Hydrovac Utility Locating

The act of locating utilities through hydrovac is becoming increasingly common. This is the safest way for workers to locate the underground utilities and it helps to minimize potential damage and downtime that would have occurred if the exact location was not known. By exposing them by hand, the utilities can be repaired, installed, and inspected more efficiently. By law in Alberta, hand exposure of underground utilities in an area where ground disturbances are intended, is a must.


Because there are so many different types of materials that are used to make and hide the underground lines, there are different detection and location methods. Electromagnetic locating equipment is used to detect metal pipes and conductive cables with help from a transmitter and receiver. For more traditional types of pipes, such as concrete or plastic, other types of radar detection is used, such as ground-penetrating radar or radiolocation.

What Could Be Encountered?

When excavating and tunnelling with hydrovac, these are some of the underground services that may be encountered:

  • Water
  • Sewage
  • Oil
  • Natural gas
  • Cable lines
  • Electric lines
  • Electric energy
  • Telephonic communications
  • Chemicals

These may be hidden inside pipes, conduits, wires, cables, valves, manholes, catch basins, ducts, and other attachments. The starting steps for locating these things start with a surface study by another company that can correctly identify the exact location of them from the surface. The term “call before you dig”, and “One-Call” are some of the terms that are used to identify the proper third-party vendors that are available for use before the ground disturbances are done. They will then identify where the utilities are by using color-coded markings to show where they are.

APWA Uniform Color Codes

If you are driving down the road and happen to see bright colored spray paint on the ground, this was probably used in preparation for hydrovac excavation. These colors are part of a color code system to identify underground lines. Colored lines or flags mark the type of underground utility so that the workers know exactly what they are exposing. If there is a flag, this usually identifies the company or utility that the line belongs to. In Canada, the use of APWA Uniform Color Codes are used which includes;

  • RED – Cables, conduit, lighting cables, and electric power lines.
  • ORANGE – Telecommunications, signal lines, cables, conduit, or alarms.
  • YELLOW – Oil, steam, petroleum, natural gas, or other flammable or gaseous materials.
  • GREEN – Drain lines and sewers.
  • BLUE – Drinking water
  • PURPLE – Slurry lines, irrigation, and reclaimed water.
  • PINK – Unknown or unidentified facilities and temporary survey markings.
  • WHITE – Proposed excavation limits or route.

Once everything is properly located, the process of hydrovac will begin the ground removal process using the colored lines and flags as guidelines. As more of the material is removed, the utilities can safely be exposed and visually identified.