/or cost? I think investing in one would be a good idea, if they're not prohibitively expensive.

Plastic pipe under low pressure can be bent back on itself to seal off the ends. The problem with this method is that you have to have enough pipe exposed, and I'm not at all for digging around an active leak. I found, and invested in (I'm getting tired of all this "investing"...), a <A target="_blank" HREF=http://www.pollardwater.com/emarket/pages/p64403%20tc1%20clamp.asp>Timberline Squeeze-Off tool</A>, which I also got from Pollard Water, that works with all plastic lines up to 1" diameter (I also got the ground rod option, of course) - any bigger than that, and I'm not messing with it anyway...

Its best to evacuate the area when there is a gas leak and let the utility company take over. In principle, I definitely agree. However, this is the second gas line I've hit in 5 years, and the gas company took longer than 45 minutes to get there in each case. The first time, we found the cutoff valve long before they got there. This last time, though, there wasn't a cutoff valve to be found anywhere on the line. When the gas company got there, I asked them about it and they said there wasn't one. I thought they were required by law, but apparently not. At any rate, I no longer want to be at the mercy of an entity that can't be relied upon, either to locate the lines in the first place, or to shut them off if the "ounce of prevention" fails. It may just be my cynicism poking through, but I don't think the "One-call" folks are as meticulous about finding the utilities as I would be, since they're not in the "hot-seat" if they make a mistake. And I know from experience that the gas companies either aren't in a big hurry to get there, or aren't set up to deal with the situation in a timely fashion. I'm not saying they have a problem they can solve, but it's a problem I think I can at least minimize, if not solve completely. I don't have a "let's do something, even if it's wrong" mentality, but I don't know how many more of this sort of "hit" my nerves will take - much less the strain of hearing all that gas escape while the gas folks take an hour to show up... Something's got to be done - preferably not hitting any more - but if I do, I'd sure like to be able to shut it down in a few seconds myself.

Egon · May 2, 2002

The positive air shut off is just a simple slide valve placed on the air intake somewhere. Something like an RV tank drain valve would work.

On some lines there is a control room located somewhere which may have the ability to sense pressure and activate isolating valves. Some lines can take a long time to depressure. If the gas goes directely up into the air chances for explosions are much less than if it can be trapped by some type of structure.

For your own familys sake its best to stand well back and wait. Jumping right in the hole can have two different results. There may be an oxygen deficient atmosphere and you pass out. Your best friend will jump in to rescue you and he passes out to. All it takes to reduce you my level of brain function is about 4 min. without air. The other result can be a fire started from a remote ignition source at the leading edge of the gass cloud where the proper concentrations are present for a fire to start. Once started this will almost instantlly be back to the source and its barbeque time in the pit.
I know its hard to stand back and do nothing but theres a time to retreat so you can attack again.

With Hydrogen Sufide leaks there are many documented cases were the first individual and up to two or three rescuer's are found lying in a row. Sometimes the last one is revivable but maybe not.

Egon

hosejockey2002 · May 2, 2002

It's true that they don't add the odorant until it leaves the distibution facility. But those facilities are often pretty far from the end user, so they use high pressure distribution lines that can run upwards of 100 psi, which will definitely send a geyser of dirt into the air. On a side note, I read an article about a gas regulator failing, sending gas at 35 psi right up to residential meters (it usually arrives at about 2 psi). The gas blew right through the meter regulators and entered houses at over 20 psi instead of the usual 0.6 psi. Within minutes, they had over 20 homes burning in the same area. /w3tcompact/icons/shocked.gif

Bird · May 2, 2002

I no longer want to be at the mercy of an entity that can't be relied upon, either to locate the lines in the first place, or to shut them

Mark, I don't know you well enough to know what all your training and work experience includes, but unless you've been trained in gas leakage repair, I'd say to wait for the gas company (don't care if it does take them 2 hours to get out there); natural gas is lighter than air, will rise and dissipate and no harm done other than the monetary loss of that amount of gas unless something ignites it. You'd be a lot safer using your tractor from now on with no seat belt and no ROPS than you'd be trying to fix or stop a gas leak yourself unless you've been adequately trained to do that.

so they use high pressure distribution lines that can run upwards of 100 psi

And there's lots of them with that kind of pressure, hosejockey2002.

for natural gas the odorant is not added until the gas reaches a distribution facility.

Correct, of course, Gerard.

when in the in the high pressure transportation pipes that run state to state there is no "smell" if you get a rupture. Of course in those lines the PSI is around 800

The gauge was sitting on 975 psi the day I checked a distribution center on the Tennessee Pipeline in Pennsylvania./w3tcompact/icons/shocked.gif That oughta move some dirt and rocks if Mark ever digs that one up./w3tcompact/icons/wink.gif/w3tcompact/icons/laugh.gif

Dozernut · May 2, 2002

I am not an expert on gas by any means, but have been through a lot of training on hazmat. You probably already know this, but if by chance you would hit an LPG, propane line, it has different properties than natural gas. It is heavier than air and will seek out the lowest level and build up, effectively making a bomb. This can be set off by almost any electronic device (ie. a pager or cell phone). Had a few houses blow up because propane accumulated in the basement or crawl space and was ignited by the furnace or hot water heater.

MChalkley · May 2, 2002

Bird - You'd be a lot safer using your tractor from now on with no seat belt and no ROPS than you'd be trying to fix or stop a gas leak yourself unless you've been adequately trained to do that. Agreed, Bird. I do plan to take a safety course. A local gas company official I know has agreed to let me unofficially sit in on a certification class. "Unofficially", of course, because they can't (or maybe won't) give me official approval to do their job. But since he figures I'm probably going to do it anyway, with or without the training /w3tcompact/icons/wink.gif, the best thing is to let me take the training... /w3tcompact/icons/smile.gif

MossRoad · May 2, 2002

My brother in law was going to plant a tree for my grandmother. He dug a hole about 3 feet around and two feet deep. The call before you dig people marked it incorrectly and he chopped the line to the house. He tried to get down in the hole to find the source of the hissing and passed out. My grandmother, somewhere over 80 yrs old at the time, pulled his head out of the hole and probably saved his life.

I agree with the others that state it is best to get everyone away, including yourself, and wait for the gas company.

If you call before you dig, and it is marked incorrectly, and you back away, and the neighborhood blows up and you live, you will still not be held liable, legally or morally.

If you call before you dig, and it is marked incorrectly, and instead of backing away you attempt to stop the leak, and the neighborhood blows up, and you live, you probably will be held liable legally and you will morally feel like it was your fault.

I know that if a contracctor hit a gas line in my neighborhood that was marked incorrectly, I wouldn't blame him. But if he decided to try to plug it instead of waiting for the gas company and blew up my house, I'd think he was a @#$%^^&!!!

Bird · May 3, 2002

Mark, you ought to at least find such classes interesting. I did. Of course, even though I had the classroom training, policies of the company I worked for prohibited me from actually doing any of the repairs (and I agree with those policies). Although it wasn't unusual for gas company employees to ask me what to do or how to do it, and I'd give my opinion always emphasizing the fact that I was not qualified to do the repairs and it was personal opinion only. It was sorta like this forum and tractors; some folks thought I was more of an expert than I am./w3tcompact/icons/laugh.gif Gas companies are like any other company; some had very knowledgeable, competent people, and some . . . well, you know./w3tcompact/icons/wink.gif And I've seen the time when I called in a grade 1 leak and waited for 2 hours for someone to show up. On the other hand, on the biggest job I did (in Pennsylvania), the longest I ever had to wait was 15 minutes and that time the guy got out of the truck apologizing for being so far off and taking so long to get there. They were really great people to work with.

LPG, propane line, it has different properties than natural gas

Absolutely, Dozernut. The job I had was primarily natural gas leakage surveys, but I also did some for LPG; the instruments would work just fine on either one, but for exposed lines, and to pick up the smallest leaks, you want the intake of the instrument above the line for natural gas and below the line for LPG. And for underground lines, we made sure to explain that to customers so they'd understand that we might not find very small leaks. The instruments worked great to check the LPG lines in my RVs though./w3tcompact/icons/wink.gif

There's an LPG pipeline running through this area a couple of miles from us. And when I first moved here, I noticed a maintainer (road grader) sitting in a field and it wasn't moved for 4 years. Then a neighbor told me it had hit that pipeline, the operator shut it down and got away safely, but the entire machine was so thoroughly frozen by the escaping propane that it was not worth trying to repair.

skent · May 3, 2002

We had one locally about 10 years ago where a constuction crew hit a gas line. They waited an hour for the Gas Co to arrive. Just before they arrived, a house two blocks down was flattened by an explosion. Strange part was the house that blew up didn't have gas service.

It seems the gas, leaking into the soil found it's way underground along side the water lines and leaked through foundation cracks in the basement. When the electic heat in the house clicked on, that was all she wrote.

Luck had it that no one was home at the house that blew up, and the people that live on either side (had windows blown out) were at the site of the gas leak.

Nothing but schredded house parts for blocks.