Reducing Confined Space Entries in Electrical Utility Underground Vaults

Electrical utilities face serious confined space hazards in underground vaults. Zistos pole cameras have enabled Eversource to reduce physical vault entries by 80%, dramatically improving worker safety and operational efficiency.

The Challenge: Underground Electrical Vaults as Confined Spaces

Underground electrical utility vaults are among the most hazardous confined spaces in the utility industry. These below-grade structures house high-voltage transformers, switchgear, cable splices, and distribution equipment, and they present a unique combination of life-threatening hazards that make every entry a serious safety event.

Hazards Specific to Underground Electrical Vaults

• Atmospheric dangers: Underground vaults can accumulate toxic gases (hydrogen sulfide, carbon monoxide), oxygen-deficient atmospheres, and explosive methane from surrounding soil and decomposing organic material
• Electrical arc flash risk: Energized high-voltage equipment creates the potential for catastrophic arc flash events, which can generate temperatures exceeding 35,000°F
• Water intrusion and flooding: Groundwater seepage and stormwater infiltration create slip hazards, electrical grounding concerns, and can submerge energized equipment
• Limited egress: Most vaults are accessed through a single manhole opening, restricting rapid evacuation in an emergency
• Biological hazards: Standing water and dark environments attract insects, rodents, and in some regions, venomous snakes

Under OSHA 29 CFR 1910.146, nearly every underground vault qualifies as a permit-required confined space. Each entry demands atmospheric monitoring, a written permit, a trained entrant, an attendant stationed at the opening, rescue provisions, and supervisory oversight. For large utilities managing thousands of vaults across their service territory, the cumulative cost and risk of physical entries is substantial.

The Eversource Partnership

Eversource Energy, one of the largest utility companies in the northeastern United States, operates an extensive network of underground electrical infrastructure across Connecticut, Massachusetts, and New Hampshire. Their crews routinely access underground vaults for equipment inspection, maintenance planning, and post-storm damage assessment.

Working with Zistos, Eversource integrated pole camera systems into their vault inspection workflow. The result: an 80% reduction in physical confined space entries across their underground vault operations.

How It Works

Instead of sending a worker down into a vault for a visual assessment, Eversource crews now lower a Zistos pole camera through the manhole opening from the surface. The camera system provides:

• Real-time HD video displayed on a surface-level monitor, allowing the crew to see the entire vault interior without descending
• Motorized articulation to pan and tilt the camera head remotely, inspecting all areas including behind equipment and in corners
• Optical zoom (10X or 30X) to examine cable terminations, splice conditions, and equipment nameplates from a distance
• Thermal imaging to detect overheating connections, transformer hot spots, and abnormal temperature conditions that indicate electrical faults
• White light illumination built into the camera head, eliminating the need for separate lighting setups

The operator remains on the surface throughout the inspection. If the visual assessment reveals that physical entry is required for maintenance or repair, the crew proceeds with a full permit-required entry, but now with detailed advance knowledge of conditions inside the vault.

Safety Impact

Inspections that previously required a worker to descend into a vault are now, in many cases, resolved through remote video assessment. Physical entry remains an option when the inspection calls for it.

This reduction directly translates to:

• Fewer worker exposures to atmospheric hazards, arc flash risk, and fall hazards
• Reduced permit-required entry costs, each avoided entry eliminates the need for standby rescue, atmospheric monitoring equipment setup, and the multi-person crew required by OSHA
• Faster inspection cycles, a remote video assessment typically takes 10–15 minutes versus the 45–90 minutes required for a full permit-required entry
• Better documentation, video recordings from each inspection create a permanent visual record for maintenance planning, asset management, and regulatory documentation

The Equipment

Eversource utilizes the Zistos APEX Industrial Pole Camera platform configured specifically for underground vault work:

• Carbon fiber telescoping poles up to 30 ft (9.1 m), depending on vault depth
• Wide-angle HD camera for initial overview assessment
• 30X optical zoom camera for detailed equipment examination
• Dual-mode thermal camera for identifying hot connections and overloaded circuits
• 7-inch ruggedized display mounted at the surface for real-time viewing
• Recording capability for documentation and post-inspection review

The entire system is portable and can be deployed from a standard utility truck without specialized lifting equipment.

Operational Workflow Integration

The key to Eversource's success with remote vault inspection is the integration of Zistos technology into their standard operating procedures. Remote video assessment is now the default first step for all non-emergency vault inspections:

• Arrive on site and secure the work area per utility safety protocols
• Open the manhole cover and conduct atmospheric monitoring at the opening
• Deploy the Zistos pole camera through the opening, no worker descends
• Conduct a systematic visual survey of the vault interior, documenting equipment condition, water levels, cable routing, and any visible damage
• Determine disposition: If the inspection objective can be satisfied by video alone, the job is complete. If physical entry is required, the crew now has detailed pre-entry intelligence to plan a safer, more efficient entry.

This workflow shift represents a fundamental change in how utilities approach underground infrastructure inspection, from "enter first, assess second" to "assess first, enter only if necessary."

Industry Implications

The Eversource deployment demonstrates that remote video inspection is not a supplemental technology, it is a primary safety control that can eliminate the majority of confined space entries in underground electrical utility work. For utilities operating thousands of underground vaults, the safety and efficiency gains are scalable across the entire service territory.

Other utility applications where the same approach applies include:

• Gas utility valve vaults and regulator stations
• Municipal water utility vaults and pump stations
• Telecommunications manholes
• District heating and cooling underground infrastructure

Any underground structure that requires periodic visual inspection and qualifies as a confined space is a candidate for remote video assessment with Zistos pole camera technology.