Road Crews Still Hard at Work

By: Adam Kramer
By: Adam Kramer

Icy conditions knocked out power and closed roads for thousands of Valley residents.

The icy and snowy conditions had Staunton Public Works working around the clock to keep the city rolling.

"When it snows, we work 24 hours a day, seven days a week until the job is done," said Tom Sliwoski, director of Public Works in Staunton.

Sliwoski said the city has used more than 200 tons of road salt in the last 10 days.

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  • Salt (sodium chloride) which usually comes from mined rock salt that has been crushed, screened, and treated with an anti-caking agent is used to clear winter roads to the bare pavement.

  • De-icing salt is relatively light--just over one ton per cubic yard--and comes as a mixture of three-eighths inch granules to fine crystals.

  • De-icing chemicals work by lowering the freezing point of water.

  • A 23.3 percent concentration of salt water freezes at -6o F. These low freezing points are what make salt useful.

  • Changing ice or snow into water requires heat from the air, the sun, the pavement, or traffic friction. Even when the pavement is below freezing, it holds some heat and can help melt snow and ice.

  • Chemical concentration, time, pavement temperatures, weather conditions, type of road surface, topography, traffic volume, width of application, and, most importantly, time of chemical application all affect the process of melting snow and ice.

  • Concentration: If too much chemical is used, not all of it will dissolve into solution and some of it will be wasted. Too little chemical may not sufficiently lower the solution's freezing point. The ice will not melt or melted snow may refreeze and waste the chemical.

  • Temperature: The surface temperature of a snow- or ice-covered road determines de- icing chemical amounts and its melting rates. As temperatures go down, the amount of de-icer needed to melt a given quantity of ice increases significantly.

  • Weather: The sun's heat warms the pavement, speeding up melting. Radiant heat may cause the pavement temperature to rise 10 degree or more above the air temperature. On clear nights, pavement temperatures will be lower than air temperatures. Use chemicals less when temperatures are rising and more when they are falling.

  • Applying chemicals during blowing snow and cold temperatures will cause drifting snow to stick to the pavement. If chemicals are not used, the dry snow is likely to blow off the cold road surface.

  • Road surface type: Snow and ice melt more rapidly on a concrete surface because it gives up heat more rapidly. Because asphalt absorbs more solar radiation it may have more heat available for melting snow. This is why snow melts rapidly next to bare asphalt pavement areas.

  • Topography Ice: Tends to form where topographic conditions, like high banks or vegetation, screen the road surface from the sun. The longer the area is shaded, the more likely that ice will form. Since pavement temperatures are lower in shaded areas, you may need more chemicals there.

  • Time of Application: Timing is the most important factor in successfully clearing snow by chemical treatment. Early application is critical. Spreading a small amount of de-icer when snow is loose and unpacked melts a little snow and turns the rest to slush. Traffic cannot pack down this slushy snow that is 15 percent to 30 percent water. This lets plows remove it easily.

Source: www.dot.state.wi.us (Wisconsin Department of Transportation Web site) contributed to this report.


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