Monday, April 30, 2012

Somerset Street Reconstruction Part 13: O-Train Pathway — Cantilevered Boardwalk

This is part 13 in the 15-part series on last year's reconstruction of Somerset Street West. Last time, I showed the construction of the tunnel that was built under the Somerset Street viaduct for the O-Train pathway.

In order to retain pedestrian connectivity while Somerset was completely dug up, a temporary boardwalk was installed off the side of the viaduct.

The bridge's railings were temporarily removed to provide access. You can see the oval-shaped railings sitting on the sidewalk here, with some connecting pieces standing on their ends in a couple of piles:

The mere removal of the railings—in another context—was a significant behind-the-scenes controversy in its own right, which I'll cover in the next post in the series.

While the boardwalk was being prepared, and before the hole was excavated, pedestrians crossing the bridge were directed by two rows of fencing to the middle of the roadway, which was closed to cars.

Just as there are few routes for pedestrians and motorists to cross the O-Train corridor, the same goes for utilities, which are tucked under the sidewalk. They had to be exposed and given alternate means of support so that the concrete conduit that carries them wouldn't collapse when the fill was removed from underneath it.

The supports for the railings were left in place, and were used to help anchor the boardwalk. A clever adaptive re-use!

The boardwalk itself is a tunnel made of wood, similar to those built on the sidewalks around construction sites. The difference, of course, is that instead of sitting on the sidewalk, it's hanging off the side of a bridge. Here you can see the O-Train tracks down below, and the preparations to cut into the side of the viaduct walls for the tunnel portal.

The east entrance of the boardwalk (visible in the first photo of this post) opens directly onto the sidewalk, but because of the length of the railing segments, a steel plate was required to diagonally bridge the gap between the boardwalk and the sidewalk on the west side. Running underneath it is the expansion joint for the deck of the bridge over the O-Train.

The interior is outfitted with all the standard features: floor, walls, top, lights...

Underneath the boardwalk, the tunnel was installed. You can just see the south portal peeking out below.

This was graded a bit to bring it up higher, though it will be completely relandscaped when the pathway is constructed this coming summer.

With the tunnel built, the street was filled back in and sidewalks were rebuilt. The boardwalk, having served its purpose, was dismantled, and the bridge's controversial railings were put uncontroversially back into place.

To understand what I mean about this controversy, you'll have to wait for the next post, part 14 in the series!

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