You almost always need a permit to build a bunker on land with any type of public utilities running through it. You’ll want to check with your local building code enforcement agency to see if this is the case for your area.  Because you’re building a structural component that often requires electricity, water, and sewage services, you’ll need to apply for permits to attach these utilities to your new property. However, off-grid-only units in rural areas may not need all or any of the permitting you’d normally find in more urban settings.