An Environmental Minute Blog


What’s with that liquid being applied to the roads? 

Throughout the fall and winter, we get regular inquiries at the City asking, “What’s that liquid you sprayed on the roads?” Or, “I thought the City doesn’t use salt?” I even received a call from a concerned resident who thought a massive fuel spill covered nearly the entire length of Olympic View Drive.  Fortunately, that was not the case, but I started thinking, if a few residents are wondering what those lines of liquid are, then there must be others and we should get everyone informed!

Those lines or bands of liquid that you can clearly see on a dry day are an indication that a freeze or snow event is likely to occur and evidence that your City of Edmonds Public Works maintenance team is preparing for such conditions.  Every winter the Public Works crews ready our streets for the dip in temperatures by applying the anti-icing, pretreatment, and de-icing agent known as calcium magnesium acetate (CMA).  Applied via a truck equipped with a reservoir and spray nozzles (hence the lines), this multi-purpose solution has many of the same benefits as the traditional use of salt. Edmonds is committed to providing a low-corrosive and more environmentally friendly form of road safety, so CMA has become our go to frosty weather treatment for the last 20 plus years.

Coating the high traffic, busy intersections, and steeped sloped surfaces with a proper CMA application prior to the wintery conditions prevents the snow/ice from bonding with the road surface to avoid slick, unsafe conditions.  City of Edmonds snow plows can also remove more snow from the streets with each pass by creating a reduced bond between the snow and roadway.  This stops the formation of ice before the actual storm begins. The unique properties of CMA interferes with particles’ ability to adhere to each other and the road surface by tying up the moisture melted and reducing the early ice formation.  Because of this, CMA is often referred to as an ‘anti-ice’ treatment rather than a traditional ‘deicer’ application such as road salt (NaCl). However, the unique performance characteristics of CMA means it can also do its fair share of deicing too - during the record breaking snows the past few years, our plows have used a CMA/sand mixture with success to help aid with the breakup and removal, clearing arterials considerably faster than without it.

Sadly, there really is no way to eliminate risk to the environment when we’re talking about snow/ice removal.  But offering a safer alternative to exclusively using road salt, which has proven to be both corrosive to vehicles and damaging to infrastructure, can provide the lowest toxicity, biodegradable alternative which performs well and keeps our roads open and residents safe. CMA biodegrades into natural byproducts CO2 and H2O, it doesn’t contain urea, chloride, or nitrogen, and has minimal impact on stormwater discharges.  It is also perfectly safe for asphalt and concrete. One drawback is that it requires reapplication between rains by our Public Works crew. As a benign anti-icing agent, it’s a shortcoming that we can happily live with. 

So, when you see the CMA spray vehicle this winter, or the plow/sanding trucks spreading a mixture of sand and CMA, please afford them a little extra space.  Our snow and ice professionals typically need a buffer to work safely and allow space on all sides to spray thoroughly and properly.  While a little CMA on your SUV is not the worst thing in the world, we do prefer to keep it on the road surface for your benefit. Stay safe and happy winter driving!


An Environmental Minute is written and maintained by Pat Johnson, Stormwater Engineering Technician.

Please contact him with comments or concerns regarding these posts.

Pat Johnson
Stormwater Engineering Technician
(425) 771-0220 x1322
[email protected]