CAT & Genny: Safe Locating of Underground Services

Preventing strikes and protecting workers before excavation

CAT (Cable Avoidance Tool) and Genny (signal generator) are together the most widely used system for locating buried utilities before breaking ground. Proper use of these tools significantly reduces the risk of striking gas pipes, water mains, electrical cables and telecoms — preventing injury, service disruption and costly repairs.

What are Cat & Genny?

A CAT (Cable Avoidance Tool) detects signals returned from buried services. A Genny (signal generator) applies a signal to a service (directly or inductively) so the Cat can trace its line. Used together, they help identify the position and route of underground utilities.

Why correct use matters

  • Striking underground services can cause serious injury, fatalities, large-scale evacuations, and environmental harm.
  • Accurate locating reduces project delays, avoids expensive damage and protects your workforce and the public.
  • Many contracts and statutory bodies require documented service-locating procedures before excavation.

Common hazards when locating and excavating

  • Inaccurate or misinterpreted readings leading to a strike.
  • Working without up-to-date plans or service records.
  • Poorly maintained or incorrectly calibrated equipment.
  • Improper use in unsuitable ground conditions or near interference sources.
  • Inadequate training and lack of competence.

Safe work procedures for CAT & Genny locating

Always combine equipment checks, safe systems and site information before excavation:

  • Plan: Obtain and review utility plans, records, and maps before work starts. Contact local utility owners where necessary.
  • Survey: Carry out a visual site survey to identify access points, visible services, and potential hazards (e.g., traffic, overhead lines).
  • Equipment check: Ensure CAT and Genny are in serviceable condition, batteries charged, calibrated if required, and that the correct probes/accessories are available.
  • Method: Use the Genny to apply a signal (direct connection, clamp, or inductive coupling) and sweep the area with the CAT at a consistent height and speed to trace the route.
  • Marking: Mark the line clearly on the ground and on plans using agreed colour codes and durable markers or paint.
  • Confirm: Use confirmatory techniques where needed (trial holes by hand-digging, potholing, or vacuum excavation) to verify depth and exact position before mechanical excavation.
  • Record: Document findings (plan updates, photos, marked lines, and any uncertainties) and communicate them to the team.
  • Control: Use protective measures (diversion of services, insulation, barriers) and follow permit-to-dig or permit-to-work systems where applicable.

Best practice locating tips

  • Sweep the CAT in overlapping passes at a consistent height; sudden movements and tilting can give false readings.
  • Be aware of signal bleed and multiples — some services can carry stray signals from nearby conductors.
  • Switch between Genny connection methods (direct, clamp, inductive) to get the clearest trace for different service types.
  • Check for interference sources (metal fences, parked vehicles, high-voltage cables) and interpret readings accordingly.
  • When in doubt, stop work and use non-destructive trial holes to confirm.

Training, competence & equipment

  • Only trained and competent staff should operate CAT & Genny equipment. Training should include practical locating, interpreting signals, and recognising limitations.
  • Training courses should cover: tool operation, signal types, inductive vs direct connection, interpreting false signals, trial-hole techniques, and safety procedures for excavation.
  • Maintain an equipment log: calibration/servicing records, battery checks, and inspection notes.
  • Supervision and refresher training help maintain competence and reduce human error.

Confirmatory excavation (potholing) and safe digging

Never rely solely on detected lines for depth. Use safe digging methods to expose services before using mechanical excavators. Typical confirmatory methods include hand digging in the marked area, vacuum excavation, or other non-destructive techniques. Follow local permit-to-dig procedures and plant isolation protocols where relevant.

Incident response

  • If a service is struck, stop work immediately and make the area safe.
  • Follow emergency procedures for gas, electricity, or chemical/aqueous leaks — evacuate if required and contact the service owner and emergency services.
  • Record the event, preserve the scene for investigation, and report as required by your incident reporting policy and any statutory reporting duty.

Practical checklist — CAT & Genny locating

  • Utility plans obtained and reviewed
  • CAT & Genny inspected, batteries charged and operational
  • Operative trained and competent
  • Site surveyed and hazards identified
  • Genny signal applied (direct/clamp/inductive) and route traced with Cat
  • Lines clearly marked and recorded
  • Confirmatory potholing planned and executed before mechanical excavation
  • Incident procedures and emergency contacts available on site

Relevant Training Courses

CAT & Genny are essential tools for safe excavation work, but they are only effective when used by competent people within a robust system of planning, verification and control. Combining good locating practice with confirmatory potholing and clear communication will protect people, the public and buried infrastructure.

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