43 C.F.R. § 3594.2 Support pillars.
Title 43 - Public Lands: Interior
Sufficient pillars shall be left during first mining to ensure the ultimate maximum recovery of mineral deposits prior to abandonment. All boundary pillars shall be 50 feet thick unless otherwise specified in writing by the authorized officer. Boundary and other main pillars shall be mined only with the written consent or by order of the authorized officer.
Title 43: Public Lands: Interior
PART 3590—SOLID MINERALS (OTHER THAN COAL) EXPLORATION AND MINING OPERATIONS
Subpart 3594—Mining Methods
§ 3594.2 Support pillars.
