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Toolbox talk · 10 min · Electrical

Overhead Power Lines

Hazards: Electrocution from a boom, mast or load contacting an energized line · Step potential — energized equipment putting voltage into the ground around it · Aluminum ladder, scaffold frame or length of pipe raised into a line · Contact while travelling with the boom or bed raised

Why it matters

Exposure to electricity killed 62 construction workers in 2022 — 5.7% of all construction deaths — according to BLS Census of Fatal Occupational Injuries data in CPWR's July 2024 Data Bulletin. Most of us are not electricians. What reaches us is the line overhead, touched by a boom, a mast, a scaffold frame or a piece of pipe somebody stood up without looking.

Key points

  • Every line is hot and bare until the utility says otherwise. 1926.1408(e) and (g)(1)(ii)-(iii): presumed energized, presumed uninsulated, no exceptions on a look.
  • Cranes: 20 feet is the trigger. 1926.1408(a)(2) — if any part of the machine, load line or load could get within 20 feet, you deenergize and ground, hold 20 feet, or work to Table A. 1926.1407(a) says the same for assembly and disassembly.
  • Table A by voltage. Up to 50 kV, 10 ft · over 50 to 200 kV, 15 ft · over 200 to 350 kV, 20 ft. The utility owes you the voltage within two working days (1926.1408(c)).
  • Everyone else: 10 feet. 1926.600(a)(6) for equipment at 50 kV or below, and 1910.333(c)(3)(i)(A) for you and the longest conductive thing in your hands.
  • Long and metal counts. Ladders need nonconductive siderails near energized equipment (1926.1053(b)(12)); scaffolds keep 10 feet from a line above 300 volts (1926.451(f)(6)).
  • Warning line, spotter, planning meeting. 1926.1408(b) is not a menu of nice ideas: the meeting, the elevated warning line and one control device are all required together.
  • On contact, stay in the cab. The ground around the machine is energized too. Nobody touches the equipment or the load until the utility confirms the line is dead.

Do / Don't

Do

  • Look up before every setup, and again if the machine moves.
  • Get the voltage in writing from the utility before you use Table A.
  • Lower the boom and the dump bed before travelling under a line.
  • Use non-conductive tag lines, as 1926.1408(b)(2) requires.

Don't

  • Judge clearance by eye from the cab — that is what the warning line is for.
  • Stand a ladder, pipe or scaffold frame up without checking overhead.
  • Touch the machine, the load or the lines after a contact.
  • Assume a coated line is insulated, or a quiet line is dead.

Quick site check

  • Mark the lines on today's site plan with their voltage and the clearance we owe each one.
  • Walk the equipment path: any place where a raised bed, boom or mast crosses under a line?
  • Confirm the warning line or landmarks are up and visible from the operator's seat.
Discussion — ask the crew
  1. Stand where the crane sets up today and look up: where is the nearest line, and how far is it really?
  2. Who called the utility for the voltage on that line, and do we have the answer in writing?
  3. Which of us can name the three options in 1926.1408 without looking at the card?
  4. If the boom touches a line, what do you do — and what do the rest of us do?
  5. What are we carrying today that is long and conductive: ladders, pipe, rebar, scaffold frames, a dump bed?
Refs: 29 CFR 1926.1408 — Power line safety (up to 350 kV), equipment operations: the 20-foot determination, Options (1)-(3), encroachment measures, Table A minimum clearance distances, lines presumed energized, and the training required at (g) · 29 CFR 1926.1407(a) — Power line safety, assembly and disassembly: the same 20-foot determination and the same three options · 29 CFR 1926.600(a)(6) — Equipment: minimum clearance of 10 feet for lines rated 50 kV or below, plus 0.4 inch per kV above 50 kV · 29 CFR 1910.333(c)(3)(i)(A) — Unqualified persons: 10 feet from unguarded energized overhead lines at 50 kV or below, for the person and the longest conductive object they may contact · 29 CFR 1926.451(f)(6) and 1926.1053(b)(12) — Scaffold clearance from power lines; ladders used near exposed energized equipment shall have nonconductive siderails · CPWR Data Bulletin, July 2024 — Fatal Injury Trends in the Construction Industry (BLS Census of Fatal Occupational Injuries 2022, chart 8)Sign-in sheet included in the printed version

Frequently asked questions

Both, for different equipment. For cranes and derricks under Subpart CC, 1926.1408(a)(2) makes 20 feet the trigger: if any part of the equipment, load line or load could get closer than 20 feet to a power line, the employer must deenergize and ground the line, keep everything 20 feet away, or use the Table A clearance for the line's voltage. For other equipment, 1926.600(a)(6) sets a 10-foot minimum clearance for lines rated 50 kV or below, and 1910.333(c)(3)(i)(A) sets the same 10 feet for unqualified persons and the longest conductive object they may contact.

From Table A of 1926.1408: up to 50 kV, 10 feet; over 50 to 200 kV, 15 feet; over 200 to 350 kV, 20 feet; over 350 to 500 kV, 25 feet; over 500 to 750 kV, 35 feet; over 750 to 1,000 kV, 45 feet. Above 1,000 kV the distance is established by the utility owner/operator or a registered professional engineer who is a qualified person for power transmission and distribution.

Ask the utility. 1926.1408(c) requires the utility owner/operator to provide the requested voltage information within two working days of the employer's request. Until you have that answer, you cannot use the Table A option — you are on the 20-foot rule.

No. 1926.1408(g)(1)(iii) requires crews to be trained that power lines are presumed to be uninsulated unless the utility owner/operator, or a registered engineer who is a qualified person for power transmission and distribution, confirms that a line is insulated. The same paragraph presumes every line is energized unless the utility confirms it has been deenergized and visibly grounded at the worksite.

Stay in the cab. 1926.1408(g)(1)(i)(B) requires training on the importance to the operator's safety of remaining inside the cab except where there is an imminent danger of fire, explosion or other emergency that makes leaving necessary. Everyone on the ground stays away from the machine, the load and the lines: (g)(1)(i)(D) covers step potential, the energized zone in the ground around the equipment.

Only as one of the measures listed at 1926.1408(b)(4), and only after the planning meeting of (b)(1) and the elevated warning line of (b)(3) are in place. A dedicated spotter must be in continuous contact with the operator, have a visual aid such as a painted line or line-of-sight landmarks to gauge the clearance, and be positioned to judge the distance.

Yes. 1926.1053(b)(12) requires ladders to have nonconductive siderails where the employee or the ladder could contact exposed energized electrical equipment. 1926.451(f)(6) sets scaffold clearances from exposed and energized power lines: 3 feet for insulated lines under 300 volts, 10 feet for insulated lines from 300 volts to 50 kV, and 10 feet plus 0.4 inch per kV above 50 kV.

Sources & references

Content checked against these sources — last reviewed August 28, 2026.

Results are estimates for planning purposes and do not replace a competent person's evaluation or an engineer's design. Follow the OSHA standards that apply to your work and your employer's written program.

By — Editorial team of SteelToeTools.com (published by LSEA SAS) Updated