‘MOUTH OF THE SHATT AL ARAB RIVER’ [‎237r] (1/4)

(24) Tlie material composing tire bar is of a nature and consistency that can
very well be dealt with by a suction pump dredger, and of this class there are three
principal -types
(i) The bow well suction dredger built with or without a cutter, discharging
its spoil through a pipe-hue, and usually self-propelling.
(ii) The self-propelling bow well suction hopper dredger, built either with
or without rotary cutter.
(in) The self-propelling stern well drag suction hopper dredger.
The following is a more detailed description of these machines:—
( 1 ) A pipe-line dredger is admirably adapted for reclamation wofk or for
work in a river where the spoil can be deposited behind a bund, or
otherwise clear of the current, but would not be suitable in a sea-way,
because, apart from the difficulty of pumping the material dredged
far enough from the channel, a sudden storm would break up the pipe
line before there was time to make it secure.
The dredgers “ Kalu ” and “ Jinga ” built for the Bombay Port Reclamation
Works, the “ Oswald ” built for the Twante Canal Works in Burma and
now at work in Mesopotamia, and the dredger 4 Pelican built for
the Rangoon River Training Works, are all good types of the modern
powerful pipe-line suction dredger.
( 2 ) A self-propelling bow well suction dredger is a type which is largely used
for work on sea and river bars, and in combination with a rotary
cutter is especially efficient in the cutting of clay and hard silt, but in
soft silt and sand a drag suction dredger is, in my judgment and from
actual experience, the more suitable machine, because the bow
suction dredger works against head moorings entailing considerable
loss of time in mooring and un-mooring, is liable to dredge in pockets,
and to form lumps from overside spill.
The dredger “ Balari ” built for the Calcutta Port Commissioners is a very
•fine specimen of a modern vessel of this class ; she carries 3,000 tons
of spoil in her hoppers, and dredges at the rate of 5,000 tons of sand
and silt per hour : but I think it is recognised that for the work she is
doing on the river Hooghly, a drag suction dredger would be more
efficient.
( 3 ) A stern well drag suction, or, as it is sometimes called, trailing suction
dredger, is a comparatively modern invention. The vessel has no
moorings, and when working steams slowly ahead dragging behind her
the suction head. So soon as the hopper is full, there is no delay in
un-mooring : the suction head is lifted and the dredger steams off to
the dumping ground, and after depositing her load returns to her
work.
The dredger “ Cormorant ” belonging to the Rangoon Port Commissioners
and recently at work on the Fao bar, is a good type of this class of
dredger ; and more powerful ones, are those built for the Argentine
Grovernment to dredge the shipping channel from the river Plate to
the Buenos Ayres docks.
As an experimental measure, the dredger Cormorant already referred to,
was procured from Rangoon and set to work on the Bar in the month of July 1916,
and between that date and April 1917, she did most useful work removing
some 400,000 tons of material and reducing the Bar by one foot to 18 inches :