Techniques for desert campsites, country roads, vineyards
In September 2006, the United States Environmental Protection Agency introduced what it described as the strongest national standards for air quality in American history. Known as the National Ambient Air Quality Standards (NAAQS), they directly address particulate matter pollution. This kind of pollution can be connected with severe health problems, including aggravated asthma and the premature death of individuals with lung and heart disease.
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Photo: Desert Mountain Corp. |
| Copolymer application to sandy soil |
The EPA considers fine particles to be 2.5 micrometers in diameter; inhaleable coarse particles are 2.5 to 10 micrometers in diameter. The action taken in September revised the previous daily fine particle standard by nearly 50% to 35 micrograms of particles per cubic meter of air. The organization estimates additional health benefits with a value between $9 billion and $75 billion annually. At the same time, the EPA retained its current yearly standard for long-term fine particle exposure at 15 micrograms per cubic meter. The organization estimates the benefits of this standard to range between $20 billion and $160 billion annually.
Addressing dust problems to meet increasing air-quality regulations may mean finding the right temporary topical solution or permanent answer by working a product into a site’s soil. Choosing the right dust control or soil stabilization product for your site will depend on a variety of issues, including soil type, fitting product costs into a project’s budget, and regional winds. Whether it’s a construction site, a heavily trafficked road, or an ecosensitive environment, dust control and soil stabilization plans play an integral role in protecting air quality.
Saddling Up, Keeping Dust Down
For the past 51 years, a group of people have met once a year in Wilcox, AZ, to take part in an old historic trail ride called Los Charros del Desierto, or “Horsemen of the Desert.” The group camps out, rides during the day, and returns in the evening, explains Martin Bowen, vice president and chief financial officer of Fine Line, based in Fort Worth, TX, who takes part in the event.
“We have had a problem [with dust] in the past. We have a campsite of 4 or 5 acres. The road was just dirt. On the road you have 150 riders. In and out, you probably had on the road maybe 75 to 100 trucks and SUVs pulling trailers,” says Bowen, noting visitors may spend three or four days at the site. This year, MonoSol’s TerraLoc was applied to the area.
In the arid climate, heavy dust can irritate the corners of a rider’s eyes or his or her nose during the event.
“We did it because we thought it would help with the people riding on the roadways,” says Bowen. “Apparently, the most important thing was keeping the pollen down and keeping the dirt out of the food. It worked very well. You don’t even know it’s there.”
The dilution rate of the biodegradable dust control product was altered to suit the treatment site. “Normally a typical dilution rate is one part TerraLoc to three parts water,” explains Christian Rath of MonoSol, based in Merrillville, IN. “In this application, it was one part TerraLoc and nine parts water. We had no product on the vegetation. This produced an effect that percolated inside the soil without residues on the substrate.”
The product was mixed in a water truck, explains Bowen, and applied a few days prior to Los Charros del Desierto. The effect the product had on pollen was noticeable, according to Bowen.
“A doctor came up to me after a couple of days,” notes Bowen. “He said this really held the pollen count down.”
People who cooked the riders’ food were also pleased with the dust control that was applied in the high desert, where the terrain consists of grasses, cactus, and rocky, rough ground, says Bowen. “It kept the dust out of the food,” he notes, commenting on the wind in the area. “They were cooking on open flames out in the desert.”
When Water Works
North Dakota Department of Transportation (NDDOT) workers used an easily accessible resource to control dust and stabilize disturbed extremely sandy soil during an ongoing bridge reconstruction project at the Liberty Memorial Bridge in Bismarck, ND.
“Really, where we are, we use water on almost everything. We’re a rural state; we have no air-quality issues,” says Tom Huncovsky, an environmental scientist with the NDDOT. “There is a lot of wind movement. Water seems to work fine for us. Depending on climate conditions, you may have to do it more or less depending how bad it gets. It’s done in some cases as a preventative measure.”
He explains, “We have a different kind of state. You’ve got badlands in the western side of the state that are highly erodible. It’s flat on the east—very different climatic conditions. You take our largest city and that’s one suburb of Minneapolis.”
An NDDOT project engineer typically oversees dust control at transportation construction sites, and a National Pollutant Discharge Elimination System [NPDES] permit is acquired.
At the Liberty Memorial Bridge project, the water is applied primarily by truck to soil located under the bridge itself. The area sees heavy traffic on a regular basis, according to Huncovsky.
“We’re doing street sweeping,” he adds. “Water is required to keep the dust down when they are doing that.”
The Oklahoma Department of Transportation (ODOT) uses water specifically on construction sites, primarily because it’s readily available and environmentally safe, according to Micky Dolan, stormwater coordinator at the ODOT. “Western Oklahoma is very wide open and flat and windy,” she says, noting that while the organization hasn’t tested some polymers, there is a concern among some about their overuse. “We haven’t had any problems with water.”
Protecting a Vineyard, Reducing Water Costs
Winding country roads or arid climates are usually what comes to mind when discussing dust control, yet the process affects products common in our everyday lives, even the glass of wine on our dinner table.
Dennis Delamore, owner of the Amber Group, a wholesale distributor of erosion control products based in Irvine, CA, shares the example of a large California grower and wine producer who came to him looking for a solution that would ultimately protect his crop.
“They have grape vineyards throughout the San Joaquin and Napa valleys,” says Delamore. “There is dust on the roads around the vineyards. The dust that lands on the vines will enhance dust mites on the leaves. The grapes will be less large, with less sugar. The dust inhibits production of the vineyard itself.”
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Photo: Desert Mountain Corp. |
| Lucky for Arizona, copolymers are not affected by heat. |
In addition to working to reduce traffic in the vineyards, the company tried polyacrylamide, magnesium chloride, and polyvinyl acetate. Still, the dust persisted.
“The problems they ran into with those products was they had too much of a tendency to form a crust on their roads rather than getting a deep binding penetration without having to get mechanical remediation,” says Delamore.
“The term dust control is really a misnomer. You are only looking to suppress the dust from rainy season to rainy season. This company had full-time dust control based on seasons.”
The winemaker continued to use water for dust control. “They ran their water trucks around the clock,” says Delamore. “The amount of water they were putting on their roads was staggering. They knew there was nothing they could put down that was within reasonable economics.”
Delamore provided the company with Alcotac from Suffolk, VA–based Ciba Specialty Chemicals Corp. as a way to control dust while at the same time reduce the man-hours spent on administering the water, as well as reduce the amount of water that was applied to the roadways.
“We were able to reduce their water consumption by 45%,” says Delamore. “You really need to have that product migrate down at least an inch and agglomerate the fine particles that exist in the surface soil profile.
“They mix it into their existing water trucks that spray through front- and rear-mounted spraybars. Their application program for a given road is based on which side of the grape vineyard that road is on. Roads with exposure to the east and the north require more frequent treatment based on the amount of sun exposure.”
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Photo: Desert Mountain Corp. |
| Expect your copolymer to last a year. |
No grading was necessary, and the Alcotac was applied directly to the roads. Toxicology testing was performed, and the product is registered and approved for use in California. The winemaker established its own application schedule. Even the roads that have infrequent traffic have benefited from the program.
“Every time it’s added to a road with very little traffic, agglomeration compounds to create a very strong binding action,” says Delamore. “They’re very pleased with it. Next summer, we’re looking at an improved application method based on what we’ve achieved in the previous two summers.”
How Cities in Different Climates Make Dust Control Happen
Dust control and soil stabilization are an important part of the construction of a water treatment plant begun in August 2006 by the City of Phoenix, AZ.
“They are pulling things out of the ground to build a water treatment plant. They are building 1-acre pools,” says Klif Rader of Desert Mountain Corp., based in Kirtland, NM. “They are making a pile of dirt. That pile of dirt needs to be held together so we don’t get dust throughout the neighborhoods; nor will we get the erosion that the weather will give us.”
Rader says a full truckload of Envirotac II, a copolymer made by Environmental Products and Applications based in Palm Desert, CA, was applied by truck to the sandy, loamy soil of the 20-acre site. He prefers using the product for this kind of an application because of its price and availability. During the product’s application, the temperature soared to 128 degrees, says Rader, but the heat didn’t affect the material. Envirotac II penetrates the surface after it’s applied and binds particles of soil together to create a transparent bond.
“We have a purchase order in place to touch it up every 12 months, because they will be excavating material as needed to try to get rid of that 20 acres of overburden,” says Rader. “We will restabilize the disturbed area. The undisturbed area is going to last for 12 to 24 months.”
Labor, fuel, and maintenance costs can also affect a city management team’s choices regarding dust control and soil stabilization. The City of Rio Rancho, NM, was able to conserve on these costs, provide a smooth surface for the driving public, and solve a dust issue in a rural community when, Rader says, it applied Glacial Technologies DC1000 to a local road.
“DC1000 is the preferred method in sandy loamy soils for the binding effect for road stabilization,” says Rader. “It’s a proven performer in the field and has been tested in several sites with the Federal Highway Administration, outperforming various other products when tested against them.”
The product is typically applied by truck once per season in an area that experiences average daily traffic of 500 vehicles or fewer, he says.
“The reason they’re using this type of product is to reduce the city’s maintenance cost on the gravel roads comparative to an untreated road,” says Rader.
Craig Prete, president of Dustbusters in Evanston, WY, uses North American Salt’s Dustgard, a magnesium chloride dust control product, in many county applications throughout Utah, Idaho, and Wyoming because of its low cost and environmental safety.
“The main place it’s used is any gravel roads that have extensive travel on them,” says Prete. “We apply it one time a year, in the spring. For dust control, it does a really good job for the cost.”
Liquid calcium is often used for dust control on high-traffic roads in some areas of the country. Wayne Cleaver, vice president of business development and partner at Recon Construction Services Inc. based in York, PA, uses North American Salt’s liquid calcium chloride on Bungalow Road in North Codorus Township in York. Several hundred vehicles cross that road daily.
“The township utilized liquid calcium in the past,” says Cleaver. “We mixed 1 gallon per square yard at a 6-inch depth. We used a Wirtgen WR 2500 Road Reclaimer and metered the product through a metering system.”
The township hasn’t regraded the area in the last three years, he explains. “They have fog sealed every year at 0.25 gallon per square yard,” says Cleaver. “The township eliminated the washouts and the raveling of the aggregate. Due to the steepness of the roadway, it was a continuing maintenance issue. We did the grading after the mixing operation.”
How Costs Dramatically Altered Plans in the Dust Bowl
Dust control has been essential during the construction of the Marsha Sharp Freeway, named for the girls’ basketball coach at Texas Tech University across the city of Lubbock, TX.
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Photo: TxDOT Lubbock District |
Dust control is a must for loamy soil, which can be easily disturbed by wind. |
The soil in the arid area is loamy and reduced to a fine powder that is easily picked up by regional winds, according to Davis Melton, the environmental studies coordinator for the Texas Department of Transportation’s (TxDOT’s) Lubbock district.
“The topography is flat. We are part of the southern great plains of America,” he notes. “Weather fronts with high-velocity winds pick up this dust and blow it. This is the Dust Bowl.”
In September 2005 alone, 253 hours of work time was spent simply to suppress dust and for soil compaction at the site.
“We were putting a lot of water on the project,” says Melton. “We were putting out 50,000 gallons every working day, essentially 1 million gallons every month.”
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Photo: TxDOT Lubbock District |
| Consider the weather when choosing a control method. |
The TxDOT considered several dust control measures for the site, testing them on five separate plots. “We put out a product called Flexterra. Then we put out a test plot with Bio-Cover. Then we put out something called guar. They grow guar south of Lubbock in a town called Brownfield,” says Melton. Guar is a legume that is also used as a thickening agent in some foods. Melton adds that Terravest, a liquid polymer, was placed on a fourth plot. “Lastly, we put out emulsion.” Emulsion, or emulsified asphalt, consists of small asphalt cement particles in water.
These different dust control and soil stabilization measures were also being considered for placement at different sections of the freeway construction site. TxDOT made a plan that would cover 80% of the bridge header banks with Bio-Cover. Emulsion was to be placed on all of the header banks that face north.
“We made a decision to put guar with mulch on it on 20% of the banks [facing] south. Then we were going to use guar itself on hot spots,” says Melton. “A lot of this is based on cost.”
Without shipping costs, Bio-Cover cost $412.50 an acre, emulsion was about $500 per acre, guar cost $250 an acre, and guar with mulch cost $350 an acre.
“When we first looked at this, assuming product only, if we sprayed 200 acres on the freeway we’d have a weighted average of $1,084.43 for those four products,” he says, adding that the total cost for the project would be $119,260. “We decided that we were willing to go with these four. What we were essentially doing was a project-wide test. We knew what emulsified asphalt would do. We were willing to take a chance [on the other three] because we needed something for the future and we were trying to stay away from emulsified asphalt.
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Photo: TxDOT Lubbock District |
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Photo: TxDOT Lubbock District |
| As air-quality regulations become increasingly strict, dust control becomes increasingly important. |
“When we put in our change order, we knew the cost was going to go up,” notes Melton, adding, however, they were unprepared at how much the cost for the products increased.
With the added shipping, contractor, and application costs, Bio-Cover now cost $2,708.55 per acre.
“The cost for emulsifier was $173.85 per acre. We had estimated more than that. The cost for guar with mulch went to $1,672.50. The cost of guar went up to $1,125 an acre. “Our weighted average cost [increased to] $1,901.60 an acre. Total cost jumped to $203,146. We had a huge jump. We didn’t expect it.”
The plans had to be altered because of the cost increase. “Because the cost jumped so dramatically, what we decided to do was spray emulsified asphalt on about 40% of the project. We also decided that if you look at the cost for erosion control, the emulsified asphalt is a short-term answer.”
The freeway project is divided into five phases. “On our next project phase, we’re going to go with a lot of erosion control compost. We can seed it, and grass will grow in it,” says Melton. “The cost for erosion control compost is higher than any of these, but we have experience. We believe erosion control compost will work.
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Photo: TxDOT Lubbock District |
| Controlling dust keeps air pollution-related illnesses down. |
“We were willing to test guar at one cost level, but when the cost level jumped up so high, we went with what we knew worked. We know that emulsified asphalt is not the answer because it’s a petroleum-based product. It’s not something we’re planning to use anymore, but it was a quick fix. Now it will give us a chance to control dust for a short term.”
The TxDOT continues to control dust at the project on an ad hoc basis, with no final decisions being made for sections of the freeway site that remain under construction.
“On those portions of the project that are not yet under construction,” says Melton, “we are planning to use erosion control compost extensively to control erosion, control dust, and grow grass.”
As air-quality regulations become increasingly stringent, fines become more difficult to avoid without a significant dust control plan in place at a project’s outset. Because controlling fugitive dust and stabilizing soil are an important part of site planning, knowing your options and air-quality limitations can make all the difference in a project’s success.
Based in Morgantown, PA, Tara Beecham writes frequently for Erosion Control. EC - May 2007
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