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Gothic revival

Monarch is relying on latest technology to keep Twenty Gothic condo that sits beside the High Park subway station from getting a bad case of the shakes

January 20, 2007

Stephen Weir
Special to The Star

The Monarch Development Corp. is relying on the latest in vibration abatement technologies to make sure that the earth won’t move for anyone buying a condominium at their soon-to-be-built Twenty Gothic at High Park infill project. Monarch’s construction crew is expected to begin the war on vibration this month on the split-level building in the trendy Toronto High Park district.

The new eight-storey building and its four-level parking garage is going to wrap over and beside the High Park subway station. Since all of the luxury suites will be directly above the station’s west-end platform, there are hundreds of good reasons each day (one every couple of minutes, in fact) to make sure that there isn’t a whole lot of shaking going on.

The tree-filled neighbourhood almost has it all – the subway, chic shopping, libraries, schools, pools and the city’s largest green space, historic High Park. What it lacks is available vacant land to construct new condos so that more people can share in this very desirable locale.

Monarch is going to extraordinary lengths politically and structurally to have a condo footprint in High Park. Not only is it putting bedrooms directly overtop of a busy subway station, platform and tracks, it is also constructing a huge underwater cistern off Gothic Ave. to protect the Bloor Street subway and business district against flooding.

Gothic Ave. is a small C-shaped street that begins and ends on Quebec Ave., just up a hill from Bloor St. Until now, the land covering the High Park subway station has been used for a private tennis court, a car lot and a small public park.

The entrance of the new condo building for residents and their cars will be on Gothic Ave. over the subway. Cars will be able to drive into the garage off this small side street and then head down into four levels of parking beside the subway line. Vehicles exit the building to a small lane that leads to Bloor St. If condo owners walk fast, they can probably make it into the subway station without getting wet or cold in inclement weather. There is going to be a garage pedestrian exit about three metres from the subway entrance.

“This has been in the works for six years,” said engineer Danny DiFazio, Monarch’s highrise project manager. “What should be a relatively simple project is very difficult because it is an infill project. It is a tight space to work in and we have had to deal with the province, city, the TTC and the neighbours to get permission to begin our work.”

Monarch has agreed to give the TTC money and a parcel of land. It has also agreed to build an emergency 600-cubic-metre underground tank under its front lawn. In the case of a rainstorm of apocalyptic proportions, this tank will divert floodwaters away from the subway and nearby Bloor St. businesses.

This winter, Monarch crews will be on site sinking 140 barrel-wide concrete tubes deep into the ground on both sides of the subway line. It will take three months to drill and pour concrete and rebar (unfinished steel used to reinforce the concrete) into the holes.

“We will be setting a drilling rig right onto the roof of the buried subway, to dig out the holes for the caissons,” said DiFazio. “The area is rated to be able to absorb 250 pounds per square foot, so the weight of the heavy equipment will have no effect on the tunnel. The holes themselves will not touch any part of the subway tunnel.”

Because Monarch’s property slopes sharply downwards from Gothic Ave. toward Bloor St., the depth of each massive caisson tube will be different. These are dry caissons – the deepest will be set 10 metres into the ground, well above the water table.

The concrete tubes, or pilings, will be the anchor on which the new building is to be constructed. The weight of the part of the building that is overtop of the subway will be borne by the pilings on the Bloor St. side of the tracks, the floor of the garage will be on solid ground.

The pilings will become the base for the new building. Steel girders will be installed on to them, adding a solid frame for the brick and concrete structure that will be constructed over the next 24 months.

Although the steel-enforced pilings are ramrod straight, there is enough play in them to allow for some ground movement. Some of the vibrations created by the subway trains rumbling undergroundcould be carried upwards through the tubes.

“What we will do is isolate the vibrations,” continued DiFazio. “We are having thick isolation pads made for us, which will absorb the noise and ground-borne vibration that would otherwise carry up to the residences. This technique is used around the world in different applications (i.e. earthquake protection) and has been used here in Toronto, too.”

The isolation pads – as thick as a couple of Toronto phonebooks and four times as wide – are placed on the pilings and act as a buffer between the parking structure and the residential tower. Rumblings from down under don’t get past these large layered slabs of vulcanized rubber and plate metal.

“We have put tenders out for the pads. They will in all likelihood be built here in Canada,” explained DiFazio. “The rubber is heat-tempered, baked…cooked for strength. These pads have to last the life of the building.”

Even when the pads are in place and the concrete framing complete, the battle against TTC tremors will continue. Heavy layers of insulation will be liberally used wherever power lines, plumbing and water pipes enter and exit suites. It will not be a simple task of wrapping a few big pipes; because the building is installing individual heat pumps in all 175 suites, there will be considerable linkage between the units and the ground below.

Of course, vibrations can travel down as well as up. While the building is being completed, Monarch crews will be working on site with a few projects that are normally not tackled at a condo site. The company will be installing a sensor system in the subway itself to make sure that the condo building isn’t affecting the integrity of the train tunnel’s ceiling and walls.

“The sensors will be, in reality, sophisticated balancing beams,” said DiFazio. “There will be a level device suspended between boxes. If during the construction phase, the tunnel would shift or move, the sensors will immediately alert (both Monarch and the TTC).”

When the work on the building is complete, the sensors will be removed from the subway tunnels. At the same time, Monarch will upgrade the roof of the tunnel and repair any damage that it might have caused to the station.

Over 60 per cent of the units have already been sold.