Sand on roads worse than salt, scientists say
Sand — one of Seattle's main weapons against icy streets — is more likely to harm aquatic life than the salt the city refuses to use out of concern for its environmental effects, say scientists who have studied the issue and officials from other cities.
Seattle Times reporters
Sand — one of Seattle's main weapons against icy streets — is more likely to harm aquatic life than the salt the city refuses to use out of concern for its environmental effects.
That's the opinion of scientists who have studied the issue and officials from other cities that use salt to clear icy roads.
Seattle doesn't use salt, an effective ice-buster used widely by other cities and the state Department of Transportation, because of environmental concerns.
Since last Thursday, Seattle has sprinkled more than 6,000 tons of sand on city streets and this week ordered 700 more tons for storage.
Instead of clearing major roads, Seattle aims to create a "hard-packed" snow surface suitable for all-wheel and four-wheel-drive vehicles, and front-wheel-drive vehicles with chains. The packed snow is then sprinkled with sand and sprayed with de-icer.
The strategy failed to clear ice from many streets, leaving drivers struggling to navigate this week. More snow was expected overnight.
Richard Sheridan, of the Seattle Department of Transportation, said the city is less concerned about sand because the streets are swept once the snow is gone. Seattle has not used salt since the mid-1990s, he said, because it corrodes metal bridges and "degrades" the marine environment. But he could not say which areas the city is concerned about.
Sheridan said sand is more environmentally friendly than salt, but scientists say sand damages waterways by clogging the spaces in gravel where insects live, making it hard for them to cling to rocks. Insects, a key part of the food chain, are an indicator of stream health.
Melting snow dilutes salt
Salt is less an issue because melting snow dilutes it, according to two scientists who studied effects of road salting on aquatic life.
"In general, what my colleagues have found, and I have found, is that sand actually has a greater impact, at least on stream systems," said University of Dayton (Ohio) professor Eric Benbow, an aquatic ecologist. "Sand's the problem, as much as people don't want to recognize it."
Canadian studies on road salting in the late 1990s found potential impacts on groundwater, roadside plants and creatures in streams near roads where large amounts of salt were used.
In a place such as Seattle, where salt is used infrequently, Benbow said he couldn't imagine the concentrations getting high enough to do any harm.
Doug Myers, of the environmental group People for Puget Sound, said salt on city streets would not likely impact saltwater in the Sound. He said he is concerned about the impact on creeks that feed the Sound because they may contain species sensitive to salt or creatures already compromised by toxic chemicals. The group has not taken a position on the use of sand, he said.
Seattle's aversion to salt is shared by Bellevue and Spokane, which use chemical de-icers.
Judy Johnson, Bellevue's street-maintenance superintendent, said the city used nothing to clear icy streets for a while. But the streets were too slick, so the city started using calcium chloride, which contains a rust inhibitor to protect cars.
"We needed something in the toolbox for ice, for safety reasons," Johnson said, noting the decision to use chemicals was driven in part by concerns about the harm from sand.
"It's a balancing act," she said. "You don't want to use a lot of any of this stuff. It's all got environmental effects."
Tacoma uses a saltwater brine before and after it snows, then follows up with a mixture of salt and sand. It has used 2,000 tons of the salt and sand mixture already this year.
Environmental concerns about salt haven't garnered a lot of attention in Tacoma, but community-relations manager Rob McNair-Huff said sand is actually of larger concern. "It both clogs up the drainage systems and can be damaging as far as the habitats of macroinvertebrates [insects] and salmon," he said.
Everett has tried several products, but its standby is an 8-to-1 mix of sand and salt, said Kate Reardon, the city's spokeswoman. Since the city's drainage is treated in combined sewers or detention ponds, it doesn't drain directly to the Sound, she said. Vancouver, B.C., also uses salt and sand.
Decisions about snow clearance are influenced as much by social, financial and political concerns as by science, said Mark Devries, chairman of the winter-maintenance committee for the American Public Works Association, a professional organization.
Budgets play big role
"We're driven by our budgets, we're driven by the level of service we're expected to give and we're driven by what's available to us in our areas," said Devries, the maintenance supervisor for McHenry County, Ill.
Professor Wilfrid Nixon, a winter-highway-maintenance expert at the University of Iowa College of Engineering, said salt is the best ice-buster around and that using it should be weighed against the environmental costs of other measures.
Plows burn more fuel when they have to plow more, and accidents caused by icy roads have environmental consequences, too, he said.
"Every crash in the winter is an environmental disaster," Nixon said. "You have spills of engine oil, gas, coolant. ... It may not be hundreds of miles of road, but the effect is intensely local."
Reporter Emily Heffter and researcher David Turim contributed to this report.
Susan Kelleher: 206-464-2508 or firstname.lastname@example.org
Copyright © 2008 The Seattle Times Company
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