After all the CCTV systems, access control systems and various other security systems are specified and installed, it comes down to what will really prohibit a determined adversary from breaching the perimeter. Barriers and bollards fill that need.
Before we begin to explore the topic, we must note that a risk assessment must be completed before we will know what we are protecting at our facility and its assets. Who is the adversary? What are their capabilities? Have they done this before? Can they do it again?
The American Heritage Dictionary defines a barrier as “a fence, wall, or other structure built to prevent passage.” By definition, we can conceivably discuss human beings, animals and motor vehicles. I will eliminate animals as not intrinsic to our discussion.
Defining the Perimeter
Bollards are a multi-function item. For nautical purposes, they are “a thick wooden post on a ship or wharf, used for securing ropes and hawsers (cable). Our discussion will focus on the “thick post” portion of the definition.
In physical security, we see barriers for pedestrians and vehicles as fences, gates, walls, doors, locks, windows, roofs and sometimes vaults.
There are several types of fences. Property lines and boundaries can be fenced with many types of materials — from galvanized wire and steel wire to even walls. Property-line fences are a marker to show the property limits of the facility. Trespass signs are placed on these barriers to give notice to those who are unauthorized to be on the property. Although it is the first barrier seen by a potential trespasser/adversary, it is not considered an effective physical barrier to a determined person(s).
Temporary fences are commonly used at places where construction is happening to give both a trespass and safety warning to persons in the area of the property. Depending on the security requirements for the property, these must not be overlooked. They must be equal to the resistance requirements of the permanent fence construction and structure.
Perimeter fences are used to prohibit access to a particular area or a facility or can be used at the property boundary as well. These fences are of a very substantial design and construction. Most feature 11-gauge, chain-link mesh wired to the outside of the posts and the top and bottom rails. They are usually 8 feet high, with outriggers facing outward at a 45-degree angle on the top, where barbed, concertina or razor wire can be mounted depending on the circumstances and the facility being protected. Perimeter fences are designed for strength by concreting the posts, and using bracing at gates, corners and other places where physical terrain requires it.
There are cases where the barbed, concertina, and razor wire mentioned above are used as an enhancement to the fence by mounting it on the fence fabric, attaching it to the outside below the top outriggers, and/or along the ground in single or multiple layers to delay an adversary from penetrating the perimeter fence and the area until a response is able to arrive at the area.
Vehicle barriers are available in multiple forms — from stationary, to moveable, to mobile. The most common forms of vehicle barriers are concrete walls, either permanent or mobile. The concrete highway median is the most common form of barrier used. The design allows for them to be interlocked to provide a long, stationary vehicle barrier, or as individual pieces arranged in a serpentine formation to prohibit a vehicle from gaining velocity by traveling in a straight line toward a gate or barrier in an attempt to crash through it. Vehicle barriers have been used to provide a barrier at seldom-used gates as well.
Vehicle barriers can be made of plastic and can be filled with water or sand and emptied for mobility. Both add considerable weight to the vehicle barriers.