Site remediation

In order to identify (potentially) contaminated sites information is compiled from sources such as municipal commercial registers. Soil sampling and measurements are not yet required at this state. The handling of environmentally hazardous substances or the treatment, storage or dumping of waste can indicate the presence of a (potentially) contaminated site.

This first survey is followed by a historical investigation. It is analysed if e.g. accidents or incidents occurred during site operation. The evaluation of maps, aerial photographs, interviews with contemporary witnesses and site inspections provide important information. In the subsequent initial assessment, the competent authority analyzes whether there are any indications of the existence of a contaminated site. The further management of (potentially) contaminated sites is prioritized in terms of time and risk.

The preliminary investigation leads to the decision whether a site is potentially contaminated or not. Technical investigation measures such as soil and groundwater sampling and the subsequent measurements provide further data and information. The indicative nature of the investigation is reflected in the effort involved (number of samples, investigation parameters). The results of the preliminary investigation are to be evaluated in particular on the basis of test values (see below).

The detailed investigation creates the data basis for the final risk assessment. It serves in particular to determine

• the quantity and spatial distribution of the pollutants,
• their mobile or mobilizable fractions,
• their potential for dispersion in soil, water and air and
• the possibility of their uptake by humans, animals and plants.

In addition, it should be determined whether the pollutants within a potentially contaminated site pose a risk and whether and how uncontaminated areas need to be protected. The results of the detailed investigation must be evaluated, taking into account the circumstances of the individual site, to determine which hazard prevention measures are required.

With the final risk assessment, the competent authority determines whether a site is contaminated or not. By law, measures must be taken for sites that are found to be contaminated. As each specific site has specific framework conditions (such as geological and hydrogeological characteristics of the site, type and extent of damage, relevance of the subjects of protection), the BBodSchV does not contain threshold values that indicate a general obligation to remediate, nor target values for remediation. Instead, the competent authorities are granted considerable discretionary powers.

The sequence of the various investigation and assessment steps in the treatment of contaminated sites must always take into account the circumstances of the individual site. If, for example, already the preliminary investigation shows that a final risk assessment is possible, the competent authority can decide that no further investigation steps are required. It then determines directly whether a contaminated site exists or not. 

The remediation investigation includes a comparative examination of possible hazard prevention measures. The technical and administrative measures (or combinations thereof) must always be adapted to the respective site conditions, pollutant properties, land use, affected subjects of protection and impact paths. They must be suitable, necessary and appropriate. When deciding on remediation measures or safety measures, natural attenuation should also be taken into account.

Contaminated sites as well as resulting contamination of water bodies must be remediated in such a way that no hazards, significant disadvantages or substantial harm arise for individuals or the general public in the long term. Various remediation measures can be considered for the prevention of hazards. Their selection depends on

• the resources to be protected
• the current and future use (permitted under planning law),
• the geological, hydrogeological and hydraulic site conditions,
• the pollutant properties,
• the relevant transfer/ exposure pathways.

Followup measures are always required if long-term maintenance of the remediation structures and facilities and/or monitoring of the exposure pathways is necessary after remediation. This may be due to residual pollutants.

In accordance with the "perpetrator principle", it is determined who must carry out remediation measures. The polluter, his legal successor, the landowner and the holder of actual control over the land are responsible. The obligation to bear the costs, on the other hand, is based on the polluter pays principle. In practice, this often poses a considerable problem, as the actual polluter often cannot be identified or cannot (or can no longer) be made to bear the costs. Depending on the measure or combination of measures, the financial and time expenditure required to achieve the remediation targets set by the authorities, including any necessary aftercare, can vary considerably.

German legislation provides the follwing criteria for hazard assessment as well as rules for their application:

• Test and measurement values for soil-human exposure pathways (direct contact, different uses)
• Test and measurement values for soil-crop exposure pathways (in terms of crop quality, different uses)
• Test values for the assessment of soil-groundwater exposure pathways

If the test values for pollutants are exceeded, it can normally be assumed that the site is contaminated. In this case, a detailed investigation should be carried out. If the concentration of a pollutant is below the respective test value, it is concluded that the site is not contaminated (with regard to the respective pollutant) and no further investigations are required.

If action values are exceeded, the extent to which hazard prevention measures are required must be assessed, taking into account the circumstances of the individual case. The methods for determining test and measurement values under German law were published in Bundesanzeiger Nr. 161a of 28 August 1999 and in the UBA’s publication titled Berechnung von Prüfwerten zur Bewertung von Altlasten (Erich Schmidt Verlag, Berlin 1999). These methods should be used for determining other test and measurement values.