An army of products helps contractors solve dust and stabilization problems downtown, on rural roads, and in mine-tailings dumps.

By Joseph Lynn Tilton

When it comes to dust and erosion control on unpaved roads, many people think pavement is the answer. Unfortunately, it's a costly option–one that also brings other problems to the fore. Besides, it's generally the dust blowing up from dry lakebeds, mine-tailings dumps, and denuded off-road areas that tends to make headlines.

Suppressant products include salts, asphalt or petroleum emulsions, polymer emulsions, new synthetic materials, polymers, surfactants, bitumens, adhesives, solid materials such as fibers and mulches, hydroseeded vegetation, and even enzymes. A major challenge is to determine which materials are best suited for the particular site involved, given the environmental requirements and objectives at the site. Another challenge is to determine the best method of application.

John Church, owner of South Western Sealcoating Inc. of Murrieta, CA, has found both ground and aerial application necessary in his 17 years of application experience. Speaking on alternatives to paving, he comments, "Other stabilization methods than paving are less expensive. As a rule of thumb, what would be spent on paving a haul, construction, or country road would provide soil stabilization and dust control for 10 to 15 years. Asphalt paving would require significant maintenance, if not repaving. Stormwater runoff is another issue pertaining to asphalt paving."

With an annual volume of $3.5 million in projects, Church notes, "There are any number of products that claim success for soil stabilization and dust control or erosion control. They vary from pure vegetable oil to asphalt emulsions, from polymers to surfactants. The products I generally use include surfactants, binders, and hydroscopic products. Surfactants require frequent watering, while binders require blade mixing into the soil. Hydroscopic products, such as magnesium chloride, work very well in the Southwest. But good practice methods of preparation and application are essential with any product used."

He points out that all products come with a material safety data sheet, and customers can read the numbers and include them in their decision concerning which product the contractor will use at their site. Stormwater runoff from a treated surface also should be considered. "I tend to use Dust-Off, a magnesium chloride product, because by the time the product moves 3 to 5 feet from the treated area on a horizontal plane, it has been diluted to the background level of the native soil."

Avoiding Delays

Whatever product is used, economical application is essential. Application delays must be avoided. Church recalls a 3,000-ac. project dealing with a mine-tailings area at San Manual, AZ. "Those tailings were really fine, like baby powder. Mountains disappeared when the dust came on. They had to shut down a school in neighboring Mammoth. A United States Senator got involved, and the school board was raising havoc."

Because time was of the essence, Church did a light initial aerial application to hold until he could follow up a couple of months later with a heavier one. The goal was to give the mine owner time to cap the tailings for a permanent solution. "The light application, which totaled 4,800 tons for the entire site, required 1,200 missions, and the heavier one twice as much product and 2,400 missions. We covered 350 acres a day on the light application and 150 to 175 acres on the heavier and finished the project in less than a month."

Logistics included nearby storage of 700 tons of product at a time, which was made possible with military fuel bladders that South Western owns. "We used a 4-inch discharge rubber hose that stretched 1,500 feet from the storage tanks and had a ground crew of 12 to support one aircraft. Personnel included a project manager, a loading crew, a campsite supervisor, and a cook to prepare three hot meals a day. Four pilots flew the Air Tractor 802, rotating every five to six hours, and we also had other pilots to fill in gaps as they occurred."

Light application began in December, but because of windy days the crew doubled night application. They set up lights on the runway and kept going 'round the clock, stopping only for aircraft maintenance.

"We were using Dust-Off, dumping 600 to 1,200 gallons per acre depending on application rate desired. It took 2.5 minutes to load, 18 seconds to unload, with a cycle time averaging eight minutes." Church adds that this was possible because of experience on earlier projects, including one in Sahuarita, AZ, south of Tucson. "There we started with a dirt runway, so we used our distribution truck to stabilize the airfield. On the San Manual project we flew so many missions that the airstrip qualified for $3 million to $4 million in federal Superfund money, which the county promptly utilized. That's how they got it paved."

Fuel storage in 1,200-gal. tanks helped make the San Manuel site fully self-sufficient. Thus, no waiting for materials; yet when completed, all spray materials were used up so none had to be trucked away. Church emphasizes, "With aerial application it is necessary to pay attention to detail, to keep production up. You need to get in and out with the window of opportunity at the least expense and downtime. You can't have a dollar waiting for a dime."

From a Manufacturer's Perspective

Because economy and effectiveness are the two vital elements in successful soil stabilization, manufacturers continue to develop and refine new products. Bob Vitale, president of Midwest Industrial Supply Inc. of Canton, OH, develops products that focus on dust control, erosion control, and soil stabilization. He reports that his firm employs 80, five of whom are involved in research and development.

"Not only do we have a broad line of products," states Vitale, "but we also have a complete soil testing lab in Canton intimately involved in the product selection and use design for our customers. There is such a range of soil types and substrates that each situation needs to be evaluated and the correct product selection made, keeping in mind that the correct volume and use of that product depends on the soil type and objectives. In fugitive dust control alone we have seven products representing four different technologies." These include polymer emulsion products (Soil~Sement, Soil~Sement Engineered Formula); synthetic fluid (EnviroKlean, EK35); polymer modified asphalt emulsion (RoadPro NT, RoadPro Plus); and surfactant blend (Haul Road Dust Control).

Looking at the industry as a whole, Vitale comments, "The trends in dust control requirements include increased performance, greater reliability, and a completely new level of environmental sensitivity relating to air quality, groundwater, stormwater runoff requirements, and even human health."

He adds that when it comes to dust control of a traffic-related site, "long-term" treatment generally would be something not exceeding a year. This would include not only dust control but rills formed from runoff and other forms of erosion control. "When dealing with open areas, long term might be for many years. For instance, in Washington State the Hanford Nuclear Plant site had a huge fire that denuded thousands and thousands of acres. The issue there is controlling erosion and dust until vegetation can reestablish itself." Midwest's application strategy includes development of natural bacteria, species indigenous to the open arid lands, and air dropping to help stabilize soil and minimize erosion more quickly.

"By providing erosion control at the source, we reduce sediment delivery to water sources," Vitale notes. "This is different than mechanical methods such as silt fences, hay bales, or retention ponds. The goal is for EC programs to eliminate 98% of erosion problems at the source and eliminate sediment delivery that otherwise would occur where mechanical methods typically might only be 50% effective."

When Paving Is Forbidden

The City of Scottsdale, AZ, has an unusual dilemma. Environmental Protection Agency and air-quality-control officials for Maricopa County have mandated that the city has to provide dust control on nonpaved roads. This prosperous community has the financial means to pave all the roads concerned–but residents adamantly oppose any paving. According to Rod Ramos, field services manager for the city, "They have horses and they want the rural character. Besides, with temperatures getting up to 115° Fahrenheit in the summer, with paved surfaces 40° hotter, pavement really creates a high heat island effect."

But residents and government officials still wanted the city to do something about the dust and to have smoother roads. "They were blading every six weeks for rutting and potholes, but still no dust control," explains Marty Koether, owner of EarthCare Consultants LLC in Tucson, AZ. "Now, with Soil~Sement applied quarterly, they have dust control, and the money saved on blading and maintenance pays for the products they're using."

This solution came about after the city arranged for a test section on a mile-long segment of road and invited contractors, including EarthCare, to put down their products on a 1/8-mi. stretch. Then, through before-and-after public meetings, citizens were able to choose the product they felt performed the best.

Ramos comments, "The native material is so much like decomposed granite that we had problems with washout during our rainy seasons in July and January. We now have our contractor treat the roads after those seasons, because water has a tendency to soften the acrylic polymer. It hardens again after a rain but can get pushed around a bit while it's still wet. We could go six months or longer without touching the treated roads but there are delaminations where the top half-inch starts to flake. If you let that go, it will pothole out. This is an ideal solution because dust never is a problem. Also, residents driving Mercedes, Jaguar, Lexus, and other luxury cars want this higher-quality surface to drive on but they don't want it paved."

Koether's firm provides turnkey services, including product delivery, preparation, and application work. Their clients include the Palo Verde Nuclear Generating Station 35 mi. west of Phoenix. "We're providing erosion control and slope stabilization for dust on disturbed areas," Koether states. "The plant has an aging 20-mile water line that comes from another wastewater treatment plant to their water treatment plant. During repairs they disturb a lot of native soil, so when a repair is completed, Soil~Sement is applied to eliminate dust and enable reestablishment of vegetation."

The City of Mesa is using the product to control dust on unpaved alleys, which total some 90 mi. "We've done 10 miles of alleys so far and expect to obtain dust control for 30 miles more each year."

In Tucson, Pima County officials have discovered that soil stabilization is essential prior to chip sealing rural roads. "In the past, potholing was a problem with chip-sealed roads," Koether comments, "In this area, after just a couple of years, potholing and cracks are common. With the stabilizer in place, only light maintenance is needed. We stabilized a mile section of Twin Peaks Road in the northwest metro area in June 1997 prior to chip sealing, and that road hasn't needed any repairs since then."

Some Like It Cold

One of the challenges with stabilization products is the freeze/thaw cycle that leads to surface cracking, which opens the way for washboarding or potholes in the treated road–all of which leads to dust and subsequent complaints from citizens. In St. Clements, MB, a handful of miles north of Winnipeg, temperatures can drop to -40°F, yet there are 550 mi. of road, 95% of them unpaved. Furthermore, all maintenance work is done by the municipal workers instead of contractors.

Assistant Public Works Foreman Bill Sinclair was especially concerned about Nanton Road, a 1.5-mi.-long heavily traveled gravel road. Yet this rural municipality of 9,000 didn't have the resources to pave the troublemaker. Then he learned about Cypher International Ltd.'s EarthZyme, an enzyme product originally formulated at the University of Manitoba that bonds with the platelets in clay. That bonding provides both dust control and soil stabilization.

Norm Burns, president and CEO of the Winnipeg-based company, worked out a demo project for St. Clements that became an international event. Recalls Burns, "The people living along Nanton Road had a huge problem. Because of the dust they never had their windows open in the summer, nor did they barbecue. We provided the material and preparation instruction, then invited more than 1,000 people internationally to see the difference the enzyme makes."

Cypher trained the municipal workers to use the product. Burns explains, "The first step is a soil analysis. If the platelet count is too low, soil content is not suitable. The soil needs at least 20% clay as well as the PI, or plasticity index, necessary for successful application and must be able to cope with the freeze/thaw cycle. Moisture content also is crucial, but once a user has the numbers, he knows how much enzyme to use, how much moisture to add."

The top 4-6 in. of soil are scarified, and the product is spread by a water truck, with 1 gal. of EarthZyme to 1,000 gal. of water. Next a grader blades back and forth, mixing the soil. Sinclair comments, "There is a learning curve, but once you know what it's supposed to look like, it's fairly simple for the operator to properly mix and spread the treated soil."

He adds, "We did the test site under the worst conditions possible. That was in June, and the skies opened up and gave us downpour after downpour. It was supposed to be a two-day project, but because of rains it took a week and a half. We did the project in two phases, 500 meters each, because of constant rain. The second half turned to pea soup, and we had to wait for it to dry up." Once the material was down and packed, they had traffic rolling on it immediately, with cement trucks using the road two days later and not affecting the surface.

"Today the road is still very good compared to the original," concludes Sinclair. "It handles the extremely cold conditions typical for our winters. Yes, there is some small potholing, but that was because of the adverse conditions we worked under. There has been no frost heave, and we plan on seal coating that road this year. We'll lay down the oil, then a fine gravel chip, and let the traffic shape it up. EarthZyme gave us a good, solid base, and we'll only need to put down a single layer of chip seal, which cuts the cost of seal coating in half."

St. Clements workers also have added EarthZyme to two other streets in the municipality, treating 1.1 km of unpaved roads for a materials cost of just $13,000 Canadian. "If we would've gone with paving, material costs would have been $45,000 per kilometer," Sinclair emphasizes.

He voices one concern with the product: "Beware of black soil; it doesn't react to the enzyme. But problems can be prevented through proper soil analysis. On George Street, we ran into a long streak of black organic, but we put down three-fourths-inch clean limestone chips, and the road tightened right up. With the enzyme, the resulting surface is much like concrete. I don't think either our Caterpillar 140H or 160H graders could touch it."

Burns explains that the product also can be used to treat road shoulders to prevent washout. "You never have to stop the traffic during the mixing and spreading. The more use the road gets, the better it becomes. More traffic leads to more compaction. Rubber has a tendency to pull moisture out of the road. When moisture and air are compacted in an EarthZyme-treated road, you have molecular bonding, higher elasticity.

"During the Nanton Road project, they pulled out a boulder. The municipal workers took soil from the ditch, mixed it with the enzyme, and tamped it in place. The cost of that patch was measured in pennies."

Burns points out that the technology also is used on mine and logging roads and can handle the 24/7 traffic as well as freeze/thaw cycles. Nor do roads have to close for workers to mix and spread the product. "With the high plasticity it provides, users can get into remote sites 12 months of the year instead of just eight."

He cautions, "Like cement or any other material, though, you can't do it in the rain. But as soon as it's compacted, it can rain all it wants. That rain in St. Clements was so hard we couldn't even see to drive, but we were able to keep out of the mud."

In Nashville, TN, Michael Pickern, national sales director for Cypher International's USA Division, comments, "It's a multienzyme product developed for workability, mixability, binding, and compaction of the soil. As with any other product, it has to be properly applied for full effectiveness, so we like to be present the first time a company or municipality uses it. But application is fairly simple because, after the surface is scarified, the liquid mix is put down by a water truck using a pressurized spray bar.

"The final step is to roll it with at least a 12-ton vibratory steel-drum roller and a rubber-tired roller. After that you can skateboard on it." Pickern reports that the cost of product is about $13,000/mi. for a 24-ft.-wide road, or about one-fifth the cost for paving.

He adds, "Cationic action binds the dust particles together, providing a longer-lasting dust-free surface. The enzyme suspends in water, so agitation is not needed. Also, it's a totally natural biodegradable product that alters and improves the soil's physical and chemical property. It takes less mechanical effort to get the density for compaction yet increases the CBR [California Bearing Ratio] as much as 1250%, with 400%-plus typical."

Pickern reports that the technology also can be used for building low-cost housing because the unfired clay blocks have no need for mortar, with a raw-material cost near zero. The catch is they must be laid within a few days of production in order to molecularly bond together.

He comments, "Unlike other road-building products, clay is a plus, not a problem. EarthZyme is environmentally safe, there are no contamination worries, and the nonpermeable surface doesn't erode. This technology is getting lots of attention because of the crackdown on environmental issues."

So while bureaucrats tend to bring up concerns, worries, and problems, and the man in the street demands somebody do something about the problem, it's still the manufacturer or businessman who provides the solution to the concern, even if the problem is road dust.

Author Joseph Lynn Tilton is a frequent contributor to Erosion Control.