Salt: How snow and stormwater are connected - Metropolitan Planning Council

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Salt: How snow and stormwater are connected

Sarah Cardona

Winter salt interferes with native plants' and grasses' ability to manage spring storms.

Our 2016 series on road salt looks at how these little crystals affect our region, from their impact on our waterways to their implications for government efficiency.

We’ve now past the summer solstice, and I’m still thinking about salt. Mainly because, I come to find out, there is a case for observing salt’s impacts year-round on our region beyond its use primarily in winter.

I was happily riding along the Lakeshore bike path recently, joined by multiple Midwesterners eager to sport shorts and flip flops, when I took this photo of road salt’s havoc on grass. Crystals of sodium chloride applied during winter months to keep streets and sidewalks safe inevitably end up along roadsides like this one by Grant Park. You can just imagine the snow pile idling there back in February, loaded with road salt. The result come spring and summer? Brown blotches of dead grass.

If you’ve ever spilled wine on your carpet or couch, maybe you used table salt to help soak up the stain. One of salt’s tricks is that it removes moisture—even from grass blades and soils. Without adequate soil moisture, grass roots begin to malfunction, not getting the nutrients and water needed to thrive.

Grass is good not only for its pleasing aesthetics or welcoming atmosphere for a picnic. It’s on the list of nature-based infrastructure solutions like rain gardens, bioswales or rooftop gardens with native plants all of which support our region’s capacity to manage stresses on the system like heavy rainfall.

They do this by collecting rain when it falls and allowing it to evaporate or filter through the soil back into the earth. Absent these nature-based solutions, rainwater simply runs off impervious surfaces, such as concrete sidewalks. In the process, it picks up toxins—such as our friend chloride—and inundates our storm and sewer water systems as well as surface water resources with polluted rainwater.

Effectively managing stormwater is a very real and actively discussed priority for the Chicago metropolitan area and communities across Illinois. Almost a year ago, the Illinois Dept. of Natural Resources put a number behind the documented flooding damages statewide between 2007 and 2014, mainly from basement flooding and sewer back-ups: a staggering $2.3 billion. The largest percentage of that documented damage came from Northeastern Illinois.

Looking ahead, several studies of future precipitation trends agree that the frequency (number of times it rains) and intensity of precipitation (really heavy rainfall) are expected to continue to increase in the future here in the greater Chicago region. It has become more pressing now than ever to work together to prepare for more wet weather events and have solutions in place to recover from them with the least amount of damage incurred.

Thanks to our work with the Calumet Stormwater Collaborative, Metropolitan Planning Council (MPC) knows a thing or two about stormwater management. Working with communities and policymakers, the collaborative has improved local investments, driven regional collaboration, and developed tools that equip residents and business owners to manage rain that falls on their property. Nature-based solutions, such as rain gardens, are one such approach.

If you’d like to see just how effective rain gardens can be at retaining and filtering stormwater, check out this easy-to-read, eight-page report by Openlands, one of the members of the Calumet Stormwater Collaborative. Other examples of projects in Chicago and the surrounding region include the planned open promenade lined with locally-sourced trees and native plants at Navy Pier.

A common denominator across these nature-based solutions to stormwater management is healthy and vibrant native plants and grasses doing their job absorbing rainwater. This means that such plant performance (and our ability to withstand heavy rains in spring as a result) is directly affected by how we handle inclement winter weather—namely our road salting practices.

“Excess salt can kill many native plants, and open the door to salt-tolerant invasive species taking over instead,” says Byron Tsang, project manager and ecologist with the Chicago Park District’s Dept. of Cultural and Natural Resources. He explained further how this shift to abundant invasive species “lessens ecosystem diversity in the long-run which could reduce the overall performance of nature-based infrastructure solutions like rain gardens and bioswales to manage stormwater.”

Bioswales and rain gardens aren’t the only victims of road salt’s damaging effects. Trees, particularly those alongside major streets and highways, are also in harm’s way. Tree roots find it difficult to uptake water as the salt level increases. What’s worse, water within tree roots, leaves and branches can actually be drawn out in high-salinity conditions.

We need trees and the multiple benefits they provide us, including cleaner air and water, habitat for wildlife, improving our quality of life in the outdoors, not to mention their function as nature-based solutions to reducing flooding and urban runoff. Trees also help us adapt to climate change by providing much-needed shade, lowering surface temperatures and releasing moisture into the atmosphere to help urban areas like Chicago reduce heat island effect.

“We can’t afford to threaten more trees with the harmful impacts of road salt” says Melissa Custic, coordinator for the Chicago Region Trees Initiative, “because our region is already on track to losing 13 million trees due to the Emerald Ash Borer.” As part of the initiative’s mission for coordinated action on key issues facing trees, they are organizing a peer-to-peer mentoring program on July 27, 2016, to discuss road salt reduction strategies.

Like any urban area that experiences snowfall, we rely on road salt as a public safety measure when conditions get slick. Yet, we must change our business-as-usual relationship with road salt given the other forces at play in our pursuit of growing a prosperous and sustainable Chicago region into a future facing significant shifts in weather patterns.

We are also a metropolitan area grappling with how to run our local government more efficiently, how to protect our environment and natural assets like water resources, and how to prepare for and withstand increasingly heavy precipitation and extreme heat events.

If anything, this series on salt has opened my eyes to the solutions available to us to get smarter about salt for a whole host of benefits. We can buy less supply (even sharing the cost with a neighboring municipality), apply less and store leftover stock more efficiently. We can plan aggressively for 2018 when the new chloride water quality standard takes effect.

Most intriguing, we can challenge ourselves to stop and think about salt even during the 90-degree days in June and consider salt's role in our region’s economic, environmental and climate change stability all 12 months of the year.

Learn more about salt with the other posts in this series.

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