Dust has long been a part of the dialect of the American West. Phrases such as “hit the dusty trail” and cowhands named “Dusty” were as much a part of the landscape of the Old West as the tumbleweed or the legend of Wyatt Earp. From Dodge City cowboys and Pony Express riders to present-day ranchers and developers, dealing with dust has been a Western tradition-part of what helped mold boys into men. Even the word “grit,” a synonym for dust, has taken on a larger-than-life meaning of unyielding courage in the face of danger or adversity. True Grit and almost every other movie about how the West was won pit the hero against a backdrop of wind, heat, dust, little water, and the usual number of snake-oil salesmen, no-good outlaws, and power-hungry political types. That saga remains pretty much the same as we saunter on into the 21st century.
Water, Dust, and PM10
It’s an inarguable fact: Water is the limiting resource in the American West. And in a La Niña year such as 2000, it’s easy to see why dust is so prevalent in the arid areas west of the Rocky Mountains.
For the last 100 years, internal-combustion engines and big industry have shouldered most of the blame for belching forth the growing layers of air pollution that hover over such major population centers as Los Angeles, Denver, Phoenix, and Las Vegas. Levels of ozone, carbon monoxide, and other airborne pollutants are dropping around the country, however, while particulate matter is on the rise. According to the Environmental Protection Agency (EPA), PM10 (airborne particles less than 10 micrometers in diameter) emissions from fugitive dust increased 2% between 1985 and 1994. And data from health professionals and EPA are pointing toward the construction industry as a major source of the dust that makes up PM10.
In a 1997 study, Kaiser Permanente health maintenance organization demonstrated what physicians have long suspected: hospital admissions for respiratory ailments are directly proportional to the amount of airborne particulates. For every 10-microgram increase in the concentration of these particulates, hospital admissions went up by 7% for patients with chronic respiratory disease, 3.5% for those with acute respiratory illness, and 3% for patients with cardiovascular disease.
According to an October 1996 EPA report on trends in air pollution, fugitive-dust sources comprised 92% of all PM10 emissions. The report states that 28% of all fugitive dust comes from unpaved roads and 23% comes from construction sites. In 1997, the then-EPA deputy assistant administrator for research and development, Joseph Alexander, told the US House of Representatives, “Controlling particulate matter will include evaluating poorly understood sources of fine particles, such as heavy-duty diesel vehicles and fugitive dust from construction sites.”
Since 1997, a lot of groundbreaking work has been done to clear up the ambiguities about the relationship between dirt roads, construction sites, and fugitive dust. And the numbers aren’t pretty.
Viva Las Vegas
Dust definitely plays a big role in the “brown cloud” that forms over Denver each winter and LA’s “auburn sky,” and it’s the single largest source of PM10 in the Las Vegas Valley. A study conducted by the Department of Civil and Environmental Engineering at the University of Nevada, Las Vegas found that construction sites contribute 29% of the PM10 in Clark County.
In March 1998, the City of Las Vegas adopted a dust control ordinance that prohibits grading more than 120 ac. at one time per development. Hailed by environmentalists as huge step toward reducing the fugitive dust from construction sites, this legislation comes up short of addressing the problem. As Clark County Air Pollution Control Division Director Michael Naylor points out, only 13 of the 1,600 dust permits issued by the county in 1997 were for sites larger than 120 ac. And those 1,600 sites still contributed almost 30% of the PM10 in Clark County!
“There’s quite a bit of construction going on in the greater Las Vegas area,” notes Naylor. “In 1999, we issued 20,300 acres of permits-that’s approximately 28 square miles of land under development.”
In most of these cases, developers scrape a site clean of vegetation and grade it in one fell swoop. This process leaves large areas of disturbed ground exposed to the elements and particularly susceptible to wind erosion. According to Naylor, each contractor must apply for a dust control permit. Each permit sets out a strict dust mitigation plan that includes water trucks and measures for controlling blowing dust or mud track-out. “Both blowing dust and track-out are enforceable offenses,” he adds.
“The most frequent problem is that contractors don’t have sufficient water trucks on-site, which leads to dust leaving the property,” continues Naylor. In 1999, his office gave out 200 dust-violation notices to contractors not in compliance, which amounted to $300,000 in fines. First-time violators receive the minimum penalty of $2,000, but multiple offenders can receive up to $10,000 fines.
Las Vegas is one of the six areas in the United States where EPA has been notified of serious nonattainment of PM10 regulations. “Construction sites are the single largest source of dust emissions in our area,” Naylor states. Federal requirements stipulate that Las Vegas needs to come up with a plan (called a “sanctions clock”) to reach attainment of a statewide implementation plan. If Las Vegas doesn’t reduce its PM10 emissions according to the timetable stated in the implementation plan, the county could lose all federal funding for nonexempt highway projects, which would amount to approximately $70 million to $80 million. “In other words,” adds Naylor, “EPA’s regulations have teeth.”
The long arm of EPA could even affect privately funded road projects that lead to new developments. If Las Vegas doesn’t do enough to achieve lower PM10 levels, building new private, unpaved roads could be banned because the dust from additional traffic-related activities would only make matters worse. You don’t have to be a rocket scientist to realize that this level of federal intervention could be a real nightmare for local contractors.
“As a land development company, we’re interested in controlling dust because if we don’t take care of it, we’re going to get fined,” says David Firestone, land development manager for Sunrise Development Company operating out of Las Vegas. “County health inspectors are on wheels throughout the county. They take pictures and write up a ticket right there on the spot. Then we’re notified of the fine and have to appear at a hearing.”
According to Firestone, once Sunrise grades its home pads, the company sprays them with Soil-Sement (a polyvinyl acrylic copolymer solution) and ropes off the area so people don’t disturb it. “Once you drive a vehicle on a treated home pad, it breaks up the material, and the [copolymer] protective layer loses its integrity and doesn’t do the same job of keeping dust down [as it could have].”
Although Firestone has had success using Soil-Sement on undisturbed areas, unpaved roads are another matter. “When it comes to unpaved roads, a coat of acrylic copolymer is next to useless,” he states. “Asphalt emulsion products are too expensive because they have to be maintained. We tried magnesium chloride on our unpaved roads, but it didn’t work well for us. We were forced to apply it over the weekends, otherwise it got on our vehicles and didn’t come off. So that wasn’t the ticket either. And the health department is adamant that something must be done, which is why we’re still watering roads. But the roads are rock and gravel, so they dry out quickly.”
Just as in real estate, the location of a construction site plays a major role in which kind of dust suppressant works best for the conditions: acrylic copolymers, magnesium chloride solutions, petroleum resins, lignosulfonate solutions, pine resins, or asphalt emulsions. According to Michael Harding, a revegetation specialist and past president of the International Erosion Control Association, “Every site requires a different treatment plan due to factors such as soil type, environmental sensitivity, slope, cost, water-quality impact, product drying time, and availability. When you include all the criteria, you end up with a list a mile long, but the only two factors that really influence the decision of how to reduce fugitive-dust emissions and erosion and enhance soil stabilization are cost and effectiveness.”
When it comes to dealing with a nuisance like fugitive dust, budgetary concerns usually outweigh environmental ones. “Let’s face it: Developers working on a construction site don’t want to spend any more money than they have to,” remarks Colin Kimball, product manager for Pennzoil Products Company in Houston, TX, makers of PennzSuppress D. “And there’s this impression that water is cheap, but it isn’t, especially in the West.” Kimball is right. Although the water itself may be relatively inexpensive, its application (equipment, man-hours, maintenance, fuel) is not. Spending a couple of thousand dollars a day running water trucks back and forth to avoid a $2,000-$10,000 fine is an inefficient use of a company’s resources. And bottom-line restrictions naturally create the temptation to use products that cost less but might not do the best job of controlling fugitive dust.Harding admits that occasionally other factors supersede cost and effectiveness. “I was part of a team of specialists working on a restoration plan for Bellingham, Washington, after its big fire. The real need there was environmental sensitivity because the Bellingham River runs right through the middle of town and supports a big steelhead run in the fall. So the process of deciding which product to use to prevent erosion was based mostly on environmental factors.”
Harding has also seen nepotism play into the process. “Sometimes the biggest influence on the decision about which product to use is what I call the ‘Bob factor.’ One time I was out in Hawaii bidding on a job, and when I was told what product was being used to control erosion, I asked, ‘Why did you pick that one? There are probably 20 other products on the market that would have done a much better job.’ One of the managers replied, ‘My wife’s cousin sells that product, so I didn’t really have a choice.'”
Fugitive-Dust Control in the People’s Republic of Boulder
Unlike Firestone, Ted Plank, county road supervisor for Boulder County, CO, has had success with magnesium chloride as a dust suppressant on the Front Range dirt roads. “We use a liquid magnesium chloride product [Dust Guard] in late May or early June after we grade the roads. The surface holds together longer if we grade them first, and as long as the product penetrates the soil, we can regrade with good results.” He admits that the product begins to break down with heavier summer road use and higher temperatures, so the county often reapplies the product before the season’s first snow (late August or early September).
In all the time that he has been using magnesium chloride, Plank has seen very little environmental damage from the product. “About 12 years ago, we had a small stretch of road where two ponderosa pine trees died and several others showed signs of damage. We eased off that section, and we haven’t seen any more damage since.”
Even though most magnesium-chloride products contain some kind of corrosion inhibitor, the products will cause corrosion if left on metal surfaces. Plank says he’s learned to fine-tune the concentration over the years to reduce the environmental damage. “The maximum strength we apply is a quart per square yard, which is half of what the manufacturer recommends. We also hose down the trucks after each application, which helps keep corrosion to a minimum.”
Plank also uses lignin-based products in more environmentally sensitive areas. “Lignin doesn’t last as long as mag chloride, so there isn’t as big a bang for your buck, but it’s more environmentally friendly. But if lignin gets on your car, it’s like trying to get pine tar off. Usually warm, soapy water does the trick.” There are also some minor downsides to the smell and color of lignosulfonate. “When you first put it down, it smells like pine tar, but that dissipates quickly. The lignin also turns the road black because of the color of the product, whereas magnesium chloride goes on clear and turns dark because of its hydrophilic [moisture-attracting] properties.
Dusty Roads
Similar to Firestone at Sunrise Development, Bill Richardson, owner of Hydroseeding Inc. in Puyallup, WA, has had positive results using an acrylic copolymer on undisturbed soils. “We used a couple-thousand gallons of Marloc to help complete the new, number-three runway at the Seattle-Tacoma Airport. The onsite soils were 90% sand, and the airport couldn’t take any chances with sand blowing up into the jets, so we sprayed Marloc at 60 gallons per acre so it would penetrate deep down and form a really strong crust.”
Richardson’s company also covered a 6-ac. area of sand with a Marloc solution for the Port of Tacoma to prevent wind erosion. “It was pure sand that sloped down to the river, so rather than mixing in seed and some kind of mulch, we sprayed Marloc diluted with water to keep the sand from blowing away. When you run Marloc without mulch or seed, it looks like milk going on but dries like a plastic bag,” he describes. “I went back three years later, and the whole area was solid except for a few places where people had gone over the fence and walked around.”
Unlike Firestone, Richardson has had success using an acrylic copolymer to control fugitive dust on unpaved roads. “In Orting, Washington, the local residents complained about a big dust problem. When we drove into town, our hydroseeding trucks sent dust 50 to 60 feet in the air. We graded the road first because Marloc (like most acrylic copolymers) works best on a freshly graded road. It grabs the dust particles and adds weight to them so the particles stay grouped together. Although we normally recommend two applications, the residents only wanted one. When we went back three months later to do another treatment, the dust only rose 10 feet off the ground and dropped quickly.”
Whining About Dust
Pat DeRose is part-owner of the DeRose Family Vineyards that produce wines in the Cienega Valley in California. A 2,000-ft. section of dirt road between vineyards had become a real pest for DeRose. “Mites like a dusty environment, and when any vehicle went down that road, it raised a dust cloud that carried into our vineyards, which weakens the vines. And mites tend to go for the weakest vines.”
DeRose tried several products to solve the dust problem, but there were very important environmental considerations involved. If a dust suppressant solved the dust problem and harmed his vines, then he would have won the battle and lost the war. He chose PennzSuppress D, a petroleum resin that combines binding and wetting agents with emulsifiers. The product did more than keep the dust down and the mites out of the vineyards, it also solved an upkeep problem. “I used to scrape the surface of the road every month because it kept washboarding. Now we have no more ruts.”
Midwest Research Institute (MRI) field-tested PennzSuppress D for 120 days on dirt roads. After four months and 5,000-7,000 vehicles, MRI compared PM10 and PM2.5 on treated and untreated roads. It found that the product controlled PM10 emissions 86-98% better and PM2.5 emissions 83-97% better than no treatment.
Because petroleum resins agglomerate small dust particles instead of forming a film like acrylic copolymers do, resins could continue to reduce fugitive-dust emissions long after a copolymer had broken down. The idea is that even when traffic stirs up dust, the heavier particles fall out of the air faster. These results, however, were not supported in a side-by-side test in the Mojave Desert.
High-Desert Results
Between January 1994 and November 1995, the Kern County Air Pollution Control District conducted a side-by-side assessment of dust palliatives on graded dirt roads near Ridgecrest, CA, in the Mojave Desert. Project DUST (Dusty Unpaved Surfaces Treatment) consisted of three operations: (1) treating unpaved residential roadways with dust palliatives, (2) placing unpaved roadway identification signs (to reduce vehicle miles traveled), and (3) placing dust control speed-limit signs (15 mph). Phase I involved treating lengths of five different roadways with seven different dust suppressants, Phase II involved retreating the same roadways with the same suppressants, and Phase III involved treating five roadways with the three most effective suppressants.
Project DUST set up three portable PM10 ambient monitors borrowed from EPA. Site 1 experienced a 40% reduction in PM10 after treatment, Site 2 was essentially unchanged, and Site 3 experienced approximately a 29% reduction in PM10. The report on Project DUST states that Site 2 was “inadvertently exposed to a nearby unpaved and untreated driveway that was first thought to be unused.”
After one year and two treatments with the same dust suppressants on the same roads, Project DUST reported the following results:
| Dust Suppressant | Effectiveness at Reducing PM10 Emissions |
| Acrylic copolymer (Soil-Sement) |
90%
|
| Pine resin (Road Oyl) |
30%
|
| Magnesium chloride (a CDI product) |
20%
|
| Calcium chloride (a CDI product) |
10%
|
| Lignosulfonate (Lignosite) |
20%
|
| Petroleum resin #1 (Coherex) |
1%
|
| Petroleum resin #2 (PennzSuppress D) |
10%
|
An interesting aside about Project DUST’s study is that several of the 15-mph speed-limit signs disappeared; however, these signs were later found reinstalled at nearby locations. Kern County Air Pollution Control officer Thomas Paxson laughed when asked about the signs. “We were a little irritated at first, but we figured that the local residents knew where the signs needed to be, so we left them where they were.”
The Sage in Bloom Is Like Perfume…
You don’t have to be an expert in soil hydrology to realize that the conditions (moisture, soil composition, porosity, and so on) near the slopes of Mt. Rainier, WA, are drastically different than those in the Nevada desert, Colorado’s Front Range, the Mojave Desert, or California’s wine country. So it should come as no surprise that the results of another side-by-side evaluation of fugitive-dust suppressants conducted by the US Army Construction Research Laboratories at Fort Hood, TX, and Fort Sill, OK, produced very different results.
In the summer of 1996, a study entitled “Dust Control Performance on Unsurfaced Roadways and Tank Trails” was performed at Fort Hood and Fort Sill. The testing evaluated four different types of dust control agents: polyvinyl acrylic polymer (Soil-Sement), soybean feedstock processing byproduct (SoyaSeal 6), calcium lignosulfonate (Lignin LS-50), and a 38% calcium-chloride solution (Dustyfyghter). These products were selected for the study based on their previous performance, suitability for a wide range of soil and climactic conditions, preapplication requirements, ease of application, ability to penetrate the soil, environmental friendliness, and curing time.
Three sections of unpaved road and tank trails were selected based on similar surface characteristics, slope, aspect, and underlying soil types. All test sections were graded prior to treatment to remove excess loose material, potholes, and washboards. After grading, each segment was treated with one of the dust palliatives, which were chosen at random. All products were applied according to manufacturers’ specifications.
Two methods were used to record the performance of each fugitive dust-controlling substance: tarred, oil-coated dust-collection pans that were placed approximately 6 ft. from the unpaved road/trail and a video camera to capture opacity from dust created by vehicles passing at 30 mph.
Sixty days after the application of the four dust palliatives, the results of the dust collection pans study at Fort Hood were as follows:
- At 30 days, all products reduced dust levels by at least 50% when compared to the control (no treatment).
- Similar trends were observed 60 days after treatment, except that dust levels had more than doubled compared to the data collected at 30 days.
- Drought conditions, zero measurable precipitation, and heavy tracked-vehicle traffic are probable reasons for deterioration of treatment effectiveness between 30 and 60 days.
Sixty days after the application of the four dust palliatives, the results of the dust-collection pans study at Fort Sill were as follows:
- At 30 days, all four products reduced dust levels by at least 66% when compared to the untreated control.
- These levels of dust control continued 60 days after treatment, except for the polyvinyl acrylic copolymer, which deteriorated rapidly between 30 and 60 days. Again, heavy tracked-vehicle traffic between 30 and 60 days broke the surface-sealing characteristic of this product, which resulted in increased levels of dust.
The widely varying results of these anecdotal experiences and various testing operations are unsettling at first. When you look past the results and numbers, however, you see that each situation has a unique set of circumstances (soil conditions, climate, weather, road use, disturbed or undisturbed soil, environmental concerns, financial considerations, and so on). The results, whether anecdotal or scientific, all point toward the need for more controlled, comprehensive testing of dust suppressants in a wide variety of conditions and soil types.
Many of the products that are used to control fugitive dust have been tested for their erosion controlling properties under a variety of slopes and soil types by the Texas Department of Transportation (TxDOT) and the Texas Transportation Institute Hydraulics and Erosion Control Laboratory on the Texas A&M campus. The results of these tests are available via the Internet at www.dot.state.tx.us. Once at the TxDOT site, click on Business, then on Material Information, and then Field Performance of Erosion Control Products.
The California Department of Transportation recently tested 13 soil-stabilization products at its new $3.5-million rain simulator at San Diego State University. Unfortunately, the results of this study were not available when this article was written. The inside scoop, however, is that many of the products tested did not live up to manufacturers’ claims.
There is support for this type of unbiased testing from within the dust control industry. “There is a real need to develop and implement appropriate testing with known methods for dust suppression,” observes Robert Vitale, president of Midwest Industrial Supply Inc in Canton, OH. “That way we could quantify information and take it out of the realm of fluffy brochures and back to data that customers can rely on.”
“Our company and Midwest Industrial Supply both pushed hard for standards for dust control five or six years ago, but the idea was not well received,” states Mark Bramson, executive vice president of Syntech Products Inc. in Toledo, OH. Perhaps the biggest reason that fugitive-dust control hasn’t kept up to speed with erosion control and soil-stabilization industries, even though many products cross over between all three concerns, is because dust wasn’t considered a significant health and pollution problem until the mid-1970s. “The dust control industry isn’t even 25 years old yet, so we’re still in the missionary stage of establishing that there really is value in good dust control, especially on construction sites,” says Vitale. “There is a lot of room for responsible growth in this industry. Even those manufacturers with good intentions have to step up to the plate with the truth about their products, and there are some people in the industry who don’t want to do that.”
Until industry standards for testing fugitive-dust emissions are implemented and repeated under controlled conditions, an element of doubt will continue to linger over the effectiveness of individual dust suppressants and the industry as a whole. Without further study, contractors will be forced to continue making decisions based on fact-based knowledge of which products work best under the conditions at hand.
