Dave: A Gritty Season

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03/07/10 - Crumbling snowmen and slowly degenerating walls of plowed snow gladden the heart of many Minnesotans in March (including mine).  But as I observed a dissipating roadside snow pile freckled with dirt and grime, I wondered where all that stuff goes.

The answer for almost all of it -- in our lakes and streams.

But what's in that melting snow anyway?  Well, although snow is pretty, the byproducts of its meltdown aren't.

One scientific paper calls falling snowflakes "effective scavengers" of airborne pollutants, including soot, which remain in the snowpack. 

Where does all that grime go?

It also mentions heavy loads of sediment (grime) and the runoff of "vehicular deposition" of petroleum products and additives and metals. Up to one-fifth of the annual volume of phosphorus running off to our waters can come from the end-of-winter melt.

And then there's the accumulated road salt of an entire winter. A quick flush from a rapid melt can significantly increase chloride levels. And don't forget pet waste under on in the snow piles -- the City of Saint Peter estimated its 710 pets generates 355 pounds of waste per day.

Snowmelt is one kind of runoff that is now regulated under the federal Clean Water Act and state laws.  Permits for municipalities often require early season street sweeping and vegetation buffers to minimize the grime.

Find out more about what's in runoff -- during snowmelt and other times of the year here.

Dave Dempsey is communications director for Conservation Minnesota.

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