Dust Palliative Selection and Application Guide
Peter Bolander, Pavement Engineer, Pacific Northwest Region
Alan Yamada, Project Leader
The author would like to first acknowledge all the Forest Service personnel and suppressant manufacturers/suppliers that have shared their wisdom and knowledge on the use of dust suppressants. Acknowledgments should also go to UMA Engineering, George Giummarra, and David Jones, for without their studies and writings, this report would have been much more difficult to pull together.
The purpose of this publication is to help practitioners understand and correctly choose and apply the dust palliative that is appropriate for their particular site, traffic conditions, and climate. In addition, this publication describes the expected performance, limitations, and potential environmental impacts of various palliatives.
This guide examines most of the commonly available dust palliatives currently available and does not endorse any particular product. Since new products will become available and existing products are likely to change this guide serves as a starting point for determining which palliative would be most appropriate for a given situation.
Dust Abatement Basics
Dust from unpaved roads is not only a nuisance but creates a safety hazard by reducing driver visibility. Dust also affects the health of road users and increases wear-and-tear on vehicles. Dust is always considered an intruder at campsites and picnic areas. In some areas there are regulations that limit the amount of particulate allowed in the atmosphere.
Fine particles, including dust, help hold the surface of unpaved roads together. With a loss of fine particles from the roadway, there is an increase in roadway surface raveling and maintenance costs. These fines are smaller than the eye can see and pass through a 75 µm (No. 200) sieve.
How can dust emissions from the roadway be reduced or eliminated? Since the fines act as a binder that holds the surface of the unpaved road together, removing them is not a good option. Sealing the surface with an asphalt or concrete pavement or Bituminous Surface Treatment eliminates the dust problem; however, the low-volume traffic on most Forest Service roads does not justify the cost of sealing the road with such treatments. Another alternative is to apply a dust suppressant product. These products are not a permanent solution and will require further applications as the effectiveness of the product decreases with time. Dust suppressants are one of many possible methods to control dust (Foley 1996; UMA 1987; Washington State Dept. of Ecology 1996).
Dust suppressants work by either agglomerating the fine particles, adhering/binding the surface particles together, or increasing the density of the road surface material. They reduce the ability of the surface particles to be lifted and suspended by vehicle tires or wind.
To select the appropriate palliative, one must understand the primary factors that generate dust. They include the following:
Selection of the proper dust abatement program must include an understanding of not only the above factors, but the total long-term cost and environmental impacts of that program. Long-term costs include road improvement, road preparation, application of the suppressant in conjunction with the number of times the palliative needs to be applied, and expected changes in maintenance practices. Environmental considerations typically include impacts to the water quality, aquatic habitat, and plant community.
Besides controlling dust, a good dust abatement program may include reduced maintenance bladings and decreased aggregate loss (UMA 1987; Addo and Sanders 1995; Lund 1973).
Dust Palliative Basics
A wide variety of dust suppressants are commercially available, and more will emerge in the future. They can be divided into seven basic categories: water, water-absorbing products, petroleum-based products, organic nonpetroleum-based products, electrochemical products, polymer products, and clay additive products. The categories are listed according to estimated past usage/popularity.
Typical suppressants in each category are:
Suppressant Selection Tips
To determine the most cost-effective dust palliative, it is recommended that the flow diagram by UMA Engineering (1987) and Washington State Department of Ecology (1996) in figure 1 be followed. Important benefiting factors (Langdon 1980) of dust palliatives to consider when evaluating and selecting the proper dust palliative include:
Suppressant Application Tips
After a suitable product is selected, determine the appropriate application rate and frequency. Table 1 lists broad ranges of application rates for various products and can be used as a guideline. Manufacturer's literature, past experience, and field or laboratory test plots over 1 m2 (1 yd2) can also be used to help determine the appropriate application rate.
Generally, higher application rates or increased frequency is required when the following conditions are present:
General Application Tips
The performance of any dust suppressant is related to many application factors. Application method, rate, frequency, and product concentration are a few of these factors. A stable, tight surface that readily sheds surface water is another. If properly applied and constructed, a longer life and higher level of service can be expected from the dust abatement efforts (Foley et al. 1996; UMA 1987; Washington State Dept. of Ecology 1996; Giummarra, Foley, and Cropley 1997). Since dust suppression and road maintenance efforts are usually combined, it is prudent to include the following practices in the maintenance and rehabilitation of road surfaces prior to applying a dust palliative:
Application tips that apply to all liquid dust suppressant products include:
Water Application Tips
Regular, light watering is more effective than less frequent, heavy watering.
Chloride Application Tips
Light compaction is recommended after a chloride brine application.
Soil type and density greatly affect the rate and amount of penetration. In all instances, it is desirable to attain a 12 to 25 mm (1/2 to 1 in) penetration. Most products (with the exception of SS- and CSS-1) will penetrate and coat most soils if they have been loosened by scarification. For surfaces which have not been scarified, only those products with low viscosities will penetrate.
Organic Nonpetroleum Application Tips
Remove loose material prior to application unless the road surface will be mixed and/or compacted after the spray application. When applying vegetable oils, the top 25 to 50 mm (1 to 2 in) of the surface should be loose to improve penetration.
Electrochemical Application Tips
Typically, these products are mixed into the road surface.
Polymer Application Tips
Light compaction is recommended after a polymer application, unless the polymer is mixed into the road surface.
Clay Additive Application Tips
Ensure that the clay and the associated water used for compaction is uniformly distributed throughout the surface material. This method requires a minimum of 8 passes with a motor-grader or use of a cross-shaft rotary mixer.
All dust suppressants have a limited lifespan and require regular applications to satisfactorily control dust on a long-term basis. Subsequent applications should be made if and when dust levels exceed acceptable levels. These subsequent applications may be lighter than the initial application.
Any suppressant ingredient may migrate due to carelessness in application, runoff, leaching, dust particle migration, or adhesion to vehicles. Carefully review the product literature, Material Safety Data Sheet, and manufacturer's instructions before purchase and use. Observe all safety precautions and follow manufacturer's directions when handling, mixing, and applying dust suppressants. Application of all dust suppressants must comply with Federal, State, and local laws and regulations. These vary by locality and need to be checked prior to implementing the dust abatement program.
The primary environmental concern with dust palliatives is how they impact the groundwater quality, freshwater aquatic environment, and plant community. Take all necessary precautions to keep dust palliative material out of water drainages and roadway ditches leading to streams.
The impact of dust palliatives on groundwater quality is based on how the suppressant migrates to the local groundwater table in conjunction with the chemicals used in the suppressant. Chemical analysis of the suppressant will assist in determining whether harmful constituents are present. Knowing the depth to groundwater and the permeability of the native soil will assist in determining how and whether the chemicals will leach to the groundwater table. A direct way to evaluate the contamination of harmful constituents to the groundwater is to conduct water quality sampling of the surrounding area before and after dust palliative application.
The impact of dust palliatives on the freshwater aquatic environment is measured by both the toxicity to fish and the availability of oxygen. Each State sets its own standards, and they may vary by watershed and the type and age of the fish population. The test to determine toxicity is the LC50 test, and the test to determine available oxygen is the BOD (Biochemical Oxygen Demand) test. The LC50 test measures the lethal concentration (LC) of product, expressed in parts per million (ppm), that will produce a 50 percent mortality rate in the test group in 96 hrs. The larger the concentration, the less toxic the material. Typically, less than 100 ppm is considered toxic, 1,000 ppm is considered practically nontoxic, and greater than 10,000 ppm is considered nontoxic. The BOD test measures the oxygen used by microbes as it digests (feeds on) the product in water. Typically, the products that are derived from organic nonpetroleum suppressants are the most likely to have high BOD results.
There are no standard tests for measuring how dust palliatives impact the plant community; however, some tests have been performed that simply observe the impact on plant life.
Addo and Sanders (1995) summarize a number of environmental impact studies on the use of various chlorides on water quality, plants, and animals. Heffner (1997) updates the work by Schwendeman (1981) concerning the environmental impacts of some of the most common dust palliatives used by the Forest Service. Based on their efforts, the following is recommended when using these palliatives once or twice a year at their typical application rates:
Lignosulfonate - Determine prior to application if significant migration (water drainage) might occur from the treated area into local streams, ponds, and lakes. Ensure that migration will not impact the oxygen needs of the aquatic community.
Calcium and Magnesium Chlorides - Restrict the use of chlorides within 8 m (25 ft) of a body of water. In areas of shallow groundwater, determine whether significant migration of the chloride would reach the groundwater table. Restrict the use of chlorides if low salt tolerant vegetation is within 8 m (25 ft) of the treated area. Typical low-tolerant vegetation includes various varieties of alder, hemlock, larch, maple, ornamentals, and pine.
Evaluations of other dust palliatives have not been made. If there is concern regarding the impact of a dust palliative on the environment, then, as a minimum, the LC50 and BOD tests should be performed. Results can be used to estimate the potential impact of the dust palliative in question on the local aquatic and plant communities.
Past Field or Laboratory Study References
Gifford Pinchot National Forest Study (1988)
"Dust Abatement Review and Recommendation," by Marjorie Apodaca and Don Huffmon (internal report).
Lolo National Forest Study (1992)
"Dust Abatement Product Comparisons in the Northern Region," by Steve Monlux, Engineering Field Notes, Volume 26, May-June, 1993.
Fremont National Forest Study (1991)
"Asphotac, A Demonstration of a Dust Palliative," by Joe Acosta, Jim Bassel, and John Crumrine (internal report).
Larimer County, Colorado Study (1995)
"Effectiveness and Environmental Impact of Road Dust Suppressants," by Jonathan Addo and Thomas Sanders, Department of Civil Engineering, Colorado State University, Report No. 95-28A, March 1995.
Forest Service Region Six Laboratory Study (1999)
"Laboratory Testing of Nontraditional Additives for Dust Abatement and Stabilization of Roads and Trails," by Peter Bolander, Transportation Research Board, Proceedings of the Seventh International Conference on Low-Volume Roads, TRR No. 1652, Volume 2, May 1999.
US Army Corps of Engineers Waterways Experiment Station (WES-1993)
"Evaluation of Methods for Controlling Dust," by Richard Grau, Technical Report No. GL-93-25, September 1993.
US Army Corps of Engineers Construction Engineering Research Laboratory (1997) "Effectiveness of Dust Control Agents Applied to Tank Trails and Helicopter Landing Zones," by Dick Gebhart and Thomas Hale, Technical Report 97/69, April 1997.
Ongoing Field or Laboratory Studies
Council for Scientific and Industrial Research (CSIR), South Africa
"Holistic Approach to Research into Dust and Dust Control on Unsealed Roads," by David Jones, Transportation Research Board, Proceedings of the Seventh International Conference on Low-Volume Roads, TRR No. 1652, Volume 2, May 1999.
Environmental Technology Evaluation Center (EvTEC), Highway Innovative
Technology Evaluation Center, Civil Engineering Research Foundation, Washington, DC "Dust Control/Road Stabilization Agents" (ongoing study).
Addo, J., and T. Sanders. 1995. Effectiveness and Environmental Impact of
Road Dust Suppressants, Mountain-Plains Consortium, Colorado State University, MPC Report No. 92-28A.
Bolander, P. 1999. "Laboratory Testing of Nontraditional Additives for Dust
Abatement and Stabilization of Roads and Trails," Transportation Research Board, Proceedings from the Seventh International Conference on Low-Volume Roads, Transportation Research Record No. 1652, Volume 2, Washington, DC
Bolander, P. 1997. "Chemical Additives for Dust Control--What We Have Used
and What We Have Learned." In Variable tire pressure, flowable fill, dust control, and base and slope stabilization, Transportation Research Board, Transportation Research Record No. 1589, Washington, DC
Foley G., S. Cropley, and G. Giummarra. 1996. Road Dust Control Techniques-
Evaluation of Chemical Dust Suppressants' Performance, ARRB Transport Research Ltd., Special Report 54, Victoria, Australia.
Giummarra, G., G. Foley, and S. Cropley. 1997. "Dust Control-Australian
Experiences with Various Chemical Additives," In Variable tire pressure, flowable fill, dust control, and base and slope stabilization, Transportation Research Board, Transportation Research Record No. 1589, Washington, DC
Han, C. 1992. Dust Control on Unpaved Roads, Minnesota Local Roads
Research Board (LRRB), Report No. MN/RC-92/07.
Heffner, K. 1997. Water Quality Effects of Three Dust-Abatement Compounds,
USDA Forest Service Engineering Field Notes, Volume 29.
Langdon, B. 1992. An Evaluation of Dust Abatement Materials Used in Region 6,
Transportation Research Institute, Civil Engineering Department, Oregon State University, Research Report 80-3.
Langdon, B., G. Hicks, and R. Williamson. 1980. A Guide for Selecting and Using
Dust Palliatives, Transportation Research Institute, Civil Engineering Department, Oregon State University, Research Report 80-13.
Lund, J. 1973. Surfacing Loss Study, unpublished, USDA Forest Service,
Scholen, D.E. 1992. Non-Standard Stabilizers, Federal Highway Administration,
FHWA-FLP-92-011, Washington, DC
Schwendeman, T. 1981. Dust Control Study-Part 2-Dust Palliative Evaluation,
USDA Forest Service, Gallatin National Forest.
Transportation Technical Assistance Office of the University of Missouri-Rolla.
1986. Operating Tips - Road Dust Suppressants, Northwest Technology Transfer Center, Olympia, Washington.
UMA Engineering Ltd. 1987. Guidelines for Cost Effective Use and Application of
Dust Palliatives, Roads and Transportation Association of Canada, Ottawa, Canada.
Washington State Department of Ecology. 1996. Techniques for Dust Prevention and Suppression, Washington Department of Ecology Fact Sheet, Publication No. 96-433.
About the Authors
Pete graduated from Michigan State University with a degree in civil engineering. He has a master's degree in soil mechanics and foundation engineering from Oregon State University. Pete began his career with the Forest Service as a geotechnical engineer on the Wilamette NF. After 10 years on the Wilamette, Pete moved to the Pacific Northwest Regional Office (Region 6) in Portland, OR, as the Regional Pavement Engineer.
Alan graduated from the University of Hawaii with a Bachelor of Science in Civil Engineering and is a licensed Professional Engineer in the State of Oregon. He served as a Zone Engineer in Region 2 and on the construction team for the Coldwater Visitor Center and Johnston Ridge Observatory within the Mount St Helens National Volcanic Monument in Region 6. Alan joined the center in December 1996 and serves as a project leader supporting the Engineering Program.
Transportation Program Leader
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