Chewing their way through sand and clay, two 500-tonne machines will dig about 14 metres a day under Eglinton Avenue. Known officially as tunnel boring machines (TBMs), but colloquially and more romantically as “moles,” one of the machines that will excavate the first new underground transit line across the city in decades was shown off to the media on Monday.
Another TBM will be assembled at the site and the pair are set to start the long-anticipated Crosstown Dig next month. Although that is nearly a year behind schedule, Bruce McCuaig, head of the regional transit agency Metrolinx, said that they have built in leeway and expect to meet the target of having the LRT line running by 2020.
Each TBM is more than six metres across and about 80 metres long when fully assembled. Resident engineer Gary Kramer said that the on-board crew will navigate according to a laser survey, steering the behemoth as it moves ahead in 1.5 metre increments. Alternating crews will keep it running as many as 20 hours a day, generating 60-80 trucks of fill and installing the tunnel lining.
In the media event was held at a gaping pit near Eglinton and Black Creek Drive.