Open this photo in gallery Houses on Springmount Street were built on the slope of a former ravine. John Lorinc/The Globe and Mail

By even the most eclectic standards of old City of Toronto neighbourhoods, Springmount Avenue, a leafy side street in the St. Clair West-Oakwood area, stands out. Developed in the 1920s, Springmount literally follows the course of a dog leg-shaped tributary of Garrison Creek as it meanders through a little ravine carved thousands of years ago in the Davenport Escarpment.

While NOW Magazine once praised Springmount as the easiest cycling route up the hill that cuts across midtown Toronto, the enclave is also notable for the fact that many of its homes were built well up the slopes of that former ravine. The street, which is connected to the adjoining Regal Heights neighbourhood by an old concrete staircase, feels uncommonly green and secluded – a meandering residential gully in the big city.

Five of Springmount’s dwellings, a row of 1920s-vintage two-storey duplexes, sit at the crest of one of those slopes; their stoops, in fact, are situated at the end of flights of steep steps that rise from the sidewalk through a grove of trees.

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The tenants, mostly artists and seniors who’ve lived there for decades, don’t seem to mind the access challenge. “They’re quite well-designed,” says Ali Garrison, a 54-year-old musician who has lived with her partner, also a musician, in one of the two-bedroom units for 15 years. The duplexes are secluded within an already secluded enclave. “We feel unfettered to make music there,” she adds.

In early 2017, the property owners revealed plans to begin demolishing the duplexes, sever their deep lots and construct three luxury row houses at the bottom of the slope. Only two of the five duplexes, at 49 and 51 Springmount, are cited in the development application, but residents are concerned the whole row, which are owned by a single entity, would eventually be redeveloped, creating a wall of eight street-level townhouses in place of the current ravine slope. The builder, Brentlane Developments, has only purchased two lots, stresses Daniel Shields, a representative of the firm.

Open this photo in gallery A photograph of renderings presented by the developer to the City of Toronto Committee of Adjustment.

Plans prepared by Richard Wengle Architect, the design firm retained by Brentlane, show the three-storey dwellings would have basement-level garages and driveways, necessitating the removal of several mature trees and underbrush that have grown there for generations. “The current dwellings on the two properties were built in the 1920s and any new dwelling being built on these properties will have an impact on the front-yard hillside elevation,” Mr. Shields says.

While the city’s community planning and forestry departments didn’t flag the proposal, Brentlane’s application ran into a wall of neighbourhood opposition. It was blocked first by the Committee of Adjustment last fall and, earlier this year, by the Toronto Local Appeal Board (TLAB) in one of its first rulings (the body has replaced the Ontario Municipal Board). The developers, who were not available to comment, have challenged the initial TLAB ruling on various technicalities; a new hearing is expected later this fall.

According to Mr. Shields, Brentlane’s architects offered to discuss alternative plans with the representatives of the local residents association and area Councillor Cesar Palacio, but they were unable to secure a meeting.

Unlike many local development fights, this one begins with a bona fide planning paradox: if today’s environmental- and ravine slope-protection laws had applied when the Springmount homes were originally built, they would never have been allowed – a point that residents of the street readily acknowledge.

The opposition, in fact, is focused on protecting what’s left of the ravine slopes, which define many Springmount properties and are especially visible in front of the five duplexes. Those dwellings are served by a rear laneway, as are several of the other homes that have been built along the street.

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“We love our green space and we want to protect it,” says Jennifer Wigmore, a resident and member of the Springmount Collective, which formed to block the proposal. She insists she and her neighbours don’t object to redevelopment generally or the construction of new rental or affordable housing on the site of those duplexes, provided the area’s greenery and Ice Age-formed contours are preserved.

Springmount’s natural topography, of course, is far from unadulterated – a point raised by the developer in its minor-variance appeal to the committee of adjustment. Several decades ago, another Springmount homeowner carved a large double garage out of his part of the slope, just a few metres north of the proposed site.

But in the past few years, two new-build residential projects, both modernist in design, have found ways to work with the steep slopes along the street. One retained its predecessor’s footprint, rear-lane garage and front-door access via three flights of steps built into the slope wall.

Ms. Wigmore points out that Brentlane’s proposed row houses would create a problematic precedent in that the lots would be served by both front-yard driveways, with curb cuts, as well as rear lane vehicular access.

The initial TLAB decision, released in March, issued a broad rebuke to both the developer and the City of Toronto departments that signed off on the project. The chair ruled the builder had offered “no persuasive evidence” that the townhouse plan would reinforce and respect the neighbourhood or protect the existing tree canopy, both requirements set out in the official plan. The ruling also noted that if the proposal went ahead, it would serve as a precedent to “support further development along the bank of the escarpment.”