Parkside Drive Relief Sewer
High Park and Earlscourt Sewersheds
Western Beaches Storage Tunnel
Year of Construction:
2.7 m brick pipe runs straight down Parkside Drive to the lake. A small sewer appears to have been run directly underneath it as well, purpose unknown.
Also Known As:
"Humble Howard" (name c/o Angels of the Underground)
The Parkside Drive Relief Sewer was built c. 1910-1912 to relieve the west end of Toronto's High Level interceptor (built concurrently) and the High Park, Junction and Earlscourt neighbourhoods that lie upstream in the sewershed. While active use of the stand-by (storage) tanks at the top of the sewer was discontinued in the 1970s with the construction of the Mid-Toronto Interceptor, the Relief Sewer continues to serve as the top-most overflow sewer for both the High-Level and the MTI.
As a relief sewer, that means that in dry weather the Parkside sewer is mostly empty. Unlike in other areas where a few local storm sewers might have at least been routed into a comparable relief sewer, Parkside is fronted on one side by High Park and on the other by a local water/sewershed that is directed parallel to it, south/southeast towards the lake and the Glendale Avenue Storm Sewer. This area was once drained by a set of small creeks that cut the reasonably deep gullies that still shape the Indian Road neighbourhood and the area north of Bloor Street around Clendenan Avenue. The fragments of Spring Creek in High Park are the last surviving remnants of this old surface watershed.
The Parkside Relief begins at the stand-by tanks beneath the northeast corner of High Park. Here the High Park and Earlscourt combined sewers once passed by the tanks before being diverted into the High-Level Interceptor. In overflow conditions, they would have poured into the tanks, which provided a certain amount of storage volume and allowed solids suspended in the sewage to settle. If the tanks also overflowed, the excess waste would pass into the Parkside Relief and flow south to outfall into the lake near the park's Lower Duck Pond. Each time an overflow happened, city workers had to rinse and shovel the accumulated sludge from the tanks into the High-Level; some small reminders of the old city works presence here remain above the tanks, along the west sidewalk of Parkside Drive, and the enormous quantity of manholes in the vicinity alludes to the complicated nature of the underground workings.
With the construction of the MTI, the connections at the tanks were restructured. Separate diversions and overflow structures now service each of the High Park and Earlscourt sewers, connecting them to the MTI. A connection to the High-Level Interceptor still exists through the standby tanks, but can be considered to be at most a passive connection, and probably completely abandoned. The tanks themselves, and a disconnected stretch of the High Park sewer, still hold a thick layer of soil, and various unsavoury debris coats just about everything in the vicinity.
Down in the Relief, things are much cleaner. A large, vaulted draft chamber runs alongside the tanks, beyond which the large brick pipe begins, most of its bricks faded and soiled to a dusky brown by the ensuing century of intermittent use. Some sort of drain or forcemain runs parallel and directly beneath the centreline of the sewer, and a series of small holes that provide access to it are hazardous places to step as you travel down the conduit. I've only ever seen something similar in one other case, in a large sewer/creek culvert in Buffalo, NY, so I can't really explain what the lower drain is for.
As you approach the Queensway, a new concrete chamber diverts the Parkside Relief down a steep slide and east to the Glendale Avenue shaft / storage tank at the top of the Western Beaches Storage Tunnel (WBST). An opening to where the sewer once ran down to the lake and provided an overflow for the Lower Duck Pond is now stopped up with metal beams, although the overflow from the pond still exists. All sewage overflows that now enter the Parkside Relief are intended to pass into the WBST.
On June 27, 2010, the Glendale Avenue shaft of the WBST "surcharged", causing untreated combined sewage to overflow into Budapest Park. This is the second time in three summers that a serious summer storm has overwhelmed the top storage shaft of the overflow diversion system for the Western Beaches.
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.