The Interior Department floated an update to a rule that seeks to clarify royalty rates for certain federal coal mines and firms to acquire more land under already operating leases.

The draft rule, to be published Monday in the Federal Register, clarified that “highwall” mines must pay the 12.5 percent rate rather than the 8 percent reserved for underground operations. The move clears up debate on whether that method qualified as surface or underground mining.

The rule also would expand the amount of acreage mining firms could add to existing leases to 960 acres, up from 160.

The mining industry cheered the Bureau of Land Management proposal, which was called for in a 2005 energy law.