Inventory of contaminated sediment
This page provides guidance on the first steps in the process of identifying and conducting an inventory of contaminated sediments.
Many hazardous pollutants can accumulate in sediments and come from many different pollution sources. Inventories enable identification of sediment sites with associated sources that need to be prioritised for further studies and possible measures.
This page is intended for
First and foremost, case officers at supervisory authorities who conduct inventories of potentially contaminated sediment sites. The guidance can also support others responsible for determining sources of pollution that risk spreading to sediments.
Useful information
The guidance is based on the inventory and prioritisation methodology developed within the Government Commission on Contaminated Sediments (RUFS). The various aspects of the methodology are briefly described.
Legislation
Environmental quality standards for water and the status of Swedish water bodies can be used as tools when identifying and conducting inventories of contaminated sediment sites and for setting priorities for further investigation of polluted sites both on land and in water.
Environmental quality standards for water include surface water (lakes, streams and coastal waters) and groundwater. The purpose of the standards is to ensure Sweden’s water quality. The standards are binding. An environmental quality standard for water describes the quality a Swedish water body is to have achieved at a specific point in time. The main rule is that all bodies of water are to achieve what, in water management, is called good status. A standard specifies a minimum permitted level. The total environmental impact on the body of water must not lead to reducing quality to below the status specified in the standard. The deterioration ban in the EU Water Framework Directive also stipulates that the status may not deteriorate or affect the possibility of improvement .
Factors that affect a body of water’s state, and thereby its status, include chemical, ecological and quantitative parameters. In many bodies of water, pollution sources with significant dispersal need to be addressed to be classified as having a good status. A pollution source can be ongoing economic operations and a polluted site (soil and sediment).
Other relevant regulations not dealt with here include :
Environmental quality standards for bathing waters (Swedish Agency for Marine and Water Management)
Introduction
Sediment is the basis of a healthy ecosystem and affects the animals and plants that live in water and the sediment. It is also an important basis for many different ecosystem services. Pollution accumulated in sediments can have a negative impact on different parts of the ecosystem and can also spread to other sediment areas and generate new polluted sites. Contaminants found in sediments can come from many different sources of pollution (ongoing inputs of pollution and previously contaminated sites) and can be added through different dispersion pathways (direct or diffuse releases).
The goal of conducting an inventory is to identify sediment sites with associated sources of pollution that need to be prioritised for further study and possible measures. Pollution sources contributing contaminants to sediments need to be prioritised for further investigation both in the supervision of ongoing economic operations and in the work with contaminated sites.
Guidance on the process for identifying sources, conducting inventories and investigating contaminated sediment sites
An inventory of contaminated sediment areas can be initiated in different ways. There may be suspected sources of contamination or a known contamination of sediments, which require determining the source of pollution and further investigation. High levels of pollution may also be found in fish or other biota, which requires conducting an inventory of potential pollution sources.
The process is similar the one for conducting an inventory of contaminated sites (link to English version) and consists of the following steps:
- Phase 0: Identification An initial desk study where potential sources of contamination are identified and assigned a sediment class (the potential to contaminate sediment).
- Prioritisation of pollution sources for Preliminary Survey (Phase 1).
- Phase 1: Preliminary Survey: This phase is an in-depth desk study. It aims to verify the potential sources of pollution.
- Prioritisation of pollution sources and sediment areas for Preliminary Site Investigation (Phase 2).
- Phase 2: Preliminary Site Investigation: A verifying field investigation is conducted to study whether the sediments are contaminated and to determine the extent of the pollution damage.
- Prioritisation of sediment sites for further study and risk assessment.
If the field investigation in Phase 2 reveals contaminated sediments and these may pose a risk to human health and the environment, the site should be prioritised for further investigation. The next step is to address the sources of pollution that release or disperse substances that can accumulate in the sediments. This can consist of a remedial measure for contaminated sites or a preventive measure that prevents the dispersal of pollution. This applies to both releases from ongoing economic operations and dispersal from contaminated sites on land and in water.
Phase 0: Identification
Identification means finding the pollution sources that can potentially lead to contamination of the sediments. Sources of contamination can include contaminated sites or ongoing operations, which can potentially disperse contaminants to the sediments.
For polluted sites, use the updated 2023 industry list to give a first indication of which industries could potentially have led to the spread of contaminants to the sediments.
Inventory of contaminated sites (including the industry list)
All objects included in the database with potential polluted areas (EBH-stödet) have been assigned a sediment class, and a GIS layer with these is available in the County Administrative Boards’ geodata catalogue.
Geodata catalogue (lansstyrelsen.se)
The potential of an industry to release contaminants that accumulate in sediments is described using a sediment class that uses one of four risk levels:
- Low
- Moderate
- High
- Very high
The purpose of the sediment classification is to label objects that have the greatest risk of dispersing and impacting sediments so that they can be prioritised for further study in the process. The prioritisation can be based on the industry list’s sediment classification and/or on local knowledge of known and potential sources of pollution that can be spread to and impact the sediments. Even the presence of industry-specific pollutants specified in the industry list can be used as prioritisation criteria in the next phase.
In the identification phase, bodies of water that have a high load of sediment-accumulating contaminants from many pollution sources must be identified. The total load from polluted sites is based on the sediment class found in the industry list. This analysis has already been conducted and is available in the County Administrative Boards’ geodata catalogue. The water bodies that have the highest overall load and the polluted sites and ongoing activities that affect the sediments in these bodies can be given priority for further study in Phase 1. When selecting which areas to prioritise for further study, include case officers working with water management and with supervision in the discussion. Also include the impact from ongoing economic operations in the assessment. Supporting material on the impact from ongoing economic operations is being jointly developed by the Swedish Environmental Protection Agency (Swedish EPA), Swedish Agency for Marine and Water Management and the County Administrative Boards within the framework for the project Full koll på våra vatten and within the Government commission SESAM (Sedimentsamverkan mellan myndigheter).
Data for Phase 0
A geographically linked database (GIS layer) have been produced, which can be used by County Administrative Boards to identify sediment areas. The GIS layer will be available in the County Administrative Boards’ geodata catalogue. A report on the identification and inventory methodology being published by SGI will describe the data in more detail and how it can be used.
The data consists of new parameters in the database with potential polluted areas (EBH-stödet) and various geographically linked data in the form of a GIS layer. The following data are available:
- Objects in the database with potential polluted areas with associated sediment class that indicate the industry’s risk of impact on sediment. This layer shows the objects that have a moderate, high and very high risk of impacting sediments.
- Cumulative load from all objects in the database located within a catchment area to the sediments of a body of water. This layer shows the potential cumulative load on the sediments from database objects located within each water body’s catchment. Loads from upstream areas are not included in this data.
GIS data on ongoing permitted environmentally hazardous activities (A and B operations) are available in the County Administrative Boards’ geodata catalogue (LST NikITa Permitted environmentally hazardous activates). Though this GIS data does not show an assessment of the potential load on sediments based on the industry’s risk, it can be used to assess the cumulative potential load.
Phase 1: Preliminary Survey
The identified potential pollution sources prioritised further from Phase 0 are to be inventoried to verify or disprove the potential impact on the sediments. A pollution source can be a polluted site or an ongoing activity for which the County Administrative Board or the municipality has supervisory responsibility. Phase 1: Preliminary Survey is in the form of a desk inventory, which is adapted according to whether there are ongoing operations or contaminated sites. The Swedish EPA recommends a site visit in this phase.
Ongoing economic operations
For a Phase 1: Preliminary Survey of an ongoing economic operations, information and documentation about the operation needs to be collected, including results from internal inspections, data from recipient controls, other relevant samplings and other relevant information. VISS include information from the impact analysis on priority substancesand river basin specific pollutants assessed to affect the body of water . It is also important to contact the County administrative boards to see if they have relevant material that are not available in VISS. If these substances have the potential to accumulate in sediments, they should be included in the assessment. Relevant information linked to what the operation produces and is permitted to release may be available from the operation’s environmental permit and to which matrices the releases occur.
The Swedish EPA’s supervisory guidance on which criteria a supervisory authority can refer to in the event of a request for re-examination of an operation’s permit is found here:
Assessing whether the requirements for environmentally hazardous activities are sufficient
When assessing and supervising an activity, it is possible to set requirements based on the general rules of consideration. Chapter 2, Section 8 of the Environmental Code states that a current or former operator or an operator that has taken measures resulting in damage or inconvenience is responsible for mitigating these until they cease.
General rules of consideration – Chapter 2 of the Environmental Code
In this context, the Swedish EPA chooses to highlight the importance of the fact that there may be unintentionally formed substances (e.g., dioxins and PAHs) that are not always included in the requirements of a permit or included in the internal inspection conducted by the economic operator . These substances are often found in the sediments and should be included in the inventory.
According to a survey by the Swedish Chemicals Agency, around 120 substances are produced and/or used on the Swedish market (2020) that may have negative impact on aquatic environments (Hazard statements H400, H410-413) and that potentially accumulate in sediments (Kow ≥3) when spread to aquatic environments. Only a few of these substances appear in permits or control programmes for ongoing economic operations. An industry list for ongoing operations based on the Swedish Chemicals Agency’s survey is being developed iwithin the projects “Full koll på våra vatten” and SESAM.
Contaminated sites
To verify the impact from a contaminated site (soil or sediment), data from already completed studies, measures and other relevant documentation need to be compiled. This can include studies on soil, groundwater, surface water and/or sediment in the relevant recipient(s). This data, together with site-specific conditions, are evaluated to verify if a contaminant source has the potential for dispersal assumed in Phase 0 or if the dispersal can be confirmed based on existing data. After the evaluation, the sediment class for the pollution source is updated in the database with potential polluted areas (EBH-stödet). If evidence is largely lacking, the object should not be de-prioritised if the potential risk is significant and other local knowledge confirms the potential for dispersal.
Information from Phase 1 linked to the specific object is added to the current objects in the database. In this step, a new sediment object is not created in the database unless the sediment contamination has already been confirmed.
In this phase, the preliminary classification made in Phase 0 is being verified. The pollution sources deemed to have the highest dispersal are further prioritised for the next phase. The water bodies that have the highest cumulative load from pollution sources are also prioritised for further investigation. There may be bodies of water with a very high load from individual sources, and these bodies can be prioritised for further investigation based on local information. The decisive factors for which pollution sources and water bodies are prioritised for further investigation can vary between different counties, and it is important not to prioritise too many pollution sources and water bodies as to make continued work unmanageable.
Upstream areas
Many sediment sites receive pollution from sources located upstream, in addition to the pollution sources located within the catchment area of the water body. This makes it also important to gather information on upstream sources of pollution.
Phase 2: Preliminary Site Investigation
The sources judged to have a high potential for dispersing pollution to sediments in the recipient water must be prioritised for a verifying field investigation. Even those water bodies with associated pollution sources judged to have the greatest load from multiple pollution sources are prioritised for a verifying field investigation. The verifying investigation is primarily intended to confirm whether the sediments are contaminated. The field investigation will also identify which pollutants have been added to the sediments as well as which point source contribute or may have contributed pollutants to the sediments.
An overall risk assessment is conducted to determine priorities for further investigations. The risk class will be added based on the measured pollution levels in the sediments as well as surrounding factors that affect the risk class such as sensitivity and protection levels (such as drinking water, protected areas).
The sediment class can also be verified for the pollution sources based on the results of the field investigation and updated in the database. The database is currently being updated to be able to handle sediment class and sediment objects. It is not yet clear how this will be accomplished.
When pollution damage in the sediment is confirmed, possible sources still dispersing pollution to the sediments, which can be both ongoing operations and/or contaminated sites (soil and sediment), need to be investigated and possibly remedied before the contaminated sediment area is remedied. Ongoing operations dispersing pollution to the sediments must be further prioritised for supervision where requirements for investigations and preventive measures must be set. Read more about this in the guidance on supervision as specified in the Environmental Code:
Supervision as specified in the Environmental Code
If a polluted site is determined as the source of pollution to the sediments, it is further prioritised for a closer investigation of the risk of dispersal and the need for preventive measures or remedial measures for the pollution damage. If there is a known economic operator, the supervisory authority can instruct the operator to investigate whether there is dispersal from the site.
The Swedish EPA wishes to highlight several factors that can influence prioritisation for further investigation.
- High natural values and risk of natural disasters, including from climate change
- Presence of highly hazardous substances
- Risk to human health and the environment
- Risk of bioaccumulation in the food web
- Risk of influencing the status of the body of water
- Spreading of hazardous substances to downstream areas
- Sensitive areas nearby
- Protective status of the water body, eg drinking water
Preventing dispersion to and from sediments
Information is needed on relevant contamination sources and dispersion pathways to enable prevention of continued dispersion of pollution to sediments. Dispersion pathways can include local releases to water, surface runoff, air emissions or stormwater and dispersion with groundwater from various operations.
With dispersion from an ongoing or historical operation, the supervisory authority should prioritise measures to prevent further dispersion. After a Phase 2 Sediment Inventory has been conducted, the supervisory authority should have a better grasp of which sources can contribute or have contributed to dispersing pollution to a confirmed contaminated sediment site. There are then a few different options for how the supervisory authority can proceed, depending on whether there are known responsible economic operators or not. The sediment site which is releasing contaminants should be prioritised for investigation of measures to prevent impact on downstream areas.
Investigation into liability
Before a Phase 2 Sediment Inventory, the extent is often unknown of the pollution damage and whether the sediment site needs to be prioritised further for investigation of risk and whether measures are needed.
If there are multiple potential sources, it is usually unknown or uncertain which of the potential pollution sources have contributed to the pollution damage in the sediments. In some cases, the initial field investigation can provide information that can be used to link pollution to current pollution sources. In more complicated cases, additional field investigation and source tracing may be required to enable linking the pollution damage to the source or sources. This information is important for investigating liability for the pollution damage.
Is there a responsible economic operator?
In cases where there is a responsible economic operator, the supervisory authority is to instruct the operator to investigate the dispersion from a pollution source and/or the contaminated site more closely to see if there is a need for measures.
Is there no responsible economic operator?
In cases where there is no responsible economic operator, the supervisory authority can prioritise which objects should be investigated further. In these cases, the Swedish EPA can provide government funding for investigations and possible remedial measures.
About this guidance
This guidance covers the steps for identifying and conducting an inventory (Phase 1 and 2) of contaminated sediments and potential contributing sources of contamination.
An identification and inventory method has been developed with the Government commission on contaminated sediments (final report January 2023 link). The methodology was developed by the Swedish EPA, the Swedish Geotechnical Institute (SGI), the Geological Survey of Sweden (SGU) and the water authorities and will be described in a report published by SGI. The methodology is summarised in this guidance and will be described in more detail in this report. This guidance will be updated as the methodology is revised and experience is gained. The guidance may also be expanded with the subsequent steps in the process.
Schematic view of how the work with contaminated sediments is divided into different steps from identification to measures. Identifying and inventorying contaminated sediments and potential contributing sources of pollution is the first step in investigating contaminated sediments before implementing necessary remedial measures.