Whe we use the salt

1. Why We UseHighway Salt?

Environmental protection, properly, is a high public priority. So is roadway safety and mobility. In our complex society, the public demands that governments keep traffic flowing smoothly and minimize the tragedy of car crashes. This is an economic

necessity, not to mention good customer service for roadway maintenance organizations.

Roads and highways must remain operational and safe even during adverse winter weather conditions. Medical emergencies like heart attacks and accidents including home fires and auto crashes occur all year long. In an emergency, a few

minutes of response time is often a matter of life or death.

The fastest, least expensive and most effective method of coping with winter’s ice and snow is highway salt. As early as 1970 the Highway Research Board concluded that

there were no reliable or economical substitutes for salt in the foreseeable future. Its

study determined that environmental concerns are site specific and could be alleviated

by proper storage, handling, application, drainage and landscaping. Since that time,

highway departments have addressed these areas, and detrimental effects of deicing

salt on the environment have been significantly reduced.

Today, thousands of municipal, state and provincial transportation agencies rely on

deicing salt to assure wintertime mobility and safety. They must have a safe, reliable

and economic means of clearing ice and snow, since, in the absence of specific protective

legislation, they may be liable for their (perceived or real) failure to keep streets

and roads in safe condition. One claim in Canada, alleging failure to provide safe and

passable roadways cost the Province of Ontario $4.5 million.

An important role of the Salt Institute is to assist states, provinces, counties and

municipalities throughout the United States and Canada, and the contractors they often

employ, in developing state-of-the-art snow and ice control programs. The Salt

Institute also encourages proper salt management by private contractors responsible for

clearing private roads, such as on college campuses and parking lots at shopping malls,

factories and businesses.

This brochure will explain why snow fighters use highway salt, how salt works, the

effects of highway salt on the environment, infrastructure and motor vehicles, and

application techniques to minimize adverse environmental impacts.

Sensible Salting Saves Lives

Snow and ice on streets and highways are a major threat to human life and limb.

Traffic accidents and fatalities climb as snow and ice reduce traction on roadways.

Lengthened emergency response times create additional risks for persons in urgent need of medical care, particularly in cases of heart attacks, burns, childbirth and

poisoning.

In the early 1990s, a study by the Marquette University Center for Highway and

Traffic Engineering in four snowbelt states examined the safety impacts of salt-based

winter maintenance. The study documented an overall accident reduction of 85% and

an even greater reduction in injury accidents, 88.3%.

1.2 Snowstorms Can Disrupt Economic Activity

As in the link of winter maintenance to traffic safety, studies have documented the vital

economic role of clearing roads of ice and snow. Ice and snow also cause higher fuel

cost as cars lose traction and spin their wheels to travel a given distance. A car that

normally gets 25 miles per gallon may get only 15 mpg on a slippery road. Snow and

ice storms have significant economic and social consequences that are tempered by

winter programs designed to keep roads operable. Failure to get snowplows out and

salt on the roads during a single day of a winter storm costs almost three times more in

lost wages than the total annual costs for snowfighting.

In just 12 states, this study found that $526.4 million a day in federal, state and local

tax revenues would be lost if impassable roadways paralyzed the region. This is more

than the $518.7 million spent by these twelve states for the entire winter season on

snow and ice control to keep the roadways mobile and safe. Lost taxes are not the

biggest economic hit to these states, according to the study. In addition, a crippling

snowstorm costs $1.4 billion per day in unearned wages and $600 million per day in

lost retail sales. To show how these losses could quickly multiply with each snowstorm,

in the Chicago area, a normal winter averages 20-30 snowstorms requiring

winter maintenance, and in New York State there are 40 average snowstorms statewide.

Even these dramatic figures are conservative. Not covered by the Standard & Poor’s

DRI study were factors such as vehicle crashes - fatalities, injuries and property damage, and increased health and insurance costs. These very real costs of inadequate

winter maintenance were beyond the scope of this study.

The new analysis confirms other earlier studies of economic disruption. In 1996,

Standard & Poor’s DRI calculated that the Blizzard of ’96 cost the Eastern states as

much as $10 billion in lost production and $7 billion in lost sales for 4 days of being

shut down, losses caused by the fact that people could not get to the store or to work.

First Union Corp. estimated the same blizzard cost, measured in lost goods and

services produced by factories, offices, shops, and other enterprises at about $4.8

billion per day in the Northeast corridor of the U.S. from Virginia to Massachusetts.

We can’t prevent snow and ice, but we can prevent much of the economic calamity

they can cause. Winter storms may be unpredictable and unique, but investments in

professional snowfighting can keep snow- and ice-storms from paralyzing local

economies, keeping children home from school and preventing emergency vehicles

from making their lifesaving trips. Good winter maintenance keeps the roads open and

saves lives. It is possibly the single most cost-effective investment of our highway tax

dollars, returning at least $60 in benefits for every dollar spent.

1.3. Why Salt Works Best

Most ice storms and snowstorms occur between 20° F and 32° F. Often after the storm

breaks, high pressure systems move in and temperatures plummet, sometimes to well

below freezing. So, it is important to apply salt early during the storm when salt will be

most effective as a melting agent and will prevent ice and hard pack from bonding to

the pavement.

The melting action of salt forms brine at the ice pavement interface. Brine prevents

water from freezing into ice and bonding to the pavement and destroys the bond

between ice and pavement. Once bonded to the pavement, ice cannot be removed by

plowing without damaging the road surface or plowing equipment. Salt is used

because it lowers the freezing point of water. If not applied before the storm as an

anti-icing treatment to prevent a bond between ice and pavement, salt is usually

applied as a deicer in conjunction with plowing because it will penetrate snow and ice

left on the pavement. Salt must sometimes be used alone when there is insufficient

snow accumulation to permit plowing. Often, salt is applied with liquid salt brine or

pre-wet with other melting agents both to prevent the salt from bouncing off the

roadway surface and to speed its melting effectiveness. The action of vehicle tires,

combined with salt, will break up hard snow and ice, and gradually move it toward the

pavement’s edge.

Highway agencies report that deicing salt is most effective at temps above 12. F (-11.

C) but it continues to melt ice and snow, although at a slower rate, to temperatures

approaching the eutectic temperature of -6. F (-21. C). Calcium chloride and magnesium

chloride, which melt ice better at much lower temperatures, can be added to

deicing salt for more rapid and effective melting when the temperature really dips.

Why not use calcium chloride or magnesium chloride all the time? Because they are

far more expensive than sodium chloride.

1.4.Other Materials (Should) Have Limited Application

Abrasives

Sand and other abrasives have been used in an attempt to avoid perceived environmental

effects of salt. However, abrasives are inert substances that provide limited traction.

Abrasives are not melting agents. They must be used in large quantities and applied

frequently, making abrasives more expensive than salt in terms of material and manpower.

Salt is frequently added to abrasives to prevent freezing. After years of experience,

for example, the City of Milwaukee, WI concluded:

“… Although the use of abrasives like sand instead of salt can be effective in

rural areas and smaller communities, heavy traffic volumes in urban areas

quickly pound down and bond untreated snow into hardpack that is extremely

difficult to remove. It takes four to seven truckloads of abrasives to treat the

same number of lane miles as one truckload of salt, and abrasives must be

reapplied frequently. Sand builds up in catch basins and sewers, necessitating

expensive cleanup.”

After natural melting has occurred, abrasives create after-the-storm hazards. On a dry

surface, abrasive materials can become a spinning-skidding hazard until road crews

remove it. Windshield damage from airborne particulates is 365% higher in areas

using sand and abrasives instead of salt. In Denver, Colorado, annual claims were

$27.1 million, and claims reached $59.6 million throughout the entire state. A build

up of abrasives can create problems such as unhealthy dust, smothered roadside

vegetation, silted waterways, plugged storm drains, and costly Spring clean-up costs.This led an environmental advocacy group to conclude:

“The main disadvantage associated with abrasives is their lack of staying

power. When applied to heavily traveled areas, sand tends to be kicked off the

roads. Therefore, it must be reapplied more frequently than road salt. Sedimentation

caused by sand run-off into lake and riverbeds and roadside drainage

ditches can create environmental problems which require occasional

dredging. …”

Another study by the Marquette University research group determined a safety

benefit:cost ratio 15 times greater when using salt than using salt/abrasive mixtures for

winter highway maintenance. Using salt to restore safe driving conditions pays for

itself at least 10 times faster than using a salt/abrasive mixture. On 2-lane roads, salt

paid for itself in the first 25 minutes after achieving bare pavement, while using salt/

abrasive mixtures did not pay for itself in the 12 hours after the period studied; for

freeways, the payback required only 35 minutes for salt compared to six hours for salt/

abrasive mixtures.

Other chloride deicers

The most popular “alternatives” to common salt (sodium chloride) are the other

chloride salts. Calcium chloride and magnesium chloride are used to melt snow and

ice more quickly at lower temperatures. They are often combined with salt to make a

more effective deicing mixture. They cost more and also contribute chloride ions to

the environment, but they enjoy operating advantages in certain storm conditions as

can be seen in the following table

Table 1 – Ice Control Chemicals

Deicing Chemical	Eutectic Temp. (F)	Concentration At Eutectic (%)	Cost Comparison
Calcium Chloride	-67	29.8	7x
Calcium & Sodium Formate	+11	32.6	17x
Calcium and Magnesium Acetates	+5/ -22	44 / 31	35x
Ethylene Glycol	-60	60	28x
Magnesium Chloride	-28	21.6	7x
Methanol	-144	100	10x
Potassium Chloride	+13	19.5	4x Greater
Propylene Glycol	-71	60	28x
Sodium Chloride	-6	23.3	1
Urea	+11	32.5	7x

As Table 1 shows, some organic chemicals have also been used to melt snow and ice.

Organics melt ice more slowly and at a higher working temperature range. They are

chosen to avoid using the chloride ion although many “alternatives” are designed to be

mixed with chlorides, enhancing their melting effectiveness. Organics also impose

(different) environmental stresses and cost significantly more than salt.

Urea, a fertilizer, adds nutrients to surface water and hastens eutrophication that also

reduces available oxygen. Calcium magnesium acetate (CMA) can also reduce

available oxygen. Recent research involving liquid CMA and a few otherliquid deicers indicated

high biochemical oxygen depletion levels meaning these

alternatives were more toxic to fish than salt brine. As the search continues for an

environmentally-friendly alternative to salt, careful studies are required to compare

these proposed substitutes with the well-understood impacts of highway salt.

Using highway salt involves trade-offs: reducing the risk of accident and injury to drivers and the economic consequences of a weather-related economic shut-down versus the risk of injury to roadside vegetation, wildlife and water quality. Fortunately,

through Sensible Salting, the environmental downside can be mitigated while preserving

the social and economic benefits of proper winter maintenance. “Use of road salt

(sodium chloride) is both cost-effective and environmentally acceptable at current

levels,” according to a study commissioned by the Michigan Department of Transportation.

The Transportation Research Board of the National Academy of Sciences

agrees – salt will remain the deicer of choice when all the alternatives are examined.

Used sensibly, salt is the best means of providing safe roads in winter.