Before revision: The shelter is composed of 42 school buses, which were buried underground as patterns for concrete that was then poured over to provide the main structure, onto which up to fourteen feet of earth were piled to provide fallout protection.
After revision: The shelter is composed of 42 school buses, which were buried underground as patterns for concrete that was then poured over to provide the main structure, onto which up to 5 meters (14 foot) of earth were piled to provide fallout protection.