Overuse of de-icing salt by Madison business

Contamination by salt has been steadily increasing in our lakes, groundwater, and drinking water. Several of Madison's wells already show levels of salt that cause concern.   The levels of salt we're already seeing in lakes and streams are enough to kill aquatic life.

West Washington Av.

By salt, I mean rock salt used on streets and sidewalks--NaCl. When refined, we call it "table salt."

Since 1973, the City has been working hard to reduce the amount of salt used on city streets--but despite improvements in equipment and methods, salt use has increased significantly.

Salt overuse is hard to control, because on the pavement of private malls and businesses, there are no legal limits to salt.  And if a little seems like a good idea, why not spread more?!
Madison's Committee on the Environment made a rough estimate of  amounts of salt used by business.  Their conclusion:  Salt was being spread at about twice the amount spread on city streets, in terms of pounds per acre.   Studies from other cities likewise show that private areas contribute a significant portion of the salt that winds up in lakes and wells.

A drive-through survey of Madison's West Side 

I surveyed mostly within an area bounded on three sides by Sequoya Commons, Hilldale Mall, and West Towne Mall.  Driving through them, I could quickly determine whether excess salt had been spread--and I took photos where I saw substantial amounts of salt.  I surveyed after two storms:

Storm 1:   A wet, sticky snowfall of several inches.  Some of the wet snow turned to ice that lasted for a few days.  I surveyed a few days later (March 14), after it warmed and the snow melted,  leaving the salt easy to see.
Storm 2:  There was light snow, followed by a minor ice storm overnight.  There was thin ice on the pavement next morning, but temperatures rose above freezing and it rapidly melted by about 9:00 am. I surveyed on March 24.

Between Storms 1 and 2, there were several days of substantial rain, at least 1.5 inches.  This was enough to wash away most or all of the salt from the first storm, so that it wasn't counted with the salt spread after Storm 2.

Results of the survey

You can get a meaningful impression from a drive-through.  There is always the chance for one accidental spill of salt--but where I saw overuse of salt, it was consistent.  If a business was overusing salt, the excess was repeated throughout their area.

After seeing quite a few parking areas, I could classify parking areas or sidewalks into light, moderate, and heavy users. 

Generally speaking, the malls were not among the most wasteful users, although a few businesses within the malls might show heavy use. 

For example, Associated Bank, at the edge of West Towne Mall, was one of the most wasteful users

In contrast, the rest of West Towne Mall (as a whole, with a few exceptions) showed light use.

Midvale Plaza showed moderate-to-heavy use on both days.   Westgate Mall showed light-to-moderate use on both days.

The heavy users tend to be organizations with a lot of foot traffic--places that want to appear "customer friendly."   Banks are a good example.  Associated Bank, M&I Bank Hilldale, World Council of Credit Unions, and UW Credit Union all showed heavy and excessive use.

The Red Cross was the most wasteful user of all.

While driving around, I  found two areas where salt was stored.  In both instances, substantial salt was being spilled onto the pavement, from where it would be flushed during the next rainstorm.  The Best Management Practice for storage of salt is zero loss from storage.

Poor storage of salt at World Council of Credit Unions. Click to enlarge.

Storm 2 occurred after the end of winter.  The overnight ice was thin, and rapid warming was predicted in the morning.  There was really no good reason to spread salt--and certainly not to spread it heavily, as some businesses did.  Heavy use might be justified early in winter--when the salt could do its work later.  But not at the end of March! 

This shows that many businesses do not take weather forecasts into account when spreading salt.

Conclusions for Madison's west side
  • Consistent with other studies, many businesses spread salt too heavily
  • In some cases, salt was stored improperly
  • Application was not consistent with predicted weather
  • Excess salt is not removed at the end of winter
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Photos of overuse of salt, Madison's west side:
March 14, 2011
March 24, 2011

More info and use and impacts of salt in Madison

1 comment:

  1. I'm appalled when I see such over-use of salts. Looking for resources to share with businesses and city councils to raise some awareness! Parking lots are lakes and rivers at 22 degrees F!! It's not right.


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