If you mean my shelter it is sealed on the inside to prevent water seepage. The top has a turban vent which allows air inside and keeps water out. The door is also sealed from the inside to keep water out. I’m not sure how the trash can shelter keeps water out. Any puncture in the side will allow ground water to seep inside. Also, I have never seen one of those type of trash cans that has a water tight lid.
I’ve seen a number of plastic, metal, or fiberglass models similar to this that seem to be pretty cost effective.
http://www.stormshieldtornadoshelter.com/