About 120 workers are represented by Local 508 of the Canadian Union of Public Employees.
They have been without a contract since December 2013.
The workers voted Wednesday to give their union a strike mandate.
The union is urging the city to return to the bargaining table in hopes of resolving outstanding issues including wages.
The workers are responsible for variety of services, including water and sewage as well as street maintenance and cleaning.Suggest a correction