Irreversible Environmental Issues
The core issue is environmental, nature versus human design. In 1966, the TTC pushed a subway through a sensitive zone fed by heavy rainfall and an ancient underground river feeding two creeks on either side of an elevated plateau and it worked flawlessly. TTC engineers, City planners, and the Ontario Provincial Government led by Premier J Robarts brilliantly created a remarkably balanced system. Now, a proposal threatens that equilibrium. What happens when two 40 storey skyscrapers are built over a 1.23-acre (4,978 square meters) as a diverted slow-moving river shifts toward the subway 20 meters away? Could this trigger further sinkholes, damage nearby homes or the subway, or even compromise the towers themselves? No one has the answers.
LAURENTIAN RIVER
The TTC Bloor subway (grey marbled strip) is buried 10 to 25 meters below the surface and effectively acts as an underground dam. It diverts a portion of the Laurentian River water (which runs above the bedrock, 60 meters below ground) through the Mountview/ Oakmount channel (red box). The redirected water moves southeast since water flows from high to low areas, and in this case from the plateau’s peak (on Quebec Avenue, the red section on the topographic heat map) at 129 meters to the low point of the Spring Creek ravine at 101 meters alongside the subway.
CANOPY ABSORPTION
This canopy of the Mountview/Oakmount channel, is a very dense area of native trees and is part of the High Park Black Oak Savanah (a rare remnant ecosystem, that is 4,000 years old, but of which only 0.5% remains intact today). Black Oak trees absorb large amounts of water and have roots that can sometimes reach 21 meters deep. One single mature tree can absorb up to 138,000 liters annually and release 95% into the atmosphere. The water absorbed by trees helps manage stormwater runoff, reduces the risk of flooding and regulates the water moving through underground rivers. The developer of the proposed skyscrapers are expected to remove many trees on their pending purchased lands (and replace them with new shrubs and trees) in concrete planters and the only ones that will remain are on private lands or adjacent to the subway and private lands. The level of the river could rise.
OUTFLOW
Proof of this phenomenon is visible in High Park itself in the form of a 20-centimeter pipe near Spring Creek. It releases 55 liters per minute or 28.9 million liters per year. To put it in perspective, babies aged 0–12 months consume about 292 liters of milk per year. With 343,000 infants in Canada (2021 Census), that totals roughly 100 million liters annually. If a single pipe releases 28.9 million liters of water per year—imagine it were milk—that would feed about 99,000 infants, or 29% of all babies in Canada. That’s a remarkable volume of liquid.
If the same amount of water coming from the pipe, was discharged across the Mountview/Oakmount channel it would equal 2.6 trillion liters per year (the Humber River Treatment plant processes 93.4 trillion liters per year).
IMPERVIOUSNESS
“Imperviousness” measures how much water is blocked from soaking into the ground by surfaces like roads and buildings. In 2018, the High Park Apartment Study area was 56% impervious, while the Mountview/Oakmount channel is estimated to be about 30%. If the proposed development proceeds, imperviousness could reach 90–100%, forcing all water to flow somewhere else and raise the river’s water level and/or flood nearby structures.
RAINFALL
Toronto’s average rainfall has risen 23% over the past 65 years, totaling 787 mm annually. On the proposed 1.23-acre (5,000 m²) development site, this amounts to 3.9 million liters per year. With groundwater only 3–6 meters below the planned skyscraper foundations, rainfall must enter sewers, storage tanks under the skyscraper’s concrete base, and merge with the underground river. The two 40-story skyscrapers “Raft Foundation” is only 2 stories or 6.7 meters deep.
The Ontario’ Ministry of Environment, Conservation and Parks has identified six well records in proximity to the Montview/Oakmount channel, where groundwater levels were measured at 3.6 m to 4.3 m below ground surface. The developer drilled test wells between May and August 2025, found groundwater was 12.7 m to 14.0 m below ground surface. However, 2025 was an unusually dry year (seventh driest in 65 years), so abnormally low water levels occurred. The shaded red dot on the graph indicates 2025's rainfall up to the end of October.
INSTABILITY
The Leaning Tower of Pisa is 57 meters tall with a 5.5-meter foundation and a famous near four-degree lean due to unstable soil. The proposed Mountview/Oakmount towers would be 144 meters tall on just a 6.8-meter foundation, over twice Pisa’s towers' height with a marginally large base and with an underground river beneath.
The developers own consulting engineers in their Geotechnic Study of the proposed Mountview/Oakmount channel, repeated the following phrase four times: “further investigation” is needed to verify that the proposed towers' foundation is appropriate given the groundwater conditions. This needs to be investigated.
