Electrical Hazards Awareness Briefing Excavation and Trenching Module 5

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Electrical Hazards Awareness BriefingExcavation
and TrenchingModule 5
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These tools must be used with care!
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Serious Injury at DOE Site when 13.2kV Cable
Struck

• A laborer was burned and rendered unconscious
  when his jackhammer hit a buried 13,200 volt
  electrical power cable.

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Typical Tasks That Expose Personnel to
Underground Power Lines

• Construction site excavation
• Jack-hammering
• Well drilling
• Landscaping
• Trenching for piping
• Fence installation

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Excavation Program Elements

• Designate a Competent Person to oversee all
  excavation jobs and train to understand the
  electrical hazard
• Use written excavation procedure and excavation
  permit
• Require an excavation/trenching checklist to be
  used in job planning
• Require non-intrusive surveys of areas and
  develop an interference map of area
• Ensure excavation planning requirements flow down
  to subcontractors

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Electrical Hazard Identification

• Perform detailed drawing and map review including
  original site drawings and recent project
  drawings
• Understand that drawings and maps, however, may
  not be up to date or indicate all field routings
  correctly
• Perform walk-down of site surrounding the
  excavation area and look for conduits and
  raceways that extend underground and could cross
  into the excavation work zone
• Discuss excavation area with facility site
  knowledge
• Look for new asphalt, manholes not marked on
  prints or disturbed soil to identify potential
  for unmarked interferences

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Field Investigation

• Perform non-intrusive surveys of excavation area
  using trained and certified utility locators
• Mark surface with interferences and verify
  immediately prior to start of excavation
• Know limitations of non-intrusive equipment
• GPR has been off target by 3 feet and may not
  identify some interferences
• Voltage proximity detectors are shielded by
  ground wire or conduit
• Current proximity detectors will not detect if
  electrical load is turned off

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Identifying Interferences

• De-energize and lockout known electrical
  hazards-Dont let schedule and convenience take
  precedent.
• Hand excavate interferences within excavation
  limits
• Look for different types of soil in the
  excavation area or for colored concrete that may
  indicate presence of underground electrical line
• Consider use of vacuum excavation technology for
  uncovering interferences
• Use caution when hand digging-even shovels and
  post hole diggers can damage direct burial cables

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Identifying Interferences

• Use appropriate PPE (voltage rated gloves and
  footwear) when identifying electrical
  interferences
• PPE is important since detection of hidden
  utilities can not always be guaranteed
• Use double-insulated electrical tools
• Use fiberglass-insulated shovels and picks when
  excavating by hand
• Use rubber mats as appropriate

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Other Safe Practices

• Stop work and call a time out if an unidentified
  obstruction is found during excavation
• Revise maps and drawings to reflect actual found
  field conditions before closing excavation permit
• Consider use of electronic drill stops when
  drilling in concrete (DOE Electrical Safety
  Handbook Section 11)
• Observe all Power Line Right of Ways and notify
  power company prior to excavation

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Conclusion

• Remember, you can avoid the pain and suffering
  that can happen when you contact an underground
  energized electrical power line
• Implement and follow the practices in this module
• Stop work when in doubt