Hugh,
One advantage of freeze drying is you pay for the electricity once, and have something light which you can store on a shelf. But while reading the reply about EMPs and freezers [1] at a local restaurant, I happened to notice an old Zenith (yes, Zenith) freezer. It might be older than me. My immediate thought was that I could probably offer to buy them a new freezer and take this antique (it might be older than I am) off their hands.
One other caution, the older freezers use Freon – R12 – which is more expensive and harder to obtain (ChloroFlouroCarbons – CFCs). R134 is the typical refrigerant used currently. One leak and you might have big problems.
If it is a cache, remember that high altitudes in the shade (maybe some of the nearby mountains with accessible roads) have snow through at least June, and that is merely shade, not insulated. Also my rather old house has a “basement” which was originally a root cellar. I’m not sure if it could be converted to an ice house – but I do remember they had ways of keeping ice for the summer. Water has a high “latent heat of fusion”, so it requires the same heat to melt ice that it does to raise water a few degrees in temperature. – R.T.