Soil remediation standards and site-specific risk assessment
The methodology for site specific risk assessment is based on the approach followed to derive soil remediation standards. A generic approach is followed for the derivation of sol remediation standards, while for site-specific risk assessments certain parameters, such as soil properties, can be adjusted.
Setting of soil remediation standards
Soil remediation standards are based on the protection of human health and on the protection of the ecosystem. Critical values for concentration in the soil are calculated based on human toxicology and others based on ecotoxicology. The most critical value is retained as soil remediation standard.
The methodology for deriving soil remediation standards based on human health is described in the document 'Basic information for risk assessment', and is named VLIERHUMAAN. This methodology takes also, rudimentarily, the risks for leaching of contaminants to the groundwater into account.
To derive soil remediation standards base on ecotoxicology, selected and relevant ecotoxdata are put into a cumulative species distribution curve. From this curve an ecotox-based standard is derived for a set protection level.
So far, only for heavy metals soil remediation are derived, using this methodology. For organic contaminants, not enough reliable ecotoxdata were available at the time when soil remediation values were derived.
Soil remediation standards for groundwater represent drinking water quality.
About every 10 years soil remediation standards are revised to take into account new research findings.
Descriptive soil investigation
Consultants, who perform soil investigations under the Decree on Soil Remediation have to be recognised by OVAM. Their recognition states that they must dispose of a groundwater model and a recognised risk assessment model.
Since the end of 1997, there is one recognised risk assessment model, called VLIERHUMAAN (Flemish Instrument for the Evaluation of Human Risks). The Dutch Van Hall Institute produces the commercial version of this model . It consists of the formulas and of the parameter values of the model used for the calculation of the soil remediation values and is adapted to the Flemish situation. Comparable models are HESP en C-Soil. Recognition of this one model does not implicate at the moment that other models can not be used anymore, but in that case it will take more time in the evaluation of the descriptive soil investigation. Other models can also receive recognition by OVAM after evaluation.
The use of recognised models does not guarantee a qualitatively satisfying descriptive soil investigation. For that reason a protocol for descriptive soil investigation has been written. The approval of this protocol is in its final phase. The protocol does not aim to give a stringent frame within which each step of the discriptive soil investigation is clearly described. It is more seen as a guidance to guarantee minimal quality and give in the same time the consultant the opportunity to use its own expertise in conducting the investigation. The protocol consists of two main parts:
- site investigation strategies;
- risk assessment