N.D. Cent. Code § 57-61-01.2

Coal or commercial leonardite is considered to be severed for the purposes of this chapter when it is first removed from where it was placed by nature, unless within thirty days of first removal it is placed into a long-term inventory storage deposit, in which case it is considered to be severed when removed from the deposit or it is pledged as collateral on a loan. A long-term inventory storage deposit is one which is so identified in a mining plan approved by the public service commission pursuant to chapter 38-14.1 and which as part of that plan is covered with soil and subjected to reclamation requirements during the time it serves as a deposit and before coal or commercial leonardite is removed therefrom.