But that was so 20th century.
Missoula officials now want to switch to sodium chloride-based de-icers and phase out their stocks of magnesium chloride. Back in 1991, local air-quality rules were rewritten to require magnesium chloride de-icer in the Missoula city limits because it reduced the need for dust-producing sand. Also, it was believed magnesium chloride would suppress any dust on the roads, further improving air quality.
But studies this year by the City-County Air Pollution Control Program found magnesium chloride actually has no dust-suppression power in winter. While it's great on dirt roads in the dry summertime, it dissolves too quickly in the presence of moisture to have much effect during the snow-and-ice seasons.
Sodium chloride - essentially table salt - had a bad reputation for accelerating rust in car bodies. And the versions that had anti-corrosion additives often depended on chemicals such as arsenic and barium, which pollute water supplies.
“But that depends on whether you have a '75 Olds or a post-2000 Toyota,” Health Board member Ross Miller said. “New cars don't corrode the same as old cars.”
Furthermore, magnesium chloride comes in liquid form. The city has been paying as much as $130 a ton for de-icer that's 30 percent active ingredients and 70 percent water. Modern versions of road salt cost about $110 a ton and are 95 percent active ingredients.
“I blew my budget last year,” said city street superintendent Brian Hensel. “We had $135,000 allocated and spent $220,000. I can't afford to do that again this winter.”
Unfortunately, the city doesn't have enough trucks equipped to spread dry salt. It will still have to use some of its liquid de-icing rigs to handle road safety this winter, and hopes to phase in new equipment over the next few years.
Making the change will take several steps. The Health Board on Thursday unanimously approved a change to its water quality regulations that allows sodium chloride de-icers to be considered for street use.
Next it goes to the Missoula City Council on Monday for a public hearing to change its own rules on sodium chloride. Assuming that passes, it may come back to the Health Board and the Missoula County commissioners to allow use of salt de-icers on the streets surrounding Missoula's city limits.
Missoula City-County Health Department director Ellen Leahy added there's an emergency ordinance wrapped in the paperwork to allow the city to make quick policy changes on de-icers.
“We need that now,” Leahy said, “because it's about to ice.”
Reporter Rob Chaney can be reached at 523-5382 or at rchaney@missoulian.com
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Fred Johnson wrote on Nov 21, 2008 10:18 AM: