Comment by huurtehoog

The design characteristics require the storage caves to support 5 drawdown cycles using "raw water" - actual phrasing in official documentation.

Also, the SPR is a complex system made up of several locations where salt massifs have been drilled and hollowed out in the shape of highly specified storage caves.

There are requirements for pumping throughput for example, and some of the concerns regarding operational life and the dozens of partial drawdowns these caves have been subjected to, relate to them loosing the ability to quickly discharge oil.

In a word: it's complicated. I encourage looking up technical documentation online, super easy to find using 'filetype:pdf'. There are a lot of details involved in building, running, and assurances required from the SPR storage system.