d) Constructing a search area for vehicles entering the area;
e) Relocating truck deliveries away from the protected facility;
f) Relocating the facility or asset to a safer location;
g) Strengthening vulnerable building elements;
h) Erecting a blast wall if shown to be beneficial in reducing pressure loading on the
If additional inexpensive land is available, it is usually easier and more cost effective
to install vehicle barriers that will provide additional standoff distance than it is to move critical
facilities (buildings) or harden (strengthen) the structures to resist explosive loading. If
additional land is not available or the cost is prohibitive, the user must decide between accepting
additional risk and the cost of vehicle barrier enhancements and structural hardening.
Alternative Solutions to Inadequate Standoff Distance. If the answer to the question,
"Is the damage and injury level acceptable?" (Steps 5 and 7 of Figure 1) is NO, then consider
various options for hardening the facility (Step 6 of Figure 1) or make a conscious decision to
accept greater risk (Step 11 of Figure 1), based on the probability that identified vulnerabilities
will not be exploited or that the event has a low probability of occurring. The impact of
accepting greater risk is the design of a facility for protection against a lower explosive threat
and acceptance of higher damage and injury levels at the higher threat level because of a lower
probability of occurrence. The site planner must consider life-cycle issues (maintenance costs),
regardless of the options selected to protect a facility.
Structural Hardening. Hardening options include structural changes to doors,
windows and window frames, columns, floors, and walls impacted by the explosive blast wave.
For further guidance on these issues, see NAVFAC P397/5M6-1300/AFR 88-22, FM 8-
9/NAVMED P5059/AFJMAN 44-151VIV2V3, and "Blast Vulnerability Guide." For design
information on hardening of glazing systems, consult MIL-HDBK 1013/12, "Evaluation and
Selection of Security Glazing for Protection against Ballistic, Bomb and Forced Entry Tactics."
NOTE: Structural hardening of a facility and designing the structure to prevent
progressive collapse are complex engineering issues and are beyond the scope of this
handbook. If additional standoff distance is not available and the potential damage to the
structure from an explosive threat is unacceptable, the service of a qualified structural
engineer, experienced in the design of structures to resist the effects of explosions, is highly