The Risk Screening System (RSS) is intended as a screening tool that consistently assesses and ranks the risk that any site presents. It does this by considering the completion of the risk pathway from a contaminant source, or hazard, to a receptor, using weighted factors for the various parameters making up the pathway. Three overall receptor pathways are considered: exposure to surface water, exposure to groundwater and direct contact. Each of these pathways is treated independently and given an equal importance, with the overall ranking of a site obtained by choosing the worst-case pathway (ie, the pathway with the highest assessed risk).
The RSS has been designed for ease of use, based on readily obtainable information. As such, it is not intended to provide a fine differentiation between sites. More detailed information (if available) will increase the confidence of the score, but the coarse nature of the ranking should still allow valid comparisons with sites that have less detailed information available.
While the RSS uses a minimum set of data to enable a rapid assessment, with most of the data readily available from public sources, the system does require some experience in contaminated site assessment for the user to be confident of the results. This is because some of the parameters, such as contaminant toxicity and mobility, require knowledge that only a person with some contaminated site (or similar) expertise could be expected to have.
The RSS is intended to be sufficient to prioritise sites for further investigation. Therefore, the assessment is not intended to be used on sites that have already been assessed on the basis of a specific site investigation, as these sites have already passed the point where the basic prioritisation decisions have been made.