Tool 4 of 7· B.C. & Alberta
Trench & slope calculator
The rules change at 1.2 m in B.C. and 1.5 m in Alberta, and again with the soil, the width and what’s next to the hole. Put in your numbers and see exactly what the walls need, drawn to scale.
Checked against B.C., Alberta and federal law on September 25, 2026 · See every source
Read before using this tool
You are responsible for your dig. Before any work begins, whoever uses this toolkit must consult, confirm and understand every law, regulation, permit, consent, crossing agreement, locate and facility owner requirement that applies to their site and their work.
This toolkit is general information to help you find those requirements. It is not a locate, not legal advice, not an engineering design and not a substitute for competent supervision. Do not rely on it to decide whether, where, when or how to dig.
Laws change, owners set stricter conditions, and every site is different. Where anything in this toolkit differs from the law, a regulator, a locate sheet or a facility owner's instructions, they govern — not this toolkit.
Drag to orbit · scroll or pinch to zoom · built from your numbers
Table 20-1 minimums for type b — likely to crack or crumble, 2.4 m
| Uprights (min.) | 38 × 235 mm, max. spacing 1.2 m |
|---|---|
| Walers (min.) | 89 × 140 mm, max. 1.2 m vertical spacing |
| Cross braces (min.) | 89 × 140 mm for a trench under 1.8 m wide; max. 1.2 m vertical, 1.8 m horizontal |
| Braces per location | 3, less than 1.2 m apart, top brace within 60 cm of the ground |
| Height | From at least 30 cm above ground to no more than 60 cm off the bottom |
| Ends | End shoring is required unless the ends are sloped (or another s. 20.81(2) exception applies); a professional engineer designs it if the end waler is over 1.8 m |
- Timber shoring (table): allowed here
Timber shoring to Table 20-1. Install top-down, remove bottom-up, keep it tight to the walls. 19 mm plywood can replace 2-inch sheathing if uprights are at 60 cm or less, cross braces don't bear directly on the plywood, and braces bear at every plywood joint.
- Spoil at least 0.6 m back from the edge
Excavated material stays 60 cm from a trench and must never be piled where it endangers workers. Spoil averaging more than 60 cm high beside a supported trench adds pressure the shoring must allow for.
- A way out within 8 m of every worker — at least 3 for 40 m
A ladder or ramp no more than 8 m from anyone in the trench, with the trench protected all the way to it: the first within 8 m of each end of the work area, then no more than 16 m apart.
- Send WSBC a Notice of Project 24 hours before work starts
A worker may enter a trench over 30 m long. The owner or prime contractor sends the notice so WSBC receives it at least 24 hours before work begins, and posts a copy on site.
- Walkways across: 50 cm wide with guardrails
Any walkway across an excavation over 1.2 m deep is at least 50 cm wide with guardrails on both sides.
- Good practice: inspect every shift, and after rain, thaw or vibration
Not a specific section of either Regulation, but how a qualified / competent supervisor meets the general duties. Look for cracks along the edge, bulging or sloughing walls, water, and spoil creeping back. Test the air before entry where gases could collect — H₂S and hydrocarbon vapours are real in the Montney.
Why it matters: one cubic metre of soil can weigh more than a car (CCOHS), and cave-ins are the excavation hazard most likely to kill. Walls give little warning, and a worker buried to the chest may not be able to breathe.
Daily excavation inspection form
This assessment plus a week of shift checks — the items WSBC and Alberta OHS expect a competent person to look at before anyone goes in.
These materials contain information that has been derived from information originally made available by the Province of British Columbia at: http://www.bclaws.gov.bc.ca and this information is being used in accordance with the King's Printer Licence – British Columbia available at: https://www.bclaws.gov.bc.ca/standards/Licence.html. They have not, however, been produced in affiliation with, or with the endorsement of, the Province of British Columbia and THESE MATERIALS ARE NOT AN OFFICIAL VERSION.
You are responsible for your dig. Before any work, whoever uses this toolkit must consult, confirm and understand every law, regulation, permit, consent, locate and facility owner requirement that applies — and must not rely on this toolkit to decide whether, where, when or how to dig. It explains the rules; it is not the rules, a locate, or an engineer. It’s built from B.C.’s OHS Regulation (Part 20) and pipeline crossing rules, Alberta’s OHS Code (Part 32) and Pipeline Rules, the federal Canadian Energy Regulator damage prevention regulations, and the published guidance of regulators and one-call centres. Where we say Law, legislation requires it. Where we say Guidance, it’s a regulator’s or industry body’s advice. The facility owner’s written instructions and the law always win. This toolkit is Alpha Training Solutions’ own work and is not made or endorsed by any regulator or one-call centre.
These materials contain information that has been derived from information originally made available by the Province of British Columbia at: http://www.bclaws.gov.bc.ca and this information is being used in accordance with the King's Printer Licence – British Columbia available at: https://www.bclaws.gov.bc.ca/standards/Licence.html. They have not, however, been produced in affiliation with, or with the endorsement of, the Province of British Columbia and THESE MATERIALS ARE NOT AN OFFICIAL VERSION.
Alberta legislation © Alberta King's Printer (OHS Code 2021, OHS Act 2020, Pipeline Rules 2023, Pipeline Act and Historical Resources Act 2000), reproduced from the consolidations at kings-printer.alberta.ca. Not the official version.
Federal law reproduced from the Justice Laws Website (laws-lois.justice.gc.ca), current to September 3, 2026. This is not an official version.