# San Bruno natural gas explosion **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2010, 9:04pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432 "2010-09-11T21:04:55Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 14, 2010, 12:23pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/21 "2010-09-14T12:23:37Z")
From thread in MPSIMS, a gas station [surveillance cam video](http://www.ktvu.com/video/24991167/index.html) of the explosion. At about 9 seconds, you see debris and dirt flying, but no flames until 14 seconds. This suggests the rupture preceded ignition. The scale of the scene is difficult to gauge from the video. It looks like the fireball is just across the street, but in the other thread, The Hamster King reports that the gas station is actually 300 yards from the blast site. ---
**Author:** ![Dr.Woo](https://avatars.discourse-cdn.com/v4/letter/d/7c8e57/32.png) [@Dr.Woo](https://boards.straightdope.com/u/Dr.Woo)\ **Post date:** [September 14, 2010, 12:27pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/22 "2010-09-14T12:27:04Z")
**matt** and **Machine Elf** , thanks for the explanation - that’s exactly what I (and I think the OP) was wondering. Your description is consistent with witness reports and the injuries sustained, which were apparently more burns than concussive injuries. There were reports from residents that they had smelled gas in the area over the last few weeks, which PG&E is investigating. Do you know if gas in a transmission line like that has odor added, or is the odor added later, at distribution points? Seems to me that it would be added pretty much at its source, but I’ve heard that’s not the case. To those surprised that a line like this ran through a residential area, I’ve read that this is one of a hundred or so similar PG&E lines, designated high-risk due to their proximity to population centers. The most recent information I’ve seen indicates the line was installed in 1948; others have said sometime in the '50’s. The houses were built in the early to mid 60’s, so the line does predate the residential development, but not by much. Seems crazy dangerous to me, but then again, the entire Bay Area is pretty heavily populated, and they have to get the gas around somehow. Also, of course, all of this hazardous substance transportation and human habitation is going on in the midst of earthquake fault lines, including some pretty major ones. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 14, 2010, 1:29pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/23 "2010-09-14T13:29:28Z")
> [@Dr.Woo](#): > > To those surprised that a line like this ran through a residential area, I’ve read that this is one of a hundred or so similar PG&E lines, designated high-risk due to their proximity to population centers. The most recent information I’ve seen indicates the line was installed in 1948; others have said sometime in the '50’s. The houses were built in the early to mid 60’s, so the line does predate the residential development, but not by much. Seems crazy dangerous to me, but then again, the entire Bay Area is pretty heavily populated, and they have to get the gas around somehow. There are tons of these situations (hazardous pipelines through residential areas). [In 1986 a 1500-psi gasoline pipeline running by my high school ruptured](http://www.startribune.com/local/12564991.html), starting a fire that leveled a block of houses and killed two people. Like the current situation, residents were shocked to learn of the existence of this high-pressure pipeline underneath their homes. After repairing the damage, the pipeline was operated at lower pressure for maybe a year or two, and then quietly ramped back up to the full 1500 psi. Life goes on… ---
**Author:** ![Annie-Xmas](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)\ **Post date:** [September 14, 2010, 1:43pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/24 "2010-09-14T13:43:25Z")
Here’s a [gas exlosion](http://www.cbsnews.com/stories/2005/12/13/national/main1122897.shtml) that hit too close to home for me. About a mile away from where I live. ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [September 14, 2010, 2:15pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/25 "2010-09-14T14:15:04Z")
> [@Dr.Woo](#): > > Also, of course, all of this hazardous substance transportation and human habitation is going on in the midst of earthquake fault lines, including some pretty major ones. I asked a question in the MPSIMS thread that didn’t get answered (maybe its a stupid question!) but I’ll repost it here:…is there any provision anywhere in the US for how things like natural gas lines are laid in seismically sensitive areas? Some type of protection from ground shift and subsequent accidental rupture? I’m thinking some type of protective sheath or something? Obviously with an all out earthquake it wouldn’t matter, but from small shifts in the earth, etc? ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [September 14, 2010, 2:40pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/26 "2010-09-14T14:40:25Z")
Before I worked in oil and gas (in Western Canada), I never realized just how prevalent these transmission lines were, especially within cities and towns. Once I started working for an O&G company and actually saw the pipeline maps, I was shocked at how many miles of pipeline are under the ground we walk on every day. I found out that there was a major crude oil pipeline not 100 meters from my home in the small town I grew up in, so the next time I visited, I took a look. Lo and behold, there are the signs warning of an crude oil pipeline right under my feet - signs I had walked and driven by but never read for years and years. I would guess that the US is similar to Canada in signage, etc., so take a look around your neighborhood. Also, just coming from that industry, I know that North America has a LOT of aging pipelines (built in the 50’s and 60’s) and companies don’t replace the lines unless they have to. However, they do run pigs often, especially on the high risk lines (due to proximity to populations or water, age, material, what’s being transported, pressure, ground movement, etc.) and identify potential weak spots due to corrosion. Once a weak spot is identified, they’ll usually do a risk analysis and will either replace it, pull a liner through, do more corrosion pigging, or leave it and check again in a few years. Many of the failures I’ve had experience with have been due to failures at the weld. That said, the root cause of these types of incidents is almost always human error. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [September 14, 2010, 2:42pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/27 "2010-09-14T14:42:28Z")
> [@Dag\_Otto](#): > > A 30 inch pipe is pretty big and I’d imagine it was working at several hundred PSI. I can’t imagine it running through a residential area. The one I wrote about in my earlier post does. It runs through the far backyard of a whole street of homes. Those homes in turn back up to an elementary school. During the “event” the kids in the school were evacuated on foot to a church farther away. If there had been a fireball while the kids had been out playing, potentially hundreds could have died. The crew that broke the pipe was in fact laying new drainage pipe to handle run-off from the school playground. They had apparently only contacted the local untility “call before you dig” people and hadn’t known that a major gas pipeline was in the area. (Like most accidents, there’s a series of goofs that leads up to it.) ---
**Author:** ![NinetyWt](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@NinetyWt](https://boards.straightdope.com/u/NinetyWt)\ **Post date:** [September 14, 2010, 3:26pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/28 "2010-09-14T15:26:25Z")
> [@FoieGrasIsEvil](#): > > I asked a question in the MPSIMS thread that didn’t get answered (maybe its a stupid question!) but I’ll repost it here:…is there any provision anywhere in the US for how things like natural gas lines are laid in seismically sensitive areas? Some type of protection from ground shift and subsequent accidental rupture? As a civil engineer but not a gas pipeline engineer: I imagine that provision for seismic factors is part of pipeline design. I do not know the particulars for how they design for it, however. > [@EmAnJ](#): > > Before I worked in oil and gas (in Western Canada), I never realized just how prevalent these transmission lines were, especially within cities and towns. Here is a [map](http://www.eia.doe.gov/pub/oil_gas/natural_gas/analysis_publications/ngpipeline/images/compressorMap.gif) showing transmission lines and compression stations in the U.S. Your comment about pigs reminded me: a friend of mine used to live in North Jackson, where there is a large line running north-south through several neighborhoods. He said sometimes he’d be on the back porch and hear a pig come squealing through. ---
**Author:** ![Dr.Woo](https://avatars.discourse-cdn.com/v4/letter/d/7c8e57/32.png) [@Dr.Woo](https://boards.straightdope.com/u/Dr.Woo)\ **Post date:** [September 14, 2010, 5:32pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/29 "2010-09-14T17:32:35Z")
> [@NinetyWt](#): > > > [@FoieGrasIsEvil](#): > > > > I asked a question in the MPSIMS thread that didn’t get answered (maybe its a stupid question!) but I’ll repost it here:…is there any provision anywhere in the US for how things like natural gas lines are laid in seismically sensitive areas? Some type of protection from ground shift and subsequent accidental rupture? > > As a civil engineer but not a gas pipeline engineer: I imagine that provision for seismic factors is part of pipeline design. I do not know the particulars for how they design for it, however. > > > [@EmAnJ](#): > > > > Before I worked in oil and gas (in Western Canada), I never realized just how prevalent these transmission lines were, especially within cities and towns. > > Here is a [map](http://www.eia.doe.gov/pub/oil_gas/natural_gas/analysis_publications/ngpipeline/images/compressorMap.gif) showing transmission lines and compression stations in the U.S. > > Your comment about pigs reminded me: a friend of mine used to live in North Jackson, where there is a large line running north-south through several neighborhoods. He said sometimes he’d be on the back porch and hear a pig come squealing through. Uh, pig? A real pig? [/whoosh] ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [September 14, 2010, 5:36pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/30 "2010-09-14T17:36:52Z")
> [@Dr.Woo](#): > > Uh, pig? A real pig? [/whoosh] A [PIG](http://en.wikipedia.org/wiki/Pig_%28pipeline%29) (Pipeline Inspection Gauge). ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [September 14, 2010, 5:41pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/31 "2010-09-14T17:41:01Z")
> [@Dr.Woo](#): > > There were reports from residents that they had smelled gas in the area over the last few weeks, which PG&E is investigating. Do you know if gas in a transmission line like that has odor added, or is the odor added later, at distribution points? Seems to me that it would be added pretty much at its source, but I’ve heard that’s not the case. There are some major pipelines of that sort in my area. As it happens, my favored bike route runs along the course of one. There are many signs warning of danger indicators including but not limited to: - patches of dead vegetation. - whooshing noises or odd air currents - congregations of birds such as turkey vultures (they’re attracted to the smell, apparently) - **smell of gas in the area** which implies the odor is added prior to sending the gas through the pipe. So, around here the stink is in the pipes. However, I am in Indiana, not California and can not speak for PG&E. Clearly, in at least some instance the odor is already added, but whether or not it’s always present in pipeline gas I don’t know. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [September 14, 2010, 6:57pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/32 "2010-09-14T18:57:48Z")
[quote=“Gary “Wombat” Robson, post:30, topic:553432”] > [@Dr.Woo](#): > > Uh, pig? A real pig? [/whoosh] A [PIG](http://en.wikipedia.org/wiki/Pig_%28pipeline%29) (Pipeline Inspection Gauge). [/QUOTE] This pipe was too old to allow pigs to be used for inspection. ---
**Author:** ![Dr.Woo](https://avatars.discourse-cdn.com/v4/letter/d/7c8e57/32.png) [@Dr.Woo](https://boards.straightdope.com/u/Dr.Woo)\ **Post date:** [September 14, 2010, 9:20pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/33 "2010-09-14T21:20:10Z")
[quote=“Gary “Wombat” Robson, post:30, topic:553432”] > [@Dr.Woo](#): > > Uh, pig? A real pig? [/whoosh] A [PIG](http://en.wikipedia.org/wiki/Pig_%28pipeline%29) (Pipeline Inspection Gauge). [/QUOTE] Thanks - I was fighting google with not much success. **Broomstick** , it makes sense to me that even the transmission lines would be scented - if for no other reason than to make the turkey vultures happy. ---
**Author:** ![Sandra\_Battye](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sandra_battye/32/552_2.png) [@Sandra\_Battye](https://boards.straightdope.com/u/Sandra_Battye)\ **Post date:** [September 14, 2010, 9:53pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/34 "2010-09-14T21:53:42Z")
Thanks everyone for your answers. The news (TV, print and internet) have been trying without much success to provide answers since my original post of Saturday morning. Apparently there was a welded seam running along the length as well as welded portions of the pipe that allowed it to dip under the road. I assume that a modern pipe would have no welds running the length of the pipe (extruded?) and be made with a smooth curve? How long would each segment be? Just long enough to allow shipping via train or semi? Are they joined with welds or is something else used? ---
**Author:** ![NinetyWt](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@NinetyWt](https://boards.straightdope.com/u/NinetyWt)\ **Post date:** [September 14, 2010, 10:04pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/35 "2010-09-14T22:04:58Z")
I just happened to get a safety brochure in the mail today from Gulf South pipeline. In addition to other signs of a leak, it says ‘A “gas smell” - although odorant may not be present in the transmission pipeline’. So, I don’t think you can count on odorant always being in the gas. You can’t smell it without it. **Sandra** , [here](http://www.ingaa.org/?ID=70) is an article explaining joint lengths and the type of welding used (along with some info on bending & coating). ---
**Author:** ![Loach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/loach/32/350_2.png) [@Loach](https://boards.straightdope.com/u/Loach)\ **Post date:** [September 14, 2010, 10:42pm UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/36 "2010-09-14T22:42:58Z")
> [@Dag\_Otto](#): > > A 30 inch pipe is pretty big and I’d imagine it was working at several hundred PSI. I can’t imagine it running through a residential area. In some states it would be nearly impossible to not be near a residential area. Here is one I [witnessed](http://www.youtube.com/watch?v=gOjPLxmL578&feature=related). Just plain luck kept this from being a horrific loss of life. The rupture shot the gas like a flamethrower directly at an apartment complex. In that area there happened to be an earthen berm. The jet of flames hit the berm and went straight up several hundred feet. The intense heat eventually set some of the buildings on fire but the inhabitants were able to get out. One death due to heart attack. ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [September 15, 2010, 12:35am UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/37 "2010-09-15T00:35:13Z")
> [@Loach](#): > > > [@Dag\_Otto](#): > > > > A 30 inch pipe is pretty big and I’d imagine it was working at several hundred PSI. I can’t imagine it running through a residential area. > > In some states it would be nearly impossible to not be near a residential area. There are towns and cities built around stations and refineries too, don’t forget, and they have many, many lines (including large transmission lines) in the ground. For instance, [Pipeline Alley in Edmonton](http://maps.google.ca/maps?f=q&source=s_q&hl=en&geocode=&q=pipeline+alley,+edmonton&sll=56.145358,-120.670223&sspn=0.015564,0.045447&ie=UTF8&hq=pipeline+alley,&hnear=Edmonton,+Division+No.+11,+Alberta&ll=53.538777,-113.367233&spn=0.063861,0.181789&t=h&z=13), AB, where most of the major pipelines in Western Canada end or begin (lots of refineries). All those circles on the map are fossil fuel tanks. [Taylor, BC](http://maps.google.ca/maps?hl=en&q=taylor,+bc&ie=UTF8&hq=&hnear=Taylor,+Peace+River+Regional+District,+British+Columbia&ll=56.145358,-120.670223&spn=0.015564,0.045447&t=h&z=15) is near where I grew up, and they have a large facility in SE part of the town. A [large explosion](http://www.cbc.ca/canada/story/1999/01/27/taylor990127.html) happened there in the 90’s and the entire town was evacuated. Here’s a tank farm in [Baton Rouge](http://maps.google.ca/maps?hl=en&q=refinery&ie=UTF8&split=1&rq=1&ev=zi&sll=30.331398,-91.210041&sspn=0.048227,0.090895&t=h&radius=3.25&hq=refinery&hnear=&ll=30.329546,-91.23064&spn=0.048228,0.090895&z=14), located very near residential areas. Here is [Garyville, LA](http://maps.google.ca/maps?f=q&source=s_q&hl=en&geocode=&q=garyville,+la&sll=30.329546,-91.23064&sspn=0.048228,0.090895&ie=UTF8&hq=&hnear=Garyville,+St+John+the+Baptist,+Louisiana,+United+States&ll=30.056911,-90.589914&spn=0.048362,0.090895&t=h&z=14), right next to the refinery. I guess what I’m saying is, yes, big pipelines run through and near residential areas in much of the US and Canada. People just don’t realize it. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [September 15, 2010, 4:05am UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/38 "2010-09-15T04:05:50Z")
I guess I just thought that they would run between residential areas, along a utility right of way or easement, rather then right through the middle of them. Of course, I know enough about how these things come about to realize that that is a pretty dumb expectation. One of the divisions where I work operates a electrical substation. There is a lot of construction going on in the area, and utility line spots are always happening. One of the customers for power is a liquid petroleum pipeline. One day we had an outage that took out an entire circuit, one that fed the pipeline. I guess they never considered a backup power option, because they were the first ones to call and complain. A little investigation and we find the cause to be an excavation that hit an underground feeder. One that was properly marked during line spotting. And the excavator that hit this marked line? That’s right, the pipeline company. ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [September 15, 2010, 4:32am UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/39 "2010-09-15T04:32:36Z")
> [@Machine\_Elf](#): > > From thread in MPSIMS, a gas station [surveillance cam video](http://www.ktvu.com/video/24991167/index.html) of the explosion. At about 9 seconds, you see debris and dirt flying, but no flames until 14 seconds. This suggests the rupture preceded ignition. > > The scale of the scene is difficult to gauge from the video. It looks like the fireball is just across the street, but in the other thread, The Hamster King reports that the gas station is actually 300 yards from the blast site. Thanks for the link. I have been having a hard time understanding an explosion that would nave been on the surface rippping an underground pipe. But what you have described maked sence. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [September 15, 2010, 6:25am UTC](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432/40 "2010-09-15T06:25:33Z")
> [@Snnipe\_70E](#): > > > [@Machine\_Elf](#): > > > > From thread in MPSIMS, a gas station [surveillance cam video](http://www.ktvu.com/video/24991167/index.html) of the explosion. At about 9 seconds, you see debris and dirt flying, but no flames until 14 seconds. This suggests the rupture preceded ignition. > > > > The scale of the scene is difficult to gauge from the video. It looks like the fireball is just across the street, but in the other thread, The Hamster King reports that the gas station is actually 300 yards from the blast site. > > Thanks for the link. I have been having a hard time understanding an explosion that would nave been on the surface rippping an underground pipe. But what you have described maked sence. What is shown in the video is pretty consistent with what the OPS and the TSA told me about the effects of an event at a regulator station. A fireball, with negligible blast/overpressure effects. In my case though, I was assured that the pipeline in question was equipped with excess flow devices that would shut off the gas if the flow exceeded a set point. I take it that these devices are not required everywhere. [Previous page](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432.md?page=1) [Next page](https://boards.straightdope.com/t/san-bruno-natural-gas-explosion/553432.md?page=3)