The recent Detroit Free Press series on Lake St. Clair was well-timed. Many of our waters are under threat, not just Lake St. Clair. Mucky green algae is not only spoiling Lake St. Clair, but also Lake Erie, Green Bay, and Saginaw Bay to name a few. At times, the algae can become so toxic it defies treatment, shutting down drinking water systems as in Toledo in 2014. Locally, in addition to Lake St. Clair, combined sewer overflows pollute the Detroit and Rouge Rivers. But crises typically present opportunity. As recognized in Thursday’s installment, green stormwater infrastructure (GSI) is a promising solution. And GSI is not just a solution to water quality. Its triple bottom line benefits can beautify our communities, create jobs and improve our health and quality of life.
Like some parts of Oakland County and other urbanized areas, Detroit operates a combined sewer system, meaning that stormwater runoff and sewage both drain into the same set of pipes. In the event of heavy rainfall, the water running through the pipes can exceed the system’s capacity, backing up into basements, flooding streets, and discharging untreated stormwater and wastewater into rivers. These discharges are called combined sewer overflows (CSOs).
But something as simple as a residential rain garden can be part of the solution. Bioretention gardens on vacant lots can be, too, as can bioswales — linear rain gardens — along roadways, bike lanes and parking lots, along with green roofs, street trees, and pervious pavement. These natural and beautiful landscapes soak up rain water and filter it back into the groundwater, keeping it out of the storm drains thus reducing the strain on the combined sewer system.
In addition to the environmental benefits, GSI saves money by serving as a substitute for more costly human engineered solutions, such as underground storage tunnels and treatment centers (gray infrastructure). Over the past 20 years, the City of Detroit has spent $1.5 billion on such gray infrastructure to reduce overflows and is now turning to GSI to avoid paying another billion. It is changing the way it charges customers for drainage (a sewerage charge that has been on water bills since 1975) so that it will be based on the property’s impervious surfaces that contribute to the combined sewer system, and it is developing a green credit program to encourage customers to install green stormwater infrastructure.