While this is an interesting idea, I have serious doubts about it working. It sounds simple to say just put some tires in it and fill them up, and voila', no more leak. The issue is the depth of 5,000 feet. At sea level the atmosphere exerts about 15 pounds of pressure on every square inch. That comes out to about one ton per square foot. Since our cavaties are filled with the same air, we don't notice it. But for about every 30 feet you go below the surface, you add one more atmosphere of pressure. At 5,000 feet that comes to about 167 atmospheres of pressure or about 2,500 pounds per square inch. Try blowing something up to those pressures. And that is just to inflate it, not blow it up to plug it. You might need 5,000 psi or greater to do that. Just don't recall seeing too many tires rated for 5,000 psi down at the Goodyear store. Even high performance tires for jumbo jets only go to around 300 psi. We are talking orders of magnatude to do this with this method.
