Want to dig a hole?

[kandrathe]

In many soil types the sides would just collapse. He really needed to put in footings around the perimeter, and then at least a 6" rebar concrete wall. I would have tied in steel I beams in a couple points across the diagonal to provide lateral support for the walls to keep them from moving. Then, walls in place, you apply a water barrier to the outside to minimize moisture from seeping in. It is unlikely to prevent all water from seeping in, so for that construct it would have been best to design a sump pump in from the start.

But... nice cistern. He should set it up as part of his irrigation system.