Case Studies of Municipal Hydrodynamic Separator Maintenance Programs


OGSmaintPage_smallpicIn Ontario, it is estimated that there are approximately 13,000 Hydrodynamic Separators (HDS), and roughly 1,000 new units are installed each year.  These devices require frequent inspection and maintenance to ensure they continue to function according to design.  When they are not maintained, the devices fill with sediment and debris, and provide little to no stormwater treatment, resulting in the degradation of aquatic life and water quality in downstream watercourses.

Unfortunately, the location and ownership of many of these units are not currently being tracked, and investigations in other jurisdictions have shown that maintenance is more often the exception than the rule.  Best estimates from manufacturer databases suggest that only about one quarter of existing HDS in Ontario have been inspected, and even fewer have been serviced.

Hydrodynamic separators are easy to ignore because they are installed underground within the storm sewer system, and are accessed through manholes that look the same as other conventional storm sewer manholes.  Consequently, property owners and tenants are often not aware that they have HDS on their property, and those that are aware have not usually been informed of their obligation to regularly inspect and service the devices.

In this project, the mechanisms and legal avenues through which municipalities and other government agencies can enforce and improve maintenance of HDS are reviewed.  Case studies from three municipalities in Ontario that have had some success in educating HDS owners and improving maintenance practices are presented and discussed.  A simple, user friendly web-based tool is introduced as a means for government agencies to track the location, inspection and servicing of existing and new HDS in the Greater Toronto Area.  Finally, recommendations are provided on how municipalities can establish programs and procedures to ensure that new and existing HDS are adequately maintained.

Photo courtesy of Minotaur Stormwater Services.