5.10 Electrical Safety, Fall Protection, Excavation & Traffic Control

Electrical Safety, Fall Protection, Excavation & Traffic Control

The ABC criteria name "comply with safe work practices (e.g., confined space entry, lockout/tagout, electrical, chemical spills)," "inspect plant safety equipment," and "train staff/contractors on safety requirements." Confined space, lockout/tagout, and chemical handling are covered elsewhere in this guide; this section covers the remaining physical hazards, which account for a disproportionate share of serious utility injuries.

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1. Electrical Safety and NFPA 70E

OSHA's electrical standards (29 CFR 1910 Subpart S for general industry, 1926 Subpart K for construction) set the legal floor. NFPA 70E, Standard for Electrical Safety in the Workplace, is the consensus standard that defines how to comply.

The governing principle

Establish an electrically safe work condition before working on or near exposed energized conductors.

The NFPA 70E steps to an electrically safe work condition:

1. Determine all possible sources of supply.
2. Open the disconnecting device for each source.
3. Visually verify that blades are fully open or drawout units are fully withdrawn.
4. Apply lockout/tagout per the written program.
5. Test each conductor with an adequately rated voltage detector - and test the tester before and after on a known live source.
6. Apply grounds where induced voltage or stored energy is a risk.

When energized work is permitted

Only when de-energizing would introduce additional or increased hazards (for example, shutting down life support or ventilation of a hazardous location) or is infeasible due to equipment design or operational limitations. Note what is not an acceptable reason: inconvenience, production, or cost. Energized work requires an energized electrical work permit, a shock risk assessment, and an arc flash risk assessment.

The two hazards and their boundaries

Equipment likely to require examination while energized must be field-marked with a label showing nominal voltage, arc flash boundary, and either available incident energy with the corresponding PPE, or the required PPE category.

Arc-rated clothing is not the same as flame-resistant clothing, and melting synthetics (polyester, nylon) must never be worn under or instead of arc-rated clothing - they melt into the skin.

Practical plant rules

• GFCI protection on all 120-volt, single-phase, 15- and 20-amp receptacles used for temporary power in construction, and in wet locations generally. Water plants are wet locations.
• Assured equipment grounding conductor program as the alternative to GFCI in construction - documented inspections and tests of cords and tools.
• Inspect cords and tools before each use; remove damaged equipment from service and tag it.
• Only qualified persons open motor control center doors, rack breakers, or take voltage measurements.
• Do not use metal ladders or tape measures near energized equipment.

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2. Fall Protection

Trigger heights

At a water or wastewater plant, "over dangerous equipment" is common - a walkway over an open clarifier, a screw conveyor, a rapid mix basin, or a chemical tank requires protection regardless of height.

The hierarchy of controls

1. Eliminate the hazard - do the work from the ground.
2. Passive protection - guardrails, covers, hole covers rated for the load and marked.
3. Fall restraint - a system that prevents reaching the fall hazard at all. Preferred over arrest.
4. Fall arrest - a personal fall arrest system that stops a fall in progress.
5. Administrative - warning lines, safety monitors. Weakest.

Personal fall arrest system requirements

• Full body harness only - body belts are prohibited for fall arrest.
• Anchorage capable of supporting 5,000 lb per attached worker, or designed with a safety factor of two under the supervision of a qualified person.
• Maximum arresting force of 1,800 lb on the body.
• Free fall limited to 6 feet and the worker must not contact a lower level.
• Deceleration distance limited to 3.5 feet.
• Prompt rescue must be planned and available - suspension trauma can be fatal within minutes.
• Inspect before each use, and remove from service any component that has arrested a fall.

Ladders

• Extension ladders: 4 to 1 ratio (1 foot out for every 4 feet of height) and extend 3 feet above the landing, secured at the top.
• Three points of contact at all times; do not carry loads that compromise it.
• Fixed ladders over 24 feet require a personal fall arrest system, ladder safety system, cage, or well - and under the current rule, cages and wells alone no longer satisfy the requirement for new installations, with a phase-out for existing ones completing in 2036.

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3. Excavation and Trenching (29 CFR 1926 Subpart P)

Trench collapse is the highest-fatality task in utility work. A cubic yard of soil weighs about 3,000 pounds - the weight of a small car.

Soil classification

Previously disturbed soil - which includes every utility trench being reopened - can never be Type A. Soil is classified by a competent person using at least one visual and one manual test.

Protective systems

Required in any excavation 5 feet or deeper unless it is entirely in stable rock. (Protection is also required in excavations less than 5 feet if the competent person finds a potential for cave-in.)

Excavations deeper than 20 feet require a protective system designed by a registered professional engineer.

The other rules that get cited

• Egress - a stairway, ladder, or ramp within 25 feet of lateral travel in trenches 4 feet or deeper.
• Spoil setback - excavated material, equipment, and materials kept at least 2 feet from the edge.
• Daily inspection by the competent person before each shift, as needed through the shift, and after every rainstorm or other hazard-increasing occurrence. The competent person has authority to remove workers.
• Atmospheric testing required in excavations deeper than 4 feet where a hazardous atmosphere could exist - which at a sewer job it always could.
• Water accumulation - workers may not work in an excavation with accumulated water unless precautions are taken, with the water removal monitored by the competent person.
• Underground utilities located before digging. In Virginia, VA811 notification is required 3 working days before excavation under the Underground Utility Damage Prevention Act; utilities must mark, and hand digging is required within the tolerance zone.
• Surcharge loads - no equipment or spoil placed where it can load the trench wall.
• Adjacent structures must be supported if the excavation could undermine them.

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4. Work Zone Traffic Control

Most water and sewer work happens in a street, and being struck by a vehicle is a leading cause of utility worker death.

• MUTCD Part 6 governs temporary traffic control. A traffic control plan is required for work in a roadway.
• The standard zones: advance warning area, transition area (the taper), buffer space, work area, and termination area.
• Taper length for a lane closure is calculated from the posted speed and lane width - the standard formula uses L = WS at 45 mph or above (where W is the offset width in feet and S is the speed in mph), and L = WS-squared/60 below 40 mph.
• High-visibility apparel is mandatory: ANSI/ISEA 107 Class 2 for most utility work, Class 3 for high-speed roadways or night work.
• Flaggers must be trained and certified, use a STOP/SLOW paddle, have an escape route, and never stand in the open lane.
• Night work requires additional lighting, retroreflective devices, and Class 3 apparel.
• Positive protection - barriers or a truck-mounted attenuator - should be used on high-speed roads rather than cones alone.
• Open manholes and excavations must be guarded at all times and never left unattended without barricades and, at night, lighting.