Surface facilities:

Area:1-2 square kilometers

Vitrified wastes are enclosed in over pack and buffer materials are produced in the surface facility. Also excavation materials are stored on surface.

Underground facilities：

Area:6-10 square kilometers

Depth: more than 300m below the ground surface

There are tunnels whose total extension is more than 200km to dispose of more than 40,000 vitrified wastes.

Source : https://www.numo.or.jp/q_and_a/faq/faq100069.html