How would you cut the top off a 500 gallon underground gas tank?

Could you fill it with water, and pump it out after.

You don't really need to cut the top off the tank to fill it with sand. There should be 4 2" fittings on the top, remove all the pipes and fill it through the fittings. Use clean dry sand and it won't take that long. I don't know where your located, but if the tank is a homeowner tank, no one really keeps track of them. Just fill it with sand, and if your worried about some one using it, cap it with concrete. gary

I abandoned a 4000 gallon gas tank after the 1998 EPA regs came into effect. Filled with water (from the nearby hydrant) until water came out the vent pipe. Then sawcut and jackhammered throught the slab to get to the tank, Sawzalled a 2x2 square, then pumped out the water (your supposed to have a vac truck properly dispose of the contaminated water), then filled with concrete slurry (3 truck loads).

You need to fill the tank with slurry to prevent explosive vapors from forming in the future, or you need to wash the tank and make sure there are zero detectable hydrocarbons, there are special meters that do such a thing, my way is easier.

"davefr"

| I buried a 500 gallon gas tank in the late '70's for farm use. I used | it for about 10 years and then pumped it dry. | | Complete removal is impractical since a small shed is built on top of | it and I don't want to demolish the shed. | | I'd really like to cut the top off and fill it with rock or dirt so | it's decommissioned once and for all. | | I checked with the state DEQ office and they told me 500 gallon tanks | are unregulated. My only obligation is to report a spill but this | tank never leaked since I quit using it very early in it's life. | | I'm not too fond of the idea of using a cutting torch. Even though | it's totally dry there could still be fumes and I don't want to get | dead. For the same reason, I really don't want to use an angle | grinder. | | I'm thinking sawsall or pneumatic chisel. | | Anyone know how underground tanks are decommissioned? I'd like to | remove a 5' X 2' portion of it's top. | | Is there a safe way to make 100% sure the tank is vented such as | injecting an inert gas that's heavier then gasoline fumes to drive | them out? | | Other suggestions?

Fill it with sand. No cutting needed and if you ever have to reactivate the tank (assuming it has not rusted trough) just vacuum the sand out of the tank. Don't laugh they've been doing this with decommissioned service stations for years.

As to making the tank 'gas free' use live steam. Again the oil industry has been doing things this was for over 50 years that I know of personally and likely longer.

A sawsall or pneumatic chisel can still generated sufficient heat/sparks to cause problems.

As to using an inert gas to drive out the fuel vapor, it's only necessary to drive out the air (O2 actually)

Filling it with sand sounds like a good option. Do you just make a big funnel and shovel it in? I know my tank has 2 large fittings at each end but I'll have to check if there are additional plugs in the middle section.

I'm guessing 2.5 - 3 cubic yards of sand should be enough..

I'm not too keen on the idea of flushing with water. If there's dried up leaded gasoline on the inner walls, I'd just soon it remain undisturbed.

One trick I've seen is to run a hose from an exhaust pipe of a running engine. The exhaust gases will drive out the gas fumes.

Dean

Use a small air compressor and a DIY sand blasting rig. Only caution don't sniff the exhaust from the tank Might have to top it off in a day or so after the sand settles a bit.

Even easier (and safer) would be to put down a hose from a compressor, and let it pump air for a day, while at the same time trying to smell the air coming out. I would think that if there is no perceptible smell, including from an air sample from the bottom, there should not be much risk of an explosion. But, better safe than sorry.

i

"Ignoramus14003"

| Even easier (and safer) would be to put down a hose from a compressor, | and let it pump air for a day, while at the same time trying to smell | the air coming out. I would think that if there is no perceptible | smell, including from an air sample from the bottom, there should not | be much risk of an explosion. But, better safe than sorry.

I would not want to bet my life on that option. Especially since the simple act of cutting can release more fumes.

Be careful. In the tank removal industry they use dry ice to displace the volatiles within the tank. We usually break about 20 lbs. of dry ice into pieces small enough to place down the 2" fill pipe. After sniffing no hydrocarbons with a tester (usually 10-24 hours) we would excavate and either remove the tank, or wash in place and then remove.

Be very careful with all tanks. There have been many instances of purged tanks, at scrap yards, exploding and killing people months and years after purging. The product is imbedded on the walls of the tank and evaporates for a long, long time. e.g. tanks that are properly cleaned and safe can become dangerous by letting them sit for a long time.

If you fill the tank, a weak concrete slurry is typical. I don't remember from my engineering days what the porosity is for sand, but, rest assured that uniformly graded sand is probably 20% voids and can hold volatile hydrocarbons making them dangerous.

Years ago, a man brought some sort or tank or drum that had held gasoline in to the shop where my father worked. Don't recall if he wanted it welded or cut, but my father refused to do it. Then, to demonstrate that he'd gotten the tank "clean", the man lit a (wood) match and stuck his hand in the tank. He hadn't.

Also, what about the glop that's left when gas deteriorates/evaporates; is it flammible?

The exhaust idea sounds a lot better than the compressed air.

Haven't you ever seen the fuel delivery guy drop his cigarette but down the hole at the gas station? No air down there to support combustion...

A compressor does not pump enough cubage. They are intended for pressure.

I get a numb nose and cannot smell anything after about the third whiff. (No, not huffing. Gas mixed with 2-stroke smells different from straight gas, and it's easy to get the cans mixed up after they've been sitting for a few weeks.)

Mine pumps about 11 cfm at about 120 PSI, continuously. It is about

100 CFM uncompressed. I would say that it is quite a bit. After a day of pumping, it would pump 144,000 cubic feet of uncompressed air. For a 500 gallon tank, which is 70 cubic feet, the day of pumping is 2,000 times the volume of the tank.

I could also tape a flexible dryer hose to the outlet tube of a leaf blower and vent it out for awhile. However that would could also create a perfect blast furnace.

I really like the dry ice idea. Do supermarkets sell dry ice these days?? Is there any common source for getting dry ice??

I read the whole string of other comments and just have to make my own: sometimes it's just better to do something right. Move the shed, get a backhoe to pull it out and haul it off. Tank is probably 4' in diameter,

5' long, perhaps 400 pounds. Then it is done and gone, no further worries.

Next door neighbors had a 1000 gall> I buried a 500 gallon gas tank in the late '70's for farm use. I used

Assuming it's rated honestly, your compressor pumps 11 SCFM of air at atmospheric pressure and temperature when it's delivering 120 psi at the outlet - closer to 200 air changes.

I'd also reconsider drawing a potentially explosive mixture into the compressor where it will be compressed and heated. If you really wanted to do this (I don't think it addresses the OP's concerns, and I'm not recommending it), drawing the fumes through a gasoline engine might be a safer approach.

Ned Simmons

I would go with the concrete idea, but you may be able to do it on the cheap. Contact concrete suppliers in your area, and ask them if you can have the extra cement mix after the trucks do their pour. There is almost always a surplus of cement in the mix truck after a foundation/footing pour, and they have a limited amount of time to get it out, and it can be a problem of where to put it (it is often buried at the jobsite, to the chagrin of a homeowner who later tries to dig out the spot). If your location is not too remote, they will gladly take it to you. Just be sure you are there when they come and have the job prepared, otherwise they will dump it in a pile on your property, rather than have it set up in the truck mixer. It will take awhile, be patient. They will also want to rinse the mixer with a hose, no problem for this type of pour since concrete quality is not that important in your application. Best wishes for your project.-Jitney

You're kidding, right? Have you ever seen sparks from sandblasting? Get one of those and he'll be posting about how to remove a sand filled 500 gallon fuel tank from the treetops.....