As we were slip-sliding around this week, questions about snow and ice removal — or the lack thereof — have drifted in.

One of those inquiries came from a colleague. The Midwestern transplant complained about the snow and ice still covering parts of I-5 and ramps more than 24 hours after the storm ended.

“In the Midwest the freeways would be bare by now thanks to salt,” said the former Michigander. “Why don’t they use it on the freeways? Fish habitat?”

He was surprised to learn that the state Department of Transportation does use salt to de-ice roads.

“We use tons and tons of salt!” said Joseph Calabro, a spokesman for the Washington State Department of Transportation, in an email.

“Salt is our most commonly used snow-fighting product. We also use liquid de-icer primarily to ‘pre-wet’ our salt in an effort to keep it on the roadway surface and help it melt ice and snow. Depending on the situation, we will use liquid de-icers, pre-wet salt, sand, or a sand-salt blend. There are different requirements along different portions of our highways, but the decision is ultimately based on the type and severity of a storm, the cost effectiveness of the different materials, as well as the type of equipment available.”

“WSDOT has been studying the effect of our salt use on the environment for several years. By controlling our application rates, using just the right amount of salt to melt the snow and ice, keeping salt on the roadway with pre-wetting products and controlling the speed at which it is placed, we are minimizing the amount of salt we use, as well as its effect on the environment.”

This week, in the northwest part of the state, 1,500 tons of salt was used, Calabro said.

My colleague from the Midwest wants to see the agency sprinkle the mineral more liberally in the future to de-ice the roads faster.

In general, WSDOT is responsible for state highways and freeways, and Snohomish County is in charge of roads in unincorporated areas, while cities clear pavement within their limits.

County roads are treated with a 5-to-1 sand-to-salt mixture, according to Steve Flude, road maintenance director for Snohomish County.

“To minimize any possible environmental impact, a few best management practices are followed: We cover all of our salt and sand-and-salt mixtures while in storage to keep it dry and out of the rain. This eliminates salt-laden runoff from unnecessarily entering the storm drainage system. We also have the ability to control the spread rate of the sand-and-salt mixture coming out of the back of the snow plow truck,” Flude said in an email.

The county has approximately 1,600 miles of roads, of which about 800 miles are designated as primary or secondary priority routes for snow and ice clearing, Flude said.

In Everett, a mixture of sand and salt is mostly used. Sometimes pure salt is laid down, depending on conditions, according to Kathleen Baxter, a spokeswoman for the city’s public works department.

“We use the mixture because the sand gives immediate traction benefits that will not dissolve and disappear. The rock salt also provides traction but will disappear as it melts the snow and ice. We work to apply the right combination of sand and salt treatment to maximize effectiveness and cost efficiency. When temperatures get warmer, we do an extensive street-sweeping operation,” she said in an email.

The city follows a snow removal plan and responds to service requests. The 24-hour dispatch number at 425-257-8821, or you visit everettwa.gov/ServiceRequest.

Lizz Giordano: 425-374-4165; egiordano@heraldnet.com; Twitter: @lizzgior.

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