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As
we handed our cameras into the Zodiac and hauled ourselves
inboard my thoughts went over the excellent dive we had just
made. Depth 12m, no current, viz 10m+, temp. 15°C and
shoals of pollock, bib and pouting.
My
younger companion as usual started the questioning. What was
a Mulberry Harbour, how large is it, how did it come to be
there off Pagham, Sussex?
For
the answers you must look back to World War II when the invasion
of Europe was being planned. The idea was to build large floating
caissons in England at various suitable sites around the coast
and then tow them across to the coast of Normandy and use
them to make a large artificial harbour and so allow the allied
forces to bring men and stores ashore. One has to remember
the area of the invasion had no natural harbour, only miles
of sandy beaches, which were useless to land this vast amount
of men and materials upon. So a prefabricated harbour was
designed and built to overcome the problem.
The
"Far Mulberry" as we know it, was classified as
an "A1 Caisson", eighty were manufactured, they
were 60 ft high, 204 ft in length, 50 ft 3 in wide and had
a displacement of 6044 tons. Draft 20 ft 3 in. The internal
walls were 9 in thick with an external wall size of 15 in.
The
A1 units also had Bofars anti-aircraft guns mounted on steel
towers located almost mid-ships and carried a gun crew and
12 tons of ammunition from the time they were towed away from
the construction berth. When in position the harbours were
at all stages protected by a formidable array of guns at approximately
200 ft spacing all around the outer perimeter, barrage balloons
were also flown from the caissons for added protection.
The
caissons when fabricated and completed were then towed by
tugs to special "waiting parks". Each unit was designed
to enable it to be gently sunk in shallow water and then when
ready for the tow across the Channel, to be re-floated by
simply blowing the internal tanks by means of valves.
Our
one, the "Far Mulberry" had been in rather deeper
water than originally intended, so It was decided to re-float
it and move it into a shallower position ready for a quick
salvage for D-Day, but owing to a misunderstanding, the necessary
tugs were not on hand to take charge when it came afloat and
the flooding valves were re-opened to allow it to settle on
the sea bed again. Unfortunately the caisson had swung round
whilst afloat and it was forced to settle down again diagonally
over a deep depression it had made on the sea bed. It immediately
twisted and cracked beyond repair.
The
unit remained here until early 1945 when it was finished off
by the Royal Air Force in practise bombing runs and that is
the position it now lies in some two nautical miles off Pagham
Beach in 12m of water.
When
you next dive the "Far Mulberry" you will know a
little more of this fascinating wreck and how it came to be
there and when those inevitable questions start from the new
divers who explore these old remains, at least you can give
them a brief history of Caisson Type A1.
If
anyone has any photographs or other facts on this Mulberry
section, I would be pleased to hear from them.
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