Surprise Creek Bridge. The 1931 flood sent 2,000 replacement ties through the tunnel, and filled the west portal cutting to a depth with of mud and debris, which took five days to dig out. Approved in 1958, the following year a single track down the centre (replacing the double tracks) provided sufficient clearance for tri-deck automobile carriers. In 1972 and 1976, the tunnel fans and housing sustained extensive damage on catching fire. In 1977, soon after departing the Glacier siding (Mile 85.9), a westbound loaded 109-car coal train lost control, and broadcast a warning that they were travelling too fast to make the curves at Illecillewaet. On hearing the radio message, a 60-car eastbound freight accelerated to safely reach Illecillewaet siding (Mile 98.1), before 3 crew members stepped clear of their train. The runaway's 3 lead locomotives, 45 cars, a remote control locomotive, and the following 22 cars, were destroyed on derailing at Mile 94.4. The impact shifted a bridge from its footings and damaged a snow shed. The crew sustained minor injuries. The line remained closed for a week. In 1985, a nearby rock slide derailed one of the four locomotives hauling a coal train. The tunnel was deepened to clearances matched with the Mount Macdonald Tunnel in 1993 to accommodate double stack container cars with future electrification. This first 24/7 work project undertaken by CP was a significant engineering challenge. In 1997, eight cars of a train derailed in the vicinity. In 2015, six cars of a westbound freight derailed on Stoney Creek Bridge. The train had diverted to the eastbound route because the Mount Macdonald Tunnel was being vented. The incident occurred when the train lost momentum on the steeper grade and stopped with the cars on the bridge. However, restarting on the curve caused the heavier cars at the front and rear of the train to lift the lighter middle cars from the track. Operation The first commercial train was December 1916, which travelled via Loop Spur, since the pass line remained in use until a few days later. The most northern part of the Loops between the two hillsides, which had been a long trestle, but likely infilled around 1906, needed to be breached by the new line. Automatic block signalling came in the 1920s. To improve visibility on the 1929 introduction of the Selkirk locomotives, trains switched to the left-hand track before entering the