vvEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/7-80-117
May 1980
Research and Development
Methodology to
Evaluate the Potential
for Ground Water
Contamination from
Geothermal Fluid
Releases
Interagency
Energy/Environment
R&D Program
Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4 Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
*-•"'.*
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EPA-600/7-80-117
August 1980
METHODOLOGY TO EVALUATE THE POTENTIAL FOR GROUND WATER
CONTAMINATION FROM GEOTHERMAL FLUID RELEASES
by
Karen Summers, Steve Gherini, and Carl Chen
Tetra Tech, Incorporated
Lafayette, California 94549
Contract No. 68-03-2671
Project Officer
Robert P. Hartley
Energy Systems Environmental Control Division
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
i',8. Environmental Protection
Region V, library
230 South Pe.-rborn Otreet
Chbugo, tUinjis 60604
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does men-
tion of trade names of commercial products constitute endorsement or recom-
mendation for use.
i 3. Environmental
ii
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly efficient control methods be
used. The Industrial Environmental Research Laboratory - Cincinnati (lERL-Ci)
assists in developing and demonstrating new and improved methodologies that
will meet these needs both efficiently and economically.
This report develops a methodology and analytical techniques to evaluate
potential impacts of geothermal fluid releases on the ground water environ-
ment. It is intended to assist both industry and regulators in planning geo-
thermal developments through better prediction of environmental consequences.
Further information on the subjects of this report can be obtained from
the Power Technology and Conservation Branch, Industrial Environmental
Research Laboratory, Cincinnati, Ohio 45268.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
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ABSTRACT
This report provides analytical methods and graphical techniques to pre-
dict potential ground water contamination from geothermal energy development.
Overflows and leaks from ponds, pipe leaks, well blowouts, leaks from well
casings, and migration from injection zones can be handled by the methodology.
General characteristics of geothermal systems and fluids and probable modes of
release are included in the report to provide typical data.
The major steps of the procedure are to determine environmental concerns
and release potential, to identify potential ground water contamination, and
to evaluate significance of contamination. Analytical methods, data require-
ments, typical data and coefficient values are included.
The methodology may be used as a regulatory tool for predicting impacts
or for testing control technologies. Geothermal developers can use the meth-
odology to predict adverse impacts at development sites and select control
methods for the conditions or locations where required.
This report was submitted in fulfillment of Contract No. 68-03-2671 by
Tetra Tech, Inc. under the sponsorship of the U.S. Environmental Protection
Agency.
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CONTENTS
Foreword iii
Abstract iy
Figures vii
Tables viii
1. Executive Summary 1
Purpose of project 1
Methodology 1
Recommendations 3
2. Introduction 5
Background and purpose 5
Uses of the methodology 6
3. Description of geothermal systems 7
Overview of existing sites 7
Plant design 7
Site characteristics 7
Fluid characteristics 13
Types of fluid releases 23
Failure modes 23
Pipe failures 23
Valve failures 31
Pond leaks 31
4. Description of methodology 39
General procedure 39
Environmental concerns 41
Release potential 42
Release points 42
Quantity of releases 44
Chemistry of released fluid 44
How injection pretreatment techniques change
flu.id chemistry 57
Ground water contamination 57
Release pathway 59
Extent of potential contamination 59
Method of surface releases - group 1 61
Method of surface releases - group 2 73
Method for releases at depth - group 3 77
How much will attenuation decrease contamination ... 87
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CONTENTS (continued)
Page
Evaluation of significance 94
Limitations of the methodology 97
References 98
Appendices
A. Solubility data 103
B. Soil properties 132
C. Adsorption coefficients 143
D. Mathematical functions 149
E. Pipe flow data 153
F. Example case 158
G. Glossary of selected terms 166
H. U.S.-metric conversion table 167
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FIGURES
Number Page
1 Map of known geothermal resource areas and geothermal
exploration sites 9
2 Sketches of general power plant cycles 12
3 Ranges of chemical constituent concentrations in geothermal
fluids 15
4 Noncondensible gases in geothermal fluids 16
5 Corrosion rate of 1010 mild steel in geothermal fluids of
varying pH 32
6 Effect of corrosion on fatigue for different alloys 35
7 Steps of methodology 40
8 Diagram to locate potential releases 43
9 Liquid flashed versus temperature at atmospheric pressure ... 48
10 Alkalinity versus pH 50
11 Alkalinity versus total carbonate, showing pH contours .... 51
12 Examples of solubility diagrams 54
13 Diagrams to determine silica scaling tendency 55
14 Solubility product versus ionic strength for barium
sulfate 56
15 Hypothetical flow paths for fluid releases 60
16 Graph of relationship of Peclet number to convective
dispersion 69
17 Schematic diagram for group 3 case 78
18 Time for release to reach steady-state conditions 86
19 Graphical solution for Wilson and Miller's equations 88
20 Cation-exchange capacity variations with pH 92
21 Effect of chloride concentration on adsorption of mercury ... 93
22 Effect of pH on adsorption of metals 93
23 Effect of adsorption on mercury transport 95
VI1
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TABLES
Number Page
1 Characteristics of Principal Geothermal Fields 8
2 Projected U.S. Geothermal Power Plants 11
3 Geologic Setting of Selected California Known Geothermal
Resource Areas 14
4 Concentrations of Various Constituents in Geothermal
Noncondensible Gases, Steam Condensates and Brine
to Show Partitioning Between Phases 17
5 Summary of Chemical Analyses of Geothermal Fluid by
Geographical Areas 18
6 Chemical Constituents of Interest in Geothermal Fluids .... 20
7 Geothermal Fluid Concentrations for Problem Constituents ... 21
8 Geothermal Fluid Concentrations of Additional
Constituents 22
9 Aquatic Life Criteria 24
10 Relative Hazards of Geothermal Fluids 25
11 Agriculture Use Criteria for Constituents in Geothermal
Fluids 26
12 Failure modes and Mechanisms of Hydrothermal System
Components 27
13 Summary of Historical Geothermal Failures in California .... 28
14 Known Well Blowouts 29
15 History of Selected Geothermal Plants 30
16 Corrosion Rates of Materials in Geothermal Fluids 33
17 Calculated Failure Rates for Pipes 34
18 Methods to Control Corrosion in Geothermal Facilities 36
19 Characteristics of Nuclear Cooling Water and Geothermal
Fluids 37
20 Volume of Potential Releases 45
21 Changes from Wellhead to Plant Outlet Temperature,
Pressure and pH 47
22 Precipitates (Scales) Found at Existing Geothermal Sites ... 52
23 Example Cases of Chemical Species Expected to Precipitate ... 58
24 Summary of Solution Methods 62
25 General Adsorption-Desorption Behavior of Selected Aqueous
Chemical Species 89
26 U.S. EPA Drinking Water Quality Standards 96
viii
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SECTION 1
EXECUTIVE SUMMARY
PURPOSE OF PROJECT
The Environmental Protection Agency has contracted with Tetra Tech, Inc.
to develop a methodology to predict potential ground water contamination re-
sulting from geothermal energy development. Operational and accidental re-
leases of geothermal fluid to ground water may be difficult to detect and cor-
rective actions may not be practical. The presence of toxic constituents in
some geothermal fluids emphasizes the need to prevent these fluids from reach-
ing usable water supplies.
The objective of this project has been to develop a methodology for use
by regulatory agencies and geothermal developers. The methodology developed
is presented in this user's manual. Policy and procedural recommendations
which minimize pollution hazards have been made. The development of the
screening procedure included the characterization of geothermal fluids, the
identification of potential release modes and locations, and the selection of
appropriate analytical methods.
METHODOLOGY
The procedure consists of a set of analytical tools for predicting the
fate of pollutants accidentally or intentionally released from liquid-domi-
nated geothermal power plants. The major steps in the procedure are:
• Determine environmental concerns
t Determine release potentials
• Identify potential ground water contamination
• Evaluate significance of contamination
The two environmental concerns considered here are the contamination of
usable aquifers by the geothermal fluid and mobilization of pollutants from
the soil/rock matrix. Available chemical data for geothermal fluids were re-
viewed and compared to water quality standards for drinking water supplies,
agricultural uses, and aquatic life. Twenty-three chemical species and total
dissolved solids were identified as pollutants of concern. The chemical
species include:
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Aluminum . Lead
Ammonia Lithium
Arsenic Magnesium
s
Barium Manganese*
Boron Mercury
+
Cadmium Molybdenum
Chloride* Nitrate1^
t +
Chromium Selenium
Copper* Silver^
Fluoride Sodium
Hydrogen Sulfide* Zinc*
Iron*
Included in primary drinking water standards (EPA, 1976a).
*Included in secondary drinking water standards (EPA, 1977).
Chemical compounds which may cause scaling problems, e.g., calcium carbonate,
silica, and certain sulfates, were also considered. Geothermal fluid chemis-
tries vary among sites and within a given reservoir. All of the chemical
species listed above may not be present in significant concentrations at any
particular site. Low pH geothermal fluids may mobilize heavy metals present
in the soil/rock matrix.
Potential release locations and modes were identified from power plant
design schematics. Diagrams have been prepared which show the types of re-
leases which may occur at different points in the power plant and the condi-
tions which increase the likelihood of a release. Geothermal experience to
date indicates that pipe leaks occur most frequently, followed by well blow-
outs, valve jams, surface pond overflows, and well casing leaks. Information
on corrosion rates of pipes carrying geothermal fluids under different condi-
tions was compiled to enable the user of the procedure to identify piping sub-
ject to high corrosion rates. Methods are included to predict chemical
changes (e.g., precipitation) in the geothermal fluid as it moves from the
production well through the plant to disposal ponds or injection wells.
Analytical methods were selected to predict movement of pollutants from
surface spills, from production or injection wells directly into usable aqui-
fers, or from releases above or below usable aquifers. The transport equa-
tions include advection, dispersion, and reaction. Attenuation of pollutants
by dilution, adsorption (or ion-exchange) and decay can be considered. A
conservative evaluation can be made first by not considering adsorption and/or
decay. If the calculations predict pollutant concentrations in excess of
standards, the case with adsorption and decay should then be evaluated. Four
analytical solution techniques were selected for use in the methodology:
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t GEOHY-GEOQAL analytical method
t Advection-dispersion method
t Bernoullii-Darcy approach
• Mass-balance approach
The analytical method used for a specific release depends on the loca-
tion and duration of the release. These analytical solution techniques were
selected to minimize data requirements and calculations so that the methodol-
ogy can be used in the early stages of geothermal development.
The significance of a potential release is evaluated by comparing the
concentrations predicted at the plant boundary with the appropriate water
quality standards. A release is considered significant if the resulting con-
centrations exceed any of the applicable use standards for the aquifer(s) in
question.
The methodology provides a step-by-step procedure for predicting the
potential movement of pollutants to ground water. Data requirements, example
cases, constants, and representative data are included in the manual. The
general data should be replaced by site-specific data whenever the latter are
available.
RECOMMENDATIONS
In the course of this project several ways were identified to minimize
the probability and effects of releases. The recommendations pertaining to
surface spills are as follows:
• Use corrosion-resistant upgraded materials for critical
plant components (e.g., piping and valves).
• Use pH control and/or additives to prevent scale
buildup and corrosion.
t Use lined ponds for emergency storage of surface spills
if underlying aquifers are usable.
• These ponds should be at least large enough to hold the
precipitation from one-in-ten-year storm and four hours
of total flow.
Recommendations for minimizing blowouts and subsurface releases are the
following:
• Monitor the pressure of the production and injection
wells continuously.
• Use carefully selected blowout preventers.
3
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• Set injection pressures high enough to move fluid into
injection zone but low enough to avoid fracturing of
the formation.
Current research programs are investigating corrosion control methods
for piping systems exposed to geothermal fluid. A detailed examination of
failure rates expected in a geothermal power plant would complement the ex-
tensive corrosion research. Control methods could then be identified for the
pipe locations where failures will most likely occur.
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SECTION 2
INTRODUCTION
BACKGROUND AND PURPOSE
The recovery of energy from liquid-dominated geothermal systems involves
large liquid flow rates. Geothermal fluids may be corrosive and may contain
high concentrations of dissolved constituents, many of which are toxic. The
operational and accidental releases of the geothermal fluid to ground water
are of particular concern. The effects of the ground water pollution may be
difficult to detect. Because of the very low flow velocities associated with
ground waters, they are not readily flushed and once contaminated they may
remain so. Direct discharge to surface water may be prohibited by state law
as in California. For these reasons this study is directed toward ground
water contamination.
Geothermal resources are commonly found in seisnrically active regions,
where the geologic formations are highly fractured, providing avenues for
contamination. Even in zones where geologic confinement appears adequate,
slow migration of conservatively behaving constituents may pollute water
supplies for future generations. If contamination can be predicted then mit-
igative action can be taken.
This report describes a methodology to identify potential ground water
contamination at geothermal energy development sites. The procedure was
developed to determine where significant impacts on ground water may occur as
a result of operational or accidental releases. The objective is to provide
a set of tools (e.g., graphical and analytical procedures) with data require-
ments and typical values which may be used at any site.
The methodology designed and presented here is for liquid-dominated sys-
tems. They are more abundant and conversion technologies are being developed.
Analytical methods have been selected which have minimal data requirements,
so that the methodology can be used in the early stages of site selection and
development. Extensive temporal and spatial data are not required.
This report describes the screening methodology. Geothermal systems are
described first (Section 3). Emphasis is on geothermal fluid characteristics
and modes of potential releases to the ground water. The methodology is then
presented (Section 4) with data requirements and analytical tools. Several
example cases are given to demonstrate the use of the methodology. Limita-
tions of the methodology are discussed including difficulties in obtaining re-
liable data. Typical data values for soil characteristics, adsorption coef-
icients, and numerical functions are included in the appendices.
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USES OF THE METHODOLOGY
The methodology can be used as a regulatory tool by the EPA and state
agencies and as a preliminary impact analysis tool by the geothermal develop-
ment companies and electric utilities. As a regulatory tool the methodology
can be used to identify the modes of release and locations where significant
impacts on ground water may occur. Thus, potential geothermal power plant
sites can be evaluated and recommendations for any needed mitigation measures
made before full-scale commercial development takes place. The suggested mit-
igating measures can then be tested to determine their adequacy. Another use
of the methodology by regulatory agencies might be to perform sensitivity
analyses on various site-specific parameters to identify areas where problems
might occur in developing monitoring programs.
The geothermal developer can use the methodology to predict potential
impacts on ground water at a given site using the proposed plant design. The
analysis would show where the most significant impacts may be expected. Ap-
propriate control measures can then be tested using the methodology. This
analysis may identify areas where a more detailed impact investigation is
warranted. By performing the detailed analysis only where necessary, costs
can be lowered and investigative effort can be allocated according to needs.
Prior preliminary assessment of significant impacts may also be helpful to
the developer and utility in estimating costs of the plant and in formulating
maintenance schedules.
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SECTION 3
DESCRIPTION OF GEOTHERMAL'SYSTEMS
OVERVIEW OF EXISTING SITES
Liquid-dominated geothermal resources have been found in many of the
western states and comprise a major part of the exploitable geothermal poten-
tial. This handbook has been prepared specifically to assist in the investi-
gation of contamination potential from electrical generating plants using
those resources. Only high temperature resources (>150°C) are considered.
Table 1 summarizes features of some major development sites and gives install-
ed electric generating capacity. Known Geothermal Resource Areas (KGRA) in
the United States are shown in Figure 1. KGRAs where power generation is
planned or currently conceived as possible are Nil and, Heber, and East Mesa,
California; Raft River, Idaho; Brady's Hot Springs, Nevada; Roosevelt Hot
Springs, Utah; and Valles Caldera, New Mexico. Projected geothermal develop-
ment for power generation is shown in Table 2.
Plant Design
The type of power plant which can be used in a liquid-dominated resource
area depends on the temperature of the resource, the steam/water ratio, and
the salinity. Three types are now being tested - direct flash, binary cycle,
and hybrid, although the flash type is the only type now in commercial opera-
tion (not in the U.S.). Other types based on total flow are in the experi-
mental stage (e.g., helical screw expander, impact turbine). Sketches show-
ing components of each type of plant are shown in Figure 2. The flash cycle
is most effective for high temperature resources with low to moderate salin-
ity. The fluid can be flashed at successively lower pressures to recover
additional heat. Binary cycle plants are suited for moderate to high tempera-
ture resources. The more common working fluids are isobutane and isopentane.
The major advantage of the binary type of plant is that the turbine is iso-
lated from the geothermal fluid by heat exchangers. However, dissolved
solids can result in scale buildup in the heat exchangers and a loss of heat
transfer efficiency. Hybrid plants use combined cycles to maximize heat re-
covery. Total flow turbines are being designed as an alternative to the con-
ventional types for use in high dissolved solids resource areas but they have
not yet proven feasible.
Site Characteristics
Many of the promising sites for development of geothermal power genera-
tion are in semiarid regions. Water availability is an important factor.
For example, both the Imperial Valley region of California and the Raft River
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TABLE 1. CHARACTERISTICS OF PRINCIPAL GEOTHERMAL FIELDS
Field
Larderello, Italy
The Geysers, Calif.
Matsukawa, Japan
Otake, Japan
Wairakei, N. Zealand
Broadlands, N. Zealand
Kamchatka, USSR
Cerro Prieto, Mexico
Niland, Calif.
Ahuachapan, Salvador
Hvoragerdi, Iceland
Reykjanes, Iceland
Namafjall, Iceland
Roosevelt, Utah
Beowawe, Nevada
Brady's Hot Springs, Nevada
Brigham City, Utah
Coso Hot Springs, California
Long Valley, California
Chandler, Arizona
Clear Lake, California
Fly Ranch, Nevada
Mountain Home, Idaho
Steamboat Springs, Nevada
Raft River, Idaho
Surprise Valley, California
Baca Ranch (Valles Caldera),
New Mexico
Reservoir
temp. °C
245
245
230
200+
270
280
200
300+
300+
230
260
280
280
171
243
193
204
227
227
178
186
171
194
193
149
171
260-315
Reservoir
fluid
Steam
Steam
Steam
Water
Water
Water
Water
Water
Brine
Water
Water
Brine
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Average well
depth_[m)
1,000
2,130
1,100
500
1,000
1,300
600
1,500
1,300
1,000
800
1,750
900
850
3,000
1,500
3,300
150
350
3,000
1,500
300
3,000
550
1,800
1,400
2,288
IDS
(ppm)
<1,000
<1 ,000
<1 ,000
4,000
12,000
—
3,000
•^15,000
260,000
10,000
%1 ,000
i40,000
-a, ooo
7,000
1,200
2,500
54,000
5,750
1,500
60,000
Low
Low
800
Low
<2,000
Low
<4,000
Installed
capacity (MWe)
365
608
27
13
160
—
6
75
—
30*
32 by 1980
--
3
--
—
—
—
—
—
—
—
—
—
~
~
—
—
*Under construction.
^Approximate.
Source: Jet Propulsion Lab, 1975 and Public Service Company of New Mexico, 1978
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Key to Numbered Areas
on next page
EXPLANATION
KIWMI C«otlMri»ol RMOMVM*
Figure 1. Map of known geothermal resource areas and geothermal exploration sites
(After U.S.6.S., 1971; Koenig, 1975; Geothermal Resources Council, 1976
and National Geophysical and Solar-Terrestrial Data Center, 1977).
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Key to Figure 1.
Locality
1
2
1
2
3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
4
1
2
3
4
5
6
7
1
2
3
1
2
3
Name
Alaska
..Pilgrim Springs
..Geyser Spring Basin and Okmok Caldera
Arizona
..Clifton
, .Chandler
. . Casa Grande
California
, .The Geysers
, .Sal ton Sea
..Mono-Long Valley
, .Calistoga
, .Lake City
- . Wendel-Amedee
. Coso Hot Springs
.Lassen
i .Glass Mountain
, .Sespe Hot Springs
, .Heber
. Brawl ey
i .Dunes
, .61 amis
. Randsburg
, . Beckworth Peak
Colorado
.Poncha
.Alamosa
.Valley View Hot Springs
.Mineral Hot Springs
Idaho
.Yellowstone
. Frazier
.Castle Creek
.Bruneau
.Crane Creek
.Mountain Home
.Boise
Montana
.Yellowstone
.Boulder Hot Springs
.Marysville
Nevada
. Beowawe
.Fly Ranch
.Leach Hot Springs
Locality
Name
4...,
5....
6....
7....
8....
9....
10....
11....
12....
13....
14....
15....
16....
17....
18....
19....
20....
21....
22....
Nevada (Continued)
.Steamboat Springs
.Brady-Hazen
.Stillwater-Soda Lake
.Darrough Hot Springs
.Gerlach
.Moana Springs
.Double Hot Springs
.Wabuska
.Monte Neva
.Elko Hot Springs
.Ruby Valley
.Warm Springs
.Pinto Hot Springs
.Dixie Valley
.Rye Patch
.Wilson Hot Springs
.Silver Peak
.Trego
.San Emidio Desert
New Mexico
.Baca Location No. 1
.Radium Springs
.Kilbourne Hole
.Lightning Dock
Oregon
.Breitenbush Hot Springs
.Crump Geyser
.Vale Hot Springs
.Mount Hood
.Lakeview
.Carey Hot Springs
.Klamath Falls
.Alford
.Summer Lake Hot Springs
.Belknap Foley Hot Springs
.La Granda
t/tah
.Crater Springs
.Roosevelt Hot Springs
.Cove Fort Sulphurdale
.Monroe-Joseph
.Thermo
.Lund
Washington
.Mount St. Helena
. Indian Heaven
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
10
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TABLE 2. PROJECTED U.S. GEOTHERMAL POWER PLANTS
Location
East Mesa, California
Valles Caldera, New Mexico
Roosevelt Hot Springs, Utah
Sonoma County, California
Brady's Hot Springs, Nevada
Raft River, Idaho
Nil and, California
Puna District, Hawaii
Developer
Republic Geothermal
Magma Power, Inc.
Union Oil Co. and New Mexico
Public Service Company
Phillips Petroleum Co., Utah
Power and Light and Rogers Int'l.
Northern California Power Agency
Magma Energy Company
Idaho Nat. Eng. Res. Lab
Lawrence Livermore Lab
San Diego Gas and Electric Co.
Hawaii Geothermal Project
and Hawaii Electric Light Co.
of Hilo
Size
48 MUe(Net)
10 MWe
50 MWe
52 MWe
110 MWe
10 MWe
5 MWe
10 MWe
10 MWe
5 MWe
Type
Double flash
Single flash
Hot water
Double flash
Flash (steam)
Binary cycle
Binary
Total flow
Binary
Flash
Status
Planned 1980
Planned late 1979
Planned
Planned
Planned 1981
Planned
Test plant
Test plant
Test plant
Test plant, 1980
-------
"T
I
FIRST STAGE SECOND STASE
EJECTOR I EJECTOB
BAROMET
CONDEI
—ft f=^\ ' ,
ss LJH rHi
NTER- X—J J
REJECT WATES
REINFECTION PUMP
a. Flash cycle
PRODUCTION
WELL
b. Basic isobutane cycle
KEY:
— Water
--- Steam
-.- Working fluid
c. Hybrid cycle
Figure 2. Sketches of general power plant cycles (a. after Huber et
al, 1975; b. after Chou et al, 1974; c. after TRW, 1974JT
12
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region of Idaho are irrigated agricultural areas. Surface spills could be
detrimental to crops. In the vicinity of some sites the ground water is used
for irrigation and for public drinking water supply. Subsurface injection of
spent geothermal fluid may protect surface waters, but care must be taken to
avoid contamination of water supply aquifers.
The geologic setting of several geothermal sites is described in Table 3.
The table shows that sites may be located on or near fault zones. Potential
damage from earthquakes must be considered as well as movement of geothermal
fluid or ground water along faults. Faults can act as conduits or as bar-
riers. Landslides may be triggered by earthquakes, potentially causing dam-
age to a geothermal site.
Site characteristics such as soils and type of geologic formations are
varied (see Table 3). Since the methodology was designed for general use no
site-specific data on soils were collected. Instead typical soil character-
istics such as mineral composition, size analysis, permeability, and porosity
were compiled and are included in Appendix B.
FLUID CHARACTERISTICS
Geothermal fluids are quite variable between sites and even within a
reservoir as shown by the ranges and typical values for most major and minor
components (Figure 3). Components of noncondensable gases are shown in Fig-
ure 4. Partitioning of the gases between fluid and steam phases at several
sites is presented in Table 4. For this study chemical data from wells and
springs in the U.S., Mexico, and New Zealand were collected. A summary of
the data is listed in Table 5. These data were then compared to U.S. drink-
ing water (see Table 26) and irrigation standards to determine constituent
concentrations which exceeded the standards. Table 6 lists the constituents
that exceed standards at one or more sites. Constituents which can cause
scaling or corrosion problems in the plant and thus contribute to failures
(accidental releases), including calcium carbonate, silica, and sulfate, were
added to the list.
Using the chemical data collected, worst and typical case fluid chemis-
tries were selected. It was felt that an example case should be based on one
area to insure chemical compatibility and a more realistic scenario. Geo-
thermal fluid from the Salton Sea area, California, was selected to represent
a worst case fluid chemistry. East Mesa, California with much lower total
dissolved solids, was selected as the typical case. For comparison purposes
the worst case values anywhere are shown in Tables 7 and 8.
To demonstrate the environmental consequences of spills, comparisons
were made between geothermal fluid concentrations and drinking water and
aquatic life standards. Drinking water could be affected by the heavy metal
concentrations and nitrate levels. The separate effects of constituents of
geothermal fluids on freshwater and marine aquatic life are illustrated in
Table 9. Cushman, ejt al_. (1978) investigated the bioaccumulation by fish of
elements present in geothermal fluids (Table 10). The Salton Sea area fluids
were directly toxic to the fish. For the East Mesa fluids, accumulations in
13
-------
TABLE 3.
Location
Coso Hot Springs
Calistoga
Geysers
Glass Mtn
Lake City
Lassen
Mono Basin
Long Valley
Sespe Hot Springs
Wende1-Amedee
Imperial Valley
East Meas
Heber
Brawley
Dunes
Salton Sea
GEOLOGIC SETTING OF SELECTED CALIFORNIA KNOWN
GEOTHERMAL RESOURCE AREAS
Geologic setting
Volcanic flows overlain
by Coso formation
Alluvium underlain by
Pliocene Sonoma
volcanics
Reservoir rock
Perlitic domes
Faults
E-W tension,
some strike-
slip
Basalt, andesite, N-S complex
rhyolite
Franciscan metamorphics Metamorphic rocks NW trend,
to Pleistocene lake beds
In old caldera, rhyolitic Lava flows
obsidian flows
Thick sediment with
interspersed volcanics
Basaltic then rhyolitic
lava flows and sediments
Quaternary volcanics
(Basalts and rhyolites)
Pliocene lake deposits
(5,000') near Mesozoic
granite rocks
Sediment basin,
faulted rift zone
Alluvium and
volcanics
Volcanics
Depression surrounded by Volcanics
Cenozoic volcanics
Volcanics
Mesozoic granitic rocks Granite
Lake sediment
numerous
Limited
Surprise
Valley fault
Some faulting
in area
Bordering
area
Postulated
faults
Mutau & Pine
Mountain
Fault
Faults act as
conduits
Partly cemented Numerous en
sandstone & shale echelon faults
14
-------
O.I
100,000
T0$
CHLORIDE
SODIUM
CALCIUM
MAGNESIUM
POTASSIUM
ALUMINUM
WON
BROMIDE
MANGANESE
STRONTIUM
•ORON
ZINC
1ARIUM
LITHIUM
CESIUM
FLUORIDE
LEAD
RUBIDIUM
IODINE
COPPER
SULFUR
ARSENIC
MERCURY
CHROMIUM
ANTIMONY
NICKEL
•ISMUTH
TIN
SILVER
CADMIUM
BERYLLIUM
SELENIUM
SULFATE
SILICA
AMMONIUM
NITRATE -N
coa
H,S
Key:
measured range
majority of data
if no wide bar - insufficient
data
Figure 3. Ranges of chemical constituent concentrations in geothermal fluids
(Hartley, 1978).
-------
CH4
CO 2
n2
°2
H\
S02
Ar
NH3
CO
H*
A>
Hg
.001
1 1 1 1
1
.01 PERCENT OF 0.1 NONCONDENSIBLE 1 GASES
1111 till
10 100
PPM WHEN NONCONDENSIBLES EQUAL 5%
1 i i i 1 1 1 1 ii in
0.1
PPM WHEN
10 100
tooo
OF TOTAL GASES
10,000
Mil 1 1 1 1 Mill 1 II TTITTT T 1 — TTH
1 10 too
NONCONDENSIklES EQUAL 0.3% OF TOTAL GASES
n 1 1 - T
1000
Note: Base graph shows individual gases as ranges of percent of total
noncondensible gases. Lower scales convert these values to parts
per million (ppm) of total (noncondensible plus condensible)
gases when noncondensibles equal the specified percentages of
total gases.
Figure 4. Noncondensible gases in geothermal fluids
(Hartley, 1978).
16
-------
TABLE 4. CONCENTRATIONS OF VARIOUS CONSTITUENTS IN GEOTHERMAL NONCONDENSIBLE
GASES, STEAM CONDENSATES AND BRINE TO SHOW PARTITIONING
BETWEEN PHASES
Constituents 1
Non-condenslble gases
H2S (ppoi) va.
Hg. (ng/0
NH3 (ug/l>
RnlpCI/ )
At (|ig/l>
Steam condensatt
H2S (ng/l)
NHj (mg/l)
Hg (ug/l)
B (ng/l)
As (»g/l)
Flashed brine
NaCl (I)
H2S (mg/l)
NHj (»g/l)
Hg (yg/0
B (mg/l)
As (ng/t)
Ratio: Noncondenslbles (I)
Sttan (kgj
Brlna flow (kg/hr)
Steam flow (kg/hr)
TMipiraturt (*c) (Incoming)
Date sampled
The Geysers Raft River
28.400-57.400 215
1.5-5.8 0.039
--
3.820-27.800*
<0.003
49-225 0.66
157-818 1.8
2.8-10 0.13
6.4-76 <0.1
0.0014-0.092 0.012
0.13
0.1
0.27
0.022
0.13
0.028
1.96-4.46 0.2S
..
..
--
10/75, 5/76 7/76
Geathermal sites
VernOHon Say East Mesa East Mesa
0.5-S 580-630 380
<0.001 2.3-3.6 3.3
130 108
10-40 280-305 1095-1262
..
2.8 0.09
98 15.5
14.4 1.45
<0.1
--
10.4 1.77
0.33 0.07
90 6.5 1.4
0.007 0.003 <0.001
40 9.8
0.045
1.6" 17.7 4.54
10.600
860
151
5/77 3/77 9/77
Niland
1390-1620
0.8-1.6
45
830-1150
--
5.5
331
2.20
5.9
-
16.5
--
394
0.020
340
--
8.8
109,000
13.600
165
5/77
Niland Heber Cerro Prieto
4670 — 15.000-20,000
1.8 <0.03 0.3-0.4
17.8
535-644 3.200-4.300
<0.016
9.5 -- 36-71
360 — 88-163
3.12 3.9 3.8-5.4
<0.1 -.0.1
0.006
2.27
0.16
400 -- 1?7
0.11 0.44 0.049
19
10.0 -- 0.50-2.3
9.27 -- 9.7
7.500 1.5B»106
7.37»105
204 161
9/77 3/77 5/76
Radon DaU from tht Geysm by Stoker and Kruger, 1973 and by Anspaugh, !!£]_.. 1977.
"No steam Mai produced. This 1s tht ratio of noncondenslblc gat to brine In I/kg.
-------
TABLE 5. SUMMARY OF CHEMICAL ANALYSES OF GEOTHERMAL FLUID BY GEOGRAPHICAL AREAS
except for pH and specific conductivity)
00
Parameter
IDS
Sp. Cond., umhos/cm
pH , units
Aluminum
Ammon i a
Antimony
Arsenic
Barium
Bicarbonate
Boron
Bromide
Cadmium
Calcium
Carbonate
Carbon dioxide
Cesium
Chloride
Chromium
Copper
Fluoride
Hydrogen sulfide
Iodide
Iron
Lead
Lithium
Magnesium
Manganese
Nickel
Nitrate
States
New
Mexico
median
1,112.0
550.0
7.7
0.14
0.1
0.032
0.0
163.0
0.39
0.62
37.6
0.0
155.0
0.006
3.0
O.D23
0.14
0.08
0.3
6.9
0.01
Eastern
Idaho
average
3,385
4,398
310
91
2.8
5.8
1,475
3.2
80.6
2.6
West and
Central
Idaho
average
320
763
127
8
22
14
7.9
2.3
0.6
Nevada
average
1,850
14
177
126
20
153
182
37
Washington
average
82
385
1.3
22.2
0.13
K G R A ' S
Sal ton Sea,
CA
average
207,639
63
424
3
10
3B6
1,663
369
76
23,746
20
133,991
4.7
3.2
10-30
14.5
1,895
102
198
481
1,026
275
East Mesa,
CA
average
4,422
12,082
0.03
12.6
1.7
0.15
2.9
389
4.3
0.24
<0.02
165
0.4
0.75
2,760
<0.01
<0.10
L_ 1-9
1.2
0.4
9.2
4.Z
0.28
0.11
0.19
Heber,
CA
average
14,493
9
4
20
5.4
935
4
8,212
0.4
1.3
10
0.8
4.2
7.9
1.3
Foreign Sites
]erro Pneto,
Mexico
average
17,000
362
2
13,378
<0.05
0.005
0.005
0.002
New
Zealand
average
3.8
70
3.1
4
8.2
1.1
1,354
1.3
6.6
9
0.5
1
7.5
0.20
0.001
0.7
(continued)
-------
TABLE 5 (continued)
Parameter
Phosphate
Potassium
Rubidium
Selenium
Silica
Silver
Sodium
Strontium
Sulfate
Sulfiae
Tin
Zinc
Scandium
Tungsten
Uranium
Molybdenum
Titanium
Mercury
Tantalium
.Cobalt
Beryllium
Bismuth
Niobium
Germanium
Vanadium
States
New
Mexico
median
0.05
10.0
0.0
50.0
167.0
81.0
0.0
0.026
Eastern
Idaho
average
171.5
56
865
167
lest and
Central
Idaho
average
66
75
35
Nevada
average
22
174
133.5
228
48
0.04
72
0.18
5.4
ashington
average
25.8
116
353
0.37
K G R A ' S
alton Sea,
CA
average
13,595
110
217
1
51,268
454
119
25
23
672
East Mesa,
CA
average
<0.1
177
0.5
207
0.01
1,619
83
125
1.5
<0.01
<0.02
<0.1
<0.005
<0.1
0.006
0.13
0.03
<0.02
0.6
0.4
<0.1
0.005
Heber,
CA
average
238
222
4,614
37
130
<4
Foreign sites
erro Prieto,
Mexico
average
0.004
6,234-5/7
0.4
New
Zealand
average
130
1.3
628
842
37
1.5
Note: Data were compiled from many sources, including unpublished data, and are included in the list of references.
Blank spaces indicate that no data were available.
-------
TABLE 6. CHEMICAL CONSTITUENTS OF INTEREST
IN GEOTHERMAL FLUIDS
Constituent
TDS
Aluminum
Ammonia
Arsenic
Barium
Boron
Cadmium
Chloride
Chromium
Copper
Fluoride
Copper
H2S
Iron
Lead
Lithium
Magnesium
Manganese
Selenium
Silver
Zinc
Mercury
Molybdenum
Sodium
Nitrate
Location of potential problems
Average
val ue exceeds
standard everywhere but Idaho.
Problem* in CA sites.
Problem
Problem
Problem
Problem
Problem
in
in
in
for
in
CA sites.
Salton Sea,
East Mesa, and Nevada.
CA and Nevada.
irrigation
East Mesa,
Average value exceeds
and central Idaho. New
Problem
Problem
Probl em
Problem
Problem
Problem
Problem
Problem
Problem
Problem
Problem
Problem
Problem
in
at
at
at
at
at
at
at
some areas
Salton Sea
Salton Sea
Salton Sea
Niland.
all sites.
•
but only place with data.
standard at all places but west
Mexico and Nevada.
although limited data available.
and Niland.
and sites in New Mexico and Idaho.
and Niland.
all sites with data.
Salton Sea,
only at Salton
at
at
in
in
CA sites.
East Mesa,
CA sites.
CA sites.
East Mesa, and Niland.
Sea.
very little data.
Data for East Mesa exceeds standard, no data anywhere else.
Data for
Harmful
Problem
Nevada exceeds irrigation standards.
for
in
irrigation
uses at most sites.
some CA sites, Idaho, and New Mexico.
A potential problem exists whenever a drinking water or irrigation standard
was exceeded.
20
-------
TABLE 7. GEOTHERMAL FLUID CONCENTRATIONS FOR PROBLEM CONSTITUENTS (mg/A)
Constituent
Aluminum
Ammon i a
Arsenic
Barium
Boron
Cadmium*
Chloride
Chromium
Copper
Fluoride
H2S
Iron
Lead
Lithium
Magnesium
Manganese
Nitrate
Selenium*
Silver
Zinc
Mercury
Molybdenum*
Sodium
TDS
Temperature, °C
PH
Pressure, psig
Worst case,
Sal ton Sea
450
570
15
1,100
745
<0.02
210,700
No data
10
18
No data
3,416
200
400
2,225
4,000
1,050
1.8
1.0
970
0.014
0.005
78,000
387,500
188-332
3.9-7.5
220-445
Worst case
at any site
450
570
40
1,100
745
<0.02
210,700
<0.05**
10
24
30
3,416
200
400
2,225
4,000
1,050
1.8
1.0
970
0.014
0.005
78,000
387,500
-
-
-
Typical case,
East Mesa
0.03
12.6
0.15
2.9
4.3
<0.02
2,760
No data
<0.1
1.9
No data
1.2
5
9.2
4.2
0.28
0.19
0.5
0.01
0.02
0.006
0.005
1,619
4,422
309-399
5.4-7.1
^60
Lowest
at any site
0.0
0.1
0.025
0.15
0.0
<0.02
0.0
<0.5
0.0
0.0
No data
0.0
0.0
0.0
0.0
0.02
0.0
0.0
0.01
0.006
0.002
0.005
0.4
10
-
-
-
*Data available only at East Mesa.
**Data available at Cerro Prieto, Mexico.
-------
TABLE 8. GEOTHERMAL FLUID CONCENTRATIONS OF ADDITIONAL CONSTITUENTS
Constituent
Bicarbonate
Bromide
Calcium*
Carbonate*
Cesium
Chromium***
Iodide
Nickel
Phosphate
Potassium
Rubidium
Silica*
Strontium ttt
Sulfate*
Sulfide
Tin
Uranium
Tungsten
Worse case,,
Sal ton Sea
6,900
146
40,000
<.01f
22
0.16+
29,900
168
625
740
621
30
23
(only 1
value)
<4ttt
150ft
Worse case
at any site
6,900
720
40,000
175
340
22
0.16+
29,900
174
625
740
5,190
1,052
180
<4ttt
150tt
Typical case,
East Mesa
389
0.31
165
4
0.75
<0.01
no data
0.11
<0.1
177
40ft
207
83
125
1.5
<0.01
0.02f+
<0.1
Lowest
at any site
0.0
0.0
0.1
0.0
0.14
0.0
0.0
0.0
40if
0.1
0.1
0.0
0.3
<0.01
0.02tf
<0.1
Constituents of interest for corrosion and scaling problems.
Data only at East Mesa.
•i-i.
Data at Nevada.
ftData for Heber only.
22
-------
TABLE 9. AQUATIC LIFE CRITERIA
Constituent
Ammonia (un-ionized)
Arsenic
Aluminum
Barium
Beryllium
Boron
Cadmium
Chromium
Chlorine
Copper
Cyanide
Iron
Fluoride
Lead
Manganese
Mercury
Nickel
Nitrates
Phosphorus
Selenium
Silver
Hydrogen sulfide
Zinc
Total dissolved
solids (TDS)
Criteria level
for fresh water
0.02 mg/1
0.11 mg/1
(soft water)
1.1 mg/1
(hard water)
.004 - .0004 mg/1
(soft water)
.012 - .0012 mg/1
(hard water)
0.1 mg/1
0.003 mg/1
0.1 96-hr LCso
0.005 mg/1
1.0 mg/1
0.01 96-hr LCso
(sol. lead)
0.0005 mg/1
0.01 96-hr LC50
0.01 96-hr LCso
0.002 mg/1
0.01 96-hr LCso
Criteria level
for marine water
0.05 mg/1
1.5 mg/1
0.005 mg/1
0.003 mg/1
0.05 mg/1
0.01 mg/1
1.5 mg/1
0.05 mg/1
0.1 mg/1
0.0001 mg/1
0.1 mg/1
0.0001 mg/1 P
0.01 96-hr LCso
0.01 96-hr LCso
0.005 mg/1
Remarks
Toxicity pH dependent
Daphnia impaired by 4.3 mg/1
Toxcity level <50 mg/1
Toxcity hardness dependent
Toxic to minnows at 19,000 mg/1
Toxic at <0.5 mg/1 all tests
Toxicity varies with pH and
oxidation state
Toxicity alkalinity dependent
Toxicity variable
Salmonids most sensitive fish
Not a problem in fresh water
High bio-accumulation and thus
affects human food
Toxicity to fish >900 mg/1
Eutrophication factor
Toxic at >2.5 mg/1
Toxicity dependent on compound
Toxic at very low concentrations
Toxicity dependent on temperature,
dissolved oxygen, hardness
Osmotic effects - variable
Source: U.S. EPA, 1977 and Federal Water Pollution Control Administration, 1968
23
-------
TABLE 10. RELATIVE HAZARDS OF GEOTHERMAL FLUIDS
El ement
As
B
Ba
Br
Cr
Cu
Fe
H9
Mn
Ni
Pb
Rb
Ti
In
TCa
(mg/1)
0.022
0.069
5.3
0.18
0.005
0.0006
0.2
0.0001
0.35
0.03
0.007
14.0
2.0
0.01
BF for
fish
333b
lc
4b
417b
4,000b
200b
100b
l,000b
660b
100b
300b
2,000b
l,000b
8,500b
DWS
(mg/D
0.05d
le
ld
3.0f
0.05d
O.lf
0.39
0.002d
0.059
0.05f
0.05d
5f
O.lf
59
TBC
(33DWS/BF)
(mg/1 )
0.005
33
8.25
0.24
0.0004
0.02
0.10
0.0001
0.003
0.02
0.006
0.08
0.003
0.02
Ratios
Sal ton Sea
Conc./TC
818
1,285
247
ge?
4
20,000
20,335
170
13,606
6
34,000
14
-
115,500
Cone. /TBC
_
-
-
-
-
-
-
-
.
,
.
-
-
-
East Mesa
Conc./TC
7
6.6
.6
1.8
4
166
6.5
60
.86
4
771
3
-
2
Cone. /TBC
.
-
.4
1.4
-
-
-
-
100
-
-
-
-
-
Sal ton
Sea
Conc/DWS
360
887
1,309
58
0.4
600
13,557
8.5
95,240
3.8
34,000
40
-
231
East
Mesa
Conc/DWS
3.2
4.6
3.1
0.11
0.4
0.1
4.3
3
6
2.4
108
8.6
-
.004
aCushman, Hildebrand, Strand, and Anderson (ig77b)
Thompson, et al_. (1972)
"•Thompson, et al_. (1976)
federal Register (1976)
eFederal Water Pollution Control Administration (1968)
fDawson (1974)
Vs.P.H.S. (1962)
Source: After Cushman, et al., 1977a
Note:
BF = Bioaccumulation factor
DWS » Drinking water standard
TC » Toxic concentration to fish
TBC = Threshold bioaccumulation concentration
24
-------
fish of barium, bromide and manganese could occur. This study does not give
hazards for specific kinds of fish and thus is approximate but it does indi-
cate the risk of indiscriminate discharge of geothermal fluids.
Some states, including California, have prohibited discharge of geother-
mal fluids to surface water because of the toxicity of some constituents to
aquatic life and agricultural crops. An accidental release to irrigation
water could result in crop-damaging concentrations of boron, heavy metals,
and total dissolved solids (Table 11).
TYPES OF FLUID RELEASES
Failure Modes
Operating experience in the U.S. with geothermal power plants is limited
to 15 years with the steam-driven power plants at The Geysers, California.
Failure modes have been derived from that experience and from experience with
similar power plant components. A general summary of types of failures and
probable causes is shown in Table 12. A review of the known geothermal plant
failures in California (Table 13) shows that all the possible types have oc-
curred. A study on energy-related accidents made by the EPA (1977) consid-
ered a well blowout to be a potential major accident. A summary of known geo-
thermal well blowouts is given in Table 14. This summary suggests that the
probability of blowouts may be significant. Pipe failures have been investi-
gated in more detail although the probability estimates should be considered
preliminary only.
Pipe Failures
Pipe failures include pressure-induced rupture due to scale blockage,
and leakage due to corrosion, abrasion, or improper connections. Table 15
summarizes the plant operating history for several foreign plants using
liquid-dominated resources to show scale and corrosion problems. In review-
ing data from geothermal plants one should realize that generally low grade
materials are used (Yasutake and Hirashima, 1970; Bechtel, 1976; To!ivia, et^
al., 1970). Listed below are examples of materials used:
Components Materials
• Piping mild steel, high chromium alloy,
carbon steel
• Well casing carbon steel
• Turbine titanium alloy, low chromium alloy
• Heat exchanger tubes titanium alloy
t Condenser 304 stainless steel and epoxy-coated
carbon steel
25
-------
TABLE 11. AGRICULTURE USE CRITERIA FOR CONSTITUENTS IN
GEOTHERMAL FLUIDS (EPA, 1976)
Constituent
Crop
irrigation
Remarks
Ammonia
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nitrates
Phosphorus
Selenium
Silver
Hydrogen sulfide
Zinc
Total dissolved
solids
Sodium
0.1 mg/1
0.001 to
0.5 mg/1
0.75 mg/1
0.2 mg/1 suggested
for acidophilic
crops
500-1,500 mg/1
suggested
No criteria suggested.
Toxicity to some crops at 0.5 mg/1;
no livestock criteria suggested.
No criteria suggested.
Crop toxicity acidity dependent; no
livestock criteria suggested.
Toxic to sensitive plants, e.g.,
citrus at <1 mg/1; no livestock
criteria suggested.
Reduced crop yields at 1 mg/1; crop
accumulation related to zinc concen-
trations; no livestock criteria
suggested.
No criteria suggested.
Toxicity for plants begins at 0.1
mg/1; no livestock criteria suggested.
No criteria suggested.
Toxic to plants at <30 mg/1; no
criteria suggested.
Toxicity to plants increases with
decreasing pH; no livestock criteria
suggested.
Bioaccumulation, but no criteria
suggested.
No criteria suggested; nutrient for
crops.
No criteria suggested; nutrient for
crops.
No criteria suggested.
No criteria suggested.
No criteria suggested.
Toxic to some crops at 0.4 to 25 mg/1;
may cause iron deficiency in plants;
no livestock criteria suggested.
Osmotic effects in plants; variable
harm to both plants and animals.
Toxic to certain plants; ratio to
other cations important; no criteria
given.
26
-------
TABLE 12. FAILURE MODES AND MECHANISMS OF HYDROTHERMAL SYSTEM COMPONENTS
Component
Well casings
Val ves
Pipes
New well
Injection well
Storage ponds
Failure mode
Blowout, crack
Jammed in open or
close position
Leak, rupture
Blowout
Blowout
Overflow
Leak
Estimate of
relative
probability
Low
Moderate
High
Moderate low
Low
Moderate
Moderate
Mechanisms of failures
Stress corrosion, erosion,
plugging up of casing
perforations and geological
formations
Scaling, plugging
Scaling
Pitting and erosion
(elbows)
Embrittlement, then
stress corrosion
Clogging, loss of control
of well
Plugging of perforations,
injection formation
Spill
Break in 1 iner
Factors responsible
High HgS, temperature,
pressure, and IDS
IDS
IDS, H2S
Pressure at elbows,
particulates
High IDS, high pressure
Particulates, bacteria,
IDS, aeration
Flow rates exceed capacity
Acidity, differential
settling
ro
-------
TABLE 13. SUMMARY OF HISTORICAL GEOTHERMAL FAILURES IN CALIFORNIA
Type
Surface
Surface
Surface
Surface
Surface
Surface
Surface
Surface
Surface
At depth
Area
Niland
East Mesa
Heber
Brawley
Casa Diablo
The Geysers
The Geysers
The Geysers
The Geysers
Niland
Date
6/16/74
12/4/76
4/29/76
1/1G/76
78?
9/10/71
9/9/74
2/28/75
6/6/75
76?
Break location
Reinjection pipe,
1/4 x 3" hole
Wellhead
Injection wellhead
Separator line
Well
Cooling tower pipe
Steam condensate pipe
Condensate pipe
Condensate pipe
Casing in well
Spill amount
1 ,000 gal .
16,000 gal.*
1,000 gal.*
Small amount went
to lined pit
Unknown
%20,000 gal. to
Big Sulfur Creek
-v4,500 gal.
^10,000 gal.
'vS.OOO gal .
Unknown
Likely cause
Crack in pipe
Jammed valve, 3/4"
open for four hours
Unknown
Plugged line for 2-3
min.
Blowout during test
Pipe failure
Mechanical failure
Break - unknown cause
Break - unknown cause
Pressure, had no
production liner
ro
CO
Water was first dumped to a lined sump pit then reinjected later.
"c = approximate.
Source: California Department of Fish and Game, 1976 and California Regional Water
Quality Control Board, 1978
-------
TABLE 14. KNOWN WELL BLOWOUTS
Location
Number of blowouts/
number of wells
Time
period
The Geysers, CA
Beowawe, Nevada
Cesano and Lardarello,
Italy
Cerro Prieto, Mexico
Wairakei, New Zealand
Dieng, Java
4/100 (4%)
3/11 (due to vandalism)
Several
2/40 (5%)
3/100 (3%)
1
1957-1978
1959-1965
1961,1972
1978
Source: Sung, e_t ^1_., 1978; TRW, 1976; and Geothermal Resources
Council, 1978
-------
TABLE 15. HISTORY OF SELECTED GEOTHERMAL PLANTS
CO
o
Location
Otake, Japan
Matsukawa, Japan
Kamchatka, USSR
Otake, Japan
Niland test plant
Plant type
Single cycle
Single cycle
Single cycle
Single cycle
Single cycle
Hours
of operation
8,700
Approx. 8,700
Unknown
5,000
51 ,900
700
Damage
None in plant
Scale, 20% decrease
in flow
Collapsed well
casing
None
10 kg SiOp, FeS
sludge
SiOg scale
3-4 mm Fe oxide
scale +Si02
.1-.2 mm rust
1 mm S tray, cracks
Some concrete
corrosion, <1 mmS on
pipe, blisters on
coating
Si02+CaC03 scale
Location
of damage
Pipeline flow cut
in half by scale
Pipes
Well was killed with
150,000 tons of cold
water
—
Receiving tank
Strainer in steam
pipe
Turbine
Turbine blades
Condenser
Hot water tank
Pipes
Source: Yasutake and Hirashima, 1970, and Uchiyama and Matsuura, 1970
Note: Fluid releases may not have occurred at these plants as a result of the damage.
-------
t Valves carbon steel
• Hot water tank stainless steel, chromium-molybdenum
steel
The nature of the brine may make corrosion a serious problem at geother-
mal power plants. Corrosion rates are site- and material-dependent. In gen-
eral, factors which influence corrosion rates include pH, dissolved oxygen,
chloride, and HpS concentrations and temperature. The variability of rates
between selected sites is shown in Figure 5.
Corrosion data from geothermal fluid testing and plant experience were
obtained from a literature survey. The tests were conducted in actual geo-
thermal fluids or in specified sodium chloride solutions. Table 16 gives se-
lected test results for actual geothermal fluids. Using these corrosion rates
and typical pipe sizes, comparative estimates of failure rates due to uniform
corrosion and pitting were calculated (Table 17).
These calculated rates are not exact rates but do show relative magni-
tudes. Failure is a stochastic process. The probability of failure in a long
section of a given pipe is likely to be greater than in a very short section.
Failure probability is higher in sections of pipe where the fluid impacts on
it directly as in pipe elbows and tees. Higher velocities may result in
higher failure rates. The calculated failure rates may also be low since
other mechanisms such as erosion-corrosion, fatigue and stress corrosion
cracking were not considered. Uniform corrosion tends to decrease the endur-
ance limit as shown in Figure 6. Methods to minimize corrosion are listed in
Table 18. Geothermal corrosion research is currently being conducted by se-
veral investigators. Knowledge of control mechanisms is thus expected to in-
crease.
Valve Failures
Valves can cause failure and allow fluid release by jamming in either the
open or closed positions. Opening or closing too quickly may cause excessive
impact pressure and rupture. Failure to open may cause overpressures and lead
to pipe or valve rupture. The failure of valves to close may cause spills
such as occurred at the East Mesa site in California (see Table 13). The
probability of a valve rupturing was estimated between 10"7 and 10~9 failures/
hr for nuclear plants (U.S. AEC, 1975). Failure of a valve to open or operate
was estimated as 1Q-6 failures/hr (U.S. AEC, 1975). Valves in contact with
geothermal fluid could be expected to jam more often because of scale buildup.
A comparison of reactor cooling water and typical geothermal fluid is pre-
sented in Table 19. The differences in water chemistries suggest that the
probability of valve failure is perhaps an order of magniture higher for geo-
thermal fluids, although detailed valve specifications were not available from
which to make a more exact estimate.
Pond Leaks
Several types of ponds may be located at a geothermal site such as tempo-
rary storage ponds to contain fluid while repairs are being made, settling
31
-------
70
Sal ton
Sea, CA
10 -
(O
01
Q.
O)
c
O
t/>
£
O
O)
8 -
6 -
4 -
2 -
Matsukawa,
Japan
Iceland •
(condensate)
New Zealand •
(condensate)
Cerro Prieto,
Mexico
Russia
New Zealand
PH
*1 mil = 0.0254 mm.
Figure 5. Corrosion rate of 1010 mild steel in
geothermal fluids of varying pH
(after Bechtel, 1976).
32
-------
TABLE 16. CORROSION RATES OF MATERIALS IN GEOTHERMAL FLUIDS
Material
Aluminum
Aluminum
Carbon "steel
Carbon steel pipeline
Low carbon steel
Epoxy coated carbon steel
Deoxidized copper
Deoxidized copper
1 Cr-1 Ho-. 25V
1 Cr-1. 25 Ho-. 25V
12 Cr steel
12 Cr steel
High cr alloy
12 Cr-XAl steel
12 Cr-.2Al
12 Cr-1 Mo-lW
15 Cr-1. 7 Mo+
Mild steel
Naval brass
Ni alloy
3.5 Ni-1.75 Cr-.5 Mo-. 12
Stainless steel
18-8 Stainless steel
304 Stainless steel
410 Stainless steel
Type of
fluid/location
Aerated steam, S CP
Condensate, H CP
Aerated steam, S CP
Steam M
Condensate, H CP
Condensate ' M
Aerated steam, S CP
Condensate, H CP
Aerated steam, S CP
Steam M
Aerated steam, S CP
Condensate, H CP
Concentrated brine SS
Steam H
Aerated steam, S CP
Aerated steam, S CP
Aerated steam, S CP
Concentrated brine SS
Condensate, H CP
Concentrated brine SS
Aerated steam, S CP
Concentrated brine SS
Condensate, L CP
Condensate M
Steam in turbine M
Uniform
corrosion rate
mm/yr
.48
.44
0.636
.66
.0084
1.11
0.64
.5
.623
.14
.09
.125
.049
.16
.23
.023
.22
<.02S
.52
<.025
.0008
.0212
.0213
Maximum
pitting rate,
mm/yr
2.9
3.65
1.7
.97
1.6
1.2
1.75
0.7
Sources: Tolivia, et_ aK , 1970, and Yasutake and Hirashima, 1970
Notes: CP « Cerro Prieto, Mexico; M = Matsukawa, Japan; SS = Salton Sea;
H • velocity of 0.5 m/sec; L * velocity of 0.02 m/sec;
S « velocity of <140 m/sec.
33
-------
TABLE 17. CALCULATED FAILURE RATES FOR PIPES
Well to separator
Material Diameter, cm
Low carbon steel
High Cr
12 Cr steel
Ni alloy
18-8 Stainless steel
Steam pipes
Aluminum
Deoxidized copper
15 Cr-1.7 Mo
12 Cr steel
114.3
86.4
76.2
61.
40.6
20.3
114.3
61.
114.3
61.
114.3
61.
114.3
86.4
76.2
61.
40.6
20.3
76.2
76.2
76.2
76.2
Wall
thickness, mm
19.05
15.9
12.7
17.4
9.5
8.2
19.05
17.4
19.05
17.4
19.05
17.4
19.05
15.9
12.7
17.4
9.5
8.2
12.7
12.7
12.7
12.7
Uniform
corrosion
rate mm/yr
.66
.66
.66
.66
.66
.66
.125
.125
.09
.09
.025
.025
.0008
.0008
.0008
.0008
.0008
.0008
.095
1.11
.023
.14
Maximum
Pitting
rate mm/yr
1.75
1.75
1.75
1.75
1.75
1.75
.97
.97
2.9
1.2
1.7
Corrosion*
failure rate
failures/hr
4 x 10"6
4.7 x 10"6
5.9 x 10'6
4.3 x 10"6
7.9 x 10'6
9.2 x 10"6
7.5 x 10"7
8.2 x 10"7
5.4 x 10"7
5.9 x 10'7
1.5 x 10~7
1.6 x 10"7
4.8 x 10'9
5.7 x 10"9
7.2 x 10"9
5.2 x 10"9
9.6 x 10"9
1.1 x 10"8
8.5 x 10"7
9.9 x 10"6
2.1 x 10"7
1.3 x 10'6
Pitting**
failure ate
failures/hr
1.0 x 10'5
1.3 x 10'5
1.6 x 10"5
1.1 x 10"5
2.1 x 10'5
2.4 x 10"5
5.8 x 10"6
6.4 x 10~6
2.6 x 10"5
1 .1 x 10'5
1.5 x 10"5
•Calculated from wall thickness/uniform corrosion rate » S,
1/S/hrs per year = failures/hr.
"Same except used pitting rate instead of corrosion rate.
Note: See Table 16 for type of fluid used In tests
34
-------
3.5Ni-l3/4Cr-0.5Mo-O.IV
ICr-IMo-'/4V
Ol2Cr
!2Cr-IMo-IW
Cr-l.7Mo
0 0.01 0.02 0.03 0.04 0.05
General Corrosion Rate (mm/year)
Note: Tests were made in low velocity
nonaerated steam
Figure 6. Effect of corrosion on fatigue for different
alloys (after Tolivia, Hoashi, and
Miyazaki, 1970).
35
-------
TABLE 18. METHODS TO CONTROL CORROSION IN GEOTHERMAL FACILITIES
CO
Equipment type
Well and wellhead
Well and wellhead
Well casing, external
Turbine blades
Pipelines
Condensers, ejectors
and cooling towers
Structures
Packings
Electronics
Pipelines in
standby mode
Cause of corrosion
Acidic brines
High velocity
Aerated and/or acidic
waters
Hydrogen sulfide
Acidic brines
H2S and 02
Spray
Air and brine
Hydrogen sulfide
Air and brine
Type of
corrosion
Surface
Erosion
Surface
Stress and
fatigue
Surface
Surface
Surface
Surface
Tarnish
Surface
Control methods
Use carbon steels
Streamline conduits
Cement suited for
geothermal applications
Use low alloy steels
Use carbon steels
Minimize 02 leakage, use
H2S04 resistant materials,
neutralization
Use corrosion resistant
materials
Minimize leakage, use
resistant materials
Exclude H2S, use
resistant materials
Exclude air
Source: After Jet Propulsion Lab, 1975
-------
TABLE 19. CHARACTERISTICS OF NUCLEAR COOLING WATER AND
GEOTHERMAL FLUIDS
Constituent
TDS, ppm
Cl 5 ppm
F, ppm
DO, ppm
at 25°C
Additives
(Li, K, or NH3)
Max Boric Acid, ppm
PH
Typical range of
geothermal fluid*
1,000-10,000
100-1,000
1-10
--
--
.4-5 as B
2_io***
Typical range of fluids
in nuclear power plant
Primary
coolant**
.5
0-0.15
0-0.1
<0.1
<25
<9800
4.5-10.2
Reactor coolant
makeup water**
<0.5
0-0.15
0-0.1
nondeaerated
--
--
6-8
*Hartley, 1978
**Considine, 1974
***Tsai, et aK, in press
37
-------
ponds for injection pretreatment, or ponds under the piping system to contain
spilled fluid. Leakage can occur from overflow or seepage through the bottom.
Overflow leaks can be minimized by proper sizing of the pond to contain, for
example, one or two day's production flow rate of fluid plus the precipitation
amount from a given frequency storm (e.g., 1 in 10 year storm). Ponds should
meet appropriate regulations for disposal of hazardous waste (40 CFR 250).
Ponds should be lined with clay or other impermeable material to minimize
leakage. Some leakage may still occur, so the ground water flow regime and
distance to nearby surface waters should be considered before siting the pond.
38
-------
SECTION 4
DESCRIPTION OF METHODOLOGY
GENERAL PROCEDURE
This chapter comprises the "user's manual" for the methodology which pro-
vides a framework to identify potential ground water contamination problems
resulting from geothermal energy development at specific sites. The methodol-
ogy is shown schematically in Figure 7 and includes the following steps:
• Determine environmental concerns
- Are there usable aquifers in power plant site area?
- Are aquifers interconnected?
- What are present and potential uses?
- What are concentrations of geothermal fluid
constituents?
- Do geothermal fluid concentrations exceed water
quality standards?
- Are geothermal fluids capable of mobilizing
pollutants from the soil?
• Determine release potential
- Where may releases occur?
- What is probability of a release to surface or
ground water?
- How much fluid may be released?
- What are physical and chemical characteristics of
the released fluid?
• Identify potential ground water contamination
- Can released geothermal fluid migrate to aquifers?
39
-------
-s
-~J
•
CO
(D
T>
n>
c+
o
CL
O
wJ
o
to
Brine Release not < Nijor Threat to Groundmter Resource
-------
- Are dilution and attenuation mechanisms adequate to
prevent significant levels of contamination?
• Evaluate significance of contamination
The procedure applies a logical sequence of questions and analytical tech-
niques to problem areas to identify those of most concern. The analysis moves
to the next step only if a potential problem is identified. Each step has a
set of associated specific methods. Data requirements, pertinent analytical
tools, and examples for each step are discussed in the following sections.
ENVIRONMENTAL CONCERNS
The first part of the methodology is to identify the environmental con-
cerns by answering the following questions outlined earlier:
• Are there usable aquifers in power plant site area?
• Are aquifers interconnected?
• What are present and potential uses of aquifers?
• What are concentrations of geothermal fluid
constituents?
• Do geothermal fluid concentrations exceed water
quality standards?
• Are geothermal fluids capable of mobilizing pollutants
from the soil?
The first step is to locate all usable aquifers in the site area and to
evaluate the extent of interconnect!'vity between the aquifers. Aquifers may
be located from geologic maps and well logs of the area. Interconnections may
be indicated or identified from water level data, pumping records, and knowl-
edge of faults. The next step is to identify present uses and to estimate
potential future uses of the aquifers. Existing uses can be determined by
examination of water supply reports in the area or well permits. These are
available from those states or local water resource agencies that require per-
mits. In the Salton Sea area of southern California, for example, the aqui-
fers are not used as drinking water sources at the present time but contamina-
tion of shallow ground water and surface spills could pose a threat to agri-
culture.
If the aquifers are used, the next step is to examine the concentrations
of constituents in the geothermal fluid. The geothermal fluid concentrations
at the site should be compared with appropriate water quality standards to
determine if any standards are exceeded. (See Table 9 for aquatic life lim-
its, Table 26 for drinking water standards, and Table 11 for agricultural use
limits.)
41
-------
Another concern is the possibility of spilled geothermal fluid mobilizing
heavy metals present in the soil. Soil analyses can be used to identify con-
stituents which can be desorbed or exchanged at the given pH range of the geo-
thermal fluid. The low pH associated with some geothermal fluids can mobilize
several heavy metals.
RELEASE POTENTIAL
The next major section of the methodology is to determine the release
potential if the user has identified possible environmental concerns should a
release of geothermal fluid occur. The steps are to determine:
• Where may releases occur?
• What is probability of a release to surface or ground water?
• How much fluid may be released?
t What are physical and chemical characteristics of the
released fluid?
Release Points
The steps for locating potential releases are:
• Examine the power plant schematic in light of the potential
release diagram (Figure 8)
• Locate places where releases are possible
t Identify likely failure modes
• Compare geothermal fluid at site with threshold values
• Check for mitigating features in plant design to prevent
failure
Potential release points include:
• Pipes, flow lines
• Valves, separators, heat exchangers
• Production wells, and
• Injection wells.
The specific locations where accidental or operational releases may
occur depend on the type and size of power plants and the fluid characteris-
tics. Figure 8 presents a general diagram to locate potential releases. The
diagram highlights the conditions which may lead to well blowouts and surface
42
-------
START
Corrosion- prone casing of production wells ) Casing leak
*high pressure
Elbows •—> P1P6 break
*h1gh pressure
Coated pipes from well
^
No elbows
Corrosion-prone pipes (e.g., mild steel) ^ pjpe break
*high H2S
^Elbows ^ Pipe break
7*high pressure
Non-corrosive pipes (e.g., stainless steeljC
No elbows
Insufficient capacity in storage pond ^ Spill
Broken liner ]> Leaching
Scale-prone pump > Blowout
*high total dissolved solids
Corrosion-prone casing of injection wells ^ Casing leak
*high H2S or *h1gh pressure
Plugged-up casing ^ Casing leak
*high total dissolved solids
, Plugged-up formation used for injection reservoir ^Blowout
*high total dissolved solids
• Decision Points
* Prerequisite Conditions
Figure 8. Diagram to locate potential releases.
43
-------
spills. It identifies the special brine characteristics which contribute to
certain types of failures. The diagram points out that factors such as pipe
elbows and tees contribute to failures caused by high impact velocities.
The conditions which may lead to a given failure mode can be expressed in
terms of threshold values. If a threshold value is exceeded, then that fail-
ure mode is more likely to occur. Threshold values are: temperature greater
than 2QO°C, pressure greater than 100 psia, flow rate greater than about 10
m/s, hydrogen sulfide concentrations greater than 0.1 ppm, and total solids
concentrations greater than 10,000 ppm.
Relative probabilities for the failure modes were given in Table 12.
Other factors such as length of time plant has been in operation and mainte-
nance procedures will influence the probabilities. Geothermal experience to
date indicates that pipe leaks occur most often, followed in frequency by
valve leaks, surface pond overflows, and well casing leaks. The information
given in Section 3 on failure modes can be used to identify piping subject
to high corrosion rates which can result in pipe leaks.
Quantity of Releases
Expected flow rates are needed at each potential release location identi-
fied in the above step. The potential total volume of fluid released at a
specific location can be estimated by multiplying the appropriate flow rate by
the anticipated operator response time to complete corrective action. Geo-
thermal fluid flow rates for a 50 MWe power plant are approximately 10,400 gpm
—total plant flow; 1,000 gpm—for a production well; and 2,000 gpm—for an
injection well.
Operator response times to actual surface spills have ranged from three
minutes to four hours. In the case of severe well blowouts, several days or
months may be required to bring the well under control. Table 20 gives exam-
ples of probable flow rates and total release volumes for several different
release locations. This table shows that the largest potential release vol-
umes will most likely be associated with injection well failures.
Chemistry of Released Fluid
The fluid chemistry varies from one part of the power plant to another.
The procedure for determining chemical changes is as follows:
• Obtain chemical data at well bottom (or before flashing),
• Calculate change in temperature and pressure,
• Determine amount of fluid which flashes, if appropriate,
• Calculate resultant chemical concentrations,
0 Calculate new pH,
44
-------
TABLE 20. VOLUME OF POTENTIAL RELEASES
cn
Release
location
Surface pipe
Surface valve
Producing well
blowout
Injection well
blowout
Casing leak in
producing well
Casing leak in
injection well
Surface pond
leak
Flow rate,
gpm
2,600*
50
1,000
2,000
100
200
1,500,000
gallon
storage
Worst case
Response
time
4 hr
4 hr
1 day
1 day
4 hr
12 hr
Break in
pond berm
Vol ume ,
gallons
624,000
12,000
1,440,000
2,880,000
24,000
144,000
1,500,000
Typical case
Response
time
.5 hr
.5 hr
2 hr
2 hr
1 hr
4 hr
Slow leak
Vol ume ,
gallons
78 ,000
1,500
120,000
240,000
6,000
48,000
Variable
*Based on one-fourth of total plant flow
-------
• Determine likely precipitates using solubility diagrams, and
t Check the concentration of corrosive chemicals in solution.
Chemical data should be obtained by measurement. If site-specific data
are not available for all constituents, values may be estimated from the data
included in Section 3 (Table 6 "Average Chemical Data from Three KGRA's and
Five States"). As an alternative, the worst and typical concentrations
(Tables 8 and 9) may be used. Table 21 gives temperature, pressure, and pH
changes from wellhead through the power plant outlet. These values were
compiled from several power plant designs.
The next step is to determine changes in concentrations due to changes in
temperature and pressure as the fluid moves from the production wells through
the power plant to the surface ponds or injection wells. As the fluid moves
up the well, the pressure drops, allowing the release of steam, carbon dioxide
and other gases. This process, known as flashing, has a concentrating effect
since most constituents remain in the liquid phase. As the pressure decreases
the temperature also decreases. The concentration of certain fluid constitu-
ents may exceed their solubility limit at the lower temperatures and precipi-
tate.
In a binary cycle plant or a total flow cycle plant the fluid would not
flash but would decrease in temperature as it flowed from the wellhead to the
heat exchangers or turbines. Precipitation may occur as the solubility limits
of constituents are exceeded.
To determine the amount of fluid flashing at the wellhead, the volume of
steam and liquid at the well site can be measured or estimated by a graphical
technique. For the latter method Figure 9, which shows the percent of liquid
flashing to steam versus temperature, can be used. Since the loss of water
as steam concentrates the remaining constituents, the new concentrations are
calculated based on the percent of remaining liquid. The new concentration
can be calculated as follows:
Cn = CQ * F (1)
where C = new concentration
n
C = original concentration
,- * • • j:t -j /i percent of liquid flashed \
F = fraction of remaining fluid = II - £ ^Q j
If the condensate re-enters the flow stream, concentrations may again approach
those in the production well.
Often information on geothermal fluids does not include values for pH.
Yet pH values are needed to predict the behavior of several heavy metals in
permeable media. If concentration values are presented for bicarbonate and
carbonate an estimate of the solution pH in equilibrium with atmospheric
gases can be made.
46
-------
TABLE 21. CHANGE!
FROM WELLHEAD TO PLANT OUTLET
TEMPERATURE, PRESSURE AND pH
Plant type.
size, and location
FVash at Heber. CA. 50 HUE
Flash at Valles Caldera,
New Mexico. 50 HWe
Flash at Raft River,
ID, 50 MUe
Dual flash at Raft
River, ID, 10.5 HWe
Z-Stage flash at East
Mesa, CA. 50 MWe
Binary at Raft River,
ID. 50 HWe
Binary cycle at Raft
River, ID, 10 HWe
Binary at Valles Caldera,
New Mexico, 50 KWe
Binary at Heber, CA,
50 HWe
Binary cycle (4 heat
exchangers) 10 (We
Hybrid at Heber, CA,
SO MUe
Hybrid (2 stage) at
Heber. CA. 50 MUe
Hybrid at Valles Caldera.
New Mexico, 50 MWe
Hybrid at Raft River.
ID, 50 MWe
Hybrid (2 stage) at
Niland, CA. 50 HWe
10 MWe design plant
Wellhead to
plant outlet
temperature, °C
182-103
260-103
149-98
150-121-98
180-104
149-92
150-110-71
260-45
182-68
200-113
182-72
182-67
260-103
149-98
230-67
177-120
Wellhead to
plant outlet
pressure
change, psia
Est. 161-103,
reinj. at 309
57
400
Est. 161-103,
reinj. at 309
600
600
290
312
840
140
Wellhead to
plant outlet
pH change
7-9.8
6.5-7.5
6.2
s.i-s.e1'
Depends on amount of CO. gas
Source: Bechtel. 1976; TRW.
ind buffering capacity.
1974; and LBL. 1976
47
-------
40-
"g 30-
~ 20-
£ 10-
150
200
250
300
Temperature, °C
Figure 9. Liquid flashed versus temperature at
atmospheric pressure (after Barr, 1975)
48
-------
First the acid neutralizing capacity [ALK] of the solution is estimated:
[ALK] = [HC03~] + [C032~] (2)
where [ALK] = alkalinity, meq/5,
[HC03~] = bicarbonate concentration, in meq/£
2_
[CO- ~] = carbonate concentration, in meq/&
The alkalinity value is then used in conjunction with Figure 10 to obtain an
estimate of pH.
Other acid neutralizing constituents which may be present include sili-
cates, borates, ammonia, organic compounds, sulfides and phosphates. At pH
values less than about 8-9, borates and silicates contribute only slightly to
the total alkalinity since they are almost fully protonated (e.g., pKp/oH)3
= 9.2 and pK$i(OH)4 - 9.5). The other substances usually add negligible
amounts to the total alkalinity since these concentrations are relatively low.
Acidity (dissociation) constants for the above substances are included in
Appendix A. These calculated values for pH are only approximations. If mea-
sured values are available they should be used.
The pH may also be calculated using equilibrium expressions for the
chemical species involved or equilibrium diagrams. These methods are de-
scribed in detail by Stumm and Morgan, Chapters 3 and 4, 1970. The graphical
method used above was selected because it is easy to use. If a more exact
answer is needed equilibrium calculations with ionic strength corrections can
be substituted.
Neutralizing agents may be added to the fluid to prevent corrosion or
scale problems. Changes in alkalinity and pH after addition of neutralizing
agents can be estimated using the alkalinity versus total carbonate diagram
(Figure 11). The appropriate alkalinity and Ph contour for the fluid before
addition of the neutralizing agents is first located on the figure. One then
moves according to the small vector diagrams at the bottom of the figure to
determine how the pH and/or alkalinity may change. This figure can be used
for low to moderate alkalinity values.
The amount and type of precipitates found in wells and pipes depend on
the chemical species present, the degree of supersaturation, temperature, and
available surface area per unit mass of fluid (Rimstidt and Barnes, 1978).
Table 22 shows the types of precipitates found at selected geothermal sites.
Chemical species likely to precipitate may be identified from solubility dia-
grams. These diagrams may be constructed in several ways depending on whether
solubility of the species is dependent on pH, temperature, or concentration.
The concentrations of metal cations are typically pH-dependent. To
determine if a metal carbonate or metal oxide-hydroxide precipitate may form,
the concentration of the metal ion can be plotted on solubility diagrams
(Figure 12a and 12b). The equilibrium concentration at different pH values is
49
-------
10
10'
,-6
10
,-4
10
,-3
,-2.
10
-1
Acidity
.Alkalinity
456
7
pH
8 9 10
Note: Other conditions were:
pC02 = 10~3-5 atm, T = 25°C.
Figure 10. Alkalinity versus pH (After Stumm
and Morgan, 1970).
50
-------
-0.5
C-r(Total carbonate carbon; mlllimoles/liter)
addition of
NaHC03
addition of
CaC03 or
Na2C03
Dilution
C., addition of strong acid
CB, addition of strong base
Figure 11. Alkalinity versus total carbonate,
showing pH contours (Stumm and
Morgan, 1970).
51
-------
TABLE 22. PRECIPITATES (SCALES) FOUND AT EXISTING GEOTHERMAL SITES
Site
New Zealand
Wa1rake1
Broadlands
Kawerau
Turkey
Klzlldere
Chile
El Tatlo
Japan
Matsukawa
Otake
Taiwan
Matsao
Iceland
Reykjavik
Namafjall
Italy
Larderello
Soviet Union
Bolshe-Bannoe
Ph1ll1pp1nes
T1w1
Tongonan, Leyte
United States
Steamboat Springs
Casa Diablo
Sal ton Sea
The Geysers
Mexico
Cerro Prleto
Type of scale (location of deposit)
Minor caldte (pipes), silica (drains)
Calclte (pipes), silica (silencers, drains)
Caldte (pipes), silica (drains)
Caldte, aragonlte (pipes and plant)
Caldte (pipes)
FeO, FeS, FeS04, silica, sediments
Calclte, silica (drain pipes)
Silica, PbS, FeS, Pb (pipes)
Fe oxides, MgO, silica (pipes, plant)
Amorphous silica, chalcedony
Silica, FeS, borates, silicates
Caldte (pipes)
Caldte
Aragonlte
CaC03, probably aragonlte (pipes)
CaC03> probably aragonlte (pipes)
Silica, hydrated Fe oxides, metal sulfides
(pipes and plant)
Siliceous material, rock dust (pipes and plant)
Caldte. silica, Fe oxides (pipes, plant)
After Ellis and Mihon, 1977
52
-------
Metal ion concentrations in equilibrium with
solid oxides or hydroxides. Temperature = 25°C
8 10 1.2.
pKs0
Sal ton Sea
b. Free metal concentrations in equilibrium with metal
carbonates. Vertical dash indicates equilibrium
concentration with pCC^ = 10-3-5. Temperature = 25°C.
Figure 12. Examples of solubility diagrams
(After Sturm and Morgan, 1970).
53
-------
shown as a line on the diagram. If the fluid concentration plots above the
equilibrium concentration, then the solution is supersaturated with respect to
the solid phase and precipitation may occur. Alternatively solubility prod-
ucts can be checked directly.
The solubility of silica is temperature-dependent with a maximum solubil-
ity occurring at approximately 300°C. Figure 13a shows the solubility of
silica between 0°C and 375°C. To determine whether silica may precipitate in
the well, plot the silica concentration at the well bottom temperature. By
drawing a line parallel to the temperature axis, one may locate the tempera^
ture at which precipitation of amorphous silica may begin. For high concen-
trations of silica the rate of precipitation decreases rapidly as the temper-
ature decreases (Figure 13b). Thus, if the cooling is fast, the amount of
precipitate (scale) may be less than predicted.
The solubility of concentration-dependent chemical compounds can be rep-
resented by thermodynarnic constants called solubility products. For the
reaction AB(s)*^A+ + B~ the solubility product is written as:
Ks'p= A+ IT (3)
where 1C = solubility product
A = molal concentration of ion A
B~ = molal concentration of ion B
*(s), indicates the solid phase
The solubility product K$p is dependent upon the ionic strength of the solu-
tion. Ionic strength is defined as:
I = 1/2 E M1 V? (4)
where I = ionic strength
j. u
M. = molal concentration of the i ion
V. = valence of the i ion
These values are calculated using the chemical, data already obtained.
The value, for the calculated solubility product Kgn is then compared to the
actual solubility product corrected for ionic strength (for correction tech-
nique see Appendix A). If the value calculated is larger, the chemical com-
pound may precipitate. Alternatively solubility-ionic strength diagrams can
be used. Values plotting above the sol utility lines indicate thermodynani-
ically unstable conditions where precipitation may occur. An example of such
a diagram for barium sulfate is shown in Figure 14.
54
-------
0 SO 100 ISO 200 250 300 350
Temperature CC
a. Quartz and Amorphous Silica Solubility as a
Function of Temperature
10O 200
Temperature "C
— Si concentration
— Degree of
supersaturation
300
b. Rate of SiOp Precipitation
Figure 13. Diagrams to determine silica scaling
tendency (a. After Ellis and Mahon,
1977; b. After Rimstidt and Barnes,
1978).
55
-------
10
-7
UJ
10'
8
2
u.
O
o
Q
O
CC
10"
9
8
0.01
100°C (212°F)
X
25°C (77°F)
0.10
1.0
IONIC STRENGTH
Figure 14. Solubility product versus ionic strength
for barium sulfate (Bechtel, 1976).
10
56
-------
Using these types of calculations and diagrams, chemical species which
may precipitate can be identified. Table 23 compares the precipitates ex-
pected with scales found at similar geothermal sites. Selected diagrams, con-
stants, and references are included in Appendix A.
Corrosive conditions may occur in the pipe sections where low pH, high
hydrogen sulfide levels, oxygen leaks, and high fluid (erosive) velocities
occur. One can predict which pipe sections will be subjected to rapid cor-
rosion using the rates given in Table 16. This table lists corrosion rates
for several pipe materials carrying geothermal fluid (steam or condensate)
under low and high velocity conditions. The corrosion-erosion rates range
from a low of 0.0008 rnrn/yr for 18-8 stainless steel pipe with fluid moving at
a low velocity to a high of 1.11 mm/yr for deoxidized copper pipe with aerated
steam moving at a high velocity.
How Injection Pretreatment Techniques Change Fluid Chemistry
If the fluid is injected into the subsurface region, chemical analyses of
the geothermal plant discharge may indicate whether plugging or corrosion of
the well casing may occur. Calcite and silica have been the most commonly
occurring precipitates found in geothermal production wells and pipes to date
(see Table 22). Pretreatment may be used to decrease silica concentrations
and remove suspended solids. Techniques which have been tried (Bechtel, 1976;
Harding-Lawson, 1978; and Quong, ejt al_., 1978) include:
t Acid addition (H2S04)
t Base addition (NaOH)
• Sedimentation and coagulation
• Application of electrical potential
• Precoat pressure filtration
• Mixed media sand filtration
• Scale inhibitor to prevent CaC03 scale
Where pretreatment is used, lab test results for the given fluid and pre-
treatment technique may be consulted to determine the expected concentration
in the injection well. If the concentrations are low and the permeability of
the formation is high, the probability of plugging and subsequently causing a
well failure are less than if concentrations were high.
GROUND WATER CONTAMINATION
The third major section of the methodology is to identify potential
ground water contamination. There are two basic questions:
• Can released geothermal fluid migrate to aquifers?
57
-------
TABLE 23. EXAMPLE CASES OF CHEMICAL SPECIES EXPECTED TO PRECIPITATE
Parameter
Al
Ba
CaC03
Cu
Fe
Mg
Mn
Ni
Pb
Sr
Zn
Si02
HS
SO,
Species found in scale*
Location
A D
A n
A
A
A a
A
Site
Pipes
Pipes & casing
Well casing
Pipes
Species calculated to precipitate
"Worst case"**
X***
X
X
X
X
X
X
X
X
X
X
X
"Typical case"
X
X
X
X
X
X
X
* A Sal ton Sea, D Cerro Prieto
** Similar chemistry to locations shown
*** X means species would be expected to precipitate
58
-------
t Are dilution and attenuation mechanisms adequate to
prevent significant levels of contamination?
These questions will be divided into steps in the
following section.
Release Pathway
Geothermal fluid may reach an aquifer by percolating downward from a
surface pond or spill, leaking out of a well casing, or migrating from the
injection zone. Figure 15 shows how the various flow paths can be divided
into three groups. Group 1 includes infiltrating flow from the ground sur-
face to an aquifer. Leakage from a storage pond is an example of a Group 1
continuous release. A break in a surface pipe or valve is an example of a
Group 1 slug release. Group 2 represents cases where a leak occurs in either
a production or injection well and discharges directly into an aquifer.
Group 3 represents a release from a well or injection zone at a point remote
from the aquifer.
The following steps are followed to determine how ground water contami-
nation may occur:
t Identify release group and type.
• Determine if release zone is isolated from aquifer(s).
Release type and group may be determined with the aid of Figure 15. If geo-
thermal fluid is stored in surface ponds, or surface spills would be routed
to ponds, the size of the pond and type of bottom liner must be determined.
The probability of leakage can be considered very low if a thick layer of
clay and a liner are used and the pond has sufficient capacity to accommo-
date the expected flows including precipitation. Downward percolation of a
release will occur in recharge areas while lateral dispersion will occur in
discharge areas.
A subsurface leak from the injection zone may be isolated from usable
aquifers if two conditions are met. A thick impermeable barrier (aquielude)
such as shale or massive basalt without fractured zones must be present be-
tween the injection zone and the aquifer. In addition, faults must not be
present near the site. Faults may provide conduits for the movement of fluid.
If these conditions are met, Group 3 type releases from the injection zone
would not be considered significant. In most instances the usable aquifer
will be above the injection zone but the procedure can-be used for the case
when the usable aquifer is below.
Extent of Potential Contamination
The procedure for determining the extent and severity of the ground water
contamination includes the following steps:
• Determine if the release may be continuous or a short-term
"slug" event
59
-------
?
*
S ! • ( \- — ?
1 ' \^T ^
fy FLASHER. TURBINE CONDENSER
SEPARATOR 6ENER-
CASED ATOR
PRODUCTION
WELL
*• ^u
T" T
-.— -2J .
. J\flyi.fejr.
'Y'v.
i=^>
POND i
INJECTION 1
WELL
-.— .-^
Production and Injection Zone
30 m
15 m
500 m
23 m
60 m
15 m
NOTE: Diagram not to scale.
Key:
Release Type
—> Group 1
—> Group 2
Group 3
Figure 15. Hypothetical flow paths for fluid releases.
60
-------
• Select appropriate solution method
• Obtain data for analyses
t Calculate resulting concentrations for aquifer of
interest at zone of entry and at plant site
boundary
• Determine degree of attenuation due to dilution,
dispersion, and adsorption
The duration of the release determines whether it should be treated as
continuous or slug flow. Continuous flow persists indefinitely and may be
considered "steady-state." Frequent pulsations of slug flow over a long time
period may be approximated by the steady-state case using average flow values.
Slug flow is a release of a fixed length of time usually less than a year.
It is applicable to the case where a leaking valve is open for a period of say
30 minutes and is then closed by an operator.
The selection of the appropriate solution method is based on the release
group and time frame as shown in Table 24. The solution techniques include:
• GEOHY-GEOQAL analytical method (Gherini, 1975)
• Advection-dispersion method
• Bernoulli-Darcy approach
t Mass balance
The following sections discuss the analytical methods for each group sepa-
rately giving data needs and example calculations. Attenuation mechanisms
are then discussed and procedures given for determining the degree of attenu-
ation.
Data required for all the cases include:
• Initial constituent concentrations in the released fluid
• Total mass flux (flow rate x concentration)
• Velocity of fluid movement in soil and aquifer
The first two requirements are determined in earlier steps of the procedure.
The last requirement can be estimated based upon water level data at the
site.
Method for Surface Releases - Group 1
Approach--
A surface release can be treated as one-dimensional flow with the pollu-
tant moving vertically downward through the soil. This case can be
61
-------
TABLE 24. SUMMARY OF SOLUTION METHODS
Release
group
1.
2.
3.
Release location
Surface pond
Surface spill (e.g. ,
pipeline rupture,
valve failure)
Subsurface release
above Aquifer
Direct release into
aquifer
(well failure)
Direct release into
aquifer
(well failure)
Release above or
below aquifer
(migration through
fractures to aquifer)
Release above or
below aquifer
(migration through
fractures to aquifer)
Time frame
Continuous
Slug
Slug
Continuous
Slug
Continuous
Slug
Solution method
GEOHY-GEOQAL-A/S,*
Mass balance
Advection-Dispersion A**
Advection-Dispersion A
Advection-Dispersion B
Advection-Dispersion A
Bernoulli -Darcy
Advection-Dispersion B
Bernoulli -Darcy
Advection-Dispersion A
*Gherini, 1975; A/S stands for analytical solution
**Wilson and Miller, 1978; B is the modification for a continuous
release. A is the modification for a slug release.
62
-------
simplified by considering the velocity, moisture content, and dispersion coef-
ficient as constant over a given depth. If the soil has several distinct
layers, calculations can be performed for each layer separately. The satu-
rated flow equation will be used to approximate flow in the unsaturated zone.
The void volume will be set equal to the field capacity.
To understand how the analytical method may be used the governing equa-
tion should be briefly reviewed. The equation describing one-dimensional ad-
vective transport with dispersion and adsorption in saturated porous media is
the following (Lapidus and Amundson, 1952; Gherini, 1975):
n 32c 3£ = 9c Ian.
D a,2 Vs 3z at + e 3t (5)
dZ
where c = concentration of pollutant in the fluid stream,
moles per liter
n = amount of pollutant adsorbed by the soil, moles
per liter of soil as packed
v = velocity of fluid flow through interstices of the
soil, m/day, approximated as vn/9f (positive
downward) u T-c'
t = time, days
VD = Darcy velocity
Of r = moisture content at field capacity, decimal
•c* fraction, e.g., 0.18
z = distance down the soil, m (positive downward)
D = dispersion coefficient of the pollutant in
solution in the soil, m2/day;
e = fractional void volume in the soil, unitless
(here e = Qf )
T • C •
The terms in this equation from left to right represent transport due to
dispersion, transport due to advection, the time rate of change in concentra-
tion of a contaminant, and last, a term which results from the consideration
of adsorption of pollutants by the soil matrix.
For adsorption, the following equilibrium expression can be used to
model the localized relation between c and n:
n = k c (6)
63
-------
where c and n are as defined above, and
k = an empirically determined adsorption equilibrium
coefficient
Use of such an expression implies the assumption of equilibrium between the
solute in solution and that adsorbed. Such an approximation approaches
reality since relatively low flow velocities are encountered here. Adsorption
and other attenuation mechanisms will be discussed in more detail later.
For the initial and boundary conditions stated below (i.e., initial con-
centration of pollutant adsorbed on the soil equals zero, initial concentra-
tion of pollutant in the soil-water solution equals zero, and the concentra-
tion of pollutant entering the soil equals a constant),
c (z,t) = 0 for z >_ 0 and t = 0
n (z,t) =0 for z >_ 0 and t = 0
c (z,t) = c for t > 0 and z = 0
where c (z,t) = concentration of pollutant in the soil-water
solution, at a distance z and time t, moles/
liter
n (z,t) = amount of the pollutant adsorbed, at distance
z and time t, moles per liter of soil as packed
The solution of equation (5) where n is defined by equation (6) is:
c(z.t) = 1
c
_. (7)
f- \ A /• n J-» M 1 •» /* *~\-. fl~ f
o
1 + erf 1 L \ + ei/J erfc
where c = pollutant concentration at z = 0
k
Y = 1 + —, a dimensionless adsorption factor
R = vs , a dimensionless time variable
z
S = ——, a dimensionless mixing factor
zvs
D = dispersion coefficient of the adsorbate in solution
2 in the soil, m2/day
z = distance down the soil, m
64
-------
erf() = the error function of
erfc(<|>) = 1 - erf()
o r$ 2
•! I *-z dz
IT J
(values for the last two functions are tabulated
in Appendix D - Table D-l)
When dispersion is small relative to velocity (i.e., S < 0.1) the last term in
equation (7) becomes negligible. This situation is typical for the conditions
in which this approach will be used. Equation (7) then becomes
c(z,t) _ 1
1 + erf
/R-T\
\V4RYS /
(8)
The time required for the pollutant concentration ratio c0 to become
equal to % at a given depth z, is called the "t^ breakthrough time" for the
propagating concentration wavefront. Inspection of equation (8) shows that
this occurs when R = Y, or (by substitution) when:
(-0
(9)
where t^ = time for localized concentration (at z) to approach one-half
the value of the source concentration, c , days
z = distance down the soil, m
v = velocity of fluid flow through the interstices of the
soil, m/day
k = adsorption equilibrium constant (as defined by Eq. (6))
e = fractional void volume in soil, dimensionless (e =
where p is porosity) ~p
The solution for the "breakthrough times" associated with other than the
£—= 0.5 ratio can be readily evaluated (Gherini, 1975). It can be shown
that the error function (erf) is related to the probability integral, such
that
erf(G) = 2$
(V1')
(10)
65
-------
where the probability integral cj)(0) = — /* e dw
By substitution into Eq. (8),
(11)
where tf>(u) =
Other terms are as defined for Eq. (6).
The values of the probability integral are presented in Table D-2 in Appendix
D. One enters the table with "area" equal to 9— - 1 and reads the value of
co 2
t1, (the so-called standard unit). This value is equated to the upper limit
of the integral in Eq. (12) resulting in a quadratic equation:
t1 =(~^\ , R2 - i~2Y + 2YS(t')2] R + Y2 = 0 (12)
\V2RYS / L J
The two roots can then be solved for the related "breakthrough times." The
larger root is associated with the higher °- ratio, such as £ = 0.90, and the
CQ Q CQ £
smaller root with the smaller complementary ratio, — =0.10. The — =0.9
breakthrough time is computed as follows: ° °
$ (u) du = I ^-- 0.5 I = |0.9 - 0.5| = 0.4 = "Area"
co
Entering the probability integral table with area = 0.4, a t1 value of 1.28 is
read (area = 0.3997 -»• t = 1.28). t = 1.28 is substituted into Eq. (12) and
the roots R are computed. A simplified form for the solution of Eq. (12) for
the two roots is the following:
66
-------
R = Ym 1 ± 1 - ±
V m<
where m
= f 1 + St'2 J
and as before,
s = —— , the dimensionless mixing factor
I/
Y = 1 + - , the retardation constant
t'= the "standard unit" from the probability tables for
£- - i taken as the "area"
co i
Given the roots R, and R? the breakthrough times are calculated as tQn = R,z
•f* — R 7 -/U JL
ho V T~
"v
Analytical Procedure--
Equation (8) may be used to calculate pollutant concentrations at a spe-
cific depth below the surface. This equation is referred to in this report
as the GEOHY-GEOQAL Analytical Solution. The steps involved in the calcula-
tions are:
• Compile site specific data
• Calculate the dimensionless adsorption factor, Y
• Estimate the dispersion coefficient, D
• Calculate the dimensionless time variable, R
• Calculate the mixing factor, S (use Eq. (8) only if
S < 0.1)
• Substitute values into equation (7) or (8) for
various combinations of z and t
Data needed include:
_
' '
= soil moisture content at field capacity (to be
used as an estimate of the void volume e)
= adsorption coefficient for each pollutant, for
conservative pollutants, e.g., Cl", assume k = 0.
67
-------
• v = seepage velocity, m/day (Vn/0,: )
j U T • C •
• D = dispersion coefficient of the pollutant in the
soil-water solution, m2/day
• z = distance down soil, m (positive downward)
• c = initial concentration of pollutant in the
solution entering the soil, e.g., mg/£
The soil moisture content at field capacity can be measured by commercial
laboratories or can be estimated based on soil composition using Table B-3 in
Appendix B. If site-specific adsorption coefficients have not been measured
by field or lab tests, approximate values may be selected from those given in
Appendix C or from values given in chemical literature. Laboratory conditions
may not be similar to those at the site and soil ion concentrations may not be
well known. Obtaining adsorption values may be difficult.
Seepage velocities can be obtained from field measurements, detailed cal-
culations based on permeability, k(0), and potential, ¥(0), relationships or
water balance calculations (e.g., Fenn, Hanley, and De Geare, 1975). Compat-
ible particle sizes and seepage velocities may be chosen from the table in
Appendix B (Table B-l) if site-specific data are limited.
The dispersion coefficient is difficult to measure independently at the
site. It can be estimated by the following procedure:
• Calculate the Peclet number, Pfi
• Use Figure 16 to estimate the ratio of dispersion to
molecular diffusion, D.'/D .
• Multiply the above ratio by D^ to obtain D^
The Peclet number (Pg) is defined as follows:
vsg
p = 3
e D,
where g = the mean soil grain size, m;
.2
D, = molecular diffusion coefficient,
v day
V = seepage velocity * Q , - where
0 = volumetric moisture fraction, dimensionless
Values for the ratio of longitudinal dispersion to molecular diffusion
can be obtained graphically using Figure 16. One obtains longitudinal dis-
persion by multiplying this ratio by the molecular diffusion constant. For
68
-------
106
io4
IO3
102
101
10°
ICT3 ID'2 ID'1
10° IO1 IO2 IO3
Pe = Vg/Dd
IO4 IO5 IO6
Figure 16. Graph of relationship of Peclet number to
convective dispersion (after Bear, 1975).
69
-------
aqueous contaminants the value of this constant at 20°C is approximately 10~
m2/day. The value of the transverse dispersion coefficient, Dz, typically
ranges from 0.1 to 0.7 times the longitudinal dispersion coefficient.
Example Problem 1 - "Breakthrough Times"
Aqueous mercury is leaking from a large unlined storage pond. Determine
the time required for the concentration of mercury in soil solution, at a
depth of 3 meters below the pond bottom, to reach 5 and 95 percent of the con-
centration in the pond. The following values have been determined for the
site from field and laboratory measurements:
V - 0.1 m/day
D = 8 x 10"5 m2/day
e = 0.4
K = 400
First calculate values for Y,
dimensionless mixing factor:
Y =
the dimensionless adsorption factor, and S, the
_ 8xlO"5 m2/da
__
Vsz " 0.1 m/day x
y = 2
3m ^-
-4
Next calculate t' for c/co =0.95
t1 = |0.95- h\ = 0.45
The area read from Table D-2 in Appendix D is 1.64.
Now the roots of Eq. (12) are evaluated
m = 1 + [2.67xlO~4 x (1.64)2
= 1.00072
R = 1001 (1.00072)
= 1040, 963
1 ± 1 -
1
(1.00072)'
70
-------
Finally, time required for the concentration of pollutant at 3 meters to
reach 95 percent of the influx pollutant concentration CQ is calculated:
t _ R* _ 1040 x 3 m = 3 12 x 1Q4 d
* ~ v_ 0.1 m/day *'li x 1U days
=85.5 years
To reach 5 percent of the influx pollutant concentration
. _ Rz _ 963 x 3 m _ ? RQ In4 ,
* " 7~ ' 0.1 m/day " 2'89 x 10 days
=79.1 years
Summarizing the example case,
t (for — = .95) = 85.5 years
co
t (for f- = .05) = 79.1 years
co
The resulting breakthrough wave of mercury is quite steep and considerably
delayed. Water molecules and constituents which are not soil interactive
(k=0) would, on the average, tranverse the same distance in only 30 days.
Resulting Aquifer Concentration--
After computing the concentration reaching the top of the aquifer, the
resulting concentration within the aquifer can be calculated in two ways: by
use of simple mass balance expressions assuming no attenuation, or by use of
advection-dispersion equations with allowance for attenuation (see for exam-
ple, Wilson and Miller, 1978). The mass balance approach is discussed in
this section. The advection-dispersion method allowing attenuation is dis-
cussed under Group 2 calculations.
The mass balance approach computes the concentration in the aquifer us-
ing the following equation:
- VP + QACA
Qp + QA
where c = resulting concentration in aquifer
Q = volumetric flow rate of liquid transporting pollutant
p into aquifer (Q = VQ A )
71
-------
VD = Darcy velocity in the downward direction (VD - V e)
A = horizontal area of pond or spill
c = concentration of pollutant at upper boundary of the
^ aquifer (unsaturated-saturated zone interface)
Q» = volumetric flow rate of aquifer (QA = Vphw)
VD = Darcy velocity in aquifer
h = thickness of aquifer
w = surface pond or spill width perpendicular to flow
direction in aquifer
CA = initial concentration of pollutant in aquifer
This approach assumes complete mixing with that portion of the aquifer di-
rectly under the pollutant source.
Example Problem 2 - "Resulting Aquifer Concentrations"
The leaking storage pond in Example Problem 1 also contains a high con-
centration (1000 mg/1) of chloride ion, a pollutant which is not absorbed by
soil. The pond has a surface area of 1200 m^. The width of the pond normal
to the aquifer flow direction is 50 meters. The thickness of the unconfined
aquifer is 15 meters and velocity of fluid movement in the aquifer is esti-
mated to be 0.08 m/day. Assume the background concentration of chloride in
the aquifer is 20 mg/H, Make an estimate of the likely resulting chloride
concentration in the aquifer.
Recall from Sample Problem 1
V$ =0.1 m/day
e = 0.4
First calculate CL and Qfl
p H
Vn = V e = 0.1 m/day x 0.4 = 0.04 m/day
U2 s
Q =0.04 m/day x 1200 m2 = 48 m3/day
3
Q. = Vphw = 0.08 m/day x 15 m x 50 m = 60 m /day
72
-------
substituting into equation (14):
= 48 m3/day x 1000 mg/a + 60 m3/day x 20 mg/Jl
48 m3/day + 60 m3/day
c = 456 mg/SL
Concentrations resulting from a slug release at the surface can be esti-
mated using the advection-dispersion method case A as described for Group 2
releases.
Method for Direct Releases into Aquifers from Wells-Group 2
Approach--
Direct releases into an aquifer may occur from an injection or produc-
tion well due to casing leaks, cement failure, or migration along the well-
bore. The pollutant concentration may attenuate by dispersion, dilution, and
adsorption within the aquifer. If the aquifer can be considered to be verti-
cally mixed, the advection-dispersion method can be used to obtain the result-
ing downstream concentrations in the aquifer.
This method is based on the following differential equation which de-
scribes mass transport in uniform steady flow in the x direction, with dis-
persion and adsorption. The derivation of the equation is presented by Bear
(1975). A solution is given by Wilson and Miller (1978), and by Codell
(1978).
D-V-XRC (15)
where c = concentration of pollutant in solution
t = time
Ix
R , = the retardation factor, 1 + - , (same as Y in
d Eq. (7))
A = first order solute decay constant (change in
tracer concentration resulting from this decay
9c
alone is expressed -£• = -Ac)
o u
DZ = longitudinal dispersion coefficient
D ,D = transverse dispersion coefficients
y x
Redefining the variables in terms of R, yields
73
-------
- + r ^ = D; s-% + D; *-§. + D; 4-| - AC (is)
For a slug release, case A, with an instantaneous injection along the x axis,
Eq. (16) after integrating in two dimensions yields (Wilson and Miller, 1978,
r.nHol 1 1Q7P^
4npt(DxDy)'s
(x - V)2
4Dxt
*2 u
4Dyt
Codell, 1978)
c(-x,y,t) = ± 5! exp - Vx - s ; y_ _ u ( }
Kd
where m" = total mass of solute injected into the aquifer per
unit thickness of aquifer (d) along the vertical z
axis, e.g., mg/ft
p = effective porosity
o
D = dispersion in x direction, m/day
A
2
D = dispersion in y direction, m/day
x,y = distance from source (flow parallel to x axis), m
Vg = seepage velocity, m/day
t = time, days
Rd = retardation factor
Solution Procedure--
The advection-dispersion equation case A may be solved by substitution
(Example Problem 3) or by a graphical technique which will be explained in
the section on Group 3.
Example Problem 3 - "Aquifer Concentration Following Slug Injection"
Calculate the pollutant concentration at the surface of an aquifer 300 m
downstream from a slug release 700 days after it occurred. The release flows
directly into an aquifer with a thickness of 9 meters and is assumed to dis-
tribute itself instantaneously in the vertical direction (within the aquifer).
The pollutant decay rate is 3.4 x 10~3 day-1. The seepage velocity in the
aquifer is 0.48 m/day in the horizontal direction. The total pollutant mass
of the slug release is 1.8 x 10^ mg. Other input data are given below:
d = 9 m
- 1.8 x 108 mg 2 x IP7 nig
m 9 m " m
74
-------
p = .35
D¥ = .93 m2/day
/\
D = .56 m /day
Rd = 1 if k = 0
Use Eq. (17):
T /v V tv2
r _ J nT
L " R
\i 4irpt(DxD )2
Substituting into Eq. (17) gives:
C = | ^-^- r exo f. OOP-(• 48x700))2 _ 3 4 1Q-3 (? 3
1 4ir(.35) 700 (.93 x .56)^ ^P L 4 x .93 x 700 J'4xl° (/Q^\
C = 2 x 10 ? exp [-2.87] = 510.8 mg/m3 = 0.51 mg/i
2.22xlOJ
The time to reach the maximum value of solute concentration (c ) in the
aquifer may be calculated by determining the derivative -rr of Eq. (17) and
setting this equal to zero. This has been done by Hunt (1978). The results
are presented by the following equation:
(18)
s
where t = time to reach maximum concentration
V = seepage velocity, m/day
r" = for 1 dimension = x, (x>0)
for 2 dimensions = \x2+y2(D /D )
x y
for 3 dimensions =
-------
D = dispersion redefined here as - D /R ,
X X Q
R, = retardation factor
d
The steps for determining the maximum concentrations are:
• Use data obtained for Eq. (17)
• Calculate time to reach maximum concentration using Eq. (18)
• Substitute the time to reach maximum into Eq. (17)
t Calculate the maximum concentration.
Example Problem 4 - "Maximum Concentration in Aquifer"
Determine the maximum concentration and the time of occurrence resulting
from the break described in Example Problem 3 at a distance of 300 meters in
the direction of flow.
Input data from Example Problem 3.
Use Eq. (18):
X
_ \ X ' I
"max ,,2
r) -l)n D
s
Substituting the data into Eq. (18) gives:
FT , . /.48 m/day x 300 m\2l ** 1 ?
t -U Ux W/d«v ) J -lj ? (.93 m2/day)
max (.48 m/day)2
= 617 days
Substituting t into Eq. (17) gives
max
_ 1 2 x 107 OYn [ (300 m - .48 m/day (617 days))2
Q — -— - - - - 1^7 CA|J I ~" O
max l 47r (.35)(617)(.93 x .56)2 L 4 (.93 mVday) 617
617
4T.56) 617
76
-------
„ _ 2 X 10
P
max 1.96 x 10
—5- exp [ - .006 - 2.10 1 = 1242 mg/nf
in-3 L J
= 1.24 mg/Jl
The concentrations in an aquifer resulting from a direct release from a
continuous source can be estimated using the advection-dispersion method,
case B. Eq. (16) is solved for the steady-state case. The procedure and an
example problem are described in the section on Method for Releases at Depth
Group 3.
Method for Releases at Depth - Group 3
Approach--
Releases above or below the aquifer of concern could migrate to the aqui
fer. Several approaches to flow in porous, fractured media were considered
(Witherspoon, 1975; Lippman, 1977; Home and Ramey, 1978). A feasible ap-
proach which does not require extensive data or calculations is to simply use
Bernoulli's equation for flow through pipes to calculate the pressure at the
location of the break in the well and Darcy's law to calculate the flow into
an aquifer. If data are available on permeability and area of the fracture
zone, then this approach is the most direct.
When such data are not available, then a conservative approach could be
taken stating that the flow rate into the aquifer is the same as at the fail-
ure location. The worst case would be a complete severing of the well and
loss of the total well flow rate to the aquifer. For casing leaks, only a
percentage of the well flow may be lost and/or enter the aquifer.
Figure 17 shows an example cross section with a hypothetical well rup-
ture. Well size and flow rate are obtained for the site.
The Bernoulli equation can be used for calculating the pressure at the
point of rupture, P2 (shown in Figure 17), as follows:
P9 P1 i vi2
_2=_L+L+fL 1
y y U 2g
where P2 = pressure at failure location
P.. = pressure at wellhead
V, = velocity in well (Vj = Q/A), m/sec
3
Q = well flow rate, m /sec
2
A = cross-sectional area of well, m
O
g = 9.76 m/sec (gravitational acceleration constant)
77
-------
Ground Surface
FLASHER, TURBINE CONDENSER
SEPARATOR GENERATOR
CASED
PRODUCTION
WELL
INJECTION
WELL
w^///%
Aquifer^
B
FISSURE
PATHWAYS
Production Zone
POND
Figure 17. Schematic diagram for group 3 case.
78
-------
Y = specific weight of liquid
f = friction factor
L = length of well down to failure location, m
D = diameter of well, m
The friction factor (f, here a constant),for the well casing can be esti
mated from the roughness of the pipe, pipe diameter, and the Reynolds number
using a form of the Moody diagram. Appendix E (Figure E-2) gives relative
roughness values for different diameters and types of pipes. The following
equation is used to calculate Reynolds number:
NR - £ CO)
where NR = Reynolds number
D = pipe diameter, m
V = velocity, m/s
o
v = kinematic viscosity of liquid, rrr/sec (values
given in Appendix E - Table E-l)
The friction factor is read from the Moody diagram (in Appendix E - Figure
E-l) based on the relative roughness and Reynolds number. Typically an itera
tive solution must be made since "f" depends upon the velocity of flow in the
pipe.
Analytical Procedure—
The steps for the "Bernoulli-Darcy" approach are as follows:
• Obtain data needed
• Estimate friction factor
• Calculate pressure at failure location
t Calculate flow into aquifer using Darcy's law
• Calculate concentration in aquifer using mass balance
approach or advection-dispersion method
Data needed are:
• Depth of well to failure location
• Diameter of well
t Well flow rate
79
-------
t Area of well cross section
• Friction factor
t Location of aquifer
Example Problem 5 - "Pressure at the Point of Rupture"
Determine the well pressure at a rupture occurring 250 meters below the
surface given the following information. Assume the friction factor has a
constant value of 0.019.
Values refer to Figure 17.
Pj = 24.6 Kg/cm2
L = 250 m
f = 0.019
D = .3 m
V^ = .43 m/sec
ratio of Ygeothermal/Ywater = l'19
fluid
Ywater = 999'4
Use Eq. (19):
P2 Pl L Vl
— = —+ L + f^ Tg
Substituting the data gives
?_2 = 24.6 x 10.000 (250) .105
Y 999.4 x 1.19 ^bU °'Uiy .3 2 x 9.76
= 206.8 + 250 + .15 = 457 m
P2 = 457 m x (1.19) (999.4 Kg/m3) (1 m2/10,000 cm2
= 54.35 Kg/cm2
For the case of a fractured aquifer the following form of Darcy's law
may be used to approximate the flow, Qo, through a fracture zone to the aqui-
fer: J
80
-------
where Q~ = flow rate into the aquifer
K = permeability of fracture zone
A = cross sectional area of fracture zone
PO = pressure in the aquifer at geothermal entry
point, P3 = hY
h = depth of water in the aquifer, if unconfined
aquifer
= hydrostatic head of water, if confined
aquifer
Y = specific weight of geothermal fluid
(L-B) = approximation to length of fracture zone flow
path (see Figure 17 - B is depth to base of
aquifer
Note: The flow is considered to be laminar in this equation
so NX must be less than or equal to 10.
NX = — , where d is an estimate of the average particle
size in the fracture zone
Example Problem 6 - "Flow at Aquifer"
Estimate the flow into the aquifer of Problem 5 resulting from the rup-
ture of the well casing.
Input data are from Example Problem 5 and the following values.
L-B = 56 m
K =9.55 m/day (£/m2/day)
p
A = 3.14 m if circular zone of 2 ft diameter
- = 457 m
= 9m
81
-------
Use Eq. (21): /P2 -
Q0 = KA
/P2 - P3\
V U-B) /
U^BJ
Q, = 9.55 m/day x 3.14 m2 x ^S," ? n}
•j \3v mj
Q3 = 23y.9 m /day = 166.6 £pm
Resulting Concentration in Aquifer--
The next step is to estimate the concentration within the aquifer using
the advection-dispersion approach for a continuous release or the mass balance
approach discussed under the section for Group 1 releases. For a slug case
the aquifer concentration would be calculated using the advection-dispersion
method case A as described under Group 2 releases. Eq. (16) (the advection-
dispersion equation) can be solved for the continuous injection rate (case B)
(Wilson and Miller, 1978) and yields
H (u, £
\ B
c(x,y,t) = -!2 - -H u, (22)
where c = concentration in the aquifer, e.g., mg/£
f' = mass flux injection rate, injected uniformly
over the aquifer thickness = qc , e.g., mg/m/day
q = volumetric injection rate per unit length,
e.g., m3/m day
c = initial concentration of pollutant (at source),
e.g., mg/&
p = porosity, decimal fraction
W(uJr) = well function
u = r2/4Y"Dt, e.g., m/day
A
B = 2D /V . unitless
A J
r = function of radial distance from source, m =
(x2 + \ y2) Y-l
D
y
= 1 + (ir^l if no solute decay u = r
s, «x*
Vs = seepage velocity, m/day
82
-------
The procedure is as follows:
• Obtain data
• Calculate dispersion constant if not measured
t Evaluate the well function
• Substitute data into Eq. (22)
• Calculate resulting concentrations in the aquifer at
points and times of interest
The mass flux, initial pollutant concentration, and injection rate can be
estimated based on data in the section on chemistry of spilled fluid. Proce
dures for obtaining the dispersion constant were discussed in the section on
Methods for Surface Releases—Group 1. The well function for r/B ratios <10
is available from plots and tables (DeWiest, 1967). For larger r/B ratios
the following approximation can be used (Wilson and Miller, 1978):
W(u, r/b) * exp (-r/B) erfc - (23)
- / (r/EV 2U\
\ 2(u)2 /
Appendix D includes a tabulation (Table D-l) of the complementary error func-
tion (erfc) and the error function (erf). For a steady-state case a modified
Bessel function (K0 (r/B)) as given below may be substituted for the well
function for cases with r/B > 1, as is typically the case here.
K0 (r/b) - - exp -r/B (24)
Eq. (22) may be solved by direct substitution. This is satisfactory if
only a small number of solutions are needed. If many solutions are desired,
then a graphical solution technique may be used.
Example Problem 7 - "Aquifer Concentrations"
Estimate the concentration increase after 667 days of a conservative
pollutant 300 m down-flow from the line of contamination in the example aqui-
fer resulting from a continuous release. Additional input data are summarized
below. The waste flows into the aquifer at about 3.78 £pm with a concentra-
tion of 200 mg/fi,.
p = .35
t = 667 days
Dv = .93 m2/day
/\
83
-------
D = .56 m/day
J
x = 300 m
y = 0 m
d = 9.15 m
Vg = .46 m/day
\ = 3.4 x 10"3 day"1
Evaluate the well function:
r 2 Dx ? i^
= x + r-y Y1 =
L uv J
2 + ^ (O)2 1.06
B = fix = 2(.93m'Vda.y)
b Vc .46 m/day 4
-------
Use Eq. (22):
f exp W(u,r/B)
C(x.y.t) =
4TTp(DxDy)
- = 5.45 X10 x 200 . 1>19 x 105 mg/nl/day
Substitute the above data into Eq. (22)
1.19 x 105 mg/m/day exp
(.35) (.93 nr/dayx.56 rrr/day)'*
22. = 5.4 mg/£
^(36.3,74.26)
'
m
To compute the steady-state concentration resulting from a continuous
leak Eq. (22) may be used. The only difference in the formulation of the
equation for the steady-state case and the time after release case is the
substitution of the modified Bessel function for the well function. The
equation then becomes
2irp (DXD )2
where C is the steady-state concentration.
The equation is solved by substituting the appropriate data as shown below
with data from Example Problem 7.
f 117 -3 \ ~% ~\
_ 1.19x10 mg/m/day exp « n^m ( '4 04) exP (-74.26)
2(Tr)(0.35)(.93 x .56)*
= 10906 mg/m3 = 11 mg/£
The time required to reach steady state can be estimated graphically using
Figure 18. The value of the term r"Vs/Dx (defined on Figure 18) is calcu-
lated and the corresponding value for t VS2/DX is read from the abscissa.
Values are substituted for Vs and Dx and the expression solved for t, the
time to reach steady state.
Alternatively, one may solve Eq. (22) graphically. The graphical solu-
tion (Wilson and Miller, 1978) involves the following steps:
85
(25)
-------
lOOO-i
100-
10-
1.0
1 dimension -j-
ions *£-
2 dimensions
3 dimensions
ions-*y /
1.0
10
100
1000
Key:
Number of Dimensions
One
Two
Three
Definition of
x (x > 0)
9 9 X1/2
+y(D/D ))
/ 9 9 9 X1/2
(x +y (VDy)+2 (VDz))
Figure 18. Time for release to reach steady-state conditions (after
Hunt, 1978).
86
-------
• Calculate r/B values for selected x and y values
• Plot r/B curves as function of x/B and y/B
• The plotted results would look like Figure 19a
if Dx/Dy = 1 or Figure 19b if Dx and Dy are
not equal
t Pick steady state concentration of interest, IT
• Calculate Cf where C1" = —r-
• Calculate C/Ct ratio
(r *}
• Determine ^ B ; value from Figure 19c
t Plot C" contours as shown on Figure 19b
How Much Will Attenuation Decrease Con tarninati oil
Mechanisms--
If the concentrations calculated without attenuation are higher than the
appropriate use standards, the concentrations should be recalculated allowing
for attenuation. The procedure is:
• Check Table 25 for degree of attenuation by
adsorption-desorption for the chemical species
of concern.
t Substitute appropriate adsorption Kp values
into transport equations in previous section
for appropriate group.
Table 25 divides the major constituents of concern present in geothermal
fluid into three groups—not adsorbed, reversibly adsorbed, and irreversibly
bound, to indicate the general extent of attenuation. Conservative species
are not adsorbed by soil or mineral particles to any significant extent and
are affected primarily by dispersive processes, i.e., advection, dilution,
dispersion, proton exchange reactions, and to varying extents microbial con-
version. Microbial activity is strongest in organic soils near the ground
surface. Total dissolved solids may be treated as a conservative substance.
Adsorption and ion-exchange can be considered ^simultaneously. The pref-
erence of a soil particle for a given ion or adsorbate depends on type of
soil and relative concentration of the species in the soil solution. General-
ly multivalent ions are adsorbed more strongly than monovalent ions and hence
are less mobile in soil water systems. The cation preference is described by
87
-------
KEY'
C" - Steady- state concentration
C - Maximum concentration
Tfx/B
KEY •
20
x/B
Contours of equal r/B and r
Concentration contours at steady-state
for Cf
(Maximum concentration >36.5 mg/l)
Figure 19. Graphical solution for Wilson and Miller's equations (after
Wilson and Miller, 1978).
88
-------
TABLE 25. GENERAL ADSORPTION-DESORPTION BEHAVIOR OF
SELECTED AQUEOUS CHEMICAL SPECIES
Constituents
Total dissolved solids
Aluminum (Al(aq))
*Ammonia (NH*)
Arsenic (HAS04 , H2AS04)
Barium (Ba2+)
Boron (H3B03)
Cadmium (Cd.II)
Chloride (Cl~)
Fluoride (F~)
Copper (Cu (II))
*Hydrogen sulfide (H2S,HS")
*Iron (Fe (II), (III))
Lead (Pb (II))
Lithium (Li )
2+
Magnesium (Mg )
"Manganese (Mn (II), (IV))
Selenium (Se03~)
Silver (Ag )
Zinc (Zn (II))
Mercury (Hg (II))
Molybdenum (molybdic acid)
Sodium (Na+)
* Nitrate (NO^)
Calcium (Ca^+)
Carbonate (CO2,")
o
Silica (sil icic acid)
Sulfate (S0^~)
Chromium (Cr (III) (VI))
Not Adsorbed
X
X
X
X
X
Adsorbed
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Irreversibly Bound**
X
*These species are susceptible to microbially mediated biochemical conversions
(e.g., oxidation-reduction). The greatest density (and activity) of soil
microflora occurs near the ground surface in-organic soil horizons.
**Very strongly bound.
89
-------
where y+ = amount of monovalent cation on (bound to)
the soil solid phase, meq/100 g soil
+
YO+ = amount of divalent cation on (bound to)
the soil solid phase, meq/100 g soil
Kg = Gapon exchange constant in Appendix C
CQ 1+ = concentration of monovalent cation in soil
' solution, meq/kg solution
C 2+ = concentration of divalent cation in soil
' solution, meq/kg solution
90
selectivity and exchange coefficients in the following equations (Bolt and
Bruggenwert, T976):
For ions of equal valence,
Y C
a - v o»a
— ~ Ka/b r—
o,b
where K ,. = Kerr selectivity coefficient (values
' given in Appendix C)
Y = amount of ion "a" on (bound to) the soil
a solid phase, meq/100 grams soil
Yh = amount of ion "b" on (bound to) the soil
solid phase, meq/100 grams soil
C = concentration of ion "a" in soil solution,
°'a meq/kg solution
C . = concentration of ion "b" in soil solution,
5 meq/kg solution
For monovalent/divalent ion preference
K C
- G_P-il+ (27)
o'2+
-------
Preferences for several soil components are given below, with the most
strongly bound (least mobile) constituents appearing on the left:
Exchange Medium Cations
clays Ca>Mg>Ba=Sr=Zn=Co=Ni=Cu
Cs>Rb>K^NH4>Na>Li
Iron and aluminum oxides Li>Na>NH.>K>Rb>Cs
Organic material Cu>Fe3+-Pb2+>NiP04»S04>N03»Cl
Cation exchange capacity (CEC) of a soil is the total amount of cations
which can be exchanged per unit mass of soil (milliequivalents/100 grams
soil). Clay minerals and organic matter contribute most of the CEC. The
clay minerals also provide the bulk of the soil specific surface area.
CEC's of clays range from 3-6 meq/100 g for micas to 200-300 meq/100 g for
montmorillonites. CEC's of soil organic matter are typically of the order
of 100-400 meq/1. Appendix B gives representative CEC values for different
soils. As shown in Figure 20, CEC varies with pH. If site-specific measure-
ments are not available, you may select a value similar in pH and soil com-
position. Anion exchange capacity (AEC) is the amount of anions which can be
exchanged. The AEC typically ranges from 1 to 5% of the CEC for most soils.
For saline soils the AEC may be 10-15% of the CEC (Bolt and Bruggenwert,
1976).
Specific adsorption includes reactions which result in insoluble com-
pounds or tightly-bound complexes. This type of adsorption can be a function
of pH and the concentration of complexing agents (i.e., Cl~) and organic
matter (Figure 21). Many metals in aqueous solution have characteristic
"adsorption edge" pH values where adsorption increases sharply with increas-
ing pH (Figure 22). Examples of metals which form chloride complexes include
mercury, cadmium, and zinc. Manganese and copper readily form organic com-
plexes. Chemical species such as fluoride and arsenic are specifically ad-
sorbed on iron and aluminum compounds.
Species which become "irreversibly bound" are adsorbed so strongly that
the concentration of the species in solution after moving through a short
depth of soil may become very small. This group includes for example silica
and phosphorus (orthophosphate form).
91
-------
o»
400
300
200
O g>
o° 100
0 I 2345678
PH
a. Cation-exchange capacities of
organic matter and clay in 60
Wisconsin Soils.
60
O, 50
O
2 40
\
o> 30
O 20
UJ
O
10
3456
PH
8
b. Cation-exchange capacities for
a group of acid California soils.
Figure 20. Cation-exchange capacity variations with pH
(a. after Helling, 1964; b. after Coleman
and Thomas, 1965).
92
-------
IOO
80
c
o
Q. 60
s-
o
10
•O
40
.|_>
C
O)
o
t.
OJ 20
D-
— i — i — j — i — i — i i i -i i i
Adsorption of Hg(ll) on SiOj
Hg,0, _• 1 84 > IO"7 M
40g/l Si02 . IO"1 M «l«ctroylt
AGchem '"4.5 Kcol /molt
_
f
/
f
MA
A
A Q
/ ^^
/ ^
/D
/ Cl"- 1O~' M
J
i t i i i i i i I 1 '
0 2 4 6 8 10 li
pH
Figure 21. Effect of chloride concentration
on adsorption of mercury (Rubin,
1976 used with permission of Ann
Arbor Science Publishers).
IOO
Concentrations were:
Fe3+ 1.2 x IO"4 M
Cr3+ 2.0 x 10"4 M
Co2+ 1.2 x IO"4 M
Ca2+ 1.4 x IO"4 M
Figure 22. Effect of pH on adsorption of
metals (Rubin, 1976 used with
permission of Ann Arbor Science
Publishers).
93
-------
Calculation of Concentrations with Attenuation--
As an alternative to solving a series of exchange equations for each
parameter simultaneously, you may determine the equivalent adsorption coef-
ficient, Kg value, and substitute this into the appropriate transport equa-
tions described in the previous section. This procedure works well especially
for the more dilute species. The "adsorption coefficient" (Kg) is an empiri-
cally-determined coefficient for a specific chemical species.
K - [Csorbed] ,
Nn - i-p— r
u LLsolutionJ
where Cor. . = pollutant concentration sorbed on
sorbed soil, mg/kg soil
C ,0 4.- = pollutant concentration in
solution £olutionj mg/Jl
In general, the KQ value is a function of chemical species, type of mineral
phases present, pH, Cl~ ion concentration, and amount of organic matter
present. For some species such as mercury, KQ can be expressed as a function
of chloride concentration, pH, and soil specific surface area. Appendix C
includes KD values for selected chemical species. The effect of adsorption
on transport of pollutants was tested using the GEOHY-GEOQAL model (Gherini,
1975). Figure 23 shows the decrease in amount of pollutant reaching a depth
of two feet and six feet when adsorption is included (note the use of log
scales).
EVALUATION OF SIGNIFICANCE
The final step in the procedure is to identify significant ground water
contamination. The concentrations in usable aquifers at the plant boundary
are compared with the pertinent water quality standards and regulations
covering effluents from injection wells. The proposed Underground Injection
Control Program mandated by the Safe Drinking Water Act protects aquifers
with total dissolved solids concentrations less than 10,000 mg/&. Aquifers
protected under these regulations should be considered a potential drinking
water source and concentrations should be compared to the present drinking
water quality standards (Table 26).
The concentrations of constituents analyzed as conservative substances
represent a worst case since no attenuation is considered. These resulting
concentrations serve as upper bounds. If no standards are exceeded under
these conditions, then ground water contamination would not be considered
significant. If the concentrations of any constituents for the conservative
case exceed standards, the concentrations with attenuation must be predicted
and evaluated.
94
-------
10
20
30
cn
o
40
50
60
At depth of 2 ft
...—*"
*-
*'
*--*
-**
.-•-*-
.-*-
..--•*•
-»-
„----"*"
.--*•
.---*•'
_.. #—-
At depth of 6 ft
KEY
# No adsorption
•Jfc With adsorption
Upper Boundary Concentration CQ = 0.1 mg Hgt/l, pH = 7
2
Specific Soil Surface Area S = 100 cm /gm
0.5 1.0 1.5 2.0 2.5
3 minutes
3.0 3.5 4.0 4.5 5.0 5.5
, Time (minutes)
7.3 months
Figure 23. Effect of adsorption on mercury transport (after
Gherini, 1975).
95
-------
TABLE 26. U.S. EPA DRINKING WATER QUALITY
STANDARDS (EPA, 1977a AND b)
Constituents
PRIMARY STANDARDS
Inorganic Chemicals
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Nitrate (as N)
Selenium
Silver
Fluoride
Radioactive Material
Combined radium 226
and radium 228
Gross alpha particle
activity
Beta particle and photon
radioactivity from man-
made radionucl ides
Tritium
Strontium-90
SECONDARY STANDARDS
Chloride
Color
Copper
Methyl ene blue active
substances
H2S
Iron
Manganese
Odor
pH
Sulphate
Total Dissolved Solids
Zinc
Corrosion
Annual average maximum
daily air temperature
op oc
53.7 and below 12.0 and below
53.8 to 58.3 12.1 to 14.6
58.4 to 63.8 H.7 to 17.6
63.9 to 70.6 17.7 to 21.4
70.7 to 79.2 21.5 to 26.2
79.3 to 90.5 26.3 to 32.5
Maximum level
0.05
1.
0.010
0.05
0.05
0.002
10.
0.01
0.05
2.4
2.2
2.0
1.8
1.6
1.4
5 pCi/1
15 pCi/1
4 mil lirem/year
20,000 pCi/1
8 pCi/1
250.0
15.0 c.u.
1.0
0.5
0.05
0.3
0.05
Threshold Order No. 3
6.5 - 8.5
250.0
500.0
5.0
No maximum level but
should reduce tendency
for corrosion
Units are mg/l unless otherwise stated.
96
-------
LIMITATIONS OF THE METHODOLOGY
The methodology presented in this manual has certain limitations. To
make the methodology simple enough for desk top (non-computer) use, analyti-
cal rather than numerical solutions were adopted. This results in some loss
in accuracy but a gain in ease of application. The analytical solutions are
designed for ground water systems with uniform properties such as porosity
and flow field. At a complex site the aquifer characteristics may change
over short distances, particularly if the area is faulted. Solving the case
for a realistic range of data values would provide likely ranges of constit-
uent concentrations. The purpose of the methodology is to provide prelimin-
ary estimates so the information obtained for the range of data would be
useful. We believe this use of analytical solutions is appropriate for a
screening procedure.
For many of the variables used in the methodology there is a preference
for field values as compared to laboratory or literature values. For example,
dispersion as measured in soil columns in the laboratory usually underesti-
mates the dispersion which occurs in aquifers due to lateral and vertical
inhomogeneities. Better estimates can be obtained using tracer tests in the
field. Porosity may be estimated from soil samples but may not be represen-
tative of the entire aquifer. Well logging with neutron logs may be helpful
in estimating a representative porosity.
Appropriate pollutant adsorption values (KD) may be difficult to obtain
for some constituents. This is an area where further research would be most
valuable.
97
-------
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102
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APPENDIX A
SOLUBILITY DATA
EQUILIBRIUM CONSTANTS
Equilibrium constants can be defined for reactions in dilute solutions
as follows:
wA + xB = yC + zD, and
K - £C]y [D]Z
[A]W [B]x
where [C], [D], [A], [B] = molar concentrations of
species A, B, C, and D
w, x, y, z = stoichiometric coefficients
In more concentrated solutions the effects of ionic interactions become more
significant and species' activities (concentrations times activity coeffi-
cients) replace the concentrations in the above equation. The equilibrium
constant is then referred to as K°.
For the case of equilibrium between a solid and its dissolved components
the reaction is written with the solid on the left. The equilibrium constant
is then referred to as a solubility product, K , where
AVB (s) = xA + yB, and
x y
[A]X [B]y = K
where [A], [B] = molar concentrations of A and B
x, y = stoichiometric coefficients
(s) = solid phase
103
-------
The concentration and activity of a solid are exactly unity.
For reactions involving dissociation of chemical species the equilibrium
constants are called ionization constants or dissociation constants, K^. For
example, for the dissociation of diprotic acids the reactions are written in
the following manner:
Hx L = HyL- + H+
+ [HL"]
where: [H ] = molar concentration of hydrogen ion
[H L~] = molar concentration of H L~
[H L] = molar concentration of undissociated acid
Reactions involving the formation of complex ions are written in a sim
ilar manner as follows:
xA + yB = Ax Bym
where: [A B..m] = molar concentration of complex ion
x y
[A],[B] = molar concentration of ions
x, y = stochiometric
m = charge of the complex coefficients
Molar concentrations are corrected for ionic strength by multiplying
the concentration by an activity coefficient. The corrected concentration
is then referred to as the activity. The activity coefficient can be esti-
mated using the extended form of the Debye-Huckel equation (Bolt and
Bruggenwert, 1976):
-log
1 + a?
104
-------
where: f. = activity coefficient of species i
z.j = charge on species i
2
I = % £ m. z^, ionic strength
m = molar concentration of species i
a? = ionic size parameter
A,B = constants: at 25°C A = .51 (mol/£)"'5,
B = .33 A0"1 mole "°'5 liter0'5
Values of a^ for selected chemical species are listed in Table A-l. Activity
coefficients f-j, for a^ values between 3 and 11 and for ionic strengths be-
tween 0.001 and 0.1 are listed in Table A-2. Ionic strength versus activity
coefficients for several species are plotted in Figure A-l.
Data have been compiled for the chemical species listed in Table 25.
The organization of the data is:
Table A-3. Solubility Products
Table A-4. Equilibrium Constants
Table A-5. Carbonate Equilibria Constants
Table A-6. Dissociation Constants of Acids
Table A-7. Formation Constants for Complex Ions
Most of the data apply to conditions of 25°C and atmospheric pressure.
The effect of temperature on the equilibrium constants for several dissolved
species is shown in Figure A-2.
105
-------
TABLE A-rl. VALUES OF THE IONIC SIZE PARAMETER a FOR SELECTED IONS
Charge
Ions
CHCOO",
, CH3OCgH4COO"
4 - 4.5
3.5
3
2.5
Li , CgHgCOO", CgH4OHCOO
CH2CHCH2COO",
CHC12COO", CC13COO
Na+, CdCl+, C102", I03", HC03~, H2P04", HS03",
Cof NH J4 ( N02J2+, CH3COO", CH2C1COO",
NH2CH2COO", +NH3CH2COOH,
OH", F", HS", Br03", I04", Mn04"
CNS", CNO", C103", C104~, K+, Cl", Br", I", CN", N02"
HCOO", H2(citrate)", CH3NH3+, fchA NH2+
Rb+, Cs+, NH,+, Ti + , Ag+
, N03",
4.5
4
Mg2+, Be2+
2-
r2+ r 2+ 7n2+ - 2+ Mn2+ CQ2+ w.2+ r 2+
Ca , Cu , Zn , Sn , Mn , Fe , NT , Co ,
H2C
2-
Sr2+, Ba2+, Ra2+, Cd2+, Hg2+, S2',
-, so32",
, f CHgCOoK2", (CHOHCOO)22", /COoL
", H(citrate)
2-
, C032", S042",
Hg22+, S2032", S2082", Se042", Cr042", HP042",
(continued)
106
-------
TABLE A-1 (continued)
Charge
3
4
o
a
9
6
5
4
11
6
Ions
.,3+ c 3+ ,. 3+ - 3+ V3+ ,.3+ . 3+ r 3+ D 3+ w,3+ Cm3*
Al , Fe , Cr , Se , Y , La , Ln , Ce , Pr , Nd , Sm
Co(ethylenediamine)3 +
Citrate3"
^4")^)M4M^*
Th4+, Zr4+, Ce4+, Sn4+
Co(s203)(cN)54-
Source: Kielland, 1937 and Klotz, 1950
107
-------
TABLE A-2. SINGLE-ION ACTIVITY COEFFICIENTS CALCULATED
FROM THE EXTENDED DEBYE-HUCKEL EQUATION AT 25°C
Activity Coefficients
Charge
1
2
3
4
\Ionic
^Strength
o N.
a >^
9
8
7
6
5
4
3
8
7
6
5
4
9
6
5
4
11
6
5
0.001
0.967
0.966
0.965
0.965
0.964
0.964
0.964
0.872
0.872
0.870
0.868
0.867
0.738
0.731
0.728
0.725
0.588
0.575
0.57
0.0025
0.950
0.949
0.948
0.948
0.947
0.947
0.945
0.813
0.812
0.809
0.805
0.803
0.632
0.620
0.616
0.612
0.455
0.43
0.425
0.005
0.933
0.931
0.930
0.929
0.928
0.927
0.925
0.755
0.753
0.749
0.744
0.740
0.54
0.52
0.51
0.505
0.35
0.315
0.31
0.01
0.914
0.912
0.909
0.907
0.904
0.901
0.899
0.69
0.685
0.675
0.67
0.660
0.445
0.415
0.405
0.395
0.255
0.21
0.20
0.025
0.88
0.88
0.875
0.87
0.865
0.855
0.85
0.595
0.58
0.57
0.555
0.545
0.325
0.28
0.27
0.25
0.155
0.105
0.10
0.05
0.86
0.85
0.845
0.835
0.83
0.815
0.805
0.52
0.50
0.485
0.465
0.445
0.245
0.195
0.18
0.16
0.10
0.055
0.048
0.1
0.83
0.82
0.81
0.80
0.79
0.77
0.755
0.45
0.425
0.405
0.38
0.355
0.18
0.13
0.115
0.095
0.065
0.027
0.021
Source: Bolt and Bruggenwert, 1976
108
-------
0.10
0.01 —
(fl
o
z
oooi-
0.00001
.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 01 0
Figure A-l. Activity coefficients as a function
of ionic strength for selected
dissolved ions (Hem, 1970),
109
-------
TABLE A-3. SELECTED SOLUBILITY PRODUCTS
Reaction*
Al(OH)3(s) =fA!3+ + 30H'
A1P04 • 2H20(s) « A13+ + H2P04~ + 20H~
NH3(g) + H20 * NH4OH
BaC03(s) = Ba2+ + W*~
BaSe04(s) = Ba2+ + Se042"
CdSe03(s) = Cd2+ + SeOj2"
CdC03(s) = Cd2+ + C032"
Cd(OH)2(s) = Cd2+ + 20H"
CdC03(s) + 2H+ = Cd2* + H20 + C02(g)
CdS(s) = Cd2+ + S2"
CaS04 • 2H20(s) = Ca2+ + SO,,2" + 2H20
CaF2(s) = Ca2+ + 2F"
CaC03(s) = Ca2+ + C032" (calcite)
CaC03(s) = Ca2+ + C032" (aragonite)
CaHg(C03)2(s) = Ca2+ + Mg2+ + 2C032"
Ca(H2P04)2 . H20(s) > Ca2+ + 2H2P04" + H20
CaHP04 • 2H20(s) = Ca2+ + HP042' + 2H20
CaHP04(s) « Ca2+ + HP042"
Ca4H(P04) • 3H20(s) = 4Ca2+ + H+ + 3P043" + 3H20
Ca3(P04)2(s) = 3Ca2+ + 2P043"
Ca10(P04)6(OH)2(s) * 10CaZ+ + 6P043" + 20H'
Ca,0(P04)6(F)2(s) = 10Ca2+ + 6P043' + 2F'
Ca3(As04)2(s) = 3Ca2+ + 2(As04)3'
CaSe03(s) = Ca2+ + SeOj2"
CaSe04(s) = Ca2+ + Se042"
T"C
25
25
25
25
25
20
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
20
20
25
Ionic
strength
0
0
Dilute
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Log K«Jf
- 32.34
- 30.50
+ 1.75
- 8.2
- 7.46
- 8.9
- 13.74
- 13.79
- 6.14
- 27.2
- 4.61
- 10.57
- 8.22
- 8.35
- 16.90
- 1.14
- 6.56
- 6.66
- 46.91
- 26.00
-113.7
-120.86
- 18.2
- 5.53
- 3.09
Reference
1
1
1
3
3
3
4
4
3
4
2
2
1
1
1
1
1
1
1
1
1
1
3
3
3
(continued)
110
-------
TABLE A-3 (continued)
Reaction*
CaMo04(s) = Ca2+ + Mo042~
Cu3(As04)2(s) = 3Cu2+ + 2As043"
CuCr04(s) = Cu2+ + Cr042"
CuSeOjU) = Cu2+ + Se032"
CuO(s) + 2H+ = Cu2+ + H20
Cu(OH)(C03)Q 5(s) + 2H+ = Cu2+ + f HgO + l/2C02(g
Cu(OH)Q 67(C03)Q 6?(s) + 2H+ =
Cu2+ + 3 H20 + | C02(g)
Fe(OH3(s) = Fe3+ + 30H'
Fe(OH)3U) = Fe3+ + 30H'
l/2a-Fe203(s) + 3/2H20 = Fe3+ + 30H"
o-FeOOH(s) + H20 ' Fe3+ + 30H"
Fe(OH)2(s) = Fe2* + 20H'
FeP04 • 2H20(s) ' Fe3+ + H2P04' + 20H-
Fe3(P04)2 • 8H20(s) • 3Fe2+ + 2P043' + 8H,,0
Fe2(Se03)3(s) = 2Fe2+ + 3(Se03)2"
FeC03(s) = Fe2+ + CO2'
am.FeOOH(s) + 3H+ = Fe3+ + 2H20
a - FeOOH(s) + 3H+ « Fe3+ + 2H20
FeAs04(s) = Fe3+ + As043'
PbCr04(s) = Pb2+ + Cr04 "
PbSe04(s) = Pb2+ + Se042"
PbC03(s) = Pb2+ + C032'
Pb(OH)2(s) = Pb2+ + 20H"
PbS04(s) • Pb2+ + S042"
T°C
25
20
25
20
25
25
25
25
25
25
25
25
25
25
20
25
25
25
20
25
25
25
25
25
I'onic
strength
0
0
0
0
0
0
0
0
0
0
3 NaC104
3 NaC104
Dilute
0
Log *£
- 8
- 35.1
- 5.44
- 7.68
7.65
7.08
7.08
- 37.5**
- 39.1**
- 42.5
- 44.0
- 15.1
- 34.9
- 36.0
- 30.7
- 10.7
3.55
1.6
- 20.2
- 12.55
- 6.84
- 13.00
- 14.93
- 7.89
Reference
3
3
3
3
2
2
2
1
1
1
1
1
1
1
1
1
2
2
3
3
3
4
4
4
(continued)
111
-------
TABLE A-3 (continued)
Reaction*
Pb3(OH)2(C03)2(s) = 3Pb2+ + 20H' + 2C03
Mg3(As04)2(s) » 3Mg2+ + 2(As04)3'
Mg(OH)2(s) = Hg2+ + 20H
MgSe03(s) = Mg2+ + Se032"
MgC03(s) = Mg2+ + C03Z"
MnS(s) = Mn2+ + S2" (precipitate)
Mn3(As04)2(s) = 3Mn2+ + 2(As04)3'
MnC03(s) = Mn2+ + COj2"
Mn(OH)2(s) = Mn2+ + 20H
MnSe03(s) = Mn2+ + SeOj2"
Hg2S04(s) = Hg2+ + SO^,2'
HgO(s) + H20 = Hg(OH)2 (aq)
HgO(s) + H20 = Hg2> + 20H
HgCl2(s) = Hg2'1' + 2C1
Hg2Cl2(s) = Hg2 + + 2C1"
HgCr04(s) = Hg * + Cr04
HgS(s) = Hg2+ + S2'
(metacinnabar)
(cinnabar)
Ag3As04(s) = 3Ag1+ + As043"
Ag2C03(s) = 2Ag1+ + C0.j2"
AgCl (s) = Ag1+ + Cl"
2AgCr04(s) = 2Ag1+ + Cr042"
Ag(OH)(s) = Ag1+ + OH"
Ag2Mo04(s)^91+^042-
T°C
25
20
25
20
25
25
20
25
25
20
25
25
25
20
25
25
25
25
25
Ionic
strength
0
Dilute
Dilute
0
0
0
Dilute
0
0
0
0
0
Log K«0tf
- 18.80
- 19.7
- 10.8
- 4.89
- 7.80
15.7
- 28.7
- 9.4
- 12.8
- 6.9
- 6.2
- 3.7
- 25.7
- 13.8
- 18.00
- 8.7
- 52.2
- 53.6
- 19.95
- 11.2
- 9.7
- 11.89
- 7.6
- 11.55
Reference
4
3
3
3
1
4
3
3
3
3
3
4
4
4
4
3
4
4
3
3
3
3
3
3
(continued)
112
-------
TABLE A-3 (continued)
Reaction*
Ag2Se03(s) = 2Ag+ + SeOj2"
Ag2Se04(s) = 2Ag+ + Se042'
SrSe04(s) = Sr2+ + SeO 2~
Zn3(As04)2(s) = 3Zn2+ + 2(As04)3~
ZnSe03(s) = Zn2+ + SeOj2"
ZnC03(s) = Zn2+ + COj2"
Zn(OH)2(s) = Zn2+ + 20H'
ZnS(s) = Zn2* + S2" (precipitate)
Zn3(P04)2 4H20(s) = 3Zn2+ + 2P043" + 4H20
ZnO(s) + 2H+ = Zn2+ + HgO
ZnC03(s) * 2H+ • Zn2+ + HjO + C02(g)
Zn(OH)1_2(C03)()_4(s) + 2H+ •
Zn2+ + 1.6 H20 + 0.4 C02(g)
T°C
20
25
25
20
20
25
25
25
25
Ionic
strength
0
0
0
Dilute
0
0
0
0
Log K|0ft
- 14.74
- 8.91
- 4.6
- 26.97
- 6.59
- 10.00
- 15.52
- 22.05
- 32.04**
11.18
7.95
9.80
Reference
3
3
3
3
3
4
4
4
1
2
2
2
*{s) = solid phase.
"Conditions noted only as not 25"C or Ionic Strength = 0
tEqual sign means reversible reaction.
tt,
K° , solubility product for use with activities.
References: 1 - Bolt and Bruggenwert, 1976
2 - Schindler, 1967
3 - Si 11 en and Martel, 1964
4 - Rubin, 1976
Note: A blank under temperature or ionic strength indicates that conditions
were not given. All pressures = 1 atm.
113
-------
TABLE A-4. SELECTED EQUILIBRIUM CONSTANTS
Reaction
A13+ + 40H" =fAl(OH)4"
A13++F"=A1F2+
A13+ + 2F" = A1F2+
Al3* + 3F" * A1F3
Al3* + S042" = A1S04+
NH3(g) + H20 = NH4OH
Ba+ + OH = BaOH
Ba+ + S04" = BaS04
Cd2+ + OH" = CdOH+
Cd2* + F" = CdF*
Cd2+ + Cl" = CdCl +
Cd2+ + 2C1 = CdCl2
Cd2+ + 3C1" = CdCl3"
Cd2+ + Br" = CdBr+
Cd2+ + S042" = CdS04
Cd2+ + Se042" = CdSe04
Ca2+ + F- - CaF+
Sr2+ + CaC03(s,calcite) • (CaKl.Srx2)C03
Cu2+ + OH" = CuOH+
2Cu2+ + 20H' = Cu2(OH)22+
Cu2+ » 30H" - Cu(OH)j"
T"C
25
25
25
25
30
25
25
25
25
25
25
25
25
25
25
25
25
25
18
18
25
Ionic
strength
0
0.53 KN03
0.53 KN03
0.53 KN03
0
0
3 LiC104
1 NaC104
0
0
0
0
0
0
0
Dilute
0
0
0
Log i
32.5
6.13
11.15
15.00
2.04
1.75
0.64
- 10
3.8
0.46
2.00
2.70
2.11
2.15
2.29
2.27
1.04
- 0.89
6.0
17.0
15.2
Reference
2
2
2
2
2
1
3
1
2
2
2
2
2
2
2
3
2
I
Z
2
2
(continued)
114
-------
TABLE A-4 (continued)
Reaction
CuZ+ + 40H" = Cu(OH)42"
Cu2+ + F" = CuF+
Cu2+ + CT » CuCl +
Cu2* + S042" = CuS04
Cu2+ + C03 = CuC03
Cu2+ + 2C032" = Cu(C03)22"
Cr+3 + C13 = CrCl3
Fe3+ + 3F" = FeF3
Fe3+ + Cl" = FeCl2+
Fe3+ + S042' = FeSO/
Fe3+ + OH" » FeOH2'f
Fe3+ + 20H" = Fe(OH)2+
Fe3+ + 40H' = Fe(OH)4'
Fe3+ + F- - FeF2+
Fe3+ + 2T~ = FeF2+
Fe2+ + S042' = FeS04
Pb2+ * S042" = PbS04
L1U + OH' = LiOH
Li1+ + N03" = LiN03
Mg2+ + OH" = Mg(OH)2
Mg2* + S042' • HgS04
Mg(OH)2 + 2H+ ' Mg2+ + 2H20
Mn2+ + OH" « Hn(OH)2
Hg2+ + Se032" • HgSe03
T°C
25
25
22
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
30
25
25
25
25
20
Ionic
strength
0
0.5 NaC104
0
0
0
0
0
0.5 NaC104
1 HC104
0.5 NaC104
3 NaC104
3 NaC104
3 NaC104
0.5 NaC104
0.5 NaC104
0
0
0
0
0
0
Dilute
Log K
16.1
1.23
0
2.3
6.77
10.01
0.60
12.00
0.46
2.31
11.17
22.13
34.11
5.17
9.09
2.3
2.62
0.13
- 1.45
1.4
2.36
16.78
- 10.6
- 1.38
Reference
2
2
2
2
2
2
3
2
2
2
2
2
2
2
2
3
3
3
3
3
3
1
3
3
(continued)
-------
TABLE A-4 (continued)
Reaction
Ag1+ + OH" = AgOH
AgU + N03" = AgN03
Ag1+ + S042" = AgS04'
AgH + Cl1" = AgCl
Na1+ + OH" = NaOH
Na1 + + C03" = NaC03
NaU + S042" = NaS04"
NaU +' HC03" * NaHC03
Si02(s) + 2H20 = H4Si04 (amorphous Si02)
Si02(s) + 2H20 = H4Si04 (quartz)
Zn2+ + OH" = ZnOH'1'
Zn2+ + 30H" = Zn(OH)2"
Zn2+ + 40H" * Zn(OH)42"
Zn2+ t F" - ZnF+
Zn2+ + Cl" « ZnCl+
Zn2+ + 2C1" = Znd2
Zn2+ + 3C1" = ZnCl3"
Zn2+ * 4C1" = ZnCl42"
Zn2+ t S042- = ZnS04
Zn2+ + Se042" = ZnSe04
T°C
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
Ionic
strength
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Log K
2.3
- 0.24
0.23
3.3
- 0.70
1.27
0.72
- 0.25
- 2.74
- 4.00
5.04
13.9
15.1
1.26
0.43
0.61
0.53
0.20
2.38
2.19
Reference
3
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
2
3
All pressures =• 1 atm.
Equal sign means reversible reaction.
References: 1 - Bolt and Bruggenwert, 1976
2 - Schindler, 1967
3 - Sillen and Martel, 1964
4 - Rubin, 1976
Note: A blank under temperature or ionic strength indicates conditions were not given. All pressures - 1 atm.
116
-------
TABLE A-5. CARBONATE SYSTEM EQUILIBRIUM CONSTANTS
(AFTER GARRELS AND CHRIST, 1965)'
Temperature,
°C
0
5
10
15
20
25
30
40
50
80
PK/
6.58
6.52
6.47
6.42
6.38
6.35
6.33
6.30
6.29
(6.32)
PK2ft
10.62
10.56
10.49
10.43
10.38
10.33
10.29
10.22
10.17
(10.12)
t-,1/ **
pK3
8.02
8.09
8.15
8.22
8.28
8.34
8.40
8.52
8.63
8.98
PKCOZ***
1.12 (0.2°)
1.47
1.64
t pK-j = -log
tt pK2 = -log
o
** PK3 - -]°9 KCaCO,
***
where
= -log
and
= the partial pressure of
Values of original authors rounded to two decimal places in present table.
117
-------
TABLE A-6. DISSOCIATION CONSTANTS OF ACIDS IN AQUEOUS SOLUTIONS (25°C)
Acid1"
HC104
HC1
H2S04
HN03
H30+
H3P04
[Fe(H20)6]3+
HF
CH3COOH
[A1(H20)6]3+
H2M0207
H2C03*
H2Cr20?
H2S
H2P04-
HP042'
HOC1
HSe032"
H2As(OH)4'
HCN
H3B03
NH4+
Si(OH)4
HC03"
H202
SiO(OH)3"
Name of acid
Perchloric acid
Hydrochloric acid
Sulfuric acid
Nitric acid
Hydronium ion
Phosphoric acid
Aquo ferric ion
Hydrofluoric acid
Acetic acid
Aquo aluminum ion
Holybdic acid
Aqueous carbon dioxide
Chromic acid
Hydrogen sulfide
Di hydrogen phosphate
Monohydrogen phosphate
Hypochlorous acid
Selenious acid
Arsenic acid
Hydrogen cyanide
Boric acid
Ammonium ion
0-Silicic acid
Bicarbonate
Hydrogen peroxide
Silicate
-Log
acidity constant,
pKA (approximate)
-7
•v-3
*-3
-1
0
2.1
2.2
3.6
4.7
4.9
5
6.3
7
7.1
7.2
7.2
7.6
8.3
9.1
9.2
9.3
9.3
9.5
10.3
-
12.6
Reference
1
1
1
1
1
1
1
3
1
1
3
1
3
1
1
3
1
3
3
1
1
1
1
1
1
(continued)
118
-------
TABLE A-6 (continued)
Acidf
HS"
H20
NH3
OH"
CH4
Name of acid
Bisulfide
Water
Ammonia
Hydroxide ion
Methane
-Log
acidity constant,
pK. (approximate)
14
14
i-23
%24
•x-34
Reference
1
1
1
1
1
^In order of decreasing strength (as measured by extent of dissociation).
References: 1 - Stumm and Morgan, 1970
3 - Si 11 en and Hartel, 1964
119
-------
TABLE A-7. FORMATION CONSTANTS OF SELECTED COMPLEX IONS
Reaction
A13+ +
A13+ +
A13+ +
A13+ +
2A13+
Ca2+ +
Ca2+ +
Ca2+ +
Ca2t +
Ca2+ +
Cd2+ +
Cd2+ +
Cd2+ +
Cd2+ +
Cd2+ +
Cd2+ +
Fe3+ +
Fe3+ +
2Fe3+ *
Fe3+ +
Fe3+ +
Fe2+ +
Fe2+ +
Fe2+ +
H2P04' =fAlH2P042+
HP042" = A1HP04+
H20 « A10H2+ + H+
4H20 = A1(OH)4" + 4H+
* 2H20 = A12(OH)24+ + 2H+
H2P04~ = CaH2P04+
HP042' = CaHP04°
SO.2" = CaSO.°
4 4
HC03" = CaHC03+
C032" = CaC03°
OH" = CdOH+
20H" = Cd(OH)2°
30H" = Cd(OH)3"
Cl" = CdCl+
OH" + Cl" » CdOHCl"
S04= = CdS04°
H20 - FeOH2+ + H+
2H20 = Fe(OH)2+ + 2H*
i- 2H20 = Fe2(OH)24+ + 2H+
3H20 = Fe(OH)3° + 3H+
4H20 •= Fe(OH)4" + 4H+
H20 = FeOH+ + H+
2H20 • Fe(OH)2° + 2H+
3H20 • Fe(OH)3" + 3H+
Log K
,3*
* 8.1*
- 5.02
-23.57
- 6.27
1.08
2.70
2.31
1.26
3.20
4.59
8.93
9.58
2.08
5.87
2.76
- 3.0*
- 6.4*
- 3.1*
-13.5*
-23.5*
- 8.3
-17.2
-32.0
Reference
1
1
1
1
1
1
1
1
1
1
4
4
4
4
4
4
1
1
1
1
1
1
1
1
(continued)
120
-------
TABLE A-7 (continued)
Reaction
Fe2* + 4H20 = Fe(OH)42" + 4H+
Fe3+ + HP042" = FeHP04+
Pb2+ + OH" * PbOH*
Pb2* + 20H" = Pb(OH)2°
Pb2+ + 30H" = Pb(OH)3"
Pb2+ + Cl~ = PbCl+
Pb2+ + 2CT = PbCl2°
Mg2+ + HC03" • MgHC03+
Hg2+ + C032" = MgC03°
Hg2+ + H20 = HgOH+ + H+
Hg2+ + 2H20 « Hg(OH)2° + 2H+
Hg2+ + 3H20 = Hg(OH)3" + 3H+
Hg2+ + Cl" = HgCl+
Hg2* + 2C1" = HgCl2°
Hg2+ + 3d" = HgCl3"
Hg2+ + 4CT = HgCl42"
HgCl2° + H20 = HgOHCl° + Cl" + H+
HgCl2 + 2H20 = Hg(OH)2° + 2C1" + 2H+
Hg2+ + Cys = HgCys2+ (Cys - Cysteine)
Hg2+ + Gly" = (Hg61y)+ (Gly • Glycine)
(HgGlyJ* + Gly' = Hg(Gly)2°
Log K
-46.4
•v. 9.75*
5.85
10.80
13.92
1.62
1.83
1.16
3.40
- 3.4
- 6.00
-20.7
6.7
13.2
14.2
15.2
- 9.6
-19.6
43.57
10.3
8.9
Reference
1
1
4
4
4
4
4
1
1
4
4
4
4
4
4
4
4
4
4
4
4
(continued)
121
-------
TABLE A-7 (continued)
Reaction
Zn2+ + OH' = ZnOH*
Zn2+ + 20H' = Zn(OH)2°
Zn2+ + 30H' = Zn(OH)3'
Zn2+ + 40H' = Zn(OH)42"
7-f 4.
Zn^ + CT « ZnCl
Zn2* t S042" = ZnS04°
Log K
4.95
12.89
14.22
15.48
- 0.56
2.8
4
4
4
4
4
4
•Temperature not given.
Equal sign means reversible reaction.
t
References: 1 - Bolt and Bruggenwert, 1976
4 - Rubin, 1976
Note: Formation constants apply to temperature « 25°C and pressure - 1 atm.
122
-------
-12
-to
-8
-6
.5-4
u
o
J
+ 2
+ 4
50 100 ISO 200
Temperature (*C)
250
300
Figure A-2. Dissociation constants of various
dissolved species as a function of
temperature. Dashed lines indicate
extrapolations (after Helgeson, 1964)
123
-------
100
4.0
11.0
12.0
13.0
PH
Figure A-3. Percentages of total dissolved carbon dioxide species in
solution as a function of pH, 25°C; pressure 1 atmosphere
(Hem, 1970).
124
-------
HCOj, IN MILLIGRAMS PER LITER
1.0 10 100 1000
2000 i 1 .1 i i
tt 100
1.0
1 I 111
\ \ \ \:
i i i ?Vi 11 X i i i rvi 11
«•*
«*
Figure A-4. Equilibrium pH in relation to
calcium and bicarbonate
activities in solutions in
contact with calcite; total
pressure 1 atmosphere;
temperature 25°C (Hem, 1970).
125
-------
ro
en
1.40
1.20
-0.80 -
-1.00
12
14
a. - Solubility of iron in moles per liter as function of Eh and pH at 25°C
and 1 atmosphere of pressure. Activity of sulfur species 96 mg/1 as SO. ,
and carbon dioxide species 61 mg/1 as HCO,~.
1.40
1.20
1.00 -
0.80 -
0.60 -
0.40 -
5
jc 0.20 -
000
-0.20 -
-0.40 —
-0.60 -
-0.80
14
b. - Fields of stability of solids and solubility of manganese as a function of
Eh and pH at 25°C and 1 atmosphere of pressure. Activity of dissolved carbon
dioxide species 100 mg/1 as HCOj". Sulfur species absent.
Figure A-5. Examples of Eh - pH diagrams for iron and manganese (Hem, 1970).
-------
ro
in
c
n>
o. m
-"• X
Ol O>
-LOG CONCENTRATION
O (O oo -g
3 -j. -j -a
3 3 Si —•
„• 3 ro
f* in in
O" VO —h O
O -vj O -h
-S ca
o
ro ro o o
3 O-C O
O -J 3
ro s «< o
T3 <-»• DJ 3
—••a ro 2
ro -"•
-s w
(/> 10
O -"•
o o
3
O
ST
o
3-
o
CL
H
O
3*°
-LOG CONCENTRATION
O
3
O
-------
10 12 14
a. Heterogeneous ZnS-Cu(II)-H20 system at 25°C
CuO
Cu(OH>2 -
Cu(OH)4 .
10 12 14
pH
b. CuO-H20 system at 25°C
Figure A-7. Log concentration-pH solubility diagrams for zinc
and copper (Rubin, 1976, used with permission of
Ann Arbor Science Publishers, Inc.).
128
-------
62 L
SOLUBILITY PRODUCT OF CALCIUM SULFATE
-S
CD
I
CO
o <
-h 01
—i* —J.
O Qi
00
00
n- o
-s -h
ro
t£3 O
3" C
CT
OI —'
fO *<
-S
•o
CO -S
fD O
O Q.
3" C
Ct- O
H) ri-
o> o
- -- fU
Oi
CO
o
O
o
O
0)
CO
c
-h
Oi
<-h
O>
O)
3
a.
en
r+
3
3
o>
r+
ro
3
o
CO
O
cr
o
-h
CO
ri-
O
3
CO
c
a>
Oi
ct
ro
tn
o
r>
p
o
SOLUBILITY PRODUCT OF STRONTIUM SULFATE
o
01
1
_ o
i
3)
m
V
-------
APPENDIX A REFERENCES
Garrels, R.M. and C.L. Christ. 1965. Solutions, Minerals and Equilibria.
Harper & Row, Publishers, New York.
Helgeson, H.C. 1964. Complexing and Hydrothermal Ore Deposition. New
York, Pergamon.
Hem, J.D. 1968. Graphical Methods for Studies of Aqueous Aluminum Hydroxide,
Fluoride, and Sulfate Complexes. U.S. Geol. Survey Water Supply Paper
1827-B. 33 p.
Hem, J.D. and C.E. Roberson. 1967. Form and Stability of Aluminum Hydroxide
Complexes. U.S. Geol. Survey Water Supply Paper 1827-A. 55 p.
Latimer, W.M. 1952. Oxidation Potentials. Prentice-Hall, New York. 392 p.
Lengweiler, H., W. Buser, and W. Feitknecht. 1961. Helv. Chim. Acta 44.
p. 796.
Lindsay, W.L. and E.G. Moreno. 1960. Soil Sci. Soc. Amer. Proc. 24. p. 177.
Nriagu, J.O. 1972. American Journal of Science 272. p. 476.
Nriagu, J.O. 1972. Geochimica et Cosmochimica Acta 36. p. 459.
Pourbaix, M. 1966. Atlas of Electrochemical Equilibria in Aqueous Solutions.
Pergamon Press, Oxford, England.
Ringbom, A. 1963. Complexation in Analytical Chemistry. Interscience
Publishers, New York.
Rubin, A.J. 1976. Aqueous-Environmental Chemistry of Metals. Ann Arbor
Science Publishers, Inc., Ann Arbor, Mich. 390 pp.
Schindler, P., W. Michael is, and W. Feitknecht. 1963. Helv. Chim. Acta 46.
p. 444.
Schmitt, H.H. 1962. Equilibrium Diagrams for Minerals. Geological Club of
Harvard University, Cambridge, Mass.
Sillen, L.G. and A.C. Martell. 1964. Stability Constants of Metal-Ion
Complexes. 2nd ed. Special Publication No. 17. The Chemical Society,
London.
130
-------
Stumm, W. and J.J. Morgan. 1970. Aquatic Chemistry: An Introduction
Emphasizing Chemical Equilibria in Natural Waters. Wiley-Interscience,
New York. 583 pp.
Wagman, D.D., W.H. Evans, V.B. Parker, I. Halow, S.M. Bailey, and R.H.
Schumm. 1968. Selected Values of Chemical Thermodynamic Properties.
Tables for the First Thirty-Four Elements in the Standard Order of Arrange-
ment. NBS Technical Note 270-3.
Wagman, D.D., W.H. Evans, V.B. Parker, I. Halow, S.M. Bailey, and R.H.
Schumm. 1969. Selected Values of Thermodynamic Properties. Tables for
Elements 35 through 53 in the Standard Order of Arrangement. NBS Technical
Note 270-4.
131
-------
INS
APPENDIX B
SOIL PROPERTIES
TABLE B-l. PARTICLE SIZE RANGES AND PERMEABILITY FOR SELECTED MATERIALS
c
*= °
1.
fl
J
Derrick STONE
One-man STONE
Fine, uniform GRAVEL
Very coarse, clean, uniform SAND
Uniform, coarse SAND
Uniform, medium SANO
Clean, Hell-graded SAND AND GRAVEL
Uniform, fine SAND
Well-graded. Sllty SAND AND GRAVEL
51 Hy SANO
Uniform SILT
Sandy CLAY
Sllty CLM
CLAY (30 to 50t clay sizes)
Collodal CLAY (-2^501)
Inches Mi lliitieters
max.
120
12
3
3/8
1/8
1/8
—
-
—
__
—
..
--
—
—
--
Um1n.
36
4
1/4
1/16
1/32
1/64
—
—
—
__
—
-.
--
-.
—
-
n
max.
-
-
80
8
3
2
O.S
10
0.25
5
2
0.05
1.0
0.05
0.05
0.01
"mln.
-
-
10
1.5
0.8
O.S
0.25
0.05
0.05
0.01
0.005
0.005
0.001
0.001
0.0005
10A
"Effective"
size
020 in.
48
6
W2
1/8
1/16
—
-
—
-
__
—
—
—
—
-
-
Dio ""•
-
--
--
0.6
0.3
0.1
0.06
o.oa
0.01
0.006
0.002
0.0015
0.0003
40A
Permeability
coefficient-*
' Ftjyr.
100 x IO6
30 x IO6
10 x 10
5 x IO6
3 x IO6
0.4 x IO6
0.1 x IO6
0.01 x IO6
4000
400
100
50
5
1
0.1
0.001
Ft. /mo.
100 x IO5
30 x IO5
10 x 10
5 x IO5
3 x IO5
0.4 x IO5
0.1 x IO5
0.01 x IO5
400
40
10
5
0.5
0.1
0.01
IO"1
ft. /day
280 x IO3
85 x IO3
28 x 10
14 x IO3
8 x IO3
1 x IO3
0.3 x IO3
0.03 x IO3
11
1
280 x IO"3
140 x IO"3
T
14 x 10
3 x IO'3
0.3 x IO'3
3 x IO"6
Cm./min.
60 X 10?
18 x 1C2
6 X 10
3 x IO2
1.8 x IO2
24
6
0.6
0.24
2« x IO"3
6 x IO"3
3 x IO"3
1
0.3 x 10 J
0.06 x IO"3
0.006 x IO"3
6 x 10"8
Cm. /sec.
100
30
10
5
3
0.4
0.1
0.01
40 x IO"4
4 x 10"4
10"4
0.5 x 10"4
J
0.05 x 10"'
0.01 x IO"4
0.001 x IO"4
10"'
*Adapted from Hough, Soils Engineering. Values listed are approximate.
-------
Values of k, cm/sec.
IO IO I 10
--• --T
•< —
• Gravels
San
ds
Fractu
jointec
Silts
Homogeneous
Clays *•
rissured, weathered Clays
Fractured 0/C Clays, Til Is
red heavily
1 Rock
Lightly jointed/
Sound Rock >.
a. Approximate Range of Permeability in Soil/Rock
1.0
— O.8
E
tr
c
*c
«
a.
O
0.6
O.4
2 0.2
cracks/m
^
to-
10"
10"
IO"
£quivalenf Permeability (cm/sec.)
10-
*number of cracks intersected by well
b. Equivalent Permeability of a Simple Array of
Parallel Cracks
Figure B-l. Graphs for estimating permeability based
on gross material characteristics
(Milligan, 1976).
133
-------
TABLE B-2. TECHNIQUES FOR MEASURING PERMEABILITY
a. Direct testing of in situ permeability in soils
Method
Augerhole
s~*\
(*)
Test Pit
^ Cased borehole (no Inserts)
( B 1
vjy
Cased borehole (inserts used)
i) Sand filter plug
0
ii) Perforated/slotted casing
in lowest section
111) Well point placed 1n hole,
casing drawn back
P i ezometer s/ Permeameters
(with OR without casing)
®
s~*\ Well pumping test
©Test excavation pumping
test(s)
Technique
Shallow uncased hole in unsaturated
material above water level
Square OR rectangular test pit
(equivalent to circular hole above)
1) Falling/rising head Ah in casing
measured VS time
11) Constant head maintained In casing,
outflow, Q VS time
1) Generally falling head, Ah measured
VS time only
11) Variable heads possible
111) As for (11) above
1) Suction Bellows apparatus
(independent of boring)
inflow ONLY measured VS time
11) Short Cell (Cementation)
(Independent of boring) outflow
ONLY measured VS time
111) Piezometer tip pushed Into soft
deposits/placed in boring,
sealed casing withdrawn/pushed
ahead of boring
Constant head, outflow measured
VS time
Variable heads also possible
Drawdown In central well monitored
in observation wells on at least
two 90° radial directions
Monitoring more extensive than (|)
during excavation dewaterlng
(Initial construction stage)
Remarks on application
Difficult to maintain
water levels in coarse
gravels
Borehole must be flushed
Possible fines clog base
(falling Ah)
Pumping (rising Ah) where
UL lowered excessively
Single tests only
Cannot be used as boring
Restricted to fine sands,
coarse silts, variable
bellows required 'k'
range 10"4 to 10"' cm/ sec
Carried out In adit or
tunnel
Possible tip 'smear' when
pushed. Au set up in
pumping tip
Danger of hydraulic
fracture
Screened portion should
cover complete stratum
tested
Expensive, but of direct
benefit to contractual
casing
Method
rating
Poor
Poor
Fair
Fair
Fair to good
i
Goo
(local
1
i
zones)
i
Excellent
(Mass
permeability
of
foundation
material)
Reference
USBR (1968)
Lacrolx (1960)
Hvorslev (1951)
USBR (1968)
Hvorslev (1951)
Colder, Gass (1963)
Colder, Gass (1963)
Gibson (1966)
Wilkes (1974)
Hvorslev (1951)
Bjerrum, et al. (1972)
Todd (1959)
to
Source: Milligan, 1976
(continued)
-------
TABLE B-2. (continued)
b. Direct testing of 1n situ permeability In rock
Method
Borehole (simple tests)
G)
Borehole packer tests
©
Permeameters/lnserts
/~\ Well pumping test
Technique
1) Water gain/loss 1n drilling
11} Simple variable/constant head
tests In open boreholes
1) Single packer tests (during
advance of boring)
11) Double packer tests (1n
completed boreholes)
Pressure tests genetally carried
out 1n BH's (AX to NX size)
Variable head tests In:
1) Sealed Individual piezometers
(local zone)
11) Continuous borehole piezometers
Normally carried out 1n open central
well. Observation wells at rad11. 90°.
Remarks on application
1) Gives possible Indication of
pervious zones. Must be
supplemented by detailed
examination of core.
11) Similar to Table a.. ®
(limited value).
Expanding leather/rubber packers
may provide Inadequate seal.
Pneumatic packers superior to
other types, but limited to
pressures < 200 Ib/sq.ln.
1) Similar to Table a. © -
local zones tested. Limited
application.
11) Possible to monitor water
pressure variation over
complete boring to 200m depth.
Needs Interpretation to assess
'k'.
Similar to Table a, © .
Screen/perforated casing often
NOT required.
Method
rating
Poor
1) Fair
11) Poor to
fair
1) Fair to
good
(local zone)
11) Fair
(Potential
good)
Excellent
(Mass
permeability)
Reference
USER (1968)
Dick (1975)
USSR (1968)
Sherard, ejt. aj_. (1963)
Sharp (1970)
Dick (1975)
1) USBR (1968)
11) Londe (1973)
CO
en
Source: MtlUgan, 1976
(continued)
-------
TABLE B-2. (continued)
c. Indirect assessment of In sttu permeability In soils (rock)
co
CTl
Mtthod
®T«sti on samples
(Inc. natural exposures)
©Geophysical
(Electric well logging)
©Observations of
natural OR Induced
seepage
Technique
1) Gradation
11) Inspection, macro-structure
111) Laboratory 'k'
1) Multi-electrode resistivity
11) Single point resistance potential
111) Fluid conductivity, temperature
Measurement and analysis of data from:
1) Observation wells
11) Pleiometari
111) Dyes, tncers, radioactive Isotopes
Remarks on application
1) 0|Q applicable to uniform
sands
11) Useful In qualitative sense
111) Often Inapplicable to field
conditions
Continuous profiling of borings
can be carried out at low cost
(Requires further correlation with
In situ direct testing)
Provides the best form of
assessing permeabilities. In situ.
In relation to engineering
problems. In soil OR rock
Method
rating
Fair
(to good?)
Poor
Fair
{Future
development
good
Excellent
Reference
Louden (1952)
Colder, Gass (1963)
Rowe (1972)
Guyod (1966)
Robinson (1974)
Walker (1955)
Terzaghl (1960)0964)
Colder. Gass (1963)
Sharp (1970)
Todd (1959)
Source Mllltgan, 1976
-------
TABLE B-3. MEAN VALUES OF FIELD CAPACITY, PERMANENT WILTING
PERCENTAGE AND AVAILABLE WATER FOR SOME SOIL
TEXTURAL CLASSES
Soil type
Sand
Sandy loam
Loam
Silt loam
Clay loam
Clay
Peat
Fractions of soil volume
Field
capacity
0.09
0.27
0.34
0.38
0.30
0.39
0.55
Permanent
wilting
0.02
0.11
0.13
0.14
0.16
0.22
0.25
Available
water
0.07
0.16
0.21
0.24
0.14
0.17
0.30
Source: Salter and Williams (1965) as presented in Monteith, 1975
137
-------
CO
D
0>
U
0)
N
CD
Grovel
Conglomerate
Sandstone
Sand
Siltstone
Silt
Claystone
Clay
7
10
20
r
30
i
40
i
50
I
60
r
70
Porosity (per cent)
Note: Value for siltstone is displaced to the
left, probably because siltstone
measurements were based on very few
samples
Figure B-2. Common range of porosity in typical sediments
and sedimentary rocks (after Longwell et al.,
1969).
138
-------
\J -
20-
(O
c
.0
§40-
H-
0
§ 60-
JJ
CL
80-
inn-
1 — - i •" - • i
AI + H ^"" ""^x Na+H
/ \
/ \
/ \
/ \
/ \
/ Ca + Mg \
/ \
/ \
\
\
/
i i
Acid Normal Sodic
Soil Classification
Figure B-3. Schematic presentation of the cationic
composition of soils (after Bolt and
Bruggenwert, 1976).
139
-------
TABLE B-4. CATION EXCHANGE CAPACITY
FOR SOME SOIL COMPONENTS
Component
Micas
Vermicul ites
Smectites
Amorphous minerals
Humus
Kaolinite
Halloysite (2H20)
Halloysite (4H20)
"111 ites" (hydrous micas)
Chlorite
Glauconite
Glauconite
Ca CEC,*
meq/lOOg
6-140
140-180
80-140
20-160
200-300
3-15
5-10
40-50
10-40
10-40?
11-30
30
K CEC,**
meq/lOOg
3-6
2-7
80-140
20-160
200-300
*CA CEC = cation exchange capacity as measured by
exchanging calcium ions.
**K CEC = cation exchange capacity as measured by
exchanging potassium ions.
Source: Data from Jackson, 1971; Garrels and Christ,
1965; and Bolt and Bruggenwert, 1976
140
-------
TABLE B-5. CATION EXCHANGE CAPACITIES FOR SELECTED SOILS
Soil type
Holland, recent marine clay
(periodically submerged)
Holland, young seaclay soil
Holland, young lake deposit
( Usselmeerpolders)
Holland, river basin soil
Surinam, acid sulphate soil
(reclaimed coastal plain)
U.S.A., gray brown podsolic (alfisol)
Holland, humus podsol (spodosol)
Puerto Rico, Latosol (oxisol)
U.S.A., reddish brown lateritlc soil
(ultisol)
Rumenia, chernozem (mollisol)
U.S.A., self-mulching clay soil
(vertisol)
U.S.A., saline soil
Turkey, saline alkali soil
India, saline alkali soil
Turkey, alkali soil
Rumenia, solodized solonetz
CaC03
(wt.X)
0.3
5.2
10.1
1.3
0
0
0
0
0
0.2
2
8
5
2
0
0
Clay
(X)
29.3
48.9
19.9
40.3
52.0
12.8
2
50.3
42.0
39.5
43.0
?
?
20.0
?
27.4
Humus
(%)
23.3
3.0
2.7
5.3
4.3
1.2
4.2
7.4
7.7
2.6
1.3
?
?
?
?
2.4
CEC
(meq/lOOg)
60.7
18.5 ,
36.5
78.1
38.0
13.1
8.8
30.4
50.6
33.9
50.8
25.6
10.4
9.0
11.2
19.7
Cationic composition
H/A1
0
0
0
0
20
33.
53.
94.
56.
10.
2.
0
0
0
0
17.
Ca
26.2
81.8
90.3
90.6
39
6 51.1
7 35.6
9 1.6
9 28.6
2 66.1
2 78.3
67
27
2
30
9 25.9
Mg
32.8
10.8
7.5
8.5
27
12.2
6.0
2.6
9.3
19.6
16.2
22
24
1
29
25.4
(X Of CEC)
K
6.9
6.5
2.0
0.6
3
3.1
3.3
0.3
5.0
1.8
3.1
3
2
2
2
1.4
Na
34.1
0.9
0.2
0.3
0.5
0.0
1.4
0.6
0.2
2.3
0.2
8
47
95
39
29.4
after Bolt and Bruggenwert, 1976
-------
TABLE B-6. SPECIFIC SURFACE AREAS
Mineral
Coarse sand
Medium clay
Fine clay
Na-illite
Na-montmori 1 1 oni te
Particle diameter
1.0 mm
0.001 mm
0.0005 mm
Specific surface area
0.0026 m2/g
2.26 m2/g
433 m2/g
50-200 m2/g
600-800 m2/g
Source: Gherinl, 1975
142
-------
APPENDIX C
ADSORPTION COEFFICIENTS
ION EXCHANGE COEFFICIENTS
Preferences for ion exchange or adsorption of selected cations or ions
can be expressed by the following equations (Bolt and Bruggenwert, 1976):
For ions of equal valence,
Ya Co a
Y~ = Ka/b ^
b
where K_,b = Kerr selectivity coefficient
Y-a = amount of ion "a" on (bound to) the soil solid
phase, meq/100 grams soil
Y = amount of ion "b" on (bound to) the soil
solid phase, meq/100 grams soil
C = concentration of ion "a" in soil solution,
' meq/kg solution
C , = concentration of ion "b" in soil solution,
' meq/kg solution
Ka/b can be shown to be related
Db"Ka/b Co
where m = cation exchange capacity of solid medium, meq/g
C = initial solution concentration ([a] + [b]),
meq/ml
For monovalent/divalent ion preference
143
-------
Y V
_± = _1
V JV2+
where Y+ = amount of monovalent cation on (bound to) the soil
solid phase, meq/100 g soil
Y2+ = amount of divalent cation on (bound to) the soil
solid phase, meq/100 g soil
Kg = Gapon exchange constant
C ,+ = concentration of monovalent cation in soil
* solution, meq/kg solution
C 2+ = concentration of divalent cation in soil
' solution, meq/kg solution
Values of the Kerr selectivity coefficients for several ion pairs are
given below:
KK/Na 5 KCa/Ba ^ l
KNH4/Na % 5 KCa/Sr ^ 1
KNH4/Rb % 5 KCa/Zn ^ l
KH/K % l KCa/Co ^ l
KCa/Mg l'2 KCa/Cu ^ 1
KCa/Ni % 1
Values of the Gapon exchange coefficient for several ion pairs are
listed below:
Kg = h. (moles/liter)"^ if concentration of ions was
Na/Ca given in moles/liter
Kr =1 (moles/liter)"^ in montmorillonitic soils
bNa/Ca
Kp - h (Ci, + C...\ if concentration of sodium (Cw_) is
K/Na '
' much greater than potassium (CK)
The Gapon exchange constant for two divalent cations where the Kerr selectiv-
ity coefficient is approximately 1 can be estimated as the sum of the concen-
trations of the two ions.
144
-------
THE DISTRIBUTION COEFFICIENT, KQ
Definition
This coefficient is used in the mass transport equations to account for
pollutant removal from solution due to "sorption" on the soil or rock. Kp is
defined for specific pollutants by the following ratio:
concentration of pollutant sorbed on soil/rock,
v _ mg of pollutant per gram of solid
i\p, —
u Concentration of pollutant in solution,
mg of pollutant per milliliter of solution
The distribution coefficient is an equilibrium constant. As such its use
requires that equilibrium conditions be maintained between the distribution of
pollutant in solution and on the solid phase. Equilibrium is more closely
approached in slow moving ground waters than in rapidly flowing surface water
systems (e.g., compare river velocities of about 1 ft/sec to seepage veloci-
ties of ground water of about 1 ft/day).
The major processes creating the observed distributions of pollutants be-
tween solid and liquid phases include adsorption, absorption, and ion-exchange.
Kp, in Relation to Pollutant Migration
The ratio of the ground water seepage velocity, Vs, to the pollutant mi-
gration velocity, V , is given by
Vs KDp
\T= l + -7T
VP P
where Kn = the distribution coefficient, defined above [m£/g]
p = the in situ bulk density of the permeable media:
weight of solids per unit volume of soil or rock
as packed [g/m£]
e = void fraction = ground water volume/volume of
solid
For a given pollutant, a KD value of zero would indicate that the pol-
lutant behaves conservatively. KD values for tritium, chloride, and nitrate
in many systems approach zero. A high KD value indicates that the pollutant
sorbs strongly on the soil/rock matrix; its migration velocity would be much
lower than the liquid seepage velocity.
Dependencies of the Distribution Coefficient
KD values depend upon several factors. Listed below are those factors
which most strongly influence KQ values:
145
-------
t Chemical form (species) of the pollutant of concern
• Mineralogical and physical characteristics of the
solid phase
• Surface coating on the solid phase (e.g., amorphous
iron hydroxide coatings)
• Concentrations of other constituents in solution
(e.g., hydrogen ions, complexing agents, ions which
form insoluble compounds with the pollutant of
concern)
• Redox state of the system
The various forms in which a pollutant can exist (e.g., for sulfur, H^S
HS", S042", R-SH, etc.) can be expected to exhibit differing migration behav
ior.
Although KQ values have been largely developed based upon the mass of
the solid phase present, the use of soil-specific surface areas is a better,
but more expensive, technical approach. The behavior of certain aqueous
pollutants (e.g., inorganic mercury) has been shown to be correlated most
strongly with the amount of surface area present. For mercury the mineralog
ical type of surface is far less important.
It should be noted that because of the above dependencies, and the com-
mon lack of documentation of such during experimental determination of KQ
values, actual values are typically site-specific.
KD Values
A considerable amount of work has been done to determine KQ values for
radionuclides associated with the nuclear power industry. Values for other
pollutant species are limited. Data can sometimes be obtained from the soil
science literature for species of agricultural interest by analysis of exper
imentally determined Langmuir and Freundlich isotherms.
The Langmuir adsorption equation is commonly presented as follows
(Adamson, 1967):
kb C
x _
m 1 + kC
where - = amount of pollutant adsorbed per unit weight of
m '
m absorbent
C = equilibrium concentration of the adsorbing compound
0 in solution
146
-------
k = constant (relates to bonding energies)
b = maximum amount of pollutant adsorbable
At the low concentrations which are common for many ground water pollutants
kC0 is small relative to 1 and the above equation reduces to
Kn can thus be approximated by the slope of the Langmuir adsorption isotherm in
the linear region. (A similar demonstration can be made using the Freundlich
equation with n = 1.)
KQ values are usually determined by batch experiments where a given
amount of soil is added to a solution of known pollutant concentration and
chemical composition. The resulting mix is agitated until the pollutant con-
centration in solution no longer decreases (equilibrium condition).
Field determination of KQ values is also possible. This requires the
use of non-soil-interactive tracers such as tritium and typically is more ex-
pensive than laboratory batch experiments. A pertinent discussion of KQ mea-
surement techniques is given in the EPA report 520/6-78-007, Vol. 1, 1978,
"Radionuclide Interactions with Soil and Rock Media."
Specific values of Kp for inorganic mercury, inorganic copper, boron,
and tritium are presented in Table C-l.
147
-------
TABLE C-l. EXAMPLE DISTRIBUTION COEFFICIENTS FOR SELECTED
SPECIES AND SYSTEM CHARACTERISTICS
00
Species
Hg- (total inorganic mercury; includes
Hg complexed with OH", and Cl")
Cu, (total inorganic copper; complexed
with inorganic SW anions)
B (fully protonated orthoboric acid
HjBO,; common form of boron in natural
waters)
3H (tritiated water)
Source:
(1) Gherini, S., 1975
(2) Emerson, R.R. and F.L. Harrison, 1978
(3) Hadas, A. and J. Hagin, 1971
(4) Ames, 1978
Conditions
[CT] = 10~3 molar
pH = 7
Hg @ trace concentrations
T = 20°C
2
Soil = silt, sp. surf area = 1 m /g
[CT] = 0.5
pH = 8
Cu @ trace concentrations
EC = 0.6 mmhos (25°C)
pH a 6.6
T = 30°C
(solid phase: Terra rossa soil gp.
[B] _< 35 ppm
Sandy soils
clays and other hydrated minerals
KD, value, mfe/gram
2.6 x 10 ! (!'
gm * '
1,000 to 45,000 5 (2)
ml/gm
(3)
0 ml/gm
0 ml/gm
(4)
-------
APPENDIX D
MATHEMATICAL FUNCTIONS
TABLE D-l. TABLES OF ERROR AND ASSOCIATED FUNCTIONS (after Crank, 1976)
X
0
005
Ol
O15
0-2
O25
O3
035
04
0-45
05
055
O6
O65
O7
O75
OS
O85
O9
O95
14
1-1
1-2
1-3
1-4
1-5
14
17
18
1-9
2O
2-1
2-2
23
24
2-5
24
2-7
28
29
34
Error Functions of X
X2
e erfc x
1-0
(V9460
O8965
0-8509
O8090
&7703
(X7346
0-7015
&6708
0-6423
&61S7
0^909
O5678
0-5462
O5259
O5069
0-4891
O4723
0-4565
04416
04276
04017
O3785
O3576
0-3387
0-3216
03060
O2917
O2786
O266S
O2554
O24S1
02356
O2267
02185
02108
O2036
O1969
O1905
O1846
OI790
4,-^xe-"'
0
O1126
0-2234
O3310
04336
a5300
O6188
0-6988
0-7692
0*294
08788
O9172
04447
04614
0-9678
O9644
O9520
O9314
O9035
O8695
O8302
&7403
O6416
&5413
04450
0-3568
&2791
O2132
0-1591
0-1160
0-0827
0-0576
04393
O0262
04171
04109
O0068
04042
04025
00015
O0008
2^ ,-»'
1-1284
1-1256
1 1172
1-1033
1-0841
1-0600
1O313
O9983
O9615
O9215
O8788
08338
O7872
O7395
&6913
0-6429
O5950
O5479
05020
04576
04151
0-3365
O2673
0-2082
O1589
O1189
O0872
O0627
OO442
O0305
OO207
OO137
OO089
OO057
O0036
04022
O0013
O0008
04004
04003
04001
erf x
0
0456372
a 112463
& 167996
0-222703
&276326
0-328627
0-379382
0428392
0475482
O 520500
&S63323
0-603856
O642029
O677801
&711156
0-742101
&770668
&796908
O820891
O842701
O880205
&910314
0^934008
O952285
O966105
0976348
O983790
0-989091
0-992790
0-995322
0-997021
&998137
O998857
O999311
O999593
O999764
O999866
O999925
O999959
&99997S
erfc x
14
O943628
O887537
O832004
0^777297
0-723674
0^671373
0-620618
(X571608
O524518
0479500
0436677
O396144
&357971
&322199
O288844
&2S7899
O229332
&203092
0-179109
O157299
O1I9795
0489686
0465992
0447715
0433895
0423652
0416210
0410909
0407210
0404678
0402979
0401863
0001143
0400689
0400407
0400236
0400134
0400075
0400041
0400022
Note: erfc(x)
erf(-x)
1 -erf(x)
-erf(x)
149
-------
en
=1 e* e« « M
11111
11
i
* sl«£S §
— — — OOO OOOOO OOOOO OOSOS SOOOO OOOOO OOOOO OOOOO OOO • —
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*— i-r* a— «
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ttun — r-« caoc4«M> c*akr» -r^-^nra
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SSoSS SISSS SSSSS S3S8S 80888 SS3S8 3S3SS SSSSS ooogS S
ooaaa aoootnai aa»a
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oa» o» o o a> c» octe
S« ct co ^ Msor^aoa
waoaoao SSaaooo
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j»«Ck«e» ooaoooaooe ^goaor—r— r-« r— f^« r- r- o
SSoSo ooooo ooooo ooooo o
5SSBS
r r f r r
pppop poop
r r r r r r r r \
SIQ M) Ml W3 K ^ ^* *T ^ ^* •» "^ "•• ^" f
poppcS ppppp pppop
r f r \ i r r r r r r r r r r r
300 O
' i i \ \ \ r 1111 \ i
His
IpSSS 2ai33 5SSS3S 55RSS S22SS SS2S2 SSSSS S35SS SR382 22S53
3SS33 SSSS3 33333 33333 33333 55333 33353 53553 55553 55555
~ *«- — ^ r-«
888S-8 8S888 §§§§§ §§
-r ne*e»-^ aoa.-r«o«ota •O-WPSCO c*e*c« — — oooc
§§§§§ SS§§§ §§§§§ §§§!§ §§§11 §§§s
iiil
lill
3...4V.C* c*c«c«coco «rt^^>«r ^r-v«iM)io io>< ..«••»«
S5555 SSS5? S
[iif
||SI| |§§§2 |§SS§ Hill S|||§ Sls|| Illil I
:lll lilli BSlil ll'li §==== ====! Illil iilii iiiii ij
i r r r r r r r r r r r r r r r i' i' i' i' r r r r r r i' r r i r i r r <»»»' <' r •' <»' '
—
KS
S SSS5S 2
SS3 ioSls pSSpS pppip SSSSS SSSS
ssS2S |SS|S HSSrS
S pSoop 000°,
ill
i§ §1
i
{III ii||| mil Hill Illll iilii Illil Illll liiii iiiii I
S.5S33 SSSSS SSt3t3S .?SSSS S.=J=KS SSF:^ 33Z3X ^SSSS SSSSS 22255 5
••evcicic* «•*•«•«««•• Mricvcvc* «o«««e*«» ••««•«•«•« ^ •*•***«* •«•••>••••• •»*•««•««« •••»•••••« ^
t i
i i i i i i
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SSSo
i" i i i"
:sss= s55is i^iSs I
5oooo ooo^^ ooooo <
i
i i
n
saa SSSSS SSSSf: S5S2S SSS5S 2S2SS 5S=S3 SSSSS S|ii
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ooo ooooo ooooo ooooo ooooo ooooo ooooo pppop ooooo pppop o
S533S SSSSS 2=22Z -=252 ^SSSS ^SSSS SSSSS 3SRSS S555? SS55S S
«•••••••«* MCMCtccc* **c«r«c«c« MCVMCVM *• ci M r« n *«••**•«« ••€«<••«<«•« WCCMMO* MC«c«e«*« «teitc«««e« ••
151
-------
TABLE D-2. (continued)
1
CM
4.01
4.02
4.03
104
US
4.06
4.07
4.08
4.08
4.11
4.12
4.11
4.14
US
4.11
4.17
4.11
4.11
4.21
4.22
4.23
4.24
US
4.26
4.27
4.28
4.29
4J»
4.31
4.32
4.33
4.34
US
4.36
4.37
4.38
4.39
C«
4.41
4.42
4.43
4.44
4.1S
4.46
4.47
4.48
4.49
CM
Am
6000
6000
5000
5000
5000
5000
5000
5000
5000
5000
5000
5000
6000
5000
6000
6000
6000
5000
5000
.5000
.5000
5000
.5000
.5000
.5000
5000
.5000
.5000
5000
.5000
5000
.5000
.5000
.5000
.5000
.5000
.5000
.6000
.5000
.6000
.5000
.6000
.6000
.5000
.5000
.5000
.5000
.5000
.6000
.6000
•tie
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.oooo
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.oooo
.0000
.0000
oooo
.0000
oooo
*l»*
«"(*)
.0070
.0019
.0019
.0011
.0011
.0017
.0018
.OOlt
.0015
.0015
.0014
.0014
.0011
.0013
.0011
.0012
.0011
.0011
.0011
.0010
.0010
.0009
.0009
.0009
.0009
.0008
.0008
.0008
.0007
.0007
.0007
.0007
.0006
.0006
.0008
.0006
.0005
.0005
.0005
.0005
.0001
.0004
.0004
.0004
.0004
.0004
.0004
.0004
.0003
.0003
.•003
Tra-
in*
-.0070
-.0067
-.0065
-.0063
-.0061
-.0059
-.0058
-.0056
-.0044
-.0052
-.0051
-.0049
-.0047
— .0046
-.0044
-.0043
-.0042
-.0040
-.0039
-.0038
-.0038
-.0035
-.0034
—.0033
— .0032
-.0031
-.0030
-.0029
-.0028
-.0027
-.0026
-.0025
-.0024
— .0023
-.0022
-.0022
-.0021
-.0020
-.0019
-.0019
-.0018
-.0017
-.0017
-.OOlt
-.OOlt
-.0015
-.0014
-.0014
-.0013
-.0013
-.0011
tin
.0218
.0212
.0207
.0201
.0195
.0190
.0185
.0180
.0175
.0170
.0185
.0160
.0158
.0151
.0147
.0143
.0138
.0134
.0130
.0127
.0123
.0119
.0116
.0112
.0109
.0105
.0102
.0099
.0096
.0093
.00(0
.0087
.0085
.0082
.0079
.0077
.0074
.0072
.0070
.0067
.0065
.0063
.0061
.0059
.0057
.0055
.0053
.0052
.0050
.0048
.•047
f
tM
4.51
4.52
4.63
4.54
US
4.56
4.67
4.68
4-59
ceo
4.61
4.62
4.83
C64
cts
4.66
4.67
4.68
4.69
CM
4.71
4.72
4.73
4.74
CTS
4.76
4.77
4.78
4.79
4.10
4.81
4.82
4.83
4J4
US
4.86
4.87
4.88
4.89
4JM
4.91
4.92
4.93
4.94
US
4.98
4.97
4.98
4.99
Arm
.6000
.5000
.6000
.5000
.6000
.5000
.5000
.5000
.5000
.1000
.6000
.6000
.6000
.6000
.6000
.6000
.6000
.6000
.6000
.6000
.5000
.5000
.5000
.5000
.5000
.5000
.5000
.5000
.6000
.5000
.5000
.6000
.5000
.6000
.6000
.5000
.6000
.5000
.6000
.6000
.6000
.5000
.5000
.6000
.6000
.6000
.6000
.5000
.5000
.6000
(Mi-
utc
«*>
.0000
.0000
oooo
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.oooo
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
oooo
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.0000
.oooo
.0000
.oooo
oooo
.0000
.0000
.0000
En?
fctin
«"<*)
.0003
.0003
.0003
.0003
.0003
.0003
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0002
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0001
.0000
.0000
.0000
.0000
.0000
TTCT
tire
-.0012
-.0012
-.0012
-.0011
-.0011
-.0010
-.0010
-.0010
-.0009
-.0009
-.0009
-.0008
-.0008
-.0008
-.0007
— .0007
-.0007
-.0006
-.0006
-.0006
-.0008
-.0006
-.0005
— 0005
-.0005
— .0005
-.0005
— 0004
-.0004
-.0004
-.0004
-.0004
-.OOM
-.0003
-.0003
-.0003
-.0003
-.0003
-.0003
— .0003
— .0003
-.0002
— .0002
— .0002
-.0002
— 0002
-.0002
-.0005
— 0002
-.0002
rar
tnt
.0047
.0041
.0044
.0041
.0041
.0031
.0031
.0037
.0031
.0034
I0032
.0031
.0030
.0021
.0027
.0021
.0021
.0021
.0024
.0021
0022
.0021
.0020
.0019
.0011
0011
.0017
.0011
.0011
.0011
.0011
.0014
.0011
.0011
.0011
.0011
.0911
.0011
.0011
.0011
.0011
.DON
.0001
.0001
.OOM
.OOM
80M
iton
<0(X) =-
Reprinted with permission from Handbook of
Chemistry and Physics by Hodgman. Copyright
1961, The Chemical Rubber Co., CRC Press, Inc.
152
-------
APPENDIX E
PIPE FLOW DATA
0.1
VaKMS ol IDVt tor witar M 60T. Mtemctar In inches, vctodty hi IL/MCJ
2 4 6 10 20 40 60 100 200 400 600 1000 2000 4000 10,000
n.
0.003-0.03
0.001-0.01
0.0006-0.003
0.00085
00005
0.0004
000015
0.000005
Riveted steel
Concrete
Wood Haw
Cast iron
Galvanized iron
Asphalted cast wen
Steel or wrought iron
Drawn tubing
0.010
0.009
0.008
2(103) 4 6 810*
2(10*1 4 i 810» 2(105] 4 6 810> 2(10*1 4 6 810' 2(10') 4 6 810*
Reynold* number, N, • ^~-
Key: D = pipe internal diameter
V = pipe flow velocity, pipe flow
divided by flow cross-sectional area
v = fluid kinematic viscosity
L • length of pipe
h. = head loss due to pipe friction
g = gravitational acceleration
e = absolute pipe roughness (see
Figure E-2)
Figure E-l. Moody diagram for estimating the friction factor
for pipes (after Linsley and Franzini, 1964).
153
-------
0.1
Pipe diam.D,tt
02 0.3 0.4 0.6 0.8 1 2 34 6 8 10 20
-—*» — ' l*"l ' I *l ' ^ti* iji * I i i \ i *i I - i1 i i * I A * _A ' \ * I _ f _ *_
0.000006
0.0000051 ' • ' '
. I . I . I I I I I IX . , .1 . I . I . I I I I I I .... I .
3 4. 5 6 8 10 20 30 40 60 100 200 300
Pin* Hiim tn
Pipe diam. in.
Figure E-2. Relative roughness for different types of
pipes (after Moody, 1944).
154
-------
TABLE E-l. PHYSICAL PROPERTIES OF LIQUID WATER
Temp,
•F
32
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
212
Specific
weight
t,
pcf
62.42
62.43
62.41
62.37
62.30
62.22
62.11
62.00
61.86
61.71
61.55
61.38
61.20
61.00
60.80
60.58
60.36
60.12
59.83
Density
P,
dugs/ft*
1.940
1.940
1.940
1.938
1.936
1.934
1.931
1.927
1.923
1.918
1.913
1.908
1.902
1.896
1.890
1.883
1.876
1.868
1.860
*
Viscosity
MX10*.
Ib-MC/ft*
3.746
8.229
2.735
2.359
2.050
1.799
1.595
1.424
1.284
1.168
1.069
0.981
0.905
0.838
0.780
0.726
0.678
0.637
0.593
*
Kine-
matic
viscosity
»X10\
ft'/sec
1.931
1.664
1.410
1.217
1.059
0.930
0.826
0.739
0.667
0.609
0.558
0.514
0.476
0.442
0.413
0.385
0.362
0.341
0.319
*
Surface
tension
• X 10',
Ib/ft
0.518
0.514
0.509
0.504
0.500
0.492
0.486
0.480
0.473
0.465
0.460
0.454
0.447
0.441
0.433
0.426
0.419
0.412
0.404
Vapor
pressure
head
P*/T,
ft
0.20
0.28
0.41
0.59
0.84
1.17
1.61
2.19
2.95
3.91
5.13
6.67
8.58
10.95
13.83
17.33
21.55
26.59
33.90
*Bulk
modulus
of
elasticity
K X 10-»
psi
293
294
305
311
320
322
323
327
331
333
334
330
328
326
322
318
313
308
300
Source: From Fluid Mechanics by Daugherty and Franzini.
Copyright © 1965 by McGraw-Hill, used with
permission of McGraw-Hill Book Company.
*Note values in the columns are interpreted in the following way:
For Temp. = 40°F u = 3.229 x 10"5, v^
a = .514 x 10"2, and K = 294 x 1(T
1.664 x 10"5,
155
-------
APPENDIX REFERENCES
Adamson, A.W. 1967. Physical Chemistry of Surfaces. Second Edition. John
Wiley & Sons, New York.
Ames, L.L. and D. Rai. 1978. Radionuclide Interactions with Soil and Rock
Media. Vol. 1. U.S. Environmental Protection Agency 520/6-78-007.
Bechtel. 1976. Conceptual Design of Commercial 50 MWe (NET) Geothermal Power
Plants at Heber and Niland, California. Report No. SAN-1124-1.
Bolt, G.H., and M.G.M. Bruggenwert. 1976. Soil Chemistry A. Basic Elements.
Elsevier Scientific Publishing Company, New York. 281 pp.
Crank, J. 1976. The Mathematics of Diffusion. Clarendon Press, Oxford.
Daugherty, R.L. and J.B. Franzini. 1965. Fluid Mechanics with Engineering
Applications. McGraw-Hill Book Company, New York.
Emerson, R.R. and F.L. Harrison. 1978. Partitioning of Copper in Sea Water
and Sediment near Nuclear Power Plants at Diablo Canyon and San Onofre, CA.
NUREG Rept. (in press).
Garrels, R.M. and C.L. Christ. 1965. Solutions, Minerals, and Equilibria.
Harper and Row, New York.
Gherini, S. 1975. A Study of Water Quality Impact of the Implementation of
Air Quality Standards. Teknekron, Inc. p. 93-207.
Hadas, A. and J. Hagin. 1971. Boron Adsorption by Soils as Influenced by
Potassium. Soil Science.
Hem, J.D. 1970. Study and Interpretation of the Chemical Characteristics of
Natural Water. U.S.G.S. Water Supply Paper 1473.
Hodgman, C.D., R.C. Weast and S.M. Selby. 1961. Handbook of Chemistry and
Physics. Chemical Rubber Publishing Company.
Hough, B.K. 1957. Basic Soils Engineering. Ronald Press, New York.
Jackson, M.L. 1971. Soil Chemical Analysis. Madison, Wisconsin.
Kielland, J. 1937. Individual Activity Coefficients of Ions in Aqueous Solu-
tions. Journal Amer. Chemical Society, V. 59. p. 1675-1678.
156
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Klotz, I.M. 1950. Chemical Thermodynamics. Prentice-Hall, Englewood Cliffs,
New Jersey.
Linsley, R.K. and J.B. Franzini. 1964. Water Resources Engineering.
Longwell, C.R., R.F. Flint and J.E. Sanders. 1969. Physical Geology. John
Wiley and Sons, Inc., New York.
Milligan, V. 1976. Field Measurement of Permeability in Soil and Rock in
Proceedings of the Conference on In Situ Measurement of Soil Properties June
1-4, 1975. American Society of Civil Engineers, New York.
Monteith, J.L. 1975. Vegetation and the Atmosphere. Academic Press.
Moody, L.F. 1944. Trans. ASME, Vol. 66. p. 673.
Rubin, A.J. 1976. Aqueous-Environmental Chemistry of Metals. Ann Arbor
Science Publishers, Inc., Ann Arbor, Michigan. 390 pp.
Schindler, P.W. 1967. Heterogeneous Equilibria Involving Oxides, Hydroxides,
Carbonates, and Hydroxide Carbonates, in Equilibrium Concepts in Natural Water
Systems. W. Stumm, Symposium Chairman. American Chemical Society, Washington,
D.C. p. 196-221.
Sillen, L.G. and A.E. Kartell. 1964. Stability Constants of Metal-Ion Com-
plexes Section I: Inorganic Ligands. Chemical Society Special Publications
No. 17, London.
Smith, R.W. 1971. Relations Among Equilibrium and Nonequilibrium Species of
Aluminum Hydroxy Complexes. In: Nonequilibrium Systems in Natural Water
Chemistry. J.D. Hem, Symposium Chairman. Amer. Chemical Society, Washington,
D.C. p. 250-279.
Stumm, W. and J.J. Morgan. 1970. Aquatic Chemistry: An Introduction Empha-
sizing Chemical Equilibria in Natural Waters. Wiley-Interscience, New York.
583 pp.
Wilson, J.L. and P.J. Miller. 1978. Two-Dimensional Plume in Uniform
Groundwater Flow. Journal of the Hydraulics Division, p. 503-514. April.
157
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APPENDIX F
EXAMPLE CASE
INTRODUCTION
In this section the methodology is applied to a hypothetical geothermal
power plant to illustrate the sequence of the procedure. The power plant is
a 50 MWe single cycle flash type. The plant is located in an agricultural
area with sandy soils. Ten production wells and five injection wells serve
the plant. Preinjection treatment ponds and a temporary storage pond are
located at the site.
Two aquifers underlying the site are used in the nearby area. Aquifer 1
is a shallow aquifer used as a drinking water supply for the surrounding
population. Aquifer 2 is a deeper aquifer used as an irrigation supply.
A typical cross-section at the plant site is shown in Figure F-l. The pro-
duction zone is located 60 meters below Aquifer 2. The spent geothermal
fluid is injected back into the production zone after passing through ponds
to precipitate silica and to remove suspended solids.
SITE CHARACTERISTICS
Power plant capacity 50 MWe
Production well flow rate 1,000 gpm
Injection well flow rate 2,000 gpm
Total fluid flow rate 10,000 gpm
Geothermal fluid characteristics:
Total dissolved solids 4,400 mgA Alkalinity 390 mg/l
(as CaC03)
Arsenic 0.15 mg/Jl Barium 2.9 mg/Jl
Boron 4.3 mg/Jl Cadmium 0.02 mg/Jl
Chloride 2,760 mg/Jl Iron 1.2 mg/Jl
Manganese 0.28 mg/Jl Mercury 0.006 mg/Jl
158
-------
T7
f
*
• •••••••*•
S L_ — ( \_ — <
i , — ^_
4f FLASHER. TURBINE CONDENSER
SEPARATOR GENER-
CASED ATOR
PRODUCTION
WELL
•** **
T T
Aqytte.r.S
r\^
fe^
JV ~L PON° 1
INJECTION i
WELL
-
-:^:-*::::::::::::::
*•*••*•••• «i
i
Production and Injection Zone '
30 m
15 m
500 m
23 m
60 m
15 m
NOTE: Diagram not to scale.
Key:
Release Type
> Group 1
— > Group 2
Group 3
Figure F-l. Typical cross-section at power plant site.
159
-------
Selenium 0.5 mg/£ Sodium l,619mg/£
Temperature at well bottom 180°C
PROBLEM STATEMENT
A preliminary analysis of the power plant and site identified three
potential problems. They are a leak from the temporary storage pond, a leak
through the casing into Aquifer 1, and a casing leak in the injection well
which could migrate into Aquifer 2. The following sections describe how the
methodology would be used to estimate the concentrations from these hypo-
thetical releases and to evaluate the potential significance.
ENVIRONMENTAL CONCERNS
The two aquifers of concern were identified from well records and test
drilling at the site (see Figure F-l). Interconnections between Aquifers 1
and 2 are considered minimal because of the very low permeability of the
shale formation between them and the absence of known faults or fractures
in the shale.
Aquifer uses were determined from water rights permits and a survey of
farmers in the area. Aquifer 1 is used as a- drinking water supply for about
150 people and for stock watering. Aquifer 2 is used as an irrigation supply
for about 50 farms. A comparison of the concentrations in the geothermal
fluid with EPA primary and secondary drinking water standards for Aquifer 1
and agricultural use limits for Aquifer 2 identified several constituents of
concern (Table F-l).
RELEASE POTENTIAL
Potential release points are identified by reviewing the power plant
schematic and comparing it to Figure 8 Diagram to Locate Potential Releases.
The geothermal fluid concentrations and power plant conditions are then com-
pared to the threshold values to identify cases where high pressures, tem-
peratures, hydrogen sulfide or TDS concentrations occur. In this example
case pressures slightly above 100 psia exist in the power plant and injection
well. None of the other threshold values are exceeded. Potential release
sites are casing leaks in an injection well, pipe breaks at elbows, and leaks
from the unlined storage pond. Three release types are further described to
illustrate the other sections of the methodology: a pond leak, a casing leak
from the injection well into Aquifer 1, and a casing leak in the injection
well which could migrate to Aquifer 2.
Release volumes are estimated for each of these cases based on well and
plant flows and Table 20. A slow leak from the pond might have a flow rate
of 450 gpd. Casing leaks in the injection well would have a maximum flow
rate of 2,000 gpm.
160
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TABLE F-l. CHEMICAL PARAMETERS OF CONCERN
Constituent
Arsenic
Barium
Boron
Cadmium
Chloride
Iron
Lead
Manganese
Mercury
Selenium
Sodium
Total dissolved
solids
Geo thermal fluid
concentrations,
mg/a
0.15
2.9
4.3
<0.02
2,760
1.2
0.4
0.28
0.006
0.5
1,619
4,422
Drinking water
standards*
units are mg/A
0.05
1.0
-
0.01
250
0.3
0.05
0.05
0.002
0.01
-
500
Irrigation
1 imits
units are mg/&**
0.1
_t
0.75
1
-
-
30
0.2 for acidophil ic
plants
-
-
high SAR
1,500
*U.S. EPA, 1976a and 1977.
**U.S. EPA, 1976b.
Dash indicates no criteria.
161
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CHEMISTRY OF RELEASED FLUID
The temperature of the fluid at the well bottom is 180°C and 104*C at
the injection wellhead. The pressure drops from 160 psia at the well bottom
to 103 psia at the injection well. The geothermal fluid moves up the well
and flashes at the production wellhead. The steam is routed to a turbine
and condenser and then is mixed with the unflashed fluid from the flash
vessel. The combined fluid then goes to the injection treatment pond and
injection well. Leaks in the part of the plant where the fluid is separated
into two phases are not likely so corrections to the fluid concentrations do
not need to be made.
GROUND WATER CONTAMINATION
The first step is to determine the appropriate solution method for the
three release cases using Table 24, Summary of Solution Methods. The slow
leak from the storage pond is a Group 1 continuous release. The appropriate
solution method is GEOHY-GEOQAL Analytical Solution and the mass-balance
approach. The leak from the injection well casing into Aquifer 1 is a
Group 2 slug release; the well was shut-in one hour after discovery of the
leak. The appropriate solution method is Advection-Dispersion Case A. The
leak from the injection well which migrates into Aquifer 2 is a Group 3 slug
release since the well was shut-in after 12 hours. The appropriate solution
method is the Bernoulli-Darcy method and Advection-Dispersion Case A. The
following sections describe the equations to be used and how they apply to
these cases. Numerical values have not been substituted into the equations
since the emphasis is on the procedure.
GROUP 1 SURFACE RELEASE
Problem Statement
Estimate the time required for the concentration of pollutant X at a
depth of 30 meters to be fifty and ninety percent of the initial concentra-
tion in the geothermal fluid. The soils are sandy with a seepage velocity
of 0.15 m/day. A tracer study in the field gave a value of 0.011 m^/day
for vertical dispersion.
Solution Method
The release is a Group 1 continuous release. Since the problem is to
determine when the concentration has reached a given value the procedure for
breakthrough times can be used. The equation to be used to calculate the
fifty percent value is Eq. (10):
t - zx- ^- [\ + i } (10)
1/2 v v \ e / '
s s x '
where all terms are as defined in Section 4.
162
-------
Data needed are depth of interest, seepage velocity, void volume in the soil,
and the adsorption equilibrium constant. The first two values were deter-
mined in the field and are given in the problem statement. The void volume
is estimated from the porosity. The porosity is .25 as estimated from cores.
The adsorption constant should be set equal to 0 initially and then may be
set equal to the appropriate value, e.g., 400 for mercury. The data are
then substituted into Eq. (10).
The time to reach ninety percent of the initial concentration at 30 m
is estimated using the simplified form of Eq. (13):
R = jm
= (l +St'2)
where m = I 1 + St1 I and other terms are as defined in Section 4
and
The resulting concentration in Aquifer 1 is estimated by the mass
balance approach using Eq. (14):
c . VP +
Qp + Qfl
This approach assumes complete mixing with that portion of the aquifer
directly under the pollutant source. Data needed include the area and width
of the pond, the velocity of the pollutant, the thickness and velocity of
the aquifer, the initial concentration of pollutant in the aquifer and the
concentration at the aquifer interface. The concentration at the aquifer
interface can be considered equal to the initial pollutant concentration
for a worst case or estimated using Eq. (8):
c(z,t) =
c o . - erf
o
/ *-^L-\ 1
\ N/4RYS/J
The resulting concentration in Aquifer 1 is then compared to the drinking
water standards.
GROUP 2 RELEASE
Problem Statement
Estimate maximum concentration in Aquifer 1 from a casing leak in the
injection well at a distance of 30 m. The flow rate was 760 £pm for one
hour which gives a total release volume of 45,600 JL The seepage velocity
163
-------
in Aquifer 1 is 0.03 m/day. Dispersion tests in the field gave a lateral
dispersion rate of 0.46 mvday.
Solution Method
The time to reach the maximum concentration at the specified distance
is estimated first, using Eq. (18):
max
(18)
Data needed are the seepage velocity, the lateral dispersion and the desired
distance. The maximum time is then used as data input to estimate the maxi-
mum concentration at the desired distance using Eq. (17):
c(x,y,t) =
m
d 4Trpt(DxDy)1/2
exp
4Dxt
- At
(17)
Additional data needed include total mass of pollutant injected into the
aquifer, effective porosity, adsorption constant, and void volume. The mass
of pollutant is estimated as the volume of released fluid times the pollutant
concentration. The mass is then expressed as mass per meter of aquifer
thickness. The conservative case would be estimated first by assuming no
adsorption so Rd = 1.
The concentrations for the conservative case would be compared to the
drinking water standards. For the constituents which exceed the standards
then the concentrations with attenuation are estimated. For these cases the
retardation factor, R^, would be computed using the appropriate adsorption
constant, k.
GROUP 3 RELEASE
Problem Statement
Estimate the flow and concentration in Aquifer 2 from a leak in the
casing of an injection well. The injection well had a flow rate of 7,600
jlpm. The well flowed for 12 hours before it was shut-in. The location of
the leak was 250 meters below the surface. The well casing is 0.3 meters
in diameter and is made of carbon steel.
164
-------
Solution Method
The flow into Aquifer 2 can be estimated using the Bernoulli-Darcy
approach. The pressure at the point of the leak is estimated using Eq. (19):
p? pi i vi2
J.= _i+ L + f t. 1 (19)
Y Y g
Data needed are the wellhead pressure, the depth to the leak, the well diam-
eter, the friction factor of the casing, and the velocity in the well. The
friction factor is estimated from the Moody diagram (Figure E-1 in Appendix E
based on the relative roughness and Reynolds number. The roughness is esti-
mated from Figure E-2 in Appendix E. The Reynolds number is estimated from
Eq. (20):
N = — (20)
NR — uu;
The next step is to estimate the pressure at the casing leak using Eq. (19).
The flow into Aquifer 2 is estimated using a modified form of Darcy's
Law. The shale between the injection zone and Aquifer 2 is known to be
fractured. The fracture zone is considered to be a circular zone 0.6 m in
diameter with a permeability of 7.6 m/day. Aquifer 2 is confined with a
hydrostatic head of 60 m. The flow into Aquifer 2 is estimated using Eq.
(21):
«3 - «-T^rfe (21)
Data needed include the permeability, approximate length, and cross-sectional
area of the fracture zone, the pressure in Aquifer 2, the head in the aquifer,
and the specific weight of the geothermal fluid.
The resulting concentration in the aquifer can be estimated in the same
manner as the Group 2 release using Eq. (17) and (18). These concentrations
would be compared to the agricultural use limits (Table 11).
165
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APPENDIX G
GLOSSARY OF SELECTED TERMS
Seepage velocity - a microscopic property, actual velocity of fluid flow
through interstices of the soil.
Darcy velocity - a macroscopic property, the velocity of fluid in the ground
water system as defined by Darcy's Law, V = -K.?JjL , where K = hydraulic
conductivity, "11= hydraulic gradient. c"
Field capacity - water content of a soil profile which has been thoroughly
wetted and allowed to drain until the rate of drainage is negligible.
Adsorption - the attachment of pollutants to soil material by various
mechanisms including for example, cation exchange.
Advection - the movement of solutes by flowing ground water at a rate equal
to the average velocity of the water.
Dispersion - the spreading of solutes as they are transported by advection.
Dispersion is caused by microscopic differences in pore velocities and by
the mixing of fluid in individual pore channels.
Longitudinal dispersion - the spreading of solutes in the direction of flow.
Transverse dispersion - the spreading of solutes perpendicular to the
direction of flow.
166
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APPENDIX H
U.S.-METRIC CONVERSION TABLE
U.S. customary
U.S. equivalent
Metric equivalent
inch (in)
foot (ft)
yard (yd)
mile (mi)
square foot (sq ft)
square yard (sq yd)
acre
square mile (sq mi)
gallon
cubic yard (cu yd)
cubic mile (cu mi)
gallons per minute (gpm)
18.2 gpd/sq ft
(for water at 60°F)
pounds per hour
cu ft per sec (cfs)
0.083 ft
0.33 yd, 12 in
3 ft, 36 in
5,280 ft, 1,760 yd
Area
144 sq in
1,294 sq in, 9 sq ft
43,560 sq ft,
4,840 sq yd
640 acres
Volume
4 quarts
27 cu ft
Flow Rate
Darcy
25.4 millimeters (mm)
0.3048 meters (m)
0.9144 m
1.609 kilometers (km)
0.0929 sq m
0.836 sq m
4,047 sq m,
0.404 hectare (ha)
2.59 sq km
3.785 liters U)
7.645 cubic meter
4.1655 cu km
icu m)
3.785 liters per minute (£pm),
6.309 x 10"5 cu m/sec
9.66 x 10~4 cm/sec
-(for water at 20°C)
1.260 x 10~4 kg/sec
28.32 fcps, 0.02831 cu m/sec
167
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-80-117
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Methodology to Evaluate the Potential for Ground Water
Contamination from Geothermal Fluid Releases
5. REPORT DATE
August 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Karen Summers, Steve Ghering, Carl Chen
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Tetra Tech Inc.
3700 Mt. Diablo Blvd.
Lafayette, CA 94549
10. PROGRAM ELEMENT NO.
1NE827
11. CONTRACT/GRANT NO.
68-03-2671
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati. Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT ~~—" '
This report provides analytical methods and graphical techniques to predict
potential ground water contamination from geothermal energy development. Overflows
and leaks from ponds, pipe leaks, well blowouts, leaks from well casing, and
migration from injection zones can be handled by the methodology. General
characteristics of geothermal systems and fluids and probable modes of release are
included in the report to provide typical data.
The major steps of the procedure are to determine environmental concerns and
release potential, to identify potential ground water contamination, and to
evaluate significance of contamination. Analytical methods, data requirements.
typical data and coefficient values are included.
The methodology may be used as a regulatory tool for predicting impacts or for
testing control technologies. Geothermal developers can use the methodology to
predict adverse impacts at development sites and select control methods for the
conditions or locations where required.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Ground water
Environmental engineering
Geothermal prospecting
geothermal
energy conversion
water pollution
pollution control
08H
10A
13B
18. DISTRIBUTION STATEMENT
Release unlimited
19. SECURITY CLASS (ThisReport)
none
21. NO. OF PAGES
176
20. SECURITY CLASS (Thispage)
none
22. PRICE
EPA Form 2220-1 (Rev. 4—77) PREVIOUS EDITION is OBSOLETE
168
v>US GOVERNMENT PRINTING OFFICE 1980-657-165/0116
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