Housing Complex

What Road Salt Does to Rivers

Conductivity spikes during snowmelt. (USGS)The District has taken a degree of crap over the last couple of months for dumping tons of salt on the roads, only to see minimal snowfall. Seeing berms of salt develop on city streets reminded me of Seattle two years ago, where officials were concerned enough about the negative environmental effects of snow on surrounding bodies of water that they used sand instead. This didn't work out too well either; the grit stayed for months, casting a brown haze over the city and not doing much for road safety either (it's no accident that the mayor got voted out in the next election). Still, it made me wonder: Isn't all this salt kind of bad for the rivers D.C. sits on?

I posed the question to the Anacostia Watershed Society, which answered that yes, it does have negative effects. The above graph shows spikes in "conductivity," which is an indication of salinity, in the Anacostia at Riverdale, Maryland. Sure, this is upstream from D.C.'s runoff, but the spikes correspond directly to the times when everybody was salting their roads in advance of storm warnings. Many forms of aquatic life don't do well in brackish water; tadpoles die in concentrations above 6,000 microsiemens per centimeter, which was reached on January 18th. Last year, Slate explained that even though the damaging effects of road salt are pretty well-known, cities still use it because it's cheap.

You can understand DDOT's position here: They can't help it if all signs point to snow, they salt the roads, and it ends up being for naught. They're also doing what they can to reduce the amount of salt needed by pre-treating the roads with beet juice and brine. So far this year, that's still come out to 24,000 tons of sodium chloride on the roads and in the river (last year, the total was 85,000 tons). The District Department of the Environment apparently did a study on alternatives, finding that something called IceBan is the safest deicer. If we're serious about cleaning up the Anacostia, it would be nice to see it at least considered.

UPDATE, Saturday, 8:20 a.m. – AWS' water specialist Masaya Maeda brings up a good point: IceBan may be better for the environment, but it's not cheap. The better solution would be for more people to just work from home when snow hits, so that road crews can clear snow mechanically. And of course, it's always easier when people live near enough to their workplace to walk there, rather than driving in from the suburbs.

Comments

  1. #1

    Places like DC use waaaay more salt than other snow-belt cities. Part of that is the challenge of the weather. It rarely just snows here, you often get rain before the snow, which can wash away all of the pre-treatment on the roads. We saw that two days ago.

    The other issue is that people (and not just snowplows, but sidewalk shovelers as well) put down way too much salt and/or icemelt. Salt is not a substitute for shoveling.

    Sand is a good alternative when it's really cold (i.e. too cold for salt to work at thawing ice), but all sand does is add traction and grit.

    From a street design perspective, improved storm water management would help drain and filter some of that salt/snow runoff before it hits the rivers.

  2. #2

    "tadpoles die in concentrations above 6,000 microsiemens per centimeter, which was reached on January 18th"

    I don't think there are too many tadpoles around on Jan. 18. Also, being upstream, Riverdale is not the place to check salinity in DC. The level there is caused by upstream Montgomery and PG counties. There is nothing DC could do to lesen rates in Riverdale. What are the levels at the confluance of the Anacostia and the Potomac? At Blue Plains or further downstream? Only there can you get a true idea of DC's impact,

  3. #3

    Remember last year when those Einsteins at D. were putting contaminated snow in the parking lots of RFK Stadium, which melted off in to the Anacostia River. How about the bag TAX scam money were is that?

  4. #4

    I wish I actually saw some of this beet juice being used. Any information on it's usage this year or how many vehicles are equipped to spread it?

  5. #5

    Not only are tadpoles not likely to be around in winter, no amphibians are. Then there is the whole thing about amphibians being the most suceptable to environmental conditions in the first place.
    As for the (good) point about needing to measure any impact DC might have downstream, if predictions of sea level rise are true in a few decades it won't much matter anyway.

  6. #6

    Aside from the environmental damage, just think what the road salt does to vehicles, bridges, landscaping, and other infrastructure. Corrosion of automobile undercarriages alone is a reason to avoid driving on salty roads if you can avoid it. Not a fan of sand, either - at least the salt eventually washes away.

  7. #7

    Keli, we do use beet juice. It is added to the brine we use to pre-treat the roadways before storms and helps it adhere to the road surface.

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