Managing Impact
Calcium chloride dust control, road base stabilization and full-depth reclamation applications reduce sediment load on waterways and save thousands of tons of aggregate that otherwise would be mined from noisy and unsightly gravel quarries. Airborne particulate matter is reduced, improving regional air quality. Road user safety is also improved when calcium chloride is used for dust suppression. Effective dust control increases motorist visibility and vehicle traction while also reducing vehicle damage and potential safety issues caused by washboards, potholes, ruts and other road surface deterioration.
These advantages of calcium chloride treatments typically far outweigh concerns about the environmental, health and safety impact of using the material when proper handling and application procedures are followed and products are applied at recommended rates. Independent research1,2 and governmental recommendations3 suggest that concerns related to the use of calcium chloride for dust control can be effectively managed. Because the content of well head brines, commonly referred to as mineral well or oil well brines, can vary from one source to the next, impact cannot be managed with the same level of confidence.
1Road Dust Suppression: Effect on Maintenance Stability, Safety and the Environment, Phases 1-3; Jonathan Q. Addo, Thomas G. Sanders, Melanie Chenard, 2004
2Surface-Aggregate Stabilization with Chloride Materials, U.S. Department of Agriculture Forest Service, December 2006.
3Best Practices for the Use and Storage of Chloride-based Dust Suppressants, Environment Canada, February 2007; and Dust Palliative Selection and Application Guide, USDA Forest Service, P. Bolander and A. Yamada, November 1999.
Impact on Waterways
The threat posed by calcium chloride contamination of ground and surface water supplies is low. Calcium chloride is classified as practically non-toxic to aquatic organisms according to U.S. Environmental Protection Agency (EPA) criteria. In fact, the calcium component of the material is a natural component of nearly all natural waters. In excessive amounts, chloride salts can be harmful, but ground and surface waters are not likely to be impacted by calcium chloride applied for dust suppression as long as proper application procedures and application rates are used.
Unlike winter ice control applications of chloride materials which can wash from the surface of the road as snow and ice melt, properly applied dust control treatments tend to remain bound in the stabilized road surface for extended periods of time. Quantities washed into the environment are typically very dilute. Magnesium chloride and calcium chloride, as well as sodium chloride (road salt) are all soluble in water and therefore can dissolve in wet weather and be transported into ground or surface waters. The tendency of salts to migrate from roads to ground and surface water depends on the application rate of the chloride; the composition and type of soil; the type, intensity and amount of precipitation; and the drainage of the road system.1 This underscores the importance of using quality gravel and proper application procedures.
While many studies of salt concentrations in ground and surface water near roadways have been related to highway deicing, a United States Department of Agriculture (USDA) Forest Service sponsored study of dust control in the western U.S., included measurement of chloride levels in the Tucannon River in western Washington before and after calcium chloride was applied on the adjacent Tucannon River Road. The study found there was no significant change in calcium- or chloride-ion levels in the river. Soil samples taken before and after treatment showed increases in chloride levels remained below thresholds for concern.2
Impact on Health and Safety
When properly handled and applied, calcium chloride does not pose a significant risk to health and safety. See Material Safety Data Sheets (MSDS) for individual products to review complete health and safety information. Calcium and chloride are considered essential constituents in the bodies of all animals and the acute oral toxicity of calcium chloride is classified as low. However, concentrations of chloride ions in drinking water are considered a health risk and subject to EPA regulation when they exceed 250 mg/l (based on U.S. EPA National Recommended Water Quality Criteria: 2002, EPA-822-R-02-047, November 2002). In most situations, the potential for contamination of drinking water supplies from calcium chloride dust suppression treatments is small as long as proper application procedures and recommended product application rates are followed. Concentrations of chloride ions detected in cased wells near treated roads are typically well below the EPA limit.
Because dry calcium chloride releases heat as it dissolves, proper protective equipment should be worn when mixing the material into solution. Protection against dust in enclosed areas and skin contact are also advisable to avoid potential irritation. Also see Calcium Chloride: A Guide to Handling & Storage.
Impact on Vegetation
Calcium is a plant nutrient and a structural component of cell walls comprising 1-2 percent by weight of dry leaf matter. However, the accumulation of salts in soil can adversely affect plant physiology and morphology and over exposure to chlorides of any kind – MgCl2, NaCl, or CaCl2 – can injure trees and other foliage. Leaf scorch and other injuries to trees and vegetation have been reported along roadsides where calcium chloride and magnesium chloride were sprayed for dust control.1,3 The likelihood of damage to vegetation can be significantly limited if dust control applications follow current recommended and standard practices. On four projects studied by the USDA Forest Service, samples taken from conifers close to treated roads showed some increase in chloride levels but not in an amount posing a long-term threat to vegetation survival. Photos of the trees taken over a period of two years revealed no discernible difference in the trees.2
Impact on Vehicles and Equipment
Noticeable corrosion of vehicles and equipment is unlikely to occur when the vehicles are driven on unpaved surfaces treated with calcium chloride. The calcium chloride is present in small amounts and tends to stay bound to the soil in the road, so there is little chance for significant contact with metal on a passing vehicle. Calcium chloride is readily soluble in water and vehicles can be easily cleaned after exposure to the material. Dust control application equipment should be thoroughly cleaned of calcium chloride residue after use as a preventative measure.
Impact on Pets & Wildlife
Animals are more tolerant of high salinity water than humans. Water with chloride levels as high as 1,500 – 2,000mg/l has been designated as suitable for livestock and wildlife in the western U.S and in some other areas of the world. Far higher levels are deemed acceptable for sustaining domestic animals.1 This suggests that levels of chlorides released into adjacent water under properly administered road dust treatment programs do not pose a significant threat to pets and wildlife.
1Road Dust Suppression: Effect on Maintenance Stability, Safety and the Environment Phases 1-3, J.Q. Addo, T.G. Sanders, M Chenard, May 2004.
2Surface-Aggregate Stabilization with Chloride Materials, USDA Forest Service, S. Monlux and M.R. Mitchell, December 2006.
3Condition of Soils & Vegetation Along Roads Treated with Magnesium Chloride for Dust Suppression, B.A. Goodrich, R.D. Kiski, W.R. Jacobi, September 2008.