SPONSORS OF UNEXPLODED ORDNANCE
If you then have two conical charges directionally opposed to each other where they are mounted in-line on either side of the UXO you create a ‘collision’ charge effect this is where you have two explosively formed jets meeting at approx 18,000m/s any explosive compounds in between will have the best chance to sympathetically detonate/produce a reliable detonation pressure shockwave and if not the whole
A decision is then made as to what deterrent mitigation systems to use, namely seal/dolphin/whale scarers that emit various frequencies of noise which is uncomfortable to each type of marine mammal.
A pressure pulse scarer for fish is then used, as they are not affected by the acoustic deterrents but need a small explosion producing a pressure pulse to
MOBILISATION
All explosives related equipment is tested, checked and mobilised.
The vessel selected is chartered along with all appropriate equipment. Use of robotics and not divers is preferred.
ON SITE/DISPOSAL • The PAM system is deployed • Full time MMO’s are in place – consideration is to time of year/species present etc), Scrammers are also placed
• The donar shaped charges are laid on the sea bed and firing cables run out to safe firing distances
• All local shipping, DSVs, MVs, coastguard, Navy etc. are informed and given an approx initiation time
PROCEDURAL STAGES • The seal, whale, dolphin acoustic scarers are turned on, for approx 20-30 mins
• Once all systems are in place the MMO’s give an agreed firing the go-ahead
• Activation of overpressure blast monitor
• Set off fish pressure pulse scarers and fire the shot
UXO will be destroyed into very small pieces due to the effect of the collision charge.
Blast Design use plastic explosives in the shaped charges along with an EBW (Exploding Bridgewire) Firing System to initiate the charges, this requires an all fire current in excess of 3,000volts and 1,000amps, which ensures a safe environment for initiation.
OPERATIONAL PLANNING Once the donar charges and firing system is agreed along with the data collected from the ‘as found’ survey, the Environmental Impact Study, Risk Assessment and Operational Procedures are put together along with operational meetings with key personnel is carried out.
MITIGATION METHOD
The mitigation method is then agreed based on the NEQ of the UXO – distances, mitigation methods etc. This would include a seabed anchored PAM system (Passive Acoustic Monitor), this will pick up the vocalisations of marine mammals which will track them from/to the target or danger area.
scare them away. Again Blast Design have designed their own ‘pressure pulse’ grenade for this purpose which after the pin is pulled out and deployed in the water, it sinks and initiates 4 tiny explosions.
PAM SYSTEM
The PAM system operates full time while on UXO site – the acoustic scrammers are put on within 30min of detonation and the fish and the fish pressure pulse grenades are fired 2 minutes before detonation.
They also have a minimum of one MMO (Marine Mammal Observer) and one PAM technician out on every UXO operation. All members of the vessel are potential MMO’s on every trip – it is all the responsibility of al personnel to look out for marine mammals.
Successful detonations are identified by the effects on the surface and also the sound/effect on the bottom of the vessel – an inspection is then made by ROV.
FINDINGS WOULD BE... • A crater on the seabed • Very small pieces of UXO lying on the seabed
Any pieces bigger than a large paint tin are recovered and an ‘as left’ survey is carried out and full report is written up.
Blast Design
www.blast.co.uk
Ed’s note – this is an abridged version. We recommend you visit Blast Design’s microsite held within our supply chain register by scanning the QR code below or clicking on the pink flash in the online magazine.
Click to view more info
www.windenergynetwork.co.uk
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