In the mid-1970s, the average age of wastewater treatment assets were at their all-time low of 13.4 years. Through several years of relatively low investments, the age climbed almost steadily to 17.4 years in 2004 before dropping to 16.9 years in 2007, on the strength of renewed investments.
As a percentage of estimated useful life, Ontario tended to run close to the national average in most years, as for the other assets. In 2007, the provincial rate was 60%, compared to 63% nationally.