General Information Document.
Search and Clearance of Explosive Ordnance from SS El Grillo.
Prepared by the Icelandic Coast Guard Explosive Ordnance Disposal Unit .
The SS El Grillo sank without casualties whilst at anchor, as a result of an air attack by three German FW Condor Aircraft from Norway on 10 Feb 1944.
At the time of sinking she was carrying a cargo of bunker oil for the replenishment of Naval vessels. Also onboard were Depth Charges held in storage racks above deck aft of the bridge – this cargo however, was not reported by the Captain at the time of sinking.
The El Grillo was a Defensively Equipped Merchant (DEM) Vessel, her armament was standard for the period and included 4 Oerlikon 20 mm Cannons for Air Defence, one 4 inch Medium Calibre Gun and one 12 Pounder High Angle Quick Fire Medium Calibre Gun. The only gun remaining on the vessel at present is the 4 inch, which is at the aft end of the vessel.
The oil removal operation by a Norwegian specialist contractor is as a result of almost continuous oil leakage from the vessel since her sinking in 1944. The operation to remove any explosive ordnance is the first step in this operation.
The Environmental Ministry is fulfilling its duty to protect the local environment and economy by funding the removal of the remaining oil, which is estimated at around 2000 tons, and at the same time making the wreck safer by the removal of any remaining explosive ordnance.
The Explosive Ordnance
20 mm API (Advanced Primer Ignition) Oerlikon Cannon Mark II.
This gun was, with the Bofors 40 mm cannon, by far the most successful Anti- Aircraft Gun of World War II and was in fact in use by he Royal Navy for many years afterwards.
API or blowback was first used during WW 1 as a method of generating automatic fire. The Swiss-made Oerlikon 20 mm Cannon was developed in the 1930´s and the design taken up by the British, Germans, Japanese and Americans for use in WW II.
The guns fitted to the El Grillo were manually operated over open sights and fired 450 rounds per minute. Their effective range was approx 1.7 km, with ammunition being of a high explosive and tracer type, with an integral nose fitted impact fuze. The ammunition was loaded into ammunition drums containing 60 rounds. The rounds were designed to hit the target and explode on contact with a rigid structure in the airframe, thus they were extremely effective, especially at shorter ranges.
4 inch (10.2 cm)/45 Mark IX and 12 Pounder (3 inch/40. 7.62 cm) HA Medium Calibre Guns.
These manually operated and sighted guns were mainly for use against surface targets, although with High Angle mountings they could engage aircraft targets. Their range, depending on ammunition was between 12 and 15 km.
Although the 4 inch Gun was of relatively new design the 12 Pounder was first brought into service with the Royal Navy in 1893.
The projectiles weighed between 6 and 15 kg and could be High Explosive, Semi-Armour Piercing or Shrapnel with Impact or Delayed Impact Fuzing, some signalling shells would also have been onboard.
The rate of fire would be between 10 and 15 rounds per minute.
Depth Charge Mark VII
The Mark VII Depth Charge was an anti-submarine weapon with a variable depth setting for detonation of up to 300 feet under the sea. It contained 147 kg of TNT or Minol and was launched by a special
special thrower device.
Parachute and Cable Rockets
These were intended to deter low flying aircraft attacks and were used in great numbers in the Battle of Britain to protect British Airfields from enemy aircraft attack.
Operation is by launching of a Rocket to which is connected a steel cable, at a predetermined height a parachute is deployed and the cable is suspended in the air. If an aircraft hits the cable it may be damaged or destroyed, but to make sure on some types a small bomb was attached which would be drawn down onto the aircraft as the cable slipped over the airframe and then explode on impact.
QUESTIONS and ANSWERS.....
It is the responsibility of the Environmental Ministry to make the work area safe for the commercial diving team carrying out the oil removal operation. It is known that explosives were on the vessel at the time of sinking and it would be part of any similar operation to carry out such a task anywhere in the world.
By using the RDN and the ICG to carry out the task the Ministry have not only ensured the job will be carried out in a safe and professional manner, but also at a reasonable cost. A similar commercial venture would be considerably more expensive.
How Much Explosive Ordnance is on the El Grillo?
This is impossible to say at present, no records of the standard ammunition scales are available for this period and the Depth Charges, of which 25 have been recovered in legal operations by the ICG were not reported on the post sinking manifest. It is thought however, that many of the accessible shells have been illegally and foolishly removed by scuba divers.
What is the Danger from the Ammunition?
All explosive ordnance is potentially dangerous by its very nature and design. Military explosives are meant to kill people and destroy property, in the case of the ordnance that may remain on the El Grillo, it is still as capable today of doing so as when first manufactured. Indeed, it is normally the case that explosives become more dangerous with time and the effects of chemical activity or corrosion.
The operation is by its very nature hazardous, therefore management will concentrate on safety with only those directly involved in the task allowed on the vessel.
What is the Greatest Danger?
Regarding the Explosives, the 12 Pounder Shells were filled with a High Explosive Filling known as Picric Acid, this deteriorates into an unstable compound and forms sensitive crystals or Picrates with time. Recent tests by the MOD in the UK have shown that in extreme conditions, Picric Acid filled shells will detonate if dropped through 40 cm of water.
Much of the information regarding the deterioration and dangers of Picric Acid have been gained from the British Royal Navy, who are engaged in a similar project to salvage oil from HMS Royal Oak in Scapa Flow.
How will the Operation be Carried Out?
The operation is a joint effort by the ICG and the RDN on behalf of the Environmental Ministry of Iceland. It is a Explosive Ordnance Disposal Operation, which will be conducted within NATO guidlines.
The Captain and Crew of ICG Inspection ship TÝR will provide the working platform and domestic and technical support to the operation. The explosive ordnance search and removal operation wil be carried out jointly by the ICG EOD Unit and RDN EOD Service with support from the ICG Diving Unit.
An ROV will make an initial survey of the vessel, with the work concentrated on areas likely to be used by the Norwegian oil removal team.
Divers will search and recover the ordnance, which will then be transported to and then destroyed at a separate location.
The Diving will be carried out by qualified EOD Divers who will be using a mixed gas system. All divers will be in constant contact with the surface and the work will be monitored by helmet mounted cameras. A de-compression chamber has been set aboard the ship in the case of emergency.
For the duration of the operation a no entry area will be established around TÝR to ensure the safety of personnel. This will be established and monitored in close co-operation with the local authorities.
The EOD operation has been mounted to ensure that the oil removal operation can proceed in safety. It is not known how much ammunition will be found, but the operational planning has taken into account all circumstances based on the known facts, with the safety of personnel and protection of the environment as the guiding considerations.