EPA-670/2-74-033
JULY 1974
Environmental Protection Technology Series
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EPA-670/2-74-033
July 1974
MANUAL FOR DEICING CHEMICALS:
STORAGE AND HANDLING
By
David L. Richardson
Project Director
Charles P. Campbell s
Raymond J. Carroll
David . I.' Hellstrom
Jane B. Metzger
Philip J. O'Brien
Robert C. Terry
Arthur D. Little, Inc.
Cambridge, Massachusetts 02140
Contract No. 68-03-0154
Program Element No. 1BB034
Project Officer
Hugh E. Masters '
Storm and Combined Sewer Section (Edison, N.J.)
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Cincinnati, Ohio 45268
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI. OHIO 45268
For sale by the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402
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REVIEW NOTICE
The National Environmental Research Center —
Cincinnati has reviewed this report and approved
its publication. Approval does not signify that
/*
the contents necessarily reflect the views and
policies of the TJ. S. Environmental Protection
Agency, nor does mention of trade names or com-
mercial products constitute endorsement or recom-
mendation for use.
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FOREWORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise.and other forms.of
pollution, and the unwise management of solid waste. Efforts
to protect the environment require a focus that recognizes the
interplay between the components of our physical environment —
air, water, and land. The National Environmental Research
Centers provide this multidisciplinary focus through programs
engaged in ore
o studies on the effects of environmental
contaminants on man and the biosphere, and
o a search for ways to prevent contamination
and to recycle valuable resources.
The study described here was undertaken to minimize the
loss to the environment of chemicals used in controlling snow
and ice on highways. Practical guidelines are presented for
good practice in the storage and handling of deicing chemicals.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center, Cincinnati
iii
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ABSTRACT
This report contains the results of a study conducted for the U.S.
Environmental Protection Agency to minimize the loss to the environment
of chemicals used in controlling snow and ice on highways. Based on
the best current practices for highway maintenance as observed during
two years of study, practical guidelines are presented for good practice
in the storage and handling of deicing chemicals.
1. Covered storage of salt and other deicing chemicals is
strongly recommended; permanent structures for this purpose
are preferable. Guidelines are given for site selection and
for design of foundations, paved working area, and site
drainage. Existing storage facilities are presented that
represent a range of costs, designs, construction materials
and storage capacities.
2. For the handling of salt and other deicing chemicals,
general precautions and good housekeeping practices are
defined.
3. Environmental responsibilities are discussed for personnel
who administer and supervise highway maintenance.
This report was submitted in partial fulfillment of Program Element
1BB034 Contract No. 68-03-0154 by Arthur D. Little, Inc., under the
sponsorship of the Environmental Protection Agency. Work was completed
in March 1974.
iv
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CONTENTS
Forward
Abstract .
List of Figures
List of Tables
Acknowledgements
SUMMARY AND RECOMMENDATIONS
PART ONE: ADMINISTRATION AND SUPERVISION
CHAPTER I - SUPERVISION REQUIREMENTS
Responsibility for the Environment
Organizational Location
Job Description
Supervisory Training
PART TWO: STORAGE FACILITIES
CHAPTER II - SITE SELECTION
Basic Siting Methodology
Operational Requirements
Environmental- Resources to be Considered
How to Obtain Necessary Information
Site Vulnerability Analysis
CHAPTER III - FOUNDATIONS AND WORKING AREA DESIGN
• Prerequisites to Foundation Design
Foundation Design Considerations
Working Area Design
CHAPTER IV - DESIGN OF STORAGES
Environmental Requirements
Functional Requirements
Arrangement Within Operations Area
Good Practice in Salt Storage
Other Storage Practices
Practices to Be Avoided
Designing for Durability
Economic Considerations
Estimating Capacity
Page
iii
iv
vii
ix
x
9
11
12
13
14
14
14
15
15
19
21
23
23
25
33
36
36
36
37
38
51
54
55
56
56
v
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PART THREE: HANDLING OF DEICING CHEMICALS
CHAPTER V - GENERAL PRECAUTIONS IN HANDLING
CHAPTER VI - PLANNING FOR NEXT SEASON
Preseason Inventory
Equipment
Estimating Quantities
Ordering and Scheduling
CHAPTER VII - RECEIVING AND STORING DEICING CHEMICALS
Putting Materials Under Cover
Specifications and Tests
Blending Materials
CHAPTER VIII - LOADING CHEMICALS FOR USE
ANNOTATED REFERENCES
Page
67
67
68
68
69
69
70
71
71
73
78
81
86
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FIGURES
No.
1
2
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Site Selection Process
Schematic Drawing of an Unprotected Salt Pile
Leaching into Aquifers Beneath Alluvial Valley
Schematic Drawing of an Unprotected Salt Pile
Leaching into a Limestone. Aquifer
Basic Elements of Salt Storage Shed
Continuous Wall Foundation (Gravity) ;
Continuous Wall Foundation ("T" Wall)
Wall Foundation Details
Plan View of Buttressed Wall and Foundation Design
Typical Sections of Strut and Solid Buttresses
Section of Shed with Steel Columns and Interior
Buttress Wall
Interior Bulkhead Walls
Plan View Showing Optional Foundation Details
Salt Brine Storage Basin
Section of a Loading Ramp
Wooden Arch Storage Building with Loading Ramp
Wooden Rigid Frame Storage Building with Loading Ramp
Dual Storage Building
Concrete and Wood Storage Building
Storage Crib with Sliding Roof
Open-Face Concrete Block and Timber Storage Shed
Braced Timber Storage Shed
Dome Storage Shelter
Page
14
17
19
25
26
26
28
29
29
30
31
32
34
35
40
41
42
43
45
46
47
49
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No.
23 Creosoted Timber Storage Shed
24 Salt Storage Under a Viaduct
25 Covered Outdoor Storage Piles
26 Alta-«type 100-ton Storage Hopper
27 Summary of Salt Storage Building Costs
28 Calculation of Storage Characteristics of Six
Shapes of Storage Piles
29 Mixing of Salt and Sand by Flight Bars in a
Spreader Hopper
30 Loading Ramp
31 Typical Loading Pattern for a Storage Building with
One Entrance
32 Typical Loading Pattern for a Storage Building with
Two Bays
33 Typical Loading Pattern for a Storage Building with
Front and Rear Entrances
Page
50
51
53
54
58
60-62
79
81
82
83
84
•viii
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TABLES
No.
1 Capacity and Cost Summary for Salt Storage
2 Properties of Materials
3 Characteristics of Salt in Conical Piles
4 Characteristics of Salt in Windrowed Piles
5 Particle Size Distribution in Type I Sodium
Chloride
6 Chemical Composition Requirements for
Calcium Chloride
7 Particle Size Requirements for Calcium Chloride
8 Percentage Composition by Weight of Calcium
Chloride Solution
Page
57
59
63-64
65-66
74
76
76
77
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ACKNOWLEDGEMENTS
This manual was prepared in partial fulfillment of Contract No. 68-03-0154
under the direction of Richard Field, Acting Chief; Anthony Tafuri, Staff
Engineer; and Hugh Masters, Project Officer, of the Storm and Combined
Sewer Section, Advanced Waste Treatment Research Laboratory, National
Environmental Research Center-Cincinnati, Edison, New Jersey 08817.
Many individuals in the following organizations have made significant
contributions of time and material, and their participation is sincerely
acknowledged.
Allied Chemical Corporation
American Public Works Association
California Department of Transportation
Chemical Corporation, Springfield, Massachusetts
Domar Modular Systems, Inc., Utica, New York
Dow Chemical Company, Midland, Michigan
Graham Bramhall Company, Covert, Michigan
Highway Research Board, Washington, B.C.
International Salt Company
Maine Department of Transportation
Massachusetts Department of Public Works
Massachusetts Turnpike Authority
Minnesota Highway Department
Morton Salt Company
New York State Thruway Authority
North Carolina Department of Transportation and Highway Safety
Pennsylvania Department of Transportation
The Salt Institute, Washington, D.C.
U.S. Army Cold Regions Research and Engineering Laboratories, Hanover, N.H|
Wheeler Lumber, Bridge, and Supply Company, Minneapolis, Minnesota
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SUMMARY AND RECOMMENDATIONS
Each year state highway departments, turnpike authorities, municipal
street departments, and other organizations (shopping centers, hospitals,
schools) purchase approximately 9,000,000 tons (8,200,000 t)* of salt
and other deicing chemicals with a total value of about $140,000,000.
From the time these chemicals are ordered to the time they are spread on
highways and parking lots, they undergo several rounds of handling and
storage. First, they are delivered from the mine, salt-producing facility,
or port of entry to regional distribution points. From there, they are
distributed (usually by truck) to highway maintenance yards. Finally,
they are loaded onto spreader trucks for their final use during storms.
At each step of the journey from mine or salt-producing facility to high-
way, there are numerous opportunities for loss of material. At any of
the storage points, salt exposed to weather is dissipated into the immediate
environment by rain and wind. Rain will reduce a salt pile at the rate
of about 1/4% per annual inch of precipitation. That figure may appear
insignificant, but in an area with 40 in. (101 cm) of precipitation each
year, a salt pile left exposed for half a year will lose 5% of its volume.
An exposed salt pile of 500 tons (450 t) would lose 25 tons (23 t) under
these conditions, not counting losses due to wind.
Loss of material provides cause for several kinds of concern. Chief
among these, from the standpoint of the Environmental Protection Agency,
is the concern for environmental damage that may result from water- and
wind-borne salt. In Massachusetts, for example, seepage from storage
piles has contaminated town water supplies. The 25 tons (23 t) of salt
carried off the 500-ton (450-t) salt pile cited above is sufficient to
pollute almost 15 million gal. (56.7 million 1) of water to the 250 milli-
grams per liter (mg/1) chloride maximum recommended by the U.S. Public Health
Service for drinking water supplies. Water of even lower salinity has
been known to cause corrosion problems in industrial plants. That same
25 tons (23 t) of salt runoff is capable of raising the sodium content
in almost 120 million gallons (454 million 1) of water to threshold level
(20 mg/1) beyond which it becomes dangerous to medical patients restricted
to low—sodium diets.
Cost is another area of concern. Although the direct cost to a highway
agency of losing 25 tons (23 t) of salt over a season is only about $400-
$500, there are additional .indirect costs. These indirect costs are
borne partly by the agency, in the form of corrosion damage to equipment
in the yard, but mostly by other segments of the public. It is very
difficult to calculate the total damage caused by salt runoff, partly be-
cause the effects are dispersed and partly because of the problem of placing
a monetary value on the deterioration of public health resulting from
sodium- and chloride-polluted drinking water.
* Throughout this report metric units are given in parentheses.
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Because of hazards posed by salt stored in exposed piles, this manual's
recommendations on salt handling practice in Part Three are based, except
as noted, on the presupposition that salt will be stored in permanent
buildings. As the data in Part Two, (which describes storage facilities)
indicates, fixed storage is not wholly uneconomical. The annual value of
salt saved by protecting it from the weather is sufficient over a period
of ten to forty years, depending on annual precipitation and construction
costs and methods, to offset much of the cost of a storage building.
THE INTENT OF THIS MANUAL
This manual aims at establishing an operational balance between two
important, but sometimes conflicting, public-policy goals—clear roads
and clean water. Keeping highways and roads clear in winter is vital
to the nation's commerce and to the safety and convenience of the traveling
public, and the most effective and economical deicing material is sodium
chloride—ordinary salt, sometimes mixed with calcium chloride or sand.
Salt runoff from highways and storage areas mixes witlfi surface waters,
and in dilute form either enters streams and lakes or seeps into the
ground. Depending on conditions of surface and soil, salt runoff may
seriously degrade the quality of the receiving water.
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Protection of the environment is the primary concern of the U.S. Environ-
mental Protection Agency. Recognizing that the nation cannot afford to
pursue a goal of clear winter roads to the exclusion of concern for water
quality, or vice versa, the EPA has commissioned studies for the purpose
of establishing the best practices for balancing the goals of clear roads
and clean water. The results of these studies appear in two manuals:
a Manual for Deicing Chemical Application Practices (EPA-670/2-74-045)
which recommends salt—application methods and maximum usage levels for
various storm and temperature conditions; and this document, a Manual
for Deicing Chemical Storage and Handling.
This manual is written for people who are directly concerned with the
storage and handling of salt. State and municipal officials will be
concerned with the initial capital-cost, environmental, and land-use
aspects of storage and handling and with possible later costs resulting
from damage to water supplies, as well as with public sentiment. Public
works administrators and yard foremen, who have the day-to-day responsibility
for storing and handling salt, will be concerned with the details of site
construction, loading and unloading, storage, and covering piles. Operators
of large non-highway installations that have large paved areas to keep
clear in winter (parking lots and driveways) need to be concerned with
both policy and operational aspects of salt handling and storage.
The manual is intended to be, above all, practical. Its recommendations
are based on the best of current practice, as observed during many weeks
spent with highway crews in snow-belt states. The recommendations recognize
that snow conditions, storage site availability, and budgets vary widely.
Exotic solutions requiring large capital outlays and special equipment
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are avoided. The manual covers the following areas:
Part One: Administration and Supervision
I. Supervision Requirements
Part Two: Storage Facilities
II. Site Selection
III. Foundation and Working-Area Design
IV. Design of Storages
Part Three: Handling of Deicing Chemicals
V. General Precautions in Handling
VI. Planning for Next Season
VII. Receiving and Storing Deicing Chemicals
VIII. Loading Chemicals for Use
Much of what this manual advocates is already recommended practice. In
recent years, salt has been stored increasingly under some protective
cover, whether a tarpaulin or a roof, and on sloped impermeable pavements
rather than on the bare ground. Design and operating practice found in
this manual are based upon, or direct borrowings of, plans and descriptions
reported by highway personnel, the Salt Institute, and researchers in
publications including state maintenance manuals; papers presented to
the Highway Research Board, the North American Snow Conference, the American
Public Works Association, and other technical and professional associations;
and corporate and institutional publications.
What, then, is the unique contribution of this manual?
valuable in several ways:
Probably, it is
e Range. The manual covers all aspects of storage and handling,
from the estimation of storage requirements to the public-policy
implications of salt storage.
• Balance. The manual concerns itself equally with operational
and environmental issues.
* Perspective.. The manual draws upon a range of literature, as
well as first-hand observation of storage and handling operations.
• Alternatives. The manual presents a procedure whereby its users
can derive operationally and environmentally satisfactory solutions
that are suited to their particular needs and constraints.
In short, this manual aims at providing a complete, sensible, usable,
down-to-earth guide to the problems and issues connected with salt
storage and handling.
Many states and municipalities will undoubtedly wish to establish laws
or regulations for ensuring the proper handling and storage of salt.
While this manual does not offer a "model code," the remainder of this
summary contains the essential points that should be included in codes
or regulations. These points are classified under three headings
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corresponding to the three Parts of this manual: Administration and
Supervision, Storage Facilities, and Handling of Deicing Chemicals.
ADMINISTRATION AND SUPERVISION
Responsibility for the Environment
Components of Supervision. Supervising maintenance engineers, in addition
to their expected competence in engineering and administrative areas,
should also be knowledgeable about the following topics:
• Basic principles of groundwater hydrology
• Emerging federal and state environmental and land-use policy
Organizational Location. Environmental responsibility should be located
at the field-office level. Each field office should have one specialist
who has clear responsibility for environmental matters. This specialist
should be able to call upon the technical expertise resident in other
state or local agencies as needed.
Supervision Requirements
Job Description. The following responsibilities should be added to the
descriptions of supervisory maintenance engineers or specialists with
environmental responsibilities:
• Design and ensure proper use of system for reporting usage of
deicing chemicals.
• - Review and interpret periodic salt use reports.
• Schedule ordering and delivery of salt so as to minimize risks
of salt runoff.
• Identify and select sites for salt storage facilities.
• Supervise design and preparation of storage-facility plans
and specifications.
• Cooperate with other government agencies on environmental and
public health aspects of storage.
• Ensure proper maintenance of storage through training and on-
the-spot inspection.
Supervisory Training. Supervising maintenance engineers should participate
in occasional in-service training courses. Topics covered should include
groundwater hydrology; environmental aspects of planning, design, and
construction; and procedures for complying with federal and state environ-
mental law.
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STORAGE FACILITIES
Site Selection
Basic Siting Methodology. Several possible storage sites should first be
identified according to their ability to satisfy operational requirements
(site size and topography, proximity to service area). These sites should
then be screened to find the one that best conforms to environmental
criteria: geologic and hydrologic, biologic and ecologic, and historical
and aesthetic. The selected site should then be designed to mitigate any
remaining potential for environmental damage.
Operational Requirements. Deicing chemicals should be stored near the
center of the road section area, close to a major right-of-way. Storage
sites should be close enough to permit a truck to reach the boundary of
the next section and return before exhausting 90% of its load. Storage
sites should have enough space for structures containing 50-100% of the
seasonal requirements for chemicals and treated abrasives. If possible,
storage sites should be located on rail sidings to permit direct receipt
of chemicals.
Geologicand Hydrologic Criteria. Basic information about the terrain
underlying a potential site should be sought as part of the site location
process. Particularly to be avoided is a site location in an aquifer
recharge area, where salt seepage may pollute wells.
Biologic and Ecologic Criteria. Species differ in salt tolerance. The
best way to prevent damage to flora and fauna is through proper design
of storage sheds and good housekeeping practices.
Historical and Aesthetic Criteria. An inventory of potential sites
should consider whether any are exposed to "landmark" areas.
Site Vulnerability Analysis. Priority should be given first to protection
of water supplies—groundwater and surface water. Next, attention should
be given to preserving a site's historical or aesthetic character.
Foundations and Working-Area Design
Prerequisites to Foundation Design^ Factors to he taken into account in
foundation design include topography (siting and shed pad higher than
surrounding terrain to prevent run-in), soil and subsurface conditions,
frost penetration and snowfall, type and layout of structure with respect
to dead and live loads, applicable building codes, requirements of material
handling operations, and aesthetics.
Foundation Design Considerations. Foundations must be designed to withstand
lateral loading by stored salt. Continuous walls or buttress walls may be
used. For either type, reinforced concrete or its strength-equivalent
should be used. The floor slab inside the building should be made of
impervious material. A minimum floor covering calls for 2.5-in. (6-cm)
bituminous concrete on a 6-in. (15-cm) compacted gravel base.
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Working Area Design. Working area must be designed to prevent brine
runoff into environmentally sensitive areas. In areas with particularly
vulnerable water supplies, all brine runoff must be contained in a lined
collection basin from which brine is pumped out for removal to a nonsensitive
area.
Design of Storages
Environmental Requirements. Storages should protect chemicals from direct
precipitation at all times, keep the material within prescribed bounds,
and not leak or burst as a result of accidents.
Functional Requirements. Storages should be large enough to hold 50-100%
of seasonal requirements without overflowing, not require special handling
procedures for rapid loading, allow enough vertical clearance for delivery
trucks and raised loader buckets, allow for maneuvering room for loaders,
and be reinforced or protected at key points.
Arrangement within Operations Area. Several different kinds of storage
areas have different characteristics. Major distribution areas receive
chemicals by rail or boat and distribute it usually within a 50-mile
(80-km) radius; storage may exceed 100,000 tons (91,000 t) under tarpaulins
or reinforced plastic film. Highway area is measured in "lane miles"
or miles of traffic lanes. .Thus a one-mile stretch of a two-lane road
measures two lane miles. District base areas -usually serve 1500 or more
lane miles (2400 lane km) and have repair and garage facilities; covered
storage should be provided for up to 3,000 tons (2,700 t) of chemicals
and for treated abrasives when used in the snow and ice control program.
Crew areas typically service about 100 lane miles (160 lane km) of road
and require covered storage for up to 1,500 tons (1,400 t) of chemicals
and for storage of treated abrasives. Reload areas, located near the
dividing line between two crew areas, require covered storage for about
500 tons (450 t) of chemicals and for storage of treated abrasives. Both
crew and reload areas should provide a ramp for loading spreader trucks.
Good Practice in Salt Storage
Good practice requires a building that meets both functional and environ-
mental requirements in the most economic manner. Numerous building types
described in the manual, already in use, fulfill these requirements.
Notable features of these sheds should be emulated whenever possible:
• Shield truck-loading operations from prevailing wind and weather
(indoors whenever possible);
• Be secure to prevent accidents to youthful trespassers;
• Have floor and paving sloped to drain any water out of the
shed and away from the salt pile;
• Have sufficient bituminous concrete pad around the exterior to
allow free circulation of trucks and loaders;
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• Offer protection to parts of the structure exposed to loading
operations;
• Have galvanized metal hardware and building elements to prevent
corrosion;
• Be adequately ventilated, particularly for indoor loading and
unloading operations;
e Have ample lighting both indoors and out-of-doors to permit
nighttime operations;
• Use durable materials that require minimal maintenance.
Other Storage Practices. Salt is sometimes stored in covered piles,
overhead hoppers, and converted grain silos. Each of these alternatives
has problems. Covered piles require exceptional measures in housekeeping
to prevent salt-brine runoff. Overhead hoppers are convenient and reliable,
but offer limited capacity at relatively high cost. Converted silos have
limited capacity and are subject to problems of salt cakes jamming their
mechanisms.
HANDLING OF DEICING CHEMICALS
General Precautions
Three major precautions should be observed during handling of bulk deicing
chemicals:
1) Keep the chemicals dry, preferably in permanent covered structures.
2) Keep the handling area and equipment clean.
3) Keep to a minimum the number of times the materials are handled.
Careful attention to these precautions will ensure that the chemicals do
not cake up and cause problems in handling and spreading and that exposure
to the environment is minimized.
Planning for Next Winter
Planning for the next winter should be done immediately after the present
winter season, while memories are fresh.
Pre-season Inventory. On the basis of recent experience, an assessment
of the adequacy of chemical quantities ordered, equipment, and personnel
complement should be made. Steps should be taken to correct deficiencies.
Equipment Used in Handling. Most maintenance yards use front-end loaders
for moving bulk chemicals. Other possibilities include bulldozers, material
throwers, and conveyors. The front-end loader is preferred because it is
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relatively trouble-free and may be used for many jobs during the remainder
of the year.
Estimating Quantities. Establishing the amount of chemicals needed for
next season's snow and ice control program should take into account the
amount used during the past season, adjusted to account for changes in
the number of road miles for which the yard is responsible or in the
recommended level of usage (tons/mile or t/km).
Ordering and Scheduling. It is recommended that a minimum of a half ^year's,
and preferably a whole year's, supply of salt be stored at each field
station, and that deliveries be so scheduled that the season's supply is
in storage by early October.
Receiving and Storing Deicing Chemicals
Putting Materials Under Cover. Salt should be delivered in fair weather
and put under cover immediately. The equipment and the unloading area
should be cleaned thoroughly at the end of the day. Similar precautions
should be observed for calcium chloride and for mixtures (sodium/calcium
chloride, sand/salt).
Specifications and Tests. Sodium chloride delivered in bulk should conform
when delivered to ASTM Standard Specifications for Sodium Chloride D632.
Calcium chloride should conform to ASTM D-98. Materials when received
should be tested for conformity to these specifications and for the presence
of anti-caking agents.
Loading Chemicals for Use
Trucks or spreaders should be loaded, if possible, inside the storage shed.
Trucks should be cleaned of loose salt before leaving the loading area.
If trucks are loaded outside the shed, the loading area should be cleaned
as soon as possible after the truck leaves. Spilled material should be
placed on the face of the pile so that it is loaded onto the next truck.
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PART ONE: ADMINISTRATION AND SUPERVISION
CHAPTER I
SUPERVISION REQUIREMENTS
The many suggestions set forth in this manual depend for their effectiveness,
of course, upon the cooperation and outlook of hundreds of highway department
employees. They take their cues, in both technical and policy matters,
from their supervisors who, even to the top level, must clearly endorse
and support a policy of safe salt storage and handling. These cues should
be explicit and unequivocal. This section points out those aspects of
proper salt storage and handling where supervision is crucial.
Although a number of specific comments and recommendations are made below,
one general point should precede the discussion. Leadership in general,
and supervision of salt storage and handling, which is merely one aspect
of highway maintenance, is by its nature not a separate commodity or
function. It cannot be bought in packages. It cannot be contracted out.
It is not the task of one man only; nor is it a full-time task performed
by a staff specialist. Instead, responsibility for salt storage and
handling is only one of the many assignments of maintenance supervisors.
Ideally, they should be knowledgeable about a number of specific topics,
to be described below. These are topics relatively new to highway
officials, the result of rising environmental consciousness during the
past several years and, therefore, not part of the standard curriculum.
As a result, busy supervisors at the middle and top levels are likely to
learn these topics on the run.
Therefore, detailed knowledge is probably less important than proper
attitudes. To store and handle road salt safely requires many "tradeoff"
decisions, balancing such goals as economy and efficiency against such
goals as safety of public water supplies. In specific siting decisions,
answers are not likely to come easily or quickly. Hence, maintenance
supervisors must first be sympathetic to the general goal of environmental
protection, as well as to the general goal of building and maintaining
good highways, and then apply common sense and good judgment to making
progress toward both goals.
In sum, good practice in salt storage and handling requires various kinds
of technical knowledge. But in the end, probably the most important
factor is responsible and sensible leadership by maintenance supervisors.
RESPONSIBILITY FOR THE ENVIRONMENT
Components
In addition to specific engineering and technical knowledge, maintenance
supervisors should also have detailed knowledge about several topics
bearing upon the environmental aspects of storage sites.
9
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First is the set of environmental impact requirements of federal, state,
and local authorities. Details vary from jurisdiction to jurisdiction,
but the general purpose is to require consideration of side effects or
secondary consequences of proposed projects on the environment.
Although actual environmental impact statements may be required in only
rare cases for salt-storage facilities, the kind of decision-making
displayed in an impact statement should be followed in construction and
enlargement of salt storage facilities. This both ensures environmentally
sound decisions as well as provides the basis for an environmental report,
should one ever be required. As of March 1974, the current guidelines
for environmental impact studies issued by the President's Council on
Environmental Quality were published in the Federal Register Vol. 38,
No. 147, August 1, 1973. State and local regulations pertaining to
environmental planning and possible environmental impact statements
should be consulted as well for guidance.
Second, supervisors must be familiar with the main principles of ground-
water hydrology, at least enough to know when to call for help from
specialists in this field. Taking care to site storage sheds far from
surface waters is not enough. Underground seepage and flows must also
be considered in relation to possible drainage of brine from a proposed
storage site.
Third, supervisors should also be aware of possible requirements of
emerging state land-use policies. At this writing, early 1974, the
topic is too new to allow useful detailed statements. However, it is
clear that concern about improving our usage of land, for both environmental
as well as developmental purposes, is rising at both the federal and state
levels. Therefore, it seems likely that, in time, state and local authorities
will be adopting new and stricter criteria governing land use, about which
highway engineers will have to become familiar.
These comments are phrased in terms familiar to state and county-level
highway maintenance personnel. They apply with equal force, however,
to engineers and turnpike authorities responsible for maintenance of
roadways for private organizations as well, including hospitals, universities,
schools, cemeteries, and commercial establishments such as shopping plazas
and truck depots. In time, all may find themselves regulated to greater
or lesser degree by state or local laws seeking to prevent further salt
contamination of the environment, especially public drinking water supplies.
Clearly, many problems can be either created or solved when one is
deciding where to site salt storage sheds. In many or most cases,
especially in settled areas with existing highways or roads, these
decisions have been made already; the problem may be, therefore, only
how to improve upon the existing facilities and system. However, where
new roads or highways are to be constructed and associated storage sites
to be chosen, supervising engineers must be sure that proper siting
requirements are considered early, during the planning and design stages.
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In many departments, the functions of planning, designing, and maintenance
are organizationally distinct, thus posing problems of coordination. For
this reason, top-level engineers, with responsibilities for supervising
all of these activities, should be sufficiently aware of the principles
of proper storage to ensure that appropriate coordination at an early
stage does in fact occur.
ORGANIZATIONAL LOCATION
The nature of the problem of siting and constructing storage sheds requires
that a Department's environmental capability be located at the field
office level, "where the action is," rather than only at a distant
central headquarters. Each field office, district or division, probably
cannot have an engineer specializing full time in storage problems.
However, each field organization should have one person who is clearly
designated with responsibility for environmental problems, who should
play a significant role in decisions about siting, designing, and constructing
storage facilities.
The designated environmentalist in an agency's field office should expect
to, and be able to call upon environmental specialists from the state
headquarters staff. A likely possibility in the immediate future would
be for the state Department of Transportation or Department of Public
Works, whichever»the organization, to request such expertise, for example
in groundwater hydrology, from another state agency concerned with natural
resources or environmental protection.
To facilitate interagency cooperation, it is desirable that the field area
of the highway agency have the same boundaries as the field area of
environmental agencies. For example, a highway district may be responsible
for constructing a road, with associated maintenance facilities, across
two watersheds for public drinking water supplies. If each watershed is
the responsibility of a different environmental protection field office,
then the highway district's environmental specialist must negotiate with
two instead of one counterpart, with resulting delays and complications.
Although the designation of field district boundaries is a decision
resting with the top levels of two or more state agencies, and further
it is a decision involving many factors beyond the scope of this manual,
it is still mentioned here as a factor that bears upon the siting of
salt storage facilities.
As noted above, planning, design, and construction are often separate
functions. Just as they must, therefore, be coordinated in general by
top-level supervisors, detailed aspects of their work should be coordinated
in fact at the field level by the environmental specialist, acting on
the authority of the field office head, for example the District Engineer.
In smaller jurisdictions such as cities or towns or some counties, these
different roles might not be required. Environmental aspects of salt
storage should be the responsibility of the central public works office,
or perhaps even of the chief engineer or highway superintendent.
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JOB DESCRIPTION
Since no distinct full-time job centering on salt storage facilities is
envisioned, no full job description for the environmental specialist is
set forth. Instead, those environmental engineering aspects are indicated
which should be added to present job descriptions of maintenance supervisors.
1. Identify and select sites for salt storage facilities, meeting
environmental as well as engineering requirements and drawing
upon expert assistance as necessary from headquarters staff.
2. Develop, or assist in the development of, environmental baseline
data required for planning and possible environmental impact
statements. Essential baseline data would include groundwater
information and annual reports of its sodium and chloride levels
(expressed in mg/1). Without such baseline data as a background,
effects of various management practices, for good or for bad,
cannot be measured objectively. Just as a planning or design
engineer inventories materials, reports, etc., the environmental
specialist should gather these data of importance in the environ-
mental aspects of engineering decisions, much of it from other
governmental agencies.
3. Supervise design and preparation of construction specifications
and plans for storage facilities, arranging for and ensuring
coordination as required among departmental offices.
4. Be responsible for, or assist in, cooperative relationships
with other governmental agencies concerned, for example, about
environmental or public health aspects of storage.
5. Ensure proper maintenance of facilities after construction,
checking, for example, the integrity of drainage channels and
basins.
6. Supervise instruction of maintenance workers in environmentally
safe handling of salt and other deicing chemicals during delivery,
placing in storage, loading, and cleaning up after storms.
7. Perform occasional on-the-spot inspections during winter operations
to observe actual handling practices and take steps to improve
sub-standard practices.
8. Design and ensure proper use of the department's system for
reporting usage of deicing chemicals, for purposes both of
divisional management and preventing use of salt in excess of
established standards.
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9. Review periodic salt use reports, interpret them as necessary
to higher authority and other agencies, such as Conservation
Commissions and public.health officers; when indicated by
abnormal reports, take corrective actions to improve storage
and handling practices.
10. Schedule annual ordering and deliveries of salt, in relation
to capacity of site(s), so as to minimize transfers, spillage,
temporary unprotected storage, and similar operations which
increase the probabilities of dissolved salt percolating into
groundwater.
SUPERVISORY TRAINING
Supervising maintenance engineers are presumed to be mid-career officials,
with time to participate only in occasional in-service training courses.
Such courses, perhaps a few days in length, should include at least three
kinds of teaching techniques: formal instruction, problem-solving exercises,
and field observation.
Formal instruction should include consideration of aspects of two basic
areas, special engineering topics and environmental protection requirements
and procedures. The special engineering topics should include groundwater
hydrology; environmental aspects of planning, design, and construction
of storage facilities and maintenance areas; and winter operations where
salt and other chemicals are used. Environmental quality topics would
vary from state to state, but generally include discussions of federal
and state environmental laws, implementing requirements prescribed by
the Federal Highway Administration and the state highway agency, and finally
specific procedures for complying with those requirements, for example,
holding public hearings, developing possible environmental impact statements,
developing programs for minimizing chemical usage, and meeting regular
reporting requirements.
Formal instruction should always be accompanied by a variety of problem-
solving exercises which are tailored to the topics and manner of presentation.
For example, trainees might be asked to select and evaluate groundwater
hydrological data, to identify and rank possible storage sites for a hypo-
thetical highway district, to draft portions of an environmental impact
statement required by a state, or to develop operations procedures that
will minimize the use of chemicals.
Formal instruction and problem-solving exercises should be complemented
by opportunities for observation in the field. Trainees might visit and
inspect examples of good storage facilities, observe or even assist in
the instruction of maintenance workers prior to the winter season, observe
a public or interdepartmental hearing on proposed storage sites.
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PART TWO: STORAGE FACILITIES
CHAPTER II
SITE SELECTION
The selection of sites for storage of deicing chemicals has traditionally
been governed by selection of road maintenance sites. These, in turn,
have often been located on scraps of land left over when the road was
built and, for the most part, little consideration has been given to the
long-term environmental impact of chemical storage on these sites. In
this section are outlined a basic siting methodology, operational require-
ments and environmental resources to be considered, sources of information
needed before sites can be evaluated properly, and guidelines for assessing
relative vulnerabilities of sites to pollution.
BASIC SITING METHODOLOGY
The placement of storage piles of deicing chemicals is largely determined
by operational requirements discussed later. This is a necessary priority
but can lead to locations that are not optimum from an environmental view-
point. As a result, the storage strategy must rely basically on exclusion
of the chemicals from the environment by careful storage building design,
careful salt handling procedures, and effective housekeeping in the storage
yard vicinity. Environmental siting parameters are, therefore, focused
primarily on•identifying and describing the relative vulnerability of
hydrological, biological and historic/aesthetic resources in candidate
storage areas.
In practice, the siting elements function in a decision path shown sche-
matically in Figure 1. Several candidate sites are usually selected
CANDIDATE
SITES
1 _
2 —
3 —
4 —
5 —
6 —
7 —
Y
P
GEOLOGIC BIOLOGIC HISTORIC
HYDROLOGIC ECOLOGICAL AESTHETIC
»•
»
»•
»
»
S
7
/
1 i
— >» — *
— »» — »
— ^ — *
S
/
— ^ — »•
— »» — -*•
/
7
/
1
— »
SELECTED
SITE
OPERATIONAL SITE
OPERATIONAL
REQUIREMENTS
ENVIRONMENTAL SITING FACTORS
Figure 1 Site selection process
14
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on the basis of operational requirements. Expert opinion is obtained from
specialists who are competent to evaluate environmental siting factors,
which will be discussed in detail subsequently. A site is then selected
for "compatibility" with all of the competing requirements. As a final
step, design specifications are derived to eliminate or minimize small,
residual environmental problems.
OPERATIONAL REQUIREMENTS
The operational requirements for storage and handling of deicing chemicals
are governed by snow and ice-control policies and user techniques. (For
techniques, see Manual for Deicing Chemical Application Practices. EPA-
670/2-74-0-045.^Briefly, some of the general requirements are summarized
as follows.
• A supply of deicing chemicals should be stored close to the
center of the road section in which it is to be used, thereby
minimizing the transportation distance between storage and
usage.
• Storage should be within or closely adjacent to the right-of-
way of a major artery of the road section so that the radius
of storage is confined within the radius of maximum usage.
e Adjacent storage locations should be close enough to permit
spreader trucks, when properly loaded and operating at normal
spreading rates, to reach the boundary of the next road main-
tenance section and to return before 90% of the chemical or
abrasives load has been exhausted.
• The storage site should have sufficient area for structures
capable of storing at least one-half (and preferably all) of
the seasonal requirements for chemicals and treated abrasives,
for one or more loading docks, and for unimpeded access when
materials are placed in storage and removed during winter
storms.
e Location of the site on a rail siding is highly desirable and
strongly advised particularly when large quantities of salt
and calcium chloride are to be stored. Shipment in covered
hopper gondolas directly from the salt mine or from the
supplier's storage minimizes transportation and handling
costs, assures quality of the chemical, prevents absorption
of moisture, and minimizes unnecessary losses into the
environment.
ENVIRONMENTAL RESOURCES TO BE CONSIDERED
Good quality.information on geology and soils is the fundamental input
needed for the assessment of ground and surface water hydrology. Biologic
resources may include but not be limited to nesting or spawing grounds,
15
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unique or endangered species and significant ecologic zones such as coastal
estuaries, lagoons, or interior wetlands. Historic and aesthetic resources
include buildings and/or sites identified by competent authorities as
having historical significance; this applies to areas of archeological
interest as well as to recreational parks and scenic areas.
The following discussion is intended to provide generally useful back-
ground information on the basic environmental siting parameters.
Hydrologic Resources
Groundwater and surface water are closely related in hydrologic terms
since, for example, stream water may infiltrate a stream bed and join
the groundwater system only later to reappear downstream as recharge to
the surface water. Hence, while the two resources are frequently considered
apart from one another, they are in fact a part of one continuous water
exchange known as the hydrologic cycle. Therefore, contamination introduced
to one part of the cycle can lead to contamination of another part.
Groundwater-
Groundwater reservoirs or aquifers, as they are commonly referred to, are
as varied in character, hydraulic behavior, extent, and vulnerability
to pollution as the geologic terrains that contain them. Groundwater
may occur in unconsolidated sand and gravel, fractures in limestone or
other consolidated rocks, the pore spaces of a sandstone, or the void
spaces in volcanic rocks. The aquifers may be under confining pressure
(artesian conditions) or in equilibrium with atmospheric pressure (water
table conditions). The aquifers may vary in extent from localized sources
capable of a few thousand gallons a day to sources as large as the Ogallala
Aquifer, which is about 800 mi (1300 km) long and 300 mi (480 km) wide,
including a surface area of 35,000 mi2 (91,000 km2) in South Dakota,
Wyoming, Kansas, Nebraska, Colorado, Oklahoma, Texas, and New Mexico.
Several typical geologic settings are described below in order to establish
their basic characteristics, a necessary prerequisite in evaluation of
their vulnerability.
Alluvial valleys -Alluvial valleys such as the one represented schematically
in Figure 2 contain unconsolidated sediments (alluvium is gravel, sand, or silt
thicknesses varying anywhere from less than 10 ft (3 m) to hundreds of feet.
Aquifers may be present at very shallow depths and can be of major significance
An example whould be the gravel aquifer serving Schenectady and Rotterdam,
New York. The top of the aquifer is about 20 ft (6 m) beneath ground surface
and is located in the alluvial valley of the Mohawk River. The aquifer
produces about 25 million gal. (95 million 1) a day of potable water.
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FLOOD PLAIN
RECHARGE ZONE
Figure 2 Schematic drawing of an unprotected salt pile leaching into aquifiers
beneath alluvial valley
Aquifers of this kind are vulnerable to pollution from a variety of
sources including sand and gravel excavation, spills of toxic substances
on the surface above them, and degraded surface waters which may be in
hydraulic contact with the aquifer. These pollution sources are most
critical when they exist or occur within an area influenced by pumping
(a recharge zone as indicated on the figure) of large amounts of water
from such an aquifer since the sediments overlying the aquifers are
usually quite permeable, that is, they are capable of transmitting very
large amounts of water to the aquifer. The recharge areas can be identi-
fied by standard groundwater hydrologic methods. Protection of these
recharge areas is extremely important since it may not be economically
practical or even technologically feasible to purify an aquifer once it
has been polluted.
Limestone (carbonate) terrains -This geologic terrain, such as is found in
Central Pennsylvania (and in many other places), is typified by limestone
bedrock with an overlying soil zone of highly variable thickness and com-
position. Groundwater occurs principally in vertical fracture zones in the
bedrock, and, therefore, groundwater flow has highly directional properties
unlike that in the alluvial aquifers. For example, a spring at Bellfonte,
Pennsylvania produces about 11 million gal. (42 million 1) of water a day
from a major fracture zone, many miles in linear extent, in the limestone.
Generally speaking, contaminants can be transmitted more rapidly in a
limestone aquifer than in an alluvial aquifer.
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Figure 3 shows an unprotected stock pile being leached by precipitation,
with subsequent percolation of the leachate into the groundwater system,
and resulting contamination of a water well.
Consolidated porous rock terrains -
A large volume of groundwater is contained in rock units, some of which
are deeply buried. These rocks contain interconnected pore volumes capable
of holding and transmitting water. The Dakota sandstone in North and South
Dakota is such a unit. Aquifers of this type are least vulnerable to
pollution from a source such as a salt stock pile. Since withdrawal
areas may be very distant from the recharge areas, the pollution problem
is potentially less severe.
Surface Water -
The situation with regard to pollution of surface waters is basically less
complex than that of groundwater. Surface waters are more accessible to
pollution but for obvious reasons are also more amenable to remedies.
From an environmental viewpoint, once again emphasis should be placed on-
exclusion of the salt from the environment, including surface water. Run-
off from a salt storage pile should not be allowed to flow into ponds,
streams, lakes, or other surface water bodies; this can be accomplished
by the proper storage shed and working area design, handling techniques,
and housekeeping practices in the storage yard.
Biologic and Ecologic Resources
Biological and ecolo'gical resources are enormous in diversity and may be
defined as broadly or narrowly as one wishes. Any or all species may be
affected by the presence of salt in the environment depending only on the
amount and concentration and on the salt tolerance of the species. Basically,
the principal of exclusion should once again be utilized to protect these
biotic elements of our environment from the effects of salt. Proper
storage building design, salt handling techniques, and storage yard house-
keeping practices are the best answers to the problem.
Historical/Aesthetic Resources
These siting criteria are perhaps the most difficult to satisfy since
they are not simply remedied by good engineering design. In practice the
best course is to inventory candidate sites for their proximity and ex-
posure to such areas. Only rarely will all candidate sites be undesirable
in this respect; however, failure to address this question may lead to
delay in gaining final site approval.
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, ZONE OF
/ FRACTURE
/CONCENTRATION
Figure 3 Schematic drawing of an unprotected salt pile
leaching into a limestone aquifer
HOW TO OBTAIN NECESSARY INFORMATION
Information required to evaluate the hydrologic, biologic, and historical/
aesthetic parameters discussed above can be derived from a number of
sources, which are too diffuse in nature and large in number to identify
in complete detail. Those basic sources are mentioned here which will
lead the inquirer to additional titles and/or experts.
Hydrologic Resources
The largest single repository of information on groundwater in the United
States is the Water Resources Division of the U.S. Geological Survey,
which conducts investigations, surveys, and research on the occurrence,
quality, quantity distribution, utilization, movement, and availability
of the Nation's surface- and groundwater resource.
The field organization of the Division is comprised of four regional
offices—Northeastern, Southeastern, Central, and Western—each headed
by a Regional Hydrologist. Each region consists of several States, and
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each Regional Hydrologist, with line authority from the Chief Hydrologist,
directs water resources programs in his region. The District offices,
each headed by a District Chief, generally are located in State capitals
with jurisdictional boundaries corresponding to State boundaries.
A series of pamphlets entitled "Water Resources Investigations in (name
of particular State)" is a project of the Water Resources Division to
inform the public about its current programs in the 50 States and Puerto
Rico. Pamphlets for all States are available free upon request to the
U.S. Geological Survey,- Washington, D.C. 20244. Pamphlets for specific
States are available from the appropriate District office listed in a
pamphlet entitled "Guide to Regional and District Offices of the Water
Resources Division U.S. Geological Survey" which is available from the
Director, U.S. Geological Survey Washington, D.C. 20242.
The Guide shows the four geographic areas that make up the regions of
jurisdiction of the Regional Hydrologists. Locations, telephone numbers,
and office hours for the Regional offices and the District offices are
also given.
Basic information on the geology of areas in the United States can be
identified by reference to the following documents:
"Publications of the Geological Survey 1879-1961"
"Publications of the Geological Survey 1962-1970"
"Publications of the Geological Survey [year-to-year]"
"New Publications of the Geological Survey [Month-Year]"
These sources will provide access to a vast amount of information.
Additional sources include the reports and studies of the State Geological
Surveys usually located in the capital cities. Universities also represent
a significant resource—particularly the Departments of Geology and Geo-
physics for groundwater-related issues and the Department of Civil Engineering
for surface-^water problems.
Finally, in local areas various earth science and engineering consulting
companies maintain staffs of experts and usually have highly pertinent
local information and experience.
Biological and Ecological Resources
A variety of information sources on the biology and ecology of various
regions is available. Clearly, however, the likelihood is small that a
highly specific study of the biological and ecological content of an area
will be available for each candidate site. Therefore, it will be necessary
to obtain qualified assistance in conducting a reconnaissance study of
the candidate sites. This assistance may be available from a neighboring
university's Biology and Botany department, state/Federal agency, consulting
firm, local horticultural group and/or Conservation Commission, State
Fish and Game Commission, the National and/or State Audubon Societies.
20
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For example, the Soil Conservation Service provides in their soil series
reports for an area, maps of the different soil series for the area with
corresponding descriptions of their producing capability and suitability
for supporting various vegetation and wildlife. In general, adequate
information is available from the sample sources suggested above to meet
the needs of the storage facility site selector.
Historical Aesthetic Resources
Local knowledge of historic sites is usually readily available from local
historical commissions and societies. Federally designated historic sites
are tabulated in the National Register of Historic Places. Aesthetic
resources are basically those associated with existing or planned park
and/or recreational areas. (This is not to say that areas outside this
definition have no aesthetic value or merit.) The most useful sources
of information on such areas are local Conservation Commissions, Planning
Boards, Park Commissions (both State and local), as well as Regional
Planning Agencies. Additional information resources include but are not
limited to the various State Audubon Societies and other groups who are
active in studying the environment.
SITE VULNERABILITY ANALYSIS
At this point a general methodology has been established for salt storage
facility siting, and several important environmental variables have been
identified, together with sources of information related to them. The .
responsible official must now, with access to technical advisors, identify
that site which is operationally and environmentally best suited to use
as a salt storage facility.
It is fair to say that salt effects on water supply have loomed largest
in terms of the environmental impact of salt storage and, most particularly,
salt usage. Biological and botanical responses to salt have largely
involved salt usage, although inadequate storage practice can lead to
similar problems. Historical and aesthetic qualities are most related in
terms of impact by the storage of salt and not to salt usage. As a
result, the following priority areas of environmental concern in terms
of salt storage are suggested.
• Protection of water supplies—groundwater and surface
water and
• Preservation of the historical or aesthetic character of
a site.
Clearly, the first of these is preeminently important in terms of
environmental protection. Sites should be excluded from consideration
if:
21
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• They are within or adjacent to a municipal groundwater
well field or an area of residential development which
is dependent on well water either on a single house basis
or from a private water company or
• They are in close proximity to surface water bodies, parti-
cularly small ones and those used for public water supply.
One additional operational problem requires special mention. Salt trucks
are generally hot-water washed for maintenance purposes. All of the
good housekeeping, storage shed design, and handling expertise is wasted
if the truck wash area runoff is either:
• Released untreated to the area's surface drainage network
or is
• Directed to a sump and allowed to percolate into the ground-
water system.
Although the decision maker must realize that salt usage in the highway
environment is perhaps the more critical problem to be addressed, the
storage facilities represent a potentially very large, concentrated
point source of pollution and must be treated as such. The selected
site should be acceptable from the viewpoint of operations and be the
least environmentally problematic of the sites examined. Any remaining
environmental problems should be minimized through appropriate design
of structures and appurtenances on the site.
22
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CHAPTER III
FOUNDATIONS AND WORKING AREA DESIGN
The foundation of salt storage buildings, the paving of the floor within
the building, and the attention given to the drainage and paving of the
working area adjacent to salt storage buildings are as important for
environmental protection as the decision to place salt under cover. In
this section are outlined basic designs for foundations of salt storage
buildings, and a loading dock, pavements within and adjacent to the
buildings, and factors to be addressed when designing the area drainage.
PREREQUISITES TO FOUNDATION DESIGN
Foundation design for salt storage buildings is not complex. In some
respects these buildings are similar to barns, which have been constructed
for centuries in all parts of the world without the benefit of either
structural or foundation analysis. Nevertheless, there are some unique
factors which should be taken into account.
The foundation designer will require data and information as follows:.
Topography (existing and proposed).
Type of soil and subsurface conditions.
Climatology.
Type and layout of structure, including dead and live loads.
Proposed salt load.
Live load due to equipment.
Applicable building codes.
• Operating and other information.
• Aesthetics.
Factors to be considered within each of these categories are discussed
below.
Topography
The elevation of the interior floor slab should be sufficiently above
the exterior yard area to prevent inflow of rainwater. If the foundation
walls extend above grade and it is desirable to use exterior earth pressure
to resist the interior salt load, it may be necessary to site the structure
by cutting into a hillside. Final grading around the shed should be
designed to slope away for drainage purposes.
Type of Soil and Subsurface Conditions
Common good practice rules for foundation design apply here. In areas
with which the design engineer is familiar, a few auger borings should
suffice. But if compressible substrata are possible or if ledge may
be encountered, borings and soil tests should be made in sufficient
23
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quantity to identify clearly the subsurface conditions. If test pits are
dug in lieu of borings, they should either be located outside of the
floor slab area or the material should be compacted when it is replaced.
Climatology
The principal items are the depth of frost penetration in the area and
the annual snow depth.
Type and Layout of Structure, Including Dead and Live Loads
The foundation designer will need to know the maximum loads to be trans-
mitted to the foundation, the points at which they are transmitted, and
the type of fasteners (e.g., anchor bolts). Thrust, shear, and bending
moment loads should be provided. On large sheds, wind loadings should
be checked to determine possible uplift loads and snow loadings should
be determined. If the foundation extends above grade, i.e., forms part
of the wall, the dimensions for doorways and locations for electrical
conduits or other piping should be provided.
Proposed Salt Load
In general, the salt load on the floor slab will be less than floor loads
from vehicles. However, the lateral loads on the walls are unique to bin
design, and the maximum height of the salt against the wall must be known.
If the shed is to be compartmented, either for storage of both sodium and
calcium chloride or to provide a vehicle parking space, the desired archi-
tectural details will be required.
Live Load Due to Equipment
The salt delivery trucks, the spreader trucks, and the loader must all be
considered.
Applicable Building Codes
These will provide such information as minimum concrete cover over re-
inforcing bars, minimum foundation depths, electrical codes, and earth-
quake criteria. Local (municipal) codes may contain special provisions,
and if the structure must comply with such regulations it is generally
advisable to use a local designer or consultant who is familiar with the
regulations.
Operating and Other Information
The foundation designer may be asked to design a loading dock in the
yard area, and the location, height, and dimensions of the dock should
be provided (see "Working Area Design"). It is also possible that a
buffer wall is to be constructed inside of the shed walls to keep the
salt away from the walls, either to prevent corrosion or to prevent the
salt from bearing on the walls. Consideration should also be given to
24
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loader operations in the shed; protrusions or dead corners which cannot
be reached should be avoided. If the foundation extends above the floor
slab grade, it should be protected from the loading bucket by a buffer
strip, extra concrete thickness, and battered sides.
Aesthetics
If the foundation is visible, it may be desirable to provide some archi-
tectural treatment to suit the locale. This would probably only involve
finishing of exposed concrete surfaces.
FOUNDATION DESIGN CONSIDERATIONS
Specific design criteria for walls and foundations can be obtained from
standard texts on foundations. The salt itself has a bulk density of
80 Ib per ft3 (1280 kg per m3) and an angle of repose of 32 degrees from
horizontal. In the absence of specific structural, subsurface, and other
data, it is not feasible to present any specific designs here; however,
some general considerations are presented through an examination of the
principal variables involved.
The basic elements of a storage shed are shown in Figure 4. The wall is
clearly the unique part of the structure since it must resist the outward
thrust of the salt load. This will in turn affect the foundation design,
and, in fact, the wall and foundation can be an integral structural unit—
at least up to the highest point of salt stockpiling. There are two
general approaches to the wall design—continuous and buttress.
ROOF
WALL
FOUNDATION
Figure 4 Basic elements of salt storage shed
25
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UPPER STRUCTURE
HEIGHT OF SALT
DEPTH TO FROST LINE AS MINIMUM
-POSSIBLE FOOTING
Figure 5 Continuous wall foundation (gravity)
I N/
•-r
, * - t ' ^ S . "•* ' i ^S^
v^Vv^'vV^/^X.
^roio'->cV$>
>'^'c x x
UPPER STRUCTURE
i^alffe
V I
\
FLOOR SLAB
HEIGHT OF SALT
DEPTH TO FROST LINE AS MINIMUM
REINFORCING ROD
Figure 6 Continuous wall foundation ("T" wall)
26
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Continuous Wall
In the continuous design, the wall-foundation is similar to an earth-
retaining wall, and the remaining structure rests on the top of the wall
in a fashion similar to the way any ordinary structure rests on a con-
tinuous footing. The continuous wall-foundation may, therefore, be
designed as a gravity or "T" wall, as shown in Figures 5 and 6. The
advantage of the gravity wall is that it needs little reinforcing steel,
but conversely it uses more concrete. For support of relatively low
piles of salt (e.g. 3 ft-4 ft or 0.9 m-1.2 m), the gravity wall-foundation
is often used.
The "T" wall utilizes the weight of soil on the loaded side to resist the
overturning moment. It is much more economical with respect to concrete
requirements, but uses more reinforcing steel which must be accurately
placed in the forms. Since salt is liable to corrode the reinforcing
steel, the "T" wall should be protected either by an impermeable coating
(such as linseed oil or epoxy) on the interior and/or use of galvanized
reinforcing.
It is important to design the portion of the wall-foundation that is above
grade so as to exclude rain leaks at the building wall sill. The top
of the wall-foundation should be sloped to the outside, and/or a flashing
should be placed along the bottom of the building wall. The interior of
the wall-foundation should have a slight batter to keep the bucket of
the loader from scraping the wall. These details are shown in Figure 7.
The continuous wall-foundation will require expansion/contraction joints
at about 30-ft (9-m) intervals. In order to protect any continuous rein-
forcing steel at such locations, a waterstop should be installed on the
salt (interior) side of the joint.
Buttress Wall
The alternative to the continuous wall-foundation is the "buttress" design,
which includes several variations. The basic concept is shown in Figures
8 and 9. The design principle is that the salt load against the side wall
is transmitted to buttresses at discrete points along the wall. The
buttress may also serve as a structural column of the building. The
buttress may consist of a strut or it may be a concrete buttress as indicated
in Figure 9.
Although the buttress design should be more economical than ithe continuous
wall design with respect to materials, it can also add design and construction
complexity since the wall must be designed to resist outward buckling forces.
An exception would be a simple building using steel columns without buttress
struts, such as shown in Figure 10. This design may incorporate cables
across the roof and under the floor slab to resist outward forces on
the columns.
27
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FLASHING
OPTIONAL
PROTECTIVE
CURB '
| FLOOR SLAB """
SLOPE TO DRAIN
AWAY FROM BUILDING
Figure 7 Wall-foundation details
For some salt storage sheds, a separate wall or bulkhead is constructed
inside of the exterior wall to hold the salt, as indicated in Figure 11.
The bulkheads may be independent units as suggested by the continuous
wall in Figure 11(top), or they may be tied to the building columns as
shown in Figure 11 (bottom) . Interior bulkheads serve to keep the salt
away from the walls, thus avoiding corrosion problems, and they permit
the use of standard pre-fab buildings not designed for bulk storage. In
an arch-support structure (Figure 11,top), they also serve to keep the
salt away from the low-roofed section of the shed that cannot be entered
by the loading equipment.
Material
Reinforced concrete will likely be the principal construction material.
Highway engineers are aware of the spalling and corrosion problems that
heavy road salting has caused on concrete pavements and bridge decks,
and the use of concrete foundations for salt storage sheds may seem to
be inviting early failure. However, highway slabs are exposed to infil-
tration of salt solution due to rains and alternate cycles of freezing
and thawing. Since the interior of the salt shed is to remain dry, it
should not be exposed to the same corrosive cycle. Nevertheless, it is
recommended that air entrained concrete or a dense (impermeable) mix be
used to avoid spalling. Reinforcing steel should have a slightly thicker
28
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SALT
PRESSURE
BUTTRESS i i
MATERIAL SUPPORT
WALL
BUTTRESS
8ft (2.4m)±
Figure 8 Plan view of buttressed wall and foundation design
COLUMN
'^ffifc^LJ
2=^
OPTIONAL
FLOOR SLAB
7
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i "
r J <
,v7
« <•
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r,r*>i
ST R UT . / ^~J7 X ^> ON,
BUTTRESS <-. - ,- x-/ \ (,£.•
/VAX
FLOOR SLAB
SOLID
BUTTRESS
Figure 9 Typical sections of strut (on left) and solid (on right) buttresses
29
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OPTIONAL/
CABLE
STEEL
COLUMN
WOOD SPACER
AT COLUMN
Figure 10 Section of shed with steel columns
and interior buttress wall
minimum cover, and it should be protected at joints. The inner wall
should be painted with an impervious material (linseed oil or epoxy) and
touched-up annually.
Doorways and Corners
The doorway and corners of the shed may require special foundation design.
From the operational viewpoint, the end of the shed should be completely
open to allow trucks and loaders to enter easily and to avoid dead corners.
However, if the entrance is to have doors, and if they are to be opened
horizontally by sliding, some space must be provided for them to occupy
when opened. This can either be along the end walls of the building or
on an extension trestle. If the latter cannot be cantilevered from the
building, exterior footings may be required.
If the door height or the lower chord of the interior roof trusses is
not high enough for a delivery truck to enter and dump the salt in the
shed, the salt will have to be dumped outside and pushed or carried
inside by a loader. If this is the case, a paved entrance area should
be provided. The sides of this area could have training walls as shown
in Figure 12 to facilitate pushing the salt into the shed.
A large entrance doorway will present special structural requirements
on the building, since in effect an entire wall is lost. As a result,
30
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Figure 11a
BULKHEAD
Figure 11b
Figure 11 Interior bulkhead wails
31
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/TYPICAL CORNER REINFORCING STEEL
OPTIONAL
FOOTING
FOR DOOR
TRESTLE
\
SHED
/
OPTIONAL CONCRETE
TRAINING WALLS
OPTIONAL PAVED ENTRANCE
Figure 12 Plan view showing optional foundation details
32
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the stub walls at the entrance will have to carry unusual loads for diagonal
stiffness and the door trestle. As a result, the doorway foundation area
may b.e subject to unusual loads and must be designed accordingly.
Paving
The floor slab inside the building should be impermeable to prevent possible
contamination of the ground by the salt. The usual practice is to use a
bituminous concrete flexible pavement similar to what would be used for
parking areas or service roads. Typically this would be a 2.5-in. (6-cm)
surface"(1.75-in. or 3.2-cm wearing course over a 1.75-in. or 3.2-cm
leveling course), laid over a 6-in. (15-cm) compacted gravel base. If
the native soil is clay-like, an additional 12-in. (27-cm) sand or gravel
sub-base should be installed. The floor should pitch to drain out of the
entrance doorway using a slope of about 0.5°. An emulsified tar coating
should be applied over the bituminous concrete to protect it from any gas
or oil spills from operating equipment.
WORKING AREA DESIGN
Drainage Considerations .
Creation of some salt brine at a salt storage facility is inevitable,
particularly during and after storms. Although diversion and collection
of the brine is possible through proper site design, ultimate disposal
of brine is itself environmentally problematic, and no completely satis-
factory method has been devised. :
In 1972, a study of control of salt brine runoff was conducted by the
Minnesota Highway Departments and illustrates the problems in disposing
of brine runoff. The only effective means of control was found to be
collection of brine in a completely sealed basin or pond. Evaporation
was not feasible as a means of disposal because of the large surface area
required and the need to limit access to and the unappealing appearance
of such a brine pond. Disposal by dumping and hauling was costly and
selection of an appropriate disposal site was found to be difficult at
best. Pumping of brine back into a. sand pile was only feasible if the
volume of brine was small or if a sand pile was available. Because most
of the annual precipitation occurs during the summer months, pumping of
brine into trucks loaded for snow and ice control was seen as a possible,
but' unlikely, means of disposal. As a result of, these findings, the study
concluded that collection facilities are a last resort and that "time,
effort, and money, in most cases, can be better spent on avoiding or
minimizing the formation of salt brine".
In areas in and around groundwater well fields or surface fresh water
reservoirs, all brine runoff must be contained in a lined catchment
basin and be disposed of in a less vulnerable area.
One salt runoff storage basin developed by the Pennsylvania Department of
Highways is shown in Figure 13. Several of these basins may be placed
33
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SLOPE FROM
DRAINAGE
SWALE 2.4° •
CEMENT BLOCK SET
IN PLACE AND LEVEL
BEFORE POURING
CONCRETE.
REINFORCED
CONCRETE PIPE
BAFFLE 2in (Scm)
(BOLT TO SIDE
OF PIPE)
, STEEL BRIDGE FLOORING
/"ASPHALTIC MATERIAL AFTER
SLOPE TO NATURAL
DRAINAGE
CONCRETE POURED IN PLACE
6!n (15.2cm)
Figure 13 Salt brine storage basin
Courtesy of Pennsylvania Department
of Transportation
in a series to increase the storage capacity. Ideally, capacity should
be sufficient so that there is no overflow, even during periods of heavy
precipitation.
Brine from basins such as the one shown is pumped onto sand stockpiles,
and crystallized salt and other settled solids are cleaned out during
the summer.
In summary, the first priority in brine control should be to eliminate
its occurence as much as possible. Proper site selection and storage
design and good housekeeping practices will all minimize the formation
of salt brine.
Loading Ramps or Docks
The efficiency of the front-end loader, overwhelmingly preferred for
salt handling and loading spreader trucks, can be greatly enhanced
through incorporation of a loading dock or a loading ramp in the chemical
and treated-sand storage area. Often, in the design of a storage area,
advantage can be taken of natural terrain to incorporate a loading dock
in front of or adjacent to the chemical storage area. The height of
this dock can vary anywhere from 2 ft to 6 ft (0.6 m to 1.8 m), thereby
reducing by this amount the height to which the operator must lift
the front-end loader when placing loads in spreader trucks. A ramp
designed by the Massachusetts Turnpike Authority shown in Figure 14 is
particularly adapted to storage areas in flat terrain.
34
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CHAPTER IV
DESIGN OF STORAGES
In this section are presented functional and environmental requirements
for storages and their surroundings, designs of storages that are
environmentally sound, designs that are acceptable, and storage practices
that must be avoided. Wherever possible, information on cost of storage
structures has been included.
ENVIRONMENTAL REQUIREMENTS
The environmental impact of storage and handling of deicing chemicals prior
to use on highways is the one major impact that can be controlled most
carefully. In the past, poor design of storages and improper handling
have been responsible for many of the environmental abuses of deicing
chemicals.
The environmental requirements for the design of storages are rules that
should never be violated:
• Storages should protect the chemicals from direct rain and
blowing snow at all times; they should keep the material dry
and out of the weather.
• They should keep the material within the prescribed boundaries
of the storage.
• They should not leak chemicals or burst particularly during
abnormally rough usage or through accidental mishandling.
FUNCTIONAL REQUIREMENTS
The functional requirements of storages for deicing chemicals are closely
interwoven with the operations of the road maintenance district and the
techniques used for handling the chemicals.
• Storages should be large enough to hold the maximum amount of
chemicals without overflowing. As a rule of thumb, the storage
should be capable of holding at least one-half of a season's
requirements and preferably all of the seasonal requirement.
• Special handling procedures should not be required to store
all of the chemical under cover immediately upon delivery.
• Sufficient vertical clearance should be provided either inside
the storage or immediately in front so that delivery trucks can
unload easily without damaging the structure.
36
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• Horizontal clearance in the storage and at the entrance should
be sufficient to enable front-end loaders to place material
within the storage and to remove it during winter storms.
• The storage should be sturdy enough or suitably reinforced at
key locations to withstand the normal rough usage that occurs
during winter operation.
• Good exterior and interior lighting should be provided for nighttime
operations.
ARRANGEMENT WITHIN OPERATIONS AREA
The location of chemical storages in operation areas depends on operational
factors (see Manual for Deicing Chemical Application Practices2). the site
terrain (including drainage), the location of access roads, and a host of
other minor factors. Included herewith are descriptions of four classes
of operation areas that illustrate important storage design characteristics.
These storages include a major distribution center, a district base area,
a crew area, and a reload area. Each of these storage areas will be
described.
Major Distribution Center
In a typical major distribution center that supplies a large geographical
area, chemicals are received by covered hopper rail cars, barges, or ocean
vessels. More than 100,000 tons (90,700 t) of chemicals may be stored
on a site of this type. Due to the large quantity involved, the material
is seldom under permanent shelter. Materials are usually stored under
tarpaulins or reinforced plastic film, which are spread on the pile and
stitched together along seams with hand-held portable sewing machines.
Material is usually removed from the pile by large front-end loaders,
is loaded into large dump trailers, and then delivered to customers within
about a 50-mi (80-km) radius. Limitations on the quantity of chemicals
that may be stored on a site of given size are governed primarily by the
requirements for vehicle circulation around the storage areas during the
loading and unloading operations.
District Base Area
The district base arear typically services an area consisting of 1500 or
more lane miles (2400 lane km) of road and has several crew areas and
reload areas under its direct responsibility. Typically, the district
base area will include repair facilities with up to 12 bays, garaging
for as many as 50 pieces of equipment, equipment storage yards, and a
chemical storage capability of up to 3000 tons (2700 t). Additionally,
there should be provision for storage of treated abrasives (sand or
cinders) when these materials are used in the snow and ice control program.
One or more ramps are provided for loading trucks with chemicals and/or
abrasives. Provision is made in the layout of the base area for vehicle
circulation and for the storage of snow that is removed from the working
area during periods of winter storms.
37
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Grew Area
The crew area typically services an area with about 100 lane miles (160 lane
km) of road. It usually consists of a heated garage with a wash rack, a
closed building with up to 1500 tons (1350 t) capacity for chemical storage,
and a ramp for loading spreader trucks. Provision may also be made for
storage of treated sand or other abrasives.
Reload Area
The reload area is typically located near the dividing line between two
crew areas and is used often by both crew areas to provide spreader trucks
with chemicals and/or grit for the return trip. Up to 500 tons (450 t)
of chemicals are stored in a small covered shed. Electric power is
provided at the site for lighting night operations and for maintaining
the front-end loader, typically used at these sites, in a state of
readiness for operation even in the coldest weather. A ramp is provided '
for loading spreader trucks.
GOOD PRACTICE IN SALT STORAGE
Many approaches to salt storage were observed during the course of this
study. Some of these combine operational features very successfully
with environmental requirements and are, therefore, considered to represent
good practice in salt storage.
The specific approaches outlined in this discussion were chosen to represent
good practice within a range of storage capacities and a sampling of
available construction materials and designs. They are shown with the
permission of corporations and highway maintenance agencies; in the case of
the latter, the specific designs shown are not necessarily representative
of all or most current practice within the agency.
Notable Features
The sample storage sheds illustrate some notable features:
1. Any salt storage (shed, overhead hopper, or pile) must be
oriented so that truck-loading operations are shielded as
much as possible from prevailing winds.
2. Storage sheds with open front faces may be protected by
ample roof overhang from intrusion of rain and snow.
3. Complete enclosure of the salt storage with doors is more
important for security reasons than for protection from
moisture. When the storage area is in or near an inhabited
area and access cannot be limited effectively by gates,
fences, or other means, doors (with locks) are often
essential.
38
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4. Within any salt storage structure, sloped floor drainage and
drain pipes are necessary to divert any accumulated water away
from the salt pile and out of the structure.
5. In addition to a solid floor within the enclosure, an asphaltic
concrete pad is essential in all loading/unloading areas near
a storage shed to insure that spilled salt does not dissolve
and percolate into the soil and can be scraped up easily for
subsequent use.
6. Ample room must be provided for operation of a front-end loader.
Any portion of the structure within its reach can be damaged
during operations. Various means of reinforcement of vulnerable
areas (especially door jambs and corners) are illustrated in
the designs shown. (See "Designing for Durability.")
7. Sharply sloping roofs such as those in arch-type and conical
structures can be protected by interior retaining rings or
timber bulkheads, which keep the salt pile (and loading activities)
away from the corners and in some cases bear the salt load.
>!
8. All hardware and metal building elements must be galvanized.
9. When loading and unloading operations are to occur inside
the storage, adequate ventilation must be provided.
10. Lighting must be provided inside of storage buildings and in
the loading area in front to illuminate nighttime operations.
Wooden Arch Storage Building V
The Massachusetts Turnpike Authority utilizes a building with laminated
wooden arches as shown in Figure 15. Spanning 60 ft (18 m) and rising to
25 ft (8 m) at the crown, the circular arches are bolted to square
foundation posts of reinforced concrete 8 ft (2.4 m) on center. Wood
purlins (2-in. by 8-in., 5-cm by 20-cm) span between arches, and the
exterior skin is formed by plywood. The end walls, supported by double
2-in. by 8-in. (5-cm by 20-cm) posts, on an 8-in. (20-cm) reinforced
concrete curb, are also sheathed with plywood. The whole structure is
painted, inside and out. A heavy timber bulkhead protects the end walls
and base of the laminated arches on the inside and supports the salt to
a height of 5 ft (1.5 m); the tongue-and-groove 3-in. (8-cm) planks are
pressure-treated. Cast-iron wheel guards protect the jambs of the front
opening from damage by loaders. The bituminous concrete floor paving
drains toward the opening. This 60-ft by 80-ft (18-m by 24-m) structure
has a design capacity of about 1000 tons (900 t).
The loading ramp (shown in Figure 15) in front of the storage building
facilitates loading of salt trucks.
39
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illiiii|^ iliiiii i i i i H
Figure 15 Wooden arch storage building with loading ramp
Courtesy of Massachusetts Turnpike Authority
Wooden Rigid Frame Storage Building
Another design (see Figure 16) developed by the Massachusetts Turnpike
Authority utilizes rigid frames of laminated wood spanning 60 ft (18 m).
The two-piece laminated frames, spaced every 20 ft (6 m), are bolted
together at the top and anchored at the bottom to a continuous reinforced
concrete parapet and wall foundation. Double 2-in. by 8-in. (5-cm by 20-cm)
posts at the side walls between frame members and 2-in. by 12-in. (5-cm by
30-cm) purlins spanning frames at the roof support the plywood skin. The
end walls have a similar reinforced concrete parapet. The whole structure
is painted inside and out.
As in the wooden arch structure, a 6-ft (1.8-m) heavy timber bulkhead of
pressure-treated, 3-in. (8-cm), tongue-and-groove planks bears the salt
load and protects the interior structure on all sides. A similar bulk-
head divides the interior space into two storage bays. Cast-iron guards
protect the jambs of the almost full-width front opening. The floor
surface is bituminous concrete. Measuring 56 ft by 77 ft (17 m by 23 m)
inside, this structure has a design capacity of 1500 tons (1400 t) of
salt.
40
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Figure 16 Wooden rigid frame storage building with loading
ramp
Courtesy of Massachusetts Turnpike Authority
Dual Storage Building
The California design shown in Figure 17 provides for separate storage of
cinders or sand and salt under the same roof. Measuring 50 ft by 100 ft
(15 m by 30 m) overall, the structure includes an 80-ft by 50-ft (24-m by
15-m) area for cinder or sand storage with access through the front
opening and a 20-ft by 50-ft (6-m by 15-m) salt storage bin across the
back of the building with access through a door on the rear side wall.
The design,capacity is 300 tons (270 t) of salt and 1700 tons (1540 t) of
cinders or sand. The basic design could be adapted for all salt storage.
A. rigid frame steel structure is metal clad, reinforced to withstand
horizontal thrusts from sand, salt, wind and seismic loading conditions.
Each frame is tied between base plates through the reinforced 6-in. (15-cm)
concrete floor slab, with sway braces in the roof and walls providing
additional stability. A 7-ft (2-m) high reinforced concrete perimeter
wall inside the rigid steel framing encloses the sides of the shed and
separates the front and rear storage areas.
41
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Figure 17 Dual storage building
Courtesy of State of California Department of
Transportation
Note: Sand and cinders are stored in the main
part of the building (left side of photo-
graph), and salt is stored in the trans-
verse salt bunker at the back of the
building (behind the pickup truck).
Both exterior openings are closed by sectional overhead doors. Columns
of 6-in. (15-cm) pipe protect door jambs from damage by mechanical loaders.
Metal cladding with light steel framing forms the skin of the upper walls
and gabled roof. Powered rotary vents at the ridge line, metal louver vents
at each <. nd, and continuous vents at the top edge of the metal cladding
facilitate ventilation, which is essential because loading of spreaders
occurs inside of the structure. Floor slabs are pitched to drain toward
the doorways.
This structure is designed in four grades to withstand the snow loading
experienced at altitudes up to 3,000 ft (900 m), 4,000 ft (1,200 m), 5,000 ft
(1,500 m), and above 5,000 ft. The cost of the shed increases with the snow
loading requirements. A new design is being developed with a steel structure
resting on top of the reinforced concrete base, raised eaves to 16 ft (5 m),
and a flat roof. Construction of this new shed is expected to be more
economical.
42
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Concrete and Wood Storage Building
One salt storage building developed by the Maine State Highway Commission
is a composite concrete and wood shelter (Figure 18). The bottom 4 ft
(1.2 m) of the shed walls are concrete with inside batter of 3 in. per ft
(25 cm per m) and outside batter of 1 in. per ft (8.3 cm per m), reinforced
at corners and at either side of the doorway, and resting on a continuous
concrete foundation. This concrete base prevents rotting of the timber-
walls by surface water and minimizes damage to the walls above by mechanical
loaders. Careful sloping of the floor prevents any accumulation of water
in corners.
Figure 18 Concrete and wood storage building
Courtesy of State of Maine Department of
Transportation
Conventional wood-stud wall construction encloses the bin and supports the
simple lumber roof trusses above. Interior walls are sheathed diagonally
with 1-in. by 6-in. (2.5-cm by 15-cm) matched sheathing. Tension cables
and I-beams reinforce the structure in both directions at the eave line.
Sliding wood doors, hung at the top, close the 14-ft (4.2-m) front opening.
The asphalt-shingled roof is substantially pitched, with overhanging eaves
to provide good weather closure.
43
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The standard structure of this type measures 28 ft by 40 ft (8.5 m by 12 m)
inside the concrete curb, with roof trusses 12 ft (3.6 m) above the floor.
The design capacity is 320 tons (290 t) of salt.
One of the most interesting features of this structure is economical con-
struction by the Maine Department of Transportation. Road crews, experienced
in construction, build these structures during the fall months. The basic
design features of this shed.have also been incorporated into a structure
that serves both as a garage and as a storage facility.
Storage Crib With Sliding Roof
The North Carolina Department of Transportation and Highway Safety has
developed a simple, low-cost salt storage crib with a roof that rolls back
to permit direct delivery by truck and to facilitate truck loading with a
front-end loader. This feature makes the total storage capacity of this
building relatively high in proportion to the size.
Constructed of reinforced concrete block, the storage crib has a retractable,
wood-frame and corrugated metal roof. The block walls are built on a
shallow, spread concrete footing, offset to withstand the lateral over-
turning forces of the salt. The crib illustrated in Figure 19 employs
12-in. (30-cm) thick block for lateral stability. If block buttresses
provide this support, smaller block can be used, although maneuverability
at the sides of the crib is limited by the buttresses. An alternate crib
of creosoted timber is supported by 6-in. (15-cm) rolled steel I sections,
which also carry the roof load. Experience has shown the creosoted timbers
to be preferable because of their greater durability.
The 6-in. (15-cm) steel wheels at the front and rear corners of the roof,
and at 6-ft (1.8-m) intervals between, roll on a continuous galvanized steel
angle track along the top of each side wall. At the rear of the shelter,
track extensions, supported vertically and horizontally by I-beams welded
to the track and imbedded in concrete, are required equal in length to the
maximum opening of the roof, thus increasing the total required ground area.
Although the metal wheels and the track are somewhat protected by a large
overhanging eave, frequent greasing of wheels, track, and extension track
prevents rusting. A reinforced timber bumper and steel eye at the front
end of the roof facilitate opening and closing of the roof by a front-end
loader. The floor is of bituminous paving with 2-in. (5-cm) pipe drains
that allow any water to escape through the walls. The inside dimensions
of the structure shown are 7.5 ft by 40 ft by 18 ft (2.3 m by 12 m by 5.4 m).
The capacity of approximately 225 tons (200 t) can be increased by raising
the walls.
44
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Approximately 20 of these storage cribs have been built in county road
maintenance yards throughout North Carolina. When salvaged creosoted
lumber and steel are used, a 225-ton (200 t) shed costs approximately
the same as one built of 12-in. by 8-in. by 16-in. (30-cm by 20-cm by 40-cm)
concrete blocks. If new lumber were to be used, the cost would be
significantly higher.
The major feature of this design—the sliding roof—could occasionally be
a disadvantage as "well. Malfunctions of the sliding mechanism (very
rare in actual practice) or human error could leave the salt exposed to
the elements. A plastic cover should be on hand for use in case of a
malfunction.
Figure 19 Storage crib with sliding roof
Courtesy of North Carolina Department of
Transportation and Highway Safety, Division
of Highways, Bridge Maintenance Unit
45
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Open-Face Concrete Block and Timber Shed
The shed shown in Figure 20 is an open-face structure of concrete block
and timber designed by the New York State Thruway Authority. Walls are
made of cement-filled 12-in. (30-cm) concrete block, reinforced vertically
through the block cells with steel that ties the block to a continuous,
reinforced concrete footing, which extends to 4 ft (1.2 m) below grade.
Additional internal reinforcing piers at midpoints on the side walls and
quarterpoints on the rear wall provide resistance to lateral overturning
forces.
oC >
Figure 20 Open-face concrete block and timber shed
Courtesy of New York State Thruway Authority
In the middle of the open front face, an 8-in. (20-cm) steel column,
bolted to a footing and protected to a height of 5 ft (1.5 m) by a rein-
forced concrete collar, supports the central steel roof beam. Timber joists
(2 in. by 12 in., 5 cm by 30 cm) spanning from the side walls to the center
beam support a diagonal tongue-and-groove timber roof deck covered with
mineral surface roofing. An eave extension (1.5 ft, 45 cm) at the side and
rear walls permits free ventilation between the joists and good weather
closure. A 4-ft (1.2-m) high plywood and batten fascia over the wide
eave at the open front helps to protect the interior from intruding weather.
The roof pitches from 20 ft (6 m) in the front to 15 ft (4.5 m) at the
rear wall. All steel and exterior wood members are painted. Two internal
46
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overhead lights are provided. Measuring approximately 27 ft by 38 ft
(8 m by 11.5 m) internally, this shed has a design capacity of approximately
330 tons (300 t).
Although this design has proven to be satisfactory for protection of
chemicals and has been quite durable, it was adopted nearly twenty years
ago when present volumes of material usage were not foreseen. At the
present time, alternative designs are being investigated that would have
larger storage capacity and lower cost per unit volume stored.
Braced Timber Storage Shed
The shed designed by the Massachusetts Department of Public Works and
shown in Figure 21 is an externally braced, timber structure, measuring
36 ft by 80 ft (11 m by 24 m) inside. The exterior walls are built of
8-in. by 8-in. (20-cm by 20-cm) pressure-treated posts [4 ft (1.2 m)3 sunk
6 ft (1.8 m) below grade and secured to concrete footings. Strapping (2 in.
by 4 in., 5 cm by 10 cm) between posts supports the exterior grade plywood
wall sheathing.
Figure 21 Braced timber storage shed
Courtesy of Commonwealth of Massachusetts
Department of Public Works
47
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An interior bulkhead wall to a height of 8 ft (2.4 m) bears the salt load.
Constructed of 8-in. by 8-in (20-cm by 20-cm) posts (placed and sunk
below grade in the same manner as the exterior walls), the bulkhead has
horizontal 3-in. by 8-in. (7.6-cm by 20-cm) timber planking and braced
buttressing extending diagonally through the outside wall to external
thrust blocks. All untreated wood members are painted or stained on the
exterior of the building.
The roof is supported by timber roof trusses, beginning 16 ft (4.8 m) above
the floor, stabilized by two-way bracing at each post and longitudinal
sway braces between trusses along the ridge. The roof consists of aluminum
panels, flashed at ridge joints and eaves. Skylight panels, equally spaced
along each side of the roof, light the interior of the shed. A sliding
masonite-sheathed door closes off the end opening, and louvers in the gable
ends provide ventilation. The design capacity of this shed is approximately
1200 (1100 t) tons.
Dome Storage Shelter
John R. Fitzpatrick of the Department of Highways, Province of Ontario,
Department of Public Works, originally designed this storage shelter, whi'ch
is marketed in the U.S. by Domar Modular Systems, Inc., of TJtica, New York.
The dome (Figure 22) is a 20-sided cone constructed of factory-produced
modules of 3/8-in. (0.9-cm) plywood and 2-in. by 6-in. (5-cm by 15-cm)
lumber, which are bolted together at the building site. Each of the 20
sides consists of nine panels forming an isosceles triangle with a ventilation
duct near the top. Since the dome is its own structural support, loading
and unloading operations are not hampered by internal supports. However,
as with any structure with a sharply sloping roof, care must be exercised
during operation of a front-end loader near the walls.
Covered with relatively maintenance-free asphalt shingles, the structure
sits on a floating concrete ring placed directly on an asphalt or concrete
pad. Around the interior of the dome, a retaining ring, supported by posts
imbedded in the floor pad, keeps the material away from the base of the
structure. This retaining wall is 4 ft (1.2 m) in all units sitting
directly on a floating ring.
The Domar structure is designed primarily as a cover rather than a container
for a pile of salt or sand and as such is not designed to bear the salt
load. The angle of the walls conforms to the angle of repose of the material
being stored—38 degrees for salt or 45 degrees for moist sand; the latter
angle is used most frequently. Filling up to 100% of storage capacity
is possible with a belt conveyor loading through a hatch near the top or
with a throwing system from below. More common practice with a front-end
loader fills the structure up to a maximum of 80% of capacity.
48
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Figure 22 Dome storage shelter
Courtesy of Domar Modular Systems, Inc.,
Utica, New York
Available in seven sizes, Domar bulk storage sheds range in diameter
from 51 ft (15.5 m) [capacity of 350 tons (317 t) of salt] to 150 ft
(45 m) [capacity of approximately 16,000 tons (14,500 t)]. The purchaser
provides the pad and prepares the site to specifications. Varying price
schedules are available if the purchaser provides the foundation and/or
erects the structure. Approximately 900 man hours are required to complete
a dome on a concrete pad previously laid.
In the Province of Ontario where the design originated, the Ministry of
Transport has 100 units in use. Approximately 40 units are under construction
or already in use in the United States, primarily in Pennsylvania, Cali-
fornia, Michigan, Ohio and Indiana. A new large-scale storage shed, a
barrel building, that has been developed is the basic dome unit cut in
half and joined by incremental 8-ft (2.4-m) modules.
Creosoted Timber Storage Shed
A shed of creosoted timber is available commercially (Wheeler, Minneapolis,
Minn.) in a pre-engineered (all materials, hardware, and working plans)
package for construction by the purchaser or his contractor. These sheds,
49
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such as the one in Figure 23, are in use in the Midwest, primarily in
Wisconsin, Michigan, and Minnesota.
The design uses braced timber framing with the primary structure of 6-in.
by 12-in. (15-cm by 30-cm) posts [4 ft (1.2 m) on center] and galvanized
tension cables tying together every other pair of posts across the top
and under the paving surface. Posts are set firmly to 4 ft (1.2 m) below
grade in post holes that are backfilled to maximum density; in some cases
concrete footings are used.
Figure 23 Creosoted timber storage shed
Courtesy of Wheeler Lumber, Bridge, and
Supply Company, Minneapolis, Minnesota
Inside the posts, sheathing of 3-in. by 12-in. (8-cm by 30-cm) horizontal
planks is used to a height of 8 ft (2.4 m) above the floor, with 2-in. by
12-in. (5-cm by 30-cm) planks from that height up to the roof trusses.
The roof is supported by simple timber trusses at each post with wood
gussets at connections. Knee braces at 16-ft (4.8-m) intervals stabilize
the structure transversely; diagonal braces in the walls and horizontal
braces at eave height at each corner provide additional reinforcing. The
roof consists of galvanized roll roofing on wood purlins or 30-pound felt
and asphalt on plywood, with vent space at the eaves and louvers at the
gable ends. All timber members are pressure-treated. A 14-ft (4.2-m)
wide bi-parting sliding wooden door on metal guides closes exterior openings.
A floor of bituminous paving is provided by the purchaser.
50
-------
This shed is available in a variety of sizes, with a standard'width of
30 ft (9 m); heights of 12, 14, or 16 ft (3.6, 4.2, or 4.8 m); and length
variable in 4-ft (1.2 m) increments (each containing approximately 44 tons
or 40 t). A structure with 920-ton (835-t) capacity measures 30 by 84
by 14 ft (9 by 25 by 4.3 m). One shed-design has several doors positioned
along one side; more common is a standard layout with both front and rear
doors. Another popular design has no doors at the openings.
OTHER STORAGE PRACTICES
Under Viaducts
A particularly convenient and economical method of salt storage utilizes
the cover provided by a viaduct as is shown in Figure 24. Piles stored
in this manner should be located away from prevailing wind and precipitation,
preferably under a wide road. A bituminous pad must be provided, and any
drainage from the road bed must be diverted away from the pile. Similarly,
the pile should not be located under expansion joints where water from the
roadway can drip through or near vertical structural members of the viaduct
that might be corroded. Depending on the degree of protection afforded by
the viaduct, a cover should be provided for the pile, at least on the
weather side.
Figure 24 Salt storage under a viaduct
51
-------
Covered Salt Pile
Storage of salt in an outside, covered stockpile is a'very commonly used,
low-cost method; among large salt distributors this is common practice.
The salt is piled and allowed to assume its natural angle of repose (32
degrees from horizontal) on a bituminous concrete pad; larger piles are
often windrow-shaped with conical ends. Sometimes cribs or bins are
constructed of materials such as telephone poles or railroad ties to help
contain the pile.
Numerous covering materials have been used, including polyethelene (often
reinforced with nylon or wire or coated with asphalt and burlap), canvas,
jute, roofing paper, cutback asphalt, and vinyl. Any cover that is completely
waterproof is suitable.
Cover materials are very vulnerable to damage; a great deal of care is
required to maintain adequate cover during and after loading and unloading
operations, and all too often salt is left exposed to wind and moisture.
A notable exception to the common experience with covered salt piles was
observed at a storage area of Chemical Corporation, a wholly owned sub-
sidiary of the Morton Salt Company, in Westfield, Massachusetts. Located
on a railroad siding, the area contains meticulously maintained outdoor
storage for 72,000 tons (65,000 t) of salt.
As shown in Figure 25, two parallel windrow-shaped piles (80 to 90 ft by
500 to 600 ft or 24 to 27 m by 152 to 183 m) are carefully built up with
a conveyor belt on asphalt pads sloped away/from the pile. Materials
for covering outdoor piles have been developed over the past 20 years by
Chemical Corporation. Currently, a canvas tarpaulin material is used for
permanent cover, with other cheaper materials used to cover more frequently
used portions of the pile. These latter materials include netting-reinforced
black polyethelene (15-ft or 4.5-m wide) with a paper cover (which faces
the weather) and 11.5-ft (3.5-m) wide tarpaulin materials consisting of
an asphalt-impregnated, randomly oriented polyproplyene fiber mat between
two outer layers of paper or mildew-treated burlap adhered to a clear
polyethelene sheet with a thick coating of black asphalt. Individual
strips are stitched together with a hand-held electric sewing machine,
and the entire cover is weighted around the base of the pile with used
automobile and truck -tires. In places where the pad is not properly
sloped to control runoff water, the tarpaulin cover is cemented to the
pad with hot asphalt. Whenever possible the cover is folded back during
loading and unloading and repositioned at the end of the day. When heavy
ice and snow coat the cover, it is merely ripped off the pile and dis-
carded. A lightweight cover is used to cover the open end of the pile
as soon as possible after loading operations are finished.
As shown by the procedures used in this storage area, good practice in
outdoor storage requires considerable and continual diligence and devotion
on the part of personnel maintaining the storage.
52
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Figure 25 Covered outdoor storage piles
Courtesy of Chemical Corp., Westfield, Massachusetts
Overhead Hoppers v
Overhead hoppers combine both the storage and truck loading functions
with a minimal requirement for manpower and equipment. Hoppers are common
practice in England and in some parts of the U.S. where they are used most
effectively when the hopper capacity is sufficient for each large storm
and refilling is performed between periods of high salt usage.
Hopper capacity averages 100 tons (90 t). Sometimes built into the side
of a hill to facilitate filling by salt delivery trucks, hoppers are more
commonly elevated on a steel frame structure and filled pneumatically. The
Alta-type bunker shown in Figure 26 has a capacity of 100 tons (90 t),
costs approximately $20,000, is of steel construction, and is loaded by
pneumatic salt delivery trucks. Salting trucks drive beneath the hopper,
and salt is withdrawn by gravity through a clamshell opening that is
controlled manually by the truck driver.
Experience with hoppers has been good; mechanical problems are rare. In
many locations, however, front-end loaders are already available, and
53
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Figure 26 Alta-type 100-ton storage hopper
Courtesy of State of California
Department of Transportation
storage sheds have proved to be more economical. This is especially
true if the salt requirements are so high during peak periods that the
hoppers must be filled frequently.
PRACTICES TO BE AVOIDED
When good practice in salt storage is the goal, any procedure that has
a high probability of failure should be avoided. More specifically the
chances for human error and mechanical failure must be minimized.
In the storage facilities visited during this study, bad practice in
salt storage was most often associated with outdoor storage in either
uncovered (undesirable in any case) or covered piles. In the case of
the latter, the meticulous maintenance required for good outdoor storage
54
-------
was frequently lacking. Covered piles maintained out of doors are
very vulnerable to damage. Covers are easily ripped during handling or
improperly anchored and blown off by high winds.
Another practice that should be avoided is any procedure that relies on
intricate mechanical systems. A good example of this has been the
experience with grain silos.
Experience with glass-lined grain silos for storage and handling of road
salt has not been successful. Salt is not only heavier than the most
common feed grains [80 Ib per ft3 (1280 kg per m3) as opposed to 48 Ib
per ft3 (769 kg per m3)] but also has different characteristics, dimensions,
and physical properties that are not well adapted to the grain handling
mechanisms in storage silos. ; The unloading mechanism in commonly used
storage silos utilizes a reciprocating table to move grain from the exit
funnel of the silo to the bucket elevator, which raises it to a discharge
chute, which in turn guides the grain to awaiting truck. These two
mechanisms, particularly the reciprocating table, are subject to jamming
with salt.
When salt is stored longer than a few weeks, there is a possibility of
a plug of solidified material forming within the silo, impeding flow
of material. Similarly, salt with sufficient moisture can freeze and form
a plug. This plug is very difficult to remove or break up. Like the
overhead hopper, the grain silo often has insufficient capacity particularly
during heavy winter Storms when its capacity can be easily used up in a
few hours. Thus resupply of the silo becomes necessary.
DESIGNING FOR DURABILITY
Designs for salt storage sheds must take into account inevitable mistakes
with or mishandling of mechanical loaders, as well as the considerable
wear and tear of normal operations. As mentioned previously, any portion
of the structure within reach of the front-end loader is vulnerable to
damage; appropriate choice of construction materials for these areas and
maximum -possible reinforcement are important.
The corners of any salt enclosure are particularly vulnerable when the
front-end loader is working close to the walls. In some shed designs,
a concrete curb or parapet extends up the walls as far as 4 or 5 ft
(1.2 or 1.5 m) beneath a lighter, more vulnerable wood or metal structure
above. Timber bulkheads or bumpers are often used for protecting corners
and lower walls in concrete block sheds or in wooden structures, especially
those with arched or conical roofs within reach of the front-end loader.
/•
Door jambs and lintels are also natural targets for damage during loading
and unloading operations. Both can be reinforced structurally (e.g.,use
of double timber or metal posts). In addition, the surfaces can be
protected by metal pipe columns, or in the case of door jambs, by cast
iron wheel guards.
55
-------
Another important consideration in designing storage sheds is to minimize
maintenance. Use of creosoted timber eliminates the need for painting of
exposed wooden exteriors. More important, in lower walls that have a
good chance of coming into frequent contact with water, creosoting prevents
rotting of timbers.
ECONOMIC CONSIDERATIONS
Cost of Specific Designs Shown
Whenever possible construction costs were obtained for the representative
storage sheds shown previously. These figures summarized in Table 1,
include inside dimensions, estimated and quoted storage capacities of
each building, and cost per ton of salt storage, based on the estimated
capacity. Variables such as local availability and costs of materials
could not be standardized; insofar as these are known, they are indicated
in footnotes.
In Figure 27, the cost figures per ton of storage capacity are plotted
against shed capacity.
Cost Savings
Considerable cost savings are possible through a variety of techniques
observed during this study.
Choice of appropriate and economical materials is crucial. Salvaged
materials or mass-produced items such as telephone poles and railroad ties
have been incorporated successfully into numerous salt storage facilities.
Within some jurisdictions, the highway department provides the labor for
design and for construction of salt storages, thus eliminating the need
for an outside contractor.
Multiple use of storage facilities can also be advantageous. Some structures
with multiple bays are ideally suited for use as garages or for storage of
other materials or equipment during summer months, although some corrosion
of equipment is possible.
One possibly economical approach to enclosed salt storage would be use of
other commercially available, mass-produced structures. With a suitable
floor and interior load-bearing bulkhead, such as those used in the sample
storages shown in this manual, any other type of inexpensive structure' could
be converted to use as a salt storage.
ESTIMATING CAPACITY
The actual capacity of any salt storage is determined by thie amount of
material that can be placed into the space, as well as the ability of
the loading mechanism to utilize efficiently the available space.
56
-------
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Figure 27 Summary of salt storage building costs
58
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It is often desirable to calculate the area and/or volume required for
storage of salt, calcium chloride, sand, cinders and various mixtures of
these. Likewise, it may be necessary to calculate the amount of material
that can be stored safely in a given building or area. The starting point
in all of these calculations is the listing of the properties of materials
found in Table 2.
TABLE 2: PROPERTIES OF MATERIALS
Chemical formula
Bulk Density (p)
Angle of- repose
Dry
Salt
NaCl
lbs/ft3 80
ton/yd3 1.08
kg/m3 1280
(from horizontal) 32°
Calcium
Chloride
CaCl2
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0.74-0.88
880-1040
25-30°
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dry
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1.2-1.4
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34°
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dry
40
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640 '
40°
The ground area, volume, and surface occupied by several basic shaped
piles of salt are summarized in Figure 28. These shapes include a
conical pile, a conical pile on a cylindrical base, a peaked windrowed
pile, a flat-top windrowed pile, and two complex shapes representing
typical salt storage shed practice. The capacity of other complex salt
storage sheds may be estimated by means of volume formulae for these
basic shapes.
The characteristics of conical and windrow salt piles containing varying
amounts of salt are summarized in Tables 3 -A and -B and 4 -A and -B
(for each table, A gives British units and B gives metric units). The.
table for the storage capacity in windrow piles gives the capacity only
for the windrow section of the pile. The dimensions of the conical shaped
end sections of a windrow can be obtained from Table 3.
Loading and unloading procedures limit the full utilization of available
storage space. The most commonly used means, the front-end loader, is
most effective within specific height ranges. In operation, the front-
end loader has difficulty scaling piles of salt for any distance and,
therefore, cannot pile salt significantly higher than the reach of its
bucket without the aid of a temporary ramp formed in the salt already
in the building.
Blowers, throwers, conveyor belts, or any other means of building a salt
pile from above enable more efficient use of available storage space.
This is illustrated very well by experience with dome structures (such
as the Domar shed) with sloping sides at the angle of repose of salt.
Although a front-end loader can fill the space to 70% - 80% capacity,
a thrower or conveyor system can fill the shed to its theoretical capacity.
59
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62
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TABLE 3A CHARACTERISTICS OF SALT'IN CONICAL PILES
(BRITISH UNITS)
Tons of
Salt
25
50
75
100
200
300
400
500
600
700
800
900
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
Diameter
(ft)
20
25
28
31
39
. 45
50
53
57
60
63
65
67
85
97.0
107
115
122
129
135
140
145
Area
(ft2)
305
483
633
764
1210
1600
1930
2240
2520
2800
3070
3310
3560
5650
7390
8950
10400
11720
13000
14200
15400
16500
Height
(ft)
6
8
9
9.5
12
14
16
17
18
19
20
20.5
21
26
30
33
36
38
40
42
44
45
Length
(ft)
11.5
14.5
17
18
23
26.5
29
31.5
33.5
35
37
38
39.5
50
51
63
68
72
76 .
79
82.5
85
Volume
(ft3)
625
1250
1875
2500
5000
7500
10000
12500
15000
17500
20000
22500
25000 s
50000 ~~
75000
100000
125000
150000
175000
200000
225000
250000
, Exposed
Area
360
570
750
900
1430
1880
2220
2640
2980
3300
3620
3900
' 4200
6660
8710
10200
12200
13800
15300
16700
18100
19400
63
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TABLE 3B CHARACTERISTICS OF SALT IN CONICAL PILES
(METRIC UNITS)
Metric Tons
of Salt
25
50
75
100
200
300
400
500
600
700
800
900
1000
2000
3000
4000
5000
6000
7000
8000
9000
10,000
Diameter
6.2
7.8
8.9
9.8
12.4
14.2
15.6
16.8
17.8
18.8
19.6
20.4
21.1
26.6
30.5
33.5
36.1
38.4
40.4
42.2
43.9
45.5
Area
Cm2")
30
47.6
62.5
75.5
120
151
191
221
250
277
302
327
351
556
729
883
1020
1160
1280
1400
1510
1620
Height
(m)
1.9
2.4
2.8
3.1
3.9
4.4
4.9
5.2
5.6
5.9
6.1
6.4
6.6
8.3
9.5
10.5
11.3
12.0
12.6
13.2
13.7
14.2
Length
3.6
4.6
5.2
5.8
7.3
8.3
9.2
9.9
10.5
11.1
11.6
12.0
12.4
15.7
18.0
19.8
21.3
22.6
23.8
24.9
25.9
26.8
Volume
Cm3")
19.5
39.0
58.6
78.1
156
234
312
391
469
547
625
703
781
1560
2340
3130
3900
4690
5470
6250
7030
7810
Exposed Area
(TUC^
35.3
56.1
73.6
88.9
141
185
225
261
294
326
356
386
413
656
860
1040
1210
1360
1510
1650
1790
1920
64
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TABLE 4A CHARACTERISTICS OF SALT IN WINDROWED PILES (POINTED TOP)
(IN BRITISH UNITS)
Windrow Width
(ft)
20
30
40
50
60
70
80
90
100
110
120
130
140
Height
(ft)
6.2
9.4
12.5
15.6
18.7
21.9
25.0
28.1
31.2
34.4
37.5
40.6
43.7
Volume
(ft)
62.4
140.6
249.8
390.5
562.2
765.5
999.6
1264.9
1562.0
1889.8
2249 . 4
2639.6
3061.8
Exposed A
(ft2)
23.8
35.7
47.6
59.5
71.4
83.3
95.2
107.1
119.0
130.9
142.8
154.7
166.6
Tons of Salt
2.5
5.6
10.0
15.6
22.5
30.6
40.0
50.6
62.5
75.6
90.0
105.6
122.5
65
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TABLE 4B CHARACTERISTICS OF SALT IN WINDROWED PILES (POINTED TOP)
(IN METRIC UNITS)
Windrow Width
(m)
10
15
20
25
30
35
40
45
50
Height
(m)
1.0
1.4
1.9
2.4
2.9
3.4
3.8
4.3
4.8
Volume Exposed Area
(m3) (m2)
0.36
0.54
0.73
0.91
1.08
1.27
1.45
1.63
1.81
11.8
17.7
23.6
29.5
35.4
41.3
47.2
53.1
59
Metric Tons of
Salt
0.46
0.69
0.93
1.16
1.38
1.62
1.86
2.08
2.31
66
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PART THREE.: HANDLING OF DEICING CHEMICALS
CHAPTER V
GENERAL PRECAUTIONS IN HANDLING -
Three general precautions apply to all aspects of salt handling, from
receiving material to loading trucks for out-shipment:
1. Keep the area clean. Immediately after any handling operation,
sweep off salt collected on loaders, conveyors, truck bodies,
etc. Then clean up any salt lying on the pad and get it back
under cover.
2. Keep the salt dry. Keep salt under cover if possible at all
times. Covering prevents brine runoff and caking. Keeping
the pile dry is particularly important for mixtures containing
calcium chloride, which absorbs water even from moist air.
Preferably, unloading and loading should be done within the
storage shed. If this is not possible, avoid handling during
inclement weather.
3. ' Handle salt- as little as possible. Road salt (ASTM Grades 1
and 2) contains a variety of particle sizes. When salt is
handled, large particles break down to finer particles, which
tend to settle out, blow off, and wash away. Neither fine nor
coarse particles, by themselves, are as effective for clearing
as a mixture of sizes.
The central aim of these precautions is to prevent the loss of salt and
damage to equipment and the environment.
Salt lying loose around the work area is liable to be blown about by
winds. It lodges in crevices in equipment and increases corrosion. It
may spread to nearby lands and buildings, causing protests from neighbors.
A messy pad area makes the operation appear suspect as a source of pollution,
even if this suspicion is unjustified.
«
Salt exposed to rain and snow cakes up into big chunks which are impossible
to use without being broken up. Some salt washes away, hopefully collecting
as brine or particulate in a catchment (assuming that the pad area is
properly sloped and drained, as described in Chapter III). Material lost
through runoff represents lost dollars.
So, in handling salt, keeping the area clean and the salt pile covered
are the two cardinal principles. How the principles are applied depends
on what part of the whole storage and handling operation is being performed.
For the sake of the discussion in the remainder of Part Three, the total
operation is described in four parts: planning for next season, receiving
and storing new material, mixing materials, and loading spreader or delivery
trucks.
67
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CHAPTER VI
PLANNING FOR NEXT SEASON
PRESEASON INVENTORY
The time for effective planning for storage and handling of deicing
chemicals and anti-skid material is during the early spring. With all
of the problems of the previous winter fresh in mind, one can plan to
minimize them the next winter. Reevaluation of storage techniques,
delivery schedules, loading techniques, material mixes, equipment, and
manpower at this time will allow maximum lead time for implementing
necessary changes.
If the snow and ice control program is being expanded, additional storage
capacity may be required. Maybe an old loader is too small or slow,
and trucks are always waiting during a storm to be loaded. Perhaps two
or three of the best men will retire this year. In any event, this is
the best time to initiate any action that will make the next winter
season's handling operations run more smoothly.
Some of the points to be considered in this end-of-the-season review
are:
Equipment and Facilities in Current Inventory
1. Are they effective?
2. Are they reliable?
3. If not, should recommendations for new equipment purchase or
facility construction be considered?
Manpower
1. Are there enough people to do the job?
2. Are they trained well enough?
3. Should there be any personnel reassignment?
Scheduling
1. Were delivery schedules convenient?
2. Will spreader truck timing change due to changes in plowing
and salting priorities next season?
3. Is the storm-warning system giving adequate preparation time?
68
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When reviewed early, these and other problem areas unique to the operation
may be ironed out before the next snowfall.
EQUIPMENT
The equipment commonly used for stockpiling and subsequent loading of
deicing and anti-skid materials are: front-end bucket loaders, both
rubber-tired arid track-laying, bulldozers, conveyor belts, and material
throwers.
Of these, the rubber-tired, front-end loader is the equipment, of choice
for this type of material handling. The articulated version of this
machine (hinged in the middle) provides maximum maneuverability for a
given sized machine. Not only is it useful for loading and unloading
salt and sand, it can also be used for keeping the stockpile area and
approaches clear of snow and year-round for a variety of construction
and maintenance tasks. Providing this machine with two different bucket
sizes results in savings of time and wear on equipment that outweigh the
added original cost. A small-volume bucket will prevent overloading of
the machine during the summer season, and a larger bucket will increase
productivity when salt, sand and snow are being handled. The machine
of preference is rated at 1.5 yd3 (1.1 m3) which, for winter operations,
could be equipped with a 2-yd^ (1.5-m^ ) bucket. Machines with 4-yd^ (3.1-m3)
or larger buckets are often used by salt suppliers and distributors for
loading large delivery trucks. There is no advantage in using these
larger machines for loading the common 5-yd3 (3.8-m3) truck-mounted
spreaders.
Although bulldozers may be used for sand and sandVsalt mixture stockpiling,
they are not suited to the task of stockpiling material in storage sheds.
They suffer two disadvantages of track-laying equipment, i.e., low speed
and high maintenance costs.
The conveyor belt is the most efficient means for handling material. However,
it requires special building and storage area design, auxiliary feeding
devices including front-end loaders'and it is quite expensive.
Material throwers are inexpensive and.mobile; in addition, they can stack
the material higher and thus make maximum use of available storage space.
However, since they have been developed only recently, problems still may
require ironing out. At least one major spreader manufacturer has proto-
type units that will move from 1 to 3 tons (.9 to 2.7 t) of salt per minute.
This unit throws salt 60-80 ft (18-24 m) and enables more efficient use
of storage capacity. This single-purpose machine can be used only for
loading of storage sheds.
ESTIMATING QUANTITIES
The quantity of deicing chemicals required during any one winter season
is completely dependent upon the weather conditions. Long-range forecasting
69
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of these weather conditions is problematical at best. , Guidelines for
estimating future salt needs are presented in the Manual for Deicing Chemical
Application Practices^ which outlines techniques for estimating needs from
records of past usage by area, by sub-area, and by road segment. Some
general rules should be applied when estimating needs:
1. Inventory the amount of salt remaining from the previous
season.
2. Calculate the amount of salt or chemical used in previous
seasons.
3. Take into account new mileage responsibilities added to the
road or street system, including routes acquired from other
jurisdictions or road areas.
ORDERING AND SCHEDULING
Although the salt and other chemicals required for a deicing and snow
control program are needed only during the winter months, attention to
procuring bids for required amounts and stockpiling of these materials
must, of necessity, occur many months prior to the winter season. The
timetable for soliciting bids for material and receiving these materials
into storages should fit the budgeting and normal procurement cycle of
the agency responsible for the snow and ice control program. Some
states require that the largest percentage of the next year's salt
requirements be placed in storage before the end of June. Others require
that it be placed in storage before the end of October. Other governmental
agencies rely upon the rapid resupply capabilities of local suppliers to
satisfy their needs for deicing chemicals and order and stockpile these
materials only on an as-needed basis.
The recommended practice is that each agency responsible for a snow and
ice control program maintain under closed storage at least one-half of
the seasonal requirements (and whenever possible a complete seasonal
supply). Such covered salt storage should be well distributed throughout
the road system in accordance with optimum operational requirements. It
is further recommended that salt supplies be placed in these sheds before
the middle of October or earlier depending on when .the winter season begins.
In addition, coordination between the supplier and the receiver should be
established so that direct deliveries from the salt mine, or port of
entry, will reduce the number of times the salt is handled and minimize
the exposure of material to wind and moisture. In short, this means
material shipments (under cover) directly from the mine, dock side, or
salt-producing facility to covered storage sites for storage with minimal
delay and with minimal handling and rehandling.
70
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CHAPTER VII
RECEIVING AND STORING DEICING CHEMICALS
The three steps in receiving and storing are: 1) getting it under cover,
2) testing the material when it arrives to ensure that it meets specifi-
cations, and 3) possible mixing of various materials.
PUTTING MATERIALS UNDER COVER
Salt (Sodium Chloride)
Most highway maintenance sections have their salt supplies delivered by
truck, since most are not near a railroad siding. Though the techniques
listed here apply to truck delivery, they are also applicable to rail
delivery.
It is desirable, though not always possible, to take delivery of salt in
dry, windless weather—particularly if the storage is a tarpaulin-covered
pile, or if the storage shed is not tall enough to allow a double-axle
trailer dump body to raise to full height. In these cases, some exposure
of salt is inevitable.
In order to minimize exposure, personnel must be prepared to put the salt
under cover immediately. If salt is dumped on the pad in front of the
shed, a front-end loader should be standing by to push the salt into the
shed immediately. If the salt is to be stored as a covered pile, personnel
should be ready with a front-end loader and suitable tarpaulin material,
hand sewing machine, and weights to begin covering the pile as it is built
up and shaped by the loader.
If the salt is to be mixed with calcium chloride, mixing at the time of
delivery is a good idea. This will avoid extra handling, which causes the
coarse and fine particles to separate out. Any salt cakes turned up during
the unloading-covering process should be broken up with the loader bucket
or put in the sand pile, where moisture will disintegrate them. What goes
into storage must be cakefree.
When stocking storage sheds, the objective is to get the maximum amount
of material into the shed with a minimum amount of work. To accomplish
these ends, the largest loader available that will maneuver within the
confines of the storage shed should be used.
To minimize the material pushing distance, the delivery trucks should
dump as close to the stockpile as is possible. If the storage shed roof
structure is too low to preclude dumping inside, then the delivery truck
should dump the material close to the door. A front-end loader can then
push the material into the shed and, as the pile builds, stack it as
close as possible to the roof structure. The pushing windrows in the
71
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in the salt, which act as channels for the material being moved, shoulxF
be cleaned up after the last load of the day has been stored. When salt
is heaped inside the storage shed, the bucket hoist capability should be
used rather than the pushing power of the loader to minimize shed wall
loading. In sheds with high ceilings, some ramping of the salt will be
necessary before maximum filling can be achieved. Caution must be exercised
when the bucket is being used near the ceiling as the building may be .„
damaged very easily when the machine is in the high-reach configuration.
As soon as the salt is under cover, the loading area is to be swept. All
stray salt on trucks, loaders, or conveyors (if used) should be swept and
put on the face of the salt pile so that the salt will be used during the
next storm.
Calcium Chloride
Bagged calcium chloride should be stored in a dry building off of the
ground on pallets or other suitable platforms that permit air to circulate
under the bags. The storage should be arranged so that the first material
placed in the storage is the first material withdrawn for use.
The same precautions and handling techniques used for salt should also
apply to the storage and handling of bulk dry calcium chloride. Because
calcium chloride is hygroscopic (readily absorbs moisture), particular
precautions must be taken in bulk storage of both straight calcium chloride
and dry mixtures containing calcium chloride. Whenever possible, all
material should be used before the end of a winter season. However, if
material remains at the end of a season, the storage of it should be
arranged so that it can be used early in the next winter season before
fresh stock is used.
Calcium chloride and calcium chloride-salt mixtures should also be stored
in dry buildings. Piles of material should, in addition, be covered with
waterproof tarpaulins or plastic film to minimize the moisture pick-up of
the material on the faces of the pile. This precaution should be carefully
observed, particularly for materials that must be stored during the humid
summer season. Otherwise, a hard crust will form on the pile that will
have to be broken up before the material can be used.
Aqueous solutions of calcium chloride should be stored in mild steel tanks
that are equipped with mild steel fittings and valves. It is recommended
that these storage tanks be placed at a sufficient height above the ground
so that transfer of solution to the distribution tanks on trucks can be
made by gravity feed, thereby eliminating the need for a pumping system.
Provisions should be made in the area surrounding the calcium chloride
solution storage tank for containing the contents of the tank should it
fail catastrophically. This precaution can easily be incorporated into
the design of a salt storage area through use of low dikes and careful
grading of the area surrounding the tank so that run-off flows to a
suitably sized sump. In the case of multiple liquid calcium chloride
storage tanks, provision should be made for containing the spill of only
the largest tank inasmuch as the occurrence of multiple failures is highly
unlikely.
72
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SPECIFICATIONS AND TESTS
The specifications outlined in this section apply to salt, calcium chloride,
and mixtures of these, and to sand and cinder abrasives. Tests for the
presence of anti-caking agents are also listed.
Sodium Chloride
The specification for sodium chloride generally adhered to is that of the
American Society for Testing and Materials (ASTM) and designated Standard
Specification for Sodium Chloride D632. The specification covers material
intended for use as a deicer and for road construction or maintenance
purposes. The specification covers material obtained from natural deposits
(rock salt) or produced from brine (evaporated, solar, or other). Summarized
below are the major requirements for this specification.
Chemical Composition - Sodium chloride (NaCl), 95.0 percent minimum.
Gradation - The gradation of Type I, sodium chloride, (used primarily
as a pavement deicer or in aggregate stabilization) when tested by
means of laboratory sieves, shall conform to the requirements for
particle size distribution in Table 5.
Permissible Variations - In the case of sodium chloride sampled
after delivery to the purchaser, tolerances from the foregoing
specified values are allowed as follows:
Gradation - 5 percentage points on each sieve size, except
the 1/2 in. and 3/8 in. for Grade 1 and 3/4 in. for Grade 2.
Chemical Composition - 0.5 percentage point.
In addition, individual jurisdictions may impose additional specifi-
cation and delivery penalty clauses. The most commonly used specifi-
cations concern presence of moisture and anti-caking agents. Typical
specifications may include one or more of the following additional
clauses:
Moisture -
• Maximum 0.5% (by weight) (values to 3% reported for some
states).
• Greater than 1% may be rejected (values to 3% reported for
some states).
73
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Table 5. PARTICLE SIZE DISTRIBUTION IN TYPE I SODIUM CHLORIDE
(percent weight passing)
Sieve Size
3/4-in. (19.05-mm)
1/2-in. (12.70-mm)
3/8-in. ( 9.51-mm)
No. 4 ( 4.76-mm)
No. 8 ( 2.33-mm)
No. 30 ( 0.595-mm)
Grade 1
100
95 to 100
20 to 90
10 to 60
0 to 10
Grade 2
100
20 to 100
10 to 60
0 to 10
NOTE: Grade 1 provides a particle grading for general application
and found by latest research to be most effective for ice
control and skid resistance under most conditions. Grade 2
is typical of salt produced in the Western U.S., is available
in states of the Rocky Mountain Region and the West and may
be preferred by purchasers in that area.
74
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Anticake (typical clauses) -
• Not more than 100 mg/1 sodium ferrocyanide (0.01 percent
by weight).
e Not less than 0.04 Ib of pure anti-caking agent per ton of
sodium chloride (20 mg/1).
• Not more than 0.5 Ib of conditioner per ton of sodium
chloride (250 mg/1).
• A certificate must be submitted giving the trade name of
the conditioner and the address of the manufacturer.
® Non-caking additive added.
9 The sodium chloride shall be treated with an anti-caking
material prior to delivery.
Delivery -
s All sodium chloride must be covered during transit with a
tarpaulin or other suitable material and delivered in a
dry condition.
Calcium Chloride
Flake calcium chloride (Type 1) is the preferred deicing chemical. It
contains between 77% and 80% calcium chloride and about 20% water of •
crystallization. The most commonly used specification for calcium chloride
is ASTM Specification D-98. Two types of calcium chloride are covered:
Type 1 - regular flake calcium chloride - and Type 2 - concentrated flake,
pellet or other granular calcium chloride. Pertinent information contained
in these" specifications is summarized in Tables 6 and 7.
Pre-Mixed Sodium Chloride and Calcium Chloride
At this time, there is no established specification for pre-mixed sodium
chloride and calcium chloride material for highway deicing. Typical
formulations range from five parts sodium chloride and one part calcium
chloride (16.6% mixture) to a mixture of three parts sodium chloride and
one part calcium chloride (25% mixture).
The basic ingredients of a specification are outlined below:
* The materials shall be throughout, a completely uniform and
free-flowing blend of the two ingredients. Mixing can be
achieved by any means suitable to produce the desired uniform
mixture.
75
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Table 6. CHEMICAL COMPOSITION REQUIREMENTS FOR CALCIUM CHLORIDE
Percent
CaCl_, minimum
Total alkali chlorides (as NaCl),
maximum
Total magnesium as MgCl2> maximum
Other impurities (not including
water), maximum
Type 1
77.0
2.0
0.5
1.0
Type 2
94.0
5.0
0.5
1.0
Table 7. PARTICLE SIZE REQUIREMENTS FOR CALCIUM CHLORIDE
Sieve size
3/8-in. (9.51-mm)
No. 4 (4.76-mm)
No. 30 (o.595-mm)
Percent passing
(by weight)
100
80 to 100
0 to 5
76
-------
• The sodixnn chloride shall conform to ASTM Specification D-632.
• The calcium chloride shall conform to the requirements of ASTM
Specification D-98, Type 1 or Type 2.
• The stipulated quantity of calcium chloride by weight of the
mixture with sodium chloride shall be a minimum quantity.
Any minus deviation on calcium chloride will be subject to
material rejection or assessment of damages.
Calcium Chloride Solutions
No specification has been established for calcium chloride solutions.
The standard test for determining the percentage composition of calcium
chloride in aqueous solution is to measure the specific gravity of the
solution at room temperature with a suitable hydrometer. Summarized in
Table 8 are the percentage compositions of calcium chloride by weight
in solutions of calcium chloride at room temperature with various specific
gravities. .
Table 8. PERCENTAGE COMPOSITION BY WEIGHT OF CALCIUM CHLORIDE SOLUTION
Percent by Weight
Specific Gravity
at 20°C (68°F)
Hydrated CaCl-
Type r
2H2°
008
017
025
033
042
051
059
068
077
085
103
1.122
1.141
160
180
200
220
241
262
284
306
328
351
375
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.398
1.32
2.65
3.97
5.30
6.62
7.95
9.27
10.60
11.92
13.25
15.90
18.55
21.20
23.84
26.49
29.14
31.79
34.44
37.09
39.74
42.39
45.04
47.69
50.34
52.99
Anhydrous (CaCl~)
Type 2
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
12.0
14.0
16.0
18.0
20.0
22.0
24.0
26.0
28.0
30.0
32.0
34.0
36.0
38.0
40.0
77
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Sand
*
Abrasives should be clean and hard with 100% passing a 0.5-in. (1.3-cm)
screen, and the minimum size should be retained on a No. 50 mesh. Larger
particles could damage passing vehicles, and smaller particles are of
no use in increasing the coefficient of friction and also retain moisture
and freeze. Cinders should be free from large uncrushed particles.
Depending on local conditions, abrasives should be mixed with salt or
calcium chloride, approximately 5% by weight, at the time of stockpiling
to keep the pile from freezing.
Tests for Presence of Anti-caking Agents
The two most common anti-caking additives in highway salt are ferric
ferrocyanide, Fe, (Fe (CN),)_ (Prussian Blue), and sodium ferrocyanide,
Na,Fe (CN)g • 10 ELO (Yellow Prussiate of soda-YPS). The presence of
ferric ferrocyanide can be detected by visual inspection of the salt for
a blue tint.
The presence of sodium ferrocyanide in deicing salt can be detected by
squirting a dilute aqueous solution (1%) of ferric chloride from a squeeze
bottle onto the salt. The material dampened by the solution will turn
blue (Prussian Blue reaction), indicating the presence of sodium ferrocyanide.
BLENDING MATERIALS
Should the operation require blends of various deicing and anti-skid
materials, a decision must be made as to whether to purchase material
blended to specification or to mix it on the site. In general, the major
salt suppliers will blend salt-calcium chloride mixtures at a lower cost
than can be accomplished on site. Some of the suppliers are equipped with
conveyor systems that mix and load in one operation.
Since salt-calcium-chloride mixture is usually delivered as premix and
handled as straight salt (though with even more careful attention to
keeping it dry), the main source of concern is sand-salt. Premixing is
desirable when this mixture is used in* preference to straight salt—for
example in climates with frequent temperatures below 10°F (-12°C)—so
that spreaders can be loaded more quickly. The same precautions apply
as for straight salt. The pile must be kept dry—water on a sand-salt
pile during mixing or afterward will leach out the salt.
There are two basic ways of mixing salt or calcium chloride with sand.
One is to prepare a "premix" pile that is transferred directly to the
spreader trucks. The other is to keep the piles of material separate
until the trucks are ready to roll in a storm, then load the desired
portions (a scoop of salt, three of sand), onto the trucks.
78
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On-site mixing of NaCl-CaCl^ and salt/sand blends may be accomplished by
spreading a layer of sand or salt on a paved pad, then adding a layer
of the second component. This material is then picked up and put into
the stockpile. Subsequent loading and spreading operations continue
the mixing action.
A second on-site mixing technique which is simpler, and which most
proponents believe just as effective, is to partially fill the spreader
hopper with sand (about 1/2), add a layer of salt to give the correct
mix, then fill the hopper completely with sand. The action of the
conveyor flight bars (after the short initial discharge of unmixed sand)
tends to mix the salt and sand as the material falls onto the flight bars.
(See Figure 29.)
HOPPER
BODY
SPINNER'
Figure 29 Mixing of salt and sand by flight bars in spreader hopper
As a result of the large quantities often used, chemically treated sand
is usually stored out of doors and uncovered. This practice should be
avoided if there is sufficient covered storage available for the quantities
required. However, first priority should be given to storage of bulk
salt and calcium chloride under cover.
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Precautions that should be taken to minimize the amount of chemical leached
out of chemically treated sand piles include:
• Pre-mixing treated sand as late as possible prior to the winter
season will minimize exposure of the sand-salt pile to fall and
early winter rains.
• Periodic mixing of chemically treated sand can occur during the
winter by taking advantage of thawing conditions when an untreated
sand pile can be worked. Periodic mixing also tends to minimize
the amount of material left over at the end of the winter season.
• Minimizing the amount of chemical used in treating sand piles is
important. Only enough chemical is mixed into the sand piles to
prevent them from freezing. The recommended mixture is 80 Ib
of sodium chloride to 1 ton of sand (4% mixture).
• Covered stock piles of chemically treated sand should be placed
on a bituminous concrete pad that is of sufficient size and is
sloped so that water runs away from the pile. In this way, no
water will flow through or around the pile and only precipitation
enters the pile.
• Chemically treated sand that must remain exposed to the weather
for periods longer than one month (such as that remaining at the _
end of the season) should either be removed to a covered shed or
suitably covered with tarpaulins, plastic film, or reinforced
plastic film and secured against wind damage.
• Continual cleaning up is essential around the area during and
after periods when chemically treated sand is being withdrawn
from the stockpile. Good housekeeping practices should be
employed at all times and spilled material should be cleaned up
after every storm.
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CHAPTER VIII
LOADING CHEMICALS FOR USE
The procedures described in this section apply to the loading of bulk salt
or calcium chloride onto trucks, either for shipment to another destination
(i.e., from mine to a regional stockpile, or from there to a maintenance
yard) or for spreading on the highways.
If possible, loading of trucks or spreaders should occur inside the salt
storage shed. This reduces spillage and cleanup problems. If the salt
or premix is stored in covered windrows, only as much of the pile exposed
will be loaded. When loading occurs outside, a loading ramp such as the
one shown in Figure 30 may be useful. (The design for such a ramp is
shdwn in Chapter III of this manual.)
Spreader trucks should be loaded with minimum loader cycle time consistent
with safe equipment operation. This is accomplished by using a minimum
number of direction reversals and turns and the shortest path possible.
The loading pattern should be designed so that the spreader truck driver
can observe the loader during loading operations. If possible, backing
up of the spreader truck should be avoided. Typical loading patterns are
shown in Figures 31-33 for several shed configurations.
If possible, it is best to use the oldest material first. This is possible
in a shed with front and rear doors or in a covered windrow. In a one-door
shed, new material may be dumped in on top of the old. If the shed is good
and dry, not being able to get the old material out of the back is not so
important—it will not lump, and it is better to leave it alone than to move
it around to make way for new material.
Figure 30 Loading ramp
81
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Figure 31 Typical loading pattern for a storage building with one entrance
82
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Figure 32 Typical loading pattern for a storage building with two bays
83
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Figure 33 Typical loading pattern for a storage building with front and rear entrances
84
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If calcium chloride is to be mixed with salt during the loading operation,
a quantity of calcium chloride sufficient to last throughout the storm,
should be put into the corner of the salt storage shed. It can then be
handled under cover. To prevent spillage from truck side way, hoppers
should be filled only to the level of the screen.
Before the truck leaves the shed or loading area, it should be cleaned—-
catwalks, top edges and ledges of the body, tanks, roof, and fenders.
This will keep the salt from spilling off where it's not wanted. The
screen also should be checked for lumps—these may stop the flow or jam
the spreader. The lumps are to be broken or thrown in the sand pile, not
abandoned. (With proper precautions taken earlier, salt should be dry
and lumpfree.) The driver should log the load, visually check out
spreader and truck (lights, tires, etc.), and then start out on his route.
Once the truck leaves, the loader operator should clean up the loading
area in preparation for the next truck. All spilled salt in the loading
area should be scraped up and put back on the face of the pile. This is
important in sheds and on and around loading docks to keep piles and
lumps from restricting the wheel movement of the trucks and loader. In
open loading areas, cleanup is important to minimize the amount of salt
that gets wet. Wet spills should be scooped into a heap at the base of
the pile to go out on the next truck. If the loader operator has to
wait for another truck, he should put his machine into the shed to keep
it from getting wet.
In summary, the ieast wasteful storage handling of salt can best be
accomplished by thoughtful planning and the exercise of reasonable care
in handling.
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ANNOTATED REFERENCES
1. Hogbin, C.E., Road Research Laboratory, Ministry of Transport, Loss
of Salt due to Rainfall on Stockpiles Used for Winter Road Maintenance,
Harmondsworth Road Research Laboratory (U.K.), Ministry of Transport
RRL Report No. 3, 1966, 4 pages.
This report describes measurements made to find the
losses due to rainfall on large stockpiles of salt
used for preventing the formation of ice on roads,
and assess the value of providing covers. It is
concluded that covering becomes economical when
the annual rainfall exceeds about 24 inches, that
is over all the United Kingdom except the East and
Southeast of England, where the saving would be
marginal. Covering also keeps the salt dry so
that it can be handled easily and spread evenly
on the road by machine. Even spreading allows a
lower rate per square yard to be used.
2. Richardson, D.L., Terry, R.C., Jr., et. al., Arthur D. Little, Inc.,
Cambridge, Massachusetts, Manual for Deicing Chemical Application
Practices, Environmental Protection Agency Report No. EPA-670/2-74-045,
1974.
This manual contains the results of a study conducted
for the U.S. Environmental Protection Agency to minimize
the use of chemicals in controlling snow and ice on high-
ways. Based on the best current practices for highway
maintenance as observed during two years of study, practical
guidelines are presented for control and removal of ice and
snow from highways by plowing and through the use of salt,
calcium chloride, abrasives, and combinations thereof.
Included are discussions of administration and supervision
of snow and ice control operations; the role of weather
forecasting and other inputs to decisions made during
winter storms; tabulations of recommended quantities of
chemicals to be applied to various classifications or
roads; recommended levels of service; operation procedures;
methods for accounting for usage of deicing chemicals;
descriptions of equipment including ground-speed-controlled
spreaders, plows, trucks, and other snow-removal equipment;
discussions of techniques for calibrating and checking the
calibration of chemical spreaders; and discussions of how
public administrators and highway maintenance personnel can
interact with the driving public and environmental and con-
servation groups.
86
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3. Pietan, R.A., Maintenance Methods Engineer, Maintenance Standards
Section, Minnesota Highway Department, Salt Brine Runoff Control
at Stockpile Sites. St. Paul Minnesota: Office of Engineering
Standards, Research and Standards Division, Minnesota Highway
Department, November 1972, 18 pages.
This report summarizes the results of a study of salt
brine pollution undertaken hy the Maintenance Standards
Section of the Minnesota Highway Department. Over 85
sites of salt and treated sand stockpiles were examined,
with special emphasis on those in which salt brine runoff
currently caused pollution or could do so in the near
future. The extent of the problem of salt brine runoff
was analyzed, and possible solutions were evaluated.
Finally, a course of action was recommended for the
Department, including time tables and costs.
Although not cited in this manual, the following publications are also
of interest,
Cohn, M.M., and Fleming, R.R., American Public Works Association,
Managing Snow Removal and Ice Control Programs. A Practical Guide to
the How. When, Where and Why of Effective Public Work Practices. American
Public Works Association Special Report No. 42, 1974, 168 pages.
A collation of papers presented at the Annual North American
Snow Conferences 1969-1973, this document is a manual of
practice presented through on-the-job accounts of leading
authorities. The manual covers preparations before the
storm, performances during the storm, practices and problems
in chemical-abrasive treatment of ice and melting methods,
and post-storm evaluations of performance and productivity.
National Cooperative Highway Research Program. Minimizing Deicing
Chemical UseSynthesis of Highway Practice No. 24, Transportation Research
Board, Washington, D.C., 1974.
With the premise that it is possible to reduce the use of
chemicals and still provide a satisfactory level of servive
on streets and highways, this report presents the results
of an investigation of minimizing the use of deicing chemicals.
Suggestions are given for approaches to reducing chemical usage
through careful planning of snow removal equipment assignment
and routes, timing of chemical applications, spreader metering
devices, relating rates of application to storm conditions, use
and control of application equipment, more dependence on
mechanical snow removal, operator training and delineation
of a management philosophy of winter maintenance.
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Terry, R.C., Jr., Arthur D. Little, Inc., Road Salt, Drinking Water, -
and Safety; Improving Public Policy and Practice, Ballinger Publishing
Co. Cambridge, Massachusetts, 144 pages.
This policy study, written initially for the Commonwealth of
Massachusetts in 1972, was greatly expanded in 1973 to report
developments in research, improvements in managerial and ' ,',,,
technical practices of highway departments, and important
legislative developments in both the United States and Canada.
It synthesizes the data now available from the fields of
chemistry, sanitary engineering, road maintenance, public
health, medicine, and administration.
88
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' TECHNICAL REPORT DATA
i (Please read Instructions on the reverse before completing)
1. REPORT NO. 2
EPA-670/2-74-033
4. TITLE AND SUBTITLE
MANUAL FOR DEICING CHEMICALS: STORAGE
AND HANDLING
: ._
7.AUTHOR(s)D. L. Richardson, Charles P. Campbell, Raymond
J. Carroll, David I. Hellstrom, Jane B. Metzger, Philip
J. O'Brien, Robert C. Terry
p. PERFORMING ORGANIZATION NAME AND ADDRESS
Arthur D. Little, Inc.
Acorn Park
Cambridge, Massachusetts 02140
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
3. RECIPIENT'S ^CCESSION-NO.
5. REPORT DATE
July 1974; Issuing Date
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
*
10. PROGRAM ELEMENT NO.
1BB034/ROAP 21ASZ/TASK AE
11. CONTRACT/GRANT NO.
68-03-0154
13. TYPE OF REPORT AND PERIOD COVERED
Final - 7/72 to 6/74
14. SPONSORING AGENCY CODE
ttS. SUPPLEMENTARY NOTES ~—
I
This report contains the results of a study conducted for the U.S. Environmental
Protection Agency to minimize the loss to the environment of chemicals used in
controlling snow and ice on highways. Based on the best current practices for
highway maintenance as observed during two years of study, practical guidelines
are presented for good practice in the storage and handling of deicing chemicals.
1. Covered storage of salt and other deicing chemicals is strongly
recommended; permanent structures for this purpose are preferable.
Guidelines are given for site selection and for design foundations,
paved working area, and site drainage. Existing storage facilities,
are presented that represent a range of costs, designs, construction
materials and storage capacities.
2. For the handling of salt and other deicing chemicals, general precautions
and good housekeeping practices are defined.
3. Environmental responsibilities are discussed for personnel who administer
and supervise highway maintenance.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
'Calcium chloride, Deicing, Deicers, *Ice,
Julk storage, Sheds, Materials handling,
Julk handling, *Snow, Trafficability,
'Sands, Highways
. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
-89-
b.lDENTIFIERS/OPEN ENDED TERMS
*Salt, Deicing chemical
storage, Deicing. chemi-
cal handling, Highway
deicing chemicals
19. SECURITY CLASS (This Report)'
UNCLASSIFIED
2O. SECURITY CLASS (This page)
UNCLASSIFIED
c. COSATI Field/Group
13B
13M
21. NO. OF PAGES
99
22. PRICE
PA Form 2220-1 (9-73)
U.S. GOVERNMENT PRINTING OH-IU: i3/t-/b/-5«t/5332 Region No. 5-I
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