Effective road dust control requires treating the cause, not just mitigating the symptom
When most people think of road dust control, they think of spraying something (usually water) onto the road surface to suppress dust particles. If they do think of using a product, they assume that a single application will resolve the issue and keep dust on the ground for good. This does not equate to effective road dust control.
Unfortunately, it’s not that simple. Dust control is a complex science, requiring an understanding of the properties of dust and the various approaches to controlling it, along with the physics of just how that dust moves.
Simply put, most products and approaches out there just treat the symptom: dust.
But knowing where dust comes from allows you to take an intelligent, thought-through approach to managing it that goes beyond just keeping dust particles out of the air.
Dust is the result of loose fines (soil particles smaller than 0.075mm) kicked up from the road surface. While traffic and wind are obvious causes of fugitive fines emissions from road surfaces, excess water, both from rain and watering programs to control dust, also plays a role. Water washes fines away from the road surface, breaking down the road surface, and therefore allowing more fines to break free of the road surface as dust once conditions dry out.
As more fines come loose from the road surface, the surface has less that is holding it together. Think of fines like glue: they fill voids in the aggregate – working as a cohesive whole to maintain compaction and lock the larger particles in place at the surface. As more fines become loose, larger aggregate that makes up the road surface becomes loose, to get kicked up by traffic or washed out by water. Eventually, this leads to issues such as rutting and potholes, requiring extensive maintenance and repairs.
In other words, given enough time (depending on the conditions described below), a road dust control issue can become a road stability issue, which significantly raises the cost of managing the road.
So what’s the answer? The right approach to dust control is, in essence, basic fines preservation. Fines preservation is proactive approach to dust control that works by preserving the as-constructed condition of the road, resulting in a dust-free surface with improved stability and ride quality.
Midwest’s EnviroKleen product has a unique binding system that uses cohesive and adhesive properties to lock the soil particles to each other, keeping them in place. This strengthens the entire road surface, meaning the road requires less maintenance and, of course, dust control occurs naturally.
But how do we design the best program to meet your site’s specific needs? It’s a complex calculation, based on a range of factors. When you start working with Midwest, our engineers and chemists will seek out information on these factors to determine how much product you’ll need and at what rates and frequency you’ll need to apply it.
Factors affecting the success or failure of your dust control program
Before ever purchasing product or beginning your dust control program, you need to collect and factor in the following types of data.
Traffic volume.
One of the most obvious factors that play into your road dust control program is the traffic volume of the road you’re considering implementing dust control on. The more traffic, the more dust (and the more of a beating your road takes, increasing maintenance expenses, etcetera).
As a baseline, consider this data cited in one of our other articles (which you can find here):
The EPA’s Environmentally Sensitive Maintenance for Dirt and Gravel Roads handbook (citing an earlier maxim from a USDA Forest Service publication in 1983) reminds us of what we could call the “rule of one”:
“One car making one pass on one mile of dirt or gravel road one time each day for one year creates ONE ton of dust.”
(A gravel road with an average daily traffic volume of just 100 cars can be assumed to be putting out 100 tons of dust per mile, per year. Think about that.)
The earlier Forest Service publication clarifies that the dust is deposited along a thousand-foot corridor centered on the road (cited in this study). Meaning the majority of gravel road dust is moving as far as 500 feet from either side of the road, covering everything in its path (from vegetation to homes).
Get to know the traffic patterns on the relevant stretch of road. If the volume is low enough, it may be hard to justify the cost of an effective road dust control program. But knowing your traffic volume will help you to quickly see the impact of dust control. If your 1-mile stretch of road sees 75 cars per day, that means that road surface is losing 75 tons of fines per year. Only you can decide if that’s an acceptable volume of loss, but you can quickly work out the impact of an effective road dust control program. For example, at Midwest, our EnviroKleen product commonly achieves 80% or more dust control. Those 75 tons multiplied by 80% equals a reduction of 60 tons of dust. At what price point would it be worth keeping those extra 60 tons of fines on your road surface?
The implication of this is that the more traffic you have, the more dust control product you’ll need to effectively control it. If your road has 300 cars per day, you’re going to need more product than with only 75. But, at the same time, keeping up with dust control for that traffic volume will be far more important.
(Keep in mind that heavier traffic, like haul trucks or machinery, will create much more dust per vehicle than a car. Factor that into your calculations.)
Climate.
Climate will clearly make a difference in how much product you need and how often you’ll need to apply it. If your local climate is wet most of the year, that will obviously reduce the time that you’ll face dusty conditions. But the downside is that excess water will wash fines out of your road surface. Erosion will require that you replace surface material on your road much more often, and it may even speed up the time till you have to rebuild the road from the base course up.
Meanwhile, longer dry spells will, of course, contribute to more dusty conditions. The more immediately visible effects of a dry climate will impact residents, visitors, employees and any other stakeholders, creating more complaints, more health issues, an increase in costs and even a loss in tourism dollars (if your roads are access points to rural attractions, like state parks or historic towns).
When Midwest’s engineers and chemists discuss your project with you, they’ll take climate into account when planning how often you’ll need to apply EnviroKleen.
Road surface course.
The actual makeup of the road surface itself also plays a role in determining how much dust control product you’ll need and how often you’ll need to apply it. Most unpaved roads have a gravel surface, although this can vary extensively in size, type and quality of gravel.
Others have a native soil surface: different mixes of clay to sand in the soil, as well as the depth and compaction of the soil, can all make a difference. Clays with high plasticity, for example, present the most difficult dust control and engineering challenges.
Generally, the finer and looser the surface material is, the more product (or more frequent applications) is required. The ideal percentage of fines in the road surface mix should be between 8-12%. This is enough fines to fill voids and bind the road together but not so much that it would negatively impact strength, compaction, ride quality, and dust emissions.
Other considerations in developing an effective dust control program
While the factors above directly affect your ability to implement an effective road dust control program, there are other impacts of your dust control program (or lack thereof) that you will want to take into consideration.
Community.
For township road managers, this includes the residents in your town or county. The effects of uncontrolled dust are obvious: unpleasant living conditions, visibility issues, damage to vehicles, difficulty breathing (with possible longer term health issues for vulnerable people) and more. Another cost includes tourism dollars (as described above), where dusty conditions on roads that access rural tourist destinations turn people off to traveling there.
For business owners/managers of industrial sites, mines, agricultural sites and more, consider the cost of employee health (along with the potential for increased healthcare costs and possible regulatory fines). Dust can cause damage to equipment and vehicles. An approach to dust control that relies on watering comes with opportunity costs: labor and equipment that could be used elsewhere is tied up in repeat watering; trucks carrying product are delayed, slowing down your operations and hurting your profit margins.
Across all these fields, public opinion can turn against the organization or local government responsible for roadways. As road surfaces deteriorate, maintenance, repair and rebuild costs increase, stretching already tight budgets or cutting into bottom lines.
The cost of using cheap dust control products may not be much better. Chlorides corrode vehicles and equipment, contributing maintenance costs at a much higher rate than the dust does in the first place. Most off-the-shelf products leach from road surfaces, creating toxic environments for people, animals and vegetation nearby.
Meanwhile, going back to the original point in this article, most off-the-shelf products deal with the symptom (dust), not the core issue (preserving the fines in place on the road surface). This means many of your problems, seen and unseen, will remain, including the cumulative damage to your road surface, ongoing problems with dust, etcetera.
An effective road dust control program will have a cumulative benefit over time, building stronger roads with improved dust control. The effect? A happier, healthier community.
Environment.
Already alluded to above, dust (and many of the cheap dust control products you can buy off the shelf) is harmful to the environment, including both plant and animal life and waterways. The primary way that dust control chemicals interact with the environment is by leeching out of the road surface during rainy or windy conditions. They can also be tracked by vehicles or people or animals walking on the road surface.
A product, like EnviroKleen, that works to bind the fines together will not leech and cannot be tracked, meaning it works to protect the environment. Additionally, EnviroKleen has been tested by third parties and confirmed to be safe for the environment. This offers a huge advantage over most of the off-the-shelf options available on the market today.
Cost.
Finally, as we’ve written about before, you need to think about cost differently. Most people think in terms of price per gallon for product, but that metric means nothing. One product may cover more area and last longer than another, meaning that even at a higher per-gallon price point it is still more cost effective. Also consider how often it needs to be applied: a high traffic mine that relies on watering multiple times a day is likely spending far more than they realize. In comparison, a product like EnviroKleen may only need to be applied monthly.
Once Midwest’s engineers and chemists have collected all the relevant data discussed above, they can provide you with a quote that includes the amount and rate of application of EnviroKleen. You’ll know exactly what to expect for each period of the year (monthly, quarterly or whatever other application rate we agree on to achieve the results you’re looking for). And because the effects are cumulative over time, you can expect your costs to decrease with consistent application. This model allows you to approach effective road dust control like an investor does a portfolio, spreading costs out over a time horizon to achieve results in the most cost-effective way possible.
This also means that, like we discussed above, you can develop a cost model of X dollar per Y result (e.g., the number of tons of dust kept on your road surface). Pricing your dust control program at dollar per result is far more effective than pricing it at dollar per gallon.
Midwest: the most effective road dust control program on the market
Dust control is more complicated than just throwing the cheapest product down on the road surface once and hoping the dust will stay away. Effective road dust control requires thinking in a more holistic, long-term way, about controlling fines at the road surface level, then considering all the factors discussed above.
For a custom, comprehensive and cost-effective road dust control program, Midwest’s Managed Service Program may be just what you’re looking for, including a product that works at the molecular level to bind dust particles to the road surface and a team of experts with vast application experience. To find out how we can help you meet your dust control and road stabilization needs, reach out today.