Excavation is the highest-risk work most plumbing companies do. A trench does not give much warning before it fails, and a cubic metre of saturated Fraser Valley soil weighs well over a tonne. Most people who are hurt in trench collapses are standing in a hole that looked perfectly stable a moment earlier.
Before The Machine Starts
- Locates first, always. Utility locates are requested and marks are confirmed on site before any ground is broken. Gas, power, telecom and water all share the same corridor as your sewer line.
- Hand expose the unknowns. Near a marked service, the last stretch is opened carefully rather than with a bucket.
- Read the soil. Sand, clay and disturbed backfill behave completely differently, and Lower Mainland ground is often wetter than it looks at the surface.
- Spoil piles back from the edge. Material stacked at the lip is weight pressing on the wall you are standing beside.
Sloping, Shoring And Boxes
There are three ways to make a trench safe to enter: cut the walls back to a safe angle, support them with shoring, or work inside a trench box. Which one applies depends on depth, soil and space, and on what WorkSafeBC requires for the conditions on that site.
What is never acceptable is entering an unsupported vertical trench because the job is small or because someone is only going in for a minute. Depth alone does not make a trench safe or unsafe; the soil and the water in it do.
Water, Access And The Boring Details
Groundwater undermines trench walls quietly, so pumping and monitoring matter on almost every job here. Access matters too: a ladder within easy reach, a spotter topside whenever the machine swings, and a route planned for getting someone out if they go down.
Why We Write This Down
Safety on a dig is not a document you produce for an inspector. It is what decides whether everyone goes home. On commercial work we are happy to provide our procedures in advance, and on residential jobs the same rules apply whether anyone is watching or not.
Related: drainage and excavation · commercial plumbing
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