In order to be effective, the guard towers should be no more than
300 yards (274.3 m) apart.
Site-Built Structures. Conduct a thorough site analysis and
review of operational requirements for the restricted area involved prior to
initiating design of guard towers. While there is no specific size or floor
spacing criteria for tower cabins, the designer should use analogous criteria
contained in NAVFAC P-80.
Structure Size. The size of the tower cabin must be based on
several factors. The first consideration is the number of personnel that will
be assigned during normal or alert operations. Make a careful review of
electronic and electrical equipment (e.g., communications equipment and,
plumbing and mechanical support equipment (HVAC), and storage space (e.g.,
AA&E storage). Provide adequate space for the equipment, in addition to
security personnel space allocations. Ensure that the surface area of any
required counter or work space is added to the overall floor space
requirements for the tower cabin.
Windows. Windows selected for tower cabins must meet the same
ballistic threat level as the cabin construction itself. Ballistic-resistant
glazing requirements are outlined in UL-752. Windows will not be less than 3
feet (0.91 m) high and will be located a minimum of 3 feet (0.91 m) above the
cabin floor surface. They must be continuous around the entire cabin to
maximize surveillance capability.
Construction. A new concept in guard tower design has been
developed by Sandia National Laboratories in Albuquerque, New Mexico. This
design consists of using precast concrete double tee beams placed vertically
to form the walls of the tower, and a precast concrete cab placed atop the
structure to house the guard quarters and surveillance equipment. Because a
completely enclosed space is formed in the interior of the double tee shell,
protection from attack and from extremes in weather conditions is provided.
Due to the possibility of towers being constructed in diverse locations of the
world, the design considered a 150-mph (241.4-km/hr) wind and zone 3 seismic
loading. The tower is assumed to be supported on a spread footing with a
maximum allowable bearing of 2,300 psf (11,230.9 kg/sq m). It should be noted
that some areas may require specialized foundations such as piles, caissons,
etc. Sandia indicated that all walls should be a minimum of 4 inches (101.6
mm) thick as this would provide excellent resistance to small arms
projectiles, because double tee concrete will have a 28-day strength of 5,000-
psi (3,515,500-kg/sq m) compressive strength. This also provides significant
ballistic properties. A recommended, guard tower designed by Sandia National
Laboratories is depicted in Figure 33. Design information can be obtained