We answer a few of the most frequently asked questions related to routing options, the Sardis-Vedder aquifer and construction impacts.

What route is Trans Mountain currently proposing through Chilliwack?

In March 2017, Trans Mountain filed an Application with the National Energy Board (NEB) requesting approval to build the Expansion Project along the existing Trans Mountain Pipeline (TMPL) right-of-way (ROW) through Chilliwack. This decision adheres to our first routing principle, which is to route within the existing easement and parallel the existing pipeline where practical. This decision eliminates the need for two separate pipeline corridors through the Sardis neighbourhood and avoids BC Hydro’s concerns associated with proximity to its transmission infrastructure.

Were other routing options considered?

Trans Mountain considered and studied different routes in Chilliwack. Prior to the March 2017 Application, we preferred to construct the pipeline corridor within the BC Hydro transmission corridor and extensively investigated this option. To determine whether or not this route was feasible, we engaged BC Hydro to do a safety study to ensure public safety and the safe operation and integrity of our respective infrastructure. BC Hydro concluded the acceptable location for Trans Mountain’s additional pipeline was on the southern edge of its ROW, in an area that would significantly impact new residents in the neighbourhood and would be outside of the National Energy Board approved routing corridor in some locations.

During early phases of the Project, the company also considered routing along Highway 1 through Chilliwack. However, Trans Mountain indicated in its filings that it would only consider this option if there were no other feasible routing options due to the restricted size of the ROW and the positioning of other existing infrastructure and future development within and adjacent to the highway.

After thorough consideration, we determined the best option is to follow the existing corridor through Chilliwack.

Will the expansion impact the Sardis-Vedder aquifer?

Through the experience gained from 65 years of operations and engineering design of TMEP, we’re confident we can mitigate risks to the aquifer, and we have a proven track record in operating the existing pipeline across aquifers and groundwater.

As part of our Groundwater Management Plan that requires approval by our regulator, the National Energy Board, potential impacts have been evaluated and mitigation strategies have been established for all phases of the Project. We’re required by the NEB to protect the aquifer, and prior to beginning operations, groundwater monitoring plans will be implemented in order to fulfill NEB Condition 130.

It’s also important to note for construction, Trans Mountain would on average require a trenched depth of just over two metres, which is above the water table of the aquifer.

The risks are also limited because the location of the pipeline will be outside or bordering the edge of the Chilliwack municipal water supply wells capture zone and the surface topography places the pipeline down-gradient of the municipal wells.

That said, to address feedback from stakeholders we’re taking extra steps to treat the Sardis-Vedder aquifer as a watercourse crossing and incorporating supplemental mitigation measures, which exceed already stringent regulatory requirements. The section of the pipeline crossing the aquifer is being designed with the same engineering considerations as a water crossing. Measures include using extra heavy walled pipe, adding an additional isolation valve upstream of the aquifer and limiting trenching to the dry season.

Will the expansion impact drinking water wells in the community of Yarrow?

The source of water for the Yarrow Wells is most likely the Vedder River, and it is highly unlikely that a release would occur at this crossing due to the risk mitigation measures in place. To safeguard this water source, Trans Mountain will employ heavy wall pipe and use a trenchless construction method that places the pipe deeper at the crossing while avoiding in-stream disturbance.

The Vedder River crossing will also have a remotely operated block valve upstream and a check valve downstream to limit the potential impact to the river in the very low likelihood of a pipeline incident or release.

In the unlikely event that a pipeline incident or release does occur, we would employ emergency response measures to limit the release volumes, minimize the spread of released hydrocarbon products and ensure a prompt cleanup response is employed.

Will construction impact the Browne Creek Wetlands?

Trans Mountain originally planned one long horizontal directional drill (HDD) crossing for the Vedder River so trenched installation in the Browne Creek Wetlands could be avoided. However, results of a geotechnical investigation indicate unfavorable conditions for this type of construction method. Therefore, we’ll cross below the Vedder River using a direct pipe trenchless construction method. However, one of the limitations of direct pipe construction is a reduced maximum length; and therefore, the length of the Vedder River trenchless crossing will need to be shorter than initially proposed with HDD construction. For this reason, open-cut trench construction will be used to cross Browne Creek.

Notwithstanding, we don’t expect the wetlands to be significantly impacted by pipeline installation. Our environment team completed field investigations of every watercourse crossing along the route. The studies show the Browne Creek Wetlands are dry in the summer months at the location of the pipeline crossing, which is Trans Mountain’s anticipated construction time frame. Construction of the crossing during dry or very-low-flow conditions will reduce potential impacts.

It’s important to note that construction will not affect the recent restoration and habitat work in the Browne Creek area and any impacts will be restored to existing or better conditions.

How does increasing the thickness of the pipe help reduce the risk?

Trans Mountain is treating the potential and mapped well capture zone of the Sardis-Vedder aquifer between Watson Road and South Sumas Road as a watercourse crossing. Because of this, we’ve committed to increase pipe wall thickness from the standard 11.8 mm to 14.7 mm in this area, as well as further east to Silverthorne Road. 

Increasing the pipe wall thickness for a water crossing strengthens the resistance of the pipeline from external corrosion and potential hydrological impacts. Increasing the thickness for this area in Chilliwack will reduce the stress in the pipe and make it structurally more resistant to impact. 

The highest risk to the pipeline in urban areas is third-party damage. When the wall thickness is increased to 14.7 mm, it reduces stress in the pipeline by 25 per cent and allows the pipeline to withstand damage sustainable by approximately 50 per cent. Similarly the dent resistance is increased by approximately 50 per cent.

How will the pipe be protected during operations?

To protect the pipe during operations, we’ll continue to allocate extensive resources to our pipeline integrity program, which identifies and repairs potential problems with the pipe before a pipeline leak can occur. And, we’re enhancing our Emergency Management Program to meet the needs of the expanded system. We continually assess new and emerging technologies to ensure we’re applying best practices to protect the pipe.

We’re confident the proactive and mature suite of programs we’ve developed over 65 years of operation will maximize the safety of the pipeline system, enhance environmental stewardship and mitigate any potential issues in Chilliwack.