That word I needed before.
The useful faculty spaces are going to be permanent (in terms of building lifetime) but removable structures, while the sea defence has a seemingly shorter lifespan (colour and material will emphasise this)
Once the faculty is moved all that will be left is the sea defence, once it starts to disintegrate (wooden?) the core concrete structure will remain. This permanent spine will be a new long term sea defence from which new ones can be attached/added.
The juxtaposition of perceived element lifetimes will reverse, as the faculty ends it’s use as a teaching resource, the full realisation of the sea defence will start.