Pile up debris at dusk, when it's going to freeze at night. Sprinkle on water, once it freezes into a crust, repeat the water, 2x. Where youll have your crawl-way entrance. break thru the crust and remove the un-needed, unfrozen interior debris. Keep adding ice and debris until the walls are a foot thick. Make the crawl-way the same way, with a cylindrical ice-plug to keep out animal. Have a pole thru this plug, into ground and thru top of crawl-way. Notch it a certain way and no claw can raise out the pole, but you can, with Cold steel shovel. grease the pole with fish oil, so that it wont freeze. Vs the mice, make an inch thick door out of ice and debris. Pour water around the door and let it freeze, no mice. Chip this edge loose with the shovel to access food, twice a week. Sometimes I think I'm a genius and the rest of the time, I KNOW it.