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Military

CHAPTER 9

ENGINEER OPERATIONS

GENERAL

 A river crossing requires specific procedures for success because the water obstacle inhibits ground maneuver in the usual way. It demands detailed planning and different technical support than other tactical operations. Extensive use of corps engineer assets are required. It is critical for supporting corps engineers to be totally involved in all facets of the river-crossing operation from initial planning through preparation and execution.

Traffic control is the most vital component of a river-crossing operation. ERPs are used to control traffic flow and permit movement across the river to be unhindered. Engineer units provide positive control and the necessary equipment to ensure maneuver forces successfully and safely cross the river in a timely and synchronized manner.

Contingency operations may require that assault river-crossing assets be used for longer periods of time because fixed bridging is not feasible or readily available. Engineer units must implement techniques that allow the long-term use of assault bridging assets without heavily affecting operations or damaging equipment. These topics will be discussed in detail in this chapter.

ERP OPERATIONS

ERPs ensure the effective use of the crossing means. ERPs and TCPs may be colocated to provide control for the river crossing. The CSC uses them to rapidly organize and move the unit through the crossing area.

The CSC establishes ERPs at the call-forward area and, if enough engineer assets are available, at the staging area and the far-shore holding area. He uses additional ERPs only when specific site conditions make it necessary for crossing-area control. ERP personnel need sufficient space to mark an area the size of a raft (mock-up raft), brief crossing procedures, and conduct necessary inspections and rehearsals. A hardstand, such as a rest stop or parking lot, is ideal for this purpose but lacks the overhead concealment usually desired. Some ERP functions may be done at separate ERPs to ensure a smooth and rapid flow of vehicles to the river. In this case, it is essential to maintain communications between ERPs.

Typically, an engineer squad mans an ERP. This maintains unit integrity and provides sufficient personnel and equipment for continuous operations. The crossing-site headquarters establishes direct communication with ERP personnel to control raft-load or individual vehicle movement. Depending on the location and purpose of the ERP, it can be used for the following functions:

RAFTING OPERATIONS

 ERP personnel configure vehicles into raft loads and send them to the river to coincide with the arrival of an empty raft. Engineers brief crossing units before their arrival in the call-forward area to make this happen as rapidly as possible. The briefing covers the-

 An engineer from the squad running the ERP can brief vehicle crews and rehearse the movement signals with them. The staging area is an ideal place to do this, minimizing the time and effort spent organizing a crossing unit in the call-forward area. Otherwise, a separate ERP should handle this task.

Figure 9-1 is an example of an ERP at the call-forward area. The engineer squad leader positions himself where he can best control vehicle movement from the call-forward area to the river line. He establishes communication with the crossing-site headquarters. As a crossing unit arrives, the assistant squad leader contacts the unit's commander, who determines the order in which his vehicles will cross. The assistant squad leader then configures individual vehicles into raft loads, while ensuring that the vehicles do not exceed either the weight limit or the maximum dimensions of the raft. He has a space marked out in the exact dimensions of a raft (mock-up raft) for this purpose. An engineer squad member guides the vehicles onto this mockup raft, using the same procedure to be used at the raft's embarking point on the river. At the same time, another engineer inspects the vehicles for the proper load classification and dimensional clearances and chalks the raft-load number on the vehicles. Once cleared through the mock-up, an engineer squad leader releases individual raft loads to the river as directed by the crossing-site headquarters

Items useful for running an ERP could include-

BRIDGE OPERATIONS

 A bridge operation requires a continuous traffic flow to the river. Units must be briefed and sent to the crossing site quickly. To accomplish this, engineers brief at staging areas and check vehicle load classification and dimensional clearances. The briefings include the following rules:

ERPs may be established along the routes to the crossing site to regulate traffic. A mockup bridge is not necessary at the ERP.

SWIMMING OPERATIONS

For swimming operations, ERP personnel have the necessary briefings and vehicle inspections. Crossing units are responsible for most preparations, but ERP personnel can assist with operations at the predip site that is established nearby and provide recovery assets. A briefing on swimming operations should include-

ENGINEER CONTINGENCY BRIDGING OPERATIONS

 Organizing and training for war fighting remains the primary mission of Army engineers. However, engineers can be called on to conduct contingency operations. For example, US Army operations in Bosnia included the mission to bridge the Sava River near Zupanja, Croatia, in December 1995. This mission was the largest river-crossing operation since World War II and was conducted under extreme conditions. Seasonal weather caused the Sava river to swell from its normal width of 300 meters to more than 600 meters. Despite harsh conditions, engineers used Chinook helicopters to deploy ribbon-bridge sections into the river while other engineers rebuilt the approaches and successfully bridged the Sava river to allow elements of the 1st Armored Division to cross. As the floodwater receded, engineers built a causeway across the floodplain. As operations in the area continued, the ribbon bridge remained the only crossing means for both military and civilian traffic while preparations were made for fixed bridging.

Versatile engineers provide unique personnel and equipment capabilities that can effectively support complex and sensitive situations in any contingency operation. Therefore, engineer force-projection planning should include the possibility that forces committed to contingency operations may become involved with combat operations. The engineer commander tailors engineer support based on contingency-operation requirements, which may be radically different than supporting combat operations. In many cases, the only difference between a wartime and an engineer contingency operation is the threat level.

Contingency operations may require the same or a greater level of logistics support to engineers as wartime operations. Combatant commanders tailor logistics support to engineers based on theater needs. Logistics efforts are integrated with host-nation or local resources and activities. Engineers invariably get involved with a wide variety of gap-crossing operations that may need flexible logistics support. Critical engineer logistics considerations during contingency operations include-

ASSAULT BRIDGES, LONG-TERM USE

 Ribbon-bridge operations normally last no longer than 72 hours. Having the ribbon bridge remain in operation beyond that time frame presents problems for the engineers that normally would not be experienced during a short duration. Equipment maintenance, anchorage systems, constant changes in the water level, and repair of approaches must be considered for long-term use of assault bridges.

MAINTENANCE

As equipment remains in use during crossing operations, maintenance services become more difficult to manage. Time must be made to allow boats and bays to be recovered from the water and completely serviced and checked for unusual wear. The techniques discussed in Chapter 7 are applicable but must include complete recovery of the equipment and movement back to the EEP where the services can be done. To accomplish maintenance services without jeopardizing bridging operations, boats and their replacements must be carefully managed. This may require procuring more boats than authorized by the table(s) of organization and equipment (TOE) to permit continued crossing operations without distribution for maintenance.

To check and service interior and end bays of the ribbon bridge, it must be broken apart and replacement interior and end bays emplaced. Time for such actions should be incorporated into the bridge-crossing time line and maneuver units notified when the crossing site will be shutdown temporarily. Synchronization of alternating times for crossing sites to be closed for maintenance can proactively re-route traffic flow and prevent major disturbances in movement across the river. To expedite the time required to replace bays needing maintenance and quickly allow traffic to resume crossing operations, engineers prepare replacement bays and boats and stage them before closing the crossing site. Daily checks of the bridge throughout the operation, considerations of the current's velocity and the amount of debris that may affect the bridge's operation, and maintaining vehicle speed across the bridge are critical to prevent damage to the bay's lower-lock devices and roadway-to-bow portion latches.

ANCHORAGE

All military bridges must be held in position by some anchorage system. Short-term anchorage is normally used for assault bridges, but if the bridge is required to remain operational for a longer period, the anchorage must be upgraded to provide long-term support.

The design of any anchorage system is influenced by several factors, including the-

 Anchorage of the ribbon bridge must occur if the bridge is used for long-term operation. During short-term crossings, boats maintain the bridge's stability against the current's velocity and keep the bridge from being damaged. However, as time permits, an anchorage system must be emplaced to provide continuous stability and provide relief for the number of boats required. Initially, the anchorage may consist of a combination of shore guys and boats. This method can still allow the bridge to be broken and permit barge river traffic access. Eventually, a semipermanent anchorage system, such as an overhead cable system, should be emplaced to keep the bridge secure.

The three basic components of all long-term anchorage systems include approach guys, an upstream anchorage system, and a downstream anchorage system. Approach guys are cables that prevent the bridge from being pushed away from the shore as a result of the impact of vehicles driving onto the ramps of the bridge. The upstream anchorage system holds the bridge in position against the force of the current's velocity. The downstream anchorage system protects the floating bridge against reverse currents, tidal conditions, eddies, and high winds or storms that might temporarily alter or reverse the natural flow of the river. The following types of anchorage systems can be used for stabilizing a bridge:

KEDGE ANCHORS

Kedge anchors lie in the streambed and are secured to the bridge bays with anchor lines. They are designed to sink with the stock lying flat and the fluke positioned to dig into the bottom. On hard bottoms, the kedge anchor is useless.

SHORE GUYS

Shore guys are cables attached from the bridges to a deadman or similar holdfasts on the shore. Shore guys can be upstream or downstream provided that the maximum anticipated current (or reverse current for downstream systems) does not exceed 0.9 MPS. Shore guys can be used for any length of floating bridge provided that a 45-degree angle be maintained between the shore guy and the bridge centerline.

COMBINATION OF KEDGE ANCHORS
AND SHORE GUYS

A combination system may be used for upstream or downstream anchorage systems in currents less than or equal to 1.5 MPS. When constructing a combination system, attach kedge anchors to every float and a shore guy to every sixth float.

OVERHEAD CABLE

An overhead cable system consists of one or more tower-supported cables spanning the river parallel to the bridge. Each end of the overhead cable is secured to the shore, preferably through the use of a deadman. Bridle lines are used to connect each bay of the bridge to the overhead cable. The cable functions like a cable used in a suspension bridge, except that its final working position is inclined toward the bridge because of the force of the current on the bridge.

TC 5-210 provides the specific criteria for the design of an overhead-cable anchorage system, to include the cable design, tower design and placement, and deadman design.

PROTECTIVE SYSTEMS

Floating bridges, particularly those that will remain in place for long periods of time, must be protected against severe weather conditions and enemy destruction. If flood conditions or heavy debris hamper bridging operations, removing of interior bays will reduce the lateral pressure on the bridge and allow the debris to pass downstream. If losing the bridge is imminent, release an end section and securely anchor the bridge parallel to the shore until conditions permit resuming bridging operations. As the river's width increases, simply add more interior bays to the bridge to compensate.

The enemy may attempt to destroy floating bridges in a variety of ways, including air attacks, land attacks, underwater demolitions teams, floating mines, or assault boats. It is necessary to construct floating protective devices to prevent waterborne forces from damaging or destroying the bridge. The three types of floating protective systems are as follows:

ANTIMINE BOOM

This device is designed to stop any mines that are sent downstream toward the bridge. The antimine boom is placed far upstream to protect the other protective devices as well as the bridge. It consists of a number of logs or other large floating structures attached to a cable running across the river. Concertina is normally placed along the length of the boom.

NOTE: Before using timber logs or railroad ties, ensure that they are not waterlogged and will float.

IMPACT BOOM

The impact boom is designed to withstand the impact of large natural or man-made debris and stop the enemy from attacking the bridge by boat. It is constructed by placing a series of floats and cables across the river. The cables absorb the impact of the debris or boat and restrain it until it can be removed or destroyed.

ANTISWIMMER NET

This net is used to stop swimmers or underwater demolition teams from reaching the bridge. The net can be constructed by suspending a mesh or net barrier from an anchorage cable to the river's bottom. Concertina may also be connected to the cable and net to prevent swimmers from climbing over the net. The net must be firmly affixed to the river's bottom or enemy divers can easily go under the net. The antiswimmer net should also be placed on the downstream side of the bridge to prevent enemy divers from reaching the bridge from downstream.

Army diver teams can assist in emplacing the protective devices and test them to ensure they are able to prevent penetrating the bridge.

APPROACHES

Over a period of time, traffic flow at the same location will eventually wear the approaches down and make them unusable. Engineers incorporate repair of the entry and exit banks and the approaches leading to the crossing site into the crossing-operation plan. Initially, the approaches may be suitable to receive heavy traffic with little effect, but implementation of reinforcing the approaches must be done for long-term traffic. When inspecting approaches, consider the following:

 Matting and rock or gravel are the best suitable materials to use to support the approaches. Maneuver units that will have to conduct long-term crossing operations should develop procedures to requisition and deliver these materials to identified crossing-site locations. Reconnaissance teams can locate local quarries where rock and gravel can be obtained through coordination with the host country.

New techniques for constructing bridge approach roads include using fabric as a reinforcement across soft soil. An impervious, neoprene-coated, nylon-woven membrane can be placed between a stone aggregate and the soft-surface soil to allow the ground to withstand heavy traffic. The most important feature that a reinforcing fabric membrane can offer is improving soil stability and strength, which creates smaller deformations from vehicle traffic than soils acting alone.

LONG-TERM GAP-CROSSING C2

More than any other mobility task, gap crossing involves managing combat power, space, time, and terrain. The controlling headquarters must be flexible enough to react to any changes in the tactical situation and scheme of crossing. This is particularly difficult when involved with long-term operations in the same area of operations. Management of the crossing site, enemy considerations, traffic-control measures, and CSS must be synchronized for long-term activities and must not be based on less than a 72-hour period.

MANAGEMENT

Traffic and movement control remain the responsibility of the C2 headquarters. Activities may direct that another unit take over the crossing operation and equipment as a whole or bring their own crossing equipment and personnel to relieve the existing units and permit them to move forward. All aspects of the operation must be covered when handing over the crossing site to the gaining unit-just as though they were conducting the crossing for the first time.

ENEMY CONSIDERATIONS

Operation of a single crossing site over an extended period of time increases the possibility of enemy interdiction. The possible use of nuclear or chemical weapons against friendly crossing activities impacts on control procedures. To prevent the friendly elements from becoming targets, forces must cross the gap as swiftly as possible to minimize the concentration of forces on either side of the gap. The controlling headquarters also varies the crossing-site location to reduce enemy threat interdiction.

TRAFFIC-CONTROL MEASURES

Staging- and holding-area control must be maintained. These areas must be located far enough away from the gap to facilitate rerouting and the use of alternate roads to crossing sites. Staging and holding areas on the far shore must be developed to handle the traffic as vehicles travel back across. New routes may be constructed and existing routes upgraded to improve traffic flow. Staging areas must be able to provide the following:

COMBAT SERVICE SUPPORT

 In a normal gap-crossing situation, the committed combat forces will be temporarily separated from their full CSS. For long-term gap-crossing operations, increased traffic flow for the service-support vehicles must be considered and controlled. Sufficient crossing sites and designated crossing times can ensure that priority is given to field trains and ensure that timely resupply operations are not hindered. Recovery of nonmission- capable equipment presents an additional problem for recovery teams transporting the equipment back to the near shore for direct-support maintenance support. Additionally, recovery resources should continue to be provided at both sides of the crossing sites so they can quickly recover a vehicle unable to cross and prevent delays.

MULTIROLE BRIDGE COMPANY (MRBC)

Today's Army must be able to respond to an increasing array of potential employments in war or in contingency operations. With the new integrated information-processing systems, river-crossing opportunities will be quickly identified and execution will rely heavily on the rapid-response capability of bridge companies.

Current bridge companies are tailored around their specific floating or fixed-span bridges, without regard for their inherent conceptual, operational, and organizational commonalty. Both types of companies are similarly organized with a company headquarters, two bridge platoons, and a support platoon. The fixed-bridge company cannot transport ribbon-bridge sections on its 5-ton dump trucks, nor does it have the required bridge boats. The float-bridge company, on the other hand, can readily transport fixed-bridge components on its transporters, but only if the loads are palletized.

Whenever both types of bridges are needed, both types of companies must deploy. Since a company owns it own unique bridge, sufficient companies must be deployed to cover all possible gaps. When a bridge company has expended its bridging materials, it reverts to a transportation mission.

The MRBC is a modular company with both dry- and wet-gap capabilities that will employ both types of bridges as needed, based on METT-T. Each bridge platoon can transport and employ both types, as ordered. The MRBC is a versatile, flexible, and modular unit that can meet the demands of the maneuver commanders. The developmental HDSB is also fully compatible with the MRBC concept. The HDSB will replace the MGB as the primary fixed bridge employed by this company, relegating the MGB to a supplemental role.

ORGANIZATION

The MRBC will be a combination of a MGB company and an AFB company. The MRBC's structure consists of a company headquarters, two bridge platoons (one MGB and one AFB), and a support platoon. The support platoon consists of a platoon headquarters, an equipment maintenance section, and a bridge-site section. The new bridge transporter, the improved common bridge transporter (ICBT), is specifically designed to function in the MRBC. The palletized-load-system (PLS) trailer will be procured as a part of the HDSB to allow the transporting of both bridges simultaneously.

BASIC CONCEPT

A typical operational mission would begin with a platoon responding to a mission with an initial basic load of the desired bridge. When it completes the bridge, the platoon moves to the next site, either picking up the next required bridge along the way or finding the bridge cached at either the engineer bridge park or the site it will be emplaced. As the forces advance, the bridges become the responsibility of the engineer units in the communications zone. As prefabricated bridging is replaced by nonstandard or more permanent bridging, the platoon responds to bridge-retrieval missions. Retrieved bridges will reenter the supply system or be stored in the unit's bridge supply yard. Bridging sets are a supply commodity and are handled as any other Class VII supplies (major end item).

The MRBC's capabilities will give commanders the ability to quickly maneuver and respond, through either fixed or float bridging or a combination of bridging appropriate for the mission. This newly structured MRBC operates within a "lane" on the battlefield (an area defined by a maneuver brigade's area of operation) and provides the necessary bridging for multiple axes of advance. Trailing closely behind combat forces, the MRBC moves forward when necessary to support assault crossings. Additional MRBCs, provided from corps assets, may be assigned to the lane when gap-crossing requirements exceed the capabilities of a single MRBC.

IMPLICATIONS

Because bridge sets are exceptionally heavy and tall and have many parts (some are small and easy to lose), they should be placed on pallets and shrink wrapped for transportability and accountability. The procedure to requisition and deliver bridges is essentially unchanged. The number of bridges needed is unaffected, since it is based on METT-T and not the bridge-company organization.

Bridges are loaded on bridge adapter pallets and boats that have the improved boat cradle, which allows the loads to be placed on the ground without damage. The pallets and cradles remain at the EEP until the bridge or boat is recovered. Treating bridging as a commodity instead of a bridge company TOE property emphasizes the critical maneuver planning that is involved by the maneuver staff and not exclusively the engineer staff. MRBC engineers cannot exist on the battlefield without support from the following branches:

TRAINING

 Engineer units' training must reflect the dual bridge capability. Currently, bridge crewmen receive advanced individual training on both fixed and float bridges. However, once they are assigned to a unit, their collective training is only on the single-type bridge of that company. Under the MRBC concept, individual bridge crewmen and leaders must maintain their proficiency on both types of bridges. Bridge specialists must continue to be proficient in all types of prefabricated bridges. Critical branch interaction during war-gaming exercises must consider employing the MRBC in current training by implementing a variety of missions, either sequentially or simultaneously, to become more accustomed to its employment. Additionally, engineer company-grade officers and noncommissioned officers (NCOs) will have increased responsibility and will need to improve their technical proficiency.

Final decisions as to the size and end-state composition of the MRBC are not being implemented yet; however, many units can expect to have the HDSB and the improved ribbon bridge carried on HEMTT-chassis transporters. Interim organizations will include basic loads of the medium-girder, Bailey, and ribbon bridges, which are carried on their current transporters. Whatever the organization's development stage, the MRBC will not be dedicated to only one bridge type.



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