An ersatz diversion structure within the overflow portion of the Garrison Creek Sewer (1885). The small egg shaped pipe is the Asylum Stream sewer (1891), which in dry weather is routed through a metal duct into the pipe mounted on the right side of the main conduit, which runs south to Wellington Street where it connects with the beginning of the Low-Level Interceptor (1912).

Garrison Creek Sewer (overflow)

Water/Sewershed:
Garrison Creek Sewershed

Year of Construction:
1885

Construction Details:
Round brick pipe (approx. 2 m diameter). Low, wide arch below rail corridor. 2xRCB at lakeshore. Built for the City of Toronto by Alan J. Browne.

Archival Material:

What is now exclusively an overflow was simply the lowest reach of the Garrison Creek Sewer when the city buried the Garrison Creek in the mid-1880s, and served in this capacity for twenty-five years until Toronto finally constructed an interceptor sewer system in 1910-1912. With the installation of the High-Level Interceptor and a diversion chamber beneath Trinity-Bellwoods Park (near today's tennis courts at the southeast corner of the park), this bottom stretch of the sewer became an overflow, seeing sewage only during wet weather, when excess flow would (and still does) pour directly into the harbour at the Bathurst Quay. As a result, much like the Relief Sewer to the west, the Garrison sewer overflow is dry, reasonably clean, and in very good condition apart from the substantial mineral deposits that have covered portions of the brickwork.

Below the Trinity tennis courts, the Garrison Sewer is routed into a diversion tunnel that carries it to the High-Level Interceptor, while a side-flow weir allows overflows to pass into the lower stretch of the sewer (pic). At the intersection of Adelaide St. and Walnut Avenue, the diversion tunnel reaches the High-Level Interceptor and this combined conduit crosses the path of the Garrison overflow at basically the same depth. As a result, the overflow is forced through a pair of shallow siphons (pic) beneath the High-Level, siphons which in dry weather are luckily not completely submerged, allowing human passage between the upper and lower parts of the overflow.

South of Adelaide, at King Street, we make a fascinating discovery. Where the small Asylum Stream Sewer (which flows from the northwestern corner of CAMH and replaces a pair of tributary streams of the Garrison Creek) reaches the Garrison overflow, it once entered the main conduit by way of a gorgeous junction. It is now routed through a duct and pipe downstream to the start of the Low-Level Interceptor, but the junction remains (pic), and carries an extra piece of history with it. A sharp, concrete wall was used to direct the confluence of flows from the two sewers, and the man who installed it -- "W. Rowe" -- went to the extra effort of signing his name and dating his work to 1891.

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Michael Cook is available to speak to your organization about infrastructure history, lost creeks, current conditions, and opportunities for change in our management of and communication about urban watersheds, and to work with teams proposing or implementing such change. Get in touch.