NEVADA CITY, Calif. August 3, 2017 – Living on an unpaved rural county road definitely has its charms. You’re likely to encounter neighbors walking their dogs, people on horseback, and the local wildlife can be seen using the thoroughfares as well.

On the other hand, come summer your car will be coated in dust and if you live close enough to the road, so will your house. For years, Nevada County mitigated the dust on some roads by “oiling” the dirt roads. On the day when the oil was applied, cars would creep at a snail’s pace along the roads, trying to avoid puddles of the gooey stuff. There was no escaping the smell for days and pets wandering on the road would bring the tar-like substance inside. But, it kept the dust down to a low-grade fog, not rooster tails.

The signs warning residents of New Rome of the oil application went up early in the week. Public Works crews prepped the roadway, grading away the ruts and smoothing the surface. Yesterday, the treatment was applied but something was very different –  no smell and no sticky puddles. The road looked wet, but not oiled – what happened?

Nevada County Public Works Director Trisha Tillotson confirmed the use of a new product, Magnesium Chloride, on a trial basis. Josh Pack, the county’s Principal Civil Engineer shared the genesis of the pilot program:

“Currently Nevada County has about 562 miles of County maintained roads. Being a rural county in nature, approximately 150 miles of our roads are unpaved. Some of these roads serve local residents, and we receive frequent requests from these residents about dust and the effects on their quality of life. Over the years we’ve developed an informal process where we’ve used a penetration oil based dust suppression product. We’ve spent about $15k annually that only covers a few miles of maintained roads and only on resident request where a majority of residents immediately fronting a moderate to higher volume dirt road support us of dust oil.

In recent year the use of dust oil has sparked debate with our local residents. Some residents demand this service annually and voice their displeasure if we are not able to provide dust oil. There are others that have environmental concerns regarding the use of dust oil and complaints about the fumes the dust oil emits when applied. Others also argue the fact that residents make a conscious choice to move onto a rural dirt road, citing that it’s not reasonable for the county to use public funds for pay for temporary dust control on any dirt road when other roads are in need of more immediate maintenance. The past reductions in transportation funding also had us looking closely as ‘convenience’ services like dust suppression that are only temporary in nature. While $15k isn’t that much overall, could that $15k be better invested in asphalt or other more permanent materials that could provide a great benefit to Nevada County residents?

Back in June 2016 I approached my peers in other counties about their dust suppression efforts and what (if anything) they were doing for dust suppression on their publicly maintained dirt roads. I received responses from 15 counties. Out of the 15 counties 8 (San Joaquin, Lassen, Tehama, San Benito, Yolo, Modoc, and Amador) provided no dust suppression on their county roads. Of the remaining 7, four (Mendocino, Riverside, Butte, and Siskiyou) used Magnesium Chloride. Three additional counties – Stanislaus, Orange, and San Diego – used other dust suppression products. We were a bit surprised to find that no other counties were using dust penetrating oil for their dust suppression.

Magnesium Chloride is a salt based non-toxic product approved by the EPA for use in dust suppression. It is hygroscopic – meaning that it can continuously absorb moisture from the air and keep road surfaces damp to create a compact, smooth surface. A single application of the product may last between 100 and 200 days. It also reduces the need for road grading, watering and gravel replacement and prevents surfaces from becoming uneven or developing potholes, resulting in lower maintenance costs and headaches if applied properly.

Earlier this week the Nevada County Roads Maintenance Division applied Magnesium Chloride along Blue Tent School Road and portions of New Rome Road in Nevada City. An additional application will take place next week to complete the remaining portions of New Rome Road and Rock Creek Road. Early public comments and feedback from road crews have been overwhelmingly positive, although it will take some months to determine the overall effectiveness of the product. It is also anticipated that the costs to apply Magnesium Chloride are less than the previous costs to apply more traditional dust oil.

While it is unlikely that the county will significantly expand the use of Magnesium Chloride on other county dirt roads, early results seem to suggest that this may be a new tool in the maintenance of these particular roads in the future.

For more questions please feel free to contact us at 530-265-1411 or visit our Facebook page at”

The dust remains gone.

3 replies on “Dust control on county dirt roads – without the smell?!”

  1. That stuffs great. Its been around for years. Our logging company used it back in the 90’s to limit the hours on our water truck.

  2. My first experience with Mag Chloride was in around 1980, on the Graniteville Road, and I’ve seen it used on logging roads many times since. It must be applied properly on a wet road that doesn’t have too much organic material in the soil that it’s applied to.
    It’s also important that people drive properly, keeping speed down and going easy around the turns, as it’s easy to tear up when abused.
    With proper application and care, it can last for a full season. I hope it works out for the county.

  3. The material has been used very effectively since at least the 80’s. Its the only allowed dust suppressant on organic farms, except water. Works great but loses its effectiveness after a lot of traffic, but so does road oil. With management it can last much longer than road oil. It works best if applied when the soil is still moist, and then occasionally rewetted with a water truck ( frequency depends on extent of traffic activity, but every 1-2 months is common). Because its hydroscopic, rewetting reactivates its dust suppression effectiveness. Heavy winter rains wash it off the road, requiring annual application. Being a salt, it is toxic to vegetation if applied directly to it. The material most commonly in use in ag is “Dust Off”, obtained from solar evaporated salt water in San Francisco Bay. Properly used, great stuff….

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