In Alberta, excavations deeper than 1.5 meters require protection against cave-ins and sliding or rolling materials [1]. This protection can be achieved by:

• Cutting back the walls of the excavation [2]
• Installing temporary protective structures [2]
• A combination of both methods [2]

If cutting back walls, ensure the following sloping angles are maintained to within 1.5 meters of the excavation's bottom [2]:

• Hard and compact soil: 30 degrees from vertical [2]
• Likely to crack or crumble soil: 45 degrees from vertical [2]
• Soft, sandy, or loose soil: 45 degrees from vertical [2]

Temporary protective structures for excavations deeper than 3 meters must be designed, constructed, and installed according to a professional engineer's specifications [3]. For excavations 3 meters deep or less, ensure the temporary protective structures are strong enough to prevent cave-ins [3].

Also, a safe point of entry and exit must be located no more than 8 meters from any worker in a trench deeper than 1.5 meters [2].