A Snug Fit Hole
Making the hole bigger than the container only makes sense, this allows more freedom and room around it. We know that Wayne purposefully left two feet of space around the container and in front of the entrance area, to allow a full rotation for the swinging door. The real project began as soon as the container was successfully fitted. Now that you really have an idea of what Wayne has in mind, the execution of it may well inspire your own DIY projects.
Underground Drainage System
It is essential for all enclosed spaces, especially those underground, to have a sump pump system. Generally found in basements, to allow the underground area to stay above the waterline, a sump pump helps drain these enclosed spaces. When you have an underground bunker for storage, the last thing you want to experience is a flood penetrating through your safe fortress. But what did Wayne plan to safeguard in his bunker?