224
A. NELSON-SMITH
single crossing, so appreciable quantities must be deposited on the
surface. Even outboard motors contribute a quantity of waste oil
which in open waters is insignificant but can accumulate appreciably
in enclosed bays, harbours and inland waters (English et al., 1963a,
196313 ; Dietrich, 1964).
B. Harbours and rnarine terminals
Many of the sources of oil spillage at sea, enumerated above, occur
equally in port. Collisions happen with the greatest frequency in
harbour approaches where the traffic is densest and other accidents
may be associated with docking activities-an unusual example is the
tanker ‘‘ Fina Norvege ”, which holed her forward fuel tanks with her
own anchor in Plymouth Sound (see Holme and Spooner, 1968).
Coastal tankers do not normally clean tanks at sea before taking on
ballast, but after a short period of separation in port much of the water
can nevertheless safely be discharged overboard and the small volume
of oily residues remaining can usually be accepted by shore facilities.
It is worth noting that in very enclosed docks, where the water is more
or less static, a series of small discharges containing 100p.p.m. of oil
or less can still lead to an appreciable concentration of oil in the
receiving water. Under still conditions this may trap silt and other
suspended matter and sink to the bottom, from which it is released to
rise to the surface again after the slightest disturbance (as, for instance,
in the Queen’s Dock, Swansea-Naylor, 1966).
Perhaps the commonest source of oil pollution from dry-cargo ships
in port is the process of bunkering with fuel oil. This is pumped through
flexible hoses which are liable to damage through wear or ship movement; an overlong one may fall between hull and jetty, becoming
kinked or crushed, whereas too short a hose may be snatched from its
couplings by sudden movements following the close passage of another
vessel. Precautions which should be taken are listed by the American
Merchant Marine Institute (1953). Unless each end of the hose is
blanked off as soon as it is disconnected, its remaining contents are
liable to drain out when it is hoisted ashore. Leakages can occur from
inlets and vents, especially if the tank overflows ; any deck spills will
reach the sea unless the scuppers are plugged. When the bunker-tank
has been used for water ballast, the sea-cock may have been left open ;
it is then possible for oil to be forced out beneath the hull, appearing as
a surface slick only at some distance from the ship. A good look-out
and efficient communication between pump and deck crews will avoid
or minimize the more obvious forms of spillage.
At oil terminals the same comments apply. With more pipes and
A. NELSON-SMITH
single crossing, so appreciable quantities must be deposited on the
surface. Even outboard motors contribute a quantity of waste oil
which in open waters is insignificant but can accumulate appreciably
in enclosed bays, harbours and inland waters (English et al., 1963a,
196313 ; Dietrich, 1964).
B. Harbours and rnarine terminals
Many of the sources of oil spillage at sea, enumerated above, occur
equally in port. Collisions happen with the greatest frequency in
harbour approaches where the traffic is densest and other accidents
may be associated with docking activities-an unusual example is the
tanker ‘‘ Fina Norvege ”, which holed her forward fuel tanks with her
own anchor in Plymouth Sound (see Holme and Spooner, 1968).
Coastal tankers do not normally clean tanks at sea before taking on
ballast, but after a short period of separation in port much of the water
can nevertheless safely be discharged overboard and the small volume
of oily residues remaining can usually be accepted by shore facilities.
It is worth noting that in very enclosed docks, where the water is more
or less static, a series of small discharges containing 100p.p.m. of oil
or less can still lead to an appreciable concentration of oil in the
receiving water. Under still conditions this may trap silt and other
suspended matter and sink to the bottom, from which it is released to
rise to the surface again after the slightest disturbance (as, for instance,
in the Queen’s Dock, Swansea-Naylor, 1966).
Perhaps the commonest source of oil pollution from dry-cargo ships
in port is the process of bunkering with fuel oil. This is pumped through
flexible hoses which are liable to damage through wear or ship movement; an overlong one may fall between hull and jetty, becoming
kinked or crushed, whereas too short a hose may be snatched from its
couplings by sudden movements following the close passage of another
vessel. Precautions which should be taken are listed by the American
Merchant Marine Institute (1953). Unless each end of the hose is
blanked off as soon as it is disconnected, its remaining contents are
liable to drain out when it is hoisted ashore. Leakages can occur from
inlets and vents, especially if the tank overflows ; any deck spills will
reach the sea unless the scuppers are plugged. When the bunker-tank
has been used for water ballast, the sea-cock may have been left open ;
it is then possible for oil to be forced out beneath the hull, appearing as
a surface slick only at some distance from the ship. A good look-out
and efficient communication between pump and deck crews will avoid
or minimize the more obvious forms of spillage.
At oil terminals the same comments apply. With more pipes and