design threat. The construction selected should be entered into the
"Facilities Exterior" portion of the appropriate worksheet (Appendix A).
<13> Is there a forced entry threat? If the design threat includes
forced entry, Elements <14> through <62> of the flow chart should be
followed. If not, the chart branches to Element <63>. Elements <14> through
<29> address exterior security associated with the site on which the building
is located referring to appropriate material in Section 4. Elements <30>
through <62> address security associated with the building referring to
appropriate material in Section 5.
<14> Exterior fence required? In general, security fences or other
barriers around the site perimeter act to deter casual intruders only. They
can be easily scaled, crawled under, or cut through. A dedicated threat will
be neither deterred nor significantly delayed by a perimeter barrier.
Security fences may be required by DoD regulations for certain facility
types, and/or to maintain an adequate blast zone for a vehicle bomb attack.
Paragraph 4.3.2 provides guidance as to when security fences are required.
If required, the flow chart branches to <16>, otherwise to <15>.
<15> Does the site have an exterior fence with IDS or tower guards?
Even though a fence may not be required by DoD regulation or otherwise, the
facility may still be located in an existing fenced enclave containing other
buildings. If this fence also has an IDS system or tower guards for threat
detection, one can take advantage of the ingress/egress time of the threat
from the fence to the building. In this case, the flow chart branches to
Element <26>, otherwise to Element <31>.
<16> Does the site have an exterior fence? Although par. 4.3.2 may
indicate that the facility requires a fence, it may be that this facility is
to be located in an existing fence enclave with other buildings. If so, the
flowchart branches to Element <18>, otherwise to Element <17>.
<17> Select exterior fence. For facilities requiring an exterior
fence, the information contained in par. 4.3.2 can be used to aid its
selection. The fence construction should be entered under "Site Perimeter"
in the worksheet. In general, the penetration time through the fence is
negligible (~0.1 minutes). This is already reflected in Item 9 of the
worksheet. On the other hand, a fence can limit the amount of tools, etc.,
that can be easily transported by a threat.
<18> Exterior fence IDS required? In general, an exterior IDS or
tower guard on an extended fence perimeter around a site is costly to install
and maintain. The added threat ingress/egress time gained may not justify
these costs. It is generally more cost effective to limit the size of the
secured area to the building and provide the hardness and threat detection
there. In some cases, DoD regulations may require a fence perimeter IDS or
tower guards. Paragraph 4.5 provides guidelines as to when this might be