43 CFR §3715.2-1

1. (a)Protecting exposed, concentrated or otherwise accessible valuable minerals from theft or loss;
2. (b)Protecting from theft or loss appropriate, operable equipment which is regularly used, is not readily portable, and cannot be protected by means other than occupancy;
3. (c)Protecting the public from appropriate, operable equipment which is regularly used, is not readily portable, and if left unattended, creates a hazard to public safety;
4. (d)Protecting the public from surface uses, workings, or improvements which, if left unattended, create a hazard to public safety; or
5. (e)Being located in an area so isolated or lacking in physical access as to require the mining claimant, operator, or workers to remain on site in order to work a full shift of a usual and customary length. A full shift is ordinarily 8 hours and does not include travel time to the site from a community or area in which housing may be obtained.