Abstract
Fire in the establishment falling under SEVESO Directive III is one of the most recurring accident scenarios both at a European level and in the Czech Republic. Runoff of firewater can cause a major accident leading to serious danger to the environment, especially to water environment. Although the Directive pays attention to the possibility of dangerous substance release in case of fires, still there are no united requirements for firewater treatment in European Union. This leads to unpreparedness of SEVESO chemical plants to a major fire, where large quantities of firewater require sufficient containment system and next liquidation. Implementation of effective safety containment system situated near the facility and verified by emergency training seems to be the best preventive approach. Lessons learned from past accidents clearly demonstrate negative effect of firewater to the environment. Approximately 80% of them reported in major accident database (eMARS) have occurred near watercourses (eMARS, 2018). Firewater may contain dissolved dangerous chemical substances and particulate materials from combustion processes or foams depending on the facility and nearby surroundings. Also standard tests of toxicity show their high ecotoxicological hazard, e.g. the acute toxicity tests with marine luminous bacteria Vibrio Fischeri (Sikorova et al., 2017b).
This paper is focused on analysis of firewater runoff in selected SEVESO chemical plant. First, risk sources with direct impact to the environment were identified. Next accident scenarios were determined. Contaminated firewater runoff was evaluated from different facilities affected by a major fire to endangered aquatic environment. The spread was considered via process sewerage system, rainwater sewerage system and own wastewater treatment plant to nearby watercourse. For estimation of consequences to the environment a calculation with H&V Index methodology was used. This methodology is highly recommended for the purposes of risk analysis according to SEVESO Directive III in the Czech Republic (Danihelka et al, 2006). In conclusion, effective safety measures for environmental impact reduction were proposed.
