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Thu January 19, 2012
Fast melt could pose environmental challenges
It’s a tough commute out there for anyone who has to drive. Snow is melting fast, and ice is a big danger.
But in Seattle at least, the consensus seems to be that the city has improved a lot in keeping main arterials clear, by deploying trucks that preemptively spray de-icer and sprinkle rock salt on the roads when it snows.
It’s not without environmental risks, but officials say they’re doing what they can to strike the balance between maintaining public safety and limiting the risks from polluted runoff.
People like treated roads
Across the street from his house in Bothell, 47-year-old Brian Scollard scrapes the road with a shovel and hoists several gallons of heavy, wet snow from the side of the road. He says he's pitching in to help clear the way for his mail carrier.
“Cause the snowplows bury the mailboxes,” Scollard says.
He says he doesn’t really need de-icer on his driveway. But he’s appreciated its use on the streets of Seattle, where he works.
“You can totally tell what the de-icer’s done for the streets this year. It’s made a world of difference,” Scollard says. He supervises construction and maintenance for a large property management company downtown.
He says, he’s not sure exactly what’s in the de-icer. But he assumes it’s safe for the environment. That, combined with the salt that's been put on the roads, has helped a lot with public safety.
“It works," Scollardsays. "A lot better than the chaos we had that one year.”
He’s referring to December 2008, when the city used a low-impact mix of sand and rubber-edged plows to deal with the snow– no salt or de-icing brine– and everything shut down.
A new era in winter storm response
Since then, the Seattle Department of Transportation (SDOT) says it has implemented a better plan.
Trucks with de-icer hit certain routes whenever the forecast is frosty, to keep ice from building up. The city has maps by district of main arterials that must be maintained by crews from SDOT.
Once snow hits, salt is routine to keep roads clear for transit and first responders, such as ambulances, police or fire trucks.
And last year, the city switched from de-icing brine that is essentially salt based, sodium chloride, to less toxic magnesium chloride brine. Magnesium chloride melts ice faster, so less needs to be used, they say. This should mean a net-improvement in curtailing the impacts on ecosystems.
(For the science-minded readers out there, here's a neat link to an explanation of why salt melts ice.)
Concern from 'green' advocates
Environmental groups say they’re taking a wait-and-see approach to the effects of the city's brine and salt use on the efforts to keep toxic runoff out of Puget Sound and away from sensitive creeks and wetlands.
Washington Governor Christine Gregoire has made the health of Puget Sound a priority and called on authorities to clean it up as soon as possible. The Puget Sound Partnership is taking comment on new storm water regulations, with a deadline recently extended till next month, and many non-profits and other stakeholders are working on them now.
People for Puget Sound Policy Director Heather Trim, a specialist in toxics, says she hopes Seattle has used due care to make sure that the main arterials they treat have been chosen with vulnerable urban ecosystems in mind.
"We agree that human health and safety is the most important thing to protect in these large snow or ice storms, Trim says. "When we do use salt on our roads, the key issues are the quantity used and timing of the melting in terms of impacting our freshwater creeks and wetlands."
Regulators say it's about tradeoffs
The state department of ecology says though there is always hand-wringing about runoff in the combined sewer systems that can end up flowing into Puget Sound untreated, much runoff does go through treatment plants before it enters the Sound, depending on where it flows.
Ecology spokesman Larry Altose says, "Some of Seattle's goes through either full treatment at West Point or primary treatment facilities that are used when there is a high volume of storm runoff."
Or at Sea-Tac airport, where they spray plane wings with liquid de-icing compound, the whole terminal area drains to a special industrial treatment system.
"The amount used to de-ice planes is much greater than what’s used for roads," Altose says. And they know how to handle that already.
SDOT commissioned a report from Seattle Public Utilities, which spokesman Rick Sheridan says serves as a de-facto environmental impact statement.
Fisheries biologist Bruce Bachen, who is SPU's Drainage and Wastewater Quality Director, says they worked independently and judiciously to analyze different possible scenarios as they might affect the aquatic environment. He thinks they have struck a good balance so far.
"I think we handled it adequately," Bachan said, adding that using staffers to do this work is a value-added solution for the city.
Source documents point to good intentions
In a memo to SDOT from December 2010, Bachen wrote that they looked to authorities in Colorado, who have studied the use of magnesium chloride brine instead of more-common sodium chloride in evaluating Seattle's decision to do so as well.
"Given the results of this study and further accounting for this difference in regional climate would suggest very low risk of environmental impacts. The study does point to the importance of ... maintaining standards to avoid undesirable contamination and this is consistent with one of the recommendations of our 2009 report," Bachen wrote.
And Larry Altose, the spokesman for the State Department of Ecology, says although there is no specific statewide law dictating what each municipality uses on its roads, they generally encourage less-toxic solutions and expect that the extra expense of salting and de-icing roads likely prevents the risk of excessive use. He notes, it costs a lot of extra money to pay overtime to road crews and purchase the salt and brine solutions they're using.