Update 3:20 p.m PDT March 22: This blog has been updated with additional details about the city's beet-derived de-icer and sensor systems.
CHICAGO--Many Chicagoans pride themselves on surviving extreme weather, and laugh when a rainy day makes headlines in California. (With snow falling at two inches per hour Friday, the second day of spring, can you blame them?)
Seeking more eco-friendly ways to clear snow and ice from more than 9,500 miles of roadways, the Windy City is combining low-tech "green" chemicals with digital sensor systems.
Extract from sugar beet juice is key in a new formula used here to prevent ice buildup on the roads. Chicago mixes a cocktail of 15 percent beet juice, a gelatinous liquid that resists freezing even in subzero weather, with 80 percent briny water, and calcium chloride.
Two days or more before the expected snowfall, city trucks release the mixture onto bridge and overpass surfaces that can become fatally slippery; blasted by winds, the elevated thoroughfares also lack warmth from the ground.
Cheap and chunky rock salt, used for more than six decades in northern cities, effectively melts ice and provides traction. But it also erodes roadways and bridges and seeps into the ground, killing vegetation.
The brine "super mix" is better ecologically but imperfect because it still contains salt, according to Matt Smith, a spokesman for the Chicago Department of Streets & Sanitation. However, most alternatives remain less safe and more costly than salt, he added.
The city continues to experiment with other natural de-icers. It has tested corn extract and other ingredients, as part of Mayor Richard M. Daley's oft-repeated goals to make Chicago America's "greenest" city.
Chicago has expanded its use of the beet recipe. The city used 450,000 tons of rock salt in addition to the beet juice cocktail in a test run last winter.
"It's not just the substance that's good but because we're able to harness new technology, we're able to put less wear and tear on the environment because trucks aren't out there as much as they used to be" wasting fuel and contributing to potholes, Smith said.
The city has a fleet of 273 snow-plow trucks each holding 10 tons of salt, plus 24 smaller plows for side streets. During heavy snowfall, some 150 garbage trucks can be outfitted with temporary plows.
Helping to direct the vehicles is an emergency communications center receiving data from close to 20 environmental sensors scattered around the city.
Sensors embedded in the ground and atop laser-outfitted poles transfer real-time data about ground temperatures and moisture via wires and wirelessly to the center, where monitors display live street scenes from 600 cameras. (Chicago has one of the world's most extensive and controversial anti-crime, public surveillance systems).
City officials pool that information with feeds from Doppler radar and the National Weather Service to send GPS-equipped snow trucks to areas needing the most attention.
"In the old days when a storm was coming through the area, the trucks were sitting there for hours and hours," Smith said. "Now we save a lot of time in winter and probably save a lot of lives."