By Edward Brown

Ask Torontoist features questions posed by you, and answered by our elite team of specially trained investigative experts (also known as our staff). Send your questions to ask@torontoist.com.

Reader Mark Altosaar asks:

During my semi-regular bike-rides through the Don Valley over the last fifteen years, I’ve always noticed these two peculiar bridges near the south end. Last year I found out that the old abandoned trellis used to be a King Street bridge earlier in the last century. I cannot for the life of me figure out what the heck the big concrete enclosed structure next to it is, though.

Two bridges spanning the Don River.

Torontoist answers:

First: the abandoned truss bridge. It once carried car and pedestrian traffic, although on Eastern Avenue rather than King Street. While in use, the Old Eastern Avenue Bridge played a pivotal role in connecting the eastern reaches of Toronto with the downtown core. Though difficult to envision now, there was a time when Eastern Avenue ran uninterrupted from Front Street to Kingston Road.
The two-lane bridge standing today isn’t actually original: it replaced an earlier wooden span that was washed out by the spring thaw of 1933. The steel version of the Eastern Avenue Bridge remained in use until 1964, the year the third section of the Don Valley Parkway (Gardiner Expressway to Bloor Street) opened. During construction of the DVP, engineers decided to reroute Eastern Avenue. Beginning around Broadview Avenue, they redirected the road slightly north. Along with a northbound on-ramp, a new overpass was constructed. The old truss bridge was never dismantled, mostly for reasons of economy. Fenced in and, for the most part, inaccessible, the abandoned bridge was left to rust.

Grey structure parallel to the old Eastern Avenue Bridge.

Running parallel to the now-unused Eastern Avenue Bridge is the peculiar grey covered structure in question. Spanning the river since 1930, this 133 foot structure isn’t actually a bridge—at least, not in the traditional sense. In its eighty years of existence, it has never been used for either pedestrian or vehicular traffic.
Once upon a time, Consumers’ Gas (now Enbridge) operated three coal gas manufacturing facilities in Toronto. One of these plants was located on Eastern Avenue, near Booth Avenue. A second was at Parliament and Front streets, and the third was across town, at Front and Bathurst streets. From these locations, massive gas pipelines snaked under the city. Pipelines serving the Eastern Avenue Consumers’ Gas facility were (and continue to be) housed in the concrete structure spanning the Don River.
When initially constructed, technology was such that it was easier to run these particularly large gas mains over the river than it was to tunnel under the river. And while it might have seemed easier to suspend the mains from the underside of the original Eastern Avenue truss bridge rather than building a separate structure, this would have been untenable. Considering the weight and dimensions of the pipelines, engineers calculated that the truss bridge could not bear such a load.
Even though coal gas was replaced by the use of natural gas long ago, the pipelines transporting the fuel remain a vital part of Enbridge’s infrastructure; thus, the continued need for the grey bridge to nowhere.
Photos by Sam Javanrouh/Torontoist.