Shipping containers topple during extreme weather events

Background

There have been many incidents involving containers, including containers stacked for advertising, which have become dislodged and fallen. Some have resulted in multiple containers toppling over causing a domino effect across the site, with containers landing on footpaths and roads.

These incidents placed employees and members of the public at significant risk of serious or fatal injuries.

Safety issues

Some of the common causes where stacked containers (empty or loaded) can become dislodged and fall, include:

• extreme weather events with strong winds or storm fronts that create a sail affect with or against the container
• changes in wind speed and direction
• unsafe stacking methods, stacks not tiered along the boundaries
• poor site conditions, for example, unstable or uneven ground
• incorrect use of mobile plant, for example, using lifting equipment that is not suitable for the task or faulty lifting equipment
• incorrect stacking practices, for example,  containers that are not stacked evenly and/or are not stacked straight
• inadequate connection points between containers
• vibrations or impacts with mobile plant

Dislodged and fallen containers and the stacks they have fallen from or against may also be unstable.

Recommended ways to control risks

Assess the risk

A risk assessment should be undertaken to identify the hazards and risks associated with container stacks. The risk assessment should determine the fall zone in the event a container becomes dislodged or falls.

The risk assessment needs to consider the following :

• any person in the vicinity of the stacks and the fall zone (employees, contractors, members of the public)
• any plant being operated in the fall zone
• damage to adjoining walls, fences or neighbouring premises

Control the risk

Advice should be obtained from a competent person (such as an engineer) to ensure the stability of shipping container stacks is maintained. Each site will have unique factors affecting the stability of a stack during extreme weather or high wind events. Factors to be considered should include, but not be limited to:

• wind speeds
• local shielding, for example, buildings higher than the stack height
• local topography and geographical factors
• container stack height, arrangement and weight of containers  (loaded vs unloaded)
• site layout
• exclusion zones

Where containers are positioned along a boundary or exclusion zone the stacks should be arranged to ensure that any dislodged or fallen containers remain within the site or the exclusion zone. Container stacks should be tiered along boundaries with a buffer or setback the distance equal to or greater than the height of the container or stack. The height of the container stacks may progressively increase as the stack moves further away from the boundary (see figure 1).

Some general techniques to further reduce the risk of containers being dislodged during high winds include:

• aligning the longitudinal axis of containers with the predominant wind direction
• stacking containers in a tiered pyramid formation to reduce the chances of isolated containers being blown over
• providing engineered wind blocking walls to shield container stacks, as required
• ensuring the surface that the shipping containers are stacked is level, well compacted and durable
• ensuring there is adequate contact between the top and bottom corner fittings with twist locks engaged
• providing additional weights inside the top and bottom containers, such as bricks or water filled Intermediate Bulk Containers (IBC's) for additional stability
• arranging containers in a formation that reduces the risk of a domino effect if one container topples over

Monitoring of wind speed and weather forecasts

Extreme weather conditions, high wind speeds and storm fronts are common in Victoria. Wind speeds and weather forecasts should be regularly monitored.

Systems to assist monitoring extreme weather events include:

• On-site weather station with a wind speed alarm programmed to sound when there are high winds.
• Portable anemometers (wind speed gauge) and windsocks as a visual guide.
• Regularly relaying extreme weather updates to site personnel (eg managers, supervisors,  container plant operators) for example via radio telecommunication. Weather updates are available from:
  • Bureau of Meteorology
  • Early Warning Network

Procedures for high wind speed conditions

Employers should have documented procedures in place to monitor and manage the site and container stability during extreme weather events.

These procedures should include, but not limited to:

• A wind speed limit for each site, taking into account the specific factors of each site and the various container stacking styles used on the site.

Note: The wind speed limit should be developed in consultation with a suitably competent person (eg engineer).

• Site preparations for when high wind speeds are forecast, such as lowering or repositioning empty containers.
• How to manage the safety of persons on site, when the wind speed limit on site is reached, such as:
  • sirens or alarms sounding
  • radio announcements made to suspend works
  • restricting pedestrians from entering or remaining in the container stacking area
  • suspending operations, including clearing trucks and mobile plant out of the area until the extreme weather event has finished and the site is made safe for normal operation to recommence
  • implementing exclusion zones
• Review and revise procedures when stacking patterns or yard layouts are altered.

Retrieving fallen containers

Before retrieving a fallen container a risk assessment should be undertaken to identify the hazards and control risks, including but not limited to:

• movement of the containers content, container unevenly weighted
• content falling from damaged containers
• damage to container and lifting points

A safe recovery procedure should be developed for the retrieval, identifying the safest method of retrieval of the container(s) as stacks may still be unstable.

Legal duties

Under the Occupational Health and Safety Act 2004, employers must:

• so far as is reasonably practicable, provide and maintain a working environment that is safe and without risks to the health of employees and independent contractors and their employees
• so far as is reasonably practicable, provide and maintain plant that is safe and without risks to the health of employees and independent contractors and their employees
• provide employees and independent contractors and their employees with the necessary information, instruction, training and supervision to enable them to do their work in a way that is safe and without risks to health
• so far as is reasonably practicable, consult with employees, independent contractors and their employees, and health and safety representatives when identifying or assessing hazards or risks and making decisions about risk control measures
• ensure, so far as is reasonably practicable, that persons other than employees are not exposed to risks to their health or safety arising from the conduct of the employer's undertaking

Under the OHS Regulations, employers and self-employed persons must:

• identify all hazards associated with the use of plant at the workplace, so far as is reasonably practicable
• control risks associated with plant so far as is reasonably practicable in accordance with the plant hierarchy of control
• ensure plant is inspected to the extent necessary to ensure that risks associated with its use are monitored

For further information on the plant hierarchy of control see the WorkSafe Plant Compliance Code.