Bayview Station to the Escarpment:
The LRT plan has the train up on top of the Bayview station (elevation about 65 metres above sea level), from which it dives down to pass under the extension of Preston Street (54.5 metres); a distance of about 250 metres, accounting for vertical curves at each end of the slope. This slope of just over 4% is not at the limit of the LRT specification, but it is also not a gentle slope. (It does exceed the maximum slope for heavy rail so conversion to a full subway is precluded by this section.)
The ‘old’ plan, which had the train dive into its western portal just east of the LeBreton Station, had to have the tracks running at grade by Preston Street since there was not room after Preston to get low enough to pass under Booth Street; and passing over Booth was not an option as the train was to go immediately into the tunnel.
This plan has some draw-backs, though. Booth Street needs to be totally rebuilt and raised from Albert Street to the Ottawa River Parkway and in order to clear the LRT and the aqueduct this will need to be raised on a structure. The fact that it will be elevated restricts where the local streets of LeBreton Flats can join onto it. Because Booth Street is one of only two trucking routes across the Ottawa River, it needs to be replaced before it can be rebuilt; this is where the extension of Preston Street comes into the plan. Although not officially part of the LRT plan (and not part of its $2.1B budget), Preston Street will be extended between Albert Street and the Ottawa River Parkway. The cross river traffic from Booth Street will be routed onto Preston Street while Booth Street is reconstructed. This means that the new section of Preston will need to be at least four lanes wide plus any auxiliary lanes so that it can handle the traffic from Booth Street. Both the Preston Street and Booth Street structures will be quite large and expensive.
Issues with the ‘new’ plan
The ‘new’ plan, however, runs under Queen Street and enters the tunnel through the portal low on the face of the escarpment. This has not changed the plans for the section of track between Bayview Station and LeBreton Station. There is still the need for the two large roadway structures; thus, all of the problems of the ‘old’ plan have continued with the ‘new’ plan.
In profile, this ‘new’ plan would look roughly like this:
Profile of ‘new’ plan
A new draw-back is created by changing the location of the western portal to the bottom of the escarpment; Commissioner Street and Wellington Street get cut off by the tracks. These streets are the only access to the main physical plant of the Parliamentary Sector buildings. Also, because the track wraps further around the aqueduct before turning under Queen, the second curve, of the reversing curves, is tighter than it would have been with the ‘old’ plan.
So the ‘new’ plan keeps the problems of the ‘old’ plan and adds a couple of new issues.
Bayview Station to the Escarpment – Alternative Design:
An alternative idea is to keep the rail line elevated and not raise Preston Street and Booth Street. The Escarpment is approximately 16 metres tall where the train will be entering the face; this gives lots of room to move the portal up. If, for example, the portal is raised six metres then there would be room under the train to maintain Commissioner and Wellington Streets; but there would still be four metres of overburden covering a six metre diameter tunnel.
Another plus is the reduced work required for the tunnel under the Escarpment Park. The cutting of a 16 metre deep trench through the rock under the park could be reduced to only 10 metres deep if the tunnel entered higher on the cliff face. With a shallower trench, there might be less risk digging (blasting) nearer the cliff edge, permitting a wider radius curve for the tunnel and a faster, smoother ride for the passengers.
If the new rail line were elevated on piers, it might be possible to build much of the line without disrupting the existing Transitway. (The section above the Empress extension would be installed once the Transitway was shut-down for construction of the Bayview Station.) Booth Street would not need to be rebuilt and the extension of Preston Street could be done when it is convenient, as opposed to being required in the near-term. By not widening Booth and Preston Streets, more traffic is not encouraged to travel through the developing neighbourhood of LeBreton Flats. Elevating the rails on piers might also mean that the section between LeBreton Station and the escarpment could be placed closer to the aqueduct and the Fleet Street Pumping Station so that the curves in that area can be wider and gentler.
With an elevated station over Booth Street, a more efficient central-platform design could be used to reduce the initial cost and the on-going operating cost.
The general alignment of the rail line would not change, with the exception of some minor ‘tweaking’ facilitated by elevating the line, but the profile would change to look like the following:
Profile of elevated rail line
So by re-thinking the elevation of this section of the rail line – something that is facilitated by the realignment of the tunnel to start at the escarpment face – the major draw-backs of the ‘new’ plan can be avoided:
• The steep slope from Bayview Station is removed, allowing for a more comfortable ride, reducing operating costs, and allowing for future up-grading to a heavy rail system if needed.
• Booth Street does not need to be replaced and elevated onto a huge, expensive structure.
• Preston Street does not need to be extended with an oversized roadway elevated on an expensive structure so that it can handle the inter-provincial traffic.
• Commissioner and Wellington Streets can remain in place to serve the Federal Government’s Physical Plant.
• And the curves in the line can be made smoother by adjusting the position of the alignment closer to the aqueduct and by curving a shallower path under the Escarpment Park.
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