Roadside vegetation is essential for managing stormwater flow and filtering pollutants so how do you ensure your road is good for wheels and wildlife?
Well in the US state of Minnesota they’ve come up with a way to do that by reusing waste materials and creating an engineered soil.
Generally eftover soil from road construction typically lacks the necessary organic matter to support plant growth and stormwater filtration. To address this, local engineers have investigated various locally available industrial by-products to create engineered soil that can effectively support vegetation and treat runoff.
Researchers selected nine potential materials, including dredge sand, recycled concrete aggregate, ash sawdust, and sugar beet tailings, evaluating each for its permeability, nutrient content and pollutant removal capacity.
Laboratory and greenhouse testing demonstrated that many of these materials effectively supported radish and oat growth, with some exhibiting strong pollutant adsorption properties.
From these materials, three engineered soil mixes were formulated, each containing 80% inorganic and 20% organic matter.
These blends were then assessed in outdoor plots for their infiltration capacity, pollutant filtration and support of grass and flower species.
All three mixes performed well, with organic elements contributing to higher conductivity and consequently, better stormwater management.
The blend containing recycled concrete aggregate and ash sawdust showed the lowest life cycle impacts, though the mix incorporating peat and biochar displayed nearly similar results.
Building on this research, adopting these engineered soils could help Minnesota roadsides better handle stormwater, reduce pollutants and make sustainable use of regional industrial by-products.
