The TTC agenda for April 18 includes a report recommending award of a three-year contract for “rubber encapsulation” for special trackwork. This technique, technically called “elastomeric isolation”, extends the mechanical isolation of track from regular tangent rails to the intersections where there is much more vibration and potential for roadbed damage.
The TTC pioneered this design for special work installation with three test sites: King & Queen (Don Bridge), Main Station Loop, and finally a large-scale project at King & Dufferin. The impending work on St. Clair at Robina and at Oakwood, as well as intersections along the Dundas line will all be encapsulated.
Other design changes are in the works according to the TTC’s Jim Teeple:
Not only have we been evaluating the polymer used for the isolation, we have also been reviewing fastener and tie technologies as well. Our primary objectives are: life-cycle (including future vehicle fleets) , in-street construction timelines (panalisation to minimise disruption), reduced preventative maintenance, ongoing maintenance costs, capital costs, in roughly that order.
The St. Clair project this year will see Hydro working between Vaughan Road and Westmount Avenue (one block east of Dufferin Street) to underground its services, while the TTC rebuilds the streetcar right-of-way from Westmount to Caledonia (where Hydro services are already underground). St. Clair West Station Loop will also be rebuilt this summer, and the work will include repair of expansion joints in the station structure.
The remainder of the line’s reconstruction (Vaughan to Westmount, Caledonia to Gunn’s Loop) will take place in 2008. There is no word on the proposed extension westward, but this is included as part of the Transit City scheme.
In a previous post about the overall plans for special work replacement, I raised the question of why some intersections on Spadina were listed even though they are comparatively new. It turns out that budget estimates are done based on formulas including service intensity and the time projected for special work to deteriorate to the point of needing replacement. The Spadina intersections were built long before the move to mechanically isolate the track and this, combined with the extremely frequent service, will bring them up for replacement sooner rather than later. However, the actual timing of the project will be based on actual conditions on site, not simply on a formula. The TTC’s track construction plans change every year, and we may see the Spadina intersections move further out if they remain in better condition than expected.