I’m back. Good morning, hope you slept well and have a safe and productive day. Here’s a nice SWP from a BC construction company that I found that you can adapt. 
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EXCAVATING AND TRENCHING
The definition of an excavation” means any cut, cavity, trench or depression in the earth’s surface resulting from rock or soil removal.
Excavations can be defined as two types: Trench Excavations which are the most common and generally less than 12 ft in width. Some examples are excavations used for pipelines and manholes.
They must be engineered if greater than 20 ft in depth. Bulk Excavations are greater than 12 ft in width and are commonly used for foundations or basements. They also must be engineered if greater than 20 ft in depth.
Other requirements for engineering on an excavation include; 1. Excavations greater than 4 ft in depth with sides sloped greater than ¾ to 1. 2. Excavations greater than 20 ft in depth. 3. Excavations next to structures. 4. Excavations in soil subject to vibration or hydrostatic pressure. 5. Excavations shored in a manner differing from the WorkSafeBC regulation. 6. Excavations as determined by the Board.
Excavation Pre-Planning
There are many factors that need to be considered prior to work being done in or around excavations.

1. All excavation work must be carried out in accordance to WorkSafeBC regulations or with the specific requirements of a registered engineer. Se above. 1a It will be mandatory that you locate and mark services prior to digging
2. Utility Services in the area such as electrical, gas, steam, water and sewer, and fibre optic lines must be located and assessed for hazard potential. If this equipment is dug into, undercut or damaged in any way, there may be an injury or death to workers, interruption of service, contamination of water, disruption of processes and expensive delays. Call BC One Call to get information on these items before you beginning work. Test holes should be dug by hand prior to equipment being used. Pointed tools must not be used for probing to locate underground gas lines or electrical facilities.
3. How large will the excavation be’ This will determine if engineering is required as per above.
4. Trees, utility poles, rocks and similar objects adjacent to an area to be excavated must be removed or secured if they could endanger workers. A clean area extending two feet back from the edge of a trench must be maintained (4 ft for any other excavation).

4a Proper permits and Authorization will be required prior to any trees or pole removal

1. The side of the excavation must be trimmed or scaled to remove any loose rock.
2. Safe access must be provided in the immediate area where workers are employed in trenches over 4 ft. deep. Ladders must extend from the bottom of the excavation to at least three feet above ground.
3. Another consideration when excavation work is being done on travelled roadway is the need for traffic control and high visibility clothing for all workers.
4. Any engineered excavation support system must have certified design documentation on site.
5. The need to identify which type of barricades should be used to prevent workers and others from falling into the excavation needs to be considered. When an excavation must remain open for the duration of the construction work, barricades, fences, and warning signs are necessary. In some cases watchers and flaggers may be required. Guard the work at night with flares, lanterns or flashing lights.
6. Consideration should be given to the prevention of excess water accumulation in the excavation if it might affect the stability of the excavation or might endanger workers. Erosion of slopes by surface water must be prevented if workers may be endangered.

10a Appropriate pumping equipment should be on site for emergency use

1. Excessive rain and thawing soil can compromise the sloping of the excavation. Ground water should be controlled. Freezing, pumping, drainage and similar control measures should be planned and directed by an engineer.
2. Consideration should be given to the positioning of mobile equipment near the evacuation. For a trench the equipment can be no closer than 2ft from the edge, for a large excavation 4 ft. from the edge.
3. An excavation could be considered a confined space and thus should be assessed for hazardous atmospheres.
4. Determine what kind of sloping or shoring is required. Refer to WorkSafeBC regulation Part 20. Sloping is a system where the sides of the excavation are flared to a safe angle. Shoring is a support system designed to keep the sides of an excavation from caving in. Where the cut back method is not possible, shoring, trench jacks, sheet piling, cages or other approved methods must be used to protect workers.

No workers will enter any trench or excavation until the walls have been adequately cut back or temporary protective structures have been installed unless said trench or excavation is shallower that the legal minimums and the soil is stable.
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Suggest you also check out the WorkSafeBC guidebook: 
https://www.worksafebc.com/en/resources/health-safety/books-guides/prevention-of-damage-to-buried-facilities-in-british-columbia’lang=en
Hope that helps. Glenn glennd@bongarde.com