3A530-R-93-002
United States Solid Waste and EPA530-R-93-002
Environmental Protection Emergency Response PB93-209 419
Agency (OS-305) August 1993
&EPA Geotechnical Systems
For Structures on
Contaminated Sites
A Technical Guidance
Document
PROTECTION
AGENCY
DALLAS, TEXAS
USURY
Printed on Recycled Paper
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GEOTECHNICAL SYSTEMS FOR
STRUCTURES ON CONTAMINATED SITES
Authors
Hilary I. Inyang, Ph.D.
Senior Geoenvironmental Engineer (IPA)
Vernon B. Myers, Ph.D.
Chief, Monitoring and Technology Section
Corrective Action Programs Branch
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC
March, 1993
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DISCLAIMER
This document is intended to assist Regional and State personnel in the evaluation of
design measures for structural foundations and non-conventional covers at contaminated sites.
Adequate implementation of the schemes discussed in this document may minimize risks to
human health and the environment at such sites. This guidance is not a regulation (i.e., it does
not establish a standard or conduct that can be enforced by law) and should not be used as such.
Regional and State personnel should exercise their discretion in using this document and others
that address relevant issues in making decisions on the adequacy of designs with respect to risk
minimization.
This document has been reviewed by technical experts within and outside the U.S.
Environmental Protection Agency. Where necessary, the comments made by the reviewers have
been addressed in this final edition. The contents of this document do not necessarily reflect the
current views and policies of the U.S. Environmental Protection Agency. Also, mention of trade
names, commercial products, or publications does not constitute an endorsement of their use
without additional evaluations.
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ACKNOWLEDGMENTS
The authors of this technical guidance document acknowledge the direct and indirect
support of the following individuals: Mr. D. Barnes, and Ms. D. Keehner of the Office of Solid
Waste, U.S. EPA; Mrs. Robin Tenney-Inyang; Mr. Michael Lease and Mr. Sam Figuli, both of
SAIC; and Mr. Harrison Abinteh of Howard University. Gratitude is also expressed to U.S. EPA
Regional personnel for the review comments they provided on the first draft of this document.
LIST OF REVIEWERS
1. Dr. S. Dendrou, Technical Director, Macro-Engineering Inc., Annandale, Virginia.
2. Dr. Yacoub Najjar, Assistant Professor of Civil Engineering, The George Washington
University, Washington, DC.
3. Dr. Ignatius Okonkwo, Project Engineer, Loureiro Engineering Associates, Plainville,
Connecticut.
4. Dr. Brett W. Gunnink, Assistant Professor of Civil Engineering, University of Missouri-
Columbia, Columbia, Missouri.
5. Dr. Lorraine N. Fleming, Associate Professor of Civil Engineering, Howard University,
Washington, DC.
6. Dr. Steven Glaser, Geotechnical Engineer, National Institute of Standards and Technology,
Gaithersburg, MD.
7. Dr. John Rohde, Associate Professor of Civil Engineering, University of Nebraska, Lincoln,
Nebraska.
8. Prof. Ronald C. Sims, Head, Division of Environmental Engineering, Utah State University,
Logan, Utah.
9. Ms. Janine Dinan, Environmental Scientist, U.S. Environmental Protection Agency,
Washington, DC.
10. Dr. David Bartenfelder, Environmental Scientist, U.S. Environmental Protection Agency,
Washington, DC.
11. Ms. Denise Keehner, Branch Chief, Corrective Actions Programs, U.S. Environmental
Protection Agency, Washington, DC.
111
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PREFACE
This technical guidance document has been developed to address some of the technical
aspects of contaminated site remediation and redevelopment. This guidance does not represent
an advocacy by the U.S. EPA for the use of commercial or residential structures to cover
contaminated media. However, at some sites where contamination is marginal or where the
primary source of contamination has been removed, it may be technically feasible to build
functional structures that can mitigate some of the environmental hazards present at such sites. If
such structures are designed adequately, their utilization will not result in significant increases in
risks to human health and the environment. The ground coverage provided by such facilities and
their ancillary structures may minimize the migration of residual contaminants from host media
through a reduction in surface water infiltration. Within the contexts discussed above,
adequately planned and implemented structural development plans may be appropriate at sites
undergoing Resource Conservation and Recovery Act (RCRA) Corrective Action. The
Corrective Action Program is described briefly in the introductory chapter. The design
approaches, configurations, mathematical equations, and sample numerical computations pre-
sented herein may be applicable to remedial projects at contaminated sites undergoing RCRA
Corrective Action. If structures are placed over marginally contaminated materials at RCRA
facilities, then conditions for institutional control and financial assurance should be specified. In
this document, "structural development" is used in very general terms. It includes civil
engineering facilities such as office buildings, storage facilities, parking ramps and parking lots.
Under more common situations involving the design of foundation systems for the facilities
mentioned above, the primary consideration is usually geotechnical stability. The risk of human
exposure to residual contaminants at redeveloped sites necessitates the consideration of environ-
mental factors as well. In tandem with geotechnical factors, these environmental factors deter-
mine the level of conservatism that should be incorporated into structural designs for
IV
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contaminated sites. These structures should be designed to protect human health and the
environment in addition to meeting other performance functions.
In developing this technical guidance manual, the authors have adopted some principles
from such fields as risk assessment, geotechnical aspects of waste disposal, soil stabilization,
hydrology, pavement engineering, and toxicology. The relative novelty of the suites of issues
and technical problems involved has made it necessary to develop original mathematical
formulations and design configurations. To enhance clarity, scenarios have been created and
relevant numerical examples provided. The Hydrologic Evaluation of Landfill Performance
(HELP) computer model has been used to evaluate one of the design configurations presented in
this document. This configuration is the one which engineers are most likely to implement
owing to its simplicity and relatively low cost. This configuration was evaluated under
hydrologic settings that are representative of various areas of the conterminous United States.
Although the HELP model was originally developed for evaluating the flow of liquids through
landfill layers, it is applicable to any set of horizontal layers provided layer material
characteristics are supplied.
Information has been provided, albeit sparsely, on actual case histories of contaminated
sites that have been developed in the United States. It is recognized that expertise exists in the
field for analyses on site-specific and structure-specific bases. Minimization of potential risks
through engineering ingenuity is encouraged. The reader should not regard the design
configurations presented herein as the complete universe of implementable designs.
This document is not a regulation but is intended to help State and Regional personnel in
the evaluation of design measures for structural foundations and non-conventional covers at
marginally contaminated sties. It provides a body of information on design techniques that could
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be adopted by facility and operators if EPA or State personnel allow the reuse of marginally
contaminated or cleaned-up land for structural purposes. Since this is a technical document, it
does not address policy issues which are subject to changes. Since this is not a policy document,
EPA and State personnel are expected to evaluate situations on site-specific basis (e.g.,
assessment of site-specific risk and corrective action objectives).
The utility of this technical document is expected to be two-fold:
1) Once it is determined that the level of contamination at a site is marginal (either due to
cleanup to a specific level or due to originally low level contamination), this document
may be used as a catalog of design schemes for indirectly reducing human health and
environmental risk associated with some operational activities at the sites. In this case,
the land use decisions at the site have already been made by the responsible officer.
2) In the second situation, the level of contamination has been deemed marginal at a site by
the responsible officer. The permission to re-develop the site may be contingent upon the
identification of suitable design measures that would protect human health and the
environment from residual contaminants that may exist at the site. This document may
be used as one of the information sources in the decision making process with respect to
allowing the redevelopment of a site.
The reader is encouraged to contact the authors for clarifications if necessary.
Hilary I. Inyang
and
Vernon B. Myers
March, 1993
VI
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TABLE OF CONTENTS
Section EagS
TITLE PAGE i
DISCLAIMER ii
ACKNOWLEDGMENTS iii
LIST OF REVIEWERS iii
PREFACE iv
TABLE OF CONTENTS vii
LISTOF FIGURES ix
LISTOFTABLES xi
1.0 INTRODUCTION 1
1.1 REGULATORY BACKGROUND : 1
1.2 RCRA CORRECTIVE ACTION STRATEGY 2
1.3 FRAMEWORK FOR THE USE OF SURFACE STRUCTURES 3
1.4 UTILITY OF SURFACE STRUCTURES 7
2.0 SUITABLE CONDITIONS FOR STRUCTURAL DEVELOPMENT 9
2.1 SITE CHARACTERISTICS 9
2.2 WASTE CHARACTERISTICS 11
2.3 FREQUENCY AND CONTINUITY OF RELEASE 11
2.4 STRUCTURE TYPE AND FUNCTION 12
3.0 MAJOR CATEGORIES OF CONTAMINATED SITES 13
3.1 WASTE CONTAINMENT SITES 13
3.2 EXCAVATED SITES WITH MINIMAL RESIDUAL CONTAMINATION 13
4.0 SELECTION OF SITE DESIGN MEASURES 16
4.1 DATA NEEDS AND SOURCES OF INFORMATION 16
4.2 GEOTECHNICAL AND ENVIRONMENTAL ISSUES 17
4.2.1 Differential Settlement 17
4.2.2 Vertical Infiltration of Moisture 22
4.2.3 Groundwater Infiltration 23
4.2.4 Migration of Residual Contaminants 26
4.2.5 Exposure of Workers and Residents 30
Vll
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TABLE OF CONTENTS (CONTINUED)
Section Page
4.2.6 Compatibility of Structures with Other Corrective Action
Measures 38
4.3 ANCILLARY MEASURES 38
5.0 DESIGN COMPONENTS AND CONFIGURATIONS 41
5.1 DESIGN OBJECTIVES AND ESSENTIAL COMPONENTS 41
5.2 DESIGN CONFIGURATIONS AND FUNCTIONS 42
5.3 COMPONENT SIZING AND Mix DESIGN 64
5.3.1 Vertical Sections Through Covers 64
5.3.2 Bituminous Cap: Options A and B 66
5.3.3 Bituminous Cap With Undercap Drainage: Options C and D 73
5.3.4 Numerical Example 93
6.0 MEASURES OF COVERAGE EFFECTIVENESS 99
6.1 COVERAGE RATIO 99
6.2 INFILTRATION RATE 99
6.3 CONTAMINANT MIGRATION RATE 99
6.4 RISK REDUCTION 100
7.0 EXAMPLES OF REDEVELOPED SITES 102
APPENDIX A—CHEMICAL HAZARD INFORMATION 106
APPENDK B—ENGINEERING CONVERSION FACTORS 130
4CES 135
V1U
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LIST OF FIGURES
Figure Page
1 Examples of candidate sites for corrective action prior to consideration for
structural development 14
2 Further examples of candidate sites for corrective action prior to consideration
for structural development 15
3 Differential settlement of a structure with a footing that rests on a residually
contaminated soil 20
4 An illustration of moisture infiltration through cracked cemented covers
(cracks are exaggerated in size and height of arrows signifies magnitude of
infiltration rate) 24
5 A schematic illustration of spatial Donation of clean-up activities at a site
(U.S. EPA 199 la) 34
6 Curves of residence times and corresponding fractions of U.S. households with
total residence times that reach or exceed indicated residence time values
(Israeli and Nelson, 1992) 37
7 A structure developed on partially remediated waste pile site. A. before structural
development, B. after structural development 43
8 A coverage scheme for a structural foundation at a reclaimed low permeability site
with residual contamination (adapted with modifications from Inyang et al. 1992) 46
9 A shallow foundation system for a structure on a reclaimed impoundment site.
A. before utilization, B. after construction 48
10 Schematic of a foundation system that may be implemented at a reclaimable site
with a high groundwater table 49
11 Surface cover, under-slab drainage system and foundation protection for a
structure at a reclaimable site 51
12 Proposed soil covering system design for residential structures on contaminated
land (Yland and Van Wachem 1988) 53
13 Protection of a footing against chemical attack in contaminated soil (Thorbum and
Buchanan 1987) 54
14 A schematic diagram of an active vapor control system for a building sited on
contaminated groundwater site (U.S. EPA 1989F). Note that this is not a
complete design. 55
15 A schematic overview of mechanisms of moisture migration in building materials
(Gavin 1985) 57
16 A schematic of the configuration of ASTM test E96-80 for measuring the vapor
transmission rate through materials 59
IX
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LIST OF FIGURES (CONTINUED)
Figure Page
17 The relationship among relative humidity, temperature, and humidity ratio
(U.S. EPA 1991c) 60
18 Vapor flow rate through cores of portiand cement concrete floor slabs placed over
various thicknesses of granular materials (Day 1992) 61
19 Optimal designs and suggested warrants/conditions for ground surface covers at
building sites with residual contaminants 65
20 A decision tree for selecting chemical stabilization agents for soils (U.S. Air
Force 1976 and Epps et al. 1970) 74
21 A schematic diagram of the variety of cracks that can develop in a bituminous
pavement layer (NRC 1990) 75
22 Pictures of severity levels of block cracks in a bituminous concrete layer. A.
Low severity—crack widths <0.25 in, B. moderate severity >0.25 in, C. high
severity—spalled (NRC 1990) 77
23 The 1-hour/1-year frequency precipitation rates in the United States (FHWA 1973) 78
24 An illustration of hemispherical flow into a subgrade due to moisture that
percolates through a cylindrical crack (actual flow is three-dimensional) 80
25 An illustration of the initial flow situation for water that flows through a
cylindrical crack into a drainage layer underneath a bituminous concrete cover
(actual flow is three-dimensional) 80
26 Approximate permeability data and other characteristics of clean coarse-grained
drainage materials (U.S. Department of the Navy 1982) 86
27 An illustration of the configuration of a bituminous concrete cover and granular
layer over a site with possible residual contamination (not drawn to scale) 88
28 Required pipe capacities for drainage layers (U.S. EPA 1983 b; the thickness of the
tributary area, b, is measured in feet) 89
29 Nomograph for determining the required collector pipe size based on flow rate,
outlet spacing, pipe gradient, and Manning's roughness coefficient (N)
(Moulton 1980) 91
30 A chart for determining the required drainage pipe diameter (SCS 1973) 92
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LIST OF TABLES
Table Page
1 General data needs and data sources for remedial actions 10
2 Some common methods of data acquisition for remedial design purposes
(U.S. EPA 1990a) 18
3 Estimates of capillary rise in various soils (Hansbo 1975, adapted from Holtz
and Kovacs 1981) 26
4 Data ranges and general effects on liquid contaminant migration from a polluted
site (Rosenberg, et al., 1990) 28
5 Data ranges and general effects on gas migration from a polluted site
(Rosenberg, et. al., 1990) 29
6 Safety personnel and responsibilities during activities at hazardous waste sites 32
7 Summary of standard default exposure factors (U.S. EPA 1991b) 36
8 A tabulation of measures that could increase the effectiveness of structural
development as a stabilization option 39
9 A summary of specific corrective measures to improve the performance of
hazardous waste facilities and minimize site contamination 45
10 Gradations of aggregates used for casting concrete slabs for vapor flow rate
measurements (Day 1992) 63
11 A summary of vapor flow rate results obtained experimentally by Day (1992) 63
12 HELP model input data and infiltration results for simple designs (A and B) of
uncracked asphalt covers for building sites with residual contaminants 67
13 Mix compositions for formed-in-place asphalt linings (Asphalt Institute 1976) 70
14 Recommended emulsified asphalt contents for various types of aggregates (Asphalt
Institute 1979) 71
15 Requirements for asphalt for use in waterproof membrane construction
(ASTM D-2521, adapted from Asphalt Institute 1976) 71
16 Climatic limitations and construction safety precautions for various chemical
stabilizing agents for soils (FHWA 1979) 72
17 Cement requirements for stabilizing various soils (USAF 1975) 72
18 A summary of recommended drainage and filter layer material gradations
(developed from Moulton [1980]) 87
19 Recommended minimum flow capacities for collector pipes in drainage systems
(Lee etal. 1984) 90
20 Some examples of redeveloped sites 104
XI
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CHAPTER l.O
INTRODUCTION
1.1 REGULATORY BACKGROUND
In 1970, Congress passed the Solid Waste Disposal Act. This was the first Federal
law that required environmentally sound methods for the disposal of wastes. As the com-
plexity of the waste management problem grew, there was a clear need for a comprehensive
program geared toward preventing contamination problems. To address this need, Congress
enacted the Resource Conservation and Recovery Act (RCRA) in 1976. RCRA laid out a
basic framework for regulating waste generators, waste transporters, and waste manage-
ment facilities. Congress revised RCRA, first in 1980 and again in 1984, under the title of the
Hazardous Solid Waste Amendments (HSWA). Under HSWA, EPA had in place three
comprehensive waste management programs: the Subtitle C program, which establishes a
system for controlling hazardous waste from its generation until its ultimate disposal; the
Subtitle D program, which establishes a system for controlling solid waste, such as
household waste; and the Subtitle I program, which regulates toxic substances and petroleum
products stored in underground tanks.
Today the RCRA hazardous waste universe consists of approximately 4,700 hazardous
waste treatment, storage, and disposal facilities. Within these facilities, there are
approximately 81,000 waste management units. In addition to those 4,700 facilities are
211,000 facilities that generate hazardous waste.
An important provision under HSWA requires that hazardous waste facilities take
corrective action for contaminant releases at facilities, including releases from past disposal.
The intent of this provision is to ensure that releases of contaminants at RCRA hazardous
waste facilities will not harm human health or the environment.
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Specific regulations on the redevelopment of contaminated sites are sparse. Relevant
issues fall within RCRA regulations for site cleanup. In the States, California promulgated
regulations that control redevelopment and use of previously contaminated sites. As
described in U.S. EPA (1986a), the California Assembly Bi1! 2370 (AB 2370) authorizes the
California Department of Health Services to impose restrictions on the use of contaminated
land for sensitive purposes. Greenthal and Millspaugh (1988) have described State haz-
ardous waste statutes that impact upon real estate transactions.
1.2 RCRA CORRECTIVE ACTION STRATEGY
The RCRA Corrective Action Program has embarked on a mission of obtaining better
information at facilities early in the Corrective Action investigation phase in order to set
' priorities for cleanup and to control releases of contaminants. While final cleanup is still the
long-term goal of the RCRA Corrective Action Program, the RCRA Stabilization Initiative
emphasizes the importance of controlling releases and preventing the further spread of
contamination. The RCRA Stabilization Initiative focuses on actions to address actual and
potential exposures (imminent risks) and to prevent the further spread of contamination. The
overall goal of this initiative is to, as situations warrant, control or abate threats to human
health and the environment from releases at RCRA facilities, and to prevent or minimize the
further spread of contamination while long-term remedies are pursued.
Implementing the RCRA Stabilization Initiative will yield substantial benefits for the
RCRA Corrective Action Program. Focusing resources in the near-term on stabilizing
environmental problems, rather than pursuing final comprehensive remedies at all facilities,
should enable the Agency to control the most serious environmental problems at a larger
number of facilities, more quickly. Furthermore, by imposing such controls, the existing
release may be significantly reduced.
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The RCRA Stabilization Initiative is a new program philosophy and should not be
confused with measures that were historically considered stabilization technologies. Many of
the stabilization technologies had the goal of immobilizing wastes and include solidification,
vitrification, and other immobilization techniques. Although these technologies may be
effective as stabilization measures in certain situations, the RCRA Stabilization Initiative is
broader and includes other source control measures along with measures that will mitigate
the further spread of contamination. This document elaborates on one type of technology that
may, in certain circumstances, be useful and adequate in controlling contaminant migration.
1.3 FRAMEWORK FOR THE USE OF SURFACE STRUCTURES
In terms of the method of treatment of contaminated materials, corrective action
approaches can be classified into two categories, namely, in situ treatment and above-ground
treatment. Several in situ remedial technologies and measures have been developed for
managing contaminated sites. Contaminant characteristics, site hydrologic conditions, and
the concentration of contaminants determine the cost-effectiveness and feasibility of alterna-
tive cleanup measures.
In situations involving high concentrations of contaminants, excavation and subsequent
treatment of hazardous wastes or contaminated geomaterials is usually desirable, especially
when the latter are not areally extensive. After excavation, residual contamination may still
exist in the host material, although it may be arguably minimal. In other situations, an
extensive area may be inhomogeneously polluted by contaminants of low concentration.
Clean zones may exist between contaminated areas within such a site. In this situation,
excavation may not be cost-effective, especially if the depth of contaminated material is
great. Furthermore, the removal effort may inadvertently result in the contamination of clean
zones at the site.
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For the contamination scenarios briefly described above, the RCRA Corrective Action
Program may require, as part of an overall remedial plan, the implementation of measures to
control the migration of contaminants from the site. The general objectives of such
engineering measures fall into one or both of the following categories: blocking of migration
pathways through the use of subsurface barriers, and reduction in the access of moisture to
the contaminated geomedia. Although both approaches can be combined to improve the
effectiveness of remedial activities as discussed in subsequent chapters herein, this report
deals primarily with the latter approach. Essentially, this approach involves covering the
ground surface above the contaminated geomaterial to minimize the infiltration of moisture,
and hence inhibit migration and the generation and migration of contaminated leachate.
Traditionally, coverage of a site with engineered low permeability layers has been the
most commonly adopted method to control infiltrating water. This measure has proven to be
effective on a long-term basis. However, the proliferation of minimally contaminated sites in
the United States has raised the issue of the need for the development of schemes that allow
for the reuse of sites for structural development. Potential site use could vary in function from
material storage through automobile parking to human dwelling. Depending on the existing
conditions at a specific site and the level of conservatism incorporated into the structural
design, these structures could be accommodated within the remedial selection process. Some
structures on contaminated sites may be temporary. This class could include storage sheds
for equipment and warehouses which are frequently needed at waste management sites.
Sometimes, their design lives approximate those of the waste management facilities for
which they were constructed.
Surface structures may fit into an overall site remedial scheme if they are adequately
designed. By providing surface coverage, they could enhance the effectiveness of ancillary
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measures aimed at reducing moisture infiltration and hence, leachate generation and
migration. The use of surface structures is more suitable to situations in which residual
contamination is of very low concentration and subsequently, the risk of exposure of people to
hazardous materials is shown to be negligible. Other pertinent geotechnical and environ-
mental considerations are discussed in the chapters that follow.
The issues of structural development of remediated land and incorporation of structures
into remediation plans are bound to be controversial in view of the large number of waste
management sites in the United States. Pressure to use contaminated land for structural
purposes will undoubtably be present in situations where land is scarce and expensive. In
other situations, buildings have existed at a site prior to land contamination, thereby necessi-
tating the implementation of protective schemes in which the existence of such buildings at
the site is considered. For high risk situations, operations within such buildings may need to
be ceased and the building demolished. Where the risk to human health and the environment
is relatively low and controllable, it may be deemed economically preferable and technically
feasible to implement remedial measures and continue operations housed in buildings located
at the affected site.
U.S. EPA (1986a) described 16 uncontrolled hazardous waste sites that have been
redeveloped in the United States. These case study sites included former U.S. Department of
Defense (DOD) properties; abandoned coal gasification sites; abandoned chemical recovery
and drum recycling facilities; sites of a former steel mill, munitions depot, fertilizer plant,
pesticide manufacturer, and coal tar refinery; and a chemical storage facility site. Some of the
land reuses at these sites include a hotel and convention complex, single family dwellings, a
public school, residential condominiums, State offices, and a housing complex for the
handicapped and elderly. Six of the 16 cases are in California. The rest are in Maryland,
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Vermont, New Jersey, Iowa, Washington, and Pennsylvania. It should be noted that there
are several other cases that were not included in the report to which reference is made above.
Remedial action at the majority of these sites involved excavation and removal of highly
hazardous material prior to structural development. Nevertheless, concerns about human
exposure to residual contaminants still necessitated the incorporation of precautionary
measures into foundation systems of structures at most of the sites.
In addition to the U.S. case-histories mentioned above, U.S. EPA (1992) describes
design and management activities which were conducted on reclaimed sites that have been
redeveloped in Europe.
A limited discussion of the technical issues that pertain to the construction and
operation of buildings in the Netherlands has been made by YLand and Van Wachem (1988).
Additional descriptions of specific cases of land recycling for construction purposes are
furnished by Anderson and Hatayama (1988) and Blacklock (1987). Also, Jackson and
Cairney (1991) have discussed various options in derelict land recycling. A general report on
highway structures in contaminated areas (TRB 1988) has been produced. A considerable
number of papers have dealt with foundation strength and stability issues at contaminated
and closed landfill sites. These include those of Natarajan and Rao (1972), Dodt et al.
(1987), Watts and Charles (1990), Luke and Gnaedinger (1972), Kumapley and Ishola
(1985), Yen and Scanlon (1975), and Sridharan et al. (1981).
Most of the technical aspects discussed in the papers referenced above are indirectly
relevant to some elements of the incorporation of structures into site remedial plans. This
technical guidance manual focuses on design configurations, and precautionary and ancillary
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design measures that should be implemented when various types of structures are included in
site cleanup plans.
1.4 UTILITY OF SURFACE STRUCTURES
Some beneficial effects of site reuse for structural development are consistent with the
goals of the RCRA Corrective Action Program. The following issues are outlined and
discussed below:
• Minimization of infiltration and leachate production
• Reduction of contaminated soil erosion
• Reduction of hazardous vapor emission from contaminated soil into the atmosphere
• Beneficial use of land during the stabilization period or permanently.
The first three goals stated above can be achieved if the cover provided by a surface
structure is enhanced by additional measures such as construction of asphalt covers around
the structure and other means of surface water control. Surface coverage is effective as a
leachate production control method when the access of moisture to the contaminated material
is found to be primarily through vertical infiltration of surface water.
After the removal of contaminated materials from a site, there is the potential that loose
residually contaminated soil materials may be eroded away from the site by water and wind.
Contaminated sediments may be deposited in water bodies, land surface, and on physical
facilities many miles away from the source. Ground surface coverage minimizes this risk.
Investigations by Ghadiri and Rose (1991) have indicated that eroded sediments often show
elevated concentrations of chemicals greater than concentrations found in the source materi-
als. This is believed to occur through the process of raindrop stripping, in which fine soil
particles that contain elevated concentrations of such pollutants are selectively eroded away,
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leaving coarser residuum. By implication, raindrop stripping is significant in wet regions of
the United States. In quantitative terms, the volume of contaminated material that is pre-
vented from being eroded can be computed through modeling of soil detachment by raindrop
impact and other processes, some of which are discussed by Muck and Ludington (1980),
Romkens et al. (1977), Juarez (1991), Al-Durrah and Bradford (1981 and 1982), Emmerich et
al. (1989), Fanner (1973), and Haith (1980). In addition, drainage of ice and snow melt
water from remediation sites is another contaminant release pathway that can be controlled
within a structural development scheme.
It is possible to adopt a similar approach to estimate the quantity of contaminated soil
material that would be prevented from being eroded by wind if surface coverage is imple-
• men ted. Relevant numerical equations, charts, parameters, and mechanisms have been
discussed by Woodruff and Siddoway (1965), Chepil (1959), Chepil and Woodruff (1954 and
1963), Gillete and Goodwin (1974), and Coffey et al. (1986).
With respect to the reduction of hazardous vapor release, active or passive vapor
control schemes can be included in the Corrective Action Plan. Vapor barriers within the soil
foundation system can be designed to direct vapors to collection points.
Site remedial activities require structures at the site for storage of equipment and mate-
rials. More permanent structures, such as automobile parking, warehouses, and residential
buildings have various levels of utility. The benefits of these types of land use in low health
risk situations are recognized. The U.S. EPA (1986a) study indicated that most of the
contaminated sites where structures have been erected are close to or in metropolitan areas.
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CHAPTER 2.0
SUITABLE CONDITIONS FOR STRUCTURAL DEVELOPMENT
Four major factors determine the feasibility of incorporating structures into Corrective
Action schemes. These factors are discussed below. Various parameters that are necessary
for evaluations of site and potential exposure pathways are presented in Table 1.
2.1 SITE CHARACTERISTICS
Generally, the following site characteristics are desirable for the development of surface
structures:
• Large depth to groundwater table
• Low potential for flooding
• Incompressible soils
• High surface coverage ratio.
At sites where the groundwater table is deep relative to the residually contaminated
material of concern, the possibility of plume generation or contact of contaminants with
structural foundations through capillary movement is also low. Deep groundwater tables also
minimize the potential of submergence of building foundations. To provide for structural
stability, sites with incompressible soils are preferable, although there are several soil
improvement techniques for unstable soils. Failure of a structure that is originally intended to
provide surface coverage may compromise its ability to serve that function. The coverage
ratio is defined as the ratio of the area covered on the ground surface to the area of the
horizontal projection of the contaminated materials. At some sites, the extent of the area to
be covered may be too large to be covered effectively by the planned structure. In other
situations, such an area may be discontinuous. For both situations, a building structure alone
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Table 1. General data needs and sources of data for remedial actions.
Method of Data
Acquisition
Data Category
Lab
Field
..fi
*• «a > 9
« >
j£ P a *
= 1 i I
< x
II
tt
Site History and Land Use Pattern
• Facility type and design
• Distribution of population near site
• Proximity of drinking water and surface water
resources to site
• Present and past ownership
• Contaminant release history
• Applicable regulations and regulatory history of site
Geologic and Hydrologic Data
• Proximity to sensitive environments
• Topography of area
• Geologic setting of site
• Precipitation data
• Groundwater depth and flow direction
• Nature of vegetation
• Type of soil overburden and bedrock
Geotechnical Data
• Soil profile (thickness and classification)
• Hydraulic conductivities of site soils
• Dispersivities of site soils
• Soil strength parameters
• Chemistry of soils
Waste Data
Water monitoring
Size and configuration of contaminated area
Type and concentration of contaminants
Physical and chemical properties (viscosity, solubility,
specific gravity, volatility, etc.)
Partition coefficients
Hazard assessments (toxicity, ignitability, persistence,
etc.)
16A, 16B
18B
18B, 11 A, 5B
12A, 14A, 16A
12A, 14B, 16A, 18B
12A, 14A, 16A, 18B
1A,4A,7A,10A,11A,12A
11 A, IDA, 15B
11A, 10A, 15B, 18B
2A, 13A, 7A, 3A
7B, 12B, 15B. IB, 6B
5A, 4A, 6A, 12B, IB
1A, 10A, 11 A, 7B, 15B
1A, 16A, 17A, 11B
15B, 17B, IB, 12B
14B,1SB
14A, 12B, ISA
14A, 1SB, 12B
14A, 15B, 12B
1) U.S. Soil Conservation Service
2) U.S. National Climatic Center
3) U.S. National Weather Service
4) U.S. National Park Service
5) ILS. Bureau of Land Management
6) U.S. Bureau of Reclamation
7) U.S. Army Corps of Engineers
8) U.S. Forest Service
9) Tennessee Valley Authority
10) U.S. Geological Survey
11) State Geological Survey
12) State Department of Natural Resources and/or Solid
Waste Management Bureau
13) U.S. National Oceanic and Atmospheric Administration
14) U.S. Environmental Protection Agency (Region or Lab)
15) Open Technical Literature
16) FacUity Owner
17) Facility Designer
18) County or City Administration
10
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may not suffice as the sole stabilization measure, since the coverage ratio would be
insufficient.
2.2 WASTE CHARACTERISTICS
The toxicity and concentration of contaminants at a site are two important parameters
that determine the feasibility of incorporating surface structures into Stabilization plans.
Sites with residual concentrations of minimally toxic contaminants are preferable to sites that
are highly contaminated with highly toxic materials. Depending on contaminant
characteristics, flammable vapors may threaten human health and safety if adequate design
measures are not implemented. Since the construction of structures on contaminated sites is
most feasible in low risk situations, exposure of individuals to contaminants during the
operation of constructed facilities is reasonably minimal. Highly contaminated materials and
wastes would require excavation and removal prior to structural development at a site.
Consequently, risks to human health and the environment at the site would be attributable
primarily to residual contamination.
2.3 FREQUENCY AND CONTINUITY OF RELEASE
Releases of hazardous substances may be dormant, active, or intermittent. For the
same set of hydrological conditions, active releases may pose the greatest risk to human
health and the environment. Substances released in high volumes as a result of spillage and
leakage from surface impoundments and tanks may permeate geomaterials without
necessarily being aided by infiltrating water. To evaluate such sites for structural
development, the initial goal should focus on stopping the release. Surface coverage of
dormant releases is generally more feasible than coverage of active releases since the
boundaries of the contaminated zones may change considerably over time, making it difficult
to assess the risks quantitatively.
11
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2.4 STRUCTURE TYPE AND FUNCTION
Generally, structures that have lightweight and shallow foundations are more suitable
for contaminated sites than those with deep foundations. A deep foundation often involves
the removal of large quantities of soil and/or groundwater. Also, construction equipment
would be exposed to prolonged contact with hazardous materials. Consequently, the risks
posed to workers may be significant. Construction procedures for deep foundations are
generally more complex. Following construction, it may be technically difficult and cost
prohibitive to implement additional remediation measures, designed to reduce contaminant
migration and/or exposure, around complex foundation systems. In most cases, it is possible
to implement conservative engineering designs to protect human health and the environment.
However, such designs may be prohibitively expensive. Risks to human health are directly
proportional to the occupancy time of people in such structures and the proximity of
contaminated materials to human activities in or on such structures. Knowledge of the range
of values for these parameters is required to perform quantitative exposure assessments.
12
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CHAPTER 3.0
MAJOR CATEGORIES OF CONTAMINATED SITES
RCRA Corrective Action sites differ in terms of the extent of contamination, physical
state of the contaminants, human and environmental exposure pathways, and the type of
facility that serves as the source of the release.
3.1 WASTE CONTAINMENT SITES
At some RCRA Corrective Action sites, waste materials are contained within engi-
neered solid waste management units such as landfills and surface impoundments. At such
sites, if wastes are removed and only residual contaminants remain, reuse of some of these
sites for structural development may be feasible. Figures 1 and 2 are examples of waste
containment units at sites. Development of surface structures on these sites would be
considered only after the removal or treatment of the primary source of contamination.
3.2 EXCAVATED SITES WITH MINIMAL RESIDUAL CONTAMINATION
In addition to existing in engineered containment structures, waste materials can exist
at a site as a result of hazardous material spillage and leaching from residue produced during
manufacturing and industrial processes. The remedy for this type of contamination may
require the excavation of site soils. This is most feasible where the volume of the material of
concern is relatively limited and the material exists at shallow depth.
13
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Buried Waste
/ to be Removed
A. With engineered liner
B. With no engineered liner
C. Waste solids in soil
D. Waste liquid In soil
Solid Particles of Waste
| Bedrock
I Waste or Contaminated Qeomedium
Figure 1. Examples of candidate sites for Corrective Action prior to
consideration for structural development
14
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Waste Pile
Partially embedded
aitoKl holding tank
E. Residual contaminants from a waste pile
F. Bedrock fissures act as conduits
Partially embedded
liquid holding tank
eeeeeeeeeeec
eeeeeeeeee
+ ;++ +
G. Leachate plume from a volatile liquid
holding tank
H. Leachate plume In soil strata with widely
different permeabilities
Cj Sandy Clay
Eal Clayey Sand
tft^ Bedrock
•• Leachate Plume or Contaminated Geomedium
Figure 2. Further examples of candidate sites for Corrective Action
prior to consideration for structural development
15
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CHAPTER 4.0
SELECTION OF SITE DESIGN MEASURES
4.1 DATA NEEDS AND SOURCES OF INFORMATION
Some site-specific factors that need to be evaluated in order to implement Corrective
Action Plans include the following:
• Environmental risks or priority of the facility concerned
• Immediacy of exposure threats
• Types of contaminants and volumes of releases
• Technical complexity of remediation
• Site hydrogeology, geotechnical characteristics, and regional geology.
These issues need to be addressed to make both technical and management decisions.
They apply either directly or indirectly to structural development plans for partially or fully
remediated land. To address each of these issues, data on suites of parameters are needed.
These data are normally acquired during the RCRA Facility Investigation (RFI) stage of the
Corrective Action process. This process, which begins at the onset of the RFI, would involve
the assessment of the potential exposure of facility users to residual hazardous substances
at a site. Various elements of the process discussed briefly above are discussed in the
RCRA Facility Investigation Guidance—Interim Final (U.S. EPA 1989a), the RCRA
Corrective Action Interim Measures Guidance—Interim Final (U.S. EPA 1988a), the RCRA
Corrective Action Plan—Interim Final (U.S. EPA 1988b), Corrective Action—Technologies
and Application Seminar Publication (U.S. EPA 1989b), and the RCRA Facility Assessment
Guidance (U.S. EPA 1986b).
The general data needs and sources of data for remedial actions that include or exclude
structural development plans are summarized in Table 1. Some of the data are available from
16
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local, State, and Federal agencies while others are obtainable only through direct
measurement in the field or laboratory. One potential difficulty with data acquired through
measurement in the laboratory is the extent to which they can be extrapolated to the site of
concern. A large body of geotechnical and environmental literature exists on field
measurement and sample retrieval techniques. These techniques are summarized in U.S.
EPA (1990a). Table 2 is a modified summary of techniques discussed in that document.
4.2 GEOTECHNICAL AND ENVIRONMENTAL ISSUES
The feasibility of implementing structural development schemes within the framework of
Corrective Action Stabilization at a site depends on a number of geotechnical and
environmental factors. Prior to plan implementation, the following relevant factors should be
addressed:
• Differential settlement of the structure
• Infiltration of moisture into contaminated soil
• Submergence of contaminated soil by groundwater
• Migration of residual contaminants from the site
• Exposure of workers and/or residents to contaminants
• Compatibility of structures with other Corrective Action Plans.
4.2.1 Differential Settlement
Differential settlement is common when soils of highly variable compressibilities and
thicknesses are loaded. The relative compressibilities of load-bearing soils under expected
moisture conditions underneath the structure should be evaluated. The magnitude of differen-
tial settlement and the damage that may result, depend on the following factors:
• Type and size of structure
• Spatial relationship between the foundation pressure bulb and contaminated soil
17
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Table 2. Some common methods of data acquisition for remedial design
purposes (U.S. EPA 1990a).
Category
Commonly
Used methods
Advantages/
Disadvantages
Geophysics (Indirect data
acquisition methods)
Electromagnetics
Resistivity
Seismic
Ground penetrating radar
Good for delineation of high
conductivity plumes
Useful in locating fractures
Limited use in shallow studies
Useful in very shallow soil
studies
Drilling
Augering
Angering with split-spoon
sampling
Air/water rotary
Mud rotary
Coring
Jetting/driving
Poor stratigraphic data
Good soil samples
Rock sample information
Fills fractures—require intensive
well development
Complete details on bedrock
No subsurface data
Ground-Water sampling
Bailer
Centrifugal pump
Peristaltic/bladder pumps
Allows escape of volatiles
(operator dependent)
Can produce turbid samples
increasing chance of
unrepresentative contamination
Gives more representative samples
Sot! sampling
Soil boring
Restricted to shallow depths
Aquifer tests
Pump test
Slug test
Samples a large aquifer section
Does not require disposal of
liquids
18
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• Compressibilities of various materials underneath the structure
• Tolerance of the structure to settlement-induced stresses
• Thicknesses of various media beneath the structure.
Several studies have been conducted to evaluate the settlement of landfills. The
prediction of settlement rates of buried waste is complicated due to the occurrence of
physico-chemical and biological processes in buried waste materials. Natarajan and Rao
(1972), Watts and Charles (1990), Dodt et al. (1987), and Lukas and Gnaedinger (1972)
have presented quantitative estimates for specific cases. Within the context of Corrective
Action Stabilization, the situation is somewhat different, considering that concentrated waste
materials may be excavated and removed. The excavated space would then be filled with
uncontaminated material. However, certain sections of the site may still contain residual
contaminants. Variations in subsurface chemistry over reasonably short horizontal distances
can also cause differential settlement under load. Certain areas of the soil profile may settle
more than others as depicted in Figure 3.
Lukas and Gnaedinger (1972) report on structural settlements and damages at Illinois
and Michigan sites on which spillages of acids and caustic materials occurred. At the Illinois
site, acetic acid was spilled. This acid reacted with soil carbonates, resulting in a net loss in
soil material weight. At the Michigan site, highly caustic sodium hydroxide spilled on high
silica sands. Sodium silicate was formed. It dissolved and drained away, thereby causing a
net loss in soil matter. Consequently, structural settlement and damage were accelerated.
When chemical reactions between contaminants and soil material result in the formation of
substances that have negligible solubility, the contaminated soil may heave. An example of
such a case is the release of phosphoric acid into wet calcareous soils. Insoluble calcium
phosphate, which can cause heaving, would be formed.
19
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j I Clean fill that was imported to replace buried waste
Site soil
Residual tow level
contamination
Settlement-induced crack
Settled Footing
Figure 3. Differential settlement of a structure with a footing that rests
on a residually contaminated soil.
20
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Differential compression of contaminated soils does not necessarily damage a structure
unless differential settlement is excessive. For a given site soil profile and loading condition,
structural damage tends to be proportional to the rate of settlement. Maximum tolerable
settlements vary with structural foundation type and soil type, but for shallow foundations of
light structures, commonly measured values are in the numerical regime of 0.002, expressed
as the tangent of angle d in Figure 3. When the depth of the contaminated soil material of
concern exceeds about one and a half times the width of square footings above it, the
contribution of the load on the footing to the compression of the soil at that depth is minimal.
This stems from the fact that at that depth, the pressure bulb reduces to about one fifth of the
load on the footing. For isolated strip footings, the limiting depth at this magnitude of
pressure extends to about three times the width of the footing. In both cases, footings above
the contaminated materials can be assumed to be isolated if their spacings exceed their
widths. For closely spaced footings, the contaminated medium should be assumed to be
significantly loaded if it is between about two and nine times the widths of square footings
and strip footings respectively.
The limiting depths of significant loading discussed above are based on elastic theory,
which is a conventional method of estimating the distribution of stresses in materials under
assumptions of material homogeneity, isotropy, and continuity. In addition to settlement,
bearing capacity failures can result if excessive loads are imposed on weak wastes or
contaminated soils that exist at shallow depths.
The foregoing discussions have centered mostly on shallow footings of structures since
they would normally be incorporated into the design of light structures for storage, single
family residences, etc. Portions of a Corrective Action site covered with bituminous concrete
layers are not prone to the same level of settlement risk and potential structural damage.
21
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Most likely, the threshold values for settlement-inducing surface loads would normally not be
highly exceeded. If settlement does occur, ponding of surface water and cracking could result.
In this case, the bituminous surface would cease to function effectively as an infiltration
barrier.
4.2.2 Vertical Infiltration of Moisture
One of the primary functions of an engineered surface layer is to prevent surface water
from infiltrating through the ground to contaminated zones of the soil profile. Structures that
are included within such systems should be designed such that they do not create the
potential for enhanced infiltration. Rainwater splash lines can enhance infiltration. Splash
lines are small depressions on the ground surface caused by the splashing action of rainwater
that falls from the roofs of engineered structures. Snowmelt water and rainwater can also
drain down exposed walls into foundation material. Design configurations for minimizing
vertical infiltration of moisture are discussed in Chapter 5.
The quantity of infiltration moisture and the rate of infiltration are controlled by a number
of hydrological, geotechnical, and topographic factors, such as:
• Rainfall and snowmelt quantities
• Runoff coefficients and damage condition of surfaces
• Lengths and gradients of slopes at/near the site
• Permeability and water content of surficial soils
• Permeability and thickness of cover layers
• Types of surface drainage controls
• Integrity of water conveying pipes associated with structures at the site.
Techniques for estimating the vertical flow of moisture through natural and engineered
material layers range from simple methods, such as the Phi index and Horton's infiltration
22
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Equation (Horton 1933), to more detailed, comprehensive computer models such as the
Hydrologic Evaluation of Landfill Performance (HELP) model. Although the HELP model
was originally developed for use in analyzing the potential for infiltration of moisture through
landfills, it can also be used to estimate vertical flow through covered and uncovered areas
around structures on Corrective Action sites. Information on the HELP model is provided by
U.S. EPA (1984a) and U.S. EPA (1984b). Among other documents that are helpful with
respect to estimating cover effectiveness and infiltration are those of Wright et al. (1988) and
Johnson et al. (1983). It should be noted that some of the infiltration equations model the
behavior of soils and not bituminous concrete or portland cement concrete covers that may be
used as temporary or permanent covers around buildings in low risk situations. As discussed
in greater detail in Chapter 6, in addition to the infiltration through the matrix of such concrete
covers, moisture can seep through cracks to the underlying soil. This would be more
significant in older bituminous and concrete layers in which exposure to weather and various
loads produces cracks. If this type of cover is intended to serve a short design life in the
Stabilization Plan, development of cracks would not be significant. For permanent covers,
however, periodic resurfacing may be necessary. Figure 4 is an illustration of both crack
infiltration and matrix infiltration through cemented covers.
4.2.3 Groundwater Infiltration
Vertical infiltration is not the only source of moisture access to residual contaminants at a
site. Groundwater may migrate through the zone of contamination laterally. Obviously,
covers are directly effective in minimizing vertical infiltration. The major factors that control
the potential saturation of contaminated soil material by groundwater are summarized as
follows.
• Groundwater gradient and flow directions relative to the locations of residual
contaminants
23
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lc - Infiltration rate through cracks
Im * Infiltration rate through cement matrix
ummtmttt
Soil stratum with residual contamination
Figure 4. An illustration of moisture infiltration through cracked
cemented covers (cracks are exaggerated in size and height
of arrows signifies magnitude of infiltration rate).
24
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• Distance between residual contaminants and the groundwater table
• Grainsize distribution of subsurface materials between the groundwater table and the
residual contaminants
• Effectiveness of underground measures undertaken to establish hydraulic barriers
between residually contaminated soil and the surrounding medium.
If the residually contaminated areas are generally close to the water table, the potential
for their saturation is high. Considering that in many locations the groundwater table
fluctuates seasonally, these factors need to be evaluated during the site study phase of the
Corrective Action Program. In site reconnaissance surveys, mottled coloration of soil may be
an indication of the depth range of groundwater table fluctuation. This is most readily
observable in iron-rich soils. Hydraulic connection can also be established between residual
contaminants and groundwater through capillary action. Using the analogy of glass tubes in a
water-filled container, the height of capillary rise can be estimated from equation 1.
he = (-4T)/(Lwgd) (1)
he = height of capillary rise
T = surface tension of water at a specified temperature
LW = density of water at a specified temperature
g = acceleration due to gravity
d = effective pore diameter of the soil medium.
Under the usual assumption that the effective pore diameter of soils is 20% of the soil grain
size (Dio), and using the properties of water at 20°C, d = 0.20Dio, T is approximately 73
MN/m, LW = 1000 kg/m3, and g = 9.81 m/s2, equation 1 becomes:
he = (-0.03)/(0.2Dio) (2)
he = height of capillary rise in meters
= soil grain diameter at which 10 percent by weight of the soil
particles are finer (m).
25
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Estimates of the capillary rise (he) for various size ranges of soil materials provided by
Hansbo (1975) are presented in Table 3.
Table 3. Estimates of capillary rise in various soils (Hansbo 1975,
adapted from Holtz and Kovacs 1981).
Coarse sand
Medium sand
Fine sand
Silt
Clay
Loose
0.03-0.12 m
0.12-0.50 m
030-2.0 m
1.5-10 m
£10 m
Dense
0.04-0.15 m
0.35-1.10 m
0.40-3.5 m
2.5-12 m
The effectiveness of temporary and/or permanent ancillary measures implemented at a site to
control groundwater intrusion also affects the potential for contaminant entry into the
groundwater system. These ancillary measures are discussed in Section 4.3.
4.2.4 Migration of Residual Contaminants
In view of the fact that Corrective Action sites that would be considered for structural
development are sites at which contamination levels are low, the possibility of extensive
migration of contaminants from such sites would most likely be low. Nevertheless,
evaluations should still be made to identify potential migration pathways and the conditions
that would enhance or inhibit the migration of contaminants from sites under consideration.
The controlling factors, some of which were previously discussed, include the following:
• Concentrations and intrinsic mobilities of various residual contaminants
• Frequency and volume of moisture supply to contaminated portions of the geomedia
• Permeability and retardation of pollutants in the geomedium
• Gas generation capacity (volatility) of the contaminant
26
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Proximity of contaminants to the ground surface and the potential for wind and surface
water erosion.
Numerical ranges for specific parameters related to those described above are provided
by Rosenberg et al. (1990) (Tables 4 and 5). For each parameter, the effects of three
quantitative levels on contaminant migration are provided. Although the matrix of the
residual contaminants is not included in Tables 4 and 5, it is also significant with respect to
contaminant migration. By implementing measures to control some of these parameters, it is
possible to minimize contaminant migration. Obviously, the numerical significance of the
parameters listed in Tables 4 and 5 is not the same. Several models are available to
estimate contaminant migration, ranging from the simple Darcy equation with no retardation
to more complex mathematical relationships. It should be noted that the more complex the
model, the more restricted the situations to which it can be applied, and the greater the
amount of data that is required. In addition, each model is as robust as the assumptions on
which it is based.
Fate and transport models are useful for estimating both the upper bound and lower
bound values of contaminant migration rate and volume. Within this context, reference is
made to some of the technical resource and guidance documents that address this particular
issue. Documents on groundwater modeling include: U.S. EPA (1978), Oster (1982),
Donigian et al. (1983), Huyakom and Faust (1983), U.S. EPA (1983a), U.S. EPA (1985a),
and U.S. EPA (1989c). Although it is important to note the difference in capability and utility
between groundwater models and contaminant fate/transport models, the former are included
in the above references because they can be used to estimate the rate of moisture infiltration
to residual contaminants at a partially reclaimed site.
27
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Table 4. Data ranges and general effects on liquid contaminant migration
from a contaminated site (adapted with modifications from
Rosenberg, et al., 1990).
Factor
Units
Increasing Migration Potential
Release-Specific Parameters
• Time since last release
Months
Long
(>12)
Medium
(1-12)
Shon
(50)
Low
(<10)
Low
(<10)
Absent
High
(>30)
Medium
(io-5-io-3)
Medium
(10-30)
Medium
(5-50)
Medium
(10-30)
Medium
(10-20)
—
Medium
(10-30)
High
(>10'3)
High
(>30)
Low
(<5)
High
(>30)
High
(>20)
Present
Low
(<10)
Contaminant-Specific Parameters
• Liquid viscosity
• Liquid density
CentiPoise
g/cm3
High
(>20)
Low
<2)
•Although the referenced authors stated this, it is subject to debate.
28
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Table 5. Data ranges and general effects on gas migration from a
polluted site (adapted with modification, from Rosenberg, et
al., 1990).
Factor
Units
Increasing Migration
Potential
Site-Specific Parameters
• Air filled porosity
• Total porosity
• Water content
• Depth below surface
%
%
%
meters
Low
(<10)
Low
(<10)
High
(>30)
Deep
(>10)
Medium
(10-30)
Medium
(10-30)
Medium
(10-30)
Medium
(2-10)
High
(>30)
High
(>30)
Low
(<10)
High
«2)
Contaminant-Specific Parameters
• Liquid density
g/cm3
Low
(<50)
Medium
(50-500)
High
(>500)
29
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For sites in which residual contaminants exist largely in the unsaturated zone, models
selected would need to address the following sequential stages of soil and groundwater
contamination:
• Generation of leachate using rainfall and snowmelt infiltration data, waste
concentration and volume data, and cover soil/cement cover layer properties and
thicknesses
• Migration rates of leachate downward in the unsaturated zone toward the water table
• Migration rate of aqueous phase contaminants away from the site (predominantly
horizontally under saturated flow conditions) and vertical migration of gaseous
phases towards the ground surface.
It should be noted that occasionally, the vadose zone may become saturated (e.g.,
during heavy rainfall). Under saturated conditions, a lateral drainage component may be
generated. However, the potential for generation and migration of leachate from residual
contaminants is relatively low in the unsaturated zone below surface covers because of the
seasonally of rainfall and snowmelt.
4.2.5 Exposure of Workers and Residents
Another set of important issues pertains to the safety and health of workers and
residents in buildings and/or other facilities on reclaimed sites. Some of the main hazards
that could exist at such sites are as follows:
• Ingestion and inhalation of contaminants
• Gas-induced fire hazard
• Uptake of contaminants by garden plants
• Skin contact with contaminated soil materials
• r3egradation of building foundation materials.
30
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Directly or indirectly, the factors listed above must be evaluated to estimate the
exposure of workers and residents to residual contaminants at facilities on reclaimed sites.
For construction workers, exposure is temporary and depends on the duration of
construction activities at the site. Although a number of guidelines on worker safety at
hazardous waste sites have been developed in response to regulatory mandates, workers
who deal with the construction of such civil engineering facilities as buildings, pavements, and
parking lots are not usually trained on hazardous waste site safety. Pertinent guidelines
should be followed. Under the mandate of the Superfund Amendments and Reauthorization
Act of 1986 (SARA), the Occupational Safety and Health Administration (OSHA) issued a
number of regulations aimed at promoting worker safety at hazardous waste sites.
Applicable regulations entitled "Hazardous Waste Operations and Response" are included in
the Code of Federal Regulations (29 CFR 1910.120). The reader is also referred to the
following technical guidance documents on worker safety: U.S. EPA (1984c), NIOSH (1985),
U.S. EPA (1985b), U.S. EPA (1986c), and U.S. EPA (1986d). Although these documents
address pertinent safety and health issues, they were not developed for RCRA Corrective
Action specifically. Site circumstances will determine the types of safety procedures that are
appropriate.
The development of a Site Safety Plan is required for projects on hazardous waste sites.
Readers who plan to be involved in the development of such plans for constructing civil
engineering facilities on Corrective Action sites are strongly urged to review U.S. EPA
(1989d), which provides guidance on sequential steps for assessing preliminary evaluations,
health and safety plans (HASPs), and offsite emergency response programs. Elements of
31
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the Site Safety Plan, all of which are relevant to both OSHA and EPA regulations, are
summarized as follows, as adapted from NCHRP (1988):
• Personnel and assignment of responsibilities
• Site characterization
• Training of workers
• Personal protective clothing and equipment
• Medical program
• Site sampling and monitoring plans
• Site control through zonation
• Decontamination procedures
• Standard operating procedures.
Some of these aspects are discussed in the following paragraphs. Some commonly used
personnel designations are presented in Table 6.
Table 6. Safety personnel and responsibilities during activities at
hazardous waste sites.
Designation
Responsibility
Project Team Leader
Field Team Leader
Site Safety Officer
Command Post Supervisor
Work Party Members
Administrator of site activities
Responsible for overall operation including safety of the field team
Primarily responsible for implementation of safety plan and operations
Serves as the communication link between site workers and outside parties
without actually entering the site except in the case of an emergency
Perform the onsite activities necessary to satisfy both project and safety
objectives
In order to select the appropriate level of personal protective equipment, the character-
istics of the chemicals that exist at the construction site and their effects on human health
should be determined. As a guide, health hazard information compiled by Barry (1991) for
various substances, including gases, solids, and liquids is presented in Appendix A. The
32
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major sources of information compiled by Barry (1991) are HSE (1989), ICRCL (1987), DE
(1981), and Parmegiani (1983). The document entitled "Pocket Guide to Chemical Hazards,"
NIOSH (1985) provides more comprehensive information on exposure limits, chemical
properties, physical properties, health hazards, target organs, relevant personal protective
measures, and first aid treatment methods for numerous substances. Additional information
on worker safety and health-related aspects is provided by U.S. EPA (1985c) and U.S. EPA
(1989e).
Figure 5 shows the zonation of a contaminated site for remedial action activities. It is
presented as an example of what has been done in other clean up programs and does not
constitute a specification.
Equation 3 is a general exposure equation which provides a framework for the
assessment of factors that influence health risks for workers and residents of structures on
contaminated sites that are being remediated.
IN = [(C)(IR)(EF)(ED)]/[(BW)(AT)] (3)
IN = intake amount of a specific chemical in a contaminated medium,
rag/kg of body weight/day
C = concentration = average chemical concentration contacted over
the exposure period, mg/1, mg/mg
IR = intake rate (or contact rate) = amount of contaminated medium
contacted per unit time or event, mg/day or L/day
EF = exposure frequency (upper bound value), days/year
ED = exposure duration (upper bound value), years
BW = body weight = average body weight over the exposure period, kg
AT = averaging time = time period over which exposure is averaged =
exposure duration for non-carcinogens and 70 years for
carcinogens, years.
33
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Estimated BotMtaiy
OTAfMWimHIghMt
Conurnirwtton
Control Ur»
NOM: AiMdtnwnslontnottowiM. Dtt
w MtwMn poms imy wy.
Figure 5. A schematic illustration of spatial zonation of clean-up
activities at a site (U.S. EPA 1991a).
34
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Further discussions on equation 3 are provided in U.S. EPA (1990b) and U.S. EPA
(1991b). Standard default exposure factors and their units of measurement supplied by U.S.
EPA (1991b) are presented in Table 7. These default values should be used when measured
data are unavailable. It should be noted that exposure assessment and risk assessment
methodologies change frequently. Equation 3 should be regarded as a generic example.
Readers are encouraged to seek information on recommended methods and the most current
exposure factors. Some issues that pertain to the use of the default factors of Table 7 need to
be clarified. These issues stem from the fact that exposure at a construction site can be
divided into the following two categories:
• Exposure during construction activities
• Post-construction exposure.
Equation 3 applies to both exposure categories, but the numerical values presented in
Table 7 would be most applicable to the post-construction stage. With respect to post-
construction exposure, residence time data for U.S. households are provided in Figure 6.
In the preceding paragraphs, measures used to minimize worker exposure at
construction sites have been discussed. Post-construction exposure levels depend on the
land use, the type and design of the structure and protective systems, and the level of cleanup
prior to structural development. Both exposure categories are not necessarily relevant to the
same group of persons.
Computations can be made for dermal exposure with assumptions of the magnitude of
skin absorption rates for contacted chemicals. With some simplifying assumptions, Hawley
(1985) recommends dermal absorption values of 0.5% per hour for adults. This value can be
doubled or tripled for children on the basis of the fact that dermal exposure is generally
35
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37
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proportional to the frequency and duration of outdoor activity. For ages above 5 years,
Paustenbach et al. (1986) suggest a skin soil deposition rate of 100 mg/day.
The exposure assessment process should be used in risk analysis to establish the
degree of conservatism of design measures for structures on residually contaminated sites.
Alternatively, they can also be used to specify an acceptable cleanup level prior to use of a
site for structural development. Further reference and discussion of these two objectives are
provided in Chapter 6. It should be noted that in the numerical examples provided above,
computations are made on a per day basis. Also, where known, absorption factors may be
incorporated in the numerator of equation 3.
4.2.6 Compatibility of Structures with Other Corrective Action Measures
In the RCRA Corrective Action Program, site remediation may be implemented in
stages. On the bases of the attained cleanup and risk levels, decisions are made on whether
or not additional cleanup is necessary. If the plan for a site requires the implementation of
additional remedial measures subsequent to structural development, the initial structural
system should be configured to be compatible with such subsequent measures. For example,
if the Corrective Action Plan calls for groundwater and contaminant extraction through
pumping after the construction of a structure, an analysis of the effects of fluid withdrawal on
the stability of the completed structure would be necessary.
4.3 ANCILLARY MEASURES
The degree of coverage of the ground surface to minimize downward percolation of
moisture and the upward migration of contaminants toward surficial structures can be
enhanced through the implementation of ancillary measures. A matrix of scenarios versus
appropriate ancillary measures is provided in Table 8. Most of the tabulated measures are
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frequently employed in the geotechnical engineering field of soil improvement A considerable
body of literature on relevant computational methods and field performance exists. However,
due to their direct influence on the performance of structural systems on reclaimable sites, the
design aspects of measures 5, 7, and 8 are further discussed in detail in Chapters 5 and 6.
40
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CHAPTER 5.0
DESIGN COMPONENTS AND CONFIGURATIONS
5.1 DESIGN OBJECTIVES AND ESSENTIAL COMPONENTS
Design objectives should be tailored to address each of the geotechnical and
environmental issues discussed in the preceding chapters. More commonly, each of the
issues discussed may not be relevant to all field situations. Each site has a unique suite of
pertinent technical and regulatory issues. In general, the following design objectives, which
directly influence the components of risks at each site, are consistent with the overall goal of
Corrective Action:
• Separation of users (residents, workers, etc.) of structures from residual contami-
nants at the site
• Control of the migration of residual contaminant from the host media into groundwater
or uncontaminated geomedia through minimization of water infiltration
• Implementation of design measures that do not compromise the structural integrity,
and hence functions, of the structure.
In practical terms, the objectives outlined above should be achieved at minimum cost.
The necessary design involves the selection of dimensions, types, and material mixes for the
following components:
• Ground surface cover: bituminous concrete
• Impervious floor seal
• Compacted clay layer
• Separation layer: geotextile
• Granular drainage layer or capillary break
• Vapor and moisture barrier: geomembrane
• Vertical barrier as needed
• Vapor control system as needed
• Ancillary measures as needed.
41
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It may not be necessary to incorporate all of the components listed above into designs
for every site. As illustrated and discussed in this chapter, site conditions and the desired
level of protection determine the degree of design conservatism. All of the suggested designs
include bituminous concrete covers. In order to enhance drainage, it is recommended that the
cover be constructed and maintained at a slope of at least 2%. The increased surface
drainage requires that adequate surface water control measures be implemented.
5.2 DESIGN CONFIGURATIONS AND FUNCTIONS
As illustrated in Figures 1 and 2, Corrective Action sites that can be developed after
chemical treatment or removal of the primary sources of contamination differ in configuration
and nature of release. For the purposes of this report, the following two broad categories are
recognized:
• Sites at which releases occur due to the damage of specific components of a
hazardous waste facility
• Sites at which facilities are not currently located but which have residual
contamination after the neutralization (by excavation or in situ treatment) of
previously existing higher concentration waste.
For the first category of sites, design involves the repair of the specific components that
have been damaged prior to structural development. This is largely feasible if the facility is
not active. Figures 7a and 7b illustrate the design of a surface structure on a former site of a
damaged waste pile. In Figure 7a, the waste pile is shown as it existed prior to structural
development. Surface moisture supplied by rainfall leached contaminants from the waste pile.
Aided by periodic rainfall, the contaminants migrated through cracks in the platform con-
structed for the waste pile and polluted the underlying native soil. To reclaim the site for
structural development, the primary source of contamination was neutralized by treatment to
concentration levels that represent minimal risk. As shown in Figure 7b, stabilized clay has
been compacted around the footings of the light structure to minimize moisture and vapor
42
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Optional Protective Soil.
Concrete, etc.
Berms
Contaminated
Soil
Leachate Collection System
:. Compacted Low Permeability Clay Liner _};.}:.}:.}:.£
NativeSoil
Figure 7A
New Bituminous
or Portland
Cement Concrete Footing
Floor Slab
Impervious Seal
Compacted Clay
Ground
Surface
!»*rFilter Medium
Portland Cement
Leachate Collection System
O
Residual (low level)
Contamination
Mfjf IMf If IMMf If IMMMf If If If IMf If IMf If If Ulf I1-. .-..;•..-.."
Figure 7B
Figure 7. A structure developed on partially remediated waste pile site.
A. before structural development
B. after structural development.
43
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migration into the structure. As an added protection, an impervious seal is incorporated into
the floor system. Several other measures that could precede or complement structural devel-
opment of the first category of sites are listed for specific types of facilities in Table 9. Most
of the tabulated measures have been recognized as interim measures by the U.S. EPA
(1988c).
Sites in the second category present much more latitude to the designer with respect to
the selection of configurations for foundation systems. The reason is that such systems do
not have to suit facilities at the site since no facilities are present. A number of
configurations are discussed below, and relevant data, computational methods, and numerical
examples are provided in the sections that follow. The use of hypothetical scenarios in the
discussion of configurations does not imply that the latter can only be implemented when
those scenarios exist.
Ground Cover and Simple Protection System for Building Foundation (Figure 8)
In Figure 8 (Inyang et al. 1992), a cover and foundation separation system for a
structure at a. low-risk site is illustrated. At this hypothetical site, the concentrations of
residual contaminants are very low. The contaminants are non-carcinogenic and are
essentially located above the water table. The native soils are highly cohesive. In this
situation, the building's foundation is sealed underneath using an impervious sheet. The
sheet acts as a moisture and vapor barrier. Migration of moisture to and from the buried
portions of the structural foundation is further inhibited by the compacted, stabilized clay
around the foundation. The sewer is displaced to a location away from the foundation. The
ground surface that surrounds the building is covered by bituminous concrete that slopes
away from the structure to enhance surface water runoff. Since the site soils are mainly
cohesive, the infiltration rate of moisture that may seep through cracks in the bituminous
44
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Table 9. A summary of specific corrective measures to improve the
performance of hazardous waste facilities and minimize site
contamination.
Facility Type or Component
Measure
Container Suck
Redruming and overpacking
Temporary cover
Construction of new storage area
Treatment prior to storage and/or disposal
Segregation
Tanks
Provision of overflow collection devices
Provision of vapor pressure dissipalors
Secondary containment
Repair
Removal
Surface Impoundments
Reduction of liquid heads
Removal of free liquids
Repair of damaged walls
Chemical fixation of residual contaminants
Run-on/mn-off control
Provision of temporary cover
Bottom grouting
Waste Piles
Stabilization of slopes
Wind barriers
Fencing to minimize contact
Temporary cover
Run-on/run-off control
Waste removal
Bottom grouting
Landfills
• Stabilization of slopes
• Temporary cap/cover
• Revegetation
• Chemical stabilization of waste
• Physical stabilization of waste
• Interceptor trenching
• Subsurface draining
• Leachate head reduction
• Liner repair
• Stabilization of foundation soils
• Run-on/run-off control
• Vertical barriers
• Waste removal
45
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Residual Contamination
Bituminous
or Portland
Cement
Concrete
Compacted and or
stabilized native soil
Ground
Surface
Water Table
Ground-Water
Flow Direction
+, +.+ +
f+ + +.
Bedrock
,+ + +
Figure 8. A coverage scheme for a structural foundation at a reclaimed
low permeability site with residual contamination (adapted
with modifications from Inyang et al. 1992).
46
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cover would be minimal. Therefore, a drainage layer or an engineered clay layer is not
provided below the bituminous concrete layer.
Ground Cover, Compacted Clay Layer and Simple Protection System for Building
Foundation (Figure 9)
Some sites may be composed predominantly of permeable soils (e.g., sandy and silty
soils). In regions with high annual rainfall (e.g., southeastern portions of the United States),
there is a high potential for rapid percolation of moisture through permeable soils. In Figure
9, a compacted clay layer is extended underneath the bituminous concrete layer to inhibit the
rapid percolation of moisture through permeable site soils to residually contaminated
portions. As illustrated, a surface impoundment existed previously at the site. Under this
scenario, the expansion of a nearby urban center increased land costs in the vicinity of the
impoundment. Upon its closure, the free liquid was drained and the settled solid material was
excavated. Although low concentrations of contaminants were measured at the site, they
were not adequately concentrated spatially to warrant excavation. The plan for utilization of
the site included the construction of a warehouse that would not extend over the entire
expanse of the closed impoundment. In Figure 9b, clean fill, preferably obtained from a
location near the site, to minimize haulage cost, is compacted into the impoundment basin.
Clay is compacted around the building foundation as previously discussed. This clay layer is
also extended underneath the bituminous concrete layer.
Ground Cover, Liner System With Moisture Withdrawal System and Groundwater
Control System (Figure 10)
At some sites, the groundwater table may fluctuate widely, increasing the risk of
submergence of residually contaminated geomedia. If risk analysis (including assessment of
contaminants toxicity) indicate that the risk of migration of contaminants through the
groundwater route is high, it may be necessary to install hydraulic barriers, especially where
the implemented Corrective Action measures are meant to be permanent. Figure 10
47
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Native Cohesiontess Soil
Contamination
Figure 9A
Residual Contamination
Bituminous
or Portland
Cement
Concrete
Compacted Clayey Soil
Ground
Surface
x*^- Boundary of
Filled Impoundment
Native Cohesiontess Soil x«-
Water Table
Ground-Water
Flow Direction
Figure 9B
Figure 9. A shallow foundation system for a structure on a reclaimed
impoundment site.
A. before utilization.
B. after construction.
48
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Residual Contamination
Low Permeability Barrier
Bituminous
or Portland
Cement
Concrete
Dewatering
System
Compacted Clay \
Poor Slab
Impervious Seal
Drainage Layer and
Capillary Break
Geomembrane
Water Table
Ground-Water
Flow Direction
Figure 10. Schematic of a foundation system that may be implemented at
a reclaimable site with a high groundwater table.
49
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illustrates the control of groundwater. A vertical barrier retains groundwater that has been
found through field testing to flow in its general direction. A groundwater withdrawal system
controls the water table and withdraws moisture that may contain components of residual
contaminants. The close proximity of the water table to the base of the structural foundation
warrants the use of geotextile and geomembrane layers. These layers act as capillary breaks
for moisture that may move upward through contaminated soils toward the inside of the
structure. To minimize the potential of leakage of rainwater and sewer fluids through open-
ings in the building's components, a collection system is included. It consists of water collec-
tion pipes embedded in a gravel or sandy gravel layer. The pipes transport uncontaminated
water that is emptied into a sewer. Where gas emissions are determined to constitute a
potential problem, a passive or active gas collection system may also be incorporated.
Ground Cover, Under-Slab Drainage Layer and Simple Protection System for Building
Foundation (Figure 11)
The design configuration presented in Figure 11 includes a drainage layer beneath the
bituminous concrete cap. Although the drainage layer illustrated is composed of granular
materials, geotextiles can also be used as the drainage medium. A drainage layer may be
necessary when the bituminous layer is thin and subject to damage under loads that can be
imposed by construction equipment. Cracks that may be formed as a result would act as
conduits for water infiltration, especially in high rainfall areas. The drainage layer slopes
toward a drainage trench from which accumulated moisture can be periodically withdrawn.
The migration of finer site soil particles into the intergranular pore spaces of the drainage
layer is prevented by the geotextile filter layer. If the site soils are highly permeable, a
geomembrane may also be incorporated below the geotextile as illustrated in Figure 11. As
in most of the previous designs, stabilized clay is compacted around the structural foundation
and the underside of the floor is sealed to inhibit the upward migration of vapors and capillary
50
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Residual Contamination
Granular
Drainage
Layer
Native Soil
Bituminous
or Portland
Cement
Concrete
Roor Slab
/ Impervious Seal
UUMMbC
Geotextite
Water Table
Ground-Water
Flow Direction
V
Bedrock
/ ++
f + +
Figure 11. Surface cover, under-slab drainage system and foundation
protection for a structure at a reclaimable site.
51
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moisture, which may be laden with contaminants, into the structure. The drainage layer is
particularly important if the design life of the system is long. Over time, bitumen ages and
cracks develop, resulting in enhanced permeability to surface water.
Other Systems (Figures 12,13, and 14)
Two other designs proposed by design engineers are presented in Figures 12 and 13.
Yland and Van Wachem (1988) proposed the design illustrated in Figure 12 for residential
houses in the Netherlands. Provision is made for the development of a garden. Various soil
and polymeric layers are used to separate the structure from contaminated materials.
Thorburn and Buchanan (1987) report on excavations at sites contaminated with alkaline
chemicals to depths beyond 600 mm beneath foundations. The protective system illustrated
in Figure 13 for a footing was designed and implemented. A trench was excavated in a
contaminated medium for foundation construction. A SO mm protected layer of concrete
separates the contaminated medium from the footing of a structure. Other configurations may
include underfloor ventilation (passive or active), vertical vents, and piled foundations. One
method of inhibiting vapor entry into buildings is presented in Figure 14 as illustrated by U.S.
EPA (1989f).
Two major concerns in the selection of construction materials and design configurations
are aggressive attack of such materials by contaminated soil and fluids, and flow of fluids
through building materials to inhabited spaces. Materials like concrete, metals, fired clay
products, wood, and plastics are commonly used in building construction. Portions of walls
and foundations that are embedded in the ground are frequently composed of concrete and
steel. If protective measures are not implemented, they may be prone to accelerated
degradation under sustained chemical attack. A great deal of research has been devoted to
the attack of concrete by sulfate-bearing fluids. There is a paucity of literature on
contaminant transport through building materials, possibly due to the fact that this concern is
52
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53
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Cavity
brick
Church building
Reinforced concrete floor slab
Continuous
reinforced
concrete
looting
Trench
excavated
in chemcal
waste
« greater J
50mm
protective
layer of
concrete
Compact
rock Ml
material
Figure 13. Protection of a footing against chemical attack in
contaminated soil (Thorburn and Buchanan 1987).
54
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relatively recent. If this problem occurs at a site, moisture may be the primary medium of
transport. Variations in environmental conditions can cause changes of state of a contami-
nant from vapor to liquid and vice versa. Gavin (1985) illustrated the mechanisms by which
moisture migrates through building materials. These mechanisms are shown in Figure 15.
Relevant mechanisms include diffusion, convection, absorption, adsorption, and evaporation.
With respect to the transmission of water vapor that may bear some trace quantities of
contaminants through floor slabs of structures, the vapor pressure difference between both
sides of the slab is very significant. If not protected, vapor may be driven upward through
cracks and floor material matrix by any vapor pressure that builds up underneath a floor slab.
The undesirable consequences would include mildew growth and absorption and periodic
release of trace contaminants by floor carpets, etc. The water vapor transmission (WVT) of
construction materials is most commonly measured using the ASTM E96-80 test technique.
As shown in equation 4, the parameter of interest is the water vapor transmission rate.
WVT = [(R)(pb - pt)]/T (4)
WVT = water vapor transmission rate (in units, e.g., kg/hr.m2)
R = average permeability (e.g., m/hr or m/s)
T = thickness of the material (m)
pb = vapor pressure below the layer (in units, e.g., N/m2).
pt = vapor pressure above the layer (in stress units, e.g., N/m2).
The quantity T/R is the average water vapor resistance Z, hence,
WVT = (pb - pt)/Z (5)
56
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Storage
Mechanisms
Phases and
Phase Changes
Transport
Mechanisms
• Surface
Adhesion
• Absorbed
Moisture
• Surface
Adhesion
• Vapor
Pressure
Absorbed
Moisture
Diffusion
Capillarity
Gravity
• Diffusion
• Convection
Transportation/
Surface
Diffusion
Figure 15. A schematic overview of mechanisms of moisture migration in
building materials (Gavin 1985).
57
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The ASTM E96-80 test involves measurement of R, the permeability, by sealing the
specimen of concern over a cup that contains water, as illustrated in Figure 16. Commonly,
the climate outside the cup is kept at a relative humidity of 50%. The specimen is weighed
periodically, and its steady state rate of weight gain is its water vapor transfer.
E = (WVT)(A)(t) (6)
E = Weight of evaporated water (kg)
A = Surface area of slab (m2)
t = time (hr).
For practical applications, the reader may seek to extrapolate laboratory test results to
full-scale building situations. The interrelationship among temperature, humidity ratio, and
relative humidity for full-scale spaces is approximated by the chart shown in Figure 17 as
presented in U.S. EPA (1991c).
Indirectly, the rate of flow of vapor upward through the floor of a building depends on the
moisture concentration differential, all other things being equal. However, ventilation of
internal spaces in buildings would help replace air that may contain trace quantities of
undesirable substances. It should be noted that the discussion furnished above is a simple
explanation of a complex phenomenon.
The porosity, pore size distribution, pore connectivity, and thickness of materials used
to construct the embedded portions of building foundations influence the quantity and rate of
migration of fluids through them. While polymeric materials and seals are largely
incorporated as bought, there is some latitude for the designer to influence the properties of
concrete walls, floors and ground cover slabs through adequate mix proportioning and
thickness selection. For water vapor permeation rates, Figure 18 shows rates through
58
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Exposed Area
External Space with
Pressure F
Specimen
Vapor Space with
Pressure PD
Water
Figure 16. A schematic of the configuration of ASTM test E96-80 for
measuring the vapor transmission rate through materials.
59
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1234
LAYER THICKNESS (INCHES)
Figure 18. Vapor flow rate through cores of portland cement concrete
floor slabs placed over various thicknesses of granular
materials (Day 1992).
61
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4.3-inch thick concrete floor slabs placed over various thicknesses of granular materials as
realized experimentally by Day (1992). The gradations of aggregates used for the concrete
are shown in Table 10. The reader can use this data in estimating the regime of hydraulic
conductivity values for known concrete mix proportions and material properties of foundation
systems. The summary of test results obtained by Day (1992), which is presented in
Table 11, indicates a range of 0.01 to 0.39 Ib/ft2/day.
Embedded foundation and floor systems also can be partially composed of wood.
Through practical commercial activities in the areas of lumber dyeing and drying, some
experience has been gained on mass transport processes through wood. Much still remains
to be done, especially on the retardation of chemicals during transport through wooden
components of building systems. Nevertheless, for the migration of relatively pure moisture
through wood, Plumb et al. (1985) have determined that it is attained essentially by capillary
action. For additional information on the migration of fluids through wood, the reader is
referred to Stamm (1963) and Tesoro, et al. (1974). Depending on the internal grain
structure, age, and environmental effects, the permeability of wood varies widely. Additional
information on the flow of fluids through building materials is provided by Chang and
Hutcheon (1956), Gummerson et al. (1980a), Hall and Kalimeris (1982), Hall and Tse
(1986), Hall (1989), Hall (1981), Figg (1973), and Gummerson et al. (1980b).
Realistically, rates of pure moisture migration through building materials are not the
same as those of contaminant-containing fluids through the same materials. Discussions
presented are underlain with the assumption that the majority of processes are similar for
both categories of materials. Within this context, measures that have been proven to be
effective in inhibiting the migration of relatively pure moisture may also be somewhat
effective in controlling contaminated fluid migration. The impervious seal incorporated
62
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Table 10. Gradations of aggregates used for casting concrete slabs for
vapor flow rate measurements (Day 1992).
Sieve Size
(1)
3/4 in.
1/2 in.
3/8 in.
No. 4
No. 8
No. 16
No. 30
No. 50
No. 100
No. 200
Percent Retained On Each Sieve
Sand
(2)
0
0
0
0
0
0.1
78.9
20.0
0.8
0.2
Pea gravel
(3)
0
0
0.7
98.1
1.2
0
0
0
0
0
3/4 in. gravel
(4)
8.9
84.6
6.5
0
0
0
0
0
0
0
Note: Gradation determined by sieve analysis performed in accordance with ASTM D 422-72.
Table 11. A summary of vapor flow rate results obtained experimentally
by Day (1992).
Test number
(D
1
2
3
4
5
6
7
8
Type of
capillary break
(2)
Medium sand
Medium sand
Medium sand
Medium sand
Pea gravel
Pea gravel
3/4 in. Gravel
3/4 in. Gravel
Layer thickness
(in.)
(3)
0.5
1.0
2.6
4.8
0.3
0.8
0.8
1.8
Dry density of
layer (pel)
(4)
87
85
85
87
94
94
78
80
Water evap-
oration (lb)
(5)
0.45
0.21
0.07
0.06
0.21
0.02
0.02
0.01
Vapor flow rate
(Ib/sq ft/day)
«)
0.39
0.19
0.06
0.05
0.18
0.02
0.02
0.01
Note: 1 in. = 25.4 mm; 1 pcf = 0.157 kN/m3; 1 lb = 453 grams; Ibs/sq ft/day = 4.88 kg/m2/day.
63
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underneath the floor systems (Figures 7, 8, 9(b), 10, 11, and 12) is meant to serve as a
barrier against the intrusion of both clean and contaminated moisture into the structural
foundation. It may be composed of ceramics, thermoplastic coatings, chemical-resistant
mortars, or polymeric membranes. Portland cement concrete is highly susceptible to attack
by the following chemicals and should be protected against them:
• Sodium hydroxide
• Sodium bisulfite
• Fluosilicic acid
• Ammonium sulfate
• Aluminum sulfate
• Aluminum potassium sulfate
• Aluminum chloride solution
• Ferric chloride
• Calcium hypochloride
• Activated silica
5.3 COMPONENT SIZING AND Mix DESIGN
In Section 5.2, various configurations are presented for foundation systems and ground
cover in contaminated sites. The authors' objective in this section is to provide more
technical details on sizing of layers, materials selection, and mix design to improve the
effectiveness of implementable measures.
5.3.7 Vertical Sections Through Covers
Vertical sections through ground cover layers discussed previously are illustrated in
Figure 19. The layer combinations that are illustrated represent alternative systems that can
be selected depending on site conditions and the desired level of design conservatism.
Suggested warrants and conditions for each design are also included in Figure 19. The level
of design conservatism increases from option A through options B and C to D. Specific per-
formance characteristics of these optional ground cover designs are discussed below.
64
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Cover Composition
Warrants and Conditions
A.
• Bituminous Concrete Cover
•Native Soil
Low potential for cracking of asphalt layer
Very low risk situation
Low annual precipitation: <80 cm/yr
Low design life: <5 yrs
Low permeability site soils: clayey soils
• Bituminous Concrete
• Stabilized Clay or Native Soil
• Native Soil
Low potential for cracking of asphalt layer
Asphalt layers with medium permeability (10"6 -10*5 cm/s)
Moderate annual precipitation: 80 -100 cm/yr
Moderate design life: 5 -10 yrs
Moderate permeability site soils: silts and clayey sands
• Bituminous Concrete
• Geotextile Drainage Layer
• Stabilized Clay or Native Soil
Moderate potential for cracking of asphalt layer
Moderate risk situation
Moderate annual precipitation: 80-100 cm/yr
Long design fife: >10 yrs
Moderate permeability site soils: silts and sandy days
'7777.
• Bituminous Concrete
• Granular Drainage Layer
• Geotextile Separation Layer
Stabilized Clay or Native Soil
High potential for cracking of asphalt layer
Moderate risk situation
High annual precipitation: >100 cm/yr
Long design fife: >10 yrs
High permeability site soils: medium sands to fine gravels
Figure 19. Optional designs and suggested warrants/conditions for ground
surface covers at building sites with residual contaminants.
65
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5.33 Bituminous Cap: Options A and B
Design options A and B suit low risk situations. The potential for excessive degradation of
the asphalt cover over a relatively short design life of 5 to 10 years is small. Furthermore,
this design may be implemented in areas with low annual rainfall such as the southwestern
United States. In the event of the development of extensive cracks, the amount of surface
water available for infiltration would be negligible. As indicated in Figure 19, sites with soils
of low to moderate permeability in dry environments are suitable for implementation of these
two options. In order to assess the potential performance of intact asphalt layers in cities
that represent the variety of hydrological settings of the United States, the Hydrologic
Evaluation of Landfill Performance (HELP) model was used to compute infiltration rates. The
HELP model is capable of providing infiltration or annual percolation values for material
layers when sets of climatic data, material layer thicknesses, moisture contents,
permeabilities, and other textural characteristics are provided. Since analysis of the utilities
of the HELP model is not within the scope of this guidance manual, the reader is referred to
U.S. EPA (1984d) and U.S. EPA (1984e).
For the purposes of this manual, four cities were selected: Boston, Miami, Topeka, and
Las Vegas. Las Vegas and Topeka represent relatively dry hydrologic settings while Boston
and Miami represent wet hydrologic settings. The HELP model supplied the latitudes and
precipitation rates for these locations. As can be seen in Table 12, annual precipitation rates
ranged from 5.28 in/year for Las Vegas to 50.96 in/year for Miami. Default values of the
evaporative zone depth were input as well as zero values for leaf area index. A conservative
bituminous (asphalt) concrete thickness of 12 inches (30.48 cm) was used for all the
locations. Typically, recommended runoff coefficients for paved areas range from 0.7 to 0.9
(FHWA [1984] and MWCG [1987]) but an intermediate value of 0.8 was used. Realistic
66
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Table 12. HELP model input data and infiltration results for simple
designs (A and B) of uncracked asphalt covers for building
sites with residual contaminants.
Location
Asphalt Cover
Layer
Output
City, State
Latitude
Leaf Area Index
Evaporative Zone Depth
Percent of Runoff that
Drains from Cover
Thickness (in)
Material Type
Porosity
Initial Moisture Content
Field Capacity
Wilting Point
Hyd. Cond. (cm/s)
Area (sq ft)
Precipitation Rate (in/yr)
Infiltration Rate (in/yr)
Boston, MA
42.37
0.0
8"
80%
12"
asphalt
0.420
0.210
0.050
0.020
1.0 E-8
10,000
40.93
0.0004
Miami, FL
25.8
0.0
10"
80%
12"
asphalt
0.420
0.210
0.050
0.020
1.0 E-8
10,000
50.%
0.0004
Topeka,KS
39.04
0.0
9"
80%
12"
asphalt
0.420
0.210
0.050
0.020
1.0 E-8
10,000
32.16
0.0004
Las Vegas, NV
36.08
0.0
18"
80%
12"
asphalt
0.420
0210
0.050
0.020
1.0 E-8
10,000
5.28
0.0000
67
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values shown in Table 12 were used for the other parameters. Note should be made of the
hydraulic conductivity of 1.0 x 10-8 cm/S) which approximates the regime of values of new,
dense asphalt concrete. It should also be noted that unlike the usual case in geotechnical
engineering practice in which moisture content is expressed in weight terms, for this analysis
it is expressed in volumetric terms to satisfy the HELP model input requirements. It is
assumed that the volumetric moisture content of the asphalt layer is half its total porosity.
The input data of Table 12 yielded percolation (used herein interchangeably with
infiltration) values of 0.0004 in/year for all the locations except Las Vegas, for which the
annual infiltration is zero. At these rates of percolation, design options A and B would be
quite effective within the limitations implicit to the input data. Further evaluation indicates
that the level of infiltration is somewhat sensitive to the initial moisture content of the
asphalt concrete layer. For the Boston area only, with all other relevant parameters in Table
12 held constant except initial moisture content, HELP model runs indicated infiltration rates
of 0.0 in/yr, 0.0004 in/yr, 0.003 in/year, and 0.0115 in/yr, for initial moisture contents of 0.1,
021, 0.30, and 0.42, respectively. The maximum annual infiltration rate obtained (0.0115
in/yr) is still reasonably low.
In some cases stabilization of clayey materials directly beneath the asphalt concrete
layer may be necessary. This would reduce the potential for damage of the overlying asphalt
layer due to volumetric changes in the underlying clayey layer. Also, in the HELP model
analyses summarized in Table 12, it was assumed that the asphalt concrete layer would be
designed such that its hydraulic conductivity is about 10"8 cm/s. The mix proportions of
concrete materials and construction quality assurance procedures used affect the
permeability. Therefore, there are two mix design aspects' as stated below:
• Mix design for the asphalt concrete layer
• Stabilization method and mix proportioning for underslab clayey materials.
68
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With respect to the asphalt concrete layer, the suitable gradations of aggregates
presented in Table 13 should be used. Approximate emulsified asphalt contents for various
types of aggregates are shown in Table 14. The physical properties of. asphalt as specified in
ASTM quality standards D-2521 are presented in Table 15. Asphalt layer thicknesses
ranging from 8 inches (20.32 cm) to 15 inches (38.1 cm) are recommended.
Stabilization of the clay layer or native soil underneath the asphalt concrete slab
involves two important design objectives:
• Selection of the type of stabilizing agent depending on soil properties as indicated in
Figure 20.
• Determination of the quantity of stabilizing agent needed per unit weight or volume of
soil.
The most frequently used chemical stabilization methods/materials are cement
stabilization, lime stabilization, bituminous stabilization, and mixtures such as fly ash/cement
and fly ash/lime. The method selected should be based on the factors that influence the
potential effectiveness with respect to minimizing clayey material permeability and
maximizing its stability. Among these factors are the fines content of the soil and the
mineralogy of its fine fraction. These two factors collectively determine the plasticity index
(PI) of soils, and hence, the type of chemical stabilizing agent that should be selected. In
Table 16, climate limitations and construction safety precautions recommended by FHWA
(1979) are presented. The term 'cutback' refers to a bitumen which has a lower viscosity due
to the addition of chemical agents. The optimal mix proportion of stabilizing agent and other
components of a layer should be determined in the laboratory through testing of trial mixes.
For general information, ranges of cement content required to stabilize various classes of
soils are presented in Table 17 as recommended by USAF (1975).
69
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Table 13. Mix compositions for formed-in-place asphalt linings (Asphalt
Institute 1976).
Sieve Size
25.0 mm (1 in.)
19.0 mm (3/4 in.)
12.S mm (1/2 in)
9.5 mm (3/8 in.)
4.75 mm (No. 4)
2.36 mm (No. 8)
1.18 mm (No. 16)
600 |im (No. 30)
300 pm (No. 50)
150 Mm (No. 100)
75 Mm (No. 200)
Asphalt cement,' percent
by wL of total mix
Mix type
Minimum recommended
compacted depth
Recommended usage
A
•
100
95-100
70-84
52-69
38-56
27-44
19-33
13-24
8-15
6.5-9.5
Well-graded
(low voids)
4cm
(1-1/2 in.)
Impermeable
surface
B
Percent Passing
100
95-100
84-94
63-79
46-65
34-53
25-42
17-32
12-23
8-15
6.5-9.0
Well-graded
(low voids)
5cm
(2 in.)
Impermeable
surface
C
100
95-100
—
72-85
53-72
40-60
30-49
22-39
16-30
11-22
8-15
6.0-8.5
Well-graded
(low voids)
6cm
(2-1/2 in.)
Impermeable
surface
•AC-20, or equivalent AR- or penetration grade, recommended.
70
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Table 14. Recommended emulsified asphalt contents for various types
of aggregates (Asphalt Institute 1979).
Type
Approximate Emulsified Asphalt Content,
Percent by Weight of Aggregate8
Processed Dense Graded
Sands
Silty Sands
Semi-Processed Crusher
Pit or Bank Run
Open Graded'
Coarse
Medium
Fine
5.0-10.0
4.5-8.0
4.5-6.5
5.0-7.0
6.0-8.0
* With porous aggregates the emulsified asphalt content should be increased by a factor of approximately 1.2. Porous
aggregates are those that absorb more than 2 percent water by dry weight when tested by ASTM Method C 127.
Table 15. Requirements for asphalt for use in water proof membrane
construction (ASTM D-2521, adapted from Asphalt Institute
1976).
Softening point (ring and ball).
Penetration of original sample:
At 25*C (77'F). 100 g, 5 s
At 0*C (32T), 200 g, 60 s
At46*C(115'F), 50 g, 5 s
Ductility at 25*C (77*F) cm
Flash point (Cleveland open cup)
Solubility in carbon tetrachloride, %
Loss on heating, %
Penetration at 25'C (77'F) after loss on heating, %
of original
79' to 93'C (175* to 200'F)
50 to 60
30min
120 max
3.5 min
218'C (425'F) min
97.0 min
1.0 max
60 min
71
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Table 16. Climatic limitations and construction safety precautions for
various chemical stabilizing agents for soils (FHWA 1979).
Type of Stabilizer
Climatic Limitations
Construction Safety Precautions
Lime
and
Lime-Fly Ash
Do not use with frozen soils.
Air temperature should be 40'F (5*C) and
rising.
Complete stabilized base construction one
month before first hard freeze.
Two weeks of warm to hot weather are
desirable prior to fall and winter
temperatures.
Quicklime should not come in contact with
moist skin
Hydrated lime [Ca(OH)2] should not come
in contact with moist skin for prolonged
periods of time.
Safety glasses and proper protective
clothing should be worn at all times.
Cement
and
Cement-Fly Ash
Do not use with frozen soils.
Air temperature should be 40*F (5*C) and
rising.
Complete stabilized layer one week before
first hard freeze.
Cement should not come in contact with
moist skin for prolonged periods of time.
Safety glasses and proper protective
clothing should be worn at all times.
Asphalt
Air temperature should be above 32'F (O'C)
when using emulsions.
Air should be 40T (5'C) and rising when
placing thin lifts (1-inch) of hot mixed
asphalt concrete.
Hot, dry weather is preferred for all types of
asphalt stabilization.
Some cutbacks have flash and fire points
below 100'F (40'C).
Hot mixed asphalt concrete temperatures
may be as high as 350*F (175*C).
1 in. = £54 x ID'2
m
Table 17. Cement requirements for stabilizing various soils (USAF 1975).
Unified Soil Classification
GW. GP. GM. SW, SP. SM
GM, GP. SM, SP
GM, GC. SM. SC
SP
CL.ML
ML. MH. CH
CL.CH
OH. MH. CH
Usual Range in cement requirement**
percent by vol.
5 -7
7-9
7- 10
8- 12
8 - 12
8- 12
10 - 14
10 - 14
percent by wt.
3 -5
5 -8
5-9
7-11 f
7- 12
8 - 13
9- 15
10 - 16
* Based on correlation presented by Air Force
** for most A horizon soils the cement should be increased 4 percentage points, if the soil is dark grey to grey, and 6
percentage points if the soil is black.
72
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The typical range of lime content in stabilized mixes is 3 to 8 percent by weight. For
additional information on soil stabilization, the reader is referred to PCA (1979), PCA (1971),
Little (1987), Bell (1976), Bell (1988), Massa (1990), and Morrison (1971). In general, a
stabilized clayey soil base with a minimum thickness of 6 inches (15.24 cm) is recommended.
5.3.3 Bituminous Cap With Undercap Drainage: Options C andD
As indicated in Figure 19, more conservative designs such as options C and D may be
necessary in higher risk situations. The primary additional feature of these two design
options is the undercap drainage system. Within a few years of its construction, the hydraulic
conductivity of the bituminous (asphalt) cap would remain reasonably constant. In the long-
term, bitumen usually ages under environmental conditions. Coupled with the effects of other
loads that may be imposed on it, the cap may degrade, leading to increased hydraulic
conductivity. In addition to matrix conductivity, cracks would also act as conduits for the flow
of moisture through the cap. This has been the realization in the field of highway engineering.
In areas of high quantity and intensity of precipitation, such as the southeastern portion of the
United States, it is necessary to incorporate undercap drainage systems to remove moisture
that infiltrates through cracks.
Various types of degradation modes can develop in bituminous caps among which are
alligator (fatigue) cracks, reflection cracks, potholes, and block cracking and raveling. Crack
spacing can also range from a few centimeters to a few meters. It should be noted that the
load magnitude and frequency of vehicular traffic on the cap also affect its rate of degradation.
A comprehensive representation of various modes of fracturing of asphalt concrete layers is
illustrated schematically in Figure 21 as provided by NRC (1990). Figure 22 comprises
actual pictures of cracks in asphalt concrete layers.
73
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STMIUZATION
B
S
V
£
C
T
i;,
74
-------
Longitudinal Cracking
Alligator
Cracking
Tranivarsa Cracking
Block Cracking
Ccga Cracking
Rtftetion Cracking
at Joint
the variety of cracks that can develop
75
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To implement design C, the computations of the quantities outlined below should be
made. The following computations-will enable the designer to select adequate design
thicknesses for the asphalt cap and geotextile drainage layer:
• Computation of the composite value of infiltration through the intact (matrix) and
cracked portions of the concrete cover
• Determination of the required transmissivity of the geotextile drainage layer that
would adequately handle the flow that percolates through the asphalt concrete cover.
The first step in computing the quantity of water that will percolate through the cover is
the estimation of moisture available at the surface. Obviously, annual precipitation values
should not be used for design purposes unless they are modified by factors less than 1.0 in
magnitude. In highway engineering practice, data obtainable from Figure 23 have been used.
Plotted precipitation data are 1 -hour/1 -year frequency precipitation rates. These rates range
from 0.2 to 2.4 in/hr (1.41x10-4 cm/s to 1.69x10^ cm/s). For the purposes of the design
discussed herein, if the composite (matrix plus crack) permeability of the bituminous cover
exceeds the precipitation rates obtainable from Figure 23, the latter should be used in
infiltration analysis. If the precipitation rate exceeds the cover permeability, then a runoff
coefficient should be applied to the precipitation rates. In the latter case, the quantity of
moisture available for infiltration through the concrete cover can be computed as follows:
W = P - [r(P)] (7)
W = water available for infiltration through the bituminous concrete
cover
P = 1 -hour/1 -year frequency precipitation for the site (obtainable
from Figure 23)
r = runoff coefficient for the cover surface (for asphalt surfaces, use
values between 0.7 and 0.9).
76
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MODtJUTE
Figure 22. Pictures of severity levels of block cracks in a bituminous
concrete layer. A. Low severity—crack widths <0.25 in, B.
Moderate severity>0.25 in, C. High severity—spalled (NRC
1990).
77
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Figure 23. The 1-hour/1-year frequency precipitation rates in the United
States (FHWA 1973).
78
-------
Field data for P are available for hourly intervals, and such data are often presented on maps
as hourly rate contours. However, within the context of equation (7), W (which is influenced
by P) is considered to be the head of water (in units of distance) available for infiltration
through ground covers. W is taken as the design value for the head of water.
For intensely cracked covers, the value of r would be very small. Other influencing
factors are the moisture content profile and permeability of the soil underneath the cracked
bituminous concrete cover.
If suction is assumed K- be negligible underneath the liner, the flow vertically through
the cover can be computed as follows:
Q = kci (8)
Q - kc (9)
Q = quantity of water that infiltrates through the matrix and cracks of
the bituminous concrete cover (units of distance per time)
kc = composite coefficient of permeability of the bituminous concrete
cover (considering both matrix and cracks)
W = the head of moisture (in units of distance) that is available for
infiltration through the cover (same as in equation (7))
t = the thickness of the bituminous concrete cover
i = hydraulic gradient through the bituminous concrete cover.
Determination of the design value of kc is a tough assignment in the sense that the
width of cracks, crack densities, and crack penetration depths into the concrete cover
influence the composite permeability of the bituminous concrete cover. Furthermore, crack
orientations relative to the magnitudes and directions of surface slopes control the infiltration
through the cover.
79
-------
Moisture Infiltration
Cylindrical Crack
(exaggerated)
Row Line
Equipotentia[
Line
Bituminous
Concrete Cover
Subgrade
Soil
Figure 24. An illustration of hemispherical flow into a subgrade due to
moisture that percolates through a cylindrical crack (actual
flow is three-dimensional).
Moisture Infiltration
Cylindrical Crack
(exaggerated)
Row Line
Bituminous
Concrete Cover
Drainage
Layer
Subgrade
Soil
Figure 25. An illustration of the initial flow situation for water that flows
through a cylindrical crack into a drainage layer underneath a
bituminous concrete cover (actual flow is three-dimensional).
80
-------
From a theoretical standpoint, it is relatively easy to model flow through isolated
perforations and linear cracks. For holes in horizontal layers, the classic case of
hemispherical flow illustrated in Figure 24 results. If a high permeability medium, of limited
thickness exists directly beneath the surface layer, as illustrated in Figure 25, the infiltrating
water may mound underneath the perforation until it develops sufficient head to drain away
from that position. In a classic geotechnical text, Harr (1962) has described hemispherical
flow. For linear cracks that extend through the bituminous concrete cover, the concept of flow
through parallel plates can be applied in the estimation of flow. Albertson and Simmons
(1964) adopted this approach.
However, the multiplicity of factors involved and the consideration of several cracks
rather than an isolated crack preclude the direct use of the approaches to which references are
made above, in practice. The following relationship is based on the analysis performed by
Albert son and Simmons (1964) using the parallel plates analogy.
kc = kj + mbZn (10)
kc = the composite (average) permeability of the bituminous concrete
cover (cracked plus intact) (cm/sec)
kj = the permeability of the intact portions of the bituminous concrete
cover (matrix permeability) (cm/sec)
b = the average crack width in the cracked portions (cm)
n = the ratio of the cracked area to the total area considered
m = crack flow constant which approximates 2.55 (cm-sec)'1.
Equation 10 can be used to estimate the permeability of bituminous concrete covers built over
soils that may contain contaminants. Using the parameters defined previously, equations 9
and 10 can be combined to arrive at the following relationship for estimating the design
infiltration rate of moisture through concrete covers.
Q = [ki + mb2n][(W+t)/t] (11)
81
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The reader should note that FHWA (1973) proposed the use of design infiltration rates
ranging from one third to two thirds of the 1 -hour/1 -year frequency precipitation rates for
pavements. General assumptions exemplified by such flat values suffice for highway design
purposes but may not be suitable for use in situations where contaminant migration is a
concern.
With regards to the design of the geotextile drainage layer which appears underneath
the cover in Figure 19, three factors are pertinent, namely: the selection of a geotextile of
sufficient in-plane permeability and equivalent operating size (EOS), computation of the
required thickness, and selection of an adequate slope. The infiltration rate computed using
equation 11 should be used as inflow into the drainage layer. The goal is to determine the
required transmissivity of the geotextile drainage layer. Using Darcy's flow relationship,
Qa = kpiAa (12)
Qa = kpi[(d)(w)] (13)
Qa = (Q)(Aa) = the volume of water that infiltrates into the drainage
layer expressed in terms of volume per unit of time
Aa = the total area on the ground surface (cracked and uncracked)
through which water infiltrates (units of area)
kp = the permeability of the geotextile drainage layer in units of
length per time
i = the hydraulic gradient of flow that may be assumed to
approximate the slope of the drainage layer (unitless)
d = the thickness of the drainage layer
w = the width of the drainage layer normal to the direction of flow.
The product of the in-plane permeability and the thicKncss of a geotextile drainage layer is
called its "transmissivity." Hence,
D = (kp) (d) (14)
D = the transmissivity of the geotextile drainage layer (in units of
square of distance per time)
82
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Transmissivity can be incorporated into equation 13 and made the dependent variable, as
shown in equation 15. In that form, -it can be used to select the minimum thickness and
permeability of the geotextile that are adequate under estimated flow conditions.
Dm = Qa/(w)(i) (15)
Dm = the minimum transmissivity of geotextile layer that satisfies
drainage requirements.
Although it is not likely, drainage of moisture from underneath structures may be
necessary in isolated cases. Perhaps the most common occurrence of this situation would be
the drainage of capillary moisture. If a geotextile is utilized in this situation, a pressure
drainage case results. Adapting the result of work by Giroud (1981), Dm, under pressure
drainage situations, can be estimated as follows.
Dm = (B2 ksy[cvT]°-5 (16)
B = width of the building
ks = coefficient of permeability of the fine-grained soil underneath the
structural foundation
cv = coefficient of vertical consolidation of the foundation soil
T = time before loading of foundation soil.
Equation 16 is applicable to saturated soil conditions and may have restricted utility to the
situations for which this report is developed. Gerry and Raymond (1983) have provided
information on the transmissivities and permeability coefficients of various types of
geotextiles under normal stresses in the regime of 830 lb/ft3 (40kPa). For both types of flow,
factors of safety between 1.3 and 1.5 should be applied.
If the geotextile layer overlies fine-grained soils (£50% passing the number 200 sieve),
clogging of the geotextile drainage layer may occur through the migration of fines into the
83
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pores of the geotextile layer. This problem can be minimized if the following criteria are met
in the selection of geotextiles.
P85 £Dg5 (17)
70 £ EOS £100 (18)
4% S Open Area £ 36% (19)
PgS = the 85th percentile pore size of the geotextile
Dgs = the 85th percentile grain size of the underlying subgrade soil
EOS = the equivalent opening size = the sieve size with openings that
are closest in size to the openings in the geotextile fabric
Open Area = the net area of openings in the fabric, which can be determined
by measuring the area of the geotextile that is non-opaque to
light rays.
The criteria stated above are based on reviews of information provided by USAGE (1941),
Steward et al. (1977), and Dupont Company (1981).
Alternatively, as illustrated in Figure 19(d), the drainage can be constructed using
granular materials. Using information obtained from site investigations and infiltration
analysis described earlier, designs need to be developed for the following aspects:
• Grain size distribution of the drainage layer materials
• Minimum thickness of the drainage layer
• Spacing, type, and size of water removal pipes
• Dimensions of the drainage trench.
The grain size distribution (gradation) of the drainage layer materials affects the
permeability of the layer. The permeability of the materials should be adequate for draining
the quantity of water that flows into the layer. The U.S. Department of the Navy (1982) has
provided information on approximate permeabilities of various gradations of drainage layer
materials. This information is presented in Figure 26. For practical purposes, various
84
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recommendations have been made on filter material gradations to minimize clogging and to
enhance rapid lateral drainage within the drainage layer. These recommendations include
those of Betram (1940), USAGE (1941), Karpov (1955), Slaughter (1973), Willardson
(1974), and Moulton (1980). The criteria specified by the latter are recommended for the
purposes of this guidance manual and are summarized in Table 18.
The thickness of the drainage blanket should exceed the height to which water will rise
in it. The parameters that control the height to which water will rise are provided in equation
20. Equation 20 was developed by Moore (1980) to estimate the height of rise of water in
drainage layers.
•max
[((L)(c)0-5)/2][((tan 20)/c) + l-[(tan 0)/c (tan20 + c)0-5]] (20)
hmax = the height to which water will rise in the drainage layer (units of
length)
L = two times the distance between drains (unit of length)
c = Q/kg (unitless)
6 = the slope angle of the drainage layer in degrees
Q = the rate of impingement of water upon the drainage layer =
design infiltration rate (length per time)
kg = the horizontal permeability coefficient of the drainage layer
material (units of length per time).
hd * hmax (21)
hd = the design thickness of the drainage layer (units of length).
The designer can control hmax a°d hence the required thickness of the drainage layer by
adjusting 0, L, and kg. Readers should note that the minimum technology guidance (MTG)
for the design of granular drainage layers (U.S. EPA 1989f) specified the following: a
85
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CLEAR SOUME OPEMM6S
lOO
US STANDARD SIEVE NUMKKS
•C « Rf » B fi 8
COEFFICIENT OT
FOR CLEAN COARSE-ORAtNEO
DRAINAGE MATERIAL
CURVE
©
7S.7
SC.»
9.41
0.13
0.01
X.M
l.tl
0.70
0.22
0.08
O.OI
Figure 26. Approximate permeability data and other characteristics of
dean coarse-grained drainage materials (U.S. Department of
the Navy 1982).
86
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Table 18. A summary of recommended drainage and filter layer material
gradations (developed from Moulton [1980]).
Purpose
Protection of layer from clogging due to
migration of fines from the surrounding soil
into it.
Enhancement of lateral flow in the drainage
layer relative vertical percolation into the
underlying soil.
Recommendation
DIS (filter) £5D85 (soil)
D50 (filter) <. 25Dso (soil)
DIS (filter) £ 5Dis (soil)
DS (filter) £ 0.074mm
Deo (filter)/DiO (filter) <, 20
NOTE: Dx = the sieve or particle size for which x percent of the material will be smaller. For example, if 15 percent
passes the No. 10 (2mm) sieve. Djf = 2mm.
minimum thickness of 12 inches (30 cm); a minimum permeability of 0.02 ft/rnin (0.01 cm/s);
and a slope that exceeds 2 percent. Although the specifications stated above were made for
landfills and surface impoundments, they can be adopted as recommendations for underslab
drainage as well. A detailed illustration of the configuration of the cover and granular
drainage layer systems is presented in Figure 27.
In order to select perforated water collection pipes, the required flow capacity for the
pipes should be established using the computed infiltration rate (or percolation rate) and the
desired pipe spacing used in equation 20. The required pipe size is selected using
appropriate charts. Lastly, to guard against potential pipe crushing, especially if the pipes
underlie structural foundations, ring deflection data for the pipes should be evaluated. U.S.
EPA (1983b) developed, a method to estimate the required flow per 1000 ft of collector pipe
in gallons per minute (Figure 28). Specific lines are supplied in Figure 28 for various widths
of the tributary area that contributes water to flow in each pipe. The width of the tributary
area can be approximated with L/2 illustrated in Figure 27. Lee et al. (1984) also have
suggested required pipe flow capacities based on the slope of the drainage layer. These
87
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Bituminous
Concrete.
Cover
Q - Infiltration
Figure 27. An illustration of the configuration of a bituminous concrete
cover and granular layer over a site with possible residual
contamination (not drawn to likely scale).
88
-------
120
100
s
I
Q.
I
80
O 60
{
IL.
I
40
20
12345
Percolation, in inches per month
Figure 28. Required pipe capacities for drainage layers (U.S. EPA 1983
b; the thickness of the tributary area, b, is measured in feet)
89
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values are presented in Table 19. A number of charts exist for determining the required pipe
diameter based on the design flow rate. The majority of these charts are partially based on
Manning's flow equation. Examples are those of the Department of the Navy (1971), FHWA
(1987), and SCS (1973). In addition to the design flow rate, among the parameters that are
usually needed to use relevant charts to select pipe diameter are pipe spacing, roughness
coefficient, pipe gradient (or hydraulic gradient of flow), and flow velocity. Not all available
charts require all of the above-listed parameters. Two nomographs for selecting drainage
pipes based on Manning's flow relationship are presented in Figures 29 and 30. It should be
noted that these charts are applicable to pipes with the specific roughness coefficients stated.
Table 19. Recommended minimum flow capacities for collector pipes in
drainage systems (Lee et al. 1984).
Slope (%)
Water Removal Rate
(cubic ft per 1000 ft of pipe
<2 1.50
2 - 5 1.65
6-12 1.80
12 1.95
Other important design aspects of the underslab drainage system are the dimensions of
the drainage trench, the placement and size of holes on the drainage pipes to prevent the
intrusion of granular materials, and the arrangement of pipe flow outlets. FHWA (1987)
recommends that the required trench width be computed using equation 22:
(22)
b - required width of trench
Qd = the design drainage rate
kg = the permeability of granular materials.
90
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91
-------
Drain Capacity Chart-N-0.016
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Figure 30. A chart for determining the required drainage pipe diameter
(SCS 1973).
92
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With respect to perforations on the pipe, the following criteria are suitable. For pipes with
slotted openings,
Dg5 (filter)/slot width > 1.2 (23)
For pipes with circular holes,
Dgs (filter)/hole diameter > 1.0 (24)
Dgs = the sieve size through which 85 percent of the trench fill
materials will pass.
5.3.4 Numerical Example
The following problem has been created and a numerical approach to its solution is
provided to illustrate how the principles discussed in this technical guidance document can be
applied. The reader should not consider the solution provided to be the only correct one.
Modification may be necessary for different situations, considering that engineering design
involves an optimization process. Furthermore, the designer may wish to apply safety
factors that are perhaps more conservative than those that are intrinsic to the equations
described in the preceding chapters and sections.
• The situation: Consider a plan to build a warehouse on a site near Tampa, Florida.
Through risk assessment and site characterization, it has been shown that residual
contaminants at the site pose only negligible threats to human health. This stems
from the fact that the primary source of contamination has been excavated and
removed from the site. Site materials are sands with DIS = 0.7 mm DSQ = 2.5mm,
Dgs = 5mm, and DIQ = 0.6mm. The annual precipitation is greater than 80 cm (31.5
in.). The entire site has an area of 14,000 square feet (1300.6m2), comprising a
building area of 1,000 square feet (92.90m2). Following recommendations provided in
Figure 19, configuration D has been chosen as the ground cover around the building to
reduce the quantity of infiltrating water that could percolate through the site and leach
residual contaminants into the groundwater. It is conservatively estimated that
about 40 percent of the 12-inch cover will be damaged within 12 years, prior to
resurfacing with a bituminous concrete cover. The average crack width is assumed to
be 0.5cm and the asphalt permeability is 10~7cm/sec. The design objective is to use
available information to produce an adequate design of the ground cover/drainage
system that will complement the structural foundation isolation system.
93
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A sample solution of the problem described above is presented below. The solution
involves step-wise computations for addressing each of the necessary elements of the
design. The initial selection of design values for parameters in each step of the computational
procedure may not result in an acceptable design. For example, the computed performance
level of the entire ground coverage scheme may be unacceptable and/or the computed design
dimensions may be unfeasible. Therefore, the computation should be repeated with new
values for the parameters that can be modified until the desired results are achieved.
It should be noted that some of the numerical values of parameters described in the
solution as 'given' would need to be estimated, possibly, by measurement The crack density
and sizes may be estimated for a large area by extrapolations from detailed measurements in
a smaller area within the cracked portion of a pavement The parameters b, n, and m can be
determined in this manner.
Step 1:. Compute the amount of water available for infiltration through the bituminous
concrete cover (W)
From equation 7,
W = P - [r(P)]
P = 2.0 in/hr = 5.08 crn/hr from Figure 23
r = 0.70 (assumed)
/.W = 5.08-[(0.70)(5.08)] = 1.524 cm/hr. However, use 1.524cm as
the head, W
Step 2: Compute the infiltration rate of water through the 12-inch thick bituminous
concrete (Q)
From equation 11,
Q = [ki + mbV|[(W+t)/t]
kj = 10*7 cm/sec (given)
b = 0.50 cm (given)
n = 40% (given)
94
-------
m = 2.55 (cm-sec)'1
t = 12 in = 30.48 cm (given)
W = 1.524 cm (computed).
Q = [10-7 + (2.55) (0.5)2 (0.4)] [(1.524 + 30.48)730.48]
Q = [10-7 + 0.255] [(1.05)] = 2.677 x 10-1 cm/sec.
Step 3: Select the desirable gradation of granular materials for use in the drainage
layer
From Figure 26, the gradation represented by curve number 6 is selected for the granular
drainage layer. The approximate characteristics are
kg = permeability = 2.08 ft/min = 1.07 cm/s
DS = 3.0mm
= 3.2mm
= 3.8 mm
= 6.0mm
= 11.0mm
The characteristics of the underlying soil are as stated below
= 0.6 mm (given)
= 0.7 mm (given)
= 2.5 mm (given)
= 5.0 mm (given)
From Table 18, for protection of the drainage layer from clogging,
DIS (filter) S 5 Dg5 (soil)
.-.3.8 < [5(5.0) = 25] (adequate)
D50 (filter) £ 25 D50 (soil)
.-.6.0 < [25 (2.5) = 62.5] (adequate)
95
-------
For enhancement of lateral flow in the drainage layer,
DIS (filter) £ 5 DIS (soil)
/. 3.8 > [5 (0.7) = 3.5] (adequate)
DS (filter) £ 0.074 mm
.-. [Ds (filter) = 3.0 mm] > 0.074 mm (adequate)
(filter)/Dio (filter) £ 20
.-.[11.0/3.2 = 3.44] < 20 (adequate)
Step 4: Select the design thickness of the drainage layer
This involves the computation of the maximum height of rise of water within the drainage
layer using equation 20. A drain spacing of 45 meters and a layer gradient of 3% will be used.
The gradient meets the 2% minimum specified in the minimum technology guidance (MTG).
From equation 20,
max
Jmax
[((tan2 0)/c) -i- l-[(tane)/c (tan2 0 + c)0-3]]
L = (2) (drain spacing) = (2)(45 m) = 90m
c = Q/kg
Q = 2.677 x 10'1 cm/sec
kg = 1.07 cm/s (through material selection)
/.c = 2.677 x 10-V1.07 = 0.249 « 0.25
0 = 3%
[((90)(0.25)0-5)/2] [((tan23)/0.25) + l-[(tan3)/0.25 (tan2 3 +
hmax = [22.5] [(0.01) +1-[(0.209)(0.502)]]
= [22.5] [0.01 +1.0-0.105]
= 20.36cm
-------
From the computations presented above, the estimated height of water in the drainage layer
is low. Therefore, the minimum drainage layer thickness of 12 inches (30.48 cm) should be
used.
Step 5: Compute the required pipe flow capacity and pipe diameter
Figure 28 or Table 19 can be used for estimating the required pipe flow capacity. However,
Figure 28 is suitable to situations in which the percolation rate is very minimal (from about
1.0 to 6.0 inches per month). Table 19 does not require the use of inflow rate which is
recognized generally as being one of the controlling factors with respect to drainage system
effectiveness.
Figures 29 and 30 incorporate most of the significant pipe drainage parameters and are based
on Manning's drainage equation. In order to use Figure 30, it is necessary to compute the
required capacity of each pipe.
From equation 13,
Qa = QAa
Q = 0.2677 cm/sec (computed)
Aa = 1300.6 m2 - 92.90 m2 = 1207.7 m2 (ground surface area given
indirectly)
/.Qa = (0.002677 m/sec)( 1207.7m2) = 3.233 mVsec
The entire site has an area of 1300.6 m2. A square shape can be assumed, implying that the
area is 36.06 m by 36.06 m in dimensions. Consistent with the pipe spacing of 45 m used
earlier to compute hmax, only a single drainage pipe should be selected for incorporation into a
36.06 m- wide drainage layer. However, a preliminary assessment using Figure 30 indicates
that the required pipe diameter for a single drainage pipe would be excessively large.
97
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Therefore, for the required drainage rate of 3.233 m3/sec (114.17 ftVsec), 4 pipes will be used.
Each pipe will need to drain percolated water at the rate of 114.17/4 = 28.54 ftVsec.
Using Figure 30, the required diameter of each pipe at a pipe gradient of 0.02 (for a
Manning's coefficient, N = 0.015) is approximately 22 inches (56 cm). It is assumed that the
four pipes will be embedded in shallow trenches below the drainage layer. Furthermore, the
reader should note that a pipe gradient of 0.02 is used, and that the drainage layer gradient is
0.03. Both gradients do not necessarily have to be of the same magnitude.
98
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CHAPTER 6.0
MEASURES OF COVERAGE EFFECTIVENESS
6.1 COVERAGE RATIO
The extent to which earthen materials containing residual contaminants are covered on the
ground surface can be expressed as the coverage ratio. This is simply the ratio of the area of the
bituminous concrete cover and building floor area to the area of the horizontal projection of the
portions of the site protected. Although this parameter influences the effectiveness of the ground
coverage scheme, it does not involve parameters such as cover permeability, thickness, etc., that
influence the percolation of moisture through the cover to the contaminated soil. Consequently,
in the hierarchy of measures of effectiveness, coverage ratio ranks low.
6.2 INFILTRATION RATE
As a measure of coverage effectiveness, the infiltration rate through the cover is dependent
on the degree of coverage and the permeability of the cover to water. Directly, it affects the rate
at which low concentration leachates may be generated from residual contaminants. The
infiltration rate that is applicable to drainage layer design is based on a design storm. To
estimate leachate generation rates, infiltration rates for longer durations such as months or years
are more suitable. In this technical guidance document, simple deterministic equations and
charts have been provided for use in estimating infiltration rates.
6.3 CONTAMINANT MIGRATION RATE
The migration rate of residual contaminants from a structural development site depends on
the effectiveness of the cover system, waste characteristics, and host media properties. The low
level of contamination that would be present at candidate sites implies that the concentrations of
contaminants in leachates would most likely be low. In highly uncertain situations, a
quantitative assessment of contaminant migration through various pathways may be necessary.
Various models exist for use in contaminant migration studies, most of which are applicable to
99
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site-specific situations. Repa et al. (1982) provided a catalogue of such models with
descriptions of their utilities, advantages, and disadvantages. Deterministic methods of
predicting contaminant migration rates range from those that are based on the simple Darcy flow
equation (Corn and Groves 1984) to more complex mathematical models exemplified by
Huyakorn and Faust (1983) and Anderson (1979). Although they require much more data for
application, probabilistic techniques can also be used. Models such as those of Thibodeaux
(1979) and Silka (1986) are applicable to gas migration analyses.
6.4 RISK REDUCTION
Indirectly, risk assessment methods incorporate most of the effectiveness measures
discussed above. As a component of risk assessment, estimation of the potential exposure of
prospective residents of structures on redeveloped sites requires the use of numerical techniques
with attendant assumptions. The coverage provided by several protective designs incorporated
into the. structure and its surroundings should reduce exposure levels significantly. Considering
that the concentration levels of contaminants at sites selected for redevelopment will be low,
reduced exposure to very low concentrations of contaminants would plausibly result in low risk
situations. Nevertheless, qualitative and quantitative assessments need to be made. Such
assessments may involve the use of mathematical models to which references were made earlier.
Information on other models that address the emission of contaminated paniculate matter from
soils and human exposure to them is provided by U.S. EPA (1985d) and U.S. EPA (1985e).
Numerical techniques that address the migration of contaminants into structures have been
developed by Johnson and Ettinger (1991), Hodgson et al. (1992), Loureiro et al. (1990), and
Nazaroff and Cass (1989).
Examples of exposure and risk assessment computations are widely available in the
literature. The reader is referred to the following documents: U.S. EPA (1990c), U.S. EPA
(1991d), Rosenblatt et al. (1982), Hadley et al. (1991), Paustenbach (1989), and Konieczny et al.
100
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(1985). When the methodologies espoused in the above-mentioned literature differ from U.S.
EPA procedures, the latter take precedence.
Contaminated sites that are candidates for redevelopment include sites that have been
remediated to an acceptable level of contamination and sites where original contaminant levels
are low. With respect to remediation, pertinent techniques may include excavation/removal
and/or in situ treatment. Risk assessment techniques can be used to establish acceptable levels of
site remediation prior to redevelopment. Numerical examples of the use of risk assessment
techniques to establish acceptable cleanup levels have been described by Ibbotson et al. (1989),
Stephanatos (1990), Schanz and Salhotra (1990), Reinert (1990), LaGrega et al. (1988), Hwang
(1992), Jessiman et al. (1992), Whitmyre et al. (1987), Taylor et al. (1987), Smith et al. (1987),
Santos and Sullivan (1988), Leu and Hadley (1988), Brown (1987) and U.S. EPA (1989g).
101
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CHAPTER 7.0
EXAMPLES OF RE-DEVELOPED SITES
A number of previously contaminated sites have been redeveloped in the United States and
abroad. The post-development land use and associated risks to human health and the
environment are important factors that have been considered in remediated site redevelopment.
U.S. EPA (1986a) identified two categories of development projects on uncontrolled waste sites,
namely, developer-initiated projects and public-initiated projects. Developer-initiated projects
are common in or near metropolitan areas where land is typically expensive and scarce.
Although the cleanup costs may be high, the advantages of redevelopment include possible sale
of the redeveloped property at a price that exceeds the developer's original investment. Under
this situation, the developer makes critical decisions on the site reclamation and structural
development schemes. Public agencies provide oversight to the project in an effort to ensure
public safety. With respect to the public-initiated redevelopment effort, there is no requirement
to recover the cost of redevelopment subsequently. Nevertheless, redevelopment of the site may
still be of direct or indirect benefit to the public.
Implementation of structural development projects within the framework of the RCRA
Corrective Action process covers the two types of projects described above. For the private
sector, use of the redeveloped site and the revenue it brings has been the major driving factor.
For regulatory agencies, inhibition of the migration of dangerous substances from contaminated
sites through the implementation of adequately designed systems is necessary. Furthermore,
cleanup cost recovery by the private sector through reclaimed land reuse may enhance its
financial capacity to implement additional cleanup projects. The latter falls within the objectives
of regulatory agencies.
In the United States, California is one of the few states that have developed a regulatory
framework for redeveloping previously contaminated sites. Redevelopment projects have been
102
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implemented more frequently in countries such as Britain, Germany, and the Netherlands. In this
chapter, examples of redeveloped sites are provided in Table 20. These examples are for
situations in which contamination existed prior to the decision to implement remediation
schemes and redevelop the sites. These situations are different from the more common
occurrence of contamination of building areas during service. The latter is exemplified by
spillages of hydrocarbons at service stations for petroleum products. The site redevelopment
examples in Table 10 are by no means the complete set of such sites in the United States and
abroad. There are plausibly hundreds of such sites that have not yet been described in literature.
More recently, U.S. EPA (1992) has described specific redevelopment projects at some
reclaimed sites in Europe. The countries covered in that report are England, Wales, Sweden, the
Netherlands, and the Federal Republic of Germany.
103
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105
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APPENDIX A—CHEMICAL HAZARD INFORMATION
(BARRY 1991)
GASES
Effective ventilation (i.e., dilution) can eliminate all risks from gases, whether toxic,
asphyxiant, or explosive.
Carbon dioxide (COi)
General characteristics
Colourless, odourless gas
Denser than air (specific gravity 1 -S3)
Present in air at 0.03% (300 ppm) by volume
Dissolves in water to form carbonic acid
Non-combustible
Relevant sources
Natural occurrences (acids on limestone)
Produced on landfill sites by aerobic and anaerobic decomposition of organic matter or
as a product of combustion
Principal effects on humans
Toxic and asphyxiant by inhalation
Concentration >3%: laboured breathing and headaches result
Concentration 5-6%: these symptoms become severe
Concentration 12-25%: victim becomes unconscious
Concentration >25%: death can occur
Occupational exposure limits 5000 ppm (8 h), 15000 ppm (10 min)
Principal effects on plants
Variable toxicity
Principal human targets
Workers in poorly ventilated trenches or tunnels (e.g., investigation and clearance
demolition workers), as CO2 is denser than air and capable of accumulating in deep
pits or excavations
After users of site (see landfill gases below)
Principal materials affected
Metals and concrete could degrade where strong solutions form
Carbon monoxide (CO)
General characteristics
Colorless, almost odourless gas
Slightly soluble in water
Burns with a violet flame
Produced during incomplete combustion of organic materials
106
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Relevant sources
Underground combustion
Principal effects on humans
Highly toxic by inhalation
Highly inflammable
Has an affinity for blood haemoglobin that is over 200 times that of oxygen, causing
hypoxia in victims
Concentration >200 ppm: headache after 50 min
Concentration >500 ppm: headache after 20 min
Concentration 1000-10000 ppm: headache, dizziness and nausea in 13-15 min; death if
exposure continues for 10-45 min
Concentration 10000-40000 ppm: death within a few minutes
Occupational exposure limits 50 ppm (8), 300 ppm (10 min)
Combustion possible at 12-75%
Principal effects on plants
Phytotoxic
Principal human targets
Redevelopment workers (in confined spaces)
Site users (in buildings)
Hydrogen cyanide (HCN)
General characteristics
Colourless and has a faint odour of bitter almonds
Soluble in water
Highly inflammable
White liquid at temperatures below 26.5 °C
Relevant sources
Combustion of complex cyanides in soil (e.g., spent oxides at gas works sites) or
acidification of cyanide salts in soil
Principal effects on humans
Highly toxic by inhalation, ingestion and skin absorption
Fire and explosion risk
Inhibits enzyme systems, especially the enzyme cytochrome oxidase, resulting in the
prevention of oxygen uptake by living tissue
Concentration <18 ppm: poisoning symptoms exhibited
Concentration 18-36 ppm for several hours: causes slight weakness, headache, confusion
and nausea
Concentration > 100 ppm for several minutes: causes collapse, respiratory failure and
possible death
Concentration >300 ppm: immediately fatal
Occupational exposure limit 10 ppm (10 min)
Lower explosive limit 6% in air
107
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Principal human targets
Site investigation workers (in confined spaces)
Site users (in buildings)
Hydrogen sulphide (H2S)
General characteristics
Distinctive, offensive odour of rotten eggs (odor threshold 0.5 parts per billion (i.e.,
109))
Dulls olfactory senses (creating impression of concentration abatement)
Sweetish taste
Soluble in water
Relevant sources
Microbial action on sulphate salts (e.g., gypsum) under anaerobic conditions
Plasterboard discarded in landfill sites
Kraft paper mill sites, oil refineries, coal carbonisation sites and chemical works
Acid soil conditions may produce H2S where high sulphide concentrations exist
Principal effects on humans
Highly toxic by inhalation
Highly inflammable
Highly malodorous
A strong irritant to the eyes and mucous membranes
Concentration >20 ppm: causes loss of smell, thus toxic limits reached without odour
warning
Concentration 20-150 ppm: causes sub-acute effects (i.e., irritation of the eyes and
respiratory tract)
Concentration >400 ppm: toxic effects occur
Concentration >700 ppm: life-threatening
Occupational exposure limits 10 ppm (8 h), 15 ppm (10 min)
Lower explosive limits 4.5% in air
Principal effects on plants
Phytotoxic
Principal human targets
Site investigation and construction workers in trenches and drains
Site users in confined unventilated spaces
Neighbourhood
Methane (CRj)
General characteristics
Colourless, odourless, tasteless gas
Lighter than air (specific gravity 0.55)
Inflammable; lower explosive limit in air 5%; upper explosive limit in air 15%
Relevant sources
Decaying vegetation in swamps and marshes (CH4 produced naturally)
108
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Natural gas and coal gas
Microbial anaerobic degradation of organic matter, principally in landfill sites
Principal effects on humans
Severe explosion risk when present in concentration range 5-15% in air
Asphyxiant as it replaces air, but non-toxic in itself
Principal effects on plants
Causes root die-back by replacing oxygen
May be oxidised to CO2 by soil bacteria
Principal human targets
Site investigation workers in unventilated pits and trenches
Inhabitants of building on or adjacent to landfill sites
Principal effects on plants
Affects vegetation on restored landfill sites and adjacent areas
Phosphine (PH3)
General characteristics
Colourless gas
Garlic-like odour
Denser than air (specific gravity 1.85)
Spontaneously inflammable in air (usually with the highly visible phosphorus pentoxide
vapour (Fig. 3.32))
Relevant sources
Deposits of phosphorus compounds
Principal effects on humans
Highly toxic by inhalation
Fire and explosion hazard
Symptoms of inhalation include headache, fatigue, nausea, vomiting, jaundice and ataxia
Strong irritant
Odour threshold 2 ppm
Occupational exposure limits 0.3 ppm (8 h), 1 ppm (10 min)
Ignites at room temperature where impurities exist
Principal human targets
Site investigation workers
Redevelopment workers
Sulphur dioxide (SO2)
General characteristics
Colourless gas with a sharp pungent odour
Denser than air (specific gravity (1.43)
Soluble in water to form sulphurous acid
Non-combustible
Strong oxidizing and reducing agent
109
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Relevant sources
Burning of sulphurous materials such as coal and oil
Released during the combustion (accidental or deliberate) of contaminated materials
(e.g., spent oxide on former gasworks sites
Principal effects on humans
Toxic by inhalation
Strong irritant to eyes and mucous membranes, causing a variety of respiratory effects
depending on concentration and individual susceptibility (bronchitis sufferers more
severely affected)
Concentrations 0.3-1.0 ppm: detectable by most individuals
Concentration 6-12 ppm: becomes and irritating gas
Occupational exposure limits 2 ppm (8 h), 5 ppm (10 min)
Principal effects on plants
Phytotoxic
Principal effects on materials
Corrosive where sulphurous acid is formed
Principal human targets
Site occupiers
Neighbourhood residents
Principal affected materials
Concrete and metals can degrade where acid forms
Landfill gas
The composite gas produced by the decomposition of biodegradable materials in most
landfilled waste sites is covered in the text
METAL COMPOUNDS
Arsenic (As)
General characteristics
Elemental As is a silver-grey, brittle crystalline solid that darkens in moist air
Forms organic and inorganic compounds that are solid and may/may not be soluble in
water
Arsine (AsHs) is a colourless gas that is soluble in water and is flammable
Relevant sources
Soil contamination as a result of mining and smelting of the metal, and extensive use of
agricultural preparations such as pesticides and herbicides
Burning of preserved wood on building sites produces harmful levels of AS2Oi (ash
may contain up to 5% As, which may be water-soluble)
110
-------
Principal effects on humans
Solid compounds highly toxic by ingestion, skin contact and dust inhalation
Ingestion results in severe diarrhoea and vomiting; 70-180 mg arsenic trioxide (As2Os)
represents a fatal dose
Skin contact causes dermatitis; As2Os linked with skin cancer (20 years latency)
Inhalation of As compounds irritates mucous membranes of the respiratory system;
AsH3 gas highly toxic by inhalation (55 times more toxic than cyanide)
Poisoning is acute or chronic according to exposure concentration and duration
Occupational exposure limit As and compounds except arsine and lead arsenate 0.2
mg/m3 (8h)
ICRCL trigger values (threshold) (see Chapter 5) As (total) 10 mg/kg (gardens), 40
mg/kg (parks, playing fields)
Principal effects on livestock
Poisoning through ingestion of contaminated herbage and As-rich soils
Principal effects on plants
Toxicity depends on oxidation state and form of the element; arsenite more toxic than
arsenate
Reduced growth occurs before toxic levels reached within plant
Accumulation in edible plants may present a hazard to humans
Principal effects off-site
Water pollution possible, arsenite or arsine may be predominant species if reducing
conditions develop
Principal human targets
Risk to site investigation workers and demolition/clearance workers through inhalation
of dusts, and gases in unventilated spaces
Risk to site after-users through ingestion of soils, plants or water; 'pica' children
especially at risk
Principal livestock targets
Animals grazing on contaminated vegetation
Principal plant targets
Vegetables have reduced yield and are contaminated
Boron (B)
General characteristics
Elemental B is a black hard solid or brown amorphous powder which is highly reactive;
it is soluble in water; dust ignites spontaneously in air
Forms organic and inorganic compounds which may be solid, liquid or gaseous and may
or may not be soluble in water
Compounds of interest include halogenated boron, boron hydrides, boric oxide and
sodium metaborate
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Relevant sources
Manufacturing wastes of certain petrochemical (e.g., nylon) or other industries (e.g.,
washing powders)
Wastes containing B compounds in glass, ceramics, porcelain and enaraelware are not in
an ingestible form unless presented as powders
Principal effects on humans
Elemental B is non-toxic
Boron dust is a fire and explosion hazard
Compounds mentioned under General characteristics may irritate or be corrosive to the
skin, nasal mucous membranes, the respiratory tract and eyes
Occupational exposure limits boron tribromide (BBr3) 1 ppm (8 h), 3 ppm
Occupational exposure limits boron oxide (6203) 10 mg/m3 (8 h), 20 mg/ms (10 min)
Principal effects on plants
Phytotoxic effects
Grasses more resistant
ICRCL trigger value (threshold) water-soluble boron 3 mg/kg (soil)
Toxicity increased in acidic soils
Principal human targets
Unlikely to be a critical hazard, but inhalation of dusts by site investigators and
demolition/clearance workers may cause ill effects
Little hazard from consumption of contaminated vegetation
Principal plant targets
Most non-grasses
Cadmium (Cd)
General characteristics
Elemental Cd is a soft blue-white malleable metal or grey-white powder; inflammable in
powder form
Forms organic and inorganic compounds which are solid and soluble in water
Relevant sources
Mining and smelting, pigments, paints, electroplating, PVC stabilisers, fungicides,
batteries, photocells, alloys and solders
Landfill is the major outlet for Cd-bearing wastes
Principal effects on humans
Highly toxic via inhalation of Cd metal or oxide as fumes or dust
Inhalation of Cd at a concentration of 1 mg/m3 for 8 hours may lead to chemical
pneumonias
Soluble compounds are toxic by ingestion; a concentration of Cd of 15 mg/ml produces
food-poisoning symptoms, but emetic action reduces poisoning risk
Long term effects include hypertension and prostatic cancer; Cd accumulates in the liver
and kidney, causing renal damage and disturbed metabolism
Occupational exposure limit Cd and Cd compounds 0.05 mg/m3 (8 h)
Occupational exposure limits cadmium oxide fume 0.05 mg/m3 (8 h and 10 min)
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Occupational exposure limits cadmium sulphide pigments 0.04 mg/m3 (8 h)
ICRCL trigger values (threshold) Cd (total) 3 mg/kg (gardens), 15 mg/kg (parks, playing
fields, open spaces)
Principal effects on plants
Phytotoxic in high concentrations
Leafy plants take up more metal, causing food contamination
Principal effects on livestock
Poisoning through ingestion of Cd-contaminated herbage and soils
Principal effects off-site
Water pollution by soluble compounds may occur
Principal human targets
Acute hazard to site investigators, redevelopment workers, Cd workers
Long-term hazard to site after-users through ingestion of Cd-contaminated food from
gardens and water supplies; children particularly vulnerable
Principal plants targets
Any vegetation
Principal livestock targets
Animals grazing on contaminated vegetation
Chromium (Cr)
General characteristics
Elemental Cr is a hard, brittle, grey metal
Compounds have strong and varied colors
Hexavalent compounds (e.g., chromic oxide, chromyl compounds, chromates, and
dichromates) are of most relevance; all are soluble in water and/or acids
Landfill is the major outlet for Cr-bearing wastes
Relevant sources
Natural occurrences; smelting and mining operations; hexavalent compounds within
wastes from Cr-plating, anodising, metal surface preparation, chemical industries,
pigment manufacture
Principal effects on humans
Elemental Cr and trivalent compounds are relatively non-toxic
Hexavalent compounds have an irritating and corrosive effect on tissue, producing ulcers
and dermatitis on prolonged skin contact; irritation of the respiratory tract and
ulceration of the nasal septum from inhalation
Paniculate inhalation linked with bronchogenic carcinoma
Occupational exposure limit Cr 0.5 mg/m^(8 h)
Occupational exposure limit Cr (II) (i.e., divalent) 0.5 mg/m3 (8 h)
Occupational exposure limit Cr (IE) 0.5 mg/m3 (8 h)
Occupational exposure limit Cr (VI) 0.05 mg/m3 (8 h)
ICRCL trigger value (threshold) Cr (VI) 25 mg/kg (all uses)
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ICRCL trigger values (threshold) Cr (total) 600 mg/kg (gardens/allotments), 1000 mg/kg
(parks, playing fields, open spaces)
Concentration >1% calcium chromate in dusty or friable waste regarded as 'special'
waste
Principal effects on plants
Phytotoxic
Uptake causes food contamination
Principal effects off-site
Pollution of water supplies is possible as ammonium, lithium, magnesium, potassium
and sodium chromates and dichromates and chromic acid are very soluble in water
Maximum permissible concentration in potable water is 0.05 ppm (Cr (VI))
Principal human targets
Long-term effect on site after-users through skin contact and ingestion of contaminated
vegetables and water supplies
Low risk to site investigators and redevelopers due to short-term contact — unless
exposed to chromic acid, dust and mist, which may cause perforation of nasal septa
Principal plant targets
Vegetation growing on contaminated sites
Copper
General characteristics
Elemental Cu is a malleable, ductile, reddish-coloured metal; non-combustible except as
a powder
Forms many organic and inorganic compounds, some soluble in water and some not
Commonly occurs as sulphates, sulphides and carbonates in the soil
Relevant sources
Smelting of Cu ores
Waste from electroplating, chemical and textile industries
Wastes from the manufacture of pesticides, pigments and antifouling paints
Principal effects on humans
Toxic by inhalation of dusts and fumes of Cu salts, and by ingestion and skin contact
Inhalation causes congestion of the nasal and mucous membranes, ulceration/perforation
of the nasal septum, and fume fever
Ingestion of soluble salts causes nausea, vomiting, diarrhoea, sweating, coma, and death
if very large doses consumed
Skin contact causes irritation
Eye contact causes corneal ulcers
Occupational exposure limit Cu (fume) 0.2 mg/m3 (8 h)
Occupational exposure limits Cu (dusts and mists) 1.0 mg/m3 (8 h), 2 mg/m3 (10 min)
Principal effects on plants
Phytotoxic, especially at low soil pH and low organic matter
ICRCL trigger value (threshold) Cu (total) 130 mg/kg (where plants are to be grown)
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Principal effects on materials
Corrosive to rubber
Principal human targets
Little risk to site investigators and redevelopers
Chronic toxicity rare
Principal plant targets
Any vegetation, but some tolerant species/cultivars exist
Lead(Pb)
General characteristics
Elemental Pb is a heavy, ductile, soft grey solid, insoluble in water (slowly soluble in
water containing a weak acid)
Present in a divalent state in most of its inorganic compounds
Lead divalent salts, lead oxides and lead sulphide have low solubility in water (except
for the acetate, chlorate and nitrate)
Relevant sources
Natural occurrence
Mining and smelting operations
Batteries, scrap metal, petrol additives, pigments, paints, glass manufacture
Principal effects on humans
Toxic principally by inhalation but also by ingestion
Central nervous system, blood and kidneys affected
Symptoms range from sickness, fatigue and loss of appetite to damage to the brain and
other organs, and death
Behavioral disorders in children
Serious effects usually the result of cumulative exposure
Soluble lead compounds more dangerous
Concentration 30% inhaled Pb and 10% ingested Pb enters the blood stream
Occupational exposure limit Pb (except tetraethyl) 0.15 mg/m3 (8 h)
Occupational exposure limit tetraethyl Pb 0.1 mg/m3 (8 h)
ICRCL trigger values (threshold) Pb (total) 500 mg/kg (gardens, allotments), 2000
mg/kg (parks, playing fields, open spaces)
Principal effects off-site
Water supplies may be contaminated in soft-water areas where Pb piping dissolves
Principal human targets
Children who ingest Pb dust due to 'pica' habit
Inhabitants ingesting Pb contamination from garden vegetables (on surface of plants and
taken up by plants) (also close to Pb works and heavy traffic)
Inhabitants of soft-water areas with old Pb piping
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Mercury (Hg)
General characteristics
Elemental Hg is silvery, extremely heavy and insoluble in water; highly volatile
Forms inorganic and organomercury compounds and amalgams with many other metals
Inorganic Hg converts to methyl Hg in soil
Relevant sources
Wastes from manufacture or formulation of Hg compounds (e.g., process wastes)
Wastes from the use of Hg compounds (e., g., slurries from the chlor-alkali, paint,
agriculture and pharmaceutical industries)
Principal effects on humans
Metallic, inorganic and organic Hg highly toxic by ingestion, skin absorption or
inhalation
Alkylmercurials most hazardous
Inorganic Hg toxicity on swalloving depends on solubility
Causes denaturation of proteins, inactivation of enzymes, severe disruption of any tissue
Skin contact causes bums and blistering
Absorption results in digestive and nervous symptoms
Occupational exposure limits alkyl Hg 0.01 mg/m3 (8 h), 0.03 mg/m3 (10 min)
Occupational exposure limits Hg and compounds 0.05 mg/m3 (8 h), 0.15 mg/m3 (10
min)
ICRCL trigger values (threshold) Hg (total) 1 mg/kg (gardens, allotments), 20 mg/kg
(parks, playing fields, open spaces)
Principal effects on plants
Phytotoxic principal effects off-site
Possible contamination of water supplies by soluble Hg compounds
Principal human targets
Low risk to site workers
Greater risk from long-term ingestion of contaminated food (i.e., vegetables from
contaminated areas), and drinking contaminated water or eating fish therefrom
Principal plant targets
Any vegetation, but some tolerant species exist
Nickel (Ni)
General characteristics
Elemental Ni is a malleable, silvery metal, inflammable as a dust or powder
Inorganic compounds of interest include nickel oxide (NiO), nickel hydroxide
(Ni(OH)2), nickel subsulphide (NijS2), nickel sulphate (NiSO4) and nickel chloride
(NiCL2)
Relevant sources
Refining of impure nickel oxide
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Wastes from metal finishing processes including electroplating, alloy and stainless steel
manufacture, enamel and battery production
Principal effects on humans
Elemental Ni toxic
Compounds toxic by skin contact (allergic dermatitis) and inhalation (rhinitis, nasal
sinusitis and chronic pulmonary irritation)
Carcinogenic effects from long-term inhalation of Ni dust and fumes, and Ni(CO)4
Ni(CO)4 inhalation also produces immediate symptoms of nausea, vertigo, headache,
breathlessness and chest pain
Occupational exposure limit Ni 1 mg/m3 (8 h)
Occupational exposure limits Ni (soluble compounds) 0.1 mg/m3 (8 h), 0.3 mg/m3 (10
min)
Occupational exposure limits Ni (insoluble compounds 1 mg/m3 (8 h), 3 mg/m3 (10
min)
Fire risk with Ni dust or powder
Principal effects on plants
Phytotoxic, especially in acid soils
ICRCL trigger value (threshold) Ni (total) 70 mg/kg (any uses where plants are to be
grown)
Principal human targets
Carcinogenic effects associated with occupational exposure and site after-users,
especially children
Risks to site workers are increased if fires are lit on heavily contaminated sites, as these
can produce toxic fumes
Principal plant targets
Any vegetation, but some tolerant species/cultivars exist
Selenium (Se)
General characteristics
Elemental Se is an amorphous red powder, becoming black on standing
Forms organic and inorganic compounds, some soluble in water and some not
Relevant sources
By-product from the smelting and refining of copper, nickel, silver and gold ores
Waste from the manufacture and reconditioning of 'xerox' drums, the pigments industry
and the production of paints containing cadmium orange
Principal effects on humans
Elemental Se is harmless
Compounds are toxic, absorbed through the lungs, intestinal tract or damaged skin
Soluble compounds (e.g., SeO2) are most toxic
Inhalation causes pulmonary oedema
Skin contact causes burns
General symptoms of absorption include a garlic odour to the breath, pallor, lassitude,
irritability, vague gastro-intestinal symptoms and giddiness
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Occupational exposure limit Se and compounds 0.2 mg/m3 (8 h)
Occupational exposure limit SeFe 0.2 mg/m3 (8 h)
ICRCL trigger values (threshold Se (total) 3 mg/kg (gardens, allotments), 6 mg/kg
(parks, playing fields, open spaces)
Principal human targets
Construction workers
Zinc (Zn)
General characteristics
Elemental Zn is a shining white metal with a bluish-grey lustre; Zn dust may form
explosive mixtures with air
Most simple salts of Zn are soluble in water (although the oxide, hydroxide, carbonate,
sulphide, phosphate and silicates are insoluble or only slightly soluble)
Relevant sources
Smelting of ore
Wastes from metal-finishing, and battery, pigment, plastics, fire-retardant and cosmetics
manufacture
Principal effects on humans
Fire and explosion risk from Zn dust in damp conditions
Zn compounds relatively non-toxic by ingestion, although large doses of soluble salts
may cause vomiting and diarrhoea
Poisoning by inhalation of ZnO fumes and dust causes metal-fume fever (i.e., shivering,
sweating, nausea, thirst, headache, painful limbs)
ZnCl2 and ZnO corrosive to skin, causing dermatitis
Zn chromate carcinogenic
Occupational exposure limits ZnCl2 (fume) 1 mg/m3 (8 h), 2 mg/m3 (10 min)
Occupational exposure limits ZnO (fume) 5 mg/m3 (8 h), 10 mg/m3 (10 min)
Principal effects on plants
Phytotoxic, synergistic effect with Cu, Ni, especially at lowpH
ICRCL trigger value (threshold) Zn (total) 300 mg/kg (any uses where plants are to be
grown)
ICRCL trigger value (threshold) Zn (equivalent) 280 mg/kg (any uses where plants are
to be grown)
Principal human targets
Low risk to site investigators, redevelopment workers and after-users
Principal plant targets
Any vegetation, but some tolerant species/cultivars exist
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INORGANIC COMPOUNDS
Acids and alkalis (pH)
General characteristics
Acids are a large class of chemicals whose water solutions have a pH value less than 7,
have a sour taste, turn litmus dye red, and react with certain metals and bases to form
salts
Inorganic acids include sulphuric (H2SO4), nitric (HNOs), phosphoric (HsPCU),
hydrochloric (HC1) and hydrofluoric (HF) acid
Organic acids include carboxylic and acetic acid, fatty acids, amino acids
Alkalis are caustic substances which in water solution have a pH greater than 7, have a
bitter taste and turn litmus dye blue
Alkalis include ammonia (NHs), ammonium hydroxide (NH4OH), calcium oxide (CaO),
calcium hydroxide (Ca(OH)2), sodium carbonate (Na2COs), sodium hydroxide
(NaOH)
Relevant sources
Inorganic acids in wastes from the fertiliser and chemical industries, metal surface
preparation and finishing, plastics manufacture
Organic acids in wastes from acetate preparation, nylon manufacture, surface metal
treatment, the food industry
Natural inorganic/organic acids
Alkalis in wastes from the glass, chemical, and paper industries, fertiliser manufacture
Principal effects on humans — inorganic acids
Fire and explosion risk if in contact with certain other chemical substances or
combustible materials; flammable hydrogen evolved on contact with metals
Corrosive, especially at high concentration; tissue damage at 0.6% nitric acid, 1%
sulphuric acid
Skin contact causes severe burns
Eyes readily damaged
Inhalation of vapours/mists causes respiratory-tract irritation
Ingestion causes severe irritation of the throat and stomach, destruction of internal organ
tissue, possible death
Occupational exposure limits nitric acid 5 mg/m3 (8 h), 10 mg/m3 (10 min)
Occupational exposure limit sulphuric acid 1 mg/m3 (8 h)
ICRCL soil trigger value (threshold) pH <5 (gardens, allotments, landscaped areas)
ICRCL soil trigger value (action pH <3 (gardens, allotments, landscaped areas)
Principal effects on humans — organic acids
Irritant to eye, respiratory system and skin
Degree of effect determined by acid dissociation and water solubility; tissue damage at
10% acetic acid concentration
Occupational exposure limits acetic acid 25 mg/m3 (8 h), 37 mg/m3 (10 min)
Principal effects on humans — alkalis
Corrosive to tissue whether in solid form or concentrated liquid solution; tissue damage
at 0.1% sodium hydroxide, 10% ammonia solution
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Severe destruction of skin and eye tissue, irritation of the respiratory tract
Occupational exposure limits sodium hydroxide 2 mg/m3 (8 h), 2 mg/m3 (10 min)
Principal effects on plants
Acidity in soils will increase the availability of certain toxic metals (e.g., Zn, Cu, Ni)
Principal effects on materials
Acids will cause degradation of building materials (i.e., metals, concrete, limestone)
Principal effects off-site
Contamination of water supplies possible
Principal human targets
Site investigators, redevelopment workers and site users
Principal plant targets
Vegetation generally
Principal materials affected
Building materials generally
Cyanides (CNs)
(HCN —see'Gases')
General characteristics
The 'simple' salts and their solutions present the greatest risk to humans (e.g., potassium
or sodium cyanide)
Crystalline complex CNs present lesser risk (e.g., sodium and potassium ferri- and
ferrocyanides)
Thiocyanates are important CN compounds
Relevant sources
Simple salts from plating works, heat treatment works
Complex CNs from photography and pigment manufacture, gasworks sites (spent oxide)
Thiocyanates from gasworks sites
Principal effects on humans
Simple CNs
Moderately toxic
Absorbed from all entry routes
Causes inhibition of enzymes required for cell respiration, preventing oxygen uptake
by the tissues; death by asphyxia if 50-100 mg ingested
Chronic exposure to very low levels causes dermatitis, nose irritation
Complex CNs
Relatively non-toxic
Ferricyanide is more toxic than ferrocyanide
Skin contact with >50 g/kg spent oxide causes skin irritation
Thiocyanate
Low acute toxicity
Large doses cause vomiting and convulsions
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Sodium thiocyanate at > 50 mg/kg is lethal
Chronic exposure causes skin eruptions, dizziness, cramps, nausea, vomiting, nervous-
system disturbances
Occupational exposure limit cyanides (except HCN, cyanogen, cyanogen chloride) 5
mg/m3 (8 h)
ICRCL trigger values
Free CN Threshold Action
Gardens, allotments, landscaped areas 25 mg/kg 500 mg/kg
Buildings, hard cover . 100 mg/kg 500 mg/kg
Complex CN
Gardens, allotments 250 mg/kg 1000 mg/kg
Landscaped areas 250 mg/kg 5000 mg/kg
Buildings, hard cover 250 mg/kg No limit
Thiocyanate
All proposed uses 50 mg/kg No limit
EEC drinking water criterion 50 mg/1
Principal effects on plants
Free and complex CN phytotoxic
Phytotoxic levels for spent oxides in soil approx. 5 g/kg, equivalent to 250 mg/kg
complex CN
Uptake causes food contamination
Principal effects on fish
Concentration > 0.001 ppm may cause fish toxicity
Concentration 0.1 ppm may cause chronic effects
Principal effects off-site
Possible groundwater pollution, as CN salts are soluble
Principal human targets
Site investigators and redevelopment workers where simple CN dumped
Particular danger where CN and acids in close proximity; may react to form HCN gas
Site after-users where vegetables are contaminated; children particularly susceptible
Principal plant targets
All vegetation
Sulphur (S) compounds
(Hydrogen sulphide, sulphur dioxide — see Gases; sulphuric acid — see acids and
alkalis)
Sulphates, sulphides and sulphur are of most importance
Relevant sources
Sulphates from acid rain, dumping of S-containing wastes (e.g., gypsum), gasworks
wastes (may be up to 20% sulphate)
Sulphides from metal ores, wastes from pigment manufacture, ceramics
Sulphate-reducing, sulphide-oxidising conditions (by bacterial action)
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Sulphur native to volcanic regions
Principal effects on humans
Toxic effects vary according to metal salt
Amount of sulphate/sulphide ion ingested itself of no significance
Ferrous sulphates more toxic than ammonium sulphate
Ingestion of small doses of ferrous sulphate (> 7.8 g) may be fatal to a 'small' child
Gastrointestinal irritation from high sulphate levels in drinking water
Inhalation of sulphur dust causes respiratory inflammation and bronchopulraonary
disease after several years
Skin contact with sulphur results in aczematous lesions
ICRCL trigger values
Sulphate Threshold Action
Gardens, allotments, landscaped areas 2000 mg/kg 10000 mg/kg
Buildings 2000 mg/kg 50000 mg/kg
Hard cover 2000 mg/kg No limit
Sulphide
All uses 250 mg/kg 1000 mg/kg
Sulphur
All uses 5000 mg/kg 20000 mg/kg
Principal effects on plants
Phytotoxic effects, although plants differ in their ability to withstand high sulphate/
sulphide levels
Phytoxicity more marked in acid soils
Soil sulphate >200-300 mg/kg considered to be of concern for plant growth
Possible microbial transformation of sulphate to toxic sulphide salts in anaerobic,
waterlogged soils
Principal effects on materials
Sulphate is corrosive to building materials (e.g., concrete); sulphide-oxidising bacteria
can create highly acid conditions; cast iron piping is particularly affected by sulphide
generated by sulphur-reducing bacteria (SRB)
Principal effects off-site
Possible contamination of water bodies with soluble sulphates and sulphides
Principal human targets
Little risk to site workers, investigators, redevelopment workers
Children and inhabitants of contaminated-water areas at risk
Principal plant targets
Some vulnerable species
Principal materials affected
May require sulphate-resisting cement and/or protective coatings where sulphate levels
greater than 0.2% in soil, 300 mg/1 in water; no effect below these levels (see BRE
digest 250 (ref. 3.9))
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ORGANIC COMPOUNDS
Coal tar
General characteristics
Black viscous liquid with naphthalene-like odour and sharp burning taste
Combustible
Only slightly soluble in water
Highly complex and variable mixture containing of to 10000 compounds
Relevant sources
Derived from the coal carbonisation process
Gasworks sites may contain up to 60% coal tars in waste
Principal effects on humans
Effects dependent on components
Risk via inhalation and skin contact
Inhalation of low-molecular-weight (i.e., volatile) aromatics presents toxicity hazard —
benzene and toluene have narcotic properties
Inhalation of polyaromatic hydrocarbon (PAH) content may cause cancer
Skin/eye contact causes severe irritation, cancer (from PAH contact)
Ingestion hazards not significant — a 20 kg child would need to ingest 100 g of material
containing 10 g coal tar per kilogram to present a poisoning risk
ICRCL trigger values (expressed as polyaromatic hydrocarbons (PAHs))
Threshold Action
Gardens, allotments, play areas 50 mg/kg 500 mg/kg
Landscaped areas, buildings, hard cover
Principal effects on plants
Phytotoxicity at 1-10 g/kg
Uptake causes food contamination
Principal effects on materials
Plastic piping attacked chemically
Principal effects off-site
Odour; soil discoloration
Contamination of drinking water, causing tainting and odour
Principal human targets
Critical groups are children and gardeners who have regular contact with contamination
Volatile substances could present a short-term risk to investigators or workers on a site
Principal plant targets
Vegetation generally
Principal materials affected
Plastic piping
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Phenols
General characteristics
A class of aromatic organic compounds that have a characteristic odour and an acrid
burning task
The simpler compounds are soluble in water
Relevant sources
By-products of the coal carbonisation industry
Present in wastes from gasworks sites (in coal tars), ammoniacal liquors,
pentachlorophenol, Pharmaceuticals, dyes, indicators
Principal effects on humans
Toxic by inhalation, skin contact and ingestion; strong irritant to tissue
Tissue damage at >1%
Ingestion causes intense burning of the mouth and throat, abdominal pain, nausea and
vomiting, diarrhoea, dizziness, central nervous system damage; dose 10-30 g is fatal
Skin absorption causes above symptoms, skin blistering and necrosis
Inhalation causes above effects, but low vapour pressure reduces risk
Occupational exposure limits 5 ppm (8 h), 10 ppm (10 min)
ICRCL trigger values
Threshold Action
Gardens, allotments 5 mg/kg 200 mg/kg
Landscaped areas, buildings, hard cover 5 mg/kg 1000 mg/kg
Principal effects on plants
Phytotoxic effects at >1000 mg/kg
Principal effects on materials
Plastic water piping and rubber attacked
May affect concrete at >5%
Principal effects off-site
Contamination of water supplies due to migration through plastic pipes; this will lead to
the formation of unpleasant-tasting chlorinated phenols (TCP* taste)
Imparts disinfectant odour to soils
Principal effects on fish
Toxic, especially in cold waters, causing paralysis and cardiovascular congention
Taints fish flesh
Water quality criterion (fisheries): <0.7 ppm phenols
Principal human targets
Site investigators and workers through direct contact
Site after-users who ingest contaminated food and water
Principal plant targets
Vegetation generally
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Principal materials affected
Plastics, rubber, concrete
Polycholorinated biphenyls (PCBs)
General characteristics
A group of organochlohne compounds
Clear, pale yellow, liquid, viscous or solid products, their consistency increasing with
their chlorination percentage
Mild aromatic odour; low solubility in water
Use is restricted to closed systems
Relevant sources
Transformers, capacitors, coolants, hydraulic fluids, lubricating oils (closed systems)
Previous use as pesticides
>1% PCB classified as 'special' waste
Principal effects on humans
Toxic, inhibits many enzymes
Suspected carcinogen
Skin and mucous membrane changes
Occupational exposure causes chloracne
Irritation of upper respiratory tract on inhalation when PCB oils heated
Ingestion causes abdominal pain, anorexia, nausea, vomiting, coma and death
Occupational exposure limits (C^HvCls (42% Cl) 1.0 mg/m3 (8 h), 2 mg/m3 (10 min)
Occupational exposure limits C^Cls (54% Cl) 0.5 mg/m3 (8 h), 1 mg/m3 (10 min)
Principal effects on ecosystem
Highly persistent
Accumulation in birds feeding on aquatic organisms leading to eggshell thinning
Some aquatic organisms killed at low concentrations (e.g., freshwater shrimps at 0.001
ppm)
Principal human targets
Occupational exposure to PCB, especially through skin contact
Site investigators and redevelopers where leakage from or break-up of transformers; use
of gloves and disposable protective clothing reduces risk
Principal ecosystem targets
Organisms at higher trophic levels (i.e., carnivores) most at risk due to accumulation
within the food chain at high persistence
Solvents
General characteristics
Organic liquids used industrially to dissolve a large number of substances
Nine groups exist: hydrocarbons, halogenated hydrocarbons, aldehydes, alcohols,
ethers, glycol derivatives, esters, ketones, and miscellaneous solvents
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Relevant sources
Wastes from industry (e.g., printing, oil extraction, degreasing, dry cleaning)
Principal effects on humans
Fire and explosion hazard with most industrial solvents
Volatile inflammable solvents form explosive mixtures with air
Toxic, mainly by inhalation, causing narcosis
Chronic poisoning affects the liver and kidneys
Skin absorption may occur, associated with localised skin injury
Principal human targets
Site investigators and redevelopment workers
Residents on or close to waste solvent sites
OTHER HAZARDOUS MATERIALS
•Asbestos
General characteristics
A group of impure magnesium silicate minerals that occur in fibrous form
Three common types: chrysotile (white asbestos), crocidolite (blue asbestos) and
amosite (brown asbestos)
Chemically inert, heat resistant, mechanically strong
Relevant sources
Wastes from previous use in pipe insulation, boilers, heating elements, wall insulation,
ceiling tiles, brake linings, ship building and breaking, railway carriage breaking,
asbestos factories
Principal effects on humans
Carcinogenic and irritant
Hazard mainly associated with confined spaces
Asbestos inhalation can cause respiratory diseases including asbestosis, bronchial cancer
and mesothelioma
No 'safe' level of exposure but different risk associated with type: blue greater than
brown greater than white for likelihood of mesothelioma development; latency period
20-30 years
Control limits (4 h) (ref. 3.10) crocidolite and amosite 0.2 fibre/ml, chrysotile 0.5
fibre/ml
Principal human targets
Workers with asbestos waste where fibres are released to the air (e.g., site investigation
and redevelopment workers); different risks (friability, structure, content) associated
with different methods of handling and stripping of wastes; asbestos cement less
likely to generate dust than other products; more risk with insulation and sprayed
asbestos; HSE may approve ball and chain demolition for asbestos-cement products
as lesser risk to workers from generation of dust and asbestos fibres than dismantling
of sheets
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Inhabitants of areas close to disposal sites at risk if fibres become airborne
Pathogens
General characteristics
Organisms capable of causing disease to man, animals and plants
Include bacteria, moulds and fungi, viruses, parasites
Relevant sources
Sewage (pathogens may or may not be destroyed by treatment; eggs or cysts of parasites
are highly resilient)
Hospital waste
Laboratory waste
Principal effects on humans
Disease
Symptoms vary widely according to organism involved
Principal effects on livestock
Disease
Danger from parasitic eggs/cysts where sewage sludge dumped on land
Principal effects off-site
Disease
Contamination of water supplies (e.g., from sewage discharge)
Spread from waste sites by insects, birds, etc.
Principal human targets
All groups
Radioactivity
General characteristics
Energy of the process emitted as alpha or beta particles or gamma rays
Alpha particles cannot penetrate the skin but are 20 times more harmful than an
equivalent amount of beta or gamma radiation if inhaled or swallowed; stopped by a
sheet of paper
Beta particles can pass through skin and penetrate the body; stopped by a fairly thin
sheet of lead or aluminum
Gamma rays are extremely powerful and penetrating; stopped by thick sheets of lead,
many feet of concrete or water
Radioactivity not affected by the physical state or combination of the element
Radioactivity of a nuclide is characterised by the nature of the radiation, its energy, and
the half-life of the process (i.e., the time required for the activity to decrease to one
half of the original)
Relevant sources
Hospital waste: mainly short-lived beta- and gamma-emitters (e.g., 1251,60-day half-
life; 99Tc, 6-hour half life)
127
-------
Laboratory waste: mainly short-lived beta-emitters, although 14C has a 5000 year half-
life
Mining wastes: uranium ore wastes contain long-lived alpha- and beta-emitters (e.g.,
238U, half-life 4510 x 106 years; ^Ra, half-life 1620 years)
Natural (phosphorus; granite areas) (e.g., long-lived alpha- and'beta-emitters of the
uranium and thorium decay series)
Principal effects on humans
Low doses induce carcinogenic and genetic damage which takes many years to emerge
Leukaemia, and thyroid, breast and lung cancer may be induced
Genetic effects involve changes in the number or structure of chromosomes, and
mutation of the genes themselves
High doses may kill cells, damage organs, and cause rapid death; damage becomes
evident within hours or days
Reproductive organs and eyes particularly sensitive
Occupational exposure limits: ICRP dose limits (1977)
50 millisievert*/year (workers), 1 millisievert/year (public, mean annual)
5 millisievert/year (public, short periods); NRPB guidance limits (1987)
15 millisievert/year (workers), 0.5 millisievert/year (public)
Principal human targets
All groups
Physical hazards
General characteristics
Instability from excavations, old mineshafts, sewers, trial pits, underground cavities and
tanks
Hazards from demolition processes
Hazards from sharp objects (e.g., glass, hypodermic needles, metallic objects)
Relevant sources
Mining areas, industrial waste land, waste disposal sites
Ground settlement/voids resulting from biodegradation or the effects of combustion
Principal effects on humans
Physical injury (direct or indirect through structural failure)
Principal effects on materials
Physical damage
Principal human targets
All groups, particularly investigation and demolition and clearance workers
Principal materials affected
All types, particularly rigid members
*The sievert is a unit of dose equivalent which takes account of the absorbed dose and
the damage potential of the particular type of radiation.
128
-------
APPENDIX B—ENGINEERING CONVERSION FACTORS
LENGTH
To Convert From
Inches
Feet
Millimeters
Centimeters
Meters
Yard
Angstrom units
To
feet
angstrom units
microns
millimeters
centimeters
meters
inches
angstrom units
microns
millimeters
centimeters
meters
inches
feet
angstrom units
microns
centimeters
meters
inches
feet
agnstrom units
microns
millimeters
meters
inches
feet
angstrom units
microns
millimeters
centimeters
feet
centimeter
meter
inches
feet
microns
millimeters
centimeters
meters
Multiply By
0.083333
2.54 X 10»
25400
25.4
2.54
0.0254
12.0
3.048 X 109
304800
304.80
30.48
0.3048
3.9370079 X lO-2
3.2808399X10-3
1X107
1X103
1 X 10-1
1 X 10-3
0.39370079
0.032808399
1X108
1X104
10
1 X 10-2
39.370079
3.2808399
1 X 10*0
1X106
1X103
1X102
3
91.44
0.9144
3.9370079 X 10"9
3.28084 X 10-10
0.0001
1 X 10-7
1 X 10-8
1 X 10-™
129
-------
Microns
AREA
To Convert From
Square meters
Square feet
Square centimeters
Square inches
Square yard
Acres
VOLUME
To Convert From
Cubic centimeters
Cubic meters
Cubic inches
Cubic feet
U.S. gallons (gal)
inches
feet
To
square feet
square centimeters
square inches
square meters
square centimeters
square inches
square meters
square feet
square inches
square meters
square feet
square centimeters
acres
square feet
square centimeters
square miles
square meters
square feet
yards
3.9370079 X 10-5
3.2808399 X 10"6
Multiply By
10.76387
1X104
1550.0031
9.290304X10-2
929.0304
144
1X10-4
1.076387 X 10-3
0.155
6.4516 X1(H
6.9444X10-3
6.4516
2.066 X 1(H
9
8361.273
3.228 X lO'7
4046.849
43560
4840
To
cubic meters
cubic feet
cubic inches
cubic feet
cubic centimeters
cubic inches
cubic meters
cubic feet
cubic centimeters
cubic meters
cubic centimeters
cubic inches
cubic centimeters
cubic meters
cubic feet
cubic inches
Multiply By
1X10-6
3.5314667 X 10'5
0.061023744
35.314667
1X106
61023.74
1.6387064X10-5
5.7870370 X HH
16.387064
0.028316847
28316.847
1728
3785
3.785 X 10-3
0.133680
231
130
-------
cubic yards
Britich Imperial gallons
liters
4.951 X 10-3
0.833
3.785
TIME
To Convert From
Milliseconds
Seconds
Minutes
Hours
Days
Months
Years
To
seconds
minutes
hours
days
months
years
milliseconds
minutes
hours
days
months
years
milliseconds
seconds
hours
days
months
years
milliseconds
seconds
minutes
days
months
years
milliseconds
seconds
minutes
days
months
years
milliseconds
seconds
minutes
hours
days
years
milliseconds
seconds
Multiply By
10-3
1.66666X10-5
2.777777 X 10'7
1.1574074 X10-8
3.8057 X 10-10
3.171416X10-"
1000
1.66666X10-2
2.777777 X 10"4
1.1574074X10-5
3.8057 X 10-7
3.171416X10-8
60000
60
0.0166666
6.944444 X HH
2.283104X10-5
1.902586 X 10-6
3600000
3600
60
0.0416666
1.369860X10-3
1.14155 X10-4
86400000
86400
1440
24
3.28767 X lO-2
0.0027397260
2.6283 X 109
2.6283 X 106
43800
730
30.416666
0.08333333
3.1536X1010
3.1536 X107
131
-------
minutes
hours (mean solar)
days (mean solar)
months
525600
8760
365
12
VELOCITY
To Convert From
Centimeters/second
Microns/second
Feet/minute
Feet/year
Miles/hour
To
microns/second
meters/minute
feet/minute
miles/hour
feet/year
centimeters/second
meters/minute
feet/minute
miles/hour
feet/year
centimeters/second
microns/second
meters/minute
miles/hour
feet/year
microns/second
centimeters/second
meters/minute
feet/minute
miles/hour
centimeters/second
meters/minute
feet/hour
feet/minute
feet/second
Multiply By
10,000
0.600
1.9685
0.022369
1034643.6
0.0001
0.000060
0.00019685
0.0000022369
103.46436
0.508001
5080.01
0.3048
0.01136363
525600
0.009665164
0.0000009665164
5.79882 X 10-7
1.9025 X 10-6
2.16203X10-8
44.7041
26.82
5280
88
1.467
STRESS
To Convert From
Pounds/square
Pounds/square foot
To Multiply By
pound/square foot 144
feet of water 2.3066
kips/square foot 0.144
kilograms/square centimeter 0.070307
tons/square meter 0.70307
atomospheres 0.068046
kilonewtons/square meter 6.9
pounds/square inch 0.0069445
feet of water 0.016018
132
-------
Feet of water (at 39.2°F)
Kips/square foot
Kilograms/square
centimeter
Tons (short)/square foot
Tons (metric )/square meter
Atmospheres
kips/square foot
kilograms/square centimeter
tons/square meter
atmospheres
newtons/square meter
pounds/square inch
pounds/square foot
kilograms/square centimeter
tons/square meter
atmospheres
inches of Hg
pounds/square inch
pounds/square foot
tons (short)/square foot
kilograms/square centimeter
tons (metric)/square meter
pounds/square inch
pounds/square foot
feet of water (39.2°)
kips/square foot
tons/square meter
atmospheres
atmospheres
kilograms/square meter
tons (metric )/square meter
pounds/square inch
pounds/square foot
kips/square foot
kilograms/square centimeter
pounds/square foot
kips/square foot
tons (short)/square foot
bars
centimeters of mercury at
0°C
millimeters of mercury at
0°C
feet of water at 39.2T
kilograms/square centimeter
grams/square centimeter
kilograms/square meter
tons (metric)/square meter
pounds/square foot
1 X 10-3
0.000488243
0.004882
4.72541 X 10-4
47.9
0.43352
62.427
0.0304791
0.304791
0.029499
0.88265
6.94445
1000
0.5000
0.488244
4.88244
14.223
2048.1614
32.8093
2.0481614
10
0.96784
0.945082
9764.86
9.76487
13.8888
2000
2.0
0.10
204.81614
0.20481614
0.102408
1.0133
76
760
33.899
1.03323
1033.23
10332.3
10.3323
2116.22
133
-------
pounds/square inch 14.696
tons (short)/square foot 1.0581
Newtons/square meter pascals 1.00
134
-------
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