Honorable Mention: Special Projects Category

Rapid Transit Tunnel Leak Remediation and Structural Repair

Toronto, Ontario, Canada

Submitted by Morrison Hershfield Limited

The leak remediation and rehabilitation of the 0.6 km (0.4 mi) long tunnel for the Toronto Transit Commission’s Harbour-front Light Rail Transit restored this rapid transit tunnel in downtown Toronto to its full function without the need for continuous maintenance or operational concern.

Extensive leakage was found in the tunnel’s slurry walls after construction in 1991, and previous grout repairs had met with little success. The situation also posed hazards to transit operation, as well as to the safety of patrons in winter due to the formation of ice on platforms and above tracks.

The project underwent comprehensive investigation, and included a trial grouting program. Construction began in November 1998 on a “round-the-clock” schedule, and was completed in the spring of 1999.

The key factor of success was the adoption of a combination of multi-stage grouting and sealing system along with an innovative joint seal design. All deteriorated concrete was also repaired with shotcrete.

An experienced inspection team involving some of the best grouting and concrete sealing experts in Canada was assembled, enabling site problems to be quickly resolved. The complete work is now leak free and public safety is greatly improved.