Ontario One Call & Utility Locates in Guelph: What Contractors Must Know

Every year in Ontario, underground utilities are struck during excavation — gas lines, fibre cables, water mains. The consequences range from costly repairs to fatalities. Ontario's utility locate system exists to prevent this, but it's only effective if contractors understand how it actually works.

Ontario One Call: The Basics

Ontario One Call (811 or ontarioonecall.ca) is the province's underground infrastructure notification centre. When you submit a locate request, One Call notifies all member utilities with infrastructure in your area. Each utility then sends a locator to mark their lines before you dig.

Timeline: Submit your request at least 5 business days before excavation. Emergency requests (for active utility strikes) are handled immediately.

Coverage: One Call covers natural gas, electrical, water, wastewater, telecom, and most other buried infrastructure. However, private utilities on private property — a homeowner's gas line from the meter to the house, for example — are NOT covered by One Call. You are responsible for locating private utilities separately.

The Locate Process Step by Step

1. Submit a locate request at 811 or ontarioonecall.ca. You'll need the site address, planned start date, and type of work.
2. Each utility has 5 business days to complete marking (some do it within hours).
3. You receive a notification for each utility that has either marked their lines or cleared the area (no infrastructure present).
4. Marks are valid for 30 calendar days from the date they were placed — confirm marks haven't faded or been disturbed before starting work.
5. If marks are unclear or you're unsure whether all utilities have responded, call One Call again before digging.

What the Marks Mean

Utility marks follow a colour code established by the American Public Works Association (APWA), used across Ontario:

• Red: Electric power lines, cables, conduit
• Yellow: Natural gas, oil, steam, petroleum
• Orange: Telecommunications, cable TV, alarm lines
• Blue: Potable water
• Green: Sewers and drain lines
• White: Proposed excavation area (marked by the contractor)
• Pink: Temporary survey markings

The Tolerance Zone and What It Means

Locate marks are accurate to approximately ±50cm in ideal conditions. The "tolerance zone" — the area within which mechanical excavation is prohibited — is generally 1 metre on each side of a marked utility (though this varies by utility owner). Within the tolerance zone, only hand tools or hydrovac are permitted under CGA Z247.

What Happens If You Strike a Utility

If you strike a utility — regardless of whether you had locates — stop work immediately, secure the area, and call:

• 911 for gas leaks, fires, or injuries
• The utility owner's emergency line (listed on marks)
• One Call to report the strike (this triggers an incident investigation)

Liability for utility strikes without proper locates is significant. In Ontario, contractors who dig without locates face fines and civil liability for all repair costs and service restoration.