Winter maintenance operations include removing snow and ice from roads through application of anti-icing and deicing products and traction materials, and plowing operations to make the road safe and passible for the driving public. Applying snow and ice control products prevents the bond between ice and pavement from forming or breaks it once it has occurred so that snow and ice is easier to remove with plowing. Approximately 70% of US roads are located in snowy regions, with nearly 70% of the US population living in these regions (FHWA, 2012b). Winter maintenance operations require roughly 20% of state Department of Transportation (DOT) budgets, spending more than $2.3 billion annually. This equates to approximately 15 million tons of deicing salt used each year (EPA, 2010). More effective use of winter maintenance products and efficient practices could result in significant economic, environmental, and social benefits.
Since the 1960's research in the areas of winter maintenance related corrosion and environmental impacts has occurred, and in the 1990's a shift in winter maintenance practices began to not only consider the initial cost of operations, equipment and products used, but to also consider the cost of the impacts to infrastructure and the environment. DOTs typically specify and test for heavy metals, pH, nitrogen/nitrates, etc. for all products used for winter maintenance and try to avoid overuse of all materials. Managing the environmental effects of winter maintenance operations can be accomplished through appropriate salt management. In Canada, a five year scientific assessment of road salts was conducted and it was determined that sufficient concentrations pose risks to plants, animals, and the aquatic environment. In response a Risk Management Strategy for Road Salts was developed to assess the risks associated with road salts and a Code of Practice was developed to provide recommendations for road authorities, including preparation of salt management plans that identify actions to improve salt storage, general use on roads and snow disposal practices (Environment Canada, 2007). A working group of members of Environment Canada and the Road Salt Working Group created the first manual titled Synthesis of Best Practices, Snow Storage and Disposal composed of current and effective practices used internationally. The manual provides local municipalities with basic guidelines that can then be tailored to fit their site specific needs. The Transportation Association of Canada (TAC) is currently working to update this manual which is heavily cited in this chapter as (TAC, 2003).
Table 8.1. Top 10 practices identified by survey respondents.
||Monitoring and Keeping Records of Maintenance
DOTs are now seeking out sustainable practices through the use of newer technology to realize cost savings while maintaining the same or better level of service (LOS). Winter maintenance practitioners were surveyed and over 50% stated that technology, tools and methods implemented in the last 10 years was for cost saving purposes and has had the side benefit of reducing the amount of winter maintenance products used. Table 1 provides a list of the top 10 approaches implemented or modified by surveyed practitioners in the last 10 years. The identified practices, or proactive approaches, can be used alone or in conjunction with one another to reduce the amount of winter maintenance products used, lost or wasted.
Reactive approaches which remove deicers following application can be costly to construct and maintain and often shifts the location of the burden of the deicers or abrasives by moving it to a retention pond or off site to a water treatment facility (Fay et al., in review). Additionally once anti-icing and deicing products go into solution, removing the products or the associated anions (e.g., chloride (Cl-)) can be challenging, as chloride ions will not break down over time and cannot be easily treated or removed from the environment. For this reason, the standard practice seems to be to simply dilute the solution not remove it.
The transition to reduced salt usage has been facilitated by great improvements in snow fighting equipment and technology in recent years. Equipment is available to facilitate precise, controlled applications of material, at reduced rates established as a result of extensive research and testing. While much of this new equipment is more sophisticated, durable, and easier to use, the potential benefits can be best realized if maintenance staff are thoroughly trained, material use is closely monitored, and feedback systems are in place. Increasingly, application rates are being tied into sensor based information systems including real time data, weather forecasts, road friction measurements, road surface temperature measurements, and global positioning equipment. As the use of this technology evolves, considerable planning, organization, and evaluation are required to ensure the best use of existing technology. Many DOTs are also taking a closer look at sensitive areas, for special consideration and/or altered practices (Montana DOT, 2002; Staples et al., 2004; Levelton Consultants, 2007; Fay et al., in review).
This chapter on environmental stewardship practices in winter operations will review the products commonly used in winter maintenance operations and their associated environmental impacts, and strategic planning and practices for reduced salt usage. Initiatives lead by DOTs, and practices and accomplishments in specific program areas to achieve such reductions and improve environmental outcomes are presented throughout the chapter.