The Guardian reporter Leyland Cecco visits an almost 100ft-tall snow mountain, one of six created in Toronto to store all the snow cleared from roads and paths across the city.

Toronto has spent more than C$1bn dollars over a decade to successfully re-naturalise the mouth of the Don River. But this is at risk because the salt contained in the snow mountains is likely to end up in water systems, causing an ‘ecological crisis’.

More than 130,000 tonnes of salt were used during the winter’s record snowfall and remains trapped in the snow mountains, along with oil, metals and dirt. Once the mountains thaw in the summer, the salt will make its way to the groundwater and become toxic to fish in freshwater systems