Actually, the bottom of your pit would need a couple feet of gravel lining with a drainage pipe running from the pit to the outside.

The container would need a couple coats of coal tar sprayed on the exterior, after having air intake & outtake pipes, and antenna & power conduits, and water piping from an exterior sealed tank, installed through the roof.

The container would be mounted on cement dragon's teeth.

Use heavy duty treated timbers to form an entrance with a dog leg in it. Then put the dirt around the sides and over the roof gently to a thickness of 2-3 feet.

Move your equipment and supplies into it.

Notes:
You would probably want to include a drainage pipe connected to your sewage line for dumping your porta potty into.

You might also consider using this as a root celler so it always has rotated foods in it.

Now you have a Root Celler, Tornado Shelter, an Emergency home (in case your home is destroyed by a tornado), and a Fallout Shelter!