Urban snow deposits versus snow cooling plants in northern Sweden: a quantitative analysis of snow melt pollutant releases

High-velocity runoff from snow deposit transports suspended grain-attached contaminants while underground snow storages trapped these contaminants within the storage. The aim here is to quantify pollutant masses from an urban snow deposit and to investigate the conditions when pollutant control was increased by turning a snow deposit into a snow cooling plant with permeable underground snow storage. Pollutant masses in an urban snow deposit in northern Sweden were: Cu = 67, Pb = 17, Zn = 160, P = 170, SS = 620,000, Cl = 1,200, N = 380 kg. A theoretical analysis showed that the fraction of surface runoff from a surface deposit largely depends on the hydraulic conductivity ( K , m s−1) of the soil. For a melt rate of 30 mm, day−1, surface runoff would be about 97% for a soil with K = 10−8, while nonexistent for K > 10−6. Similar soil conductivities are needed to ensure that all snow melt could be transported as groundwater from an underground storage. The largest pollution-control advantage with underground snow storage compared to a surface deposit would thus be that piping and filters for operation of the plant could be used to filter surface snow melt runoff before rejection.