Construction of Submerged Bridge, WWII Tactical and Technical Trends, No. 29, July 15, 1943 (Lone Sentry)

The following description of the construction of a submerged bridge is a condensation of an article originally appearing in the Soviet "Red Star."

It was pointed out in this article that bridges built above the water are easily observed from the air and on aerial photographs, whereas bridges built below the surface of the water cannot be detected from altitudes greater than 900 feet and will not show up on aerial photographs.

Satisfactory conditions for use of submerged bridges are (1) that the enemy has not previously photographed the area of the crossing, or that the approaches to the crossing do not reveal the location -- either by the fact that existing roads are used or new ones constructed along the bank above and below crossing points; and (2) that there are no sharp changes in water level. It is sometimes more advisable to construct a submerged bridge within 2 kilometers of an already existing bridge above water. In such cases the enemy may bomb the latter, not knowing the submerged bridge is there.

The changes in water level cannot vary more than 10 inches. Any greater change will either cause the bridge to become impassable or be exposed.

The construction of submerged bridges is somewhat more complicated than the other types. Working under water increases the time necessary, and at times divers are needed; this requires special personnel, although well-trained troops can usually do the job without divers.

The actual construction of this type of bridge does not differ greatly from that of other bridges except perhaps in that prepared lumber is always necessary.

Care must be taken to have firm approaches; otherwise the disturbance of the water by crossing vehicles causes the approaches to wash away. This can be prevented, however, by constructing retaining walls and filling in with rock or gravel.

It is estimated that a 40-meter (130-foot) bridge with a 60-ton capacity requires 8 men 24 hours to prepare (but not drive in) the piles. Remarks: Our Military Attache in Moscow, commenting upon this type of construction, remarks as follows: "It was noted several days, ago in the Soviet press that such bridges had been used by the Red Army, and in view of the recent creation of the medal 'Distinguished Pontoneer' it is possible that the use of such bridges has been successful."