Natech Accident
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Type
Natech Accident
Date
2002/08/15
Time
12:47
Status
Published

Units Involved

  1. Name
    Tanks 6 - 9
    Type
    Storage: Pressurized storage tank
    Year of Construction
    1979
    Description
    4 tanks with 80 m3 storage capacity for liquefied chlorine in a store housing 5 tanks. The tanks contained different amounts of chlorine with some containing only gaseous chlorine as a residue after discharging, and some being filled up to 20% of their capacity. Each chlorine tank was located in a concrete basin designed to retain the entire tank contents.

    A second store with the same internal arrangement + a smaller blow-case tank was also located onsite and was also flooded. The chlorine storehouses were designed to allow all entrances to be closed in case of accidental chlorine leakage and gaseous chlorine to be exhausted from the inside by the so-called emergency exhaust to the sodium hypochlorite plant.
  2. Name
    Tank 10
    Type
    Storage: Pressurized storage tank
    Year of Construction
    1979
    Description
    The fifth tank in the storehouse with 80 m3 capacity and filled to 80% with chlorine (= 85 tons which corresponds to the maximum filling level). Located in a concrete basin designed to retain the entire tank contents.

    This tank was involved in the chlorine release on 15 August.
  3. Name
    Tank 9
    Type
    Storage: Pressurized storage tank
    Year of Construction
    1979
    Description
    This tank with a capacity of 80 m3 was involved in the chlorine release on 23 August 2002.

Event Sequences

  1. Name
    ES 1 (Displacement of the chlorine storage tanks)
    Unit
    1. Tanks 6 - 9
    Description
    After being flooded with water exceeding the 'hundred year water level' by 1.3 m, the empty and less filled tanks were lifted by the buoyancy forces according to Archimede's law and displaced from their normal positions. The upwards movement of the tanks deformed and lifted the walkways situated above the tanks.
    Contributing Factors
    Organisational: Design of plant / equipment / system: Inadequate
    The plant was hit by large-scale flooding for which the implemented anti-flooding measures were inadequate.
    Initiating EventCritical EventMajor Event
    Natural Hazard: Floating off of storage tanks / equipment
    The different facilities of Spolana are located at 160-163 m above sea level. The maximum inundation height at Spolana occurred on 15/8 at 15:00 and was 164.5 m above sea level.
    Component (Structural): Dislodging / displacement
    -
    Event Sequence: ES 2 (Release of chlorine I - 15 August 2017)
  2. Name
    ES 2 (Release of chlorine I - 15 August 2017)
    Unit
    2. Tank 10
    Description
    The safety fittings in the full tank got caught in the walkway and were completely torn off as the walkway kept moving upwards. As a consequence of the valves being torn off from the full tank, a massive leakage of chlorine occurred.
    Substances Involved
    1. Name
      Chlorine
      CAS No
      7782-50-5
      Involved Quantity
      80.841 ton
      Description
      In total, 80.841 tones of chlorine were released in the Natech events.
    Initiating EventCritical EventMajor Event
    Event Sequence: ES 1 (Displacement of the chlorine storage tanks)
    Component (Non-structural): Damage to rails, ladders, vents and other protruding parts
    The walkway above the tanks was lifted due to tank floating.
    Component (Non-structural): Damage to couplings between tanks and pipeline
    The lifted and deformed walkway came into contact with the safety fitting on Tank 10. The welding of the spacers under the closing fittings on Tank 10 failed which led to the complete detachment of the fittings from the tank.
    Release: Unknown
    Gas release to water.
    Release: Gas, vapour, mist, or smoke release to air
    Dispersion: Substance in air
  3. Name
    ES 3 (Release of chlorine II - 23 August 2017)
    Unit
    3. Tank 9
    Description
    After the floodwater receded it was found that 3 tanks that had floated off their foundations in the storehouse remained partially caught in the walkways. Remedial action was taken to safely empty a damaged tank through transfer of chlorine to another tank. Once the transfer started, the receiving tank gained weight and got further immersed. As a consequence, the walkway blocked the tank's armature and tore off the welding on the inlet pipe, thus leading to another, smaller, chlorine release on 23 August.
    Substances Involved
    1. Name
      Chlorine2
      CAS No
      7782-50-5
      Involved Quantity
      80.841 ton
      Description
      In total, 80.841 tones of chlorine were released in the Natech events.
    Initiating EventCritical EventMajor Event
    Natural Hazard: Floating off of storage tanks / equipment
    Component (Non-structural): Damage to rails, ladders, vents and other protruding parts
    The floating tanks bent the walkway located above them.
    Component (Non-structural): Damage to couplings between tanks and pipeline
    Release: Unknown
    Gas release to water.
    Release: Gas, vapour, mist, or smoke release to air
    Dispersion: Substance in air

Emergency Response

Response Planning
Emergency response plan takes Natech events into consideration: Yes
Emergency response plan is sufficient in taking Natech events into consideration: No
Response Planning Activities
The plant had implemented 100-year anti-flooding measures. However, the flood exceeded the 100-year flood by 1.3 m, and the severity of the flood was not forecast by authorities and was hence not expected by the plant.
Difficulties in Response to the Natural Hazard
Insufficient personnel and equipment to respond to both emergencies: No
Natech event prevents efficient operation of personnel in the natural hazard affected area: Yes
Response Teams and Equipment Involved
  • On-site systems (e.g. sprinkler, water cannon)
  • On-site fire fighting team
  • On-site hazmat team
  • Local fire fighting team
  • Local hazmat team
Sheltering and Evacuation due to the Natech event
Off-site sheltering
Response to the Natech Event
In addition, police and military were involved in the emergency response.

In the wake of the release a class III chemical alert was declared as a precaution although the chlorine concentrations within the plant borders were below the class III alert threshold.

Measured aimed at containing the spreading of chlorine, and the safe transfer of the chlorine remaining in the damaged tanks to alternative storage once the floodwaters had receded. Also, the public was alerted by the media to shelter in place for protection.

Consequences

Human Health Impacts
Staff and emergency responders were at risk from the chlorine release.

In addition to the chlorine release, significant quantities of hazardous substances (e.g. dioxins, etc.) were released from the plant into the Elbe river, however, it was sustained that no risk to human health existed.
Environmental Zones Impacted
  • Inland (e.g. grassland, cropland, forest)
  • Freshwater (e.g. pond, lake, stream)
Environmental Impacts
Severe damage to flora in the surroundings of the site was observed (chemical burns).

Analyses in the aftermath of the event showed that dangerous quantities of dioxins that leaked from the plant settled in sediments on the shores of the Elbe River. It was found that dioxin levels in the village of Libis, half a kilometre downstream from the flood-damaged facility, were three times higher than safety norms.

The most critical flooding of old ecological loads was detected in a locality of the chemical plant (installation for amalgam electrolysis (mercury) and dioxin installations). The flooding of these installations was reflected in an increase in mercury and dioxin in water and sediments. However, the Czech Environmental Inspectorate sustained that this increase was of a local importance except for contamination of Libis locality.
Economic Impacts
A newspaper article estimates that the economic losses due to the flood-related damage amount to 750 million Czech Crowns (approximately 29 million Euro).
Community Disruption
The public had to shelter in place.

Remedial Activities

Restoration Activities
Following the accident, technical and organisational protection measures were implemented to prevent the re-occurrence of such an accident in case of a flood of the same or higher severity.

Lessons Learned

Lessons Learned on Equipment
After the accident, a guide-rail structure for vertical guiding of the tanks was installed. This will avoid unwanted horizontal motion of the tanks in case of displacement. This measure was accompanied by a segmentation of the walkways which will move together with the tanks in case of floating.
Lessons Learned on Organisational Aspects
Chlorine storage was reduced to 50% of the capacity before the accident and therefore to one storehouse only, thereby significantly reducing the accident risk.

Also, prior to each scheduled shutdown of the sodium hypochlorite plant, chlorine is removed from the manifolds and pipelines, and before each scheduled power outage or disruption of cooling water supplies, the pipeline connecting the tanks in the storehouse must be disassembled.
Lessons Learned on Mitigation Measures
Based on the experiences of the accident, all entrance doors to the storehouse were replaced with gas-tight doors with fuses against internal pressure overload. If the pressure exceeds the building's design pressure limit, special windows will open, release the pressure, and a balance weight will close them again. Water curtains were also installed to capture the chlorine that escapes in this way.
Lessons Learned on Emergency Response Aspects
Before the accident, emergency monitoring detectors had been installed only around the storehouse. Afterwards, detectors with a control light and an uninterrupted power supply were also placed inside the storage at an elevated location to prevent them from being affected by flooding.

The emergency exhaust system was improved to allow suction of the released chlorine from the upper part of the storehouse. This is important if the retention basis are flooded.
ID: 6, Created: Serkan GIRGIN, 2010-12-10 10:41:43 – Last Updated: Amos NECCI, 2021-01-14 17:40:04

Attachments

NoDescriptionFile Size
1.Gautam, Van der Hoek, 2003 335.50KB
2.Hudec, P., Lucš O., "Flood at SPOLANA a.s. in August 2002", Loss Prevention Bulletion, 180:36-39, 2004 208.63KB
3.ICIS New February 2003 490.63KB
4.Masaryk, 2004 3.83MB
5.Public accident information from eMARS database 132.37KB
6.ReliefWeb 1 - Dioxin spill was a real danger 465.94KB
7.ReliefWeb 2 - PCB toxic substances might have leaked 387.92KB
8.Vácha, Poláček, Horváthová, 2003 238.98KB