We went through the upcoming revision of the ANSI Z133 Safety Standard, pulling out and listing here in sequential order all the relevant parts that affect lift operations near conductors. These apply to conventional truck-mounted lifts as well as “boom-supported elevated work platforms,” or compact lifts.

Climbers must maintain minimum approach distance (MAD) at all times. All photos courtesy of John Ball.

Job-site hazard assessment and job briefing
The employer shall provide the qualified arborist in charge of performing a job briefing with available information on the known hazards pertaining to each job.

Electrical Hazards Checklist at end of article

Prior to the beginning of work, the arborist in charge shall ensure that hazards pertaining to the work or task at hand are identified, and that measures are taken to reduce, eliminate or avoid the identified hazards.

A job briefing shall be performed on the job site by the arborist in charge before the start of each job. The briefing shall be communicated to all affected workers. The job briefing shall cover the hazards associated with the job, work procedures involved, job assignments, special precautions, energy-source controls and PPE requirements.

An inspection shall be made by a qualified arborist with specific training in electrical-hazard recognition to determine whether an electrical hazard exists before performing arboricultural operations.

General requirements for working around electrical hazards
The employer shall ensure that the arborist’s training and degree of training in electrical hazards are determined by the risk to the arborist for the hazard(s) involved. Such training shall include, but is not limited to:

• The minimum approach distance (MAD) for the maximum voltage within the area, as well as the skills and techniques necessary to maintain that distance.
• That under normal operating conditions, electric supply lines are energized and could cause serious injury or death if direct contact or indirect contact occurs.
• That under abnormal conditions or configurations (e.g., natural disasters), all wires and cables have the potential to become energized. In such situations, all utility infrastructure is to be considered energized and could cause serious injury or death if direct or indirect contact occurs.
• That the human body is conductive and will provide a path for the flow of electricity to a grounded object or to the ground itself.
• That vegetation is conductive.
• That electric shock can result in debilitating injuries and may lead to electrocution (death), and may arise from direct contact with an energized electric supply line or indirect contact with an energized tree part, tool, equipment, a human body or other energized object. Step potential and touch potential are forms of indirect contact.

Storm work and emergency conditions create special hazards. Only authorized representatives of the electric-utility-system operator/owner shall perform tree work in these situations when energized electric supply lines or electrical conductors are involved.

Due to the hazards of step and touch potential, if the distance between the aerial device and energized electric supply line (s) is unintentionally less than required, workers on the ground shall alert all persons to move away and remain clear of the aerial-device vehicle and attached equipment (e.g., chipper) until the aerial-lift operator has been notified and the required MAD is reestablished.

Arboricultural operations in proximity to energized electric supply lines shall not be performed during adverse weather conditions, such as thunderstorms, high winds, snowstorms or ice storms.

When working in proximity to energized electric supply lines with insulated covers, blankets, hoses, sleeves or any other covering or coating, MAD shall be maintained.

Pole tools used in proximity to energized electric supply lines shall be constructed with fiberglass reinforced plastic (FRP) or wood.

The Electrical Level 1 (unqualified) Arborist
Electrically unqualified arborists and trainees shall receive fundamental
electrical-hazard-awareness training prior to performing tasks where electrical hazards exist. However, they have not received related training nor have they demonstrated competency in the skills and techniques necessary to qualify for an Electrical Level 2 Arborist – Low Voltage, Electrical Level 3 Arborist – Primary Voltage, or Electrical Level 4 Arborist – Line Clearance.

The Electrical Level 1 Arborist shall not access or perform work that is within the MADs shown in Table 1 [i.e., 10 feet], and shall not cause any vegetation to violate the applicable MADs shown in Table 1.

Operations using knuckleboom-mounted grapples and grapple saws are addressed in the new ANSI Z133. Inset: All arborists need to be aware of electrical hazards.

Aerial-equipment requirements
Aerial-lift annual inspection and dielectric testing shall be performed and documented per manufacturers’ recommendations.

Before the aerial device is set up for use, the work site shall be surveyed for hazards, including overhead obstructions and electrical conductors.

During pruning/removal operations, the aerial-device operator shall have a hand saw while working aloft.
Booms, platforms (aerial buckets) or any other part of the aerial device shall not be allowed to make contact or encroach upon minimum approach distances (MADs) with energized electrical conductors, poles or similar conductive objects.

Due to hazards of step and touch potential, if the distance between the aerial device and energized conductor(s) is less than the required MAD, workers on the ground shall move away and remain clear of the aerial-device vehicle and attached equipment (e.g., chipper) until the required MAD is reestablished.

Aerial-device equipment with an elevating structure that raises the turret and booms and changes the reach of the device’s uninsulated portions shall be positioned so that no portion of the aerial device and its elevating structure encroach upon the MAD from energized electrical lines, as specified in this standard. One or more spotters shall be used when the aerial lift is working close to the MAD and could potentially encroach upon the MAD.

When the MAD could be encroached upon, the spotter shall warn all ground personnel, including the equipment operator and direct ground personnel, to keep clear of the vehicle and attachments until the MAD is visually established and communicated.

Electric cables/cords used with tools, lights or other conductive material shall not be run from the vehicle or other power source to the platform (aerial bucket) when arborists are working in proximity to energized electrical conductors.

Platforms (aerial buckets) on insulating aerial devices shall not have through-cracks or holes below the lip of the platform. Insulating liners shall have no holes below the lip of the liner or cracks greater than 6 inches (15.24 cm) from the lip of the liner or the onset of the crack.

During aerial-device operations, arborists and other workers shall maintain a MAD from energized electric conductors in accordance with the appropriate table of this standard as required by their level of training.

Arborists and other workers shall be instructed that aerial platforms (aerial buckets) do not protect them from other electric paths to the ground, such as paths through trees or guy wires, or from phase-to-phase contact. All paths of electric contact shall be considered to cause death or serious injury.

Insulating, boom-supported elevating work platforms shall meet the dielectric safety requirements of ANSI/SIA A92.

When an electrical hazard is present, uninsulated units, including those that may have an insulated liner or other insulating properties, shall follow MADs as laid out in Table 1.

Due to hazards of electric step and touch potential, workers on the ground shall remain clear of the aerial device and attached equipment when the boom is aloft.

Arborists are exposed to many hazards, from passing traffic to operating at heights. Photo courtesy of John Ball.

Electrical Hazards Checklist

The following checklist is from the “Aerial Lift Operations 1: Fundamentals” course in TCIA’s Brightspace Online Learning Platform.

General Precautions to Avoid Electrocution

• Use extreme caution when operating aerial lifts and tree-trimming equipment around utility lines.
• You must call the utility if there is an electrical hazard, such as a tree limb closer to the line than your minimum approach distance.
• Plan ahead to have power lines de-energized or shielded if possible.
• Never use a non-insulated lift device around utility lines.
• Keep far enough away from the utility lines to allow for sway of the boom and sway of the lines.
• Never drill holes in the bucket or bucket liner; this will decrease the effectiveness of insulation, if so equipped.
• Insulated booms must be dielectrically tested at least once a year.
• Never rely on boom insulation to protect you. An insulated boom may or may not work based on environmental factors, voltage involved, nature of the contact, condition of boom, etc.
• On the ground, never touch, lean on and/or jump on and/or off the aerial lift when it is in use around utility lines.
• On the ground, avoid the area around the outriggers when the aerial lift is in use around utility lines.