The contribution of accidental discharges to the total emission of contaminating substances in surface waters is relatively increasing, as regular discharges are reduced.
In The Netherlands a program has been started to develop a quantitative risk analysis method to be used within the discharge permitting process. The methodology takes into account the type of activities and related accident scenarios in terms of failure frequencies and source sizes, correction factors according to specific circumstances, as well as the nature of the receiving system (types of surface waters, but also public sewage water treatment plants). The methodology will provide an indication of the risk reduction needed in terms of reducing the frequency and/or the volume of possible spills.
The method itself, the use of it within the legal framework and the relation with the EC-Directives are discussed.