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May 1976
Environmental Protection Technology Series
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five "Broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are: ;
1. Environmental Health Effects Research
2. Environmental Protection Technology
3, Ecological Research
4. Environmental Monitoring '.
5, Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-105
May 1976
AN ECONOMIC ANALYSIS OF THE ENVIRONMENTAL IMPACT
OF HIGHWAY DEICING
by
Donald M. Murray and Ulrich F. W. Ernst
Abt Associates Inc. •
Cambridge, Massachusetts 02138
Contract No. 68-03-0442
OMB Clearance No. 158S 74012
Project Officer
Hugh E. Masters
Storm and Combined Sewer Section
Wastewater Research Division
Municipal Environmental Research Laboratpry (Cincinnati)
Edison, New Jersey 08817
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommendation
for use.
ii
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FOREWORD
The Environmental Protection Agency was created because of increasing public
and government concern about the dangers of pollution to the health and
welfare of the American people. Noxious air, foul water, and spoiled land
are tragic testimony to the deterioration of our natural environment. The
complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solution
and it involves defining the problems, measuring its impact, and searching
for solutions. The Municipal Environmental Research Laboratory develops new
and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment of
public drinking water supplies, and to minimize the adverse economic, social,
health, and aesthetic effects of pollution. This publication is one of the
products of that research; a most vital communications link between the re-
searcher and the user community.
The study contained herein involves an extensive examination of the costs
incurred by society as a result of the use of highway deicing chemicals.
The costs, which are examined separately for damage to each sector of the
natural environment and to manmade goods, are shown to be substantial.
Francis T. Mayo
Director
Municipal Environmental
Research Laboratory
ill
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ABSTRACT
This study involves an analysis of the cost of damages that res.ult from the
use of salt (sodium chloride and calcium chloride) on highways to melt
snow and ice. A large literature search and several surveys were carried
out to determine the types and extent of damages that have occurred. The
report contains a Bibliography with over 320 references. :
An in-depth analysis was performed on all of the data obtained. The major
cost sectors examined were: water supplies and health, vegetation, highway
structures, vehicles, and utilities. For each of the sectors, a cost estimate
was developed. The total annual national cost of salt related dametge approaches
?3 billion dollars or about 15 times the annual national cost for salt purchase
and application. While the largest direct costs result from damages to vehicles,
the most serious damage in the long run seems to be the pollution of water
supplies and the degradation of health which may result. It is, particularly
difficult to assign costs in this latter area and therefore the estimate may
substantially understate the actual indirect costs to society.
These findings indicate that the level of salt use should be reduc€*d. The
amount of the reduction should be determined on the basis of local conditions.
This report was submitted in fulfillment of Contract No. 68-03-0442 by Abt
Associates Inc., under the sponsorship of the Environmental Protection Agency.
iv
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CONTENTS
Abstract
List of Figures
List of Tables
Acknowledgements
SECTIONS
1.0 FINDINGS AND CONCLUSIONS
1.1 Summary of Findings
1.2 Conelus ions
2.0
RECOMMENDATIONS
3.0 INTRODUCTION
3.1 The Use of Salt for Deicing
3.2 Summary of Approach
4.0 SALT RELATED DAMAGE,
4.1 Damages to Natural Resources
4.2 Damage to Man-Made Goods
5.0 THE COST OF SALT RELATED DAMAGE
5.1 Methodology
5.2 Costs of Water Supply Contamination
5.3 Costs of Damages to Vegetation
5.4 Costs of Damages to Highway Structures
5.5 Costs of Automobile Corrosion
5.6 Other Damages
5.7 The Direct Costs of Salt Application
5.8 Summary of Costs
Page
iv
vii
viii
ix
1
1
2
5
5
8
10
13
24
43
43
48
65
68
74
88
89
89
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CONTENTS (Cont'd)
SECTIONS
6.0 BENEFITS OF ROAD SALTING
6.1 Salt and Safety
6.2 Time Savings
BIBLIOGRAPHY
APPENDIX A
APPENDIX B
Page
: 91
91
94
, 95
120
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LIST OF FIGURES
Page
FIGURE
1. Fate of Salt in the Environment
2. Massachusetts - Ground Waters
3. Massachusetts - Surface Waters
4. Connecticut - Ground Waters
5. Connecticut - Ground Waters
6. New Hampshire - Ground Waters
7. Rhode Island - Surface Waters
8. Example of Deck Spall on Underside of
West Side Highway, New York City
9. Collapse of West Side Highway at Ganesvoort
Street on 12/15/73, New York City
10. Typical Stringer Web Deterioration on
West Side Highway Structure, New York City
11. Schematic Overview of Cost Generation
Framework
12. Rhode Island - Surface Waters
13. . Corrosion of Reinforcing Steel in Highway
Structures
14. Hourly Demand and Capacity
15. Cumulative Demand and Capacity
11
16
16
17
17
18
18
31
36
37
44
49
70
73
73
Vll
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LIST OF TABLES
TABLE
1 Page
1. Dimensions of Costs Associated with Salt
Contamination of Drinking Water • ', 51
i
2. Direct Costs Associated with Salt
Contamination of Drinking Water Supplies 56
3. Costs of New Hampshire Well Replacement •
Program : 60
4. Differences in Cardiovascular Death Rates
for Different Levels of Sodium in Drinking
Water (per 100,000) . 64
5. Basic Values of Shade Trees (For Perfect [
Specimen Shade Trees) 67
6. Summary of Microeconomic Costs , 70
7. Estimated Depreciation Rates for Selected
Cities 80
8. Cost of Automobile Depreciation 85
viii
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ACKNOWLEDGEMENTS
The contents of the report are a product of many contributors across
the nation, and from several foreign countries. The project staff have
been impressed by, and greatly appreciative of, the concern on the part
of hundreds of individuals and agencies which have provided valuable
information. Sincere thanks goes to all those who have helped make this
possible.
Special thanks go to Adrian Clary of the Highway Research Board and
Richard Hay of the Federal Highway Administration for their comments
on a first draft of the highway and bridge damage section. Thanks also
go to Robert C. Terry, Jr. of Arthur D. Little and The Salt Institute
for their advice and assistance. The City of New York provided some
very important reports on the damage to the West Side Highway.
This report was written by Donald M. Murray and Ulrich F. W. Ernst.
Research Assistance was provided by Judy Poole, Ramon Estrada and
Janice Darling.' Advice given by Malcolm FitzPatrick was appreciated.
Thanks go to Robert C. Anderson for his contributions, especially in the
area of bridge and automobile damage, and to Gary J. Stensland for his
work on the atmospheric content of salt. Mary Hobson displayed great
patience in typing many drafts during the production of this report and
her efforts are also appreciated.
The support of this effort by the Wastewater Research Division (Edison,
New Jersey) of the USEPA Municipal Environmental Research Laboratory,
Cincinnati, Ohio, and especially Mr. Hugh E. Masters, Project Officer,
for his guidance, suggestions and inputs, and thorough manuscript review
is acknowledged with gratitude.;
IX
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SECTION 1
FINDINGS AND CONCLUSIONS
1.1
SUMMARY OF FINDINGS
There have been a substantial number of reports of salt related damage
in the literature. Most of the reports are deficient in hard cost data.
Consequently, by examining different small subsets of the data, various
individuals have arrived at opposite conclusions: in some cases that
salt damage is insignificant and in other cases, that road salting must
be discontinued completely. Examination of all of the literature and
contact with hundreds of persons and agencies who are aware of salt
related damage has led to the finding that> in general, the damages
are very large although not uniform across all localities. Through
analysis of all of the available data, the best estimate (in many cases
the lower bound) of the annual cost to the snowbelt states that results
from the use of road salt is as follows:
Water Supplies and Health
Vegetation
Highway Structures
Vehicles
Utilities
Salt Purchase and Application
Total
Total (in millions)
$ 150
50
500
2,000
10
200
$ 2.91 Billion
Furthermore, heavy salt use in many instances upsets the natural ecological
balance resulting in damages which cannot be assigned a dollar figure.
This is one of the many reasons that the above dollar amounts must be
considered as lower bounds. The most potentially serious of all these
damages are the irreversible ones, such as the risk of increased hyper-
tension that results from the heightened levels of sodium in water
supplies. For example, groundwater supplies have been most severely
affected. Over 90 communities in Massachusetts have one or more supplies
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with a sodium content greater than 20 mg/liter, the maximum ; allowed for
persons on low sodium diets. Over 30 water supplies in Connecticut con-
tain more than 20 mg/1 sodium and the number is increasing. . As much as
5% of the population consuming water contaminated by road salt may be
adversely affected.
The use of salt for winter maintenance generally results in better trac-
tion on the highways, but because of a number of confounding factors,
especially driver behavior, the link between salt and safety has not been
proved. While several studies have reported that salt reduces accidents,
the methods of data collection and analysis have been found to be mathe-
matically unsound. •
Finally, carefully designed reduced salting policies seem to have gained
public acceptance as a result of public information programs. The most
notable case is the State of Connecticut where state salt use was reduced
by 33% because of rising sodium content in water supplies. There is
every reason to believe that the residents of individual cities and
towns or other states would accept a salt reduction if the salt related
damages were made known to them.
1.2 CONCLUSIONS :
In the past a number of claims have attempted to downgrade the serious-
ness of road salt related damage by placing emphasis on the comparisons
of the effectiveness of salt and sand, or by concentrating on the lack
of importance of vegetation in comparison to human lives (i.e., safety
on the roads). Because these claims do not address the whole problem,
they are superficial, misleading, and in a few cases, irresponsible.
The facts are:
Several states have experienced significant increases of
salt in groundwater and surface drinking water supplies
that have been directly linked to the use of deicing salts.
In particular cases, the levels exceed Public Health Service
safety standards set in 1962 and in most cases the levels
exceed the standards set by leading researchers, heart
specialists and the American Heart Association.:
The cost in terms of permanent health degradation is extremely
difficult to measure, but is likely to be very high.
The cost of actual damage to vehicles, highways and struc-
tures, utilities, and vegetation are immense. The annual
damage costs at a very lower bound, approach $3 billion.
This "hidden" cost is almost 15 times the annual national
budget for the purchase and application of road salt, and
about 6 times the entire annual national budget for snow
and ice removal.
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The implications of these facts are clear. Without a doubt the most serious
problem is our water supplies. While the cost of damage to bridge decks
and vehicles is high, but reversible, the damage to health may not be reversed.
We can no longer afford to ignore the fact that we are depositing large
quantities of salt into the water that nature provides us and upon which
are dependent every moment of our lives. The most advanced medical research
indicates that water with more than 20 mg/1 sodium is unhealthy and detrimen-
tal to a substantial fraction of the population. The American Heart Assoc-
iation supports this fact. Disregard for the quality of drinking water in
this and any instance is extreme negligence and we must face the issue
squarely. Road salt may be only one of the many serious pollutants in our
environment, but that is no excuse to allow the present situation to exist
any longer. In order to avoid further damage and high costs, salt use for
winter .maintenance must be reduced in many areas.
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SECTION 2
RECOMMENDATIONS
The level of salting should be reduced by an amount determined by local
conditions such as the effect of salt laden runoff on water supplies, the
level of public demand for bare pavement, and the size of the winter main-
tenance budget. Greater emphasis should be placed on non-chemical methods
of snow and ice control (such as increased plowing and sanding.) Determin-
ation of the required level of bare pavement is a burden that should not be
the sole responsibility of highway maintenance departments. The depart-
ments should seek advice from all interested groups and the public at large
in order to achieve the best possible level of road maintenance within
given environmental constraints. Through public affairs programs, the
public should be made aware of the tradeoffs and alternatives involved.
Changes to winter road policies should have public support and should be
given a thorough public announcement before they are commenced.
There should be a greater emphasis on the training of drivers so that
they will have the ability to drive under conditions of snow.and ice, and
less emphasis on the concept of guaranteed "June travel in January".
Moreover, an operating policy to encourage motorists to stay off the roads
during and immediately after storms would facilitate snow and ice removal.
Restricted driving under short term emergency snow conditions should be
considered.
The snow belt states should provide for testing of public and private
water supplies, and should provide funds for replacement of public and
private wells (as has been done in the State of New Hampshire). State
legislation should be passed allowing individuals to have standing in
court to sue for damages when water supplies show an abnormal and hazar-
dous increase in sodium content. The law should place the burden of
proof on the highway departments that the cause was not from'road salt.
Finally, the states should consider instituting a requirement that all
salt users file an Environmental Assessment.
While these measures may seem burdensome, they are necessary in order to
insure that we maintain our high quality of water and that large costs
are not incurred as a result of winter highway policies. ;
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SECTION 3
INTRODUCTION
3.1
THE USE OF SALT FOR DEICING
Extensive use of salt, both sodium chloride (NaCl) and calcium chloride
(CaCl2), for snow removal operations began during the early 1960s. Prior
to that time highway maintenance departments depended primarily on abrasives
such as sand and cinders, in combination with plowing, to clear snow and
ice from highways. Salt was generally used as an additive to the abrasives
to prevent freezing. However, from practical experience, maintenance
departments began to appreciate the effect that salt had on accelerating
the melting rate of ice and snow. Through experimentation, maintenance
engineers learned that direct application of salt before, during and/or
after a snowstorm greatly facilitated their snow removal operations, both
in terms of time and in terms of budget. Since that discovery, the obvious
has occurred. The use of salt for snow and ice removal has grown rapidly,
in some cases by as much as 900% in the past 15 years (299). The extensive
use of salt has been associated with a significant amount of damage. While
there have been many reports on this damage, there has not been a compre-
hensive examination of the total impact of all salt related damage.
There is no question that salt is an excellent tool in snow removal opera-
tions. There also is no question that in terms of time and budget constraints
for snow removal operations alone, the usage of large quantities of salt in
conjunction with plowing is essential. Highway departments, operating
under the goal of creating the safest driving conditions, believe that a
policy of maximum bare pavement in a minimum time is optimized through
extensive use of salt, given their budget constraints. In fact, some high-
way departments, in their eagerness to perform well and meet their goals,
have often used salt in an inefficient manner. This has largely been
eliminated now by education and understanding as a result of activities of
the Salt Institute (312,313), the Environmental Protection Agency (304, 310),
the Massachusetts Special Commission on Salt Contamination (4) and many
others (see Bibliography: Maintenance Procedures and Regulations). The
result has been a more effective use of salt with essentially no reduction
in its level of usage (288, 298, 290). Total salt use for snow and ice
removal in this country now stands at approximately 9 million tons each
year. As the number of miles of highways increases, so also.can we expect
the amount of salt usage to increase if we continue with our present policy
(and if no alternative method of snow and ice removal is found).
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The concept of June travel in January, better known as the "bare pave-
ment policy," has led the highway departments and the publib to the
situation in which we currently find ourselves. This situation; has
become increasingly complicated over the past 10 years, and especially
during the past 4 to 5 years, because of the growing number of reports
of damage to water supplies, vegetation, and the very vehicles and
highways that originally served as the only focus of attention.
The concern over salt related damage has been increasing rapidly,
probably exponentially, as the large (but only representative)
bibliography at the end of this report demonstrates. The reports
on instances of damage are extensive and well documented. There have
been several excellent works done to summarize these reports (1,4,15,
16,26,38,42) and there have been many excellent in-depth studiess on
certain areas of damage (see Bibliography). Probably the best
example of the latter is the work done for the Massachusetts Special
Commission (4) and the follow-up by Robert Terry (53). Upon careful
examination of all these studies.and the other literature which has
been reviewed, one can only come to the conclusion that the, problem
is potentially very serious. The situation has required a very
careful assessment and the current guidelines under which snow
removal procedures operate requires thoughtful consideration.
It is in this context that the idea for this project was formulated.
Previous studies, as thorough as they were, did not assess the entire
problem of damage in comprehensive terms including an economic
analysis. Logically, no amount of damage claims, without the necessary
economics, could enable a rational salting policy to be determined,
except in the most extreme cases. Without such an economic analysis,
no alternative to salt, whether it be more snow left on the highways
or a more expensive replacement for salt, could ever be economically
justified.
Consequently this analysis of damage from road salt was undertctken in
order to assess the situation in the best possible manner. In all
phases of the study there has been a constant effort to make the
analysis quantitative. In some instances, because of the lack of cost
data, this has simply been impossible . However in these cases every
effort to perform an unbiased qualitative assessment has been made.
The authors have been impressed not only with the extensive reports
of damage and the cost of that damage, but with the extensive amount .
of damage in one sector. Rusted vehicles and bridges, while costly
can be replaced. Damaged vegetation can be ignored by those who do
not incur the cost. But pollution of our water supplies is a serious
matter. This is not to say that all road salt usage leads :to water
pollution, but it has in many instances. The medical implications
of salt in drinking water is not a matter to be taken lightly.
Because of many unknowns, the economic analysis of the damage to water
-------
supplies is not able to point out how potentially serious the problem
may be. However each reader, knowledgeable of the facts on road salt
damage in our environment, must make a decision for himself. Hopefully
in this way a rational solution will be found, and serious damage to our
environment will be prevented.
The fact that damage from salt has reached the magnitude that it has
should come as no surprise to anyone who understands the way in which .
our current situation has evolved. Highway maintenance departments
have as their primary goals the requirement for providing maximum safety
and convenience on the highways. The departments have performed well,
especially considering the complexities involved in snow and ice removal.
While the current practices may be near optimal in terms of the department
goals (and the highway budget constraints), in many locations the prac-
tices are far from optimal in terms of our whole environment, man-made
and natural. This situation has occurred primarily because (1) those
who determine present maintenance policies are largely unaffected by the
adverse environmental conditions (that is, they do not incur the full
cost of the damage), (2) legal liability in some instances may have
forced highway departments to give undue weight to accident prevention
and (3) there have been no outside forces to regulate the department's
activities. The result is a prime example of a situation in which exter-
nal diseconomies (social costs not borne by those making decisions as to
the level of activity) lead to a failure of unregulated markets to achieve
efficient outcomes. Determining the precise level or combinations of
winter maintenance policies that maximizes social well being within cer-
, tain constraints is the crux of the problem. Theoretically, at least,
this is accomplished by assigning prices to the various social and envir-
onmental values and choosing that outcome which maximizes total net value.
However, as the presentation and analysis in Sections 4 and 5 demonstrate,
it is not possible to assign exact costs to all items because their value
is subjective. It is especially difficult in cases where irreversibilities
are involved, such as with permanent health damage and vegetation death.
It is interesting to note that the concept of "public pressure for bare
pavement" may have evolved simply because the public was unaware of
environmental damage and thought that more bare pavement resulted only
in a small increase in the maintenance budget. This attitude seems to
be rapidly changing as the public becomes more aware of the need for a
sound environment.
An observation of public opinion has surfaced as a result of a large scale
survey concerned with road related issues in Pittsburgh. (69) Question
33 in that survey asked, "Would you be willing to see cinders or sand used
as an alternative to salt if less road deterioration would result?" A
"yes" response was given by 73.3%, a "no" response by 24.6%, and no
response by 1.8%. Question 46 asked, "If it were shown that salt caused.
serious damage to your car, would you be in favor of discontinuing the
use of salt?". A "yes" response was given by 69.6%, a "no" response by
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26.8%, and no response by 3.6%. Although the phrases "less road deterio-
ation" and "serious damage" are not defined in terms of cost, and although
the respondents may not have been fully aware of the impact that salt reduc-
tion may have on snow removal or highway budget,these figures still seem
to indicate that the "public pressure" may not be as unanimous as is gene-
erally thought by the maintenance departments, especially considering that
only one cost sector was mentioned in each of the two questions. This is
particularly true when the public is informed of the tradeoffs in terms of
environmental damage. As a result of road salting contamination of many
water supplies, the state of Connecticut has developed a differential salting
policy with a total reduction in salt use of one third. Through public
information programs and the resulting public awareness, the policy change
seems to have been favorably received. There is every reason to believe
that a rational and holistic salting policy would be welcomed by every
community.
Section 4 of this report presents the evidence on the link between road
salt and damage, and demonstrates the extent of that damage. ; Section 5
contains a thorough economic analysis of the damage and a summary of the costs
involved.
3.2 SUMMARY OF APPROACH
This study involved the collection of a great deal of material, both from
the literature and through personal contacts. Subsequently this material
was examined for its validity and thoroughness, forming the basis for analy-
sis. Assessment of this material, in both quantitative and qualitative terms,
was then undertaken. ;
3.2.1 Literature Review, Surveys, and Personal Contacts
During the course of the project a complete review of the literature on snow
and ice removal, salt use, and salt damage was made and the most relevant
documents, over 450 in number, were obtained (out of an estimated 700 or
more). Each one of these documents was carefully screened for its validity
and relevance and over ;300 have been retained in a bibliography at the end
of this report.
The second portion of the research involved the mailing of surveys and
letters to universities, Public Works Departments, Public Health Departments,,
and water companies. There were over 100 respondents who indicated that
they had incurred damage, knew of damage in their area, or provided us with
documents or contacts relating to salt related damage. Follow up was done
in many cases in order to clarify responses or obtain further information.
As a result of the literature and surveys, close to 200 personal contacts
were made either by letter or phone. Almost all of these contacts provided
up-to-date information on salt related damage; as in the case of the liter-
ature, and the surveys, "hard" data on costs of damage was minimal.
Finally, all of the material gathered from the search and surveys was reviewed
and evaluated. This forms the basis for the presentation on salt related
damage in Section 4. :
8
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2.2.2 Approach, to Analysis
Since the study was essentially restricted to readily available data,
either in published form or in the form of accessible records, the
analysis of the 'economic costs of damages attributable to the use of
deicing salts was constrained by the opportunities offered by the
available data. In order to generate key points of reference, the. cost
analysis was based on a general model which expressed the expected (or
average) annual cost in a particular damage category as the product of
the expected magnitude of total damages (which in turn is the product
of the probability of occurrence times the damage per occurrence) and the
cost per "unit" of damage.
This general cost model provided the basis for examining the literature
and other materials that had been accumulated in the study. Considerable
efforts were undertaken to adapt the available information to. fill the
data needs of the study. However, in most cases, the estimation pro-
cedures used to quantify certain parameters of the cost function were
too broad, given the nature of the available data. In these cases, costs
were estimated on an ad hoc basis, e.g., by a weighted extrapolation of
detailed cost data for a particular state or region.
The analysis comes closest to the ideal in the case of automobiles, in
which the study could draw on previous work in the appropriate direction
by one of the consultants to the study. The analysis of the costs of
accelerated corrosion of automobiles used detailed data on depreciation
rates in a significant sample of metropolitan areas, and estimated the
net effects of deicing salts through multivariate analysis.
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SECTION 4
SALT RELATED DAMAGE
As stated in Section 3.1, the purpose of this study has been to factually
ascertain the types, extent, and monetary value of damage that has taken
place in the total environment as a result of road salting. The purpose
of this section of the report is to present a summary of the material
which has been gathered from an extensive literature review and from
personal contact with highway officials, public health officials, researchers,
manufacturers, utility companies, and others. In the individual sections
on damage, reference is made to major studies and in some instances- to
specific research, but space simply does not allow an examination of all
of the documents listed in the Bibliography. The presentation is primarily
centered around an explanation of how damage occurs, accompanied by actual
case examples.
It is essential to have a basic understanding of the paths that salt can
take through the environment. All salt applied to the roads will eventually
end up in the ocean (or in rare cases in underground pools of]water such
as fossil geologic water supplies) or will be stored in the environment
for an indefinitely long period of time (chiefly in soils). Between the
time of its application and the time of its eventual storage, salt is
capable of upsetting many ecological balances. Once salt has been applied
to a highway, it is dispersed into the environment in a number of different
ways. (See Figure 1)
Splash — ;
As vehicles pass over the salt solution, some of it will be splashed
onto the surrounding roadside. The salty water will then percolate
downward into the ground. Depending on the type of soil, some fraction
of the sodium ions (or calcium ions in the case of calcium chloride)
will bind with the soil. The remaining sodium and chloride ions will
then be available for uptake into vegetation or will eventually enter
into the groundwater supply. Salt solutions may also be splashed
directly onto roadside vegetation.
Runoff —
Solutions of highly concentrated salt may also run off the highway
directly onto the surrounding roadside causing problems as outlined
above, or it may be carried in storm drains or gutters as runoff to
another location. Such runoff can also damage vegetation, enter into
groundwater supplies, or enter into surface waters, such as streams,
rivers, ponds, lakes, and reservoirs. Runoff has been observed with
10
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ATMOSPHERIC
REDISTRIBUTION
FALL-OUT OR
PRECIPITATION
WIND
EVAPORATION
PICK-UP
DISCARD
LEACHING
SPLASH &
PERCOLATE
DISSOLVE &
RUN-OFF
STREAMS
/ 1 V"-
/ \ \
RIVERS 1 -x
,A Y
LAKES
SOIL
BINDING
NA+
CA++
Cl
GROUNDWATER
UPTAKE INTO
PLANTS
\
CHRONIC
EFFECTS
OCEAN
WELLS
WATER SUPPLIES
GEOLOGIC WATER
"I
STORAGE .
TOXIC
EFFECTS
DEATHS
(PLANTS)
(Source: Adams, Franklin
S., "Highway Deicing Salts
are Potential Environmental
Contaminants," Farm
Economics, Pennsylvania
State University, University
Park, Pennsylvania (1973).
Figure 1. Fate of Salt in the Environment
11
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concentrations as high as 35,000 mg/1 (325), approximately the same
concentration as ocean water.
Pick Up and Discard
I
In many areas salt-laden snow may be scooped up and carried by truck
to another location. Large quantities of such snow may contain a great
deal of salt. Depositing the snow anywhere other than in the ocean or
in an already highly polluted river will very likely lead to severe
groundwater damage and/or vegetation decline.
Atmospheric Redistribution
Road salt can enter into the atmosphere via the dispersion of small
droplets when cars and trucks pass over roads covered with a salt solu-
tion. The larger drops of salt solution, referred to as "splash", will
fall out very near the highway (probably within a maximum of about 100
meters). The smaller droplets will evaporate to an equilibrium size
consistent with the ambient relative humidity and be dispersed over a
large area. If the ambient relative humidity is near 50% or less, the
solution droplets will evaporate to a dry salt particle whose very small
size will be a function of the highway salt solution concentration.
(322) Also the dry salt residue remaining on the highway after the mois-
ture has evaporated can be scattered into the air by the passage of
vehicles. Calculations by Stensland (324) have shown that about 1 to
1.5% of the road salt is passed into the atmosphere.
Before turning to the discussion of specific damage, it is important to
separate out the effects of road salt from the effects caused by salt
spray from the ocean. Analysis of precipitation chemistry data by
Stensland (321, 322, 323) has shown that during the winter months in
locations where road salt is used, salt water spray from the ocean
(larger droplets that fall out r.apidly) dominate over road salt, spray
only in very close proximity to the coast. The affected range is any-
where from a few hundred meters to a few kilometers depending on geo-
graphic and climatic conditions, especially wind speed and direction.
Furthermore, the atmospheric content of salt particles will be dominated
by road salt sources more than 10-50 kilometers from the ocean, the dis-
tance again depending on geographic and climatic conditions. Since the
amount of road salt and ocean salt in the atmosphere is very small in
comparison to the total amount of salt entering into the environment,
it must be concluded that in areas where road salt is used, the sea salts
become a dominant factor only in very close proximity to the ocean.
Examples in which sea salt would prevail are: bridges or other struc-
tures which pass over or are directly adjacent to the ocean and which
receive salt spray; vehicles which are parked along the ocean front.
The conclusion is that for all the areas where road salt is' used, sea
salt is a significant cause of damage in a very small fraction (1% or much
less) of the cases.
12
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In addition to damage to the natural environment, man-made goods also
receive substantial damage from road salt.; Vehicles passing over the
salt solution on the highway receive a spray of a highly concentrated
salt solution, depositing the salt on the metal surfaces where it will
remain and cause accelerated corrosion. Splash from vehicles and
direct runoff can coat highway and surrounding structures with a salt
solution, making those structures more vulnerable to corrosion. Seepage
of the salt solution through pavement (or cracks in the pavement) will
eventually cause damage to the roadway. Runoff and percolation will
allow the salt solution to eventually attack underground wires and
pipes, again accelerating corrosion and providing problems for industrial
users.
4.1 DAMAGES TO NATURAL RESOURCES
Mention of damage from road salt to natural components of the environ-
ment has been frequent in the literature. There is an abundance of
information on the means by which the damage occurs and numerous reports
of specific damage cases and, in some instances, the cost incurred.
Nevertheless, the proponents of salt use have continually opposed the
significance of such findings and the subject is usually dismissed with
responses such as "the value of a..tree does not compare to the value of
human life." Examination of the literature reveals that damage to vege-
tation, while extensive and costly, is not the major component. The
real concern is over contamination of water supplies and the resultant
impact on human life.
In this section, the nature and extent of salt related damage to natural
resources will be examined. The fact that there is a link between road
salt and damage has been proven throughout the literature. This section
serves to summarize the established research.
In general, salt damage to natural resources is usually characterized
by the fact that it is either irreversible, 'too costly or difficult to
reverse, or only the passage of time will allow the effects to disappear.
There is a significant amount of risk involved when irreversibilitv is
an issue because the true meaning of the damage may only become fully
known at a future time, at which point it is too late to make a change.
Assessment of damage to natural resources from road salt has always been
a difficult problem. Not all the processes by which damage occurs or
the exact relationship between salt use and damage are known, thereby
making assignment of damage difficult. The effects of salt in nature are
often cumulative and therefore require lengthy studies for complete
understanding. Finally, because the concept of irreversibility is so
little understood, there is often disagreement over the cost of damaged
goods, making it difficult to assign costs. The cost analysis of
damage to natural resources which appears in Section 5 is conservative.
The cost figures which are developed provide a lower bound; actual costs
may actually far exceed these numbers.
13
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4.1.1 Water Supplies (Drinking) and Health
The contamination of water supplies is possibly the most serious damage
that results from the use of road salt. Salt can enter into ground-
water supplies as it percolates down through the soil. It can also enter
into surface supplies as direct runoff from highways. Processing water
to remove salt is an extremely expensive and complicated matter, and is
therefore rarely done. Typically, the safest means of preventing the
salt from reaching water supplies is to catch the highway runoff and
direct it to a high flow stream or river which eventually reaches the
ocean without entering into another water supply. While provisions for
runoff can be provided for new highways, the cost of the provisions must
be considered. Such design has not been incorporated into a majority
of the existing roadways, and to do so now would be very costly, if even
possible.
The concentration of sodium chloride in the groundwater is a function
of many factors, most notably: 1) the amount of salt applied to the
highway and distance from the groundwater; 2) the type, frequency
and quantity of precipitation; 3) the type of soil and geologic
material; 4) direction and rate of flow of the groundwater;•and 5) the
highway drainage design.
The concentration of sodium chloride in surface waters is also
dependent on many factors, but primarily a function of: 1) the amount
of salt applied to highways which eventually reaches the body of
water; and 2) the volume of flow of water into and out. of that body.
Depending on the rate of flow, some surface waters are able to handle
large quantities of salt without a dangerous increase in the equili-
brium level of sodium and chloride. Consequently, the effect on
groundwater is usually more significant and possibly more serious
because of the slow movement of the water involved. While some
groundwaters show a significant movement within a matter of months,
in some cases the time required for the water surrounding a ^ell field
to change may be on the order of years. Consequently, the ground-
water sodium and chloride levels typically show a lag in response
to the actual date of salt application. Surface waters are jgenerally
affected much more immediately. >
The reports of infiltration of road salt into drinking water supplies
are numerous and growing (see Bibliography - Water). Some of the
first cases of serious salt infiltration were found to have been
caused by improper salt storage facilities. It was assumed for some
period of time thereafter that most salt pollution was the result of
poor storage. It has been shown that this is not the case. In fact
most salt pollution that is presently occurring is apparently caused
by runoff from streets and highways (53, p. 25). \ •
The details of salt contamination in various parts of the country have
been extensively recorded. Since the literature is filled with some
14
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outstanding works on this subject, this section does not attempt to
review or mention all of the findings. However it does contain an
updated report on the trends for some of the New England states. The
reader who wishes to substantiate the findings should refer to the
literature, most notably the work by the Massachusetts Special
Commission (4), EPA (15), Terry (53), Hutchinson (95), the Massachusetts
Department of Public Health (101), and Motts (104).
Sodium and chloride content in water is measured in terms of milligrams
per liter (mg/1) or, equivalently, parts per million (ppm). Until
several years ago, chloride tests were easier to perform than sodium
tests and therefore the older literature generally refers to salt in
terms of chloride levels. Measurement of sodium in addition to chloride
is now universal.
A portion of the sodium entering water supplies through the ground is
usually bound into the soil so that not all of the sodium reaches the
groundwater. In Massachusetts the ratio of sodium to chloride in most
public supplies has been- reported to be between 1:3 and 2:3 (53). Thus
a water supply which has reached the limit of 250 mg/1 chloride may con-
tain between 83 and 167 mg/1 of sodium. There are currently no federal
guidelines on the allowable level of sodium in drinking water supplies.
However for chlorides, the U.S. Public Health Service recommended in 1962
a maximum safe level of 250 m/gl. In 1968, the Federal Water Pollution Con-
trol Administration advised a maximum "desirable" chloride level of 25mg/l.
Some of the most recent data on water supplies show that the trends in
chloride and sodium content are in most cases still, increasing, while in
other cases remaining nominally stable or in equilibrium. The accompany-
ing graphs (see Figures 2, 3, 4, 5, 6, and 7) show the latest average
trends for four New England States. The sodium content could be estimated
at between one-third and two-thirds the level of chloride given in these
graphs. Prior to 1940, all Massachusetts data indicated chloride content
less than 10 mg/1.
Initial examination of the most recent Massachusetts data (285, 326) reveals
that there appears to be a slight decline in the number of communities with
one or more public water supplies containing sodium above 20 mg/1:
1970
69
1971
77
1972
96
1973
95
1974
90
However, the figures for 1970-1972 period were established by Robert Terry
(53), and there may be a slight difference in the methods of analysis.
Also salt storage facilities have been improved over the past few years,
possibly accounting for the small decline.
Richard S. Woodhull, head of the Water Division of the Connecticut Depart-
ment of Health, reports that most water supplies in Connecticut have been
15
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showing a continually growing content of sodium chloride*. A few
supplies have appeared to level off, probably in response to the 33%
cut in the state's use of salt. (This cut was initiated because of
salt infiltration. Some cities and towns have followed the state's lead).
In 1964 the State of New Hampshire established the Special Services
Division for the purpose of replacing wells contaminated by salt. The
budget for the Division had been set at $100,000 for 8 years. In 1974
and 1975, it was raised to $200,000, apparently to cover the cost of
increasing well damage.
Although the trends appear ominous, there are many who claim that the
current levels of sodium and chloride in the water supplies are not a
problem. An early argument was that the level of salt was below the
taste threshold, and therefore safe. Such an argument does not consider
the fact that there are highly poisonous chemicals which are either
tasteless or odorless.: The claims by salt interest groups that concen-
trations of chloride as high as 2,000 mg/1 (between 667 and'1,333 mg/1
sodium) are not harmful (42) are not supported by experimental data; in
fact, the scientific evidence is totally contrary.
For some years now, medical research has established that intake of
sodium chloride is a critical factor, affecting many health conditions,
including hypertension, cardiovascular diseases, renal and liver dis-
eases and metabolic disorders (135). Intake of salt also presents a
danger to a large percentage of pregnant women (135).- Consumption of too
much salt can generally contribute to hypertension (and eventually con-
gestive heart failure), poor circulation, and stress on the internal
organs (132, 133, 134). The most recent research has further confirmed
the link between salt and hypertension, and between salt and the other
diseases and problems mentioned above (134, 138, 139, 140).
As mentioned earlier, there is no public health standard for sodium in
water. However, the American Heart Association (19), backed by many
leading medical researchers and physicians, has recommended a limit of
22 mg/1 sodium in drinking water for patients whose diets are restric-
ted to less than 500 milligrams of sodium per day (19, 135).** Accor-
ding to recent estimates approximately 23 million Americans are
Personal Communication, July 2, 1975.
**Note for example that a person restricted to 500 milligrams of salt per
day who consumes 3 liters of water (including cooking purposes) containing
100 mg/1 of sodium will be consuming 60% of his allowed daily intake.
Since most foods contain some sodium, it is impossible at this level to
prescribe a diet which would supply enough food (natural and unsalted) with-
out causing the person to exceed his allowed intake. (141). The 22 mg/1
guideline has been established to allow a patient to maintain an adequate
diet.
19
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suffering from hypertension and should restrict their sodium intake
(132). This group, together with other persons who should restrict sodium
intake to 20 mg/1 comprise at least 20 to 25% of the population, with
some researchers claiming the percentage to be as high as 40% (138).
Unfortunately, many of those who should restrict their salt intake are not
aware that their life is at risk and therefore consume much more salt
than they should. Therefore for a particular individual, water with a
sodium content of more than 20 mg/1 may not present a significant danger.
However, such water is potentially harmful to those persons on low sodium
diets (approximately 4-5%). In addition, further education of the public
will undoubtedly result in greater awareness of hypertension and a greater
percentage of the population will restrict their salt intake. Since
complete reversal of the sodium trends might take years once action is
taken, more people are endangered than just those currently on salt
restricted diets.
Furthermore, one must consider the remainder of the population which is
not yet hypertensive or diseased. Dr. Lewis Dahl, who has researched
salt and hypertension for years, has written that heightened intake of
sodium from the time of infancy is unhealthy (134). Dr. Lot Page,
who has been involved in some of the most extensive studies on hyper-
tension and is currently Chief of Medicine at the Newton-Wellesley
Hospital in Newton, Mass., has written that man was not meant to
consume salt other than what is to be found in natural food sources and
the more salt that is consumed, at all times in life, the higher is the
probability of eventual hypertension. Research does show that the
consumption of excess salt during infancy may lead to hypertension later
in life (140). The two facts that (1) salt has been linked with hyper-
tension and, (2) that blood pressure is the chief indicator of life
expectancy (for both physicians and insurance companies) can lead
to no other conclusion than road salt pollution of our water supplies
is presently a highly dangerous situation. While the use of salt on
food is optional, consumption of salt in^.the watervis obligatory.
Most serious of all, tne presence of sodium in water is unknown to most
of those who consume it. Dr. Lewis Dahl and Dr. Lot Page have both
stated that the infiltration of road salt into our water supplies is
a very serious and urgent problem.*
4.1.2 Other Water Resources i
Examination of the literature has shown that deicing salts**-usually have
very little effect upon large rivers and streams. Because :the rate of
flow is so large, especially during the spring thaw when the bulk of
the salt is released into the river, the sodium chloride is substan-
tially diluted. Large rivers rarely show an increase of more than 10
to 20 mg/1 of sodium chloride (91, 93, 108).
* Personal Communication, June 10, 1975 and June 11, 1975 respectively.
** Primarily sodium chloride with the rest calcium chloride.
20
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Smaller streams and brooks may be much more seriously affected depending
on their flow rate and the amount of highway runoff. During a study
of the Irondequoit Bay Drainage Basin in Monroe County, New York, it
was observed that the principal input to the Bay, Irondequoit Creek,
reached a winter maximum of 670 mg/1 chloride. Maximum concentrations
in ten small creeks were found to range from 260-46,000 mg/1 chloride
during the winter (73, 80).
The final destination of such streams must be examined closely in order
to determine the resultant effects. For example, Diamond Lake in
Hennepin County, Milwaukee, Wisconsin was reported in 1970 to contain
the equivalent of 3,780 mg/1 sodium chloride (48). Undoubtedly in some
cases the effects on aquatic life in the receiving bodies may be serious.
It has been observed that heavy flow of salt may prevent complete mixing
and prolong stratification of the water. Such extended stratification
can result in oxygen deprivation in its lower depths and has caused
death of organisms living in the lower depths. Since these animals
are-an important link in the food chain, fish kills have, resulted (89,
97). The use of road salt has led to similar but less serious damage
in Irondequoit Bay, Rochester, New York. If salting continues at the
current level, serious damage may occur when the dissipation of salt
in the drainage basin reaches a steady state of equilibrium. In dis-
cussing the potential effects of salt on lakes and ponds, Adams stated
that, "...it is well within the realm of possibility that the addition
of significant amounts of salt could contribute to the biological
process of aging in lakes called eutrophication." (1)
Other studies have shown that under special conditions, the entry of road
salt into freshwater can cause mercury and other toxic heavy metals to be
released from contaminated sediments (82). Release of these metals in ponds,
lakes or reservoirs that do not have a high inflow/outflow rate might
present a serious hazard to the aquatic and human life.
4.1.3 Soil
While discussion ,of damage to roadside soils may seem unnecessary in
addition to an examination of vegetation and water damage, it is indeed
an element of the environment which is very definitely degraded by salt.
High concentrations of salt in the soil will not only lead to the death
of existing vegetation, but in many cases will also lead to an almost
irreversible situation in which proper drainage is seriously affected
and only a limited variety of vegetation, if any at all, may grow in
the soil.
Sodium and calcium chloride are highly soluble in water and easily
disassociate into sodium, chloride, and calcium ions. The chloride
ion, having a negative charge, is repelled by the negative charges
of clay and other organic colloids and therefore is easily leached out
of the soil by water passing through. However, the positively charged
sodium and calcium ions are attracted to the negatively charged clay
21
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and other colloidal soil particles (20). Thus, depending on the type
of soil, amount of salt applied,, and the amount of water leaching
through the soil, as a result of precipitation, a substantial percen-
tage of the sodium and calcium ions may be retained. The high
sodium content may result in a number of undesirable soil properties,
especially loss in permeability (24, 199). In addition the presence
of the sodium will lead to the leaching of other positively charged
ions such as potassium, calcium, and magnesium which are essential for
plant growth (20). All of these factors can result in a poor
roadside environment for vegetation growth. Depending on the severity
of the situation, it may take many years for the sodium to leach out
into the groundwater, rendering the soil useless to all but a few
hardy varieties of vegetation, such as high salt tolerant grasses.
Loss of vegetation has in some cases led to severe soil erosion; and1
the high soil content runoff has clogged drain sewers (155).
As expected the highest salt content in soil is generally found near the
highway and near the ground surface. Concentration generally decreases
with depth and distance from the road surface. Some salt in soil has
been found as far as 30 meters from the road but usually the concentration
is significantly decreased at 7 to 18 meters from the highway. (This
does not include situations where runoff is collected and diverted to
other locations, of course.) (24, 96, 199) In addition, studies have
shown that roadside soil concentration of salt increases with the number
of years salt has been applied (193). The implication of this finding
is that application of road salt has a cumulative effect on the roadside
soil. Continued application of road salt will very likely increase the
salt concentration to the point where eventually the soil will be
highly alkali and possibly unfit for most vegetation.
Studies by F.E. Hutchinson under a cooperative program between the Maine
Agricultural Experiment Station and the Maine State Highway Commission
have shown that high rates of application of gypsum (3 kg/squar.e .meter)
to roadside soils can lead to a reduction in sodium in the topsoil.
(Reduction of sodium in the subsoil has not yet been proved.) (195,
196, 197) While these findings provide some encouragement> the cost
of the gypsum application must be considered. :
4.1.4 Vegetation
Sodium chloride applied to highways to aid in ice and snow removal has a
significant effect on the decline of roadside trees and vegetation.
While drainage conditions are an important factor in determining the dis-
tance to which vegetation is affected, most damage occurs within 9 meters
of the edge of the highway. Other factors such as drought low soil fer-
tility, low soil permeability, air pollution from vehicle exhaust, and
mechanical injury to roots also contribute to the damage (175). However,
in-depth studies have shown that salt in many cases is the'prime factor
leading to death of vegetation (20, 156, 157, 174). These•studies were
based on soil samples and analysis of sodium and chloride content in
22
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Heavy salt use and the resultant damage to vegetation can lead not only
to personal property damage and possibly some crop damage, bub also to
the creation of unsightly conditions along the highway, reducing the
property values and negating the highway beautification programs.
Although difficult to assess, there are real costs involved in terms of
increased highway maintenance for removal and replanting.
4.1.5 Fish and Wildlife
The literature contains a few reports of death of fish and wildlife
attributed to salt (15, 48). While there has been a small amount of
research on short-term toxic levels of salt, there is little known
about the long-term effects of less toxic levels. Until further
.research is carried out, it is not useful to speculate on the possible
extent of the damage. However, it is probably fair to state -that bodies
of water which have significantly increased levels of sodium chloride
due to road salt runoff will demonstrate noticeable changes .in their
ecosystem. Such changes are unlikely to be beneficial.
4.2 DAMAGE TO MAN-MADE GOODS
The mechanisms by which salt damages man-made goods are described in
this section. Claims and accounts of salt-related damage, predomin-
antly to bridges and automobiles, are numerous. The literature presents
sufficient evidence to directly link the damage to deicing salt use.
Reports of public officials as well as professional engineers and con-
cerned citizens leave no room for doubt as to the nature or extent
of the damages.
Such damage is more easily observed than is the damage to;the natural
environment. A sampling of some of the specific reports is presented.
Section 5 will present an economic assessment of the damage caused by
deicing salts.
4.2.1 Corrosion of Motor Vehicles
It is likely that more people have directly observed vehicular corrosion
than any other form of salt-related damage. The link between the
application of salt on highways and the corrosion of automobiles is
well documented (see Bibliography). This section of the report will
discuss the corrosion process and examine parts of the automobile
susceptible to it. Section 5.5 contains an economic analysis of the
probable costs of this corrosion.
The Corrosion Process —
The corrosion of steel is an electrochemical reaction in which iron is
oxidized to the ferric state. In the presence of moisture and atmos-
pheric oxygen, the free energy of the reaction is such that iron is
spontaneously oxidized to form the insoluble hydrated ferric oxide
(rust). This is the typical reaction occurring in the near neutral
environment of auto body steel. When acids are present, oxygen is not
24
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required and the iron is first oxidized td the ferrous ion. This ion
can be further oxidized to the ferric state and react with hydroxyl
ions to form ferric oxide. Both reactions (with water and oxygen or
with acid) can be prevented by eliminating contact between the
metal surface and any of these elements. This is the motivation behind
such rustproofing procedures as painting and asphaltic coating of steel.
Galvanizing sheet steel protects the steel for a longer period of time
because zinc is electrochemically more active and is thus oxidized
in preference to the iron. Dipping steel in a zinc rich paint initially
protects it by preventing moisture and oxygen from contacting the
surface; and offers further protection though preferential oxidation
of the zinc. Unlike aluminum, an exterior layer of oxidized steel
offers no protection from further oxidation and in fact may accelerate
the corrosion process.
Because steel is not a homogenous, cyrstalline product, there are small
differences in surface composition in ordinary sheet steel which can
cause minute electrical potentials to develop. Further exacerbating
this tendency is the presence in motor vehicles of other metals, spot
welds, and stresses from metal forming. In contrast to the general,
overall even oxidation that will occur in untreated steel in the
presence of moisture and oxygen, minute electrical potentials in the
steel itself result in the potentially more serious pitting corrosion.
Pitting is attributed to differential oxygen concentrations at the
metal surface. Those parts in contact with oxygen become cathodic with
respect to oxygen deficient areas. In cathodic regions hydroxide
ions are produced, while in the anodic regions iron goes into solution
as the ferrous ion. It is in the anodic regions, which are protected
from oxygen by paint, undercoating or other layers of steel, where the
serious pitting takes place. This has led some experts to question the
wisdom of protective coatings, unless they can be so thorough as to
prevent any contact with moisture and oxygen. Even totally protective
coatings may be subject to attack by vibration at joints.
A number of other parameters have been shown to effect corrosion
rates including temperature, the presence of electrolytes, and the
removal of corrosive products from the anodic and cathodic regions.
Chemical reactions are temperature dependent; the rate of reaction
approximately doubles for every 10°C rise in temperature. Electrolytes
such as salt, fertilizers and the soluble products of atmospheric
pollution accelerate the corrosion process by facilitating electron
transfer. It can be inferred that autobody steel will corrode^most
rapidly when protection from oxygen is only partial, and when it is
placed in a warm, humid environment in the presence of neutral or
acidic electrolytes.
Experimental Evidence of Auto Corrosion —
A series of experiments that have sought to define the role of deicing
salts in the corrosion of automobiles was initiated in the mid 1950s
25
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in response to the unprecedented corrosion that was being observed
in and around headlights, wheel wells and door panels on the new cars
of that era. These field tests are discussed below with respect to
the parameters assessed.
Atmospheric Conditions — •
Relative humidity has a significant effect on the oxidation of many
metals. Condensation on metal surfaces will tend to occur at relative
humidity levels far below 100% due to impurities on the metal surface
or in the atmosphere. Reports from Switzerland, Germany and Canada
(206) indicate that when the relative humidity exceeds some critical
value ranging from 60% to 75% the*.'corrosion rate is markedly increased.
Increasing attention has been given recently to the role of atmospheric
pollutants in the corrosion process. Craik and Yuill (206) found the
atmospheric corrosion rate to be higher in the city of Winnipeg,
Canada, than in the surrounding suburbs. Atmospheric corrosion rates
in eight different areas across Canada were measured by Frbmm (205)
by attaching test metals coupons to automobiles. Conditions in these
areas ranged from very dry to very humid; from coastal to inland; and
exhibited a wide range of atmospheric pollutant concentrations. In
high density areas where the atmosphere contains large concentrations
of sulphur dioxide, the corrosion rate is approximately four times
that of rural areas. Corrosion rates are also markedly increased
when in proximity to a large body of salt water.
Deicing Salts —
Several experiments have sought to quantify the partial effect of deicing
salts on the corrosion rate of automobiles. In the investigation by Fromtn
(205), traffic simulator tests performed with and without deicing salts
indicated that salts and atmospheric pollutants each increased the
corrosion rate by approximately the same amount in the Toronto area.
In the test sponsored by the Research Foundation of the American
Public Works Association (APWA) (209), three groups of automobiles were
driven over controlled road sites in the Minneapolis suburbs for three
winters. The partial effect of atmospheric pollution in this region
was measured by test coupons attached to automobiles (where the
combined effect of atmospheric pollution and salting would I be measured);
and other coupons placed in the vicinity, but removed from'deicing
salts. While the fraction of the corrosion rate attributed to salt
varied from 15.9% for a spring exposure to 65.2% for a winter exposure,
the report concluded that a likely figure for the area was approximately
50%.
The principal difficulties associated with using the APWA study to pro-
ject national corrosion estimates attributable to road salting are
(1) climatological and atmospheric variation is lacking due to testing
in only one location, and (2) an ordinal index of severity ' (0,1,2) was
26
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improperly used to compute a cardinal measure of percent corrosion
attributable to salt. Additionally the use of only one make of
automobile (1968 Ford Falcons from the Kansas City production line)
may have produced biased estimates if this make and vintage is not
representative of the "typical" automobile in use.
In a related test sponsored by the National Association of Corrosion
Engineers (NACE) (207), electrical resistance probes were attached to
automobiles in 14 different cities. The experiment was designed to
measure the partial effect of deicing salts and reached similar
conclusions to those of the APWA study. No attempt was made to
statistically analyze the separate impacts of atmospheric pollutants,
humidity, temperature, and the use of deicing salts on the measured
corrosion rates. Such an analysis would be highly desirable but is
not possible because of gaps in the data caused by failure of certain
probes.
In the APWA-Salt Institute test (209), and in earlier experiments in
Canada and Europe, various chemicals were tested for their effectiveness
as corrosion inhibitors. Typically the chemicals were mixed with the
salts before application to highways. Corrosion inhibitors were shown
to have very limited potential in reducing salt induced corrosion of
automobiles. In addition, they posed serious adverse environmental
consequences such as the health endangering effects of hexavalent
chromium (15).
Other Factors —
Storage of an automobile in a closed, heated and poorly ventilated
garage during the winter may exacerbate corrosion in areas where
snow, ice, and deicing chemicals have been deposited. The apparent
explanation for this circumstance is, as mentioned earlier, that
chemical reactions are temperature dependent.
The corrosion rate of an automobile is significantly affected by the
shape and construction of the automobile body. Of particular impor-
tance are those steel surfaces accessible to moisture, oxygen and
electrolytes. Since pockets which collect dirt and debris tend to
retain moisture long after other surfaces have dried out, they are
sites of the most severe corrosion. Felt, fiber glass, rubber and other
materials that tend to retain moisture accelerate the corrosion process
when in contact with steel.
Areas Affected by Corrosion in Vehicles —
The safety and the economic value of an automobile are adversely
affected by corrosion in three main areas: the chassis and box sections,
the braking system and the electrical system. The most visible
effects of corrosion occur in the box sections which are made up of
thin steel sheets connected by welding. Structural weakness caused by
corrosion of the chassis and box sections reduces the protection offered
27
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by the automobile in an accident. The corrosion of floor panels
eventually allows exhaust gases to enter the passenger compartment.
For automobiles manufactured with unitized body construction, the
replacement of a corroded section frequently costs more than the value
of the car.
The most vulnerable parts of the braking system are the hydraulic brake
lines. These lines are quite thin and are exposed to moisture,, salt
and other electrolytes, and oxygen. If pitting corrosion is initiated,
perhaps because of partial protection offered by rubber mounts,. the
ultimate consequence can be serious. The semi-permanent rusting-in-
place of items such as wheel lug nuts, spark plugs, brake drums; and
exhaust system clamps, accelerated by exposure to deicing salts, makes
work on these parts much more difficult and thus increases the costs
of repairs. Performance of the electrical system is also adversely
affected by corrosion. Failure of headlights and turn indicators is
a frequent consequence.
There is evidence that corrosion is initiated on the exterior of the
exhaust system as well as from the interior, and that deicing salts are
one of the factors causing this external corrosion, in combination with
humidity and temperature. In the snow belt, Midas Mufflers Inc. found
that non-galvanized mufflers lasted an average of 18 months and that
galvanized ones lasted 24 months. Outside the snow belt the typical life
of a galvanized muffler is 48 to 60 months.* The .two-fold increase in
muffler life away from the snow belt (and deicing salts) may imply a
strong role for deicing salts in the exhaust system corrosion process.
There has been a variety of 'damages reported by :K'ighwa'y engineers.
Vehicle corrosion for maintenance trucks rates high on this: list of
associated damage for which costs are incurred by the publig at large.
In Lancaster, Pa., reports one survey respondent, "The beds of all
pick-up trucks become corroded and eaten out very rapidly. Despite
constant washing of the beds the chemicals become lodged between the
wooden bed and sides of the truck body. In less than two years the
sides of the truck body become eaten out."+
According to the same individual, "Another frequent repair is with
brakes and hydraulic brake lines of trucks with salters mounted on
them. The salt becomes embedded in the brake shoe adjusting mechanism
and corrodes the surface to a point where complete dissassembly of
the brake is necessary. The hydraulic brake lines that are!fastened
with clips to the body for support become corroded and require frequent
replacement."$
* Per spokesmen of Midas Mufflers, Inc. and A.P. Auto Parts*
+ Lancaster, Pa., respondent to Highway Department survey.
* Ibid.
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A spokesman for the New England Telephone Company indicated that rust
is a greater problem than mileage in terms of maintenance on their
fleet of 9,800 vehicles. Despite salt preventive measures taken by the
service department — rust proofing, patching, and washing the vehicles
on a regular basis — their sedans are held for only two or three years
and their trucks for four or five years, compared to a nine year average
life expectancy for Southwestern Bell, Texas* fleet vehicles. These
vehicles remain in service almost a decade despite their exposure to
sea salt spray along the gulf coast and some deicing salt use for
icing conditions in the pan handle area. This clearly illustrates
the impact of continued use of high volume chloride salt on the utility
companies maintenance costs. Of course these increased costs of
providing service will be passed directly on to the consumer.
An unusual extension of highway department maintenance problems
related to salt use occurred in Saginaw, Michigan, where the "in-
floor radiant heating system in the main storage garage deteriorated
in approximately five years due to salt runoff from vehicles." The
only available means to correct this difficulty was to "replace
the heating system with.overhead gas blowers (at a cost of $18.5
thousand)".+
4.2.2 Damage to Highways and Highway Structures
There have been many claims of salt-related damage to highways, bridges,
and other highway structures. A thorough research of the literature
and a survey of all snow-belt state highway departments and approximately
100 large city highway departments have disclosed that there has been
extensive salt-related damage to bridge decks. By comparison, damage
to highways in general has been small. There were only a very few
reports of damage to other highway structures. Apparently guard
rail deterioration can be a problem, but frequent painting seems to
prevent the deterioration. No cost data could be obtained on this
added maintenance.
In this section, the process by which bridge deck damage occurs is
explained. This process has been verified by many sources. (See
Bridge references in Bibliography.)
Damage to Bridges --
Bridge deck deterioration ranks high among major maintenance problems
on our nation's highways. The most common forms of deterioration are
cracking, scaling, and spalling. Cracking is not considered to be a
very serious problem, although it can lead to the formation of potholes.
* Paul Le Blew, Southwestern Bell, San Antonio, Texas, in a telephone
call 6/19/75.
+ Respondent, Saginaw, Michigan, Highway Department questionnaire.
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Scaling is principally a surface phenomenon and is largely :eliminated
by the use of high quality, air-entrained concrete and the periodic
application of linseed oil. Spalling produces cracks and potholes and
is serious and difficult to control. In addition, the supporting struc-
ture for the bridge may be significantly damaged.
The Nature of Cracking and Scaling,—
In bridges, cracking may be caused by (1) shrinkage- of concrete due to
excessive evaporation rates during the drying process; (2) design features
associated with dynamic tensions and flexing in the bridge which result
in material fatigue; (3) inadequate materials, especially the use of
improper material ratios in mixing concrete; (4) faulty construction
techniques; and (5) various environmental factors such as weather, mois-
ture, and the loads carried. With proper attention to design, materials,
and construction, cracking may largely be controlled. Scaling is a surface
phenomenon that can be caused by freeze-thaw action in the :absence of
deicing salts. Scaling has also been observed in salt contaminated con-
crete surfaces not subject to freeze-thaw action, such as the underside
of the Biscayne Bay Bridge and Key West bridges in Florida. Scaling is
most severe when concrete is subject to freeze-thaw cycles in the presence
of saline contamination. (226).
The process of drying ordinary concrete produces small capillary cavities.
When water saturates these cavities in the concrete and is frozen, the
freezing action alone can cause scaling as the volume of water in the cap-
illaries expands by about 9%. This expansion frequently causes; a flaking
or scaling of the thin layer of concrete over the cavities.
Air-entrained concrete in part prevents this scaling. Air entrainment
is produced by incorporating large air bubbles in the concrete as it is
produced. Since water preferentially seeks smaller capillaries, these
large cavities remain relatively dry in water saturated concrete and pro-
vide a point for pressure relief when freezing temperatures are reached.
In a systematic test of 110 different coatings (235, 244), linseed oil
treatments were found to be one of the most effective and economic means
of preventing scaling when applied to air entrained concrete.
Salts provide more moisture on the surface of the'pavement by lowering
the freezing point of water. They also create additional freezing below
the pavement surface. This latter phenomenon, known as thermal shock,
occurs when heat is absorbed from the pavement as ice goes into solution.
Spalling —
Spalling is the process by which the pressure from rusting reinforcing
bars cracks a concrete cover. (See Figure 8). The preponderant amount
of deterioration from spalling is associated with the use of deicing
salts and ocean salt sprays. The corrosion process of reinforcing rods,
which deicing salts accelerate, creates a pressure of about- 280 kg/sq, cm.
(4,000 Ibs/sq. in.) aasily sufficient to crack the concrete cover over
the rods (231). Inspections of bridge structures have revealed that
30
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Figure 8. Example of Deck Spall on underside of West Side Highway
(Photograph courtesy of Department of Highways, New York City)
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transverse cracks in concrete may result from freezing and thawing in
the presence of saline contamination. Transverse cracking in freshly
poured concrete is frequently observed as the deck moves under the weight
of the concrete, and as the concrete slowly settles around the reinforcing
steel. An effective means of closing these incipient transverse cracks is
the revibration of the concrete several hours after it is poured (226).
Transverse cracks may also be caused by too shallow a concrete cover over
the rods and by shrinkage during the drying and curing of the concrete.
Such cracks provide access to moisture which then can attack the underlying
steel. The rust process is greatly accelerated by the presence of salts
and air along with the moisture. Experiments by Herman (212) indicate
that pH reduction may be a contributing factor- in steel corrosion. Rein-
forcing steel is typically protected in chloride free concrete because of
the high pH of the soluble calcium hydroxide originally present in the
cemet. This high pH induces the formation of a protective coating of
ferric oxide on the surface of the steel.
Because of the porous'nature of the concrete, rusting of reinforcing
steel can take place without preliminary cracking since saline solutions
will slowly penetrate the concrete cover. It has been found that the
chloride ion concentration around the reinforcing steel is reduced by
approximately one half for each additional inch of concrete cover (236).
Age of concrete before exposure to salt solutions is an important
factor in inhibiting corrosion. It has been observed that bridges
built before the 1940s, when salts were first used extensively for
deicing, have in many instances survived better than newer bridges.
This may be attributed to the substantial length of time required for
concrete to properly cure, though it may also be partially explained
by a process of "natural selection" and examples of superior:workman-
ship and materials.
Advanced cases of spalling on a bridge deck are easily detected by the
presence of large potholes on the surface. These cracks and;holes can
cause discomfort and reduce the safety of passing motorists and cause
damages to automobile shock absorbers, bearings, and ball joints. In
infrequent instances, reinforcing steel is corroded to such an extent
that a bridge is incapable of carrying its designated load. :Less
advanced cases of corrosion can be detected by a variety of techniques
including electrical potential measurement to pinpoint the corrosion
site (236).
Repair Techniques —
Accepted methods for repairing bridge deck spalling involve temporary
patching of holes, partial restoration of the deck or replacement of
the entire deck cover. Patching of holes without removal of cracked and
salt contaminated concrete is an unsightly and usually only a temporary
means of repairing spalled sections. A large fraction of patches made
in a freeze-thaw environment will fail in less than a year. Many of
the potholes form during the winter months, a time when patching is
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more difficult and driving hazards greater than during the summer. Main-
tenance patching, even when properly done, may be less desirable than
other methods of repairing damaged bridges. Although highway departments
view the dollar outlay for maintenance patching as minimal, the full social
costs including safety hazards, damages to vehicle suspensions, and traffic
delays must be considered.
Partial restoration involves devising more permanent patches, with esti-
mated life of about 15 years, by removing the concrete surrounding the
corrosion site. The. resulting hole is patched with Portland cement con-
crete, or epoxy concrete when the speed of setting is important to minimize
traffic delays. The surface is sealed and an overlay of asphalt concrete
is applied. The practice of sealing the surface of partial restorations
also has been questioned by Kliethermes who feels that such deck covers
may accelerate corrosion in previously undamaged sections of the deck (230).
Unfortunately removal of active corrosion regions usually is not sufficient
to halt the corroding process, and other sections may begin to spall soon
after the repair is completed. Formerly passive sites can quickly switch
to being active sites as electrons flow to the sections having the greatest
positive potential in the deck.
Replacement of an entire bridge deck is an expensive process with repair
costs reported between $400,000 and $1,200,000 for large bridges, and is
normally justified only when the spalling damage is extensive. Most bridges
do not remain part of the highway system for a period as long as 50 years.
Partial restoration seems to be more desirable when the time value of money
is considered, since expenditures 15 to 30 years from now should hot get
equal weight in a comparison with outlays today for replacement. Until
complete replacement is possible, Kliethermes (203) advocates temporary cold
mix bituminous patches on bridges which exhibit active corrosion on 50%
to 100% of the deck. For decks where 20% to 60% of the structure contains
corrosion sites, concrete removal and patching of chloride contaminated
areas is recommended. For bridges containing active cells in 25% or less
of the deck, he suggests removal of chloride contaminated sections followed
by placement of a waterproof membrane and an asphaltic, concrete wearing
course. These recommendations are based primarily on economic considera-
tions .
Deck seals are commonly used in replacement of existing decks and on new
decks. In Europe, the use of waterproof membranes, designed to prevent
the intrusion of moisture and salts to the reinforcing steel has
gained widespread acceptance for new construction and for the repair
of existing bridges (233). Many different materials have been used as
membranes including: copper sheeting, butyl rubber sheeting, bitumen-
aluminum sheeting, bituminous felt, and adhesive coated polypropolene
fabric. Dissatisfaction with these methods has led to experimentation
with epoxy resins and polyurethanes. In the United States prior to
1970, membranes were frequently produced on site by applying several
coats of a coal tar pitch to the concrete surface, and sandwiching a
layer of glass fabric between coats if reinforcing is desired. The
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ability of the membrane to reseal itself in periods of warm weather
significantly adds to its waterproof qualities (238). In Europe
and in the United States, preformed sheet type membranes are more commonly
used now. Over both types of membrane an asphalt wearing course is
applied. '
Experience with membranes indicates that they frequently do not perform
as well as anticipated. Membranes are hand placed and as such are
subject to poor workman performance. Additionally, the application
of hot asphalt may melt the membrane. In situations where the grade
exceeds 4% or there are centripetal forces from curves and braking,
the asphalt overlay tends to slide across the membrane. This limits
the situations where membranes may be successfully utilized. The
typical membrane leaks after a few years, though still offering some
protection to the underlying steel.
A number of other procedures to inhibit corrosion of reinforcing steel
have been tried, including various coatings applied to the steel before
placement. Although many different coatings - including asphalt epoxy,
epoxy, nickel, copper and zinc all have been used in experiments, the
epoxy coating appears to have the greatest promise (234). Epoxy coated
steel is approximately twice as expensive to place as ordinary steel,
and results in an increase in total cost comparable to the waterproof
membrane. Special tests have been designed to insure that the coated
reinforcing rods will not (1) allow passage of chloride ions to the
steel, (2) suffer cracks in the coating when bent at an angle of 120°,
or (3) abrade during placement.
Cathodic protection is an experimental method of preventing the destruc-
tive flow of electrons necessary for the oxidation of reinforcing steel. .
It has been shown to be capable of halting corrosion in decks already
thoroughly contaminated with chlorides. In a paper delivered at the 1975
meetings of the Transportation Research Board, Harold Fromm, of the Ontario
Highway Department, described the results of continuing experiments with
cathodic protection. Following upon Stratfull's pioneering work, bridges
were protected by placing graphite anodes in the deck, covering them with
asphalt concrete, and applying approximately 3.23 milliamps of current per
square meter. Preparation of the deck in this manner took approximately
two days and resulted in minimal traffic disruption. Power requirements
for the entire bridge are approximately 1.5 watts per hour, and were so low
that the power company considered it-not worth installing an electric meter.
Actual costs of cathodic protection were $96.82 and $39.37 per square meter
on the first two bridges, but were expected to fall to only $9.25 on the
fourth installation. The general feeling is that cathodic protection is
best applied to bridge decks that are still in sound condition, and that
badly deteriorated decks are best replaced.
Experimentation with the composition of concrete dates back to at least
the 1940s. Since that time, a latex modified concrete (Dow SM--100) has been
marketed for patching bridge decks. The repairs have performed well and
the Federal Highway Administration is now using this concrete for overlay-
ment on some bridges. In the early 1960s, silicones were investigated as
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an admixture to prevent scaling (220). The FHWA is currently studying
the feasibility of impregnating concrete with polymers (212). In this
process, which is being field tested by the U.S. Bureau of Reclamation
in Denver, dry heat is first applied to a deck. Next, approximately
1/2 cm of dry sand is spread and saturated with liquid monomers (typically '
lucite or methyl methacylate). The sand appears to significantly .aid
penetration, which is carried to a depth of about 2 1/2 cm, and leads to
uniformity in application rates on uneven surfaces.* Finally the monomer
is polymerized in situ with heat. Polymer impregnated concrete has many
advantages over ordinary concrete. It is impermeable to chlorides, improves
abrasion resistance by providing a harder surface, and has greater freeze-
thaw resistance. It is unknown at this time how resistant the new concrete
will be to cracking; cracks could prove serious if they allow intrusion of
chlorides to the reinforcing steel. Costs of this method are uncertain
primarily because they involve the consumption of liquid monomers far in
excess of current production capacity. The ultimate cost may be comparable
to present waterproof membranes.+
Another promising modification of concrete is the incorporation of small
pieces of wax in the mix as it is poured. After the concrete has cured,
heat is applied, melting the wax and sealing the cappillaries. Initially
beeswax was used but because of greater availability and lower cost, mon-
tan wax, and later a mixture of parafin and montan wax, was used. In field
tests to date, this treatment appears to produce a concrete that is imper-
vious to attack by moisture and salt solutions.
Damage to the West Side Highway in New York City
While it has been an accepted fact that deicing salts can cause
serious damage to bridges and highway structures, and while there have
been numerous reports and research on the matter, by far the most
devastating damage that has occurred is the general deterioration of
the West Side Highway in New York City (221,222,223,224). On
December 15, 1973, the northbound roadway between Little West 12th
Street and Gansewoort Street collapsed. (See Figure 9). At that
time the Transportation Administration of New York closed the section
of the highway between the Battery and 46th Street for an indefinite
period. Immediately thereafter the Division of Bridge Design of the
* Lehigh University is currently under contract to the Highway Research
Board to investigate the feasibility of impregnating concrete to the depth
of the reinforcing rods.
+ According to Hay (225), polymer impregnated concrete contains by weight
approximately 6% polymer, or about 3.6 kg of polymer per square meter of
surface to the depth of 2 1/2 cm. Current costs of Lucite range from $.66
to $.88 per pound indicating a direct cost of monomer of $2.37 to $3.27
per square meter. The remaining costs would be attributable to heating and
labor.
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"™' •.'•'.- •-"?• -''""-"• ''i1"
Figure 9. Collapse of West Side Highway at Ganesvoort Street on 12/15/73
(New York Times Photograph)
Department of Highways performed a preliminary survey between the
Battery and 59th Street and confirmed the extreme structural deter-
ioration of the connections between longitudinal girders and transverse
floorbeams. (See Figure 10).
There had been no inspection of this city-built highway for 40 years.
Following the 1967 collapse of the Siver Bridge in West Virginia, from
I-Bar failure related to stress, National Bridge Inspection Standards
36
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Figure 10. Typical Stringer Web Deterioration on West Side Highway Structure
(Photograph courtesy of Department of Highways,, New York City)
were instituted in 1968. For the city to determine the true condition of
the West Side Highway, however, the Transportation Administration contracted
Hardesty and Hanover, Consulting Engineers, to conduct a complete examin-
ation. Their analysis, conducted from July 9 to November 14, 1974, resulted
in four substantive volumes, the last dated May 30, 1975. The following
quotes are taken in-context from the most recent report:
"The deterioration of. the West Side Highway has been a continuous
problem. As early as the mid-fifties public officials had antici-
pated its early demise. The use of salt to remove ice, combined
with heavy traffic, has caused disintegration of large sections of
the roadway. On several occasions, prior to the December 15, 1973
failure and closing, portions of the roadway slab have fallen into
West Street. The asphalt overlays, which replaced the original
granite block wearing course, are also in poor condition with
holes and surface cracking. The damaged concrete has been tem-
porarily repaired by covering the holes with steel-plates supported
by the steel superstructures which, in certain areas, has been sub-
jected to extensive corrosion." (224, p. 21)
"Our inspection between the Brooklyn Battery Tunnel and midtown
reveal that serious conditions and deterioration exist at many loca-
tions on the West Side Highway; therefore, the entire roadway south
of 46th Street should remain closed until a decision is made whether
to demolish the structure or to proceed with repair and rehabilitation."
37
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"The deterioration is a direct result of water and waterborne
salt leaking through the expansion joints and the concrete
deck. Water passing through the wearing course follows the slope
of the concrete deck to the longitudinal girders where it leaks
through cracks or through the joint between the deck and the
girder web. Depending on the cross slope either the exterior or
the interior floorbeams are affected." (224, p. 25)
The report concludes that although restoration of the highway is
feasible, the cost of the work is almost prohibitive. The chief
engineer* for the New York City Department of Highways estimates that
it will cost $58 million to perform a partial rehabilitation ;of the
West Side Highway from the Battery to 72nd Street. Hardesty and
Hanover suggest that restricted rehabilitation for maintenance of the
existing structure including "new deck, median barrier, lighting,
painting, and steel repairs would cost about $66 million in 1976." (224)
A complete rehabilitation including some updating or modernizing would
entail $88 million according to a New York City Highway Department
representative. The fourth and most expensive serious alternative^
presently before the city council is a proposal to demolish the existing
elevated highway and build a new interstate highway to be called the West-
way.
Not surprisingly, the consultants conclude, in part, "Use of salt for
deicing should be minimized. Other methods and materials for maintaining
traffic during ice and snow conditions should be considered.1! (224, p. 35)
The chief engineer* affirms that deterioration of the West Side Highway
structure was accelerated by the brine of dissolved rock salts compounded
by the problem of poor drainage.
While the cost of the repairs to the West Side Highway may not be represen-
tative of typical bridge damage, there are other examples of costly salt
induced deterioration. Recently it was reported that four Washington, D. C.
bridges had become dangerous to traffic because salt had caused extensive
corrosion of the reinforcing steel. The cost of the repairs is i$11.7
million. (330)
Pavements —
With proper attention to design, materials and construction,;cracking
can largely be controlled. Concrete pavements are less vulnerable to
spalling than are bridge deck pavements due to a number of factors:
(1) bridge decks are subject to greater flexing stresses; (2) rein-
forcing steel is not as common in highway construction but where it
exists the concrete cover is.generally twice as thick as the.2 inches
normally used in bridge deck construction; (3) transit mix concrete,
which is more variable because of the use of several mixers, is usually
used to cast bridge decks; central mix concrete is normally used for
highways; and (4) other factors including reduced homogeneity resulting
* Personal Correspondence with the Chief Engineer, Division of Bridge
Design, Department of Highways, New York City.
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from extensive hand finishing, and increased surface exposure sub-
jecting parts of the bridge structure to environmental stresses such
as freeze-thaw action that the underside of pavements are protected
from. For these reasons, salt related damage to highways is far less
frequent than damage to bridge decks.
4.2.3 Utilities
There have been a number of reports of corrosion damage to underground
water mains, telephone cables and electric lines (15,26) resulting
from the use of deicing salts. There have also been reports of damage
to above ground electrical insulators from airborne roadsalt (318).
The evidence at the time of these reports did not clearly show that
road salts were to blame. That link has now been clearly established
by two very thorough analyses.
Telephone and Electric Power Transmission Lines —
The first study was carried out between February and June of 1974 under
the direction of Joseph D. Block, Executive Vice President of Consoli-
dated Edison Company of New York (246). Mr. Block took on the study ,
in response to the statement that there is "little data available either
to substantiate or to disprove these reports" of corrosion to under-
ground power transmission lines in the 1972 report, Deicing Salts and
the Environment produced by the Habitat School of Environment and the
Massachusetts and National Audubon Society (26). On June 3, 1974,
after extensive analysis of corrosion damage and salt use in all
boroughs of New York City between 1970 and 1974, Mr. Block wrote
the following to the Habitat School of Environment:
"Con Edison operates in New York City the largest system of
underground electric facilities in the world. We had a unique
opportunity in the past two years to assess the damage to this
system by reason of the use of salt on the City streets. The
winter of 1972-73 was quite mild and there was very little
snow. The City used only about 20,000 tons of salt during the
winter and I suspect most of this was used on bridges and
bridge approaches, etc., which are more apt to be subject to
rain freezing on road surfaces than are average City streets.
During the past winter there were two storms of serious
proportions when the streets were heavily salted. One of these
storms was in December, the other was in January. The City
used approximately 120,000 tons of salt this past winter or
100,000 tons more than the winter before.
The effect of this salt on our.electrical system becomes evident
almost immediately after it is used and continues for two to three
months as thawing snow and rainstorms .wash the resultant brine
through our subway systems. Our secondary cables (generally
rubber insulated and operating at 120 volts) develop short
39
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circuits and catch fire. There were approximately 1,400 more
manhole fires this past winter than the previous winter. These
additional manhole fires required extensive repairs and the
replacement of almost 1,000 sections of secondary cable
at a cost in excess of $4,000,000.
The effect of the salt on our primary feeders (cables operating
at 13,000 and 27,000 volts) develops more slowly because of the
heavier insulation and better coverings than are used on
secondary cables. For the first four months of 1974 we had
125 more failures on our primary feeders than we did during
the corresponding period of 1973. Replacement of cable
associated with these failures cost Con Edison approximately
$250,000. ;
We know that the brine has corrosive action on our underground
transformers, switches and other equipment. It also has,, as
mentioned in your report, a deleterious effect on the concrete
in the manholes and ducts used in our subway systems. Because
these effects do not become apparent for several years, we
cannot place a price on the deterioration caused this past
winter.
Altogether, it is safe to estimate that the salt spread on
the streets of New York City resulted in additional expendi-
tures by Con Edison in excess of $5,000,000 during the winter
of 1973-74 (245)."
No estimate of the cost to consumers as a result of power outages has
been made. Based on the data collected by Mr. Block, several hundred
power outages during the severe winter months can be attributed
to road salt use. The cost of such extensive power losses is very
significant in terms of inconvenience, lost production time, and lost
personal time.
It is likely that the costs incurred by Consolidated Edison are far
larger than those incurred by any other municipal electric company.
Very likely many other instances of electrical damage that have not
been so well documented and analyzed will be found to be salt related.
Mr. Block's analysis will hopefully pave the way for other large
utility suppliers (and users) to document and to investigate their own
reports of salt-related damage more thoroughly. ;
As explained at the beginning of Section 4, it has been shown that
deicing salts enter into the atmosphere and are carried farther from
the initial point of dispersal (highways) than occurs from splash and
runoff. In general, air pollutants (participate and gaseous) can
cause a variety of problems in the operation of electrical apparatus.
The buildup of pollutant films on the contacts of electrical connectors
hampers the flow of electrical current and thus impairs operation.
Particulate matter deposited on the contacts can also prevent the
connector from closing completely and again the current flow is impeded.
40
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In a paper on the influence of air pollutants on electrical connectors,
the economic importance of air pollutant problems is- discussed (317).
The paper points out that connector miniaturization was being limited
by the difficulty in maintaining clean surfaces due to air pollution.
In addition, any estimate of the economic losses due to air pollutants
probably do not include the factor of expensive chemically resistant
materials, such as gold, being required in place of cheaper materials
which would not be as resistant to air pollutants.
A very serious problem in the transmission of electrical energy is the
contaminant buildup on insulator surfaces. The problem is not unique
to salt particles but sea salt is one of the most conspicuous offenders.
One survey (318) specifically noted road salt as the cause of some power
outages.
The reliable and uninterrupted operation of modern power systems depends
on insulation which must not deteriorate or allow disturbances,
flashovers, and/or line outages. The deterioration and flashovers
that do occur are mainly the result of air-borne deposits from natural
(sea salt),as well as man-made (generally industrial) sources including
road salt.
The accumulation of pollutant layers on insulators is a complicated
process depending on electrostatic, gravitational, and wind forces and
influenced by insulator shapes, the surface conditions, corona dis-
charge, and rainfall (319). Dry deposits usually do not lead to dis-
turbances such as flashovers. Natural processes such as high relative
humidity, fog, dew, frost, and rainfall cause the pollutant layer to
become moist (especially when_ the__depc)sits _are hygroscopic as are salt
layers). These moist layers were reported in 1966 to be the second
major cause of line outages (320).
The processes leading to pollution flashover on electrical insulators
are as follows. When the insulator surface becomes moist, current
flows across the surface and the resistive heating leads to the formation
of dry bands. Flashovers occur if one of the discharges across the dry
bands propagates across the entire wet surface (320).
That electrical insulator contamination is a serious problem is evident
from the rather large number of papers on the subject in the IEEE
Transactions on Power Apparatus and Systems. An incomplete survey of
the literature noted over 25 papers on the subject since 1969.
In 1971, the results of a survey of the problem of insulator contamination
in the U.S. and Canada were published (318). A questionnaire had been
sent to 90 utilities and 59 responded with 309 case histories of
transmission line outages. Each case may contain a great number of
flashovers on different insulators and numerous outages. Determination
of cause was made by the utility company engineers. Road salt was
most often a source of outage in fog conditions. Although this survey
found only 20 of the 473 outages were attributed to road salt, from
other information gathered since 1971 it is likely that the true extent
41
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of salt as a causative factor has been understated. Since deicing salts
appear to be widely dispersed throughout northern U.S. urban areas in
the winter and spring months, it appears that there are a ^number of
variables (proximity of power lines along high speed highway, amount of
salt used, type of insulator, etc.) that make power failures caused by
deicing salts more common in certain areas. The resulting frequency
of outages in a few areas means an even higher cost of inconvenience
to the users affected.
Underground Pipe Corrosion — ,
Soil moisture is a necessary condition for the external corrosion of gas
and water mains to occur. The corrosion process is enhanced by a number
of additional factors, one of which is the presence of sodium and
chloride ions from dissolved deicing salts. Natural soil resistance to
electrolyte migration is decreased by salt in solution, The electro-
magnetic corrosion process discussed in Section 4.2.1 is similar in the
case of underground pipe corrosion. Decreased electrical resistance of
the soil allows the electromagnetic field set up between anode and
cathode to expand, and thus charged ions can travel greater distances
through the soil and the corrosion rate increases. (245)
Summary —
The continued use of chloride salts in winter months will affect
utility companies' equipment, through direct corrosion where brine
contacts metal and concrete surfaces and through changes in electrical
insulation caused by airborne particulate salt debris. When these
damages are allowed to continue unabated, . we will find ourselves
absorbing social costs in inconvenience, interruption of service,
exposure to increased chances of electrical fire or gas or water main
leakages, in addition to more out of pocket costs as the utilities
pass on repair costs to the consumer. These costs are more fully
detailed in Section 5.
4.2.4 Industrial Production
The impact of sodium chloride in water used for industrial production
has received mention in the literature. The maximum allowable levels
of chlorides for some of those industries are as follows: Carbonated
beverages, food equipment washing and paper manufacturing (Kraft) - 200
to 250 mg/1; steel manufacturing - 175 mg/1; textiles, brewing and
paper manufacturing (soda and sulfate pulp) - 60 to 100 mg/1; dairy
processing, photography and sugar production - 20 to 30 mg/1 (15).
However, there is little mention in the literature of actual cases
in which there were costs incurred by industries because of concentrations
above these levels. One industrial user in Peoria, Illinois was
forced to switch to city water because of salt contamination of its
private well (126). :
42
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SECTION .5
THE COST OP SALT-RELATED DAMAGE
5.1
METHODOLOGY
The evidence summarized in the preceding section suggests strongly that
deicing salts may and do cause damages that frequently are not taken into
consideration by those responsible for winter highway maintenance. Part
of the problem lies in the fact that — while the possibility of these
damages is generally known — their likely extent and incidence are only
vaguely perceived, in order to improve the decision making process
relating to the intensity and pattern of salt application, it is necessary
to provide policymakers with the means to evaluate the total costs of
salt use. Unfortunately, most of the research that has been conducted
on the potential damages of deicing salts has been more of a case study
nature. This orientation has led to a situation in which research fin-
dings are interesting, but often irrelevant to or useless for decision
making, at the local or state level.
The present study examines the available evidence for its potential to
yield some indication of the likely total costs of salt use. It is
clear that there is a critical constraint:' the basic orientation of past
research. It is difficult, if not impossible, to infuse decision rele-
vance into research that was never intended to be designed to yield infor-
mation for policymakers. The method in this study has been to clarify
prior constraints, to approach the problem of cost determination and
estimation from a comprehensive framework, to assess the usefulness of
available research against this framework, and finally to use the (often
extremely sparse) empirical evidence to derive some indicators of the
potential range or approximate order of magnitude of costs for various
damage categories.
Figure 11 sketches the broad framework describing the ways in which the
application of road salts generates direct and indirect costs to indivi-
duals and society. Basically, direct costs are required expenditures by
either individuals or government as a representative of society; indirect
costs denote losses in welfare which may affect members of society indi-
vidually or collectively. The application of deicing salts introduces
into the environment a foreign substance which changes characteristics of
natural or man-made resources directly or indirectly (by affecting the
environmental conditions determining their survival or life expectancy)
in a way that reduces their usefulness. These reductions in usefulness
can be related, at least at a conceptual level, to dollar costs which
43
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44
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describe the damages in terms of a common denominator. These costs
(estimated or imputed) are an expression of the value of the "lost use-
fulness" of the respective resource, or the cost of restoring that resource
to its full usefulness. :
The main problem in the application of this framework to the actual estima-
tion of costs is the nature of the relationships between damages and
salt application. The damages resulting from the introduction of salt
into the environment are the result of complex processes. Generally,
numerous factors other than salt must be taken into consideration in
analyzing the. relationships between salt use and any suspected damages.
Present knowledge of .the interaction of these factors is limited. In
addition, the processes also depend on the timing of certain phenomena.
For example, in many instances, the damages associated with salt brine
runoff from the highways to vegetation or water supplies depend on pre-
cipitation patterns. Since precipitation fluctuates randomly over the
year, it is entirely possible that the same amount of salt applied in
two winters produces completely different effects as the result of dif-
ferences in precipitation patterns, all other things being the same.
Moreover, the amounts of salt applied tend to vary considerably over time
in response to differences in the incidence of snow and ice on highways.
All of these elements interact to produce considerable uncertaintly in the
known relationships between damages and salt application. This uncertainty
impedes the development of a micro-analytical model which translates the
relationships shown in Figure 11 into functional and quantifiable expres-
sions.
Part of this problem could be overcome by treating the uncertainty in
the functional relationships between deicing salt use and associated
damages through a probabilistic approach. This approach can be sketched
schematically in a form of the following expression:
Cost = Probability of Damage per Unit of Resource Exposed X
Population (Number of Units of that Resource) at Risk X
Cost per Unit of Damage
The resource in question may be water supplies, automobiles, underground
cables, or any of the other elements that have been identified as being
adversely affected by deicing salts.
The formal presentation of the probabilistic approach to deal with un-
certainties identifies the data required for its implementation. The
most important data element is the determination of the probability of
damage for a given resource exposed to the effects of deicing salts.
The estimation of these probabilities requires a considerable amount of
45
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data, which allow for the isolation of the net effects of deicing salts
either tinder controlled conditions, or through multivariate analysis
which can account for other relevant factors. In a controlled situation,
experimental data have to be sufficient to describe some form of dosage-
response relationship, while non-experimental data have to be obtained
through such methods as epidemiological studies. For generalization,
the latter requires a sufficient sample of the population at!risk (which
may be quite small, depending on the problem). The non-experimental
approach therefore implies that population-at-risk figures are already
available for the selection of the sample used in estimating1the damage
probabilities. ,
Data on the population at risk are needed regardless of the way in which
damage probabilities were derived to estimate the total (expected) inci-
dence of damages. This figure can then be multiplied by some equivalent
of the cost per unit of damage.
The data requirements and analytical steps can best be illustrated .by means
of an example. In order to compute the costs of salt-related damages to
roadside vegetation, primarily trees, the probability of damage could be
defined as the probability of death for a given amount of sodium accumul-
ation in the soil. (Assume for simplicity that death is the only rele-
vant damage category, which abstracts from a more continuous spectrum of
damages). For different kinds of trees, these probabilities;may have
been established through controlled experiments. Available studies on
sodium concentrations in soils at different distances from the highways
that can be attributed to deicing salts could then be used to define
and enumerate the population at risk (e.g., all trees within a 9 meter band
along "bare-pavement" highways.) Multiplying the probability of death
by the number of trees exposed to the risk would then yield the expected
number of tree deaths attributable to the use of deicing salts. Unit
costs per dead tree, finally, could be derived from available estimates
of the value of shade trees. i
In this particular example, the only information item that is available —
although with certain qualifications — is the unit cost. Actual experi-
ments, for example those reported in "Salt Damage to Trees and Shrubs"
(168), have tended to yield less than conclusive evidence on the damage
probabilities. However, more important is the absence of data (any data)
on the population at risk. Trees along highways that are candidates for
deicing salt application simply have not been counted. Similar data gaps
exist with respect to other natural or man-made resources that are
affected by salt-related damages.
In the absence of any data required to implement a more comprehensive
approach, ad hoc methods have been used to take advantage of certain
pieces of information that give some impression of the magnitude of the
problem. This step had to be taken in a number of damage categories
discussed below.
46
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The analysis comes closest to the ideal approach with respect to damages
to automobiles, where multivariate analysis is used to determine the
incidence of salt-related damage, motor vehicle registrations provide
reliable data on the total population at risk, and car prices can be
used to determine the unit cost of salt-related damage. It is interesting
to note that this method yielded the highest cost estimate of all cate-
gories examined.
47
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5.2
COSTS OF WATER SUPPLY CONTAMINATION
Water supplies have been and continue to be contaminated by the runoff
of deicing salts from highways. The degree to which salt applied to
the road surface infiltrates water supplies in the form of sodium and
chloride ions may vary in response to factors such as soil consistency,
distance, topography and climatic conditions.* But the evidence sum-
marized in Section 4.1.1 is sufficient to demonstrate that; the use of
deicing salts has led to serious problems in assuring the supply of
high-quality water in many portions of the snowbelt region. The pre-
sent section complements this summary of the technical evidence by
examining the magnitude of damages to water supplies, primarily drinking
water, in economic and social terms.
The evaluation of the total social costs of water contamination as a
result of deicing salts faces a number of conceptual and empirical ob-
stacles. The very nature of the costs incurred by government and
individuals as a result of salt contamination of drinking water supplies
hampers their enumeration and evaluation. In contrast to damages to
physical structures, such as highway bridge decks or automobiles, which
require scarce resources for any remedial action, it is possible that
the contamination of water supplies may be mitigated as a consequence
of natural processes (such as precipitation) . Empirical data show
considerable fluctuations of sodium and chloride levels around critical
pattern.
The occur-
values. + These fluctuations exhibit a random
rence of acute contamination problems (sodium or chloride concentrations
exceeding some criterion level) therefore can be predicted only as a
probable event. This problem can be illustrated by Figure ; 12 which
shows chloride concentrations in surface waters in Rhode Island (291) .
If 60 mg/1 are regarded as a critical level
a (crude) probability
estimate for the East Providence case to exceed this level in any given
year would be 40%, since the threshold was crossed twice in five years.
In addition to the occurrence , the extent of contamination - and its dura-
tion are also subject to random factors.
These characteristics influence the behavior of any direct or indirect
costs over time. Since these costs arise in response to the occurrence
and extent of any contamination, neither , their occurrence nor their
* The discussion here focuses on groundwater contamination, since
runoff into surface water constitutes different problems, at least in
standing water bodies. In flowing surface water, salt concentrations
rarely reach significant levels.
+ These random fluctuations occur against a steady, and often acceler-
ated upward trend in the sodium and chloride levels of drihking water
supplies.
* The chloride level at which the sodium content exceeds 20 mg/1 with
near certainty
48
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Chloride
mg/1
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Figure 12. Rhode Island - Surface Waters
Reprinted (with modification) by Permission from Ref. 291
49
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magnitude follow a regular pattern over time. This feature hampers
the development of a micro-analytical cost model for water supply con-
tamination.
The conceptual issues are compounded by problems of data availability.
Neither the direct nor the indirect costs of excessive levels of sodium
and chloride in drinking water have been measured in a comprehensive
manner at any level of aggregation. For example, even simple cost
items (such as the costs of more frequent testing once chloride levels
are approaching threshold levels) cannot be culled from existing expen-
diture records, since accounting procedures at the local or state level
tend to lump these costs with expenditures on routine activities. The
empirical evidence required for the cost analysis at the necessctry
level of detail thus often simply does not exist.
Finally, apart from the problem of the appropriate conceptual framework
and data availability, the analysis also has to cope with a serious
issue of a more philosophical nature. Probably the most important
indirect cost of salt contamination of drinking water supplies is
related to the health effects of increased sodium intake by users. High
levels of sodium intake have been found to contribute significantly
to increased morbidity and shortened life expenctancies (e.g., in 134).
The evaluation of such effects in economic terms faces a number of issues
that have been debated in health economics for some time. While several
methods have been developed to "cost out" the detrimental effects of some
substance or factor on public health, none of these.techniques resolves
the basic philosophical dilemma — placing a dollar value on human life.
Generally, the costs of ill health can be measured by including direct
expenditures on diagnosis and treatment, as well as the opportunity
costs of losses in productive activity, i.e., 'the value added foregone
by society. While this approach is useful in a purely economic context,
it has the serious drawback that the ill health of "non-productive"
members of society (persons outside the labor force) cannot be directly
evaluated in this manner. The analysis below therefore provides! only
estimates of the likely ranges of health effects, without attempting to
translate them into dollar figures.
Given the problems of conceptual complexity and of observation and
measurement for estimating the costs of salt contamination of drinking
water supplies, the approach taken here focuses on the development of
a comprehensive framework designed to cover all direct and indirect
cost elements on a per capita basis. The cost model is subsequently
used to explore the range of likely total costs on the basis of avail-
able information and reasonable assumptions about specific unit costs.
This discussion is followed by an assessment of the principal health
effects associated with increased sodium levels in drinking water
supplies.
50
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5.2.1 Cost Estimate Framework
As noted in Section 5.1, several dimensions of the cost analysis can
be distinguished. For the costs resulting from the chloride and
sodium contamination of drinking water supplies, the general breakdown
can be illustrated by means of selected examples shown in Table 1.
This breakdown distinguishes direct and indirect costs. Direct costs
involve expenditures or use of resources to remedy any damages related
to salt contamination. Indirect costs can be viewed as damages to
individuals or society as a whole that involve a reduction in the level
of welfare of the party or parties concerned without requiring any direct
outlays.
Table 1
Dimensions of Costs Associated with
Salt Contamination of Drinking Water
(with Sample Cost Items)
Cost Type
Direct
Indirect
Cost Incidence
Individuals
Cost of replacement
of private wells as
a result of the
contamination of
existing wells-
Losses in private
property value in
areas exposed to
the risk of drink-
ing water contam-
ination through
deicing salts.
Society
Cost of installa-
tion of special
drainage ditches
and catch basins
to keep salt runoff
from water supplies .
Losses in value
added as a result of
the reduced produc-
tive capacity of
individuals with a
hypertension condi-
tion exacerbated by
sodium in drinking
water . *
* Largely a cost to society, since individuals are at least partially
compensated through some form of transfer-payment.
51
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In terms of the incidence of costs, two major groups can be distin-
guished: government (at all levels) as a representative of society
as a whole, and individual members of society. Although this distin-
ction is somewhat arbitrary, it is useful by allowing for a more
detailed breakdown of the types of costs incurred as a result of the
contamination of drinking water supplies. In addition to contributing
to a more structured analysis, the distinction also allows for an
assessment of the equity implications of alternative institutional
arrangements. One example may illustrate this point. As a consequence
of the application of deicing salts, private wells have become contam-
inated in several states. In most areas, it is the primary responsi-
bility of the individual well owner to finance measures necessary to
cope with this problem, at least ,in the shortrun.* In-a few instances
this problem has been reflected in losses in property value that can
be directly attributed to the salt problem. The incidence of costs
can be shifted from affected individuals to society. There is at least
one instance in which the state has accepted the responsibility for
any costs related to the contamination of private wells through deicing
salts. New Hampshire instituted a well replacement program as far
back as 1956, with the state paying for the replacement of:wells that
have been determined to be contaminated by salt runoff from highways
(265). While this program does not imply a complete shift of the cost
burden from the individual to society as a whole (there is a substan-
tial waiting period involved, partially because of the large volume of
claims), it may result in a more equitable distribution of the net
costs (or net benefits) of the use of deicing salts. The discussion
will return to an examination of the equity aspects below.!
The examples shown in Table 1 .suggest some of the difficulties of
delineation of cost categories. Particularly in the area of direct
vs. indirect costs, a general line cannot be drawn. Too much depends
on the particular arrangements and the extent to which water contamin-
ation may go unnoticed. The discussion below therefore focuses on
the cost implications of remedial measures that restore affected water
supplies to their original quality (e.g., through well replacement).
The analysis of indirect costs focuses on health effects only.
Direct Costs —
The identification of the relevant direct costs to either society
or individuals calls for a look at the process which gives rise to
these costs. Since the contamination of drinking water supplies is
* There are of course several possibilities in the longer term to
shift any costs to society, for example, by lobbying successfully for
any form of compensation, or for the construction of special drainage
ditches that will prevent salt runoff into private wells.
52
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primarily a public health problem, analogies from medical care can be
used to structure the cost-generating process. The direct costs in-
curred by either water supply agencies or users of public or private
water supplies can be grouped into three broad categories: the costs
of prevention, of diagnosis and of treatment.
Prevention: The growing awareness of the potential impact of
the use of deicing salts on the contamination of public or private
water supplies with chlorides and sodium has led to an increased
emphasis on preventive measures. These measures include the installa-
tion of special drainage ditches and catch basins for salt brine run-
off from highways, the selection of well locations at a sufficient
distance from highway drainage areas, the incorporation of water supply
locations in highway route planning, and any other measures designed
to lower the chances of infiltration of salt brine runoff into private
or public water supplies.
Diagnosis; Practically all public drinking water supplies are
monitored on a periodic basis with respect to a variety of constituents.
As a result of the accumulating evidence concerning sodium and chloride
contamination, these monitoring activities have been stepped up in a
number of instances. For example, the State of Massachusetts tradi-
tionally had limited its tests to the determination of chloride levels
(together with a variety of other substances). Recent concerns over
the salt contamination of drinking water supplies have led to the intro-
duction of sodium tests as part of the regular monitoring procedure in
1970 (see 53). Diagnostic costs also include outlays for studies
designed to identify the source(s) of observed contamination problems,
assess their implications for the future, and determine appropriate
remedial steps. Finally, the category of diagnostic costs also covers
all incremental expenditures incurred in handling user complaints and
inquiries and in following up on specific cases. Such costs apply,
for example, to the U.S. Environmental Protection Agency's mandate to
participate in the supervision of"drinking: water quality.
Treatment; Once a serious contamination problem has been identi-
fied, persons responsible for a given water source (either public
or private) have to take some form of remedial action. The definition
of a "serious contamination problem" may vary across the snowbelt
region. In terms of chloride, most states and local water supply
agencies focus on the recommended limit established in 1962 by the Public
Health Service at 250 mg/1. However, in several instances, levels con-
siderably below this limit have been taken as a cause for action.
Particularly with the increasing concern over the sodium content of
drinking water supplies, chloride levels as low as 30-70 mg/1 may be
cause for concern*.
* While the relationship between sodium and chloride contamination
varies in response to soil consistency and precipitation patterns, a
rough guideline is a ratio of 2:3 to 1:3. A chloride level correspon-
ding to a sodium concentration of over 20 mg/1 may therefore be cause
for concern.
53
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Remedial action or treatment may assume several forms. Itjmay range
from modifications of the current water supply system and its environ-
ment to a complete replacement of the water source bv some alternative.
Modifications of the current system include, for example, attempts to
reduce the chloride or sodium concentration by "flushing" the well,
changes in drainage system for the area (which may involve;the instal-
lation of special drainage ditches or the implementation of any of the
other measures discussed under prevention), or reduction of production
from the affected well(s) in the hope that sufficient dilution will
occur. Such measures are likely as long as the observed concentrations
do not yet pose a public health problem.
Once the concentrations approach or exceed the critical level — generally
defined in terms of the recommended chloride limit of 250 mg/1 — the
principal course of action followed by public water supply officials
or users is the switch to other water sources. The cost implications
of such a course of action vary considerably with the characteristicss
of the system. For example, a town that is dependent on one main well
may have to purchase water from other sources at substantial additional
cost, or may have to invest in the development of a new well. In con-
trast, a town employing a number of wells may just have to[increase
production from non-affected wells to replace a well that had to be
closed because of chloride contamination. For private water supplies
affected by salt runoff, the only alternative is generally;the drilling
of a new well, preferably at a sufficient distance from the highway
drainage area. Several studies have indicated that a .minimum distance
of approximately 15 meters from the highway shoulder is necessary to
reduce the likelihood of deicing salt contamination of private water
supplies, e.g., (95), on some lots such as relocation may be difficult,
because of the location of the septic system. :
Another possibly major cost element is the reaction of users to current
sodium levels in drinking water. Persons on a low-sodium diet for medi-
cal reasons may become concerned over the possibility of excess sodium
in their drinking water, preferring instead to purchase bottled water
(which may or may not be "pure"). Without a specific survey, it is
impossible to predict what percentage of the population follows such
a course of action. Here again, it is important to remember that sodium
concentrations vary randomly as a result of natural factors or because
of variations in the amounts of salt applied. Since it is: virtually
impossible for the individual user to test the drinking water himself,
his or her decision as to the use of tap vs. bottled water generally is
based on haphazard information from the media, or responses to inquiries
to water-supply agencies. This information base tends to leave a sub-
stantial uncertainty. Given the potentially high risk for individuals
with a hypertension condition, the best course of action may be to pur-
54
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chase bottled water.* The likely costs of these purchases must be
included under the treatment, category.
These considerations establish a basis for listing the major direct
cost items associated with the contamination of drinking water supplies
by deicing salts. Table 2 presents a fairly comprehensive list of
these cost items, together with an assessment of the relative magnitude
of the costs and the likelihood of their occurrence. The assessments
of magnitude and occurrence are based on the evaluation of the relevant
literature. As noted above, no comprehensive data base exists that
would allow for a complete enumeration of cost elements and their like-
lihood of occurrence. The analysis therefore must be based to some
extent on best judgment.
The distinction of magnitude and likelihood of occurrence is necessary
to obtain a representative estimate of total social costs. The dis-
cussion above has mentioned that the degree of water contamination
varies over time in response to a variety of environmental factors.
The process which causes direct costs (as well as indirect costs)
therefore is a random process. Since complete data on the behavior of
these processes in the past are not available, the total direct costs
cannot be evaluated directly. Any cost estimate therefore becomes an
expected cost -- the product of the actual costs and their probability
of being incurred.
This point deserves additional emphasis. The direct (and indirect)
costs associated with the actual contamination of drinking water sup-
plies vary as a result of two factors. First, the physical processes
leading to contamination levels are strongly subject to random varia-
tions in the occurrence and strength of important factors involved.
Secondly, for the same level of contamination, any direct cost may
vary considerably over time and across regions and towns as a consequence
of differences in reaction on the part of those responsible, and in
relation to differences in environmental and economic conditions. Since
action alternatives to municipal and state officials are generally
delineated in terms of budgetary constraints, actual direct costs may
be higher in more affluent towns or states. While these differences
are at least partially offset by differences in indirect costs, economic
factors may produce substantial variations in the type of response and
the associated costs. Under these conditions, representative expected
costs constitute the principal option for the analysis.
* A Massachusetts highway official acknowledged that this may be the
best alternative to hypertensives by suggesting, perhaps somewhat cyn-
ically, that the state would still be better off by continuing its cur-
rent salting policy and supplying hypertensive individuals with bottled
water. (Quoted in the Boston Globe.)
55
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Table 2
Direct Costs Associated with Salt
Contamination of Drinking Water Supplies
Cost Factor
Relative Magnitude
of Costs
Likelihood of
Occurrence ;
Incurred by
Prevention
Installation of
drainage ditches
along highways
Location of new
private wells beyond
12 meter strip along
salted highways
Maintaining a suffi-
cient distance from
water supplies in new
highway routing
Reduction of the
salt/sand ratio used
in application
Improved monitoring
of likely salt needs
and actual salt use
by individual
spreader trucks
Purchase of land
around public water
supplies
Medium
Generally low
Generally low,
but may add
signicantly to
costs
Extremely low,
probably nega-
tive (i.e.,
savings)
Nominal
Medium-High
High for
"bare pave- !
ment" highways
Low, only for
new develop-'
ments
Low, only for
new construc-
tion
High, likely
to be included
in all winter
highway main-
tenance
High, likely
to be included
in all winter
highway mainf
tenance
Medium
Society
Individuals
Society
Society
Society
Society
Diagnosis
Increased monitoring
and testing of water
supplies
Low
High
Predomin-
antly
Society
56
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Table 2 (Continued)
Direct Costs Associated with Salt Contamination
of Drinking Water Supplies
Cost Factor
Relative Magnitude
of Costs
Likelihood of
Occurrence
Incurred by
Studies' to determine
causes of observed
contamination and
identify appropriate
treatment
High
Low, but
increasing
Predomin-
antly
Society
Studies/tests to
ascertain role of
deicing salts in
contamination of
private wells
Handling of com-
plaints and inquiries
concerning sodium
chloride contamina-
tion of public water
supplies
Low to medium
Low, but
increasing
Nominal per case
Medium,
Increasing
Predomin-
antly
Individuals
Society
Treatment
Replacement of con-
taminated private
wells
Purchase of water
from other sources
"Flushing" of con-
taminated wells
High
Generally
Low to medium individual
but may be
society
(N. H.)
Medium
Medium
Low
Low
Individual
and Society
Society
Installation of
protective devices
(drainage ditches,
catch basins)
Replacement of
contaminated
public wells
Medium
High
Low
Very low
thus far
Society
Society
57
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Indirect Costs —
Principally, all indirect costs associated with the contamination of
drinking water supplies through deicing salts relate to the health
effects While it may be possible that water users experience a loss
in welfare as a result of bad-tasting water, the costs of chloride con-
tamination (below the threshold level of 250 mg/1 established by the
Public Health Service standards) are primarily in the nature of direct
costs The discussion here therefore deals primarily with the potential
health effects of comparatively high levels of sodium in the drinking
water Because of the role of this public health hazard, ;the analysis
focuses on health hazards related to hypertension (high blood pressure).
The evaluation of the indirect costs related to these health effects is
difficult, since they can assume different forms. The discussion of
direct costs above already indicates that such indirect costs can be con-
verted into direct expenditures, if the individual concerned decides to
forego public (or private) water supplies as a source of drinking water
and purchases bottled water instead. In other cases, the;risk of any
adverse health effects associated with the drinking water,quality in a
particular town may result in direct economic losses in terms of property
values.
The problem of indirect cost evaluation is further complicated by the role
of ignorance and uncertainty in determining the actual health effects.
Under conditions of perfect information, the opportunity cost of sodium
contamination in drinking water supplies would be the cost of supplying
individually approximately 20% of the population who are or should
be on a low-sodium diet with "pure" water for drinking purposes, e.g.,
in the form of bottled water. However, since this option has been rarely
exercised, the appropriate cost measure refers to the likely health effects
of higher sodium levels in drinking water supplies which are in fact con-
sumed. Based on these considerations, the exploration of the empirical
dimensions of the problem below focuses on the likely health effects
actually caused by the salt contamination of drinking water.
5.2.2 Review of the Empirical Evidence
As noted above, no effort has been undertaken to measure direct or indirect
costs of the salt contamination of drinking water supplies in any compre-
hensive form at any level of aggregation. The thorough review of published
and unpublished literature as well as the survey of operating agencies
conducted as part of this study yielded very little useful information
that would allow for an estimation of direct or indirect costs for more
than specific instances. The approach here therefore reviews briefly the
relevant information that has been obtained, and uses this information
to derive some broad indicators of costs on a per capita ;basis, which
can then be used to delineate the range of total costs associated with
the contamination of drinking water supplies.
58
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Direct Costs —
Probably the best data base for an evaluation of the likely range of
direct costs is available for New Hampshire. The State of New Hampshire
has shown considerable concern with the effects of highway salting
policies on the environment, particularly water supplies. This concern
has led to the institution of a well replacement program as early as 1956
(265). The program operates on a complaint basis only. The wells affected
must be located near state-maintained roads. Well inspectors observe a
well which has been contaminated for a year to determine whether the contam-
ination (chloride level) is significant over a three to four month period.
In order to quality for the replacement program, chloride levels must be #-
iround the 1962 PHS recommendation of 250 me;/l. However in practice a number of
considerations are involved in determining^'whether a well should be replaced.
Corrective action generally requires-about a year to 18 months. The state
will replace the well and the pump, once it has been established that the
well is in fact contaminated as a result of state salt runoff from high-
ways .
Budgeted for this program is an amount of $200,000 per year (up from
$100,000 prior to 1973) for.the well replacement itself. In 1974, 50
wells were replaced at a total cost for labor and materials of $132,000.
Table 3 shows the number of wells replaced since 1965 and the associated
total costs and costs per well. There is no evidence for any trend in
the figures, except for a long-term increase in the cost per well,
(although these costs have declined over the last three years), which is
attributable to inflationary patterns. Aside from this trend, cost per
well varies considerably over the years. These variations tend to reflect
variations in construction conditions. For example, additional costs are
incurred, if deeper wells have to be drilled or more elaborate pumps
(other than simple jet type pumps) have to be installed.
The costs shown in Table 3 only refer to the direct costs of well replace-
ment. In addition, the Special Services Division of the New Hampshire
Department of Public Works responsible for the well replacement program
maintains a payroll of about $80,000 (1974). The actual costs of^operating
the program also include maintenance and depreciation for five cars, the
costs of approximately 200 water samples annually, and any costs incurred
as the result of drainage corrections requested by the Division and imple-
mented elsewhere. (265)
All these costs taken together amount to approximately $0.25 per capita
per year. Since the well replacement program only refers to wells contam-
inated by state salt, the actual required costs for maintaining an ade-
quate water supply in New Hampshire are higher. Given that state salt
amounted in 1972 to approximately 24.5 percent of the total for the state,
the total direct costs associated with deicing salts in New Hampshire may
amount to $1.00 per person,- or $700,000 for the state as a whole. While
this figure appears very high, it should be kept in mind that it would
constitute a catch-all figure for all the direct costs that would be
59
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Table 3
Costs of New Hampshire Well Replacement
Program
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
Number of Wells
Replaced
44
53
62
42
40
38
17
30
27
50
Costs
(in thousands)
$ 80.3
128.4
109.4
85.6
97.8
85.6
41.9
93.9
77.5
132.0
Costs per
Well
$ 1,8.25
2,421
;i,765
,2,038
2,329
2,253
. 2,465
3,130
2 , 870
2,640
involved in restoring a water .supply system to a state characterized by
tolerable levels of chloride contamination. In this sense, it can be
regarded as a total expended cost figure.
Extrapolation of this figure to the U.S. as a whole is difficult. It would
be misleading to use the per capita cost figure for New Hampshire as indi-
cative for all other states. At a minimum, two factors must be taken into
account: salting intensity (total salt per lane mile) and;the relative
importance of wells, which are much more susceptible to salt contamination
than reservoirs, as sources of the population's water supply. Using only
salting intensity by state as a weighting factor for extrapolation, the
New Hampshire per capita costs to the nation yields a total cost estimate
of $46.5 million per year. Since New Hampshire tends to rely on ground-
water as sources of water supply at a slightly lower rate than the nation as
a whole (20% vs. 21%), the potential cost of replacing contaminated wells
would be slightly higher. However, the available evidence, scant as it
60
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is, suggests that this figure may not be too high. The following para-
graphs summarize illustrative examples that have been identified in the
literature search and contacts with practitioners in the field.
Perhaps one of the most visible examples of well contamination and related
public debate has been the town of Burlington, Massachusetts. In the late
1960s, Burlington experienced the contamination of wells as a result of
road applications and storage. The main water station was closed down
because of a chloride content of 283 mg/1. According to estimates prepared
by the U. S. Geological Survey, 40% of the contamination problem could be
attributable to salt use (both application and storage) by the town of
Burlington, 30% to applications by the Massachusetts Department of Public
Works (primarily on Route 128, a major circumferential artery), and 15%
to applications by the neighboring town of Lexington. The remaining 15%
was attributed to septic tanks and industrial contamination.
City officials indicated no particular costs as a. result of the shutdown
of the main water station/ since production from nine other wells less
affected by the contamination problem could be increased to cover the
demand. Other than outlays for an engineering study to determine the
causes of the problem and identify simple remedial measures (approximately
$15,000), no additional costs have been recorded. This particular statement,
probably neglects a number of costs that may have been incurred, such
as the actual costs of closing the well, incremental costs of increasing
production from other wells, more frequent testing during the period of
higher contamination levels, outlays for the changes in the drainage sys-
tem recommended in the engineering study (114), and any costs that have
been incurred as a result of intensive debate in the town regarding the
advisability of a ban on street salting which was subsequently implemented
for a two-year period. While these costs may be comparatively small for
a town with 20,000 inhabitants, similar costs for the nation as a whole
could be sizeable.
A different situation occurred in Goshen, Massachusetts, which experienced
the contamination of seven wells which are owned privately, and one well
owned by the local school committee. The source of the problem has been
primarily the application of salt on nearby Route 9, also a highly frequented
highway. The contamination was first noted in 1972; subsequent readings
have failed to show any significant improvement. Several homeowners whose
wells were affected by the contamination problem have placed their homes
for sale at expected losses to them. (Further investigation could not
determine the size of these expected losses.) Others have incurred signi-
ficant costs for drilling new wells and replacing pumping equipment and
pipes.
The School committee was forced to close the contaminated well and pur-
chase bottled water for the school years between December 1971 and March
1973, a total cost of $650. The state has responded to the problem by
building a drainage system along a quarter mile stretch near the affected
wells in order to carry the salt runoff further down the road. This
61
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effort was partially successful for the wells affected, but resulted in
the contamination of yet another well. Efforts by the town to have the
wells replaced by the state have failed.*
Two final examples may round out this review of some of the evidence
gathered in the study: two towns in Massachusetts, Weston and Norwell,
both experienced severe contamination of their water supply because of
salt application and storage. As a result, their wells had to be closed.
The new wells cost approximately $150,000 in each of the two towns.+
Given this evidence, the estimate obtained above on the basis of more
detailed data for the State of New Hampshire does not appear to overstate
the total direct costs incurred by society and individuals as a result
of the contamination of water supplies through deicing salts.
Indirect Costs —
The evaluation of indirect costs of salt contamination of drinking water
supplies is hampered by conceptual problems, as indicated above,, and by
more severe data problems. Many of the examples of well contamination
that have been encountered were defined in terms of chloride levels. Com-
paratively little is known about the incidence of sodium. While data on
chloride levels are widely available (and have been used to .study the
relationships between road salting and water contamination), comparatively
little has been done to monitor sodium levels. Any inferences concerning
the relationship between road salting and sodium contamination therefore
rely on the "rule of thumb" that sodium reaching water supplies is approx-
imately one-third to two-thirds of the corresponding amount of chlorides.
These factors make an assessment of the absolute magnitude of health
effects a rather uncertain undertaking. Review of water quality monitoring
data indicates that in Massachusetts, approximately 27% of the towns and'
cities have one or more water supplies with a sodium level above* 20 mg/1
which can be taken as a cutoff point beyond which the water may constitute
a serious health problem for the 4% to 5% of the population on low-sodium
diets, or the 10% to 25% who have been estimated to be affected by hyper-
tensive conditions. However, very little evidence in terms of epidemio-
logical studies relating cardiovascular diseases (primarily hypertension)
to sodium in drinking water is available. Part of the problem is that
the recognition of the role of sodium in cardiovascular disease has been
established firmly only recently.
Research on the relationships between characteristics of drinking water
and cardiovascular diseases focused originally on the hardness of water.
In 1960, Shroeder published a paper showing a negative correlation between
the water hardness of potable water and cardiovascular deaths. This
finding was confirmed in a number of subsequent studies. A study published
* Personal communication with the Chairman of the Board of Health, Go.shen,
Massachusetts, May, 1975.
* Personal communications with Massachusetts Public Health Department,
May, 1975.
62
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in 1967 in a Russian medical journal (329) indicated a statistically
significant difference in the incidence of hypertension among two groups,
one using water supply with a "normal" amount of sodium, the other using
water supply with an "elevated" sodium content. These results are some-
what problematic to .interpret since "normal" and "elevated" were insuf-
ficiently defined. According to Wolf and Moore (145), "normal" in this
article referred to a sodium level of 263 mg/1 and less, while "elevated"
sodium concentrations were in the range of 470-1180 mg/1. These levels
are not typical for sodium concentrations in drinking water attributable
to deicing salts.
Wolf and Moore (145) used data for areas in Dallas County, Texas to
examine the possibility of any association between sodium content of the
drinking water and cardiovascular deaths. Grouping communities into low
sodium water supplies and high sodium water supplies, the authors then
compared weighted average (cardiovascular) death rates per 100,000 for
the two groups. The results of this comparison are shown in Table 4»
Except for men in the age group 45 - 59, death rates are significantly
higher for the high sodium communities. The authors suggest that the
exception may be due to the fact that men in this age group tend to be
economically active, spending a major portion of their time in the city
of Dallas (a low sodium community).
The implications of these differences in age-specific death rates can be
illustrated by examining their implications for a sample group. For the
60 - 74 age group, the difference in death rates between low and high
sodium communities is 400 per 100,000, or .004. If this figure holds
generally, the age-specific survival rate would be lowered by this differ-
ential. For men in the age group 60 - 64, the national survival rate
is approximately .835. This rate corresponds to an average life expectancy
for men in this age group of 5.6 years. If the survival rate is lowered
by .,004 to .831, the average life expectancy declines to 5.4 years. Higher
levels of sodium concentration in the drinking water thus would imply a
reduction in the life expectancy for this age group by almost 4 percent.
Extrapolating these data to the national level is impossible because of
the limited nature of the study and because of lack of data relating
to the incidence of sodium concentrations in drinking water over a suffi-
cient time period.
An indicative estimate of the cost of salt contamination of drinking
water supplies in terms of their health effects can be obtained by esti-
mating the expenditures required to remove the hazard. A rough assessment
of the total cost can be obtained by assuming that all people affected
by conditions of hypertension would purchase bottled water for drinking
purposes, once their water supply exceeded a sodium concentration of 20 mg/1.
For the normal adult, an average drinking water consumption of 2.2 liters
has been estimated. This estimate can be used to obtain a rough estimate
of the potential cost of supplying all persons on low-sodium diets affected
by sodium concentrations over 20 mg/1 with bottled water. A gallon (3.8
liters) of bottled water sells currently for about $.50. The average
person would therefore spend approximately $106 (2.2/3.8.365.50) per year
to satisfy his or her drinking water needs entirely through bottled water.
63
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Table 4
Differences in Cardiovascular Death Rates
For Different Levels of Sodium in Drinking Water
(per 100,000)
Age Group
High Sodium*
Low Sodium
45 - 59
60 - 74
Males
375
1,730
Females
91
990
Males
447
1,330
Females
74
570
* 120 mg/1 or more
+ 25 mg/1 or less
The number of persons on low sodium diets exposed to sodium concentrations
in the drinking water above 20 mg/1 attributable to road salt is extremely
difficult to estimate. The Massachusetts' experience indicates that appro-
ximately 27% of the water supplies (not necessarily the population) are
affected by high sodium concentrations attributable to road salt. As a
broad estimate, it can be assumed that roughly 25% of the population under
conditions similar to those in Massachusetts are affected. :Four percent
of the population have been estimated to be on a low-sodium diet. Using
salting intensity as a weight to make other states in the snowbelt com-
parable to Massachusetts yields an estimated total cost for ithe nation of
$105 million. Since Massachusetts relies more heavily on groundwater
than the nation as a whole (23% vs. 21%), the estimate should be somewhat
lower, i.e., $96 million.
In summary, the direct .and indirect costs of water supply contamination
may add up to almost $150 million nationwide. This figure provides an
impression of the magnitude of the damages, rather than describing actual
costs. It should be noted that the considerations in this section do not
include any costs to industry as a result of special requirements for
processed water.
64
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5.3 COSTS OF DAMAGES TO VEGETATION
Experiments and empirical studies have clearly demonstrated that (a)
many of the trees used for roadside planting in the snowbelt (notably
sugar maples) are sensitive to increased sodium concentrations in the
soil, and (b) there is a direct link between the deterioration or death
of roadside vegetation and salt application.
Essentially, roadside vegetation (whether public or private) may suffer
as the result of two major factors. First, vegetation may be affected by the
runoff of salt brine and the retention of sodium ions in the soil. This
possibility is particularly acute in highway stretches characterized by
conditions that favor a fast runoff of salt brine from the road surface
to the area of vegetation, combined with a comparatively poor drainage
in the area itself. The second, possibility, which impacts particularly
upon shrubs and hedges in urban areas, is the practice of dumping salt-
saturated snow along the edges of the road,, after plowing. This practice
may lead to extremely high salt concentrations around the plants affected.
Since many of these plants are characterized by shallow root systems, and
since much of the sodium remains in the upper layers of the soil, destruc-
tion of shrubs and hedges is a common occurrence.
However, most of the research on the effects of deicing salts on roadside
vegetation has focused on the damages to trees along suburban and rural
roads. The affected strip extends approximately 9 to 12 m from the edge
of the road. Salt concentrations beyond this distance in the soil have
been found to be negligible. Within this strip, salt affects vegetation
in two ways. Firstf it directly interferes with the chemical processes
by which plants absorb nutrition; it affects the osmotic balance, thus
inhibiting the water intake of plants, and it may replace vital nutrients.
In addition to these direct effects, sodium in the soil may also result
in a rapid deterioration of the soil itself. According to Westing (191),
"...when sodium comes to occupy more than about 15% of the total cation
exchange capacity of the soil, soil structure begins to deteriorate.
...permeability and water-holding capacity decrease markedly."
While the botanical and chemical evidence is sufficient to suspect wide-
spread deterioration of roadside vegetation in areas characterized by
the heavy use of deicing salts, the empirical backup is somewhat meager.
Aside from studies of specific stretches of highway and their vegetation
(such as Button [156, 157]), the data base relating to the interaction
between deicing salts and vegetation damage at a macroscale is limited to
reports of specific instances. For example, Rich (175) reports that in
1957, the New Hampshire Highway Department removed 13,997 dead trees
along 3,700 miles of highway. The estimated cost of removal was $1 million
or more than $70 per tree. According to other reports, Winchester,
Massachusetts, which has applied as much as 55 tons of salt per mile, has
lost an average of 56 trees per year since 1963. (26) Similarly, Newton,
Massachusetts which also tends to apply salt amounts far above the average
for towns and cities in the state, is reported to have lost about 500
65
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trees per year between 1965 and 1970 (40) .
The problem with, the evaluation of these reports is that they tend to
relate tree deaths from all causes to salt application. Since no national
statistics are available concerning the number of dead trees per year, it
is impossible to identify the net effects of deicing salts in terms of
damages to roadside trees statistically. Similarly, data on the population
at risk (i.e., roadside trees possibly exposed to deicing salt runoff),
which would be useful in applying micro-analytical findings to a macro-
level framework, are unavailable.
As a result, national damage estimates simply cannot be generated. The
following discussion therefore explores possible cost ranges, including
both direct and indirect costs associated with tree damage that can be
related to deicing salts. Direct costs relate to the cost of maintenance
and removal in the case of death, while indirect costs concern the losses
in welfare to society or individual property owners resulting from the
disappearance (or deterioration) of a fully grown shade tree, which may or
may not be replaced by a small young tree. From a conceptual point of
view, it is of course the evaluation of indirect costs that constitutes
the most difficult task.
Fortunately, a number of studies have been undertaken to determine the
monetary value of shade trees. According to the International Shade
Tree Conference (169), three basic factors must be considered in deter-
mining the monetary value of a shade or ornamental tree: size, kind and
condition of the tree. Tree size is generally measured in terms of dia-r
meter at breast height (dbh), where breast height is defined as 1.37 meters
above ground. In August, 1973, the International Shade Tree Conference
adopted $10.00 per square inch (1.55/sq. cm) of truck cross-section as
the conservative value of a perfect specimen shade tree. Table 5 presents
the base values of shade trees for different dbh values. This material
would imply, for example, that the indirect costs associated with the
New Hamsphire example mentioned above would add about $10 million to the
direct costs (using a fairly conservative average of 10-inch (25.4 cm)
dbh for the 13,997 trees removed.)
While the measures established by the International Shade Tree Conference
may be somewhat arbitrary and, more importantly, apply primarily to
urban trees, they provide an indication of the potential magnitude of
the problem. If only 6% of all tree deaths in the New Hampshire example
can be attributed to deicing salts, the total cost figure, including
both direct and indirect costs, would be comparable to the total costs
computed for the water contamination damages, or $46.5 million.
66
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Table 5
Basic Values of Shade Trees
(For Perfect Specimen Shade Trees)
Trunk Diameter
Inches
Cross Section Area
Square Inches
Basic Value (in
Dollars)*
2
5
10
15
20
25
30
35
40
45
50
55
60
3.14
19.64
78.5
176,7
314.2
490.9
706.9
926.1
1,256.6
1,590.4
1,963.5
2,375.8
2,827.4
31
196
785
1,767
3,142
4,909
7,069
9,621
12,566
15,904
19,635
23,758
28,274
Calculated on the basis of $10.00 per square inch (1.55/sq. cm) of cross-
section trunk area at 4.5 feet (1.37 m) above ground.
(Note: One inch = 2.54 cm; one square inch = 6.45 sq. cm.)
67
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5.4 COSTS OF DAMAGES TO HIGHWAY STRUCTURES
Deicing salts contribute to the deterioration of bridges, decks and
supporting structures, highway surfaces and other highway istructures.
The review of the available evidence on the physical and chemical
processes involved, presented in Section 4.2.2, provides the background
for an exploratory assessment of the cost implications of the incre-
mental damage caused by deicing salts. This assessment focuses on
bridge decks, since the technical evidence of causal relationships is
most convincing in this case.
The true cost to society of salt-induced bridge damages includes direct
outlays by highway departments for activities such as inspection, repair,
and replacement, as well as indirect costs to the public including
that portion of Federal research outlays, vehicular deterioration, lost
time, and increased accidents which may be attributed to the use of salt
(e.g., rear end collisions in traffic lines resulting from repair work).
This section first summarizes the direct costs, presents a partial
analysis of the indirect costs, and finally gives an estimate of the
full social costs of salt damage to the nation's highway bridges. The
cost estimation approach is characterized by extreme conservatism; areas
in which the available evidence or required data are either not avail-
able or not sufficiently reliable are treated with deliberate skepticism.
This procedure implies that the total cost estimate describes the lower
boundary of the actual costs.
5.4.1 Direct Costs
The actual cost outlay by state highway departments for the repair of
bridge decks was estimated to be $40 million or more in 1971. (230)
This estimate of private costs is conservative in that it -ignores the
costs of installing improved design features such as waterproof mem-
branes in new bridges, and also because maintenance on spalling decks
has been insufficient to maintain a constant average quality. The
result is a substantial understatement of true costs. Outlays for
repair that would halt the deterioration in quality were estimated by
Kliethermes to be some two to three times actual expenditures, or $80
to $120 million*
Recent evidence from individual states, particularly West .Virginia,
provides a check on Kliethermes' cost figures. The cost of maintaining
West Virginia's 6,000 bridges in good condition was recently estimated
to be approximately $12 million, or about $2,000 per bridge. The
number of bridges affected by salting of the nation's highways can be
derived from a map in the Kliethermes article (230) which depicts
regions of severe, moderate, and no deterioration throughout the country.
* Personal communication with J. Kliethermes, Federal Highway Administra-
tion, December, 1974.
68
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Although the total number of highway bridges was readily obtained, the
number in each state could not be determined, and it became necessary
to estimate their distribution. Following a suggestion of Adrian Clary*,
of the Transportation Research Board, the distribution of bridges
was estimated in proportion to the distribution of the human population
throughout the country. Using Kliethermes1 data on regional damages
as shown in Figure 13 and assuming that 100% of the bridges located in
severe regions require periodic maintenance and repair of salt induced
damages, whereas only 20% of the bridges in moderate regions are so
affected, we conclude that nearly 100: thousand bridges are adversely
affected. Assuming that the West Virginia estimates are representative
of costs in other severe deterioriation regions, a yearly cost for the
nation's bridges of $200 million is estimated"*".
This of course provides only a rough overall estimate. A more differ-
entiated approach, using microeconomic cost data for each of the possible
activities related to the detection of salt-related damages, and
resulting repair and replacement, could be employed to explore the imp-
lications of alternative damage configurations for highway bridge decks.
The microeconomic cost data are summarized in Table 6.
* Personal communication with Adrian Clary, November, 1974.
+ During the winter of 1969-1970, West Virginia used an average of 3
tons of salt per lane mile and 20 tons of salt per bare pavement lane
mile. (Not all roads are required to be kept bare; thus these figures
may be very different in some states.) Many other states in the snow
belt exceeded these figures, for example:
Salt Per :
Lane Mile Salt Per Bare
State (tons) Pavement Lane Mile
Connecticut
Maine
Massachusetts
New York
Pennsylvania
Maryland
Ohio
Illinois
33
8
35
19
11
19
25
10
33
20
35
19
34
31
25
19
These figures indicate that the problems in West Virginia might be
expected to be less serious than in other snow belt states; and, con-
sequently/ the costs of maintenance and repair may be higher in other
states.
69
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gffljg MODERATE-SEVERE (100 - 80%)
p5*l LIGHT-MODERATE (20 - 30%)
I I NONE-LIGHT (Less than 20%)
Figure 13 Corrosion of reinforcing steel in highway structures
(from Kliethermes, Reference 230)
Table 6. Summary of Microeconomic Costs
Activity
Estimated
Cost per Square Foot
Estimcited
Life Expectancy
Visual Inspection
Chloride Detection
Maintenance Patch
Restoration
Replacement
Nominal
Variable - $.25
Variable - $.50+
$9.00
$15.00
New Techniques:
Polymer Impregnation $1.
Membranes $1.
Epoxy coated steel $1.
Latex modified concrete $.50
Wax in concrete $1.
Cathodic Protection $.50+
One year
Variable
Few imonths to few
years
Up to 15 years
Up to 50 years
Up to 50 years
Up to 15 years
Up to 50 years
?
Up to 50 years
70
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All figures in the table are to be taken as estimates, and were derived
from the available literature, consultation with highway department
officials, and our judgment as to the probable trend of costs once a
technique becomes, proven (viz. cathodic protection whose costs in large
scale use are largely unknown - but mav be quite low). The life of a
bridge is taken to be 50 years, in a salt-free environment — thus no
activity could be expected to produce a life expectancy greater than
50 years.
It should be noted that the estimates provided include not only mainten-
ance and repair costs, but also incremental costs of preventive measures
through the improvement of construction techniques for new bridges. The
technical discussion of bridge-deck repair in Section 4.2.2 reviews
the experimental evidence that polymer impregnation of concrete is quite
cost-effective; given its extreme durability it will probably become
the most inexpensive method of protecting new concrete decks. The annual
cost of'incorporating'polymer-impregnated concrete in all new bridge
decks constructed in the snow belt can be estimated by multiplying the
number constructed each year by their average size by the cost per square
foot. Annual construction volume in the snow belt ranges from 1,000 to
1,500 bridge decks, with an average size of about 8,800 square feet
(818 sq. m.)* At a cost of roughly $1 per square foot, ($ll/sq. m.)
the total cost would be approximately $9 to $13 million.
Adding the incremental cost of bridge-deck construction required to
prevent salt damage to the estimated maintenance costs thus yields a
total direct cost figure for bridge decks alone of approximately $210
million. Again, it should be emphasized that this estimate is based on
very conservative assumptions. Projecting these costs into the future
is difficult. While preventive measures are likely to reduce the need
for maintenance and repair, the exact reduction in the latter costs is
uncertain. In addition, given the total number of bridge decks and
their maximum life expectancy, it would appear that the current annual
construction volume is insufficient to replace all of the bridge decks
within the time period of 50 years. Stepping up construction activity
would result in corresponding increases in the costs of prevention.
Based on these considerations, and the cost estimates derived above, it
is reasonable to assume that the annual direct costs associated with
salt damages to bridge decks will be in the neighborhood of $200 to $250
million annually in the next few years.
This figure refers primarily to bridge decks. In addition, the relevant
direct costs attributable to salt-induced damages should also include
the costs of necessary repairs because of structural damages. While these
damages are insufficiently documented for the nation as a whole, specific
* According to Richard Hay of the Federal Highway Administration.
71
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instances can be cited to provide an impression of the potential magni-
tude of this problem. For example, damages to the West Side Highway
Viaducts in the Borough of Manhattan in New York City were severe enough
to require rehabilitation efforts at a cost of approximately $96 million,
or almost $50 per square foot ($4.65/sq. m.) of highway*. While this
particular example.may be exceptional, it illustrates the possible magni-
tude of additional costs associated with major "damage cases related to salt
use.
5.4.2 Indirect Costs
The direct cost estimates include only expenditures by highway agencies
for special design features on new bridges and the repair of existing
structures to counter the adverse effects of road salting. Full social
costs would include delays to motorists during repair, repair costs for
damages to ball joints and front end alignment from travel on uneven
bridge surfaces, and the cost of accidents which are attributable to
rough bridge deck surfaces., Some of these latter costs, though poten-
tially important, would be exceedingly difficult to measure accurately.
Therefore, the analysis here focuses on the value of lost time.
The discussion of vehicle behavior at sites of traffic obstruction in
a recent OECD report (260) provides a basis for estimating times loss
during bridge repair. In the hypothetical example to follow, a typical
repair of a three lane bridge deck (each way) in an area subject to
congestion at rush hour is examined. A's such it probably represents a
maximum estimate for time loss during bridge repair. Obstructions such as
bridge repair lower highway capacity. Studies of freeway traffic in
Los Angeles indicate that the capacity of a three lane highway that has
been constricted to two lanes is reduced from a range of 4,000 to over
5,000 vehicles per hour to the lower range of 2,400 to 3,200 vehicles
per hour. Congestion feeds upon itself; as traffic begins to slow,
drivers will respond by more frequent lane switching and other maneuvers
that only serve to aggravate the situation* . (260) '
* The engineering reports cited deicing salts as one of the major factors
contributing to the structural weakening of the bridge. See: Hardesty
and Hanover, Consulting Engineers: Reports on the Inspection and Analysis
of the West Side Highway (Miller Highway). For the City of New York,
Department of Highways, Contract No. THXM 152E, Capital Project No. HW19.
Four reports October, 1974-May, 1975. (References 221, 222,. 223, 224).
+ This example excludes a myriad of technical questions- Other factors
which affect traffic flow include: (1) the length of the obstruction, (2)
the control of traffic speed at the obstruction, (3) controlled gaps in the
flow which may actually increase the capacity of the obstructed section,
and (4) the opportunity for using reversible lanes can significantly reduce
the impact of the obstruction.
72
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Figure 14 portrays the hourly traffic capacity and demand for inbound
vehicles and Figure 15 the cumulative capacity and demand for this
highway. Total waiting time for venicles using this road segment is
given as the shaded area between the given capacity of the system and
cumulative demand on the system. The delay for traffic entering at
a given hour is given by the horizontal distance between the cumulative
demand and cumulative capacity. The total area between the two curves
may overestimate actual waiting time to the extent that motorists are
diverted to uncongested alternative routes. If motorists' decisions to
use alternative routes also produce congestion on the alternative routes
the estimate could conceivably be understated. In this example, total
waiting time before the lane obstruction is 4,000 hours, and after the
lane restriction about 17,200 vehicle hours. Valuing an hour's wait at
$3.00 per hour provides an estimate of $51,600 per day.* Assuming the
repair requires 50 working days, and that repairs to outbound lanes
will require similar delays to motorists, the total cost of delay may be
estimated as in excess of $5 million. Although delay costs of this
magnitude may be extreme, several such instances probably occur in or
near large metropolitan regions every year. Until better data are avail-
able on the actual number of bridges being repaired and the typical time
delays involved, no accurate national cost figures can be reported for
motorist's delays.
Cumulative Capacity
2800/houi
Demand
5,000
4,000
3,000
2,000
1,000
20
18
•rH
1 16
(Ti
Demand
Capacity
&
0)
10
8
6
O
umulative Capacity
4000/hour/
Cumulative
Demand
AM 6 7 8 9 10 11 12 1P.M. A.M.6 7 > 9 10 11 12 1P.M.
Time of Day Time of Day
.Figure 14. Hourly Traffic Capacity Figure 15. Cumulative Traffic Capacity
and Demand
* Economists (see Owen, "The Value of Commuter Speed," Western Economic
Journal, June 1969) have argued that the costs of delay increase more than
proportionately with the length of the delay. The $3.00 figure is an
approximate average of the costs of short and long delays.
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5.4.3 Estimates of Total Costs
While it is difficult to get a firm handle on the relevant cost categories,
both direct and indirect, for evaluating the national costs of salt-related
damages to bridge decks, the available information is sufficient, to sug-
gest that society incurs substantial costs as a result of bridge deck
deterioration. A very conservative estimate of the direct costs of reha-
bilitative and preventive measures associated with this problem places
the total national cost at close to $250 million. The analysis of one
indirect cost category yields estimates of up to $5 million for a single
bridge. Since nearly 100 thousand bridges are affected by required repairs,
even a low probability of occurrence of such costs attributable to increased
waiting times as a result of lane closings for repairs would still yield
substantial total costs. Even if only one bridge in 2 .thousand (.05%)
were similarly affected, the total indirect costs of increased waiting times
would amount to $250 million. These extreme costs are admittedly very
infrequent. However, it is likely that smaller waiting costs are incurred
at more bridges. An estimate of $250 million for the indirect costs of
waiting therefore is probably again on the low side.
In summary, the total annual costs of bridge deck damages related to salt
use can be estimated to exceed $500 million.
5.5 COSTS OF AUTOMOBILE CORROSION
Sufficient evidence has been presented in Section 4.2.1 to support the
assertion of a causal relationship between deicing salts and:corrosion
of automobiles. This corrosion in turn results in a variety of costs to
automobile owners. Four major cost categories can be distinguished:
• costs of protective measures both by manufacturers
and by owners;
• costs of repairs required to maintain the ability of the
automobile to function at the same level as without salt-
induced corrosion;*
• losses in economic value of the automobile as a result
of salt-induced corrosion; and
• costs of accidents attributable to automobile malfunctioning
associated with salt-induced corrosion.
The first category presents a number of difficulties in measuring the
relevant costs. The main problem is the attribution of design changes
or other protective measures to the salt problem. Any measure of costs
in these categories is therefore fraught with considerable uncertainties.
* The relevant costs here refer only to that portion of outlays required
to restore the corrosion damage which actually impairs the level of ser-
vice provided by the automobile.
74
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In the interest of reliable cost measures, this category will not be
included as an integral part of the total cost estimate.
A similar reasoning applies to the second cost category. It is difficult
to assess the degree to which expenditures on repairs are actually required
to restore or maintain the automobile's ability to provide the same level
of services as in a salt-free environment. Generally, relevant repairs
tend to go beyond the required level. In addition, expected repair costs
associated with salt-induced corrosion are reflected in the loss of eco-
nomic value of the'automobile.
The third category is the most important one, since it is possible to
attribute depreciation rates to the influence of salt. Under the general
assumptions of economic theory, the loss in economic value accurately
reflects the expected costs associated with a reduction in the automobile's
ability to provide the desired services. These expected costs include
direct outlays for restoring at least part of the loss. While the ideal
conditions assumed in economic analysis (such as perfect information
without uncertainties) are consistently violated in the real world, the
concept of the loss in economic value reflecting expected future costs
(or losses in benefits) is sufficiently broad to cover the full spectrum
of monetary equivalents of the corrosion damage caused by deicing salts.
In fact, the concept is comprehensive enough, to include the likely costs
of accidents, the fourth category of, costs. Provided the consumer is
able to assess the likelihood of an accident as a result of corrosion
damages to certain components of the automobile, the reduction in econo-
mic value of the car includes the expected costs of such accidents (or in
risk associated with this cost category). This interpretation is useful,
since it eliminates the need for an estimation of the highly uncertain
costs of accidents attributable to salt-induced corrosion damages.
These considerations determine the approach presented here. The analysis
first examines the formal framework for expressing depreciation rates as
a function of the use of deicing salts. This discussion is followed by
an empirical analysis of the relationship on the basis of used car prices
in different Standard Metropolitan Statistical Areas (SMSAs) of the country.
The section concludes with an assessment of the costs of undercoating and
other preventive or restorative measures.
5.5.1 Depreciation of Automobiles
The analysis of the relationship between original purchase price and
current value of a car (as described by the current market price) can draw
on established models in capital theory. Ackerman (268) has developed
such a model of used car prices. This model is sketched in Appendix B;
it results in a simple exponential decay expression with a constant
depreciation rate:
75
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(1)
where P(v)
P(0)
v
B
a
P(v)/P(0) = Be
or P (v) = P(0)Be
= the current price of the car
= the original purchase price of the car (new)
= age of the car
= a constant
= the constant depreciation rate
On the basis of data on prices of cars at age v and their corresponding
original purchase prices, the two unknown coefficients in this expression
B and a — can be estimated by applying ordinary least squares to the
logarithmic form of the depreciation function:
(2)
In P(v) - In P(0) = In B - av.
The major data source for prices of used cars are the guidelines prepared
by the National Automobile Dealers Association (NADA) which are published
on a regional basis. Ackerman (268) estimated the coefficients of Equation
(2) using NADA prices from the July price books for the period 1956 to 1965
for several makes and two production years (1956, 1958). She obtained
the following results for the constant depreciation rate, a:
Make
Chevrolet (1956)
Ford (1956)
Plymouth (1956)
Chevrolet (1958)
Ford (1958)
Plymouth (1958)
Annual
Depreciation Rate
27.9%
29.4%
34.2%
28.8%
29.7%
33.2%
This model of used-car prices establishes a framework for assessing the
effects of external factors on the overall depreciation rate. This assess-
ment is based on the assumption that the depreciation rate, a, in Equations
(1) and (2) is not a constant for a given make and production year, but
varies by geographical region in response to environmental conditions (such
as climate or the use of deicing salts), use and maintenance practices for
the car, and prevailing preferences and tastes. Observations on these
76
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factors require a much smaller level of aggregation than implicit in the
NADA regions. The unit of observation used in the analysis here is therefore
a city; the discussion below describes sample selection and data-gathering
procedures, following a review of the likely impact of different factors
on automobile depreciation.
Environmental Factors: Characteristics of the physical environ-
ment in~which the car is operated directly affect corrosion and thereby
the loss in economic value. These characteristics include ambient tem-
perature, atmospheric humidity, sulfur dioxide concentration in the
atmosphere, and other pollutants that are known to contribute to corro-
sion. Similarly important is the incidence of cases in which automobiles
are exposed to moisture, such as measured by rainfall or snowfall.
Finally, an important factor concerns the characteristics of roads on which
the cars are driven. These characteristics may include elements such as
road surface and road dirt. Most road dirt, for example, clings to parts
of the automobile body, retains moisture and thereby.fosters the process of
corrosion. Similarly, loose aggregate may result in scratches in the body
finish, making it vulnerable to corrosion. Unfortunately, this factor is
almost impossible to measure except in an experimental situation. The
most important road characteristic, at least for the purpose of the inves-
tigation here, is the incidence and intensity of deicing salts on the
road surface.
Use and Maintenance of Cars: The depreciation of a given automobile
depends to a large extent on its expected useful life, which in turn
reflects its past use as well as any maintenance efforts by the owner.
One important factor is the mileage the car has been driven. Another
factor is the frequency and thoroughness of washing the car, which may
delay corrosion by eliminating pockets of dirt and moisture as well as
removing salt from the body or structural parts of the automobile.
Again, many of the relevant aspects of use and maintenance cannot be
measured at an aggregate level with any degree of accuracy. For example,
there are few if any data on the frequency and thoroughness with which
a car is being washed. Similarly, the extent of garaging —' which may
modify the importance of ambient temperature as a determinant of corro-
sion — is unknown on a large-scale basis.
Teistes and Preferences; It is entirely possible that differences
in depreciation rates among cities reflect little more than interregional
differences in terms of preferences for new vs. used cars. For example,
areas in which public transportation provides an efficient alternative
to the private automobile, two-car families may be rare. Alternatively,
in areas in which a second car is owned by many families, the structure of
tastes and preferences may be such that the demand for used cars is strong
and used car markets are active.
77
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No reliable indicators of such regional differences in tastes and pre-
ferences exist. While the potential importance of these factors in deter-
mining the rate of depreciation of cars is recognized, the analysis here
therefore does not attempt to isolate this particular factor.
Specification of the Regression Equation; The influence of the
type of factors examined in the preceding paragraphs on the depreciation
rate for automobiles has been examined through multiple regression analysis
designed to test the existence of any functional relationships of the
form:
Depreciation Rate = f(Environmental Factors, Use of Maintenance,
Tastes and Preferences) :
Primarily, for reasons of simplicity, the linear additive form of this
functional relationship was examined to isolate the net effects of deicing
salts. The specification of a linear relationship between the depreciation
rate and independent variables clearly is questionable for certain var-
iables, as illustrated by means of an example, under the simplifying
assumption that depreciation is directly related to corrosion of struc-
tural parts or the body of the car. It is known that the rate of chem-
ical reation (i.e., corrosion of steel) is temperature dependent: the
rate of reaction doubles for every 10°C increase in ambient temperature—
clearly a non-linear relationship. The linear relationship hypothesized
in the regression model may not be a close approximation, even over the
relatively narrow range of temperatures that are encountered.! However,
the specification error may be relatively small compared to the inherent
measurement error. It is extremely difficult to determine the appropriate
temperature measurement to use for assessing its impact on corrosion. Is
it the temperature of a heated garage in winter (a major factor contri-
buting to corrosion), the average ambient winter temperature, or some
annual mean? The actual effect of temperature is therefore difficult
to determine. ;
The relationship for other variables such as salting intensity is probably
specified in the theoretically correct form. Tests discussed earlier by
the APWA and NACE indicate that the corrosion rate increases approximately
linearly in the range of salt concentrations encountered by automobiles in
typical winter driving conditions. Overall, given the current understanding
of the determinants of corrosion and their effects on automobile deprecia-
tion, no alternative specification of the equation used in the regression
analysis appears more appropriate than the linear one.
5.5.2 Data Collection for Empirical Analysis
As already mentioned above, the data on used car prices available through
NADA price books are at too aggregate a level to be useful in tessting
the effects of the three types of factors distinguished above. The anal-
ysis here, therefore, requires estimates of the depreciation rates for the
same make of vehicle in different environments to allow for the use of
characteristics of these environments to "explain" the variation,, if any,
78
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in the rates. A suitable definition of environment refers to cities in
the continental U.S.
Estimating decay rates, in the same way as Ackerman (268), for different
cities is complicated by problems of data availability. This approach
would require sufficiently accurate statistics on used car prices for
a relatively long period of time, such as ten years, for each city. Such
statistics can be obtained from newspaper advertisements, but the labor
requirements for searching newspapers from an adequate number of cities
over such a time period are prohibitive. However, given Ackerman"s findings,
the data requirements for the analysis here can be reduced substantially.
Since these findings suggest that the exponential depreciation model
with constant rates fits reasonably well, representative depreciation
rates can be calculated on the basis of new car prices and a single obser-
vation on a used car price.*
The procedure followed to estimate decay rates was to obtain several
price observations (30 on the average) on each of the three makes of used
cars in 44 metropolitan regions, and to calculate the rate of deprecia-
tion for each observation required to yield the used-car price. For each
city, a representative depreciation rate was calculated as the simple
arithmetic average for the respective observations. These estimates are
shown in Table 7 . All of the estimated rates are lower than those
reported by Ackerman and shown above. This may be partially due to the
composition of the sample of car makes: Chevrolet Bel Air, Chevrolet
Impala, and Volkswagen. The inclusion of Volkswagens, which depreciate
at unusually low rates, lowers the overall average. In addition, there
is the possibility that estimates of new car prices are somewhat inaccu-
rate. However, neither of these factors should affect the estimated
variation in depreciation rates across cities; in other words, there is
no reason to believe that such measurement errors would introduce any
bias into the sample.
Table 7 presents depreciation rates by broad categories of exposure to
deicing salts. There is a fairly consistent trend across the three
categories distinguished: depreciation rates rise as the intensity of
salt use increases. However, this trend should not be overemphasized:
the measured depreciation rates may be inaccurate, or other factors that
are actually responsible for interregional variations happen to be cor-
related with salt use.
* New car prices were estimated as 90% of suggested list price plus
dealer preparation costs and transportation charges. Adjustments for
optional items (e.g., air conditioning) were made, if advertised.
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Table 7 ;
Estimated Depreciation Rates for Selected Cities
Salt more than 25
tons per lane mile
Salt between 5 and
25 tons per lane mile
Salt less than 5
tons per lane mile
Hartford, Conn. 23.5
Chicago, 111. 24.2
Portland, Me. 25.1
Baltimore, Md. 23.3
Boston, Mass. 24.1
Springfield, Mass. 23.5
Detroit, Mich. 25.1
St. Paul, Minn. 25.2
Concord, N.H. 26.9
Syracuse, N.Y. 26.1
Cincinnati, Ohio 22.1
Cleveland, Ohio 23.4
Philadelphia, Pa. 22.9
Providence, R.I. 23.6
Pittsburgh, Pa. 25.5
Salt Lake City, Ut.23.0
Burlington, Vt. 26.6
Milwaukee, Wise. 22.7
Mean 24.3
Wilmington, Del.
Indianapolis, Ind.
Des Moines, la.
Augusta, Me.
St. Louis, Mo.
Omaha, Neb.
Newark, N.J.
Oklahoma City, Oh.
Memphis, Tenn.
Richmond, Va.
Laramie, Wyo.
22.1
22.1
21.2
26.8
22.0
21.3
2.18
22.4
20.3
21.5
22.6
Phoenix, Ariz.
Los Angeles, Cal.
Denver, Col.
Tampa,' Fla.
Atlanta, OSa.
Gt. Falls,. Mont.
Reno, Nev.,
Albuquerque, NM.
Portland, Ore.
Charles ton, S.C.
Dallas, Tex.
Seattle, Wash.
19 :-4
19.8
21.5
20.
20.
20.
21.8
19.4
19.
20.
21.
.1
.2
.1
.5
.7
.5
21.4
Mean
22.2
Mean
20.5
80
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the NADA regions and compared to.the NADA price guidelines. Within
regions considerable variations in depreciation rates were observed:
for example, within the New England region, Providence, Rhode Island
showed a composite depreciation rate of 23.6%, while the corresponding
rate for Concord, New Hampshire was 26.9%. .Average prices for regions,
though, were much closer to the NADA figures; in each case, the two
prices were within 10%, with the typical difference being much less.
Overall the newspaper prices averaged approximately 2% less than prices
in the NADA guides. Since the actual prices for cars advertised in
newspapers are likely to lie below the stated asking prices, the compar-
ison indicates that the two markets differ substantially. Differences
may be attributable to quality differences in the cars offered for sale,
or to better resale preparation by used-car dealers.
These considerations established a set of observations for the dependent
variable in the regression equation. As the discussion of the potential
range of independent variables above indicates, within each of the three
categories of factors distinguished, several measures can be used to
describe the elements influencing regional variations in depreciation
rates. The following measures have been selected for the analysis reflec-
ting the principal emphasis on the importance of environmental variables
as determinants of corrosion.
5.5.3 Environmental Conditions^
State salt refers to the number of tons of salt applied per lane mile of
bare pavement on state highways for the winter of 1969-1970. (Bare pave-
ment is the highway engineer's term for pavement that is kept free of ice
and snow year round through plowing and liberal application of deicing
chemicals.) In cases in which salt usage for this winter differed sub-
stantially from that for the winter of 1966-1967 (the other year for which
these data were compiled by the Salt Institute), the mean of the two
figures was used.
City salt refers to the number of tons of salt applied per lane mile of
bare pavement on city highways during the winter of 1969-1970. Cases
with substantial differences between 1969-1970 and 1966-1967 were handled
in the same way as described for state salt.
Snow fall has been measured in inches for the winter of 1969-1970 for
each city. If this value differed by more than 25% from normal levels,
the average snowfall for the three winters (1966-1967, 1969-1970, and
1970-1971) was used.
Temperature was measured as the mean ambient January reading for each
city in degrees Centigrade.
Humidity/rainfall; humidity statistics proved difficult to obtain, and
consequently rainfall in inches per year was substituted for humidity.
81
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Proximity to ocean was included as a dummy (0/1) variable in the
regression analysis.
Sanding intensity was measured as tons of sand applied per mile of high-
way in each state.
Air pollution was measured in the regression by a single variable, the
annual mean concentration of sulfur dioxide in ug/m3.
Use and Maintenance
As already discussed above, the measurement of many of the relevant
aspects of use and maintenance of cars on a non-experimental basis is
extremely difficult, if not impossible. The analysis therefore used
only one measure, the average number of miles (in thousands) traveled
by a vehicle in each of the states. Unfortunately, vehicle mileage was
not available for the cars offered for sale. i
Tastes and Preferences :
The discussion above indicates that tastes and preferences themselves
are almost impossible to measure in a way that would yield meaningful
descriptors for the analysis here. In an attempt to include these
possibly important characteristics, income per capita.and vehicles per
capita were used in the regression as imperfect proxies of 'the determin-
ants mentioned above.
5.5.4 Regression Results
Given the limited understanding of the possible functional relationships
between corrosion and car values, the corrosion and environmental factors,
the regression equation was tested in its simplest, i.e., linear form,
as discussed above. The approach was largely empirical, that is, all
variables assumed to influence depreciation rates were used in different
specifications as explanatory variables in the regression analysis. The
following functional form showed the best performance: i.
DEPRECIATION RATE = 15.7 + .038 STATE SALT + .019 CITY SALT
(2.01) (3.03)
+ .029 SNOW + .170 MILES
. (3.67) (1.48)
The figures in parentheses under the regression coefficients refer to
the t-statistics of the coefficients, a measure of statistical
82
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significance.* The multiple correlation coefficients for this equation
was .79, which implies that the variation of the four independent
variables "explains" 79% of the variation of the dependent variable
across the 41 metropolitan areas finally used in the regression analysis.+
The t-statistics shown indicate that both 'city salt and snow have coef-
ficients that are significantly different from zero at the 99% confidence
level; the significance level for state salt is 95%, while the coeffic-
ient of miles traveled is significantly different from zero only at the
90% confidence level. All coefficients have the expected sign.
None of the other explanatory variables used in the series of regression
analysis runs showed any systematic relationship to the depreciation
rate. A partial exception concerns the two indicators of tastes and pre-
ferences, income per capita and vehicles per capita. When either of these
variables was included in the entire regression, the coefficients were
not significantly different from zero. When used with the salting intensity
and snowfall variables separately, the coefficients of both income per
capita and vehicles per capita were significant, income havina a negative
sign (depreciation being lower with higher per capita incomes) and vehicles
per capita having a positive sign (more used cars on the markets resulting
in lower prices). The most likely explanation for these differing results
is that income per capita is spuriously correlated with snowfall and salting.
The North-Central, Mid-Atlantic and New England regions all have above
average income and also have greater than average snowfall and use corres-
pondingly more salt.
The reliability of the estimated coefficients for the salt use variables
in the regression equation shown may be questioned on several grounds.
First, some positive collinearity between salt use and snowfall is
possible, which may imply that part of the variation of the depreciation
rate associated with variations in snowfall is erroneously attributed
to salt use. However, the relatively high t-statistics for the respec-
tive coefficients and the comparatively low correlation between salt and
snowfall (.64 or less) suggest that this problem is not severe*. Even•-
so, it is difficult to answer this question with precision.
Second, relationships between environmental factors and automobile
depreciation are confounded by the fact that cars are rarely exposed to
one environment alone. Exposure of automobiles to different environments
as the owners move or vacation is likely to reduce the variation in
measured depreciation rates as compared to cases in which cars are less
* Generally, t-statistics greater than 2.0 indicate that the regression
coefficient is significantly different from zero, i.e., that there exists
a relationship between the dependent and independent variables.
+ Because of missing observations, three of the cases had to be excluded
from the analysis.
$ This comparatively low correlation may reflect the fact that many mid-
west and western communities rely on plowing and sanding for winter high-
way maintenance.
83
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mobile. As a result, the regression coefficients estimated above may
seriously understate the true relationships between independent and
the dependent variables.
Third, the years chosen for the measurement of snowfall and salt use
may not be representative. Consequently, fairly large errors in the
measurement of the independent variables may be expected. Such errors
can be shown to produce regression coefficients which are biased toward
zero. In this case, the regression coefficients again would understate
the true relationship.
Fourth, the analysis does not account for more recent improvements of
design and corrosion resistance by manufacturers. Since most recent
vintage automobiles were not included in the study, the estimates may
overstate both the depreciation rates and their dependence on snowfall
and salt use.
Given the data situation — as well as the level of theoretical under-
standing of the problems involved — the net effect of these factors on
the reliability of the regression estimates cannot be determined with
precision. All that can be done is to acknowledge these issues and take
them into consideration in interpreting the findings reported here.
5.5.5 Estimation of Total Costs of Automobile Depreciation
The results of the regression analysis can be used to calculate the total
economic costs of the incremental depreciation of automobiles attributable
to the use of highway deicing salts. The procedure used for this purpose
is straightforward: we need to determine the value of the stock of auto-
mobiles in various environments and multiply the stock value (by vintage)
by the incremental depreciation attributable to salt use. Since adequate
data on the composition of the total automobile stock by region and vintage
are not available, data on the proportion of automobiles of each vintage
still remaining registered (from R.L. Polk & Co'.) have been used to
translate total registrations into a total dollar value; Appendix B
describes this procedure in greater detail.
Table 8 shows the results of these calculations. The first column con-
tains the number of registrations by state, the next two columns show
salt-use intensity, the fourth column displays the incremental deprecia-
tion computed on the basis of the regression estimates, and column 5 the
incremental loss in the economic value of automobiles attributable to
the effects of the use of deicing salts. This estimate is based on an
average value per car of $1,500, as derived in Appendix B.
The total yearly national cost of the accelerated depreciation of auto-
mobiles due to the effects of deicing salts on corrosion is .estimated at
$1.4 billion, or $14 per car — which corresponds roughly to 1% of the
value of the average automobile. Since this measure is an overall average
it is clear that the relative economic loss attributable to accelerated
84
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Table 8
uost or AutomoDiJLe ue
State
AL
AK
AZ
AR
CA
CO
CT
DE
FL
GA
HI
ID
IL
IN
IA
KS
KY
LA
ME
MD
MA
MI
MN
MS
MO
MT
NE
Estimated 1973
Registration
(in thousands)
1,837
109
1,052
743
11,007
1,359
1,771
284
4,358
2,538
413
412
5,095
2,332
1,480
1,217
1,613
1,614
462
1,938
2,653
4,414
Ii959
963
2,077
412
813
State Salt
X .038
.1
1
1.5
33
12
1
19
12
8.8
4.6
.12
20
30.9
35
29
11
15,1
.1
1.4
City Salt
X .019
2
1
1
40
25
.5
60
22
6
7
6
70
33
50
100
45
25
1
13
preciation
Depreciation
X 100
.042
.057
.076
2.014
.931
,
.048
1.862
.874
.448
.308
.570
2.090.
1.801
2.280
3.002
1.273
1.049
.023
.300
Col. 1
X 4
31
627
103
3,567
264
20
9,487
2,038
663
406
919
965
3,488
6,048
13,242
2,494
2,178
9
244
Loss in Value
X 1500, X 10
(in millions)
.46
9.41
1.54
53.51
3.96
.30
142.31
30.57
9.95
6.09
13.79
14.48
52.32
90.72
198.63
37.41
32.67
.14
3.66
85
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Table 8 (Continued)
State
NV
NH
NJ
NM
NY
NC
ND
OH
OK
OR
PA
RI
SC
SD
TN
TX
UT
VT
VA
WA
W
WI
WY
DC
Estimated 1973
Registration
(in thousands)
318
393
3,686
530
6,360
2,702
304
5,567
1,377
1,328
5,730
500
1,286
323
1,919
5,808
565
223
2,329
1,786
704
1,871
183
222
101,237
State Salt
X .038
.3
39
6
1
18.7
5
.4
25.5
.5
.1
34
35
.2
4.1
.7
39
44
10
3
25
15.8
.2
27
City Salt
X .019
.3
120
24
1
50
3
1
50
6
1
30
25
2
• 1
8
30
20
2
20
50
8
15
Depreciation
X 100
.068
3.762
.684
.057
'1.661
.247
.034
1.953
.133
.023
1.862
1.805
.045
.175
.027
1.634
2.242
.760
.152
1.330
1.550
.60
1.311
.917
Col. 1
X 4.
22
1,478
2,521
30
10,558
667
10
10,872
183
31
10,669
903
15
336
157
923
500
1,770
272
936
2,900
29
304
92,879
Loss in Value
X 1500, X 10
(in millions)
.33
22.17
37.82
.45
158.37
10.01
.15
163.08
2.75
.47
160.04
13.55
.23
5.04
2.36
13.85
7.50
26.55
4.08
14.04
43.50
.43
4.56
1.392
Billion
86
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automobile corrosion is substantially higher in regions affected by
deicing salts. For example, for Massachusetts the estimate per automo-
bile is over $34, or more than 2% of the value of the average car.
It can therefore be concluded that the average annual loss attributable
to the use of deicing salts varies between 1% and 2% of the value of the
automobile.
In interpreting these figures, it should be remembered that the estimates
obtained are based on the most conservative set of assumptions, as dis-
cussed above. For example, the estimated costs do not include additional
expenditures on maintenance (such as more frequent trips to the car wash)
or repair attributable to salt damage. Particularly the expenditures on
undercoating would constitute a sizeable additional cost,* which is at
least partially related to an attempt to reduce the effects of deicing
salts. ' Cost data on the Ziebart rust-proof ing process may be used to
illustrate this aspect.
The Ziebart technique involves the application of a soft wax to steel sur-
faces in order to deny access to moisture, dirt, salts and soluble atmos-
pheric pollutants. The present cost of this treatment ranges from $120 to
$130, depending on the size and complexity of the car, with $130 a typical
cost figure. Approximately 1.5 million automobiles have been treated
by Ziebart since its incorporation. ,
Assume that the value of a car operated under ideal conditions deprecia-
tes at a constant exponential rate of 25% per year. The calculations
in Appendix B show that Ziebart treatment then becomes economically justi-
fiable if it prevents additional depreciation in the range of 1% to 1.5%
per year (depending on the discount rate used). Since 1.5 million car
owners have found it appropriate to pay for this treatment, it can be
concluded that the incremental depreciation estimated above and presented
in Table 6 is approximately in the correct range.
The costs of losses in economic value of passenger cars must be comple-
mented by a rough estimate of the costs to trucks and buses. Although
the present study has attempted to secure sufficient data for a statis-
tical analysis of these costs, the data obtained provide little more
than guidance for a relatively crude assessment. Based on information
from truck fleet owners, incremental depreciation of buses and trucks as
a result of corrosion is minimal, primarily because of greater efforts
in terms of maintenance and treatments. The annual costs per vehicle
have been estimated at $30 on the average on the basis of discussions with
truck fleet owners and managers. For the 23,000,000 buses and trucks
registered nationwide, the total annual costs of preventing salt-related
corrosion damage would therefore be $690 million.
* This cost is not necessarily an alternative to accelerated deprecia-
tion since the observed differences in depreciation rates occur in spite
of differences in the relative emphasis on undercoating in different
environments.
87
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Under very conservative assumptions, the total annual cost ;of deicing
salt use to owners of motor vehicles therefore is estimated here as being
in excess of $2 billion.
5.6 OTHER DAMAGES
The review of damages attributed,to deicing salts in the preceding sec-
tions has illustrated the broad variety by which salt runoff may alter
natural environmental conditions, thereby initiating or aiding processes
that result in real economic losses. By entering both the soil and
the atmosphere, salt is contributing to a change in general environmental
characteristics, primarily with respect to the ion balance., which affects
patterns of corrosion and deterioration of materials exposed to these
conditions. Consequently, damages that have been attributed to the use
of deicing salts, have been noted in areas other than those discussed in
the preceding sections. The available evidence on such "other" damages
of course, is limited to reports on a few instances. However, a brief
review of this evidence suggests that the potential effects of deicing
salts on underground cables and electric utility lines may be substantial
on a national scale.
One of the best-documented instances of salt-related damage to underground
power transmission lines is the case of Con Edison's facilities in. New
York City. This company maintains in New York City the largest system of
underground electric facilities in the world. The winters.of 1972-73 and
1973-74 offered a striking contrast in terms of salt applications and in
terms of resulting damages to this underground cable system. The winter
of 1972-73 was comparatively mild, without much snow. The ;city used very
little salt that year, about 20,000 tons, most of which was applied to
bridges, ramps and critical intersections. In contrast, the winter of
1973-74 was characterized by two heavy snow storms leading to intensive
salting; the city used about 120,000 tons that winter. :
The effects of salt runoff on underground cables become evident almost
immediately after application. These effects continue for two to three
months as the salt brine is washed through the underground system. As
a result, secondary cables (generally rubber-insulated and carrying 120
volts) develop short circuits resulting in fires. According to data
furnished by Con Edison, there were approximately 1,400 more manhole
fires in the winter of 1973-74 than in the preceding winter. These
additional manhole fires necessitated extensive repairs and the replace-
ment of almost 1,000 sections of secondary cable at a total cost of
$4,000,000. In addition, there is evidence that the primary feeders
(cables operating at 13,000 and 27,000 volts) are also affected by salt
runoff from city streets. Since these cables are generally better insul-
ated and protected, these effects develop more slowly.
In total, the company estimates that the salt spread on the streets of
New York City resulted in additional expenditures by Con Edison in
excess of $5,000,000 for the winter of 1973-74. This is a direct cost;
added to it should of course be the costs of power outages to consumers,
which are unknown. (The company has been lobbying for the adoption of
other substances, such as magnesium sulphate, to replace salt at least
on an experimental basis).
88
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While this example constitutes an extreme case, it does suggest that
the cost of damages to power transmission lines underground may be sub-
stantial on a national scale. In this particular case, the cost to Con
Edison exceeded direct expenditures on the salt and its application by
the city. Since these estimates do not include indirect costs to con-
sumers nor damages to above-ground power transmission lines, it is rea-
sonable to assume that the total national cost of these damages is at
least double the cost for New York City, or $10 million a year.
5.7 THE DIRECT COSTS OF SALT APPLICATION
Before providing an estimate of the total costs of deicing salt use,
it is necessary to estimate the actual costs to users of salt applied
for snow and ice control. As mentioned above, salt use varies consider-
ably from one winter to the next in response to snow and ice conditions.
Therefore, the calculation of the annual direct costs of salt applica-
tion refers to the annual average. (The annual figure must be an esti-
mate of an average since supply conditions and transportation costs
lead to sizeable variations in the price per ton of salt.)
Available data (307) suggest that the cost per ton of sodium chloride
to users lies somewhere in the $10 - $20 range; the corresponding cost
figure for calcium chloride is $30 - $35 per ton. In addition to these
costs, the user also must account for the cost of application, which
is about $5 - $10 per ton. Since the present annual salt use at the
national level is approximately 9 million tons, the total annual costs
can be estimated as about $200. million.
5.8 SUMMARY OF COSTS ,
The analysis in this section indicates that the actual costs of using
salts for highway snow and ice control actually exceeds the direct costs
of purchase and application by an order of magnitude. To recapitulate,
the costs of the contamination of water supplies have been estimated
at $150 million; those for vegetation at possibly $50 million, for cars
at $2 billion, for bridge decks at $500 million, and for utilities as
more than $10 million. Together with the cost of purchase and appli-
cation, the use of deicing salts may cost the nation close to $3.0
billion.
The major share of this cost has been estimated for accelerated damages
to vehicles, a case for which available data allowed for a direct appli-
cation of the general cost estimation model. While it is somewhat spec-
ulative, it is reasonable to assume that other costs are likely to be
higher. Howeverf present data limitations do not allow for the explora-
tion of the full range of these costs.
89
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Since the available data allow only for illustrative estimates of the
costs associated with different damage categories, a reasonable break-
down into direct and indirect costs to society and individuals is
difficult. Since these breakdowns depend on institutional arrangements
(cost sharing between society and individuals for certain damages) and
actual practice (complete restoration may turn an indirect cost into
a direct cost), on which only few observations exist, the best conclu-
sions possible is that the major share of the cost is borne by the
automobile owners (who, of course, also enjoy any benefits of bare pave-
ment in the middle of winter). The remaining $1 billion are approxi-
mately evenly divided between individuals and society.
90
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r
SECTION 6
BENEFITS OF ROM) SALTING -
There are three benefits which have been ascribed to the use of salt
for snow and ice removal: savings in terms of dollars, lives (safety),
and time. The dollar savings is in terms of producing bare pavement
in a given time under a constraint of a limited highway budget. As
demonstrated in Section 5, the savings in snow removal from salt use
cost that should be considered; indirect costs resulting from salt use
are much higher than savings in snow removal costs. Consequently in
terms of total direct dollar savings, (excluding safety and time savings
for the moment), heavy salt use does not provide a cost savings, but
instead incurs a net cost, and is therefore not a benefit.
On the other hand, salt is beneficial to the extent to which it increases
safety and time savings. The relationship between salt use and these two
factors is highly complex, especially with regard to safety. It is not
within the scope of this project to perform an in-depth analysis of the
functional relationship. However, it is appropriate to take a brief
look at the work that has been done in these areas.
i.l
SALT AND SAFETY
The extent to which alternative winter maintenance policies affect highway
safety is not established by the direct comparison of accident rates with
maintenance policies unless driver behavior is explicitly incorporated as
a parameter of the analysis. Although one would expect considerable re-
search to have been directed toward understanding situations which involve
the risk of injury and death, surprisingly little is actually known. ^Human
behavior under conditions of financial uncertainty has a rich theoretical
and applied literature, but such models are largely inappropriate for the
analysis of accident risk, and attempts to model human behavior in sit-
uations involving the risk of life or limb have not been very successful.
The existing evidence for a connection between safety and alternative
winter maintenance policies is both meager and inconsistent.
It is often tacitly assumed that deicing salts improve driving conditions.
Courts, in assessing liability for single-vehicle winter accidents, have
found highway department officials negligent for not applying enough
salt to provide an acceptable level of safety for motorists. Also, the
assumed causal relationships between deicing salts and highway safety is
a major rationale offered by highway department officials for the twenty-
fold increase in the annual use of salts for highway deicing since 1950.
91
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There is no question that salt can result in an increase in' the coef-
ficient of friction between the tire and road in most cases. Experi-
ments have verified that under proper temperature conditions* the coef-
ficient of friction for a snow covered pavement can be increased by the
application of deicing salts (.05 kg. per square meter raises the coef-
ficient of friction from 2.5 to over .40). (252) (In the same study
sand, even when applied at ten times the rate, resulted in only a slight
increase in -the coefficient of friction on snow-covered pavement).
Three studies contain information which support the belief that deicing
salts reduce highway accident rates during the winter months. One study
was conducted by the city of Ann Arbor, Michigan. (258) In 1967, the
last year before the use of salt for deicing became general practice in
Ann Arbor, 315 accidents were reported; the accident toll fell to 196
and 186 during the next two years. However, because no informcition is
available as to the number of winter storms, or other measures of severity
of the winters, this data alone does not provide conclusive evidence.
The second study was done by the American Public Works Association (APWA)
in Chicago during the winter of 1963-1964. (253) The APWA study contains
numerous statistical tabulations of accident reports; for our purposes
the most illuminating is the proportion of accidents which occurred on
major and local streets under normal and adverse conditions. During
periods of normal weather (dry roads), four-fifths of Chicago's winter
highway accidents occurred on major roads. This percentage1 fell to two-
thirds during periods when city-wide driving conditions were adversely
affected by snow and ice, suggesting that winter maintenance, which is
directed toward major streets, does improve highway safety. Although
the data suggest that Chicago's chosen policy of maintenance, which relies
heavily on salt for deicing, is effective, the accident reduction may be
more dependent upon prompt plowing of major streets than it is on the use
of salts for deicing.
The third study consisted of a survey conducted on salt use and effects
in 116 U.S. cities during 1971-1972 (116 responses out of 504 requests
(287). One of the findings of this study was given wide publicity and
acclaim by salting proponents: "Salt deicing cuts accidents by 75%
according to new 116-city survey." (259) However this statistic was
based on responses from only 14 cities which were able to give a per-
centage breakdown of accidents in response to the question: "From these
accident records, how many occurred on snow and ice-covered pavements
against streets treated with deicing materials?" Furthermore, in response
* That is, in the temperature range in which salt melts snow and ice
above -9°C for NaCl.
92
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to the question, "Do your accident records show a relationship between
weather and street conditions and damage to vehicles and/or personal
injuries?", 42.2% of cities responded "yes", 40.6% responded "no", and
17.2% did not respond.
While the results of the study may be seriously questioned on the basis
of the response sample, there are other serious research problems. First,
the responses should be weighted by the percent of the salt treated areas
in each city. Second, there was no backup in terms of snowfall. Third,
the seriousness of accidents was unknown. Fourth, the extent of salt use
on different types of streets was unknown. Fifth, the basis for informa-
tion (accident records) is questionable, and probably not comparable
between cities. Very honestly, all of these factors make the findings
useless.
However, other studies have noted a potentially serious effect from the
application of salt: invisible wetness. Salt in solution on a road has
the effect of temporarily or indefinitely prolonging the drying of the
surface, thus lowering tire friction. This situation is particularly
dangerous because the road may appear dry. The greater the concentra-
tion of the salt solution, the longer the drying time. Higher air humi-
dity will cause the salt to have a greater effect in delaying the drying
rate. (254) In addition, under very low temperatures (-27°C for NaCl and
-51°C for CaCl2)r too much salt decreases the melting rate and in some
instances may assist the formation of ice (2). While these adverse con-
ditions may occur only a very small fraction of the time, they still must
be considered as a negative effect of salt. In a study of accidents in
rural and urban cities within Oakland County, Michigan, it was found that
as the use of salt increased, the percentage of accidents occurring under
icy conditions decreased (249). This is to be-expected since salt will
reduce the frequency of icy conditions. However, it does not necessarily
prove that salts increase safety, for the same study also found that the
total number of winter accidents increased with increased use of salt.
This apparent contradiction might be attributed to an increase in traffic
as driving conditions improved, though this tentative conclusion remains
unchecked because no statistics were recorded on vehicle density. The
researchers commented that salting may create a false sense of security
in many drivers (249). While this statement remains unproved, it is im-
portant to point out some analogous findings.
Two economists (Peltzman and Anderson) have noted that an improvement in
safety, either in vehicles (automobile seat belts in the Peltzman study)
or in highway conditions (Anderson), could elicit an increase in motorist's
speed sufficient to. render indeterminant the impact of safety improve-
ments on accident rates (248, 257). Under hazardous winter conditions
drivers do slow down, probably enough so that their perceived risk of
injury is the same as under normal driving conditions (risk of minor acci-
dents may rise or stay the same). Whether the perceived risk is the same
as the actual risk is unknown. However, it is reported that an Ottawa,
Canada consulting firm found from accident records that accidents occur-
ring on icy roads are generally property damage, while accidents occurring
93
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on bare (dry or wet) pavement, during the winter are more likely to
involve personal injury. (53)
Substantial research of the relationship between salt and safety is a
necessity. While salt does serve to increase friction under proper use
on a stretch of highway, this is not the only factor which determines
accident rates. Research must consider continuity of conditions along
a roadway, speed, and most of all, driver behavior. Such research will
be extremely difficult indeed because determination of risk taking under
varying driving conditions is a difficult (if not impossible) task.
However, until such research is performed, it is false to assume that salt
and safety are synonomous.
6.2
TIME SAVINGS
Anyone who has driven under snow and ice conditions knows that his progress
is slowed, especially during rush hour. There have been scattered esti-
mates of the cost of lost time (10), but there has been no major effort
to assess the true value of the lost time. While the costs1 may be high,
a certain amount of care must be taken in developing the figures. For
example, it is false to suggest that a one hour delay for all persons in
a city will result in a loss of one-eighth'of the economic activity for
that day. While there may be a one hour loss because of a shutdown of a
continuous industrial process, there is probably little if any loss in
terms of shopping expenditures. Shoppers will simply defer their errands
to a later time with the result that there will be only a short-term loss
to the stores. As a result of a survey on the impact of snowfall on man-
ufacturing and retail activities in selected cities in the U.S.,, one
study reported that:
"Probably the most significant and best supported fact to
emerge from the survey was the relatively small problem that
snow appeared to pose for all types of manufacturing industry.
Few, if any, of the firms interviewed felt seriously threatened
by snow and the majority took only the most rudimentary pre-
cautions to ensure that operations were not disrupted. Also
there was no conclusive evidence to support the contention that
attitudes or actions were significantly altered by the cictual
snow environment" (Ref. 59, p. 110)
While this attitude may certainly be a result of the presently efficient
snow removal procedures, it does seem to imply that a slightly increased
delay in clearance of snow and ice would not produce disastrous results.
Nevertheless, the question of actual cost of lost time from snowstorms
is still a problem very open to research.
Better planning for the possibility of hazardous snowstorms; would
probably help to reduce business losses.
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BIBLIOGRAPHY
Sections
1. General Environmental
2. Costs of Snow and Ice Removal
3. Water
4. Medical
5. Vegetation
6. Soils
7. Vehicles
8. Highways and Bridge Decks
9. Utilities
10. Safety
11. Legal Implications
12. General Reference Material
13. Maintenance Procedures and Regulations
14. Salt in the Atmosphere
15. Additional References
95
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BIBLIOGRAPHY
General Environmental
1. Adams, Franklin S, "Highway Deicing Salts are Potential Environmental
Contaminants," Farm Economics, Pennsylvania State University, University
Park, Pennsylvania, (1973).
2. Adams, Franklin S., "Highway Salt: Social and Environmental Concerns,"
Highway Research Record No. 425, Highway Research Board, Washington,
D.C.,(1973). .
3. American Automobile Association, "Deicing Salts: The Environmental Cost
of Bare Pavement," Environmental News Digest, A.A.A., Washington, D. C.,
(1972).
4. Arthur D. Little, Inc., "Salt, Safety and Water Supply: Toward an
Improved.Public-Policy for Using Road Salt," A policy study for the
Special Commission on Salt Contamination of Water Supplies, Massachusetts
General Court, (1972).
5. Behnke, Clifford C., "Road Salt is Harmful, Assembly Unit Told,"
Wisconsin State Journal, Madison, Wisconsin, (1973).
6. Bried, Raymond, "The Great Salt Controversy," Yankee Magazine, (1973).
7. Chance R.L., "Corrosion, Deicing Salts, and the Environment," General
Motors Research Laboratory, (1974) .
8. Dadisman, Quincy, "Close Watch Urged on Use of Road Salt," Milwaukee
Sentinel, Milwaukee, Wisconsin, (1973).
9. Public Works, "Deicing Salts and the Environment," Public Works,
Vol. 102, No. 12, pp. 54-56, (1971).
10. Dickenson, William E., "Snow and Ice Control - A Critical Look at its
Critics," Highway Research Record No. 227, Highway Research Board,
Washington, D. C.,(1968).
11. "Department of Public Works: Report Defending Road Salt Rejected by
Environment Secretary," Boston Globe, Boston, Massachusetts,
(1975). ;
12. "Economic Impact of Pollution Control," Environmental Protection Agency-
A Progress Report, December, 1970 - June 1972, pp. 47-57, (1972).
96
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13. Massachusetts Department of Public Works, "Environmental Impact Report:
Snow and Ice Control Program, (1974).
14. "Facts You Should Know About Effects of Deicing Salt on the Environment",
A review of National Cooperative Highway Research Program Report No. 91,
Effects of Deicing Salts on Water Quality and Biota, Literature Review
and Recommended Research., American Public Works Association Reporter,
(1971).
15. Field, Richard, et. al, "Environmental Impact of Highway Deicing,"
Environmental Protection Agency, Water Quality Research, Edison, New
Jersey, (1971).
16. Field, Richard, et. al, "Water Pollution and Associated Effects from
Street Salting," Paper presented at the 45th Annual Conference of the
Water Pollution Control Federation, Atlanta, Georgia, (U.S. Environmental
Protection Agency) (1972).
17. Gould, Whitney, "Road Salt Takes a Licking as Traffic Hazard Polluter,"
The Capital Times, Madison, Wisconsin, (1973).
18. Gould, Whitney, "EPA Expert Backs Road Salt Warning," The Capital Times,
Madison, Wisconsin, (1973).
19. Hanes, R.E., Zelanzy, L. W., and Blaser,,R. E., "Effects of Deicing
Salts on Water Quality and Biota: Literature Review and Recommended
Research," National Cooperative Highway Research Program Report No. 91,
Highway Research Board, Washington, D. C.,(1970)-
20. Hanes, R.E., et. al., "The Effects of Deicing Salts on Plant Biota
and Soils — Experimental Phase," National Cooperative Highway Research
Program, Project 16-1-Final Report, Highway Research Board, Washington,
D.C., (1972).
21. Heydon, Howard S.,"The Environment — Not New But Current," Public Works,
p. 69, (1973).
22. Hughmanick, Ronald N., "Environmental Effects of Snow and Ice Control
Programs," American Public Works Association llth Annual Show Conference,
Chicago, Illinois, April, 1971, Pennsylvania Department of Transportation,
Bureau of Maintenance, Harrisburg, Pennsylvania.
23. Hutchinson, F.E., "The Effect of Deicing Salts Applied to Highways on
the Contiguous Environment," Department of Plant and Soil Sciences,
University of Maine, Orono, Maine [n.d.]
24. Hutchinson, F.E., "Environmental Pollution from Highway Deicing
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97
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113. Raymond, Lyle S., Jr., "Synopsis: Salt Pollution of Water Supplies,"
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118. Soderlund, G., Lehtinen, H., Friberg, S., "Physiochemical and Micro-
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142. Simkins, Michael H., "Feasibility Report on Regulating Water Supplies
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106
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163. Hall, R., Hofstra, G., Lumis, G.P., "Leaf Necrosis of Roadside Sugar
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164. Hofstra, G., Hall, R., "Injury on Roadside Trees; Leaf Injury on Pine
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D.C., Area during the 1966-1967 Winter," Plant Disease Reporter,
52:5:350-354 (1968).
191. Westing, Arthur H., "Plants and Salt in the Roadside Environment,"
Phytopathology, 59:9:1174-1181 (1969).
192. Zelazny, Lucian, "Salt Tolerance of Roadside Vegetation," Symposium:
Pollutants in the Roadside Environment," edited by Edwin D. Carpenter,
University of Connecticut, (1968).
Soils
193. Brandt, G.H., "Potential Impact of Sodium Chloride and Calcium Chloride
Deicing Mixtures on Roadside Soils and Plants," with discussion by
Hutchinson, Westerman, Rubins, and Rich, Highway Research Record 425,
Highway Research Board, Washington, D.-C. (1973).
194. Hutchinson, F.E., B.E. Olson, "The Relationship of Road Salt Applications
to Sodium and Chloride Ion Levels in the Soil Bordering Major Highways,"
Highway Research Record 193, Highway Research Board, Washington, D. C.
(1967).
109
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195. Hutchinson, Frederick E.r "Dispersal of Sodium Ions in Soils,"
Materials and Research Technical Paper 71-10C, University of Maine,
in cooperation with the Main State Highway Commission, (1971).
196. Hutchinson, F. E., "Dispersal of Soil-Bound Sodium from Highway
Salting," Public Works, pp. 69-70, (1972).
197. , "Supplemental Report II for Cooperative Project
Entitled 'Dispersal of Sodium Ions in Soils'," University of Maine,
Orono, Maine, (mimeographed), (1974).
198. Prior Dr., George A., "Salt Migration in Soil," Symposium: Pollutants
in the Roadside Environment, edited by Edwin D. Carpenter, University
of Connecticut, (1968).
199. Prior, George A., Berthouex, Paul M., "A Study of Salt Pollution of
Soil by Highway Salting," Highway Research Record 193, pp. 8-21,
Highway Research Board, Washington, D. C. (1967).
200. Zelazny, L.M., Blaser, R.E., "Effects of Deicing Salts on Roadside
Soils and Vegetation," Highway Research Record 335, Highway Research
Board, Washington, D. C. (1970). :
201. Zelazny, L.W., Hanes, R.E., Blaser, R. E., "Effects of Deicing Salts
on Roadside Soils and Vegetation: I. Movement Distribution in a Vergennes
Soil," Virginia Polytechnic Institute Research Division, Blacksburg,
Virginia, [n.d^](unpublished paper). :
Vehicles
202. Bishop, R.R., "Corrosion of Motor Vehicles by Deicing Salt - Results
of a Survey," Road Research Laboratory Report #LR232, Road Research
Laboratory, Crowthorne, England (1968).
203. Bishop, R.R., "The Development of a Corrosion Inhibitor for Addition
to Road Deicing Salt," Transport and Road Research Laboratory, Crowthorne,
England, (1972).
204. Burke, Mark A., "What Ever Happened to Automobile Body Corrosion,"
Vehicle Safety Engineering and Standards Department, Motor Vehicle
Manufacturers Association.
205. Fromm, H.J., "Corrosion of Auto-Body Steel and the Effects of Inhibited
Deicing Salts," Highway Research Record 227, Highway Research Board,
Washington, D. C. (1968).
206. Motor Vehicle Corrosion and Influence of Deicing Chemicals, Paris:
Organization for Economic Cooperation and Development, Road Research
Group C2 (1969),
207. Palmer, J.D., "Corrosive Effects of Deicing Salts on Automobiles,"
Materials Protection and Performance, pp. 38-43, (1971).:
110
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208.
209.
210.
Thurmann, Moe T., Ruud, O.E., "Vehicle Corrosion Due to the Use of
Chemicals in Winter Maintenance and the Effect of Corrosion Inhibitors,"
Oslo: Norwegian Road Research Laboratory, 44:15-29, (1973).
"Vehicle Corrosion Caused by Deicing Salts," Special Report 34, American
Public Works Association, (1970).
Waindle, R.F., "Automotive Body Rusting-Causes/Cures," Presented at the
meeting of the Institute of Traffic and Engineering, U.C.L.A., Extension,
Los Angeles (1967).
Highways and Bridge Decks
211. Herman, H.A., "The Effects of Sodium Chloride on the Corrosion of
Concrete Reinforcing Steel and on the pH of Calcium Hydroxide Solution,"
FHWA-RD-74-1, Federal Highway Administration, Washington, D. C., (1974).
212. Berman, Horace, Chaiken, Bernard, "Techniques for Retarding the
Penetration of Deicers into Cement Paste and Mortar," Public Roads,
38:1:9-19,
213. Blackburn, Robert R., et. al., "Economic Evaluation of the Effects of
Ice and Frost on Bridge Decks," Midwest Research Institute, Project
#3564-E, p. 261, Kansas City, Missouri, (1971).
214. Boulwane, R.L., Stewart, C.F., "Bridge Deck Restoration Aid Procedures:
Field Electrical Measurements for Bridge Deck Membrane Permeability
and Reinforced Steel Corrosion," California Division of Highways, (1973).
215. Carroll, Robert J., "Evaluation of the Effectiveness of Membrane Water
Proofing for Concrete Bridge Decks," Ohio Department of Transportation,
Bureau of Research and Development, (1973).
216. Clear, K.C., "Evaluation of Portland Cement Concrete for Permanent
Bridge Deck Repair," FHWA-RD-74-5, Federal Highway Administration, (1974).
217. Clear, K.C., Hay, R.E., "Time to Corrosion of Reinforcing Steel in
Concrete Slabs Volume I: Effect of Mix Design and Construction Para-
meters," Interim Report FHWA-RD-73-32, Federal Highway Administration,
Washington, D. C. (1973).
218. Clifton J.F., Beighly, H.F., Mathey, R.G., "Non-Metallic Coatings for
Concrete Reinforcing Bars," FHWA-RD-74-18, Federal Highway Administration,
(1974).
219. "Corroding Elevated Highway Closed Poor Maintenance Cited," Engineering
News Record, p. 21, (1974).
220. Grieb, W.E., "Silicones as Admixtures for Concrete," Highway Research
Record 18, Highway Research Board, (1963).
Ill
-------
221.
222.
223.
224.
Hardesty and Hanover, "Report on the Inspection and Analysis of the
West Side Highway (Henry Hudson Parkway) 72nd Street-79th Street,"
Capital Project No. HW-152, for the Transportation Authority, New York,
(1974). .
Hardesty and Hanover, "Report on the Inspection and Analysis of the
West Side Highway (Henry Hudson Parkway) 42nd Street-59th Street,"
Capital Project No. HW-19 for Transportation Authority, New York City,
(1974).
, "Report on the Inspection and Analysis of the
West Side Highway (Henry Hudson Parkway) 59th Street-72nd Street,"
Capital Project No. HW-152 for the Transportation Authority, New York
City (1975).
, "Report on the Inspection and Analysis of the
225.
226.
227.
228.
229.
230.
231.
232.
233.
234.
West Side Highway (Henry Hudson Parkway) Battery to 42nd Street,"
Capital Project No. HW-19 for Transportation Authority,\ New York City
(1975).
Hay, R.E., Personal Correspondence with Robert Anderson on August 1974.
Hilsdorf, H.K., Loff, J.L., "Revibration of Retarded Concrete for
Continuous Bridge Decks," National Cooperative Highway ^Research Program
Report 106, Highway Research Baord, Washington, D. C. [n.d., ]
Houston, J.T., et. al., "Corrosion of Reinforcing Steel Embedded in
Structural Concrete," Research Report 112-1F, University of Texas at
Austin, (1972).
Kaiser Cement and Gypsum Corporation, "Effect of Various Sxxbstances
on Concrete and Recommended Protective Treatments," Concrete Topics,
Technical Service Department Bulletin No. 16 [n.d.]
Kallas, B.F., "Performance of Asphalt Pavements Subjected to Deicing
Salts," Highway Research Record 24, Highway Research Board,, Washington,
D. C., (1963).
Klietherraes, J., "Repair of Spalling Bridge Decks," Highway Research
Record 400, Highway Research Board, Washington, D. C. (1972).
"Concrete Bridge Deck Desirability," National Cooperative Highway
Research Project, Synthesis of Highway Practice #4, Highway Research
Board, Washington, D. C. (1970).
"Winter Damage to Road Pavements," Paris" Organization for Economic
Cooperation and Development, Road Research Group C2, (1972).
"Waterproofing of Concrete Bridge Decks," Paris: Organization for
Economic Cooperation and Development, Road Research Group C2, (1972).
Pike, R.G., et. al., "Nonmetallic Coatings for Concrete Reinforcing
Bars," Public Roads, 37:5:185-197 (1973).
112
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235. Snyder, M. Jack., "Protective Coatings to Prevent Deterioration of
Concrete by Deicing Chemicals," National Cooperative Highway Research
Program Report #16, Highway Research Board, Washington, D. C., (1965).
236. Spellman, D.L., Stratfull, R.F., "Chlorides and Bridge Deck Deterioration,"
Highway Research Record 328, Highway Research Board, Washington, D. C. (1970.
237. Stark, David, "Studies of the Relationships among Crack Patterns, Cover
Over Reinforcing Steel and Development of Surface Spalls in Bridge Decks,"
Special Report 116, Highway Research Board, Washington, D. C. (1971).
238. Stewart, C.F., "Deterioration in Salted Bridge Decks," Special Report
116, Highway Research Board, Washington, D. C., (1971).
239. Stewart, C.F., "Bridge Deck Restoration — Methods and Procedures:
Bridge Deck Seals," California Division of Highways (1972).
240. , "Bridge Deck Restoration — Methods and Procedures:
Repairs," California Division of Highways, (1972).
241. Stratfull, R.F., "Experimental Cathodic Protection of a Bridge Deck,"
Transportation Laboratory, Department of Transportation, California
(1974).
242. Stratfull, R. F., Van, M.V., "Corrosion Autopsy of a Structurally Unsound
Bridge Deck," California Division of Highways, (1973).
243. Tripler,'A.B., et. al., "Methods for Reducing Corrosion of Reinforcing
Steel," National Cooperative Highway Research Program Report 23,
Highway Research Board, Washington, D. C., (1966).
244. Yamanskir R.S., "Coatings to Prevent Concrete from Damage by Deicer
Chemicals: A Literature Review," Journal of Paint Technology,
39:509:394-397 (1967).
Utilities
245. Berthouex, Paul M., Prior, George A., "Underground Corrosion and Salt
Infiltration," Journal of the American Water Works, 60:3:345-355, (1968).
246. Various memos on salt usage and salt-related damage, Con Edison, New
York (1974).
Safety
247. Anti-Skid Program Management and Related Papers, Highway Research Record
376, 22 reports, Highway Research Board, Washington, D. C. (1971).
248. Anderson, Robert C., "The Economics of Highway Safety," Traffic Quarterly,
pp. 99-111, (1975).
113
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249. Arvai, Ernest S., "The Effect of Salt on the Number of Winter Accidents,"
HIT Laboratory Reports, Highway Safety Research Institute, University
of Michigan, (1971) .
250. Committee on Winter Driving Hazards, "1973 winter Test Program," National
Safety Council, Stevens Point, Wisconsin (1973).
251. Dadisman, Quincy, "Salt on Roads Blamed in Some Crashes," Milwaukee
Sentinel, Milwaukee, Wisconsin, (1973).
252. Ichihara, K.> Mizoguchi, M., "Skid Resistance of Snow or Ice-Covered
Roads," Special Report 115, Highway Research Board, Washington, D. C.
(1970). ]
253. Lockwood, R.K., "Effect of Winter Weather on Traffic Accidents," Chapter
8 in Snow Removal and Ice Control in Urban Aaeas, Research Report #114,
American Public Works Association, (1965).
254. Mortimer, Thomas, P., Ludema, Kenneth, C., "The Effects of Deicing Salts
on Road Injury Rates, Tire Friction, and Invisible Wetness," Highway
Research Record 396, Highway Research Board, Washington,; D. C. (1972).
255. Perspectives on Benefit-Risk Decision Making, National Academy of
Engineering, Washington, D. C. (1972).
256. "Accident Facts," National Safety Council, Chicago
257. Peltzman, S., "The Regulation of Automobile Safety," Journal of Political
Economy, forthcoming (1975).
258. "Safe Winter Driving in Ann Arbor," Ann Arbor, Michigan City Hall, (1971).
259. "Salt Deicing Cuts Accidents by 75% According to New 116-City Survey,"
American City, p. 19, (1973).
260. Traffic Operation at Sites of Temproary Obstruction, Paris: Organization
for Economic Cooperation and Development, (1973).
Legal Implications
261. "Federal Environmental Legislation and Regulatiions as Affecting
Highways," Research Results Digest 25, National Cooperative Highways
Research Program, Highway Research Board, Washington, D. C. (1971).
262. Kelley, James P., "Hunt vs. the State of Iowa," Law No. 123796, 3rd
Judicial District, Crawford County, Iowa (1974).
263. "Analysis by the Legislative Reference Bureau: Statutes 86.37, 86.38,"
Legislative Reference Bureau - 6581/1, Madison, Wisconsin (1973).
114
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264. "Analysis by the Legislative Reference Bureau 1: Statutes 36.218,
84.53, 114.025," Legislative Reference Bureau - 6580/1, Madison,
Wisconsin, (1973).
265. "Information and Data with Respect to Department's Responsibility in
Wells and Water Supplies," New Hampshire Department of Public Works and
Highways, (1964).
266. U.S. Congress, Senate, Committee on Interior and Consular Affairs,
' Subcommittee on Water and Power Resources, "Saline Water Program;
Hearing on S.1386," 93rd Congress, First Session (1973).
267.' U.S. Congress, Senate, Committee on Interior and Consular Affairs,
Subcommittee on Water and Power Resources, "Salinity Control Measures
on the Colorado River, Hearing on S.1908, S.2940, and S.3094,"
93rd Congress, 2nd Session (1974).
General Reference Material
268. Ackerman, S.R., "Used Cars as a Depreciating Asset," Western Economic
Journal, 11:436^474 (1973). '
269. Ackerman, William C., "Minor Elements in Illinois Surface Waters,"
Technical Letter 14, Illinois State Water Survey, Urbana, Illinois (1971).
270. Andrews, Richard A., "Economies Associated with Size of Water Utilities
and Communities Served in New Hampshire and New England," Water Resources
Bulletin, 7:5:905-912 (1971).
271. "Automobile Facts and Figures," Automobile Manufacturers Association,
In., (1974).
272. Bennett, W.B., "Consumption of Automobiles in the United States,"
American Economic Review, 57:841-849 (1967).
273. Boiteux, M.," L'Amortissement-Depreciation de Autombiles,"
Revue de Statistique Appliguee, 4:57-72 (1956).
274. Burdick, George E., Lipschuetz, Morris, "Toxicity of Ferro and Ferricyanide
Solutions to Fish and Determination of Cause of Mortality," American
Fisheries Society, 78:192-202 (1948).
275. Cherner, Morric, "Property Values as Affected by Highway Landscape,
Developments," Highway Research Record 53, Highway Research Board,
Washington, D. C., (1963).
276. Chow, G. C., Demand for Automobiles in the Unites States: A Study
in Consumer Durables, Amsterdam: North Holland, (1957)
277. Cramer, J.S., "The Depreciation and Mortality of Motor Cars," Journal of
the Royal Statistical Society, 121:18-59 (1958).
115
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278. Harraeson, Robert, et. al., "Quality of Surface Water in Illinois,
1966-1971," Bulletin 56, Illinois State Water Survey, Urbana, Illinois,
(1973).
279. International Shade Tree Conference, Inc., "Shade Tree Evaluation,"
2nd revised edition, edited by Clarence Lewis, Urbana, Illinois (1970.
280. Larson, T.E., "Mineral Content of Public Ground Water Supplies in
Illinois," Circular 90, Illinois State Water Survey, Urbana,
Illinois (1963).
281. Moench, A.F., Visocky, A.P., "A Preliminary 'Least Cost1 Study of
Future Groundwater Development in Northeastern Illinois," Circular 102,
Illinois State Water Survey, Urbana, Illinois, (1971). ;
282. NADA Official Used Car Guide, National Automobile Dealers Used Car
Guide Company, [n.d.]
283. Patterson, Alan, "Testing a New Approach to Determining the Monetary
Value of Urban Shade Trees," (mineographed), (1974).
284. "Public Water Supplies," New Hampshire Water Supply and Pollution
Control Commission, (1974). ;
285. "Report of Routine Chemical and Physical Analyses of Public Water
Supplies in Massachusetts," Massachusetts Department of; Public Health,
Division of Environmental Health, Boston, Massachusetts (1973).
286. Schicht, R.J., Moench, Allen, "Projected Groundwater Deficiencies in
Northeastern Illinois, 1980-2020," Circular 101, Illinois State Water
Survey, Urbana, Illinois (1971).
287. Scott, John B., Saunders, M., "The American City Survey of Deicing Salt-
An Analysis of Salt Usage in U.S. Municipalities above 25,000 Population,"
Municipal Government Marketing Report No. B6-1172, The American City
and Municipal Index, (1972).
288. "Survey of Salt, Calcium Chloride and Abrasive Use in the United
States and Canada for 1973-1974," Salt Institute, Alexandria, Virginia,
(1975).
289. "Survey of Salt, Calcium Chloride and Abrasive Use in the United States
and Canada for 1969-1970," Salt Institute, Alexandria, Virginia, (1970.
290. "Survey of Salt, Calcium Chloride and Abrasive Use for Street and
Highway Deicing in the United States and in Canada for 1966-1967,"
Salt Institute, Alexandria, Virginia (1967).
291. Taylor, Floyd B., Our New England Water Supply, New England Public Health
Association, Portsmouth, New Hampshire, (1974).
292. "Chemical Analyses of Public Water Systems," Texas State Division of
Health, Division of Environmental Engineering, Austin, :(rev. ed.) (1974).
116
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293. "Water Analysis for Fiscal Year 1972-1973," Utilities Department,
Treatment Division, City of Ann ARbor, Michigan [n.d.]
294. "1970 Water Resources Data for Massachusetts, New Hampshire, Rhode
.Island and Vermont:. (1) Surface Water Records; (2) Water Quality
Records," U.S. Department of the Interior Geological Survey, Boston,
Massachusetts, (1971),
295. "1972 Water Resources Data for Massachusetts, New Hampshire, Rhode
Island and Vermont: (1) Surface Water Records; (2) Water Quality Records,
U.S. Department of the Interior Geological Survey, Boston, Massachusetts,
(1974) .
296. Wykoff, F., "Capital Depreciation in the Post-War Period: Automobiles,"
Review of Economics and Statistics, 52:168-172 (1970).
Maintenance Procedures and Regulations
297. "Memoranda Concerning the City's Use of Salt for Snow and Ice Control-
Environmental Considerations, Research, Recommendations, etc.," Ann
Arbor, Administrative Environmental Committee, the Mayor's Committee
on Natural Resources (1970).
298. "Article V(a) Tow Away Zone Regulations," Department of Public Works,
Brookline, Massachusetts.
299. Cohn Dr. Morris M., Fleming, Rodney R., Managing Snow Removal and
Ice Control Programs, A collection of papers presented at the Annual
North American Snow Conferences 1969-1973, American Public Works
Association, Special Report 42, (1974).
300. Cross, Seward E., "Snow Removal Regulations and Enforcement,"
Department of Highways and Traffic, Washington, D. C., Paper presented
at American Public Works Association Snow Conference, Chicago, Illinois,
(1971).
301. "Maintenance Manual: Sections 5-290-295," Department of Highways,
Idaho, (revised) (1966).
302. Keyser, J. Hode, "Deicing Chemicals and Abrasives: State of the Art," "
Highway Research Record 425, Highway Research Board, Washington, D.C.,
(1973)..
303. Mammel, Fred, Rothbart, Harold, "Recommendations on the Use of Salt as
an Ice Control Agent on City Str.eets," Administrative Environmental
Committee, Ann Arbor, Michigan, (unpublished memo) (1970).
304. "Snow and Ice Control," Maintenance Manual, Massachusetts Department of
Public Works, Boston, Massachusetts, [n.d.]
305. Mellor, Malcolm, "Snow Removal and Ice Control," Cold Regions Science
and Engineering, Part III, Section A3B, U.S. Army Cold Regions Research
and Engineering Laboratory, Hanover, New Hampshire (1965).
117
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306. Minsk, L.D., "Survey of Snow and Ice Removal Techniques," Technical
Report 128, U.S. Army Cold Regions Research and Engineering Laboratory,
Hanover, New Hampshire, (1964).
307. Murray, Donald M., Eigerman, Maria R., A Search: New Technology for
Pavement Snow and Ice Control, Environmental Protection Technology Series,
EPA R2-72-125. Environmental Protection Agency, Washington, D. C. (1972).
308. Picardi, Leo D., "Snow Regulations: Real or Unreal ?" Department of
Public Works, Brookline, Massachusetts, Paper presented at a North American
Snow Conference, (1970).'
309. Richardson, David L., Manual for Deicing Chemicals; Storage; and Handling,
Environmental Protection Technology Series, EPA-670/2-74-033, Environmental
Protection Agency, Cincinnati, Ohio (1974).
310. Richardson, David L., et. al., Manual for Deicing Chemicals Application
Practices, Environmental Protection Technology Series, EPA-670/2-74-045,
Environmental Protection Agency, Cincinnati, Ohio (1974).
311. Snow Removal and Ice Control Research, Special Report 115, Highway
Research Board, Washington, D. C. (1970).
312. "The Snowfighter's Salt Storage Handbook," Salt Institute, Alexandria,
Virginia (1968).
313. "The Snowfighter's Handbook," Salt Institute, Alexandria, Virginia (1967).
314. "Symposium on Snow Removal and Ice Control Research," Highway Research
Circular 103, Highway Research Board, Washington, D. C.; (1969).
315. Minimizing Deicing Chemical Use, National Cooperative Highway Research
Program, Synthesis of Highway Practice 24, Transportation Research Board,
Washington, D. C. (1974).
Salt in the Atmosphere
316. Warner, P.D., et. al., "Effects of Street Salting on Ambient Air
Monitoring of Particulate Pollutants in Detroit," Paper presented at
the 6th Central Regional Meeting, American Chemical Society, Detroit,
Michigan, (1974).
317. Antler, M., J. Gilbert, "The Effects of Air Pollution on Electric
Contacts," Journal of Air Pollution Control Association, 13:943-950,
(1963).
318. IEEE Working Group, "A Survey of the Problems of Insulator Contamination
in the United States and Canada Part I," IEEE Trans, on Power Apparatus
and Systems, pp. 2577-2585, (1971).
118
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319. Kimoto, I., T. Fujimura, and K. Naito, "Performance of
Insulators for Direct Current Transmission Line Under Polluted
Condition," IEEE Trans, on Power Apparatus and Systems,
May/June 1973, 943-950.
320. Lambeth, P.J., "Pollution Performance of HVDC Outdoor Insulators,"
Paper No. 77, September 1966, Conference on High Voltage D.C.
Transmission, 372-374.
321. Stensland, G.J., unpublished data for atmospheric deicing salt
measurements in Pennsylvania in 1972.
322. Stensland, G.J., "Numerical Simulation of the Washout of Hygrossopic
Particles in the Atmosphere," Ph.D. Dissertation, Meteorology
Department, Pennsylvania State University and Technical Report
327-73, Center for Air Environment Studies, Pennsylvania State
University, University Park, Pennsylvania, 1973, p. 145.
323. Stensland, G.J., unpublished data for Troy, New York atmospheric
deicing salt levels in 1974 and 1975.
324. Stensland, G.J., "The Flow of Deicing Salt into the Atmosphere,"
Rensselaer Polytechnic Institute, May 1975 (Unpublished Paper).
Additional References
325. Jodie, James B., "Quality of Urban Freeway Stormwater," M. S.
Thesis, University of Wisconsin-Milwaukee (1974).
326. :".Report of Routine Chemical and Physical Analyses of Public Water
Supplies in Massachusetts," Massachusetts Department of Public Health,
Division of Environmental Health, Boston, Massachusetts (1973).
327. "Deicing Salts, Their Use and Effects," NACE Publication 3N175,
pp. 9-14, (1975).
328. Schroeder, H.A., Nason, A. P., Tipton, I. H., and Balassa, J. J.,
Essential Trace Metals in Man: Zinc. Relation to Environmental
Cadmium. Journal of Chronic Diseases, 20, 179 (1967).
329. Fatula, M.I., The Feequency of Arterial Hypertension Among Persons
Using Water with an Elevated Sodium Chloride Content. Sovetskaia
Meditsina 30, 134 (1967).
330. Feaver, Douglas B., "Four Bridges to be Restored," The Washington
Post, Washington, D. C., Sept. 15, 1975.
331. Shellenberger, David E., "The Road Salt Problem: A New Analysis,"
Brookline, Massachusetts, 1975.
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APPENDIX A
GUIDELINES FOR ASSESSING ALTERNATIVES
The purpose of this appendix is to provide the reader with some very
basic guidelines for evaluating alternative methods of snow and ice
control. It is likely that many readers who are responsible for winter
maintenance may have already performed equivalent evaluations many
times before. However this appendix serves to point out some of. the
factors which must be considered in trying to reachri a decision.
The foremost idea to be remembered is that the budget for winter main-
tenance is not the only constraint on the problem. The ideal solution
would provide maximum safety and time savings while minimizing a total
cost function. The total cost function would consist not only of the
cost for snow removal, but also of the cost for vehicle, highway,, utility,
vegetation and water damage. However, as demonstrated in Sections 4
and 5, the development of a total cost function is impossible because
of the difficulty in assigning costs to human health degradation from
water pollution and to vegetation damage. Factors such as these may
be used to impose additional constraints on the problem, rather than be
included in a cost function. For example, to do this a community could
impose the constraint that salt could not be used above a set amount
on all highways within or bordering on a watershed area.
A second factor to consider is the requirement for bare pavement.
Representatives of the community should help provide guidelines as to
the importance of keeping various highways bare. Although there is
certainly a time savings in keeping the highways bare, the link between
bare pavement and safety has not been proven. Therefore, it is important
to obtain input from the community on their concern for convenience
versus their concern for the damage that results from salt. As pointed
out earlier, under some circumstances the desired level of bare pave-
ment may not be possible because of other constraints such as water
pollution.
Once the level of bare pavement and all other constraints have been
determined, the highway maintenance department should make an estimate
of the probable reduction in salt use and the equivalent increase
(if needed) in other activities to achieve the required level of bare
pavements and to meet the other constraints. (Currently the safest
activities to increase are plowing and sanding). The highway engineers
should attempt to assess all local cost factors as well as possible
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(as has been done on a general level in Sections 4 and 5). Assuming
that the effect of salt reduction is linear (a simple but not unreasonable
assumption given the findings in Section 5), cost of salt damage for
both the old and new situation can be estimated. As best as is possible,
the cost analysis should consider the reduction in cost of damage to
water supplies, vegetation, vehicles, highway structures, utilities,
and any other elements unique to the community. This reduction should
be compared to the possible increased cost of alternative snow removal
procedures and the possible increased cost of loss time. All additional
costs of the alternatives, such as other types of damage or spring clean-
up of sand, must be included.
It is especially important that such an assessment be undertaken with
the support and assistance of community representatives. In addition,
if there are state highways passing through the town or if there is a
water source within the town that supplies other communities, it will be
necessary to bring state or other community representatives into the
decision process so that all environmental factors can; be included in
the analysis. It should not be the sole responsibility of the highway
department to make such a decision since the community has many subjective
factors at stake, such as water quality, highway aesthetic value and
property values, vehicle corrosion, and taxes for highway damage.
AN EXAMPLE
The following example is supplied to demonstrate how an assessment might
be made as a practical matter. This example is in no way meant to
represent a typical community situation, but the simple approach used
should help pave the way for communities to perform their own analysis.
Let us examine for an entire winter season the case of a hypothetical
town which has 20,000 families, a total population of 60,000, 25,000
vehicles, and 150 miles of two-lane highways. There are no state
highways passing through the town and the town does not supply any
water outside its borders. All of the water supplies are wells, both
public and private. Approximately half of the vehicle.corrosion damage
from salt is attributable to the use of salt in the town (the remaining
damage resulting from use of the vehicles outside the town.) Therefore,
average vehicle damage from town salt has been set at $15 per vehicle.
(see Section 5.4 for justification of a $30 cost per vehicle.)
Under the current winter policy, there is moderate to heavy use of salt,
sand, and plowing. A majority of the wells .in the town are showing
dangerous levels of sodium, ranging from 30 to 100 mg/1, with the average
level at 60 mg/1. The town has decided to undertake an evaluation of
an alternative. The people of the town are concerned about their water
and are willing to sacrifice some bare pavement to improve the water.
The highway maintenance engineers feel that they can produce approximately
the same level of bare pavement under most winter conditions (except
121
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possibly freezing rain or other special weather situations*) by tripling
the plowing and increasing sand use fivefold in exchange for a 50%
decrease in the salt use. The highway department and the community
leaders have agreed to notify the community of the policy change through
the news media and with prominent signs along the highways and at entry
points into the town. Figure A-l shows the comparison of the proposed
Policy B to the current Policy A. . :
While Policy B shows a tremendous community savings over Policy A, it
is important to note that any change that might occur in safety and
time savings has not been accounted. These two factors are subjective
in nature and they should be given careful evaluation by the highway
engineers and community representatives. With proper public education
and planning the importance of these factors can be minimized even if
the same level of bare pavement cannot be maintained.
* However, these conditions might even be handled by reserving heavy salt
for the occasions and using even less salt under normal circumstances.
122
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Table A-l
Cost Comparison of "Two Snow Removal Policies
Policy A
Cost
Policy B
Cost
Salt use per two-
lane mile
Total salt use
Total applied salt
cost @ $20 per ton
Plowing cost
Total sand use
Total applied sand
cost @ $4 per ton
Cost of clean-up
of sand
20 tons
3,000 tons
2,000 tons
60,000
50,000
8,000
5,000
Total Snow Removal Budget $123,000
Corrosion cost per
vehicle attributed
to salt used in town
Total cost of vehicle
corrosion
$15
375,000
10 tons
1,500 tons
10,000 tons
30,000
150,000
40,000
25,000
$245,000
$7.50
187,500
Damage to 5 bridges $500 per bridge 2,500 $250 per bridge 1,250
attributed to salt
Utility corrosion
costs
Average Na+ content 60 mg/1
of all water supplies
500
250
30 mg/1
1%
Percent of population 5%
affected which should
use bottled water*
*While this cost may not be incurred directly, it is certainly less than
the actual cost incurred in terms of health degradation.
123
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Table A-l (continued)
Cost Comparison of Two Snow Removal Policies
Cost of bottled water
at $.10/liter and 3 liters per
day per person
Total Damage Cost
Total Cost to Community
Policy A
Cost
328,500
$706,500
$829,500
Snow Removal Budget Increase $122,000
Damage Cost Decrease $451,800
Net Cost Savings to Community $329,800
Bolicy B
Cost
65,700
$254,700
$499,700
124
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APPENDIX B
DEPRECIATION OF AUTOMOBILES
Previous economic studies of used-car prices indicate that a constant
exponential decay model fits the data well*. Here some of the underly-
ing causes of the depreciation of automobiles are examined and the
separate contributions of certain factors including salts in the environ-
ment are estimated. We begin with a model of used-car pricing.
Ackerman has developed an economic model of used-car prices based upon
widely.accepted principles of capital theory. In her approach, the price
of an automobile of a given vintage, K, can be expressed as the discounted
present value of its remaining services.
(1)
P(K) =
where :
K = present.age of car
T = age of scrappage
x = age
r = discount rate
S(x) = services provided by car of age x
P(K) = price of car of age K
Differentiation of equation (1) with respect to K yields equation (2)
(2)
P'(K) = -S(K) + rP(K)
which indicates that the rate of price 'change for a car can be broken
into two components, the flow of services and the opportunity cost of
capital invested in the car. Equation two may be rearranged to obtain
the service function:
(3) S(K) = -P'(K) + rP(K) continuous time version
or (31) S(K) = -AP(K) + rP(K)/(l+r) discrete time version
* See studies by Ackerman (268), Bennett (272), Boiteux (273), Chow (276),
Cramer (277), and Wykoff (296).
125
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In order to estimate the service function it is necessarv to mak<= some
explicit assumptions about the time profile of services. Ackerman chose
to model services as falling at a constant exponential rate with age.
(4) S(x)
where:
= hP(0)e
-ax
= constant
P(O) = price of car when new
a = constant rate of exponential decay of car
services
substituting (4) in the expression for used-car prices, (1), one obtains
(5) P(K)
T
= |hP(0)e
-ax -r(x-K)
dx
The price of cars of age K relative to the price of new cars is:
(6) P(K)/P(0)
he
rk
T
-(a + r) x
-h
K
a + R
-) (e
dx
rK -(a + r)T
-aK,
- e
As T, the age of scrappage, approaches infinity this expression can be
simplified since the value of erK~(a + r)T
be zero in the limit.
Thus:
(7) P(K)/P(0)
Be
-aK
where B
h
~a 4- r
Equation (7) is the familiar result that used-car prices decline at a
constant exponential rate. It may be estimated in the least squares
format by converting to logarithms:
(8)
In P(K) - In P(0) = In B - aK
For a given make and production year, one needs price statistics over a
span of several years. Equation ,(8) is then estimated by least squares,
the coefficient a is the estimate of the constant rate of decay.
AGE DISTRIBUTION OF CARS
The estimation of the total annual costs attributable to accelerated
automobile depreciation because of deicing salts assumes an average
car price of $1,500.
The $1,500 figure is obtained by taking the average new car price of
$4,200 and a decay rate of 25% per year in price. The proportion of
automobiles of each vintage still remaining registered can be obtained
from R.L. Polk & Co data. It indicated the proportion of each vintage
is as follows:
126
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Age
Proportion
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
10 - 11
11 - 12
12 - 13
13 - 14
over 14
.08
.12
.11
. .10
.09
.09
.08
.07
.06
.05
.05
.03
.02
.01
.04
127
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-76-105
2.
3. RECIPIENT'S ACCESSION«NO.
4. TITLE AND SUBTITLE
AN ECONOMIC ANALYSIS OF THE ENVIRONMENTAL IMPACT
OP HIGHWAY DEICING
5. REPORT DATE
May 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Donald M.
Ulrich F.
8. PERFORMING ORGANIZATION REPORT NO.
Murray
W. Ernst
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Abt Associates Inc.
55 Wheeler Street
Cambridge, Massachusetts 02138
10. PROGRAM ELEMENT NO.
1BC611
11. CONTRACT/
68-03-0442
NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final '8/74 to 7/75
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
Hugh Masters, Project Officer, FTS 342-7541
16. ABSTRACT
This study involves an analysis of the cost of damages that result from the use of
salt (sodium chloride and calcium chloride) on highways to melt snow and ice. A large
literature search and several surveys were carried out in order to determine the types
and extent of damages that have occurred. The report contains over 320 references.
An in-depth analysis was performed on all of the data obtained. The major cost
sectors examined were: Water supplies and health, vegetation, highway structures,
vehicles, and utilities. For each of the sectors a cost estimate was developed. The
total annual national cost of salt related damage approaches $3 billion dollars or
about 15 times the annual national cost for salt purchase and applicsition. While the
largest costs result from damage to vehicles, the most serious damage seems to be the
pollution of water supplies and the degradation of health which may result. It is
particularly difficult to assign costs in this latter area and therefore the estimate
may substantially understate the actual indirect costs to society.
These findings indicate that the level of salt use should be reduced,, -The amount of
the reduction should be determined on the basis of local conditions.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Deicers
Snowstorms
Ice Control
Economic Analysis
Sodium
Chlorides
Water Pollution
Salt
Stormwater Runoff
Environmental Impact
Snow Control
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
138
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
128
*U.S. GOVERNMENT PRINTING OFFICE: 1978— 757-140/6833
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