Author Topic: UNDERWATER EXPLOSIVES REMOVAL  (Read 1446 times)

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Offline T101

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« on: August 12, 2014, 10:38:59 AM »

Physiological Hazards From Underwater Explosions:

On land when a blast occurs, injury and death can occur from three main causes: projectiles, over-pressure, and heat. Special kevlar bomb disposal suits and helmets are worn to protect the bomb disposal technician from these hazards. Underwater, when a blast occurs, projectiles and heat are not as serious a concern. The projectiles will be slowed down greatly and only travel a short distance due to the viscosity of water. The main concern about an underwater blast is the over-pressure shock wave. On land, a great deal of the over-pressure shock wave will go around or bounce off the body. Additionally, air can be compressed whereas water cannot. Underwater, since the body is the same density as water, the shock wave will pass directly through the body. As it does, it will rupture hollow organs such as the lungs and bowels.

Under normal conditions, the human body can withstand a maximum shock wave of 50 psi. From that point to 300 psi, injury will take place. Over 300 psi, death can and will occur. Using a one pound (0.4 54 kg) charge of explosive as a test standard, if detonated underwater, a completely submerged diver would need to be at least 72 yards (69 meters) away from that blast to be struck by a shock wave of less than 50 psi.

Diver Safety Equipment:

To limit the shock wave from passing from the water through the body, certain precautions can be taken. One such precaution would be a dry suit with an insulated garment between the suit and the diver’s skin. This air space will greatly reduce the shock wave reaching the body. Also beneficial to the diver is a full diving helmet, such as the Kirby Morgan Superlite 17C. This provides protection to the sinus cavities, ears, and eyes of the diver if a detonation occurs. How much protection a dry suit and full diving helmet provide depends on how close the diver is to the detonation. If an explosion occurs underwater, in close proximity to a completely submerged diver, then in all likelihood serious injury or death will occur. This shock wave can be reduced, but never eliminated.

Specialized Procedures and Equipment:

If possible and can be done safely, the explosives, military ordnance, or improvised explosive device (lED) should be remotely brought to shore to be rendered-safe or disposed of in a safer and more hospitable environment. This can be accomplished in one of two ways. One way, using a strong line, secured and originating from shore, is gently tied to the explosive or device by the UERS Diver, who then exits the water. The line should be a minimum of 200 feet (61 meters) in length. The larger the explosive, the longer the line should be. A minimum area of 300 feet (92 meters) around the explosive should be cleared of boats, citizens, the press, and fellow team members. Again, the larger the explosive, the larger your clear area should be. After determining that the area is safe and the diver is out of the water, an individual wearing bomb protective attire and helmet with face visor firmly grasps the line, never moving his/her hands, and slowly walks away from the water dragging the unseen item to shore. (Never “reel” the explosive in toward you while standing in one spot.) This will ensure a constant safe distance from that person to the explosive if a detonation does occur. The problem with dragging the item across the bottom is that it may become entangled underwater on rocks, branches, or debris.

The second method, which solves the problem identified in the first, is the use of specially designed remote filling lift bags, manufactured by SubSalve/Inflatable Technology of Providence, Rhode Island. These unique, low profile lift bags, after carefully being secured to the explosive by the UERS Diver who then exits the water, can be remotely filled from shore using a high pressure hose attached to a spare SCUBA cylinder. After the bag with the explosive attached rises to the surface, it can be pulled to shore using the same hose. The same procedure in dragging the item to shore as described in the first technique is used. When the explosive or hazardous device is on shore, it can be disposed of or rendered- safe by the UERS Diver or other qualified Bomb Disposal Technicians. Military ordnance, explosives, or improvised explosive devices (even if only suspected of being explosive) should never be carried out of the water. Only remote removal procedures should ever be used to retrieve these hazardous items.

If it is too dangerous for a diver to secure a line to an underwater explosive-type device for fear touching it may cause it to explode, it should either be remotely “blown in place” by detonating an explosive charge in close proximity to the item, or remotely rendered-safe. These techniques are highly confidential and dangerous procedures only taught and known to Underwater Explosive Recovery Specialists and Navy EOD Divers.

Military Ordnance and Explosive Safety Guidelines:

#1. Only trained and qualified Bomb Disposal Technicians, who are certified SCUBA Divers with advanced training in Underwater Explosive Recovery, should ever attempt the recovery or render-safe of explosives, military ordnance, or improvised explosive devices (lED) that have been placed, discarded, or hidden underwater.
#2. Explosives, military ordnance, or lEDs located underwater that require recovery should only be retrieved using remote removal techniques and equipment when the diver is completely out of the water.
#3. Always assume the military ordnance or lED you are searching for or have located is armed, ready to detonate if moved or disturbed.
#4. Always assume the explosive, military ordnance, or lED you are searching for or have located has been tampered with or even booby-trapped.
#5. Never use metal detectors, electronic dive computers, or any other item of electronic equipment in an area where suspected or known military ordnance, explosives, lED or blasting caps may be.
#6. In conducting underwater post blast investigations, always assume that other undetonated, but armed, explosive devices or military ordnance may be in the area. It is becoming more prevalent that time delayed or booby-trapped secondary explosive devices are used against individuals who have responded to an area where a blast has already occurred.

David Giroux
ANDI Instructor Trainer #170
ANDI Tri-Mix Instructor L5
ANDI Technical Trimix Wreck Instructor L3
ANDI Gas Blender & Service Technician.
PADI IDC Staff +21 Specialties;
DDI, EFR & DAN Europe Instructor;
Trimix Master Class diver -145m;
Commercial Diver & Public Safety Diver/ERDI