LAGOON MINEX
By CPODR Graham, LDR Ormsby & LDR Keyworth, Operational Diving Team
In 1942 the US forces laid Defensive Minefields in strategic locations around New Caledonia. Approximately 1900 mines were laid in 12 fields to defend the island from Japanese sea-borne attack. (Japanese submarines patrolled in the Coral and Tasman Seas throughout 1942–43.) The mines that were laid were British Buoyant MKXIV and MKXVII sea-mines, which are set off by chemical hertz horns or switch horns respectively. The mines were designed to defend against surface and subsurface craft and packed a real punch with 320–500lbs of high explosive in them. At the end of WWII, sweeping operations were conducted to part the mooring wires and then the now floating mines were sunk by rifle fire.
In 2008 the RNZN, USN and RAN were requested, by the French, to assist in locating, identifying, disposing and/or destroying these sea mines which have lain undisturbed for over 60 years. The RAN committed two mine hunters and Clearance Diving Team One. The Americans committed the MK 7 Mine Hunting Dolphins, Explosive Ordnance Disposal Divers and an Autonomous Underwater Vehicle (AUV) team, while our Navy committed components of the Littoral Warfare Support Group (LWSG): nine Clearance Divers from the ODT and six personnel from the MCM Team, all embarked in HMNZ Ships MANAWANUI and RESOLUTION.
Force Integration Training
A variety of briefs, on command, communications and medical; all facets of the exercise were practiced including MCM Diving procedures, mine-lifting serials and visual/sonar reacquisition of the targets. During the initial briefings our lads were given a chance to dive in the French Clearance Divers set (CRABBE), and their attack swimming re-breather (FROG). This was a good experience and gave us a chance to compare our own Clearance diving set (the Viper SC) against theirs. Another big attraction during the first week was meeting the American Mammal team; sceptical of the dolphins’ effectiveness to begin with, we walked away amazed at the intelligence and skill of these creatures.
The ubiquitous trade winds would reach a crescendo during early afternoon, turning the millpond morning seas into a cauldron of sea state 3 – 4. When you’re being thrown around in a small Zodiac RIB, these conditions make diving difficult so the decision was made to dive at 0530 daily. Interestingly this coincided with the known shark feeding time for this area! Diving involves trade offs and risk mitigation—shark attacks are one in a million, the trade winds are always present.
The Operation
We joined the poisonous sea snakes, sharks, jellyfish and blue-ringed octopus that live in the lagoon. The depths dived varied between 22 to 54 m.
We were given the green light to raise, tow and blow one of the mines. Countermining involves placing an explosive charge on or near the mine to destroy it in place. We were unable to destroy in situ (on the seabed) as the lagoon is protected by UNESCO. We had to raise the mine from the seabed, move to a demolition site and suspend it 10 m below the surface using a disposable float, consisting of four 44 gallon drums and two pallets (expertly lashed by CPOSCS Mills and seamen from MANAWANUI).
We also discovered our Enclosed Mine Lifting Bag (EMLB) was defective and it resisted the efforts of LDR Ormsby and LTCDR Barrett (CO MCMT). The EMLB is supposed to inflate remotely, in order to give the diver time to safely clear the mine danger radius should the mine explode on lifting. With this in mind a ‘Kiwi No.8 wire’ approach was employed, enabling our open ‘tear drop’ lifting bag to inflate remotely after a five minute delay. Additionally, the Explosive Charge Packs designed for this type of work are no longer produced (last used by the RNZN in the 1980s), so ingenuity was applied by LDR Keyworth to make packs, to attach to the mine for detonation.
After all that, conditions were marginal for diving, let alone underwater demolitions. But the evolution went off without a hitch, thanks to PODR Dimond and LDR Keyworth who had to deal with the dangerous swell whilst placing a live explosives charge on a real mine that was bouncing like a yoyo. Challenging, yet very rewarding as we witnessed the detonation!
Another factor was the tidal stream in Prony, on the southern end of New Caledonia, where a WWII minefield was found by the RNZN MCM team the previous week. Both the Supervisors and divers were stretched to their limits, clearing up to 30 contacts a day despite strong tidal streams and poor visibility. The nautical charts did little to warn of the extreme tidal streams; it took only one dive to understand we would be exposed to confusing tides which reached 3 knots when flooding. The surface support crew frequently lost sight of the float marking the diver and the diving supervisors never relaxed ….
This was further exacerbated with the depths dived in this area (to 54 m) and the decompression schedules required. One occasion saw a diver swept 800 m from the original datum, which apart from giving the Dive Supervisor a near heart attack, meant additional decompression stops for the diver.
Marine life in this part of the world is fascinating and colourful. There is a plethora of lethal mammals and invertebrates, some of which are capable of inflicting paralysis, others use their teeth and simply devour prey. I’m no fan of snakes, on land or in the sea!
Sharks can cause some moments of concern. PODR Darren Mills was buzzed at very close range by a 1.5 metre shark. We knew nothing of this until he arrived on the surface and yelled through his VIPER mouth piece (you cannot remove it quickly) “SHARK, get me out of the ‘***’ water.” It took 3 or 4 seconds (1 hour in distressed diver time) for the support crew to interpret his muffled message! Once we clicked, Darren was rapidly hauled from the water. (I should add within five minutes he was back in to complete his planned diving schedule.)
The exercise was a great experience and our diving success was due to the accurate target information provided by the MCMT and its REMUS. They achieved 11 days of continuous REMUS operations with two REMUS missions up to 8 hours each day, over 60 hours of REMUS water-time and 12.2 million square metres (3.56nm²) searched and analysed. The ODT completed 115 dives, investigated 109 targets, positively identified 40 mines and raised and destroyed a live mine safely.
None of this would have been possible without the support from RESOLUTION and MANAWANUI. Please accept our sincere appreciation; we can all be proud of what was achieved. You will be able to see some of this in a TV “Coastwatch” episode later this year.
MANAWANUI & RESOLUTION — A Midshipman’s View
By MID Trent Nancekivell, RNZN
When I was told that I would be going to New Caledonia I imagined long days on the beach admiring the local scenery! Of course that’s not what happened … I joined MANAWANUI and we soon departed for the passage north. It was exciting to get away and I was fortunate enough to earn endorsement as an OOW, after days of work pouring over the Navigation Data Book and the Bridge File, studying the ships systems, and conducting various exercises.
The days started with brilliant tropical sunrises at 0500 followed by sun all day—and the trade winds, which blew from 1000 through the remainder of each day, making boat work difficult.
The French were good hosts and put on an enjoyable cocktail party the first week, we were there. This was the first chance, we had to meet our international counterparts, the crew of two Australian mine hunters, HMAS GASCOYNE and HMAS YARRA, the Australian Navy divers, the US Navy MCM Dolphin Team, and also the crew of the French ship FNS JACQUES CARTIER.
Our first day started with OOWMANS and a VERTREP using the French helicopters. I was lucky enough to get onboard GASCOYNE during the OOWMANS. It was interesting to see the different systems of another Navy.
Taking MANAWANUI around the lagoon was often stressful, as there appeared to be wind- and kite-surfing competitions everyday, with the participants taking a particular interest in MANAWANUI. The constant flotillas of yachts also made for eventful watches.
One of the memorable moments was the explosive countermining, with MANAWANUI, RESOLUTION and the French Navigational Safety Vessel DUMBEA all present. At the time I was in RESOLUTION (for a few days to gain experience on MCM operations). The majority of our ships’ companies were on the upper decks, looking expectantly at the buoy that marked the mine. We saw the RHIB full of divers make a beeline back to MANAWANUI and the countdown began. The detonation was not at all like the movies, where depth charges send water hundreds of feet in the air!
The few days alongside (if not on duty) consisted of sun, sand, sea, the occasional baguette and plenty of sunblock. Our wallets were considerably lighter—a 600 ml Coke cost around $6.00 and a Big Mac around $20. The language barrier was also a challenging experience! In summary, LAGOON MINEX 2009 was a busy, eventful and hot exercise which allowed for some good training opportunities.
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