Published 7 September 2026
The most dangerous thing on a demolition site is often the thing nobody can see. Buried gas, hydro, water, and telecom lines run under most GTA properties, and older lots hide private lines that never made it onto a single map. This is why experienced demolition contractors never dig on assumption. Before any excavation, a proper professional residential demolition service starts with locating exactly what is underground. Knowing that unmapped lines exist changes how the entire job is planned.
This guide explains how buried utilities are safely handled during a demolition. We cover the free Ontario locate service, why some lines are unmapped, how services get shut off, and where potholing and hydrovac excavation come in. This is essential planning information for homeowners, not a do-it-yourself excavation guide.
In This Article
Start With an Ontario One Call Locate
Every demolition that involves digging in Ontario should begin with a strict locate request. The service is Ontario One Call, which is the province’s free click-before-you-dig system. You or your contractor submit a request, and the utility owners send professional locators to mark their buried gas, hydro, water, and telecom lines directly on the ground using colored paint and flags. It is free, it is legally expected, and it is the single most important step in avoiding a struck line.
The marks tell the crew exactly where the known public utilities run so they can dig with care or avoid those zones entirely. On a demolition site, this locate is arranged well before excavation, and no responsible crew starts digging until the marks are down and current.
Quick Take
Every dig starts with an Ontario One Call locate. It is totally free, it marks the known buried lines, and absolutely no excavation should begin until the marks are down. It is the absolute foundation of safe demolition, not an optional extra.
Why Some Lines Are Unmapped
Here is the catch that surprises many homeowners: a public locate marks the utility lines up to your property line, but it does not cover everything buried on your land. Private lines that a previous owner ran themselves are frequently undocumented and will never show up on a standard locate. On older GTA lots, these unmapped lines are incredibly common.
- A gas line running to a pool heater, detached garage, shed, or backyard fire feature.
- Electrical feeds buried out to a detached garage, shed, hot tub, or elaborate landscape lighting.
- Irrigation and sprinkler lines threaded randomly across the yard.
- A private water line to an outbuilding, or an old abandoned well or cistern.
- Septic components, drainage pipes, and sump discharge lines.
- Abandoned services that were never properly capped, removed, or recorded.
Because these private additions will not appear on the public locate, the demolition crew has to treat the yard as if unknown lines are present. This is where your personal knowledge of the property matters. Anything you or a past owner installed underground is worth flagging before work starts.
Did You Know?
Private locates exist for exactly this reason. Beyond the free public locate, a homeowner can hire a private locator to scan the property for buried services the public system does not cover. On older lots with pools, outbuildings, or a heavy history of renovations, that extra scan can be well worth the investment before demolition starts.
Shutting Off Gas, Hydro, and Water
Locating lines is only half the picture. Before a structure comes down, the services feeding it have to be fully shut off and disconnected by the right party, not just marked with paint. Each utility has its own specific process, and none of them is a do-it-yourself task.
Gas is shut off and the line is safely capped by the gas utility. Hydro is disconnected by the electrical provider, since a live service line inside a wall during demolition is a massive hazard. Water and sewer are shut off and confirmed by the local municipality. A responsible crew confirms every one of these disconnections in writing before demolition begins, because an inspector will check and a missed disconnection is incredibly dangerous.
Red Flag: Assuming a Service Is Dead
Never assume a utility is disconnected just because a building looks abandoned or the power seems off. Meters get removed while lines stay fully live, and services to outbuildings can run on entirely separate feeds. Every gas, hydro, and water connection must be confirmed disconnected by the provider before demolition. Assuming instead of confirming is how people get hurt.
Potholing and Hydrovac: Digging Safely
When a locate shows a line running near where the crew needs to dig, marks on the surface are simply not precise enough to trust with an excavator bucket. That is where potholing comes in. Potholing means carefully exposing a buried line to confirm exactly where and how deep it is before any heavy digging happens nearby.
The safest way to pothole is using a hydrovac truck. Hydrovac uses highly pressurised water to break up the soil and a strong vacuum to remove it, exposing the line without a metal blade ever touching it. It is slower and costs more than swinging a bucket, but next to a gas or hydro line, that trade-off is obvious. Crews use it whenever a live line is close to the work area.
- Precision: Potholing confirms the exact position and depth of a marked line before machine excavation begins nearby.
- Safety: Hydrovac exposes lines with water and suction, so no blade contacts the fragile utility.
- Standard Practice: It is standard procedure near gas, hydro, and major water lines where a strike would be catastrophic.
- Protection: It protects both the crew and the surrounding neighbourhood from a severe service outage or worse.
Pro Tip
When you review the demolition plan with your contractor, ask how the crew will handle any line the locate shows near the work. Hearing the words “potholing” or “hydrovac” is a very good sign. It means they respect the risk and are not planning to dig blindly next to a marked utility.
Who Handles What
Utilities on a demolition site involve several different parties, and it helps to know who does what. This keeps you from assuming your contractor handles something that is actually the utility company’s job, or the other way around.
| Utility or Task | Who Handles It | How It Is Located or Done |
|---|---|---|
| Public buried lines | Utility owners via Ontario One Call | Free locate, marked with paint and flags |
| Private buried lines | Homeowner and a private locator | Owner disclosure plus a paid private scan |
| Gas shutoff and cap | The gas utility | Line capped and confirmed before demolition |
| Hydro disconnection | The electrical provider | Service disconnected, confirmed in writing |
| Water and sewer shutoff | The municipality | Shut off at the property and confirmed |
| Digging near marked lines | The demolition contractor | Potholing or hydrovac to safely expose |
Please note: This table is general guidance for GTA homeowners and does not replace the specific procedures of your local utilities and municipality, which can differ and change over time. Locating, disconnecting, and excavating near utilities is highly specialised work for the utility owners and licensed contractors. Always confirm the process for your specific property before any demolition.
How Contractors Plan Around the Unknown
Warning: The information below explains professional practice so you know what to expect. Locating, capping, and excavating near utilities is dangerous, specialised work. Never dig or disconnect services yourself. Always hire a licensed demolition contractor and the proper utility providers. ALMAR Demolition is not responsible for injury, damage, or cost from work attempted based on this article.
A good crew builds the whole job around the assumption that the ground holds surprises. They start with the Ontario One Call locate, add a private locate where the property history warrants it, confirm every service disconnection in writing, and pothole or hydrovac wherever a line sits near the work. Then they dig cautiously in any zone that could hide an unmapped line, constantly watching for the tell-tale signs of an old service as they go.
Your part as the homeowner is straightforward. Tell the crew everything you know about what is buried, from the pool heater gas line to the old sprinkler system a past owner mentioned. That local knowledge, combined with proper locates, is what keeps an unmapped utility from becoming an emergency. For more on the hidden risks of any teardown, see our comprehensive guide on avoiding common demolition hazards.
Save Your Money
A struck gas or hydro line can mean emergency repairs, massive municipal fines, a neighbourhood outage, and a completely stalled project. Paying for proper locates and hydrovac excavation up front is a fraction of that cost. Prevention is always cheaper than a strike, and far safer.
“The public locate came back clean, but I mentioned the old gas line the previous owner ran to the pool heater. The crew potholed and found it exactly where I said. That one conversation avoided a disaster.”
— GTA Homeowner, Demolition Project
Download the Free Quick Guide
A one-page checklist for locates, shutoffs, and safe digging around known and unmapped lines.
Frequently Asked Questions
Concerned about what is buried under your property before a teardown? ALMAR Demolition arranges proper locates, coordinates utility shutoffs, and digs safely around known and unmapped lines across Toronto, Etobicoke, Brampton, and the wider GTA. Get a free estimate today and we will secure the utility side before any digging begins.