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.
UCI was called on by Imperial Oil and its consultants, SNC-LAVALIN, to inspect the corroding product pipe tunnel under Vidal Street in Sarnia and recommend a solution to extend its life.
Inspection revealed an original liner plate tunnel with a corrugated steel pipe connected to it to accommodate a road widening many years ago. Both tunnel types had areas of severe corrosion which jeopardized the structural integrity of the tunnels. Any collapse onto the active petroleum product piping would be a serious situation.
The recommended solution is the building of slightly smaller tunnel liner sections within the existing corroded tunnel at three locations. The annular space between the existing and new culverts will be filled with concrete grout.
Working conditions within the tunnel are difficult. The multitude of pipes and the necessity of workers carrying self contained breathing apparatus and dragging an extraction line to meet Imperial Oil confined space requirements will severely impede productivity.
The work is being fast-tracked for completion in late 2010.
UCI client, AVERTEX Utility Solutions Inc., utilized the Vermeer AXIS Guided Boring System to install 40 metres of 250 mm sanitary as the outlet for a new sewer that eliminated a worn out pumping station. The installation was carried out as a demo for engineers from many of the larger municipalities in Southern Ontario.
In spite of having to cut through some cobble encountered in the clay till, the cutting head arrived at the existing manhole on precise line and grade. The cutting head and following cans were pulled back to the shaft and a 250 mm PVC pipe threaded into the bored hole in the till.
The Vermeer AXIS system can install conduits up to 450 mm in size on line and grade and from manhole to manhole.