What Really Happened During the Gas Explosions in the Merrimack Valley?

A summary of one of the worst natural gas disasters in US History.
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On September 13, 2018, a pipeline crew in the Merrimack Valley in Massachusetts was hard at work replacing an aging cast iron natural gas line with a new polyethylene pipe. By the end of the day, over a hundred structures would be damaged by fire and explosions, several homes would be completely destroyed, 22 people (including three firefighters) would be injured, and one person would be dead.
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[@PracticalEngineeringChannel]

🌌Get Nebula using my link for 40% off an annual subscription: go.nebula.tv/Practical-Engineering 🛠What engineering disaster would you like to see me cover next?

[@15muffinz]

The way you pronounced Winthrop really bothers me. Lmao.. Yeah I remember this first hand. I live in a neighboring city.. I remember when all they were talking about was terrorism, and that's one of the biggest reasons why New Hampshire and Maine in every neighboring city hopped in. I remember seeing even all the way down to nearly Boston, people were displaced and forced to move south where there was more housing, and everyone was afraid to move in somewhere with similar infrastructure owned by the same company after the dust settled. That was super scary.

[@TheBitter73]

What is the method/process/algorithm/checklist that should have been done to let someone know that the sensor needed to be moved? How was someone in the management chain supposed to know that the sensor needed to be moved? Or that it was there? Also, why doesn't the value have a top end to prevent an accidental over pressure? If someone punches a hole in the line and the pressure keeps dropping no matter how much that valve opens, that seems like a recipe for disaster. I understand that a sign off by a licensed PE is recommended but what are they doing differently? Are there some standards they are using to examine the plans against to know to ask "what about the sensors?"

[@dangriggs332]

Deepwater Horizon Disaster

[@genericscottishchannel1603]

leave nebula

[@danbrit9848]

why do you promote a lawyer that fails at the basics of we have a constitution it shuld be the law first...when the grate shut down comes remember you simped to the vary people that installed it...other then that grate vid ...sad you support the destruction of our rights tho

[@NHDOTGUY11]

Thank you for this video. I was one of the many firefighters from New Hampshire that responded down there. Was one of the scariest days in my career.

[@kurotsuki7427]

That sounds like a really bad day at work. Glad you made it out.

[@jasongreene303]

Stay safe and make it home every night, brother.

[@goosenotmaverick1156]

Glad you're safe after that, and thank you for doing the job you do, stay safe.

[@aspuzling]

How long did it take for you to realise what was happening?

[@NHDOTGUY11]

@@aspuzling listening to the fire radio and the at the moment we crossed the Haverhill/North Andover town line we could smell gas in the air.

[@Xeonerable]

I can't say I remember hearing about this back then. Imagine being a gas utility worker* doing that job and you realize the whole town started blowing up, that must be awful. Seeing that map of all the locations that were on fire was frightening.

[@gus473]

Imagine driving to them!

[@AnonOmis1000]

Yeah I have no memory of this event.

[@enekuda05]

I do recall seeing this in some sort of news, but didn't realize how crazy it was! My memory seemed to think it was like 2 or 3 houses...

[@freetolook3727]

Typical news blackout. Remember the recent train wreck in Ohio where it took 13 days to become reported in the news?

[@drooplug]

​@@freetolook3727 This was a big story as it happened. The East Palestine derailment was immediately reported in national news the day after it happened.

[@Psrj-ad]

Considering how many leaks and resulting fires there were, The fact only 1 person died is actually insane.

[@selina7318]

The person who passed away wasn't even in a fire or house. They were sitting in a parked car when the chimney blew off a house and landed on them.

[@hauntedshadowslegacy2826]

@@selina7318 Oof, now that's what rolling a nat 1 looks like...

[@MrBrianholman]

Yup it was a freak thing….

[@MrIhatethisprocess]

@@hauntedshadowslegacy2826 Heartbreaking, iirc it was a 16yo kid who was going for his driver's test to get his license like, the next day, and he was just sitting in the family car when the neighbor's chimney fell on him

[@nbkknlq]

You should do a collaboration

[@dougmoore6612]

I often have the same fear in my work as a helicopter mechanic. My thoughts run something like this, “What if I do this work order completely correctly but the guy before me cut a corner I couldn’t even know about without me doing his already completed work again for him?” The end result is that in safety critical jobs, we, the workers doing the actual work in the field, have to be able to trust that the people before us did the job correctly. Otherwise, nothing gets done.

[@Wulthrin]

as i understand it, everything is logged? so in the moment you have to trust, yes, but your trust is more in the process itself than in the guy before you. i'm automotive and im definitely not jealous of the work amp's do

[@dougmoore6612]

@@Wulthrin you are right. We log things to the nth degree. The fear of course, is that people can and do log whatever they want. At my company, I’m thankful that my coworkers are pretty great! The skill, experience, and care they have is better than I have seen in many other places.

[@RevMikeBlack]

Adherence to protocols and good record keeping are the keys to safety. The fact that you're worried about doing a good job means that you ARE doing a good job.

[@xXJerry202Xx]

​@@dougmoore6612 just today we found a rod end for the LH engine control cable missing, nothing written up anywhere in the work order, nobody knows who did it 😂😂

[@xXJerry202Xx]

We do engine runs after every plane leaves the hangar so we would've noticed something but still, why?? 😂

[@denisbeaudoin4618]

I was one of the electricians who worked on restoring all this and making sure houses were safe. All over Lawrence and Andover. It was crazy times

[@Kessoku]

cool

[@General12th]

cool

[@eruilluvitar]

Wow. Thank you so much for your work on this!

[@KevCanvin]

I lived in Haverhill at the time and was at work in Ward Hill, I remember how everyone was terrified that it would continue happening in more towns.

[@JeremySpidle]

Great excuse to abandon gas and go all electric.

[@kenchorney2724]

As a former controls programmer, I am a bit surprised that there were no high pressure shutdowns (measurement and valves) built into the discharge side of the regulators.

[@zyeborm]

You would think they would have a "short loop" control as well as the long loop. Set it to whatever the absolute max pressure rating the low side supply has. Turbulence should never trip that, and the cost vs risk of failure... But then again it's easy to say these things from our armchairs after the fact.

[@goury]

I am still surprised Americans don't understand basics of sensor loop design. Yet they are multiplying faster than they are killing themselves.

[@brucelytle1144]

Right?! I too program control systems. The hardest, most time consuming part is to program what to do when things don't work the way it's supposed to.

[@JeffreyBue_imtxsmoke]

@@zyeborm Well stated sir.

[@zachary_fb]

I work in this industry, and am pretty familiar with Merrimack. A large number of our control systems are purely mechanical, only relying on control lines and regulators. We have some SCADA, but it's really only for monitoring. Most of the controls are on the large points of delivery sites that operate at the 500-1000 PSIG range. Benefit to the mechanical ones is that they operate 24/7 regardless of conditions or power. Most modern regulators have great turndown, so as long as there's even some pressure differential from the high to low side they will regulate well enough. Modern regulator stations are typically monitor operator, with two downstream points to measure pressure. The operator reg actually controls the pressure, and the monitor is there to take over if the operator fails, as they usually fail open. Downstream of that is a relief valve, usually a pop relief that blows at a set pressure and prevents downstream buildup, or, more rare now, a security valve (slam shut valve is what i've also heard these called) that deteces overpressure and shuts off all flow. The kicker with all of this is that you can hop the fence at any major regulating station in any rural state, clamp a control line (which tricks the reg into thinking it's 0 PSIG downstream) and dump 600 PSIG into a town. Lots of stations out there with absolutely 0 security.

[@alexanderlavoie5461]

Massachusetts resident here. This was HUGE news. I remember seeing dozens of houses on fire, and blown apart houses. Massachusetts is such a quiet and safe state so this really rocked us. The company that bought out Columbia Gas is called Eversource and they seem to be taking things exceptionally seriously, which is good to see.

[@AuntieSullivan]

Yes. Columbia was forced out by the Commonwealth. Charlie Baker, the Governor at the time, was not putting up with anymore from Columbia. There must have been quite a history of mistakes, not just this one.

[@johnbroski1993]

We deal with eversource in CT and Jesus are they incompetent..

[@bbeen40]

Did you really just call Massachusetts a safe state??? Lol

[@BobClemintime]

@@bbeen40It’s top 10, maybe top 5 for life expectancy for US states, so definitely more safe than average

[@conor2439]

​@Mr. Pig Massachusetts is incredibly safe and a great place to live. Essex and Middlesex Counties, as well as Southern New Hampshire, are home to some of the most desirable zip codes in the country and rank very high in every metric measuring quality of life.

[@hhearst]

I live in North Andover MA, one of the towns impacted by this. Thankfully, my family was not impacted, but the day was very surreal. Fires, power turned off, traffic from evacuations, school closures, schools turned into shelters were all experienced. Thank you to all the firefighters and other first responders who helped that day. And, Grady, thanks for making this video. I never really understood the cause until now.

[@flow5718]

Hope you have your own high pressure valve just in case.

[@ucfsub]

@@flow5718 As far as I know every house has a regulator on it now in that area.

[@ucfsub]

As a lineman for Mass Electric I'll never forget that night. I've never seen Lawrence so dark. I remember getting called in the evening and making it down 495 only to hit gridlock and having to have a state police escort to get me through the gridlock on every road surrounding the area, finally making it to a very strange feeling rte.114 which had no cars on it. We worked I believe 5 days of around the clock shifts, energizing areas as we were given the ok by the fire marshal. Then spending all fall and winter upgrading transformers that were overloaded by the mad rush to install electric water heaters and such.

[@b3j8]

I was under the impression that the gas line pressure at each property was also regulated by that property's meter. Apparently not.

[@ucfsub]

@@b3j8 No, that whole system was run as a low pressure system, only regulated by those regulators that got blocked off. It was basically just a gas pipe from the street right into the basement, the only regulator it hit along they was was that on the individual appliances.

[@davea4245]

It is good to see the NTSB didn't try to throw the trades under the bus and showed that management totally dropped the ball.

[@MichaelSteeves]

In serious incident investigation, management has a share of the blame in almost every situation. For example: if untrained workers do a slipshod job -- who is really to blame?

[@heptex8989]

​@@MichaelSteeves Could dig a bit deeper, Maybe the certification issuers did a slipshod job actually examining their candidates ability. Can't always blame management

[@leerman22]

I think if they had the backup sense line already attached to the new line it wouldn't have ended this way.

[@hgbugalou]

Thats not the NTSBs way. They know hanging people out to try leads to coverups and that makes things unsafe. All they care about is making things safer and preventing the same things from happening again.

[@screetchycello]

@@heptex8989 That's still management. It's their job to make sure people are actually qualified, too.

[@ClebyHerris]

I can’t imagine being the guys installing the pipe and just hearing and seeing explosions in the distance and just know that something went wrong

[@_--9286]

I feel bad for those workers thinking they messed up bad when in reality, it was the poor management and boneheaded engineering practices of the firm

[@xonx209]

Shouldn't the workers themselves understand pressure regulators and pressure sensing lines?

[@ClebyHerris]

@@xonx209 that’s like getting an oil change then the wheels exploding. Just not near each other. This kinda works But yeah they probably know about how they work but they are doing what they are told

[@user-pg9jg2xe4n]

Seriously! Talk about your heart sinking

[@elvingearmasterirma7241]

​@@user-pg9jg2xe4n Id probably be mentally preparing to be fired- Like it wasnt their fault but they didnt know that

[@chickenwing111]

I live nearby and watched this unfold on the local news. When fires appeared all over the area it was apparent that they had over pressurized the gas system. People reported stove pilot lights shooting flames out/up several feet. Every gas stove, heater, water heater and clothes dryer in the area had to be replaced, as did most of the underground piping and meters. The person that was killed was a teenage boy who had just received his driver's license. He was in a driveway and was crushed by a chimney when the house blew up (see @13:50).

[@zanepetty7854]

I remember discussing this immediately after the NTSB released the information about it. I’m an Instrumentation and Electrical Technician for a major pipeline company. We discussed this in a safety meeting even though we don’t operate low pressure systems. This video was so good that I might show it in this month’s safety meeting.

[@skipd9164]

Then you will understand the regulator department should of been there. I have made many comments on this thread and I made 1 video even though picture is off. They never allowed it to be seen for over a year. I have read almost every document in the NTSB reports. The only deposition that makes no sense is the general manager in charge of the departments. Eliminated communication unless job on computer and kept the regulator guys out of the loop .

[@willlock3644]

Don’t get stuck on the problem being the low pressure line. The problem was sequence and planning.

[@skipd9164]

@@willlock3644 actually 1 upper manager said the regulator department was not needed. There were spaces for that department to sign off but it was determined they weren't needed. Imagine a line that comes out of the pit and someone saying they were not needed. It is true and in depositions on file. Even though this was always the procedure

[@willlock3644]

@@skipd9164 I work in industry. I get it.

[@skipd9164]

@@willlock3644 no problem

[@AnAcceptedName]

As an oil and gas operator, this is one of my biggest fears. Not tying in the sensing instruments to the control loop. Especially dangerous when commissioning a new line/equipment. Really not sure how this would be missed though. Hot Taps usually have very intensive oversight.

[@Jehty21]

Why aren't there more safety features? For example a pressure gauge that automatically shuts off the line when an overpressure is detect may have prevented or at least softened this event.

[@CptJistuce]

​@@Jehty21 Only if it was hooked to the right place. The existing pressure regulators weren't malfunctioning, they were just monitoring an abandoned pipe. Any additional mechanisms installed before the new line was laid would likely also be monitoring the old line, and this would probably still have been overlooked during planning to switch over to the new line.

[@WildRapier]

I've hot tapped a water line at 120 psi, I would not want to hot tap a gas line. But, how else are you going to get the job done? Don't envy you!

[@MrLuc420]

Intensive oversight can be so expensive though

[@zyeborm]

​@@CptJistuce putting distributed (electronic) pressure sensors throughout the network would be how I'd do it. Not just one or two mind, think more like 20 for every regulator. They phone home their data every once in a while or instantly for a fault. One giving a high reading gives a warning 10 giving high readings triggers an automatic shutdown of the segment. The sensors don't have to be $10k a pop either. Few hundred $ will suffice as failures of any sensor don't really matter. As a bonus you'll get detailed data for the whole network, probably find some leaks that'll pay for the cost in a few months i'd wager.

[@christopherg2347]

The scary part is that there are still up to 30 states that haven't fixed the insufficient oversight by removing the excemptions.

[@xsk8rat]

@inpressi75 The rest of the states: Texas Yes Amend statute Utah Yes Amend statute Vermont No Virginia Yes Amend statute Washington No West Virginia No Wisconsin Yes Amend statute Wyoming Yes Amend statute

[@kds5065]

I stated this in a separate comment, but: Just because you have a PE does not mean you are a competent/qualified engineer. It means you passed a test. Heck, there could be a PE Engineer signing off on natural gas drawings but said PE Engineer has no natural gas experience. Ask me how I know...

[@jacklinde7568]

Lobbyists are scary things. And where there's money at stake, there are corners to be cut.

[@paulvarjak7378]

@@kds5065 I'm somewhat obligated to stick up for us PE's.... In my state you have to have a BS with transcripts from all colleges/universities attended, documented applicable work history showing progressive experience reviewed by two independent licensed engineers and they have to agree the experience is adequate, you have to demonstrate a minimum of 4-years under the direct supervision of another PE who writes a recommendation letter to the board on your behalf, then you have to get a minimum of three additional PE's who know your work to recommend you for licensure. All told, I had two eight-hour exams, lots of paperwork and a total of seven licensed engineers involved in getting my license. Not making any attempt whatsoever to claim competence of any kind. But there is slightly more involved than just passing a test. Also, you do actually become liable when you stamp things. So PE's 'typically' (not always) will care just a bit more than those who are not licensed. There are plenty of people with stamps that probably shouldn't have them, but if given a choice, I would prefer any bridge that I cross be stamped by a PE rather than a non-PE. It's hardly perfect, but nothing is. -Cheers

[@kcgunesq]

@@BiggaNigga69 Agreed. Utility companies are the parties with the most expertise. Simply having a stamp doesn't mean you have any more skill, experience or qualification than the degree holding utility engineer with 20 years experience.

[@codyhufstetler643]

This is seriously up there with Tacoma Narrows and Hyatt Regency walkway collapse in terms of cautionary tales to teach engineering students. It's easy to explain what happened, and it's a mistake anyone could see themselves making if it slid across their desk on an off day. It has so many implications about proper documentation, multiple levels of scrutiny, making sure you fully understand the system you're working with, the importance of risk analysis...

[@MrMisterDerp]

As an hvac tech in the Boston area I can honestly say this was the most stressful day of work I ever had. Our phones were ringing off the hook and every service tech where I worked pulled a 10+ hr day running calls

[@jackoliver7506]

What did you do just shut off gas mains to the house all day

[@TheGuruStud]

Lmfao. A normal day is 10+ hrs for hvac tech/installer. Get out of here, sissy.

[@Banrion]

I lived in Andover during the explosion. We finally got heat and hot water back at Thanksgiving and it was another 2 months to get our stove replaced. Thanks for covering this one.

[@Teh_Random_Canadian]

What happened to your appliances? Did they just shoot gas out at insane pressures? Did it actually break your stove?

[@Banrion]

​@@Teh_Random_Canadian nothing dramatic happened inside my house. All appliances connected at the time of the incident were condemned and replaced.

[@zazuch]

@@Teh_Random_Canadian Depends on if they have a constant pilot light on or not. Ex some furnaces even during summer time have a small pilot light always burning. It would make that into a flame thrower possibly. Hopefully it wouldnt spread. Or worse the increase in gas would extinguish the pilot light allowing natural gas to fill your home. Until it found an ignition source and was at the right air mixture and ignites.

[@boby115]

@@zazuch , you are correct but even electronic Ignition gas appliances become hazardous with 75 psi of gas pressure on a gas valve rated for a 1\2 PSI . Could you imagine a hot surface igniter getting hit with an excessive amount of gas flow , even in the five second lock out time you could cause a pretty good explosion.

[@zazuch]

@@boby115 I didn't mean to make it seem like they weren't a hazard. Letting free flow gas into any structure is a recipe for disaster haha.

[@TheMythbustersrule]

As a MechE who is going for his PE, this is so absolutely chilling. Really puts into perspective my complaints about how annoying 16 hours of testing is. Such a simple oversight shook tens of thousands of people's faith in the systems that are meant to keep them safe. Really makes you wonder what other everyday devices we normally just take for granted as being safe are one simple oversight from upending our lives. Truly horrific.

[@the_undead]

And this is why I prefer using the electric grid wherever possible, this kind of catastrophic failure is not realistically possible with the electric grid without outside sources coming in to play. And if something like this did happen with the electric grid substations would probably explode long before too many homes caught fire

[@gcflower99]

So, champ, are you still just trying to get through the 16 hours of testing? "Such a simple oversight..." wasn't. It was a major failure of "big picture" thinking (aka common sense) during project design and procedure development. YOUR life SHOULD depend on your competency, not just the lives of folks affected by your work product. Every engineer (all fields) should have some sort of common sense test before they can graduate and/or promote (e.g., replace all the spark plugs and wires on an older V-8, using the manual, and make sure it runs OK).

[@kylancook3477]

Takata airbags anyone?

[@yosefmacgruber1920]

@@the_undead It should be pointed out that some gas appliances still work normally in the event of a power failure. That is certainly a worthy consideration. My gas logs are not even aware of a power failure, as even the wall thermostat is powered by the thermo-couple or thermo-pile of the lit pilot light, operates much the same as a gas water heater. In fact, during a dark power failure, I once soaked in the bathtub. Why not? Plenty of hot water.

[@ThuhOthers]

Thank you so much for covering this! As a resident of MA, it's been disappointing learning about what little publicity this received outside of the New England area versus how important it truly is. Let this be a stark reminder of why licensing exists.

[@paulhaynes8045]

As a Brit who follows the news daily, both home and abroad, I was amazed by this - I don't remember any coverage of it at all!

[@dannydaw59]

I never saw this in the news in Michigan.

[@adel19997]

I don't recall this incident I'm from California where fires jump freeways, homes, mountains. I would've thought it similar to CA crazy fires if I were to watch those reports.

[@crystalsoulslayer]

Fossil fuel processing and distribution systems have accidents pretty frequently. If this article is to believed: en.wikipedia.org/wiki/List_of_pipeline_accidents_in_the_United_States_in_2019 > "For natural gas alone, the Pipeline and Hazardous Materials Safety Administration (PHMSA), a United States Department of Transportation agency, has collected data on more than 3,200 accidents deemed serious or significant since 1987." That's 88.8 "serious or significant" accidents per year, on average, that the PHMSA knows about. It's rare for such incidents to receive significant media coverage, especially coverage outside the immediately affected area. Which is weird, because you'd think that would be newsworthy. Apart from being a flammable inhalant hazard, methane is also an extremely potent greenhouse gas. Reducing the need for the natural gas distribution network would not only reduce the inherent risk of having tubes full of explosive gas in cities, it would reduce the severity of climate change. Of course, people gotta heat, so how do we manage that transition away from gas safely and fairly and efficiently? What a spectacular combination of discussion topics for the news talky people! And what a worryingly frequent occurrence these leaks are! It's surprising that we don't hear about this all the time, really. I'm sure the reasons for that are entirely innocuous, and unworthy of any scrutiny from investigative journalists or law enforcement. 👼

[@tsm688]

@@crystalsoulslayer whether you burn the methane at home or at the power plant, you're still burning methane. safer for you, but not really "migrating away"

[@erniecolussy1705]

I have worked in job environments where asking questions was discouraged. My supervisor's attitude was, "If it isn't in our scope of work it isn't our concern." I caught many problems by asking questions. I saw many others miss things because they were too focused on only the scope of the project. Everyone make mistakes. When we insist on not helping other prevent mistakes things get bad.

[@StarkRG]

It's a natural result of punishing individuals for genuine mistakes. 99 times out of 100 (probably more), a problem has a systemic fault. If you punish individuals, you make it so they don't want to report their own mistakes, but you also make it so they don't want to take on the responsibility of pointing out other people's mistakes. This is a lesson that NASA learned with the Challenger accident, and one that numerous industries insist on learning for themselves, sometimes repeatedly.

[@FerralVideo]

I have sincerely lost count of how many times I was rebuked growing up for asking questions, "That does not concern you." It's given me a bit of a "stay in your lane" mentality, even though I've been actively praised at work for my ability to spot problems and ask the right questions.

[@mrz80]

@@StarkRG Working at NASA at the time, anything along these lines tends to bring STS-51L very forcefully back to mind.

[@StarkRG]

@@mrz80 Yeah, I'll bet. It's always my go-to when I need an example of a relatively minor engineering flaw massively exacerbated by severely flawed organizational culture. It's also my go-to when I need an example of an industry that completely reformed its culture for the better in the wake of tragedy. Sadly STS-107 showed that, without constant vigilance, that reformed culture can become corrupt again.

[@TimeSurfer206]

I am an Electrician, and I _ALWAYS_ double check the Engineer. Hey, my name is going on that work too!

[@jasondeleon4811]

I remember this day very vividly. I was still in school and hanging out near the LHS park. The first time a saw the cloud was towards the direction of KFC. I had run over a mile to get my parents as the streets were closed and the smell of gas was potent. Rip Leo, I met him back in middle school and it’s sad that we never got the opportunity to graduate together as this was our final year in HS

[@Bowler4Ever]

I really appreciate this video, Grady! As someone who lived very close to this disaster, the news didn't exactly shed the best light on how this actually happened. Your explanation made it very straight-forward! If memory serves me right, that dark blue home at 9:54 was actually owned by a firefighter, who saw it on fire and could do nothing about it because he already had to respond to other fires that were reported before his. It's amazing--and shocking--how one small mistake caused so much damage and changed the lives of many.

[@anthonygross226]

Living in nearby southern New Hampshire (20 minute drive away), I remember seeing so many of our local firefighters heading south to Massachusetts with urgency and an immense amount of bravery. The news reporting a cascade of homes exploding one after the other, I couldn't even begin to imagine the horror that everyone found themselves in. I cannot overstate the bravery and professionalism that first responders all over the region showed in the face of overwhelming danger - true guardians of our cities. Let us hope this never happens again.

[@yosefmacgruber1920]

I seem to recall some "Rescue 911" type TV show, maybe it was this incident?, showing appliance gas pressure regulators just suddenly opening up and coming apart, under the excess pressure. But of course that would be a re-creation of the event, that depiction could be inaccurate unless based upon actual forensic evidence. Did it actually take almost a century for movie-makers to figure out that the Titanic broke in half before it sank? What about the 100s of witness accounts? Does almost nobody do diligent research?

[@paulzagieboylo7315]

My sister was living just a few blocks north of this regulator, in the Washington Mill apartments just across the Merrimack River. Fortunately the gas system doesn't cross the river anywhere near here, so she was isolated from the direct effects, but she did lose power and was evacuated for 3 days. It was absolutely terrifying for all of us to hear about, and even more so for her to live it. Thank you for this video.

[@phasm42]

Didn't know the NTSB investigated pipeline accidents.

[@crime_wavcorp]

A product is being transferred through a pipe is the way they see it.

[@dascandy]

NTSB investigates most major accidents - they have a youtube channel and very 90's style animations, but thorough information too.

[@phasm42]

When I think accident investigation, I think USCSB (they also have a great KZbin channel).

[@lizj5740]

@@phasm42 * United States Chemical Safety and Hazard Investigation Board

[@OrigamiMarie]

I used to work in a utility mapping office, i worked on the electric side but there was gas mapping there too. I remember at some point during a safety talk (since maps are critical to safety) someone said that typically an error in electricity puts the line workers in danger, while an error in gas more often puts the public in danger.

[@SirCutRy]

Exactly. Electrification ought to happen sooner than later.

[@stevemitz4740]

@@SirCutRy In a Godless psychotic nation that pushes EV as salvation yet curse's & fears clean atomic energy!

[@user-ri5ff8ll4z]

When this happened I was a freshmen Civil Engineering student at Merrimack College in North Andover. I remember when classes resumed the following Monday morning. The entire eng 1000 class discussion suddenly changed to pipe pressure that day. Fortunately the community stepped up to take care of the displaced and make sure Columbia gas was held accountable for its missteps.

[@RevMikeBlack]

I'm not an engineer, but I have friends who are. I've always been impressed by the self-policing nature of the engineering profession. Simply put, good engineers do not like bad engineering and will do whatever they can to stop it. Knowing this, I have to wonder how something like this could happen.

[@yosefmacgruber1920]

People should take pride in going good and neat work. And why isn't there more redundancies and protections in the system? Why wasn't there something down-line that would react to the over-pressure? If we are talking about 30 miles of pipe-line, wouldn't the cost of safety monitoring devices be small in comparison?

[@jonasghafur4940]

as a medical student, and someone who worked in the "lower classes" of healthcare before having the chance to become a physician, i sincerely wish my profession would be a little more generous with their interpretation of self-policing. Don’t get me wrong, this works in many cases, but things like physicians shilling alternative medicine for moolah, physicians that profit from a new kind of pill mill, the telemedicine kind, physicians who perpetuate this feudal system of being allowed to abuse your staff in the name of hierarchy and many more should be f*** shunned

[@SpencerHHO]

I understand the frustrations that regs can cause but just about "every safety regulation is written in blood". Standards and regulations come into effect usually after someone is killed.

[@Br3ttM]

Depends on the standards. Many regulations aren't written in blood, they're written by businesses to block competitors. There are many cities where you can't legally set up a taxi, moving, or ambulance company without either proof that the existing ones aren't sufficient, or permission directly from the companies you would compete with themselves.

[@jasonreed7522]

​@@Br3ttMyou missed the key word "safety". Every line of the national building code (each code book being atleast 200 pages) is written in blood. The only exception is the energy code which is about conservation of resources not safety. (And its filled with exceptions related to making a safer design)

[@SpencerHHO]

@Br3ttM I said safety for a reason. I'm not saying that there aren't problems broadly with regulations. Many of the changes are useless beurocratic fluff but safety and design standards exist for a good reason and my comment is more a rebuke of the infantile views of some libertarians.

[@antcommander1367]

Yet that won't apply to the gun control, when something bad happens. Unlike rest of the normal world. Instead blame something else or banning stuff like backbags (in michican), reason being "you can hide weapons in them"

[@baronvonlimbourgh1716]

Regulation exists for a reason. Getting rid of them usually just brings back the exact problem big or costly enough that people where willing enough to create regulation over in the past.

[@WildRapier]

As a follow up, having discussed pilot operated regulator valves, you could discuss the same but on the water side for storage tank level control. For example, I saw one PWS consistently overflow one of their tanks because the altitude valve was not adjusted properly and the height was controlled via another storage tank. Every day as I was driving through the town, there was either sign of overflow or the tank was actively overflowing. Try to hit USEPA unaccounted for water (10%) when you're dumping water, at cost to the consumer (everyone). This might not be the norm, but it does happen and everyone pays for it! The towns unaccounted for water was @ 24%, think about that the next time you get a water bill! I won't even get into the wastewater side of things!

[@thomas_james]

I work in Massachusetts installing underground gas main for one of the largest utility companies in New England. I still hear different stories about what really happened,as I started working in this industry a couple years after this happened. To work on site you need to have operater qualifications, depending on the company you work for could be 50+. You need to pass either a hands on or written test for each one and renew them every 1-3 years. Engineers, supervisors and DPU are constantly coming by the job site to hopefully avoid something like this ever happening again. I’m happy I came across this video, this definitely answered a lot of questions I had. This is very dangerous but rewarding work and I’m grateful I am part of building americas infrastructure. Love your content ❤

[@mfk12340]

I remember when this happened. Literally every fire department around me went to this, nobody really knew what was going on initially, and a lot of people around me ended up removing their natural gas service. Either switching back to propane or oil.

[@happyhome41]

Fascinating episode. Our neighborhood has 80 psig lines running under the street with individual regulators at residences and businesses. This episode also underlines the importance of systems engineering, and "systems thinking" in many aspects of life.

[@m9ovich785]

In 1976 We had High Pressure to the Regulator at the Meter... Central Wisconsin

[@keent]

not living in a country where it has natural gas pipe lines directly but first thought was why not put individual regulators instead of a common one? could be budget issue?

[@JTech625]

Very cool to see this coverd I live in one of the neighboring cities to Lawrence and can remember the panic, and all of us scrambling to turn off our gas not fully knowing what was happening . Following the explosions many homes in my area had there gas meters/regulators relocated from the basement to outside the home i think so that if something similar ever occurred again the outdoor regulators would vent the excess pressure outside instead of into the structure.

[@KevCanvin]

Same! Haverhill here. Very scary day.

[@pbenga]

At the time i lived in Andover but very close to the Lawrence line. I remember the rows and rows of cars with people being evacuated out of the city. My wife was away on business and when she came back, had to figure out how to get home because many of the exits on 93 were closed.

[@stevebabiak6997]

There are lower pressure gas distribution systems, and there are higher pressure distribution systems (note that the latter are coming into more use as a result of peak demands due to tankless water heaters becoming more popular). The older low pressure systems do not require a “pressure regulator” at each meter. The higher pressure systems DO require a “pressure regulator” at each meter. Now, those “pressure regulators” basically just dump gas when it comes in at excess pressure, and those “frisbee type disks” you see at the meter are the “pressure regulator”, and if you look closely you can see that the discharge opening will usually be threaded - this allows for piping the discharge to the outside in cases where the best practice of having the “pressure regulator” outdoors cannot / is not being followed. So if you have one of those “pressure regulators” inside of a building, make sure the discharge opening is piped outside. It’s best if the “pressure regulator” is completely outside of course. And I use the quotes around “pressure regulator” because they are called that, but when I think of regulating flow I think of something a bit finer in granularity than just dumping excess. And in the event of a system overpressure situation, an entire neighborhood could have lots of gas discharged to prevent that excess pressure from entering the equipment in the building - but just one open flame at the wrong time …

[@paulhaynes8045]

Here in the UK, it's been regulation, at least since the 80s, to have gas meters (etc) outside the house. I never understood why (I thought it was to make reading the meter easier!), but I do now. My (very old) house still has the meter in the cellar/basement...

[@skipd9164]

In Massachusetts when installing a new high or intermediate pressure line or replacing one they have too be outside

[@2010WRXLimited]

Hi G, I like the way you pay respect to the loss of life and people who suffered by this disaster. You're a good man to say "Hey let's talk about this" and "we can learn" . We hope nobody will have to go through this again. You're a good engineer in that way.

[@Jake-tq6uc]

As someone who lives in the area impacted, your coverage of this incident was excellent, Grady!

[@rossjr6739]

I'm from Northeastern Massachusetts and was going to college in New Hampshire at the time. I don't think people understand how big this incident was, and the scale of the fire department response. The Newmarket fire truck in the picture is from about 50 miles away. Also, to this day you can drive through Andover and Lawrence and see where every gas line was replaced. Eventually they'll repave all the streets, but for now it's still a bit haunting driving around there.

[@notmyname9625]

Also worth noting that 50 miles covers a lot more other towns than it would in most areas of the country. Theres probably like 50 other towns in that area between newmarket and lawrence.

[@BillMSmith]

Thank you Grady. This happened in an area I used to work in. Our office was in Lawrence and the affected neighborhoods were our neighbors, there were a lot of great small local restaurants , sub shops and pizza joints run by local families. Although this happened 30 years after I was there it shook me when it happened. This is the best, most concise, explanation I've seen. Kudos.

[@justinrosa56]

I thank you very much for making this video and shedding more light into this event. I was one of the affected in the Lawrence area, I used to live in the same neighborhood as where that one person died, just a couple blocks away. South Lawrence was basically a ghost town since everybody was evacuated and it just seemed surreal in the aftermath. People often don't realize how their lives can change in just a matter of seconds, living peacefully their entire lives and then boom, a catastrophic event like this happens or even worse. Its a complete shock once you experience it yourself. Cheers to everybody and anybody that reads this✌🏼

[@frogjmon]

For some reason, I could listen to Grady describe how some terrible thing happened and what could have been done to prevent it all day. Probably my favorite content on this channel!

[@hauntedshadowslegacy2826]

The combination of his teddy-bear voice and that calm yet mentally stimulating music is chef's kiss, for real.

[@midship_nc]

You might like plainlydifficult. Tons of content about radiological incidents/lost sources etc. with a touch of English humor.

[@lavaentity9621]

So I lived in Andover when this happened, it was truly surreal experience. Thankfully the street I lived on didnt have a natural gas line, so we ended up having a bunch of friends who couldnt stay in their own houses over until they could get the lines under control. I feel like this event is/has been criminally under-reported and I really appreciate seeing more well-thought content on it.

[@jjbarajas5341]

As something that looks like an action movie set piece, I'm surprised it wasn't national news.

[@MTGeomancer]

@@jjbarajas5341 Have to remember the time. Back then the national news only covered (well, 95+%) a single topic 24/7. It was mentioned, but only talked about for 30 seconds because they had a new tweet to report on.

[@0WierdAsHell]

I live in the Merrimack Valley and was part of the evacuation teams, so seeing this video be made was a throwback to a very long day. It's kinda sad to live in a world where a disaster like this happens and my immediate assumption of it being because of corporate greed is almost always correct.

[@jjbarajas5341]

It's not always greed. Sometimes it's just incompetence.

[@adel19997]

Where's the greed? Who's gaining from the greed?

[@infernaldaedra]

​@@jjbarajas5341 incompetence is born out of cutting corners aka greed

[@jjbarajas5341]

@Infernal Daedra Fair point, but straight up incompetence in company management *does happen.

[@infernaldaedra]

@@jjbarajas5341 I agree There's so many different ways people can be incompetent

[@sb2261]

I was one of the transportation engineers developing traffic management plans and working with the town and state while crews replaced the lines. I worked many 100 hour weeks to push through trench permits and TMPs te get closures approved. Scary and awful times. People really came together. It was incredible to see.

[@Intrafacial86]

It’s always wild when you happen to cover something I actually know just enough about to anticipate what happened. When you got to the pilot regulators I just had this gut wrenching moment of “Oh . . . *oh no.”*

[@DallasHerrmann]

Similar, I'm a mechanic with a background in engineering, and as soon as the regulator setup was described, I kinda saw the writing on the wall.

[@yosefmacgruber1920]

@@DallasHerrmann So what happens when decades-old tired regulators finally go into some form of failure mode? Are they sure to get replaced at some point before the end of their expected lifetimes? Or only when there is no gas pressure and something needs obvious fixing?

[@Highraven]

I wish more people would watch channels like this. If they saw the complexity of engineering feats, maybe they wouldn't be shouting "deregulation" so quickly.

[@spencertherren6806]

Drill baby, drill.

[@Freek314]

There's nothing wrong with deregulation so long as tort laws heavily punish dangerous practices.

[@Freek314]

Most people who want deregulation are talking more about occupational licensure for things like barbers, anyways.

[@tsm688]

@@Freek314 I wish. There's a lot of scary things been quietly happening.

[@gcflower99]

Regulation or deregulation is not the issue...it's the competency of the humans involved, at all levels of the organizations and inspectors.

[@cordial001]

Great video once again. I was in Victoria, Australia when the Longford gas plant exploded. It's only after things go wrong that you realize how complex these networks are and how dangerous they can be if they're not properly overseen

[@trixrabbit8792]

I used to live in a small town in northwest Pennsylvania. The contractor I worked for and I were digging a hole next to the road to put in a stone pillar. My boss had done a One Call several days in advance and the utility companies had marked their lines. The backhoe operator hit a live unmarked gas line. It took almost 2 hours for us to get it capped. My boss called the gas company and they sent a crew out to investigate. They found another line across the street and they had no record of either line. They called in the white hat’s. After a long powwow they dug a hole down the street and found a 3rd line. It was a good thing that my boss had done the OneCall. The gas company made the decision to run all new lines for the entire town and abandon the existing system all together. Had my boss not done the OneCall he would have been held accountable for part of if not all of the fall out. And god only knows what that would have cost him. But on the up side. We got to see first hand how a horizontal boring machine works.

[@DrZygote214]

Did you find out how old were those mystery lines (when were they installed)?

[@timengineman2nd714]

I wonder if any of those Mystery lines were hooked to a Meter! (Wouldn't be the first time someone put in (or paid someone to put it in) their own pipeline for free gas (or water) even electrical hook-ups are not unheard of! (But if you've got overhead wires for power, they are easier to find, but the power company kinda has to look for them...)

[@trixrabbit8792]

@@timengineman2nd714 nope it was an entire system that the gas company couldn’t explain. I figured that it predated the current to the time system that was abandoned and forgotten about. Just some how was tied into the supply line somewhere.

[@NoName-zn1sb]

white hats

[@yosefmacgruber1920]

I love seeing all that complicated infrastructure in movies and in video games. But in real life, not so much, imagine all the stuff that could go wrong with it. And then we have all these people retiring or leaving the job, the very people who best understood the system.

[@TRG972]

I was working in Andover, MA when this happened. Many of my coworkers homes were affected and had to stay in hotels for several weeks during the recovery. Great to finally see the details of the cause. I've been a subscriber to your channel and always enjoy your videos. Especially apreciate this one.

[@kenbrown2808]

a bit of information on gas disasters: the evacuation distance for a natural gas leak was established by taking a donated house, filling it with a perfect mix of gas and air, and setting it off. then they simply measured the greatest distance shrapnel flew. so remember that if you want to crowd up to the barricades for a closer look at an emergency scene.

[@tommasomorandini1982]

Just curious, are you trying to make a point or is it just fun fact you wanted to share? In the latter case: very interesting, thank you

[@kenbrown2808]

@@tommasomorandini1982 well, the fact it was a deliberate gas explosion counts as fun. the fact that many people will go through their lives without ever having to evacuate qualifies as a fun fact. but there is also the fact that the kinds of accidents that require safe distances are relatively common means that there is a point: and the point is if an emergency crew tells you to back up, then you should back up.

[@HopefullyUnoptimistic]

More annoying than interesting, a bot ended up copying your comment about two hours after you posted it. May be worth reporting it, even if it is an endless game of whack-a-mole.

[@DrewskisBrews]

This is tragic in general, and in particular for its avoidability. The technical details are very interesting, thank you for the content

[@ChrisNeuhahnArt]

I worked on a pretty fascinating case in the 90s when I used to do trial graphics and animation. A local radio station blew up after a wild string of events. The metal grid under an electrical sub station was electrified from a bird strike, the grid arced to and old out of service gas line, which was in contact with a water main, the water main arced to an in-use gas line more than a block away, burning a hole in the line. Gas leaked into the basement of the radio station. Somehow that gas was touched off. The DJ working that day was pretty severely burned. It was determined that the gas line and water main were built too close to each other allowing the arc.

[@churchofseabass9227]

imagine being one of the guys working on the pipe then you look up and see explosions in the distance, the feeling of horror

[@KevCanvin]

As a resident of the Merrimack valley and a long time follower of your channel I am so surprised to see you covering this.

[@TheTomBevis]

I once worked for a bridge building company. One morning, we went to drive steel piling for an abutment, and drove the piling right through a high pressure gas line that been installed in the wrong location. That was an exciting day.

[@mrz80]

A new building was being built on campus where I worked, and I happened to be looking out the window at the construction site when there was suddenly a very loud hissing sound and a lot of screaming and yelling and running construction workers, followed within five minutes by a bunch of fire trucks and the local utility company arriving on site. Backhoe operator had nicked a high pressure gas line that wasn't on the site drawings. Documentation updates people, documentation updates! :)

[@five-toedslothbear4051]

Excellent video, Grady. Indeed, my neighborhood had the old cast iron distribution lines replaced by polyethylene (PE) lines at high pressure. Not only do we have a regulator at each building, but new code requires the meters and valves to be on the exterior of the building...probably safer against potential leaks, and allowing the gas to be easily shut off. (It was a huge project...we had our storm and sanitary sewers separated for flood control, so much of the neighborhood got new sewers and new water mains as well as new gas lines while the streets were torn up). Also, Chicago had a similar pressure-related explosion disaster on January 17, 1992 in River West. That was the same year of the Chicago Flood (April 13), where old freight tunnels were punctured under the Chicago River, as well as the double-deck Michigan Avenue Bridge flipping upwards, catapulting a crane into the air (September 24). The flood was particularly interesting. I worked in River North, and I remember some people looking on with concern at a whirlpool in the river at the Kinzie bridge. I got to see much of the engineering effort to plug and dewater the tunnel every day on the way to and from work.

[@seanriopel3132]

I spoke with a gas worker a month after this happened and this is almost exactly what he thought occurred. Great video.

[@friendstype25]

I lived in the Merrimack Valley at the time, and I remember being busy in Boston, just dropping everything and hopping on the T when I thought of my family. My grandparents were evacuated, they erected tents in Salem, but nobody I knew was hurt, thank goodness.

[@angelamorley9921]

I was working on highway traffic management when this happened. We had people running up onto I-495 to escape the area closure and get rides from the highway, because cars weren't allowed in or out of the area. It was crazy.

[@mikefarrington7141]

My brother was a cop in Lawrence at the time and he almost lost consciousness pulling someone out of a house who themselves had lost consciousness in their basement due to gas build up.

[@jackwoodward3103]

This is fantastic content! I have the typical always-curious "hive mind"that all engineers share, a propensity to constantly want to know "how things work." Having engineered a piece of low pressure test equipment for automotive testing @13"wc, I followed your video about the natural gas disaster carefully. Very nicely done and very informative.

[@crime_wavcorp]

crime_wav 4 minutes ago I work for a gas utility in regulation. You did a pretty bang on job. The reason they would run them so far was to get away from any turbulence. Imo low pressure systems can be a little scary because there is no regulation in the system other than the regs upstream making the pressure cut. There may have been relief valves downstream and if they were placed and sized right, they should get rid of that pressure. But being that regulation set had a backup regulator, they may not have had to have a relief valve on it because the backup reg is your backup. At least with a medium pressure system, say 10-20 psi, the house meters are going to have a regulator on them that could handle some pressure. Low pressure system, whatever pressure is coming to that meter is going into the house.

[@pbenga]

I'm from this area and remember very well what was going on. My brother-in-law lived on the opposite side of the block where one of the kid died. His basement also caught on fire but he managed to put out the fire before it got too crazy. I remember for the next few days how dark and empty the streets were in Lawrence, almost apocalyptic like. The house that completely burnt down wasn't too far from where i live also. It was a pretty crazy time.

[@ElliLavender]

That's exactly why I have such big respect for people who work with huge and complex systems like this. You basically need to know exactly where all the pipes (that aren't somehow isoloated from each other) go and how they are connected with each other. Ofc there are plans and documentation, but this accident shows how horrible the consequences can be if you are wrong.

[@Comm0ut]

The "thermostat in the freezer" analogy is elegantly simple.

[@Aquatarkus96]

Whoever decided that gas pipelines need that PE exemption needs to think long and hard about their life choices. What a braindead decision!

[@Raykkie]

I wish this was an issue isolated to Gas, but sadly the US has almost everything exempted from any sort of competent oversight. From the gruesome case of that Kansas waterpark, to the Ohio trains, and without forgetting how many people there don't have access to running water, it truly is a strange place

[@hn396]

@@Raykkie The Ohio train derailment had absolutely nothing to do with infrastructure oversight, a wheel on the train jammed and overheated which caused the train to derail.

[@jasongreene303]

It's a good buddy state. Someone saved a large amount of cash by not requiring them, therefore said savings may or may not have been shared.

[@jameshisself9324]

@@Raykkie I'm not a democrat, but the reason this happens is republican lobbying in the name of reduced govt and business expense. The folks who yell that their taxes are too high and then vote that way create these situations all over the US.

[@EUC-lid]

This is the libertarian dream in action. Who needs regulations? The market will correct these problems naturally. /s

[@jessicahunt6569]

Why would they not have overpressure relief valves in the system? would it not be safer to have it vent in controlled locations than what happened?

[@Jehty21]

Or an automatic shutoff if overpressure is detected down the line.

[@damienknapman2308]

So the original installation that could have fitted those valves was done in the 1900s and they probably weren't thinking about how that system would be retired and replaced many years later. As it was, they had redundant control systems with independent sense lines, it may have already felt like overkill for some. They're never going to be added during any routine maintenance or overhauls if the system seems to work well and again nobody is planning for what may go wrong when the system is eventually replaced. Of course, in hindsight we can see that such a solution would have prevented this particular accident and you'd hope it would be a wake-up call but when calls for upping basic engineering standards are being ignored, how are you going to get such changes made?

[@DisinterestedObserver]

Not sure if relief valves sized big enough to relieve the amount of gas being introduced during this event wouldn’t have introduced another problem by venting so much gas in a small area which could have ignited, too.

[@mrtasky2479]

Great video. I work directly in this industry and in a control room that actually monitors/controls the components listed in this video (FCVs, Compressors, etc...) and have shared this with my coworkers/shift mates. Moments like these are what we fear the most in our work life. Though we do not primarily oversee residential lines, I found this very educational and a great safety lesson to share. Thanks!

[@223556762308]

Thank you Grady. I like the Chemical Safety Board style video. I show these type of videos to my managers at work to stress the importance of clear information and quality decision making.

[@Tyani-sz6cg]

Thank you for all the hard work you put into these videos. They're always very interesting topics you share with us.

[@nekkowe]

I'm curious about the balloons that block the gas during the installation - how are they inserted and extracted without causing a leak?

[@AnAcceptedName]

The process is called hot tapping. It uses very well sealed drill bits to cut a hole in the pipe. The bit is then removed and replaced with the pneumatic balloons behind a valve added to the cutting junction. Once in position, they are inflated to create a temporary seal in the pipe.

[@zombieregime]

@@AnAcceptedName Very cool! I was wondering the same thing, thanks for the explanation. PE, or one of the other engineering channels, should do a few episodes on the little industry tricks like that. Also, the main feed being at 1/2psig?!?!? Thats crazy! Youd figure a supply would be at high pressure, but, this event aside, its a bit mind blowing that the system pressure is so low having assumed for so long it would be at double digit pressures at least.

[@bruceringrose7539]

In the public water supply world, the balloons are called inflatable plugs. Grady did not show how the plugs are installed in his graphic. It takes a lot less pressure to move the required volume of gas to operate the household appliances, so 1/2 pasig is sufficient. By contrast, it requires a lot more pressure to move the required volume of water and lift it to the second floor of your home, so the pressure in your water service is typically 60-100 psi. Much more than 100 psig will shorten the life of your appliances and responsible plumbers and home builders will install a pressure regulator on the service line in the basement.

[@natejones331]

In my area, when working with low pressure (1 PSIG MAOP) there is some leakage of gas, this is normal. Crews work quickly to insert cloth bags/balloons that are then inflated to seal the inside of the line. A simple covering of the hole with a rag is enough to keep most of the gas in the line and the pressure up. Pressure can be measured at your lowest assumed point (end of line, at a meter riser) to ensure you have no “gas out” events. For anything above LP, “stopples” will be used by TDW, it’s their “shorttstop” line of products. A simple KZbin search will show you tie in procedure. I highly recommend if you are interested. And, yea you cannot hold back enough gas to keep a line pressurized using just a rag on an MP system and higher - this type of system is definitely needed unless you’re shutting the line down completely.

[@skipd9164]

They actually double bag each side

[@joshuabarosin779]

I was living in Georgetown, about 20 minutes east of the area. My town was one of many that responded to Andover and Methuen. I had friends in my boy scout troop that lived in North Andover, thankfully not on the gas side. I remember coming home from school and just watching the news, seeing the camera footage from the helicopters. Talking to my friends, it was one of the scariest things us growing up. As an engineering major in college it's great seeing what caused incidents like these, I feel like it will allow me to become a better engineer (although I'm studying mechanical). Thank you for posting videos like this, it definitely helps people understand what happens within our complicated world.

[@BetweenTheBorders]

My first analysis job was a fatal blast analysis. It turned out it was deliberate; the home owners damaged their regulator and ended up killing their neighbors. The thought of that level of damage across an entire distribution system is absolutely chilling. Thanks for the rundown and letting us know that, at least in that region, PEs now have oversight on these systems.

[@mikeholmstrom1899]

People who steal utilities often do so without knowledge of the correct pressure for gas systems, and, use substandard materials. Electricity theft often ignores current limits. All of this asks for disaster.

[@vex-nh]

Great video. I'm surprised this disaster hasn't received more attention. I remember getting an alert on my phone that showed a map of multiple explosions and fires and wondering if it was some sort of terrorist attack. Thankfully, the Merrimack Valley has excellent fire departments. The one fatality was due to a chimney collapsing on an occupied vehicle, one occupant died, the others survived. I can't imagine what a horror that must have been.

[@skylined5534]

While anyone dying or getting injured is a terrible thing seeing how severe this was I'm glad it wasn't anywhere near as bad as it could have been given how much damage and devastation resulted. The self regulation reminds me of the fill valves on washing machines and the like, with careful engineering of the water flow internally they seal using the pressure of the mains water pressure its self. Neat!

[@DisinterestedObserver]

Thank you for producing this. This is a good summary of the event and its cause. It was truly a horrendous day. I grew up several houses away from the burning house depicted at 9:28. It is hard to capture the chaos surrounding this. The contemporary radio reports were not exactly helpful. There was a lot of confusion. I remember it was very hard to move around town as power was cut off leaving traffic lights inoperable with people being told they had to evacuate (though I didn’t know it at the time) and all driving in the direction opposite I was heading to get to my home. I finally reached it and eventually heard police traveling down the street and announcing general evacuation. I ended up at my sister’s house several towns away and even hours later I could hear sirens on I-495 as mutual aid poured in constantly. I had friend that lives closer to Boston and he told me that I-93 was the same way for hours that evening with siren after siren. Having lived through it and it’s aftermath shows what was needed as the NTSB pointed out was a competent engineering team and checklists to guide the review process. I’m an engineer and sat the licensing exams and can say a PE stamp in and of itself would not necessarily have prevented this despite the NTSB recommendation. It can’t hurt and places the engineer stamping the plans in legal jeopardy so they might be a bit more thorough if their professional ethics were not enough. Beyond the engineering aspect of this, other systems that people depend on worked well with Governor Baker taking charge and bringing needed resources to bear with no delays in the days that followed. The mutual aid system worked admirably and the help from dozens of cities and towns from up to 75 miles away was really appreciated. No city or town could staff or equip an emergency fire response to handle this and, since adjacent towns were affected, a much larger regional response was called on and worked. I have a much better understanding now of the impacts of these sort of rare but catastrophic events that I read or see videos about after going through something like this. Your video had me reliving that day even though it is now 4.5 years ago. One personal thing that sticks in my mind was later looking at my Apple Watch’s record of my pulse rate from that day as I attempted to get back to my home only to have to leave and seeing it showed I was in “fight or flight mode” for several hours

[@Ydnar1155]

It's amazing the difference in pressure that exists in gas transmission pipes. One time I stopped a yard forklift driver from yanking on an s shaped 15 foot pipe sticking out of the ground. Yeah I called the gas company and it the feeder line to an old gas meter to a house that was there 50 or so years ago...it was still charged and obviously still strong.

[@Drjtherrien]

It's strange seeing you cover something that happened in my "back yard". I remember the terror and confusion as the news broke. It left a lot of us thinking about how much implicit trust there is in everyday systems functioning as they should.

[@WolfSeril107]

That trust is exactly why I started watching this channel and many others. You simply cannot assume that companies/the government have done an adequate job making things safe. You have to educate yourself and be extremely skeptical of everyone else, or you'll end up in a house that falls off a cliff or a bridge that collapses under you or a power grid that turns off when it gets cold.

[@theunconsciousshadow]

I truely appreciate the content you make, always informative and always interesting! Thank you!

[@danightfly]

It is so much fun watching you break the engineering explanation down into digestible nuggets. You do a great job Grady!

[@47CryXMA]

The Tenerif accident is also well covered by Mentour Pilot. He does an excellent job describing the issues, and what could have / should have been done better.

[@MrVenona]

And the accident was not the fault of the 747 entering the runway without permission.

[@HeisenbergFam]

My respect goes to firefighters risking their lives to get this nasty situation under control

[@brittster182]

How are you everywhere I am lmao

[@BalaenicepsRex3]

The new Justin Y.

[@LazyLifeIFreak]

@@brittster182 Using bots.

[@MattyEngland]

That's what they are paid for.

[@roderickcampbell2105]

@@MattyEngland Matty, you're what known as a troll/bot. An especially bad one. Heisenberg paid respects to those who risk, have risked and perhaps lost their lives, and your response is "that's what they were paid for"? Shame on you. Unless you are a troll/bot in which you know no shame. I concur with Heisenberg.

[@hdog679]

Town: Explodes 31 Governors: I’m gonna pretend I didn’t see that

[@Zeppathy]

Government: Did someone have an oopsie? OK, but don't do it again.

[@kevincsellak296]

One thing I've noticed you do that I really like, is that you mention the date and location of the event both before and after you describe it. That way, I have the context I need going into the intro, and get reminded in case I forgot when going into the actual main section. And I _do_ forget, because your intros always flow so well and I just get interested in the subject matter and the substantive points, not the secondary facts strewn about throughout.

[@joestocker660]

Thanks for mentioning the Nebula content again. I paid the yearly sub through your link about a month ago, but found it a bit hard to find relevant creators. It’s still a massive value, but I’m currently watching the airport disaster video. It’s well done, and will give me some options more to my personal prefs. Thanks for all you do Grady, I’ve enjoyed hours of your content. 👍😎

[@chriskelvin248]

Obviously, the entire panel of the NTSB investigating the incident is much more highly qualified than I am, but…coming from a gas worker in another NE state here. 1) We were told the control lines to the regulator station were damaged by another previous incident and the damage was not known. As a lessons learned for our own system, a new procedure was put in place such that any excavation occurring within 200’ of regulator station control lines had to be reported and overseen by an additional special inspector from the utility company itself- before the excavation was to take place. 2) Gas as a utility is over 100 years old. There is a hybrid of new and legacy systems out there that feed customers, depending on the history of the individual system. A cast iron main is a legacy pipe material and only suitable for low pressure systems. All downstream customers will have low pressure coming into their homes and those types of systems do not have regulators at the house or business.

[@trevor61396]

As an engineer in oil & gas, thank you for touching on one of the most important industries for reliable cheap energy over the last 100+ years. Hope to see more.

[@azurplex]

Thanks for sharing the technical cause of this crisis. I attended many press conferences with then mayor and governor who, to their credit, focused mostly on meeting the residents' cooking and heating needs going into the fall and winter seasons and keeping them updated as the repairs progressed.

[@eDoc2020]

I had known that they ended up with high pressure on low pressure lines but I was under the impression it was a direct connection. When you got to the point where you mentioned separate sense lines I immediately guessed what the mistake was going to be.

[@GaryT1952]

This happened not far from me...by far the most easily understood explanation and it only took 5 years to make sense of it...thank you PE for telling us what the utilities would not

[@michaelchownyk5255]

Thank you for treating this KZbin video. I did not know of this accident. In the city where I live, there is a section of houses that have low pressure gas piping and it’s only about 7 inches of water column. The same kind of failure mode could occur there as well. I’m glad I’m aware of this now. Thank you.

[@Lessinath]

These videos where you talk about real engineering related disasters and break down what went wrong are some of your best videos, but also some of the hardest to watch.

[@dalewun]

Thanks Grady for covering another story I can directly relate to. I was mapping lines in Western Mass when this happened. It changed workers mood instantly even though they were not directly involved. I heard that some of the really older systems run at an even lower pressure, and can’t handle current distribution pressures. So to make it more complicated, there are areas with 3 different pressures of lines. Since the event in the other side of the state, I found it strange that my house and a few other neighbors who might be knowledgable about the gas system were the first to get their meters updated and moved out of the basement.

[@mbryson2899]

Great video, thanks for researching and sharing. SCARY stuff! Have you ever covered the 2010 San Bruno, CA gas explosion? I was about 1/4 mile away, had just finished grocery shopping at Lunardi's, when it went off. It was loud, and the pressure wave hit like a gust of wind even that far away. I saw the huge column of smoke and got the heck out of Dodge; I honestly thought that an airliner out of SFO had gone down (the area was right on their departure path). Well before I got a few blocks firetrucks were zooming by. I pulled off at the first sidestreet I could and sat for about 45 minutes listening to the sirens wail. I hunted through the radio stations but no one knew what was actually going on until much, much later; it was that unexpected.

[@emfournet]

This is a great video as always! You mentioned the rapid activation of hundreds of outside firefighting groups and emergency resources. It would be really cool if one day you could do a video on that process or one like it. As a Louisiana resident, I'm used to routine emergency declarations in the face of incoming hurricanes, but I would love to know how its done when there is no warning and an emergency comes out of the blue sky.

[@swissfreek]

They flew people in from all over the country. We don’t get responses like that up here as often as you all get hurricane and tornado response teams down there, so it was really interesting to watch. Then came all the gas and electric crews for the repairs.

[@mrbigsmile3902]

Your presence on Nebula convinced me to go use it. Great videos!

[@tommy2u]

Thanks Grady. Great presentation as always. We look forward to your videos coming out. :D

[@quinndtxd]

I was just reading about the tmi-2 nuclear accident and was wondering why an automatic valve was called a pilot operated valve, thanks for explaining it :) great video

[@rosieposie1760]

My aunt and uncle lived in Andover in the middle of it. I remember getting a text from my aunt asking for my wifi password while I wasn't home. and I was like whhhhhyyyy? her response "everyone's ok...." invoked one of the worse feelings I've felt ever.

[@Chris_In_Texas]

I know back in the mid-late 80's when I lived in Kansas, the local gas utility company was replacing the cast iron lines to the houses with poly lines. They would simply insert a poly line inside the cast iron and then re-terminate the line into the main. They used high pressure lines behind the houses up to the regulators at the house, as when they added a new saddle tee onto the main, was it loud with the pressure of the gas coming out. They just worked fast to replace the saddle so that they could plug the hole and stop the venting of gas to the atmosphere. Once the saddle was on they connected it to the new poly pipe and filled the excavated hole back with dirt and on to the next house. Rinse and repeat for every house in the city!