"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)