By 2009 Shoreview, Minnesota had the largest stretch of permeable pavement in NA.
Initially, the reason for using this pervious pavement was because the city was working on improving water quality. The issue was road salt and their desire to reduce ice without using so much of it.
“(The roads project) was designed to solve the stormwater management problem,” says Mark Maloney, Shoreview’s public works director. “… We learned that there were suggestions that permeable pavement in colder climates had the potential to be somewhat self-cleaning when it came to snow and ice accumulation.”
Road salt is popular because of its low cost, but there are “downstream costs of chloride-based road salts, which rust cars and contribute to the erosion of bridges.” Chloride is toxic to fish, can pollute lakes, streams and the water supply, is corrosive to infrastructure, and once it is in the water, you cannot take it out.
“My opinion is that what we’re most worried about is ice. With permeable pavement, though, the water moves right through it so you may not have as many ice conditions as we have currently,” commented John Gulliver, a professor and researcher at the University of Minnesota’s Department of Civil, Environmental, and Geo- Engineering who specializes in stormwater pollution prevention.
This information is from How a Twin Cities Suburb Has Led The Way With Permeable Pavement
Last week, the Oxford University Press published a paper entitled: Road salt impact on soil electrical conductivity across an urban landscape in Next City.
In the introduction, it states: “The desire to reduce and optimize salt use is widely held. In addition to the negative environmental and drinking water impacts of excessive salt application, the purchase and distribution of salts is an economic burden to local governments, and road salts accelerate rusting of personal vehicles and infrastructure, such as bridges and steel-reinforced concrete. As a result, understanding the movement of salts from paved surfaces and their retention in terrestrial and aquatic urban ecosystems provides critical information for maximizing both environmental and economic value.”
It goes on to explain that although the problems of using road salt often focuses on aquatic environments, its negative impact is much more far-reaching.
“While a large proportion of road salts are flushed directly to aquatic systems via storm sewers, a portion can end up in terrestrial soils due to misapplication, salt bounce, aerosolization from traffic, flooding and application in areas without drainage infrastructure. Like aquatic environments, road salts can have detrimental effects on terrestrial urban environments. Saline soils near roadways negatively affect the health and growth of urban trees through osmotic stress and ion toxicity. Airborne salts can also have a direct impact on plant tissues and especially leaves, when salts come in contact with plants through misapplication or aerosolization from traffic. In soils, high concentrations of salts can mobilize potentially toxic heavy metals including lead, cadmium and mercury, which are known to bioaccumulate in terrestrial and aquatic food webs. In addition, excess salt concentrations promote nitrate leaching, and sodium ions deflocculate (disperse) clay particles within the soil, which block pore spaces and limit water infiltration. The resultant decreased hydraulic conductivity may lead to increased surface runoff, erosion and anaerobic soils.”
This data in this study exposes the many dangers of road salt. This could be an effective argument for the use of pervious concrete paving in cold, icy climates.
Thomas P Shannon, Sam J Ahler, Alex Mathers, Carly D Ziter, Hilary A Dugan, Road salt impact on soil electrical conductivity across an urban landscape, Journal of Urban Ecology, Volume 6, Issue 1, 2020, juaa006, https://doi.org/10.1093/jue/juaa006