Analysis of the emergency situations and the consequences thereof

The analysis of the consequences of the possible emergency situations for the personnel, the population and the environment on the territory of Bistritsa PWTP, the city of Sofia, is prepared on the basis of the requirements of art. 35, par. 1, it. 1 of the Disaster Protection Act. The main objective is to determine the most severe damage from identified accidents and to plan and take adequate measures to reduce the risk of major accidents and mitigate the consequences thereof. Within the scope of the assessment of possible emergency situations are the activities carried out with hazardous chemical substances and mixtures on the territory of Bistritsa PWTP, while the analysis of potential impacts also covers areas outside the establishment, to the extent applicable. The greatest hazards have been identified in the activities related to receiving and handling chlorine at the company’s chlorination unit. 

The possible accidents resulting from the analysis are:
-   Fire and explosion from natural gas leak;
-     Chlorine leakage when unloading from vehicles;
-    Leakage of a large amount of chlorine from the technological system;
The risk analyses and modelling taking account of the most significant potential damage include a scenario with a sudden leakage of a large amount of chlorine from the technological water disinfection system.

Safety measures planned by the company

Zone 1 – high mortality zone

This zone is located in the immediate proximity to the leakage point, where the exposure to high concentration of the toxic vapours of chlorine (20ppm) may have a lethal outcome due to respiratory arrest, corrosive organ changes, danger of tracheal perforation, pulmonary edema, etc. High mortality is anticipated in this zone.
Regarding this zone, the main control measures are the use of the appropriate class of equipment for all chlorine-related activities, maintenance of the technical and emergency systems in good order (non-destructive control of vessels and pipelines, hydraulic tests, gas detection, ventilation, maintenance of the scrubber system and the deactivation pits, etc.), adequate technical maintenance of the equipment by a competent personnel, strict compliance with the instructions on safe unloading, storage, transportation and handling, inspections, trainings on the hazards and the control measures, and application of good practices. 
If it is not possible to stop the leakage of hazardous chemical substances and mixtures, employees have to be evacuated. Then it is necessary to take measures for separating the area and denying access to external persons. Medical assistance and emergency rescue assistance should be concentrated in this zone. 

Zone 2 – severe damage zone

This is the zone immediately after Zone 1, where there may also be fatalities, but here, mainly serious adverse effects will be seen. The remoteness from the source of release determines the presence of less adverse health effects.
The specific smell of chlorine makes it easy to detect, and the normal behaviour of a person is to want to get out of the area if they smell it.  In such situations, it is possible for panic to set in, making evacuation difficult especially among vulnerable persons (sick, mobility impaired, etc.), creating a prerequisite for physical accidents in case of collision with vehicles trying to leave the area. 
The main measures are timely alerting through a warning system and readiness for evacuation from the affected area. 
Compared to the first zone, here the provision of first aid is a lower priority.

Zone 3 – zone of special attention

This is the zone furthest from the site where the accident has occurred and where adverse effects are also expected, but weaker. Specific measures should be planned for it in terms of vulnerable areas (kindergartens, hospitals, nursing homes, etc.), if any, and zone entry control should be in place.
The main measures are related to the vulnerable areas, preventing zone entry, as well as measures for ensuring information and timely communication. 

First, in order to prevent the occurrence of emergency situations, and then, to limit the spread of the accident and eliminate the consequences both within and outside the area, the company has taken and maintains the following measures:
-    only tested equipment in good technical order is used and maintained for all chlorine-related activities;
-    maintenance of emergency systems (scrubber system, degassing pits, gas detection, ventilation, etc.);
-   adequate maintenance of the equipment of the chlorination plant by competent staff;
-    technical inspections and control of safety critical elements of the facilities (detection of defects of containers and pipes, water samples, inspection and calibration of sensors, shut-off valves, etc.);  
-    controlled access to the site and hazardous chemical substances and mixtures storage areas;
-    organization of work to avoid sources of ignition and associated risks (for example, hot works permit, etc.);
-    maintenance of emergency response team and emergency equipment;
-   physical control during unloading of hazardous chemical substances and mixtures;
-   instructions and rules for safe handling, unloading, storage and transportation of hazardous chemical substances and mixtures;
-   information, training and H&S briefing on dealing with hazardous chemical substances and mixtures;
-    provision of resources for maintaining the fire-fighting equipment in order (fire-alarm systems, fire-extinguishing equipment, hydrants, internal fire hydrants, etc.);
-    development and implementation of inspection and control program covering the technical measures for protection, accident prevention, and mitigation of the consequences thereof;
-    information provided to the external teams for adequate interaction and support (Fire Safety and Population Protection Service, municipal disaster response headquarters, emergency medical service, etc.);  
-    joint drills with the Fire Safety and Population Protection Service, the municipal disaster response headquarters, the emergency medical service, etc. to improve coordination. 

Major Accident Prevention Policy – Sofiyska Voda AD