How do you construct an underpass below a busy rail line? Build a bridge

To a non-engineer, looking at the construction of the city's new underpass on 78th Avenue in Ogden is a bit mystifying.

But there's plenty of method to what's going on. It's just that most people can't see what's happening or how it fits with the final vision.

The underpass is needed for a few reasons.

First, CPKC plans to close the level rail crossing at 69th Avenue southeast.

Second, the underpass will provide vehicle and pedestrian access to the Ogden shop/CPKC campus from the west, once the 69th Avenue rail crossing closes.

Third, building the new access point now will make it easier for the Green Line LRT to come through the area next to the CPKC line. The Green Line also will pass over 78th Avenue on a new bridge.

The project manager, Colin Stang, said there is a lot of co-ordination with CPKC to ensure this work is done safely.

"We are diverting a main line track that sees upwards of 20 trains every day. There's a lot of train movement in this area. So the co-ordination is the biggest challenge on this project. Other than that, it is a fairly typical bridge structure."

So what are the steps to getting this project built?

Earlier this year, freight trains on the busy CPKC line were diverted onto new tracks laid down on the top of a temporary embankment that was built on the west side of the existing embankment.

Stang said a lot of care went into that. "The hardest part was building the diversion embankment because we were right up beside their main line track when we were doing this."

Once the trains were running on the temporary track, work crews cut into the original CPKC embankment and removed the portion where 78th Avenue will eventually go through the site.

Then workers built a concrete support wall to shore up the temporary embankment.

Support piles were driven into the ground on the east side of the underpass site. These piles will help support a new rail bridge that will be going up in the coming months.