Public works crews encounter electricity in offices, treatment plants, and homes, on construction sites, along roads, and up in trees. Given such a diverse and shape-shifting workplace, how do you keep them safe?
“Everything we work with is electrified,” says Scott Drabicki, engineer for the Village of Gurnee, Ill. “Even putting a backhoe into the ground is an electrical hazard.”
Different environments expose workers to different electricity types, including single-phase, three-phase, voltages from 120 to 480, delta systems, and wye systems. All can be dangerous, and even a seemingly benign situation can turn deadly. Case in point: A North Carolina meter reader was electrocuted while attempting to access a residential water meter located behind a boiler. In maneuvering between the water pipes and the boiler, he contacted exposed, 120-volt low-water cut-off switch terminals.
In addition to nonelectrical work that poses hazards, employees perform electrical tasks ranging from simple wiring to servicing traffic signals.
“Personnel learn on the job from their old-timer mentor and there may not be any formal training,” says Drabicki. “Once a new hire gets into the lights and signs division, they’re exposed to basic troubleshooting and wiring and learn the ropes of repairing street lights and controller systems found in the field. The next thing you know, a problem comes up in high-voltage pump station and someone says, ‘Call the streetlight guy and have him take a quick look at it; maybe it’s a simple fix.’”
In short, public works employees often do jobs that, if performed by a contractor, would require a licensed electrician. This scenario inspired Drabicki to join forces with the local American Public Works Association chapter to stage a half-day course on electricity essentials (see sidebar on training).
Hazards fall into three categories: shock, burns, and explosions. Occupational Safety and Health Administration (OSHA) regulations for guarding against these are covered in 29 CFR 1910.269, Electric Power Generation, Transmission, and Distribution, and 29 CFR 1910.333, Selection and Use of Electrical Work Practices.
Danger: Live Power Lines
Nebraska—While installing a storm sewer drain, a backhoe operator hit an electrical conduit. A crew member who was digging in the trench with a shovel came in contact with the live conductor and received a deadly shock.
Abandoned, often unmarked underground utilities are one potential hazard. In some metropolitan areas, a rat’s nest of electrical, communication, petroleum, gas, and sewer lines may be stacked in a vertical space up to 25 feet deep. To avoid explosions, electrocution, flash burns, and other hazards, identify live lines before beginning repairs or installations.
California—On a windy, rainy day, a tree trimmer operating a chainsaw was killed when he cut a branch that hit a high-tension power line.
Contact with overhead power lines is a leading cause of electrical-related fatalities. Public works employees such as tree trimmers and traffic signal technicians often work near overhead wires. Even on the ground, operators of machinery must keep booms and other protruding parts a safe distance from overhead lines.
Job Hazard Assessment
According to OSHA, power lines should be de-energized and grounded before work begins nearby and even then you should assume lines are energized and dangerous. OSHA 3071, Job Hazard Analysis, explains how to conduct an assessment before work begins.
OSHA recommends using personal protective equipment (PPE) such as insulating gloves, sleeves, hoods, and hard hats. Insulating protective equipment (IPE), such as line hose, blankets, and covers, may also be used.
OSHA requires specialized training for employees who must work within 10 feet of power lines that might be energized. All others must keep their work and equipment at least 10 feet away from electric power lines.
The City of Flagstaff, Ariz., Public Works Section Safety Manual includes instructions for conducting a job hazard analysis. The procedure assigns supervisors such responsibilities as:
- Checking utility plans and contacting public utilities for assistance in locating underground or overhead services near the jobsite
- Personally inspecting the area to identify potential electrical hazards
- Instructing workers about hazards and how to use PPE
- Maintaining utility phone numbers to immediately report accidental contact with live wires.
Danger: Arc Flash
Alabama—A technician was killed by an electrical arc to the head when he inadvertently touched a live electrical box while working in a hydroelectric facility powerhouse.
Illinois—While working on a three-phase transformer in an old well house, a public works employee was shocked by the 480-volt wire, an unexpectedly high voltage for the application. Although uninjured, the worker was jettisoned from the electrical panel.
An arc fault is a high-power discharge of electricity between two or more conductors. The light and heat emitted by the explosion is known as the arc flash; the pressure wave is the arc blast. These events account for three-quarters of all electrical injuries.
Arc flashes burn human skin, ignite clothing, melt metal, rupture eardrums, collapse lungs, and damage brain function. UV radiation causes retinal damage. Arc blasts turn personnel and loose equipment into projectiles. If the current is high enough, arcs start fires. Even low-energy arcs cause explosions in atmospheres that contain explosive vapors or combustible dusts.
The National Electric Code (NFPA 70) requires equipment to be de-energized before work is performed (exceptions: when performing diagnostic tests such as checking for voltage and current; if de-energizing the equipment would create a greater hazard; or if the system voltage is below 50 volts).
As with work near utility lines, OSHA also calls for risk assessment in potential arc flash environments. This procedure is essential in choosing the proper PPE, as noted in an April 2015 APWA Reporter article: “Even in what would be considered a small arc flash, clothing choice can literally mean life or death.” PPE for arc flash zones generally includes flame retardant (FR) clothing as well as FR eye and hearing protection.
Other components to promoting arc flash safety include proper training and equipment maintenance. But some work environments require even more precautions. According to an October 2013 Public Works article, engineering controls add another layer of safety in water and wastewater facilities, where current and voltage levels are particularly high. For example, methods such as virtual mains, zone-selective interlocking, and differential relaying help reduce arc duration, thereby reducing energy.
Lockout/Tagout
Designed to protect against the unexpected start-up of machines or equipment, lockout/tagout (LOTO) procedures apply whenever employees are exposed to electrical hazards while working on, near, or with conductors or systems that use electric energy. OSHA spells out LOTO provisions in Standard 1910.147, The Control of Hazardous Energy (Lockout/Tagout).
Lockout refers to the use of a physical device, such as a lock (key or combination), blank flange, or bolted slip blind, to hold an energy-isolating device in the safe position and prevent the energizing of a machine or equipment. Tagout is a prominent warning that equipment may not be operated until the lockout device is removed.
OSHA stipulates use of lockout devices whenever possible, and allows tagouts only on machines or equipment incapable of being locked out and only if the tagout program provides protection equivalent to that of a lockout program.
The standard defines “authorized employees” as those who lock out or tag out machines or equipment to perform servicing or maintenance on that machine or equipment. “Affected employees” are those whose job requires them to use equipment being serviced under LOTO or work in an area where the service is being performed. Training is required for both employee categories.
The City of Flagstaff’s safety manual provides a LOTO procedure performed by authorized personnel to ensure electrical power is disabled on all equipment before cleaning, greasing, oiling, or repair. The Robert F. Reeves Water Reclamation Facility in Bloomington, Ill., uses a locking procedure on its supervisory control and data acquisition (SCADA) system to de-energize equipment during maintenance.
Danger: Carelessness
Ohio—When a tree trimmer drop-started his power pole saw, the pole contacted a 7.2-kV transmission line and the worker was electrocuted. The practice of drop-starting—simultaneously pulling the start cord while dropping the saw—is prohibited by the American National Standards Institute’s (ANSI) Safety Requirements for Arboricultural Operations.
Oklahama—A lineman on an aerial work platform asked a coworker to throw a tool up to him. When he reached to grab it, his arm contacted a 14.4-kV line. He suffered third-degree burns to 30% of his body.
While unsafe conditions and faulty or defective equipment are a significant hazard, equipment misuse and other unsafe work practices by employees contribute to many accidents. In addition, workers sometimes are reticent about refusing to do a job they aren’t trained for or objecting to conditions that make them uncomfortable.
Basic precautions in any work environment—office, plant, or field—are generally well known. To make sure all employees are on the same page, the City of Flagstaff safety manual enumerates many of these:
- Electrical cords. They should be properly sized and in good condition. Dispose of defective cords at the hazardous product center. Don’t run extension cords across aisles or through oil or water. Don’t overload power strips.
- Metal hand tools and other objects. Avoid using items that have conductive properties (for example, metal measuring tapes, fabric tapes containing woven metal strands, rope with wire cord, and jewelry) near energized electrical circuits or equipment.
- Ladders. Use fiberglass, not metal, ladders when working on overhead lighting or electrical fixtures, above dropped ceiling grids, or any other situation that might involve electricity.
- Power tools. All electrical tools must be grounded. Each electrical tool or machine must be visually inspected each time it’s used for damage to cords and ground connections. Ground fault circuit interrupters (GFCI) are required when tools are used outdoors, in wet or damp environments, or where significant conductors or metals are present.
- Electrical panels. Keep control panel circuit breaker or fuse boxes closed and at least 3 feet from obstructions and debris. Circuit breakers or fuses that blow continually indicate an overload or short and should be reported.
- Horseplay. Employees who participate in horseplay and practical jokes on the job are subject to disciplinary action.
