Street Division - Update

When the storm on January 12 finally began to wind down on January 13, temperatures were below the threshold for salt to be effective. Then, it snowed again on January 13 into the early morning of January 14 with the same frigid conditions.

• When temperatures get below 20 degrees, salt is less effective at our maximum application rate, so staff switches to applying sand. 
• The Streets Division's maximum application rate for salting is 300 pounds of salt per mile of traffic lane.

Sand on top of snow and ice helps provide traction. It can't melt snow or cut through the hard pack of snow/ice, but it gives grip. 

• Sand is applied at the hills, curves, and intersections where it is needed most. However, it disperses when people drive through as tires carry it away. 
• Sand also gets pressed into the snowpack as people drive over it.

Streets Division has had crews on around the clock addressing the issues

• sand gets spread to help, 
• the operator moves on to the next area or call, 
  • it takes a while before they can rotate back and spread more sand 
• It takes time to address all of the concerns and rotate back to the original spot again. 

When you put salt onto snowy roads, the salt turns the snow into liquid, creating a saltwater brine with a lower freezing point than regular water. 

• The snow will get slushy, and then a plow comes through and pushes that fluff off to the side. 

Plow trucks cannot press down to the road surface to peel up that final layer of snow on the road. 

• Plow trucks don't provide downforce like you can when shoveling snow from your sidewalk. 
• Plows glide over the road, shoving snow to the sides, creating a hardpack layer on the streets. 

After the plows come through, they leave behind a road surface with a layer of salt and snow mixed,

• the salt slowly turns that thin leftover layer into the water to finish the job on the bare pavement

As the temperatures get colder, the chemical process of salt turning snow into water slows significantly. 

• The water you are creating will freeze into ice.
• Salt would not work in temperatures like what we have now. 
• The melted water would refreeze. 

The other element in applying salt on roads is how this process works during active snowfalls.  

• After you've spread salt, snow turns to salt water.
• Snow keeps falling.
• The saltwater made by spreading salt on the roads will get diluted by the freshly falling snow.
• The mixture of saltwater waters down, and it is more likely to start freezing
• The harder it snows, the quicker it dilutes.

The salt reaction isn't instantaneous; it needs time for the chemical process to work, and the temperature also impacts it.

which

During active snowfalls, all at the same time:

1. Salt is turning the snow into water, 
2. The falling snow is diluting the water and 
3. The cold temperatures are working to freeze the water to ice 
4. Plows push off the melting slush so that it does not refreeze

Continue looping the routes while accessing the next steps.

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We cannot dismiss the severity of this long storm with plummeting temperatures. The storm began around midnight on January 12 (some people would call that the evening of January 11, but technically, it was January 12) and wrapped up on January 13. 

• The snow was sometimes hefty, with high winds blowing snow onto the roads. 

The Streets Division's response to the storm was to apply salt when possible; when the temperatures plunged and the snow & winds intensified, the focus turned to keeping the roads plowed and passable. T. The road conditions are challenging but expected as they are similar to other storms we have had in the past, namely a weather system we had in 2018-2019, though this time we got both more snow and longer-lasting arctic cold than the 2018-2019 event. 

• Streets Division is working hard to keep sanding the streets; the resulting roads would have been far worse to manage if more salt had been used during the severe snowstorm and plunging temperatures, creating ice throughout the entire City.
• Smaller communities with fewer miles to maintain may have the ability, with their resources, to cycle more frequently through the main street or streets of their City to perform the salt-plow-salt rotation over and over continuously. 
• The weather conditions from the severe storm also call for a higher salt application than our maximum salt rate to keep up with the heavy snowfall and the cold temperatures to compensate for the cold temperatures and dilution due to the snowfall. 

There are also other chemicals you could apply. 

• The City of Madison does not use calcium chloride or magnesium chloride. 
• The salt used by the City and most places is sodium chloride, just like what is on your dinner table. 
• The other chlorides are far more expensive. 
• Madison will spend $900,000 this year on just purchasing salt alone (this does not include labor costs in spreading it – this is just purchasing the actual salt). 
• Adding more expensive chemicals to use in extreme situations will undoubtedly add cost. 
• These other chemicals come with challenges as well. For example, both alternatives are far more corrosive to vehicles and infrastructure than regular sodium chloride. 
• Calcium chloride, in particular, can be tricky to use because misuse in the wrong humidity conditions can make roads more slippery.  

Salt has well-documented adverse side effects. 

• The salt spread on the roads, sidewalks, and parking lots all winds up in the water we drink and our lakes. 
• To protect the water we drink, the lakes we enjoy, and the wildlife in these lakes, we have to be cautious with our salt use. 
• For clarity's sake, whenever "salt in the water" is discussed, it is the shorthand for chloride in the water supply. Sodium chloride, magnesium chloride, and calcium chloride will put chloride in the water.

This storm is rare and filled with many temporary challenges, but our decisions around salting are not temporary hindrances to our waterways. 

• Re-evaluating our community's priorities and values regarding our commitment to protecting our lakes and drinking water may have to be discussed. 
• These discussions have citywide implications and budget impacts. For example, increasing resource levels for staff, equipment, and budgeting are difficult discussions that need to happen before the winter arrives.