At a Darigold farm in Chehalis, the state Department of Transportation is brewing up a product that has been quite handy this wintry December. Saltwater left over from rinsing whey is mixed with a chemical and molasses to create a road de-icer.

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At a Darigold farm in Chehalis, the state Department of Transportation is brewing up a product that has been quite handy this wintry December.

Saltwater left over from rinsing whey is mixed with a chemical and molasses to create a road de-icer.

The product is so effective, said Paul Simonsen, DOT maintenance superintendent in Chehalis, that White Pass was bare and wet within two hours of application last year after a storm that dumped 42 inches of snow in the mountains.

Simonsen said the state facility at the farm can produce 40,000 gallons of the de-icer a day, which is a mixture of 75 percent saltwater, 5 percent calcium chloride and 20 percent de-sugared molasses to stick to the roadway.

The saltwater is collected from an Eastern Washington cheese factory and shipped to the Chehalis farm. The water is left over after the salty whey is washed so it can be used as animal feed.

In the DOT recipe, the water used in the de-icer is 23.3 percent salt (by comparison seawater is 3.3 percent salt). Some of the salt comes from the whey and the rest the DOT gets from rock salt.

Simonsen said the calcium chloride, another form of salt, makes the product work in below-zero temperatures. By adding the molasses, Simonsen said, the mixture can be effective on highways for up to three days.

The state first used the product last year on White Pass, and it now is being applied throughout Southwest Washington, as well as on the Tacoma Narrows Bridge. “White Pass remained bare and wet [this month], and didn’t close when Snoqualmie Pass closed,” Simonsen said, adding that White Pass was bare and wet Tuesday.

The DOT saves thousands of dollars by making the product itself, he said. Where it was once paying $1.30 a gallon for a de-icer, the Chehalis product costs only 48 cents a gallon.

Plus, the DOT can adjust the recipe based on the temperature. Add more calcium chloride if it’s cold; reduce it if it’s warmer.

“This was the silver bullet,” Simonsen said of the recent snowstorm. “With this storm we got tested right out of the box, and the reviews are just great.”

The Darigold farm is the only manufacturing site in the state, but the DOT is considering putting one site in each of its six regions and supplying the de-icer for the entire state.

Susan Gilmore: 206-464-2054 or sgilmore@seattletimes.com