There are regulations covering storing enormous quantities of oil, including certification of the holding tanks etc.

For example, any container over 55 gallons is subject to EPA regulation and counts towards the total permitted site quantity. Storing more than 1,320 gallons above ground requires the site to have an approved SPCC (Spill Prevention, Control, and Countermeasures) plan.

You can store 42,000 gallons below ground but that requires excavation, permits etc.

Basically: it's difficult to do on short notice.

Further reading: https://www.epa.gov/ust/aboveground-storage-tanks