David Sirois is an Engineer based out of our Edmonton office. Recently, we sat down with him to discuss an interesting transit project he is working on.

Thanks for making time with us today, David. Tell us about the project.

Right now, I’m part of an Entuitive team working on the design and contract administration of five LRT station rehabilitation projects in Edmonton. Today, we’ll focus on the first station we worked on, McKernan-Belgravia.

Going into it, we knew that this particular station would be the most difficult of the five, in terms of the work required. Our goal was to replace 20% of the existing platform, complete a number of spot repairs, and implement a preventative corrosion protection solution. The station was to be closed for two months to complete the most disruptive work.

That sounds like a pretty complex project with a tight schedule – did you face any challenges during the course of work?

I think you hit the nail on the head. One of the biggest issues was scheduling, especially when we had trains still passing through the station, which meant that work had to be completed on one side at a time.

To make the schedule work, we collaborated closely with our team, including RPK Architecture, Graham Construction, LRT operations, and the City of Edmonton project management team to understand feasibility and constructability within the constraints presented to us. There was lots of goodwill on the project that helped us to move forward and get the work done on time.

From the technical side, there were several unique challenges as well. The portion of the platform that we were working on was built as an extension and underneath it was enclosed. We didn’t know what to expect due to the enclosure when considering factors like buried services, for instance.

The platform during the assessment phase.

The existing structural drawings showed a high-voltage, high-risk duct bank running under the platform that curved toward the southbound track, and there was a risk that it would interfere with the installation of new foundations. To mitigate the risk, we worked with the construction manager to review several foundation construction options and ended up choosing cast-in-place (CIP) piles excavated with a hydrovac rig.

This provided two distinct advantages: the hydrovac could be parked on the road running parallel to the station, which eliminated the need for special rail vehicles and kept equipment away from the overhead catenary system; and the pile location and dimensions could easily be adjusted to accommodate poor soil conditions and interfering elements (such as the aforementioned duct bank). We ended up placing five pairs of piles from south to north with this method.

During construction, the existing platform was removed, and the duct bank was revealed to be narrower than expected, yet it still interfered with three of the pile locations where only two had been anticipated. We had devised a simple and repeatable grade beam solution for the first two locations, so we were able to tweak that for the third location to minimize the impact two weeks into an already tight construction schedule.

A progress shot of the platform replacement.

Another technical challenge came with performing spot repairs on cantilevers on the other 80% of the platform. Here, when the original warning tile was removed, the project team identified extensive corrosion staining and decided to explore further. With some destructive investigation we found that there was substantial loss of reinforcing material that needed to be acted on.

Mohammad Moayyed and I decided the best solution would be to lop off the full extent of the cantilevers, and we looped in Mike Hillcoat from our Toronto office to verify this approach. Knowing that this would be a substantial change item, we first generated a written report for the stakeholder group to review and approve.

A shot of the cantilever replacement pull test.

This second challenge is an example of how Entuitive was able to respond efficiently to help solve a problem. The fact that we were brought on and given the space to determine the best solution is reflective of the goodwill and trust amongst the members of the project team I mentioned earlier.

That’s great. What was your favourite part of working on the project?

It felt like the whole project team was pulling on the same rope.

Actually, the corrosion protection specialist that I was working with said it best. The part of his job that excites him the most is travelling all over North America delivering lunch and learns and seminars, and he had felt a great impact on his usual way of life due to COVID-19. He mentioned to me that it felt so great to be working to tailor an effective solution to meet the owners’ and end users’ needs and that it felt like, with the work we were undertaking, we were really doing right by the stakeholders and end users of the LRT station.

I agree – we worked collaboratively to dig deep and understand the owners’ challenges and needs and were uncompromising in our ability to provide effective, efficient, and low-maintenance solutions that could be implemented with little disruption to the transit system.

Any final thoughts on the project?

Collaboration was key to the success of rehabbing this station on schedule, especially with all the technical issues and design updates we faced before and during construction.

It was nice to leverage the support of Mike and work with folks across offices to get advice and feedback and it reminded me how important our One Company philosophy is to everyone’s success.

The platform upon completion.

As I reflect on the work I did on this station, I have to say I really did enjoy it. Sure, design changes and tight schedules are stressful, but it’s a lot of fun to manage it all. Also, at the end of the day, it feels great to look back and say, “Wow, how the heck did we pull this off?!”

To discuss the project with David, you can reach out to him here.

All images c/o David Sirois.