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CODE	DEFINITION
A.	Relocatable: Designed for specific purpose of being readily erected, disassembled, stored, and reused. includes tentage.
B.	Pseudo-Relocatable: Not specifically designed to be dismantled and relocated, but could be, with considerable effort and loss of parts. Rigid-frame building included.
C.	Nonrecoverable: A structure not designed to provide relocatability features or one where the cost of recovery of the shelter exceeds 50% of the initial procurement cost. Bolted tanks and steel bridges included.
D.	Disposable: Those temporary structures having low acquisition and erection costs which are not designed for relocation and reuse and may be left on site or destroyed, such as SEAHUNTS.

EXCAVATIONS AND SHORING

Working in, working around. or directing a crew in a trenching or excavation job can be dangerous. The following paragraphs will give you some of the accepted engineering requirements and practices. Think safety, not only for your workers but for the other persons that may encounter your work area.

EXCAVATIONS

Preplanning before starting any excavation will save time and avoid costly mistakes. Give attention to personal safety equipment, underground utility installations, personnel/vehicular traffic interruptions, security, and public safety. Make sure your crew is aware of the safe working area around a specific piece of excavating equipment. Set up daily inspections of excavations for possible cave-ins or slides. Moving ground must be guarded by a shoring system, sloping of the ground, or some other equivalent means. Excavated or other materials must not be stored closer than 2 feet from the edge.

When crews are working in trenches 4 feet or more in depth, access into or exits out of excavations should be by ramps, ladders. stairways. or hoists. Crew members should not jump into trenches or use bracing as a stairway.

Banks more than 5 feet high must be shored or laid back to a stable slope, or some other equivalent means of protection must be provided where crew members may be exposed to moving ground or cave-ins. Refer to figure 1-6 as a guide in sloping of banks.

Sides of trenches in unstable or soft material, 5 feet in depth, are required to be shored, sheeted, braced, sloped, or otherwise supported by sufficient strength to protect the crew members working within them.

Sides oftrenches in hard or compact soil, including embankments, must be shored or otherwise supported when the trench is more than 5 feet in depth and 8 feet or more in length.

SHORING

The determination of the angle of repose and design of the supporting system must be based on careful evaluation of many features: depth or cut; possible variation in water content of the material while the excavation is open; anticipated changes in materials from exposure to air, sun, water, or freezing; loading imposed by structures, equipment, overlying