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Anti-icing.

Part One

The pressure to provide more efficient winter maintenance services is increasing. Working to do more with less is compounded by increasing concerns about the impact of winter operations on ground, water, and air quality. The focus on these issues is causing many transportation agencies to evaluate new winter road maintenance practices. Anti-icing is one practice that is gaining considerable attention and trial.

Anti-icing is the practice of applying a chemical freeze-point depressant to the road surface before or during the initial part of a storm event. The primary objective of anti-icing is to prevent the bond between snow/ice and the pavement surface.

It is critical to point out that anti-icing is not a cure-all for winter road maintenance. As with all tools, use it when appropriate. Anti-icing provides public works agencies the opportunity to lower total costs, increase service levels, and reduce the environmental impact of winter maintenance.

The documented benefits of anti-icing range from a ratio of 2:1 up to 11:1. The benefit comes from using less material, labor, and equipment time to provide the same, or better, level of service.

Sand reduction is one way to gain significant cost savings. The total cost to purchase, store, maintain, and spread sand is significantly greater than the purchase price alone. Furthermore, when you include cleanup operations after the storm or winter season, the total cost of sand skyrockets.

One state that has begun documenting the total cost of winter maintenance is Washington State. In its report Experiments with Anti-icing in Washington State[1], the state tracks the total cost (by line item) of anti-icing and the state's traditional practices.

The Washington State Department of Transportation documented case studies where the benefit-to-cost ratios range from 2:1 to 9:1 (not including the cost to clean up sand). The range increases to 3:1 to 11:1 when sand cleanup was included.

The traditional winter road maintenance practice is deicing, or the removal of snow and ice from the road surface. Often the standard operating procedure is to wait until there is a given amount of accumulation on the road, then salt, sand and/or plow. This reactive approach has one inherent problem: there is at least one point in every storm when traction is reduced due to snow or ice on the road, and the risk of an accident occurring is increased.

On the other hand, the objective of anti-icing is to prevent the bond from forming between snow pack and the road surface. This allows users to eliminate or reduce snow pack in two basic fashions. First, snow pack may not occur due to the melting process alone. Second, if snow pack does occur, but a bond has not formed, then plows can drop to the road surface to easily remove any buildup.

In the Federal Highway Administration's Manual of Practice for an Effective Anti-icing Program[2], the authors point out that anti-icing is a preventive practice that "provides the maintenance manager with two major capabilities: the capability for maintaining roads in the best conditions possible during a winter storm, and the capability to do so in an efficient manner.... Anti-icing has the potential to provide the benefit of increased traffic safety at the lowest cost."

Increased service levels benefit not only the driving public, but the maintenance crews as well. Anti-icing applications are made before or during the early part of a storm event. Therefore, your crews realize the benefit of working on bare and dry roads too.

Environmental Perspective

From an environmental standpoint, anti-icing has several positive impacts. Anti-icing enables the winter maintenance crew to provide the same or better service level with less material. Given the proactive nature of anti-icing, keeping an ice-to-pavement bond from occurring requires less material than removing the bond once it is in place. Less material on the roads means less material contacts vehicles, roadside vegetation, and water sources.

In addition, anti-icing reduces or eliminates the need for sand. Sand is detrimental to the environment in two ways: road sand enters water drains that can run off to streams, and road sand is a major contributor to high particulate matter (PM-10) levels. Less sand on the road means less sand in the drains and streams, and less particulate matter in the air.

Anti-icing applications are typically a liquid product applied to the road surface before the storm. Anti-icing also can be accomplished using dry materials. However, road traffic can limit the amount of material that stays on the road before the storm.

Use of liquid materials allows for control of application in two fashions: control over the exact amount of material on the road, and control of where the material is applied. This practice is not new. It is the same technology the agricultural industry has been using for decades to apply fertilizers and herbicides.

Small volumes of liquid material provide effective coverage with the active melting ingredient until it dilutes out. A common initial application rate is 30 gallons per lane mile. The liquid becomes the carrier for the active ingredient allowing operators to place the material only on desired locations. The liquid settles on the porous road surface where it stays until it begins working when the storm arrives.

A common issue with the application of dry products is the loss of product to bounce and scatter during application and in passing traffic. With the use of liquids, traffic benefits the application by tracking material where it is needed most: the driving lanes.

Keys to Getting Started

The first key to getting started with an anti-icing program is educate operators on anti-icing and how ice-control materials work. It also involves educating the public on new winter practices.

The second key is to establish realistic expectations. Anti-icing is not a cure-all. Properly used, it is the first in a series of strategies and tools for each winter storm event. The effective and efficient use of anti-icing is a learning process. There is no replacement for education and experience. Anti-icing has proven successful; it is our ability to effectively use it that is to be determined.

The third key is to learn from other users. Many transportation agencies have used anti-icing technology for several years, and can be helpful to you. Anti-icing is also a presentation topic at almost every winter maintenance conference.

The demands on winter maintenance resources are growing. Anti-icing is a growing technology that is helping transportation agencies increase service levels, lower maintenance costs, and reduce environmental impact.

"Anti-Icing Part II: Hitting the High Points" is scheduled for publication in the February issue of Public Works.

References

1. Experiments with Anti-Icing in Washington State: D. Dye, H. Krug, D. Keep, & R. Willard (Washington State DOT); January 1996.

2. Manual of Practice for an Effective Anti-icing Program: A Guide for Highway Winter Maintenance Personnel. S. Ketcham, L. Minsh, R. Blackburn, E. Fleege; Publication No. FHWA-RD-95-202; June 1996.

Mr. Scott Barger is a Market Development Specialist with Great Salt Lakes Minerals Corporation, Overland Park, Kansas.
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Title Annotation:Relieving the Pressure.; winter maintenance services; part I
Author:Barger, Scott
Publication:Public Works
Date:Jan 1, 1997
Words:1169
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