The Neckarwestheim interim storage facility is located on the site of the Neckarwestheim nuclear power plant. This means that casks only need to be moved a short distance from the reactor building to the interim storage facility and that no public roads need to be used.
The interim storage facility at the former quarry site is built below ground to save space. The interim storage facility consists of an above-ground entrance building and two parallel east-to-west underground storage tunnels which are joined at the end by a connecting passage with a ventilation structure and escape structure. The underground storage tunnels are 90 and 84 metres long, around 14 metres wide and a good 17 metres high. Both tunnels together provide 151 spaces. Tunnel 1 consists of the container cleaning room and a storage area with a surface area of 1,170 m². Tunnel 2 has a surface area of 1,230 m² and is used entirely as a storage area. Tunnel 1 and Tunnel 2 are joined by a connecting passage. Both storage tunnels run parallel to each other at a distance of approximately 13.8 m, are joined by a connecting passage and end at the ground-level entrance building.