FEATURE
ALL MARINE PROJECTS DESERVE THE VERY GREENEST OF UXO SOLUTIONS BY ANDREW WOOLLVEN AND HARDEEP SIDHU
H
uman intervention and encroachment into the marine environment are growing at an unprecedented pace. There are predictions for example, that by the early part of the twenty-first century in excess of 70% of the population of the United States will be located in coastal regions. As our reliance on renewable energies grows, large areas of coastal zone and shallow seas are being taken up by offshore windfarms and will no doubt be followed in the near future by wave and tidal power generation. Growing global population demands increased infrastructure developments that in turn require connectivity for power transmission and communications. Developments such as these face a significant threat from one other human activity, war. It is estimated that the two world wars left approximately 1.6 million tonnes of munitions in the German North Sea and Baltic Sea, while WWII resulted in excess of 3,800 shipwrecks with unknown quantities of unexploded ordnance (UXO) in the East Asian-Pacific region alone. Munitions from conflicts, firing ranges, training exercises and wrecks include air-delivered bombs, land and sea mines, torpedoes, depth charges, projectiles and chemical weapons. These munitions are not only a potentially devastating explosive risk but also present risks from carcinogens and chemical (metals and organics). Disposal therefore demands techniques that offer the highest level of safety and lowest impacts on the physical and natural environments. Disposal by ‘Low Order’ (LO) deflagration safeguards marine life and the seabed, and generally costs
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less than conventional ‘High Order’ (HO) detonations. Consequently, support for LO deflagration is now growing amongst environmental support groups and offshore sectors.
LOW ORDER DEFLAGRATION
The conventional HO detonation method of disposal of UXO is effectively unchanged since the end of WWII and requires a bulk donor charge (usually 5-25 kilograms of explosive) to be placed next to the unexploded ordnance and detonated. This causes the UXO to detonate with its full design force, with highly destructive results to both the seabed and marine life. LO deflagration is the process of burning out the explosive fill of an item of UXO to render it safe, provided the munition casing is intact. A small, shaped charge (typically 15-300 grams) is used to inject a high velocity plasma jet through the UXO casing to instantaneously ignite (not detonate) the explosive contents of the UXO. The explosive content burns at very high temperatures (circa 5000°C), releasing gases, increasing the internal pressure and causing the casing to burst open, without the UXO detonating. The explosive contents are oxygen enriched, containing sufficient oxygen to burn without needing air, which is why UXO is able to function underwater where there is no air to fuel the detonation. The explosive material/fill is contained within the munition during deflagration and not spread over the surrounding environment.
