Maintains Safe Work Environment
Chapter A6 – Maintains Safe Work Environment
Prerequisite Knowledge:
Topic 1 – Identify Hazards When Working in Confined Spaces and Excavations
Confined Space Hazards
According OHS Regulations, a confined space is defined as an “enclosed or partially enclosed space that is not designed or intended for human occupancy except for doing maintenance work and has restricted means of entrance and exit”. There are two classifications of confined spaces: confined spaces (as described above) and hazardous confined spaces. Hazardous confined spaces fit the criteria listed but also contain harmful gases due to poor ventilation. Some examples of confined spaces are storage tanks, silos, manholes, under ground utility vaults, and septic tanks.
Workers who will be working in confined spaces require training to recognize hazards, how to take precautions against those hazards, and how to use protective and emergency equipment. Some hazards that may be present in a confined space are:
When working in a confined space the contractor must ensure the following is done:
- If any of the above is present, personal protective equipment must be worn
- Atmospheres are monitored using specific instruments
As part of working in confined spaces, the contractor must also ensure there is a confined space entry plan in writing. This plan includes:
- This includes respiratory protection, body harness, and lifelines
- Workers must wear a body harness at all times when the means of exit is from above to assist with rescue procedures in the event it is required
Trenching and Shoring
While many trenches seem shallow and free from hazards, a trench that is less than even 6’ deep can pose a serious hazard to workers. The greatest risk when working in a trench is the potential for cave ins. The stability of the soil is the primary consideration made when evaluating a trenches safety and hazards. Type of soil, water table, and weather conditions are some of the factors which can affect the stability of the trench walls.
OHS Regulations lists four types of soils:
Type I soils are the most stable for trenching whereas type IV is the least stable. The type of soil present is the number one factor in determining the trench design and protections against cave ins required. Cave ins can be prevented by a number of means:
If a trench is more than 1.2 meters deep, proper egress must be provided to the workers. OHS requires that a ladder is placed no more than 8 meters from a worker at any given time when working in a trench. A competent worker must also be stationed on the bank and in communication with the workers at all times to monitor the trench and aid in an emergency.
Once work is completed, a trench should be backfilled immediately to prevent water seepage. If a trench is left overnight, it needs to be barricaded.