Figure Revetment Facing

1-5. Special Construction Considerations. Special construction considerations consist of camouflage and concealment, drainage, maintenance, repairs, and security.

a. Camouflage and Concealment. The easiest and most efficient method of preventing the targeting and destruction of a position or shelter is use of proper camouflage and concealment techniques. Major considerations for camouflage use are discussed in FM 5-103. Following are some general guidelines for position construction.

(1) Natural concealment and good camouflage materials are used. When construction of a position begins, natural materials such as vegetation, rotting leaves, scrub brush, and snow are preserved for use as camouflage when construction is completed. If explosive excavation is used, the large area of earth spray created by detonation is camouflaged or removed by first placing tarpaulins or scrap canvas on the ground before charge detonation. Also, heavy equipment tracks and impressions are disguised upon completion of the construction.

(2) Fields of fire are not overcleared. In fighting position construction, clearing the fields of fire is an important activity for effective engagement of the enemy. Excessive clearing is prevented in order to reduce early enemy acquisition of the position. Procedures for clearing allow for only as much terrain modification as is needed for enemy acquisition and engagement.

(3) Concealment from aircraft is provided. Consideration is usually given to observation from the air. Action is taken to camouflage position interiors or roofs with fresh, natural materials to prevent contrast with the surroundings.

(4) During construction, the position is evaluated from the enemy side. By far, the most effective means of evaluating concealment and camouflage is to check it from a suspected enemy avenue of approach.

b. Drainage. In addition to using materials that are durable and resistant to weathering and rot, positions are protected from damage due to surface runoff and direct rainfall, and are repaired quickly when erosion begins. Proper position siting can lessen the problem of surface water runoff. Excavating intercepted ditches uphill from a position or shelter exclude surface water. Preventing water from flowing into the excavation is easier than removing it. Positions are located to direct the water runoff into natural drainage lines. Water within a position or shelter is carried to central points by constructing longitudinal slopes in the bottom of the excavation. A very gradual slope of 1 percent is desirable. Positions and shelters are designed to take advantage of natural drainage patterns of the ground. They are constructed to provide for

• Exclusion of surface runoff.

• Disposal of direct rainfall or seepage.

• Bypassing or rerouting of natural drainage channels if they are intersected by the position.

c. Maintenance. If water is allowed to stand in the bottom of an excavation, the position is eventually undermined and becomes useless. Sumps and drains are kept clean of silt and refuze. Parapets around positions are kept clear and wide enough to prevent parapet soil from falling into the excavation. When wire and pickets are used to support revetment material, the pickets may become loose, especially after rain. Improvised braces are wedged across the excavation (at or near floor level) between two opposite pickets. Further twisting tightens anchor wires. Anchor pickets are driven in farther to hold the tightened wires. Periodic inspections of sandbags should be made.

d. Repairs. If the walls are crumbling in at the top of an excavation (Figure 1-21), soil is cut out where it is crumbling (or until firm soil is reached). Sandbags or sod blocks are used to build up the damaged area. If excavation walls are wearing away at the floor level, a plank is placed on its edge or the brushwood is shifted down. The plank is held against the excavation wall with short pickets driven into the floor. If planks are used on both sides of the excavation, a wedge is placed between the planks and earth is placed at the back of the planks. If an entire wall appears ready to collapse, the excavation is completely revetted.

Sandbags

Sandbags

Before repair

After repair

Before repair

After repair

Damage at ground level

Damage at ground level

Stakes or holdfasts placed here

After repair Damage near floor level

Figure 1-21. Excavation Repair

After repair Damage near floor level

Stakes or holdfasts placed here

Figure 1-21. Excavation Repair e. Security. In almost all instances, teams of at least two personnel prepare fighting and protective positions. During construction, adequate frontal and perimeter protection and observation are necessary. Additional units are sometimes required to secure an area during position construction. Unit personnel can also take turns with excavating and providing security.

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