Quebec wastewater treatment assets stood at a more or less a steady average age from 1961 until 1990, averaging 13.8 years. However, the relatively low investments in most years thereafter caused the age to increase steadily to an average of 19.1 years in 2007.
As a percentage of estimated useful life, Quebec was much below the national average in 1991 at 48% compared to 54% nationally. This situation has now reversed. In 2007, wastewater treatment plants in Quebec had passed 68% of their estimated useful life, compared with a national average of 63%.