Tunneling is progressing well on McNally/Aecon JV’s two sewer projects for the York Durham Sewer System, north of Toronto, Canada (T&TI, Oct 07, p36). On the $70.5 million 19th Avenue (YDSS Interceptor) project, the 10.6ft (3.25m) diameter Lovat EPBM “Motorclara” has been mining well, reaching the last shaft on its 2.24-mile (3.6km) long drive in November. The mining operation was then relocated to this shaft to allow clean out and patching of the 1.43-miles (2.3km) of completed tunnel concurrent with the remainder of the drive. “Motorclara” was re-launched in January and to date has completed nearly 400 of the 1100 rings on this drive.

On the Langstaff Trunk Sewer (which is being constructed with the Bathurst Collector under a single $79.5 million design-build contract) another 3.25m diameter Lovat EPBM “Enviro” has also advanced well, despite some challenges. “The ground is highly variable, switching between firm clays to very fine silts, sand and gravel within the space of one push,” explained Steve Skelhorn, McNally’s Project Manager on 19th Avenue. “The ground conditioning system required a lot of experimentation to reach a set-up that would allow us to adjust the foam/polymer injection at a moments notice. The downhill grade added to the problems, as any water would flow into the TBM making life difficult for the crews.” To date 1100 of 2900 rings have been built at Langstaff.

On the Bathurst Collector the third of the JV’s identical Lovat EPBMs, “Laura”, completed the first of two drives in mid-December. This 1.3-mile (2.1km) downhill drive was primarily through consolidated tills and clay. TBM removal proved challenging with a relatively small diameter 18ft (5.5m) recovery shaft, located in a very small site on a busy intersection. In January 2008, the TBM was re-launched from the same drive shaft for the second 1.55-mile (2.5km) drive. To date 350 of the 2100 rings have been completed.

It is anticipated that 19th Avenue project will be completed in summer of this year and the Langstaff and Bathurst projects in late autumn. n