Utility locate marks field guide: colours, validity, and what to photograph before excavation

You filed your locate request with Info-Excavation -- following the steps in our call before you dig guide -- and now there are coloured lines, flags, and stakes across your property. What do they all mean? This field guide explains the colour code, how long marks stay valid, what the tolerance zone requires, and why you should take photos before the first shovel hits the ground.

The APWA colour code for underground utilities

Canada and the United States follow the same standardized colour system established by the American Public Works Association (APWA). Each colour represents a specific type of buried infrastructure:

Red paint crossing your yard means an electrical line. Yellow means gas -- see our gas line safety guide for the specific precautions required around yellow-marked lines. Orange means a telecom cable. Knowing the code helps you understand the risk level at every point in your dig zone.

How marks are applied

Locators use several methods to indicate underground infrastructure:

• Spray paint directly on the ground surface
• Pin flags (small flags on wire stakes)
• Wooden stakes with coloured tops
• Chalk marks on paved surfaces

The method depends on the surface type, weather, and utility company preferences. On grass, paint and flags are most common. On asphalt or concrete, you'll typically see paint or chalk.

The tolerance zone: where hand-digging is required

Locate marks show the approximate centre line of a buried utility, but there's inherent imprecision. That's why every mark comes with a tolerance zone on either side. Within this buffer, you must dig by hand or use soft excavation methods.

Energir, Quebec's gas utility, requires a 1-metre buffer on either side of the marked pipe. Within that zone, the only approved methods are:

• Manual digging with a shovel
• Hydro-excavation (pressurized water)
• Vacuum excavation

Mechanical equipment like excavators and augers must stay outside the tolerance zone. The Canadian Guidelines for Safe Excavation provide detailed procedures for working safely within these areas.

How long locate marks stay valid

Locate marks don't last forever. They're valid for a limited period from the date they're placed. Several factors shorten their lifespan:

• Rain washing away paint
• Lawn mowing removing flags or dispersing paint
• Snow covering marks in winter
• Foot and vehicle traffic wearing down surface marks
• Construction activity disturbing the area

If your project gets delayed, check whether your marks are still visible and still within their validity period. When in doubt, file a new locate request with Info-Excavation. It's free and takes only a few minutes.

According to Info-Excavation's FAQ, if marks fade or become unclear during your project, stop work and request an update before continuing.

What to photograph and when

Taking photos of locate marks is one of the simplest things you can do to protect yourself.

Before you start digging

• Wide shots showing the full layout of marks across your property
• Close-ups of each colour/mark type with a reference object for scale
• The relationship between marks and your dig area (white marks vs. utility marks)
• Address or landmark in frame to establish location
• Date and time stamps (most phone cameras do this automatically)

During the project

• Any exposed utilities you encounter while digging
• The condition of marks at the start of each work day
• Changes to marks caused by weather or activity

Why photos matter

If a utility gets damaged during excavation, the first question will be whether locate marks were present and respected. Timestamped photos provide clear evidence that you followed the process. Without them, it becomes a he-said/she-said situation.

What to do if you find an unmarked utility

If you hit something underground that wasn't marked, stop digging immediately. Don't try to pry it loose or dig around it. Contact Info-Excavation and the relevant utility. An unmarked utility is a problem for the utility company, not for you, but only if you had a valid locate request on file.

What Info-Excavation doesn't cover

Worth understanding the limits of a locate request. Info-Excavation covers infrastructure belonging to its member utilities, which include Hydro-Quebec, Energir, Bell, TELUS, Videotron, and others. However, the service doesn't mark:

• Private utility lines (your own sewer lateral, sprinkler system, or private electrical feed)
• Abandoned infrastructure that's no longer in service
• Municipal infrastructure that isn't part of the member network

For private lines, you may need to hire a private utility locating company, especially if you're digging near an older property where previous owners may have installed underground features.

Depth isn't guaranteed

Locate marks show the horizontal position of a utility, not its depth. According to Energir, "natural gas lines are not always buried at the same depth." The same applies to electrical, telecom, and water lines. Depth can vary due to previous construction, erosion, or frost heave.

This is exactly why the tolerance zone and hand-digging requirement exist. You need to carefully expose utilities to confirm their actual depth before bringing in heavy equipment.

Quick reference checklist

Before you break ground:

• File a locate request at info-ex.com or call 1-800-663-9228
• Wait at least 3 business days for processing
• Verify all utility marks are in place
• Photograph every mark with timestamps
• Identify the tolerance zones (1 metre on each side)
• Confirm you have hand-digging tools for tolerance zones
• Keep marks visible throughout the project

Need help with a landscaping project that involves digging? Call Montreal Paysagement Pro at 514-900-3867. We handle locate requests, follow safe excavation practices, and make sure your project goes smoothly from first dig to final cleanup.

Sources:

• Info-Excavation - Official website
• Info-Excavation FAQ
• Canadian Guidelines for Safe Excavation
• APWA Uniform Color Code
• Energir: check before you dig