Saturday, October 1, 2016

Part 4 - Our Proposed Allignment

Our Proposed Alignment

Most subway tunneling in Toronto, like the Sheppard Subway to Don Mills Station, the Spadina Subway extension to Vaughan and the Crosstown LRT now under construction under Eglinton is done with twin tunnel boring machines [TBMs] each of which is +\-6 m diameter.

Twin tunnels of 6m are wide enough to accommodate one track in each tunnel. They are not wide enough for stations. Where the subway needs cross over tracks or emergency passages from one tunnel to the other, difficult and expensive connecting passageways have to be constructed.

To build stations with the 6m twin TBM system you have to cut open the ground, excavate a massive trench down to the tunnel level, keep the sides from caving in with huge retaining walls and wait for the TBM’s to ‘break through’ into the future station.

Such massive excavations often require that underground utilities like sewers and water mains be rerouted. The disruption to the city at the surface can be extraordinary.

Here’s an aerial view of Keele Street with the station under construction on the Spadina Vaughan Subway.

 For the Scarborough Subway Extension, the TTC is thinking of using one TBM of around 10 m diameter. That would be wide enough for both sets of tracks to run in the one tunnel. It would not be wide enough for the station. So for our subway, like the Spadina-Vaughan Subway, the TTC would cut open the parking lot in the east side of the Town Centre Mall, east of the movie theatres, and excavate a huge trench like the one on Keele, all the way down to track level.

 We have been advocating that the subway start on the west side of the Town centre Mall, on the Big Grassy Field on the east side of Brimley, in the approved alignment of the Sheppard Subway. It would run east under Triton Road, under the existing

Scarborough Centre SRT-Bus Station and then begin a gentle curve south around the north side of the YMCA, curve still further south under the Freshco store, cross under Ellesmere and then continue straight down McCowan as per the TTC’s plan on its way to Kennedy Station. We call this The Big Curve alignment.

TTC’s main objection has been, well, if we did that, we would have to close down the SRT and demolish the Scarborough Centre Station right on day one in order to start excavating the massive trench we would need for the new subway station. Below is what Triton Road would look like while they dig down to track level.

Everybody who today rides the SRT or who gets to Scarborough Centre Station by bus to connect to another bus would be displaced to a temporary bus station for 3 to 5 years.

 Not good. Very expensive. So they don’t want to do it.
 We have been researching how subways are being built all over the world. The TTC’s

tunneling contractor for the Scarborough Subway Extension, Hatch Engineering is a world leader in tunnel construction. They are constantly looking for a better, faster, less disruptive way to do it. They are pioneering the use of large TBM’s in the order of 13 meters diameter.

Here’s what Michael Schatz Managing Director of Hatch says:

By using large TBMs – in the range of 12 to 13 m – station excavation can be completed without the need for disruptive and expensive cut-and-cover excavation. “You get a better solution for less cost,” Schatz said.

What Hatch is saying is if you use a 13m TBM, you can build the stations inside the tunnel…anywhere along the line.

No more massive, time consuming, very expensive and very disruptive trench excavations like the ones pictures above.

Plus: Once the tunnel is built, you can build the station[s] underground wherever you want them. Once the station platforms etc are built inside the tunnel, you excavate shafts down to the new station from ground level to create the stair, elevators, ventilation, wiring etc to connect the new station with the street level. Practically zero disturbance to street level activities. Amazing!

If we did this for the Big Curve alignment here’s how it would work:

1.      The Big Grassy Field on the west side of the Town Centre becomes the TBM insertion site and the ‘work site’;

2.      The 13m TBM is inserted there and then bores east under Triton Road, under the existing Scarborough Centre Station and bus depot, and carries on tunneling around the big curve and south down McCowan.

3.      While tunneling is under way all the excavated material comes back to the TBM insertion site on the Grassy Field to be trucked a short distance to the 401 for disposal.

4.      All tunnel liners and other material to build the tunnel and track is lowered down to track level at the Grassy Field.

5.      When the tunnel work is completed, the material needed for building the station is brought to the Grassy Field work site, lowered down to track level and brought forward to the station location;

6.      The SRT and the Scarborough Centre bus terminal continue to operate while the tunnel and the station is under construction.

Here’s our plan:

Red Area: TBM insertion and work site
Green Rectangle: Scarborough Centre Station
Blue Arrow: Points to Lawrence Station

Advantages compared to the TTC’s plan:

·         No need to purchase-expropriate the east parking lot from the Town Centre mall.
·         No need to purchase-expropriate the Lazy Boy site on the north side of Progress.

·         No need to purchase-expropriate our plaza and the gas station on the south side of Ellesmere.

·         No need to expropriate homes on Stanwell;
·         No lost taxes from any of these properties;
·         No impact of the vital intersection of McCowan-Ellesmere.

·         No heavy truck congestion at the traffic signals on McCowan at Ellesmere, Bushby, Triton.

·         No need for a temporary bus terminal.
·         No need to buy a fleet of buses to carry SRT passengers.

There would be some interruption of the Scarborough Centre bus station while they dig out the shafts needed to get stairs etc down to the new station…but that does not take 3 or 4 years. With some relatively minor interruption the bus terminal could keep operating.

It may even be possible to excavate a lateral tunnel so you can walk directly from the new subway station into the lower level of the Town Centre mall.

AND…it means we have a chance to get a station at Lawrence! For our hospital!

The possibility of a Lawrence Station was abandoned because of the huge cost of opening up the ground and excavating all the way down to the subway tunnel. The tunnel is quite deep at Lawrence because it has to go under Highland Creek just north of Lawrence. So the TTC’s usual open cut technique would mean an immense and very deep

trench. Very expensive. Heaven knows what the impact on this important intersection would be for a couple of years. Not possible.

 BUT with the large diameter TBM Hatch is talking about, they could build the station at Lawrence inside the tunnel. The only disturbance at ground level is shafts to get people etcetera down to the new station. Has to be TONS cheaper.
Our hospital has over 3,000 employees. 730 people volunteer at the hospital. It treats thousands of patients and generates thousands of visitors per year. Hospitals are prime generators of transit trips. We have nursing homes, medical centres and Jack Goodlad Seniors’ apartment all within walking distance of a subway stop at Lawrence-McCowan. Use Hatch’s plan for a large TBM. Build a station at Lawrence!

What we need, what City Council needs, is for the TTC to commission an engineering study by Hatch of the feasibility and cost of building the Big Curve alignment using a 13m TBM with stations at Scarborough Centre AND Lawrence Avenue. Show us they can bore this tunnel under Triton without affecting the foundations of our Scarborough Centre SRT Station.

We need you to get involved. It’s your home. It’s your business. It’s your community
·         Email our Councillor Glenn DeBaeremaeker
Email our Mayor John Tory
Email our MPP Brad Duguid
·         Email our Federal MP Salma Zahid.

Tell them you want a thorough analysis and cost estimate by Hatch of The Big Curve alignment with the 13m TBM.

Prepared by Lorne Ross for the Glen Andrew Community Association.

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