30 CFR § 75.508
Map of electrical system.
The location and the electrical rating of all stationary electric apparatus
in connection with the mine electric system, including permanent cables,
switchgear, rectifying substations, transformers, permanent pumps, and
trolley wires and trolley feeder wires, and settings of all direct-current
circuit breakers protecting underground trolley circuits, shall be shown on a
mine map. Any changes made in a location, electric rating, or setting shall
be promptly shown on the map when the change is made. Such map shall be
available to an authorized representative of the Secretary and to the miners
in such mine.