3 Trends and initiatives in
3.5 Contaminated sediments in
3.5.2 Which areas are polluted?
Classification of different types of areas
A number of surveys of the levels of pollution in sediments have been carried out in Norway (cf.
Report 98:11 from the Norwegian Pollution Control Figure 3.10 Areas which are the subject of dietary advice or restrictions. These are areas where the con-tent of environmental pollutants is so high that the food authorities have introduced bans on the sale of fish and shellfish and/or given advice on the upper consumption limit.
Source: Statens næringsmiddeltilsyn/Statens forurensningstilsyn (Norwegian Food Control Authority/Norwegian Pollution Control Authority)
Harstad
Tromsø
Hammerfest
Honningsvåg
Hommelvik
Ramsund
Stavanger Sandnes
Flekkefjord
Farsund
Arendal
Ranfjorden
Sunndalsfjorden
Årdalsfjorden Bergensfjorden
Sørfjorden Karmsundet
Eidsbotn
Vefsfjorden
Saudafjorden
Fedafjorden
Kristiansandsfjorden Tvedestrandsfjorden
Grenlandsfjorden Sandefjordsfjorden
Drammensfjorden Oslofjorden
Existing dietary advice PCB
PAH Dioxins Metals
Authority). These surveys have revealed high con-centrations of environmental pollutants in sedi-ments more or less everywhere in the vicinity of industrial sites and densely populated areas. Alto-gether, the Norwegian Pollution Control Autho-rity’s surveys have revealed high concentrations of hazardous substances in more than 100 areas.
Different types of areas require different reme-dies and initiatives depending upon the size of the polluted area, the damage being done by the hazar-dous substances in the area, the degree to which the pollutants are migrating to other areas, the technical solutions most suitable for the area and whether the liability picture is clear. This report therefore attempts a breakdown into four catego-ries (cf. Box 3.3). The purpose of the subdivision is to simplify assessment of the different measures
and means described in this report, but the catego-ries are not sufficiently precise to constitute a new tool for use in further work on contaminated sedi-ments.
A characteristic of high-risk areas is very high concentrations of environmental pollutants within a fairly small, restricted area. Often just one or a small number of activities are responsible for the pollution and therefore the sources of the pro-blems are more often known in such areas than in larger problem areas. The high concentrations of environmental pollutants mean that there is a con-siderable danger of them spreading to new areas, even though the risk of migration varies from one area to another depending on natural conditions and the degree of human influence. Surveys con-ducted have revealed about 35 high-risk areas, 15–
20 of which are believed to entail a danger of migra-tion, although it is emphasised that the figures are not certain. The large number of point sources which can be assumed to have possibly caused this type of pollution indicates that the number of high-risk areas may be significantly higher than the sur-veys conducted to date have been able to uncover.
Port areas often suffer from extremely high concentrations of environmental pollutants, but are often larger than the areas classified as «high risk».
Further, pollution problems are often more com-plex. In addition to actual port activities and ship-ping, industrial discharges and more diffuse dis-Box 3.2 Dietary advice and restrictions
on sales
In areas where fish and shellfish contain high concentrations of hazardous substances the Norwegian Food Control Authority has provi-ded advice on limiting intake of fish and shell-fish (dietary advice) and has introduced restrictions on the sale of fish from the area.
Dietary advice is today being provided in 26 ports and fjord areas in Norway. The extent of the advice varies from area to area. In most of the areas it simply amounts to advising against the consumption of fish liver and/or mussels, but in a few areas the advice is to avoid eating fish at all. People in a number of these areas are further advised to avoid eating shellfish. In one of the areas people are advised not to eat it more than once a week, while in the other areas they are advised not to eat it at all. Sales restrictions have also been introduced in five of the areas. The total area for which dietary advice is provided was reduced from 1 008 km2 in 1991 to around 840 km2 in 2001 mainly as a consequence of reduced discharges from industry. Neverthe-less, dietary advice was introduced in three new areas in 2001 on the basis of results from surveys carried out in areas, which had not previously been the subject of study. It is expected that the number of areas for which dietary advice is given will increase since more areas are now under investigation.
Box 3.3 Categories of problem areas – High-risk areas: Smaller areas, high
con-centrations of environmental pollutants, often with a risk of migration and a small number of bodies responsible.
– Ports: Medium-sized areas, relatively high concentrations, risk of migration, large number of polluters, but a single body responsible for the area (the port autho-rity).
– Entire areas of coast or fjords: Large areas, varying concentrations (including areas with high-risk zones and ports), minor risk of migration out of the area, large number of polluters.
– Industrial fjords: Special cases in fjords.
Large areas, high concentrations, small number of polluters.
Figure 3.11 Areas with contaminated sediments already mapped. Areas with contaminated sediments are divided into categories high-risk areas, port areas, whole coastal and fjord areas and industrial fjords, on the basis of the size of the areas, the pollution concentrations, the risk of migration and the number of polluters. (cf. Box 3.3 Categories of problem areas). The information on the areas is very approximate.
Source: Statens forurensningstilsyn (Norwegian Pollution Control Authority)
Oslo
High risk areas Port areas
Whole coastal and fjord areas Industrial fjords
Oslo Trondheim
Bergen
charges from towns or other densely populated areas certainly add to the high pollution levels.
Ports constitute a special problem because port traffic leads to the spread of environmental polluta-nts as a result of eddies in sedimepolluta-nts caused by propellers. Streams and rivers often carry sedi-ments to the port area. Quite apart from the need for clean up operations because of pollution, many ports need continuous dredging (removal of mas-ses of loose material from the seabed) in order to keep the shipping lanes open. Up to now, heavily contaminated sediments have been recorded in approximately 36 port areas in Norway, 15–20 of which are judged to entail a risk of migration. Die-tary advice has been given in 14 of these areas.
A number of fjords and coastal areas have high levels of environmental pollutants in sediments across their entire area. These areas feature a com-plex pollution picture involving many types of pol-lution and sources. Concentrations of environmen-tal pollutants vary both between and within areas.
A fjord can contain both what are classified as high-risk areas, ports and areas with lower levels of envi-ronmental pollutants. The inner fjords close to towns and other densely populated areas typically show a more complex pattern of pollution from a wider range of sources than the outer fjord areas where pollution problems are more often associa-ted with a single source. Surveys already con-ducted have revealed heavily contaminated sedi-ments in approximately 20 coastal and fjord areas
Box 3.4 Current cleanup measures When all discharges have been stopped natural
sedimentation will cause pollutants to be covered with clean material. However, under Norwegian conditions it will take 50–100 years to establish sufficient new cover and eddies or biological activity can also disrupt the process.
This is therefore not considered sufficient in most areas.
Covering up creates a physical barrier, which prevents environmentally hazardous substances from leaking out and organisms from coming into contact with the contaminants. This is an approach, which has been pursued in Eitrems-vågen and may be used in other places.
However, this procedure is not suitable for shal-low areas where the seabed is affected by ship-ping or physical intervention. Covering over is a fairly acceptable solution, but reuires supervi-sion during and after the work.
Contaminated sediments can be treated in situ whereby the hazardous substances are conver-ted into less harmful substances and the toxic materials rendered less accessible. Experience of this treatment is meagre and the methods available are considered to have major limita-tions given the technologies on offer today.
Removal of the contaminated material on the seabed may solve the problem in the area con-cerned, but in this case the large quantities of material must either be treated or disposed of in an acceptable manner.
Untreated, contaminated material requires spe-cial disposal measures. Up to now dumping of such sediments has been rare, mainly because it is difficult to find suitable landfill areas for it.
Dumping of large amounts of material in land-fills is also costly.
Disposal in shoreline landfills involves dum-ping the contaminated material in a closed area of sea close to land. A number of such dumps have been established in Norway, one of them being in Haakonsvern. These dumps have to be monitored and restrictions have to be introdu-ced with regard to use of the area. The scope for creating such dumps depends on local condi-tions. Costs also vary depending on the barriers that need to be used and on the quality we want to achieve in the area being used.
In Norway we have many fjords which con-tain relatively deep basins often with oxygen-free water at the bottom and absence of life on the bed and in the masses of water closest to it.
These basins may be suitable for dumping of contaminated materials. The disadvantage is that they may be difficult to check on and will need to be monitored for a long time to come.
Further, renewal of the water and changes in the water quality can mean that the environ-mentally toxic substances become more acces-sible to marine organisms.
Treating contaminated sediments is a labori-ous and costly process. Such material requires special measures because the contaminants contain many different particle sizes and there-fore need several stages of treatment.
in addition to the port areas and high-risk areas referred to above.
Features of the fjords described as «industrial»
are that they have one or more industries as the main source of pollution problems throughout the fjord and that the pollution picture is relatively uni-form. In these areas the activity responsible for the pollution is often known. Today there are 14 indus-trial fjords, which are seriously affected by environ-mental pollutants.
3.5.3 Special challenges associated with