It took almost a year, but Imperial Oil’s Vidal Street utility tunnel has been reinforced over half its length to alleviate the concerns of a structural failure. On UCI’s recommendation, slightly smaller diameter Armtec Tunnel Liner Plate was installed within the existing corrugated steel tunnel and the annular space between the two liners pressure grouted.
The sizing of the new liner plate was a challenge due to varying tunnel inside diameters and the need to clear the existing pipes and pipe racks. A laser survey was done in the tunnel to determine the best fit of the liner plate using standard dimensioned liner plate rings.
The biggest challenge was physically installing the new plate within the confined space of the tunnel with the interference of all the pipes. Imperial Oil safety practices required a maximum two workers in the tunnel at any one time. The workers had to wear coveralls and a hoisting harness as well as carrying a short duration breathing apparatus harness with a bottle and mask and an H2S detector. You can imagine how difficult it was to do physical work in the tunnel which was very warm due to the internal steam pipes. Kudos to the workers from Curran Contractors for there perseverance.
There were a few setbacks along the way. On removing one of the discontinued pipes to facilitate installing the new liner, H2S gas leaked from the pipe prompting a safety shutdown. The laser survey also had failed to pick up several pipes which were hidden behind other pipes. One pipe could be moved slightly to provide enough clearance while an N2 line had to be completely relocated requiring a 3 month shutdown while that work was coordinated throughout the plant.
It was also determined that concreting the ends of the liner plate sections was not going to be practical with there being very limited access to the roof. It was decided to use commercial expanding foam to seal the openings. The foam held the grouting pressures which were kept as low as possible.
There were a few days in July when it was just too hot to work in the tunnel, however, by mid August the lining and grouting had been completed and a new concrete invert poured.