I work around mines & quarries on occaision & my advice to you is to ask your Federal MSHA inspector for advice. After all, if you get this wrong, he's the one who will cite your company.
I've found most MSHA inspectors to be very knowledgeable about Federal mining laws, to the point that if they cite you, you will likely lose on appeal. They are, however, very weak on the NEC, so try to comply with their requirements first, then comply with the NEC.
Or, you could try their web site http://www.msha.gov/ComplianceAssistance.HTM
[This message has been edited by Tom (edited 07-23-2004).]