Risk assessment of the contaminated site and assessing the need for remediation

When the investigation of soil or groundwater contamination is completed, a report on the work is prepared. The report presents the research results and assesses the contamination and risks of the area. The risk assessment examines whether the hazardous substances found can endanger or harm the environment or human health. 

In order to determine the level of contamination, the concentrations, total quantities and location of contaminants are examined in the soil of the area and, if necessary, in the groundwater and indoor air of buildings. The transformation and migration of substances are also assessed, and persons and organisms that may be exposed are charted. The risk assessment and assessing the need for remediation are based on this information.

Even if contaminants are found, they do not always pose a significant risk. Consequently, the risks and need for remediation are assessed on a case-by-case basis. The risk assessment shall take into account:

  1. concentrations, total quantities, properties, location and background concentrations of hazardous substances;
  2. soil and groundwater conditions in the area and the migration and spread of hazardous substances;
  3. current and planned use of the area and its environment or groundwater;
  4. potential for exposure to hazardous substances over a short and long period of time;
  5. the severity and likelihood of harm to the health or the environment as a result of exposure.
     

If hazardous substances found in soil or groundwater do not pose an environmental or health risk, they can be left unremediated. However, a need for measures to be taken or an obligation to monitor water may remain in place for the area. The Finnish Supervisory Agency (in Helsinki and Turku, the City) reviews the risk assessment and decides on the need for remediation and its objectives. If soil or groundwater is found to be contaminated and hazardous substances are estimated to cause harm or pose a hazard to the environment or health, it must be remediated.

Reference values support risk assessment and assessing the need for remediation

The environmental and health impacts of the contaminated area and the need for remediation are assessed on the basis of, for example, reference values laid down in legislation.

  • The reference values in the PIMA Decree (214/2007) are used to assess soil contamination. Risk assessment is also guided by the Environmental Administration Guideline Pilaantuneen maa-alueen riskinarviointi ja kestävä riskinhallinta (Risk assessment and sustainable risk management of contaminated land).
  • There are no guideline values for assessing groundwater contamination in Finland. Other regulations, such as environmental quality standards (Government Decree 341/2009) and quality requirements for domestic water, can be used in the assessment. 
  • Contamination of surface water can be assessed in relation to environmental quality standards for surface waters (Government Decree 1022/2006).

According to the PIMA Decree, soil contamination should be assessed if one or more pollutants exceed the threshold value or the natural background concentration of a given area. The need for remediation is assessed based on risks and makes use of two reference values defined for different pollutants:

  1. The lower guideline value applies to sensitive areas (residential or recreational). 
  2. The upper guideline value is applied, for example, in industrial areas.

What is meant by risk and harm?

Risk = Assessment of the nature and likelihood of harm to the health or environment

Risk assessment = Procedure for identifying, defining and describing harms and risks

Harm to health = A disease that can be diagnosed in people, other health disorders or the presence of a factor or circumstance that may impair the health of the population or an individual

Environmental harm = Ecological harm caused to nature and its functions; or a worsening of the quality of the environment

Source: Valtion tuki alueiden pilaantuneisuuden selvittämiseen ja pilaantuneiden alueiden puhdistamiseen - opas lainsäädännön soveltamiseen