ANTHROPOGENIC IMPACTS ON THE DEEP SEA
435
should not, however, have any effects on man (Thiel
et al., 1998).
No scuttled munition ship seems to have been monitored adequately. Had this been done, knowledge of
impacts would not have remained merely hypothetical,
and one would have been able to evaluate the effects of
disposal of large structures such as are described in the
next section. Probably more is known than is officially
published; such information should be released and
made available for science and the public worldwide.
Offshore installations
Large structures like oil rigs have not been dumped
into the deep sea. During the summer of 1995, however,
the Brent Spar affair taxed the minds of many people
in Europe and world wide. The oil companies Shell
and Esso intended to decommission the oil storage
platform Brent Spar by disposal into the deep sea to the
northwest of Britain. The “Greenpeace” organization
demonstrated against this mode of decommissioning
by occupying the platform while it was still in place,
and later while it was being towed from the North
Sea into the Northeast Atlantic. The oil companies
and governmental agencies became aware that the deep
sea is not just a remote storage place, and that the
public can be mobilized to protect such little-known
environments. Finally dumping was abandoned, and
large compartments of the storage platform were used
for other purposes, such as harbour construction.
Brent Spar was one of the few platforms in the
North Sea which stored oil until it was transported
ashore. During storage, residues of hydrocarbons and
radioactive scale of low specific activity precipitated
in the tanks and on the pipe linings. These materials
are difficult to clean off. By contrast, all other offshore
installations are used for drilling and extracting oil;
they do not accumulate much residue and are easy to
clean. However, they produce drilling muds which will
contaminate the deep sea when oil extraction moves
down the continental slope; depths of 3000 m are the
target for the near future. Although in shallow waters
of the Gulf of Mexico some offshore installations have
been dismantled and used to create artificial reefs,
in many regions this is not useful, and certainly not
in the deep sea. According to recommendations of
the International Maritime Organization, most of the
platforms are to be totally removed and recycled, or
deposited on land. All platforms to be installed from
1998 should be constructed for total removal from the
sea. Thus, the number of large structures for which
deep-sea disposal may be proposed is small, and should
approach zero after one or two decades.
If an oil-storage structure like the Brent Spar had
been dumped to the west of northern Britain at a depth
of a few thousand metres, the impacts would have
been similar to that of a sunken ship or a scuttled
munition transporter: sediment disturbance around the
platform, the development and distant resettlement of
a plume, and chemical contamination, which might
start immediately through dissolution if the storage
tanks broke up on impact with the bottom, or might
be delayed if they slowly disintegrated by corrosion.
Dissolved substances would be carried downstream,
and since the dumping would have been near the
edge of the Exclusive Economic Zone, they would
certainly not have remained inside this imaginary
boundary but would have entered international waters.
It is not important in whose Exclusive Economic
Zone any material is dumped; the currents will mix
it together with contaminants from other sources,
and cumulatively over long periods of time effective
concentrations may be reached.
There is little that can be done to understand and
evaluate potential effects of the dumping of large
structures. However, if impacts of similar events like
sunken ships or scuttled munition transporters had
been investigated, some deductions would have been
possible. Since those opportunities have never been
used, one must rely on imagination as to what may
happen. To discuss the problems and controversial
disputes which arose during the Brent Spar affair, the
British Natural Environment Research Council (NERC)
asked an international group of oceanographers and
engineers to report on and evaluate the dumping of
offshore installations (Natural Environment Research
Council, 1996). Their recommendations included the
study of impacts from shipwrecks of known sinking
dates, from the dumping of radioactive wastes and
sewage sludge, or natural events like sediment slides.
Broad impact studies of known deep-sea uses and
of natural events could have helped in evaluating
dumping requests, and should do so in the future.
A comprehensive description and evaluation of the
Brent Spar event have been presented by Rice and
Owen (1998). Finally it was decided that much of
this storage platform should be recycled for various
applications.
Radioactive wastes
Nuclear waste products were deposited in the deep
sea of the Northeast Atlantic Ocean between 1949
435
should not, however, have any effects on man (Thiel
et al., 1998).
No scuttled munition ship seems to have been monitored adequately. Had this been done, knowledge of
impacts would not have remained merely hypothetical,
and one would have been able to evaluate the effects of
disposal of large structures such as are described in the
next section. Probably more is known than is officially
published; such information should be released and
made available for science and the public worldwide.
Offshore installations
Large structures like oil rigs have not been dumped
into the deep sea. During the summer of 1995, however,
the Brent Spar affair taxed the minds of many people
in Europe and world wide. The oil companies Shell
and Esso intended to decommission the oil storage
platform Brent Spar by disposal into the deep sea to the
northwest of Britain. The “Greenpeace” organization
demonstrated against this mode of decommissioning
by occupying the platform while it was still in place,
and later while it was being towed from the North
Sea into the Northeast Atlantic. The oil companies
and governmental agencies became aware that the deep
sea is not just a remote storage place, and that the
public can be mobilized to protect such little-known
environments. Finally dumping was abandoned, and
large compartments of the storage platform were used
for other purposes, such as harbour construction.
Brent Spar was one of the few platforms in the
North Sea which stored oil until it was transported
ashore. During storage, residues of hydrocarbons and
radioactive scale of low specific activity precipitated
in the tanks and on the pipe linings. These materials
are difficult to clean off. By contrast, all other offshore
installations are used for drilling and extracting oil;
they do not accumulate much residue and are easy to
clean. However, they produce drilling muds which will
contaminate the deep sea when oil extraction moves
down the continental slope; depths of 3000 m are the
target for the near future. Although in shallow waters
of the Gulf of Mexico some offshore installations have
been dismantled and used to create artificial reefs,
in many regions this is not useful, and certainly not
in the deep sea. According to recommendations of
the International Maritime Organization, most of the
platforms are to be totally removed and recycled, or
deposited on land. All platforms to be installed from
1998 should be constructed for total removal from the
sea. Thus, the number of large structures for which
deep-sea disposal may be proposed is small, and should
approach zero after one or two decades.
If an oil-storage structure like the Brent Spar had
been dumped to the west of northern Britain at a depth
of a few thousand metres, the impacts would have
been similar to that of a sunken ship or a scuttled
munition transporter: sediment disturbance around the
platform, the development and distant resettlement of
a plume, and chemical contamination, which might
start immediately through dissolution if the storage
tanks broke up on impact with the bottom, or might
be delayed if they slowly disintegrated by corrosion.
Dissolved substances would be carried downstream,
and since the dumping would have been near the
edge of the Exclusive Economic Zone, they would
certainly not have remained inside this imaginary
boundary but would have entered international waters.
It is not important in whose Exclusive Economic
Zone any material is dumped; the currents will mix
it together with contaminants from other sources,
and cumulatively over long periods of time effective
concentrations may be reached.
There is little that can be done to understand and
evaluate potential effects of the dumping of large
structures. However, if impacts of similar events like
sunken ships or scuttled munition transporters had
been investigated, some deductions would have been
possible. Since those opportunities have never been
used, one must rely on imagination as to what may
happen. To discuss the problems and controversial
disputes which arose during the Brent Spar affair, the
British Natural Environment Research Council (NERC)
asked an international group of oceanographers and
engineers to report on and evaluate the dumping of
offshore installations (Natural Environment Research
Council, 1996). Their recommendations included the
study of impacts from shipwrecks of known sinking
dates, from the dumping of radioactive wastes and
sewage sludge, or natural events like sediment slides.
Broad impact studies of known deep-sea uses and
of natural events could have helped in evaluating
dumping requests, and should do so in the future.
A comprehensive description and evaluation of the
Brent Spar event have been presented by Rice and
Owen (1998). Finally it was decided that much of
this storage platform should be recycled for various
applications.
Radioactive wastes
Nuclear waste products were deposited in the deep
sea of the Northeast Atlantic Ocean between 1949