"mstrspy" wrote in message
news
The tank has been abandoned for at least 50 years (ie) no raw sewage
for 50 years The steel cover rotted. That's why it collapsed. I will
fill with sand and keep adding sand until it doesn't ettle anymore.
Then I will use topsoil. The lawn in that part of my yrd isn't the
greatest so I'm not concerned about how it will look. Only concerned
about safety.
M

The boulders will give a margin of safety compared to a big hole that you'd
not be able to climb out of. Boulders piled near the top prevent you from
falling very far.