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By Cook County Highway Maintenance Supervisor Josh Dix, Cook County MN - August 27, 2021

There’s no doubt that the hot, dry weather is the talk of Cook County this summer. 

While its effects on the forest and the risk of wildfire are front of mind, what may be less obvious is the negative effect it also has on our gravel roads. Grading becomes impractical, and requests for calcium chloride come in regularly as our gravel roads choke in dust and rattle with washboard. Here is how we address it, how we’re looking to improve, and what you can do to help.

While they may seem relatively simple, gravel roads can be very high maintenance when compared to asphalt or concrete. Gravel is made following a “recipe” that specifies the different sizes of rock in the mix and a certain percentage of fines, or the small particles that hold it all together. When the road surface dries out and the dust flies, what you’re seeing is the loss of those fines, leaving behind only the larger rock on the surface.  That loose rock is prone to washboard, especially in areas of acceleration like hills, curves and intersections. 

In a typical year, graders are the tool of choice for removing washboard.  However, there must be moisture present to reincorporate fines from further down in the roadbed back in with the loose surface rock. Without it, the fines won’t bind with the larger rock, and the washboard can return as soon as the next day, depending on traffic load. Put simply, when it rains, we grade; without rain we currently have no effective method for correcting washboard roads. In fact, we could be making them worse by attempting to grade them while they’re dry.

Calcium chloride is an effective tool to keep moisture on the road surface, trapping the fines and keeping them from becoming “dust in the wind.” While the obvious effect of dust control is what garners the most attention, keeping the road surface intact also results in a smoother ride and a reduced need for adding gravel.  There are many factors that affect where we apply calcium chloride: cost, traffic volume and speed, COST, environmental issues, COST… you get the idea.  We couldn’t possibly treat all of the county roads without a significant tax levy impact, so we do the best we can to target our treatments where they’ll do the most good while staying within budget. 

This summer, nearly all of our calls from the pubic regarding dust control have been requests for more treatment. Dust control is applied by a contractor on our behalf and, once our allotment has been applied, they move on to other communities and we are done for the year: we do not have the capability to store or apply dust control chemicals at the highway department. 

Further, it’s important to remember that, while dusty roads clearly impact air quality in the immediate area, applying dust control chemicals adds chloride pollution to local waters similar to applying winter deicers, and it is corrosive to vehicles.  These are pro and cons to consider whenever dust control chemicals are applied.

With the drought bringing these issues to the forefront this summer, we’re considering ways we can work better in future dry years.  We’ll be trying out water sprayers to see if we can put enough moisture down to grade especially rough sections of road.  We’ll also be investigating what is needed to do some of the dust control treatments in-house, thereby adding flexibility as to when and where it gets applied.  

Travelers can help, too. The easiest thing you can do to help our dry roads is slow down: driving at high speeds kicks up more dust and blows away a key component to our gravel roads.  Accelerating hard up hills and after curves deepens washboards with every pass. 

Our hope is that, by the time this article is published, we’ll have seen a few inches of rain and graders will out working hard to smooth out Cook County’s gravel roads. Until then, please drive carefully and know that, as soon as we get rain, our graders will be on the way  in short order.

County Connections is a column on timely topics and service information from your Cook County government. Cook County – Supporting Community Through Quality Public Service.