Thanks for all the replies. The job is done.

I used the dry ice method to purge the fumes. Then I used my cordless
Sawzall to decapitate a 2' X 6' section of the top. (it actually cut
easier then I thought). The inner walls and bottom looked clean and
in good condition so I just filled it with dirt and compacted it as
best I could.

Cost:
$15 for 10# of dry ice
$8 for a 5 pack of bi metal Sawzall blades.
About $5 in tractor diesel getting fill dirt
$28 Total (not including a couple gin and tonics for my sore back)



On Sat, 12 Mar 2005 15:52:07 -0800, davefr wrote:

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 decommisioned 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 decomisioned? 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?