Abstract
Environmental management of discharges to the marine environment can be based on an assessment of the environmental risks of these discharges. For offshore discharges from the oil and gas industry like produced water risk-based management tools have been developed earlier. For coastal regions, however, modeling the fate and transport of discharged components is much more complicated compared to offshore waters. In addition, the limited mixing near shore causes a need to evaluate risks associated with other stressors like temperature change and potential oxygen depletion. The Environmental Impact Factor (EIF) for coastal discharges was developed especially to evaluate environmental risks in near shore areas and addresses special characteristics of these areas. The risk approach is based on a comparison of the Predicted Environmental Concentration (PEC) and the Predicted No Effect Concentration (PNEC). Toxicity risks as well as risks from temperature increase, oxygen depletion and suspended particles are included in the tool. The EIF is calculated for both that water column and the seafloor representing the volume or area of the recipient where PEC exceeds PNEC. The main elements causing the risk are presented in a pie chart which facilitates the definition of risk mitigating measures. The methodology has been tested on a fictive discharge from a petrochemical plant (Mongstad) located on the Norwegian coast. This case study showed that the EIF tool can be used to assess the overall environmental risk in near shore areas and to identify the main risk contributors in the discharge.
