I have a gap underneath these stairs that seem to be welded to the foundation of my house (outside). they lead to a basement door. You can look in that hole and see the bottom of the pit of my foundation. IÂd like to plug it to prevent any kind of water/rain from going to the bottom of my house and engage my sump pump. WhatÂs the best way to seal this gap? I tried to put dirt there, but it just cascades down this cave thing. I can take a picture and post if it helps to visualize this. PS. I havenÂt seen water actually going down there, but knowing that I have plugged will give me piece of mind. Also an animal or animals could possibly use it to nest.