Human Resources Branch
Date of Issue: February 7, 2001
The Ministy of National Resources undertakes a wide variety of field operations that involve working on ice. This statement is a consolidation of previous direction and is intended to describe the minimum requirements for all operations.
Work, travel, and parking on frozen water bodies should be undertaken as a planned work activity that recognizes and reasonably addresses the hazards associated with a floating ice cover.
Before beginning work operations on a frozen water body, the overall condition of the ice should be ascertained to ensure the ice could support the planned activity.
Where the depth of water under the ice is sufficient to allow a personal flotation device (PFD) to be effective, a PFD should be worn and a self-extrication tool carried by the employee.
Application and Scope:
This policy applies to all Ministry operations.
Where the Ministry has contracted with other parties to deliver services on its behalf, this policy also applies.
To provide province-wide operating guidelines for Ministry field operations where work is required on frozen water bodies. These are to be included in local on-ice operating procedures.
To address Ministry requirements arising from of the Occupational Health and Safety Act.
Work activities over ice must include provisions for ensuring the well-being of Ministry staff. This may include but not be limited to a check-in, check-out system; communication arrangements; and/or a buddy system as appropriate for the work activity. This requirement should be integrated into the local out-of-headquarters work procedures.
When an approved PFD is required to be worn, floatable vests, jackets, or suits may be used. When the employee is not enclosed by any type of cab (i.e. vehicle cab) a naturally buoyant PFD should be worn. If the employee is enclosed by a cab, or other like feature where a naturally buoyant PFD may restrict emergency egress, an inflatable vest may be worn.
Ice conditions can vary on a daily basis and be influenced by temperature extremes, changing water levels and snow loads. Local ice conditions should be determined prior to undertaking on-ice activities. Where ice information is not available, consideration should be given to conducting ice testing to determine ice thickness and bearing capacity. An ice testing procedure is contained in Appendix One.
Parking of vehicles or other equipment on an ice cover approaching the minimum thickness requirement for the load should be limited to a duration of not more than 2 hours. Longer times may decrease the bearing capacity of the ice.
When an employee requires a PFD, a local rescue plan should be in place. The type of anticipated local on-ice activities governs the content of the plan. Consideration must be given in the plan for procedures designed to limit hypothermia.
Manager Reviews work activities to determine application of this policy.
Ensures that work is organized in accordance with this policy and that mandatory requirements have been addressed, and implemented into local operating procedures.
Ensures that employees required to work on ice have been provided instruction.
Examples of Minimum Ice Thickness:
Examples of minimum clear blue ice thickness requirements:
Person: 4 inches of ice, employees a minimum of 10 feet apart.
Snowmachines with one occupant and an equipment trailer:
7 inches of ice, vehicles separated by a safe operating/driving distance.
Light duty vehicles: 13 inches, vehicles separated by a safe driving distance.
The above are examples and reference should be made to the Bearing Capacity Table in Appendix One for the recommended ice thickness for the specific activity.
Information regarding the use of ice covers for aircraft operations is available from the Ministry Aviation Services Section.
Appendix One: Ice Testing Procedure:
Research local conditions to determine currents, springs, or other factors that may affect the consistency of the ice.
Testing is to be conducted by at least two crewmembers out on the ice. The lead member is to wear a safety harness attached to a polypropylene rescue rope a minimum of 3/8 inches in diameter, 65 feet long, held by the trailing crewmember. Crewmembers are to be at least 30 feet apart.
Over unknown water or known moving water (i.e. river, area of springs, etceteras), the lead crewmember should cut test holes every 25 feet or so. The distance may be increased over known calm water, and decreased for known currents or eddies. If the distance between test holes is increased, then the trailing crewmember must trail further back and be behind the previous satisfactory test hole.
On lakes the distance between test holes may be substantially increased with the trailing crewmember remaining well behind. Extra caution needs to be exercised along shore, as the floating ice sheet may actually be thinner at the shore. As well, as progress is made across the lake, sampling distances will need to be shortened as the ice thickness begins to decrease.
If any sample reveals clear blue ice of less than 4 inches thick, the crewmembers are to leave the area immediately.
While sampling the crew should also be checking the ice for cracks and noting the snow load.
Three types of ice may typically be encountered. 1) Clear Blue Ice, which is strongest. 2) White or Opaque Ice is less dense and, therefore, weaker than clear blue ice. 3) Gray Ice, which is indicative of thawing ice and water. Gray ice is not considered load-bearing ice.
Only the thickness of largest continuously frozen ice layer is to be considered in determining the ice thickness. The maximum thickness to be used for determining bearing capacity is the minimum thickness determined during sampling.
Ice thickness is calculated by using blue ice as the reference. Ice thickness is determined by adding the full thickness of blue ice to half the thickness of white ice. For example: a sample indicates 3 inches of blue ice and 8 inches of white ice. The equivalent thickness of blue ice would be the 3 inches of blue ice plus 4 inches (half of the 8 inches of white ice) for a total of 7 inches.
The minimum equivalent thickness of ice is used to determine the bearing capacity of the ice.
Bearing Capacity of Ice:
The bearing capacity of ice can be calculated by plotting the load (weight) to be carried by the ice and the ice thickness on the graph below. By first plotting the ice thickness, the maximum load capacity can be determined. Conversely, by plotting the weight to be carried (eg. people and equipment) by the ice, the minimum ice thickness required may be established.
Cracks in the ice can affect its bearing capacity. A wet crack indicates a shearing or fracture of the ice through to the water below. Conversely, dry cracks have not penetrated the ice through to the water.
Filling in with water or slush can repair dry cracks. Wet cracks are already filled with water and can refreeze as strong as the original ice. Sampling should be conducted to determine the depth of healing of wet cracks when they refreeze.
Adjustments to Bearing Capacity Because of Cracks or Absence of Blue Ice:
Single 1-inch or wider dry crack.
For this type of crack reduce the maximum load by one third. For example, plot ice thickness, determine the maximum load capacity, then reduced the maximum load capacity by one third.
Intersecting 1 inch or wider dry cracks:
Where this type of cracking occurs reduce the maximum load bearing capacity by two thirds.
Single wet crack:
Reduce the maximum bearing capacity by one half.
Right angle wet cracks:
Reduce the maximum bearing capacity by three-quarters.
White Ice Only:
The maximum load should be reduced by one-half.