Green Tech Solutions to Aging Sewers

Stormwater Drain


June 19, 2014

This spring’s heavy rains did more than dampen spirits across the country. They also had nasty consequences for outdated sewer systems in some Canadian cities. 

In April, more than 78 million litres of diluted raw sewage overflowed into the Ottawa River from the city’s sewers. The incident provided the latest indication that something must be done to ease the pressure on aging sewer infrastructure.

And these days, many North American cities are looking to green technology as an important part of the solution.

Ottawa, like most other major cities in Canada and the U.S., still relies in part on combined sewers—pipes that carry both rainwater and raw sewage to treatment plants. A rapid influx of storm water can overwhelm a combined sewer system, causing untreated sewage to spill into surrounding waterways.

The problem is becoming more urgent as cities feel the impacts of climate change, including heavier rain and more frequent flooding.

Some cities have undertaken to separate their sanitary and storm water sewers, so that flooding will not disrupt sewage treatment. Vancouver is one example—but the separation will likely cost $1 billion and take 30 years to complete.

Other municipal governments have looked to cheaper green technology instead. The city of Portland completed a 20-year combined sewer overflow control program in 2011, which reduced the city’s annual overflows to the Willamette River from 50 to four. The program adopted a wide array of green infrastructure, like green roofs and roadside swales—vegetated areas that absorb water instead of funnelling it into sewers.

Toronto launched a 25-year Wet Weather Flow Master Plan in 2003. So far, initiatives have included a green roof incentive plan and a downspout disconnection program that requires homeowners to manage rainwater on their own properties rather than directing it into sewers.

Earlier this year, the U.S. Environmental Protection Agency highlighted the importance of green tech when it released guidelines for managing sewer overflows with green infrastructure that includes swales, rain gardens, green roofs, and porous pavement.

In 2012, Environment Canada released its first set of wastewater regulations, which simply required that wastewater system operators develop plans to reduce combined sewer overflows.

The federal Green Infrastructure Fund, which targeted projects that would “improve the quality of the environment and lead to a more sustainable economy,” devoted much of its $1 billion to wastewater treatment plant upgrades rather than innovative green technology. That funding was used up in 2011.