From the TTC's "Sidewalk Superintendents' Manual"
This is a section of Yonge Street before excavation has begun. The first operation is to dig a trench or series of trenches (1) on each side of the street along the outside lines of the subway excavation. These trenches locate the water pipes and other utility feeders (2) to buildings so that they may be avoided during pile driving. Along the trenches, steel piles (3) are driven every 6 feet. They provide support for the sides of the excavation and for the temporary street decking. (A)-- Hydro conduits and Telephone conduits. (B)-- Gas Mains. (C)--Water Mains. (D)--Main Sewer.
When the excavation reaches a sufficient depth, steel trusses or girder beams (1) spanning the excavation are placed every 12 feet, resting on alternate pairs of piles. (The trusses are used at stations where the span is too wide for the girder beams.) These trusses or beams carry the temporary street decking of 12" x 12" timbers (2). Additional steel reinforcing is placed under the street car tracks. To hold back the earth at the sides, 3" planks are inserted horizontally behind the flanges of the piles (3). The pipes and conduits of the utilities are suspended from t he trusses or beams. Two small temporary sewers (4) are installed at the side of the excavation. Flow in the main sewer has been diverted to the new trunk sewer under Victoria Street.
The excavation is shown completed to the required depth, the earth having been carried up ramps to the surface for disposal. The planking between the piles has been carried to the bottom of the excavation. Additional wood bracing (1) is installed as required. During the process of excavation, the exposing and supporting of the utility services buried in the roadway are jobs that must be done with great care. A slip of a drill might interrupt hydro, telephone or water service to buildings over a large area. Expert technicians from the Hydro System and Telephone Company are in attendance to supervise this part of the job. To avoid the danger of explosion, gas mains are moved to a temporary location outside the excavation (2)
At some locations, drills and shovels unearth pipes or conduits that cannot be identified, even after a search of all available plans. These must be tested carefully before they are removed, as they might be uncharted but still used sections of some of the utilities. The buried foundations and footings of long destroyed buildings are other items that present unexpected and formidable obstacles during excavation. In this illustration, the timber bracing has been removed after the 3-foot slab of concrete has been poured for the subway floor (1). Then the concrete for the outside walls is poured inside the rows of steel piles and planking.
This is a section of Yonge Street and the completed subway, showing station platforms. After the central wall and the reinforced concrete roof of the subway (1) are constructed, the open area above is filled with sand and the utilities (2) are returned to suitable positions. New local sewers (3) are installed outside the subway. Then a temporary pavement is laid, streetcar tracks are relaid and normal traffic is resumed. The street cars will remain in service on Yonge Street until the rapid transit line is completed to Eglinton Avenue, and until all stations and equipment are installed. The street car tracks will then be removed and Yonge Street will be repaved.
