Building a pipeline is a step-by-step process. Safety of the public and workers, and protection of the environment are primary considerations. Determining the optimal pathway for the Trans Mountain Expansion Project (TMEP) pipeline helps minimize potential risks.

Sometimes, walking through a section of the potential right of way is sufficient to confirm it is suitable ground for construction and long-term operations. In some areas, however, a more detailed geotechnical investigation is necessary.

Geotechnical studies continue at a few TMEP locations in the Lower Mainland of British Columbia and other spots where Trans Mountain wants to understand how the surficial and subsurface geology may or may not impact pipeline construction and subsequent operation of the expanded pipeline. As well, Trans Mountain wants to understand the potential impact on the surrounding area and nearby infrastructure.

Locations for these studies include places where Trans Mountain plans trenchless (underground) watercourse crossings, including the Fraser River in the Lower Mainland. Trenchless technologies can also span roads, highways and third-party infrastructure such as water mains and electrical, natural gas and communications systems.

Similar geotechnical studies are often carried out for construction of large buildings, highways and other underground utilities and services including telecommunications, water mains and rapid transit.

For Trans Mountain, experienced geotechnical engineers and geoscientists direct these investigations. In the Lower Mainland for example, these experts are registered with Engineers and Geoscientists BC.

“A geotechnical investigation is an attempt to determine how the ground — whether it’s near-surface materials or anything really deep — is going to behave or respond as a result of construction,” explained Dr. Alex Baumgard, a principal geotechnical engineer who is leading the TMEP studies. “This investigation could be to assess for short term activity such as during TMEP construction or the eventual long-term, operational life of the expanded pipeline.”

Baumgard has carried out assessments for more than 50,000 kilometres of new and existing pipelines on three continents over a career of almost 20 years. Recently, he has led the geotechnical team for TMEP. This work includes directing a team of experts designing river crossings, assessing seismic issues and investigating the geotechnical feasibility of tunnels, all with the objective of ensuring the stability of the expanded pipeline and maximizing pipeline safety.

“A geotechnical study is very similar to other investigations that go on along the Project right of way,” Baumgard added. “We’re looking to see how the ground will react to construction and make sure that work doesn’t cause problems for safety or the environment.

“We start with a general survey or assessment of the area, looking at imagery from satellites or other maps. We figure out the most important areas and carry out a field investigation. People walk over the area to see if there are indications of instability or ground that may prove problematic during construction or over the long-term.”

“If it’s a section where the pipeline is going to go into a conventional trench, then it’s usually only the upper few metres of soil that are of interest. If it’s a subsurface installation, we could investigate that deeper ground with a drill rig — we prefer to do drilling because there is less impact on the environment than an excavation with a backhoe.”

We look for the least intrusive way to get the equipment into the location,” Baumgard said. “We try to bring in the smallest possible piece of equipment.

“The key goal is to remove unknowns. We have a general understanding of the geology in an area but a more detailed investigation may be necessary to improve our understanding. By drilling, we can better evaluate what is down there.”

A field walk-over typically takes just one day. However a drilling program may continue for one to two weeks depending upon the number of holes and the depth the drill needs to get down to. The drill itself is typically a small (many are six-inch diameter) hole.

Trans Mountain is committed to minimizing disruptions caused by these studies to communities and the environment and will return any areas affected to their original state or better. Notifications will be completed in advance of the work taking place. All necessary permits will be obtained.

The work is carried out in respect of local noise bylaws to avoid disturbing nearby residents at night and on weekends.

Sometimes, Baumgard noted, vegetation has to be cleared away to make the area safe for the workers who carry out the job. “There are often what are called danger trees — trees that are overhanging and may be unhealthy, posing a falling risk for the workforce,” Baumgard said. Those will often be trimmed back or taken down if they’re dead.

“All efforts are made to protect wildlife and their natural habitat, such as trees, and keep them intact. Where it’s possible we will move the investigation location to accommodate this.”

After the investigative work is finished and the equipment removed, Trans Mountain carries out a restoration of the area under the direction of a certified arborist and horticulturalist.