Photo: Soilworks LLC Sprayer trucks can apply various soil stabilizers.Dust particles of a 10-micron size, known as PM10, are large enough to be easily seen in the air. PM2.5 dust particles are invisible to the eye but can still be breathed in, causing health problems, and can wreak havoc with equipment. The EPA has handed down regulations for contractors to control the amount of even these small particles from worksites. Reaching the new levels can seem an almost impossible task, but the fines for noncompliance can be hefty.Dusty East Washington
Wildland Inc. of Richland, WA, is a full-service restoration company that has handled multiple highway and pipeline projects. Eric McCrea, managing partner, says the company has tried several polyacrylamide (PAM) products. These products usually break down in two to three months. The soil in eastern Washington is a sandy loam that doesn’t compact well. McCrea notes that it is almost impossible to meet clean air requirements for dust control in traffic areas. PAM products work better if they are wet occasionally, and the lack of rain in the area means that doesn’t happen. Use of the PAM products over the last year has allowed his company to learn the products’ limitations and plan their uses accordingly.McCrea has found that Dust Floc from Apex Resources of Louisville, KY, meets the company’s requirements. “It is a cost-effective product and meets regulations for about eight months,” he says. “Dust Floc has the best bang for the buck.” The product is biodegradable, based on guar gum. Very little mixing is required, and the mixture can be applied with water trucks or hydroseeding machines. Additional water is not required later. The product can be mixed with mulch for erosion control, both water and wind, and used for non-traffic areas. For an Ace Distribution Center project, Dust Floc was applied over the 65-acre site during construction. The application rate was 50 pounds per acre, along with 500 pounds of wood mulch, in 3,000 gallons of water. Even with no added water, the product worked for eight months without UV breakdown.Minnesota Likes Water
For Trueman Welters in Buffalo, MN, a major part of the business is highway work. Big equipment causes lots of dust no matter how careful the operator is. Trueman Welters worked with Imperial Industries Inc. of Wausau, WI, to develop the Dust Control Wagon. This equipment applies water as a mist, allowing for better compaction and dust control. By designing a specific machine, the company has built a flexible vehicle that holds up under severe conditions. David Zachman of Trueman Welters says that contractors often say they don’t want to put anything on their sites that might be polluting. He adds that a few years ago, you could locate the construction sites by the dust in the air. Now, very little dust is seen. An aggregate pit near the intersection of Interstates 494, 694, and 94 in Minneapolis had a severe dust problem. Dust from the pit could cause visibility problems on the nearby highways. Other alternatives had been tried, but Zachman says most Minnesotans don’t want added chemicals to their environment. This means no salt additives or other chemicals. Also, Minnesota has an abundance of water. The Imperial Dust Control Wagon sprayed water on the site, cutting the dust significantly.Military Dust
Military action in the sandy Middle East has revealed a dire need for strong dust control. The fine sands of Iraq and Afghanistan cause brownouts and possibly catastrophic crashes and damage equipment, including engines and helicopter rotor blades. Two companies have received government contracts to supply the military with dust control.
Soilworks LLC of Gilbert, AZ, has been in business about three years. Owners Chad and Dorian Falkenberg manufacture a dust control product called Soiltac. Many dust suppressants are created from byproducts of other industries. These products can have low concentrations of active ingredients, leading to inconsistent performance. Some dust control products sold to the military have had bacterial contamination, giving a rotten egg smell. Others are contaminated with the products they left behind. Soiltac has been formulated from the ground up to be a consistent, clean product. Classified as a vinyl acetate copolymer emulsion, the chemical is a concentrated liquid that is diluted with water onsite. Once cured, it has long-lasting power even under strong UV exposure, high temperatures, and alkaline soils. During testing by the US Army Corps of Engineers, Soiltac was proven pure and effective. For price and performance, it was contracted for by the General Services Administration for use in Iraq and Afghanistan as well as for military bases in the United States.In the environment of the Middle East, Soiltac is mixed with water at a 2:1 ratio and applied at a rate of 0.65 gallon per square yard with a hydroseeding machine. After a few hours of cure time, the sand surface is solid enough to handle even the largest Sea Stallion helicopter. Depending on the concentration, applications have lasted from 30 days to two years.
Andy Stevens, vice president of Enviroseal, notes that there are two applications for the company’s product in military situations: erosion control and dust control. The military needs products that can stop dust at places such as helicopter pads and plane landing strips. Enviroseal, based in Port St. Lucie, FL, manufactures soil stabilizers for different types of applications. The amount of holding power depends on the concentration of a product and the application method. For military uses, two types of products have proven themselves: cement and acrylics, such as Enviroseal’s product M10+50. The acrylic polymer liquid is mixed into the soil to a depth of 6 to 12 inches and allowed to cure. The treated soil turns into a solid mass, ideal for a landing strip or helicopter pad. The strength of the mass approaches that of low-grade concrete at 1,750 psi. In Iraq, fully loaded cargo planes are landing on strips prepared with M10+50, and the soil has remained firm under this heavy traffic load.The M10+50 is mixed as a percentage of dry density of the soil. For sandy soil in the Middle East, a mixture of 2.5% is used. That equates to about 5 gallons per cubic yard. For a clay/sand soil mix, the application rate is 0.5 gallon per cubic yard; for gravelly soils, the rate ranges up to 10 gallons per cubic yard. The optimum mixture depends on the soil moisture content and the compaction rate. The product is resistant to UV degradation.
For undisturbed land or areas not subject to traffic, the suppressant can be applied as a topical spray. It reintroduces the fines into the depth of the soil and makes them unavailable to become airborne dust. When the fines are glued into place, they can’t migrate so they fill the pore space and provide stability for all the soil.A 3M plant in Illinois had limestone-based soil that remained soft and broke easily even when compacted. Spraying with the Enviroseal product stabilized the area enough to keep dust to a minimum.
Two factors in choosing a dust control product are ease of use and performance. Lennar Construction chose TerraLOC, manufactured by MonoSol LLC, to treat a construction site. Drew Neptune, area environmental manager for Lennar, explains that the new development in Tucson, AZ, required protection from both wind and water erosion. Stricter regulations have construction companies looking for stronger, more effective dust control products. The site, Vista Montana Estates, has silty sand, prone to dust, so Lennar has laid out test plots for TerraLOC. Some areas received an application of 75 gallons per acre, some 110 gallons, and others 150 gallons. “We want to see what is the least amount that’s effective,” Neptune says.A dramatic decrease in dust was seen immediately. The product did a good job of binding the fines. Before application, a person just walking across the site would cause a dust bloom. According to Christian Rath of MonoSol, TerraLOC is designed to handle both wind and water erosion. It is also designed for ease of application and cleanup. TerraLOC is a polyvinyl alcohol, so it is water soluble and not as sticky as some products. It has no smell and no color and is nontoxic. Accidental spray on electrical boxes causes no harm. Neptune adds that he appreciates the product is non-staining on streets, block walls, and pedestals. This decreases the amount of labor that might have to be hired to clean those surfaces.
Neptune says that the product is fairly expensive-about $1,000 per acre for product only, according to Rath. However, Neptune says it will be worth it if the good results continue. Some lots of the development may be built on in a few weeks, while others might sit empty for six more months. Dust control requirements need to be met for that entire time. One problem faced in Arizona is breakdown of product in sunlight. That aspect will also be tested in the plots sprayed with TerraLOC. “We worry more about UV than about runoff,” Neptune says.The application of TerraLOC was simple: dump it in a water truck and drive around, Neptune says. Curing time varies with conditions, but ranges from three to 20 hours. The person doing the application was Tracy Castell of Windswept Organix in Tucson. He notes that the equipment was easily cleaned up with water and was not sticky. “I’m excited about the possibilities,” he says.
Midwest Industrial Supply Inc. of Canton, OH, recently was contracted for help on a challenging project on the West Coast. A company planned to develop a site that had been contaminated with petroleum products, heavy metals, and volatiles. The site had undergone remediation for about 12 years, and the developer wanted to begin building offices and commercial properties. A dust control product was needed that would not recontaminate the site. Extensive monitoring would be required to enforce regulations for both wind and water erosion.Midwest Industrial has a widely used product called Soil Sement. However, tests showed a residual trace of toluene, so that product could not be used on the site. The list of banned chemicals included 75 volatile chemicals, 50 semi-volatiles, heavy metals, and petroleum hydrocarbons. With such strict requirements, the company chose Soil Sement Engineered Formula. This product is usually recommended for projects requiring strength in both wet and dry conditions. The strength was higher than needed, but the other factors made the Engineered Formula the best choice.Working with the developer, Midwest Industrial was able to design a product to meet all these requirements. Cheryl Detloff, chief chemist for Midwest, says it was a daunting but interesting task. With tighter manufacturing standards, the company was able to create a product meeting all the requirements. The formula was applied in different concentrations on several sites last fall. After a heavy rain season, the product has performed well and the customer says it looks like “it was coated with armor.” Detloff says that choice of a dust control or erosion control product depends not only on soil type and cost, but also on location. In the West, dust is an ongoing issue, so many customers want the armored look. In the wetter East, customers want some percolation into the soil to reduce water runoff and erosion. Different dilutions and application rates can be used in each situation. Whether the challenge is dust on an airfield in Iraq or from a new housing development down the street from your neighborhood, there are a variety of products for the job. Choosing the right one is a matter of factors: How long the control needs to lastSoil type: soil consistency and percentage of fines ClimateCost-effectiveness
