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.

Tony
"davefr" wrote in message
...
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?