Data that are sometimes entered and sometimes computed
There's no hard-and-fast rule here.
This pattern is very common, and here you could either:

Have application logic update the StorageFacility.Capacity (etc) every time a StorageTank is added, removed, or perhaps undergoing maintenance.

or

Store the data only at the StorageTank and roll it up as needed.

Things like the frequency of changes, the level of complexity of the roll-up rules, frequency of query, etc should make your decision.
In either case I don't believe it'helpful that &quot;Application code should treat a collection of StorageTanks at the same Location as an aggregated StorageFacility&quot;.  You should simply have two seperate entities.