Treating Icy Road Conditions

updated: Monday, April 02, 2012

Standard Road Salt: Road salt is a great material to use but it is not a cure-all for all things icy and it does not work well on its own. Salt must first dissolve into a brine which is what actually melts snow and ice. A source of heat is generally needed to begin melting the snow/ice to dissolve salt into a brine. Heat can be provided by direct sunlight, vehicle traffic, or very large amounts of salt. Vehicle traffic continues to be beneficial as it spreads the brine around so it can work across larger areas.

Without traffic, 4-5 times the “normal” amount of salt is needed to generate the heat required to begin forming brine. This is why highways/freeways/county roads clear faster – higher traffic volumes generate heat needed to begin and accelerate the melting process.

Salt becomes ineffective when pavement temperatures fall below 15 degrees Fahrenheit It is important to note that salt’s effectiveness is a function of pavement temperature – which can be several degrees higher than the air temperature if the pavement is in full view of the sun.

Treated Road Salt: Treating road salt with Magnesium Chloride, or another additive, can lower its effective temperature. The major problem with treated salt, however, is it is extremely expensive to use (as much as 30 times the cost of standard salt). Consequently, St. Louis Park only uses Magnesium Chloride-treated salt on our main plow routes (higher volume streets).

Straight Sand: Straight sand is rarely used anymore. Sand is a temporary cure at best because it is either driven into the hard-pack snow/ice or scattered outward by vehicle tires. Each spring, sand must be swept off the streets to keep it from clogging storm sewer lines or filling in waterways or storm ponds.

Additionally, sand is also plowed up onto the boulevards during snow removal operations. Over time, accumulated sand literally raises boulevards trapping water on sidewalks causing summertime ponding or winter icing conditions.

Chemical / Sand Mix: Prudent use of a chemical / sand mix is the industry standard treatment for extended low temperature conditions (less than 10 degrees F). The sand provides an immediate improvement in traction and the salt is available to attack the ice should pavement temperatures reach 15 degrees during the day.