The Impossible is Now Possible:
The Evolution of Trenchless Technology

It is said that the word “sewer” is derived from the term “seaward” in Old English. Early sewers in London were open ditches which drained into the Thames River, which then flowed down to the sea, or seaward. We have come a long way since then. Here is a glimpse of how we have progressed in the cleaning, inspection, assessment and repairing of our subterranean infrastructures.

Conversion of the Cleaning Process

In the old days, cleaning a sewer line meant sending a worker down a manhole with a bucket. Eventually a powered machine was developed with a bucket attached to a cable that was dragged from one manhole to the next, eliminating the need for crews to enter the sewers.

Then hydraulic sewer cleaning became the norm. Attaching hoses to water pumps and nozzles to hoses, high pressure water was used to flush the pipes. This technology dramatically changed the industry – sewers were cleaned more efficiently and with less risk to the crews.

The technology evolved even more. Now, as the sewerage is flushed out of the pipes, the dirt is separated from the water and the recycled water is reused. This process lowers the volume of sewerage sludge, and generates grey water which can be re-used to continue with the cleaning.

Cameras can also be fitted to the nozzle of the pipe, giving the operator a real-time view as to where to apply water pressure to clean more effectively. The data collected by the camera can also be downloaded for further off-site assessment.

Evolution of the Inspection

In the past manholes were not installed as often as they are now. In their place lampholes were installed – essentially 150mm diameter viewing ports that extend from the sewer to the surface. Workers would use lampholes to inspect sewers with a flashlight. If there were anomalies with flow, they would use a bucket machine to move or dislodge whatever was in the way. However, if the pipe was big enough for someone to enter, they would send a person in to conduct a more detailed inspection. These methods were dangerous, labour intensive and the reporting was very subjective.

Today PACP’s standards are adhered to so that all data and observations are presented in a uniform language. Using state-of-the-art trenchless technology, crews can now conduct inspections in much greater detail with a common language and data dictionary.

Some of the features of modern day inspection equipment include:

  • Sensors for hydrogen sulfide to identify potential future corrosion in the pipe;
  • Sonar scanning to see what’s happening below the waterline;
  • Sewage temperature sensors to find water infiltration
  • 3D Lasers that can measure the diameter of the pipe, and
  • Floating cameras attached to umbilical cords for visual inspection in fast flowing systems;
  • Miniature versions of tanks like The RedZone® responder robot which has multiple sensors and can be used in large diameter trunk sewers in any flow conditions;
  • Electric current application to identify leaks not visibly apparent.

Inspecting the interior of the pipe is not enough, however, so to see what is going on outside of the infrastructure, acoustic and backscatter tomography was developed. Ground penetrating radar was adapted from surface scanning to inside the pipe, while pipe penetrating radar looked for voids outside the pipe. Seismic sensors help identify the thickness of the pipe walls and conditions around the pipes, identifying voids, potential sink holes and other possible problems.

Inspection technology took another leap forward with the introduction of radioactive isotope technology. A Canadian invention, it is like a CAT scan for infrastructure – a form of industrial diagnostic imaging to enhance the understanding of structural soil conditions around CMP assets.

Pinpointing the exact location and depth of the infrastructure has also evolved considerably. Over the years, 3D mapping and modelling using GIS technology and GPS location information from inside the pipe can show exactly where the pipe is in real space.

Adaptation of the Assessment

Historically, it was a challenge to obtain accurate information to get a clear picture of the condition of sewers. Crews relied on some rudimentary procedures to assess the infrastructure, including water quantity and quality, flow rate and the physical appearance of the pipe. If they detected a problem, they would dig up the pipe for a closer look and record their findings – a subjective and messy exercise.

Today’s Electro Scan infiltration assessment provides an effective way to manage, protect, operate, and certify infrastructure. An electric current device is used to help rate pipes on infiltration potential. This is important because infiltration can cause a loss of bedding around the pipe, which can lead to the pipe settling, changing the stress pattern and possibly causing cracking or deformation of the pipe.

Combining the Electro Scan information with the PACP coding system for classifying defects in the pipe allows for more comprehensive pipe condition assessments. This information, combined with other data collected from the sensors, can be used for prioritizing new projects, repairs and rehabilitations.

Revolution of the Repair

In days gone by, the only options were to leave the damaged pipe in situ, install a new one, or dig it up and repair it. Since trunk sewers can be over 30 meters deep and residential sewers can be 5-10 meters below the surface, this was a very invasive and costly exercise.


Some of the repair techniques used today are:

Grout in Place (GIPP)

Grouting might be the oldest technology, but it is still used today because it works. Grouting involves the injection of a flexible grout, filling the voids behind the pipe to stop water from coming in, and reshoring the structure around the pipe to keep the pipes intact. Today’s grout is made from more advanced materials and can be tested to ensure the problem has been fixed.

Cured in Place (CIPP)

Cured in situ pipeline repairs came later in the ‘70s. In this process, a resin soaked, flexible material that conforms to the internal diameter of the pipe, regardless of shape, is applied over the damaged area and with the addition of energy, causes it to cure and become hard.

The original materials required heat to cure, whereas the newer materials are cured with UV light and have reinforced fabric, making it more efficient and stronger. Now engineers can even say how thick the material must be and how long the pipe will last – even up to 75 years.

Spray in Place (SIPP)

A spray in place repair involves spraying a polymer like epoxy on corroding structures that have begun to deteriorate due to chemicals and hydrogen sulfide gas in the pipe. This technology is becoming more popular in the last 10 years and is suited to man entry large pipes or smaller pipes using robotic application.

Pulled in Place

As the name suggests, a new piece of pipe is pulled into an older/damaged pipe. This method is best used on large pipes and care must be taken to select the correct type of material for the job. The void between the two pipes is then filled with grout.

Steel Sleeves

Steel sleeves are suitable for short repairs and spot fixing. The steel sleeves are jacked into position by man or robot and spring locked against the damaged section of the pipe. The sleeve is then left in place, resulting in a localized, durable spot repair.


The evolution of trenchless technology has made the impossible now possible. All of these NODIG technologies allow you to make better, more informed decisions about the maintenance and repair of your subterranean infrastructure – with no digging, less mess and fewer disruptions.

Robichaud has the most cost-effective, long-term rehabilitative NODIG processes available, providing every type of trenchless sewer, pipeline and culvert cleaning, inspection, assessment and repair system imaginable. With our expert team of qualified technicians and fleet of specialized sewer rehabilitation trucks and robots, we have the expertise and equipment to help you maintain your infrastructure.