Water tank explosion....yes, a water tank 5

[fel3]

https://www.yourcentralvalley.com/n...tures-deadly-water-tank-explosion-in-lemoore/

This happened in my area. I am very familiar with Lemoore and its water system because twice I was at firms that served as the contract City Engineer and I have designed some elements of that water system. My first stint was long before the Well 7 site was developed. My second stint was after the well and first tank at this site had been constructed. I helped the engineer who designed the water treatment vessels and second storage tank at this site sort out some piping connections, but I can't tell you if it was the older or newer tank that just blew up and my records are in storage.

Apparently, someone was welding something to the outside of the tank and it sparked flammable gas inside the tank (that's what the City's Public Works director speculated about in an on-site interview I saw online). This tank appears to have had a good amount of water in it, so I'm having trouble understanding how a flammable gas got into the headspace of the tank. More details will certainly come in the next days/weeks/months.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[waross]

Dissolved natural gas in the well water?
My last home was on a 500 Ft. deep well and we got a lot of natural gas.
At times the taps would spit gas instead of water.
It could be lighted and a ball of flame would rise up towards the curtains.
Once of that was enough!

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[JohnRBaker]

At least the escaping water prevented any fires ;-)

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
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[JStephen]

Almost certainly dissolved natural gas collecting in the tank.
The City of South Houston blew the roof off a tank years ago with a similar scenario.
On a tank that size, it would be expected to blow the roof off rather than pulling the tank loose from the bottom. It makes me curious if they had the roof beefed up for some reason.

 

[TugboatEng]

One thing I notice that welders universally don't understand is that the smoke generated from coatings inside of a tank during welding isn't actually smoke but vaporized hydrocarbons resulting from pyrolysis. If there was a substantial amount of welding happening or the tank coating was smouldering I could see a building of flammable gasses.

 

[fel3]

Waross...

Maybe. I don't recall if there is methane in the groundwater here, but it's certainly possible since there is oil in many places up and down the San Joaquin Valley.

Back in the early 1990s, I designed a 2000 gpm well in the middle of town (Well 7 is on the western outskirts). My well was drilled to about 1540 ft and was the first local well to get below the Corcoran Clay (which, IIRC, is about 600 to 800 ft down in this area). Above the Corcoran Clay the groundwater under the City has sulfur, among other things, but below the water is (or least was) pristine with no methane, minimal iron and manganese, etc. Before my well, the City got all its water from relatively shallow wells in a well field adjacent to the King River, so basically filtered river water. But, times change. My well now has some iron and manganese and a couple other constituents I have forgotten in the four years since I last dealt with it.

I don't know how deep Well 7 is, but I'll bet it's a deep one like the one I designed. If so, it might just be picking up methane too. From the pics and videos I have seen, it appears that the remaining tank (which I now think is the older tank) has only one static vent. I had recommended to the design team for the new tank and the treatment vessels to install a turbovent on the tank and additional static vents, but I left the firm before the plans were finished so I don't know what the final design looked like. A turbovent is just like you see on house roofs, just larger. My boss in the early 1980s came up with this idea as a way to help "pump" humid air out of the headspace of tanks to reduce corrosion, but it should also help for methane build-up. Over the years, I have used turbovents (mostly Romlair) on all my tanks. IIRC, the smallest turbovent I have used was 18" and the largest was 48".

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[fel3]

JStephen...

As I recall, this tank had a knuckle roof, so the weakest joint would have been floor/shell. If it had had a cone roof, I think only the roof would have blown off.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[LittleInch]

Never seen anything like this before.

https://m.youtube.com/watch?v=Y0tKDTVmwFQ

Something looks very odd though in the final shot where it looks almost like there is a bag inside the tank?

What's a knuckle roof?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

Potable water tanks will often have an elastomeric coating of substantial thickness. I don't know that it would all peel off in one big sheet during an explosion.

https://versaflex.com/project/2-5-million-gallon-potable-water-storage-tank-aquavers-405/

 

[JStephen]

In the aerial footage of the tank afterwards, the only thing resembling a bag is the roof plate.
This whole thing is a well-known effect in petroleum tanks, and there have been a number of cases investigated by the Chemical Safety Board that were similar.
One similar launch caught on video was at a tank fire in Lamesa, smaller tank, but similar effect:

https://www.youtube.com/watch?v=6qcrwNM74sg

The problem here is that people don't expect anything flammable in the vapor space of a water tank, so they don't take the precautions they otherwise would.

 

[bimr]

Methane in groundwater is not explosive, but when water with dissolved methane comes into contact with air, the methane escapes from the water. If this occurs indoors or in a confined space and the level methane in the indoor air reaches 5%, there is a danger of fire or explosion.

Link

Illinois requires well vents to terminate outside of the well building as the vented gas may be flammable.

Link

 

[LittleInch]

To complete the data above, the explosive range is 5% to 17%.

It was just the white shape which confused me but this could easily be a liner, though the interior walls do look quite rusty so maybe the roof has inverted.

The video seems to show the roof bulging outwards as it moves upwards to an unbelievable degree. and then lifts off.

The way water is seen as non hazardous does tend to dull the sensitivities too much when it comes to hot work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SwinnyGG]

It was just the white shape which confused me

That's the tank roof. The tank is on the ground upside-down.

 

[LittleInch]

Still looks odd

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IRstuff]

I think the interior ceiling of the tank is painted white like the outside. You can see that where the white roof ribs touched the ceiling, there is no white paint

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[fel3]

I was texting with a friend and ex-coworker last night. He has even more experience in Lemoore that I do. He speculated that hydrogen sulfide might have built up in the tank's headspace. The shallow groundwater has H2S, but I don't recall it being found in the deeper aquifer and I strongly suspect Well 7 only taps the deeper aquifer, so maybe this isn't it. However, I have only one personal point of reference on this topic: the well I mentioned above, which is about 1.8 mile ENE of Well 7.

BTW, I misspoke above about which tank blew. I found my records and it was the old tank that blew, not the new one. Based on Google Earth imagery, the first tank was constructed some time between May 1994 and July 2003. The adjacent junior college was constructed in 2002, so I'll bet Well 7 and the first tank were constructed simultaneously.

I have attached a link to .kmz file that will take you to the tank that blew. The latest Google Earth imagery is from 2018, so the new tank and the treatment vessels are not shown.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[LittleInch]

It's still pretty impressive that the roof actually didn't come off like a flying saucer.

H2S explosive limits are apparently 3.9 to 45.5% in air.

Wow, never knew that. I knew it was lethal in very low concentrations, but didn't realise it exploded.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[fel3]

LittleInch...

For a knuckle roof tank like this one, the weakest joint is the floor/shell joint. For a cone roof tank, it would be roof/shell. Here, the weight of the water kept the floor in place and the floor/shell joint broke due to the upward explosive force.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[fel3]

SwinnyGG...

That's the roof and shell that are upside-down, still attached to each other.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[SwinnyGG]

Right.. that's exactly what I said. The tank walls and roof are mangled and upside down next to the floor of the tank which is still sitting where it was originally.