This is the ventilation building located at the west portal of the Connaught Tunnel as it appeared in 1972. The double tracks through the tunnel were removed by 1959. A diesel engine in each tower powered a large squirrel cage fan which forced air along a wooden false ceiling inside the tunnel. Exhaust stacks for each diesel engine are visible on the outer end of each tower. The short siding was used to deliver diesel fuel by tank car. For many years, there were three or four houses behind the ventilation building which housed the fan operators and their families.