30 CFR § 57.4130
Surface electric substations and liquid storage facilities.
The requirements of this standard apply to surface areas only.
(a) If a hazard to persons could be created, no combustible materials shall
be stored or allowed to accumulate within 25 feet of the following:
(1) Electric substations.
(2) Unburied, flammable or combustible liquid storage tanks.
(3) Any group of containers used for storage of more than 60 gallons of
flammable or combustible liquids.
(b) The area within the 25-foot perimeter shall be kept free of dry