# Presentation: 486512

## Electrical Hazards Awareness BriefingExcavation and TrenchingModule 5

## These tools must be used with care!

## 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.

## Typical Tasks That Expose Personnel to Underground Power Lines	

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

## 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

## 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

## 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

## Identifying Interferences

- De-energize and lockout known electrical hazards-Don’t 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

## 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

## 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

## 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