1.1 The requirements of Annex
II apply to all ships carrying Noxious Liquid Substances in
bulk. Substances posing a threat of harm to the marine environment
are divided into three categories, X, Y and Z. Category X substances
are those posing the greatest threat to the marine environment, whilst
Category Z substances are those posing the smallest threat.
1.2
Annex II prohibits
the discharge into the sea of any effluent containing substances falling
under these categories, except when the discharge is made under conditions
which are specified in detail for each Category. These conditions
include, where applicable, such parameters as:
-
.1 the maximum quantity of substances per tank
which may be discharged into the sea;
-
.2 the speed of the ship during the discharge;
-
.3 the minimum distance from the nearest land
during discharge;
-
.4 the minimum depth of water at sea during discharge;
and
-
.5 the need to effect the discharge below the
waterline.
1.3 For certain sea areas identified as "special area" more
stringent discharge criteria apply. Under Annex
II the special area is the Antarctic area. In addition, under chapter 2 of
part II-A of the Polar Code, more stringent discharge criteria apply in Arctic
waters.
1.4
Annex II requires
that every ship is provided with pumping and piping arrangements to
ensure that each tank designated for the carriage of Category X, Y
and Z substances does not retain after unloading a quantity of residue
in excess of the quantity given in the Annex. For each tank intended
for the carriage of such substances an assessment of the residue quantity
has to be made. Only when the residue quantity as assessed is less
than the quantity prescribed by the Annex a tank may be approved for
the carriage of a Category X, Y or Z substances.
1.5 In addition to the conditions referred to
above, an important requirement contained in Annex
II is that the discharge operations of certain cargo residues
and certain tank cleaning and ventilation operations may only be carried
out in accordance with approved procedures and arrangements.
1.6 To enable the requirement of paragraph 1.5
to be met, this Manual contains in section
2 all particulars of the ship’s equipment and arrangements,
in section 3 operational
procedures for cargo unloading and tank stripping and in section 4 procedures for discharge
of cargo residues, tank washing, slops collection, ballasting and
deballasting as may be applicable to the substances the ship is certified
to carry.
1.7 By following the procedures as set out in
this Manual, it will be ensured that the ship complies with all relevant
requirements of Annex II to MARPOL
73/78.