cause erosion and thereby assist an intruder in penetrating the area. Where surface stabilization is impossible or
impracticable, use concrete curbs, sills, or other anchoring devices that extend below ground level.
Modifications to existing chain link fencing to conform to these requirements are unnecessary if the existing
fencing provides an equivalent or greater penetration resistance, as determined by the commander concerned.
The barrier must have vehicular and pedestrian gates consistent with operational requirements. These gates must
be structurally comparable to, and provide the equivalent penetration resistance of, the adjacent fence. They must
also be designed so that the traffic through them will be under the positive control of the security force. Unless
they are continuously manned, the gates must be provided with a lock approved by HQDA (DAPE-HRE). Hinge
pins and other hardware must be welded or otherwise secured to prevent removal.
Drainage structures and water passages penetrating the barrier must be barred to provide penetration resistance
equivalent to the fence itself. Openings to drainage structures having a cross-sectional area greater than 96 square
inches, and having a smallest dimension greater than six inches, must be protected by securely-fastened, welded-
bar grills. As an alternative, drainage structures may be constructed of multiple pipes, each pipe having a
diameter of 10 inches or less, joined to each other and to the drainage culvert. Multiple pipes of this diameter
may also be placed and secured in the inflow end of the drainage culvert to prevent intrusion into the area.
Building walls may be incorporated into the barrier system if they provide penetration resistance equivalent to the
perimeter barrier and are subject to observation.
Clear zones must extend 12 feet on the outside and 30 feet on the inside of the perimeter fence, where possible.
These clear zones must be free of all obstacles, topographical features, and vegetation over eight inches tall that
could reduce the effectiveness of the physical barrier, impede observation, or provide cover and concealment for
an intruder. Vegetation or topographical features that must be retained in clear zones for erosion control, for
passive defense, or for legal reasons must be trimmed or pruned to eliminate their concealment potential, or they
must be checked by security patrols at irregular intervals. Perimeter light poles, fire hydrants, steam pipes,
barricades for explosives safety purposes, entry control buildings within the clear zone, and other objects that
provide no aid to circumvention of the perimeter barrier and no concealment to an intruder do not violate the
requirements of clear zones.
Fencing needs must be evaluated and determined for each installation on a case-by-case basis. The erection of
large quantities of new security fencing around an outer perimeter may not be cost effective. The following
factors should be considered:
If the installation's outer perimeter has adequate security fencing, fencing of inner zones may not be required.
If the installation's outer perimeter has barbed-wire fencing or no fencing, security fencing of inner zone
storage areas may be more practical and cost effective.
If the installation's outer perimeter is partially fenced, it may be more cost effective to complete the loop
rather than to install fencing around inner zone storage areas.
If natural barriers (such as mountains, cliffs, rivers, seas, or other difficult-to-traverse terrain) form portions of
the perimeter and provide equivalent or better security than fencing, then the security fencing of inner zone
storage areas may not be required.
MM0170
3-8
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