49 CFR 193.2905
Protective enclosures.
(a)The following facilities must be surrounded by a protective enclosure:#
(1)Storage tanks;#
(2)Impounding systems;#
(3)Vapor barriers;#
(4)Cargo transfer systems;#
(5)Process, liquefaction, and vaporization equipment;#
(6)Control rooms and stations;#
(7)Control systems;#
(8)Fire control equipment;#
(9)Security communications systems; and#
(10)Alternative power sources.#
The protective enclosure may be one or more separate enclosures surrounding a single facility or multiple facilities.#
(b)Ground elevations outside a protective enclosure must be graded in a manner that does not impair the effectiveness of the enclosure.#
(c)Protective enclosures may not be located near features outside of the facility, such as trees, poles, or buildings, which could be used to breach the security.#
(d)At least two accesses must be provided in each protective enclosure and be located to minimize the escape distance in the event of emergency.#
(e)Each access must be locked unless it is continuously guarded. During normal operations, an access may be unlocked only by persons designated in writing by the operator. During an emergency, a means must be readily available to all facility personnel within the protective enclosure to open each access.#