New knowledge assures clean harbours

Four years of intensive research are now yielding results. New cleansing methods may lead to Norwegian harbours soon being awarded a clean bill of health.

"The best solution, to put it bluntly, is to let the contaminants stay where they are as far as possible. We achieve nothing by transferring contaminants to somebody else's backyard," says technical expert and project manager Gijs Breedveld at NGI.

Norwegian seafood contains mercury, PCBs, cadmium and lead from earlier industrial activities. The amount of toxin seafood can contain before it is regarded as a health hazard depends on how dangerous the toxins are and the quantities consumed, according to the Norwegian Food Safety Authority. Polluted seabeds are a problem in more than 100 harbour and fjord areas along the Norwegian coast, and in 31 areas the situation is so serious that the authority warns people against eating fish and shellfish from these areas too often.

"What should we actually do with polluted sediment on harbour floors or further out in the fjord? Relatively little was known about this field in 2003 when the Research Council of Norway funded the project 'Stability of polluted sediments'", relates Breedveld.

The project will not finish until spring 2008, but it is already possible to draw some conclusions.

"There is a limit to how far it is environmentally defensible to transport large quantities of sediment, because the transport itself can cause larger emissions of environmentally harmful substances than there were initially," says Breedveld.

Another conclusion is that each contaminant is unique, and that customised solutions should therefore be developed for each and every harbour and fjord area that is polluted. There are no standard solutions that can be used in all harbours and fjords in Norway.

"We have also learnt not to use more 'artillery' than necessary to solve a local pollution problem. They key phrase is environmental efficiency, which means that we mustn't solve the pollution problem in a way that creates even more pollution,"explains Breedveld. "This applies, for example, to incineration, which is both highly energy-intensive and results in emissions to the air," adds chartered engineer Magnus Sparrevik at NGI.

In the report 'Working together for a toxin-free environment' which was presented to the Storting (Norwegian parliament) in 2006, the government singled out 17 areas where it is really urgent to get to grips with problems. In a number of the areas, such as Oslo and Hammerfest harbours, action is already under way, in some cases with enthusiastic public involvement.

The report to the Storting establishes that `existing pollutants in the ground or under water shall be prevented from dispersing further or from being taken up by plants, animals or humans'.

"This is a very good formulation. Contaminants are not actually a problem if they do not come into contact with living organisms, and in some cases this is best achieved by allowing contaminants to remain undisturbed and if relevant to cover them with unpolluted material, so that the environmental toxins do not diffuse into the water. But if local conditions indicate that this is not possible, the polluted layers must be dredged and deposited elsewhere. Then we have to be aware that the dredging process itself will cause some spreading," explains Breedveld.

These methods are already being used in a number of projects, including Oslo harbour and the northern town of Hammerfest. The Oslo harbour project involves dredging layers from the seabed and depositing them in deep water further up the fjord, while the Hammerfest project involves dredging the seabed layers, mixing them with cement and using the mixture to make a new foundation for a civic centre on the edge of the sea.

Ranfjord represents another ingenious solution. The floor of the fjord is severely polluted after many years of heavy industry discharges. Meanwhile, in the same area Rana Gruber is discharging substantial quantities of particles from its production of raw materials for the metal and pigment industry.

"The instinctive reaction would be to order removal of the polluted sediments and to tighten up the requirements concerning manufacturing discharges, but in fact the new discharges consist only of stone particles that do not contain environmental toxins. They actually function as a 'free' cover for the polluted sediments, and receive special mention in the action plan for Ranfjord. This is a revolutionary approach," explains Sparrevik.

NGI has a separate Environmental Technology Department with expertise in mapping and the planning of measures to deal with polluted marine sediments. We help with sampling and laboratory testing of polluted sediments, risk and impact analyses of existing pollution, and in developing and engineering plans of action. We also develop methods for monitoring and surveillance of the environment.