Sewage system

Descriptions of sewer systems

The City of Dollard-des-Ormeaux has two sewer systems; one for sanitary waste water and the other for storm water. Waste water from residential and commercial users empties into the City of Montréal’s underground sewer main, which runs across the City to the east end of the Island of Montréal. This waste water is treated and returned to the St. Lawrence River (for more information, please consult the City of Montréal’s waste water treatment website at
Runoff flows into the sewer system through catch basins located along street gutters. Some of the water collected in this way is temporarily held in the Centennial Lake (retention pond), before being discharged into the Rivière des Prairies.
A permit must be obtained and administrative charges paid for every new sewage connection to the public sewer system. Please refer to our By-law R-2014-095 for additional questions or contact the Engineering Division at 514-684-1033.


Since storm water is not treated before being discharged, it is strictly prohibited to empty toxic or dangerous products into the storm water system through the grates located along the streets. These products require a special collection.

Prevention and obligations

All sanitary waste water systems have rats. The City’s system is no exception. While the City hires a company to put rat poison each year in sewer manholes to reduce the rodent population and limit its spread, rats cannot be eradicated completely.

In addition to preventing rats from entering the home, this back water valve prevents sewer backups.

Possible situations and interventions

Foul odours

Sewer backflow

Boil water advisory in effect in the DDO territory