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From Cook County, MN - June 7, 2024

By: Cook County Highway Maintenance Superintendent Matt Nesheim

Dust was a hot topic last summer. Last July, I wrote a County Connections article to explain the symptoms of drought on gravel roads and treatment options available. To summarize: dry conditions lead to separation of fines (or “binder”) from coarse gravel. That binder is what we see as dust. The faster the traveling public, the more airborne dust and washboarding occur. Without moisture in the roadbed, maintenance operations such as grading are ineffective and detrimental.

It’s been a wet spring, so dust is hardly a concern now, but could be soon as summer progresses. We want to make sure that residents know what the Cook County Highway Department is doing about it within budgetary constraints.

Calcium chloride, a chemical relative of salt, is one solution commonly used for dust control. Applied to a roadway, it attracts moisture and stabilizes the gravel components. Less separation of components means less airborne dust. The road will look wet even when we haven’t experienced rain for weeks. Results can last for a month or two, but sometimes the effects can be seen the next year.

The Highway Department budgets for the application of calcium chloride annually. It’s no surprise that the price has been going up: the cost per gallon has increased 50% in 5 years, from $1/gallon to $1.50/gallon. The budget for chloride has also varied over the years, from $0 to $275,000 based on competing priorities. The rising cost and limited funds require us to prioritize how and where we apply calcium chloride for maximum impact. While the official policy is still taking shape, here are some criteria that we’re considering: hills, hauling, or >100 average daily traffic (ADT).

I’ll explain the rationale. 

Hills: Cook County is “hilly country.” Cars traveling up hills must accelerate, and acceleration often causes tires to throw gravel and cause washboarding. 

Hauling: there are many gravel pits and plenty of contractors doing good and necessary work in the county. Roads that service gravel pits are often traveled by a greater number of heavier vehicles and need all the help they can get. 

ADT: data collected by the State gives us a quantifiable idea of the roads that are used more often than others, and the more use a road gets the more potential for dust and deterioration.

What that leaves out are some of the lower-traffic residential roads. We don’t have the funding to treat every mile of county roadway on which residents and taxpayers live. That said, residents can help by simply driving at slower speeds, especially during dry summer conditions. That, and a prayer for rain never hurts.

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