WATER POLLUTION CONTROL RESEARCH SERIES 11040 GKK 06/71
Environmental Impact
of
Highway Deicing
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and progress
in the control and abatement of pollution of our Nation's waters. They provide
a central source of information on the research, development and demonstration
activities of the Water Quality Office of the Environmental Protection Agency,
through in-house research and grants and contracts with the Federal, State
and local agencies, research institutions, and industrial organizations.
Previously issued reports on the Storm and Combined Sewer Pollution Control
Program:
11023 FOB 09/70
11024 FKJ 10/70
11024 EJC 10/70
11023 — 12/70
11023 DZF 06/70
11024 EJC 01/71
11020 FAQ 03/71
11022 EFF 12/70
11022 EFF 01/71
11022 DPP 10/70
11024 EQG 03/71
11020 FAL 03/71
11024 FJE 04/71
11024 DOC 07/71
11024 DOC 03/71
11024 DOC 09/71
11024 DOC 10/71
Chemical Treatment of Combined Sewer Overflows
In-Sewer Fixed Screening of Combined Sewer Overflows
Selected Urban Storm Water Abstracts, First Quarterly
Issue
Urban Storm Runoff and Combined Sewer Overflow Pollution
Ultrasonic Filtration of Combined Sewer Overflows
Selected Urban Runoff Abstracts, Second Quarterly Issue
Dispatching System for Control of Combined Sewer Losses
Prevention and Correction of Excessive Infiltration and
Inflow into Sewer Systems - A Manual of Practice
Control of Infiltration and Inflow into Sewer Systems
Combined Sewer Temporary Underwater Storage Facility
Storm Water Problems and Control in Sanitary Sewers -
Oakland and Berkeley, California
Evaluation of Storm Standby Tanks - Columbus, Ohio
Selected Urban Storm Water Runoff Abstracts, Third
Storm Water Management Model, Volume 1 - Final Report
Storm Water Management Model, Volume II - Verification
and Testing
Storm Water Management Model, Volume III -
User's Manual
Storm Water Management Model, Volume IV - Program Listing
To be continued on inside back cover
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Environmental Impact of Highway Deicing
ENVIRONMENTAL EROTECTION AGENCY
WATER QUALITY RESEARCH
Edison Water Quality Laboratory
Storm and Combined Sewer Overflows Section, R&D
Edison, New Jersey 08817
11040 GKK
June 1971
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
ii
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ABSTRACT
Deicing agents for removal of Ice and snow from highways and streets
are essential to wintertime road maintenance In most areas of the U.S.
Due to the ever-Increasing use of highway delclng materials, there has
been growing concern as to environmental effects resulting from these
practices. This state-of-the-art report critically reviews the avail-
able Information on methods, equipment and materials used for snow and
Ice removal; chlorides found In rainfall .and municipal sewage during
the winter; salt runoff from streets and highways; delclng compounds
found In surface streams, public water supplies, groundwater, farm ponds
and lakes; special additives Incorporated Into delclng agents; vehicular
corrosion and deterioration of highway structures and pavements; and
effects on roadside soils, vegetation and trees. It Is concluded that
highway delclng can cause Injury and damage across a wide environmental
spectrum. Recommendations describe future research, development and
demonstration efforts necessary to assess and reduce the adverse Impact
of highway delclng. This report was prepared by the Storm and Combined
Sewer Pollution Control Section, Edison Water Quality Laboratory, Water
Quality Office of the Environmental Protection Agency.
KEY WORDS: Additives, concrete deterioration, environmental damages,
groundwater contamination, highway delcing, plant toler-
ances, public water supplies, salt storage, vehicular
corrosion, water pollution effects, wintertime highway
runoff.
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Auszug
Enteisungsmittel zur Beseitigung von Els und Schnee von Landstrassen und
Strassen sind ftlr die Strassenunterhaltung im Winter in den meisten Bezirken
der Vereinigten Staaten Wesentlich. In folge des "limner grosser werdenden
Gebrauches von Strassen enteisungsmitteln, wurde man Immer meht urn die
daraus entsprlngenden EinflUsse aud die Umwelt besorgt. Dieser Bericht
betrachtet kritisch die gegenwSrtigen Kenntnisse von den Methoden, GerSten
und Meterialien die zur Beseitigung von Schnee und Els benutzt werden; von
Chloriden die sdch im Winter im Regenwasser und in. stadtischen AbwSssern
vorfinden; vom Salzabfluss von Strassen und Landstrassen; von Enteisungs-
verblndungen die sich in OberflSchenwaaser laufen, im Wasser von Hffentrichen
Wasserverteilungsanlagen, in GehSft teichen und in Seen vorfinden; von den
Son derzusatzmitteln die in der Enteisungsmitteln einverlelbt werden; von
der Korrosion von Fahrzeugen und der allmBhliche Zerstb'rung von Strassen-
bauwerke und - pflastern; und von den Wirkunken auf den Erdboden, die
Fflanzen und die Baume an den Landstrassenr&ndern. Man konmt zu dem Schluss
dass die Landstrassenenteisung es vermag Verletzungen und Schaaen in einen
brelten Band des Umweltspektrums zu verursachen. Empfehlungen betreffen
zukdnftige Forschungs- und Entwlcklungstatigkeit sowie Versuchsmassnahmen
die erforderllch sind um den ungtinstlgen Einfluss der Landstrassenentiesung
auszuwerten und zu vermindern. Dieser Bericht wurde von der Abteilung fUr
Verunreinlgungskontrolle von Regenwasser- und Hischkanalisatlon des Edison
Wasseruntersuchungslaboratoriums des WasserqualitHtsamtes der Umweltschutz-
verwaltung.
Schldsselworte: Zusatzmittel, Betonzerstorung, Umweltschaden, Grundwasser-
ver unreinigung, Landstrassenentelsung, Planzentoleranzen,
Bffentliche Wasserversorgungsanlagen, Salzlagerung,
Fahrzeugkorrosion, Auswirkungen der Wasserverunreinigung,
Landstrassenwasserablauf 1m Winter.
ill
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Resume
Les agents degivrants pour 1'enlevement de la glace et la nlege des chemins
et des rues sont^essentiels a 1'entretlen des voles en hivers dans la plupart
des regions des Etats Unis. Du a 1'utilisation toujours plus repandue des
materiaux degivrants pour les chemins, un aouci s'eleva concernant les effets
environnementals resultant de cette technique. Cet rapport de presente une
revue critique de 1'information disponible sur las mfithodes, 1'outillage et
lea materiaux employes pour 1'enlevement de la glace et la nelge; sur les
chlorures qui se trouvent dans 1'eau de.pluie et les eaux d'egouts municipales
en hlver; sur le decoulement du sel des rues et des chemins; sur les composes
degivrants qui se trouvent dans les fleuves superficiels, les approvisionne-
ments d'eau publics; leas eaux souterraines, les abreuvoirs et les lacs; sur
des additifs spe'ciaux incorpore's aux agents degivrants; sur la corrosion
vehiculaire et la deterioration des structures et des par 1men13 des chemins;
et sur 1'effets sur les sols, la vegetations et les arbres situea au bord des
voles. On conclut que la degivration des chemins peut faire du tort et du
dommage au travers une bande epandue du spectre environnemental. Les
recommendations d£crivent les efforts futurs de recherche, de developpement
et de demonstration qui seront n£cessaires a eValuer et a reduire 1'Impact
adverse de la degivration des chemins. Cet rapport fut prepare par la
Section de Controls de la pollution des egouts d'eau de pluie et des egouts
mixtes de la Laboratoire Edison pour determination de la qualite d'eau du
Bureau de Qualite d'eau de 1'Administration de Protection environnementale.
Hots clef: Additifs, deterioration du bgton, dommages environnementals,-
contamination des eaux souterraines, degivration des chemins,
tolerances des plantes, approvisionnements d'eau publics,
magasins du sel, corrosion vehiculaire, effets de la pollu-
tion d'eau, decoulement des chemins en hlver.
Resumen
Agentes descongelantes para la eliminacidn de hielo y nieve de las calles y
carreteras son esenciales para el mantenimiento de las vias de comunicacidn
en la mayor parte de los Estados Unidos durante el invierno. Debido al
aumento constante de materiales descongelantes en las carreteras existe una
creciente preocupacirfn en cuanto a los efectos surgidos como resultado de
estas practices en el medio ambiente. Este informe de estado-del-arte
revisa criticamente la informacifin existente sobre metodos, equipos y
materiales uaados para la remocidn o eliminacidn de nieve y hielo; cloro
encontrado en depositos de lluvia y desagues municipales durante el in-
vierno; sal derramada en las carreteras y calles; compuestos de materiales
descongelantes encontrados en la superficie de arroyos, de abastecimientos
de aguas publicas, aguas subterraneas, estanques de granjas y lagos,
agregados especiales incorporados a los agentes descongelantes, corrosion
de vehfculos y deterioracidn de estructuras de las carreteras y pavimentos;
y sus usos sobre el terreno contiguo a las mismas, su vegetaci£n y arboleda.
Como conclusion se ha determinado que la descongelacidn de carreteras puede
causar grandes danos y perjuicios a una gran parte del medio ambiente. Las
recomendaciones describen investigaciones a realizarse en el futuro, ex-
plicando y demonstrando los esfuerzos neceaarios requeridos para estimar
y reducir los impactos adversos en el descongelamiento de carreteras.
Este informe fue preparado por la Seccidn de Control Combinado de Tormentas
y Polucidn de Cloacas en el Laboratorio Edison para la Cualidad del Agua,
Oficina de Cualidad del Agua de la Agenda de Protecci6n del Medio Ambiente.
Falabras Claves: Agregados, Deterioraci<5n del Cement o, Daflos al Medio
Ambiente Contaminacio'n de Aguas Subterraneas, Desconge-
lamiento de Carreteras, Tolerancia de Plantas, Abaste-
cimiento de Aguas Publicas, Reservas de Sal, Corrositfn
de Vehfculos, Efectos de Polucio'n en el agua, Derrames
en las Carreteras durante el invierno.
RESUHO
Agentes para o degelamento, na remogao do gelo e da neve das auto-estradas
f ruas, sao essenciais para a manutengao das vias de comunicagao na maior
parte dos Estados Unidos, durante o inverno. Devido ao constante aumento
no uso de materials degelantes nas estradas tern havido uma crescente preo-
jjupagao quanto aos efeitos resultantes destas priticas ao meio ambiente.
Este relatOrio do estado-da-arte revisa criticamente a informagio existente
sobre os metodos, equipamento e materials usados para a remogao de neve e
de gelo; chlorureto encontrado em depdsitos de chuva e esgotos municipals
durante o inverno; sal escoado das ruas e estradaa^ compostos de materials
degelantes encontrados na superficie de rios, em abastecimento de aguas
pnblicas, aguas subterraneas, estanques de fazendas e lagos; aditivos
especiais incorporados aos agentes degelantes; corrosio de velculos e
deterioramento das estruturas e pavimentacao de estradas; e efeitos nos
solos proximos as estradas; na vegetagio e drvores. Foi concluido que o
degelamento de estradas pode causar danos e prejuizos a uma larga faixa do
meio ambiente. As recomendagoes descrevem as pesquisas para o futuro, fazem
uma explanagao e demonstracao dos esforcos necessaries para^a determinag^o
e a redugao do impacto adverso no degelamento de estradas. Este relatdrio
foi preparado pela Secgao de Controle Combinado das Tempestades e da
Poluigao de Esgotos, Laboratdrio Edison para a Qualidade da Agua, Escri-
t6rio da Qualidade da Agua da Agenda de Protegao ao Meio Ambiente.
Palavras chaves: Aditivos, deterioramento do cemento, danos ao meio ambiente,
contaminagao das £guas subterraneas, degelamento de estradas,
tolerancia de plantas, abastecimento de aguas publicas, re-
servas de sal, corros§o de veiculos, efeitos da poluigao da
agua, escoamento das estradas no inverno.
IT
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CONTENTS
Section Page
- ABSTRACTS i
- FIGURES vi
- TABLES ix
- FOREWORD xi
I - CONCLUSIONS 1
II - RECOMMENDATIONS 5
III - SNOW AND ICE REMOVAL - MATERIALS AND OPERATIONS 11
Deicing Materials - Bare Pavement Policy 11
Abrasives 15
Chloride Salts and Properties 16
Marine Salt 17
State Usage 18
Highway Salt Applications 18
Costs of Highway Salts 19
Operations, Equipment and Methods 20
Other Deicers 32
Salt Storage 32
IV - RAINFALL AND OTHER SOURCES 45
V - SEWAGE 47
VI - RUNOFF FROM STREETS AND HIGHWAYS 51
Wisconsin Studies 51
Syracuse, New York 51
Chicago, Illinois 51
Des Moines, Iowa 52
VII - SURFACE STREAMS, RIVERS 55
Various Rivers in the State of Maine 55
Meadow Brook, Syracuse, New York 55
Major Rivers in the United States 56
Sleepers River Basin, Vermont; 56
Hydrologic Salt Balance
Chloride Levels in Milwaukee Streams 57
Oxygen Demand of Deicers 57
Dumping of Snow into Nearby Streams and 58
Water Bodies; Chloride, Oil and Lead
Content
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CONTENTS (Cont'd)
Section
VIII - FARM PONDS, LAKES
Farm Ponds-State of Maine 59
The Great Lakes, Lake Erie 59
Wisconsin 59
First Sister Lake, Ann Arbor, Michigan; 60
Salt-Induced Stratification
Irondequoit Bay, Rochester, New York; 60
Salt-Induced Stratification
Possible Salt Stimulation of Algal Growths 61
IX - WILDLIFE 63
X - DEICING ADDITIVES 65
Ferric and Sodium Ferrocyanide, Anti-Caking 65
Agents
Corrosion Inhibitors 67
Chromate Additives Used As Rust Inhibitors 67
Phosphate Additives Used As Rust Inhibitors 69
XI - PUBLIC WATER SUPPLIES, GROUNDWATER, INDUSTRIAL 71
WATER USES
Public Water Supplies 71
Groundwater, Well Supplies 71
Michigan 71
Wisconsin and Illinois 72
New Hampshire 72
Maine 72
Ohio 73
Connecticut 73
Massachusetts 73
Industrial Water Supplies 75
XII - CORROSION OF VEHICLES 77
Cost Damages 77
How Corrosion Occurs 77
Comparative Studies 78
Mufflers, Tailpipes 79
Rust Inhibitors 79
Other Preventative Measures 79
Vi
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CONTENTS (Cont'd)
Section Page
XIII - EFFECTS ON HIGHWAY STRUCTURES AND PAVEMENTS 81
Review by Massachusetts Research Council 81
And Findings of U.S. Highway Research
Board and Representative States
Comments of Calcium Chloride Institute 82
and Portland Cement Association
Other Deicing Compounds 83
Effects on Underground Utilities 83
XIV - EFFECTS ON SOILS, VEGETATION, TREES 85
Soil Chemistry, Salt Movement Through Soil 85
Into Plants
Wintertime Infiltration 88
Salt Levels In Roadside Soils Along Maine 88
Highways
Chloride Content of Soils and Plants on 90
National Park Grounds, Washington, D.C.;
Correlation With Plant Injury and Death
Sodium And Chloride Content Of Grasses, 91
Salt Tolerances
Salt Injury to Trees, St. Paul, Minnesota 92
Sodium And Chloride Levels In Sugar Maples 92
And Silver Maples In New Hampshire,
Massachusetts, Vermont And Connecticut;
Correlation With Injury And Death
Salt Tolerance Of Individual Plant Species; 94
Fruit, Vegetable And Field Crops, Grasses,
Trees And Ornamentals
Effects Of Salt Spray On Vegetation And Road- 96
side Environment
XV - SUMMARY 101
XVI - ACKNOWLEDGMENTS 105
XVII - REFERENCES 107
vii
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FIGURES
Figure Title Page
1 Diesel powered truck with wing plow and 21
straight blade
2 Snow blower 21
3 Diesel powered dump truck with salt spreader 22
insert and snow plow
4 Left to right: dump truck with salt spreader 22
insert and plow, truck with interchangeable
plow, front-end loader, and snow blower
5 Twin-disc salt spreader with tail-gate screens 23
(placed inside truck body) to prevent salt
lumps from reaching feeder ports
6 Salt spreader 23
7 Salt spreader 24
8 13-Ton salt spreaders with V-plows 24
9 New design salt spreader with screen grid over 25
top to preclude salt lumps
10 Salt spreader being loaded at salt storage depot 25
by front-end loader
11 Department trucks plowing city streets 26
12 Front-end loader removing cleared snow into 26
receiving trucks
13 Front-end loader clearing city streets 27
14 Front-end loaders keeping city streets open 27
15 Heavy-duty snow blower 28
16 Snow blower removing street accumulated snow into 28
receiving trucks
17 Front-end loader depositing snow into snow- 29
melter
viii
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FIGURES (Cont'd)
Figure Title Page
18 Dumping snow into nearby waterway 29
19 Open salt storage pile, downtown Chicago, Illinois 35
20 Open salt storage pile, Milwaukee, Wisconsin, 35
estimated quantity 41,000 tons
21 City stockpile of rock salt remaining after winter's 36
use, mid-February, Milwaukee, Wisconsin
22 Typical salt storage pile in downtown New York 36
City
23 Moving salt by front-end loader inside enclosed 37
storage structure
24 Covered salt stockpile located adjacent to the 37
Maumee River in Toledo, Ohio
25 Salt storage - Approximate construction cost 38
$3 to $5 per Ton of capacity
26 Salt storage - Approximate construction cost 38
$3 to $5 per Ton of capacity
27 Salt storage - Approximate construction cost 38
$3 to $5 per Ton of capacity
28 Salt storage - Approximate construction cost 39
$50 to $75 per Ton of capacity
29 Salt storage - Approximate construction cost 39
$50 to $75 per Ton of capacity
30 Salt storage - Approximate construction cost 39
$50 to $75 per Ton of capacity
31 Salt storage - Approximate construction cost 39
$50 to $75 per Ton of capacity
32 Salt storage - Approximate construction cost 40
$15 to $20 per Ton of capacity
33 Salt storage - Approximate construction cost 40
$10 to $30 per Ton of capacity
ix
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FIGURES (Cont'd)
Figure Title Z2SS
34 Salt storage - Approximate construction cost 40
$20 to $30 per Ton of capacity
35 Salt storage crib 41
36 Salt storage shelter ^
37 Salt storage building 41
38 The "Beehive" - Concrete base forms removed; 42
note posts for retaining ring roughly placed
39 The "Beehive" - Third ring of panels being 42
placed; placing of panels by electrical truck
40 The "Beehive" - Fourth ring completed 42
41 The "Beehive" - Building with all panels in 43
place; note air vents at top
42 The "Beehive" - Method of loading; first stage 43
by truck and dozer
43 The "Beehive" - Method of loading; second stage 43
by conveyor
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TABLES
Table Title Page
I Reported Use (Tons) of Sodium Chloride, Calcium 12
Chloride and Abrasives by States and Regions in
the United States, Winter of 1966-1967
II Chloride Content of Various Waters 45
III Monthly Chlorides at Milwaukee Sewage Treatment 48
Plant (mg/1), 1965-1969
IV Special River Sampling, Milwaukee Sewerage 49
Commission, January 16, 1969
V Salt Tolerance of Fruit Crops 97
VI Salt Tolerance of Vegetable Crops 97
VII Salt Tolerance of Field Crops 98
VIII Salt Tolerance of Grasses and Forage Legumes 98
IX Salt Tolerance of Trees and Ornamentals 99
xi
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FOREWORD
Under provisions of the Federal Water Pollution Control Act, as amended,
the Office of Water Quality Research in the Office of Research and Moni-
toring within the Environmental Protection Agency, is authorized to
conduct various basic and applied research; and to develop and demonstrate
the results of this research. These activities are undertaken through
in-house efforts of the EPA Laboratories, or accomplished through various
grants and contracts funded and sponsored by the Office of Water Quality
Research — Research, Development and Demonstration Program.
This report, Environmental Impact of Highway Deicing, has been prepared
by the staff of the Office of Water Quality Research — Storm and Com-
bined Sewer Pollution Control Branch, and represents a significant effort
in compilation of broad-base information available in the subject area
and assessment of the full impact of highway deicing practices on the
environment. This program of the Division of Applied Science and Tech-
nology in the Office of Water Quality Research, has continuing active
interest in highway deicing because of its inherent responsibilities in
the evaluation, control and treatment of waste overflows from combined
sewers and discharges of sewered and non-sewered urban runoff. Because
of serious pollution existing in many receiving streams in this country,
and the increasing public awareness of these ever important problems, ,
it is appropriate that the environmental issues concerned with highway
deicing be reviewed and examined in much greater depth.
The use of deicing salts and other materials for removal of ice and
and snow from highways, roads and streets, is essential to wintertime
road maintenance operations in most areas of the U.S. This report is
mainly derived from a detailed review of the literature, and from con-
tacts with various groups and individuals knowledgeable of the potential
and real consequences of highway deicing. This report focuses on the
characteristics of snowmelt runoff and the effects of highway deicers and
their associated additives upon surface streams, rivers, lakes, ponds,
groundwaters, private, public and industrial water supplies. The report
also describes snow removal operations, chlorides in rainfall, the effects
of deicing salts upon wildlife, roadside vegetation, and the corrosion
of vehicles and highway structures caused by highway salts.
Several research projects in the past have studied alternative deicers
in place of the chloride salts, and various non-chemical methods for
removing ice and snow from roads and highways. None of these materials
and methods in contrast to the sodium and calcium chloride salts, are
apparently considered economical or reliable for widespread use.
Except for a) limited research by State highway departments and possibly
by the Federal Aviation Authority; b) investigations nearly completed
by the Virginia Polytechnic Institute for the U.S. Highway Research
Board; and c) recent completion of corrosion studies by the American
Public Works Association, there is no known large-scale research being
xii
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carried forth at the present time on highway deicing and its environmen-
tal effects. The majority of results from the VPI-HRB study have been
previously made available. National Cooperative Highway Research Program
Report 91 by VPI and HRB published in 1970, contains considerable informa-
tion on the subject of highway deicing and constitutes an important refer-
ence used by this EPA study.
Suggestions and recommendations are given in identifying present research
and development needs toward alleviation of detrimental effects caused by
highway deicing. This report should also serve to outline and describe
procedures that may be necessary for complying with current Federal regula-
tions on environmental protection during the design phase of highway
projects. The National Environmental Policy Act of 1969, Executive Order
11514 on "Protection and Enhancement of Environmental Quality," and the
Highway Act of 1970 make provisions for determining environmental impact
of major Federal actions including all Federal-aid highway projects.
Adherence to these provisions could involve various aspects such as calcu-
lating salt runoff concentrations and loads; modification of existing surface
drainage; suitability of roadside plantings and vegetation cover; the fate
and disposition of salt runoff after leaving the highway surface; and the
possible need for runoff treatment.
xiii
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SECTION I
CONCLUSIONS
1. Review of the literature, and numerous contacts with groups and
individuals knowledgeable of highway deicing operations and the
associated consequences, indicate that highway salts can cause
injury and damage across a wide environmental spectrum. Further-
more, it is believed that many of these effects although not yet
evident in certain areas of the country, may well appear in the
near future. Effects of highway deicing appear most significant
in causing contamination and damage of groundwaters, public water
supplies, roadside wells, farm supply ponds, and roadside soils,
vegetation and trees. Deicers also contribute to deterioration
of highway structures and pavements, and to accelerated corrosion
of vehicles.
2. Sodium chloride and calcium chloride are used almost exclusively
as deicing agents because of their efficiency in melting ice and
snow, availability, and relatively low material cost. Most deic-
ing salts are now applied "straight" onto streets and highways.
In 1947, less than one half million tons of deicing salts were
used in the U.S. Annual use of these salts increased to around
9 million tons in 1970, and by 1975, annual use is expected to
approach 12 million tons. Quantities of sand, cinders and other
abrasives for wintertime road maintenance have decreased consider-
ably in recent years. Chemicals are fast-acting whereas abrasives
attack the problem only after ice and snow are formed.
3. Practically all highway authorities in the U.S. firmly believe that
ice and snow must be removed as quickly as possible from roads and
highways, and that "bare pavement" conditions are essential to pro-
tect the lives and safety of motorists using these roads. This
policy is also considered proper in minimizing disruption of normal
business, commercial and public activities and services which could
be seriously affected by adverse winter conditions. Maintaining
bare pavement conditions does, however, require frequent and liberal
applications of road deicers and/or more precise spreading.
4. Road salts are usually applied at rates of 400 to 1,200 pounds of
salt per mile of highway per application. Over the winter season,
many roads and streets may receive more than 20 tons of deicers
per lane mile, which is equivalent to 100 tons salt or more applied
per mile of roadway for multiple-lane highways. In using highway
deicers, it is not necessary to melt more than 10 percent of the
ice cover and possibly much less. Vehicular traffic will normally
melt the remaining ice and snow quickly and efficiently.
Excessive application, misdirected spreading and wasting of road
salts occur frequently. Improved spreading practices if equated in
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terms of direct annual cost savings, may possibly amount to several
million dollars Nationwide without sacrificing the quality of winter-
time road maintenance. -*
5. Materials storage sites are a frequent source of salt pollution to
groundwaters and surface streams. Deicing salts are often stock-
piled in open areas without suitable protection against inclement
weather. Salt-laden drainage often has direct access to nearby
water supplies. Careful site selection and properly-designed materi-
als storage facilities would serve to minimize incidents of water
supply contamination and provide for better product handling and
quality control. In certain cases, diversion and interception of
salt drainage are indicated, and treatment of these flows may also
be required.
6. The special additives found in most road deicers cause considerable
concern because of their severe latent toxic properties and other
potential side effects. Significantly, little is known as to their
fate and disposition, and effects upon the environment. The complex
cyanides used as anti-caking agents and the chrornate compounds used
as corrosion inhibitors have been found in public water supplies,
groundwaters, and in storm and combined sewer flows. Unusually
small amounts of cyanide and chromium are sufficient to cause rejec-
tion of public water supplies and cause death of fish and associated
aquatic organisms. The phosphate additives also used for corrosion
control, may contribute significantly to nutrient enrichment in
lakes, ponds and streams leading to algal blooms and noxious condi-
tions .
Recent information supplied by the salt industry cites reduction in
the amounts of sodium ferrocyanide added to highway salts and further-
more, that sale of chromium-treated salts was stopped in early 1971
by the largest supplier in the field. These changes are not con-
sidered sufficient to modify the recommendations in this report con-
cerning deicer additives. These measures are viewed in terms of the
potentially serious nature of both cyanide and chromium additives, the
continuing importance of these compounds, and the absence of field
data on the fate, disposition and persistence of these materials in
the environment.
7. A sufficient number of incidents and detailed studies have been
described to show the adverse impact and significant damages caused
by deicing salts to groundwaters, public water supplies, household
supplies, farm ponds, lakes and small streams. Use of deicing salts
has caused many wells and groundwater supplies to be abandoned or
replaced. In less severe cases of salt intrusion into public water
supplies, salt-free patients have been cautioned to make certain
changes, possibly converting to use of bottled water. Unfortunately,
rectification of a contaminated groundwater aquifer generally requires
many years after remedial measures are first initiated.
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8. Road deicing salts are found in high concentrations in highway run-
off. Large salt loads enter municipal sewage treatment plants and
surface streams via combined and storm sewers, and direct runoff.
Concentrations of chlorides as high as 25,000 milligrams per liter
(mg/1) have been found in street drainage, and up to 2,720 mg/1 in
storm sewers. Surface streams along highways and those in urban
areas have been found to contain up to 2,730 mg/1 chlorides. Influ-
ence of highway salts upon major rivers in the U.S. at this time
appears relatively minor. Nevertheless, it is recognized that there
is inadequate surveillance data to clearly define this area and more
information is necessary.
Earlier reports in the literature inferred for highway salt appli-
cation, that approximately one-half of these salts would be readily
flushed into the surface runoff and receiving streams, whereby the
remaining salts would be generally retained in the local area. How-
ever, recent studies carried forth in Chicago, Syracuse and north-
eastern Vermont, indicate that most if not nearly all this salt load
given sufficient time, in certain cases, may find its way into down-
stream waters. Both the Syracuse and Vermont investigations noted
that these loads were being contributed to street sewers and surface
streams throughout the year, and were adding significant salt to
stream baseflows particularly in the summertime. Additional studies
providing material salt balances for selected watersheds, are con-
sidered important in better understanding hydrological influences in
the overall transport of these deicing salts.
9. Much of the general literature is somewhat inconclusive on vehicular
corrosion and deterioration of highway structures and pavements
caused by deicing salts. Some of the more recent reports however
are more definitive.
The majority of in-depth studies support the conclusion that deicing
salts are a major cause of vehicular corrosion. Likewise it is con-
cluded from the literature that rust inhibiting additives do not
produce results which would Justify their continued use. Frequent
car washing is likely the best protection possible.
Concrete pavements and concrete bridge floors and decks show least
resistance to attack by road deicers. It probably would be best
never to apply road salts to concrete surfaces but a compromise
is necessary between deicing, progressive surface deterioration,
protective treatments, and preventive and corrective maintenance.
It is also recognized that deicers may attack and cause damage to
telephone cables, water distribution lines, and other utilities
adjacent to streets and highways.
10. There is no doubt that highway deicers can seriously disturb a
healthy balance in soils, trees, and other vegetation comprising
the roadside environment. Total soluble salts, and sodium and
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chloride ions reduce soil fertility and structure, depress plant
water uptake, and are toxic to plants and vegetation above certain
limits. Total soluble salt increases in soils have been noted up
to 100 feet from previously salted highways, and progressive accumu-
lation of salts in the roadside area has been verified. The state of
health of vegetation, or conversely the degree of damage to vegeta-
tion, may be correlated with chloride and sodium levels in plants
and soils. Salt tolerance varies considerably between different
plant species and is an important criteria in properly selecting
vegetation along new highways. Following severe damage by salts,
extensive corrective measures may be indicated.
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SECTION II
RECOMMENDATIONS
Based on Conclusions detailed in Section I of the report, it is recom-
mended that:
1. A Deicer Users Manual be developed describing snow and ice removal
practices and the best systems of applying deicing chemicals to
streets and highways. Several highway agencies and the salt indus-
try are known to have various instructional materials which are
principally directed to operational performance. The best data in
this area should be incorporated into the Manual. Pollution of the
surrounding environment and potential in cost savings do not warrant
excessive salting, and the Deicer Users Manual should give utmost
priority to environmental protection. The Manual should include but
not be restricted to:
a) Absolute minimum amounts of deicing chemicals necessary
to maintain safe traffic flows;
b) Critical points or places of application;
c) Higher degree of instrumentation, improved calibration,
and increased reliability of existing and new deicing
equipment;
d) Proper maintenance and repair schedules;
e) Methods of salt spreading to optimize operational and
manpower efficiencies;
f) Means for rating materials and methods;
g) Development of suggested prime systems and alternatives;
h) Incorporation of European and British practices as they
may apply in the United States.
2. A Manual of Design and Recommended Practice be prepared for storage
facilities and methods of handling deicing materials throughout
storage. Although certain instructional materials are available
from highway agencies and the salt industry on proper salt storage,
there has not been an adequate acceptance of approved practices
and a proper recognition of pollution problems associated with
materials storage. Many storage sites are located on marginal lands
adjacent to streams and rivers, deicing materials are often stock-
piled unprotected in open areas, and too frequently these sites
have become chronic sources of ground and surface water pollution.
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As a minimum, the Manual of Design and Recommended Practice should
describe:
a) Proper siting of materials storage to eliminate pollution;
b) Adequate covering of storage sites to protect materials
and preclude surface drainage;
c) Suggested design of storage facilities, particularly
enclosed structures;
d) Adequate foundation and footings;
e) Desirable sequence and timing of materials delivery;
f) Best methods for handling and moving products to and
from, and within the storage facility;
g) Suggested precautions in placing, mixing, treating
and withdrawing materials to reduce product waste
and damage;
h) Materials quality control methods;
i) Minimum supervision requirements for the various
operational phases;
j) Suggested minimum codes for deicing materials storage
to be adhered to by Federal, State, county, local and
other authorities responsible for wintertime road
maintenance.
3. Increased recognition of environmental pollution problems caused by
highway deicing be fostered at Federal, State, county, and local
levels. This recognition should include program development and
funding so as to provide for greatly increased training, environ-
mental impact awareness, and demonstration of optimum procedures
and techniques necessary in wintertime highway deicing. This con-
certed effort in training and education should be primarily directed
to highway department personnel at the working levels, and it is
believed this program would be most appropriately and effectively
carried forth by the State highway departments and their designees.
Training support by the industry should improve such programs.
4. Detailed investigations be conducted both in the laboratory and
field on the various additives mixed with deicing materials to
determine their potential hazards, and safe levels of use. In
view of the limited amount of data available on deicing additives
and toxic nature of some additives, proper justification on the
continuing use of these products is sought. This should include
comparative merits of substituting and/or developing other additives,
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or none at all. These studies should additionally cover but not be
restricted to:
a) Collection and analysis of data obtained from continuous
monitoring of selected deiclng storage and application
areas.
b) Basic research particularly on the cyanide and chromium
additives, with regard to chemical reactions and pathways;
environmental interferences; and direction, movement,
persistence and degradation of additives through soil,
vegetation and water.
c) Relationship of present water and air quality use criteria
to those levels of additives expected to be found in water,
air and soils.
d) Development of a comparative test for rating the toxicity
level and potential hazards of various additives.
e) Determination if purposes intended by product use are
being met.
5. Consideration be given to initiating a program designed to obtain
base-line data on long-term environmental changes that may be
taking place due to the increasing use of deicing chemicals. Such
a program would denote need for preventive and corrective measures
before severe and irreversible damage to our natural resources
occurs. Program implementation would require support from State,
county and local water resource agencies, and various highway
authorities, as well as the Federal government. The program should
provide continuous data for:
a) Levels of deicing chemicals present in surface waters,
groundwaters including recharge areas, and in highway
runoff;
b) Levels of deicing chemicals found in selected soils and
vegetation;
c) Corrosion levels prevailing for selected vehicles, high-
way bridges, pavements, buildings, etc., correlated with
known uses of deicing chemicals;
d) Presence of deicing ions in other critical areas as future
needs indicate.
6. Federal, State and local highway authorities give appropriate con-
sideration in highway design to road deicing and the control,
collection and treatment of ensuing salt runoff. Where intensive
deicing operations warrant, initial plans may include rerouting
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new highways to minimize adverse effects upon roadside resources,
and providing for accelerated runoff away from susceptible soils,
grasses and trees. Broader implementation of salt runoff control
may involve extensive drainage, alteration of existing drainage
patterns, diversion canals, underground pipelines, and various
ponds and lakes. Conveyance and storage units should be aestheti-
cally blended into the roadside landscape. Collected drainage
utilizing flow regulation, may possibly be released safely down-
stream. Otherwise, terminal point storage or treatment of this
drainage may be necessary.
In control and treatment of highway runoff, it may be advantageous
to separate the concentrated salt flows from dilute flows. Recy-
cling of salt flows and recovery of salts by evaporation or other
means may be proved feasible. Treatment of these flows would be
enhanced by research, development and demonstration of alternative
concepts and methods.
7. Information be compiled and disseminated on best selection of road-
side plantings, and remedial measures for restoring roadside
vegetation damaged by deicing chemicals. Plantings should be gener-
ally chosen on the basis of maximum salt tolerance, but trade-offs
are indicated with respect to shape and contour of the land,
protection of other resources, existing plantings, local climate,
State highway codes, availability of highway maintenance funds, etc.
Damage of natural or implanted growth in roadside areas is fre-
quently followed by accelerated erosion of side slopes, loss of
aesthetics, and severe sedimentation of nearby streams. Treatment
of soils by gypsum and lime, and treatment of foliage by certain
liquid sprays, are indicated as being practicable for restoring
roadside vegetation where deicing chemicals have stunted natural
growth, reduced soil fertility or created toxic conditions in
vegetation. Review of remedial methods presently available is
considered highly appropriate. New methods should be developed by
additional research and demonstration. In cases of severe damage,
greater use of artificial materials and functional settings may
be possible.
8. Continued practices of removing and dumping the enormous quantities
of snow from streets and highways into nearby water bodies or onto
water supply watersheds be fully evaluated, particularly in terms
of unit pollutant loads and various effects imposed upon these re-
ceiving streams. These snow and ice accumulations have been shown
to contain high content of chlorides, oils and metallic lead due
to road deicing, vehicular traffic and other urban wastes. This
problem has received scant attention, and only recently have these
snow deposits been cited as a significant contributing source of
roadway pollution. There is immediate need for both monitoring and
case study data in order to determine the extent and severity of this
problem. Such results should serve to define possible requirements
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in modifying current snow dumping practices and developing safer
means of ultimate snow disposal.
9. The various suppliers and highway authorities make available full
information on marine salts - their current and future expected
use in highway deicing, chemical composition, physical properties
including melting efficiencies, and comparison with the common
chloride salts. Marine salts may be different in composition and
have even greater pollutional consequences compared to the mined
sodium chloride salts. Further evaluation of the environmental
impact of marine salts should be made after background data are
available.
10. Results, findings and recommendations of past studies dealing with
corrosion of automobiles and deterioration of highway structures
and pavements potentially caused by road deicers, be made readily
available to outside users. Timely presentation of pertinent
findings should be given in the widely-used technical journals.
Considerable data is believed to exist on deicer-caused damage to
structures and vehicles, which if made available, may suffice most
needs in this area. Continuing evaluation is nevertheless required.
11. Highway authorities and the suppliers of deicing materials investi-
gate and make available their full results and experience on the
merits and demerits of various substitute materials that could be
used in place of the common chloride salts. A major objective is
to identify those highway deicers having high efficiency and demon-
strated minimum side effects. Can current products be modified for
greater deicing efficiency, less damage, or even beneficial impact?
Would lesser known products compete successfully if they were produced
in much larger quantities? It is intended under this recommendation
that similar data would be made available on those deicers presently
used for ice control around airports and around the home.
The various agencies, users and suppliers of highway deicers should
thoroughly investigate previous methods that have shown potential
promise, and likewise research and development of new concepts
of snow and ice removal should be accelerated. Increased use of
abrasives may be indicated for various conditions supported by
economic comparison studies. Dark materials which could potentially
absorb more solar energy when spread onto streets and highways, merit
attention. Greater use of rubberized snow plows, air jet snow throw-
ers, and substitution of studded tires by polyurethane tire chains
represent some of the ideas coming on scene today. New concept
development would seem to hold reasonably high promise as alterna-
tive methods of the future.
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SECTION III
SNOW AND ICE REMOVAL-MATERIALS AND OPERATIONS
Deicing Materials-Bare Pavement Policy
Each winter across this country, highway snow removal and deicing opera-
tions begin anew. Chemicals and deicing materials for highway mainten-
ance over the winter of 1966-1967 approximated 6.3 million tons of sodium
chloride, 0.25 million tons of calcium chloride, and 8.4 million tons
of abrasives. Requirements for Canadian highways over this same period
were estimated as 1.1 million tons sodium chloride, 18,000 tons calcium
chloride and 3.4 million tons of abrasives(1).
Looking ahead we can expect a substantial increase in over-all use of
highway deicers. For sodium chloride alone, deicing use in the United
States is estimated around 9 million tons for the past winter of 1970-
1971. Projected annual use for 1975 is 11 to 12 million tons(2,3).
The twenty-one States in the eastern and north-central sectors of the
United States use more than 90 percent of all sodium chloride and calcium
chloride sold as highway deicers across the country. The eastern States
also are heavy users of abrasives, consuming more than 70 percent of
the U.S. total, whereas the north-central States and western States,
respectively, utilize about 10 percent and 12 percent of this total.
Data are presented in Table I giving reported amounts of sodium chloride,
calcium chloride and abrasive materials deployed for highway deicing by
individual States and Regions during the winter of 1966-1967.
We may well ask why are the chloride salts preferred for highway deicing
and why are such enormous quantities necessary? Winter highway mainten-
ance is a complex problem involving large amounts of resources, manpower
and materials at considerable cost. In 1964, the Highway Research Board
reported that the cost of snow and ice removal in the 33 snow-belt
States was $151 million, or 8 percent of all highway maintenance costs
in that year for those States. Recent costs are undoubtedly much higher.
Snow removal is a vital function for many towns and cities and may cost
the municipality from 25-50 percent of its entire street maintenance
budget(2).
Until the 1960's, highway maintenance departments principally relied on
the use of abrasives such as cinders, sand, washed stone and slag screen-
ings for snow and ice control. Abrasives are intended to embed into the
snow and ice surface and to provide increased traction and skid preven-
tion. Unfortunately abrasives compared to chemical deicers are less
efficient in melting snow and ice (aided by highway traffic); may easily
be blown off the road by wind and traffic conditions; require greater
application time; and are more costly both in their application and
cleanup. At the end of the winter, large amounts of abrasives must be
retrieved from shoulder areas, catch basins, and conduits in order to
establish proper road drainage(4).
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TABLE I
REPORTED USE (TONS) OF SODIUM CHLORIDE, CALCIUM CHLORIDE
AND ABRASIVES BY STATES AND REGIONS IN .THE UNITED STATES,
WINTER OF 1966-1967^'
STATE
EASTERN STATES
Maine
New Hampshire
Vermont
Massachusetts
Connecticut
Rhode Island
New York
Pennsylvania
New Jersey
Delaware
Maryland
Virginia
NORTH-CENTRAL STATES
Ohio
West Virginia
Kentucky
Indiana
Illinois
Michigan
Wisconsin
Minnesota
North Dakota
SOUTHERN STATES
Arkansas
Tennessee
North Carolina
Mississippi
Alabama
Georgia
South Carolina
Louisiana
Florida
SODIUM
CHLORIDE
99,000
118,000
89,000
190,000
101,000
47,000
472,000
592,000
51,000
7,000
132,000
77.000
1,975,000
2,146,000
1,000
17,000
CALCIUM
CHLORIDE
1,000
1,000
6,000
3,000
1,000
5,000
45,000
6,000
1,000
1,000
22.000
92,000
511,000
55,000
60,000
237,000
249,000
409,000
225,000
398,000
2,000
12,000
9,000
1,000
6,000
10,000
7,000
3,000
14,000
1,000
63,000
2,000
ABRASIVES
324,000
26,000
89,000
423,000
335,000
86,000
1,694,000
1,162,000
70,000
2,000
40,000
204.000
4,455,000
43,000
230,000
77,000
60,000
6,000
102,000
84,000
13.000
615,000
75,000
18,000
2,000
75,000
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TABLE I (Cont'd.)
STATE
WEST-CENTRAL STATES
Iowa
Missouri
Kansas
South Dakota
Nebraska
Colorado
SOUTHWEST STATES
Oklahoma
New Mexico
Texas
WESTERN STATES
Washington
Idaho
Montana
Oregon
Wyoming
California
Nevada
Utah
Arizona
District of Columbia
1966-1967 REPORTED TOTALS-'
c/
SODIUM
CHLORIDE
54,000
34,000
25,000
2,000
10,000
7,000
132,000
7,000
7,000
3.000
17,000
2,000
1,000
4,000
1,000
1,000
11,000
4,000
28,000
52,000
36.000
4,376,000
CALCIUM
CHLORIDE
2,000
3,000
2,000
1,000
8,000
165,000
ABRASIVES
68,000
31,000
36,000
6,000
150.000
291,000
2,000
1,000
3,000
155,000
47,000
80,000
200,000
43,000
94,000
50,000
56,000
725,000
6,164,000
a/ Data taken from Salt Institute 1966-1967 Survey for U.S. and
Canada(1).
b_/ Represents data by all governmental authorities reporting within
each State.
c/ Overall values given in Table I represent about 75 percent of true
values (reported and unreported) of salts and abrasives used in
1966-1967. With confidential data and appropriate adjustments,
the Salt Institute estimates that U.S. total consumption for the
winter 1966-1967 was 6,320,000 tons sodium chloride, 247,000 tons
calcium chloride, and 8,400,000 tons abrasives.
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The demand that roads be safe and usable at all times, and that June
driving conditions be provided in January, has in recent years led to
adoption of a "bare pavement" policy by practically all highway depart-
ments in the snow belt region. This has required greatly increased
use of deicing salts, in many cases replacing the abrasives previously
used. Chemical deicers directly attack and melt the ice and packed
snow surfaces. As the salt dissolves and melts the upper ice, the
resulting brine solution penetrates through the ice and most importantly,
causes a break in the tight bonding of ice to the pavement. Chemicals
also prevent the formation of new ice.
In 1947, less than one-half million tons of salts were deployed through-
out the U.S. for highway deicing, and most of this was admixed with sand
and cinders to keep the abrasives from freezing and to facilitate
materials handling(2,5). Today, the very large majority of sodium
chloride and calcium chloride is applied "straight" onto highways and
total amounts exceed 9 million tons annually.
Various chemical deicers are commercially available including rock salt,
calcium chloride, and other chlorides, the common ammonium salts, various
alcohols, glycerol, and special composition products(6,7,8) . Potentially
any material which readily mixes with water and lowers the freezing point
of water may be appropriate for melting ice and snow. Some deicers produce
excess heat which serves as an advantage. Availability, cost and effi-
ciency are considered main criteria in selecting a deicer, and because
of these factors, sodium and calcium chloride are used almost exclusively
for highway ice and snow control. Of the chloride salts used, sodium
chloride represents about 95 percent and calcium chloride 5 percent.
It is the firm philosophy of highway authorities in the U.S. that bare
pavement conditions are essential to adequately guarantee the safety
and lives of motorists using these roads and highways. Highway
officials state that savings from the use of highway salts cannot be
adequately measured. For example, it can never be known the number
of lives saved, the number of personal injuries avoided, and how much
automobile and property damage is averted by substituting bare pavement
for ice and snow packed roads. It is generally true that little
sympathy or understanding is shown by the average motorist caught
within an unexpected or untimely traffic jam or when a quick early
morning freeze causes solid ice on every road in the area. If things
go wrong, public reaction is vehement and instantly directed to the
duly-elected public officials, the city government, or to supervisors
and work personnel in the highway department.
Highway officials believe the general public is not adequately appraised
of improved safety and reduction in highway deaths. Rather they feel
the public and others unjustifiably stress corrosion damage to cars,
vegetation damage, and salts in ground and surface waters, as being
all too important. Infrequently, but sometimes, the well-intentioned
defenders of highway salting do show a tendency to overstate their
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position. We cite a few cases from the literature such as: "We might
ask the question - Is a life worth a shrub", or, "I wonder how many
motorists would go along with a policy that would possibly spare a tree
and cost them their lives...", or, "All it (salt) does is keep some
of the taxpayers around to see another winter"(2,4,5,6,7,9). At this
point, let us turn to the specifics of snow removal operations and the
various ways in which deicing chemicals are used.
Abrasives
Although the use of abrasives has declined, some 6-9 million tons of
abrasives spread onto roads during 1966-1967 show that abrasives are
still quite important for wintertime highway maintenance. Some States
such as Oregon, because of alleged damage caused by deicing chemicals
to automobiles and concrete roadways and structures, continue to depend
almost exclusively on abrasives. Salts are used only in emergency
situations(4) and data in Table I show that Oregon in 1966-1967 used
only 1,000 tons of chemicals compared to 200,000 tons of abrasives.
Abrasives such as cinders and sand are treated with sodium chloride or
calcium chloride at the rate of 50 to 100 Ib. salt per cubic yard
material. This treatment measure prevents freezing of the material
in storage, and enables better handling, loading and spreading of the
abrasives. Salts may be added to the abrasives in dry form or as a
brine spray. This treatment also serves to increase the embedding
potential of sand, cinders, etc. Abrasives are mainly used to improve
traction in critical areas, especially on hills, curves, intersections,
bridges, etc. It is reported where previously eight 4-ton truck loads
of abrasives were required to cover 4 miles of roadway, in contrast,
using salts, the same area can be covered with only one 4-ton truck
load of salt. Today's safety standards are indicated as requiring
immediate attention to snow and ice control before serious hazard is
created. Unfortunately abrasives attack the problem after ice and snow
have accumulated(4,5,9).
The Idaho Department of Highways in a recent report of April 1971(10),
indicates that they will continue to rely on a "complete" sanding program,
which is determined to be more feasible than complete salting. "When
the public demand becomes more inclined toward the increased convenience
and safety of salting than toward the monetary outlay required, then the
complete salting policy or modification thereof may be more feasible."
The current sanding policy of the Idaho Department of Highways gives
Immediate priority for sanding hazardous locations such as sharp curves,
high grades, combination of grades and curves, bridge decks, interchanges
and intersections. However, if availability of sand becomes critical,
and/or extreme hazardous conditions develop, the Department may then
consider straight salt. This report(10) attempts to economically compare
the alternatives of complete salting and complete sanding vs. the present
sanding policy used by the Department. In 1970, the Department expended
around $600,000 for wintertime sanding of State roads, and it is recognized
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the annual cost of sanding is steadily increasing. Experiences in Oregon,
Idaho and other western States show the need for realistically comparing
abrasives and deicing salts with respect to cost, effectiveness, and
environmental problems. The Idaho results also suggest that use of sand
in place of salt particularly for less critical areas, should be given
greater consideration.
Chloride Salts and Properties
Sodium chloride and calcium chloride are generally used separately, but
may be mixed together to satisfy certain road conditions. Chlorides are
quite prevalent in nature comprising about 0.15 percent of the earth's
crust and 2 percent of seawater. Chlorides are important in the human
body in maintaining critical body functions and physiological processes,
and are recognized as a vital ingredient for sustaining plant and animal
life. Calcium and sodium likewise are considered essential elements
which respectively comprise 3.6 percent and 2.6 percent of the earth's
crust. These chemicals are purchased as rock salt and calcium chloride
in relatively unrefined states. Rock salt is 94 to 97 percent sodium
chloride, and the ASTM specification for purchasing calcium chloride for
highway use specifies a minimum of 94 percent calcium chloride(9).
Calcium chloride is appreciably more soluble than the sodium salt in
water and due to its solubility, the calcium salt creates a lower
freezing point and will dissolve more ice than an equal amount of sodium
chloride. The calcium salt liberates heat going into solution, and
has deliquescent and hydroscopic properties. The calcium salt will
readily absorb moisture when the relative humidity is higher than about
30 percent, which gives it certain advantages over rock salt in highway
deicing. Because it absorbs water, calcium chloride also finds use
in controlling dust from unpaved roads in the summer. However, serious
difficulties are oftentimes encountered in storing calcium chloride(4,5,9).
In ice control, sodium chloride is considered more effective over longer
periods and cuts deeper, but the calcium salt reacts faster. Conse-
quently, the two salts are frequently mixed in different ratios depending
upon given weather conditions so as to utilize the best characteristics
of both chemicals. Calcium chloride becomes increasingly effective
the greater the temperature differential below freezing. Many recom-
mendations may be found in the literature on the best ratio of calcium
to sodium mix. An APWA Research Report describes a satisfactory mixture
for storm conditions (other than that controlled with straight sodium
chloride), as being made up of 1 part calcium chloride and 2 parts rock
salt by volume. For hard-packed snow and heavy ice, they indicate
sometimes a 1:1 mix is used. Mention was also made of a 15 percent
calcium mix. The Massachusetts Legislative Research Council report(4)
describes a 1:3 mixture of calcium:sodium as being effective near 30°F,
ranging to a 1:1 mixture found effective under very severe icing condi-
tions and very low temperatures. The Council also indicates that a
mixture of two parts chemical (1:3 calcium to sodium by weight) to one
- 16 -
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part abrasive would be almost as effective as straight chemical in melting
action and furthermore would provide good skid protection(4,6).
From the standpoint of equilibrium, it has been calculated that 600
pounds of sodium chloride applied per mile of 20 foot width road coated
with 0.2 inches ice (or 2 inches of snow) would melt about 10 percent
of this ice cover. This is sufficient to loosen the surface bond and
maintain bare pavement conditions. It should be specially noted that
except under very low temperatures (below 10°F) and very light traffic,
the rate of ice or snow melting will primarily depend upon traffic
volume rather than the melting properties of the deicing chemicals used.
Although 8,000 pounds of salt are theoretically required to completely
melt a one-eight inch covering of ice from one mile of two-lane roadway
at 20 F, good highway practices would use only 300-500 pounds of salt,
which when combined with traffic load, would produce adequate snow and
ice removal(4). Fast experience indicates that deicing chemicals are
effective and economical when the snowfall is relatively light, up to
depths of 2-3 inches. For heavy snowfalls there must be heavy reliance
upon plowing and other mechanical means of removal(4,6).
Marine Salt
The State of Massachusetts in the early 1960's, conducted field tests
comparing the efficiency of rock salt with marine (solar) salt and found
encouraging results for the marine salt. This deicing agent obtained by
evaporating sea water, was reported approximately equal to rock salt in
cost, and was successfully used by several New England towns on their
local roads(4). Marine salts are reported to have generally similar
characteristics to the commercial deicers but there may be notable dif-
ferences, particularly in smaller particle size of the marine salt
possibly creating a faster melting action compared to straight sodium
chloride. Although there is a lack of firm data in the literature, it
appears that substantial quantities of salts originating from sea water,
have been marketed in recent years as highway deicers. Marine salts
are probably being sold separately or mixed together with commercial
rock salt amounting to hundreds of thousands of tons annually.
The industry more or less uses the term marine salt as "meaning a homoge-
nous crystal or occluded crystal containing all of the sea's ingredients"(11).
On the other hand, solar salt would seem to broadly encompass all salt
derived from the ocean whether recently evaporated salt, or the salt de-
posits laid down many millions of years ago, today being mined from the
land by conventional means. Commercially manufactured marine salt is
reported to be normally produced by fractional crystallization. Sodium
chloride, with a minimum of impurities, is selectively precipitated
within concentrating and crystallization ponds over aQrather narrow oper-
ating range of solution densities (i.e., 25.5 - 29.5 Baume)i/. The
TJA term frequently used in the chemical industry to designate densities
of solutions. Based upon an arbitrary scale of specific gravities de-
veloped by the French chemist Antoine Baume. At 60/60 F, for materials
heavier than water, °Be=145-145/Sp. Gravity of material; for materials
lighter than water, °Be=140/Sp. Gravity of material-130.
- 17 -
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large majority of calcium carbonate, calcium sulfate, magnesium sulfate
and other impurities precipitate outside this range. The sodium chloride
salt is separately collected, and then washed and refined to yield a
reasonably high assay(11,12).
It is known that the composition of major constituents in sea water
approximate 30.5% sodium, 55.1% chlorides, 3.7% magnesium, 7.7% sul-
fates, 1.2% calcium, 1.1% potassium, 0.2% bromides and 0.4% bicarbonates
and carbonates(13,14,15). Although commercial marine salts exclude im-
purities to a large extent, information on product composition is not
readily available. Further data on marine salt is greatly desired as
to its composition; its comparative deicing efficiency; and significantly,
the potential consequences of sulfates, magnesium, potassium and other
available constituents possibly contributing to environmental pollution.
State Usage
The States experiencing greatest use of deicing chemicals are those
located in the eastern and north-central regions of the U.S. In the
100,000-200,000 ton per year use category, we may include the States of
Maine, New Hampshire, Vermont, Connecticut, and Maryland (data in
Table 1 adjusted for sources not reporting). In the 200,000-400,000 ton
category, we have the States of Massachusetts, Indiana, Illinois and
Wisconsin. The leading States in highway salt consumption as of the
winter of 1966-1967 were Minnesota - about 570,000 tons, Michigan -
590,000 tons, New York - 680,000 tons, Ohio - 740,000 tons, and Pennsyl-
vania - 850,000 tons (see Table I). It is noted the State of New
Hampshire although relatively small in area, has used highway salts
since the mid-40's, and over this period the cumulative use of highway
salts in that State alone has probably exceeded 2.3 million tons.
Highway Salt Applications
The common sequence generally starting as soon as possible after the
snowfall arrives is salting the highway, plowing, then resalting as many
times as necessary during the storm. In Massachusetts, salting com-
mences when snowfall is about one-inch, and the salt is permitted to
remain about 60 minutes before snowplowing. In other areas, snowplows
will follow immediately behind salt application, which seems less desir-
able. Environmental problems are minimized by deploying chemicals as
sparingly as possible to maintain safe traffic flows. However, the
literature also emphasizes that the "bare pavement" policy requires
frequent and liberal applications of deicing chemicals. In some cases,
salts are applied as soon as or even before snow occurs, based upon
weather forecast probability. We tend to believe there have been
frequent instances where highway salts were used but no snow followed.
Salt application rates represent an important operational criteria.
A 1966 APWA report(7) indicates that highway authorities in the U.S.
- 18 -
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tend to fall into one of two categories using either 0.04 Ib. salt/square
yard/application, or 0.25 Ib. salt/square yard/application. In his review
of practices in Connecticut(16), Prior found that single applications
of 1,000 Ib. salt per mile on main highways are not uncommon; that rates
of 0.14 to 0.20 Ib. salt per square yard per inch of snow (equivalent to
1.4 tons per mile of two-lane road per inch of snow) are suggested for
effective snow removal; and also, that annual salt used on certain high-
ways in ConnecticutQmay exceed 20 tons per mile. Hanes et. al.,(5)
notes at 20 F to 25 F or above, recommended rates are 500-800 Ib. sodium
chloride per mile of two-lane road and 800-1,100 Ib. per three-lane mile.
However, in certain cases, rates as low as 200 Ib. per mile give satis-
factory results. When temperatures are below 20°F-25°F, rates are nearly
the same but mixtures of calcium chloride and sodium chloride are used.
Recommended ratios are in the range of 1:10 to 1:1 calcium to sodium salt.
Highway salt consumption in Maine is approximately 400 Ib. per lane mile
per application, equivalent to 25 tons salt per season used on a two-
lane highway(17). Over the 1965-1966 winter, Massachusetts, the District
of Columbia, Pennsylvania and Illinois are known to have applied an
average of 20 to 37 tons of salt per lane mile. Additionally, the 1970
summary by Hanes et. al.,(5) estimates that several States apply more
than 20 tons per lane mile over the season to a number of their highways.
In response to this latter study(5), 13 States cited definite damage
to trees and vegetation caused by highway salts, and 12 States reported
incidents of water contamination. Schraufnagel from his experiences in
Wisconsin, further estimates during the winter of 1964-1965, the State
applied an average of 15.8 tons of salt per mile of roadway. Nevertheless,
salt applications for certain counties in Wisconsin were much higher than
the State average. For example, the data show that Milwaukee County over
the winters of 1961-1964 applied 66.8 to 92.1 tons per year of chloride
salts per mile of State highways in that county(9). We believe that cer-
tain sections of major State highways and toll roads in the U.S. currently
receive in excess of 100 tons of salt per mile road during the winter
season.
Although the total use of calcium chloride for dust control and road
shoulder stabilization appears to be only around 20,000-30,000 tons
per year in the U.S.(5), applications are relatively heavy at times
and some damage has resulted from these practices. Schraufnagel(9)
reports that dust control involves applications of calcium chloride
around 1-2 Ib. per square yard equivalent to 6 to 12 tons per mile for
a 20 foot wide roadway. Road bed stabilization requires in the order
of 6 to 12 tons per mile per inch of compacted depth. Therefore, a
6 inch compacted depth for a 20 foot wide road would use 36 to 72 tons
calcium chloride per mile.
Costs of Highway Salts
Purchase costs for the straight chloride salts will depend upon many
factors but chemical costs will fluctuate less than those required in
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applying the salts onto roads and highways. Schraufnagel(lS), based
upon Wisconsin experiences, reports in 1967 that rock salt was about
$10 per ton delivered in bulk, and calcium chloride about $47 per ton
delivered in bag lots. He also notes that costs of both salts were
lower at that time compared to 1960. A 1964 Massachusetts study(4)
reports that calcium chloride was purchased in bags at $40 per ton,
and the average cost for sodium chloride (presumed to be bulk) was
around $13.50 per ton. Sodium chloride is preferably shipped in the
summer months and protected in storage by use of laminated paper,
canvas tarpaulins or polyethylene sheets.
A price of $1.20 per ton was quoted for sand in Massachusetts, to which
must be added hauling and spreading costs, $6-10 per ton for spring
cleanup of sand, and $3 for each of the 25,000 catch basins in the State
requiring subsequent cleaning. Current costs for sodium chloride in
Massachusetts approximate $12 per ton for purchasing rock salt, and
another $6-8 for hauling and spreading, giving a total cost around
$18-20 per ton salt applied(19). In Maine, these same functions may
require higher costs ranging from $12-15 per ton for purchasing sodium
chloride and $8-10 per ton for its application(17). Costs for mixing
calcium chloride with rock salt for a 1:1 or 1:2 (calcium to sodium
salt) blend are quoted around $1.25 for each ton of calcium chloride
used(6).
Since practically all deicing salt sold today is treated with anti-caking
additives(20), it would seem the above costs include these anti-caking
agents. Deicing salts containing added corrosion inhibitors such as the
chromate or phosphate salts are reported 30-40 percent greater in cost
compared to plain rock salt(21).
Operations, Equipment and Methods
The large majority of deicing salts and abrasives are currently applied
to road surfaces by various mechanical means. Tail-gate spreaders and
hopper-type spreaders are commonly used for highway salting. Standard
dump trucks with discharge pipes; front-end loaders; angle loaders;
public service trucks, jeeps, etc., equipped with ready-mounted plows;
portable and non-portable melters, and other devices may comprise the
snow and ice control equipment available at any one time. New York City
having an extensive array of snow-fighting equipment available has
recently received ninety-five "electronically-controlled" 10-wheel salt
spreaders to complement its snow cleanup operations. This spreader is
capable of distributing 14 cubic yards or 15 tons of salt before re-
loading (22, 23). Various types of snow-fighting and deicing equipment
found in current use are illustrated by Figures 1 to 18.—'
Chemicals are often spread in about an 8-foot concentrated width down
the center of the pavement or driving lane. The disc spinner spreads
a/ Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the Environmental Protection
Agency.
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FIGURE 1
Diesel powered truck with
wing plow and straight blade
FIGURE 2
Snow blower
Courtesy of city of
Chicago, Illinois
21
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FIGURE 3
Diesel powered dump truck with
salt spreader insert and snow plow
FIGURE 4
Left to right: dump truck with salt spreader
insert and plow, truck with interchangeable
plow, front-end loader, and snow blower
Courtesy of city of
Chicago, Illinois
22
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FIGURE 5
Twin-disc salt spreader with tail-gate
screens (placed inside truck body) to prevent
salt lumps from reaching feeder ports
Courtesy of city of
Milwaukee, Wisconsin
FIGURE 6
Salt spreader
Courtesy of city of
New York, N.Y.
23
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f
FIGURE 7
Salt soreader
FIGURE 8
13-Ton salt spreaders with V-plows
Courtesy of city of
New York, N.Y.
-------
FIGURE 9
New design salt spreader with screen
grid over top to preclude salt lumps
FIGURE 10
Salt spreader being loaded at salt
storage depot by front-end loader
Courtesy of city of
New York, N.Y.
25
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FIGURE 11
Department trucks plowing city streets
FIGURE 12
Front-end loader removing cleared
snow into receiving trucks
Courtesy of city of
New York, N.Y.
26
-------
FIGURE 13
Front-end loader clearing city streets
FIGURE 1<*
Front-end loaders keeping city streets open
Courtesy of city of
New York, N.Y.
27
-------
FIGURE 15
Heavy-duty snow blower
FIGURE 16
Snow blower removing street accumulated
snow into receiving trucks
Courtesy of city of
New York, N.Y.
28
-------
FIGURE 17
Front-end loader depositing
snow into snow-melter
FIGURE 18
Dumping snow into nearby waterway
Courtesy of city of
New York, N.Y.
29
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the salt over a much wider width of pavement compared to "dribbling"
techniques. For many spreaders, the rate of salt application will depend
upon the gate opening, spreader engine speed, and truck speed. Many
spreaders appear to have an application range from 0 to about 2,000 Ib.
salt per mile with incremental settings of 200 Ib. This equipment is
frequently known to have good precision but to be lacking in reasonable
accuracy. Furthermore, much of the available equipment is not metered.
Volumetric devices for controlling the rate of spread include gravity
and belt conveyances, or a screw drive utilized for delivery of material
through an orifice. The positive displacement ability of a helical
screw or grooved cylinder turning at a fixed speed is also used for
metering. Within a typical town or community, the most economical
approach usually involves purchase of equipment to handle the average
winter storm expected and to contract for equipment and services beyond
the average demand. Contract services frequently include plowing and
hauling(5,6,7).
The proper application and spreading efficiency of highway salts have
generated some studies but nonetheless this area has not received
deserved attention. The Highway Research Board in a 1967 report(24)
indicates there are several challenges presented by previous research
findings. One important task is to improve present maintenance prac-
tices including the over-application of highway salts where conditions
do not warrant; poor regulation of spreading equipment which distributes
salt material beyond the pavement break; and too many improperly-located
and inadequately-protected stockpiles of chloride salts. Greene(25)
cites the viewpoint of the Bureau of Public Roads that improper calibra-
tion of salt spreaders is extremely common. Improper calibration and
operation of equipment leads to excessive salt application rates, which
not only increase over-all costs but also contribute to damage of
vegetation and water supplies, and increased deterioration of concrete
pavement and structures.
In Ontario, it is claimed $1 million per year is saved in better appli-
cation of highway salts(25), and in the State of Maine over recent years
salt use is reported to have been reduced some 30,000 tons annually due
to improved practices(17). Greene estimates operational savings of
several million dollars per year are possible Nationwide without reduc-
ing the quality of wintertime road maintenance(25).
Partly due to improper snow control practices but also because environ-
mental side effects are not given careful consideration, snow mixed
with brine is piled alongside highways representing heavy localized
salt concentrations. During salt spreading, a portion of the salt is
scattered off the side of the road. In plowing, the snow may be easily
pushed 15 feet or more from the edge of the pavement. This snow has
been found to contain up to one-percent salt, i.e., 10,000 mg/1. After
the ridges disappear, salt accumulations and burned-out vegetation are
often observed as white strips parallel to the roadway. There is con-
siderable wasting of salt due to misdirected or excessive spreading(5
17,19,24).
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Significant improvements in wintertime road maintenance practices would
be derived from better field testing and control, good equipment with
good maintenance schedules, greater use of mechanized equipment, fre-
quent calibration, increased reliance and improvement of salt metering
instrumentation, education and awareness through the ranks particularly
at the working level, concerted effort and increased training most
appropriately carried forth at the State highway department level, and
due consideration given to proper environmental protection.
Besides chemical melting, various methods of thermal melting are avail-
able which may become more prominent in the future. External and
in-slab thermal melting systems have greatest application in areas
where any accumulation of ice and snow is considered extremely hazardous.
Such areas include expressway ramps, bridge decks, busy intersections,
toll plazas, etc. External systems are either gas or electric operated
and utilize infrared energy for melting. In-slab systems may comprise
embedded, electrically-heated cable, pipes carrying heated liquid or
steam, or electrically-heated reinforced wire mesh. In-slab systems,
although protected, are subjected to stress and strain caused by slab
movement and invite high maintenance and repair costs because the system
is buried within the slab. External systems are easier to maintain but
are more vulnerable to damage caused by vehicles, vandalism, and similar
conditions(6,7). Electric grids were installed in a test section of a
street in Washington, D.C., but the system was reported too high in cost
and power demand to enable widespread use(26).
In contrast to thermal melting systems which prevent the formation of
ice and snow, "snow melters" are available used in clearing streets as
an alternative to the ever-rising costs of snow hauling and dumping.
These machines which come in various sizes up to 85 tons per hour gen-
erally consist of a heat source, melting chamber, and discharge system.
Mobile melters are deployed on urban streets with discharge into storm
drains, whereas stationary or pit melters are centrally located or
situated in heavy-use areas such as airports, large parking lots, etc.(6),
An 80 ton/hour melter can handle 6 inches of snow on 200,000 square feet
of pavement in about 3.5 hours. Description was given(7) of a 75
ton/hour melter in Boston positioned at a street intersection and fed
by two 3-cubic yard front end loaders. Lockwood et. al.(7) comment
that unless streets are so narrow as to impede movement of trucks,
there is little savings in removal time provided sufficient trucks are
on hand to otherwise equal the capacity of the snow melter.
Purchase of a snow melter is generally based upon savings in cost of
hauling and dumping snow. As of 1965, there were some 50 mobile and
stationary snow melters available in the U.S. and Canada(6). Special
conditions may justify the use of snow melters or installation of
thermal melting systems described above. However, even today both
methods are generally considered quite expensive compared to spreading
of deicing salts on city streets followed by normal snow removal opera-
tions .
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Other Deicers
There is consistent opinion in the literature that possible alternatives
to sodium chloride and calcium chloride, which are reliable and economi-
cal, will not come into large-scale use in the foreseeable future.
Substitute deicing compounds which meet special conditions or which are
otherwise suggested for possible use include urea, urea combined with
calcium formate, the various chlorides such as magnesium, potassium,
aluminum and lithium chloride, ammonium acetate, methyl and ethyl alcohol,
isopropyl alcohol, ethylene glycol, glycerol, aldol, mixed amides, and
chemical dyes. From available data, it appears that the above chemicals
are considerably higher in unit cost compared to rock salt. Experience,
operational data, and knowledge of environmental effects are lacking for
the substitute deicers. However, certain of these compounds are suspect
in terms of toxicity, increased corrosion of metals and concrete, eutro-
phication potential, and hazards in handling(4,5,6,7,18).
Urea, mixtures of urea and ammonium-sodium nitrate and phosphate salts,
and mixed amides appear to be most frequently deployed for airport
runway deicing. Urea is less corrosive than sodium chloride but
must be used in quantities about twice that for rock salt, and is about
6 times higher in unit product cost. The aviation industry is mainly
concerned about stress corrosion in aircraft metals, consequences to the
air frame and structural failure. Cost of chemicals and effects upon
concrete pavement and ground structures are of secondary importance.
Ethylene glycol has in the past been used by airports and is also im-
portant for deicing car windshields. Calcium chloride and the ammonium-
potassium nitrate and phosphate salts are sold for home use in clearing
sidewalks and driveways of ice and snow(4,5,6,8,18).
Salt Storage
Cities, towns, counties and other highway authorities receive large
quantities of deicing salts shipped by truck, barge and rail car.
These shipments generally arrive throughout the summer and fall months.
The governmental authority should logically plan and select appropriate
sites for storing these materials for wintertime use. Salt suppliers
recommend that these products be received and stockpiled over the
summer, usually no later than September. As more cities, counties, and
States are changing to "straight salt" programs, timely deliveries are
becoming more difficult. For deliveries late in the year, many towns
and cities may pay more for shipments that require greater time to
receive. Replacements in January, February and March may be extremely
scarce or almost impossible to locate, particularly during severe winters
when many authorities are seeking additional stock(20,27). Typical salt
storage areas in New York City, Chicago and Milwaukee are shown in
Figures 19 to 23. Figure 24 illustrates a covered salt stockpile in
Toledo, Ohio. From the standpoint of water pollution control, fully
covered stockpiles as illustrated in Figures 23 and 24 are highly pre-
ferred over open storage.
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Bulk salt represents the most economical material obtainable and bulk
salt storage generally provides maximum availability and convenience
at least overall cost. The large majority of highway salts have been
previously stored outdoors with or without covering, and placed directly
on the ground or upon bituminous or concrete pads. In recent years
however, more highway authorities have turned to protected or roofed
enclosures and others have provided suitable covering for open stock-
piles. Enclosed structures are recommended in order to: 1) abate
contamination of nearby streams, wells, and groundwater by excess salt
runoff; 2) improve aesthetics in the local area; 3) prevent formation
of lumps and reduce frozen crust in the salt piles; 4) eliminate heavy,
caked salt in the pile thereby facilitating easier handling by mechanical
equipment; and 5) enable better control over stored materials and more
efficient loading and unloading(20,27).
Deicing salts may be stored in unused buildings, garages, covered sheds,
elevated storage bins, domed structures, cribs, and upon elevated plat-
forms, or pallets. Stockpiles outdoors are preferably placed on storage
pads and should definitely be covered with heavy tarpaulin, canvas or
other protective materials. Salt storage sites should permit easy access
by trucks, front-end loaders and similar equipment, and be situated so
that trucks and salt spreaders do not have to "dead-head" long distances
before reloading. The Salt Institute recommends that all storage pads,
cribs and similar structures be located at sites completely free of
groundwater. They suggest that bituminous pads be placed upon crushed
aggregate and salt-stabilized subgrades. Fads should be crowned to
enable drainage away from the pile on all four sides. Additionally,
drainage ditches, pipes or tiles may be necessary around salt storage
areas to prevent contamination of local ground and surface water
supplies. In certain instances, impoundment basins may be essential
to capture and retain this salt drainage(20,27).
Examples of the types of salt storage facilities most frequently used
in the United States are illustrated in Figures 25 to 37. It is noted
that construction costs as given for these storage facilities were
prepared around 1965, and are undoubtedly somewhat below current esti-
mates. The more expensive structures are often reported to be the least
expensive to use depending on local climate, amounts of stored materials,
type of equipment available and services. For bulk salt storage, the
following figures are useful:
Stored salt ** 80 Ib. per cubic foot
One cubic yard salt = 2,160 Ib.
One ton salt = 25 cubic foot
One ton salt » 0.926 cubic yards
With the natural angle of repose of rock salt of 32 , 1,000 tons of salt
stored in a conical pile covers a ground area circumscribing a circle
67.1 feet in diameter or 3,540 square feet. The height of the pile is
21 feet and the exposed surface area of the pile (for purposes of cover-
ing) is about 4,180 square feet(27).
- 33 -
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In a Salt Institute publication of 1967(20), it is reported the State
of Ohio has used various wooden structures providing shelter for up to
100,000 tons bulk salt. Floors are constructed of asphaltic concrete
and the capacities of individual structures range from 200 to 1,000 tons
salt. The State of Iowa indicates they have built some 160 pole-wood
structures giving protection to stored salt. Three sizes are used:
a 20x30 foot building with 100 tons capacity; a shelter 20 by 40 feet
with 150 tons capacity; and a structure 28 by 56 feet holding 300 tons
of salt. The buildings are supported with treated timbers 6x8 inches
lined on the inside with 2x12 inch lumber, and have galvanized steel
roofs and sliding doors.
Fitzpatrick(28) of the Ontario Department of Highways has described a
dome-like structure or "beehive" now being used to store large quantities
of sand-salt mixtures in the Province. The beehive is rather unique in
storing up to 5,000 cubic yards of sand-salt under one roof with a clear
span free of posts, poles or pillars. Trucks, front-end loaders and
other equipment can easily move about the structure for loading and un-
loading. The beehive during and after assembly is shown in Figures 38
to 43. A 24-inch thick concrete foundation is used into which is
inserted a series of posts inside the vertical walls for purposes of
adding a sand retaining ring so as to keep the stored material away
from the base of the structure. The beehive approximates a cone
100 feet in diameter by 50 feet high, and consists of a 20-sided shell
constructed of 2x6 inch lumber overlaid by three-eighth inch plywood and
asphalt shingles. Each of the 20 sides is in the form of an isosceles
triangle made up of 9 panels diminishing in width to the top of the
structure. The 20 sides are bolted together and the top is added to
complete the beehive. The Department of Highways indicates they can
load the building with sand up to 80 percent of full capacity, and with
improved handling procedures they will eventually fill the entire dome.
The structure requires about 900 man-hours for completion once the pad
has been laid. Costs are reported around $3.50 per square foot of floor
area equal to $5.00-$6.50 per ton of sand-salt mixture stored(28).
- 34 -
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I
FIGURE 19
Open salt storage pile, downtown Chicago, 111.
Courtesy of city of
Chicago, Illinois
FIGURE 20
Open salt storage pile, Milwaukee, Wis.
estimated quantity 41,000 tons
Courtesy of city of
Milwaukee, Wisconsin
35
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FIGURE 21
City stockpile of rock salt remaining after
winter's use, mid-February, Milwaukee, Wis.
Courtesy of c ity of
Milwaukee, Wisconsin
FIGURE 22
Typical salt storage pile in
downtown New York City
Courtesy of city of
New York, N.Y.
-------
FIGURE 23
Moving salt by front-end loader
inside enclosed storage structure
Courtesy of city of
New York, N.Y.
FIGURE 2U
Covered salt stockpile located adjacent
to the Maumee River in Toledo, Ohio
Courtesy of the
Salt Institute,
Alexandria, Va.
37
-------
FIGURE 25
Approx. Construction Cost $3 to $5 per ton of capacity
Rock salt can easily be stored outdoors. This shows a rec-
tangular-conical pile of bulk salt covered by a tarpaulin
held down by stakes. The platform is approximately 30'
square and is composed of 3" planks held up by V by V
wood sills. It will hold approximately a 40-ton minimum
carload of bulk salt.
FIGURE 26
Approx. Construction Cost $3 to $5 per ton of capacity
Rock salt may also be stacked against a garage or shed wall.
Here a portable conveyor stacks it. The pile is covered by
a tarpaulin and anchored at the lower end by large rocks.
FIGURE 27
Approx. Construction Cost $3 to $5 per ton of capacity
Open bin storage like this is favored by many Ohio communities,
and the dimensions shown here are given to scale. The roof
has « very large overhang in order to protect the open salt
from the weather. Trucks are backed up to the bins and the
salt is partly dumped and partly shoveled in. It is removed
by shoveling into trucks, or portable conveyors may be used.
Courtesy of the
Salt Institute,
Alexandria, Va.
38
-------
FIGURE 28
FIGURE 29
Approx. Construction Cost
$50 to $75 per ton of capacity
Approx. Construction Cost
$50 to $75 per ton of capacity
Standard steel bins like those used by
contractors for cement, sand and gravel
provide excellent rock salt storage
space. Dump trucks feed salt into the
portable conveyor, which carries it up
to the bin.
The same type of bin as that shown in
Figure 28, except that a vertical chain
and bucket elevator is used.
FIGURE 30
FIGURE 31
Approx. Construction Cost
$50 to $75 per ton of capacity
Approx. Construction Cost
$50 to $75 per ton of capacity
In hilly communities the bin may be
placed close to a hillside to facilitate
loading.
This variation on the bin in Figure 30
follows the contour of the hill.
Courtesy of the
Salt Institute,
Alexandria, Va.
39
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FIGURE 32
Approx. Construction Cost $15 to $20 per ton of capacity
Many communities use this method of storing bags of rock salt
outdoors. The sketch shows 50 tons of bags placed on a plat-
form about 30' wide with the bags many layers deep. The
planks are 3" and supported by V by 4" sills. The bags are
covered by a tarpaulin held down by rocks. Note the method
of piling bags on the outside of the pile. Trucks are apt to
bump into the pile while backing up for loading, and it is
important that the stacking be in such a way that the bags, stay
firmly in place or else fall inward.
FIGURE 33
Approx. Construction Cost $10 to $30 per ton of capacity
Bulk salt stored under a shed. The salt is loaded in by a
portable conveyor, which is also used for getting it out and
onto trucks for distribution.
FIGURE 34
Approx. Construction Cost $20 to $30 per ton of capacity
This piling arrangement, similar to that in Figure 32, features
a platform about 3' off the ground in order to facilitate load-
ing onto trucks. Under these conditions, the storage is not
over 40 tons of salt as a rule. The tarpaulin is held in place
by tying underneath to the posts.
Courtesy of the
Salt Institute,
Alexandria, Va.
ho
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FIGURE 35
Salt Storage Crib
Here is a crib with walls built of 2 x 6 tongue and
grooved creosote treated material. Posts are railroad
ties set three feet apart on center. Note the 2x4 cleat
nailed to crib wall posts as tie-down for tarpaulin or
other covering.
FIGURE 36
Salt Storage Shelter
Umbrella structure protects material from weather.
Panel on both sides keeps salt from collecting around
posts.
Courtesy of the
Salt Institute,
Alexandria, Va.
FIGURE 37
Salt Storage Building
Tie corner posts of storage buildings together with
underground galvanized cables with turnbuckles.
-------
FIGURE 38
The "Beehive" -
Concrete base forms
removed; note posts
for retaining ring
roughly placed
FIGURE 39
The "Beehive" -
Third ring of panels
being placed; placing
of panels by
electrical truck
FIGURE 40
The "Beehive"
Fourth ring
completed
Courtesy of J. R. Fitzpatrick,
Dept. of Highways, Ontario, Canad;
U2
-------
FIGURE 41
The "Beehive" -
Building with all
panels in place; note
air vents at top
FIGURE 42
The "Beehive" -
Method of loading;
first stage by
truck and dozer
FIGURE 43
The "Beehive" -
Method of loading;
second stage by
conveyor
Courtesy of J. R. Fitzpatrick,
Dept. of Highways, Ontario, Canada
43
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SECTION IV
RAINFALL AND OTHER SOURCES
The amount of impurities and the mineral quality of rainwater, particu-
larly chloride content, has been of continued interest to scientists,
agronomists, chemists, and others. Special stormwater studies conducted
by the Taft Sanitary Engineering Center in Cincinnati, Ohio provided
analysis of rain samples of August 1963 through November 1964(29).
Average data for rainfall at this location shows the following: pH - 4.8;
total suspended solids - 13.0 mg/1; chemical oxygen demand - 16.0 mg/1;
total nitrogen (N) - 1.3 mg/1; inorganic nitrogen (N) - 0.7 mg/1; hydro-
lyzable phosphates (PO^) - 0.24 mg/1; and organic chlorine (mostly re-
flecting chlorinated hydrocarbons) - 0.28 mg/1.
Junge et. al.,(30) studied rainfalls in many areas of the United States
and concluded that the oceans are a major source of chlorides in rain-
water. They found that calcium content of rainfall is the highest for
storms over the Southwest principally derived from dust storms(29,30).
Fanning and Lyles(5,31) believe that salt content of rainwater decreases
in proportion to the logarithmic distance inland. The rainfall at
Cirencester, England, was found to contain an average chloride content
of 3.2 mg/1 over a 26-year period equivalent to an annual deposit of
36 pounds NaCl per acre(32). At Mount Vernon, Iowa, the average level
of chloride in rainwater was 10.6 mg/1 from October 1913 to June 1914,
and 7.1 mg/1 from October 1914 to June 1915(5,33,34). The following
table prepared by Klein(35) compares rainwater with surface waters,
groundwaters, sewage, and seawater in terms of average chloride content.
TABLE II
CHLORIDE CONTENT OF VARIOUS WATERS5-'
\
Type of Water Chlorides (mg/1)
Rainwater 2
Upland Surface Water 12
Unpolluted River Water <15
Spring Water 25
Deep Well Water 50
Drinking Water 10-20 (but variable)
Weak Sewage 70
Medium Sewage 100
Strong Sewage Up to 500
Urine 4,500-5,000
Sea Water 20,000
a/ From Klein, 1959(35)
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Besides chlorides being universally present in rainfall, other sources
of chlorides include the leaching of salt from underlying rocks and soils
which is more common in the western and mid-west U.S.; salt contribution
by domestic, commercial and industrial wastewaters; salinity present in
irrigation return flows particularly in the western States; air pollution
fallout from industrial stacks, automotive emissions, open dumps, etc. It
is much beyond the scope of this report to describe and document each and
every source of chlorides. The information given herein focuses on road
deicing salts, although some data are given for rainfall and municipal
sewage. Unless indicated otherwise, extreme care has been taken with all
data presented in this report to describe the various effects and conse-
quences of highway salts on the environment, and to exclude all other
influences.
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SECTION V
SEWAGE
Domestic and municipal sewages contain high chloride content relative to
surface and groundwaters, but quite low compared to sea water (see Table
II). Chlorides are generally considered a persistent or non-degradable
type of pollutant. The chloride content of sewage is essentially un-
changed as it passes through conventional sewage treatment plant processes.
Furthermore, the chlorides in treated waste effluents are not significantly
changed after discharge into receiving surface waters nor are the chlorides
biologically assimilated to any large degree. These chloride sources
directly add to the total chlorides already existing in surface streams(5,
9,35).
Human wastes, particularly urine, contain appreciable amounts of chlo-
rides. Sawyer indicates the excreta represents an average of about
6 grams chlorides per person daily, and adds approximately 15 mg/1
chlorides to the composite sewage flow(9,36). Domestic sewage has a
chloride level around 50 mg/l(9,37). O'Conner and Mueller(38) cite
values of 5-9 grams chlorides per person daily, equivalent to 4-7 pounds
per capita per year. To allow for kitchen wastes and the effluents from
commercial and small manufacturing establishments, a value of 20 pounds
chlorides per capita per year is often used. This is equivalent to
40-80 mg/1 chlorides added to sewage, depending upon the per capita
water consumption. In Madison, Wisconsin where the water supply has a
hardness of about 300 mg/1, Schraufnagel(9) indicates household water
softening could easily raise the chloride content in domestic sewage by
100 mg/1.
The chloride level in the effluent from the Nine-Springs sewage treat-
ment plant in Madison, Wisconsin was 287 mg/1 in April 1965(9). At
Green Bay, Wisconsin, operational data collected by the Metropolitan
Sewerage District showed average chlorides of 255 mg/1 in the treatment
plant sewage over the 12 months of 1964. In contrast, the municipal
water supply of Green Bay has a chloride content of only 7 mg/1. It is
noted that monthly chloride values in Green Bay sewage were 285-312 mg/1
from January through April representing the period of street deicing,
compared to 196-283 mg/1 over the remaining months of 1964(9).
An excellent record has been maintained on chloride content of incoming
sewage and effluents taken every 8-hours at the Jones Island East and
West treatment plants of the Milwaukee Sewerage Commission over the
period of at least the last five years. The question has been raised
whether increasing chlorides, particularly in the wintertime, have any
possible effect on Milwaukee treatment plant efficiencies. This ques-
tion cannot be adequately answered. Nevertheless the summary of
monthly chloride values from 1965-1969 given in Table III shows a
well-defined annual pattern. There was little difference in chloride
content between treatment plant influent and effluent(39).
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It is readily observed that chloride content in Milwaukee sewage was
highest in the winter months of January, February and March coinciding
with the period of street salting and snowmelt. The next highest
chloride values were recorded for the months of December and April.
Milwaukee has an extensive combined sewer system serving approximately
15,000 acres, of which about one-half is in the downtown area. Street
runoff and snow melt are collected into these combined sewers and
received at the Jones Island treatment plants. Higher concentrations
of chlorides in municipal sewage during the winter is believed to be a
typical pattern in many cities due to highway salting and the lower
sewage flows experienced at this time of the year.
TABLE III
MONTHLY CHLORIDES AT MILWAUKEE SEWAGE TREATMENT PLANT
(mg/1), 1965-1969*/
Month Average 1965-1969 Range
January 203 175-245. ,
February 200 190-23(£'
March 196 170-230
April 172 160-185
May 154 140-160
June 137 120-155
July 126 105-145
August 125 110-135
September 127 115-140
October 131 120-150
November 140 125-160
December 169 150-190
a/ From Milwaukee, Wisconsin Sewerage Commission, May 1970(39).
b_/ Excludes one February value.
Milwaukee personnel indicated to the best of their knowledge, there are
no unusual or extraneous contributions to the sewerage system in the
wintertime that would not also exist in the summertime(39). Thereupon,
total daily chloride loads were calculated for both winter and summer
months. Each monthly chloride value was an average of approximately
240 separate samples. It is shown that average daily chloride loads in
the wintertime are 140-170 tons, compared to 90-110 tons per day in the
summertime. For separate years of record, chloride loads were 40-50
percent higher in winter compared to summer.
The Milwaukee data also show surprisingly high chloride sewage concen-
trations for individual days, e.g., 570-600 mg/1 for January 16-18, 1969,
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and 500 mg/1 for February 26, 1969. These chloride loads were around
330 tons per day or three-fold the normal summertime loads. Additional
results collected by the Milwaukee Sewerage Commission on January 16,
1969 for chloride levels in the Milwaukee River and other major water-
ways in the Metropolitan area are given in Table IV. The large majority
of chlorides found in the Kinnickinnic, Menomonee and Milwaukee Rivers
on January 16 is believed directly attributable to deicing salts placed
on the streets and highways in the Milwaukee area. The Commission
reports(39) that over the last two years, annual salt application by
the city of Milwaukee has been around 36,000 tons, and another 90,000
tons of salt have been applied by Milwaukee County. Direct street run-
off from salted streets in Milwaukee during mid-January 1969 likely
contained chlorides in the range of 2,000 to 5,000 mg/1.
TABLE IV
SPECIAL RIVER SAMPLING, MILWAUKEE SEWERAGE COMMISSION,
January 16, 19691'
Water
Location Temperature ( C) Chlorides (mg/1)
Kinnickinnic River at 10.0 2,005
Chase Avenue
Menomonee River at 13th St. 10.5 200
and Muskego
Menomonee River at 70th and 5.0 2,730
Honey Creek Pkwy.
Milwaukee River at Silver 4.0 2,680
Spring Road
Milwaukee River at Port 6.5 1,510
Washington Road
a/ Records received from the Milwaukee Sewerage Commission, May 1970(39),
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SECTION VI
RUNOFF FROM STREETS AND HIGHWAYS
Wisconsin Studies
Schraufnagel reports(9) during 1956-1957 that sampling stations were
established throughout Wisconsin to study the runoff from salt-treated
highways. In the Chippewa Falls area, wintertime highway runoff was
found to contain up to 10,250 mg/1 chlorides, but the receiving stream
did not exceed 46 mg/1 chlorides. Street runoff during the summer
contained only 0-16 mg/1 chlorides and the receiving stream had
0.5-2.0 mg/1 chlorides. In Madison, Wisconsin, wintertime street run-
off had chloride levels ranging up to 3,275 mg/1. It is interesting
to note for street runoff in Madison, suspended solids were as high as
3,850 mg/1, reflecting considerable sand and dirt flushed off the streets
during the winter. This drainage generally had BOD levels in the range
of 20-30 mg/1, although 3 of the 12 samples contained around 100 mg/1
BOD. For another case in Wisconsin of drainage originating from a large
snow pile along Lake Monona, this runoff showed a chloride level of
1,130 mg/l(9).
Syracuse, New York
The fate of deicing salts following their application onto streets and
highways is not precisely defined. It is known that these salts within
the hydrologic system may be stored in the soils, groundwater, and vege-
tation comprising the roadside environment. Hawkins(40) believes that
deicing chemicals may also be stored in the street itself, including:
the snow and ice cover; on the street surface; and directly within the
street masonry concrete, cobbles and other street construction materials.
Hawkins observed summer "leakage" of salt upward onto the surface of
street concrete and cobbles for several hills and grades in Syracuse,
New York, previously receiving heavy amounts of deicers. A white-colored
cast on the road surfaces and interstices persisted well into the early
fall, and the presence of salt was easily confirmed by the "fingertip"-
taste test. The resupply of salt from lower depths in the street layer
or below the street was strongly suggested by the reappearance of salts
after spring and summer rains. These salts find their way into street
and storm sewers throughout most of the year(40).
Chicago, Illinois
During the winter of 1966-1967, the American Public Works Association
studied the chloride content in runoff from Kennedy Expressway in
downtown Chicago, Illinois. The highway drainage area consisted of
102 acres of which about half, or 52 acres were paved. Runoff samples
were collected from February 16 to April 1, 1967, during which time
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there was 14 inches of snowfall and 126 tons of salt applied to the test
area. At all times except during the most severe temperatures, runoff
flows were in excess of 0.1 cfs(41,42). When highway salts were not be-
ing applied, the chloride content of drainage varied from 1,900 to
4,500 mg/1, and runoff was as high as 0.3 cfs. During snowfalls, the
chloride in highway runoff ranged from 11,000 to 25,000 mg/1, and the
flows varied from 0.1 to 1.5 cfs. This study further indicates that
nearly all the deicing salts subsequently left the area in the form of
runoff.
The APWA study in Chicago also calculated that a chloride level of
1,300 mg/1 could be expected in the runoff, assuming 1.5 tons of salt
are applied per mile of two-lane highway for each inch of snowfall(41).
In comparison to these figures, the 1970 Highway Research Board litera-
ture review(5) determined that 600 Ibs. of salt ger mile if applied to
a 20 foot wide road with 0.2 inches of ice at 25 F will produce an
initial salt solution of about 69,000 mg/1; at 10 F, the resulting salt
solution will be around 200,000 mg/1. These saturated solutions will
of course become more dilute as melting of the snow and ice continues.
Considering these values, it is not surprising to see various references
citing several thousand parts per million salt being carried in highway
runoff. The salt content of highway drainage will depend upon many factors
including ambient temperature, amounts of precipitation, quantity of salt
applied, traffic patterns, and volume and rate of surface flow.
Sullivan(41) recognizes that wintertime highway runoff will eventually
run into freshwater streams and natural or man-made lakes or ponding
areas. He cautions that unless there is adequate dilution, the salt
concentration in street runoff may in the future have adverse effects
upon fish life or vegetation. The suggestion is made that "monitoring
of such storm areas should be carried on at various depths to detect
significant changes in concentration". Secondly it is advised..."if a
chloride balance is to be maintained in a river to limit chloride to an
acceptable level for potable water supplies, (then) the runoff from
urban areas must be accounted for and allowances made in the discharge
rates (permitted) from industrial plants at the time of any low winter
flows."
Des Moines, Iowa
Henningson, Durham and Richardson, Inc. recently completed a detailed
study for the FWQA on combined sewer overflows and stormwater runoff
in the city of Des Moines, Iowa(43). Part of the program was directed
to characterization of wintertime runoff, and chloride data were
collected from a number of combined sewers and storm drains over the
period of December 1968 through March 1969. The drainage areas are
largely residential and there are no large concentrations of commercial
and business establishments where exceptionally heavy street salting
may be expected. The Des Moines area experienced a relatively severe
winter in 1968-1969 and quantities of road deicing materials used from
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December 1968 through March 1969 approximated 9,270 tons untreated rock
salt, 295 tons of calcium chloride and 225 tons of rock salt treated
with a rust inhibitor. Total deicers used were 9800 tons, with a
chloride equivalent of 5830 tons.
The Thompson Avenue storm drain serves an area of 315 acres classified
mainly as residential. Results for this storm drain showed that approx-
imately 15,000 pounds of chlorides were carried off in the runoff from
January 15 to March 2, 1969, which approximates 48 pounds per acre.
The study indicates: 1) although appreciable snow and sleet, and heavy
salt applications occurred prior to January 15; 2) little snowmelt had
taken place before mid-January but nevertheless; 3) much of the salt
applied before January 15 was no longer on the streets. Four discrete
snowmelt periods provided the following data for the Thompson Avenue
drainage area:
January 15-16, 1969
February 4, 1969
February 5, 1969
February 25, 1969
0.236 inches runoff
0.049 inches runoff
0.038 inches runoff
0.149 inches runoff
3.75 Ibs. Cl~/Acre
11.80 Ibs. Cl~/Acre
3.52 Ibs. Cl~/Acre
1.63 Ibs. Cl~/Acre
Total = 20.7 Ibs. Cl~/Acre
Sequential sampling illustrates that chloride levels are highest at the
beginning of runoff and concentrations decrease rapidly thereafter.
Individual results for the Thompson Avenue storm drain ranged from a
low of 9 mg/1 chlorides on January 17, 1969 to a maximum of 2,320 mg/1
on February 21, 1969. Typical data for individual samples collected on
February 4-5, 1969 are given below(43).
February 4, 1969
February 4, 1969
February 4, 1969
February 4, 1969
February 5, 1969
February 5, 1969
February 5, 1969
February 5, 1969
2:15 PM
3:15 PM
4:15 PM
5:15 PM
12:15 PM
1:15 PM
3:15 PM
4:15 PM
Flow - 3.9 cfs
Flow - 3.7 cfs
Flow - 2.5 cfs
Flow - 1.1 cfs
Flow - 0.2 cfs
Flow - 1.5 cfs
Flow - 3.1 cfs
Flow - 2.5 cfs
1477 mg/1 Cr
1228 mg/1 cr
1045 mg/1 el'
920 mg/1 cr
743 mg/1 cr
260 mg/1 el'
579 mg/1 cr
502 mg/1 cr
Salt levels in the runoff collected from the Cummins Parkway storm drain,
serving a predominately new residential area of 356 acres, demonstrated
patterns similar to the Thompson Avenue storm drain(43). Periods of
snowmelt produced high chloride concentrations and the range of indi-
vidual results varied from 18 mg/1 on January 16, 1969 to a maximum of
2,720 mg/1 on February 21, 1969. Measured flows in the Cummins Parkway
drain varied from 0.0 to 47.9 cfs compared to 0.0 to 9.9 cfs for the
Thompson Avenue storm drain. In the combined sewer systems, a maximum
chloride concentration of 866 mg/1 was found in the South Side Trunk
sewer on February 4, 1969.
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Henningson, Durham and Richardson also collected wintertime samples from
the Des Moines River and Raccoon River above and below the city of Des
Moines starting January 1969. The report(43) concludes that chloride
levels in the river waters were significantly higher in the winter months
than in the summer. In January and February, chlorides were around
30-50 mg/1 for the locations upstream of Des Moines, and the highest
result was 56 mg/1. Downstream of Des Moines, the chlorides commonly
exceeded 56 mg/1 and the maximum level was 86 mg/1. During the spring
and summer months, the chlorides throughout the area were below 20 mg/1,
but as stream flow diminished in the autumn, the chlorides increased to
between 20-30 mg/1.
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SECTION VII
SURFACE STREAMS, RIVERS
Various Rivers in the State of Maine
Hutchinson(44,45,46,47,48) analyzed seven major rivers in Maine for
sodium and chloride levels over the period 1965-1967. These ions were
generally 1-2 mg/1 at the headwaters and increased to as high as
15-18 mg/1 at the mouths of the respective rivers. Highest levels of
sodium and chloride were shown in the southern section of the State
where highway miles were greatest, but other factors also were present.
Based upon these data, Hutchinson concluded at least at that time, no
adverse effects of highway salting upon river water quality could be
shown.
Hutchinson sampled the Kenduskeag Stream in the Bangor, Maine area both
upstream and downstream of the city, together with two storm drains and
a brook entering into Kenduskeag Stream. Also included in this study
was a culvert carrying surface drainage from one mile of Interstate
Highway 95. The survey was conducted for 60 consecutive days from
March 1 to April 29, 1966. The upstream waters of Kenduskeag Stream
contained sodium and chloride levels of 3.9 mg/1 and 6.5 mg/1, respec-
tively. Downstream of the storm drains and the brook, the Kenduskeag
Stream through the center of the city showed average sodium and chloride
levels of 5.3 and 10.0 mg/1, respectively. The two storm drains
contained runoff with average sodium content of 26.8-28.8 mg/1 and
average chlorides of 73.9-84.6 mg/1. The highway culvert exhibited the
highest level of sodium and chloride with mean values of 168 mg/1 and
570 mg/1, respectively. Hutchinson concludes since there was little
industrial pollution in the area, it appears safe to consider that "road
salt contamination" was significant in these waters. Although it was
apparent that sodium and chloride levels in the Kenduskeag Stream are
definitely affected by surface drainage from the city of Bangor, the
salt concentrations downstream remain low because of considerable dilu-
tion in the stream(44,45,46).
Meadow Brook, Syracuse, New York
The surface waters of Meadow Brook watershed in southeastern Syracuse,
New York, have been studied by Hawkins(40) from October 1969 through
the present. Meadow Brook drains about four square miles of suburban
Syracuse, described as approximately two-thirds developed land, which
receives heavy annual snowfall as well as moderate residential traffic.
From past results, Hawkins found a large variation in mineral content
of the Brook, particularly chloride concentrations. From late-November
to mid-March, chlorides were usually in the range of 200-1,000 mg/1,
but frequently exceeded a few thousand mg/1. For example, a sample in
December 1969 showed about 11,000 mg/1 chlorides. Over the remaining
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months of the year, chlorides were relatively low and in the range of
30-150 mg/1. Hawkins more or less concludes that: 1) salt runoff from
the watershed is discharged in several high concentration surges during
the winter and melt season; 2) salt concentration in the stream is a
function of available snow and salt and the prevailing temperatures;
3) chlorides diminish through the spring and summer but still remain
suspiciously high, suggesting some retention in the watershed and the
contribution of this salt to summertime base flows; and 4) a close
correlation indeed exists between road salting and stream chlorides(40).
Major Rivers in the United States
Effects of highway salts upon major rivers in the U.S. appear small
compared to other sources. Chloride content of major rivers are rela-
tively low compared to wintertime road runoff and ditch drainage.
Unfortunately, adequate data does not exist on sodium and chloride
levels for most rivers of the northeast and north-central U.S. Heavy
snowmelt will also coincide with the start of rising streams during
late winter and early spring, making it difficult to distinguish road
salts. Nevertheless from the limited data available on streams, increas-
ing chloride trends are evident for some of the large rivers in the U.S.
Highest salt loads are generally present in these streams from the end
of February to the end of May(5).
Hanes et. al., in their 1970 report for the Highway Research Board(5),
utilized chloride curves for major rivers in the U.S. based upon Public
Health Service water quality monitoring data over the Water Years of
1958-1963. The amounts of chlorides in terms of mg/1 and tons/day were
plotted for the Delaware River near Philadelphia; the Hudson River below
Poughkeepsie, N.Y.; the Mississippi River at East St. Louis, 111.; the
Missouri River at Kansas City, Kansas; the Ohio River at Cairo, Illinois;
and the Potomac River at Great Falls, Md. Chloride concentrations in
these curves did not vary greatly throughout the year, and in all but one
case were below 35 mg/1. Only the Hudson River and the Ohio River showed
increase in chloride levels during the February-May period. However, the
report concludes the chloride levels are clearly increasing from year to
year in the Hudson River and the Delaware, and even though present levels
are low,..."this increase could be a potential danger"(5). It is recog-
nized that other factors such as sea water intrusion and cyclic patterns
may be present in this 1958-1963 data.
Sleepers River Basin, Vermont; Hydrologic Salt Balance
Kunkle(49) provided annual salt budgets for the Sleepers River basin in
northeastern Vermont from 1968-1970. A 2.5 mile section of U.S. High-
way 2 traverses one of the watersheds in this basin, which receives heavy
traffic and large amounts of deicing salt in the wintertime. The various
watersheds not influenced by the highway showed streamflow chloride levels
of only 2-5 mg/1. However, sampling stations downstream of the highway
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were typically an order of magnitude higher. Due to high runoff per unit
area in the watersheds, excessive salt concentrations in the watercourse
proximate to the highway were appreciably diluted a few miles downstream.
Chloride levels were highest in the summertime baseflow of the highway
watershed. Some of the deicing salt apparently entered into the soils
near the road and later appeared in the summer flows. Individual seeps
sampled close to the highway showed chlorides in excess of 200 mg/1.
The Vermont study showed that stream salt concentrations were lowest in
the springtime due to considerable dilution. Nevertheless, during spring
thaws, much of the salt from the highway was being flushed from the high-
way to the stream, and salt delivery rates (in tons/day) were highest at
this time of the year. On the other hand, the control stations demon-
strated little seasonal fluctuation in salt delivery rates. Sodium chlo-
ride yields for the control watersheds averaged about 7 tons/square mile/year,
Subsequent calculations for the highway watershed yielded about 83 tons/year
of sodium chloride in excess of background amounts. From highway department
records, observations and other field data, Kunkle estimated that 65 to
100 tons salt were applied annually to the highway section in the watershed.
It therefore appears the large majority of highway deicers eventually en-
tered into the surface streams(49).
The older reports in the literature indicate that about one-half of deicing
salts applied onto highways are usually discharged with the runoff, and
about one-half is retained within the area. However, the Vermont study
given above, the results previously cited by the American Public Works
Association for the Kennedy Expressway in Chicago (see Section VI), and
likewise the assumptions made by 0'Conner and Mueller in estimating road
salt inputs to the Great Lakes (see Section VIII), strongly imply that
the large majority of these salts over a sufficient period of time, may
find their way into downstream surface waters. Additional studies provid-
ing material balances over defined intervals of time and of sufficient
duration, would be extremely useful in assessing the fate and behavior
of deicing salts previously applied to roads and highways. Such studies
could also lead to a proper understanding and application of methods
whereby salt sensitive areas could be protected, and promising salt re-
covery/reuse techniques utilized.
Chloride Levels in Milwaukee Streams
High concentrations of chlorides in various river waters in the Milwaukee
area during mid-January 1969 were previously given in Section V of this
report.
Oxygen Demand of Deicers
Schraufnagel, in discussing substitute deicing compounds, describes the
glycols and alcohols in particular, as having extremely high biochemical
oxygen demand (BOD), ranging from 70 to 133 percent of the product
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weight(18). In contrast, urea has a 5-day BOD:weight ratio of only 9
percent and sewage only 0.02 percent. Schraufnagel makes the point that
certain deicers, such as ethylene glycol, if released into a nearby
stream can exert tremendous demand on existing dissolved oxygen. It is
indicated that one pound of deicing compound with a BODrweight ratio of
1.0, if discharged into a waterway having 7 mg/1 dissolved oxygen, will
utilize all the oxygen available in about 140,000 pounds (17,000 gallons)
of streamflow(18).
Dumping of Snow Into Nearby Streams and Water
Bodies; Chloride, Oil and Lead Content
Following the plowing, sanding and/or salting of streets and highways,
significant accumulations of snow, slush or ice are often collected into
receiving trucks and transferred to outlying areas for final disposal.
Frequently these large volumes of snow are deposited or dumped into the
nearby stream, into a bay or river (see Figure 18), or onto the banks of
a water supply reservoir. Most cities indicate they have discontinued
such disposal practices. Nevertheless, they continue to deposit this
snow onto areas lying within the flood plains or higher lands leading
directly into a waterway. Realistically, the latter means of disposal
is no more acceptable than direct dumping into the stream.
Data is generally lacking on the chemical makeup of snowfall after becom-
ing impregnated with deicing salts; oils, greases and dirt from vehicular
traffic; and other urban wastes. Data given previously in this report
show maximum chloride levels of up to 10,000 mg/1 in a typical snowbank
along the highway. Studies in Stockholm, Sweden(50),indicate during their
normal winters, about 1,100,000 cubic yards (30 x 10 cubic feet) of snow
from city streets are dumped. Unmelted snow from selected street loca-
tions in Stockholm were found to contain 2-105 mg/1 oils and 1-100 mg/1
metallic lead. Median values were respectively, 21 and 18 mg/1. The
oil and lead in snowfall were reported to be related in this study to
vehicular traffic, particularly the unburned gasoline and the components
of tetraethyl lead condensates spread onto the cold snow surfaces. Addi-
tional samples of untouched snowfall from one of the Stockholm parks
interestingly enough showed as much as one mg/1 oil as well as traces
of lead.
The high lead content found in snowfall in Sweden is supported by recent
information from Columbus, Ohio(51). Snow collected from streets in
Columbus, Ohio, contained "about 15 times more lead than the safe limit
set for drinking water by the Public Health Service." Samples taken at
locations distant from city roads showed lower concentrations suggesting
that motor vehicle exhaust is a major factor contributing to this lead.
The best means of removal and ultimate disposal of excess snow, slush
and ice from urban centers, deserves careful attention and considerable
research in the future.
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SECTION VIII
FARM PONDS, LAKES
Farm Ponds-State of Maine
Twenty-seven farm ponds located along various highways in Maine, were
sampled by Hutchinson in April, July and August, 1966-1968. The April
samples were significantly higher in both sodium and chloride content
compared to the summer collections. Sodium levels ranged from 1 to
121 mg/1 with an average of 33 mg/1. The chloride range was 1-490 mg/1,
and average levels were 110 mg/1 for April and 80 mg/1 for August. Nor-
mal chloride levels for farm ponds in this geographic area are 5-10 mg/1.
It was concluded that road salts have significant seasonal influence on
chloride content of farm ponds, and that repeated yearly salting is stead-
ily increasing the salt levels in some of these ponds(5,41,45,52).
The Great Lakes, Lake Erie
Long-term studies of Lake Erie have shown that average chloride content
has increased three-fold in the last 50 years, from 7 mg/1 in 1910 to
about 23 mg/1 in 1964. Although it is reported that present uses are not
adversely affected, a continued rate of chloride buildup could cause ser-
ious impairment of water uses in the future. Highway salts are estimated
to contribute 11 percent of the total annual input of chlorides into Lake
Erie waters(5,53). Road salts entering Lake Erie on an annual basis were
estimated by O'Conner and Mueller(38) to be 750,000 tons in 1960. Similar
estimates of road salt inputs for Lake Superior, Michigan, Huron and
Ontario were respectively 91,000 tons; 438,000 tons; 198,000 tons, and
525,000 tons(38).
Wisconsin
The State of Wisconsin and other public authorities have maintained a
long-term monitoring program on the quality of various lake waters in
the Madison, Wisconsin area. One of the smaller lakes in the area is
Lake Wingra, which is spring-fed, but which also receives runoff from
nearby streets and urban lands. Through 1940-1947, average chlorides
in Lake Wingra were 4-5 mg/1. In March 1959, the chloride content of
the lake had increased to 18 mg/1, but in July of the same year the
chlorides had stabilized to between 9-11 mg/1 measured from top to
bottom in the lake. Concern was expressed when subsequent sampling of
lake waters in the summer of 1965 showed chloride concentrations of
41-43 mg/1. Although existing water uses apparently are not affected
by current water quality, chlorides have increased four-fold since 1959
and eight-fold since the 1940-1947 period (9).
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Also in Wisconsin, samples taken in the winter of 1959 from Beaver Dam
Lake at Cumberland, Wisconsin, showed a density stratification of
chlorides with lake depth. The chloride concentration was 8 mg/1 near
the lake surface, and 33 mg/1 at the 15-foot depth near the lake bottom.
Schraufnagel suggests this chemical stratification is due to highway
runoff entering Beaver Dam Lake(9).
First Sister Lake, Ann Arbor, Michigan;
Salt-Induced Stratification
Judd in 1965-1968 studied the impact of highway salt runoff on First
Sister Lake, a small body of water surrounded by a residential subdivi-
sion, an interstate highway and other well-travelled roads in the Ann
Arbor, Michigan area(54). Storm runoff from adjacent streets and roads
enters First Sister Lake mostly through storm sewers. The lake is
approximately 450 feet by 650 feet with a maximum depth of about 25
feet, and the lake has a single outlet used only for about 1-2 weeks
in the spring.
Judd found the salt flows moving through First Sister Lake have the
tendency to sink to lower depths causing density stratification of the
waters. With normal snowfall and road salting, the levels of salt in
the lake create sufficient stratification to preclude complete wind
mixing of the lake in the spring. Chloride concentrations at the
23-foot depth were around 150 mg/1 compared to 60-85 mg/1 in the sur-
face waters. Through the summer, some of the salts eventually find
their way into the bottom muds, and lake stability.!/ is lowered to
enable complete mixing of the waters in the fall months. If salts had
not been absorbed into the bottom muds, it is speculated there would
be no lake overturn not only in the spring but also in the fall. This
stratification is associated with extended periods of low dissolved
oxygen in the deeper waters, and detrimental changes in animal and
plant life in the lake. Even assuming previous fall overturn, Judd
indicates through 1967, the deeper zones of the lake were likely with-
out oxygen for some ten months, and the entire lake below the 10-foot
depth was virtually devoid of dissolved oxygen for about eight months(54),
Irondequoit Bay, Rochester, New York;
Salt-Induced Stratification
Recent studies by Dlment and Bubeck in 1969-1970 for the Irondequoit Bay
drainage basin near Rochester, New York, show that salt runoff has
markedly affected the water quality within the Bay(57). The basin has
a relatively dense population with total population around 210,000 persons.
Irondequoit Bay is fed by Irondequoit Creek and empties into Lake Ontario
via one narrow channel. The water body is approximately 3.7 miles long
by 1 mile wide, with average and maximum depths of 24 feet and 75 feet,
T7"Stability" of a lake is defined by Schmidt(55,56), as the amount of
work required to mix the total body of water to uniform temperature with-
out adding or subtracting heat.
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respectively. During the winter of 1969-1970, highway salts were applied
to basin streets at the rate of 85,000 tons. These deicers are reported
as the single major source of salt into the Bay.
Diment and Bubeck describe Irondequoit Bay as a striking example of salt
accumulation. Approximately two-thirds of the yearly salt input enters
the Bay from December through March. For 1970, the average chlorides in
the surface waters of the Bay were about 160 mg/1, compared to an average
of 320 mg/1 chlorides contained in the incoming wintertime flows, 1969-1970.
Except during fall overturn, chlorides in the bottom waters of the Bay
were 220 to 400 mg/1. From January to November 1970, intense physical and
chemical stratification prevailed, and the bottom waters showed no more
than 1 mg/1 dissolved oxygen. Overall results showed of the 85,000 tons
of deicing salts introduced in the basin, some 35,000 tons left in the
lake outflows. Therefore, more than one-half of these salts were re-
tained in the soils and groundwaters of the basin or in the Bay muds(57).
Diment and Bubeck conclude that winter influx of salt into Irondequoit
Bay causes significant differential in vertical density, which is suffi-
cient to prevent the Bay waters from completely mixing in the spring.
During 1939-1940, the only previous period for which comparable data were
available, the Bay exhibited normal tendencies of a typical deep lake in
a temperate continental climate with stratification and complete mixing
both in the spring and fall. Apparently the lack of spring mixing is
not unusual for very small, deep lakes, but is rare for a lake as large
and shallow as Irondequoit Bay. The above changes are not viewed with
serious alarm by the investigators, but nevertheless, salt runoff has
convincingly modified the characteristics of the Bay. Similar conditions
could occur elsewhere. The rising chloride levels also imply the need
for careful monitoring of water quality conditions in the Irondequoit Bay
drainage basin, and that serious consideration be given to the local
distribution and storage of deicing salts in the groundwaters(57).
Possible Salt Stimulation of Algal Growths
A new development in salt pollution concerns the potential role of sodium
serving as a trace element toward stimulating excessive growth of blue-
green algae. Recent data indicate in addition to nitrogen and phosphorous,
adequate amounts of sodium and potassium may also need to be present for
the growth of blue-green algae. Certain blue-green species may require
one of these monovalent elements, whereas other species may require both.
One reference states that sodium concentrations greater than 40 mg/1 may
be necessary for triggering undue growth of blue-greens. Another refer-
ence infers that 5 mg/1 of sodium provides for optimum growth of Anabaena
cylindrica, which is common in nuisance algal blooms. Further investi-
gation is essential on the suspected relationship between eutrophication
and sodium buildup from deicing salts(58,59).
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SECTION IX
WILDLIFE
Over the winter of 1958-1959, a number of wildlife mortalities in
Wisconsin were attributed to salt poisoning caused by highway deicing
chemicals(9). Within a 40-mile radius of Madison, Wisconsin, cases of
salt poisoning were diagnosed in wild rabbits, pheasants, a quail and
a pigeon. Although the gizzard contents of the dead quail were stained
blue with ferric ferrocyanide, which is a common additive in highway
salts, the additive was not implicated as the cause of death. As part
of their follow-up studies, the State of Wisconsin experimentally induced
single doses of 3 grams sodium chloride into test animals including
adult pheasants and rabbits weighing 1100 to 1400 grams each (454 grams =
one pound). This dosage generally produced death in the animals within
24 hours, and mortality was highest when water intake was restricted.
Heavy snows and cold weather in the winter of 1958-1959 likely contributed
to this problem by reducing food and drinking water available to the
animals, and in turn creating "salt hunger" conditions. It should be
noted that the literature source for the above study does not provide
ample description on the particular test procedures used(9). Hanes et.
al.,(5) also express some reservations concerning these results. Animal
husbandry practices in the midwest and western U.S. often provide wild
animals such as deer with free access to "salt licks" in the wintertime.
Apparently this question has not been fully resolved.
Hanes et. al.,(5) consider ungulate animals being attracted onto highways
in their search for salt, to constitute a much greater hazard not only
to the animals, but to motorists alike. In the State of Wisconsin,
approximately 120,000 deer are killed annually, the large majority by
hunters. However, State personnel estimate that nearly 12,000 deer or
10 percent of the total, are killed along Wisconsin highways by motor-
ists (60). The frequency of this type of accident appears much higher
in the wintertime when large amounts of deicing salts are left remaining
on the highway.
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SECTION X
DEICING ADDITIVES
Special substances may be added to sodium chloride and calcium chloride
to reduce corrosion, or for reasons of better efficiency in handling and
applying deicing salts. Materials such as Prussian blue, sodium ferro-
cyanide (yellow prussiate of soda), chromates, phosphates, etc., are
listed in the literature as available for use. The manufacturer recom-
mends these agents be added in the amounts of 0.5 to 2 pounds or more,
per ton of deicing salt(5).
Ferric and Sodium Ferrocyanide, Anti-Caking Agents
The two most common additives to highway salts are ferric ferrocyanide
(Prussian blue) and sodium ferrocyanide, both used as anti-caking
agents. Ferric ferrocyanide is relatively insoluble in water, and accord-
ing to various reports will not release cyanide upon acidification.
Laboratory tests by the Wisconsin State Laboratory found that blunt-nose
minnows do not appear adversely affected when placed into a 9600 mg/1
concentration of Prussian blue for 48 hours(9).
Sodium ferrocyanide, unlike Prussian blue, is soluble in water and will
liberate cyanide in the presence of sunlight. The cyanide ions are far
more lethal to fish and aquatic life than the sodium ferrocyanide. The
cyanide ion will react with hydrogen in water to form hydrogen cyanide.
The dissociation of hydrogen cyanide is pH-dependent. At pH 7 or below,
only one percent of the hydrogen cyanide will exist as the cyanide ion,
whereas at pH 9, the cyanide ion will comprise 42 percent of the total(5).
Studies on sodium ferrocyanide show toxic levels for Daphnia magna at less
than 600 mg/1(61), and 540 mg/1(62). A toxic threshold of 170 mg/1 sodium
ferrocyanide has been found for Polycelis nigra(63). Subsequent tests
conducted by the Wisconsin State Laboratory determined that a 15.5 mg/1
solution of sodium ferrocyanide, if exposed to sunlight for 30 minutes,
would produce 3.8 mg/1 of cyanide. With increased exposure time, this
level of cyanide remains fairly constant. Since a similar solution of
sodium ferrocyanide in the dark produces relatively little cyanide in
solution, this reaction is considered light-sensitive, i.e., photochemi-
cally-induced(5,9).
Comparable test results may be obtained using potassium rather than
sodium ferrocyanide since chemical reactions of the two chemicals in
water are reported to be nearly alike(5,9). Schraufnagel(9), in his
report, makes note of the work of Burdick and Lipschuetz in 1948(64)
on the toxicity of potassium ferrocyanide and potassium ferricyanide.
It was originally thought these two compounds were relatively innocuous
to fishlife. However, Burdick and Lipschuetz found that sunlight
rapidly decomposed the potassium derivatives to produce cyanide ions
toxic to fishlife. With very low light intensity or dark conditions,
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4,000 mg/1 potassium ferrocyanide was required to generate 0.3 to 0.6 mg/1
cyanide which killed 100 percent of the test fish in 48 hours. In con-
trast, with direct sunlight, 0.36 to 0.48 mg/1 cyanide was generated by
only 2 mg/1 of either potassium ferrocyanide or potassium ferricyanide
in solution, sufficient to kill various fish within 60 to 90 minutes(5,64).
The potassium compounds as far as known, are not used as salt additives,
but should serve to predict similar effects of the sodium ferrocyanide
in receiving waters.
Schraufnagel(9,65) comments that cyanides are toxic to fishlife at con-
centrations of 0.1 to 0.3 mg/1. The U.S. Public Health Service Drinking
Water Standards of 1962(66) state that levels of cyanide above 0.2 mg/1
would constitute grounds for rejection of a public water supply. The
1969 U.S. Public Health Service "Manual for Evaluating Drinking Water
Supplies"(67) further indicates that cyanide in municipal supplies should
not exceed 0.01 mg/1. However it should be noted this manual is primarily
intended as a guide in evaluating these systems and not as a requirement
for approval or rejection of any public water supply. Pertinent data in
unpublished guidelines(68) also suggest the following objectives: desir-
able and permissible cyanide limits in public water supplies - respec-
tively 0.01 mg/1 and 0.1 mg/1; and for body contact recreation, fisheries
use and farmstead supply - a limit of 0.02 mg/1 cyanide. Numerical limits
for cyanide are among the lowest and most critical of all the trace ions
to be tolerated for various water uses. The literature is fairly
generous in giving data on whole body dosages of cyanide and hydrogen
cyanide considered toxic to man(5,62,69,70,71,72), and to domestic
animals(5,62,73). Additional references are available on toxicity of
cyanides to fish, and effects of temperature, dissolved oxygen and
chlorination on varying toxicity(5,62,65,74,75,76,77,78,79,80) .
Schraufnagel(9) has calculated "if sodium ferrocyanide were used...at a
rate of 2 pounds per ton of salt and...the amount of cyanide released is
equal to about one-fourth the additive's concentration, an 800 mg/1 con-
centration of rock-salt deicer would present a hazard to fish life and
water supplies because of the accompanying cyanide. This is equivalent
to about 500 mg/1 of chloride, a value which is frequently exceeded in
road runoff, but to our knowledge has not been exceeded in surface
waters..." Chloride levels exceeding 500 mg/1 were however obtained
for the Kinnickinnic, Menomonee and Milwaukee River waters in January
1969 in the Milwaukee area, as previously cited in Section V of this
report. Schraufnagel also estimates that between one-half to two-thirds
of all rock salt used for deicing in the State of Wisconsin is specially
treated with anti-cake agents.
Recent information(11) indicates that the amounts of sodium ferrocyanide
added to salt stocks have somewhat decreased over the past few years.
The salt industry as of May 1971, cites the figure of 0.5 pounds sodium
ferrocyanide ten-hydrate added per each ton of rock salt, although it
is thought this figure does not necessarily apply to all deicing salts
sold across the country. The industry contends that no environmental
hazards are caused by the cyanide additives. Nevertheless, the conclu-
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sions and recommendations given in this report concerning these additives
are considered highly appropriate and valid, not only because of the
serious nature of cyanides but also due to an absence of field data on
the prevailing level and fate of these additives in the environment.
Corrosion Inhibitors
Special additives are available for reducing the levels of corrosion
and rusting associated with highway salts. Unfortunately, only
fragmentary data exists on past and present use of these additives,
their costs, and proven effectiveness in minimizing corrosion. It is
believed that past use of corrosion inhibitors has been significant.
Three products in particular have received greatest attention:
a) a chromium-base inhibitor used in the 1950's but apparently later
discontinued; b) a sodium hexametaphosphate product manufactured by
Calgon, Incorporated; and c) a product introduced by Cargill, Incorpor-
ated around 1964, which consists of chromate salts mixed with an organic
inhibitor, emulsifier and sodium chloride(5,9,81).
Chromate Additives Used As Rust Inhibitors
In Michigan during the winter of 1955-1956, a chromium-base rust inhibi-
tor had been used with calcium chloride for highway deicing. In one
area of Michigan, however, there was great concern because snowpiles
alongside the road were yellow in color. Fortunately, local personnel
quickly recognized the possible danger of chromium entering into the
nearby groundwater supplies and stopped all further use of the chromium-
treated salt(82). In other parts of the country on certain occasions,
streets and highways have also turned blue, green, or yellow following
heavy road salting.
The U.S. Public Health Service Drinking Water Standards of 1962(66) state
that a concentration of 0.05 mg/1 hexavalent chromium provides sufficient
grounds for rejection of a public water supply. Pertinent data contained
in unpublished guidelines(68) also suggest the following objectives:
desirable and permissible hexavalent chromium limits in public water sup-
plies - respectively 0.02 mg/1 and 0.05 mg/1; for farmstead supply - a limit
of 0.05 mg/1; and for body contact recreation and fisheries use - a limit
of 1.0 mg/1.
Although relatively stringent limits have been placed on hexavalent
chromium, particularly for drinking water, the carcinogenic potential
of hexavalent chromium is good reason to preclude its entry into a
potable water supply(83). Trivalent chromium generally is not con-
sidered physiologically harmful, and the U.S. Public Health Service
Standards do not place specific limits on this constituent. However,
trivalent chromium has been occasionally found more toxic than the
hexavalent ion to some aquatic plants and animals including Daphnia
magna(65).
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Numerous references are given in the literature for effects of hexava-
lent and trivalent chromium on biological sewage treatment processes and
sludge digestion. The trivalent form of chromium is fairly easily oxi-
dized to the hexavalent form, whereas the reaction may be reversed
under the influence of heat, presence of organic matter or reducing
agents. Toxicity of chromium ions to bacteria is governed by many
variables. Under aerobic conditions, the toxicity of the trivalent ion
is generally higher than hexavalent chromium. In the absence of oxygen,
the oxidized form if present, is considered far more toxic to bacteria(65).
The Cargill report in describing its 1965-1967 studies(81), assigned toxi-
city ratings to each of the major ingredients found in its deicing product.
Since chromate salts comprised a small percent of the total product, the
manufacturer indicated that sodium chloride (major component in the
product) "is really the critical toxic ingredient in this formation and
not the chromate salts". This report described studies conducted in
Winnipeg, Canada where 1-3 percent (10,000 to 30,000 mg/1) sodium chlo-
ride was found in puddles after highway salting. Cargill calculated
"this would be equivalent to 40-120 mg/1 sodium chromate"(81). Con-
siderable sampling was undertaken in the Minneapolis-St. Paul area of
storm sewer flows, streams and rivers principally during the winter of
1965-1966 and again in 1967. Samples were analyzed for trivalent,
hexavalent and total chromium and chloride content.
From December 1965 to February 28, 1966, the consumption of Carguard
(Cargill) salt in Minneapolis was 13,258 tons. Samples of December 29
taken of street runoff in Minetonka Village, Minneapolis, showed a salt
concentration of 1.1 percent (11,000 mg/1) together with 24 mg/1 of
sodium chromate. From various sewers in the Minneapolis-St. Paul area,
many values of hexavalent chromium and trivalent chromium were reported
in the range of 0.3 - 0.8 mg/1; and maximum values were 1.7 mg/1 hexa-
valent chromium, 2.2 mg/1 trivalent chromium and 3.9 mg/1 total chromium.
These chromium concentrations were considerably above desired levels.
For surface water samples, Cargill indicated none exceeded 0.05 mg/1
hexavalent chromium. The chloride results for wintertime sewage flows
in the Minneapolis-St. Paul area (presumably both storm and combined
sewers) showed high chloride concentrations as follows: Bridal Veil
Falls Sewer (Minneapolis), January 22, 1967 - 2590 mg/1, February 24,
1966 - 3050 mg/1, February 28, 1966 - 1060 mg/1; Broadway Sewer (St.
Paul), February 8, 1966 - 2670 mg/1; and Smith West Sewer (St. Paul),
February 8, 1966 - 720 mg/1, January 22, 1967 - 2520 mg/1, March 20,
1967 - 1610 mg/1(81).
The Henningson, Durham and Richardson study recently conducted for the
FWQA on combined sewer overflows and stormwater runoff in the city of
Des Moines, Iowa, provided certain data on effects of highway salts on
street runoff(43). Chloride results obtained from the HDR study are pre-
viously described in Section VI of this report. Although considerable
highway salts were used in Des Moines during the winter of 1968-1969,
only a small quantity of chromium - treated salt was deployed over the
study area. Various samples taken from two drainage systems containing
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combined sewage and storm water, showed that total chromium content was
below 0.1 mg/1 in all but one sample. The latter sample contained
0.13 mg/1 chromium. It was presumed all chromium values in the Des Moines
report were given in terms of total chromium. For two storm sewers,
specifically the Thompson Avenue and the 20th Street storm drains, street
runoff contained less than 0.2 mg/1 chromium in all but one sample. Only
within the Cummins Parkway storm system were chromium levels significant.
Snowmelt runoff in this storm drain routinely showed chromium in the
range of 0.1 to 0.3 mg/1 during January-March 1969, and three samples
had chromium levels of 0.35, 0.88, and 1.21 mg/l(43).
Information recently provided by the Salt Institute(11) states that the
single reported supplier of chromium-treated salt, has in the past few
months, discontinued the sale of its product. The results given in this
report on the use of chromium additives with road salt and the levels of
chromium found in the environment, nonetheless, are considered highly
pertinent. These results reflect the fact that chromium additives have
been deployed over a long period of time and probably were supplied from
many different sources. The chromium-treated salt cited above was taken
off the market because cost overshadowed its effectiveness as a corrosion
inhibitor, and not principally due to environmental considerations. The
effects of past use of chromium additives may still be present in soils
and groundwaters, but more importantly, there is no guarantee that these
compounds are no longer being used and will not be used in the future.
Rather than discount the importance of chromium, environmentalists should
be aware that rapid changes are possible also in the deicing industry.
Such changes could lead to new products and additives, which in turn could
either minimize or further intensify the pollution problems caused by
highway deicing.
Phosphate Additives Used As Rust Inhibitors
Another corrosion inhibitor commonly mixed with highway salts is sodium
hexametaphosphate. This type of rust preventative is probably best
exemplified by the product, Banox, manufactured by Calgon, Inc. which
contains sodium hexametaphosphate as the effective ingredient(5,9).
Schraufnagel(9) in 1966, indicated that Banox mixed with salt would
represent an additional cost of $3.00 to $4.50 per ton of salt. Other
reports(5,9) emphasize this product may represent an effective nutrient
source and contribute to eutrophication in surface waters, particularly
lakes and ponds. Sawyer in 1947(84) showed prolific growth of algae
in lakes when the average concentration of inorganic phosphorous was
greater than 0.01 mg/1, and Curry and Wilson(85) suggest that 0.01 mg/1
of phosphorous is the maximum value permitted without producing undesir-
able biological growths(5). Schraufnagel calculates if this additive
is mixed with salt at a one percent ratio, the resulting street runoff
will contain about one part of phosphate for each 200 parts of chloride.
Schraufnagel also speculates if all chlorides applied in Dane County,
Wisconsin during the winter of 1965-1966 had been so treated, the total
phosphate would have been equivalent to the phosphate discharged by the
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Madison, Wisconsin sewage treatment plant over a two-month period of
time(9).
Smith(86) clearly points out the danger of salt additives in that they
may be extremely toxic, especially to fishlife, and produce a variety of
objectionable side effects such as encouraging algal growth. Smith infers
that any chemical proposed for use as a salt additive should be very care-
fully evaluated for the extent of any and all detrimental effects.
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SECTION XI
PUBLIC WATER SUPPLIES, GROUNDWATER, INDUSTRIAL WATER USES
Public Water Supplies
Public water supplies in both the States of Wisconsin and New Jersey
have fairly low chloride content(5). Of 471 water supplies in Wisconsin,
the average chloride level is 13 mg/1 and the median 7 mg/1. Sixty-six
percent of the Wisconsin supplies show 10 mg/1 chlorides or less. Of
356 water sources in New Jersey, the average chloride level is 15 mg/1
and the median 9 mg/1. Fifty-eight percent of the New Jersey supplies
have chlorides of 10 mg/1 or less. For the two States, more than 80
percent of the supplies had less than 21 mg/1 chlorides, and more than
95 percent had less than 51 mg/1 chlorides. However, even relatively
low chlorides may adversely affect certain water uses. In Springfield,
Massachusetts, following the opening of the Massachusetts Turnpike in
1958, a significant chloride increase was experienced in the city's
water supply. Prior to 1958, chloride content was around 2.0 mg/1,
which increased to 12.4 mg/1 in 1966. Although chlorides were still
low, a large industrial water user in Springfield, which requires low
electrical conductivity in its supply, indicated difficulty with this
water. This municipal water supply thereby, was considered far less
desirable for industrial use purposes(4,87).
Groundwater, Well Supplies
The Massachusetts Legislative Research Council Report(4) indicates in
general, highway maintenance engineers do not believe road salts are an
important cause of groundwater pollution. However, when there is salt
contamination of well supplies, the engineers usually place the blame
on the runoff from salt storage piles or improper drainage alongside
the highway(5). Salt contamination of a secondary water supply along
the New York State Thruway was successfully corrected by minor revision
of a particular highway drainage ditch(4,5).
Michigan
A 1963 Michigan study showed that roadside runoff containing highway
salts, in essence, represented contaminated recharge(82). Roadside
wells within the intercepting shallow aquifer in Manistee County
receiving such recharge were found highly vulnerable to chloride
contamination. One of these wells, 300 feet from a highway depart-
ment salt pile, contained 4,400 mg/1 chlorides. In this case,
dissolved salt from the salt storage pile had flowed into a broken
section of storm sewer and moved into the groundwater aquifer(5,82).
Also in Michigan in Delta County, contamination of shallow parts of
the Black River Limestone was caused by salting practices of the
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Road Commission. Construction of sheds and tarpaulin coverings were
suggested for the salt storage areas to minimize salt leaching and
percolation into the water table.
Wisconsin and Illinois
In Wisconsin, five wells were contaminated by salts leaching from a
sand-salt stockpile and the well waters ranged from 19 to 1,345 mg/1 in
chloride content. The local aquifer normally contains less than 12 mg/1
chlorides(5,9). Recently in Peoria, Illinois, the city salt storage
facility was discovered to be the source of serious chloride pollution
to industrial water-use wells along the Illinois River valley(88).
It was concluded that this pollution will probably continue for some
time even after the salt storage facility has been abandoned unless the
salt-saturated earth underlying the storage area is also removed.
Rigorous short-term corrective measures are suggested for this area, but
nevertheless, it may require several years to purge excessive salts from
the aquifer(88).
New Hampshire
The New Hampshire State Highway Department started in 1953 to replace
roadside wells adversely affected by chlorides, and this program has
increased over the years with 37 wells being replaced in 1964, the last
year of reported data. Some of the wells contained in excess of 3,500
mg/1 chlorides whereas these groundwaters are normally around 10 mg/1
chlorides(5). Most of the problems have been associated with shallow-dug
wells and 90 percent of the replacement wells have been of drilled con-
struction. It is reported elsewhere, that up to 1965, the State of New
Hampshire had replaced some 200 roadside wells at a total cost of more
than $200,000(18).
Maine
Throughout the State of Maine, from 1966-1968, Hutchinson conducted
analyses of 115 wells located along various State highways(44,45,52,89).
Samples were taken in April and July-August. Normally sodium and
chloride levels are in the range of 3-4 mg/1, but wells adjacent to
highways showed average sodium and chlorides around 75 mg/1 and 160 mg/1,
respectively. One well had 846 mg/1 sodium and 3,150 mg/1 chlorides.
Another well contained 343 mg/1 sodium and 1,163 mg/1 chlorides. In
1967, about one-half of the wells near a salt-treated road exceeded the
chloride level of 250 mg/1. Groundwaters in most cases showed higher
chlorides in April compared to summer, indicating a relatively quick
response in groundwaters following salt application. It is noted that
Hutchinson's contaminated wells were mainly shallow, hand-dug wells.
Drilled wells insulated with casing are far less susceptible to salt
intrusion.
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Hutchinson in his studies in Maine, furthermore found high levels of
salt in the snowpiles alongside highways pushed by snowplows as much as
20-30 feet from the edge of the pavement. Maximum sodium and chloride
concentrations within a typical snowbank were 713 mg/1 and 585 mg/1,
respectively. At one site, wind-blown snow was found 60 feet from the
edge of the pavement, and also heavily loaded with salt. Based upon
these findings, Hutchinson recommends that "private water supplies,
wells or ponds, should not be located within a minimum distance of
40 feet from highways because of possible contamination by salt ions".
He also suggests certain management practices can serve to partially
alleviate the salt problem, e.g., providing intercepting surface drains
at the edge of the roadway and chemical treatment of affected soils(44,
45,52,89).
Ohio
At Barbertown, Ohio in 1949-1950, it was found that groundwater on the
opposite side of the Tuscarawas River from a salt disposal area con-
tained more than 20,000 mg/1 calcium chloride caused by induced infil-
tration. Groundwater resources could not be developed on either side
of the river, and consequently, Barbertown had to close down its entire
municipal well field(90,91).
Connecticut
For the State of Connecticut, two cases of water supply contamination
caused by highway salts are described by Scheldt(92). Tastes and odors
in one municipal water supply were duly noted and attributed to the
presence of sodium ferrocyanide (an anti-caking agent) originating from
salt storage piles. Recommendations were made that amounts of sodium
ferrocyanide mixed with the salt be reduced from 250 ppm to 50 ppm, and
that suitable covering be provided for the storage piles to minimize
salt penetration into the groundwater aquifer. The other instance in-
volved contamination of groundwater from salt storage piles adversely
affecting the well supply serving four families. Excessive salt content
not only affected taste and quality of the potable water supply but also
was reported responsible for corrosion damage to the plumbing and heating
systems. Regarding drainage from salt storage piles, there should be no
question that such severe contamination of water supplies must be
stopped(92).
Massachusetts
The State of Massachusetts which deploys large amounts of highway salts,
due to these deicing compounds, has experienced a wide range of environ-
mental pollution problems. During the winter of 1966-1967, approximately
170,000 tons of sodium chloride and calcium chloride were applied to
9,000 miles of State highways and toll roads in Massachusetts(1). These
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figures do not include deicing materials used by the City of Boston and
the various counties and towns in the State.
In 1964, the U.S. Geological Survey commenced groundwater sampling along
heavily travelled highways located within a 50-mile radius of Boston, Mas-
sachusetts. Small diameter observation wells were sunk 19 to 60 feet
deep and located 15 to 30 feet off the highway. The study, undertaken
in joint cooperation with the Massachusetts Department of Public Works,
at the present time comprises more than 40 wells situated within 6 test
areas. The highways passing through the test areas include both relatively
new and old roadways. The overall objective of the study is to trace the
spread of highway salts through roadside soils by means of long-term
measurement of vertical and lateral movements(19,93,94). Tentative
findings show that a large percentage of the groundwaters are approaching
250 mg/1 chlorides, which is the upper limit recommended for public water
supplies. The U.S.G.S. investigations, contrary to many previous studies,
show a relatively slow movement of salt through the unsaturated zone,
then through the groundwater. In one case where the water table was only
2 feet below the ground surface, approximately 12 months lapsed before
the salt horizon reached the observation well only 30 feet from the
highway. Other lapse times varied from a few months to a few years.
Peaks in chloride data generally occur in the period July to December.
From these results, as many as 70-80 discrete steps are perceived in
downward percolation of salt into the observation well zone. Recharge
of groundwater by snow continues through the winter, although at reduced
rates compared to the rest of the year. Chlorides are steadily increas-
ing each year. Continuing studies planned beyond 1970 should further
define the chloride curves, which could extend beyond the 250 mg/1
limit(19).
The Massachusetts Legislative Research Council in 1965(4) reported:
"It is well known that both well and surface supplies of drinking water
have been affected by increased use of salts". In mid-1964, the Massa-
chusetts Department of Public Health alerted all water supply authorities
in the State to the danger of chloride contamination and consequently
some water supplies were abandoned. The Department of Public Health
described drainage originating from salt storage piles and street runoff
as two important sources of hazard. Accordingly, the State Department
of Public Works was instructed to cooperate with the Department of Public
Health in efforts designed to minimize these conditions(4).
Specific cases of water supply contamination in Massachusetts merit our
attention. The town of Becket in 1951 found the water in one of its
wells had drastically increased in chloride content to about 1,360 mg/1
whereas the other town wells showed a rise in chlorides to about 50 mg/1.
These adverse changes were attributed to a salt storage pile located up-
hill from the well field(95). In recent years, the North Chelmsford
Water Commission, through action of the town selectmen, have threatened
court action to remove salt stored in a highway garage which was thought
to endanger the district well field.
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Private and public water supplies in the Weymouth, Braintree, Randolph,
Holbrook, Auburn and Springfield areas were among those believed to be
affected by highway salts, in Massachusetts. Large salt storage piles
located at Routes 128 and 28 in Randolph, and located alongside the Blue
Hill River, were suspected of introducing contamination into Great Pond,
which serves as water supply for Braintree, Randolph and Holbrook. Water
supplies in Tyngsboro and Charlton were similarly experiencing salt
increases, and two wells in Charlton were likely to be abandoned(96).
Also, in the general Boston area, snow removal and disposal practices are
cited as contributing to heavy salt content in the Mystic Lakes(97).
Early in 1970, the Massachusetts Commissioner of Public Health was re-
ported to have given a warning to all physicians and local health boards
regarding the care of patients on salt-free diets (specifically sodium-
free diets) within salt-affected communities(87). Sodium chloride
increases had been recorded in the water supplies of 63 Massachusetts
communities at least in part due to highway salting and salt storage
piles. Sodium intake must often be restricted for those persons experienc-
ing chronic congestive heart disease, high blood pressure, renal disease,
cirrhosis of the liver, and pregnancy(87). The report indicates that
persons in normal health will perceive no effects using these water supplies,
but adjustment may be necessary for salt-free patients including possible
use of bottled water. Many of these communities now have water containing
in excess of 20 milligrams salt per quart (21 mg/1), compared to the upper
limits of 25-40 milligrams per quart (27-42 mg/1) that are being prescribed
for many salt-free patients. The Massachusetts findings are supported
by previous guidelines of the American Heart Association(5,98,99), which
for people on moderate or strict sodium diets, indicate maximum limits
of 20 mg/1 sodium permitted in drinking water. The Massachusetts medical
alert specifically named the 63 communities so affected(87).
Industrial Water Supplies
On the subject of industrial water use, Schraufnagel(9,18) found that
chlorides have been responsible for the corrosion of various metals
including stainless steels. Schraufnagel cites a previous recommendation
of the Ohio River Valley Water Sanitation Commission that monthly average
chloride concentrations in the Ohio River not be permitted to exceed 125
mg/1 in order to minimize corrosion of industrial structures. The Ohio
River Valley Water Sanitation Commission further recommends that 250 mg/1
chlorides not be exceeded at any time to combat corrosion. Schraufnagel
also cites an industry statement that "increasing the salinity average
above the then 40 to 50 mg/1, or lengthening the periods of high salinity,
would increase corrosion of all metals used in the handling system"(9,18).
Although McKee and Wolf in 1963(65), in their extensive review of the
literature, found that 50 mg/1 chloride generally would not be harmful
to industrial water users, they also advise that no "standard" chloride
level would be acceptable to meet the demands of all different industrial
processes. McKee and Wolf summarize chloride tolerances for various
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Industries as follows: food canning and freezing - 760 mg/1; 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(5,65).
Other reviews on water quality needs for industry including chloride
limits also are available(100,101).
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SECTION XII
CORROSION OF VEHICLES
From the standpoint of the public, there is considerable controversy as
to whether highway salts contribute to automobile corrosion. Some cri-
tics contend that all rusting on vehicles is due to highway salts. On
the other extreme, the statement is frequently made that salts have no
harmful effects whatsoever to the finish on cars and trucks. The real
situation probably lies between these two extremes. Various changes
introduced by automotive manufacturers over the past ten years which
include electroplating; deep-dip priming; special paints particularly
the acrylic finishes; use of aluminum parts in place of chrome; under-
coating; and redesign of trouble-spots where rust occurs, have appreci-
ably reduced this corrosion potential(4). However, at the same time
the overall use of highway salts has increased significantly. It is
extremely difficult to define potential and existing corrosion due to
highway salts because of the lack of reliable and conclusive data in
the general literature.
Cost Damages
Besides corrosion of vehicles, airborne salt crystals may be carried onto
structural steel, buildings, house sidings and other property alongside
streets and highways, causing appreciable corrosion damage to these
structures. The amounts of airborne salt may comprise up to 10 percent
of the total salt spread during a given storm(4). A rough order of
damage magnitude is given in a 1968 report for the Society of Automotive
Engineers which indicates "the private car owner pays for rust destruc-
tion at the rate of about $100 a year"(26). Lockwood, et. al.,(6) express
little doubt that highway salts contribute substantially to corrosion
of vehicles.
How Corrosion Occurs
Various studies have been conducted concerning the corrosive effects of
highway salts on car underbodies and the outer decorative surfaces of
vehicles. Corrosion commences when the outer paint finish is broken or
cracked so that water and/or brine solution comes in contact with the
underlying metal. Once corrosion starts it can spread rapidly under the
paint film in any direction. The outer finish is forced upward exposing
both rusted and new metal which hastens the corrosion process. Breaks
in the painted surface are the result of flying gravel, stones, highway
debris; blows and scratches particularly on car doors; and poorly fit-
ting parts on a car, e.g., molding strips, trunk lids, etc. Crevices
which tend to retain water and brine also make these areas susceptible
to attack. Corrosion is caused by atmospheric oxygen combining with
exposed metals, especially iron and steel, in the presence of moisture
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to produce iron oxide, otherwise known as rust. The literature points
out that salt and brine as such, do not cause corrosion(A). Neverthe-
less, it is well known when the metal is exposed to salt water, the
electrolytic reaction converting the metal to its oxide will proceed
at a much faster rate compared to water alone(102).
The normal conditions under which an automobile must operate are condu-
cive to maximum potential corrosion of exposed metal surfaces. During
the wintertime, vehicles are frequently exposed to salt spray, dirt,
grime, etc., and this material accumulates particularly on the underside
and lower parts of the car body. Studies in Iowa show for normal appli-
cation of highway salts, about 50 percent of the salts are removed from
the roadway by traffic, 25 percent is carried off by surface water, and
about 12 percent leaches through the soil(103). We do not know what
part of this 50 percent is retained on the car body. Under such condi-
tions, salt and brine may be responsible for considerable damage to
automobiles.
Comparative Studies
Some of the earlier corrosion studies involved large numbers of CMC
cars located in various U. S. cities which were closely inspected for
corrosion damage under paint films and chrome surfaces. These studies
generally showed the percentage of cars experiencing corrosion was
much higher in locations using highway salts, as compared to warm cli-
mate locations. One such survey found that 58 percent of cars examined
in Detroit had corrosion along chrome moldings, whereas this ratio was
only 35 percent in Miami, Florida(4).
Another survey made of 14,000 cars in 44 States indicated where little
or no road salts were used, the chrome condition was judged good for
95.6 percent of the cars. In salt application regions, the percentage
of cars with good chrome was only 80.4 percent. The chrome trim on
cars is especially vulnerable to rusting since it is highly porous, and
moisture and oxygen may more readily penetrate the underlying steel.
Chrome is less important today, being partially replaced by aluminum(4).
A special corrosion study only recently completed by the American Public
Works Association, evaluates the effects of deicing salts and rust inhibi-
tors upon nine Falcon automobiles tested for up to three years in the
Minneapolis, Minnesota area(21). Findings show that up to 50 percent of
vehicle corrosion can be attributed to deicing salts on streets and high-
ways. Rust inhibitors under controlled use, especially the Carguard product
manufactured by Cargill, Inc., are found to reduce corrosion of bright
metal parts, but do not provide similar protectibn for sheet metal parts.
The APWA report contains recommendations on need for a) more comprehen-
sive purchase specifications by governmental authorities; b) post-assembly
corrosion protection; and c) closer examination of highway deicing pro-
cedures (21) .
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In 1964, various reports(4,104,105) indicated that corrosion of automobile
trim systems was increasing due to the greater use of calcium chloride
on U.S. highways. Subsequent investigation(4) produced the following
findings:
a. At low humidity, calcium chloride is more severe than
sodium chloride in its attack, but there is essentially
no difference if the surfaces are continuously wetted.
b. Stainless steel is more susceptible to attack than
other trim systems.
c. Corrosion can be alleviated by improving exterior
trim systems, making salt products more alkaline,
and by washing cars frequently during winter(4).
Mufflers, Tailpipes
The short life of automobile mufflers and tailpipes has frequently been
cited as a damaging consequence of using highway salts. It has been
said that replacement of these underbody parts costs the Nation about
$500 million annually. However, conflicting information has been sup-
plied by one automotive company official stating that muffler and tail-
pipe deterioration is the result of engine emission acids rather than
salts. Likewise, there is diverging opinion as to whether industrial
and other air pollution may cause generalized corrosion in automobiles(4,
106).
Rust Inhibitors
The merits of adding rust inhibitors to road salts have not been satis-
factorily proved. A committee attached to the Detroit Engineering
Society previously concluded the use of inhibtors is of doubtful value
in protecting the exterior finish of automobiles. However, certain
agents may reduce the weight loss of metals susceptible to corrosion.
Comparison studies are open to question but the majority of results do
suggest that the car owner benefits little from the use of these inhibi-
tors (4). Canadian researchers have similarly found that the large costs
for adding an inhibitor to road salts generally are not justified. The
Canadian report concludes these inhibitors slow down, but do not eliminate
the corrosion of vehicles caused by highway salts(4).
Other Preventative Measures
The best rust prevention treatment recommended by automotive engineers
is frequent car washing. The general literature also advises the car
owner that his best protection is frequent washing and periodic waxing.
However, more than one reference cites waxes, chrome lacquers and
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similarly applied coatings as possibly doing more harm than good because
the protective coating may serve to seal in moisture thereby promoting
corrosion. Conflicting thoughts likewise are expressed concerning the
merits of undercoating, because in time, chipping and peeling of the
undercoat occurs. The original car paint, if applied to the underside
of the car, may, because of its tighter bond, reduce the corrosion
potential compared to undercoating. Regular car washing is relatively
effective not only in removing road salts, but also in minimizing dirt,
road grime, industrial contaminants, road tars, etc., all of which are
detrimental to car finish and appearance(4).
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SECTION XIII
EFFECTS ON HIGHWAY STRUCTURES AND PAVEMENTS
Review by Massachusetts Research Council and Findings of
U.S. Highway Research Board and Representative States
The 1964 study of the Massachusetts Legislative Research Council(4) gave
particular attention to a Symposium of the U.S. Highway Research Board
held in 1962, which considered effects of deicing chemicals on highway
structures(107). The Board was primarily concerned with bridge floor and
deck deterioration in portland cement concrete structures. The Symposium
noted that blame for public works damage in question could not be placed
solely on deicing agents and that the available data was inconclusive.
The evidence did indicate that concrete structure deterioration could be
at least partially attributed to inadequate field inspection and failure
to follow proper techniques in mixing, transporting, laying and curing
the concrete. Air-entrained concrete introduced in the late-1940's and
which later gained widespread acceptance, did not meet the fullest ex-
pectations unless construction practices were rigidly controlled. It was
emphasized that various concrete mixes, even air-entrained concrete, over
the first six months do not develop their maximum resistance. If salts
are applied over this period of time, there could be significant struc-
ture damage. Laboratory studies have also shown that sodium chloride and
calcium chloride may have damaging effects on concrete. Defects caused
in bridge structures include hairline and larger cracks, splitting or
shelling out of the surface layer of the deck, aggregate popouts, scaling,
surface pitting, chipping, peeling, progressive deterioration from the
edges inward, i.e., raveling, and leaching of the deck, gutters, hub-
guards and sidewalks(4,107).
The State of Illinois made its recommendations to the Symposium as follows:
a) improving the quality of concrete used in structures and pavements;
b) improving drainage design for better removal of brine and abrasives
from bridge surfaces; c) more rigid control over construction practices;
d) better maintenance; and e) less corrosive ice-removal compounds. On
the other hand, the State of Massachusetts did not find that salts were
detrimental to bituminous concrete pavements or bridge decks covered with
cement concrete(4,107).
Highway departments and others have used various materials and surface
treatments in order to protect concrete surfaces from damage by deicing
salts. However, experience indicates such measures are usually unneces-
sary if concrete is properly laid. The U.S. Bureau of Public Roads con-
ducted a series of tests which showed that surface protective coatings
are generally of little benefit in minimizing concrete scaling, although
in a few cases, certain admixtures are beneficial. The Massachusetts
Research Council, in their review of the literature, describes two short-
comings in bridge maintenance which may significantly contribute to con-
crete damage: a) failure to clear-away chemical-laden accumulations of
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snow and ice along gutter and sidewalk sections; and b) failure to remove
soil, debris and other obstructions from the gutters, causing poor drain-
age. Standing salt water can saturate underlying concrete, lowering its
resistance to damage, and this water may also seep through construction
joints and cracks causing interior damage to the bridge deck(4,107).
Application of deicing salts to concrete roadways in the New York Thruway
system have caused few difficulties, but serious problems have been en-
countered with bridge structures. In order to counteract progressive
deterioration of concrete bridge decks, a preventive and corrective
maintenance program was established. Additionally, to minimize the
effects of salt brine and water passing through bridge expansion joints
onto the abutments and piers, the procedures for painting steel members
in the structure were modified(4,107).
The report by the State of Kansas to the Symposium gave evidence that
highway salting in Kansas is greatly accelerating the scaling of concrete
structures. The chlorides also contribute to rusting of reinforcing
steel which leads to concrete spalling. Recommendations were given that
all decks be sealed with a water repellent material and then carefully
covered with a bituminous coating. It was further suggested that steel
and timber be waterproofed with paints, asphalts, resins, silicones or
equivalent(4,107,108). Similar experiences in Ontario, Canada, however,
indicate that asphalt surfacing over concrete tends to trap considerable
salt onto the surface of the concrete. The salt solution not only pene-
trates under the asphalt at the curb zone but also enters into cracks in
the asphalt. Excess moisture sealed in by the waterproof coating was
considered detrimental to the bridge decking. The Ontario study concludes
that adequate drainage must be provided, and no surface coating can ade-
quately overcome defects in design, construction or materials which lead
to water and salt being trapped on the bridge decks(4,107).
Comments of Calcium Chloride Institute and Portland Cement Association
A 1961 report by the Calcium Chloride Institute(109) stresses suitable
precautions must be taken in using deicing chemicals and that scaling
of concrete attributed to salt "is not a chemical attack". The
Institute infers that scaling will occur when concrete is less than
"ideal". This study emphasizes chemicals should not be used on air-
entrained concrete less than 12 months old unless specific measures
are followed. For non air-entrained concrete, chemicals should not be
applied for at least one year, and in the maximum case, up to four
years(4,107). With deicing chemicals, the ability of the chlorides to
attract water, and their capability in depressing the freezing tempera-
ture of liquids, represent potential hazards to concrete. Salt
application will increase the number of freeze-thaw cycles and raise
the level of water in the concrete which leads to scaling and spalling.
Another study conducted in Massachusetts concludes that highway salts
can penetrate the capillaries, particularly in non air-entrained concrete,
and cause disruption and scaling of the concrete material at an acceler-
ated rate(4,107).
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The Portland Cement Association correlates surface scaling of concrete
pavements with the increasing use of sodium chloride and calcium chlo-
ride. The severity of scaling is said to depend upon the amount and
frequency of salts used. The Portland Cement Association strongly
recommends air-entrained concrete where frost action and salt application
occur. The Association cautions that concrete pavements may be damaged
by heavy salt applications, especially relatively new roadways. Pave-
ments less than four years old are much more vulnerable than older high-
ways. Protective treatments are advised in most cases particuarly for
concrete pavements less than four years old. Without protective treat-
ment, the Portland Cement Association recommends that heated abrasives
be substituted(4,107,110,lll). The Massachusetts Legislative Research
Council Report specially notes New Jersey provisions, which prohibit
the use of salts within 500 feet of a bridge 50 feet or more in length(4).
Other Deicing Compounds
Concerning deicing compounds other than the chlorides, caution was ex-
pressed in a concrete industry trade journal as early as 1961, on the
corrosiveness of many of these chemicals to concrete. Certain of the
agents were found to contain large amounts of ammonium nitrate. These
materials are sold under trade names without reference to composition,
and also sold in small plastic bags being promoted for sidewalk and
driveway use. Unfortunately, the harmful effects of the ammonium
compounds and some of the other agents to concrete surfaces, seem to
far outweigh their merits in melting ice(4,18,107,112).
Effects on Underground Utilities
Schraufnagel(18), based upon a fact-finding study by Hamman and Mantes(113),
describes the corrosive damage of deicing salts upon underground tele-
phone lines and water mains. The Bell and Chicago Telephone Companies
previously noticed that corrosive failure of underground cables and
transformers was occurring in proximity of highway salting. In Buffalo,
New York, the National Association of Corrosion Engineers surveyed
the chloride content of manhole waters at 25 locations over a three and
one-half year period. Of 175 samples taken in Buffalo, 74 samples had
chloride levels in excess of 1,000 mg/1. In Milwaukee, Wisconsin in 1965,
the Water Engineering Division, studying the chloride content of ground-
waters near buried water mains, found chlorides of 170-225 mg/1 near
streets routinely salted, compared to 10 mg/1 for groundwaters in unsalted
areas. Concern was raised as to foreseeable corrosion damage to the water
distribution system.
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SECTION XIV
EFFECTS ON SOILS, VEGETATION, TREES
Deicing salts applied to roads and highways are eventually carried by
surface runoff into roadside ditches and receiving streams, or these
salts will infiltrate into the soils bordering the highway. Through
infiltration, deicing salts are carried into groundwaters, remain in
soil solution, or are absorbed by soil particles. Soils may be
adversely affected as to their fertility and their ability to support
desirable plant growth. Because of poor soil conditions, the uptake
of salt ions by trees and vegetation, and the toxic properties of these
ions, moderate to severe damage is frequently inflicted upon grasses,
vegetation, plants, shrubs, bushes and trees. Exposure of plantings
is usually most severe in the highway median strip.
This section of the report reviews effects of highway salts upon road-
side soils, vegetation, and trees. However, in contrast to previous
sections of the report where the literature was relatively sparse, there
are numerous reports in this area of study. Keeping in mind the objec-
tives of this report, we have been quite selective in the particular
references used for judging effects of salts on soils and plant biota.
The materials presented in this section are broadly arranged into
discussion of: a) general soil chemistry; b) nature and movement of
salts through soils; c) salt uptake by plants and correlative effects;
d) salt tolerance of individual species; and e) effects of salt spray
on vegetation.
Soil Chemistry, Salt Movement Through Soil Into Plants
Many researchers, particularly those in the western U.S., have studied
effects of salts on plants and the occurrence and movement of salts
through soils. The problem can be viewed in many ways although total
soluble salt content (salinity), and the levels of specific ions are
of great importance. Symptoms of injury in plants and trees include
advanced coloration of foliage, leaf scorch, defoliation, stunting,
and eventually, die-off. Symptoms may however be similar whether due
to sodium or chloride, high salinity, or drought conditions. Also,
because sodium and chloride salts in themselves give rise to salinity,
it is oftentimes difficult to determine the extent of damage caused by
each factor(114).
Salinity or total soluble salts cause interference with the mechanism
whereby a plant absorbs moisture from the soil. Soil water enters the
plant root through a membrane across which an osmotic pressure differen-
tial is maintained. The flow of water through the membrane is in the
direction of higher salt concentration and therefore, increasing salinity
in the soil makes it more difficult for water to be taken in by the
plant. The sensitivity of a plant is related to the type of soil present,
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the soil "wilting" percent moisture, and amount of salinity per unit
weight of soil. Besides short-term damage caused to plants by saline
soils, some data show that low salinities over extended periods can
cause cumulative damage in due time. In general, other factors being
equal, plant growth will be retarded by increased salinity because of
increasing salt load or reduced soil water. In similar context, when
salinities are raised, more water will be required, to be supplied by
rainfall or irrigation, in order to maintain previous plant growth.
Leaching of soluble salts from the soils, is inferred as an alternative
procedure(114).
The sodium, chloride, and calcium ions are of special significance when
deicing salts are used. Chloride per se, is not reported to cause ad-
verse effects on soil characteristics, although it does add to salinity.
Chloride ions possess a negative ionic charge the same as that of soil
particles. Consequently, chloride ions freely flow through soil parti-
cles compared to the cations such as sodium and calcium which are
absorbed onto soil particles or precipitated by soil reactions. However,
high levels of chlorides do appear as pollutants in groundwater and as
toxicants taken in by plants. Excessive chloride accumulates in the leaves
causing leaf burn, but also seems to locate in the twigs(52,114).
The sodium ion is important because it not only changes the character
of the soil but also exerts a toxic effect on various plants. Cations
are absorbed onto soil particles and maintained in equilibrum with
cations in the surrounding soil water. If sodium salts are applied to
the soil, the equilibrium is changed whereby sodium ions replace calcium
ions on the soil grains. With loss of calcium, the soil may become less
fertile and also less permeable. High sodium levels can cause dispersion
of collodial soil particles, which eventually leads to alkali soils
characterized by lack of aggregation and structure, and poor drainage
properties. Sodium is often considered toxic to trees and other plants
with translocation to the leaves and twigs causing burning and browning.
Although thought to be generally non-essential to plant growth, sodium
can interfere with uptake of potassium, an essential plant element, and
even serve in its place(114,115).
Calcium is a commonly found element in soils and appears essential for
plant growth. Calcium may be added to soil as lime or gypsum to replace
undesirable sodium ions and restore soil fertility. However, excessive
calcium can cause high salinity and may be specifically toxic(114).
The 1963-1964 winter season was the first time the National Capital
Region of the National Park Service authorized the use of sodium
chloride on Park roads in the Washington, B.C. metropolitan area.
Various research included microscopic examination of Kentucky bluegrass
leaves and roots, and observations of damage to vegetation and trees
along approximately 70 miles of Park roads. Although this study con-
ducted in 1964 did not reveal detectable injury to plant biota, the
results provided comparative background for significant salt damage
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experienced the following winters. In his early 1964 studies, Thomas(116)
found the most important factors associated with sodium chloride injury
were:
1) Amount of salt applied
2) Amount of salt reaching vegetation, and retained
and absorbed by the plants
3) Availability of water
4) Temperatures during plant growth
5) Wind velocities
6) Soil characteristics
7) Dormancy of plants and onset of plant growth
8) Plant tolerances and individual species sensitivities
9) Cumulative or long-term effects of salt
Salts reaching vegetation are reduced where curbing and storm sewers
are established. Available rains may leach out excessive salts from
soils but Thomas from his review(116) indicates this rainfall in humid
regions must do more than merely saturate the soil in order to produce
adequate salt leaching. Light rains appear to have little effect.
Sodium chloride, total soluble salts, particular soil types, and shallow
plants and soils will serve to intensify "drought" conditions. It had
been previously recommended that total soluble salts in soils be main-
tained below 100 ppm, but as early as 1964, soluble salts adjacent to
salted parkways were already in the range of 1,860-2,580 ppm (1 ppm =
1 yg/g or 1 mg salt/kg soil). It is extremely advantageous if salts
can be leached from the soils before active plant growth starts in the
spring. For this reason, a late salt application around the beginning
of March may be much more harmful than a heavy mid-winter application.
Thomas(116), based upon his review, also points out that damaging effects
of salts may not become apparent for several years, that sub-lethal salt
doses may cause plants to become more generally susceptible to disease,
and that salt changes in soils and vegetation may more subtly, but more
importantly, be affecting entire natural ecosystems.
Prior and Berthouex(16,114) studied the movement and accumulation in
roadside soils of highway salts applied by the Connecticut State Highway
Department. Soils were sampled at the surface, one, two and three foot
depths, and at distances 5, 25, 50 and 100 feet from the highway. Soil
samples were analyzed for total soluble salts, chlorides and sodium.
Greatest salt concentrations were found near the highway and close to
the soil surface, as anticipated. In a number of cases, salt was shown
as travelling more than 100 feet laterally from the highway, but the
predominant movement was downward. Total soluble salts, sodium, and to
a lesser degree, chlorides, were significantly higher within the soils
in January-February compared to the other months of the year. This
seasonal difference was also noted in the soils 100 feet from the highway.
Salts were readily leached from the upper several feet of soil and by
April the majority of salts were displaced downward. Salt concentrations
were reduced to minimal levels through the summer and fall before salt
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applications were due to be resumed the following winter. Since all
data were collected in one year, no estimate is possible of salt
accumulations in successive years(114).
Wintertime Infiltration
The question of how much infiltration occurs in the wintertime is quite
important in predicting the portion of highway salt loads contained in
highway drainage vs. that entering the soil horizon. The majority of the
literature tends to indicate that infiltration will occur throughout the
year except when the ground is frozen. During the winter, we may there-
fore expect little or no infiltration, and snowmelt would largely take
the form of surface runoff. However, observations in Massachusetts and
other locations indicate this may not be the case. In the Boston area,
long-term studies have shown that infiltration and groundwater recharge
continue throughout the winter although at slower rates(19). Prior(114)
in Connecticut, found almost normal infiltration occurring in forest
soils frozen to a depth of 4 inches. Light textured soils allow for
greater infiltration during times of freeze. Prior indicates even with
frozen ground conditions, at least some water and salt will infiltrate
into the roadside soils.
Salt Levels in Roadside Soils Along Maine Highways
Hutchinson extensively studied sodium and chloride levels in soils
adjacent to salted highways in Maine from mid-1965 through 1969.
Hutchinson selected his sampling sites on the Maine Turnpike and
Interstate 95. Soils were collected at 6 and 18-inch depths, and in
5-foot increments from the edge of the road up to a distance of 45
feet. A minimum of 12 borings was composited for each sample. Samp-
ling sites were also established along a number of other major highways
in the State. In this second series, samples were secured at discrete
distances of 0, 30 and 60-feet from the road embankment(115,117).
Different sections of Interstate 95 were opened in various years, and
Hutchinson was able to correlate sodium and chloride levels with the
number of years these roadside soils had received deicing salts. One
section of roadway after a single winter demonstrated a five-fold
increase in sodium at the 6-inch soil depth near the edge of the high-
way. Increases in sodium were shown at the 6-inch depth up to 30 feet
from the highway. At the 18-inch soil depth, this increase was evident
over 10 feet lateral distance. Background sodium values were generally
30-40 ppm (yg/g), compared to a maximum value of 235 ppm sodium found
after the one winter of salting. Chloride background values were all
recorded as trace amounts. After salting, chlorides at the 6-inch
soil depth varied from 30-174 ppm over the 45 feet of lateral distance.
At the 18-inch soil depth, chlorides ranged from 38-107 ppm(115,117).
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Four other sites on the Maine Turnpike and Interstate 95, which had
received yearly salting for 2,3,5 and 18 years, respectively, were also
sampled. All soils in this study series were derived from marine sedi-
ments adding uniformity to the results obtained. Compared to background,
the sites salted for 2 and 3 years, showed sodium increases in the 6-inch
deep soils of 4 to 8 fold near the edge of the highway. Sodium content
was significantly high at both the 6 and 18-inch soil depths extending
outward some 30-35 feet from the highway.
The section of highway receiving salting over 18 winters indicated very
high sodium levels in the soils directly adjacent to the road. High
sodium content prevailed over the entire 45 foot lateral distance
sampled. Compared to the background levels of 30-40 ppm, the sodium
content averaged 333 ppm for all soil samples taken at the 6-inch
depth; the maximum value was 488 ppm for surface soils 5 feet from the
highway. For all samples at the 18-inch depth, the average sodium
content was 218 ppm, with a maximum value of 307 ppm for the soils
5 feet off the roadway(115,117).
Chloride levels for the above four highway sites showed the same soil
relationships as sodium but quantitative results were lower since
chloride moves more rapidly through the soils. With trace amounts of
chloride serving as background, the sites receiving 2 and 3 winters
of highway salting exhibited 46-100 ppm chlorides in the surface soils
next to the road, diminishing to 12-24 ppm in the surface soils 45
feet from the road. The site with 18 winters of salting had 183-217 ppm
chlorides in the surface soils 5-15 feet from the roadway diminishing to
115-117 ppm in the outer periphery(115,117).
At other highway sites in the State of Maine sampled by Hutchinson,
(a total of 22 locations), the levels of salt ions in surface soils
exhibited wide variation, with sodium ranging from 14 to 1,056 ppm
and chlorides ranging from 8 to 768 ppm. The various roadside soils
across the State, on the basis of being collected 0, 30, and 60 feet
from the highway, showed respective average sodium values of 281, 139
and 96 ppm. Associated chloride values were respectively 116, 79, and
54 ppm. Sodium and chloride content of soils immediately adjacent to
the highways were 6 and 115 times higher than are normal for soils in
the State of Maine. Considering the width of highway right-of-ways,
it was concluded that private properties and soils were very much be-
ing affected by highway salting(46,89,117).
At one roadside location where the soils were examined in greater
detail, Hutchinson found that the cation exchange capacity of the Buxton
soil series present at this particular site was 23 percent saturated
with sodium cations. In the western U.S., soils having a sodium satura-
tion greater than 15 percent are designated as "alkali" soils. A number
of roadside soils in Maine may likewise be placed in this "undesirable"
classification. In summarizing Hutchinson's findings, it is seen that
levels of both sodium and chloride ions in the soils along major highways
in Maine have increased markedly as a result of highway deicing. It is
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clearly demonstrated that deicing ions have moved laterally at least 60
feet and downward at least 18 inches with time over which these roadways
were salted. A strong correlation was shown between the consecutive num-
ber of years of salting at a given location vs. the increasing levels of
sodium and chloride ions in adjacent roadside soils. The carry-over and
accumulation of salts within the soils from one year to the next was
strongly suggested. Hutchinson also expresses the need to study soil
treatment measures using compounds such as calcium sulfate and calcium
carbonate in flushing excessive sodium from damaged soils. These soil
treatments may be required only once every two or so years(46,89,115,117).
Chloride Content of Soils and Plants on National Park Grounds,
Washington, D.C.; Correlation with Plant Injury and Death
In continuation of the study on effects of salts on National Park lands
in Washington, D.C. during 1964, ensuing investigations were carried out
by Thomas and Bean in 1965(118), and Wester and Cohen in 1967(119).
Thomas(120) also reports upon a qualitative analytical method used to
determine "excessive" or "normal" amounts of chloride present in soils
and the roots of Kentucky bluegrass receiving highway salts. In March
1965, extensive die-off of bluegrass sod was noted next to sidewalks
and roads in National Arlington Cemetery and within the parking lot of
the National Capital Regional Office Building. In March-June 1965, samples
were collected of soils and plant roots for chloride analyses from the salt-
affected areas, and also from various parkways in and around Washington,
D.C. Control samples were taken in areas not receiving salts. The study
attempted to correlate the "vigor" of vegetation with the presence of
chlorides. Unhealthy conditions included observation of dead, chlorotic
or stunted plants.
Thomas and Bean(118) found the time of the year at which tests are con-
ducted to be quite important. For example, salt could kill the plant,
be leached out of the area, and not suspected or proved later as the
cause of death. On the other hand, with adequate salt leaching there
could be subsequent plant recovery. Also, salt uptake by the plant
could cause it to be slightly chlorotic, but it is not certain when and
if these plants would show significant damage. However, another winter
of salting would likely aggrevate this condition. Although observed
damage was confined mostly to areas proximate to road shoulders and
walkways, excessive chlorides were found in soils 20 feet from the edge
of the road. Good correlations were established between the state of
health of bluegrass vs. ppm soluble salts in soils (break point of
843 ppm); and between excessive chlorides in soils vs. ppm soluble salts
in soils. Qualitative (excessive) soil chlorides were considered a more
reliable indicator of salt injury and loss of plant vigor than the
measurement of chlorides in plant roots. The authors conclude with the
increasing use of salts in the Washington, D.C. area, that decline and
death of vegetation will continue(118).
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Following the relatively severe winter of 1966-1967 in the Washington,
D.C. area during which 37 inches of snowfall occurred, Wester and
Cohen(119) found severe salt damage to vegetation. The effects of
heavy wintertime salting were compounded by a serious lack of rainfall
in April, 1967 which provided little opportunity for natural leaching
of salts from the root zone. Observed and recorded plant damage was
most prevalent in Kentucky bluegrass, California privet, Canadian
hemlock, sugar maple, American elm and Quebec linden. Samples were
taken for qualitative levels of chlorides in plant leaves and quantita-
tive levels of chlorides in soils. Both affected and non-affected areas
were sampled for comparative results. Much of the damage was associated
with accumulations of salts previously deposited by snowplows and front-
end loaders. Chloride concentrations of soils in non-salted areas varied
from 0.000 to 0.001 percent, compared to levels of 0.01 to 0.09 percent
for salted areas (note 0.01 percent = 100 ppm, and 0.1 percent = 1,000
ppm). The high chloride content of 0.09 percent was derived from roadside
soils underlying a privet hedge in Fort Myer, Virginia in August 1967,
where almost all plants were killed.
At the Walter A. Reed Army Medical Center in Washington, D.C., severe
damage in 1967 was caused to a section of Canadian hemlock adjacent to
a parking lot and to street-side plantings of sugar maples. There was
also some damage to turf caused by runoff from uphill salted areas. The
maples showed symptoms of stunted growth, marginal leaf scorch, foliage
thinning, pre-season defoliation, sun-scald of bark and leaders because
of undue tree exposure, and eventual die-off. Wester and Cohen(119)
classified their observations on plant damage into three categories:
moderate damage, severe damage, and complete kill. There were no plants
within the non-salted areas falling into any of these categories. How-
ever, the vegetation on salted land areas, depending upon the site, was
rated from 0-100 percent in each category. The authors comment that any
salt damage may greatly shorten the life of affected trees; and shrubbery
and turf can be killed in a single season. They suggest that salted
snow should be kept within street curbings rather than placed in prox-
imity to plants and vegetation. Furthermore, potentially-affected areas
should be heavily watered in the early spring if at all possible(119).
Sodium and Chloride Content of Grasses, Salt Tolerances
Along Interstate 80 in Johnson County, Iowa, unsuccessful attempts were
made in 1964 and 1965 to establish turf in the roadside areas. Salt
contamination was considered the major cause preventing establishment
of seedlings. Studies by Roberts and Zybura(103,121) were designed to
evaluate salt tolerance and suitability of various coarse texture
grasses for roadside use in Iowa. Soluble salt determinations in soil
samples indicated salt levels sufficiently high to reduce grass growth
up to 10 feet from the road. Greenhouse pot and field plot tests showed
salt tolerance was greatest for Kentucky 31 fescue, decreasing through
slender wheatgrass, intermediate wheatgrass, western wheatgrass, followed
by other varieties. The grasses exhibited increased foliar growth at
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sodium chloride levels up to 631 ppm, but it was noted that soil dis-
persal and deflocculation occurred at the 1,262 ppm salt level; and
above 1,000 ppm, injury to grasses became more evident. Unfortunately,
long-term effects of moderate salt levels on grasses were not determined.
Of all grasses tested, Kentucky 31 fescue not only had good sod and root
development, but also showed best physiological and overall growth when
used in a salted roadside environment.
Verghese et. al.,(122) conducted several tests both in the field and the
greenhouse to determine effects of deicing salts on various grasses used
along highways. They found a close relationship between rates of salt
applications and the amounts of sodium and chloride ions in roadside
grasses. Chloride accumulations within grasses were several times
higher than sodium. Salt applications decreased the yield of all
grasses studied. Of the various grasses, Kentucky 31 fescue showed
good adaption to reasonably high salt levels. Nitrogen soil treatments
seemed to counteract decreasing grass yields due to sodium chloride,
but nitrogen also tends to increase the uptake rate of sodium and
chloride in tissues. Other results indicate that potassium phosphate
may be effective in reducing salt injury to grasses, but phosphate
stimulates plant growth providing more surface area for salt absorption.
Other soil improvement measures include addition of soluble calcium
salts, gypsum, or anhydrous ammonia to the soil(5,46,117,123,124).
Gypsum is reported to be an effective and inexpensive amendment for
saline soils.
Salt Injury to Trees. St. Paul, Minnesota
French in the late 1950's(5,125), observed salt-injury symptoms of Amer-
ican elm and other species of trees along various city streets in
St. Paul, Minnesota, following winters of heavy road salting. Tree
leaves turned yellow, then brown, generally coinciding with the start
of hot dry weather and this phenomena became more pronounced through
the summer. French noticed that tree defoliation and serious injury
were more prominent on the side of the tree fronting the street.
Although soluble salts in the soils appeared to be below the danger
level, injured parts were shown to contain abnormal levels of sodium.
These findings were duplicated in greenhouse experiments when sodium
chloride - calcium chloride mixtures were applied to American elm
seedlings.
Sodium and Chloride Levels in Sugar Maples and Silver Maples in
New Hampshire, Massachusetts, Vermont and Connecticut;
Correlation with Injury and Death
Rich and LaCasse from various studies in New Hampshire determined that
sugar maples and other trees along a heavily-travelled and heavily-
salted highway were moderately to severely injured. Trees within 30
feet of the highway were usually injured, whereas trees greater than
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30 feet away were almost always healthy. Symptoms included leaf scorch,
early coloration and defoliation, reduced growth, browning of twigs and
branches, and eventual die-off of severely-affected trees. Injury could
not be correlated with size or age of tree, soil type, fertility, or
prevalence of parasites. Foliage from affected trees showed abnormally
high sodium content and the sap from injured trees was high in soluble
salts. Later studies in New Hampshire showed that maple trees along
salted State roads displayed considerable injury, whereas almost no in-
jury was observed for similar trees along unsalted town roads in the
same general area. These investigations found that chloride content was
a somewhat better indicator than sodium for determining damage to foliage,
but in tree sap, sodium was the better indicator. For the healthy, mod-
erate, and severe injury classes, sodium levels in foliage were respec-
tively, 0.02, 0.03 and 0.17 percent. Chloride levels were higher showing
0.06, 0.28 and 0.42 percent, respectively(126,127,128,129).
Rich and LaCasse(128) have repeatedly found of the various deciduous
trees, that maples are most prone to injury and damage caused by highway
salts. Kotheimer et. al.,(5,130) conducted studies in New Hampshire of
maple trees receiving highway salts compared to similar trees receiving
little or no salt. Sugar maples were seen to be more susceptible to
highway salts than the red maples. Kotheimer concluded that road salt
application was definitely associated with less vigorous and deteriorat-
ing maples alongside New Hampshire highways. Westing(5,131) in his
review of sugar maple decline, notes that many causes may be responsible
for this decline including adverse environmental conditions, disease, or
completed life cycle. Salt may only be one of these causes, albeit an
important one. Westing mentions symptoms such as reduced growth, loss of
coloration, marginal necrosis in leaves, twig and branch die-off, and
premature leaf loss. Sixteen States in the northeast and north-central
U.S. have become concerned with this problem, but the sugar maple decline
has been particularly prevalent in the State of New Hampshire.
Additional studies have been undertaken by Holmes and Baker(132) on
sugar maple decline in Massachusetts, and by Zelazny et. al.,(133) on
silver maple decline in Vermont. Following extensive investigations
from 1961-1964, Holmes and Baker concluded that foliar chloride levels
in sugar maples could be correlated with injury levels, and salt does
injure and even kills sugar maple trees. Holmes and Baker take the
position that roads must be kept safe in the winter. However, care
should be taken to minimize damage to maples by judicious use of a salt
in sand mixture applied after plowing. They make it equally clear that
more lavish use of salt will increase both foliar chloride uptake and
injury to sugar maples. Salts may also affect the vulnerability of trees
to other injuries or disease, and these other agents may affect the in-
tensity of salt injury. Holmes and Baker observed minimal or no injury
symptoms in the range of 0.05 to 0.6 percent foliar chlorides (1 to 12
times normal); slight or moderate symtoms were present in the range of
0.4 to 1.0 percent foliar chlorides; and severe symptoms were experienced
above 1.0 percent chlorides. It was moreover concluded that foliar
symptoms when correlated with chloride levels in excess of 0.3 percent
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should not be attributed to factors other than salt. Regarding foliar
sodium levels, these were shown to be much lower than chlorides. Trees
with severe injury had foliar sodium from 0.004 to 0.053 percent; and
those with less severe symptoms had 0.0006 to 0.084 percent sodium(132).
Zelazny et. al.,(133) undertook studies in an area of extensive silver
maple decline in Vermont attributed to highway salts. Heavy salt appli-
cations reached roadside soils and were consequently absorbed into the
leaves and stems of nearby trees. Chloride toxicity was judged more
critical than total soluble salts. The test results indicated that
chloride levels of 0.20 percent in the leaves produced leaf scorch,
whereas chloride percentages in excess of 0.50 percent were correlated
with leaf scorch, defoliation and ultimate plant death. Sodium levels
were much higher in damaged trees compared to healthy trees (respec-
tively, 0.005 - 0.146 percent vs. 0.002 - 0.016 percent in the leaves),
and thought to be one of the possible reasons for overall plant deterior-
ation. The authors recommend that woody vegetation should be located
as far from the highway as possible, that plants be selected on the
basis of salt tolerance, and the highway drainage be diverted away from
roadside vegetation(133).
Unpublished work by Button and Peaslee reported in the 1970 Highway
Research Board literature review(5,134), indicates that high levels of
sodium and chloride may be expected in trees exposed to highway drain-
age. Observed symptoms included leaf-burn injury, decline in vigor,
and defoliation. The leaves of sugar maple trees showing margin burns
contained around 5,000 ppm chlorides, and trees near die-off had around
9,000 ppm chlorides. Low levels of highway salts applied over a suf-
ficiently long period of time could accumulate within the plant causing
serious injury and plant death. The range of chlorides within the
leaves of damaged trees was 0.26 to 0.94 percent. For healthy trees
these levels were 0.03 to 0.31 percent(5,135,136,137).
Allison from his observations on various species of plants, indicated in
1964 that chloride accumulations around 1-2 percent (i.e., 10,000-20,000
ppm) would cause marginal burn, leaf drop, twig dieback, and death of the
plant. These chloride accumulations will occur when chlorides in soils
are in the approximate range of 700 to 1,500 ppm. Sodium content of 0.05
percent or even less, also produces leaf burn and significant plant in-
Jury (5,138).
Salt Tolerance of Individual Plant Species; Fruit, Vegetable and
Fi«ld Crops, Grasses, Trees and Ornamentals
The subject of salt tolerance and variability between plant species is
a most interesting one. Salt tolerance of various plants has been
studied and classed with respect to: 1) relative plant yield on saline
soils compared to non-saline soils; 2) plant yield on saline soils; and
3) the ability of the plant to survive on saline soils. The majority
of the Information developed on salt tolerance is based upon the first
-------
and second criteria given above. This is because most research on salt
tolerance has been carried out in the arid and semi-arid regions of the
U.S., and within these areas crop yields have been of high importance.
Keeping in mind the third criteria is probably of greatest interest to
highway personnel, that is the ability of the crop to survive in saline
soils, information on salt tolerance can nevertheless be used as a use-
ful guideline in selecting roadside plants and vegetation. The data
presented in Tables V through IX below would appear to represent some
of the best and most concise information available. Tables V, VI, VII,
and VIII respectively, give the salt tolerance of various fruit crops,
vegetable crops, field crops, and grasses. These tables are taken from
the 1970 Highway Research Board literature review(5) but the original
source material is found in previous publications of the U.S. Department
of Agriculture. Table IX gives the salt tolerance of trees and orna-
mentals taken from Zelazny, 1968(139). Each table gives major plant
or major crop arranged according to whether the plant is salt tolerant;
moderately tolerant/sensitive; or sensitive. Within each class, the
plants are listed in decreasing order of salt tolerance; however,
differences of 2 or 3 places in the columns may not be significant.
The discussion following gives further information on the salt tolerance
of ornamental shrubs and trees which is of particular interest to this
report.
Various researchers have studied the salt tolerance of ornamental trees
and shrubs. Monk and Peterson(5,144) using one-year old seedlings, clas-
sify 20 different species as follows: 1) Most Salt Tolerant - black
locust, honey locust, Russian olive, squaw bush, and tamarix; 2) Salt
Tolerant - Silvery buffalo berry, golden willow, ponderosa pine, and
green ash; 3) Moderately Tolerant - Japanese honeysuckle and eastern
red cedar; 4) Least Tolerant - Blue spruce, Douglas fir, black walnut,
little-leaf linden, barberry, winged euonymus, multiflora rose, spiraea,
and arctic blue willow.
Rudolfs(5,145) finds that oak has greatest salt tolerance, birch has
intermediate tolerance, and maple is most sensitive. Zhemchuzhnikov(139)
concludes that trees with greatest salt tolerance are light-loving
species with a fair degree of drought resistance and usually located in
arid climates. Hanes, et. al.,(5) also point out that vegetation not
subject to annual harvesting could, over time, accumulate sufficient
salt within the plants to cause serious damage. This effect is important
when considering the tolerance of perennial woody plants. Zelazny(139),
based upon an extensive literature review, has classified the salt
tolerance of 67 various trees and ornamentals as shown in Table IX.
We have previously described the three criteria determining the type
of salt tolerance data and plant classifications generally available.
Zelazny(139) with reference to these criteria does not believe high
yields are necessary, or even desired in some cases, for highway vegeta-
tion. Rather it is desirable that roadside vegetation be maintained the
year around with minimum effort and cost, erosion be prevented, and the
roadside environment be aesthetically attractive. Since the majority of
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salt tolerance data were developed in the arid U.S., we should compare
climate conditions of the western U.S. with that existing in the highway
salting regions of the northeast and north-central U.S. Zelazny(139)
finds that arid and semi-arid areas usually experience high salt levels
and water shortage. In the northeast and north-central States, the
climate is cooler and more humid, implying that toxicity of specific
salt ions is more important than water shortage. Vegetation in the
western U.S. has also been exposed to saline conditions for thousands
of years which undoubtedly has created a natural selection of plants
to salt tolerance. Such a selection has not occurred to as high a de-
gree in the eastern U.S. It appears ironical that many plants capable
of tolerating high salt concentrations in the West are not able to with-
stand the cool, moist climate in the East(139). Conversely, plants and
vegetation in the highway salting regions of the U.S. lacking this
natural selection, would appear to be significantly more sensitive to
salt injury.
Effects of Salt Spray on Vegetation and Roadside Environment
Two separate studies have described the effects of salt spray on vegeta-
tion alongside highways. Where calcium chloride was sprayed on roads to
reduce dust, Strong(5,146) found there was frequent injury to roadside
trees particularly leaf scorch, and at times even tree die away. With
small concentrations of calcium chloride, symptoms of leaf scorch and
needle burn could not be readily ascribed to salting as distinguished
from drought. However, higher levels of calcium chloride produced more
rapid injury. Direct application of calcium chloride and dust mixtures
to leaves did not appear to cause symptoms of leaf scorch, but rather
produced a brown spotting of the leaves. Sauer(5,147) believes that
salt spray from highways may often be the major cause of roadside plant
injury rather than salt being absorbed from the soil. Sauer observed
that certain portions of roadside plants which were directly behind
snow or beam barriers and thereby protected from the spray, were conse-
quently spared salt injury.
Following heavy snowstorms, motorists frequently perceive a salty
atmosphere prevailing along the highway. This haze of airborne crystals
and dissolved salt stirred up by vehicular traffic will tenaciously
adhere to automobile windshields, increasing the opportunity for traffic
accidents. A much higher potential also exists for accelerated corrosion
of automobile finish and metal parts. It was estimated in Milwaukee
County, Wisconsin, that up to 10 percent of the highway salt on any one
day may become airborne, which could represent nearly 25 percent of the
total air pollution load normally prevailing in that County(26,60).
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TABLE V
SALT TOLERANCE OF FRUIT CROPS^-'
Moderately
Tolerant Tolerant Sensitive
Date palm Pomegranate Pear
Fig Apple
Olive Orange
Grape Grapefruit
Cantaloup Prune
Plum
Almond
Apricot
Peach
Strawberry
Lemon
Avacado
ITOriginal Source, Bernstein, L., 1965(140)
TABLE VI
SALT TOLERANCE OF VEGETABLE
Moderately
Tolerant Tolerant Sensitive
Garden beet Tomato Radish
Kale Broccoli Celery
Asparagus Cabbage Green bean
Spinach Cauliflower
Lettuce
Sweet corn
Potato
Sweet potato-yam
Bell pepper
Carrot
Onion
Pea
Squash
Cucumber
2?Original Source, Bernstein, L., 1959(141)
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TABLE VII
SALT TOLERANCE OF FIELD CROPS-
Moderately
Tolerant Tolerant Sensitive
Barley Rye Field bean
Sugar beet Wheat
Rape Oats
Cotton Sorghum
Sorgo (sugar)
Soybean
Sesbania
Broadbean
Corn
Rice
Flax
Sunflower
Castorbean
~Tl Original Source, Bernstein, L., 1960(142)
TABLE VIII
4/
SALT TOLERANCE OF GRASSES AND FORAGE LEGUMES—
Moderately
Tolerant Tolerant Sensitive
Alkali sacaton White sweet clover White dutch clover
Saltgrass Yellow sweet clover Meadow foxtail
Nuttall alkali-grass Perennial ryegrass Alsike clover
Bermuda grass Mountain brome Red clover
Tall wheatgrass Harding grass Ladino clover
Rhodes grass Beardless wildrye Burnet
Rescue grass Strawberry clover
Canada wildrye Dallis grass
Western wheatgrass Sudan grass
Tall fescue Hubam clover
Barley Alfalfa
Birdsfoot trefoil Rye
Wheat
Oats
Orchard grass
Blue gamma
Meadow fescue
Reed canary
Big trefoil
Smooth brome
Tall meadow oatgrass
Milkvetch
Sourclover
4?Original Source, Bernstein, L., 1958(143)~~~
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TABLE IX
SALT TOLERANCE OF TREES AND ORNAMENTALS-'
5/
Tolerant
Common matrimony vine
Oleander
Bottlebrush
White acacia
English oak
Silver poplar
Gray poplar
Black locust
Honey locust
Osier willow
White poplar
Scotch elm
Russian olive
Squaw bush
Tamarix
Hawthorne
Red oak
White oak
Apricot
Mulberry
Moderately
Tolerant
Silver buffalo berry
Arbor vitae
Spreading juniper
Lantona
Golden willow
Ponderosa pine
Green ash
Eastern red cedar
Japanese honey suckle
Boxelder maple
Siberian crab
European black currant
Pyracantha
Pittosporum
Xylosma
Texas privet
Blue spruce
Douglas fir
Balsam fir
White spruce
Beech
Hard maple
Cotton wood
Aspen
Birch
Poorly
Tolerant
Black walnut
Little leaf linden
Barberry
Winged euonymus
Multiflora rose
Spiraea
Arctic blue willow
Viburnum
Pineapple guava
Rose
European hornbeam
European beech
Italian poplar
Black alder
Larch
Sycamore maple
Speckled aider
Lombardy poplar
Red maple
Sugar maple
Compact boxwood
Filbert
5/ From Zelazny, L., 1968(139)
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SECTION XV
SUMMARY
Current annual use of highway deicing compounds in the U.S. is estimated
around nine million tons of sodium chloride, one-third million tons of
calcium chloride, and eight million tons of abrasives. About 40 States,
mostly in the northeast and north-central U.S., employ highway deicers.
"Bare-pavement" conditions for streets and highways in the wintertime
are considered necessary to adequately protect the lives and safety of
motorists using these roads. The use of sodium chloride and calcium
chloride as deicers has increased rapidly over the past 15 years. The
leading States in total use of highway salts are Pennsylvania, Ohio,
New York, Michigan and Minnesota.
Highway salting rates are usually in the range of 400 to 1,200 pounds
of salt per mile of roadway per application, and many roads and highways
in the U.S. may receive more than 20 tons salt per lane mile or more
than 100 tons per road mile over the winter season. Snow-control equip-
ment includes tall-gate and hopper-type spreaders, trucks, front-end
loaders, snow blowers, plows, thermal melting systems, etc. Considerable
wasting of highway deicing salts occurs because of excessive application,
misdirected spreading and general wintertime difficulties.
Salt storage is necessary for sustaining highway deicing operations,
but these facilities too frequently become a major contributing source
of groundwater and surface water salt contamination. Salts are stored
unprotected in open areas, or placed in unused buildings, garages,
sheds, cribs, storage bins and upon elevated platforms or pallets.
Because of water supply contamination and desirability of better product
handling, many communities have turned to covering of salt piles, en-
closed structures, and diversion and collection of salt-laden drainage.
Street runoff from the melting of ice and snow mixed with chloride salts,
finds its way via combined sewers to the local sewage treatment plant,
and via storm sewers to nearby receiving streams. Daily chloride loads
were shown to be 40 to 50 percent higher for winter months as compared
to summer months in municipal sewage at Milwaukee, Wisconsin. During
days of heavy snow-melt, daily chloride loads were three-fold the normal
summertime loads.
Runoff samples collected from a downtown Chicago expressway in the winter
of 1967 showed chloride content from 11,000 to 25,000 mg/1. It has been
calculated that 600 Ib. salt when applied to a one-mile section of road-
way 20 feet wide containing 0.2 inches of ice, will produce an initial
salt solution of 69,000 to 200,000 mg/1 in the temperature range of
10 F - 25°F. At Milwaukee on January 16, 1969, extremely high chloride
levels of 1,510 to 2,730 mg/1 were found in the Milwaukee, Menomonee and
Kinnickinnic Rivers, believed directly attributable to deicing salts enter-
ing these streams via snow melt. The dumping of extremely large amounts
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of accumulated snow and ice from streets and highways, either directly
or indirectly into nearby water bodies, could constitute a serious pollu-
tion problem. These deposits have been shown to contain up to 10,000
mg/1 sodium chloride, 100 mg/1 oils, and 100 mg/1 lead.
A 1966-1968 survey of twenty-seven farm ponds along various highways in
the State of Maine showed that road salts have strong seasonal influence
on the chloride level of these waters, and that salt concentrations were
increasing yearly. Density stratification of chlorides was observed in
Beaver Dam Lake at Cumberland, Wisconsin, in First Sister Lake near Ann
Arbor, Michigan, and Irondequoit Bay at Rochester, New York, all three
cases attributed to salt runoff from nearby streets entering these lakes.
Highway salts are also estimated to contribute 11 percent of the total
input of waste chlorides entering Lake Erie annually. Sodium from road
salts entering streams and lakes may additionally serve to increase
existing levels of one of the monovalent ions essential for optimum
growth of blue-green algae, thereby stimulating nuisance algal blooms.
Special additives are present within most highway deicers sold today and
may create pollution problems more severe than caused by the chloride
salts. Ferric ferrocyanide and sodium ferrocyanide are commonly used to
minimize caking of salt stocks. Sodium ferrocyanide is quite soluble in
water and will generate cyanide in sunlight. Tests by the State of
Wisconsin showed that a 15.5 mg/1 solution of sodium ferrocyanide pro-
duced 3.8 mg/1 cyanide after 30 minutes. Levels of cyanide toxic to
fishlife range downward to 0.1 mg/1, but desired levels are sought as
low as 0.01 mg/1. Maximum and desired levels of cyanide in public water
supplies range from 0.2 to 0.01 mg/1.
Chromate and phosphate additives have been used in highway deicers as
corrosion inhibitors. As with cyanide, chromium is quite toxic, and
limits permitted in drinking water and other waters are quite low. The
maximum amount of hexavalent chromium allowed in public water supplies
is 0.05 mg/1. In the Minneapolis-St. Paul area, during the winter of
1965-1966, snow melt collections showed maximum values of 24 mg/1 sodium
chromate, 1.7 mg/1 hexavalent chromium, and 3.9 mg/1 total chromium.
Serious groundwater pollution has occurred in a number of locations, due
to heavy amounts of deicing salts applied onto highways and inadequate
protection given to salt storage areas. The State of New Hampshire, up
to 1965, is reported to have replaced more than 200 roadside wells at a
total cost of more than $200,000, because these waters had been contam-
inated by highway salts. Some of the wells exhibited chlorides in excess
of 3,500 mg/1. In Manistee County, Michigan, a roadside well located
300 feet from a highway department salt storage pile, was found to contain
4,400 mg/1 chlorides.
Tastes and odors in a municipal water supply in Connecticut were ascribed
to sodium ferrocyanide originating from a salt storage pile. Also in
Connecticut, a salt storage area was responsible for contaminating the
well water supply serving four families. Within Massachusetts, salt
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increases have been noted In the water supplies of some 63 communities,
at least in part due to road salting and salt storage piles, and certain
water supplies have been abandoned.
Road salts not only promote vehicular corrosion, but additionally may
affect structural steel, house sidings, buildings and other property
alongside the highway. It has been estimated that the private car owner
pays for corrosion in the amount of about $100 per year. Frequent car
washing is still generally recommended as the best protection possible.
Deicers may cause appreciable damage to highway structures and pavements.
Concrete pavements and bridge floors and decks constructed of Portland
cement concrete show greatest susceptibility to salt attack. Air-entrained
concrete is reported superior to non air-entrained concrete in its re-
sistance to salts. Nevertheless, deicing chemicals should not generally
be applied even to air-entrained concrete for at least one year, after
it is poured.
Significant damage of roadside soils, vegetation and trees has been caused
by liberal application of highway salts. Symptoms of injury in plants
and trees include leaf scorch, defoliation, stunting, and ultimately,
plant die-off. Soil damage includes loss of fertility and permeability,
and dispersion of soil colloids, resulting in lack of aggregation and
poor internal drainage. Many of the studies dealing with salt injury
and death of roadside trees have focused on sugar maple decline which
is occurring over a 16-State area, but mostly in the New England States.
Foliar (leaf) chloride levels in sugar maples have been correlated with
extent of injury, when in excess of 0.3 percent chlorides.
Included in this report are a series of tables giving relative salt
tolerance of various fruit crops, vegetable crops, field crops, grasses,
forage legumes, trees and ornamentals. These data, are intended to
serve as approximate guidelines for highway authorities and others in
selecting roadside plants and vegetation. It is believed that plants of
the northeast and north-central U.S. may be inherently more sensitive to
salt injury than has been previously thought.
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SECTION XVI
ACKNOWLEDGMENTS
The advice and assistance of the following persons and organizations who
contributed to this report are gratefully acknowledged:
Mr. Frank Wood of the Salt Institute, Alexandria, Virginia, who provided
the use of sketches of salt storage facilities and various other informa-
tion for incorporation into this report.
The City of New York, New York and its Department of Sanitation; the
City of Chicago, Illinois and its Bureau of Equipment Service; the City
of Milwaukee, Wisconsin and its Department of Public Works, for their
cooperation in making available numerous photographs on deicing and snow
removal equipment and salt storage areas.
Mr. Clifford Risley and his staff of the Office of R&D, Great Lakes
Region, EPA, Chicago, Illinois, for their assistance in obtaining the
photographs from Chicago and Milwaukee.
Mr. J. R. Fitzpatrick of the Ontario Department of Highways for provid-
ing a series of photographs on the "Beehive" dome used for deicing
materials storage in the Province.
Mr. Raymond Leary, Director, and Mr. Lawrence Ernest of the Milwaukee
Sewerage Commission who supplied chloride data on the Milwaukee sewerage
system and other information for the Milwaukee area.
Mr. Ken Henries of the Wisconsin Division of Natural Resources, Milwaukee,
and Dr. Raymond Kipp of Marquette University, Milwaukee, for information
received on highway salting for Milwaukee and the State of Wisconsin.
Dr. F. E. Hutchinson of the University of Maine at Orono, who provided
detailed description and reports of his field investigations carried out
in Maine on soils, groundwater, farm ponds, and vegetation.
Also, the many individuals who supplied copies of published and unpublished
materials for incorporation into this document, and the many persons who
generously gave their time and helpful suggestions during review of the
Interim Report on Highway Deicing previously released by the Edison Water
Quality Laboratory in December 1970.
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SECTION XVII
REFERENCES
1. "Survey of Salt, Calcium Chloride and Abrasive Use for Street and
Highway De-Icing in the United States and in Canada for 1966-1967",
The Salt Institute, 33 pp., Alexandria, Virginia, Date not given.
2. "Snow and Ice Control - A Critical Look at the Critics", Dickinson,
W. E., Paper appearing in the "Proceedings of the Symposium:
Pollutants in the Roadside Environment", pp. 6-14, University of
Connecticut, February 29, 1968.
3. Personal communication with The Salt Institute, Alexandria,
Virginia, 1970.
4. "Legislative Research Council Report Relative to the Use and
Effects of Highway De-icing Salts", the Commonwealth of
Massachusetts, 80 pp., January 1965.
5. "Effects of Deicing Salts on Water Quality and Biota - Literature
Review and Recommended Research", Hanes, R. E., et. al., National
Co-operative Highway Research Program Report 91, Virginia Poly-
technic Institute and Highway Research Board, 70 pp., 1970.
6. "Snow Removal and Ice Control in Urban Areas, Research Project
No. 114, Volume I", Compiled and Edited by Lockwood, R. K.,
American Public Works Association, 126 pp., August 1965.
7. "Snow Removal and Ice Control in Urban Areas, Research Project
No. 114, Vol. II", Compiled and Edited by Lockwood, R. K.,
American Public Works Association, 125 pp., June 1966.
8. "The Role of Deicing Salts in the Total Environment of the Automo-
bile", Wood, F. 0., Paper Presented at NACE Symposium, 18 pp.,
March 2, 1970.
9. "Chlorides", Commission on Water Pollution, Schraufnagel, F. M.,
20 pp., Madison, Wisconsin, 1965.
10. "Complete Salting - Sanding Economic Study", Hopt, R. L., 50 pp.,
Maintenance Division, Idaho Department of Highways, Boise, Idaho,
April 1971.
11. Personal Communication with F. 0. Wood, Technical Director, The
Salt Institute, Alexandria, Virginia, May 3, 1971.
12. "Salt - The Universal Deicing Agent", Wood, F. 0., Paper Presented
at Street Salting Urban Water Quality Workshop, SUNY Water Resources
Center, Syracuse University, May 6, 1971, Syracuse, New York.
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13. "The Encyclopedia of Oceanography", Encyclopedia of Earth Sciences
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712 pp., Academic Press, London and New York, 1965.
15. "The Chemistry and Fertility of Sea Waters", Harvey, H. W., 240 pp.,
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16. "Salt Migration in Soil", Prior, G. A., Paper appearing in the
"Proceedings of the Symposium: Pollutants in the Roadside Environ-
ment", pp. 15-23, University of Connecticut, February 29, 1968.
17. Personal communication with F. E. Hutchinson, University of Maine,
Orono, Maine, May 1970.
18. "Pollution Aspects Associated with Chemical Deicing", Schraufnagel,
F. M., Paper appearing in the "Highway Research Record Report
No. 193 on Environmental Considerations in the Use of Deicing
Chemicals", pp. 22-33, Highway Research Board, Washington, D.C., 1967.
19. Personal communication with U.S. Geological Survey, Federal
Building, Boston, Massachusetts, May 1970.
20. "Storing Road De-icing Salt", The Salt Institute, 16 pp.,
Alexandria, Virginia, 1967.
21. "Report Discusses Salt Corrosion", APWA Reporter, pp. 4,
October 1970.
22. "Mayor Sees Demonstration of New Salt Spreader", Article appear-
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26. "What is Highway Salt Doing to Us?" Newspaper article appearing
in the Milwaukee Journal, May 4, 1970, Milwaukee, Wisconsin.
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Institute, Alexandria, Virginia, 1968.
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28. "Beehives Protect Snow-Removal Salt and Prevent Water Pollution",
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34. "Nitrogen, Chlorin, and Sulfates in Rain and Snow", Artis, B.,
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35. "River Pollution. I. Chemical Analysis", Klein, L., Butterworths,
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36. "Chemistry for Sanitary Engineers", Sawyer, C. N., McGraw-Hill
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37. "Preventive Medicine and Hygiene", Rosenau, M. J., 6th Edition, D.
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38. "A Water Quality Model of Chlorides in The Great Lakes", 0'Conner,
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39. Personal communication with members of the Milwaukee Sewerage
Commission and personnel at the Jones Island sewage treatment
plant, May 1970.
40. "Street Salting and Water Quality in Meadow Brook, Syracuse, New
York", Hawkins, R. H., Preliminary Draft Report Received from
Author, of Paper Presented at Street Salting Urban Water Quality
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May 6, 1971, Syracuse, New York.
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41. "Effects on Winter Storm Runoff of Vegetation and as a Factor in
Stream Pollution", Sullivan, R. H., American Public Works
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April 12, 1967, 6 pp., Milwaukee, Wisconsin.
42. "Water Pollution Aspects of Urban Runoff", Final Report on the
Causes and Remedies of Water Pollution from Surface Drainage
of Urban Areas - Research Project No. 120, Contract No. WA 66-23,
conducted by the American Public Works Association for the
Federal Water Quality Administration, 272 pp., January 1969.
43. "Final Draft Report - Engineering Evaluation: Rainfall-Runoff
and Combined Sewer Overflow", FWQA Contract No. 14-12-402,
Henningson, Durham and Richardson, Inc., March 1970.
44. "Progress Report No. I, July 1, 1965 - June 30, 1966, The
Influence of Salts Applied to Highways on the Levels of
Sodium and Chloride Ions Present in Water and Soil Samples",
Hutchinson, F. E., Project No. R1086-8, 22 pp., 1966.
45. "Progress Report No. II, July 1, 1966 - June 30, 1967, The
Influence of Salts Applied to Highways on the Levels of Sodium
and Chloride Ions Present in Water and Soil Samples", Hutchinson,
F. E., Project No. R1086-8, 26 pp., 1967.
46. "Project Completion Report, July 1965 - June 1969, The Influence
of Salts Applied to Highways on the Levels of Sodium and Chloride
Ions Present in Water and Soil Samples", Hutchinson, F. E.,
Project No. A-007-ME, 20 pp., June 1969.
47. "Concentration of Nine Inorganic Ions in Maine Rivers", Hutchinson,
F. E., Research in the Life Sciences, pp. 8-11, Winter 1968.
48. "Effect of Highway Salting on the Concentration of Sodium and
Chloride in Rivers", Hutchinson, F. E., Research in the Life
Sciences, pp. 12-14, Winter 1968.
49. "Effects of Road Salt on a Vermont Stream", Kunkle, S. H., Paper
Presented at Street Salting Urban Water Quality Workshop, 7 pp.,
SUNY Water Resources Center, Syracuse University. May 6, 1971,
Syracuse, New York.
50. "Physicochemical and Microbiological Properties of Urban Storm-
Water Runoff", Soderlund, G., et. al., Paper Presented at Fifth
International Water Pollution Research Conference, pp. 1-2/1 to
1-21B, San Francisco, California, July-August 1970.
51. "Snow Heavy With Lead", Newspaper Article Appearing in the Daily
News, Columbus, Ohio, April 15, 1971.
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52. "Effect of Highway Salting on the Concentration of Sodium and
Chloride in Private Water Supplies", Hutchinson, F. E., Research
in the Life Sciences, pp. 15-19, Fall 1969.
53. "Chlorides in Lake Erie", Ownbey, C. R. and Kee, D. A., Tenth
Conference Great Lakes Research, First Meeting International
Association of Great Lakes Research, 14 pp., Toronto, Canada,
April 1967.
54. "Effect of Salt Runoff from Street Deicing on a Small Lake",
Judd, J. H., Thesis Submission, 145 pp., University of
Wisconsin, Madison, Wisconsin, 1969.
55. "Uber Temperatur und Stabilitatsverhaltnisse von Seen",
Schmidt, W., Geogr. Ann., 10, pp. 145-177, 1928.
56. "A Treatise on Limnology, Volume I", Hutchinson, G. E.,
John Wiley and Sons, Inc., Publishers, New York, N.Y., 1957.
57. "Runoff of Deicing Salt: Effect on Irondequoit Bay, Rochester,
New York", Diment, W. H. and Bubeck, R. C., Paper Presented at
Street Salting Urban Water Quality Workshop, 18 pp., SUNY Water
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New York.
58. Personal Communication with L. E. Reup, Technical Studies Branch,
Division of Technical Support, National Field Investigations Center,
U.S. Environmental Protection Agency, Cincinnati, Ohio, 1971.
59. "Road Salt as a Polluting Element", Special Environmental Release
No. 3, Sharp, R. W., Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior, Federal Building, Fort Snelling,
Twin Cities, Minnesota, 55111, December 14, 1970.
60. Personal communication with Members of the State of Wisconsin,
Division of Natural Resources, Milwaukee, Wisconsin, May 1970.
61. "The Apparent Thresholds of Toxicity of Daphnia magna for Chlorides
of Various Metals when Added to Lake Erie Water", Anderson, B. G.,
Trans. Amer. Fish. Soc., 78, pp. 96-113, 1948.
62. "Report No. 3, Subcommittee on Toxicities, Metal Finishing
Industries Action Committee", Ohio River Valley Water
Sanitation Commission, 1950, Contained in "Water Quality
Criteria", by McKee, J. E. and Wolf, H. W., 2nd Edition, State
Water Quality Control Board, Sacramento, California, 1963.
63. "A Study in the Relative Toxicity of Anions, with Polycelis nigra
as the Test Animal", Jones, J. R. E., Journal Exp. Biol., 18,
pp. 170-181, 1941.
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64. "Toxicity of Ferro-and Ferricyanide Solutions to Fish, and
Determination of the Cause of Mortality", Burdick, G. E. and
Lipschuetz, M., Trans. Amer. Fish. Soc., 78, pp. 192-202, 1948.
65. "Water Quality Criteria", McKee, J. E. and Wolf, H. W., 2nd Edition,
State Water Quality Control Board, Sacramento, California, 548 pp.,
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66. "Public Health Service Drinking Water Standards - 1962", Public
Health Service Publication No. 956, 61 pp., U.S. Department of
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Washington, D.C., 1962.
67. "Manual for Evaluating Drinking Water Supplies", A Manual of Prac-
tice Recommended by the U.S. Public Health Service, 76 pp., U.S.
Department of Health, Education and Welfare, Public Health Service,
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68. Materials in the Files of the Storm and Combined Sewer R&D
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69. "Some Factors Influencing the Detoxication of Cyanides in
Health and Disease", Bodansky, M. and Levy, M. D., Arch.
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70. "Toxicologic Methods for Establishing Drinking Water Standards",
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71. "The Detection of Poisons in Public Water Supplies", Smith, 0. M.,
Water Works Engineering, 97, pp 1293-1312, 1944.
72. "The Merck Index, Edition 7", Stecher, P. G., Editor, Merck and Co.,
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73. "Poisoning of Animals by Cyanides Present in Some Industrial
Effluents", Clough, G. W., Vet. Rec., 13_, pp. 538, 1933.
74. "Influence of Temperature and Oxygen Tension on the Toxicity
of Poisons to Fish", Wuhrmann, K. and Woker, H., Proc. Inter.
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75. "River Pollution - General and Chemical Effect", Lovett, M.,
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76. "Treatment and Disposal of Industrial Waste Waters", Southgate,
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77. "Water Pollution: General Introduction", Southgate, B. A., Chem.
and Ind., pp. 1194-1199, 1955.
78. "Effects of Cyanide on Black Hills Trout", Karsten, A., Black
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79. "The Effect on Fish of Effluents Containing Cyanide", Lehmann, C.,
L. F. Fischerei, 1926; Wass u. Abwass, 24, pp. 84, 1928; Abstracts,
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80. "Handbook of Toxicology", Spector, W. S., Technical Report
No. 55-16, Wright Air Development Center, Air Research and
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1955.
81. "Toxicity and Pollution Study of Carguard Chemicals, 1965-1966",
33 pp., Cargill, Incorporated, Minneapolis, Minnesota.
82. "Ground Water Contamination and Legal Controls in Michigan",
Deutsch, M., Water Supply Paper No. 1691, U.S. Geological
Survey, U.S. Department of the Interior, 1963.
83. "Standard Methods for the Examination of Water and Wastewater",
12th Edition, Prepared by the American Public Health Association,
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1965.
84. "Fertilization of Lakes by Agricultural and Urban Drainage",
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61, pp. 109-127, 1947.
85. "Effect of Sewage - Borne Phosphorous on Algae", Curry, J., and
Wilson, S., Sewage and Industrial Wastes Journal, 27, pp. 1262-1266,
1955.
86. "Progress Report on NCHRP Project 16-1; Effects of Deicing
Compounds on Vegetation and Water Supplies", Smith, H. A., Paper
presented at 54th Annual Meeting of the American Association of
State Highway Officials, 7 pp., Minneapolis, Minnesota,
December 5, 1968.
87. "Salt Buildup in Drinking Water a Danger to Some Bay Staters",
Newspaper Article appearing in the Boston Globe, Boston,
Massachusetts, May 8, 1970.
88. "Salt Piling - A Source of Water Supply Pollution", Walker, W. H.,
Pollution Engineering, 2_, 3*, pp. 30-33, July-August 1970.
- 113 -
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89. "Progress Report III, The Influence of Salts Applied to Highways
on the Levels of Sodium and Chloride Ions Present in Water and
Soil Samples", Hutchinson, F. E., Project No. R1088-8, 28 pp.,
1968.
90. "The Groundwater Resources of Summit County, Ohio", Smith, R. D.,
Ohio Division of Water, Bulletin No. 27, pp. 130, 1953.
91. "Movement of Dissolved Salts in Groundwater Systems", Rahn, P. H.,
Paper appearing in the "Proceedings of the Symposium: Pollutants
in the Roadside Environment", pp. 36-45, University of Connecticut,
February 29, 1968.
92. "Environmental Effect of Highways", Scheldt, M. E., Journal of
the Sanitary Engineering Division, Proceedings of the American
Society of Civil Engineers, 93, No. SA5, Paper No. 5509,
pp. 17-25, October 1967.
93. "Side Effects of Salting for Ice Control", Article appearing in
American City, 80, pp. 33, August 1965.
94. "Salting Highways Could Contaminate Ground Water", Article
appearing in Reclamation News, April 1965.
95. "Road Salt Blamed for Souring Water", Newspaper article appearing
in the Boston Globe, Boston, Massachusetts, April 1970.
96. "Do Road Salts Poison Water Supplies?", Newspaper article appearing
in the Boston Globe, Boston, Massachusetts, 1968 or 1969.
97. "Alewife Brook Polluted", Article appearing in the Boston Globe,
Boston, Massachusetts, May 1970.
98. "Your 500 - Milligram Sodium Diet", American Heart Association,
55 pp., 1957.
99. "Your 1,000 - Milligram Sodium Diet", American Heart Association,
55 pp., 1957.
100. "Tolerable Salt Concentrations in Drinking Waters", Moore, E. W.,
A Progress Report to the Sub-committee on Water Supply of the
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Society for Testing and Materials, Committee D-19 on Industrial
Water, 336 pp., 1953.
102. "Corrosion", Kallen, H. P., Special Report, Power, pp. 73-108,
December 1956.
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103. "Effect of Sodium Chloride on Grasses for Roadside Use",
Roberts, E. C., and Zybura, E. L., Paper appearing in the
"Highway Research Record Report No. 193 on Environmental
Considerations in Use of Deicing Chemicals", pp. 35-42,
Highway Research Board, Washington, D.C., 1967.
104. Article appearing in Automotive Industries, February 1, 1964.
105. Article appearing in Steel, March 2, 1964.
106. "New Cars Resist Salt Corrosion", American City, August 1961.
107. "U.S. Highway Research Board Bulletin No. 323", Washington, D.C.,
1962.
108. "Bridge Deck Deterioration and Repair Techniques", Delp, L. R.,
AASHO Conference, Portland, Oregon, 1963.
109. "Publication No. 98", Dickinson, W. E., National Ready Mixed
Concrete Association, Washington, D.C., 1961.
110. "The Elimination of Pavement Sealing By Use of Air Entraining
Portland Cement", Portland Cement Association, Chicago, Illinois,
HB 18.8.
111. "Protection of Existing Concrete Pavements from Salt and Calcium
Chloride", Portland Cement Association, Chicago, Illinois, HB 1-2.
112. "Warning - Use the Right Deicer", Lerch, W., Modern Concrete,
May 1962.
113. "Corrosive Effects of Deicing Salts", Hamman, W. and Mantes, A. J.,
Journal American Water Works Association, 58, 11, pp. 1457-1461,
November 1966.
114. "A Study of Salt Pollution of Soil by Highway Salting",
Prior, G. A. and Berthouex, P. M., Paper appearing in the
"Highway Research Record Report No. 193 on Environmental
Considerations in Use of Deicing Chemicals", pp. 8-21,
Highway Research Board, Washington, D.C., 1967.
115. "The Relationship of Road Salt Applications to Sodium and Chloride
Ion Levels in the Soil Bordering Major Highways", Hutchinson, F. E.,
and Olson, B. E., Paper appearing in the "Highway Research Record
Report No. 193 on Environmental Considerations in Use of Deicing
Chemicals", pp. 1-7, Highway Research Board, Washington, D.C., 1967.
116. "Notes on Winter Road Salting (Sodium Chloride) and Vegetation",
Scientific Report No. 3, Thomas, L. K., Jr., 22 pp., National
Capital Region, National Park Service, U.S. Department of the
Interior, March 31, 1965.
- 115 -
-------
117. "The Relationship of Road Salt Applications to Sodium and Chloride
Ion Levels in the Soil Bordering Major Highways", Hutchinson, F. E.,
Paper appearing in the "Proceedings of the Symposium: Pollutants
in the Roadside Environment", pp. 24-35, University of Connecticut,
February 29, 1968.
118. "Winter Rock Salt Injury to Turf (Poa pratensis L.)", Scientific
Report No. 5, Thomas, L. K., Jr., and Bean, G. A., 22 pp.,
National Capital Region, National Park Service, U.S. Department
of the Interior, August 23, 1965.
119. "Salt Damage to Vegetation in the Washington, D.C. Area During
the 1966-1967 Winter", Wester, H. V. and Cohen, E. E., Reprint
from Plant Disease Reporter, 52, 5, 5 pp., May 1968.
120. "A Quantitative Microchemical Method for Determining Sodium Chloride
Injury to Plants", Scientific Report No. 4, Thomas, L. K., Jr.,
10 pp., National Capital Region, National Park Service, U.S.
Department of the Interior, 1965.
121. "Effect of De-icing Chemicals on Grassy Plants", Roberts, E. C.,
Paper appearing in the "Proceedings of the Symposium: Pollutants
in the Roadside Environment", pp. 48-49, University of Connecticut,
February 29, 1968.
122. "Sodium Chloride Uptake and Distribution in Grasses as Influenced
by Fertility Interaction and Complementary Anion Competition",
Verghese, K. G., et. al., Unpublished Report, 15 pp., Virginia
Polytechnic Institute, Research Division, Blacksburg, Virginia,
1969.
123. "Soil Salinity and Irrigation in the Soviet Union", Bower, C. A.,
et. al., U.S. Department of Agriculture ARS Report of a Tech.
Study Group, 41 pp., 1962.
124. "Some Effects of Salt Water on Soil Fertility", Plice, M. J.,
Soil Science Soc. Amer. Proc., 14, pp. 275-278, 1949.
125. "Boulevard Trees are Damaged by Salt Applied to Streets",
French, D. W., Minnesota Farm and Home Science, XVI, 2, 9, 1959.
126. "Maple Decline in New Hampshire":, LaCasse, N. L., M. S. Thesis,
University of New Hampshire, 1963.
127. "Maple Decline in New Hampshire", LaCasse, N. L. and Rich, A. E.,
Phytopathology, 54, pp. 1071-1075, 1964.
128. "Salt Injury to Roadside Trees", Rich, A. E. and LaCasse, N. L.,
Forest Notes, Winter 1963-1964, 2-3.
- 116 -
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129. "Effect of Deicing Chemicals on Woody Plants", Rich, A. E.,
Paper appearing in the "Proceedings of the Symposium: Pollutants
in the Roadside Environment", pp. 46-47, University of Connecticut,
February 29, 1968.
130. "Salt Injury to Roadside Trees - A Progress Report", Kotheimer, J.,
Niblett, C., and Rich, A. E., Forest Notes, 85, 3-4, 1965.
131. "Sugar Maple Decline: An Evaluation", Westing, A. H., Econ,
Botany, 20, 2, pp. 196, 212, 1966.
132. "Salt Injury to Trees, II. Sodium and Chloride in Roadside
Sugar Maples in Massachusetts", Holmes, F. W. and Baker, J. H.,
Phytopathology, 56, 6, pp. 633-636, June 1966.
133. "Effects of Deicing Salts on Roadside Soils and Vegetation, II.
Effects on Silver Maples (Acre saccharinum L.)", Zelazny, L. W.,
et. al., Unpublished Report, Virginia Polytechnic Institute,
Research Division, Blacksburg, Virginia, 1970.
134. Unpublished data from Connecticut State Highway Department,
Department of Research and Development, and Connecticut
Agricultural Experiment Station, Button, E. F., and Peaslee, D. E.,
New Haven, Connecticut.
135. "Influence of Rock Salt Used for Highway Ice Control on Natural
Sugar Maples at One Location in Central Connecticut",
Button, E. F., Report No. 3, Connecticut State Highway Department,
1964.
136. "Influence of Rock Salt, Salt Used for Highway Ice Control on
Natural Sugar Maples at One Location in Central Connecticut",
Button, E. F., Report No. 3A, Connecticut State Highway
Department, 1964.
137. "Ice Control Chlorides and Tree Damage", Button, E. F., Public
Works, 93_, 3, p. 136, 1965.
138. "Salinity in Relation to Irrigation", Allison, L. E., Advances
in Agronomy, 16, pp. 139-180, 1964.
139. "Salt Tolerance of Roadside Vegetation", Zelazny, L. W.,
Paper appearing in the "Proceedings of the Symposium: Pollutants
in the Roadside Environment", pp. 50-56, University of Connecticut,
February 29, 1968.
140. "Salt Tolerance of Fruit Crops", Bernstein, L., U.S. Department
of Agriculture, Agricultural Information Bulletin No. 292, 8 pp.,
1965.
- 117 -
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141. "Salt Tolerance of Vegetable Crops in the West", Bernstein L.,
U.S. Department of Agriculture, Agricultural Information
Bulletin No. 205, 5 pp., 1959.
142. "Salt Tolerance of Field Crops", Bernstein, L., U.S. Department
of Agriculture, Agricultural Information Bulletin No. 217, 6 pp.,
1960.
143. "Salt Tolerance of Grasses and Forage Legumes", Bernstein, L.,
U.S. Department of Agriculture, Agricultural Information
Bulletin No. 194, 7 pp., 1958.
144. "Tolerance of Some Trees and Shrubs to Saline Conditions",
Monk, R. W., and Peterson, H. B., Proc. American Soc. Hort. Sci.,
81, pp. 556-561, 1962.
145. "Influence of Sodium Chloride Upon the Physiological Changes
of Living Trees", Rudolfs, W., Soil Science, £, pp. 397-425,
1919.
146. "A Study of Calcium Chloride Injury to Roadside Trees", Strong, F. C.,
Michigan Agr. Exp. Sta. Quart. Bull., 27, pp. 209-224, 1944.
147. "Damage by De-icing Salts to Plantings Along the Federal Highways",
Sauer, G., News Journal, German Plant Protective Service, 19, 6,
1967.
Additional Suggested Reading - Supplementary References
"Pollution Control Board Conducts Hearing on Salting of Streets", Oklahoma
Environmental Reporter, 12, Report No. 13, page 2, March 17, 1971.
"Rules on Salt Use Adopted", Newspaper Article Appearing in The Daily
Oklahoman, April 13, 1971.
"Snow Job", Newspaper Article Appearing in the Syracuse, New York Herald
Journal, Syracuse, New York, May 6, 1971.
"Maintenance Manual", Sections 5-290, 5-291, 5-292, 5-293 and 5-295,
respectively giving information and instructions on Snow Removal; Equip-
ment; Organization and Practice; Operating Snow Plows; and Ice and Snow
Removal by Chloride Salts; Revision of July 1966, Idaho Department of
Highways, Boise, Idaho.
"The Effect of Highway Salt on Water Quality in Selected Maine Waters",
Hutchinson, F. E., Paper Presented at Street Salting Urban Water Quality
Workshop, SUNY Water Resources Center, Syracuse University, May 6, 1971,
Syracuse, New York.
- 118 -
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"Lake Stratification Caused by Runoff from Street Deicing", Judd, J. H.,
Water Research, 4^ 8, pp. 521-532, August 1970.
"Effects of De-icing Salts on Roadside Soils and Vegetation", Zelazny, L. W.
and Blaser, R. E., Paper Appearing in "Highway Research Record No. 335,
Roadside Development and Maintenance", pp. 9-12, Highway Research Board,
National Research Council, National Academy of Sciences - National Academy
of Engineering, Washington, D.C., 1970.
"Sodium Chloride Uptake in Grasses as Influenced by Fertility Interaction",
Verghese, K. G., et. al., Paper Appearing in "Highway Research Record
No. 335, Roadside Development and Maintenance", pp. 13-15, Highway Research
Board, National Research Council, National Academy of Sciences - National
Academy of Engineering, Washington, D.C., 1970.
"Salt Tolerance of Trees and Shrubs to De-icing Salts", Hanes, R. E.,
et. al., Paper Appearing in "Highway Research Record No. 335, Roadside
Development and Maintenance", pp. 16-18, Highway Research Board, National
Research Council, National Academy of Sciences - National Academy of
Engineering, Washington, D.C., 1970.
"Non-Chemical Methods of Snow and Ice Control on Highway Structures",
National Cooperative Highway Research Program Report 4, National Coopera-
tive Highway Research Program, Highway Research Board, National Research
Council, National Academy of Sciences - National Academy of Engineering,
Washington, D.C., Date Unknown.
"Protective Coatings to Prevent Deterioration of Concrete by De-icing
Chemicals", National Cooperative Highway Research Program Report 16,
National Cooperative Highway Research Program, Highway Research Board,
National Research Council, National Academy of Sciences - National
Academy of Engineering, Washington, D.C., Date Unknown.
"Economical and Effective De-icing Agents for Use on Highway Structures",
National Cooperative Highway Research Program Report 19, Boles, D. B. and
Bortz, S., 19 pp., National Cooperative Highway Research Program, Highway
Research Board, National Research Council, National Academy of Sciences -
National Academy of Engineering, Washington, D.C., 1965.
"Methods For Reducing Corrosion of Reinforcing Steel", National Coopera-
tive Highway Research Program Report 23, National Cooperative Highway
Research Program, Highway Research Board, National Research Council,
National Academy of Sciences - National Academy of Engineering, Washing-
ton, D.C., Date Unknown.
"Physical Factors Influencing Resistance of Concrete to De-icing Agents",
National Cooperative Highway Research Program Report 27, National Coopera-
tive Highway Research Program, Highway Research Board, National Research
Council, National Academy of Sciences - National Academy of Engineering,
Washington, D.C., Date Unknown.
- 119 -
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"Facts You Should Know About Effects of De-icing Salt on the Environment
A Review of National Cooperative Highway Research Program Report 91",
16 pp, American Public Works Association Reporter, January 1971; Reprint
Made Available by the Salt Institute, Alexandria, Virginia.
"Deicing With Salt - Some Pros and Cons", Pryzby, S. R., Public Works
Magazine, pp. 80,81,98, March 1971.
"Snow and Ice Removal and Ice Control Research", Proceedings of a Sympo-
sium held at Dartmouth College, Durham, New Hampshire, April 1970,
Highway Research Board Special Report No. 115, Highway Research Board,
Washington, D.C.
"Town Fights Road Salting to Protect Water Supply", Newspaper Article
Appearing in the Boston Globe, Boston, Mass., December 29, 1970.
"Effects of Winter Storm Water Runoff on Vegetation and as a Factor in
Stream Pollution", Bugher, R. D., Paper Presented at the Seventh Annual
Snow Conference, 6 pp., Milwaukee, Wisconsin, 1967.
"Environmental Effects of Snow Removal and Ice Control Programs",
Smith, H. A., Paper Presented at the Eleventh Annual North American
Snow Conference, 16 pp., Chicago, Illinois, April 14, 1971.
"Vehicle Corrosion Caused by Deicing Salts - Evaluation of the Effects
of Regular vs. Inhibited Salt on Motor Vehicles", American Public Works
Association Special Report No. 34, American Public Works Association
Research Foundation, APWA-SR-34, Chicago, Illinois, September 1970.
"Eleven Principles of Design", Society of Automotive Engineers J447A,
Date Unknown.
"Effect of an Inhibitor on the Corrosion Autobody Steel by Deicing Salt",
Adair, T. H., Ontario Research Foundation, Report of Investigation
M-60110, 1961.
"Salt Corrosion of Automobiles", Joint ASM - AICE Seminar on Corrosion,
University of Toledo, Toledo, Ohio, March 28, 1969.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
11040 GKK 06/71
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Environmental Impact of Highway Deicing
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Edward Struzeski, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Storm & Combined Sewer Section
U, S. Environmental Protection Aeencv
Edison, N.J. 08817
10. PROGRAM ELEMENT NO.
IB C 611
11. CONTRACT/GRANT NO.
11040 GKK
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
Reprint-Final Report
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
PrQ.-ject Officer:
Edward Struzeski,. Jr. 201/548-3347x541 (8-342-7541)
16. ABSTRACT
Deicing agents for removal of ice and snow from highways and streets are essential
to wintertime road maintenance in most areas of the U.S. Due to the ever-
increasing use of highway deicing materials, there has been growing concern as to
environmental effects resulting from these practices. This Stat-of-the-Art report
reviews the available information on methods, equipment and materials used for
snow and ice removal; chlorides found in rainfall and municipal sewage during the
winter; salt runoff from streets and highways; deicing compounds found in surface
streams, public water supplies, groundwater, farm ponds and lakes; special addi-
tives incorporated into deicing agents; vehicular corrosion and deterioration of
highway structures and pavements; and effects on roadside soils, vegetation and
trees. It is concluded that highway deicing can cause injury and damage across a
wide environmental spectrum. Recommendations describe future research, develop-
ment and demonstration efforts necessary to assess and reduce the adverse impact
of highway deicing. This report was prepared by the Storm and Combined Sewer
Section, Wastewater Research Division, MERL, (formerly the Edison Water Quality
Laboratory), Edison, NJ.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
additives
chlorides
concrete durability
corrosion
deicers
economic analysis
ice control
public water serv.
runoff
snows torms
sodium
toxic tolerances
water pollution
environmental damages
groundwater contamination
salt storage
urban runoff
vehicular corrosion
wintertime highway runoff
13 B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
121
•4USGPO: 1976 — 657-695/5444 Region 5-11
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Continued from inside front cover....
11022 — 08/67
11023 — 09/67
11020 — 12/67
11023 — 05/68
11031 — 08/68
11030 DNS 01/69
11020 DIH 06/69
11020 DES 06/69
11020 — 06/69
11020 EXV 07/69
11020 DIG 08/69
11023 DPI 08/69
11020 DGZ 10/69
11020 EKO 10/69
11020 — 10/69
11024 FKN 11/69
11020 DWF 12/69
11000 — 01/70
11020 FKI 01/70
11024 DOK 02/70
11023 FDD 03/70
11024 DMS 05/70
11023 EVO 06/70
11024 — 06/70
11034 FKL 07/70
11022 DMU 07/70
11024 EJC 07/70
11020 — 08/70
11022 DMU 08/70
11023 — 08/70
11023 FIX 08/70
11024 EXF 08/70
Phase I - Feasibility of a Periodic Flushing System for
Combined Sewer Cleaning
Demonstrate Feasibility of the Use of Ultrasonic Filtration
in Treating the Overflows from Combined and/or Storm Sewers
Problems of Combined Sewer Facilities and Overflows, 1967
(WP-20-11)
Feasibility of a Stabilization-Retention Basin in Lake Erie
at Cleveland, Ohio
The Beneficial Use of Storm Water
Water Pollution Aspects of Urban Runoff, (WP-20-15)
Improved Sealants for Infiltration Control, (WP-20-18)
Selected Urban Storm Water Runoff Abstracts, (WP-20-21)
Sewer Infiltration Reduction by Zone Pumping, (DAST-9)
Strainer/Filter Treatment of Combined Sewer Overflows,
(WP-20-16)
Polymers for Sewer Flow Control, (WP-20-22)
Rapid-Flow Filter for Sewer Overflows
Design of a Combined Sewer Fluidic Regulator, (DAST-13)
Combined Sewer Separation Using Pressure Sewers, (ORD-4)
Crazed Resin Filtration of Combined Sewer Overflows, (DAST-4)
Stream Pollution and Abatement from Combined Sewer Overflows •
Bucyrus, Ohio, (DAST-32)
Control of Pollution by Underwater Storage
Storm and Combined Sewer Demonstration Projects -
January 1970
Dissolved Air Flotation Treatment of Combined Sewer
Overflows, (WP-20-17)
Proposed Combined Sewer Control by Electrode Potential
Rotary Vibratory Fine Screening of Combined Sewer Overflows,
(DAST-5)
Engineering Investigation of Sewer Overflow Problem -
Roanoke, Virginia
Microstraining and Disinfection of Combined Sewer Overflows
Combined Sewer Overflow Abatement Technology
Storm Water Pollution from Urban Land Activity
Combined Sewer Regulator Overflow Facilities
Selected Urban Storm Water Abstracts, July 1968 -
June 1970
Combined Sewer Overflow Seminar Papers
Combined Sewer Regulation and Management - A Manual of
Practice
Retention Basin Control of Combined Sewer Overflows
Conceptual Engineering Report - Kingman Lake Project
Combined Sewer Overflow Abatement Alternatives -
Washington, D.C.
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