Driver, Whither Thy Road Salt?
You Can’t
Spell “Driver” Without “river”
(This article appeared in the Summer 2008 issue
of the DuPage Sierran)
As you read this, it is the middle of summer, and the warm air feels reassuring and well deserved. Winter is nothing but a faint, grim memory; an occasional flashback triggered by a travel website or an old email.
But, not everything moves at the speed of your cable modem - certainly not water analysis or even the lead times for this newspaper, and so we are just now reporting on this past winter’s road salt problem. With subzero temperatures safely behind us, let’s rewind a few months to the beginning of the year…
To refresh your memory, winter 2008 was a traditional Chicagoland winter - cold, snowy, and slippery. Ice - that both underfoot and falling from rooftops - was an ever-present nuisance, laughing derisively at the riders on your health insurance policy. Thankfully, the roads were relatively free of the stuff, having been scraped and salted like so much mutton; that due in no small part to the heroic efforts of municipal road crews –and their dwindling inventories of road salt.
But, did you ever stop to think about where all of that salt went after it did its job?
A road deicer like rock salt has the neat characteristic of disposing itself after completing its job. By melting snow, salt creates the vehicle in which it will be carried away - water. Together, they flow to the nearest storm sewer, which is connected (directly or indirectly) to the nearest body of water; most likely, a nearby stream.
“Snow what?” you might snarkily ask, slightly embarrassed by your bad pun.
River Prairie Group (RPG) tests of streams in Cook and DuPage counties this past winter showed that salt concentrations exceeded the state’s regulatory limit of 500 milligrams of chloride per liter of water (mg/L). In fact, we found levels in excess of 600 mg/L -and since we are limited to testing on a schedule rather than in response to weather events, it is probable that actual concentrations exceeded our values when we weren’t looking.
600 mg/L is equivalent to a half-teaspoon of salt in a gallon of water - enough to taste! (Really. Try it.) Another way of looking at it is that it is equivalent to dumping about a half-cup of salt into your ex-boyfriend’s 40-gallon fish tank. (Really. But, don't try it.)
Think about that for a moment: most pollutants in the environment are so dilute that they are found in the parts-per-million range (or smaller) and require an $8000 piece of laboratory equipment to detect. But, there was so much salt in Chicagoland rivers in the first three months of 2008 that you could have actually tasted it. Yikes.
A report on road salt funded by the New York State Department of Transportation clearly outlines the hazards of high, chronic chloride exposure to aquatic life:
“The most dramatic (and easily detected) consequence of increased salt concentration in water is death, but a subtler consequence is increased energy expenditure caused by physiological mechanisms to cope with increased salinity and by increased movement to avoid contamination. This leads to slower growth and lower reproductive output. Community composition can change, as less tolerant species are out-competed by more tolerant [and nuisance species], and less-tolerant prey are more easily captured by predators (Evans and Frick 2001).
Based on a
review of toxicological studies, USEPA has produced some general guidelines
that have been adopted by many other agencies in the
This underscores the importance of RPG’s water testing programs. In these days of shrinking budgets, government agencies no longer have the funds or manpower to fully monitor local rivers (federal- and state-funded environmental projects being yet just another casualty of the costly and errant “war on terror”). In fact, RPG is the only agency currently testing and publishing data for the three local rivers!!
Chloride is the most seasonal pollutant that we monitor – a trend easily observed from the cyclic appearance of any of our chloride graphs
(http://www.illinois.sierraclub.org/rpg/watermonitorproj.htm)
Contrary to popular perception, chloride levels in rivers do not revert to zero after winter subsides; again, a quick glance at our graphs shows a baseline of approximately 125 mg/L.
Part of this baseline is natural:
a study by the DuPage River Salt Creek Workgroup (DRSCW) estimates that salty
groundwater contributes 51 mg/L of chloride to Salt Creek and 106 mg/L to the
Below is our winter 2008
chloride data, which bears the signature of road salt. Note that one-third of the values violate
January 12, 2008: Salt Creek = 607.5 mg/L; 610.0 mg/L
January 12, 2008: East Branch = 505.0 mg/L; 445.0 mg/L; 475.0 mg/L
January 12, 2008: West Branch = 442.5 mg/L; 335.0 mg/L; 367.5 mg/L
February 2, 2008: West Branch = 512.5 mg/L; 472.5 mg/L ; 472.5 mg/L
March 1, 2008: West Branch = 542.5 mg/L; 525.0 mg/L; 432.5 mg/L
April 5, 2008: West Branch = 340.0 mg/L; 272.5 mg/L; 302.5 mg/L