Several kilometres up the former Borough of York's Central and Eastern Trunk Sewer, sixty feet beneath Rogers Road.

Alas, Poor York

York Central and Eastern Trunk Sewer

Borough of York Central and Eastern Sewer District
former Lavender Creek watershed
overflows to Black Creek

Year of Construction:

Construction Details:
Concrete arch tunnels ranging from 2500 down to 2000mm and smaller, much of which would have been tunnel-excavated. Overflow structures lead to late 1960s bored RCP beneath Hyde Avenue which connects with large CSO storage tank and outfall at Keelesdale Park.

Also Known As:
Hillary Combined Sewer (Metro-era name)

Further Reading:
Angels of the Underground: Keelesdale Park

Folks exploring Toronto storm drains have known for a long time about the storage tank beneath the southern edge of Keelesdale Park. However, until 2009, no one seems to have found the tank when it was reasonably empty and followed the source pipe up behind it into the bowels of the old Borough of York. What is behind the tank is an exciting set of overflow structures known as the Hillary Overflow, and a full-on combined sewer known in the past as the York Central and Eastern Trunk Sewer.

The eastern part of the Borough of York was built up in the first two decades of the twentieth century, with housing replacing farms and obliterating most of what had once been a small tributary of the Black Creek called Lavender Creek. It is likely that initially many of the homes relied on backyard septic systems, with sewer service coming later. By 1930, however, the Borough of York had excavated the Central and Eastern Trunk Sewer, and constructed a sewage treatment plant adjacent to Rockcliffe Avenue and the Black Creek to treat the effluent now captured by this sewer. Much of the trunk sewer was tunnel-excavated beneath Rogers Road, and in places is as much as 60 feet underground. Another, smaller arm runs parallel to it beneath Kitchener Avenue, joining the main trunk at Keele Street where they turn southwest and drop into the Black Creek valley on their way to the former treatment plant site.

In 1954, Metro Toronto government assumed responsibility for wastewater treatment throughout the area that has now been amalgamated as the current city, and moved to close the outer borough's smaller treatment plants, build new sanitary trunk sewers up the city's river systems, and centralize operations at large plants along the waterfront. The Rockcliffe plant was one of those closed, and the York Central and Eastern Trunk Sewer was extended downstream to feed into the Humber Sanitary Trunk Sewer. A works yard and large area of cleared land still occupy the former Rockcliffe site, and several CSO outfalls remain along the canalized Black Creek that runs along the northern edge of the site.

In the late 1960s, additional overflow capacity was built into the system upstream of Rockcliffe. A 7,800 m3 storage tank was constructed at the end of Hyde Avenue, on the southern edge of Keelesdale Park, and a large new overflow diversion was provided for the York Central and Eastern Trunk at Hillary Avenue. Despite this added storage, a report from 1986 reveals that overflows were a frequent occurrence in this sewer catchment: in 1979, there were overflows from the pipes near Rockcliffe Avenue during 27 storm events (or as the report notes, everytime the area received more than 4mm of rain), while the Hyde Ave/Keelesdale tank overflowed 7 times. 1 It is unclear what measures were implemented to improve these results; the report did propose changes to the structure of various overflow points in order to reduce the number of overflow events.

In the Sewer

Getting to the Central and Eastern Trunk Sewer, involves hiking a kilometer up the small RCP that feeds the Keelesdale tank. This pipe appears to have been installed with a tunnel boring machine (there is just a single, large construction shaft midway along its length), but it wasn't dug carefully and fails to maintain a constant grade as it comes down from Keele and Hillary to Hyde Avenue. As a result, the remains of filth-laden overflows pool in the low spots along its length, and aren't removed to the tanks and the Black Creek Sanitary Trunk Sewer for eventual treatment, making the hike more than a little unpleasant.

Reaching Hillary Avenue, there is a stepped fall structure which we like to call "the Hillary Step". Overflows originating upstream at Rogers Road fall down fifteen feet to the step, which directs them 90 degrees to the right, where they fall another ten or so feet to the RCP which conveys them to the storage tank. I unfortunately don't have a photograph of the step itself, but you can find one on Jon's photo blog. Above the step there is a large chamber where the Central and Eastern Trunk flows behind a very tall weir which would only ever overflow during very severe events or when a gate was closed to permit maintenance downstream. The more typical overflow is upstream of here, a hundred meters up a pair of concrete ducts that do have an appropriate grade and as a result are dry, clean, and almost homey.

At the actual overflow, the flows of from the trunk sewer's two arms — the Rogers Road arm and the Kitchener Ave. arm — come together in a long chamber with two 'windows', which are equipped with low weirs and allow overflows to pass into the ducts mentioned above. I have only travelled up the Rogers sewer, but together they drain almost all of York's sewage in the area east of the Black Creek. We also haven't travelled downstream, where the sewer must make its way down a substantial and likely unsafe fall structure in order to end up in the bottom of the Black Creek valley.

The Central and Eastern Trunk is a mess of a sewer, and I mean that with a certain amount of love. It's all finished in slightly horseshoe-shaped, arched concrete, and it has a few fantastically big access chambers that were left over from the excavation shafts that were used to bring men in and excavated material out while it was being built. However, just upstream of the overflow point and for about a kilometer, the tunnel shrinks to about 2 meters in height (about the same height as the High Park Trunk Sewer, but entirely concrete), flows faster (because there is more water in less space, and possibly because the grade is increased) and becomes incredibly humid. It is not a pleasant place to be, and would change my overall impression of the sewer were it not for the fact that further upstream the trunk is larger again, relaxed, and the atmosphere much improved. It is in this upstream reach of the sewer that the photographs were taken.

Somewhere east of the end of Rogers Road, the end of the original drift of the sewer is blocked of with a brick wall coated with a thin layer of mortar. In the mortar, the men who put the wall in inscribed "A.D. April 4 1930." Flow comes in here from a much smaller arched duct, perhaps 1.2 m diameter. It's most likely that the main sewer always terminated here and that the wall simply caps the excavation drift, but it's also possible that there is a section of abandoned tunnel sitting forgotten beyond this terminus.


  1. 1. Toronto Area Watershed Management Steering Committee. 1986. Humber Sewershed Combined Sewer Overflow Study, Technical Report #7.
