Here in Ottawa we are having a near record snowfall winter. We are well over 4m of snow so far. With so much snow comes road and highway maintenance that I'm sure is costing the city a fortune. Also they are dumping record amounts of salt on the road. I'm sure that we are all aware that salt is put on the road in order to decrease the freezing point of water, thereby melting snow and ice on the road. Of course, the effectiveness of salt is only good down to -18C at which point salty water still freezes, so sand and gravel are also used.
If you have ever seen the amount of salt on the road in the winter in Ottawa it is incredible. Canada uses about 10 million metric tonnes of rock salt for deicing purposes. It stains my shoes and pants. But probably of more concern it catalyzes rust formation, not only on cars but on infrastructure like bridges and drainage systems. I don't think these concerns are considered in the evaluation of the true costs of rock salt. I wear some pretty fancy pants.
It is a necessary evil, of course, because road safety is really not an option. Too many people still get killed and seriously injured due to winter road conditions in this country despite heavy salt usage.
However the environmental impact of salt usage is a concern. Ontario has done some work trying to minimize salt usage by more efficient storage and more sophisticated methods of application to the road surface. Environment Canada recognizes that chlorides have detrimental effects on our environment, but road salt gets a exemption from regulation. Chlorides are poisonous to plants and aquatic environments if present at high concentrations. And there are alternatives to sodium chloride, but they are more expensive (good article). Calcium Acetate seems to me to be one of the best. Here is a huge report that contains some great data on environmental impacts of salt and deicing alternatives. The punchline is that sodium chloride is, by many criteria, the worst for the environment.
Interestingly just because there is more ice and snow this year doesn't necessarily mean more negative environmental consequences of the increased salt usage since it will be diluted in that much more water when it all melts.
I emailed Environment Canada specifically at an address that is responsible for road salts (roadsalts(at)ec.gc.ca) asking if there is any consideration of evaluating alternatives to rock salt and they only pointed me to the large (american) report. Lame.