30 CFR § 56.4202
Fire hydrants.
If fire hydrants are part of the mine's firefighting system, the hydrants
shall be provided with
(a) Uniform fittings or readily available adapters for onsite
firefighting equipment;
(b) Readily available wrenches or keys to open the valves; and
(c) Readily available adapters capable of connecting hydrant fittings
to the hose equipment of any firefighting organization relied upon by the
mine.