In some cases, treatment of sites in which soil, soil gas or groundwater contamination was discovered is very complicated or not financial.
In these cases it is recommended to perform a risk assessment at the site, which will test the level of risk of the contamination for human health and for the environment and will present recommendations on how to manage the risk.
The risk assessment survey is performed according to the IRBCA methodology and with a designated mathematical model. This methodology is based on the American RBCA methodology written by the ASTM and has been modified to fit Israeli soil and groundwater characteristics.
The risk assessment includes several stages:
1. Preparation of a Conceptual Site Model (CSM) – site description, activities on and around the site, hydro-geological description of the site and its surroundings, soil structure, contaminated “hot spots” location and description of contaminants distribution in time and in space in the soil, the soil gas and in groundwater.
2. Building of an exposure model – receptors identification (all who might be harmed by the contamination, such as residents, workers, animals, plants) at the site and in its surrounding area and description of exposure pathways of the receptors to the contaminants.
3. Contamination delineation – determination of the expansion areas of the contamination and their barriers, while calculating representing values for contaminants concentration in soil, soil gas and groundwater.
4. Performing a risk assessment (RA):
4.1 Tier 1 determination – comparison of contaminants concentration in the different media to Risk-Based Target Levels (RBTLs) from tables attached to the IRBCA guidelines by using a designated software. In the case where contaminants concentrations at the site exceed threshold values it should be determined whether the site should be remediated or the assessment should continue according to Tier 2.
4.2 Tier 2 determination – calculation of Site Specific Target Levels (SSTLs) by using a designated software.
4.3 Tier 3 determination – determination of contaminants expansion by using hydrological models and evaluation of remediation options, with the presentation of site-specific threshold values.
At the end of the survey threshold values for site remediation are determined, which will guarantee that no harm will be caused to human health or to its environment and a contamination management plan is presented, which includes remediation options suggestion, contaminants expansion prevention methods and a long-term management plan.
