Step by step: a look at how integrity digs help prevent pipeline leaks

In our step-by-step series, we’re outlining a few of the processes and technologies that help keep Canada’s transmission pipelines safe. So far we’ve taken a step by step look at pipeline design and leak detection technology. This week, we’re going to explain how an integrity dig works – from start to finish.

Why do pipeline companies decide to do an integrity dig?

An integrity dig is when a section of pipeline is excavated to give pipeline operators an up-close view of the pipeline to determine if a repair or replacement is required. The process begins when a routine inspection detects something out of the ordinary. 

Operators use many different technologies including sensors and in-line inspection tools called smart pigs, all of which can detect anomalies, such as metal loss or corrosion that could eventually result in a leak. Smart pigs, like the one below, use a variety of technologies such as sensors, transmitters, GPS, magnetic fields, eddy current, ultrasonics and acoustics to find anomalies:

smart pig pipeline leak detection technology

How the pipeline is safely exposed

If a potential flaw is identified, the operator evaluates the anomaly and takes the required steps to ensure the continued integrity of the pipeline – such as an integrity dig.

The first step in this process is determining the exact location for the integrity dig and notifying and cooperating with landowners.

Then the pipeline operator inspects the pipeline right of way and identifies and marks any other underground utility services using a One-Call service.

Then the pipeline is exposed – operators carefully strip the topsoil, followed by the other layers, preserving each layer to be re-used later. Machines are used to dig alongside the pipeline, but the pipe itself is exposed slowly and carefully by hand:

hand exposing pipeline during an integrity dig

Finding the anomaly

Once the pipeline coating is removed, the operator visually inspects the pipeline. The anomaly may be very hard to see with the naked eye – either because it is so small, or because it is on the inside of the pipeline. The anomaly is found using magnets and water containing iron particles, which will line up along any breaks in the pipeline, and with ultrasound technology:

using magnets to detect a pipeline anomaly

Mending and reinforcing the pipeline

No matter how small the anomaly, it is taken very seriously by the pipeline operator. Before repair and maintenance begins, the operator will carefully divert the product around the segment that’s being repaired. One of the most common methods of repair is to re-coat the pipeline with epoxy and cover the entire section with a sleeve. This is then clamped to a specified pressure to ensure an effective seal, and the seams of the sleeve are welded:

Sleeve used to fix pipeline

Protecting the pipeline 

Once the pipeline has been fixed, it is coated and then wrapped twice to protect it during the backfill process:

wrapping a pipeline for protection

Third party inspection

Operators clean up and return the land to its original state. In addition, an independent environmental inspector is on-site during the integrity dig to ensure that the land and the environment are protected at all times during the entire process. For instance, they help to ensure that, after the dig, the soil is replaced in its natural layers.

environmental expert

To learn more about the steps described in this post, check out the integrity video below:

For other posts in our step by step series, check out A look at pipeline design and A look at pipeline leak detection technology. And then take a look at our integrity dig factsheet, which explains more about this important safety process.


The Canadian Energy Pipeline Association represents Canada’s transmission pipeline companies who operate approximately 119,000 kilometres of pipelines in Canada. In 2015, these energy highways moved approximately 1.2 billion barrels of liquid petroleum products and 5.4 trillion cubic feet of natural gas. Our members transport 97 per cent of Canada’s daily natural gas and onshore crude oil from producing regions to markets throughout North America.