What about using sthe pray-on coating used to preserve aircraft in storage? That may work a one of the barriers. Regardless, in my plan, the container does not come in contact with the soil. Once on the foundation, a wall of cinderblocks is built around the cluster and earth is then filled-in against the outer cinderblock wall. I am working on what to use to cover the top of the cluster.
Either that, or maybe the white shrink wrap they put on high end boats and cars for transport. That stuff is really tough.
I think most important, though, is a good drain to allow the water to go somewhere besides into the structure. It's tough to make a below ground structure completely waterproof. My current home has a basement blasted into solid rock from 2' below the surface to the bottom of the footers. Before I built the house over the hole I had blasted I noticed that the water runs across the rock shelves and pours directly into the hole. I realized fairly quickly that a good drain would be essential to a dry basement. I put in extra large French drains and a lot of gravel to make sure the water had somewhere to go. Lots of fiber reinforced tar on the walls and then two sheets of plastic. I backfilled with chert, which is basically clay with some gravel in it, then compacted it using a plate compactor. I brought the fill up about a foot at a time, then compacted. The result is a bone dry basement, even in the wettest weather. It's still dry even now some 14 years later.
Look into a roofing product called "Sarnafil". It's a membrane roofing material that is used on commercial buildings. They roll it on and seal the seams with heat. I have this material on a commercial rental property I own in Florida and it's worked very well, even through huricane Ivan. My building took the right front eyewall and came away leak free.