Purpose

Design an underground cable route using risk-managed excavation, mechanical protection, thermal data and maintainable records.

Learning objectives

• Plan and locate services
• Reject a universal depth
• Specify route protection
• Record as-built position

Burial depth alone does not make a route safe. HSE guidance centres on planning, plans, locating and safe excavation; HSE also notes there is no single statutory depth for underground cables.

Core theory

Obtain utility and owner records, survey with suitable locating equipment, mark the route and use safe digging methods. Plans are guides, not proof of exact position; unknown services must be treated as live.

The electrical design must coordinate current capacity, soil/duct thermal conditions, grouping, warning/route identification, mechanical damage, water, chemicals, joints, pulling forces and future excavation risk.

Record verified as-built route, depth, crossings, ducts, joints and landmarks. Ground levels change, so records never replace locating and safe digging before later work.

Assumptions: Cable position has not been traced.

1. Stop: A plan is only a guide and depth may have changed.
2. Manage: Plan the work, obtain all records, locate/mark services and assess isolation.
3. Excavate safely: Use the HSG47-aligned method, trained people and repeated locating as work progresses.

Do not excavate from the plan alone; establish and follow a controlled safe system of work.

Reasonableness check: Incorrect records or levels can place live cables directly in the excavation path.

Knowledge check

Answer: No. Use plans with competent locating and safe digging.

Practical exercise

Write a pre-excavation control sequence for a supplied site plan, including uncertainty and stop conditions.

Summary

• Plan, locate and dig safely
• No universal depth
• As-built records supplement locating but never replace it