Ontario’s upcoming standards will change the way stormwater is dealt with

By William Curry

Old school engineering design was to get rid of stormwater as soon as possible by conveying it to a receiving water course. Low-impact development (LID) is a term used in referring to a way of managing stormwater runoff via planning and engineering as part of green infrastructure. The LID approach implements engineered hydrologic controls in watersheds via storing, infiltrating, filtering, evaporating, and attenuating or detaining runoff close to its source. Some refer to this approach as Green Infrastructure.

The Province of Ontario is working towards providing minimum LID standards that will change the way stormwater is dealt with in the future. Imagine a newly developed subdivision that uses every type of green infrastructure available. These include bioswales, subsurface infiltration systems, rain gardens, rain barrels, permeable pavement and green roofs, to name a few. The immediate benefit is environmental protection, with secondary benefits including smaller storm pipes and smaller stormwater ponds. LID can also improve groundwater quality and quantity.

We are seeing an increased intensity and frequency of larger rainstorm events within a single year. These events can be isolated and localized within a municipality, but they seem to be occurring with increased frequency. With changing design concepts such as LID within municipalities, new problems arise. How do we maintain green infrastructure and educate municipal staff and the public about it?

Residents may not see the increase in these storms, but may only see that their properties or their street are not draining as well as they remember. They may think that the catch basins in the roadway must be blocked, as they are also not draining as quickly as they used to. So, the perception is that the stormwater infrastructure is not working. However, the reality is that it has reached capacity and the road network is now conveying the excess water.

Some residents have asked why we don’t build larger storm sewers to drain water away immediately on the street in front of their house.

The City of Ottawa has an abundance of information on its website to help individuals with many types of issues, from enquiries to service requests and even complaints. Also in place are response teams and professionals to quickly deal with on-site issues. The Province and municipalities will have to educate the public to the LID development concept in the years ahead.

Are municipalities prepared to maintain LID as an owner?

Municipalities will have to adapt to the new LID standards by becoming proactive rather than reactive. Appropriate resources will need to be in place to provide the required maintenance for LID assets.

Permeable concrete pavers as sidewalks along an entire street may only require mechanical sweeping and pressure washing annually. Sub-surface infiltration pipes may require regular cleaning as needed. Bioswales within a municipal right-of-way will need regular maintenance. It may mean regular staff inspection, removing road and bioswale debris that previously would have been captured in city catch basins and removal of degraded plants and vegetation that is generating foul smells and impacting residents. Time will tell what requirements will be needed.

LID components should be treated as an asset. Municipalities in general will have to adapt to the maintenance needs of each specific type of asset as an owner. If a city-owned bioswale is filled with leaves or decaying vegetation and street debris, it is likely not functioning as designed and more importantly may be a public eyesore. Municipal staff will have to become familiar with the types of ongoing issues and expected resident complaints.

Municipalities may have hurdles to overcome at first with emerging low impact development green infrastructure, whether it is public concern or staffing requirements.

William Curry, C.E.T., is with Planning, Infrastructure and Economic Development, City of Ottawa. Email: william.curry@ottawa.ca