Contaminated sediments
The Swedish Environmental Protection Agency provides guidance on certain aspects of working with contaminated sediments on a national scale, where issues and methods differ between contaminated sites on land and in sediment. The Swedish EPA is also responsible for coordinating, prioritising, and following up on the remediation of contaminated sediments on a national level.
Sediment is essential to aquatic ecosystems, providing habitat for bottom-dwelling species, yet sediments in many of Sweden’s lakes, rivers, and marine environments are highly polluted. Pollutants from industrial and municipal discharges, as well as urban and agricultural runoff, can accumulate in the sediments and affect the aquatic environment. The pollutants can be taken up by benthic organisms and be transported up the food chain, potentially reaching levels that affect human health.
Responsibility for contaminated sediment sites
Several actors are involved in the management of contaminated sediments in Sweden, each with specific responsibilities. Key authorities—the Swedish Environmental Protection Agency (EPA), Swedish Geotechnical Institute, Geological Survey of Sweden, Swedish Agency for Marine and Water Management, and County Administrative Boards—are working together to improve guidance to reduce sediment pollution. The County Administrative Boards together with the municipalities are responsible for controlling ongoing industries that they comply with the Environmental Code and other regulations.
The Swedish EPA plays a central role by distributing state grants for sediment remediation in sea, lake, and river environments to the County administrations, as well as providing guidance on how to assess and remediate contaminated areas. The work to remediate contaminated sediments follows the same principles as those used for contaminated land, primarily guided by chapter 10 in the Environmental Code, although additional legislation related to sediment may also apply.
Since the 1990s Sweden has investigated contaminated land sites, with the premise that the polluter pays. For contaminated sediment sites the assessment of liability for pollution follows the same principles, but different issues may arise than on land due to the dispersion conditions in water areas. Special circumstances may exist for the inventory, risk assessment and source tracing as well as when investigating property boundaries and distribution of responsibility.
Guidance on liability investigations is provided on the Swedish EPA's website and on the EBH portal, which is managed by the County Administrative Boards.
More information about contaminated sediments is also available on a platform run by the County Administrative Boards in collaboration with several other authorities:
Environmental quality standards and water management
Environmental quality standards for water and the status of Swedish water bodies according to HVMFS 2019:25 can be used as tools for inventorying contaminated sediments and for prioritising work with contaminated sites both on land and in water. These binding standards cover surface waters (lakes, streams, coastal waters) and groundwater, and aim for water bodies to achieve "good status".
Water body status is influenced by chemical, ecological, and quantitative factors. To achieve good status, pollution from both specific sources (such as contaminated land and sediment sites) and diffuse sources (such as agricultural runoff and air emissions) must often be addressed. The status of each water body is reported on the website viss.lansstyrelsen.se and guidance on water management is given by the Swedish Agency for Marine and Water Management.
The Swedish Agency for Marine and Water Management provides guidance on water management as well as water operations such as dredging and handling of dredged masses, dumping of dredged masses and environmental quality standards for surface water.
Environmental quality standards for surface water (havochvatten.se)
Inventory and priorities
Contaminated sediments are widespread in Sweden and identifying and prioritising sites for further investigation is essential. Prioritisation for remedial measures follows the same principles as for contaminated land, focusing on acute risks to human health and the environment, if there are important objects for protection at the site or if there is an unacceptably high dispersion of prioritised substances from the site.
More information on the sediment inventory process can be found in this document:
Studies and investigations
Many hazardous pollutants can accumulate in sediments and come from various pollution sources. Inventories enable the identification of sediment sites with associated sources that need to be prioritised for further studies and possible measures.
Investigations are needed to assess the risks associated with the contaminants, their dispersion pathways, the sensitivity of the area and necessary actions.
The Swedish EPA provides guidance on questions related to contaminated sites in general and on environmentally hazardous activities that may be relevant, for example, when handling dredged masses on land.
Contaminated sites (naturvardsverket.se)
Waste guidelines (naturvardsverket.se)
Undersökningsportalen (translated: The Investigation Portal) run by the Swedish Geotechnical Society, offers support and information on investigating contaminated sites, including separate information on sediments.
Undersökningsportalen (in Swedish) (fororenadeomraden.se)
Investigations and remediation of contaminated sediments also require knowledge of conditions and applicable methods for aquatic environments. A platform with further links to websites related to sediments is the website renasediment.se.
Risk assessment
The purpose of risk assessment in remediation is to evaluate risks and determine the necessary reductions to protect the environment, health, and natural resources for current and future generations.
The risk assessment is based on the Swedish EPA’s basic assumptions for contaminated sites, including sediments, with a focus on protecting human health and the environment. Pollution dispersion should not raise background levels or risk contaminating groundwater and surface water. The risk assessment helps determine appropriate actions and measurable targets for remediation.
Risk assessments may also be needed when contaminated sediments are affected during activities like dredging, even if the primary purpose is not remediation. The assessment helps evaluate risks of pollution spread and necessary protective measures.
Several factors must be considered when assessing risks at sediment sites, including levels of various substances, bioavailability, and dispersion potential.
Assessment criteria
Assessment criteria help assess the level of contamination in sediments. Assessments can have different purposes. For example, to assess whether the contaminated site affects the status in a surface water body according to the Water Management Ordinance (VFF) and HVMFS 2019:25 (water management), or to determine if the site should be classified as contaminated under Chapter 10 of the Environmental Code based on collected data.
When presenting the results, it’s important to clarify the purpose of the assessment and its intended use.
Effect-based and indicative threshold values as support
Effect-based threshold values help assess the risks at sediment sites. Sweden has threshold values for certain priority substances (anthracene, fluoranthene, cadmium, lead, and tributyltin) in sediments for assessing chemical status, as listed in regulation HVMFS 2019:25 from the Swedish Agency for Marine and Water Management. There are also criteria for river basin specific pollutants (siloxanes D4 and D5, and copper) in sediment used in assessing ecological status.
The Swedish Agency for Marine and Water Management also provides indicative values for certain substances. See report 2018:31 for values that indicate where follow-up investigations may be needed, such as for identifying significant sources.
Reference values for metals and organic contaminants in sediment
The Swedish EPA and the Geological Survey of Sweden have produced tables presenting the distribution of metal and organic contaminant levels in Swedish marine sediments and metal levels in lake sediments. These values are intended for comparative purposes only, such as determining whether contaminant levels are above national background levels. Classification with these values does not automatically indicate environmental damage.
Tables with the levels divided into five classes can be found in a report from the Swedish Geotechnical Institute on background levels in sediment (in Swedish):
Bakgrundshalter i sediment (DiVa)
Please note that the general threshold values for soil are not suitable for use when evaluating sediment data.
Choosing remedial action
Sediment is part of the water environment and is partly also covered by other regulations and environmental and sustainability goals than what applies on land. When designing overall and measurable goals for remedial measures, it is important to take this into account.
Remediation methods for contaminated sediments differ from those for soil. Site conditions, such as water depth, bottom slope, objects, and contaminant dispersion, must be thoroughly investigated, as they strongly influence the choice of method. Current and future land use also affects the choice and necessity of measures.
Ongoing emissions from contaminated land sites and ongoing economical operations need to be addressed first, before any remedial actions are performed within the contaminated sediment site. In many cases it is beneficial to combine different methods to achieve the remedial goals.
Åtgärdsportalen (translated: “the Measures Portal) run by the Swedish Geotechnical Society offers further information on remediation methods for sediment sites.
Support and regular guidance
The Swedish EPA, the Geological Survey of Sweden, and the Swedish Agency for Marine and Water Management are regularly consulted by supervisory authorities and other stakeholders on contaminated sediments, following each authority's specific routines. SGI also provides expert support funded by the remediation budget.