Initial Effects of a New Highway Section on Soil and Groundwater
2012
Earon, Robert | Olofsson, Bo | Renman, Gunno
The environmental impacts of 16 different contaminants originating from the E18 Highway (17,510 annual average daily traffic) were studied over the initial months of the highway’s operational life. Investigative methods used included electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modeling, and transportation modeling of contaminants. The study conclusively showed a year-round infiltration due to melting of the snowpack from road salt, and a strong preferential, anthropogenic pathway due to increased hydraulic conductivities of road construction materials relative to in situ soils. The resistivity surveys produced values well below the expected values for the highway materials, indicating increased ionic content within the unsaturated zone. Time lapse resistivity modeling showed a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m. Elevated concentrations of nearly every studied contaminant relative to baseline values were observed, with many metal concentrations within the snow pack averaging values in excess of the Swedish Environmental Protection Agency’s groundwater limitations. Distribution modeling demonstrated a potential offset of peak values from the road surface due to plowing and splash transport processes, and indicated different distribution behavior during winter months than during summer months. One-dimensional transport modeling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to groundwater and provided an estimate for potential long-term contaminant concentrations.
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