v>EPA
United States
Environmental Protection
Agency
Office of Water
Washington, D.C.
EPA832-F-99-016
September 1999
Storm Water
Management Fact Sheet
Minimizing Effects from Highway Deicing
DESCRIPTION
The United States is critically dependent on its road
system to support the rapid, reliable movement of
people, goods, and services. Even in the face of
winter storms, we expect roads and highways to be
maintained to provide safe travel conditions. In
many states, this requires substantial planning,
training, manpower, equipment, and material
resources to clear roads and streets throughout the
winter.
The dependency on deicing chemicals has increased
since the 1940s and 1950s to provide "bare
pavement" for safe and efficient winter
transportation. Sodium chloride (common table
salt) is one of the most commonly used deicing
chemicals. Concern about the effects of sodium
chloride on the nation's environment and water
quality has increased with this chemical's usage.
Automobile and highway bridge deck corrosion has
also become a concern. However, in most cases
sodium chloride is the most cost effective deicing
chemical. Such concerns have led to maj or research
efforts by the Strategic Highway Research Program
(SHRP), the highway community, industry,
government, and academia. This ongoing research
is exploring many different areas in an effort to
maintain the safest roads possible in the most
economical way while protecting the environment.
This fact sheet summarizes research addressing
water pollution and associated effects from deicing
chemicals, and describes the methods used to
control snow and ice on roadways while minimizing
impacts on the environment. Because of this topic's
breadth, sources for research and alternative
methods are listed and can be referenced for more
detail. This fact sheet emphasizes methods and
practices for snow removal that are feasible and cost
effective for local governments to implement and
that are also consistent with sound environmental
quality goals.
APPLICABILITY
Beginning in the late 1940s and 1950s, the "bare
pavement" policy was gradually adopted by highway
agencies as the standard for pavement condition
during inclement weather. The policy provided
safer travel conditions on roadways and became a
useful concept for roadway maintenance because it
was a simple and self-evident guideline for highway
crews. Dispersion of city populations into suburbs,
higher travel speeds, and growing dependence upon
automobiles for commuting and commerce
increased the need for snow and ice removal for
safer roadways (Lord, 1988). Salt was first used on
roads in the United States for snow and ice control
in the 193Os (Salt Institute, 1994). In the 1960s, the
use of salt as a deicing chemical became widespread
in the United States because salt was readily
available, effective on ice and snow, and the lowest
cost alternative (Salt Institute, 1994).
A common perception that "more is better" led to
practices of high application rates of salt. By the
late 1950s, however, damage to roadside sugar
maples (a salt- intolerant species) in New England
had given rise to concern about the widespread use
of salt. Shortly thereafter, contamination to
drinking water from wells located near unprotected
salt storage areas heightened this concern (Lord,
1988). Other adverse effects from the runoff of
road salts, including the pitting and "rust out" of
automobiles and corrosion of highway structures,
especially bridge decks (Lord, 1988) were also
becoming apparent.
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These environmental concerns have spawned a
number of research programs. The goal of this
research has been to minimize the environmental
effects of deicing while still providing a cost
effective means of clearing roadways for safe travel.
Early in the 1960s, research began on alternative
deicing chemicals, reduced chemical use, improved
operational practices, pavement heating, pavement
modification, and mechanical approaches (Lord,
1988). More recently, a "Snow and Ice Control"
study was conducted by the SHRP, a unit of the
National Research Council that was authorized by
Section 128 of the Surface Transportation and
Uniform Relocation Assistance Act of 1987 (SHRP,
1994b). The snow and ice control research included
five major initiatives: improved operational
procedures; road weather information systems;
alternative deicing chemicals; pretreatment; and
mechanical approaches. These are discussed further
in the Implementation section below.
ADVANTAGES AND DISADVANTAGES
Highway ice and snow removal is essential both to
public safety and to local and interstate commerce.
However, the traditional method of deicing roads
through the use of salt has several drawbacks. First,
the use of salt has led to degraded habitats in areas
where salt accumulates in runoff. Second, the
storage and use of salt can be expensive. In a 1988
paper, Lord estimates that 400,000 tons of salt,
approximately 5 percent of the 8 million tons used
annually in the United States is lost from uncovered
stockpiles. An estimate of $30 per ton of salt
equates to a monetary loss of $12 million dollars
each winter (Lord, 1988). A well planned and
operated snow and ice removal program is essential
to ensure public safety and to minimize
environmental effects and costs.
IMPLEMENTATION
Many initiatives have been taken to control ice and
snow on roadways while minimizing any associated
environmental effects. Several of these initiatives
are discussed below
Improved Operational Practices
Clearing roadways after winter storms accounts for
a large portion of the highway maintenance budget
for many northern states. According to the Salt
Institute's 1991 Snowfighter's Handbook, snow
removal in 33 snow belt states accounted for 16.2
percent of total highway maintenance costs and 3.6
percent of all highway expenditures (Salt Institute,
1991).
To aid highway management personnel in improving
operational practices, the Salt Institute initiated a
"sensible salting" program in 1967 (Lord, 1988).
These guidelines have evolved with technology to
include the following: planning; personnel training;
equipment maintenance; spreader calibration; proper
storage; proper maintenance around chemical
storage areas; and environmental awareness (Salt
Institute, 1994). Further information on the
"sensible salting" program can be obtained from the
Salt Institute, located in Alexandria, Virginia.
While all of these guidelines reflect key concerns,
proper storage is considered one of the most
effective in source control of deicing chemicals
(U.S. EPA, 1974a). Guidelines for siting and
designing deicing chemical storage facilities are
provided in the Manual for Deicing Chemicals:
Storage and Handling (U. S. EPA, 1974b).
In addition to reducing the amount of salt lost due
to runoff, the actual amount of salt used on the
roads can be reduced. The Regional Groundwater
Center (1995), estimated that 10 million tons of salt
are used each winter in the United States to melt
snow and ice on roads and surface streets (Regional
Groundwater Center, 1995; Salt Institute, 1994).
Salt application rates range from 300 to 800 pounds
per two-lane mile, depending on road, storm, and
temperature conditions (Salt Institute, 1994).
One of the most effective measures for reducing
chemical application has been the use of a calibrated
spreader using the optimal application rate.
Automatic controls on spreaders are recommended
to ensure a consistent and correct application rate.
The spreader should be calibrated prior to and
periodically during the snow season, regardless of
whether automatic or manual controls are used.
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Uncalibrated controls and poor maintenance are
often responsible for excessive salt use (Salt
Institute, 1994). Guidelines for the calibration of
spreaders and determination of application rates are
given in the Salt Institute's Snowfighter's Handbook
(1991) and in the EPA document Manual for
Deicing Chemicals: Application Practices (U. S.
EPA, 1974a).
Road Weather Information Systems
In an effort to maximize the effectiveness of control
efforts and to reduce costs, the SHRP has
sponsored research using road weather information
systems (RWIS) for highway snow and ice control.
Components of the RWIS include meteorological
sensors, pavement sensors, site-specific forecasts,
temperature profiles of roadways, a weather
advisor, communications, and planning (SHRP,
1993b, 1993c).
The RWIS can maximize the effectiveness of icing
and plowing efforts by pinpointing and prioritizing
roadways that need attention. It can also eliminate
unnecessary call-outs and improve scheduling of
crews based on estimates of the extent and severity
of the storm. Research indicates that the use of the
RWIS technologies can improve efficiency and
effectiveness as well as reducing the costs of
highway winter maintenance (SHRP, 1993b). Thus,
RWIS may improve snow and ice removal service.
This report concludes that road weather information
system technology may improve service. The report
recommends that every agency that regularly
engages in snow and ice control consider acquiring
some form of road weather information systems; at
a minimum, forecast services should be used.
The SHRP has also pointed out that additional
research beyond the scope of the original RWIS
project would be helpful (SHRP, 1993b).
Additional information about RWIS and intelligent
and localized weather prediction is provided in the
following SHRP manuals: Road Weather
Information Systems, Volumes 1 and 2 (SHRP,
1993b, 1993c); and Intelligent and Localized
Weather Prediction (SHRP, 1993a).
Alternative Deicing Chemicals
The most commonly used salts for deicing are
sodium chloride (NaCl) and calcium chloride (CaCl)
(Salt Institute, 1994). The eastern and north-central
sectors of the country use more than 90 percent of
the approximately 10 tons of salt used each year
(Lord, 1988). However, sodium chloride has
several drawbacks, including its harmful
environmental effects. Therefore, due to both
environmental concerns and the importance of snow
and ice removal programs in terms of public safety
and economic factors, there has been an abundance
of research on alternative deicing chemicals.
An acceptable alternative deicer must have an
effective melting range similar to salt's, and must be
cost-comparable or less expensive. One such
chemical is calcium magnesium acetate (CMA).
CMA is made from delometric limestone treated
with acetic acid. While CMA does not overcome all
the undesirable characteristics of salt, it is still an
effective deicer. CMA is frequently used because it
has less potential to affect the environment and is
not as corrosive as salt. However, to achieve the
same deicing effectiveness as salt, CMA materials
need to be applied in larger quantities. In addition,
CMA's cost exceeds salt's by a factor of 10 to 20
(Lord, 1988). Continual efforts are being made to
find a more effective production technology to
lower the cost of CMA, but these efforts have had
limited success (Lord, 1988).
Because of the growing interest in deicing
technology, the SHRP published a handbook to
standardize testing procedures used to evaluate
deicing chemicals (SHRP, 1992). Deicing chemicals
are evaluated based on their fundamental properties
(e.g., ice melting potential, thermodynamic factors),
physicochemical characteristics, deicing
performance (e.g., ice melting, ice penetration, ice
undercutting), materials compatibility, and
additional engineering parameters. Additional
information on these testing procedures is provided
in the Handbook of Test Methods for Evaluating
Chemical Deicers(SHKP, 1992).
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Pretreatment
Limited experience (mainly in Scandinavian and
other European countries) has shown that applying
a chemical freezing-point depressant on a highway
pavement prior to, or very shortly after, the start of
accumulation of frozen precipitation minimizes the
formation of an ice-pavement bond (SHRP, 1994a).
A liquid salt solution has been applied prior to a
snowfall in Scandinavia and has proven successful
for pretreatment (SHRP, 1994a). This anti-icing or
pretreatment practice reduces the task of clearing
the highways and decreases the amount of chemical
applied from that required when deicing chemicals
are applied after snow and ice have begun to
accumulate.
When properly implemented, pretreatment practices
may reduce costs and be more effective than
conventional practices. However, most state
highway agencies have not adopted pretreatment
because they are uncertain how and when to
implement it. Other concerns with pretreatment
practices include the imprecision with which icing
events can be predicted, the uncertainty about the
condition of the pavement surface, and the public's
perception of wasted chemicals. Some early
attempts to utilize pretreatment practices in the
United States have failed because of these problems
(SHRP, 1994a).
Technological improvements in forecasting weather
and in assessing pavement surface conditions, as
previously mentioned, offer the potential for
successful implementation of pretreatment.
Research during the winters of 1991-92 and
1992-93 by the SHRP indicated that a 40 percent
and 62 percent reduction, respectively, in chemical
usage was possible using pretreatment (SHRP,
1994a). Pretreatment's success depends on accurate
RWIS, a technology that is still evolving.
Development of spreaders specifically designed or
retrofitted to distribute prewetted solid material or
liquid chemicals, calibration and evaluation of
spreaders, training of maintenance personnel, and
effective communication also need further attention
to ensure the success of a pretreatment program
(SHRP, 1994a). Additional information on
pretreament is available in the SHRP manual entitled
Development of Anti-Icing Technology (SHRP,
1994a).
Mechanical and Structural Approaches
Many mechanical and design approaches have been
and are being evaluated in an effort to improve
snow and ice control practices. Some of these
attempts have been very successful, while others
have had limited success or need additional
research. This section examines several mechanical
and design approaches, including pavement heating,
pavement coatings, mobile thermal deicing
equipment, snow fences, and snowplows. This list
is not comprehensive.
Because of cost or feasibility, pavement heating and
pavement coatings have had limited success in snow
and ice removal. Pavement heating systems are
costly to install, and operational costs exceed those
of salt on the order of 15 to 30 times (Lord, 1988).
Pavement coatings involve using hydrophobic or
icephobic coatings to reduce the adhesion of ice and
snow to the roadway. Pavement coatings are
required to weaken or prevent bonding, while not
decreasing vehicle traction in no-snow conditions.
They are also required to persist in extremely harsh
conditions. Pavement coatings were generally
unsuccessful because they were unable to meet
these goals (Lord, 1988 andU. S. EPA, 1976b). A
1976 EPA Manual, Development of a Hydrophobic
Substance to Mitigate Pavement Ice Adhesion (U.
S. EPA, 1976b), describes this research. Mobile
thermal deicing equipment has also been evaluated
and determined to be impractical.
Snow fences are used to keep snow from being
blown into drifts. Studies show that snow fences
minimize costs associated with snow clearing,
reduce the formation of compacted snow, and
reduce the need for chemicals. Mechanical snow
removal costs approximately 100 times more than
trapping snow with fences (SHRP, 1991).
One concern regarding snow fences focuses on their
position and design. About 20 years ago, it was
very common to find that 4 foot picket snow fences
had buckled under the weight of accumulated snow
(SHRP, 1991). When properly designed and
positioned, a taller snow fence is more effective than
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the traditional low picket snow fence. Not only is
size relevant to the fence's performance, but so is its
weight. A lightweight plastic, for example, allows
for the construction of a portable fence up to 8 feet
tall (SHRP, 1991). A 15-foot-tall snow fence used
in Wyoming is shown in Figure 1. To minimize
improper positioning and design of snow fences, the
SHRP has provided publications such as Design
Guidelines for the Control of Blow ing and Drifting
Snow (SHRP, 1994b), Snow Fence Guide (SHRP,
1991), and a 21-minute video entitled "Effective
Snow Fences."
Snowplow designs in the United States have
evolved empirically. These designs, however, have
neglected to incorporate the effects of the physical
properties of the materials handled by the plow and
the aerodynamic and hydrodynamic principles
involved in the flow of fluidizing snow.
Consequently, more energy is expended in
displacing snow than is necessary, and the short cast
distance necessitates rehandling of the snow (Lord,
1988). The SHRP has funded research at two
universities to improve development of plow blade
design and cutting edges for the plow blades
(SHRP, 1991). The first research project,
conducted by the University of Wyoming
Department of Mechanical Engineering, focused on
developing an improved snowplow blade that
minimizes energy needed to throw snow clear of the
roadway. The plow design, based on analytical
methods and laboratory scale experiments, showed
a 20-percent improvement in efficiency over
conventional plows. The plow underwent testing in
West Yellowstone, Montana during the winter of
1990-1991 (SHRP, 1991). Research for additional
technological advances in plow design is ongoing.
Another research project, conducted by the
University of Iowa Institute of Hydraulic Research,
sought to improve snowplow efficiency by
improving cutting edges of plow blades (SHRP,
1993e). Laboratory tests were performed with a
hydraulic ice-cutting ram to determine the effects of
the geometry of the cutting edge of a snow plow
blade on the force required to remove ice from a
highway pavement surface. Results of this research
indicate that changes in the cutting edge geometry
result in substantial improvements in ice cutting;
cutting edge performance may still benefit from
further studies (SHRP, 1993e). An Iowa
Source: Reprinted with permission, Tabler and Associates, 1972.
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Department of Transportation "plowing truck"
cutting ice is shown in Figure 2. Additional
information can be obtained in the SHRP manual
entitled "Improved Cutting Edges for Ice Removal"
(SHRP, 1993e).
COSTS
The United States and Canada spend over $2 billion
dollars each year on snow and ice control (SHRP,
1993b). However, very little cost data has been
generated to show the direct costs of, or the cost
reductions due to, the specific snow removal
alternatives and process improvements discussed in
this fact sheet. Some cost information has been
generated for alternative deicing chemicals. NaCl is
both the most common and the most cost-effective
deicing agent, with costs per ton ranging from $17
to $30 (Lord 1988; Jesperson, 1995). The
Michigan Department of Transportation drew this
conclusion in a recent evaluation. The evaluation
examined the costs of sodium chloride (road salt),
CMA, CMS-B (also known as Motech), CG-90
Surface Saver (a patented corrosion-inhibiting salt),
Verglimit (patented concrete surface containing
calcium chloride pellets), and calcium chloride
(MOOT, 1993). Most of the alternative deicers
ranged in cost from $200 to $700 a ton (Jesperson,
1995), and were thus significantly more expensive
than sodium chloride.
REFERENCES
1. Jesperson, K., 1995. "Road Salt and
Groundwater, Is It a Healthy Combination?"
On Tap, Volume 4, Issue 2.
2. Lord, B.N., 1988. Program to Reduce
Deicing Chemical Usage, Design of Urban
Runoff Quality Controls.
3. Michigan Department of Transportation
(MOOT). 1993. The Use of Selected
Deicing Materials on Michigan Roads:
Environmental and Economic Impacts.
Lansing, MI.
Source: Iowa Institute of Hydraulic Research, 1993.
FIGURE 2 A PLOWING TRUCK CUTTING ICE
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4. Regional Groundwater Center, University of 15.
Michigan, 1995. Water Fact listed in On
Tap, Spring 1995, Volume 4, Issue 2.
5. Salt Institute, 1991. "The SnowFighter's 16.
Handbook. Alexandria, Virginia, 1991.
6. Salt Institute, 1994. Deicing Salt Facts: A
Quick Reference. Alexandria Virginia.
17.
18.
19.
20.
7. Strategic Highway Research Program
(SHRP), 1991. Snow Fence Guide. SHRP
- National Research Council, Washington,
D.C., SHRP-W/FR-91-106.
8. SHRP, 1992. Handbook of Test Methods
for Evaluating Chemicals Deicers. SHRP
- National Research Council, Washington,
D.C., SHRP-H-332.
9. SHRP, 1993a. Intelligent and Localized
Weather Prediction. SHRP - National
Research Council, Washington, D.C.,
SHRP-H-333.
10. SHRP, 1993b. Road Weather Information
Systems, Volume 1: Research Report.
SHRP - National Research Council,
Washington, D.C., SHRP-H-350.
11. SHRP, 1993c. Road Weather Information
Systems, Volume 2: Implementation Guide.
SHRP -National Research Council,
Washington, D.C., SHRP-H-351.
12. SHRP, 1993d. SHRP Innovations - Snow 22.
and Ice Control. H-200 Series Contracts,
No.20. Video - 12:41 minutes, SHRP-
National Research Council, Washington,
D.C.
21.
SHRP, 1994b. Development of Anti-Icing
Technology. SHRP - National Research
Council, Washington, D.C., SHRP-H-385.
Tabler, R., 1972. Evaluation of the First
Year Performance of the Interstate 80 Snow
Fence System. Prepared for Wyoming
Department of Transportation.
U. S. EPA, 1971. Environmental Impact of
Highway Deicing. Water Quality Office,
Edison, New Jersey, 11040 GKK 06/71.
U. S. EPA, 1972. A Search: New
Technology for Pavement Snow and Ice
Control. Office of Research and
Development, Washington, D.C.,
EPA-R2-72-125.
U. S. EPA, 1974a. Manual for Deicing
Chemicals: Application Practices. Office
of Research and Development, Cincinnati,
Ohio, EPA-670/2-74-045.
U. S. EPA, 1974b. Manual for Deicing
Chemicals: Storage and Handling. Office
of Research and Development, Cincinnati,
Ohio, EPA-670/2-74-033.
U. S. EPA, 1976a. An Economic Analysis
of the Environmental Impact of Highway
Deicing. Office of Research and
Technology, Cincinnati, Ohio,
EPA-600/2-76-105.
U. S. EPA, 1976b. Development of
Hydrophobic Substance to Mitigate
Pavement Ice Adhesion. Office of Research
and Development, Cincinnati, Ohio,
EPA-600/2-76-242.
13. SHRP, 1993e. Improved Cutting Edges for
Ice Removal. SHRP - National Research
Council, Washington, D.C., SHRP-H-346.
14. SHRP, 1994a. Design Guidelines for the
Control of Blowing and Drifting Snow.
SHRP - National Research Council,
Washington, D.C., SHRP-H-381.
23. U.S. EPA, 1978. Optimization and Testing
of Highway Materials to Mitigate Ice
Adhesion (Interim Report). Office of
Research and Development, Cincinnati,
Ohio, EPA-600/2-78-035.
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ADDITIONAL INFORMATION
Center for Watershed Protection
Tom Schueler
8391 Main Street
Ellicott City, MD21043
City of Hartford, Connecticut
Denise Horan
Metropolitan District Commission, Engineering and
Planning Department
555 Main Street, P.O. Box 800
Hartford, CT 06142-0800
Massachusetts Highway Department
Clem Fung
Research and Materials Group
400 D Street
Boston, MA 02210
State of Minnesota
Lou Flynn
Minnesota Pollution Control Agency
520 Lafayette Road North
St. Paul, MN 55155
Southeastern Wisconsin Regional Planning
Commission
Bob Biebel
916 N. East Avenue, P.O. Box 1607
Waukesha, WI53187
The mention of trade names or commercial products
does not constitute endorsement or recommendation
for the use by the U.S. Environmental Protection
Agency.
For more information contact:
Municipal Technology Branch
U.S. EPA
Mail Code 4204
401 M St., S.W.
Washington, D.C., 20460
!MTB
Excdence Ih compliance through optltaal technfcal sokrtfons
MUNICIPAL TECHNOLOGY BRANCH^
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