15.1.1 All
spoil spaces are to be arranged to allow the safe and efficient overboard
discharge of excess water in all weather conditions in which the ship
is classed to operate. In ships over 90 m in length and in all ships
classed for unrestricted service the spoil space overflows are to
be arranged via enclosed overflow trunks so designed as to keep the
decks of the ship clear of spoil and water.
15.1.2 In
general, bulwarks are not to be fitted in way of open top spoil spaces
on dredging and reclamation craft.
15.1.3 Where
a ship operates at the maximum draught that could be assigned in accordance
with the International Convention on Load Lines, 1966,
the overflow arrangements fitted should ensure that when the spoil
space is loaded, this draught is not exceeded.
15.1.4 Where
a hopper dredger having releasing arrangements for cargo dumping,
e.g. bottom doors, etc. is permitted by an Administration to be assigned
a freeboard less than that which could be assigned by the International
Convention on Load Lines, 1966:
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The structural
strength and bending moments are to be acceptable for the deeper draught
indicated, and
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the dredger
is to be operated in a zone of operation and in such weather conditions
as are considered appropriate.
15.1.5 Adequate
arrangements are to be fitted to prevent overloading under any condition
of loading having due regard to trim. The size and position of the
overflows are to be confirmed by a loading trial, which is to be carried
out when the spoil space is loaded with dredgings of the same density
as is likely to be loaded in service.
15.1.6 The
cutting of overflow discharge trunk openings in the sheerstrake is
to be avoided wherever practicable. In ships over 70 m in length,
spoil space overflow discharge trunk openings are not to be cut within
800 mm of the upper edge of the sheerstrake. They are to have corner
radii of not less than 150 mm, and suitable compensation is to be
arranged. In no case is a discharge trunk to pierce the sheerstrake
in way of discontinuities such as breaks of superstructure.