Overhead Line Clearance on a Tight Urban Site
You are the appointed person for a mobile tower build on a narrow city plot. The tower must reach a working platform height of 9 m to access a parapet. On the delivery drawing, a bare 11 kV overhead line runs parallel to the building at an estimated 8.5 m above ground, but the exact height is unverified because the line crosses a neighbouring car park you have no access to. The only flat ground for the tower footprint places the long side roughly 2.5 m horizontally from the line's assumed route. Wind is forecast to gust to 35 km/h by mid-afternoon. The client wants the platform up by lunchtime and says the line 'looks high enough'. Two operatives are available, one of whom has not built this make of tower before.
1. What must be established before any component is lifted, and how should the build proceed if the clearance cannot be confirmed?
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The 'looks high enough' judgement is not acceptable. Overhead lines are a live hazard and clearance must be confirmed and documented, not estimated from a drawing. Steps:
- Verify the line: contact the distribution network operator (DNO) to confirm voltage, route and height, and request a site visit or written confirmation. Until then, treat the height as unknown.
- Apply the safe clearance distance for the stated voltage from the relevant guidance (for 11 kV this is typically measured including the tower, any equipment and the operative's reach, not just the structure). Do not assume the horizontal offset is constant along the build.
- Re-site or redesign if the confirmed clearance cannot be met - move the footprint, reduce platform height, or request the DNO isolate/divert the line (with a permit).
- Do not erect into an unverified exclusion zone. Record the decision and inform the client.
If clearance is confirmed adequate, still plan for the forecast gusts: stop-lift thresholds for the tower's wind class, and no lifting of long components near the line in gusty conditions. The inexperienced second operative should work under direct supervision and only on tasks within their competence.
2. The client pushes to start. How do you handle the pressure and what do you record?
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You hold the stop. The appointed person owns the erect/dismantle decision; client urgency does not override a live-line hazard. Practical response:
- Explain the specific risk in plain terms (unknown height, 9 m platform, gusting wind) and the consequence (arc flash / electrocution).
- Offer a constructive alternative: a revised footprint, a shorter tower, or a booked DNO visit - this keeps the job moving without accepting the risk.
- Record the hazard, the unverified clearance, the decision to pause, who was informed and when, and the actions required to release the hold. This protects you and evidences a proper risk assessment.
- Brief the whole team on the exclusion zone so nobody improvises a lift while you are off site.