Snow removal

Snow removal or snow clearing is the job of removing snow after a snowfall to make travel easier and safer. This is done by both individual households and by governments and institutions.

De-icing and anti-icing

De-icing is defined as removal of existing snow, ice or frost from a roadway, airport runway, or other surface. It includes both mechanical means (plowing or scraping) or chemical application of salt or other ice melting chemicals. Anti-icing is treatment with ice melting chemicals before or during the beginning a storm, to prevent or delay the formation of ice, or the adhesion of ice and snow to the surface. Brine or wetted salt is usually applied shortly before a snowstorm arrives. Properly performed, anti-icing can significantly reduce the amount of salt required, and allows easier removal by mechanical methods (snowplows).

De-icing of roads has traditionally been done with salt, spread by snowplows or dump trucks designed to spread it, often mixed with sand and gravel, on slick roads. Sodium chloride (rock salt) is normally used, as it is inexpensive and readily available in large quantities. However, since salt water still freezes at −18 °C or 0 °F, it is of no help when the temperature falls below this point. It also has a strong tendency to cause corrosion: rusting the steel used in most vehicles and the rebar in concrete bridges. More recent snowmelters use other salts, such as calcium chloride and magnesium chloride, which not only depress the freezing point of water to a much lower temperature, but also produce an exothermic reaction. They are somewhat safer for concrete sidewalks, but excess should still be removed.