United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
PO Box 15027
Las Vegas NV89114
EPA 600 7 78 207
November 1978
Research and Development
Geothermal Environmental
Impact Assessment
Subsurface Environmental
Assessment for Four
Geothermal Systems
Interagency
Energy-Environment
Research
and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. The 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 systems. The goal of the Pro-
gram is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by providing the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
pollutants and their health andecological effects; assessments of. and development of.
control technologies for energy systems; and integrated assessments of a wide range
of energy-related environmental issues.
This document is available to the public through the National Technical Information
Service. Springfield, Virginia 22161
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EPA-600/7-78-207
November 1978
GEOTHERMAL ENVIRONMENTAL IMPACT ASSESSMENT
Subsurface Environmental Assessment
for Four Geothermal Systems
by
Geonomics, Inc.
Berkeley, California 94703
Contract No. 68-03-2468
Project Officer
Donald B. Gilmore
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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DISCLAIMER
This report has been reviewed by the Environmental
Monitoring and Support Laboratory-Las Vegas, U.S. Environmental
Protection Agency, and approved for publicatiqn. Approval does
not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute en-
dorsement or recommendation for use.
ii
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FOREWORD
Protection of the environment requires effective regulatory
actions which are based on sound technical and scientific infor-
mation. This information must include the quantitative descrip-
tion and linking of pollutant sources, transport mechanisms, in-
teractions, and resulting effects on man and his environment. Be-
cause of the complexities involved, assessment of specific pol-
lutants in the environment requires a total systems approach which
transcends the media of air, water and land. The Environmental
Monitoring and Support Laboratory-Las Vegas contributes to the
formation and enhancement of a sound monitoring data base for
exposure assessment through programs designed to:
• develop and optimize systems and strategies for
monitoring pollutants and their impact on the
environment
• demonstrate new monitoring systems and technologies
by applying them to fulfill special monitoring needs
of the Agency's operating programs
This report is the second in a series of five reports cover-
ing the following subjects:
• baseline geotechnical data for four geothermal areas
in the United States
• subsurface environmental assessment of geothermal
development
• a guide for decision makers
• a pollution control technology guidance manual
• a groundwater monitoring methodology for geothermal
developments
The first two reports cover the baseline data necessary for
the development of the fifth report which will contain the strat-
egy for monitoring change in groundwater quality as a result of
any geothermal resource development, conversion and waste disposal.
iii
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The -third report will be a guideline for those persons
charged with responsibility for issuing permits for geothermal
exploration, development, conversion and waste disposal.
The fourth report will cover justification of the need, by
way of regulatory or anticipated regulatory requirements, for
control of constituents of raw wastes and a description of waste
control technology alternatives.
For further information on these reports, contact the
Monitoring Systems Research and Development Division of the
Environmental Monitoring and Support Laboratory. Las Vegas,
Nevada .
George B. Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
iv
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ABSTRACT
Geothermal systems are described for Imperial Valley and The
Geysers, California; Klamath Falls, Oregon; and the Rio Grande
Rift Zone, New Mexico; including information on location, area,
depth, temperature, fluid phase and composition, resource base
and status of development. The subsurface environmental assess-
ment evaluates potential groundwater degradation, seismicity and
subsidence. A general discussion on geothermal systems, pollu-
tion potential, chemical characteristics of geothermal fluids and
environmental effects of geothermal water pollutants is presented
as background material.
For the Imperial Valley, all publicly available water qual-
ity and location data for geothermal and nongeothermal wells in
and near the East Mesa, Salton Sea, Heber, Brawley, Dunes and
Glamis KGRAs have been compiled and plotted. The geothermal
fluids which will be reinjected range in salinity from a few
thousand to more than a quarter million ppm. Although Imperial
Valley is a major agricultural center, groundwater use in and
near most of these KGRAs is minimal. Extensive seismicity and
subsidence monitoring networks have been established in this area
of high natural seismicity and subsidence.
The vapor-dominated Geysers geothermal field is the largest
electricity producer in the world. Groundwater in this mountain-
ous region flows with poor hydraulic continuity in fractured rock.
Ground and surface water quality is generally good, but high
boron concentrations in hot springs and geothermal effluents is
of significant concern; however, spent condensate is reinjected.
High microearthquake activity is noted around the geothermal
reservoir and potential subsidence effects are considered minimal.
In Klamath Falls, geothermal fluids up to 113°C (235°F) are
used for space heating, mostly through downhole heat exchangers
with only minor, relatively benign, geothermal fluid being pro-
duced at the surface. Seismicity is low and is not expected to
increase. Subsidence is not recognized.
1
Of all geothermal occurrences in the Rio Grande Rift, the'
Valles Caldera is currently of primary interest. Injection of
geothermal effluent from hydrothermal production wells should
remove any hydrologic hazard due to some potentially noxious con-
stituents. Waters circulating in the LASL Hot Dry Rock experi-
ment are potable. Seismic effects are expected to be minimal.
Subsidence effects could develop.
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CONTENTS
Page
Figures x
Tables xiii
Acknowledgements xvi
1. GENERAL CONSIDERATIONS
1.1 Introduction 1
1.1.1 Obj ectives 1
1.1.2 Scope of Investigation ! 3
1.1.3 Subsurface Environmental Impact
Report 4
1.2 Background 4
1.2.1 Legislative and Regulatory Aspects 5
1.3 Geothermal Systems 7
1.3.1 Geothermal Resource Types 7
1.3.2 Pollution .Jrom Geothermal Operation 9
1.3.3 Chemical uiaracteristics of
Geothermal Fluids 11
1.4 Environmental Effects of Water Pollutants 19
1.4.1 General 19
1.4.2 Human Consumption 24
1.4.3 Aquatic Life 24
1.4.4 Agricultural and Livestock Use 27
1.4.5 Industrial Water Supply 27
1.4.6 Thermal Pollution 32
References 34
2. IMPERIAL VALLEY
2.1 Introduction 36
2.1.1 Summary 36
2.1.2 Background 3 9
2.1.3 Summary of Imperial Valley
Geotechnical Data 40
2.2 Geothermal Systems 42
2.2.1 East Mesa KGRA 46
2.2.2 Salton Sea KGRA 59
2.2.3 Heber KGRA 66
VI
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Page
2.2.4 Brawley KGRA 67
2.2.5 Dunes and Glamis KGRA 68
2.3 Water Pollution Potential 70
2.3.1 Summary of Baseline Water
Characteristics 77
2.3.2 East Mesa KGRA 78
2.3.3 Salton Sea KGRA 94
2.3.4 Heber KGRA 106
2.3.5 Brawley KGRA 111
2.3.6 Dunes and Glamis KGRAs 116
2.4 Seismicity 120
2.4.1 Summary of Baseline Seismicity and
Seismic Risk 121
2.4.2 Potential Induced Seismicity 127
2.5 Subsidence 129
2.5.1 Baseline Data and Monitoring
Programs 130
2.5.2 Potential Subsidence 139
2.6 Pollution Control Technology 141
2.6.1 Current Practices 141
References 143
THE GEYSERS
3.1 Introduction 151
3.1.1 Summary 151
3.1.2 Background 151
3.2 Geothermal System 152
3.2.1 Definition of System 152
3.2.2 Potential Pollutants 158
3.3 Water Pollution Potential 161
3.3.1 Summary of Baseline Water
Characteristics 161
3.3.2 Potential Water Pollutants 163
3.3.3 Potential Pollution Mechanisms and
Pathways 163
3.3.4 Level of Potential Pollution 163
3.4 Seismicity 164
3.4.1 Summary of Baseline Seismicity and
Seismic Risk 164
3.4.2 Potential Induced Seismicity 170
vii
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3.5 Subsidence 171
3.5.1 Baseline Data 171
3.5.2 Potential Subsidence 171
3.6. Pollution Control Technology 172
3.6.1 Current Practices 172
3.6.2 Anticipated Technology 172
References 175
KLAMATH FALLS
4.1 Introduction 177
4.1.1 Summary 177
4.1.2 Background 177
4.2 Geothermal System 178
4.2.1 Definition of System 178
4.2.2 Potential Pollutants 185
4.3 Water Pollution Potential 185
4.3.1 Summary of Baseline Water
Characteristics 185
4.3.2 Potential Water Pollutants 185
4.3.3 Potential Pollution Mechanisms and
Pathways 186
4.3.4 Level of Potential Pollution 186
4.4 Seismicity 186
4.4.1 Summary of Baseline Seismicity and
Seismic Risk 186
4.4.2 Potential Induced Seismicity 187
4.5 Subsidence 188
4.5.1 Baseline Data 188
4.5.2 Potential Subsidence 188
4.6 Pollution Control Technology 188
4.6.1 Current Practices 188
4.6.2 Anticipated Technology 188
References 189
RIO GRANDE RIFT ZONE
5.1 Introduction 190
5.1.1 Summary 192
5.2 Geologic Setting 195
5.2.1 Topography and Drainage 195
viii
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5.2.2 Physiography and Geomorphology 198
5.2.3 Soils and Vegetation 198
5.2.4 Structure 198
5.2.5 Heat Flow 199
5.2.6 Stratigraphy and Paleography 199
5.2.7 Water Bearing Characteristics 203
5.3 Hydrologic Setting 204
5.3.1 Introduction 204
5.3.2 Climate 204
5.3.3 Stream Flow 208
5.3.4 Ground Water 208
5.3.5 Water Chemistry 210
5.4 Geothermal Development 212
5.5 Potential Pollution 217
5.5.1 Caldera Area 217
5.5.2 Hot Dry Rock Experiment 217
5.6 Seismicity 218
5.7 Subsidence 220
5.8 Conclusion 220
References 221
Appendices
A. Abbreviations and Chemical Symbols 224
B. Explanation for Description of Wells Tables 228
C. U.S.-Metric Conversion Table 230
D. Glossary 232
ix
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FIGURES
Number Page
1.1 Location of study areas 2
1.2 Comparison of concentration ranges of
constituents in geothermal and potable waters 21
2.1 Physiographic setting and location of Imperial
Valley, California 37
2.2 Temperature gradient map showing locations of
KGRAs in Imperial Valley, California 38
2.3 Geothermal well locations, heat flow contours
and mapped faults, East Mesa KGRA 47
2.4 Pressures, temperatures and total flow rates,
Mesa 6-1, Mesa 5-1 and Mesa 8-1 50
2.5 Surface pressures and total flows, wells flowing
full open, Mesa 6-2, Mesa 5-1 and Mesa 8-1 50
2.6 Specific injection and discharge at Mesa 5-1
during initial injection and discharge
operations 54
2.7 Chemical profile of geothermal wells, Mesa
anomaly 56
2.8 Block diagram of isothermal surfaces -
Salton Sea geothermal field 62
2.9 Location of wells in East Mesa, Heber, Dunes and
Glamis KGRAs 82
2.10 Location of wells in Salton Sea and Brawley
KGRAs 96
2.11 Microearthquake epicenters recorded in East
Mesa, June 10 to July 15, 1973 122
2.12 Location of seismograph stations and earthquake
epicenters in the Imperial Valley,
June 1, 1973 through May 31, 1974 124
IX.
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Number Page
2.13 Epicenters of earthquakes of the Brawley swarm,
January 1975 125
2.14 Strong-motion stations and epicenters in
the Imperial Valley area 126
2.15 Seismograph networks in Imperial Valley 128
2.16 Geodetic measurements in the Imperial Valley
from 1934 to 1967 131
2.17 Local leveling network in Salton Sea
geothermal field 133
2.18 Regional first- and second-order level network
and vertical movement in Imperial Valley
1972-1974 134
2.19 Regional network of horizontal control 136
2.20 Network'of horizontal control in Salton Sea
geothermal area • 137
2.21 Ground motion detection instrumentation
installed at East Mesa geothermal area 138
3.1 Location of The Geysers study area 153
4.1 Physiography of Klamath Falls, Oregon vicinity 179
5.1 Thermal areas of the Rio Grande Rift in
New Mexico 191
5.2 General features of the Jemez area 193
5.3 The Jemez River Basin 194
5.4 Geology of the Jemez area 196
5.5 Relief map of the' rocks of Precambrian age
in the Jemez area 200
5.6 Relation of annual mean precipitation to
altitude 205
5.7 Relation of annual mean potential evapotrans-
piration to altitude 206
xi
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Number Page
5.8 Simplified cross section through the Valles
Caldera and GT-1. The surface trace of the
section is perpendicular to the Rio Grande 216
5.9 Locations of microearthquake epicenters in
north-central New Mexico, September 1973 to
December 1975 219
5.10 Magnitude-frequency relationship for all
earthquakes within 225 km of Los Alamos,
September 1973 to December 1975 219
xii
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TABLES
Number Page
1.1 Some Chemical Index Properties of Geothermal
Waters 13
1.2 Chemical Composition of Geothermal Waters
Worldwide 14
1.3 Relative Abundance of Maximum Reported
Concentrations of Chemical Composition in
Geothermal Waters Worldwide 17
1.4 Gas Composition of Geothermal Vapors
Worldwide 20
1.5 Comparison of Inorganic Chemical Water
Standards with Geothermal and Seawater
Analyses 22
1.6 Pollutants Limited by Water Quality Standards
in States with Geothermal Potential 25
1.7 Aquatic Life Criteria for Constituents in
Geothermal Fluid 26
1.8 Agricultural Use Criteria for Constituents
in Geothermal Fluids 28
1.9 Minor and Trace Element Tolerances for
Irrigation Water 30
1.10 Relative Tolerance of Plants to Boron 31
1.11 TDS in Industrial Waters 32
2.1 Estimates of Stored and Recoverable Heat in
the Geothermal Resources of Imperial Valley 44
2.2 Casing and Completion Records, East Mesa Test
Site 49
2.3 Bottom-hole Shut-in and Flowing Pressures and
Temperatures, East Mesa Wells 52
xi'ii
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Number Page
2.4 Injection Schedule, Mesa 5-1 55
2.5 Summary of Production Characteristics for Geo-
thermal Wells in Salton Sea KGRA 63
2.6 Estimated Daily Fluid Production for Imperial
Valley Geothermal Developments 74
2.7 Estimated Projected Total Daily Chemical Con-
stituent Production from Potential Geothermal
Development in Imperial Valley 75
2.8 Description of Wells in and Within 1.6 km (1 mi)
of East Mesa KGRA 79
2.9 Chemical Analyses of Geothermal Fluids in and
Within 1.6 km (1 mi) of East Mesa KGRA 84
2.10 Chemical Analyses of Water from Nongeothermal
Wells in and Within 1.6 kir (1 mi) of East
Mesa KGRA 88
2.11 Description of Well Sites and Water Samples
in and Within 1.6 km (1 mi) of
Salton Sea KGRA 95
2.12 Chemical Analyses from Specified Sites and Non-
geothermal Wells in and Within 1.6 km (1 mi)
of Salton Sea KGRA 97
2.13 Chemical Analyses of Geothermal Fluids in and
Within 1.6 km (1 mi) of Salton Sea KGRA 101
2.14 Description of Wells in and Within 1.6 km (1 mi)
of Heber KGRA 107
2.15 Chemical Analyses of Water from Nongeothermal
Wells in and Within 1.6 km (i mi) of Heber
KGRA 108
2.16 Chemical Analyses of Geothermal Fluids in and
Within 1.6 km (1 mi) of Heber KGRA 110
2.17 Description of Wells in and Within 1.6 km (1 mi)
of Dunes, Glands and Brawley KGRAs 112
xiv
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Number Page
:2.18 Chemical Analysis of Water from Nongeothermal
Wells in and Within 1.6 km (1 mi) of Dunes,
Glands and Brawley KGRAs 113
2.19 Chemical Analyses of Geothermal Fluids in and
Within 1.6 km (1 mi) of Dunes KGRA 118
3.1 Noncondensible Gases in Steam Supplied to
Turbines at The Geysers 156
3.2 Potential Pollutants Reported from Steam at The
Geysers 158
3.3 Expected Daily Production of Selected
Pollutants from 907 MW (net), Anticipated
in 1980 159
3.4 Typical Drilling Mud Composition, The Geysers 160
i
3.5 Earthquake Recurrence Intervals for the
Central Coast Range 167
4.1 Chemical Analyses of Waters from Springs and
Wells, Klamath Basin, Oregon 182
5.1 Cumulative Percent of Mean Monthly Precipita-
tion for Stations in the Jemez Area 207
5.2 Stream Gaging Stations in the Jemez River
Basin 209
5.3 Chemical Analyses of Surface Waters in the
Upper Jemez River Basin 213
I
5.4 Chemical Analyses of Thermal Waters in the
Upper Jemez Basin 214
xv
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ACKNOWLEDGEMENTS
This report was prepared by an interdisciplinary team of
scientists from Geonomics, Inc., GeothermEx, and W.K. Summers
and Associates. The participants in the preparation of the
various aspects of this report include:
Project Management: Geonomics, Inc., H. Tsvi Meidav,
Project Manager, and Subir K. Sanyal, Deputy Project Manager.
f
General Section and Imperial Valley: Geonomics, Inc.,
Richard B. Weiss, Subir K. Sanyal and Theodora Oldknow.
The Geysers and Klamath Falls Sections: GeothermEx.
Rio Grande Rift Zone Section: W.K. Summer and Associates.
Editor: Geonomics, Inc., Evelyn Bless.
i
Donald B. Gilmore, the Project Officer, was responsible
for administration and general guidance of the project for the
U.S. Environmental Protection Agency.
xvi
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SECTION ONE
GENERAL CONSIDERATIONS
1.1 INTRODUCTION
This is the second in a series of reports concerning the
environmental assessment of effluent extraction, energy con-
version and waste disposal in geothermal systems. The primary
objective of the study is to provide the U.S. Environmental
Protection Agency (EPA) with a monitoring approach to detect
any ground water pollution caused by geothermal resource devel-
opment. This approach is expected to serve as a model for
monitoring any geothermal area. An important part of this study
involves subsurface environmental impact assessment of geo-
thermal development in four areas: Imperial Valley and The
Geysers, California; Klamath Falls, Oregon; and the Rio Grande
Rift Zone, New Mexico (Fig. 1.1). Each of these areas is repre-
sentative of a distinct type of geothermal system. The Imperial
Valley is representative of an intermediate to high temperature,
liquid-dominated system; The Geysers, of a vapor-dominated
system; Klamath Falls, of a low temperature, liquid-dominated
system; and Rio Grande Rift, of a hot dry rock system, and a
high temperature, liquid-dominated system.
The first report in this series prepared by Geonomics,
Inc., is titled "Baseline Geotechnical Data for Four Geothermal
Areas in the United States" (in press). That report includes
compilation and assessment of baseline data on geologic, hydro-
logic, climatic and seismic conditions, as they pertain to
potential subsurface environmental impact, in each of the four
geothermal areas mentioned above. The present report defines,
within the limits of available data, the geothermal systems and
potential subsurface environmental impact of geothermal energy
development in each of the four areas. From the data base
provided by these assessments, a monitoring system will be
designed, implemented and evaluated at one of the four areas.
1.1.1 Objectives
The objectives of the overall study are to acquire and
analyze data for the purposes of:
a. identifying pollutants as a result of geothermal
development,
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\^vivo N-' |2°,;
0
h
0
' .'.
APPROXIMATE SCALE
(miles)
100 200
• I I , - t .
100 200 300 4OO
(kilometers)
IMPERIAL7 d
VALLEY
105°
Figure 1.1 Location of study areas
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b. identifying pathways into the underground water
environment,
c. identifying ecological hazards involved with long-term
operating facilities,
d. designing a groundwater monitoring approach that will
be applicable to any geothermal resource development
and conversion facility, and
e. applying the methodology to a selected site and oper-
ating the system to verify its applicability.
The primary emphasis is on the environmental effects of
changes in the groundwater regime, both chemical and hydraulic,
as a result of geothermal resource utilization. The environ-
mental effects to be considered are potential groundwater
pollution, subsidence and induced seismic events, which in turn
may affect the ecology and socioeconomic conditions of the area.
1.1.2 Scope of Investigation
The scope of work is outlined in five tasks to be accom-
plished in three stages. Stage I is an assessment stage that
includes Tasks 1 and 2. Task 1 defines the geology, hydrology,
climatology and seismicity of the four geothermal areas, in-
cluding identification of aquifers. Task 2 defines the various
geothermal systems and quantifies the pollutants from geothermal
resources development, including phase of the produced fluids,
subsidence possibilities, seismic effects, fluid disposal meth-
ods and thermal losses, and their possible effects on the ground-
water of each area. This report is the result of the Task 2
investigation.
Stage II is a design and research stage that includes Task
3, resulting in the design of a groundwater monitoring system
for one of the four areas.
Stage III includes Tasks 4 and 5 and is a groundwater
monitoring, analysis and evaluation stage. Task 4 involves
implementation and operation of the monitoring program under the
direction of the Project Officer. Recommendations for improve-
ment in the monitoring plan will be incorporated into Task 5.
As a result of the experience in designing and operating a
monitoring system, recommendations for a general groundwater
monitoring methodology that will be most apt to meet the re-
quirements of any geothermal resource development will be the
culmination of Task 5.
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1.1.3 Subsurface Environmental Impact Report
The first (Task 1) report (Geonomics, in press) of this
study considered baseline geotechnical data on the four geo-
thennal areas. This second (Task 2) report defines the geo-
thermal systems in each area. To the extent that data are
available, the definition of the system includes location, area,
depth, temperature, phase of fluid, chemical composition of
fluids, estimated resource base and recoverable heat reserve,
the status of field development, projected development, existing
well data and anticipated operational problems. Another aspect
of Task 2 is the identification and quantification of potential
pollutants in the geothermal effluents from each of the four
areas. The third aspect of Task 2 is to assess, within the
limits of available data, the potential subsurface environmental
impact of geothermal resource development in each of the four
areas. The so-called "subsurface" environmental impact study
considers timely underground environmental factors such as
groundwater quality and seismicity, but also some near-surface
but aboveground environmental factors such as chemical and
thermal pollution of surface water bodies and subsidence of the
ground surface. This study specifically excludes consideration
of aboveground environmental factors such as air and noise pol-
lution. The remaining facet of Task 2 is consideration of the
available and anticipated technologies of disposal of the geo-
thermal pollutants.
Based on the Task 1 and Task 2 reports, a monitoring pro-
gram can be formulated for each of the four geothermal areas,
and more important, a general monitoring strategy can eventually
be developed that will be applicable to any geothermal area.
1.2 BACKGROUND
Geothermal resources are a relatively new source of energy.
The first electrical power generator, utilizing geothermal
steam, was operated at Larderellp, Italy, in 1904. The first
geothermal power plant was established at the same site in 1913.
New Zealand began harnessing geothermal energy for electricity
in the 1950s. The next major development was at The Geysers in
the United States in the 1960s. Suddenly, in the 1970s, geo-
thermal energy development became an important goal in national
planning in many countries. This turn of events was precipi-
tated by the "energy crisis" of the early 1970s. By 1976, the
total geothermal electrical power capacity in the world had
reached 1,325 MW, the new geothermal electrical power producers
being Mexico, Japan, El Salvador and the U.S.S.R. In the United
States, the present generating capacity of geothermal electrical
power is 502 MW. The goal of the U.S. Energy Research and
Development Administration (ERDA) is to achieve a minimum geo-
thermal electrical power capacity of 6,000 MW by 1985 and more
than 20,000 MW by the year 2000 in the United States.
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While electrical power production from geothermal resources
is a relatively new industry, geothermal steam and hot water
have been used in various forms in many countries from time
immemorial. For example, the use of geothermal water for balne-
ological purposes has been popular in many parts of the world
since biblical times. More recent nonelectrical uses of geother-
mal energy include space heating, process heating, greenhouse
operation, etc. A number of countries, for example Hungary and
Iceland, have developed considerable capacity for nonelectrical
uses of geothermal energy. In the United States, space heating
by geothermal energy has been in use for several decades in
Klamath Falls, Oregon, and Boise, Idaho. The growing shortage
of natural gas is expected to cause a rapid increase in the
utilization of low-grade geothermal heat for direct heat uses,
the high-grade geothermal resources being lucrative sources for
electric power production.
It is interesting to note that although geothermal water
has been used for therapeutic purposes for millennia and as an
energy source for decades, not until the 1970s has any serious
concern been expressed about its possible adverse environmental
impacts. Traditional belief in the therapeutic value of natural
hot water may have delayed concern about environmental implica-
tions of geothermal development. The expansion in geothermal
capacities and volume of hot water use has coincided, however,
with the new environmental consciousness df the past decade.
Environmental impact data relevant to geothermal resource
development are sparse, since there are only three sites in the
world (Lardarello, Italy; Wairakei, New Zealand; The Geysers,
U.S.A.) with a significant history of geothermal power genera-
tion. The existing data on the nature of pollutants in geo-
thermal fluids are inadequate, considering their extreme diver-
sity in chemical composition (see section 1.3.3). However,
effort has begun in earnest during the last few years to collect
data on geothermal fluid pollutants and their effects on the
environment. Considerable research is also being carried out to
improve technology and to develop new methods to control pol-
lution due to geothermal fluids. Research and development
programs are being sponsored by government agencies such as EPA
and ERDA, resource companies, utilities, etc. The environmental
awareness of the late 1960s and 1970s has given birth to impor-
tant legislation, at both federal and state levels, to safeguard
thxi environment. Most of these regulations do not specifically
address geothermal pollutants; they nevertheless have a strong
impact on the geothermal industry as discussed in the following
section.
1.2.1 Legislative and Regulatory Aspects
The following federal laws and regulations, applying to all
industrial development, are also relevant to the geothermal
industry: _
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1. National Environmental Policy Act (1969)
2. Clean Air Act as amended (1970)
3. Federal Water Pollution Control Act Amendments (1972)
4. Noise Control Act (1972)
5. Marine Protection, Research and Sanctuaries Act (1972)
6. Wilderness Act
7. Fish and Wildlife Coordination Act
8. Endangered Species Act (1973)
9. Safe Drinking Water Act (1974)
10. Resource Conservation and Recovery Act (1976)
11. Toxic Substances Control Act (1976)
Most of these laws provide for and encourage relegation of
enforcement power to the state, and sometimes to the local
government level, upon satisfaction of certain requirements.
Three other federal laws concerned wholly or in part with geo-
thermal energy development have some bearing on the environ-
mental impact aspects. These laws are:
1. Geothermal Steam Act (1970)
2. Federal Nonnuclear Energy Research and Development Act
(1974)
3. Geothermal Energy Research and Development Act (1974)
A discussion of the provisons of these laws and those
listed earlier is beyond the scope of this report. Besides
these federal laws, the state and local governments have their
own laws and regulations. Most of these regulations are closely
related to and implement federal regulations. These state and
local regulations may impose more restrictions but cannot reduce
the restrictions placed on pollutant discharges and emissions by
federal rules. It should be noted that as yet there are no
federal discharge and emission standards for geothermal pol-
lutants. As a result, some of the states are developing strin-
gent and perhaps arbitrarily restrictive regulations on accept-
able pollutant levels in discharges or emissions from geothermal
operations. Diverse requirements by various political juris-
dictions may unduly increase the cost and reduce the pace of
development of geothermal energy. EPA, in cooperation with the
-------
Interagency Geothennal Coordinating Committee (formerly Geo-
thermal Advisory Council), is developing an interim, "recom-
mended" set of standards for geothermal pollutants (EPA, 1977b).
This set of standards is not to be construed as enforceable, but
as a guideline based on available information and formulated in
coordination with state environmental agencies and appropriate
private organizations. Eventually, as the geothermal industry
becomes well established, equitable and legally enforceable
standards for geothermal effluents are expected to evolve.
1.3 GEOTHERMAL SYSTEMS
1.3.1 Geothermal Resource Types
Five broad classes of geothermal resources are usually
recognized: hot water, dry steam, "geopressured" hot water, hot
dry rock, and magma. The following discussion of these classes
is largely extracted from Sanyal (1976) and Chen, et al. (1976).
Of these types of geothermal resources, the first three
exist as "reservoirs," implying a body of stored fluid in the
pore space of a subsurface rock formation. Geopressured hot
water reservoirs are those that contain hot water at an abnor-
mally high pressure. The hot dry rock geothermal resource is a
heat resource which may have to be exploited by flowing a fluid
through fractures created artificially in otherwise impermeable
rock. Electrical power generation from dry steam reservoirs has
been practiced profitably for many years at The Geysers in
California and at Lardarello, Italy. The technology of power
generation from hot water reservoirs has been amply demonstrated
at various places in the world, for example, New Zealand,
Mexico, Japan, U.S.S.R., etc. The other types of geothermal
resources have not been proven commercially feasible at the
current state of technology. Hence the rest of this report will
focus on dry steam and hot water reservoirs only.
Essentially, a geothermal reservoir is a hot, porous rock
formation containing fluids. Such reservoirs are encountered
typically where the earth's crust is thinner than usual, at the
boundaries of tectonic plates, and in areas of geologically
recent volcanism. These conditions give rise to higher than
normal geothermal gradients, making it possible to extract
commercially useful hot water from a relatively shallow depth.
Under unusual circumstances, even an area of normal geothermal
gradient can provide water hot enough for some uses, such as
space heating. The definition of an economically extractable
geothermal resource is intimately dependent on both physical and
economic factors: the quantity and physio-chemical properties
of the water in the reservoir, the distribution, quantity and
depth of wells necessary for production, the type of production
and utilization facilities, operating procedures and practices,
-------
and costs of alternative energy sources in the area. An eco-
nomic geothermal resource at one place may be considered non-
commercial at some other location.
In areas of thin crust, tectonic plate boundaries or geo-
logically recent volcanism, molten rock may occur at a rela-
tively shallow depth. Heat is transferred to the overlying
solid rock mass by conduction. Percolating surface water be-
comes heated by heat transfer from the rock. This creates large
scale natural thermal convection cells through the porous rock.
In many geothermal reservoirs a cap rock layer of very low
vertical permeability prevents the escape to the surface of
ascending hot water. In some cases the hot water reaches the
surface either because of lack of a cap rock or by seepage along
faults, giving rise to hot springs, geysers, fumaroles, etc.
Hot Water Reservoirs—
These reservoirs are so defined because liquid water is the
continuous, pressure-controlling fluid phase. White and
Williams 'X1975) define a "hot water system", as having a water
temperature greater than 150°C (302°F). One can infer continu-
ity of the liquid phase from reservoir pressure distribution and
the abundance of'certain chemical constituents that are soluble
in water but have low vapor pressures, and hence lack signifi-
cant solubility in low pressure steam. The most critical con-
stituent in distinguishing hot water systems from dry steam
systems is the chloride ion. Most metal chlorides have high
solubility in water and the chlorides are easily leached from
most rocks by hot water. These metal chlorides by and large
have negligible volatility at temperatures as high as 400°C
(752°F), and do not have appreciable solubility in low pressure
steam.
The vast majority bf known geothermal systems are hot water
reservoirs at elevated pressure, and produce steam due to flash-
ing as the fluid pressure drops in the well bore or at the
surface. The steam quality (i.e. the percentage of steam in the
total effluent) of the well effluent is a function of many
variables: the flow rate, bottom-hole temperature and bottom-
hole pressure of the fluid; presence of chokes and valves; and
the wellhead pressure. However, the initial fluid temperature
and the final separating pressure are by far the most critical
parameters that determine steam quality at the steam separator.
For example, water flashed to a separator pressure of 3.51 kg/
sq cm (50 psig) from an initial temperature of 300°C (572°F)
yields 33% steam; 200°C (392°F) yields 11% steam; 150°C (302°F)
yields less than 1% steam. The temperature of hot water reser-
voirs ranges from near ambient to 370°C (698°F).
Hot water reservoirs generally display higher contents of
arsenic, boron, chloride, cesium, fluoride, lithium, sodium,
rubidium, and silica than cooler ground water. Plugging
8
-------
of the porespace around well completion and scaling in the well
bore, pipes and surface equipment often occur in hot water
systems. Silica precipitation is the most important cause of
these problems because quartz is the most abundant natural
mineral and its solubility increases rapidly with temperature.
Less commonly, calcite, zeolite, sulfides and clay minerals may
also cause plugging problems. Geothermal waters with very high
or low pH will be highly corrosive in some cases.
Dry Steam Reservoirs—
These reservoirs produce dry (superheated) steam with no
associated liquid. Such systems are relatively rare. So far
only five major dry steam reservoirs have been definitely iden-
tified worldwide. These reservoirs are located at The Geysers,
California; Larderello, Italy; Matsukawa, Japan; Omikobe, Japan;
and Monte Amiata, Italy. These reservoirs are characterized by
temperatures in the range of 220° to 250°C (428° to 482°F) and
pressures around 35 kg/sq cm (500 psia). Wells in dry steam
reservoirs normally produce superheated steam with a few degrees
of superheat. Condensate from the steam usually has very low
total dissolved solids (TDS) content. The steam usually shows
low concentrations of chloride (less than 15 parts per million
[ppm]) and high concentrations of boron, ammonia, sulfate and
magnesium. The steam may contain a considerable amount of
noncondensible gases such as hydrogen sulfide and carbon diox-
ide. At The Geysers these concentrations may be greater than 5
ppm for boron, and average 194 ppm for ammonia, 222 ppm for
hydrogen sulfide and 3,260 ppm for carbon dioxide (Reed and
Campbell, 1976) (see section 3 on The Geysers).
1.3.2 Pollution from Geothermal Operation
Exploration and Development Phases—
During the exploration, development and construction phases
of a geothermal conversion system, the sources of environmental
pollution are likely to be transient and of minimal consequence
in the long run. Such pollution may include construction mate-
rial and vegetation debris; noise, machine exhaust and dust;
disturbed soil; waterborne silt, mud solids, drill cuttings,
cement, etc.; and accidental spills or well blowouts. Blowouts
are usually preventable by proper drilling practices. All of
the types of pollution listed above are minimized by enforcement
of state and federal regulations on noise, solid waste and other
pollutants.
Production and Utilization Phase—
Themainsourceof pollution during the operation of a
geothermal energy conversion facility is the geothermal fluid
itself; noise and possible change of landscape are minor fac-
tors. Depending on the nature of the geothermal fluid and the
design of the conversion facility, the environmental impact may
range from negligible to very serious. The pollutants in the
-------
fluid are: dissolved and suspended solids, dissolved and ent-
rained gases, products of chemical reactions between the fluid
and the materials it comes in contact with, and waste heat.
Theoretically, environmental pollution is prevented if the
conversion facility is a closed system. In such a system, all
the fluid is reinjected into the reservoir after power conver-
sion (or heat-exchange, in case of direct heat use) in a closed
loop from the production to the injection well. Such closed
loops can be designed for both binary and flash power conversion
systems. However, high cost or technical problems may make a
perfectly closed loop impractical. At the other extreme, a
completely open conversion facility can be designed so that all
waste liquid and gases after power conversion (or heat-exchange)
are released untreated to surface drainage or the atmosphere.
Such a system potentially would present the worst possible case
of geothermal pollution. However, the extent of actual pol-
lution would depend on the chemical characteristics of the
geothermal fluid. In some geothermal reservoirs, the water is
potable, and consequently, discharge of untreated waste geo-
thermal water into surface water bodies might be acceptable. If
a geothermal fluid must be treated for constituent removal (for
example, in order to avoid scaling of pipes) prior to injection,
a considerable amount of solid waste may be created. The solids
may, at one extreme, have commercial value as useful chemicals.
At the other extreme such solid wastes may be harmful chemicals
subject to con/.nement and other regulatory control.
In reality, a geothermal conversion system will be some-
where between the extremes of the totally closed and the totally
open systems. The exact extent of pollution of the atmosphere,
land, and surface water bodies will depend on the amount and
nature of pollutants in the waste and the rate, volume and
disposal methods. The amount and nature of pollutants in the
waste will depend on the chemical characteristics of the geo-
thermal fluid as well as the conversion process. It must be
pointed out that even in a completely closed system, there will
be some thermal pollution.
Even if the conversion system design eliminates any dis-
charge of waste into the aboveground environment, the possibil-
ity exists of potential chemical and thermal pollution of ground
water aquifers during injection of waste. Several possible
situations where reinjection of waste geothermal fluid may cause
pollution of ground water include the following potential pol-
lutant pathways or mechanisms:
1. Well seal or casing deterioration or failure
2. Escape of reinjected fluid through structural or
stratigraphic pathways
10
-------
3. Hydrofracturing or confining formations with high
pressure injection
4. Accidental spills
5. Percolation from evaporation ponds (enhanced by higher
temperatures)
6. Percolation from discharge of mineralized fluids
through surface conveyances
7. Chemical migration due to osmotic forces
Well seal deterioration or failure would allow fluids to
flow vertically up or down the well bore, depending on where the
failure occurred. Well casing deterioration or failure would
allow escape of fluid directly into the stratigraphic unit
adjacent to the failure. This could occur by corrosion or
shearing of the casing. At The Geysers, wells drilled on land-
slides have had blowouts when the landslides reactivated and the
downslope movement sheared the well casing. Vertical movement
of fluid up and/or down the wellbore could occur, again the
extent would depend on where the failure occurred and the ef-
fectiveness of the initial cement seals.
Structural and stratigraphic pathways, such as faults,
ineffective caprock or buried stream channels may allow fluid to
travel along pathways that have not been previously recognized.
Hydrofracturing of confining formations due to high pressure
injection may also create structural pathways in the form of
micro-fractures or joints.
Accidental spills at the surface, percolation from evapo-
ration ponds, or percolation or leakage from surface conveyances
would entail similar pathways. The fluids would percolate from
the surface downward directly into the nearer surface aquifers.
A spill, if not contained, would also discharge fluid directly
to surface streams, lakes or canals.
Osmotic forces can cause slow migration of chemical con-
stituents of the waste fluid to a groundwater aquifer through
an intervening caprock, which may act as an osmotic membrane.
However, pollution due to this effect is anticipated to be
extremely minor and insignificant.
1.3.3 Chemical Characteristics of Geothermal Fluids
The chemical characteristics of geothermal fluids vary over
a wide range, in both the number of chemical species and their
concentrations. For example, TDS range from about 50 to 388,000
ppm and pH from 2 to 10 units. From the environmental impact
point of view, the geothermal waters can vary in character from
11
-------
entirely benign and potable to highly corrosive and saline. The
fluid characteristics may vary from one reservoir to an?^6^,
from one well to another in the same reservoir, and with time in
the same well.
The geographical variation in the chemical characteristics
may be attributed mainly to variation in the nature of the
subsurface rocks, temperature, and distance from the source of
recharge, if any. The temporal variation in the chemistry of
geothermal fluids at a particular site can have a number of
causes, the most important being the variation in the rate of
fluid recharge (natural or by injection) into the reservoir.
Table 1.1 lists reported ranges of gross chemical properties of
geothermal water. The table also indicates the reasons for
measuring these properties. Table 1.2 is an exhaustive com-
pilation of the concentration ranges of various chemical con-
stituents in geothermal waters. The data are largely taken from
Tsai, et al. (in press). The right hand column in Table 1.2
lists pertinent comments on each of the chemical constituents.
The comments pertain to toxicity and operational problems (such
as corrosion and scaling of pipes) associated with a particular
constituent. These concentration ranges, based on a thorough
literature search, cover geothermal reservoirs from all parts of
the western United States as well as from various other coun-
tries with known geothermal reservoirs. It should be noted that
the minimum reported concentration for a great majority of the
constituents is zero or near zero. Based on the maximum re-
ported concentration (Table 1.3), the chemical constituents in
geothermal water can be grouped for convenience under the fol-
lowing categories:
Major constituents - those with maximum concentration
greater than 10,000 ppm
Secondary constituents - those with maximum concentration
1,000-10,000 ppm
Minor constituents - those with maximum concentration
1-1,000 ppm
Trace constituents - those with maximum concentration
generally less than 0.01 ppm
Table 1.3 presents this grouping of constituents according to
their relative abundance. The "major constituents" are those
chemicals most commonly found in highest concentration in geo-
thermal systems; they play the most important role in chemical
reactions occurring in the system. The "secondary" and "minor"
species may also participate significantly in chemical reac-
tions, e.g. scaling and composition. Trace elements contribute
very little to the chemical reactions in the system but may have
considerable implication in environmental impact. For example,
12
-------
TABLE 1.1 SOME CHEMICAL INDEX PROPERTIES OF GEOTHERMAL WATERS
Water
Characteristics
Reported Range In
Geothermal Waters
Reasons for
Measurement
TDS
47-387,500 ppm
PH
Redox
Potential
Conduc tivi ty
Alkalinity
Hardness
Suspended
Solids
Turbidity
Measure of material
in solution, impor-
tant in assessing
scaling and solid
waste problems
Hydrogen ion impor-
tant to water chem-
istry and corrosion
Important to water
chemistry
Indication of TDS
Ability of water to
absorb acid
In general a measure
of Ca + Mg
Measure of particu-
lates which may
clog equipment
0-2,000 Jackson Estimate of
Turbidity Units(JTU) suspended solids
-400 to + 500 mV
500-50,000 ymho/cm
50-1,000 ppm as CaCO-
5-20,000 ppm as CaCO-
13
-------
TABLE 1.2 CHEMICAL COMPOSITION OF GEOTHERMAL WATERS WORLDWIDE
(Tsai, et al. in press)
Constituent
Aluminum (Al)
Ammonium (NH ^ )
Arsenic (As)
Barium (Ba)
Boron (B)
(HB02)
Bromide (Br)
Cadmium (Cd)
Calcium (Ca)
Carbon Dioxide (C02)
(HC03)
(C0
(HC0
HC0
2 3
Cesium (Cs)
Chloride (Cl)
Cobalt (Co)
Copper (Cu)
Fluoride (F)
Germanium (Ge)
(C03)
+ C03)
+ C0)
Hydrogen Sulfide (H2S,
total)
Concentration in ppm
0 - 7,140
0 - 1,400
0-12
0 - 250
0 - 1,200
13.6 - 4,800
0.1 - 3,030
0-1
0 - 62,900
0 - 490
0 - 10,150
0 - 1,653
20 - 1,000
15 - 7,100
0.002 - 22
0 - 241,000
0.014 - 0.018
0-10
0-35
0.037 - 0.068
0.2 - 74
Comments
Health hazard
Human death if
>550 rag dosage
Deleterious to plants
Toxic to fish if
>0.2 ppm
Clogging scale
Clogging scale
pH control
Major corrosion
constituent
Toxic to life in
large amounts
Health hazard if
>1 ppm
Healthful if <1.5 ppm
pH control, corrosion-
scale agent
(continued)
14
-------
Constituent _
Iodide (I)
Iron (Fe)
Lanthanum (La)
Lead (Pb)
Lithium (Li)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Nitrate (N03)
Nitrite (N02)
Oxygen (02, dissolved)
Phosphate (PO^)
-------
TABLE 1.2 (continued)
Constituent Concentration in ppm Comments
Sulfur (S) 0-30
Total Dissolved Salts 47 - 387,500
Zinc (Zn) 0.004 - 970 Toxic to fish if
> 0.3 ppm
Zirconium (Zr) 24
The following are trace elements found at Sinclair No. 4 well,
Salton Sea, California:
Antimony (Sb), Beryllium (Be), Bismuth (Bi). Cerium (Ce),
Dysprosium (Dy), Erbium (Er), Europium (Eu), Gadolinium (Gd),
Gallium (Ga), Grid (Au), Hafnium (Hf), Holmium (Ho), Indium (In).
Iridium (Ir) , I -itetium (Lu), Neodymium (Nd) , Niobium (Nb) ,
Osmium (Os), Palladium (Pd).Platinum (Pt), Praseodymium (Pr) ,
Rhenium (Re), Rhodium (Rh), Ruthenium (Ru), Samarium (Sm),
Scandium (Sc), Selenium (Se), Tantalum (Ta), Tellurium (Te) ,
Terbium (Tb), Thallium (Tl), Thorium (Th), Thulium (Tm).
Titanium (Ti), Tungsten (W), Uranium (U), Vanadium (V),
Ytterbium (Yb), Yttrium (Y).
16
-------
TABLE 1.3 RELATIVE ABUNDANCE OF MAXIMUM REPORTED CONCENTRATIONS
OF CHEMICAL COMPOSITION IN GEOTHERMAL WATERS WORLDWIDE
(Tsai, et al. in press)
Major Constituents Secondary Constituents
(maximum > 100,000 ppm) (maximum 1,000-
10,000 ppm)
Chloride
Sulfate
Sodium
Calcium
Magnesium
Potassium
Bicarbonate
Aluminum
Iron
Bromide
Manganese
Strontium
Carbonate
Silica (total)
Ammonium
Boron
Minor Constituents
(maximum 1-1,000 ppm)
Arsenic
Barium
Cadmium
Cesium
Copper
Fluoride
Hydrogen Sulfide(total)
Iodide
Lanthanum
Lead
Lithium
Mercury
Nickel
Nitrate
Phosphate(total)
Rubidium
Silver
Zinc
Zirconium
Trace Constituents
(maximum <0.01 ppm)
Antimony
Beryllium
Bismuth
Cerium
Dysprosium
Erbium
Europium
Gadolinium
Gallium
Germanium
Gold
Hafnium
Holmium
Indium
Iridium
Lutetlum
Molybdenum
Neodymium
Niobium
Osmium
Palladium
Platinum
Praseodymium
Rhenium
Rhodium
Ruthenium
Samarium
Scandium
Selenium
Tantalum
Tellurium
Terbium
Thallium
Thorium
Thulium
Titanium
Tungsten
Uranium
Vanadium
Ytterbium
Yttrium
-------
secondary and minor constituents such as boron, nickel, zinc,
arsenic, rubidium, strontium and barium may be harmful to plant
and animal life; most of the heavy metals are involved in forma-
tion of scales in pipes.
It is difficult to make a meaningful comparison of the
published data on chemistry of geothermal effluents from various
parts of the world, because on the one hand the surface and
subsurface environments may vary drastically from place to
place, and on the other hand the techniques of sampling and
analysis of effluents may differ in different reported cases.
It is conceivable that some of the data reported in the litera-
ture are in error (Ellis, 1976). As the geothermal industry
grows and data gathering continues the ranges listed in Table
1.2 will most likely expand.
Usually, low TDS is associated with relatively low con-
centrations of all constituents, and vice versa. In general,
higher temperature waters contain higher concentrations of
constituents. Also, the waters with highest salinity appear to
have the lowest pH.
The data in Tables 1.1 and 1.2 are biased greatly by the
chemical data on the geothermal waters from the Salton Sea KGRA
(Imperial Valley, California), where unusually high concen-
trations of most constituents are common (see Table 2.13). The
great majority of the known ge thermal reservoirs contain waters
with far less TDS than the Salton Sea reservoir.
Because of the inherent diversity in. the chemical charac-
teristics of geothermal waters it is difficult to arrive at an
average value of concentration of each constituent. As more
data become available, statistically significant average and
median values of each constituent may be determined, at least
for certain geographical areas. The median value of TDS for
geothermal water will likely fall in the 1,000 to 10,000 ppm
range. Most geothermal fluids appear to be acidic with a. pH
of less than 7.
With reliable data, chemical composition of geothermal
effluents can provide much useful information about the res-
ervoir, since the kinds and amounts of constituents depend on
the reservoir environment: formation lithology, rock-water
interaction, rock-mineral-chemical equilibria as well as pres-
sure and temperature. The major environmental concerns in a
geothermal system are noxious constituents in the effluent.
Corrosion in casing, surface plumbing and equipment may cause
leakages and consequent contamination of the environment by
geothermal fluid; scale formation may make disposal of spent
geothermal effluent difficult, and creates a solid waste dis-
posal problem. Chloride, oxygen, sulfide, and pH are princi-
pally responsible for corrosion and calcium carbonate scale
18
-------
formation. Silica, sulfide and hydroxide are the other possible
scale-forming constituents. Temperature and pressure also play
an important role in determining the nature and extent of cor-
rosion and scaling processes. Chemicals may be added to geo-
thermal effluents to reduce possibilities of corrosion and
scaling or to precipitate certain constituents in ponds or
settling tanks. However, it is conceivable that some of these
added chemicals may make the waste geothermal fluid environ-
mentally more detrimental than the reservoir fluid.
Besides the dissolved and suspended solids, geothermal
water and steam contain, a range of noncondensible gases, some of
which may be detrimental to the environment. Hydrogen sulfide,
a noncondensible gas constituent of many geothermal fluids, has
drawn considerable attention at The Geysers because of its odor.
Ammonia, carbon monoxide, sulfur dioxide and mercury vapor are
the other major noxious components of many geothermal vapors.
Table 1.4 lists the reported concentrations (in volume percent)
of most of the known constituents of geothermal vapors (Tsai, et
al. in press). The right-hand column in Table 1.4 includes
pertinent comments on the environmental implications of these
vapor constituents. Usually, noncondensible gases constitute
between about 0.3% and 5% of the flashed steam from geothermal
fluids (Wood, 1973).
Geothermal fluids usually contain certain radioactive
elements in low concentrations, mainly radon, radium and iso-
topes of uranium and thorium. The most thoroughly studied
radioactive element in geothermal fluids is iadon-2**, a radio-
active gas. A study of 136 natural geothermal springs showed a
range of 13 to 14,000 picocuries per liter (pCi/1), with a
median around 510 pCi/1 (O'Connell and Kaufman, 1976).
It is of interest to compare the chemistry of geothermal
waters with other types of waters. Figure 1.2 compares the
ranges of major chemical constituents in geothermal water and in
potable water. In general, the reported maximum concentrations
of dissolved constituents in geothermal water exceed those in
potable water. The situation is similar when geothermal water
is compared with drinking, irrigating, livestock feeding or sea-
water (Table 1.5).
1.4 ENVIRONMENTAL EFFECTS OF WATER POLLUTANTS
1.4.1 General
Geothermal fluids, if released to surface or groundwater
bodies, can potentially cause chemical and thermal effects.
This section discusses the environmental effects related to the
chemical characteristics and waste heat content of geothermal
fluids.
19
-------
TABLE 1.4
GAS COMPOSITION OF GEOTHERMAL VAPORS (Tsai, et al. in press)
Constituent
Ammonia (NH3)
Argon (Ar)
Arsenic (As)
Boric Acid (H3B03)
Carbon Dioxide (C02)
Carbon Monoxide (CO)
Helium (He)
Hydrocarbon (C and
greater) 2
Hydrogen (H2)
Hydrogen Fluoride (HF)
Hydrogen Sulfide (H S)
2
(H2 + H2S)
Mercury (Hg)
Methane (CHJ
Nitrogen (N2)
(N2 + Ar)
Oxygen (02)
Sulfide Oxides (S02)
Concentration in volume percent
0 - !
0 - 6.3
0.002 - 0.05
0 - 0.45
0-99
0-3
0 - 0.3
0 - 18.3
0-59
0.00002
0-42
0.2 - 6
0.007 - 40.7 (ppb)
0 - 99.8
0 - 97.1
0.6 - 96.2
0-64
0-31
Remarks
Noxious gas, signifies
reducing conditions
Minor inert gas
Health hazard,
volatile
Deleterious to plants
Scale formation
Health hazard
Innocuous
Potential fuel source,
denotes reducing
conditions
Provides data on
oxi dati on-reducti on
environment
Extremely corrosive
and reactive
Noxious gas,
environmental hazard,
corrosion agent
Health hazard
Potential fuel source
Major inert gas
Important for oxidation-
reduction reactions,
can be corrosive
Corrosion agent,
harmful to environment
20
-------
to
Al3*
NH/
Br-
o 2+
Ca
HC03
cof-
Cl
F"
I
c> 2-f
Fe^
Pb2+
Li +
. . 2-f
Mg*+
Mn2+
1 I 1 1 1
/'^/'^^|/j/^^^XXV^/y'XyrXXXXyr/y^XXX//yr/////X>yXX//^XX/r/yryr/X/X/Xy^/y/>|
V^V%^/^/'/'/3
^X//X///XXX//X/////>r/XXX/////y^X///jC>Vr//////////X/X/'JX/>y'/'yl
^-^
s ss // ss SSS//S/////S/ s/s/s //////////// sFy/ /////£££j£SA
i*»*»»»»>»*>»r»,,,i»>,,,» ,,,, >,J±> » » » j » f > > * r> > > jf^ > > >
1
2
r//////////// /////// ////// / / / / / ' / // fy~/~^
rS///s ///////////////////////////// //£25^\
f f f if^j^j/ ///////////////////////// ///~7~7 S / \
ffffff ts ///////////////// SS // SS/ ///// / / / / / X/// y^/*/!
_ A
'»"»3
K +
Rb +
Si02
No+
Sr2*
so|"
Zn24
TDS
,-,
r////////x//x/x////y///////x xx xxx xxxxj
A
(///'/'xx x x !/ /iCir^ ^ x/xx x xxxxx xxxxxxx x x xx'xl
EXPLANATION
E2GEOTHERMAL WATERS
— POTABLE WATERS
O TYPICAL SEA WATER
A USPHS/NI DWR
r— 71
^ / >> y >> >> yi
II III
I0~' I 10' 10* I03 I04 I05
CONCENTRATION RANGES ( parts per million)
Figure 1.2 Comparison of concentration ranges of constituents in
geothermal and potable waters (modified from Tsai, et al.
10'
in press)
-------
TABLE 1.5
COMPARISON OP INORGANIC CHEMICAL WATER STANDARDS
WITH GEOTHERMAL AND SEAWATER ANALYSES
Substance
Drinking Mater* (mg/1)
U3PHS USPHS
Recommended Mandatory
Irrigating Hater1*
(ppm)
Threshold Limiting
Arsenic
Barium
Bicarbonate
Boron.
Cadmium
Calcium
Chloride
Chromium
Copper
Fluoride
Hydrogen
sulfilde
Iron
Lead
Magnesium
Manganese
Mercury
Nitrate
Selenium
Silver
Sodium
Sulfate
line
TDS
PH
0.01
-
—
-
-
250R
_
1.0h
1.7
— f.
0.3h
-
v
0.05n
45
_
-
—
250
sh
500h
-
0.05* 1.0 5.0
1.0*
_ — —
0.5 2
0.01*
100 350
0.05*
0.1 1.0
2.2
h
0.05"
_ — —
0.05*
- - -
0.002h
109
0.01*
0.05*
_ — —
200 1,000
_ — -
500 1,500
6.5-8.5" 7.0-8.5 6.0-9.0
•USPHS, 1962} EPA, 1976| EPA, 1977a
bTodd, 1970
°Taai, et al.. In press "
^Goldberg, 1963
^includes NO2~, NHi, and dissolved nitrogen gas
Livestock Feeding
Haterb (ppm)
Threshold Limiting
1
-
500
—
5
500
1,500
_
1
_
-
—
250
-
—
200
-
—
1,000
500
—
2,500
6.0-8.5
_
-
500
—
-
1,000
3,000
_
6
_
-
—
500
-
—
400
-
—
2,000
1,000
_
5,000
5.6-9.0
Geo thermal
Watorc
(ppm)
Range
0- 12
0- 250
0- 10,000
0- 1,200
0- 1
0- 63,000
0-240,000
0- 10
0- 35
0.2- 74
0- 4,200
0- 200
0- 39,000
0- 2,000
0- 10
0- 35
trace1
0- 2
0- 80,000
0- 84,000
0- 970
47-390,000
2- 10
Sea W/iterd
mefZi
0.003
0.03
142
4.6
trace"
400
19,000
0.003
1.3
w
0.01
trace£
1,350
0.002
trace'
0.5°
0.004
trace*
10,500
2,700
0.01
34,560
-
*Trace=<0.001 ppm (or mg/1)
^Maximum contaminant level specified in National
Interim Primary Drinking Hater Regulations (EPA, 1976)
"Maximum contaminant level specified in National
Secondary Drinking Hater Regulations (EPA, 1977a)
-------
In order to determine if nongeothermal groundwater will be
polluted by geothermal groundwater a definition must first be
established to distinguish one from the other. The following
excerpt exemplifies some of the ambiguity involved in such a
definition.
Strictly defined, any spring [ground] or well
water whose average temperature is noticeably above
the mean annual temperature of the air at the same
locality may be classed as thermal. Among European
springs that are developed commercially, only those
whose temperature is higher than about 20°C (68°F) are
classed as thermal. In the United States, only those
springs are called thermal whose temperature is at
least 8.3°C (37°F) above the mean annual temperature
of the air at their localities. In areas where the
mean annual air temperature is low, some springs that
do not freeze in winter because of natural protective
conditions are considered to be thermal; in tropical
areas some springs that are only a few degrees warmer
than the temperature of the air may be considered
thermal. (Waring, 1965).
Note that these are functional criteria based on temper-
ature. Ideally, a definition of geothermal water would depend
on its genesis since it is possible that a water that has come
in contact with a geothermal heat source may be relatively cool
by the time it reaches the surface. However, it is much more
involved to determine water's genesis than to determine its
temperature at a collection point. Therefore, a definition
based on a somewhat arbitrary temperature differential is used
in this report. In Imperial Valley, for example, water hotter
than 50°C (122°F) is considered to be geothermal. This rather
high figure was selected since geothermal water can be defined
relative to ambient air temperatures, and summer air temper-
atures reach this level in Imperial Valley (Hely and Peck,
1964).
The effects on living things of some of the chemical con-
stituents discussed in section 1.3.3 are not fully known. Even
when the effects of a chemical constituent on human, animal or
plant health are well known, the actual environmental impact due
to that constituent may vary depending on many factors, which
include the concentration of that constituent in the geothermal
waste fluid, the rate and the cumulative volume of the pollutant
released, density of human or animal population in the area, the
extent and type of plant life around the pollutant discharge
area, and the nature of the discharge area (ocean, lake, river,
dry land, subsurface reservoir, etc.). For example, saline
discharges to marine waters may be of little consequence while
the same discharges may cause a catastrophic impact in a fresh
water lake.
23
-------
Table 1.6 lists the types of Federal-State Water Quality
Standards in various states with geothermal potential. Tne
table also indicates whether the criterion for a specific con-
stituent applies statewide or to a designated water. Table i.b
presents the Drinking Water Standards of the U.S. Public Health
Service (USPHS) (1962). It should be noted that limits for many
of the chemical constituents of geothermal fluids are not speci-
fied in either set of standards.
The following sections summarize the hazards of the various
pollutants known to occur in geothermal waters. The hazards are
discussed in very general terms as regards human consumption,
aquatic life, agricultural and livestock uses, and industrial
water supply. The toxicity of the various chemical elements in
water has been studied for many years and voluminous litera-
ture is available. However, the possible synergistic or antag-
onistic effects of the combination of various elements in water
have received little attention so far.
1.4.2 Human Consumption
Pollution of drinking water supplies is one of the major
potential impacts of discharging geothermal wastes into the
environment. Of the chemical constituents discussed in section
1.3.3, boron, arsenic, mercury, chromium, antimony, cadmium,
selenium, fluoride, lead and nitrate are known to be definitely
toxic to human beings, and may cause irreversible damage to
human health. Barium, lithium, iodine, bismuth and copper are
toxic to a lesser extent and usually do not cause irreversible
damage. The USPHS water quality standard specifies limits for
arsenic, cadmium, selenium, fluorine, lead, nitrate, barium and
copper only (Table 1.5). The National Interim Primary Drinking
Water Regulations (1976) (Table 1.5) by EPA specify limits of
0.002 mg/1 for mercury and 0.05 mg/1 for chromium. The USPHS
drinking water standards of 1925 had a recommended limit of 20
mg/1 for boron. Neither the 1962 USPHS standards nor the
Interim water quality standards (EPA, 1977a) of EPA include
boron limits. Several investigators have reported that boron
concentrations of 20 to 30 mg/1 are not harmful in drinking
water, but above this concentration, boron may interfere with
digestion (Chen, et al. 1976). There is no limit in the exist-
ing federal standards for antimony, lithium, iodine and bismuth.
Several other constituents of geothermal water may show minor,
usually reversible toxic effects, but significant data are
lacking.
1.4.3 Aquatic Life
Table 1.7 is a list of limits suggested for aquatic life in
both fresh and marine water. The table also provides remarks on
the toxicity of each constituent. Several elements (aluminum,
24
-------
TABLE 1.6 POLLUTANTS LIMITED BY WATER QUALITY STANDARDS
IN STATES WITH GEOTHERMAL POTENTIAL
(modified from EPA, 1977b)
I
Total Dissolved Solids
Chloride
Iron
Manganese
Boron
Zinc
Barium
Fluoride
Lead
Iodine
Copper *
Sulfur
Arsenic
Mercury
Chromium
Nickel
Silver
Cadmium
Selenium
Sulfate
Nitrate (+ nitrite)
pH (range)
Radioactivity
Total Dissolved Gas
Toxic Materials
Temperature
Dissolved Oxygen (min. )
Phosphorus
Conductivity
Alaska
d
s
d
d
d
s
Arizona 1
d
d
d
d
d
d
d
d
d
d
d
d
d
s
f
d
d
California |
s
s
s
s
s
s
s
s
d
Colorado |
s
s
f
d
s
Hawaii
d
s
d
s
Idaho |
s
s
s
d
s
Louisiana |
d
d
d
s
s
s
d
s
Montana |
d
d
d
d
d
d
d
d
s
d
s
s
d
d
Nevada |
d
s
d
s
s
s
f
d
s
d
New Mexico
d
d
d
s
s
s
d
s
d
d
Oregon |
d
d
d
d
d
d
d
d
d
d
d
d
d
d
s
s
s
d
s
d
Texas 1
d
d
s
s
s
s
s
s
s
s
s
s
s
s
d
s
s
s
d
s
-------
TABLE 1.7 AQUATIC LIFE CRITERIA FOR CONSTITUENTS IN GEOTHERMAL
__^_ FLUID (EPA, 1977b)
Criteria for
Fresh water
Criteria for
Marine water
Remarks
Ammonia 0.02 mg/1
(un-ionized)
Arsenic
Bar iurn
Beryllium
Boron
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nitrates
Phosphorus
Selenium
Silver
Hydrogen
Sulfide
Zinc
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
0.1 96-hr LC
0.005 mg/1
Toxicity pH dependent
Daphnia impaired by
4.3 mg/1
Toxicity level <50 mg/1
Toxicity hardness
dependent
Toxic to minnows
at 19,000 mg/1
Toxic at <0.5 mg/1
all tests
50
Toxicity varies with
pH and oxidation state
0.1 9C-hr LC Toxicity alkalinity
50
1.0 mg/1
0.01 96-hr LCC,
(sol. lead)
0.0005 mg/1
0.1 mg/1
0.0001 mg/1
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
0.0001 mg/1 P Eutrophication
factor
0.01 96-hr LC5Q 0.01 96-hr LC Toxic at >.2.5 mg/1
0.01 96-hr LC 0.01 96-hr LC5 Toxicity dependent on
compound
0.0002 mg/1
0.01 96-hr LC
0.002 mg/1
50
Total Dissolved
Solids (TDS)
Toxic at very low level
Toxicity dependent on
temperature, dissolved
oxygen, hardness
Osmotic effects -
variable
26
-------
bromine, strontium, lithium, cesium, fluorine, rubidium, anti-
mony, nickel and boron), which are known to be toxic to humans
are not included in Table 1.7. It is conceivable that these
elements are also toxic to aquatic life. Although no criteria
are shown for arsenic, barium and boron in Table 1.7, these
elements may have toxic effects on aquatic life. Many of these
omissions are due to the fact that these elements are not common
or are present in insignificant concentrations in surface
waters, on which these criteria were based.
The pH of surface waters has been related to productivity,
with the most productive waters between pH 6.5 and 8.5. Not
only may acids and alkalis be toxic in themselves, but an in-
crease or decrease in pH may raise the toxicity of various
constituents, e.g. ammonia.
1.4.4 Agricultural and Livestock Use
Table 1.8 lists the limits suggested on chemical constit-
uents as they pertain to livestock watering and crop irrigation.
Remarks on toxicity of each constituent are also included in
that table. Again, it should be noted that no limits are sug-
gested in Table 1.8 for many constituents which are known to be
toxic* to humans. However, Table 1.9 lists minor and trace
element tolerances established for irrigation water by the U.S.
Department of Agriculture (USDA) in 1962. The concentration of
these elements in geothermal waters, as exemplified in Table
1.2, will exceed the USDA guidelines in many cases.
Table 1.5 includes inorganic chemical quality standards for
water used in livestock feeding and crop irrigation. Boron is
particularly harmful for many plants. Table 1.10 groups common
crop plants according to their tolerance of boron into "sensi-
tive", "semi-tolerant" and "tolerant" classes.
1.4.5 Industrial Water Supply
Rather than concentrations of individual constituents, TDS
is usually the most important criterion that determines the
utility of a water for industrial purposes. Table 1.11 presents
the maximum TDS content of surface waters that have been used as
industrial waters.
27
-------
TABLE 1.8 AGRICULTURAL USE CRITERIA FOR CONSTITUENTS IN
GEOTHERMAL FLUIDS (EPA, 1977b)
Crop
Irrigation
Remarks
Ammonia
Arsenic
Barium
Beryl liuir.
Boron
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nitrates
0.1 mg/1
0.001 to
0.500 mg/1
0.75 mg/1
0.2 mg/1 suggested
for acidophilic
crops
-------
TABLE 1.8 (continued)
Crop
Irrigation
Remarks
Phosphorus
Selenium
Silver
Hydrogen Sulfide
Zinc
Total Dissolved 500-1,500
mg/1 suggested
Sodium
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.
t
Toxic to certain plants;
ratio to other cations
important; no criteria
given.
29
-------
TABLE 1.9 MINOR AND TRACE ELEMENT TOLERANCE FOR
IRRIGATION WATER (Economic Research
Service, 1962)
Element For Water Used For Short-Term Use
Continuously on on Fine Textured
All soils Soils Only
mg/1 mg/1
Alumi nun
Arsenic
Beryllium
Boron
Cadmium
Chromium
Cobalt
Copper
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Vanadium
Zinc
1.0
1.0
0.5
0.75
0.005
5.0
0.2
0.2
5.0
5.0
2.0
0.005
0.5
0.05
10.0
5.0
20.0
10.0
1.0
2.0
0.05
20.0
10.0
5.0
20.0
5.0
20.0
o'.os
2.0
0.05
10.0
10.0
fc
30
-------
TABLE 1.10 RELATIVE TOLERANCE OF PLANTS TO BORON (USDA, 1954)
Sensitive Semi-tolerant Tolerant
Lemon Lima bean Carrot
Grapefruit Sweetpotato Lettuce
Avocado Bell pepper Cabbage
Orange Pumpkin Turnip
Thornless blackberry Zinnia Onion
Apricot Oat Broadbean
Peach Milo Gladiolus
Cherry Corn Alfalfa
Persimmon Wheat Garden beet
Kadota fig Barley Mangel
Grape (Sultanina Olive Sugar Beet
and Malaga) Ragged Robin rose
Apple Field pea Palm (Phoenix
Pear Radish canariensis)
Plum Sweet pea Date palm (P.
dactylifera)
American elm Tomato Athel (Tconarix
Navy bean Pima cotton aphylla)
Jerusalem-Artichoke Acala cotton Asparagus
Persian (English) Potato
walnut
Black walnut Sunflower (native)
Pecan
31
-------
TABLE 1.11 TDS IN INDUSTRIAL WATERS (EPA, 1977b)
Use Maximum TDS (mg/1)
Textiles 15°
Pulp and Paper 1,080
Chemical 2,500
Petroleum 3,500
Primary Metals 1,500
Copper Mining 2,100
Boiler Make-up 0.5-3,000*
aFrom American Society for Testing Materials, 1966.
As discussed in section 1.3.3, TDS in geothermal water
varies over a large ranp^, the median being a few thousand ppm.
Thus many geothermal waste waters can actually be used as indus-
trial water. Some industrial processes, such as food and bever-
age processing, may need as high or higher quality water than drink-
ing water in order to maintain consistency of product quality. In
such cases, geothermal waste can be a serious pollutant.
1.4.6 Thermal Pollution
Up to 85% of the available heat may be wasted in geothermal
electric power generation because of the relative inefficiencies
of low temperature conversion. If external once-through cooling
water is used, most of this waste heat will be discharged to
surface waters. If cooling towers are used, with the cooling
water recycled, and blowdown reinjected, most of the waste heat
will be dissipated to the surrounding air. Once-through surface
water discharges would be particularly detrimental, with large
volumes released at temperatures as high as 50°C (122°F). Che-
mical and heat contamination are likely to be much less in dis-
charges from nonelectric uses of geothermal fluids. One of the
principal reasons is that those uses will deal with lower tem-
perature waters which are inherently less saline. Another is
that nonelectric systems probably will demand the use of rela-
tively clean water because they will be in more intimate contact
with the ultimate energy user.
Waste heat may have particularly significant effects upon
aquatic life. Excess heat as expressed by artificial tempera-
ture rise or temperature fluctuations can disturb aquatic com-
munities to the extent of complete elimination and replacement.
Most water quality standards limit artificially induced stream
temperature rise outside a mixing zone to 2.6°C (5°F) or less.
32
-------
Generally, the standards also include a maximum stream temper-
ature tailored to the preferred temperature of native fish
species.
Over many years, continuous thermal pollution may change
the microclimate of an area. If extensive geothermal energy
development takes place worldwide and thermal pollution from
other sources remains unchecked, the possibility of global
effects, such as the melting of the polar ice caps or signifi-
cant change in weather patterns, cannot be ruled out (Axtmann,
1975).
Even if thermal pollution of surface water bodies can be
prevented, the microorganisms in soils and porous subsurface
rocks may be destroyed by possible excessive thermal pollution
outside the reservoir. But the subsurface as a biological
habitat is yet to be fully understood (McNabb and Dunlap, 1975).
Usually 100°C (212°F) is considered to be the temperature above
which bacteria perish, but most micro-organisms are actually
killed by temperatures above 50°C (122°F).
33
-------
REFERENCES
American Society for Testing Materials. First National Meeting
on Water Quality Criteria, ASTM Publication No. 4-6, 1966.
Axtmann, R. C. Environmental Impact of A Geothermal Power
Plant. Science, v. 187, No. 4179, March 7, 1975.
Chen, J. Y., S. K. Gupta, W. Choi and B. Eichenberger. Chem-
istry, Fate and Removal of Trace Contaminants from Low to
Medium Salinity Geothermal Waste Waters. National Science
Foundation Report, November, 1976.
Economic Research Service. Major Uses of Land and Water in the
United States. Agriculture Economic Report No. 13,
Economic Research Service, U.S. Department of Agriculture,
1962.
Ellis, A. Geothermics - Special Issue, No. 2, p. 516, 19/76.
Geonomics. Baseline Geotechnical Data for Four Geothermal Areas
in the United States. United States EPA, Environmental
Monitoring and Support Laboratory, Las Vegas, Nevada, in
press.
Goldberg, E. D. Chemistry - the Oceans as a Chemical System; in
Composition of Sea Water, Comparative and Descriptive
Oceanography, M. N. Hill, v. 2 of The Sea, New York, Inter-
science Publications, p. 3-25, 1963.
Hely, A. G. and E. L. Peck. Precipitation, Runoff and Water
Loss in the Lower Colorado River-Salton Sea Area. USGS
Prof. Paper 486-B, 1964.
McNabb, J. F. and W. J. Dunlap. Subsurface Biological Activity
in Relation to Ground-Water Pollution; in Proceedings,
Second National Ground Water Quality Symposium, Co-
sponsored by U.S. Environmental Protection Agency and the
National Water Well Association, Denver, Colorado, 1975.
O'Connell, M. F. and R. F. Kaufman. Radioactivity Associated
with Geothermal Waters in the Western United States
Office of Radiation Programs, Las Vegas Facility Las
Vegas, Nevada, Technical Note ORP/LV 75-8A, 25 p., 'l976.
34
-------
Reed, M. J. and G. E. Campbell. Environmental Impact of Devel-
opment in The Geysers Geothermal Field, U.S.A.; in Pro-
ceedings, Second United Nations Symposium on the Develop-
ment and Use of Geothermal Resources, San Francisco, Cali-
fornia, v. 2, p. 1399-1410, 1976.
Sanyal, S. K. Geothermal Reservoirs: Exploration, Development
and Assessment. Geothermal Resources Council Short Course,
Snowbird, Utah, September, 1976.
Todd, D. K. The Water Encyclopedia, Water Information Center,
Port Washington, New York, 559 p., 1970.
Tsai, F., S. Juprasert and S. K. Sanyal. A Review of Chemical
Composition of Geothermal Effluents; in Second Workshop on
Sampling and Analysis of Geothermal Effluents, February
15-17, 1977, Las Vegas, Nevada. U.S. Environmental Pro-
tection Agency, Environmental Monitoring and Support Lab-
oratory, Las Vegas, Nevada, in press.
U.S. Department of Agriculture. Handbook 60, 1954.
U.S. Environmental Protection Agency. National Interim Primary
Drinking Water Regulations. Office of Water Supply, EPA-
570/9-76-003, 159 p., 1976.
. National Secondary Drinking Water Regulations. 40
CFR Part 143, Federal Register, v. 42, No. 62, p. 17143-
17146, Thursday, March 31, 1977a.
. Quality Criteria for Water. Office of Water and Haz-
ardous Materials, EPA 440/9-76-023, 1977b.
U.S. Public Health Service. Public Health Service Drinking
Water Standards. PHS pub. 956, U.S. Govt. Printing Office,
1962.
Waring, G. R. Thermal Springs of the United States and Other
Countries of the World - a Summary. USGS Prof. Paper 492,
383 p., 1965.
White, D. E. and D. L. Williams. Assessment of Geothermal
Resources of the United States-1975. USGS Circular 726,
155p., 1975
Wood, B. Geothermal Power; in Geothermal Energy Review of
Research and Development, ed. by H. C. H. Armstead, UNESCO,
Paris, 1973.
35
-------
SECTION TWO
IMPERIAL VALLEY
2.1 INTRODUCTION
This section discusses the potential subsurface environmen-
tal impact in geothermal areas of Imperial Valley (Figs. 2.1 and
2.2) with emphasis on potential water pollution. First back-
ground information is presented, followed by discussions of the
geothermal system, potential water pollution, seismicity, sub-
sidence and pollution control technology currently practiced or
anticipated.
The following discussions on the geothermal systems and
water pollution are divided into five subsections, one each on
the major potentially developable geothermal resources at the
Salton Sea, East Mesa, Heber and Brawley KGRAs and one section
on the remaining KGRAs in the valley. It was not advantageous
to divide the summary of Imperial Valley geotechnical data,
seismicity, subsidence and pollution control technology sections
into geographic subsections.
2.1.1 Summary
There are six "Known Geothermal Resource Areas" (KGRAs) in
Imperial Valley (Fig. 2.2). The East Mesa, Salton Sea, Heber
and Brawley KGRAs are considered potentially suitable for elec-
tric power production. Electric power production test facili-
ties are operating or are planned for the East Mesa, Salton Sea
and Heber areas. The geothermal well effluents at East Mesa
average from 2,000 to 3,000 ppm TDS, at Salton Sea 200,000 ppm
TDS, at Heber 15,000 ppm TDS, and at Brawley 100,000 ppm TDS.
The trace element contents of these brines are generally di-
rectly proportional to the TDS contents, i.e. the higher the TDS
the higher the content of each trace element.
Based on various assumptions, approximations and extrapo-
lations, the estimates of the recoverable heat in Imperial
Valley range from 20 x 1018 to 200 x 1018 J (1 9 x 1016 to
1.9 1017 BTU). The 30-year electric power potential for Imper-
ial Valley is estimated at 4,590 megawatts (electricity) (MWe).
It is estimated that a total brine mass of 6.02 million kg/day
(13.29 million Ib/day) will be produced from this projected
36
-------
09
CD San Bernardino Mtns.
© Desert Hot Springs
® India Hills
@ Little San Bernardino Mtns.
© Mecca Hills
<£) Santa Rosa Mtns.
Son
Gorgonio-%
' Pots
© Orocopia Mtns.
(D Tierra Blanco Mtns.
(§) Split Mountain Gorge
© Carrizo Wash
Superstition Hills
! NEV. I UTAH I
\
CALIFN
Figure 2.1 Physiographic setting and location of Imperial
Valley, California (Coplen, ]976)
-------
u>
00
TEMPERATURE GRADIENT MAP
OFTflE IMPERIAL VALLEY CALIFORNIA
10 (MI in)
LEMPERAfuRE GRADIENTS
. . 0REATER THAN IO*F
I I PER 100 FEET IN DEPTH
8° TO 10° F PER 100 FEET
IN DEPTH
6"TOB«F PERIOOFEET
IN DEPTH
tTAtl Of CAU'OAMIA
DIVISION or OIL a o*s
LEGEND
' <^* AREAS WITH HIGH
TEMPERATURE GRADIENTS
FAULTS WITH REPORTED SURFACE
RUPTURE DURING HISTORIC TIME,
SINCE 1769
FAULTS WHICH APPEAR TO DISPLACE
QUATERNARY ROCKS OR DEPOSITS
4»TO«»F PER
IN DEPTH
[ ~\ LESS THAN Z'f PER 100
FEET IN DEPTH
TEMPERATURE GRADIENT DATA
COMPILED & INTERPRETED BY
JIM COMBS, U.C. RIVERSIDE
SEPT. 1971
Figure 2.2 Temperature gradient map showing locations of KGRAs in Imperial
Valley, California (Palmer, 1975)
-------
maximum power development and will contain from 345,000 to
391,000 kg (760,000 to 862,000 Ib) TDS. This mass of hot brine
and its contained solids will constitute the major potential
source of subsurface pollution due to geothermal development in
Imperial Valley. If the spent geothermal fluids are allowed to
escape into surface water bodies or very shallow aquifers,
considerable thermal pollution may result in addition to chemi-
cal pollution.
For Imperial Valley the major pollution control technology
envisioned is injection of spent fluids into the producing
formation. This technology may affect natural groundwater
conditions, seismicity and subsidence. A preliminary compi-
lation of wells and well use in Imperial Valley disclosed very
limited groundwater use in the KGRAs, (or limited use in non-
geothermal groundwater aquifers up-gradient from potential
geothermal development).
Imperial Valley is a region of high seismicity and sig-
nificant tectonic movement. Descriptions and preliminary data
are presented here describing seismicity and subsidence moni-
toring networks. These networks will provide extensive baseline
data to aid in distinguishing the high levels of naturally
occurring seismicity and subsidence from that potentially in-
duced by future geothermal development.
2.1.2 Background :
Numerous studies are being conducted to evaluate and uti-
lize the geothermal potential of Imperial Valley. The first
geothermal well was drilled in 1927 near fumaroles and mud pots
by the southern shore of the Sal ton Sea. The steam from this
well, although not of sufficient quality or quantity for power
production, contained carbon dioxide gas and was utilized from
1934 to 1954 to produce dry ice. In 1957, a wildcat oil well
encountered 315°C (600°F) brine at a depth of 1,430 m (4,700 ft)
about 8 km (5 mi) south of the previously explored area. In
1968, the U.S. Bureau of Reclamation (USER) began funding Imper-
ial Valley geothermal exploration studies through the University
of California at Riverside (U.C.R.). These studies involved
gravity, resistivity, magnetic and temperature gradient surveys
and they identified eight areas with temperature gradients
greater than 3.6°C per 100 m (2°F per 100 ft) of depth. Six of
these areas are currently designated as KGRAs and four of them
are considered to have geothermal power production potential.
The Brawley and Heber KGRAs, the westernmost portion of the
East Mesa KGRA, and the landward portion of the Sal ton Sea KGRA
lie within irrigated agricultural land, roughly defined by the
area between the East Highline and Westside Main Canals (Fig.
2..2). Presently, 103,125 ha (254,827 acres) are designated as
KGRAs. This represents about one-tenth of the land area of
39
-------
Imperial County. Of the 192,000 ha (475,000 acres) of
agricultural land in Imperial Valley about 57,000 ha (140,000
acres) or approximately one-third is included in designated
KGRAs.
The climatology, baseline chemical characteristics of
water, geology, hydrology, and historic seismicity of Imperial
Valley are discussed in detail in "Baseline Geotechnical Data
for Four Geothermal Areas in the United States" (Geonomics, in
press) and are summarized below.
2.1.3 Summary of Imperial Valley Geotechnical Data
The Salton Trough is an area of high regional heat flow and
contains numerous geothermal anomalies (Fig. 2.2) (Combs, 1971).
It is one of the most seismically active areas in the United
States and significant subsidence rates have been measured.
Geologic evidence shows that the trough has experienced inten-
sive crustal deformation, active faulting (Richter, 1958; Allen,
et al. 1965; Brune and Allen, 1967), and subsidence (Elders, et
al. 1972), and that deformation is currently continuing.
The Imperial Valley is a hot, naturally arid area with a
mean annual precipitation of less than 80 mm (3 in.). It is a
relatively flat alluvial valley with the central portion heavily
irrigated. The valley is a broad structural and topographic de-
pression that has been filled with over 6,000 m (20,000 ft) of
later Tertiary deltaic and lacustrine sands, silts and gravels
overlain by alluvium and lake sediments. The underlying pre-
Tertiary granitic and metamorphic complex is intensely step-
faulted down from the mountains on both sides of the valley.
The combination of graphic chemical-analytic representa-
tions presented in Geonomics (in press) provides an effective
basis for establishing baseline water quality parameters in
Imperial Valley. Three depth zones were defined based on per-
forated well intervals. They are shallow, from 24 to 91 m (80
to 300 ft); intermediate, from 91 to 457 m (300 to 1,500 ft);
and deep, more than 457 m (1,500 ft). Modified Stiff diagrams
aided in defining the areal and depth distribution of five water
types in Imperial Valley. These are a sodium chloride water, a
high sulfate water, a sodium chloride with high calcium water, a
sodium chloride with high sulfate and/or magnesium water and a
sodium bicarbonate water. The Stiff diagrams depict the great
variation in the chemical characteristics of groundwater
throughout the valley, from the purest waters coming off the
Peninsular Range to the hypersaline brines occurring in the
Salton Sea geothermal area. A salinity gradient exists from the
southeastern end of the valley with salinity increasing to the
west and north as well as with depth.
40
-------
The geology of the Imperial Valley is complicated with
myriad fault traces and thousands of meters of discontinuous,
folded and layered sediments. The San Andreas, San Jacinto,
Elsinore and Salton Trough Fault Zones are all components of the
San Andreas System that fractures the sediments and basement of
the valley. A detailed compilation of these faults has been
prepared (Geonomics, in press) and many fault traces have been
located in each of these fault zones. Many other concealed
traces in alluvial areas remain to be discovered with further
detailed investigation. The Salton Trough Fault Zone has been
defined as a unique zone, containing parallel, subparallel and
orthogonal fault traces between the San Andreas and San Jacinto
Fault Zones. Most of the faults in this zone are concealed and
have been inferred from geophysical evidence (Meidav, et al.
1976).
Rocks in the Salton Trough range in age from Precambrian
basement complex to Recent alluvium and dune sands, and cor-
respondingly from dense, competent hard rocks to totally uncon-
solidated sedimentary deposits and young volcanics. Most of the
central valley is Pliocene and younger. One deep well near
Brawley intercepted over 4,000 m (13,000 ft) of interbedded fine
grained sandstone and siltstone. The main source of the thick
section of Eocene to Holocene nonmarine sediments has been
Colorado Plateau debris transported by the Colorado River, with
some contribution from local sources. Tertiary volcanic and
intrusive rocks occur within the sedimentary section.
Imperial Valley groundwater generally flows northward and
westward as underflow from the Colorado River, canal leakage and
irrigation discharge. This flow is generally distributed into
shallow and deep water bearing strata. Flow pattern complica-
tions arise from the presence of faults and stratigraphic aqui-
tards which channel and restrict water flow. It is conjectured
that local convective patterns tend to cause regional waters to
flow radially inward towards the geothermal anomalies. All
water is discharged from the closed Salton Sea drainage basin
through evaporation and evapotranspiration.
The flow rate of wells is quite variable throughout the
valley, from over 3,800 1pm (1,000 gpm) in a shallow well in the
southeastern valley to essentially nil in some shallow wells in
the central portion. However, deep wells in the central valley
flow as well or better than wells at the valley margins (Loeltz,
et al. 1975).
The total volume of water in storage has been estimated
between 0.20 and 0.59 billion ha-m (1.6 and 4.8 billion acre-ft)
(Rex, 1970), with another estimate of 0.97 billion ha-m (8.0
billion acre-ft) of usable and recoverable water in storage
(Dutcher, et al. 1972).
41
-------
Artificially induced recharge of Imperial Valley ground-
water from canal leakage and irrigation applications has notaDiy
raised groundwater levels, especially in the southeastern
portion of the valley.
Seismic activity is widespread and abundant in Imperial
Valley. Nine earthquakes of magnitude 6.7 or greater have
occurred in the Imperial-Coachella Valley area since 1850; the
Imperial Valley earthquake of 1940 was the most significant
event in terms of human disturbance. It has been difficult to
correlate much of the historic seismicity with active faults,
correlation of microseismicity with active faults has been more
fruitful.
Microearthquake activity is sometimes associated with geo-
thermal anomalies, and its occurrence may increase with geo-
thermal development or injection of geothermal fluids. A number
of microseismic monitoring networks have been installed in
Imperial Valley by the U.S. Geological Survey (USGS), California
Institute of Technology (Cal Tech), and Chevron Oil Company.
Changes in earthquake recurrence statistics and/or in the depth
and location of events from pre-production activity may be used
to detect production-induced seismicity.
Two reports on environmental impact of geothermal develop-
ment in Imperial Valley, which cover aspects complementary to
those covered in this report, have been published recently by
the Imperial Valley Environmental Project of Lawrence Livermore
Laboratory (LLL). These reports include:
"A Description of Imperial Valley, California for the
Assessment of Impacts 'of Geothermal Energy Development";
D. Layton and D. Ermak; August 26, 1976.
"Imperial Valley Environmental Project: Progress Report";
P.L. Phelps and L.R. Anspaugh, eds.; October 19, 1976.
!
The following report on the geotechnical aspects of the en-
vironmental impact of geothermal development in the Heber KGRA
has been published by the Electric Power Research Institute of
Palo Alto:
"Some Geotechnical Environmental Aspects of Geothermal
Power Generation at Heber, Imperial Valley, California";
Geonomics, Inc.; EPRI ER-299; October, 1976a.
2.2 GEOTHERMAL SYSTEMS
There are at least seven geothermal systems in the Salton
Trough structural province. One is located at Cerro Prieto
Mexico and the remaining six are in Imperial Valley. All of
42
-------
these systems are intermediate to high temperature hot water
systems with salinities ranging from over 1,000 ppm in the Dunes
and East Mesa KGRAs to 385,000 ppm in the Salton Sea KGRA. Fluid
temperatures range from 135°C (275°F) for the low salinity fluid
to 340°C (644°F) for the hypersaline brine. A knowledge of the
quantity of the resource is pertinent in assessing environmental
impact in order to estimate the amount of fluids and chemical
constituents that will potentially be produced. The following
discussion is largely extracted from Ermak and Buchanan (1976),
who have recently summarized the geothermal resource of Imperial
Valley.
Estimation of the geothermal resource of Imperial Valley is
difficult at this time due to the lack of factual data on actual
reservoir temperatures, volume, heat capacity and water-to-rock
ratios for all but a small percentage of the potential resource.
Since only about 5% of the potential resource has been proven by
drilling (Towse, 1975) many assumptions must be made to estimate
it. Previous estimates have ranged over five orders of mag-
nitude (Anderson and Axtell, 1971; Combs, 1971; Dutcher, et al.
1972; Helgeson, 1968; Rex, 1970), but more recent investigations
have narrowed the discrepancy to one order of magnitude (Towse,
1975; Renner, et al. 1975; Biehler and Lee, 1977; Nathenson and
Muffler, 1975). These current potential geothermal resource
estimates, each utilizing different methods and assumptions of
reservoir properties, are summarized in Table 2.1 and are dis-
cussed below.
Renner, et al. (1975) estimated a reservoir depth of 3,000
m (10,000 ft), considered only fluids with temperatures above
150°C (302°F) and assumed a volumetric specific heat of 0.6
cal/cm3-°C to arrive at a total estimated stored heat of 175 x
1018 joules (J) (1.66 x 1017 BTU) for the Salton Trough. Nathen-
son and Muffler (1975), in their assessment of electric power
generation potential, assumed that 25% of the Renner, et al.
(1975) stored heat would be recoverable for an estimated total
of 43.7 x 1018 J (4.14 x 1016 BTU). Towse (1975) defined the
geothermal reservoir volume from a temperature gradient map
(Combs, 1971), assuming that usable geothermal fluid extended to
whichever was less, 300 m (1,000 ft) below the 230°C (446°F)
isotherm or a maximum depth of 2,100 m (7,000 ft). He estimated
that 59% of the reservoir would be composed of permeable sand-
stone with a specific yield of 0.16 (Dutcher, et al. 1972). The
water enthalpy was estimated at.590 x 106 J/kg (560 BTU/lb) and
the specific gravity of the water at 1.0. Towse states that
specifying other reservoir properties could increase the total
recoverable heat estimate of 20 x 1018 J (1.9 x 1016 BTU) by as
much as 150%.
Biehler and Lee (1977) estimate the heat stored in the
recoverable fluid from "excess mass" calculations based on
gravity anomalies. The reservoir volume is computed by dividing
43
-------
TABLE 2.1 ESTIMATES OF STOKED AND RECOVERABLE HEAT IN THE GEOTHERMAL
RESOURCES OF IMPERIAL VALLEY
Salton Sea
Heber
East Mesa
Brawley
Glamis
Dunes
E. Brawley
TOTAL
Total
Stored Heat
in Rock
and Water
Heat in Recoverable Fluid
(All values in 1018 J)
a
87.
46.
23.
12.
1.
2.
0.
174.
9
0
0
6
7
5
8
5
b
22
11
5
3
43
.0
.5
.8
.2
.4
.6
.2
.7
c
11
3
3
1
1
0
20
.0
.5
.0
.0
.0
.5
-
.0
35
8
10
13
0.
67
.4
.3
.4
.2
06
.4
d
to
to
to
to
-
to
-
to
106
25
31
39
0.
202
.1
.0
.2
.6
2
.1
e
14.1
7.4
3.7
2.0
0.3
0.4
0.1
28.0
aRenner, et al. (1975)
^Modified from Nathenson and Muffler (1975), based on Renner, et al.
(1975) and using a thermal energy recovery factor of 0.25
CTowse (1975) and Ermak and Buchanan (1976)
dfiiehler and Lee (1977)
on Rennerf et al. (1975) and using a thermal energy recovery
factor of 0.16 (see text for explanation)
-------
the total "excess mass" by the density contrast. The reservoir
volume will vary depending on what density contrast is assumed
between different masses. Biehler and Lee (1977) provide a
range of estimates based on possible density contrasts of 0.1
g/cc (6 Ibs/ft3), 0.2 g./cc (12 Ibs/ft3), and 0.3 g/cc (19
Ibs/ft3), an average porosity of 20%, an average yield of 80%, a
fluid density of 1 g./cc (62.43 Ibs/ft3) and a fluid enthalpy of
.590 x 106 J/kg (560 BTU/lb). This approximation provides a
range of estimates from 67.4 to 202 x 1018 J (6.38 x 1016 to
20 x 1017 BTU) for the heat content in the recoverable fluid,
which is much higher than the Towse (1975) or Nathenson and
Muffler (1975) estimates. The upper limit is even higher than
the total stored heat in the rock and fluid in the Imperial
Valley estimated by Renner, et al. (1975).
Another estimate of the recoverable heat resource for
Imperial Valley is proposed here. In this estimation, the total
resource estimate of Renner, et al. (1975) is accepted and an
area specific recovery, factor (the amount of recoverable fluid
in the reservoir) is applied to it. This is similar to the
approach of Nathenson and Muffler (1975), but instead of using
the general recovery factor which they applied to all geothennal
areas in the United States, a recovery factor based on the
physical properties of the reservoirs is used. This recovery
factor uses an average porosity value of 20% and an average
yield of 80% (Biehler and Lee, 1977) for an average recovery
factor of 0.16. Using these figures, the heat in storage in the
recoverable fluid is 28.0 x 1018 J (2.65 x 1016 BTU) for the
entire Imperial Valley. This estimate is nearly midway between
the Towse (1975) and Nathenson and Muffler (1975) estimates.
However, this estimate does not account for a dynamic hydrologic
system, where both natural recharge and injection of geothennal
waste water can take place. Both natural recharge and injection
will increase the amount of total energy recovered from the
reservoir.
It is important to consider that the Renner, et al. (1975)
estimate is for the total heat contained in the rock and water
while the Nathenson and Muffler (1975), Towse (1975) and Biehler
and Lee (1977) estimates are for the potentially recoverable
resource.
All investigators agree that the Salton Sea geothermal
field contains the major portion of the resource, with Renner,
et al. (1975) estimating it as 50%, Towse (1975) as 50% and
Biehler and Lee (1977) as 40%. It is apparent from these
studies that considering the current state of technology, only
the Salton Sea, East Mesa, Heber and Brawley fields contain
commercial quality and quantity of geothermal water.
Descriptions of the individual geothermal fields are out-
lined below.
45
-------
2.2.1 East Mesa KGRA
High temperature gradients, relatively low salinity
and a thick section of fluid saturated rock make the East Mesa
geothermal field an attractive area for potential geothermal
energy development. The sedimentary rocks and sediments are
relatively flat-lying (Randall, 1974) and difficult to cor-
relate. Vertical groundwater flow is limited by the lenticular
nature of the more impermeable sediments (Black, 1975). The
fluid is assumed to flow via fractures in the deeper, more
brittle rocks (U.S. Bureau of Reclamation, 1971). This assump-
tion is supported by core samples from the deep production zone
at 2,250 m (7,400 ft) in Mesa 6-1, which consists of well-
cemented sandstone of low intergranular permeability. Core
samples from a depth of 2,133 m (7,000 ft), 120 m (400 ft) above
the sandstone, contain shale with slickensides and calcite-
filled fractures.
Randall's (1971) correlations show that the surficial
deposits are underlain by a thick wedge of sandstone, up to
3,700 m (12,000 ft) thick (Biehler, et al. 1964). The sandstone
is derived from the coarser deposits of the Colorado River Delta
and from windblown sand. This is corroborated by sand grain
surface features on drill cuttings indicating the origin as dune
sand, dune plain sand and dune sand reworked during lacustrine
processes (Rex, et al. 1971).
The Mesa anomaly exhibits high thermal gradients (Combs,
1971), low resistivity (Meidav and Furgerson, 1972), seismic
noise, microearthquake activity at depth (U. S. Bureau of Rec-
lamation 1974), and a positive gravity anomaly (Biehler, 1971).
The low resistivity is indicative of either high salinity or
high temperature water or both. The positive gravity anomaly is
indicative of more,, dense rock. From calculations based on this
gravity data, Biehler (1971) and Meidav, et al. (1975) hypothe-
sized that the density contrast is mostly within the sedimentary
section, and is a result of silica or calcium carbonate depo-
sition in the interstitial pore spaces of the sandstone. Silica
would be precipitated as the hot geothermal fluids rise and
cool. Calcium carbonate would be precipitated if calcium car-
bonate-rich cooler water is heated as it mixes with hotter
geothermal brine. However, no siliceous cap rock, such as has
been discovered in East Mesa, can be found in the nearby Dunes
area (Coplen and Kolesar, 1974; Combs, 1972). Black (1975)
proposes that the higher density mass in the area must be caused
by the presence of an igneous intrusion at depth, or by higher
density thermally metamorphosed rocks resulting from rising geo-
thermal fluids. The absence of a magnetic anomaly suggests that
there is no igneous intrusion and thereby tends to support the
thermal metamorphosis explanation of the gravity anomaly.
46
-------
20,000 lint) »»i"
7 CCOTKMUl
Figure 2.3 Geothermal well locations, heat flow contours, and mapped faults,
East Mesa KGRA (modified from U.S. Bureau of Reclamation, 1974)
-------
Four faults have been mapped on the Mesa anomaly since 1970
(Fig. 2.3). Typical of faults in the alluvial parts of Imperial
Valley, all of these faults have been identified by geophysical
,
techniques and none of them has surface expression. The
patria Fault (Meidav and Rex, 1970) location was based on an
electrical resistivity survey; however the control in _the sou-cn-
ern part of the survey was poor and the location of the rauj-t
through the East Mesa geothermal field is quite conjectural.
The unnamed fault cited by Rex (1970) and U.S. Bureau of Recla-
mation (1974) is, in fact, the Calipatria Fault. The Mesa Fault
(Combs and Hadley, 1977) has been located by a microseismic
monitoring network. The Holtville Fault (Babcock, 1971) has
been located by aerial and infrared photography and its actual
existence is uncertain.
Some or all of these faults may allow upward flow of geo-
thermal fluid, thereby controlling the location of the East Mesa
geothermal anomaly. However, faults may be aquitards as well as
conduits. Though the fault itself may not function as the
actual conduit, a fracture zone associated with the inferred
faults is postulated as the vertical conduit for the geothermal
fluids (Black, 1975).
Resource Base and Production Potential —
The resource base at East Mesa has been estimated by
Renner, et al. (1975) at 2.30 x 1019 J (2.18 x 1016 BTU). Of
this total stored heat in the water and rock, estimates of the
heat content in the recoverable fluid range from 3.0 x 10 18 J
(2.8 x 1015 BTU) (Towse, 1975) to 3.12 x 1019 J (2.96 x 1016
BTU) (Biehler and Lee, 1977). For this field, the Biehler and
Lee (1977) maximum estimate of heat content in the recoverable
fluid is greater than the Renner, et al. (1975) estimate for the
total heat in storage in the rock and fluid. If we accept the
Renner, et al. (1975) value for the total heat and apply the
0.16 recovery factor (described in section 2.2), the heat in the
recoverable fluid is estimated as 3.7 x 10 18 J (3.5 x 10 1S BTU)
for the East Mesa area.
The Mesa anomaly was chosen by the USSR as the site for
five geothermal test wells, all drilled to depths greater than
1,800 m (6,000 ft). The locations of these wells were based on
the results of geophysical surveys and they were drilled between
August 1972 and June 1974. Casing and completion data for these
wells, named Mesa 6-1, 6-2, 5-1, 8-1 and 31-1, are given in
Table 2.2. This table includes casing outside diameters and
depths, slotted and perforated intervals, and average Saraband
sand permeability index.
Flow rates and pressures were measured for all the wells
except Mesa 31-1. Fig. 2.4 shows flow rate versus wellhead
gauge pressure for Mesa 6-1, '6-2, 5-1 and 8-1. As would be
expected, the flow rate for these wells decreases as the well-
48
-------
TABLE 2.2
CASING AND COMPLETION RECORDS, EAST MESA TEST SITE
(Mathias, 1975)
CO
Mesa+
well
number
6-1
6-2
5-1
8-1
31-1
Casing
outside
diameter
(in.)
20
13
9
7
20
11
7
20
13
7
20
13
7
20
13
7
3/8
5/8
3/4
5/8
3/8
5/8
3/8
5/8
3/8
5/8
Kelly Average
bushing Saraband
elevation Depth Slotted Perforated sand
(m above interval interval interval permeability
msl) (m) (m) (m) (md)
18 0-116
0-763
0-223 2075-2179 230
2213-2443 2238-2433 1.5
12 0-19
0-301
0-1816 1663-1816 70
15 0-18
0-312
0-1830 1525-1830 69
20 0-18
0-304
0-1829 1508-1829 39
16 0-18
0-309
0-1882 1652-1882 62
+Well locations shown on Figure 2.9.
*From Black, 1975
All Kelly bushings are about 5 m above ground surface, except Mesa 6-1
which is about 7mabove ground surface. (U.S. Bureau of Reclamation)
-------
EXPLANATION
Q M>
p
& M.
P
O M.
* M.
X «•
o 61 t»f<
r forolion
0 6 1 oft*
r lorotion
0 6 J
o 5 1
o 8 1
I 100% liquid
« upholr
uphol*
15«C
WELIHEAD GAUGE PSESSURE Box
Figure 2.4 Pressures, temperatures and total flow rates,
Mesa 6-1, Mesa 6-2, Mesa 5-1 and Mesa 8-1
(Mathias, 1975)
15
o
<
OS
MESA CEOTHERMAL FIELD, PRELIMINARY EVALUATION
=*>-^
10 )00
HOURS FLOWING FUU OPEN
I i I I I I I
EXPLANATION
0 Mno 62
* Meio 51
X M«o 8 I
Wellhead Prttlure
Total Flow Rot*
1500
1000
500
1000
Figure 2.5 Surface pressures and total flows, wells flowing
full open, Mesa 6-2, Mesa 5-1 and Mesa 8-1
(Mathias, 1975)
50
-------
head pressure is increased. These flows are representative of
rates occurring after several days of well operation and were
recorded after 24 to 48 hours of stabilized flow. The only
equilibrium condition at the lower flow rates was reached at
well 6-1 after uphole perforation.
In Mesa 6-1, after reperforating in a much more permeable
interval, the flow rate varied from almost 1,600 kg/min (3,500
Ib/min) at 1.7 bars (25 psig) wellhead gauge pressure to about
300 kg/min (660 Ib/min) at about 6.4 bars (93 psig) pressure and
166°C (331°F). In Mesa 6-2 the rate varied from 1,100 kg/min
(2,500 Ib/min) at 2.1 bars (31 psig) and 134°C (273°F) with 7%
steam by weight, to approximately 190 kg/min (420 Ib/min) at 5.9
bars (86 psig) and 154°C (309°F) where the fluid is 100% liquid.
In Mesa 5-1 the flow rate was measured at over 800 kg/min (1,800
Ib/min) at 0.8 bar (12 psig) and 104°C (219°F). The fluid
contained 6.2% steam, by weight, at the wellhead. The flow rate
for Mesa 8-1 varied from 1,394 kg/min (3,073 Ib/min) at 2.0 bars
(29 psig) and 127°C (261°F) with 7.7% steam to about 190 kg/min
(419 Ib/min) at 6.8 bars (99 psig). Surface temperature and
pressure of 120°C (248°F) and 1 bar (14.5 psi) were measured at
Mesa 31-1, but no flow test results have yet been published.
Fig. 2.5 shows the variation of wellhead pressures and
total flows with time for Mesa 6-2, 5-1 and 8-1 flowing full-
open. Long-term full-open flow tests have not been conducted
due to limited fluid disposal facilities and these tests have
been terminated at 200 hours. Although the trends in Fig. 2.5
have little quantitative use because of the effect of scaling on
the decreasing flow rates and pressures, it can be seen that
equilibrium flow rates have not been achieved for any of the
wells and that the decline in pressure and flow rate is similar
for all three. Mesa 8-1 had the highest flow rates, from about
1,340 kg/min (2,950 Ib/min) at approximately 2 bars (29 psig)
to about 1,100 kg/min (2,400 Ib/min) at approximately 1.6 bars
(23 psig). Mesa 5-1 had the lowest flow rates, from about 880
kg/min (1,940 Ib/min) at approximately 0.8 bars (12 psig) to
about 500 kg/min (1,100 Ib/min) at approximately 0.3 bars (4.4
psig). The full-open flow rate of Mesa 6-2 declined from about
1,140 kg/min (2,500 Ib/min) at approximately 2.1 bars (31 psig)
to about 800 kg/min (1,800 Ib/min) at 1.7 bars (25 psig).
During these tests some of the wells developed downhole calcium
carbonate scales, especially Mesa 5-1, which was constricted to
the point where it was impossible to lower small diameter in-
struments down the hole. Injection of 15% inhibited hydro-
chloric acid was necessary to clear the well bore. Further
downhole pressure data is necessary to define fully the long-
term flow characteristics (Mathias, 1975) of these wells.
Table 2.3 shows bottom-hole shut-in and flowing pressures
and bottom-hole shut-in temperatures. The shut-in pressures and
temperatures were measured after the wells had been idle for a
51
-------
few weeks. The flowing pressures were obtained at full-open
conditions within a few hours of startup. The total tlow rates
are shown in Fig. 2.5.
TABLE 2.3
1
BOTTOM-HOLE SHUT-IN AND FLOWING PRESSURES AND TEMPERATURES
EAST MESA WELLS (Mathias, 1975)
Mesa
well
number
Depth
measured
(m)
Bottom-
hole
shut-in
pressure
(bar
gauge )
6-1
6-2
5-1
8-1
31-1
Bottom-
hole
pressure
while Total
flowing flow
(bar rate
gauge) (kg/min)
2,422 219
1,809 169
1,814 169
1,821 168
No tests run
159
134
156
157
1,600
1,134
800
1,394
Bottom-hole
shut-in
temp/depth
(°C) (m)
204/2,442
188/1,816
157/1,830
179/1,830
Pressure drops between bottom-hole and wellhead of over 150
bars (2,176 psi) are shown for Mesa 6-1, 5-1 and 8-1, and drops
of about 130 bars (1,886 psi) are shown for Mesa 6-2. Bottom-
hole temperature of 204°C (400°F) was measured for Mesa 6-1
while wellhead temperatures ranged from 130°C (266°F) to 160°C
(320°F). Similarly, temperature differences were observed from
188°C (370°F) bottom-hole to 134°C (273°F) to 154°C (310°F)
wellhead for Mesa 6-2, from 157°C (315°F) bottom-hole to 104°C
(219°F) wellhead for Mesa 5-1, and from 179°C (354°F) bottom-
hole to 127°C (261°F) to 157°C (315°F) wellhead for Mesa 8-1.
Interference tests were conducted at Mesa 6-2 and Mesa 31-1
to determine transmissivity (Witherspoon, et al. 1976). Sensi-
tive pressure gauges on wells Mesa 6-1 and Mesa 8-1 were used
for observation measurements while Mesa 6-1 was flowing. Early
drawdown data suggest a transmissivity of 11,200 millidarcy feet
(md-ft) and a storage capacity (
-------
An interference test was conducted on Mesa 31-1 with Repub-
lic Geothermal RG-38-30 used as an observation well. Type-curve
matchings of the early drawdown data suggest a transmissivity of
29,500 md/ft (0.004 kg/sec) and a storage capacity of about
0.065 cm/bar (1.47 x 10 4 ft/psi).
The transmissivity here is almost three times that indi-
cated from the tests at Mesa 6-1 while the storage capacity is
somewhat more than one-third of that 'indicated for the Mesa 6-1
test. This test also indicates the presence of barrier boundary
from 335 to 730 m (1,100 to 2,400 ft) from RG 38-30.
Flow rates and specific discharge during injection opera-
tions in Mesa 5-1 are shown in Fig. 2.6 (Mathias, 1975). The
discharge curve starts to asymptotically approach about 45
cu m/day/m head (1 gpm/psi) after about 60 minutes of operation.
Injection of fluid from a holding pond was started February 28,
1975 and continued sporadically at average flow rates from 300
to 1,281 cu m/day (55 to 235 gpm) (Table 2.4). As can be seen
from Fig. 2.6 the specific injection rate decreased as the in-
jected quantity of the 50,000 mg/1 TDS, pH 7.5 fluid increased.
Initially higher injection than discharge values are attributed
to improved reservoir properties due to pre-perforation acidiz-
ing (Mathias, 1975). Pressure pumping began about 48 hours
after injection started and after ten days it was up to 5.5 bars
(gauge) (80 psi) at 398 cu m/day (73 gpm). Fluids were being
less readily accepted and intermittent pumping was conducted,
with a wide range of pressure and rate variations (Table 2.4).
It was calculated that 1,030 kg (2,270 Ib) of suspended solids
were injected. The high corrosion noted in the lower portion of
the hole was attributed to high quantities of dissolved oxygen
(Shannon, 1975).
Chemical Composition of Fluids—
The geothermal fluids at East Mesa have relatively low
salinity, ranging from about 1,500 mg/1 in Mesa 5-1 and 8-1 to
somewhat over 25,000 mg/1 in Mesa 6-1. The lower salinity
waters generally appear to have relatively higher bicarbonate
content than the higher salinity waters which generally have
high concentration of only sodium and chloride. Table 2.9 shows
major constituent and trace element analyses of East Mesa geo-
thermal wells and one analysis of water from the Mesa 6-2 hold-
ing pond.
The change of salinity (TDS) with depth is shown on depth
vs. salinity (sodium chloride equivalent ppm) for 10 geothermal
wells in the East Mesa geothermal field (Fig. 2.7). These plots
are based on interpretation of electrical resistivity and self-
potential well logs. In general, they show two higher salinity
layers at 600 to 1,200 m (2,000 to 4,000 ft) and 1,800 to 2,300
m (6 000 to 7,500 ft) with a lower salinity layer between. The
plots show fluid salinity increasing to 3,000 to 5,000 ppm at
53
-------
'00
TIME SINCE START- MINUTES
1000
Figure 2.6
Specific injection and discharge at Mesa 5-1 during
initial injection and discharge operations
(Mathias, 1975)
54
-------
TABLE 2.4 INJECTION SCHEDULE, MESA 5-1 (Mathias, 1975)
Date 1975
Feb. 28
Mar. 11
Mar. 11
Mar. 12
Mar. 12
Mar. 13
Mar. 25
Apr. 2
Apr. 2
Time
1015
0730
1020
0745
0840
1330
1450
2100
0915
1525
0955
1300
Operation
Begin injection
Stop injection
Begin injection
Stop injection
Begin injection with booster pump
Stop injection
Begin injection
Stop injection
Begin injection
Average flow during injection
Stop injection
Begin injecting shallow well water
Stop injection
Average
flow rate
(m'/day)
1 090
398
398
125
1 281
600
441
578
1 128
273
343
300
<00
Cumulative
quantity flowed
(m1)
0
6968
7 222
7416
-
7 490
11 184
11 441
55
-------
en
(LOCATION OF WELLS SHOWN ON FIG. 2.2)
RPPM = ELECTRICAL RESISTIVITY LOG
SPPM= SELF POTENTIAL LOG
INTERPRETATIVE AVERAGE OF RPPM AND SPPM
PARTS PER MILLION
WELL NO. 6-2
(USBR)
•ooo teoo loooo *«oo «jooo uooo MOOO *HOO >«ooo
PARTS PER. MILLION
WELL NO. 6-1
PARTS PER MILLION
WELL NO. 31-1
(USSR)
(USBR)
Figure 2.7 Chemical profile of geothermal wells, Mesa anomaly
(Littleton and Burnett, in press) (continued)
-------
(LOCATION OF WELLS SHOWN ON FIG. 2.2 )
RPPM= ELECTRICAL RESISTIVITY LOG
SPPM = SELF POTENTIAL LOG
INTERPRETATIVE AVERAGE OF RPPM AND SPPM
in
PARTS PER MILLION
WELL NO. 44-7
(MAGMA POWER)
000 1000 MOO 40CO WOO
PARTS PER MILLION
jWELL NO. 8-1
(USSR)
PARTS PER MILLION
WELL NO. 48-7
(MAGMA POWER)
Figure 2.7 (continued)
-------
(LOCATION OF WELLS SHOWN ON FIG. 2.2)
RPPM = ELECTRICAL RESISTIVITY LOG
SPPM= SELF POTENTIAL LOG
INTERPRETATIVE AVERAGE OF RPPM AND SPPM
tn
00
III i
o
III
III
III
O*>00
• «x» mo JDOD «ooo woo n
PARTS PER MILLION
WELL NO. 5-1
(USBR)
PARTS PER MILLION
WELL NO. 16-29
PARTS PER MILLION
WELL NO. 18-28
PARTS PER MILLION
WELL NO. 38-30
(REPUBLIC GEOTHERMAL)
(REPUBLIC GEOTHERMAL) (REPUBLIC GEOTHERMAL)
Figure 2.7
-------
750 to 900 m (2,500 to 3,000 ft) depth and then decreasing with
depth to 2,000 to 4,000 ppm at 1,800 m (6,000 ft). Logs for
wells 6-1 and 48-7 show a more concentrated brine of 5,000 to
9,000 ppm around the 2,100 m (7,000 ft) depth. The profile is
different for wells 38-30 and 18-28, where the salinity starts
increasing at about 1,460 and 1,160 m (4,800 and 3,800 ft)
respectively and continues to increase for the total 2,400 to
2,700 m (8,000 to 9,000 ft) depth of the well log. The log for
wells 6-1, 6-2, 18-28 and to some extent 48-7 in general show
somewhat higher salinities than the remaining wells.
Relative to USPHS drinking water standards, the East Mesa
fluids are high in arsenic, boron, cadmium, chloride, fluoride,
iron, manganese, sulfate, and TDS. These potential pollutants
are discussed in more detail in section 2.3.1 on water pollution
in East Mesa.
Field Development Status—
USER has been concentrating on evaluation of the East Mesa
geotherraal field since the early 1970s. Their participation has
resulted in drilling and testing of the five geothermal wells
previously discussed. They have initiated a pilot desalination
program to determine the feasibility of desalting mineralized
geothermal fluids (Fernelius, 1975). At the same time power
generation feasibility studies and materials investigations will
be conducted. Two desalination units have been installed and
are successfully operating to produce 75 to 190 cu m (2,650 to
6,700 cu ft) of distilled water per day. No silica scaling has
occurred and other scaling and corrosion problems have been
minor.
In addition, USER and ERDA (in conjunction with Lawrence
Berkeley Laboratory) have designated East Mesa KGRA as a na-
tional geothermal test site to allow industry, institutions and
private investigators to conduct tests of geothermal materials
and equipment in actual field conditions. Magma Power Company
is currently constructing an 11,200 net kW "dual binary cycle"
plant. They expect it to be operational by the spring of 1978
(Hinrichs and Falk, 1977). This is viewed as a research plant
and will require three production wells to provide approximately
290 kg (130 Ib) of well flow per kW.hr, and two injection wells.
2.2.2 Salton Sea KGRA
The Salton Sea KGRA includes the southeastern part of the
Salton Sea and adjacent land area (Fig. 2.2). This geothermal
field contains the greatest quantity and highest temperature
geothermal fluid of any area in the Imperial Valley. Unfortu-
nately, exploitation of these great reserves is hampered by the
technical problems caused by the extremely high salinity geo-
thermal brines.
59
-------
The Salton Sea geothermal anomaly is generally regular in
shape and isothermal surface locations are apparently unaftectea
by geologic and structural features. Presently, the size ana
shape of the geothermal field appears to be controlled solely r>y
distance from the magma body that caused the anomaly. It is
hypothesized that the emplacement of the heat source is geolog-
ically very recent; hence, the heat decay necessary for the
shape of the isothermal surfaces to define stratigraphic and
structural features has not yet occurred (Randall, 1974).
Recent volcanic activity is evidenced by the Salton Buttes,
which are five rhyolite domes near the southeast shore of the
Salton Sea. Emplacement of one of these domes has been dated at
16,000 to 50,000 years ago (Muffler and White, 1969).
The Salton Sea geothermal anomaly is an area of high heat
flow and high temperature gradients. Hot brines, with temper-
atures to 360°C (680°F) at depths from 1,500 to 2,500 m (4,900
to 8,200 ft) have been recovered from the area. The fluids have
salinities to 385,000 ppm with sodium, chloride and calcium as
major constituents. These hot brines have produced a green-
schist metamorphic facies below depths of 1,000 m (3,300 ft). A
decarbonation reaction has been commercially exploited through
the production of carbon dioxide from wells penetrating this
facies (Randall, 1974).
The depth to bedrock, and hence thickness of the sedimen-
tary section of interbedded fluviatile and lacustrine sands,
silts and clays, varies from less than 3,300 m (10,000 ft) to
more than 4,900 m (16,000 ft) (Rex, 1970). Superimposed on the
pattern of thickening of sedimentary fill towards the center of
the valley is the effect of many faults (see Geonomics, in
press), producing vertical displacements in the thick sedimen-
tary section. These displacements can be minor or up to about
700 m (2,300 ft), such as that shown on the Calipatria Fault in
this area (Rex, 1970). These fault features, in addition to the
discontinuous nature of the sediments, make stratigraphic cor-
relations extremely difficult.
Resource Base and Production Potential—
The resource base of the Salton Sea geothermal field is
estimated to contain about half of the total recoverable heat
energy in the Salton Trough (Table 2.1). Renner, et al. (1975)
estimate the total stored heat in the water and rock of the
Salton Sea geothermal field as 8.7 x 1019 J (8.3 x 1016 BTU).
Estimates of the recoverable resource range from 11 x 1018 J
(1.0 x 1016 BTU) (Towse, 1975) to Biehler and Lee's (1977) range
of 35.4 to 106.1 x 1018 J (3.4 to 10.1 x 1016 BTU). It is felt
that Biehler's estimates are somewhat high and the actual amount
of the recoverable resource is nearer to the lower estimate.
Status information is available for 24 geothermal wells
drilled by private companies in the Salton Sea geothermal field
60
-------
(Table 2.11) (Palmer, 1975). The first six wells were drilled
in the late 1920s and early 1930s to depths between 180 m (590
ft) and 450 m (1,480 ft) and were used for carbon dioxide pro-
duction. No additional drilling was done in the area until the
late 1950s and early 1960s when 12 wells were drilled to depths
between 520 m (1,700 ft) and 2,500 m (8,100 ft). Six more wells
were drilled in the early 1970s to depths between 732 m (2,400
ft) and 1,331 m (4,368 ft). It appears from the narrower range
of depths drilled in the 1970s that the producing geothermal
intervals have become somewhat better defined with additional
drilling and exploration.
Temperature gradient measurements are available for 17
individual geothermal wells and this information was compiled to
construct a block diagram of isothermal surfaces for the Salton
Sea geothermal field (Fig. 2.8) (Palmer, 1975). The diagram
shows 50° to 350°C (122° to 662°F) isothermal surfaces for a
northwest-southeast trending rectangular prism approximately in
the middle of the KGRA. These data represent the best informa-
tion available, but are not necessarily accurate due to differ-
ences in temperature measurement instruments, procedures and
techniques. It is believed that some of the earlier data is for
noneguilibrium conditions (Palmer, 1975). Fig. 2.8 shows indi-
vidual isothermal surfaces closer to the ground surface under
the Salto-n Sea, and located at greater depths to the east. From
west to east the 50° C (122°F) isothermal surface occurs at
depths from 100 m (330 ft) to 500 m (1,640 ft), the 100°C
(212°F) surface occurs at depths from 150 m (490 ft) to 1,000 m
(3,300 ft), the 250°C (482°F) surface occurs at depths from
450 m (1,480 ft) to 1,900 m (6,230 ft) and the 350°C (662°F)
isothermal surface occurs at 1,000 m (3,300 ft) depth beneath
the southeast shore of the Salton Sea. None of the isothermal
surfaces vary linearly and the gradient increases steeply to the
southeast. Common temperature ranges for wells in the Salton
Sea KGRA are 200°C (390°F) to over 300°C (570°F).
Production data for geothermal wells in the Salton Sea KGRA
are summarized in Table 2.5. These data, including wellhead
pressure, orifice size and percent steam in the wellhead efflu-
ent, are mostly from California Division of Oil and Gas records
and are considered reasonably reliable (Palmer, 1975).
Geothermal wells in the heated water reservoir of the
Salton Sea KGRA will not flow naturally and must be stimulated
to begin flowing. This is usually done by injecting nitrogen
into the bottom of the borehole, thereby lifting the entire
column of water. This allows for thermal expansion, reduction
of fluid density, and initiation of flow, which generally con-
tinues unaided at relatively high production rates. Flow from
these wells is typically several hundred thousand kilograms per
hour, with 10 to 20% steam accompanying the hypersaline brine.
The maximum listed flow rate at well I ID No. 1 has been sus-
61
-------
Garst Road
Sal ton Sea
2000
350 300
Temperature — °C
Salton Sea
Geothermal
Reid Boundry
Vertical
exaggeration
4X
Figure 2.8 Block diagram of isothermal surfaces
geothermal field (Palmer, 1975)
- Salton Sea
62
-------
TABLE 2.5 SUMMARY OF PRODUCTION CHARACTERISTICS FOR GEOTHERMAL
WELLS IN SALTON SEA KGRA (Palmer, 1975)
Production Wellhead
Well Rate (Ib/hr) Pressure (psi) Date Steam (%)
Magma max //I
Magma max //I
Magma max //I
Magma max //I
Magma max #1
Magma max //I
Magma max //I
Sinclair #3
Sinclair #4
IID #1
IID #1
IID #1
IID #1
IID #1
IID #1
IID #2
IID #2
IID #2
IID n
IID #2
Sportsman #1
Sportsman #1
Sportsman //I
State #1
State #1
State #1
Elmore #1
Hudson #1
niirAi- Panr>Vi il
542,000
405,000
349,000
339,000
369,000
399,000
467,000
593,000
450,000
625,500
172,000
375,000
462,500
500,000
532,000
377,000
440,000
349,700
319,700
395,400
327,000
293,000
324,000
305,000
364,000
405,000
316,000
432,333
1 244.700
160
96
102
122
117
103
110
185
250
200
585
485
385
285
185
212
225
263
215
225
248
205
200
465
400
347
-
-
_
4-28-72
4-29-72
4-30-72
5-1-72
5-2-72
5-3-72
5-4-72
5-23-63
5-2-64
6-62
90-day
Test
12-8-65
12-9-65
8-2-65
-
-
3-64
3-64
3-64
3-64
3-64
4-61
4-61
-
6-64
6-64
6-64
-
8-64
4- day
Test
10-65
13
14
14
15
10
13
14
12
20
25
10
11
14
17
20
18
18
16
15
14
15
16
17
15
18
20
35
22
20
Orifice (in.;
8
8
8
-8
8
8
8
8
-
7
-
-
-
-
-
8
8
8
8
8
5-1/2
5-1/2
5-1/2
8
8
8
. ».'- _
7
7
63
-------
tained at 283,725 kg/hr (625,500 Ib/hr) for a 90-day test Period
and the well Hudson No. 1 has sustained a 196,105 kg/hr (432,3JJ
Ib/hr) flow rate for four days. Several other wells have pro-
duced for up to 18 months without appreciable decrease in the
flow rate (Helgeson, 1968). Wellhead pressures vary from 6.7b
kg/sq cm (96 psi) to 41.1 kg/sq cm (585 psi) with orifice size
varying from 14 cm (5.5 in.) to 20 cm (8 in.).
Chemical Composition of Fluids—
Chemical composition, including trace element analyses for
Salton Sea KGRA geothermal wells, is tabulated in Table 2.12.
The brine analyses show extremely high TDS contents, as high as
385,000 ppm. Sodium, chloride and calcium constitute essen-
tially 100% of the major constituents, generally with chloride
being the major anion, and the percent reactance of sodium
usually being more than double that of calcium.
Concentrations of iron and manganese reach a few thousand
mg/1, while concentrations of silica and strontium are in the
hundreds to a thousand mg/1 range, with one strontium analysis
of 4,800 mg/1 in Sinclair No. 4 well. Values of 1,200 mg/1
nickel and 1,050 mg/1 nitrate have been reported for Sinclair
No. 4 and Pioneer No. 3 wells, respectively. The concentrations
of aluminum, boron, barium, bromine, cadmium, lithium, ammonium,
lead, rubidium and zinc commonly range from a hundred to several
hundred mg/1 in Salton Sea geothermal wells, with some anoma-
lously high values of a few thousand mg/1 for barium, rubidium
and zinc in Sinclair No. 4 well. Arsenic, cesium, copper and
fluorine typically occur in the few tens of mg/1 range.
Field Development Status—
The lack of economic and practical methods for extraction
of heat energy from the brines in the Salton Sea KGRA has pre-
vented the development of this large, high temperature resource.
The major problems are the high salinity of the brines, averag-
ing 250,000 to 300,000 ppm TDS; corrosivity of the effluent; the
significant amount (3% by weight) of noncondensible gases in the
fluids; scale deposition; and high production rates (nominally
1.8 x 10s kg/hr [4 x 105 Ib/hr]).
Numerous well production tests have been conducted since
the early 1960s (Table 2.5), and power generation test facil-
ities are presently being tested to eyaluate scaling and cor-
rosion control techniques. The first successful attempt at
generating electric power using Salton Sea geothermal brines was
a 3,000-kW steam-operated power plant constructed in 1965 at I ID
well No. 1. Minor amounts of electricity were produced but
scaling and corrosion problems caused the plant to shut down.
In 1965, mineral recovery was accomplished by solar evapo-
ration from brine ponds; calcium chloride, potassium chloride
and other salts were marketed by Imperial Thermal products until
declining mineral prices made the venture unprofitable.
64
-------
Earth Energy Company also attempted to generate electric
power and extract minerals from Salton Sea geothermal brines in
1964 and 1965. They operated out of River Ranch well No. 1 in
the Niland area, but met with limited success.
The Colorado River Basin Regional Water Quality Control
Board ruling in 1963, that prohibited geothermal well discharge
to any channel draining into the Salton Sea, caused Earth Energy
Company and Imperial Thermal Products to initiate reinjection of
spent geothermal fluids in 1965. Brine from River Ranch No. 1
was injected into Hudson Ranch well No. 1 and brine from I ID
well No. 1 was injected into IID well No. 3.
Sinclair No. 4 well, located on the Sinclair Ranch, was
used as early as 1966 in conjunction with 77 acres of evapora-
tion ponds to produce calcium chloride. This operation is still
continuing under the auspices of Lee Chemical. Sinclair wells
began in 1972 to establish a reliable brine production and
injection system, to address scaling and corrosion problems, and
to study power production from geothermal brines. The operation
is still underway; two Sinclair wells have been reconditioned,
and well flow tests have been conducted to establish the nature
of the fluids, determine well characteristics, identify hydrau-
lic-mechanical relationships and set up dynamic system tests.
San Diego Gas and Electric Company (SDG&E), in conjunction
with ERDA and LLL, has developed, is operating and is field
testing a four-stage flash-binary simulated 10 MW electric power
generation system. It is designed to accept flow from two
production wells at 182,000 kg/hr (400,000 Ib/hr) each, at 190°C
(370°F) and 11.6 kg/sq cm (165 psig). As of April 1, 1977, the
facility has accumulated over 2,580 hours of successful opera-
tion using the total flow from only one well (Magmamax No. 1)
(Jacobson, 1977). The process has allowed 1) removal of scale,
2) anticipation of operational problems and 3) limitation of
maintenance costs. Further modifications are planned to improve
performance. Major problems have been with injection pump
seals, scale deposition and injection well plugging.
New Albion Resources Company and Imperial Magma are cur-
rently operating two production wells and two injection wells to
provide fluid supply and fluid disposal for the SDG&E/ERDA
experimental facility at Niland. Magmamax No. 1 has been a pro-
lific producer, with well head temperatures above 200°C (392°F)
and volumes greater than 3,800 1pm (1,000 gpm). Woolsey No. 1
well had not initially produced enough fluid and was deepened to
1,064 m (3,490 ft). The flow rate has not yet been increased,
but wellhead temperature and pressure have been greatly im-
proved, to 93°C (200°F) and 28 kg/sq cm (400 psig), respec-
tively. Magmamax No. 3 well accepts cool brine from the plant
and Magmamax No. 2 well is connected as a backup well. In-
creasing wellhead injection pressures and buildup of scale in
65
-------
the injection pipeline after eight months of operation neces-
sitated a workover of Magmamax No. 3. This resulted in the well
accepting 1,500 1pm (400 gpm) at 14.8 kg/sq cm (210 psi) and
6,060 1pm (1,600 gpm) at 22.9 kg/sq km (325 psi) (Nugent and
Vick, 1977). Union Oil Company had conducted a one year injec-
tion test at Niland during 1964 and 1965. The injection rate
was 2,270 1pm (600 gpm) and there was no loss of injectivity or
reservoir response during the entire test (Chasteen, 1975).
i
2.2.3 Heber KGRA
The Heber KGRA is located in the south-central part of the
Imperial Valley (Fig. 2.2). Boreholes show that dominantly
Quaternary deltaic sands and shales derived from Colorado River
sources (Muffler and Doe, 1968) persist to a depth of at least
2,500 m (8,200 ft) (Randall, 1971), although a 25 m (82 ft)
thick gabbroic sill was encountered in one well. The greatest
basement depth thus far encountered in the valley is at Heber
and is estimated from seismic surveys (Biehler, et al. 1964) to
be 7 km (4.3 mi).
Based on deep and shallow borehole data, Rex, et al. (1972)
estimate that the Heber heat flow anomaly occupies about 35 sq
km (13.5 sq mi). Numerous geophysical surveys were conducted in
the Heber area (Kovach, et al. 1962; Meidav and Furgerson,
1972), and it was found that the area has electrical resistivity
and gravity anomalies associated with high heat flow. Meidav
and Furgerson (1972) showed that the Heber field has a low
resistivity anomaly, although it was noted that the observed
resistivity contrast is small because the background resistivi-
ties are also very low (less than 2 ohm-m). These low back-
ground resistivities were probably caused by high water salini-
ties resulting from incomplete mixing and sluggish transport of
regional groundwater. The incomplete groundwater mixing was
explained by Meidav and Furgerson (1972), who showed that the
Imperial Fault in the Heber area serves as an aquitard which
separates the brackish central valley waters from fresher waters
to the east. Biehler (1971) discovered a 2 milligal (mgal)
positive gravity anomaly over Heber of approximately the same
shape and size as the region of high heat flow. This low grav-
ity anomaly contrasts with the much larger positives found over
the Salton Sea, Brawley and East Mesa geothermal fields.
Biehler (1971) postulated that this lower gravity pointed to the
possible existence of a pure steam phase at the Heber field, but
to date, drilling has not confirmed his assertion. An analysis
of a detailed gravity survey of the Heber area by the Chevron
Oil Company indicates that the relative gravity high is sur-
rounded by a moderate gravity low. This may indicate a selec-
tive leaching and deposition process whereby minerals are dis-
solved from the rocks on the periphery and deposited in t&e
central portion of the field.
66
-------
Chemical Composition of Fluids—
Major constituents of the geothermal fluids at Heber are
sodium chloride, with notable calcium and sometimes bicarbonate.
The TDS are generally between 10,000 and 17,000 mg/1, which is
less than 10% of the TDS of the Salton Sea geothermal fluids.
Analyses of Heber geothermal fluids are given in Table 2.15.
Trace element analyses show up to 8 mg/1 boron, up to 6.6 mg/1
lithium, up to 168 ppm silica and up to 42 ppm strontium. The
chemical constituents of the geothermal fluid are discussed in
more detail in the water pollution section of this report.
Resource Base and Production Potential—
The resource base of the Heber geothermal reservoir, in-
cluding the total stored heat contained in the rock and water,
is estimated by Renner, et al. (1975) as 46.0 x 1018 J (43.6 x
1015 BTU) (Table 2.1). Estimates of the recoverable resource
range from 3.5 x 1018 J (3.3 x 1015 BTU) (Towse, 1975) to
Biehler and Lee's (1977) range of 8.3 to 25.0 x 1018 J (7.9 to
23.7 x 1015 BTU). The lower estimates are probably closer to
the value of the actual recoverable resource.
The Heber area has been considered a potential heat anomaly
since 1945 when the temperature log of the Amerada Timkin No. 1
oil test well showed a higher than average temperature gradient.
Chevron drilled a shallow test hole in 1963 and confirmed the
heat anomaly. Three additional wells were drilled in 1972. A
program to determine production and injection capabilities of
the Heber reservoir was initiated in 1973. Chevron's Nowlin
Partnership No. 1 well and Magma's Holtz No. 1 well were pro-
duced and recovered fluids were injected into Magma's Holtz No.
1 well. Three more wells were drilled in 1974 for further
tests. There are at present ten deep wells besides the Amerada
Timkin No. 1 in the Heber field.
Direct heat-exchange operations may be feasible with Heber
fluids so SDG&E is collecting information on heat exchanger per-
formance from a recently installed test module at the Chevron
Nowlin Partnership well No. 1. Presently information on pro-
duction rates and reservoir estimates is proprietary. No power
production facilities have been completed. A 50 MWe binary
demonstration geothermal power plant is being considered for in-
stallation at the Heber site to be funded by ERDA, EPRI and
several other organizations. A series of reports on this demon-
stration power plant project has been published by EPRI,
(Geonomics [1976a] and Geonomics [1976b]).
2.2.4 Brawley KGRA
Detailed data on the Brawley KGRA are not presently avail-
able. A discussion from Geonomics (in press) is outlined below
with additional reservoir and development data.
67
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The Brawley KGRA, also known as the North Brawley geo-
thermal area, is located southeast of the Salton Sea, near the
town of Brawley (Fig. 2.2). Meidav (1972) identified the North
Brawley thermal anomaly by the very low resistivity of 0.35-
0.76 ohm-m at depths greater than 600 ft. This is a four-fold
decrease in resistivity compared to surrounding rocks. An
eight-fold increase in temperature gradient would be required to
produce such a decrease in resistivity if salinity and strati-
graphic factors are ignored. There is evidence of at least one
and perhaps two hydrologic discontinuities from the Sand Hills
to a few kilometers northwest of the town of Brawley which would
signify faults and would account for salinity and/or strati-
graphic changes along the line. These discontinuities are the
Brawley and Calipatria Faults. The Brawley fault first appeared
in the literature on maps by Rex (1970). Later, gravity surveys
confirmed the presence of large vertical displacements beneath
the valley alluvium.
The sedimentary section from 0-328 m (0-1,100 ft) in the
Brawley area contains a lower percent volume of sand bodies than
some other fields in the Imperial Valley. In Brawley, the
Amerada Veysey No. 1 well has 61% sand. The deposits of usable
and recoverable water in storage have been estimated to be about
3,900 m (13,000 ft) thick in Brawley (Dutcher, et al. 1972) and
the depth to basement in this area is estimated to be about
6,100 m (20,000 ft) (Rex, 1970).
The Brawley anomaly exhibits no natural geothermal fluid
discharge at the surface. Chemical analyses of geothermal
fluids have not been published for the Brawley geothermal field
but it is believed to have an average TDS content of 85,000 to
100,000 ppm. The reported fluid temperature of 200°C (390°F) is
based on an old oil test (Renner, et al. 1975). Renner, et al.
(1975) estimates the resource base, the total stored heat in the
rock and fluid, as 12.6 x 1018 J (1.2 x 1016 BTU) (Table 2.1)
where the size of the resource is based on a temperature gradi-
ent survey. Estimates of heat in the recoverable fluid range
from 1.0 x 1018 (Towse, 1975) to 3.2 x 1018 J (9.5 x 1014 to
3 x 101S BTU) (Nathenson and Muffler, 1975), with Biehler and
Lee's (1977) "excess mass" estimate ranging from 13.2 to 39.6
x 1018 J (1.25 to 3.76 x 1016 BTU).
There has been interest in the private sector in developing
this area and Union Oil Company presently plans to drill four
exploratory wells (Palmer, et al. 1975).
2.2.5 Dunes and Glamis KGRAS
The Dunes and Glamis KGRAs are not yet considered to be
viable geothermal resources in Imperial Valley. The present
resource estimates are quite low, especially in comparison with
the other thermal anomalies in Imperial Valley (Table 2.1).
68
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They are on the order of 2 x 1018 J (1.9 x 1015 BTU) total
resource base (Renner, et al. 1975), and less than 1 x 1018 J
(0.9 x 1015 BTU) recoverable heat for each area (Towse, 1975).
Therefore, only cursory coverage will be given to these areas
and the following discussion, largely extracted from Geonomics
(in press), outlines their setting, development and history.
Dunes Geothermal Area—
The Dunes geothermal area is located in southeastern Imper-
ial Valley, east of Holtville and adjacent to the Sand Hills
(Fig. 2.2). Numerous shallow wells have been drilled in the
area and many have geophysical logs. Randall (1971) described
upper portions of the Cenozoic section in terms of percent
volume of sand bodies per 150 m (490 ft), and observed that
major parts of the section contain as much as 90% unconsoli-
dated, highly porous sand bodies, with minor amounts of shale.
Elders and Bird (1974) noted the importance of these shale
layers in confining the hydrothermal system, preventing surface
expression. They observed that impermeable shale layers served
as sites for silica deposition by the upward circulating hydro-
thermal waters. This continuing deposition eventually formed a
mushroom-shaped cap rock that served to seal the hydrothermal
system.
•
Coplen (1972) suggests that local waters are almost totally
derived from the Colorado River. These waters are notably low
in salts and therefore are vastly different from the waters in
northern parts of the valley (Rex, et al. 1972).
Much of the known regional structure of the Dunes area has
been deduced from geophysical studies. Kovach, et al. (1962)
and Biehler, et al. (1964), on the basis of seismic refraction
data, observed that basement depth increases from 700 m (2,300
ft) to 3,500 m (11,500 ft) as the Sand Hills are crossed from
east to west. Numerous workers have postulated that a south-
eastern extension of the San Andreas Fault System traverses the
axis of the Sand Hills (Biehler, et al. 1964; Garfunkel, 1972).
Combs (1972) and Elders and Bird (1974) have speculated that
this and related faults might be responsible in part for the
formation of the Dunes hydrothermal system.
On the basis of shallow thermal gradient boreholes, the
Dunes anomaly was discovered by Combs (1971). Combs (1972)
suggested that the anomaly is an oval-shaped feature 2.5 sq km
(1 sq mi) in area, with the hottest regions near the center; he
also suggested the importance of the self-sealing mechanism. In
the hottest holes, UCR No. 115 and DWR Dunes No. 1 (estimated
heat flow 25 HFU; [Combs, 1972]), a silica-cemented sandstone
was encountered between 60 and 115 m (197 and 377 ft) depth.
Biehler (1971) completed a detailed gravity survey over the
Dunes anomaly and obtained a 2-mgal positive closure that cor-
responds in shape with the thermal anomaly, although the gravity
69
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closure is centered almost 2 km (1.2 mi) to the northeast of the
thermal anomaly. Biehler (1971) attributed this closure to the
existence of the higher density silicified sand body as en-
countered at UCR No. 115. Black, et al. (1973) measured two
orthogonal 3 km (1.9 mi) long resistivity profiles over the
center of the Dunes anomaly, indicating that resistivity drops
by 50% over the geothermal anomaly, at least to a depth of 200 m
(660 ft). Van De Verg (1975, pers. comm.) did seismic refrac-
tion profiling over the Dunes and noted that basement depths do
not change greatly at or near the Dunes anomaly. In summary,
the Dunes anomaly can be characterized as a 2.5 sq km (1 sq mi)
region of high heat flow, local positive gravity, and depressed
electrical resistivity. However, the reversal of the tempera-
ture gradient at about 100°C (212°F) and 300 m (1,000 ft) depth
(Coplen, et al. 1973) reduces hopes of developing this area at
this time.
Glamis Geothermal Area—
The Glamis KGRA is about 32 km (20 mi) east of the town of
Brawley, astride the Sand Hills and the trace of the San Andreas
Fault (Fig. 2.2). Interest in this area was precipitated by a
temperature gradient reported to be greater than 22°C/100 m
(12°F/100 ft) (Rex, 1970). However, this gradient was based on
one shallow drill and further exploration in this area has been
disappointing. The initial drill hole probably intersected an
isolated hot spring. Basement is shallow here and a gravity
anomaly, often typical of geothermal reservoirs, is not present.
2.3 WATER POLLUTION POTENTIAL
Chemical characteristics of surface and ground water, as
well as quantity and types of water use, are important inputs to
evaluating potential environmental impact on the groundwater
system. Study of waters allows comparison of relative chemical
compositions, consideration of the relative merits of different
water applications and comparison between the effects of current
and projected water uses. To facilitate this comparison, tables
have been compiled for Imperial Valley describing the wells,
well use, water use, and well completion data (Tables 2.8, 2.11,
2.14 and 2.17). Separate tables giving chemical analyses for
geothermal and nongeothermal waters in each KGRA have also been
compiled from available data (Tables 2.9, 2.10, 2.12, 2.13,
2.15, 2.16, 2.18 and 2.19).
For this report, groundwater in Imperial Valley was
considered geothermal if it had a temperature 50°C (122°F) or
higher. This rather high temperature was chosen based on ground-
water use and the fact that summer ambient air temperatures
reach this level. That is, some waters with temperatures from
20°C to 50°C (70°F to 122°F) were used for agricultural purposes
or livestock watering, and these utilized waters must be con-
70
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sidered in the baseline for comparison with potential effects of
pollution by geothermally used production fluids. USPHS water
standards (USPHS, 1962) were used in the discussions since they
essentially represent the combination of the newly recommended
National Interim Primary and Secondary Drinking Water Regula-
tions [EPA, 1976, EPA, 1977a] Table 1.5).
It is important to note that detailed field work and fur-
ther checks on well use and well properties would be necessary
to accurately establish water use in each geothermal area. The
data from the tables compiled for this report is probably incom-
plete or outdated. Many wells are listed with "other" uses or
"unused." A well listed as an industrial well may, in fact,
currently be a geothermal well; therefore, the water well survey
should be updated and verified.
Comparisons of geothermal and nongeothermal uses and chem-
ical characteristics, and comparisons of fluids with USPHS water
standards, will be discussed below for each KGRA; an estimate of
the amounts of pollutants released from the maximum potential
power development will also be made. It is imperative to estab-
lish these baseline data and comparisons as early as possible.
In fact, ranchers near the East Mesa geothermal area have
charged that even pre-production geothermal test drilling has
already had adverse effects on their water wells (Lofgren,
1974).
Potential hydrologic environmental impact of geothermal
development in Imperial Valley can be divided into two cate-
gories: first, accidental escape of degrading geothermal ef-
fluents into the fresh groundwater system; second, accidental
escape of degrading geothermal effluents onto agricultural land
or into surface drainageways. The result of escaping geothermal
fluid would be the increase, from natural conditions, in-salin-
ity and trace element concentration. This effect woul& vary
depending on the degree of dilution involved in each potential
mechanism and pathway, and on the concentrations of detrimental
or toxic chemicals. It should be understood that chemical
analyses for many trace elements and for many of the geothermal
fluids are not available, and those that are available seem to
be somewhat fortuitous in occurrence. Therefore, the discussion
of trace elements is based on a very limited, and perhaps un-
representative sample of analyses. However, they provide the
most current and complete available data on the fluids in these
areas. We must bear these limitations in mind and understand
that as more data are gathered the picture may change.
Geothermal fluid escaping into the groundwater system in
Imperial Valley may or may not degrade the naturally occurring
groundwater depending on the composition of the geothermal
fluid and the composition of the groundwater . The effects of
the escape of geothermal fluid into the groundwater system
71
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would depend on the direction, rate and path of ground water
flow. A general idea of these properties is known for Imperial
Valley, but there are also many individual zones where the
direction and rate of motion departs from the general trend.
This could occur at fault zones, buried stream channels, other
permeable conduits or impermeable boundaries. This detailed
structure is not presently known for any appreciable area in
Imperial Valley, so discussion of the flow directions, rate and
pollutant pathways must be limited to general trends and to
potential pollution mechanisms and pathways, discussed in sec-
tion 1.3.2. The potential pathways and mechanisms would be
determined more specifically by detailed, site-specific geologic
and hydrologic studies and specifications of detailed production
and disposal methods at a particular site.
Despite the fact that the salinity of geothermal fluids is
fairly high, the salinity of much of the naturally occurring
groundwater is also high, so each area is discussed individ-
ually in the following sections. There are geothermal fluids in
Imperial Valley with less than 2,000 mg/1 TDS and there is
naturally occurring groundwater with 10,000 to 15,000 mg/1 TDS
in the central part of the valley. Trace element content gen-
erally increases as salinity increases, so it would be expected
that higher salinity fluids would also have higher trace element
contents that may degrade natural ground or surface water.
Escape of geothermal fluid at the ground surface in a
cultivated part of the valley would directly affect the current
agricultural use of the land inundated and the salt balance of
the irrigated tract. The degree of these effects would depend
on the amount of escaping fluid. All other factors being equal,
the greater the amount of fluid, the larger the area inundated.
In the agricultural area the majority of the geothermal fluid
would percolate down to the tile drain system and then be car-
ried via canals and the New or Alamo Rivers into the Salton Sea.
Quite a large amount of highly concentrated geothermal fluid
would have to escape and drain into the Salton Sea to noticeably
affect its salinity. Increase of Salton Sea salinity would only
be a consideration if geothermal waters would be continually
disposed of into the sea.
During the period 1961-1963, the average annual inflow to
the Salton Sea from the Alamo and New Rivers and 30 other chan-
nels was 156,700 ha-m (1,300,000 acre-ft) or an average daily
inflow of about 430 ha-m/day (3,500 acre-ft/day). Taking an
extreme case and assuming an uncontrolled blowout of 75.8 kg/sec
(167 Ib/sec), a production well would produce 6,500,000 kg/day
(14,400,000 Ib/day) of geothermal fluid. Assuming the fluid has
the density of seawater, 1,015 kg/cu m (63.86 Ib/cu ft) gives a
conservative estimate of 6,340 cu m/day (222,000 cu ft/day), or
0.63 ha-m/day (5.1 acre-ft/day) of escaping fluid. This amounts
to somewhat more than 0.01% of the average daily inflow to the
72
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Salton Sea. If the fluid had a concentration 200 times the
average inflow concentration, this fluid would contain the
amount of TDS equivalent to 20% of the average daily inflow.
This type of inflow would have to continue uncontained for some
period of time, probably more than a week or so, to have an
appreciable long-term effect on the salinity of the Salton Sea,
although, before adequate dilution, short-term effects may be
significant in a localized area.
The effect of disturbing the salt balance of the inundated
tract would be much more localized and much more pronounced. It
would probably require re-flooding and percolating freshwater
through the heavily salt-laden soil.
No organic pollutants are anticipated to be involved in
disposal of geothermal effluents. Geothermal fluids are con-
sidered to be organically very clean due to the fact that the
high temperatures and salinities provide an inhospitable envi-
ronment for organisms. Geothermal development may produce some
biological effects due to potential thermal, noise, air and
water pollution. However, biological effects are beyond the
scope of this report and will not be discussed.
Quantity of Produced Pollutants—
Estimates of the amount of chemical elements that would be
produced by Imperial Valley geothermal fluids have been calcu-
lated in order to aid in assessing the potential environmental
impact (Tables 2.6 and 2.7). These calculations for the East
Mesa, Salton Sea, Heber and Brawley geothermal fields are based
on the best available information on reservoir temperatures, re-
source potential and chemical constituents. However, these are
currently only order of magnitude estimates, and will certainly
change as further exploration, development and exploitation
generates additional, more detailed data on the properties of
the respective geothermal reservoirs. These limitations should
be kept in mind when using the estimates.
The basis of the calculation is an estimation of the daily
fluid production rate multiplied by the chemical constituent
concentration. The production rate was estimated fiom a cor-
relation chart of fluid temperature vs. MWe per 1,000 gpm flow
rate (Geonomics, 1976b) and from the electric power output
potential for each Imperial Valley gedfthermal reservoir. The
reservoir temperature was taken from Renner, et al. (1975) and
the corresponding MWe per 3,800 1pm (Mwe per 1,000 gpm) was read
off the flash process curve of the Geonomics (1976b) correlation
graph. The Nathenson and Muffler (1975) MWe - century estimate
for electric power output potential for each reservoir was
divided by 3.33 to arrive at a 30 year total production capacity
estimate. Multiplying the potential production rate in MWe by
the flow rate required per MWe for each reservoir gives the
fluid production at maximum expected reservoir output. This
number must then be converted from volume to mass to account for
73
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TABLE 2.6 ESTIMATED DAILY FLUID PRODUCTION FOR IMPERIAL VALLEY
GEOTHERMAL DEVELOPMENTS
Maximum Total
Estimated Estimated Brine Brine
Average Electrical Production Density Mass6
KGRA Temperature
(°C)
East Mesa 180
Salton Sea 340
Heber 190
Brawley 200
TOTAL
Capacity MWe per. Flow Rate TDS pb 5
(MWe for 30 yr) 1,000 gpm (103 gpm (ppm) (lb/ft3)
490
2,800
970
330
4f590
1.4 350
10 " 280
1.8 540
2.3 140
1,310
2,000 to
30,000 53.7
300,000 50.3
15,000 53.3
100,000 55.9
(109 kg
day)
1.64
1.26
2.52
.68
6.10
FOOTNOTES:
From Renner , et al. (IS75)
2 From Nathenson and Muffler (1975) modified from MWe-cent to MWe for 30 years
3 From Geonomics (1976b), assuming flash process
** Subir Sanyal, personal communication, 1977
5 p. = Pstp/Bw assuming one phase flow where pstp is a function of TDS @ 14.7
psia and 60°F, Bw is a function of temperature and pressure,but pressure
term is negligible at most wellhead pressures; therefore it has been
omitted.
6 Total Brine Mass (kg/day) = p,(lb/ftj) x Flow Rate(gpm) x 0.1337 ft3/gal x
0.4536 kg/lb x 1,440 mih/day
7 Average value from 53.3 lb/ft3 for 2,000 mg/1 TDS and 54.1 Ib/ft3 for 30,000
mg/1 TDS
-------
TABLE 2.7 ESTIMATED PROJECTED TOTAL DAILY CHEMICAL
CONSTITUENT PRODUCTION FROM POTENTIAL GEOTHERMAL
DEVELOPMENT IN IMPERIAL VALLEY
KGRA
Estimated
Brine
Production1
TDS2
Solids Produced for Constituent
Total Concentrations of:
Solids 0.01 0.1 1.0 10.0 100 1,000 10,000
Produced ppm ppm ppm ppm ppm ppm ppm
East Mesa
Salton Sea
Heber
Brawley
1.64
1.26
2.52
0.68
2,000 to
30,000
300,000
*
15,000
100,000
3.28 to
49.2
378
37. 8
68. 0
0.0164
0.0126
0.0252
0 .0068
0.164
0.126
0.252
0.068
1.64
1.26
2.52
0.68
16.4
12.6
25.2
6.8
164
126
252
68
1,640
1,260
2,520
680
16,400
12,600
25,200
6,800
TOTAL
6.10
487 to
533
FOOTNOTES:
'From Table 2.10
2Estimated average
-------
the difference in the density of the fluid at elevated geo-
thermal temperatures and under the standard conditions of the
chemical analyses. This conversion then allows computation of
the total brine mass produced in 106 kg/day (22 x 106 Ib/day)
for each geothermal field at anticipated maximum production
capacity (Table 2.6). Multiplying the total brine mass by the
TDS (in appropriate units) gives an estimate of the TDS produced
each day at each geothermal field (Table 2.7). Solids to be
produced daily at each geothermal field for chemical constit-
uents in concentrations from 0.01 ppm to 10,000 ppm are also
given in Table 2.7- The table was constructed in this general-
ized manner to allow estimation by the reader of the quantity of
any constituent (perhaps from analyses that were not available
to us).
The total brine mass that would be produced from full-scale
electric power production in Imperial Valley would be 6.10
billion kg/day (13.42 billion Ib/day). This fluid would contain
approximately 487 to 533 million kg/day (1,071 to 1,173 million
Ib/day) of TDS. Total fluid production for the projected 30
year power production would be about 6.7 x 1013 kg (14.7 x 1013
Ib) and TDS in this fluid would be approximately 5.3 to 5.8 x
1012 kg (1.17 to 1.28 x 1013 Ib). Estimates for individual
fields are discussed in the respective subsections on each
field.
One can obtain a very rough estimate of the total volume of
the solids that would result from the full-scale development of
geothermal power in Imperial Valley if all of the solids were
extracted, as would occur, for example, if spent fluids were
evaporated in holding ponds. Assuming a total solid mass of 5.3
to 5.8 x 1012 kg (1.17 to 1.28 x 101* Ib), to be generated over
a 30 year period as discussed before, and a solid density of
2.165 g/cm3 (density of sodium chloride crystals), the maximum
volume of solids to be generated is 2.4 to 2.6 x 109 cu m (85 to
92 x 109 cu ft).
Data Sources—
The water use and water quality data used in this report
were taken from the following sources:
"Selected Data on Water Wells, Geothermal Wells, and Oil
Tests in Imperial Valley, California"; by W. F. Hardt
and J. J. French (1976); a compilation of groundwater
quality data for 436 wells; this source is a compila-
tion of analyses that have previously been unpublished
or have appeared in many separate publications.
"Chemistry of Thermal Water in Selected Geothermal Areas of
California"; by M. J., Reed (1975); a report that
includes chemical analysis of groundwater from 48
76
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wells, mostly from the artesian aquifer in eastern
Imperial Valley.
"Lawrence Berkeley Laboratory Brine Data File"; by S.
Cosner and J. Apps (1977); a compilation including 27
chemical analyses of geothermal well waters in
Imperial Valley.
"Geotechnical Environmental Aspects of Geothermal Power
Generation at Heber, Imperial Valley, California"; by
Geonomics (1976a); includes analyses of a number of
geothermal wells in the Heber and Cerro Prieto geo-
thermal areas.
"Preliminary Findings of an Investigation of the Dunes
Thermal Anomaly, Imperial Valley, California"; by
T. B. Coplen, et al. (1973); includes analyses of DWR
Dunes well No. 1.
A complete field canvass was conducted by the USGS, Water
Resources Division, Yuma in the 1960s and the results are in-
cluded in Hardt and French (1976); the data contained is ex-
pected to give a fair representation of well use in Imperial
Valley. Unfortunately, very little trace element data were
available for the nongeothermal wells so most of the comparisons
must be limited to major constituents.
2.3.1 Summary of Baseline Water Characteristics
Baseline chemical characteristics of groundwatear in three
depth intervals in Imperial Valley are presented in "Baseline
Geotechnical Data for Four Geothermal Areas in the United
States" (Geonomics, in press). The report includes discussion
of the ground water regime in the context of aquifer depth
zones, or hydrologic depth units, in an attempt to define ground
water flow within proposed hydrologic units; thus all chemical
data that did not specify sample depth intervals were omitted
from the survey. In this report, however, since water pollution
is defined relative to existing or natural chemical composition
and use, all water chemistry data have been included for com-
parison. For all geothermal and nongeothermal wells within 1.6
km (1 mi) of each Imperial Valley KGRA, tables have been pre-
pared which describe 1) well location, completion data, water
and well use, water level and yield, and 2) chemical composi-
tion. These tables allow comparison of water chemistry between
geothermal and nongeothermal wells and will aid in defining
chemical differences, potential pollution and the current uses
of nongeothermal wells in the areas that are likely to be af-
fected by geothermal development. Geonomics (in press) should
be referred to for a detailed description of groundwater char-
acteristics and distribution, hydrologic regimen and surface
water characteristics.
77
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A wide variation exists in the chemical character of geo-
thermal fluids, groundwater and surface water in each of the
Imperial Valley geothermal areas. The TDS content ranges from
over 1,000 mg/1 in East Mesa and the Dunes KGRAs to more than
385,000 mg/1 (Cosner and Apps, 1977) in the Salton Sea KGRA.
The Dunes sample is characterized by an appreciable proportion
of calcium, sodium, sulfate and bicarbonate, similar to Colorado
River water, while the Salton Sea geothermal fluid is character-
ized by high sodium and chloride with significant calcium.
Three additional characteristic types of ground water both
geothermal and nongeothermal, have been defined in Imperial
Valley by Geonomics (in press). They are a sodium bicarbonate
water, a sodium chloride water, and a sodium chloride with high
sulfate and/or magnesium water. The TDS content of these waters
varies, depending on areal location and depth, from a few hun-
dred mg/1 to over 50,000 mg/1. Surface water quality varies
from the purest waters running off the Peninsular Range to the
west, to imported Colorado River water, to agricultural return
water, to Salton Sea brine. Peninsular Range runoff commonly
contains only a few hundred mg/1 TDS. The TDS of Colorado River
irrigation inflow has varied from 637 to 912 mg/1 in the 25
years from 1941 to 1965 (Irelan, 1971) and is currently about
900 mg/1. The salinity of agricultural return waters flowing
into the Salton Sea varies according to the proportions of canal
water and drainage water. The range of TDS for the Alamo and
New Rivers, flowing into the Salton Sea, is commonly about 2,500
to 7,000 mg/1. In 1967, the average TDS for Salton Sea water
was about 36,000 mg/1, which is slightly more saline than sea-
water .
Because of these wide aerial variations in water character
and quality each of the geothermal fields is discussed indi-
vidually in an attempt to characterize the geothermal fluids and
groundwater for each locality. However, a major factor to
remember is that even in an individual locality the TDS content
and amount of individual constituents can vary considerably.
This is often exemplified in different samples from the same
geothermal well (for example, see two analyses of well No. 811
[Magmamax No. 1] in Table 2.13).
2.3.2 East Mesa KGRA
Well and water use, and well completion data for all wells
identified in and within 1.6 km (1 mi) of the East Mesa KGRA are
given in Table 2.8. The locations of these wells are shown in
Fig. 2.9. Of the 73 wells identified in this area, 12 have been
used for domestic applications, four for industrial purposes, 40
are not used and there are 17 other or unknown applications.
The pattern of well use shown in Fig. 2.9, with different sym-
bols for domestic/industrial and geothermal wells, shows essen-
tially all the domestic/industrial wells on the western portion
78
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TABLE 2.8
DESCRIPTION OF WELLS IN AND WITHIN 1.6
(modified from Hardt and French, 1976)
KM (1 MI) OF EAST MESA KGRA*
vo
MAP
NUM-
BER
205
208
209
210
215
216
217
219
220
221
223
224
225
226
311
312
313
314
317
318
319
320
321
322
323
325
327
333
334
335
336
337
342
343
STATE NUMBER
15S/16E-22F01
15S/16E-24G01
15S/16E-25G01
15S/16E-27N01
15S/16E-35Q01
15S/16E-36E01
15S/17E-20N01
15S/17E-29N01
15S/17E-30G01
15S/17E-31D01
15S/17E-31N01
15S/17E-32R01
15S/17E-33D01
15S/17E-34N01
16S/16E-01B01
16S/16E-01C01
16S/16E-01M01
16S/16E-03C01
16S/16E-11K01
16S/16E-12A01
16S/16E-12N01
16S/16E-12Q01
16S/16E-12R01
16S/16E-13B01
16S/16E-14A01
16S/16E-15B02
16S/16E-24A01
16S/17E-05D01
16S/17E-05D02
16S/17E-05E01
16S/17E-06B01
16S/17E-06J01
16S/17E-08F01
16S/17E-09K01
OWNER OR NAME
D. STARR
USGS
USBR 201
C. MARTINEZ
MAG EN SHARP 1
B. NUSSBAUM
USBR 126
USBR 203
USBR 202
U.C.R. #124
USBR 204
USBR 210
U.C.R. 1125
USBR 211
USBR 225
USGS-USBR
I.I.D.
DATE CITY STORE
ALLENGRANZA-CLK
USBR 206
SCHNEIDER
USGS
USBR 223
LINDEN GRAVEL
KEITHMETZ 11
OLD ALAMO STORE
USBR 222
USPR 122
USGS-USBR
USBR 123
USBR 205
USBR
USBR 212
USBR 128
0
R
Y I
E L
A L
R E
D
1961
1973
1972
1961
1971
1973
1973
1973
1973
1971
1973
1974
1975
1947
1972
1973
1961
1973
1950
1974
1971
1975
1971
1973
1973
1971
0
W S
N H
E I
R P
F
F
F
P
N
P
F
F
F
F
F
F
F
F
F
F
W
N
P
F
P
F
F
N
N
P
F
F
F
F
F
F
F
F
W
A U
T S
E E
R
H
U
U
H
H
0
U
U
z
U
U
z
U
U
z
z
H
H
U
U
U
N
H
H
U
U
Z
U
U
z
U
U
W U
E S
L E
L
W
0
H
W
Z
U
H
H
H
H
H
H
T
H
H
0
H
W
H
W
0
H
W
W
W
H
H
0
H
H
T
H
H
D
I
A
M
(IN)
2
1
6
2
6
1
6
6
6
6
1
6
4
4
16
6
1
6
2
1
4
1
6
2
D
E D
E E
P P
E T
S H
T
(FT)
650
142
503
6,070
630
562
463
503
562
403
303
511
323
1,105
1,100
132
596
1,166
503
825
142
983
810
800
1,117
343
562
742
562
303
150
313
562
DC D
E A E U
PS P E
T E T L
H D HI
(FT) (FT)
113 115
360 430
1,100
8 132
1,008 1,166
103 105
343
742
303
ALTI-
TUDE
OF
LSD
(FT)
3
45
42
-3
15
40
49
50
40
30
34
75
71
80
22
5
17
20
20
30
30
30
17
12
35
65
52
48
42
36
47
57
W L
A E
T V
E E
R L
(FT)
F
29
18
F
F
31
26
11
51
51
F
4
F
F
2
13
9
9
F
29
DATE
WELL
MEA-
SURED
7-61
61
11-73
7-61
7-61
10-73
11-73
11-73
12-73
12-73
3-74
9-61
7-61
4-72
9-73
10-61
12-73
12-73
9-61
10-73
C A
H N
YIELD E A
OF ML
WELL I Y
C S
A E
L S
(GPM)
3 x
X
X
X
X
X
X
X
X
X
X
*see Appendix II for explanation
(continued)
-------
TABLE 2.8* (continued)
00
o
HAP
NUM-
BER
344
345
346
347
348
349
350
351
352
356
357
358
359
362
363
364
365
366
416
417
418
419
420
421
422
423
424
425
739
741
742
746
747
801
802
STATE NUMBER
16S/17E-12R01
16S/17En4D01
16S/17E-16Q01
16S/17E-16Q02
16S/17E-17B01
16S/17E-20N01
16S/17E-21A01
16S/17E-23R01
16S/17E-27D01
16S/18E-15N01
16S/18E-17R01
16S/18E-18R01
16S/18E-20R01
16S/18E-28L01
16S/18E-28R01
16S/18E-29J01
16S/18E-32G01
16S/18E-32R01
17S/18E-01801
17S/18E-02B01
17S/18E-03801
17S/18E-03B02
17S/18E-04A01
17S/18E-04B01
17S/18E-05B01
17S/18E-05R01
17S/18E-06A01
17S/18E-06B01
15S/16E-15P01
15S/16E-22L01
15S/16E-23F01
16S/16E-14A02
16S/16E-15B01
16S/17E-05A01
16S/17E-06J02
OWNER OR NAME
USBR 214
USBR 213
H. SCHAFER
H. SCHAFER BARB 1
USBR 127
USBR 216
USBR 207
US6S
USBR 217
USBR 221
USGS
USBR 215
USBR 208
USBR 114
USBR 218
USGS
USBR 209
USGS LCRP 18
IID
IID
IID
USBR 219
IID
IID
IID
USBR 220
IID
IID
R. GAREHAL
D. STARR
L. FOSTER
HATTON LABOR CAMP
ALAMO SCHOOL
USBR MESA 5-1
USBR MESA 6-1
D
R
Y I
E L
A L
R E
D
1974
1974
1960
1958
1971
1974
1973
1964
1974
1974
1964
1974
1974
1971
1974
1961
1974
1964
1974
1952
1974
1953
1943
1960
1955
1974
1972
0
H S
N H
E I
R P
F
F
P
N
F
F
F
F
F
F
F
F
F
F
F
F
F
F
H
W
W
F
W
W
W
F
W
W
P
P
P
P
N
F
F
W
A U
T S
E E
R
U
U
N
N
Z
U
U
U
U
U
U-
u
U
Z
U
U
U
U
U
U
U
U
N
U
U
U
U
U
H
H
H
H
G
G
W U
E S
L E
L
H
H
U
P
T
H
H
0
H
H
0
H
H
H
H
0
H
0
0
0
0
H
W
0
0
H
0
0
W
W
W
W
H
H
D
I
A
M
"
(IN)
6
6
6
10
10
1
6
1
6
1
1
6
1
6
1
1
1
10
1
12
1
3
2
2
4
9
D
E D
E E
P P
E T
S H
T
(FT)
330
410
217
8,017
1,406
432
498
177
423
503
177
330
510
1,463
311
192
525
815
528
195
332
800
750
561
1,100
6,016
8,030
D C
E A
P S
T E
H D
(FT)
45
155
155
155
140
179
452
1,128
864
7,280
D
E W
P E
T L
H L
(FT)
75
157
157
157
630
195
542
1,128
877
8,015
ALTI-
TUDE
OF
LSD
(FT)
105
93
83
84
50
45
85
90
85
120
116
112
120
120
122
120
117
118
126
124
119
119
117
115
105
105
101
94
0
2
15
17
12
70
36
H L
A E
T V
E E
R L
(FT)
33
42
48
42
34
31
32
31
31
34
28
F
F
F
F
F
DATE
HELL
MEA-
SURED
2-74
2-74
4-60
10-73
2-64
1-74
2-64
2-74
1-71
12-61
6-64
7-61
7-61
9-61
7-61
12-72
C A
H H
YIELD E A
OF M L
HELL I Y
C S
A E
L S
(GPM)
X
x
x
x
X
x
X
X
X
X
X
X
X
X
3 x
26 x
X
4 x
X
X
*see Appendix II for explanation
(continued)
-------
TABLE 2.8* (continued)
00
MAP
NUM-
BER
803
804
805
910
911
912
913
914
STATE NUMBER
16S/17E-06L01
16S/17E-08D01
15S/17E-31D02
15S/17E-30P01
15S/17E-29N02
15S/17E-28N01
16S/17E-07L01
16S/17E-07P01
OWNER OR NAME
USBR MESA 6-2
USSR MESA 8-1
USBR MESA 31-1
REPUBLIC 38-30
REPUBLIC 16-29
REPUBLIC 18-28
MAGMA 44-7
MAGMA 48-7
D
R
Y I
E L
A L
R E
D
1973
1974
1974
0
W S
N H
E I
R P
F
F
F
N
N
N
N
N
W
A U
T S
E E
R
G
G
G
G
G
G
G
G
W U
E S
L E
L
H
H
H
H
H
H
H
H
D
I
A
M
•
(IN)
11
8
7
D
E D
E E
P P
E T
S H
T
(FT)
6,005
6,205
6,231
8,890
8,021
8,001
7,328
7,528
D C
E A
P S
T E
H D
(FT)
6.383
D
E W
P E
T L
H L
(FT)
7,022
H L
ALTI- A E
TUDE T V
OF E E
LSD R L
(FT) (FT)
24
50
30
C A
H N
DATE YIELD E A
WELL OF ML
MEA- WELL I Y
SURED C S
A E
L S
(GPM)
X
X
X
*see Appendix II for explanation
-------
00
to
EXPLANATION
O GEOTHERMAL WELL
• DOMESTIC OR INDUSTRIAL WELL
OTHER TYPE OF WELL
DOMESTIC/INDUSTRIAL AND OTHER TYPE OF WELL
(§) 6EOTHERMAL AND OTHER TYPE OF WELL
LAMiS KGRA
—f.
L CENTRO
24I\242
237,289,^00
MFXiCALI
Figure 2.9 Location of wells in East Mesa, Heber, Dunes and Glamis KGRAs
-------
of the East Mesa KGRA, with one oil or gas well (No. 346) to-
wards the south-central part of the area and all the geothermal
or "heat reservoir" wells in the central or eastern portion.
Some of the domestic wells penetrate the artesian aquifer, with
perforated intervals between 138 m (452 ft) and 267 m (877 ft).
The other domestic wells are up to 355 m (1,166 ft) deep.
Many of the wells listed as "heat reservoir" are less than 330 m
(1,000 ft) deep and therefore penetrate depths similar to those
of domestic wells. The distinct areal separation in location of
the domestic and geothermal wells possibly suggests a distinct
hydrologic separation, either cultural, stratigraphic or struc-
tural or some combination. In fact, the contact between the
Quaternary lake deposits (consisting of lacustrine silt, sand
and clay), and the Quaternary alluvium (consisting of alluvial
and deltaic sand, gravel and silt) is coincident with the line
separating the two well-use areas, except for one domestic well
tapping the artesian aquifer slightly to the east of the con-
tact. This also happens to coincide with the division between
the agricultural and nonagricultural land, i.e. the East High-
line Canal.
The direction of shallow groundwater flow is generally
northwest, and the domestic wells lie down-gradient from the
geothermal wells. Therefore, assuming there is no hydraulic
barrier between these two well areas, if geothermal fluids were
injected in groundwater aquifers up-gradient from the domestic
wells the fluids could eventually flow to them.
All available chemical analyses for East Mesa geothermal
fluids are given in Table 2.9, and for nongeothermal fluids in
Table 2.10. The chemical characteristics of the nongeothermal
wells vary widely throughout the KGRA, from sodium chloride
water in the shallow western portion to sodium bicarbonate water
in the intermediate western portion, to waters with greater
proportions of bicarbonate and/or sulfate in the eastern part.
All of the domestic wells that have analyses available have
1,300 to 1,830 mg/1 TDS content. This is a somewhat high TDS
content for domestic water and is far above the USPHS recom-
mended limit of 500 mg/1 TDS.
Shallow and intermediate depth nonthermal groundwaters,
occurring between 24 and 457 m (80 and 1,500 ft) in the East
Mesa area, have TDS contents ranging from about 700 to 2,500
mg/1, with much of it under 1,000 mg/1. Although the analyses
for some of the geothermal wells in the area show TDS contents
not much above these domestic wells, in the 2,000 mg/1 range,
the anticipated production wells (e.g., Mesa 6-1, No. 802 on
Table 2.9) will have TDS contents of 20,000 to 30,000 mg/1 as
well as significant amounts of trace elements. This implies a
potential pollution threat if the more highly concentrated
83
-------
TABLE 2.9
CHEMICAL ANALYSES OF GEOTHERMAL FLUIDS IN AND WITHIN
1.6 KM (1 MI) OF EAST MESA KGRA
MAP NUMBER
Date
Reference
Units
Temp . -C
EH
Sp.Grav.
Sp.C.-jjmho
TDS-smn
Ca
Mg
Ha
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
WU4
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
348
1/73
H
mg/1
83.3
7.5
-
5,940
3,267
44
3.2
1,195
27
329
60
1,710
_
—
-
-
4.1
-
—
-
-
-
-
1.1
-
-
-
-
-
-
-
-
-
-
—
58
—
-
-
-
17
801 801b
4/74 5/74
H C
mg/1 mg/1
131
6.7 9.12
- -
-
2,390 1,575
4S 16.2
4 2.1
793 593
48 29
717 331.5
196 102
825 454
w _
_ _
_ _
-
— -
_ _
— -
— —
- -
- -
-
— —
-
_ _
— _ —
-
- -
- -
- -
-
-
- -
_ _
130 201
- —
- -
_ _
- -
J29 -e
802C
7/73
C
rag/1
166
7.7
-
50,800.
33,250
1,360
20.8
9,845
1,173
45.7
<20
19,400
m^
_
_
_
_
42
_
<0.01
12.4
_
0.06
1.6
0.25
_
30
—
1.26
83
_
<0.5
0.2
<1
6
341
56
<0.005
_
—
'£•9
802d
2/74
C
mg/1
166
6.66
-
30,664
18,847
642
13.8
5,774
898
223
<10
10,942
0.06
_
0.009
—
_
18
..
<0.04
26
—
0.03
1.23
3.4
<0.0005
, 37
f
0.95
41
0.1
<0.5
0.17
<1
7.2
300
58
0.1
w
-
:f,h
802d
6/76
C
mg/1
166
5.45
—
40,000
26,300
1,360
17.2
e . 100
1,050
202
42.8
15,850
<0.013
0.04
-
0.2600
9.75
14
_
<0.01
—
0.06
<0.1
0.99
8.8
<0.002
40
<0.005
0.95
40.75
0.1
<0.02
<0.5
0.01
_
320
_
_
--
_
If'i
(continued)
84
-------
TABLE 2.9 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
Sp . Grav .
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
Si02
sr
Zn
Zr
H2S
C02
Others
803d
3/76
C
mg/1
_
6.12
-
6,000
5,000
16.4
0.24
1,700
150
560
156
2,124
<0.01
0.03
-
.22
7.45
0.25
-
<0.01
-
<0.01
<0.1
1.23
<0.1
<0.002
4
<0.005
0.05
14.7
<0.1
0.1
<0.5
<0.2
-
269
6.4
<0.01
—
-
-j
-
803d
9/73
C
mg/1
»,
7.70
-
3,862
2,377
13
0.012
760
68.8
715
202
710
<0.004
-
-
.045
-
<0.1
-
<0.002
1.82
-
0.89
3.2
0.06
804d
9/74
C
mg/1
143
7.68
-
-
2,463t
41.1
1.6
723
42
668
225
556
—
-
-
-
3.3
-
-
-
-
-
-
-
1.1
0.00735 -
4
-
<0.01
17
<0.02
<0.1
<0.02
0.8
0.6
250
.17
0.008
—
—
"k
2
-
-
-
-
-
-
-
-
263
1.6
-
~
—
••
••
804d
6/76
C
mg/1
M
6.27
-
3,200
1,600
8.5
<0.05
610
70
417
173
500
<0.01
0.02
-
.053
1.6
0.15
-
<0.01
-
<0.01
<0. 1
1.6
<0.1
0.014
1.1
<0.005
<0.05
4.95
<0 . 1
0.34
<0.5
<0.1
-
389
2.1
<0.01
—
—
~Q_
••
805d
6/76
C
mg/1
_
6.27
-
4,700
2,900
8.9
<0.05
730
85
845
183
510
<0.01
0.02
-
.025
2.5
0.15
-
<0.02
-
<0.01
<0.1
1.42
<0.1
0.008
0.6
<0.005
<0.05
2.45
<0 .1
0.43
<0.5
<0.01
-
274
1.4
<0.01
••
••
~m
805d
11/74
C
mg/1
127
7.72
-
-
2,311t
96.6
1.1
782
25
467
172
490
—
-
-
-
2.2
-
-
-
-
-
-
-
2.4
-
1.8
-
-
-
—
-
-
-
—
88
2.3
—
"
"
•"
•
tTDS Residue on evaporation at 103°C
(continued)
85
-------
TABLE 2.9 (continued)
FOOTNOTES
= Hardt and French, 1976
C = Cosner and Apps, 1977
Flowing steam and brine
after steam flashed
^nflashed brine
e' The following radioactivity measurements are from O'Connell and
Kaufmann, 1976. Sampling data are not specified.
222Rn= 1240 ± 31.93 _
226Ra= o.25 ± 0.08 pCi/1
pCi/1
pCi/1
234 U=<0.10
238 u=<0.10
230Th= o.80 ±
232Th=<0.14
gBe=<0.004
Cr= 0.03
Sb=
-------
TABLE 2.9 (continued)
FOOTNOTES
AU= 0.024 mAu= 0.08
Be=<0.02 Be= 0.15
Bi=<0.005 Bi=<0.005
Ce= 0.14 Ce= 0.2
Cr=<0.01 Cr=<0.01
Ge=<0.1 Ge=<0.1
In=<0.1 In=<0.1
Ir=<0.1 Ir=<0.1
Nb= 0.4 Nb= 0.4
Pd=<0.1 Pd=<0.1
Pt=<0.1 Pt=<0.1
S= 1 S= 0.3
Sb= 1.2 Sb= 1.0
Se= 0.5 Se= 1.8
Ta= 0.12 Ta= 0.1
Ti=<0.1 Ti=<0.1
V=<0.005 V=<0.005
W=<0.1 W=<0.1
87
-------
TABLE 2.10
CHEMICAL ANALYSES OF WATER FROM NONGEOTHERMAL WELLS
IN AND WITHIN 1.6 KM (1 MI) OF EAST MESA KGRA
MAP NUMBER
Date
Reference
Units
Temp.-C
§H
p . Grav .
Sp . C . -pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NHH
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
205
3/58
H
mg/1
37.2
7.7
-
1,674
17
6
545
4
320
124
588
_.
—
-
—
-
-
_
-
-
_
-
2.4
0.06
-
—
_
_
—
_
0.08
_
-
—
-
-
_
-
-
10
-
205
7/61
H
mg/1
32.2
8.2
1,180
663
4.8
1.7
251*
-
336
52
163
«.
_
-
_
-
-
_
-
—
_
—
1.7
-
-
—
_
_
_
_
-
_
-
-
21
—
« ^ *
»
-
3.4
-
206
7/61
H
mg/1
37.8
8.2
2,740
1,550
17
5
571*
-
404
135
588
_
-
-
-
-
-
-
-
_
-
-
-
-
-
—
-
—
—
-
-
-
-
-
29
-
-
-
-
4.1
•-
206
12/70
H
mg/1
34.7
8.3
2,740
1,600
17
5.5
570
3.7
410
170
600
_
_
-
_
2.9
—
_
-
-
_
-
-
0.14
-
0.16
—
_
0.72
—
-
—
-
-
22
0.44
-
-
-
3.3
-
207
12/70
H
mg/1
34.1
8.3
1,610
987
6.7
2
370
2.1
560
140
160
M
_
-
™ (
3.5
_
_
-
_
_
_
3.4
0.04
-
0.13
—
—
0
_
—
_
-
_
23
0.009
_
-
-
4.5
-
208
1/62
H
mg/1
_
8.1
-
12,700
7,110
384
232
2,010*
-
293
217
4,120
_
_
-
_
_
_
.
—
_
_
_
-
—
-
-
_
_
_
_
—
_
-
_
5
-
_
.
-
3.6
-
210
7/61
H
mg/1
31.7
8.4
-
1,110
706
6
1
264*
-
444
80
100
_
_
-
_
—
_
_
_
_
_
_
—
_
-
-
_
_
_
.
_
_
_
_
31
_
_
_
-
2.8
_
H = Hardt and French, 1976
*Na + K value
(continued)
88
-------
TABLE 2.10 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
PH
Sp.Grav.
Sp.C.-Mmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
L?
Mo
NH4
Ni
N03
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
216
7/61
E
mg/1
38.3
8.3
-
1,360
787
8.2
1.6
300*
-
450
76
159
-
••
-
_
-
-
-
-
_
3
-
—
-
_
-
—
_
-
14
-
-
-
-
3.6
-
313
6/50
H
mg/1
_
-
-
1,320
811
81
35
153*
-
189
310
142
-
^^
-
_
-
-
-
-
-
-
-
—
-
_
-
—
-
-
-
-
-
-
-
-
—
314
12/52
H
mg/1
32.2
8.1
-
1,380
_
_
-
304*
-
482
98
161
- '
^
1.01
_
_
-
-
-
_
1.5
-
—
-
_
-
—
-
—
-
—
-
-
—
6.1
—
314
9/63
H
mg/1
_
8.2
-
1,510
885
14
1
327*
-
456
100
187
-
^
-
_
-
-
-
-
-
3
-
—
-
_
-
••
-
-
25
—
-
-
-
4.6
—
319
1/72
H
mg/1
42
8.3
_
-
_
7
-
315
1.6
-
-
154
-
^
-
_
0.2
-
-
-
-
-
-
—
-
_
-
—
-
.—
-
—
-
—
-
-
—
320
1/62
H
mg/1
28.3
8.0
_
4,340
2,550
101
55
750*
_
265
600
900
-
^
-
_
-
-
-
-
-
-
-
—
-
-
-
•
-
—
13
—
-
—
—
4.2
—
322
1/72
E
mg/1
49
7.8
-
-
_
24
-
840
5.2
-
-
995
:
^
-
_
0.8
-
-
-
-
-
-
—
-
-
-
•*
-
—
-
•
—
—
—
—
••
^ = Hardt and French, 1976
*Na + K value
(continued)
89
-------
TABLE 2.10 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
PH
Sp . Gr av .
Sp.C.-ymho
TDS-sum
Ca
Mg
Na
K
HC03
SO4
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
323
12/70
H
mg/1
43
8.1
-
2,800
1,520
17
3.5
560
3.6
300
120
630
_
—
—
—
3.4
-
_
_
_
_
_
2.1
0.05
_
0.25
-
_
0.52
—
-
—
-
—
26
0.57
-
-
-
3.8
-
337
3/72
H
mg/1
33
8.4
-
—
_
24
-
405
3.9
-
-
—
_
-
_
_
-
-
_
_
_
_
_
—
_
-
—
_
_
—
_
-
_
-
_
-
-
—
_
-
-
-
351
10/63
H
mg/1
M
4.3
-
4,450
2,620
130
">.2
736
_
-
4
1,380
—
_
_
_
-
_
H
_
_
.
_
-
_
_
_
_
..
_
_
—
_
-
_
16
—
_
_
-
—
—
357
9/63
H
mg/1
33.9
2.6
-
3,260
1,960
65
8.3
589
_
-
200
898
_
_
_
_
-
_
_
_
—
^ .
M
1.2
_
_
M
M
—
_
_
-
w
_
_
_
_
_
M
_
_
_
364
2/64
H
mg/1
_
8.1
-
1,370
804
12
7.3
271*
—
192
165
224
—
_
_
_
_
_
—
.
_
mf
_
1.9
—
_
^
_
--
_
^
_
—
_
^
27
_
_
^
_
2.4
366
6/64
H
mg/1
—
8.0
-
1,460
874
23
8.6
272
4
208
235
200
M
_
_
_
0.64
_
—
.
—
mm
—
1.7
—
_
^
^
^
_
^
0.5
M
—
27
I
^
—
3.3
B. = Hardt and French, 1976
*Na + K value
(continued)
90
-------
TABLE 2.10 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
Sp . Grav .
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Eg
Li
MO
Ni"
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
416 417
7/64 7/64
H H
mg/1 mg/1
23.9 25
6.5 7.8
- -
1,180 1,190
708 714
79 52
24 23
131 169
- -
46 133
312 300
152 121
_ _
-
-
-
- -
-
- -
-
-
_ •
- -
0.7 0.7
- -
_
-
•" "•
^ , ^
- -
- -
-
— —
2 1
— —
- -
- —
- -
23 3.4
- -
418
7/64
H
mg/1
26.1
9.0
_
2,920
1,750
3.8
1.6
718
_
1,380
190
175
_
-
-
-
—
-
-
-
-
-
-
0.6
- •
-
-
—
"•
—
—
—
-
1
—
—
—
—
2.2
—
420
6/64
H
mg/1
M
7.8
_
1,170
704
23
8.1
213*
_
162
208
143
_
-
-
-
-
-
—
-
-
-
-
1.5
-
-
-
_
•
—
—
—
—
26
••
—
—
-
4.1
—
421
7/64
H
mg/1
25
10.1
_
1,410
846
2
-
300
_
540
105
74
_
-
-
-
-
-
-
-
-
-
-
0.3
-
-
-
^
_
—
—
—
—
-
™
-
—
-
0.1
~
422
7/64
H
mg/1
23.3
7.9
_
1,070
642
15
5.5
194
_
63
217
144
_
-
-
-
-
-
—
-
-
-
-
0.6
-
-
-
~
_
-
—
-
-
-
~
-
—
-
1.3
—
424
7/64
H
mg/1
24.4
10.0
_
1,730
1,040
1.4
0.1
354
_
401
258
124
_
-
-
-
-
-
-
-
-
-
-
0.6
-
-
-
*
_
-
—
-
-
-
~
—
—
-
0.1
••
*H = Hardt and French, 1976
*Na + K value
(continued)
91
-------
TABLE 2.10 (continued)
MAP NUMBER
Date
Reference
Units
Temp.-C
PH
Sp . Gr av .
Sp . C . -pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Ll
Mo
k-in
NH4
Ni
N03
Pb
P04
Rb
SiO2
Sr
Zn
Zr
H2S
C02
Others
425
7/64
H
mg/1
27.8
11.2
-
3,460
2,080
1.4
0.1
699
—
1,400
-
198
_
-
—
-
-
-
_
—
_
_
-
-
-
-
-
_
-
-
—
-
_
-
_
1
—
-
_
-
0.0
-
739
12/70
R
mg/1
32
8.39
-
1,920
1,460
7.6
2.7
420
2.2
600
160
220
_
—
—
—
2.7
—
_
—
_
-
_
3.9
0.10'
-
0.12
_
_
-
-
-
_
-
_
25
0.10
_
_
-
-
-
741
12/70
R
mg/1
34.7
8.15
-
2,880
3 830
17
5.5
570
3.7
430
170
600
_
_
-
—
2.9
—
_
_
_
_
.
2.2
0.14
-
0.16
-
—
—
—
-
_
-
_
22
0.44
_
_
-
-
-
742
12/70
R
mg/1
34.1
8.38
-
1,750
1,300
6.7
2
370
2.1
580
140
160
_
—
_
_
3.5
—
_
_
_
_
_
3.4
0.04
-
0.13
_
_
—
—
-
_
-
_
23
0.09
_
_
—
-
-
746
12/70
R
mg/1
43
8.09
-
3,290
1,680
17
3.5
560
3.6
310
120
630
_
—
_
_
3.4
_
_
_
_
_
_
2.1
0.05
-
0.25
_
_
_
_
—
_
—
_
26
0.57
_
_
_
_
_
747
12/70
R
mg/1
37.2
8.33
-
2,210
1,420
10
2.7
420
2.4
510
130
310
_
-
-
-
2.2
—
_
_
_
_
_
2.3
0.05
-
0.10
..
_
_
_
_
M
_
w
25
0.41
M
_
_
_
_
= Hardt and French, 1976
R = Reed, 1975
92
-------
geothermal fluid escaped into the shallow or intermediate ground-
water system or to the surface waters.
In addition to possible increased salinity problems if geo-
thermal fluid escapes into the groundwater or surface water
systems, some trace element contamination may also result. For
East Mesa geothermal fluids, trace elements that have been ana-
lyzed (Table 2.9), and are above USPHS limits for drinking water
use (Table 1.8), are arsenic, barium, fluoride, lead, selenium
and silver. Trace elements which are above USPHS recommenda-
tions are iron and manganese. Arsenic concentrations of 0.26
mg/1 and 0.22 mg/1 have been reported for Mesa 6-1 and 6-2
respectively. These values are about four to five times the
0.05 mg/1 limit for arsenic. A number of high barium concentra-
tions have been reported, up to 42 mg/1 in Mesa 6-1, which is
over forty times the 1 mg/1 USPHS limit. Fluoride concentra-
tions slightly above the 2.2 mg/1 USPHS limit have been reported
for Mesa 6-1. However, similar fluoride concentrations slightly
over this limit have also been reported for domestic artesian
wells. A lead concentration of 0.2 mg/1 has been reported for
Mesa 6-1, which is about four times the USPHS limit of 0.05
mg/1. A 0.5 mg/1 concentration of selenium has been reported
for Mesa 8-1, compared to the 0.01 mg/1 USPHS limit. A silver
concentration slightly over the 0.05 mg/1 USPHS limit hac been
reported for Mesa 6-1. Concentrations of iron and manganese
have been reported that are above USPHS recommendations. Values
of 8.8, 2.2, and 1.1 mg/1 iron have been reported for Mesa 6-1,
31-1, and 8-1, respectively, compared to the USPHS 0.3 mg/1
recommendation. A 1.26 mg/1 manganese concentration, about five
times the USPHS recommendation, has been reported for Mesa 6-1.
Water salinity is an ubiquitous problem in East Mesa with
respect to irrigation and livestock water, although the upper
limit of 5,000 mg/1 TDS for livestock may allow some of the less
concentrated geothermal fluids to be used for this purpose.
Trace element concentrations exceeding irrigation standards are
boron and copper. Boron concentrations commonly range from over
2 to 10 mg/1 for many geothermal wells, and from 2 to 3.5 mg/1
for many domestic artesian wells. Boron concentrations over
about 3 mg/1 are not good even for boron-tolerant crops (Table
1.13) and concentrations over 1 mg/1 are not good for boron-
sensitive crops. A copper concentration of 0.89 mg/1 is re-
ported in Mesa 6-2 while the crop threshold value, the value
where a farmer should become concerned about the concentration,
is 0.1 mg/1.
Based on a production fluids TDS concentration from 2,000
to 30,000 mg/1, the projected total amount of dissolved solids
brought to the surface by potential geothermal production at
East Mesa is estimated to be 3.28 to 49.2 million kg/day (7.2 to
108 million Ibs/day) (Table 2.7), or from 35.9 to 539 billion kg
(79.2 to 1,188 billion Ibs) over the anticipated 30 years of
93
-------
power production. This will result from an estimated total
brine mass production of about 1.64 billion kg/day (3.62 bil-
lion Ibs/day) (Table 2.6). For chemical constituents with
concentrations of 0.1 ppm or 100 ppm, the daily plant chemical
throughput would be 164 and 164,000 kg/day (362 and 362,000
Ibs/day, respectively (Table 2.7). It is anticipated, however,
that the great majority of these chemical constituents would be
injected back into the hydrologic unit they were removed from,
thereby minimizing pollution or waste disposal problems.
2.3.3 Salton Sea KGRA
Of the 31 wells listed on Table 2.11, Description of Wells
in and within 1.6 km (1 mi) of the Salton Sea KGRA, at least 12
are geothermal wells. The location of these wells is shown in
Fig. 2.10. None of the groundwater is used domestically in
this area, although wells supply water for industrial or recre-
ational use. The remaining well water is unused or is listed as
having "other" uses. Only four of the wells are listed as water
withdrawal wells and three of these are geothermal.
From this preliminary survey of groundwater use in the
Salton Sea KGRA it seems that the major groundwater use is for
potential geothermal energy production and therefore possible
ground water degradation is not as critical here. This is
supported by the fact that groundwater flow towards the Salton
Sea leaves only one recreationally used well somewhat down-
gradient from the geothermal wells. However, the possibility of
chemically degraded and thermally polluted shallow groundwater
seepage recharging the Salton Sea must also be considered. At
this point, little information is available concerning this
mechanism.
The areal distribution of the different types of wells
(Fig. 2.10) suggests a clustering of geothermal wells with the
other well types around the geothermal cluster. There appears
to be a general northeast-southwest trend to the geothermal well
locations. They occur near the southeast shore of the Salton
Sea, with a suggestion of clustering along the Brawley and
Calipatria Faults. All of the wells in this area penetrate
surficial Quaternary lake sediments.
The two samples of shallow depth interval (24 to 91 m [80
to 300 ft] depth) nongeothermal groundwater (wells No. 36 and
73), within the Salton Sea KGRA proper, seem to be a mixture of
the characteristic sodium chloride calcium Salton Sea geothermal
water, and the sodium chloride with high sulfate or magnesium
Salton Sea water, although the TDS concentrations are much lower
than either: 1,600 mg/1 for well No. 36 and 5,600 mg/1 for well
No. 73 (Table 2.12). Two groundwater analyses just outside the
KGRA boundary (wells No. 67 and 79 in Geonomics [in press] ) are
characteristic sodium chloride with high sulfate or magnesium
94
-------
TABLE 2.11
DESCRIPTION OF WELL SITES AND WATER SAMPLES IN AND WITHIN 1.6 KM
(1 MI) OF SALTON SEA KGRA* (modified from Hardt and French, 1976)
vo
Ul
MAP
NUM-
BER
31
32
34
35
36
41
44
45
46
47
48
52
69
71
73
74
75
76
806
808
809
810
811
812
813
814
815
816
818
901
902
STATE NUMBER
'
11S/13E-10L01
11S/13E-10L02
11S/13E-13D02
11S/13E-13K01
11S/13E-22H01
11S/13E-23P01
11S/13E-28K01
11S/13E-33F01
11S/13E-33L01
11S/13E-33L02
11S/13E-33M01
11S/14E-19E01
12S/13E-04Q01
12S/13E-10D01
12S/13E-15L01
12S/13E-19A01
12S/13E-24601
12S/13E-24K01
11S/13F-27M01
11S/13E-23F01
11S/13E-22J01
11S/13E-23C01
11S/13E-33Q01
11S/13F-10L03
11S/13E-24D01
12S/13E-10D02
12S/13E-04Q02
11S/13E-23G01
11S/13E-33R01
11S/13E-27N01
11S/13E-25L01
10S/13E-27B01
12S/12E-29N01
11S/11E-21P01
11S/13E-22H01
OWNER OR NAME
PIONEER 11
PIONEER 12
J. MASSION
E.E.INC HUDSON 1
USGS
IMP PROD CAL 1
SALTON SEA CHEM
USGS-USBR SS 1
MPC MAGMAMAX 3
MPC MAGMAMAX 4
MAGMAMAX 2
CH. STATION 1
SINCLAIR 2
KIC SINCLAIR 1
USGS
GRACE 1
SARDI OIL BIFF 1
SARDI 1
E E ELMORE 1
O'NEILL IID 1
IMP PROD IID 2
IMP PROD IID 3
MPC MAGMAMAX 1
PIONEER 13
EE RIVER RANCH 1
HGC SINCLAIR 3
WGI SINCLAIR 4
SPORTSMAN 1
MPC WOOLSEY 1
ELMORE 13
SALTON SEA CHEM
MUD VOLCANO, ETNA
POE ROAD SPRING
SALTON SEA
ALAMO RIVER
D
R
Y I
E L
A L
R E
D
1927
1927
1964
1962
1964
1932
1975
1972
1972
1972
1935
1961
1958
1962
1963
1962
1961
1964
1962
1963
1965
1972
1927
1964
1963
1964
1961
1972
1974
1933
0
W S
N H
E I
R P
N
N
P
N
F
N
N
F
N
N
N
N
N
F
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
H
A U
T S
E E
R
N
N
R
G
U
G
Z
G
G
G
G
G
G
U
N
U
N
G
G
G
G
G
N
G
G
G
G
G
G
surface water
surface water
surface water
surface water
W U
E S
L E
L
U
U
0
U
Z
0
R
0
H
2
H
U
0
H
U
P
U
U
U
R
H
U
U
U
U
M
U
U
D
I
A
M
•
(IN)
5
2
6
1
7
6
9
3
20
6
3
1
16
11
8
7
7
8
8
6
8
9
5
8
16
9
0
ED DC
E E E A
P P PS
E T T E
S H H D
T
(FT) (FT)
727 452
1,263
6,141 5,855
152 145
4,840 4,435
1,054
500
4,000 2,618
2,567 2,376
4,368 3,784
590
4,720 3,370
127 113
1,200 1,000
6,350
5,620
7.117 4,745
5,230 4,900
5.826 3,490
1.699
2,805 1,797
1,473
8,100 3,890
6,922 3,788
5,306 4,254
4,729 3,980
2,400 1,866
2,510 2,007
960 450
D
E W
P E
T L
H L
(FT)
727
6,122
147
4,806
3,076
2.518
4,360
3,445
115
7,087
5,212
5,303
2,264
8.093
6.868
5,047
4,720
2.375
2,505
500
W L
ALTI- A E
TUDE T V
OF E E
LSD R L
(FT) (FT)
-231
-231
-226 F
-220
-229 +2
-225
-175
-227 +4
-226
-226
-227
-216
-217 4
-214
-202 10
-216
-196
-196
-225
-229
-230
-230
-222
-231
-225
-213
-217
-228
-222
sample
sample
sample
sample
C A
H N
DATE YIELD E A
WELL OF ML
MEA- WELL I Y
SURED C S
A E
L S
(GPM)
9 x
X
5-62 x
X
4-75
8-62
2-62 x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
*see Appendix II for explanation
-------
-. WALTON
o
•
<»
GEOTHERMAL WELL
DOMESTIC OR INDUSTRIAL WELL
OTHER TYPE OF WELL
SURFACE WATER
GEOTHERMAL,AND DOMESTIC /INDUSTRIAL WELL
GEOTHERMAL AND OTHER TYPE OF WELL
Figure 2.10 Location of wells in Salton Sea
and Brawley KGRAs
96
-------
TABLE 2.12
CHEMICAL ANALYSES OF WATER FROM SPECIFIED SITES AND
NONGEOTHERMAL WELLS IN AND WITHIN 1.6 KM (1 MI) OF
SALTON SEA KGRA
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
Sp . Gr av .
Sp . C . -pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
LI
do
Mn
NH4
_*_^
Ni
NO3
v» — • ^
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
36
5/62
H
mg/1
27.8
7.4
3,120
1,600
134
49
384*
-
100
275
710
_
-
-
—
—
-
—
-
-
—
-
_
_
-
_
_
-
_
_
_
-
-
-
3
_
-
-
—
6.4
-
73
7/62
H
mg/1
27.8
7.2
9,370
5,600
476
202
1,300*
-
40
700
2,900
_
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
—
-
-
-
—
—
2
—
-
—
—
4
••
Mud
Volcano
Etna
3/67
CDWR
ppm
20
6.0
61,730
51,632
2,083
1,714
13,500
410
2,013
1,536
27,900
-
-
-
-
84
-
-
-
-
-
-
3.6 '
-
-
-
-
-
-
-
17
-
—
—
-
-
-
—
—
~
—
Mud
Volcano
Etna
3/67
CDWR
ppm
_
_
-
—
_
-
-
-
-
-
-
—
<0.004
<0.15
-
-
-
<0.2
-
<0.4
-
0.046
0.009
-
0.10
<0.4
60
0.001
3
—
0.066
-
0 . 0044
—
—
-
150
0.02
—
••
~b
Poe
Road
Spring
5/76
CDWR
ppm
21
6.8
-
6,831
4,656
249
285
990
32
2,300
453
1,150
—
-
-
-
5
-
-
-
—
-
-
0.6
-
-
-
-
-
—
-
24
-
••
••
-
-
-
••
—
*
•
Poe
Road
Spring
5/67
CDWR
ppm
_
_
-
—
_
-
-
-
-
-
-
—
0.0001
0.2
-
-
-
0.04
-
-------
TABLE 2.12 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
PH
Sp.Grav.
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
i-jn
MH4
Ni
N03
Pb
P04
Rb
SiO2
Sr
Zn
Zr
H2S
C02
Others
Sal ton
Sea
6/67
CDWR
ppm
25
7.7
-
42,100
37,032
954
1,078
10,500
172
203
8,146
15,000
_
-
-
-
9.2
-
-
-
—
-
-
3.2
-
-
-
-
-
-
-
14
-
-
_
-
-
-
—
-
-
-
Sal ton
Sea
6/67
CDWR
ppm
_
-
-
—
_
-
-
-
—
-
-
-
0.0008
<6
_
-
-
<0.002
_
<0.005
—
<0.0005
0.005
_
o.oib
<0.2
-
0.016
0.01
_
0.003
-
<0.002
-
_
-
11
0.062
—
-
~j
_Q
Alamo
River
5/67
CDWR
ppm
24
8.0
-
3,510
2 538
191
101
483
14
220
782
639
_
-
_
-
0.26
-
_
_
_
-
-
0.9
-
-
—
-
—
—
-
31
-
-
_
—
-
-
—
-
-
-
Alamo
River
3/67
CDWR
ppm
_
-
-
—
_
—
-
-
—
-
-
-
<0.004
<0.1
_
-
-
0.02
_
<0.4
_
<0.002
0.0074
_
0.032
<0.4
0.133
0.0016
0.038
-
0.0032
_
0.0034
—
_
—
0.76
0.011
_
-
-
_e
34
2/68
H
mg/1
40
-
-
33,780
23,270
854
232
7,200
504
1,684
377
12,420
_
—
_
0.03
50
-
2.5
_
_
-
_
1.8
—
-
_
_
-
_
_
0
—
_
_
_
_
_
_
—
j_
1=3.9
(continued)
98
-------
TABLE 2.12 (continued)
FOOTNOTES
H = Hardt and French, 1976 i
CDWR = Cal. Div. Water Resources, 1970
bAu=<0.04
Be=<0.004
Bi=<0.08
Cr=<0.002
Ga=<0.08
Ge=<0.2
La=<0.08
Sb=<0.4
Sn=<0.08
Ti=<0.5
Tl=<0.08
V= 0.01
CBe=<0.002
Bi=<0.0005
Cr=<0.001
Ga=<0.0005
Ge=<0.1
Sb=<0.2
Sn=<0.04
Ti=<0.04
V=<0.002
dAu=
-------
waters with TDS concentrations of 1,490 and 15,200 mg/1, re-
spectively. Although these waters are top saline for drinking
or irrigation uses some of the lower salinity fluids may pos-
sibly be suited for livestock applications.
The rest of the wells in the area penetrate the deep depth
interval (deeper than 457 m [ 1,500 ft]) and contain highly
saline sodium chloride calcium brines with TDS contents from
34,000 to over 300,000 mg/1, with about 200,000 mg/1 average
(Table 2.13). This is obviously very saline water--not suit-
able for any drinking, irrigation or livestock use.
Highly concentrated brines such as the geothermal fluids
also commonly have high trace element concentrations, which are
discussed below (Table 2.13). However, it should be kept in
mind that to isolate one component of the brine and call it
toxic when the entire brine itself is toxic may be somewhat
misleading.
Boron concentration, a critical element for agricultural
applications, ranges from 92 mg/1 in well No. 815 to 540.5 mg/1
in well No. 816. This is far above the 0.33 to 0.67 mg/1 range
acceptable to boron sensitive crops (Table 1.13). There are no
boron analyses available for nongeothermal wells in this area;
however boron content for surface water ranges from 5 ppm at Poe
Spring, to 9.2 ppm at the Sal ton Sea, to 94 ppm in the Etna mud
volcano (Fig. 2.10). The boron content of agricultural return
water measured at the Alamo River (Fig. 2.10) had values of
0.42, 0.8, 0.7 and 0.26 in 1955, I960, 1964 and 1967, respec-
tively. Even the highest value here is within the "permissible
for sensitive crops" range (Table 1.13). Boron contamination
would be an extremely serious problem in the agricultural econ-
omy of Imperial Valley.
The geothermal fluids are also above USPHS drinking water
standards (Table 1.8) in cadmium, arsenic, fluoride, copper,
barium, iron, lead, manganese, silver, zinc and radium-226.
Cadmium concentrations, above the USPHS drinking water
standard of 0.01 mg/1, of 2 ppm and less than 40 ppm are re-
ported for wells No. 808 and 815, respectively, while surface
water samples from the Etna mud volcano and Alamo River are less
than 0.4 ppm.
Arsenic concentrations, above the USPHS drinking water
standards limit of 0.05 mg/1, are reported to be 0.16 to 100
mg/1 at wells No. 810 and 815, respectively. There are no
arsenic analyses currently available for other wells or surface
water.
Fluoride concentrations in geothermal wells range from an
acceptable level of 0.8 mg/1 in well No. 815 to 15 ppm in well
100
-------
TABLE 2.13
CHEMICAL ANALYSES OF GEOTHERMAL FLUIDS IN AND WITHIN
1.6 KM (1 MI) OF SALTON SEA KGRA
MAP NUMBER
Date
Reference
Units
Temp . -C
PH
Sp.Grav.
Sp . C . -pinho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
sio'2
ft
sr
Zn
Zr
H2S
C02
Others
41
C
b,c
ppm
_
-
-
-
219,
21,
47,
14,
-
-
12,
-
-
-
-
-
-
-
1,
-
-
-
—
-
-
_
-
-
—
5,
500
100
27
800
000
700
<1
290
190
17
2
200
180
950
80
65
500
000
S=30
806d
C
mg/1
191.
4.
-
-
318,
31,
62,
20,
185,
_
-
-
_
-
-
-
-
2,
-
-
-
-
-
—
-
-
1,
—
—
-
1
9
000
500
16
8?0
800
40
49
000
<15
350
480
12
500
270
570
100
050
Cr=
-------
TABLE 2.13 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
Sp.Grav.
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
no
Mn
NH4
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
811
I/I?
C
mg/1
240
6.6
1.022
-
38,900
2,818
47
8,562
142
-
—
20,548
_
-
—
811e
3/74
C
mg/1
240
6.10
-
22,697
203,406
23,600
110
47,300
7,960
61.6
<10
123,390
0.43
-
—
812
-
C
mg/i
_
6.5
-
-
110,000
16,000
4,000
20,400*
-
300
200
68,000
_
-
—
813
-
C
mg/1
_
4.0
-
-
372,000t
39,700
59
74,700
21,900
-
-
216,000
•
56
_
0.1870
-
-
-
-
-
-
-
-
95
-
29
—
9.8
-
-
-
-
-
-
108
-
-
—
-
-
-
55.7
— .
1.12
-
-
-
12
-
172
1.4
—
-
570
-
1.05
36.2
<0.8
50.4
435
102.4
283
-
-
-
-
-
-
-
—
-
-
-
50
-
-
-
4,000
-
-
1,050
-
-
-
-
-
-
-
-
-
Be=0.08
Bi=5
Cr=0.3
Cs=250
Sb=6 . 7
Se=<0.
001
518
241
—
-
-
-
5.5
-
1,515
-
239
-
1,480
,1 478
X
41
155
-
-
560
482
740
-
-
-
Cr=0.8
814
4/62
C
ppm
_
5.30
1.114
24,736
153,300
14,550
780
36,340
7,820
60
58
93,650
0
-
_
10
210
540
-
—
-
-
0
2.4
166
-
49
-
410
340
-
-
80
-
—
350
360
-
-
-
-
Sb=0.2
815
7/67
C
ppm
>100
5.3
1.220
—
266,560t
26,992
736
58,443
14,918
0
19
154,590
M
-
_
10
332
-
25
-
-
—
-
14
1,148
-
287
—
1,025
442
-
5
-
-
_
90
434
-
_
-
-
1=13
815
4/75
C
mg/1
255
-
-
—
-
-
39
-
-
-
-
-
<3
0.5
_
100
92
2,600
<2
<40
52
<0.8
130
0.8
4,100
<3
-
<8
7,500
_
1,200
_
500
-
5,300
-
4,800
6,100
24
—
_
_9»k
*Na = K value
tTDS Residue on evaporation
(continued)
102
-------
TABLE 2.13 (continued)
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
sp . Gr av .
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Li
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
816
-
C
mg/1
199
4.0
1.207
—
321,400
34,220
18
66,000
24,400
-
-
192,100
-
-
-
-
540.5
-
-
-
-
-
-
-
4,130
54
-
-
-
-
-
—
-
—
5
-
-
-
—
-
816 818
— —
P P
ppm ppm
.. •»
6.2
1.207 1.076
-
334,987 131,732
34,470 8,550
18 651
70,000 49,257
24,000 2,881
-
34
201,757 59,015
_ _
- -
-
-
149
-.
-
-
-
- -
-
- -
4,200 84
150 65
- -
121
-
- -
- -
- -
- -
— —
5 112
— —
— —
_ — i
•• ••
— ™*
818
2/72
H
mg/1
171
6.4
-
98,600t
7,800
120
30,000
3,200
-
-
52,000
—
-
-
-
-
-
-
-
-
-
-
-
150
67
-
160
-
-
—
—
—
—
150
—
""
—
"*
••
818
3/72
H
mg/1
_
6.2
-
167,000t
14,000
150
55,000
7,200
-
-
92,000
—
-
-
-
-
-
-
-
-
-
-
-
i 270
100
-
540
-
—
—
—
—
—
200
—
~
~
^
—
818
10/76
C
ppm
_
5.71
—
_
11,000
-
23,000
5,080
-
-
85,700
-
-
-
-
.
-
-
-
-
-
-
-
64.8
93
-
-
—
—
~
"
•
"•
513
""
~
^
~
^
tTDS Residue on Evaporation at 180°C
(continued)
i
103
-------
TABLE 2.13 (continued)
FOOTNOTES
aC = Cosner and Apps, 1977
H = Hardt and French, 1976
P = Palmer, 1975
340° C Temp, measured 6/64
GAverage of several hundred analyses
181°C Temp, measured 1964
eBrine after steam flashed
i
Unf lashed brine
gAu=<3 S=390 Ga=<2 Nb=<2 In=<2 I=<2 Nd=<3 Tb=l
Be=<0.05 Sc=<0.5 Ge=5 Ru=<5 Sn=<20 La=20 Sm=<3 Dy=<3
Si=24 Ti=<8 Se=g20 Rh=<2 Sb=<3 Ce=
-------
No. 808. Surface water analyses of 3.6 and 3.2 ppm, somewhat
above the USPHS drinking water standard limit for fluoride, are
reported for the Etna mud volcano and the Sal ton Sea, respec-
tively .
Copper concentrations range from 2 to 130 mg/1 for geo-
thermal wells No. 41 and 815, respectively. All the copper
analyses for geothermal wells are above the USPHS Drinking Water
Standard recommendations, while all the surface waters appear to
have acceptable copper contents. No copper data is available
for other wells in the area.
Barium concentrations range from 3 rag/1 in geothermal well
No. 810 to 480 mg/1 in geothermal well No. 806. All of the
geothermal wells are above the USPHS limit of 1 mg/1 for barium,
while all the surface water analyses indicate acceptable barium
values. No barium data is available for other wells in the
area.
All the Salton Sea geothermal wells have iron contents
higher than the USPHS drinking water recommendation of 0.3 mg/1.
The reported range is from 0.7 mg/1 in well No. 810 to 4,200
mg/1 in well No. 816. All reported surface water samples have
acceptable iron contents.
Lead contents much higher than the USPHS drinking water
limit of 0.05 mg/1 are reported for all the geothermal wells.
They range from 60 mg/1 in well No. 815 to 50*0 mg/1 in another
analysis of the same well. All of the reported surface water
analyses have acceptable lead contents.
Reported manganese contents of Salton Sea geothermal wells
range from 9.8 mg/1 in well No. 811 to 7,500 mg/1 in well No.
815. The USPHS limit is 0.05 mg/1 and surface water samples at
the Etna mud volcano and Poe Spring have manganese contents of
3.0 and 0.240 mg/1, respectively, while Salton Sea and Alamo
River waters are below the USPHS manganese limit.
A silver content of 1.4 mg/1 has been reported for well No.
808. This is considerably above the USPHS limit of 0.05 mg/1.
All the surface water samples have acceptable silver content.
All the geothermal wells have excessive zinc contents
ranging from 500 mg/1 in well Nos. 41 and 801 to 6,100 mg/1 in
well No. 815. All of the reported surface water analyses are
under the USPHS limit of 5 mg/1.
Based on a production fluid TDS concentration of 300,000
mg/1, the projected total amount of dissolved solids brought to
the surface by potential geothermal production of the Salton Sea
geothermal field is estimated to be 378 million kg/day (832
million Ibs/day) (Table 2.7), or 4.1 x 1012 kg (9.1 x 10r2 Ibs)
105
-------
over the anticipated 30 years of power production. This would
result from an estimated total brine mass production of about
1.26 billion kg/day (2.8 billion Ibs/day) (Table 2.6). For
chemical constituents with concentrations of 0.1 ppm or 100 ppm,
the daily plant chemical throughput would be 126 and 126,000
kg/day (277 to 277,000 Ibs/day), respectively (Table 2.7). It
is anticipated, however, that the great majority of these chem-
ical constituents would be injected back into the hydrologic
unit they were removed from, thereby minimizing pollution or
waste disposal problems.
2.3.4 Heber KGRA
Groundwater level contours (Loeltz, et al. 1975; Butcher,
et al. 1972) indicate that water entering the shallower water
bearing strata in the eastern part of the Heber KGRA will flow
to the west, then turn northward and flow toward the Salton Sea.
Shallow groundwater entering the western portion of the Heber
KGRA, from the Mexicali Valley, will only flow northward towards
the Salton Sea. This means that any pollution escaping into the
groundwater system will form northward-growing plumes and their
shapes will depend on the number and relative location of the
pollution sources.
A total of 22 wells are reported within the Heber KGRA
(Table 2.14, Fig. 2.9). Seven of these are listed as heat
reservoir or geothermal wells and six of them are being used.
There are nine wells listed as observation wells, one test hole,
one geothermal recharge well, two unused water withdrawal wells,
and two are reported as destroyed. This compilation indicates
that there is currently no domestic or agricultural use of
groundwater in or within 1.6 km (1 mi) of the Heber KGRA.
Currently, all of the geothermal wells lie on an east-west
trending line, about 8 km (5 mi) south of El Centre, all within
the irrigated, agricultural area. They penetrate Quaternary
lake deposits consisting of lacustrine silt, sand and clay on
the surface and lie between mapped traces of the Imperial Fault
and San Jacinto Fault. Additional fault traces in the Heber
area, which would be more intimately related to the geothermal
system, v/ill probably be identified with further drilling and
detailed geophysical investigations.
Available shallow groundwater analyses indicate a sodium
chloride water with a small proportion of calcium, magnesium and
sulfate (Table 2.15). The TDS range for these waters is from
about 3,000 to 10,000 mg/1. Based on these few nongeothermal
well water analyses there appears to be a shallow groundwater
salinity gradient, with TDS consents increasing from about 3,000
mg/1 in the southeastern corner of the Heber KGRA, and increas-
ing -'to the north and west, to about 10,000 mg/1 in the northwest
corner of the KGRA. One deep nongeothermal well, USGS-LCRP 7
106
-------
TABLE 2.14
DESCRIPTION OF WELLS IN AND WITHIN 1.6
(modified from Hardt and French, 1976)
KM (1 MI) OF HEBER KGRA*
o
-j
HAP
NUM-
BER
297
298
299
300
301
304
307
308
309
310
400
401
402
403
404
405
406
407
500
502
503
504
STATE NUMBER
16S/13E-13N01
16S/14E-27F01
16S/14E-27M01
16S/14E-28M01
16S/14E-29G01
16S/14E-32K01
16S/14E-34F01
16S/14E-34N01
16S/15E-17L01
16S/15E-33D01
17S/14E-14Q01
17S/14E-14Q03
17S/14E-18M01
17S/15E-10N01
17S/15E-16K01
17S/15E-16K02
17S/16E-18P01
17S/16E-18Q01
16S/14E-33K01
16S/14E-31J01
16S/14E-32B01
16S/14E-33E01
OWNER OR NAME
USGS
CHEVRON GTW2
CHEVRON GTM1
A. TIMKEN 1
CHEVRON HULSE 1
MAGMA HOLTZ 1
CHEVRON GTH3
USGS-USBR HEB.l
USGS
REPUBLIC
H. LACHEMEYER
USGS LCRP 7
TEXACO JACOBS 1
I.I.O. DT 2
I.I.D.
I.I.D.
USGS
CHEV NOWLIN PR1
MAGMA HOLTZ 2
C.B. JACKSON 1
J.D. JACKSON 1
D
R
Y I
E L
A L
R E
D
1962
1975
1975
1945
1974
1972
1975
1975
1962
1975
1961
1962
1951
1958
1961
1961
1961
1961
1974
1972
1974
1974
0
W S
N H
E I
R P
F
N
N
N
N
N
N
F
F
P
P
F
N
W
H
W
F
N
N
N
N
W
A U
T'S
E E
R
U
G
G
G
G
G
Z
U
G
U
U
U
U
U
U
G
G
G
G
W U
E S
L E
L
0
H
H
Z
H
W
H
0
0
H
0
0
Z
T
0
.0
0
0
W
R
H
H
0
I
A
M
•
(IN)
1
8
8
8
4
1
10
1
8
1
1
1
1
8
D
E D
E E
P P
E T
S H
T
(FT)
147
3,000
3,400
7,323
6,000
5, .147
4,000
1,000
162
6,067
162
1,000
7,505
500
162
10
162
27
SlOOO
D C
E A
P S
T E
H D
(FT)
145
3,765
1,000
145
71
260
110
150
8
150
25
3,906
0
E W
P E
T L
H L
(FT)
147
5,107
147
73
330
450
152
10
152
27
4,945
ALTI-
TUDE
OF
LSD
(FT)
-25
-9
-8
-15
-16
10
-4
-4
-15
12
-35
-30
-10
22
20
18
25
25
10
-10
-8
H L
A E
T V
E E
R L
(FT)
11
4
+4
9
9
+2
11
DATE
WELL
MEA-
SURED
2-62
2-62
5-61
10-60
5-61
5-61
5-61
C A
H N
YIELD E A
OF ML
WELL I Y
C S
A E
L S
(GPM)
X
X
X
X
X
90 x
X
X
X
X
X
*see Appendix II for explanation
-------
TABLE 2.15 CHEMICAL ANALYSES OF WATER FROM NONGEOTHERMAL
WELLS IN AND WITHIN 1.6 KM (1 MI) OF HEBER KGRA
MAP NUMBER
Date
Reference
Units
Temp . -C
§H
p.Grav.
Sp . C . -iimho
TDS-sum
Ca
Mg
Na
K
HC03
SO4
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
NO,
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
297
7/62
H
ing/:.
26.7
7.3
16,600|
9,540
362
211
3.020*
-
45
175
5,750
_
—
-
-
-
-
_
-
_
-
-
-
-
-
—
-
-
-
-
-
_
-
•
2
—
-
-
-
3.6
•»
309
7/62
H
mg/1
26.7
7.4
16,100
9,410
376
214
2,920*
-
267
400
5,350
_
—
-
-
-
-
_
-
_
_
-
-
-
-
-
_
-
-
—
-
_
-
_
14
—
-
_
-
17
.
400
1/62
H
mg/1
«.
7.9
11,000
6,980
448
261
1,720*
_
304
1,350
3,040
_
_
_
-
-
-
..
-
_
_
-
-
-
-
-
_
-
-
„ i
-
_
-
_
10
—
-
-
-
6.1
-
401
3/62
H
mg/1
_
7.7
8,350
4,920
175
122
1,480*
_
199
800
2,240
_
_
_
-
-
-
_
_
_
.
-
—
_
•
-
_
-
-
-
-
_
-
_
5
—
-
-
-
6.4
_
403
4/58
H
mg/1
_
7.5
8,500
5,610
253
143
1,541
19
299
1,450
2,040
_
—
_
-
0.05
-
_
_
_
_
—
-
-
-
-
_
-
-
-
-
-
-
_
18
—
-
-
-
15
_
404
1/62
H
mg/1
_
_
-
8,890
5,410
244
161
1,530*
_
257
850
2,490
_
_
_
_
_
_
«
_
..
_
_
_
_
_
_
_
_
_
_
_
_
_
_
11
—
_
_
-
_
_
406
1/62
H
mg/1
-
7.5
-
4,800
3,020
103
48
953*
-
198
538
1,280
_
_
—
-
-
_
w
_
.
—
_
-
_
_
_
_
_
_
_
_
.
_
—
3
_
_
_
-
10
B = Hardt and French, 1976
*Wa + K value
108
-------
(No. 401), is 2,288 m (7,505 ft) deep and contains only 4,920
mg/1 TDS. This is lower than the analyses of well No. 400,
which is perforated from 21.6 to 22.2 m (71 to 73 ft), indi-
cating 6,980 mg/1 TDS. However, increased salinity at this
depth may result from percolation through agriculturally used
soils.
Analyses available for the deeper geothermal fluids indi-
cate a TDS range from 11,800 to 19,000 mg/1. These minima and
maxima for the Heber geothermal fluid both occur in Magma Holtz
No. 1 (No. 304, Table 2.16). The lower value occurred in water
sampled from 1,544 to 1,569 m (5,066 to 5,147 ft) depth in-
terval, and the higher value in water from 1,202 to 1,227 m
(3,945 to 4,026 ft) depth interval. With the limited number of
analyses available it is impossible to tell if this difference
in salt concentration is due to distinctly different waters in
different hydrologic units, to variations in the chemistry of a
"parent" geothermal fluid from related hydrologic units, to well
and aquifer flow conditions, or to contamination. These geo-
thermal waters are mainly sodium chloride in composition, some
with the significant calcium content characteristic of the
Salton Sea geothermal fluid.
The TDS content of all the Heber geothermal fluids is above
the USPHS standards for drinking, irrigation or livestock use so
the concentration of the major constituents will not be dis-
cussed further. The pH range of the geothermal fluids is from
5.8 to 7.1, the lower value being somewhat low for livestock or
irrigation use.
Boron concentrations range from 4.8 mg/1 in C. B. Jackson
No. 1 (No. 503, Table 2.16) to 8 mg/1 in Magma Holtz No. 2 (No.
502, Table 2.16). All the boron concentrations reported for
geothermal wells are above the USPHS irrigation water limits.
Analyses for copper indicate a range from 0.2 mg/1 reported
in Chevron Nowlin No. 1 (No. 500, Table 2.16) to 0.4 mg/1 in
three other Heber geothermal wells. These values are within the
USPHS drinking water standards. Fluoride concentrations are
reported to be from 0.6 to 1.6 mg/1 for Heber geothenual wells,
which are below the USPHS drinking water standards. Iron con-
centrations in Heber geothermal water from 0.9 to 20 mg/1 in
Chevron Nowlin No. 1 (No. 500) and C. B. Jackson No. 1 (No.
503), respectively, are all above the USPHS drinking water
standards. Manganese values from 0.9 to 1.9 mg/1 have been
reported from Heber geothermal water. The USPHS drinking water
standard for manganese is 0.05 mg/1. Zinc concentrations are
reported to be from 0.1 to 0.5 mg/1, which are well within the 5
mg/1 drinking water standard.
The projected total amount of dissolved solids brought to
the surface by geothermal production at Heber is estimated to
109
-------
TABLE 2.16- CHEMICAL ANALYSES OF GEOTHERMAL FLUIDS IN AND
WITHIN 1.6 KM (1 MI) OF HEBER KGRA
MAP NUMBER
Date
Reference
Units
Temp . -C
pH
Sp.Grav.
Sp.C.-|jraho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
N03
Pb
Rb4
Si02
Sr
Zn
Zr
H2S
C02
Others
500
-
G
ppm
_
7.1
—
—
14,100
880
2.4
3,600
360
20
100
9,000
_
0.04
-
-
4.8
-
_
_
-
-
0.2
1.6
0.9
-
6.6
-
-
-
—
-
0.1
I I
120
—
0.68
_
-
—
Ll=4
304b
-
G
ppm
_
-
—
—
13,168
1,062
5.6
5,500
220
-
100
7,420
_
15
-
-
4.1
6
_
_
-
_
0.5
1.7
15
-
4
—
0.9
-
—
-
1.6
_
268
37
0.3
_
-
_
304b
3/72
H
mg/1
_
6.4
-
—
ll,900t
780
30
3,700
230
-
-
6,300
_
-
_
_
_
_
_
_
-
-
-
-
- •
-
3.7
_
-
-
—
-
—
_
98
•
-
_
-
—
502C
6/72
H
mg/1
_
6.4
-
—
12, 800|
860
4.7
3,200
220
-
-
6,500
_
—
—
-
_
-
_
_
-
_
-
—
—
-
3.2
_
—
-
_
-
—
».
75
-
-
—
-
—
502C
-
G
ppm
_
7.4
—
—
16,330
1,062
23
4,720
231
-
148
8,242
_
12
-
_
8
3
_
_
_
_
0.4
1.5
5
-
4.1
_
0.9
-
_
-
0.6
—
187
42
0.1
_
-
_
503
-
G
ppm
* -
5.8
—
—
15,430
891
4.7
4,688
181
-
152
8,320
_
0.5
-
-
4.8
3
_
-
-
-
0.4
0.9
20
-
2.8
_
1.3
-
—
-
0.6
_
267
32
0.4
-
-
-
504
-'
G""~~7j
ppm '
-
6.5
—
••
15,275.
781
3.8
4,563
197
-
150
8,076
_
18
-
-
5.2
3
_
- .-
-:-'• ••
_
0.4
0.6
10
-
3.4
_
1.9
-
-
-
0.9
^
268
36
0.5
_
-
-
tTDS Residue on evaporation at 180°C
G = Geonomics, 1976
hH = Hardt and French, 1976
"170°C Tercp. measured 5/72
163°C Temp, measured 7/72
110
-------
be 37.8 million kg/day (83.3 million Ib/day) (Table 2.7) or 414
billion kg (913 billion Ib) over the anticipated 30 years of
power production, based on an estimated average TDS content of
15,000 mg/1 for the Heber geothermal fluid. This will result
from estimated brine mass production of 2.52 billion kg/day
(5.56 billion Ib/day) (Table 2.6). For chemical constituents
with concentrations of 0.1 ppm or 100 ppm, the daily plant
chemical throughput would be 556 and 556,000 Ibs, respectively
(Table 2.7). It is anticipated, however, that the great major-
ity of these chemical constituents would be injected back into
the hydrologic unit they were removed from, thereby minimizing
pollution or waste disposal problems.
2.3.5 Brawley KGRA
It appears that there is very little, if any, non-geother-
mal ground water use in or near the Brawley KGRA. The shallow
sediments here have very low permeability and the groundwater
generally is too saline for most drinking, irrigation or live-
stock uses. Therefore, the emphasis in this area would be on
maintaining natural groundwater conditions and preventing the
highly saline geothermal brines from escaping to the surface.
There are only seven wells listed in or within the Brawley
KGRA (Table 2.17, Fig. 2.10). Six of these are geothermal,
observation or petroleum exploration wells and only one (No.
147) is listed as being domestically used. The one well that
has reported domestic use is also quite warm (51.4°C [124.5°F])
and is included in the nongeothermal well chemical analysis
table (Table 2.18). This well is about 8 km (5 mi) up-gradient
from the geothermal wells and it would be unlikely that poten-
tial pollutant plumes would extend this far up-gradient.
At the surface, all of these wells penetrate Quaternary
lake deposits. The geothermal wells are located east of the
concealed trace of the Brawley Fault, defined by Meidav, et al.
(1976) and Hill, et al. (1975a), and west of the projection of
the concealed trace of the Fondo Fault, defined by Meidav, et
al. (1976). These geothermal wells probably tap a reservoir
genetically related to part of the complexly faulted Salton
Trough Fault Zone (Geonomics, in press), lying between the
mapped traces of the Fondo and Brawley Faults, but there is not
enough data available yet to substantiate this speculation.
Although the few published groundwater analyses in the
Brawley KGRA area (Table 2.18) show TDS contents from 3,120 mg/1
("thermal" well, No. 147) to 15,200 mg/1 (USGS observation well,
No. 96) it is reported in the geothermal industry that the
geothermal fluid from the Brawley geothermal field will contain
TDS on the order of 85,000 to 100,000 mg/1. This is much more
concentrated than any of the other available analyses and it
would also contain considerably more trace elements. Therefore,
111
-------
TABLE 2.17
DESCRIPTION OF WELLS IN AND WITHIN 1.6 KM (1 MI) OF DUNES, GLAMIS
AND BRAWLEY KGRAS* (modified from Hardt and French, 1976)
HAP
NUM-
BER
DUNES
233
234
235
236
237
239
240
241
242
367"
600
GLAMIS
133
134
135
BRAMLE'
79
92
93
94
95
96
147
STATE NUMBER
1SS/19E-19H01
15S/19E-28N01
15S/19E-33C01
15S/19E-33D01
15S/19E-33G01
15S/19E-33L02
15S/19E-33N01
15S/19E-33R01
15S/19E-33R02
16S/19E-02N01
15S/19E-33L01
13S/17E-35P01
13S/17E-35P02
13S/18E-33A01
1
12S/14E-21J01
13S/14E-09R01
13S/14E-15M01
13S/14E-16P01
13S/14E-21G01
13S/14E-21K01
14S/15E-06B01
OWNER OR NAME
USGS
USGS
USBR 121
USBR 117
USBR 120
USBR 115
USBR 118
USGS
USBR 119
USGS
CDUR DUNES 1
USGS
USGS
A. SMITH
USGS
VEYSEY 11
UNION VEYSEY 1
UNION TOW 1
UNION VEYSEY 2
USGS
N. FIFIELD
D
R
Y I
E L
A L
R E
D
1964
1964
1971
1971
1971
1971
1971
1964
1971
1961
1972
1961
1962
1972
1962
1945
1975
1975
1975
1962
1965
0
U S
N H
E I
R P
F
F
F
F
F
F
F
F
F
F
S
F
F
P
F
N
N
N
N
F
P
U
A U
T S
E E
R
U
U
Z
I
Z
Z
Z
U
Z
U
G
U
U
H
U
N
N
N
U
H
W U
E S
L E
L
0
0
T
T
T
T
T
0
T
0
H
0
T
H
0
P
H
H
H
0
U
D
I
A
M
*
(IN)
1
1
6
8
6
6
6
1
6
1
4
1
8
1
12
12
1
2
D
E D
E E
P P
E T
S H
T
(FT)
177
172
562
563
562
375
542
177
562
142
2,007
142
162
681
152
8,350
8,385
5,921
152
1.290
D C
E A
P S
T E
H D
(FT)
155
153
155
134
340
25
158
520
145
5,200
145
D
E W
P E
T L
H L
(FT)
157
155
157
136
1,918
27
160
680
147
147
ALTI-
TUDE
OF
LSD
(FT)
138
145
155
150
150
142
140
143
143
154
142
110
110
330
-176
-150
-170
-141
-140
-160
-132
U L
A E
T V
E E
R L
(FT)
43
43
41
24
28
35
33
40
7
12
227
0
+8
F
DATE YIELD
WELL OF
MEA- WELL
SURED
(GPM)
3-64
2-64
3-71
2-71
2-71
3-64
3-71
10-61
10-61
3-62
4-72
2-62
5-62
2-62
C A
H N
E A
M L
I Y
C S
A E
L S
X
x
X
X
X
X
X
X
X
X
fsee Appendix II for explanation
-------
TABLE 2.18
CHEMICAL ANALYSES OF WATER FROM NONGEOTHERMAL WELLS IN
AND WITHIN 1.6 KM (1 MI) OF DUNES, GLAMIS AND BRAWLEY
KGRAS
Dunes
Glamis
MAP NUMBER
Date
Reference
Units
367
2/62
H
mg/1
234
1/62
H
mg/1
241
3/64
H
mg/1
133 134 135
10/61 5/62 4/72
H H H
mg/1 mg/1 mg/1
Temp.-C
pB
Sp. Gr av.
Sp.C.-pmho
7.8
41.1
7.8
39.4
8.6
1,170 5,060 3,180
7.8
1,270
7.8
1,150
6.8
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
751
65
22
153*
136
316
102
2,760
143
5.6
885*
94
225
1,410
1,710
111
10
505*
98
233
775
850 709
97 73 79
30 32
144* 121* 1,135
86
163 126
362 300
119 113
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F.
Fe
1.9
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
2.5
sr
Zn
Zr
H2S
C02 3.4
Others
*Na + K value
39
29
16
2.4 0.4
4.1
3.2
(continued)
113
-------
TABLE 2.18 (continued)
Brawley
MAP NUMBER
Date
Reference
Units
Temp . -C
PH
Sp.Grav.
Sp . C . -pmho
TDS-sxim
Ca
Mg
Ma
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hg
Li
Mo
Mn
NH4
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
79
7/62
H
mg/1
25.6
7.4
-
19,800
15,200
810
822
3,400*
-
408
4,050
5,850
-
-
-
—
-
-
-
-
-
-
-
-
-
-
-
-
—
-
-
-
-
-
—
18
—
-
-
-
26
-
96
7/62
H
mg/1
-
7.1
—
16,500
10,300
930
608
1,990*
-
294
1,250
5,400
—
—
-
—
-
-
-
-
-
-
-
-
-
-
-
-
—
-
—
-
—
-
—
15
-
-
-
-
37
-
147
12/70
H
mg/1
51.4
8.4
-
5,550
3,120
40
15
1,200
6.9
420
310
1,300
-
-
-
-
2
-
-
•• *
-
-
-
1
0.32
-
0.23
-
-
3.2
-
-
-
-
-
30
1.2
-
-
-
c17
W
*Na •*• K value
(continued)
114
-------
TABLE 2.18 (continued)
FOOTNOTES
and French, 1976
The following radioactivity measurements are from O'Connell
and Kaufmann, 1976. Sampling data are not specified.
222Rn=1100 ±55 pCi/1
226Ra=0.85 ±0.14 pCi/1
GThe following radioactivity measurements are from O'Connell
and Kaufmann, 1976. Sampling data are not specified.
222Rn=300 ± 35 pCi/1
226Ra=0.37 ± 0.095 pCi/1
234 U=0.30 ±0.07 pCi/1
248 U=0.18 ±0.05 pCi/1
230Th=0.64 ±0.23 pCi/1
232Th=<0.10 pCi/1
115
-------
it would be misleading to discuss the one "thermal" fluid anal-
ysis we have in the Brawley area as representative of the Braw-
ley geothermal fluid. It would be much more realistic to say
that it will be a highly saline brine, probably similar in
character to the Salton Sea geothermal fluid, with many trace
element concentrations exceeding USPHS drinking, irrigation and
livestock standards and it would be harmful for this fluid to
escape into the ground or surface water systems of Imperial
Valley.
The Brawley geothermal field lies along the approximate
location of a northerly trending rise in groundwater salinity
discussed by Geonomics (in press). Shallow groundwater along
this trend would be expected to have much higher salinities than
shallow groundwater to the east, and somewhat higher than in
areas to the west.
The two available shallow groundwater analyses have chem-
ical characteristics similar to those of Salton Sea water, but
less concentrated. Well No. 96, a USGS observation well located
in the south-central part of the Brawley KGRA (Fig. 2.10), with
a 44.2 to 44.8 m (145 to 147 ft) perforated interval, has a TDS
content of 10,300 mg/1. The proportions of the major constit-
uents show this to be a sodium chloride water with notable
quantities of calcium, sulfate and magnesium. These character-
istics suggest a possible mixing of a sodium chloride calcium
Salton Sea geothermal fluid with the sodium chloride sulfate
magnesium groundwater commonly found south of the Salton Sea.
Groundwater from well No. 79, a* USGS observation well located
just north of the Brawley KGRA (Fig. 2.10), has a TDS content of
15,200 mg/1 and is typical of the sodium chloride sulfate mag-
nesium groundwater just mentioned. This well is also per-
forated between 44.2 and 44.8 m (145 to 147 ft). No trace ele-
ment data are available for the observation wells.
The total daily brine mass estimated to be produced uti-
lizing Brawley's full geothermal capacity, estimated at 330 MWe
for 30 years, will be 68 million kg/day ( 150 million Ib/day)
(Table 2.6). For a chemical constituent with a concentration of
1 ppm, 680 kg (1,500 Ib) day will be produced; for a concen-
tration of 1,000 ppm, 680,000 kg/day (1.5 million Ib/day) will
be produced. Most of these quantities will, however, be inject-
ed back into the producing aquifer.
2.3.6 Dunes and G lam is KGRAs
The water pollution discussion for the Dunes and Glamis
areas will be limited due to: 1) the virtually nonexistent
groundwater use, 2) the lack of groundwater data, and 3) the
previously discussed extremely low probability of geothermal
development in these areas.
116
-------
Dunes KGRA—
There are currently ten wells located in the Dunes KGRA
(Table 2.17, Fig. 2.9). Nine are test or observation wells and
the remaining one is a geothermal test hole. There is no known
groundwater use in this area.
The Dunes wells are drilled on both sides of the contact
between Quaternary alluvium, on the western side of the San
Andreas Fault and Quaternary windblown sand east of the San And-
reas Fault. Minor occurrences of Quaternary lake deposits appear
along this contact. The wells are clustered near the inter-
section of an unnamed fault and the trace of the San Andreas Fault.
The unnamed trace trends northwest-southeast, and is about 30 km
(19 mi) (Loeltz, et al. 1975).
Shallow groundwater flows northwesterly through the Dunes
geothermal area, but shallow groundwater levels have increased
significantly in this area since operation of the Coachella
Canal, beginning in the 1940s. (See discussion in economics, in
press).
Three chemical analyses for the Dunes CDWR No. 1 geothermal
test well are shown in Table 2.19 (Nos. 600A, B and C) and
analyses for three nongeothermal wells are shown on Table 2.18.
The TDS concentrations from different perforated intervals in
the geothermal well range from 1,410 to 2,530 mg/1 and from 751
to 2,760 mg/1 in the nongeothermal wells. It should be noted
that the geothermal samples may not be representative of the
geothermal fluid in the reservoir since these were all bailed
samples. If we accept the samples then we may note salinity
decreasing with depth for the geothermal well: from 2,530 mg/1
in a 117 m (384 ft) sample to 1,410 mg/1 in a 575 m (1,886 ft)
sample. This water has relatively low salinity compared to
other Imperial Valley geothermal waters and, in fact, is less
saline than much of the natural groundwater in the valley.
These are sodium chloride waters with high sulfate content
suggestive of mixing with other waters or of Colorado River
water reacting with subsurface sediments. The geothermal sample
from 575 m (1,886 ft) depth (No. 600C) is within 2 km (1.2 mi)
of the Coachella Canal and has chemical characteristics similar
to evaporated Colorado River water.
The proportions of the major chemical constituents appar-
ently change more significantly than the change in TDS contents.
Shallow groundwater samples No. 234 and 241 are basically
sodium chloride waters with some calcium and sulfate. These
samples are probably more representative of natural groundwater
character than sample No. 367 directly beneath the Coachella
Canal, which contains 751 mg/1 TDS and has the very high sulfate
with high sodium, chloride, calcium and bicarbonate water char-
acteristic of the Colorado River.
117
-------
TABLE 2.19
CHEMICAL ANALYSES OF GEOTHERMAL FLUIDS
IN AND WITHIN 1.6 KM (1 MI) OF DUNES
KGRA
MAP NUMBER
Date
Reference
Units
Temp.-C
pH
sp.Grav.
Sp.C.-pmho
TDS-sum
Ca
Mg
Na
K
HC03
S04
Cl
Ag
Al
Ar
As
B
Ba
Br
Cd
Cs
Co
Cu
F
Fe
Hff
\j
Ll
Mo
Mn
NE»
Ni
N03
Pb
P04
Rb
Si02
Sr
Zn
Zr
H2S
C02
Others
600CT
CC
ppm
88
8.4
—
1,410
201
6.1
206
23
-
416
188
_
-
-
0
0.6
0.3
0.66
0
-
-
0.07
1.4
O.J.6
0.13
-
0
-
0
-
0.04
-
—
19
—
0.6
-
•-
-
1=0.021
600B
CC
ppm
92
—
—
2,190
23
3
686
94
-
675
570
_
-
-
0
1.2
0.2
3
0
*
-
0.12
10
0.05
0.32
-
0
-
0
-
0.05
-
-
1.9
-
0.22
-
-
-
1=0.019
. 600Ad
CC
ppm
92
8.5
—
2,530
37
9.4
800
84
-
605
854
_
-
-
0.01
1.9
0.2
2
0
-
—
0.15
8
0.12
0.53
-
0
-
0
-
0.11
-
-
29
-
0.09
-
-
—
1=0.023
(continued)
118
-------
TABLE 2.19 (continued)
FOOTNOTES
aCC = Coplen, et al. (1973)
Perforation interval 572-584 m (1,876-1,916 ft) bailed from 575 m
(1,886 ft)
Perforation interval 259-271 m (850-872 ft) bailed from 276 m
(905 ft)
Perforation interval 104-116 m (341-380 ft) bailed from 117 m
(384 ft)
119
-------
No estimates of potential quantities of pollutant produc-
tion have been made for the Dunes KGRA since geothermal devel-
opment is not currently foreseen.
Glamis KGRA—
Onlythree wells are listed in the Glamis KGRA (Table
2.17), and none are geothermal wells. Two of these are USGS
test (No. 134) and observation (No. 133) wells in the western
part of the designated KGRA, near the Coachella Canal, and one
is a domestic well (No. 135) located in the dastern portion of
the KGRA. The USGS wells penetrate Quaternary alluvium at the
surface and are just west of the trace of the San Andreas Fault.
They are perforated in the shallower hydrologic unit between 47
and 48 m (154 and 157 ft) and between 48 and 49 m (157 and
161 ft), respectively. The domestic well is located on Quater-
nary alluvium in an area traversed by three mapped traces of the
Sand Hills - Algodones Fault (Loeltz, et al. 1975; Jennings,
1967; Jennings, 1975). This well perforates the intermediate
depth hydrologic unit from 158 to 207 m (520 to 680 ft).
The two shallower USGS wells are drilled essentially be-
neath the Coachella Canal; the water from these wells is almost
pure Colorado River water, probably derived from downward perco-
lation from the canal. These waters have the high proportion of
sulfate characteristic of Colorado River water and TDS contents
of 850 and 709 mg/1, respectively.
The TDS content is not available for the domestic well, but
it has a sodium plus potassium content of 1,211 mg/1, which is
about ten times the amount in the lower salinity well mentioned
above. No trace element analyses are available for any of the
well water. So it seems that the two USGS wells have water
suitable for drinking or other uses, but it is probably more
representative of Coachella Canal water than natural ground-
water. The high sodium plus potassium content of the domestic
well suggests that this water will not be suitable for drinking
or irrigation use.
Groundwater elevation contours (Loeltz, et al. 1975)
indicate that groundwater flows northwest through the Glamis
KGRA towards the Salton Sea.
2.4 SEISMICITY
A potentially significant subsurface environmental effect
of geothermal development is seismicity induced by fluid ex-
traction and withdrawal. Currently the Imperial Valley is among
the most seismically active areas in the United States. This
naturally occurring high level of macro- and micro-seismicity
makes it difficult to differentiate from seismicity potentially
induced by extraction and injection of geothermal fluids.
120
-------
Presently, extensive and exhaustive baseline seismicity data
must be collected prior to development to provide a detailed
basis for comparison of pre- and post-development seismic ac-
tivity. To this end, the following discussion will outline
historical seismicity, seismic risk, ongoing programs that are
currently collecting baseline seismicity data, and potential
induced seismicity for Imperial Valley.
2.4.1 Summary of Baseline Seismicity and Seismic Risk
The Salton Trough in general, and the Imperial Valley in
particular, are characterized by a high level of seismic ac-
tivity and a large amount of strain release. Seismicity within
Imperial Valley is characterized by both swarm activity and main
shock-aftershock sequences (Hileman, et al. 1973; Richter,
1958). Richter reports that 12 earthquakes of magnitude 6 or
greater have occurred in the Salton Trough since 1900, and nine
earthquakes greater than magnitude 6.7 have occurred since 1850.
High levels of microseismic activity have been recorded in the
Salton Sea, Brawley and East Mesa KGRAs (Hill, et al. 1975a).
The geographic distribution of instrumentally recorded
earthquakes from 1932 through 1975 shows the density of epi-
centers to be much greater in the western part of the valley,
especially along the San Jacinto Fault Zone. A minimal number
of epicenters are located along the San Andreas Fault Zone in
the eastern part of the valley, (see Geonomics, in press, Plate
2.10). Although earthquakes are generally correlated with
faults, this is not apparent from the distribution of these
historic macroseismic events. The apparent scatter in epicenter
locations is probably due to inaccurate epicenter locations,
currently unidentified fault trace locations, possibly dipping
fault planes, arid the fact that much strain may be released
through fault creep.
Earthquakes occurring in the San Andreas Fault System
typically have focal depths of 5 to 8 km (3 to 5 mi) , which
is the basement-sediment interface. A limiting depth for hypo-
centers in southern California is about 12 to 15 km (7 to 9
mi), but in geothermal areas of Imperial Valley this limiting
depth is about 8 km (5 mi), due to higher geothermal tempera-
tures closer to the surface which allow plastic, as opposed to
brittle, deformation (Johnson and Hadley, 1976).
Microseismic activity in the valley has been documented on
several occasions (e.g., Hill, et al. 1975a, 1975b; Sharp, 1976;
Johnson and Hadley, 1976; Combs and Hadley, 1977). In most
cases the locations of these microseismic events are accurate
enough to define fault traces correlated with the activity.
A microseismic net was operating for five weeks during the
summer of 1973 in the East Mesa KGRA in order to establish back-
121
-------
ro
to
/*MollvHI. * ~" " """"1
/ <>,„',.,*, . !
EXPLANATION "
O FOCiL DEPTH 0-BOOO FEET
FOCAL DEPTH 8000-12000 FEET
O FOCAL DEPTH BELOW IZOOO FEET
RECORDING STATION-USgfllTEUPORART SEISMIC NET)
8 RECORDING STATION-USGS (PERMANENT SEISMIC NET)
ZONE OF MICROEARTHOUAKE ACTIVITY
• GEOTHERUAl WELL-USSR
OUTLINE OF EAST
MESA KGRA |
4000 0 4000
1000 0 1000 3000nwt«rt
|
Figure 2.11 Microearthquake epicenters recorded in East Mesa, June 10
to July 15, 1973 (U.S. Bureau of Reclamation, 1974)
-------
ground seismicity prior to geothermal power development (Combs
and Hadley, 1977). The recording station and epicenter loca-
tions from this survey are shown in Fig. 2.11. This study
established that the occurrence of microseismic events is not
constant with time. On the majority of days, only one or two
locatable events occurred; while two-to three-day swarms of up
to 100 distinct local events per day occurred twice during this
recording period. Additionally, hundreds of smaller events
(nanoearthquakes), some clustered in swarms, were recorded by
each seismograph. More than half the events had focal depths
between the approximate depths to basement of 4 km and 8 km (2.5
to 5 mi).
Epicenters located from the USGS-Cal Tech seismograph
network during the period between June 1973 and May 1974 are
shown in Fig. 2.12 (Hill, et al. 1975a). This figure shows the
location of all events recorded at four or more stations in the
net. Although many magnitude 1 earthquakes are included, cover-
age is only considered complete for events of magnitude 2 or
greater, due to the high seismic noise levels in the cultivated
areas of the valley.
This survey shows a linear seismicity trend in the central
part of thej valley, along the Imperial and Brawley Faults.
Marked concentrations of events occurred along the Imperial
Fault, directly east of El Centre, and in the north and south
portions of the Brawley geothermal field. Smaller concentra-
tions occurred near Obsidian Buttes, on the western portion of
the Salton Sea geothermal field, and along the San Jacinto Fault
Zone. Most of the events in this study occurred in four swarjns
between June 20 and July 17, 1973; otherwise, the seismic ac-
tivity developed in a fairly uniform manner (Hill, et al.
1975a).
Another example of swarm activity in Imperial Valley is
reported by Johnson and Hadley (1976) from January 23 to 31,
1975 in the Brawley area (Fig. 2.13). The swarm was most in-
tense for four days, with 75 events of 3.0 to 4.7 local magni-
tude along a 12 km (7.5 mi) zone. Hypocenters were located for
264 earthquakes with local magnitudes greater than or equal to
1.5. Basement depth here is about 6 km (3.7 mi), and hypo-
central depths ranged from 4 to 8 km (2.5 to 5 mi), as Combs and
Hadley (1977) found in East Mesa.
A swarm of over 400 earthquakes occurred near Calipatria
from November 3 to 8, 1976 (Porcella and Nielson, 1977). Seven
events of local magnitude equal to or greater than 4.0 occurred
within an eight-and-a-half-hour period on November 4, 1976 (Fig.
2.14). These earthquakes, as well as two local magnitude 3.8
and 3.9 events on April 26 and 14, 1976, respectively, were
reported in reference to the national strong motion accelero-
graph network. The strong motion accelerograph network program
123
-------
33°45'
32°I5'-
A USGS STATION
A CAL TECH STATION
MAGNITUDE KEY
O 3.5-45
O 25-35
* 15-25
« 0.5-15
<0.5
0~ 10 20 30 (km)
3 • •
0 5 10 15
K6RA SYMBOLS
B - BRAWLEY KGRA
D DUNES KGRA
E EAST MESA KGRA
6 GLAMIS KGRA
H HEBER KGRA
8 SALTON SEA KGRA
—'MEXICO
II4°45'
Figure 2.12 Location of seismograph stations and earthquake
epicenters in the Imperial Valley, June 1, 1973-
May 31, 1974 (Hill, et al. 1975a)
124
-------
33°00'
Tl5°34' 32' 30' 28' 26' II5°24'
(See Fig. 2.15 for location and explanation)
Figure 2.13 Epicenters of earthquakes of the Brawley swarm,
January, 1975 (Johnson and Hadley, 1976)
125
-------
EXPLANATION
• Accelerogroph with verticol storter
A Accelerogroph with horizontal storter
-l with verticol and horizontal
storter •
picenter
WILDLIFE
REFUGE
12 KILOMETERS
MILES
CALIPATRIA^-/
7 EVENTS
-4-76
OVER 400 EVENTS
NEARjCALIPATRIA
l»/3 TO 11/8/76
WESTMORELAND
SUPERSTITION
MOUNTAIN
PARACHUTE
TEST FACILITY
BRAWLEY
FAULT -N0.3
Meadows
Union
Imperial County
Services Buildin
IMPERIAL
FAULT
USA
MEXICO
Figure 2.14 Strong-motion stations and epicenters in the Imperial
Valley area (Porcella and Nielsen, 1977)
126
-------
provides critical information on ground response that is applied
to the development of earthquake-resistant engineering design.
Microseismic Monitoring Networks—
USGS, in cooperation with Cal Tech, established a regional
18-station telemetered seismograph network in 1973 in Imperial
Valley (Hill, et al. 1975a). This network was specifically set
up to record earthquakes related to geothermal phenomena. The
location of these stations is shown by triangles in Fig. 2.15.
In October, 1976 the USGS installed six seismometers in the
Salton Sea geothermal field region in conjunction with the
ERDA/LLL Imperial Valley Environmental Project (Phelps and
Anspaugh, 1976). These seismometers will also be incorporated
into the USGS telemetered network. Their locations are shown by
black circles in Fig. 2.15.
Chevron Oil Company has established a closely spaced seis-
mic net in the Heber area to gather background baseline seismi-
city data and to detect potential seismicity induced by geo-
thermal production.
Although not a microseismic monitoring network, an exten-
sive array of 24 strong motion accelerograph stations has been
established in Imperial Valley (Fig. 2.14). These stations will
hopefuly provide additional information on many of the larger
microseismic events. This dense array is operated jointly by
USGS, the California Division of Mines and Geology, and Cal Tech
to fulfill such specific research needs as source-mechanism and
ground-motion attenuation studies (Porcella and Nielson, 1977).
A general discussion on seismic risk in Imperial Valley is
presented in Geonomics (in press). This discussion concludes
that once it has been established that a region, such as the
Salton Trough, has had or will have large earthquakes, then
ground condition and structural design at a specific site are as
critical as the exact magnitude or location of an anticipated
earthquake. So, although recurrence statistics show that Imper-
ial Valley should experience a magnitude 7 earthquake about once
every thousand years, and 12 earthquakes of magnitude 6 or
greater have occurred since 1900, seismic risk must be evaluated
on a detailed site and structure-specific basis.
2.4.2 Potential Induced Seismicity
A general discussion of the relationship between earth-
quakes and geothermal activity is presented in Geonomics (in
press). This discussion notes that geothermal activity is often
associated with naturally high seismicity levels, and that fluid
withdrawal associated with geothermal production, with or with-
out injection, may trigger local seismic activity.
127
-------
33°30'
33°00
32°30'
Banning-Mission Creek Fault
0 10 20 km
A COT
5 10
mi
Index map
AAMS
A WL K
>GLA
A ING
A RUN
SGLA U.S.A.,, .
___________ MEXICO
PIT
BnN ABCK _____ -i
_rfSH --------
116000'
115°30' 115°00'
EXPLANATION
114°30'
A USGS regional telemetered network, seismograph
stations and identifying codes.
• ERDA/LLL seismograph stations added to USGS
regional telemetered network in October, 1976.
(Three additional Cal Tech stations shown on Figure 2.12.)
Location of area shown in Fig. 2.13
L..
Figure 2.15 Seismograph networks in Imperial Valley (Crow, 1976)
128
-------
The currently producing geothermal field, The Geysers, in
northern California, is associated with a much higher level of
microseismicity than the. surrounding area (Bufe, et al. 1976).
However, the pre-production microseismicity rate is not known,
so it cannot be determined if these earthquakes are a result of
the geothermal production or of natural geothermal activity. It
is anticipated that this after-the-fact lack of information will
be avoided in Imperial Valley due to the extensive microseismic
monitoring nets discussed in the previous subsection.
Although there are no empirical geothermal production-
induced seismicity data currently available for Imperial Valley,
Biehler and Lee (1977) discuss a theoretical evaluation of
earthquake potential induced by geothermal energy extraction in
Imperial Valley. This evaluation estimates that the seismicity
rate will be 6.5 times the current historic rate for 1000 MWe
power production and 2 times for a 100 MWe production. This
estimate is based on many approximations and assumptions. The
basis for the calculations is that extraction of fluid from a
geothermal reservoir will induce volumetric contraction and
thermal stress. Thermal contraction is used to calculate the
seismic moment and the temperature change is coupled to the
power production rate. The induced thermal stress will be added
to the existing tectonic stress. Energy extraction can be
related to thermally induced stress drops, which can thereby be
related to magnitude. It is estimated that a 100 MWe plant will
generate a 4.4 maximum magnitude earthquake per year, or if the
stress were accumulated, one 5.4 maximum magnitude earthquake
per 30 years.
Biehler and Lee (1977) further state that earthquakes may
be induced by mechanisms other than the thermal contraction
process which they describe, and that "induced seismic hazards
are perhaps greater for higher rates of fluid injection or
withdrawal than for low flow rates." It is recommended that the
original report be consulted for the working details of the
estimates.
2.5 SUBSIDENCE
Differential ground subsidence in Imperial Valley would
have extremely significant environmental impact, particularly by
disrupting the vast networks of gravity-flow irrigation canals
which support the valley's agriculture and economy. Ground
subsidence has been noted in other geothermal fields (Stilwell,
et al. 1975) as well as in areas of oil, water or gas withdrawal
and injection (Poland and Davis, 1969). Surface movement may
also be caused by natural geologic processes, such as faulting,
fault creep or other tectonic forces, induced hydraulic gra-
dients, thermal changes or landslides; or by other agricultural
or industrial processes; or by geothermal fluid withdrawal and/
129
-------
or injection. A subsidence detection committee was formed in the
Imperial Valley to study subsidence in connection with agricul-
tural operations, but the county surveyor's office knew of no
localized subsidence caused by agricultural operations.
Since Imperial Valley is one of the most tectonically
active areas in the United States (Elders, et al. 1972), and
does exhibit natural tectonic subsidence, one of the major
objectives of a subsidence monitoring program in Imperial Valley
will be to distinguish between ground movement caused by geo-
logic processes and by geothermal power development. This will
require years of baseline monitoring data collection and anal-
ysis. To this end, regional and local horizontal and vertical
control networks, as well as tiltmeters and extensometers, have
been installed in Imperial Valley to monitor pre-geothermal pro-
duction baseline conditions, that is, naturally occurring hori-
zontal and vertical ground movement. Periodic resurveys of these
networks will provide data to calculate the changes that occur.
Much additional work has been done since Lofgren (1974) and
Crow (1976) published papers describing the subsidence monitor-
ing program in Imperial Valley. Although the program is basi-
cally the same as that described by Lofgren (1974), it has been
considerably expanded. The existing network was releveled in
the spring of 1977 and the data is currently being processed by
the National Geodetic Survey in Rockville, Maryland. The USGS
is planning to release an open file report in the fall of 1977
presenting the results of this current•leveling survey, a dis-
cussion of the currently monitored horizontal and vertical
control networks, the expansion of the networks since 1974, and
planned expansion of the current program (B. Lofgren, 1977,
pers. comm.). It is expected that this upcoming USGS open file
report will considerably update the following discussion which
is based largely on Lofgren (1974) and Crow (1976).
2.5.1 Baseline Data and Monitoring Programs
Triangulation and leveling data for the period 1934 to 1967
show complex horizontal motion and subsidence in Imperial Valley
(Fig. 2.16). The northern and central parts of the valley show
the greatest subsidence and the highest rate of downward move-
ment has occurred around Brawley. The maximum subsidence
of 1.5 to 3.0 cm (0.6 to 1.2 in.) may be related to the large
number of recent earthquakes (Hill, et al. 1975), and the high
strain rate on the Brawley and Imperial Faults (Elders, et al.
1972; Johnson and Hadley, 1976).
Chevron Oil Company has conducted a level survey in the
Heber area which suggests a slight upward movement relative to
El Centro, but the major portion of movement has been the more
regional downward tilting northward and eastward, as discussed
in the following section on vertical control networks.
130
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CHANGES IN ELEVATION 1931 - 1941
DATUM FOR ELEVATION CHANGE
CHANGE OF ELEVATION IN CM.
UP -DOWN
PROGRESSION OF POSITION VECTORS
1934 - 4 I
1941 -54
1954 - 67
O IH
VECTOR SCALE
BASE LINE
As FIXED STATION
A MOVING STATION
Figure 2.16 Geodetic measurement in the Imperial Valley from 1934 to 1967
(Elders, et al. 1972)
-------
Presently, the USGS, the U.S. National Geodetic Survey, and
the Imperial County surveyor are cooperating in the operation of
the Imperial Valley subsidence monitoring networks. The Imper-
ial Valley Environmental Project of LLL is conducting a survey
of subsidence monitoring in Imperial Valley and is attempting to
work with existing agency programs. They will establish second
order leveling nets in the Salton Sea geothermal field area, the
Coachella Canal northeast of the Salton Sea, the Brawley KGRA
and the Heber geothermal field area, and will establish a hori-
zontal control trilateration network in the Salton Sea geother-
mal area. (Crow, 1976). The proposed locations of the addi-
tional stations for the LLL second-order level net in the Salton
Sea area are shown in Fig. 2.17.
Existing subsidence monitoring networks are divided into
three categories for the following discussion: 1) horizontal
control networks, 2) vertical control networks, and 3) other
measurement programs. Networks of both regional and local
extent have been established. The vertical network consists of
first- and second—order level lines, allowing maximum vertical
errors, in mm, of 4.0 RX and 8.4 R! respectively, where Rt is
the distance surveyed, in kilometers. The regional horizontal
network is capable of accuracies of 1 in 107 units, while the
local networks are capable of accuracies of 2 in 106 units. The
other measurement programs include sensitive local arrays of
tiltmeters and extensometers. In addition, developers of geo-
thermal wells are required by state and county ordinance to
install several benchmarks near each well and to periodically
resurvey and tie them into the first- or second-order level
lines, in order to detect subsidence that may be related to
geothermal production.
Vertical Control Network—
A regional network of first- and second-order leveling lines
has been established in Imperial Valley (Fig. 2.18). There are
north-south trending and east-west trending first—order level
lines. The second-order lines are somewhat more ubiquitous and
are distributed more irregularly throughout the valley. These
lines have been surveyed several times prior to 1971, producing
indications of significant tectonic movement.
The first-order lines (Fig. 2.18) were releveled in the
winter of 1971-72 by the National Geodetic Survey and this
survey was established as the reference datum. The second-order
lines were established and tied into the first—order net by
other agencies under the direction of the National Geodetic
Survey.
A resurvey of the first- and second-order nets in 1973-74
showed the two-year change in elevations (Fig. 2.18). For this
survey a bedrock tie west of El Centre was considered stable.
132
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SALTON SEA
''Ov^~~- •
X W XX
SCE site
0 X - X
3 Km
•Approximate location of Imperial County first- and second-order bench marks.
o Approximate location of company second-order bench marks.
x Approximate location of additional ERDA/LLL second-order bench toarks.
Figure 2.17 Local leveling network in Salton Sea geothermal field
(Crow, 1976)
133
-------
Riverslde County
115°
H
U)
Imperial County
1st Order
2nd Order
-6 2-yr change, cm
SALTON SEA
5 10 miles
i
15 15 km N
-2 Holtville
-1-5 El Centro
I
Calexico
Mexico
Figure 2.18 Regional first- and second-order level network and
vertical movement in Imperial Valley 1972-1974
(Lofgren, 1974, redrafted by Crow, 1976)
Canal
-------
This vertical control data shows a definite northward-down
tilting of 13 cm (5 in.) in the 85 km (53 mi) north-south length
of the survey, with benchmarks near Calexico and the bedrock tie
east of El Centre showing little or no change in this two-year
period. The east-west pattern of elevation changes is not as
distinct. They show the center of the valley dropping about 20
mm (0.79 in.) with respect to the mountains on the east and west
margins.
Local level networks are being monitored by developers in
the Salton Sea, East Mesa and Heber areas to detect subsidence
that may accompany geothermal production.
Two continuous (water level) stage recorders were installed
at strategic locations near the southern shore of the Salton Sea
to. enable correlation of water-level fluctuations with two con-
tinuous stage recorders of long record on the western shore.
These correlations may enable detection of elevation changes
occurring on the southern margin of the Salton Sea, although
they probably would not allow distinction between elevation
changes due to tectonic readjustments or to geothermal develop-
ment. Each of these stage gauges is tied into the valley-wide
vertical control network and will be able to detect elevation
changes of less than 1 cm (2.5 in.) around the southern margin
of the sea.
Horizontal Control Network—
Thereare both regional and local horizontal control net-
works in Imperial Valley. The regional network of horizontal
control (Fig. 2.19) is an extremely precise trilateration net
consisting of 18 benchmarks spanning the valley. This net is
intended to measure regional tectonic movement, while the local
arrays of precise distance measurements at Salton Sea (Fig.
2.20), East Mesa (Fig. 2.21) and Heber are intended for de-
tection of ground movement induced by geothermal development.
However, the control lines in the local arrays do extend across
structural zones where tectonic movement might occur. In fact,
as much as 5 mm/yr (0.2 in.) of right lateral horizontal tec-
tonic movement has been detected in the Obsidian Buttes area, on
the southeast shore of the Salton Sea, along the Brawley Fault.
Although a number of geothermal wells have been drilled in this
area, the tectonic movement predates the drilling.
Distance measurements are being made at arrays in the
Salton Sea (Fig. 2.20), East Mesa (Fig. 2.21) and Heber areas by
the USGS. They can detect distance changes of only a few mil-
limeters along these controlled lines using electronic distance
measuring equipment. This is a relatively inexpensive technique
and enables the collection of potentially useful extra measure-
ments. This technique has been more successful at the Salton
Sea area, where elevated reference points are available, enabl-
ing long line-of-sight controls, than at the flatter East Mesa
and Heber areas.
135
-------
116
Riverside County_
Imperial County
115'
lOtmi
16km
\ %\ \N-
\ N \A \ Xl
k. \U«1 4-willp»^'..\ 1 X !
33 w-
Fault
Dashed where approximate:
dotted where concealed
Probable extension of
Brawley Fault
£
Bench mark
Figure.2.19 Regional network of horizontal control
(Lofgren, 1974, redrafted by Crow, 1976)
136
-------
11535
Rock
Hill
ROCK i
Obsidian/32
Butte _
g
BUTTE
i4-Magma max/Magma max
No. 2^>C No. 3 '
County bench mark
Private bench mark O
Geological Survey nail
Horizontal distance
Geothermal well
Geological survey bench mark
National Geodetic Survey -
Geological Survey bench mark
11/20 1 km
Figure 2.20 Network of horizontal control in Salton Sea
geothermal field (Lofgren, 1974, redrafted
by Crow, 1976)
137
-------
R.16 E..R.17 E.
CO
00
EXPLANATION
PRODUCTION WELL
INJECTION WELL
TILTMETER
EXTENSOMETER
HORIZONTAL CONTROL
Figure 2.21 Ground motion detection instrumentation installed at
East Mesa geothermal area (Lofgren, 1974)
-------
Other Measurement Programs—
Tiltmeters and extensometers have been installed in the
East Mesa area (Fig. 2.21) to aid in defining precisely the
mechanism of the ground motion associated with geothermal sub-
sidence. This will aid in distinguishing between subsidence due
to geothermal fluid withdrawal and injection and potential
subsidence due to ground water pumping or other mechanisms. The
extensometers are being installed in several locations where
shallow groundwater is being pumped close to geothermal devel-
opments. Two mid-depth extensometers to monitor changes in
water levels and compaction in the upper 350 and 430 m (1,150
and 1,400 ft), respectively, of alluvial deposits, are located
between the geothermal development and nearby farmlands. These
extensometers will help differentiate between deep compaction
caused by geothermal production and shallow compaction due to
shallow groundwater withdrawal. The tiltmeters will help deter-
mine whether the ground deforms as a stressed beam, develops
vertical shear planes with geothermal subsidence, or perhaps
deforms with some combination of the two mechanisms. Two sensi-
tive tiltmeters installed at East Mesa (Fig. 2.21), in 3 m (10
ft) pits in order to minimize thermal interferences, are located
between four production wells and one injection well.
2.5.2 Potential Subsidence
The degree of land subsidence resulting from geothermal
development in Imperial Valley can only be conjectured at this
time. Since it is anticipated that the spent geothermal fluid
will be injected, subsidence due to brine production will prob-
ably be quite small, not larger than ground motion due to nat-
ural tectonism. However, since differential subsidence can
wreak havoc with the gravity-flow irrigation canals, detailed
analyses of this potential problem must be conducted prior to
and during production.
Geonomics (1976a) provided a preliminary estimate of sub-
sidence for geothermal development of the Heber reservoir. This
report concludes that land surface elevation changes can be
caused by changing reservoir fluid pressures, which are in turn
affected by fluid withdrawal and injection. Studies conducted
in the Wilmington Oil Field, Long Beach, California have suc-
cessfully projected subsidence rates based on the relation
between benchmark elevation changes, net fluid withdrawal and
reservoir pressure differences. However, this technique re-
quires data collected during actual production, and reliable
estimates of future subsidence at Heber or other reservoirs
cannot be made until such data are obtained.
The next best approximation of future subsidence may be
made using computer models. However, it is a considerable
problem to choose physical parameters that properly represent
the reservoir. Many of these parameters, such as the elastic
139
-------
properties of the reservoir rock, distribution of in situ
stresses, etc., are not known for the Imperial Valley geothermal
reservoirs. However, preliminary results from a Chevron Oil
Company computer model of the Heber reservoir suggest that
subsidence due to production at Heber should pose no serious
problem (Lloyd Mann, 1976, pers. comm.)
A rough estimate of possible subsidence at Heber, based on
a method discussed by Geertsma (1973) and by Raghaven and Miller
(1975), has been made by economics (1976a). It should be noted
that this is a very crude estimate and that the method does not
account for temporal drawdown pressure variations or for any
time lag in subsidence. The calculations were based on the
following simplifying assumptions:
a) fluid production rate equals fluid injection rate
b) fixed overburden pressure
c) reservoir pressure drop of 6.8 to 20.4 atm (100 to 300
psia) around the well bores for a 200 MWe plant
d) average pressure drop for entire reservoir less than
6.8 atm (100 psia)
e) reservoir thickness of 734 m (2,408 ft)
f) a cylindrical disc shaped reservoir
g) Poissons1 ratio of 0.2 for reservoir
h) the reservoir is isolated by an impermeable boundary
i) fluid withdrawal takes place from a circular array of
wells; injection takes place through a concentric,
outer, circular array of wells (S.K. Sanyal, 1977,
pers. comm.)
The parameters used in the compaction and subsidence cal-
culations are gross estimates and the assumed reservoir was
idealized so the resulting "average" subsidence estimate of
-0.21 m (-0.7 ft) during the estimated 30-year production life
of Heber reservoir can only be considered as an "order-of-magni-
tude" estimate. It is believed that this is a conservative
estimate and that the true "average" value will probably be
less, but subsidence is expected to be greater around the pro-
ducing wells.
140
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2.6 POLLUTION CONTROL TECHNOLOGY
2.6.1 Current Practices
There are several geothermal injection wells in Imperial
Valley for the purpose of waste disposal. Reinjaction has been
tested in several KGRAs in Imperial Valley which include Heber,
East Mesa and Salton Sea. In Heber, successful reinjection for
over one year has been recently carried out by Chevron Oil
Company through Holtz No. 2 well. In East Mesa, well No. 5-1
has been used by USER for injection of geothermal water during
recent years. During 1964-1965, Union Oil Company carried out a
successful reinjection test in the Salton Sea field. During the
test period about 480 million liters (126 million gallons) of
water were reinjected at the rate of 2,270 1pm (600 gpm). In
all these cases reinjection was reasonably successful. However,
considerable problems of scaling and corrosion of casing and
pipes as well as plugging of reservoirs can be a serious problem
in Imperial Valley, particularly in the Salton Sea and Brawley
KGRAs where salinities are very high.
Ponding of geothermal wastes for temporary storage or
evaporation has been successfully used in Imperial Valley. For
example, in the 1960s, evaporation ponds were used for mineral
extraction from geothermal waters in the Salton Sea area. To
prevent contamination of groundwater at the East Mesa test
facility prior to reinjection, waste brines are stored in a
holding pond lined with a 0.254 mm (10 mil) PVC.
Electrohydraulics Corporation has installed a portable
treatment facility for geothermal wastes in the East Mesa KGRA. Here
wellhead geothermal water is subjected to a high voltage spark
generated shock wave which reportedly precipitates soluble
constituents; these constituents are removed by microstrainers
(Chen, et al. 1976). Although Electrohydraulics Corporation
claims that 80% to 90% of the soluble trace metals can be re-
moved by this patented process, Chen, et al. (1976) could not
make any definite conclusion as to the effectiveness of this
treatment process. This company has a working agreement with
Magma Electric, Inc. to evaluate their process.
For the past few years, USER has been experimenting with a
desalination facility for geothermal water at East Mesa. They
have installed a multistage flash distillation unit and a ver-
tical tube evaporator distillation unit in order to test and
evaluate various procedures for desalting geothermal fluids.
Product water having a TDS content of approximately 100 ppm can
be obtained by this process. There have been scaling problems,
with deposition of barium sulfate, strontium sulfate, calcium
carbonate and silica in the tubes of the desalting units (USER,
1977). The concentrated brine produced from the process is
141
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diverted to a holding pond where it undergoes; evaporation.
Presently, injection of this concentrate is being attempted.
142
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Meidav, T., R. James and S. Sanyal. Utilization of Gravimetric
Data for Estimation of Hydrothermal Reservoir Character-
istics in the East Mesa Field, Imperial Valley, California.
Stanford Geothermal Program Workshop on Geothermal Reser-
voir Engineering and Well Simulation, Stanford University,
1975.
Meidav, T., R. West, A. Katzenstein and Y. Rotstein. An Elec-
trical Survey of the Salton Sea Geothermal Field, Imperial
Valley, California. Lawrence Livermore Laboratory Project
No. 8432305, 1976.
Muffler, L. J. P. and B. R. Doe. Composition and Mean Age of
Detritus of the Colorado River Delta in the Salton Trough,
Southeastern California. J. of Sed. Petrol., v. 35, p.
384-399, 1968.
Muffler, L. J. P. and D. E. White. Active Metamorphism of Upper
Cenozoic Sediments in the Salton Sea Geothermal Field and
Salton Trough, Southeastern California. Bull. Geol. Soc.
Am. v. 80, p. 157-182, 1969.
Nathenson, M. and L. J. P- Muffler. Geothermal Resources in
Hydro-thermal Convection Systems and Conduction - Dominated
Areas; in Assessment of Geothermal Resources of the United
States - 1975, D. E. Williams and D. L. Williams, ed., USGS
Circ. 726, p. 104-121, 1975.
Nugent, J. M. and L. R. Vick. Well Operations Salton Sea Geo-
thermal Field; in Geothermal: State of the Art, Geothermal
Resources Council, Transactions, v. 1, p. 233-234, 1977.
O'Connell, M. F. and R. F. Kaufmann. Radioactivity Associated
with Geothermal Waters in the Western United States. U. S.
Environmental Protection Agency, Office of Radiation Pro-
grams, Las Vegas Facility, Las Vegas, Nevada, Technical
Note ORP/LV 75-8A, 25 p., 1976.
Palmer, T. D. Characteristics of Geothermal Wells Located in
the Salton Sea Geothermal Field, Imperial County, Cali-
fornia. Lawrence Livermore Laboratory, UCRL-51976, 54 p.,
1975.
148
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Palmer, T. D., J. H. Howard and D. P. Lande. Geothermal Devel-
opment of the Salton Trough, California and Mexico. Law-
rence Livermore Laboratory UCRL-51775, 1975.
Phelps, P. L. and L. R. Anspaugh. Imperial Valley Environmental
Project: Progress Report. Lawrence Livermore Laboratory,
UCRL-50044-76-1, 214 p., 1976.
Poland, J. F. and G. H. Davis. Land subsidence due to With-
drawal of Fluids; in Reviews in Engineering Geology, v. 2,
p. 187-269, 1969.
Porcella, R. L. and J. D. Nielson. Preliminary Report on the
Calipatria, California, Earthquake Swarm: November, 1976;
in Seismic Engineering Program Report, October-December,
1976, R. L. Procella, ed., USGS Circ. 736-D, p. 1-3, 1977.
Raghavan, R. and F. G. Miller. Mathematical Analysis of Sand
Compaction; in Compaction of Coarse-Grained Sediments I, G.
V. Chillingarian and K. H. Wolf, eds., Developments in
Sedimentology ISA, p. 403-524, 1975.
Randall, W. Percent Volume Sand Bodies in the Imperial Valley:
Preliminary Report; in Cooperative Geological-Geophysical-
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Imperial Valley Area of California, R. W. Rex, Principal
Investigator, University of California, Riverside, p.
119-124, 1971.
. An Analysis of the Subsurface Structure and Stra-
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Valley, California. University of California, Riverside,
Ph.D. Dissertation, December 1974.
Renner, J. L., D. E. White and D. L. Williams. Hydrothermal
Convection Systems; in Assessment of Geothermal Resources
bf the United States - 1975, D. E. White and D. L.
Williams, eds., USGS Circ. 726, p. 5-57, 1975.
Reed, M. J. Chemistry of Thermal Water in Selected Geothermal
Areas of California. Calif. Div. Oil and Gas, Report No.
TR15, 1975.
Rex, R. W. Investigations of Geothermal Resources in the
Imperial Valley and Their Potential Use for Desalination of
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149
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Shannon, D. W. Economic Impact of Corrosion and Scaling Prob-
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East Mesa Test Site, Imperial Valley, California, A Status
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East Mesa Test Site, Imperial Valley, California, Status
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p., 1976.
150
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SECTION THREE
THE GEYSERS
3.1 INTRODUCTION
3.1.1 Summary
Field development at The Geysers is continuing with at
least 41.5 sq km (16 sq mi) of productive reservoir proven, 502
MW electricity currently being generated, and 400 MW electric
generating capacity under construction. Steam, with less than
1% average of noncondensible gases, is produced from wells
averaging 2,130 m (7,000 ft) in depth. Excess condensate is
reinjected into the deep reservoir under hydrostatic head.
However, approximately 80% of the condensate is evaporated into
the atmosphere during the cooling process in the cooling towers
of the 11 operating power plants. The steam contains an average
of 222 ppm hydrogen sulfide and abundant carbon dioxide, with
hydrogen sulfide emissions exceeding air quality standards.
Cool regional groundtfaters contain abundant calcium, mag-
nesium and bicarbonate, abundant boron and carbon dioxide, and
sparse chloride or sulfate. Thermal waters of a wide region are
enriched in boron, hydrogen sulfide, carbon dioxide and some-
times chloride. These appear to be derived from interaction of
hot water with Franciscan Formation and other rocks. The heat
source is a suspected magma at several miles in depth. No
magmatic constituents are recognized.
The region is seismically active. However, no induced
seismicity is recognized as a result of steam production or
reinjection activities. Similarly, no ground subsidence is
recognized.
Work is underway to reduce hydrogen sulfide emissions to
meet state and local standards. Stringent control over water
discharges essentially prevents geothermal fluid from entering
surface or shallow groundwaters.
3.1.2 Background
Data for this study come from several sources. These
include Water Supply Papers prepared by the USGS for several
water basins (but not including The Geysers); geological mapping
151
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by geologists from federal, state, university and private organ-
izations; and published articles from symposia volumes, short-
course curricula, field trip guidebooks and environmental impact
statements. These data deal with aspects of reservoir manage-
ment, steam well characteristics, fluid composition, status of
field development, and existing or hypothesized operating prob-
lems. ' Other data come from unpublished reports and files, and
deal with chemical compositions, field development schedules and
well performance.
There are significant gaps in the data. Very little is
available from any source on possible freshwater aquifers
within the geothermal field. Almost nothing exists on chemistry
of local groundwaters at The Geysers, other than for the ori-
ginal fumaroles and boiling springs. So little is available on
long-term productivity of the geothermal field, especially on
the deeper sections, that this is a topic of intense argument.
Many specific questions remain unanswered, such as the lateral
and vertical distribution of noncondensible gases within the
field, or the possible variation with time of gas concentration
in wellhead fluid.
Meteorological monitoring has been underway for some time
by Pacific Gas and Electric Company (PG&E), Stanford Research
Institute and others. Results to date appear not to have gene-
ral significance.
Although many unanswered questions, incomplete analyses and
hypothesized situations remain, there currently is sufficient
data available to define many aspects of pollution potential.
Data from current and future projects and investigations will
answer many questions and clarify many of the presently ambig-
uous situations.
3.2 GEOTHERMAL SYSTEM
3.2.1 Definition of System
The Geysers geothermal field is located about 130 km (80
mi) due north of San Francisco, in the Mayacmas Mountains of the
California Coast Ranges, in Sonoma and Lake Counties (Fig. 3.1).
The field extends across at least 41 sq km (16 sq mi), and may
exceed 52 sq km (20 sq mi) in area. The actual extent is un-
known and is problematic. Certain relatively cool and/or hot
but low yield wells at the west, northwest, northeast and south-
east margins of production may represent field boundaries.
However, occasional holes within the field have been nonpro-
ductive. This complicates any attempt to quantify resource
extent.
152
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I
I23°00'
I
I
I22°00'
1
Clear
Lake
-39°00'-
' ••**»•_**•_ i
% VILLE -,,
% AMt.Hannoh
^
The Geysers
Production Area
.Mt.St. Helena
\Lake
Y \Berryessa
v^
Pacific Ocean
SCALE 1: 1,000,000
(kilometers)
0 10 20 30 40
Figure 3.1 Location of The Geysers study area
153
-------
It is known that the geothermal fluid comes to within
several tens of meters of the surface at Big Sulphur Creek,
where fumaroles and boiling springs issued in earlier days.
This part of the system apparently is fed by leakage from a
deeper and much more widespread system, upward along the north-
west-southeast trending Sulphur Creek Fault.
Original drill holes in the 1920s encountered dry, super-
heated steam at depths of 60 to 150 m (200 to 500 ft) along this
fault, in or adjacent to fumarole banks. The steam flowed at
about 14 to 18 kg/sq cm (200 to 250 psig), 5 kg/sec (40,000
Ib/hr), and with 2.8° to 16.7°C (37° to 62°F) of superheat.
Wells drilled in the late 1950s entered this same part of the
system, at depths that reached 300 m (1,000 ft) or slightly
greater. Superheat in these shallow holes gave rise to the
often-quoted statement that The Geysers is a superheated system.
Continued drilling encountered a deeper, stronger, higher
pressure system, whose fluid is dry steam at about the maximum
enthalpy for saturated conditions. Specifically, temperatures
are about 232° to 243°C (450° to 470°F), shut-in pressures
commonly range from 32 to 35 kg/sq cm (450 to 500 psig), flows
initially average 19 to 25 kg/sec (150,000 to 200,000 Ib/hr)
from a. 22.2 cm (8 3/4 in) hole, and enthalpy usually is 2.79 to
2.82 x 106 J/kg (1,338 to 1,350 BTU/lb). Pressure and enthalpy
values are clouded somewhat because of the presence of about 1%
of noncondensible gases.
The deeper system has been first encountered from as shal-
low as 610 m (2,000 ft) along Big Sulphur Creek to over 2,300 m
(7,500 ft) in outpost wells to the northeast and west. Maximum
depth of steam occurrence is over 2,600 m (8,500 ft), with no
indication that permeability had been restricted or eliminated
below that depth. Absolute elevation of the producing deeper
steam reservoir varies between sea level and -2,000 m (-6,600
ft). The depth given is that of the commercially producing
horizon.
Therefore, in calculating resource extent, it is common to
assume an average of about 1,520 m (5,000 ft) of producible
formation. This calculation yields a minimum reservoir volume
of some 67 cu km (16 cu mi). Few wells are drilled to over
2,600 m (8,500 ft) because friction-limited maximum flow usually
is achieved at shallower depth. However, certain wells have
been redrilled or deepened to increase flow at some time after
initial completion. Precise data is held confidential by field
operators.
Calculations of the resource usually are based on the net
kilowattage of electricity generated. That is, approximately
9 kg (20 Ib) of steam produce 1 kW.hr of electricity. Well
yield declines with time, as either local depletion occurs or
154
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wells are damaged by scaling, corrosion or other factors.
Therefore, despite initial productivity that may reach 38 kg/sec
(300,000 Ib/hr) of steam, average sustainable production is
about 19 kg/sec (150,000 Ib/hr). This yields about 7,500 kW
(7.5 MW) per well of continuous electric generation.
Well spacing is an arguable point. Initially, no thought
was given to spacing and possible interference, with the result
that wells were located as close as 61 m (200 ft) apart (0.8 ha
[2 acre] spacing). These wells interfered badly, and were
depleted rapidly. Today, 16-ha (40-acre) spacing is accepted
generally or 6 per sq km (16 per sq mi), with opportunity for
drilling make-up wells at 8-ha (20-acre) centers or 12 per sq km
(32 per sq mi) over an assumed 30-year plant life.
Budd (1973) published performance curves suggesting non-
linear but rapid declines in steam flow at 2-ha (5-acre) spac-
ing, such that a 50% decline might be expected within 6 years of
production. However, for 8-ha (20-acre) spacing this was less
than 30% decline; and for 18-ha (45-acre) spacing, decline was
about 18%. Further, these decline rates were leveling off.
Therefore, using 7.5 MW per well, 16-ha (40-acre) spacing,
and a minimum of 41 sq km (16 sq mi) of proven field, a pro-
duction of almost 2,000 MW electricity is predicted for a plant
life of 30 or more years. Reed and Campbell (1975) suggested
5,000 MW from an area of 1,000 sq km (400 sq mi) as the ultimate
developable capacity. This figure appears high, and cannot
easily be supported.
Natural recharge into the field is debatable. Probably
some flow of water takes place into the field. This has been
estimated from 1 or 2% of withdrawal per unit area to perhaps 10
to 15%. It is supplemented by reinjection of some 18 to 20% of
blowdown from the plant cooling tower (condensed steam). There-
fore, total natural and induced recharge probably does not
exceed one-third of production under most favorable conditions.
Formation porosity is estimated by several methods to be 5
to 10%, distributed irregularly as fractures. Allowing for the
greater specific heat of water, some 80 to 90% of the heat
content of the system is in the rock, with only 10 to 20% in the
fluid. Therefore, even recharge of up to one-third of the fluid
mass should withdraw only 3 to 7% additional of the total heat.
This assumes conductive heat recharge to be negligible.
However, because the distribution of fractures is irregu-
lar, the effect of recharge may be to deplete heat locally from
the rock. This might cause fluid enthalpy to drop to the point
where liquid water would locally dominate vapor in the rock.
155
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Probably there is liquid water in coexistence with steam in
the formation; this is indicated by the enthalpy values. The
source of this water may be 1) recharge, or 2) convection within
the formation from greater depth. The latter presupposes exist-
ence of a water table at some great but unknown depth, as sug-
gested by several workers.
Chemically, the fluid produced is over 99% pure steam
(Finney, 1973). The nature and concentration ranges of noncon-
densible gases are given in Table 3.1 (Allen and McCluer, 1975;
Finney, 1973).
TABLE 3.1 NONCONDENSIBLE GASES IN STEAM SUPPLIED
TO TURBINES AT THE GEYSERS
Plant Design
(volume % of
Total Flow
0.79
0.05
0.05
0.07
0.03
0.01
Range, %
Gas
Carbon diox-
ide (co2)
Hydrogen sul-
fide(H2S)
Me thane (Ch4)
Ammonia(NH3)
Nitrogen(N2)
Hydrogen
-------
Steam discoveries have been made by companies or groups of
companies operating jointly: Magma Power Company-Thermal Power
Company-Union Oil Company; Aminoil USA, Inc. (successor in
interest to Signal Oil Company and Burmah Oil and Gas Company);
Thermogenics Inc. (successor in interest to Pacific Energy
Corporation and Geothermal Resources International, Inc.); Shell
Oil Company; Geothermal Kinetics, Inc.; and McCulloch Oil Cor-
poration. PG&E is the only consumer to date; however, the
Northern California Power Association (NCPA) has negotiated
purchase of steam from Shell oil Company.
Exploratory drilling will continue on the northeastern,
northwestern, western and southeastern boundaries of the known
field according to permit applications on file with various
agencies. Drilling will be done by the companies listed above
and by Chevron Oil Company, AMAX Exploration, Inc., Sun Oil
Company, Republic Geothermal, Inc., and possibly others.
The effect of this planned work may be to expand known
field boundaries.
In any event, in-field development drilling may be expected
to continue for the indefinite future, to meet the anticipated
development schedule for PG&E. Some 502 MW of power plant
capacity are in operation presently; over 400 more are approved
for construction, and may be on line by 1980. Applications for
additional plant sites can be anticipated from PG&E and NCPA.
All production to date is of steam with little or no water
content. This steam is scrubbed free of rock particles and
passed through condensing turbines, barometric condensers and
cooling towers. Evaporative cooling releases some 80% of the
fluid to the atmosphere as water vapor. The remainder of the
water, as noted above, is reinjected as excess condensate.
With increasing production, reinjection, and development
beyond the presently known field boundary, wet steam or even hot
water may be produced, at least locally. This may require
additional separation prior to use, or even development of a hot
water or binary cycle system. It is unknown what changes in
nature and concentration of noncondensible gases will be found
with time, distance from the center of the field or with con-
tinued reinjection.
The Geysers region is believed to be active seismically, as
is much of northern California. Continued or accelerated pro-
duction from the geothermal field may have an effect upon seis-
micity and seismic risk. This is discussed in section 3.4
below. Ground subsidence is not believed to represent a problem
in this area of metamorphosed sedimentary and igneous rock (see
section 3.5 below).
157
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The potential for renewed volcanism has been discussed by
Hearn, Donnelly and Goff (1975). If geothermal production is
achieved closer than at present to the very youthful eruptive
centers around Clear Lake (Mount Konocti and other places),
approximately 20 km to the north, there is an extremely remote
possibility that an unpredictable future volcanic eruption would
involve the geothermal system in some way as to cause increased
discharge of pollutants from production facilities. This is
considered highly improbable.
3.2.2 Potential Pollutants
Pollutants, or potential pollutants, from The Geysers geo-
thermal system fall into five major categories: pollutants to
the atmosphere; pollutants to ground or surface waters; noise
pollution; aesthetic or visual degradation; degradation of the
land surface.
Atmospheric pollution, noise, aesthetic considerations and
land use factors are beyond the scope of this study, so, al-
though it is realized that the current major environmental
problems at The Geysers are due to air and noise pollution, the
major emphasis of this section is on water pollution potential.
Potential pollutants from steam at The Geysers are reported
in Table 3.2. Argon and xenon were reported by various sources,
but were not quantified in any satisfactory manner. All of the
pollutants* listed in Table 3.2 may be volatilized and liberated
into the atmosphere. However, it is most likely that all of
these will be present in the steam condensate, concentrated by
evaporation of water in the cooling process, along with varying
amounts of ammonia or its oxidation products, nitrate and carbon
dioxide.
TABLE 3.2 POTENTIAL POLLUTANTS REPORTED FROM
STEAM AT THE GEYSERS
Measurement
Pollutant Concentration,Unit Point
Radon (Rn)
Boron (B)
References
8.3 picocuries/1 Steam sample Reed & Campbell
from well (1975)
0.01 ppm
5.0 ppm
0.02 ppm
well Thermal Anderson (1975)
#7
well DX-State Anderson (1975)
3395-1
well Sulfur Anderson (1975)
(continued)
158
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Pollutant
Measurement
Concentration,Unit Point
TABLE 3.2 (continued)
References
12-223 ppm
Boric Acid
(HB02)
Arsenic (As) 0.002-0.05 ppm
Ranges of Reed & Campbell
values, wells (1975)
Range of Reed & Campbell
values, wells (1975)
Mercury (Hg) 0.00031-0.018 ppm Range of Reed & Campbell
values, wells (1975)
There is great uncertainty in the range of values reported
for these pollutants. This may reflect stratification, or
regional enrichment in these gases in certain (unspecified)
parts of the reservoir. However, these figures suggest the
following daily production of pollutants in 1980 when 907 MW
(net) are expected to be on line (Table 3.3).
TABLE 3.3
Constituent
EXPECTED DAILY PRODUCTION OF SELECTED POLLUTANTS
FROM 907 MW (NET), ANTICIPATED IN 1980
Mercury (Hg)
Arsenic (As)
Boric Acid (HB02)
Range, Unit/Day
2.27 - 133 gm (0.08 - 4.7 oz)
15.0 - 371 gm (0.53 - 13.1 oz)
89.5 - 1,661 kg (197 - 3,655 Ib)
As described previously, these pollutants are likely to be
produced from an area of about 23 sq km (9 sq mi) (2,330 ha
[5,760 acres-]), and to be brought in with steam to some 15
central collection points (power plants). If one or more were
to discharge to the surface, significant pollution could occur.
However, all condensate water is reinjected and none has been
discharged to surface drainage since 1971.
Steam condensate is evaporated in cooling towers, so that
nearly 80% is evaporated to the atmosphere. Little of the boric
acid, and very little of the mercury and arsenic, is evaporated;
hence, concentrations in the condensate taken for reinjection
are nearly four times those given in Table 3.2. Obviously,
protection of surface and subsurface waters against contamina-
tion by the reinjectant becomes an important goal.
Other sources of possible pollutants come from the drill-
ing, road building and plant construction processes. This in-
159
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eludes silt and dust raised by stripping of vegetation and by
movement of cars and trucks; cement wastes from construction;
rock cuttings from drilling operations; paper, plastic and metal
wastes from construction; human wastes; fuels and lubricants
spilled accidentally; and drilling muds and additives. Of
these, only drilling muds can be discussed in any quantitative
terms.
Reed and Campbell (1975) reported a typical drilling mud
composition, as given by Union Oil Company. This appears as
Table 3.4 below.
TABLE 3.4 TYPICAL DRILLING MUD COMPOSITION,
THE GEYSERS
Component Composition Volume %
Water H2O 93 . 09
Bentonite Na A1 Si- -O(OH) 5.93
Quebracho Organic 0.45
(Wood extract)
Caustic soda NaOH 0.32
Sodium Bicarbonate NaHCO3 0.09
Lignin (Tannathin) C212H171°41H3S °*12
Additional Material Used to Control Lost Circulation
Cottonseed hulls Organic
Walnut shells Organic
Mica K Al3Si3O10(OH)2
Reed and Campbell (1975) also reported that approximately
240 cu m (8,000 cu ft) of drilling fluid are used in an average
well. Some of this enters the formation and is not recovered.
The remainder may be stored in a specially constructed clay-
lined sump or in a steel tank, partially evaporated, and then
transported to a disposal site. Nontoxic mud wastes may be
evaporated to dryness and used as fill in an area protected from
erosion. Toxic (or suspected toxic) wastes must be hauled to a
Class 1 Disposal Site.
Despite rumors of heavy metals as selected additives in
drilling muds, only the relatively inert mineral barite can be
documented at The Geysers, and then only rarely is it used.
160
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Of all the pollutants described in this section, hydrogen
sulfide presents the greatest potential problem. If emitted to
the atmosphere without control, emissions can reach levels
exceeding the local Air Pollution Control District (APCD) regu-
lations in settled areas, since air patterns may carry it east,
to Cobb and Collayomi Valleys.
PG&E has installed experimental scrubbing units on indivi-
dual plants which, if used successfully on a permanent basis,
could reduce hydrogen sulfide emissions to less than 2.7 metric
tons (3 tons) per day. This would be almost one-eighth of the
present loading; but even at this reduced level it obviously
will permit further degradation of air quality. Additional
hydrogen sulfide may be emitted during testing of individual
wells (from 24 hours to 24 days) or during accidental well
blowout. No control has been designed for these situtions.
3.3 WATER POLLUTION POTENTIAL
3.3.1 Summary of Baseline Water Characteristics
Very little is available on water quality or local and
regional aquifers in The Geysers geothermal field. Elsewhere,
as in Big Valley on the southwest side of Clear Lake, or in the
Collayomi Valley, east of The Geysers (Upson and Kunkel, 1955),
data have been compiled and evaluated. For a discussion of
this, see Geonomics (in press).
Generally, water wells are confined to alluvium, which
rarely is deeper than a few meters, except in Big Valley. Few
wells penetrate bedrock. Therefore, almost all chemical and
flow data pertain to surface streams and/or unconfined aquifers.
Very fragmentary published and unpublished analyses show
ground water and surface streams and springs to be dominated by
calcium and sodium bicarbonate. Locally, especially in the
vicinity of serpentinite bodies, water contains higher magnesium
than sodium and occasionally even than calcium values. This is
not surprising, as serpentinite is hydrous magnesium silicate,
and breaks down readily under surface weathering.
Chloride concentration varies appreciably, but does not
appear to exceed a few tens of ppm in cool ground or surface
waters. Most analyses report between 1 and 7 ppm of chloride.
Sulfate, where data are available, is similar in concentration.
Certain thermal waters northeast of The Geysers field have high
chloride concentrations, reaching a maximum several thousand ppm
of chloride at Wilbur Springs. However, that area is far beyond
the scope of this report.
161
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TDS range from a few dozen ppm in bedrock springs to per-
haps over 1,000 ppm in deeper waters of Big Valley. This is
based on several partial analyses and measurements of specific
conductance.
There is a significant regional boron anomaly in cool and
thermal groundwaters across the Mayacmas Mountains of Lake,
Sonoma and Napa Counties. This extends from north of Clear Lake
to south of Calistoga, a distance of over 65 km (40 mi). Levels
of boron reach 7 ppm in Big Valley in cool groundwater (Cali-
fornia Department of Water Resources, 1957), and reportedly
reach over 100 ppm in selected thermal waters. For example, the
thermal springs and shallow wells at Calistoga have several tens
of ppm of boron, and at Sulphur Bank on the northeast side of
Clear Lake boron have exceeded 100 ppm in certain incomplete
analyses.
A major anomaly in ammonia, reaching several hundred ppm,
is recognized at Clear Lake in thermal waters (Roberson and
Whitehead, 1961), and may extend into thermal areas to the
south.
Fumaroles at The Geysers have discharged copious quantities
of hydrogen sulfide, ammonia, boric acid and carbon dioxide for
centuries. Significant local anomalies existed at the surface
before geothermal development began. Obviously, names like Big
Sulphur Creek and Sulphur Bank reflected actual conditions. It
is impossible to quantify these discharges with any certainty,
as most fumaroles have ceased to discharge.
Other thermal springs of the region discharged one or more
of the following: carbon dioxide, chloride, ammonia, boric
acid,, hydrogen sulfide. Carbon dioxide seeps are widespread
along shores of Clear Lake and in major stream canyons. Extinct
hydrogen sulfide seeps are marked by sulfur deposits at several
places.
In summary, cool surface and unconfined groundwaters are
dominated by calcium and bicarbonate, with abundant magnesium
and sodium, occasional boron and minor chloride and sulfate.
TDS is low (1,000 ppm maximum). Carbon dioxide seeps are com-
mon. Thermal waters are sodium bicarbonate, with subsidiary
calcium, magnesium and locally abundant chloride and sulfate.
Boron, ammonia, carbon dioxide and hydrogen sulfide may be
abundant. Certain thermal waters contain great quantities of
these constituents. Fumaroles of The Geysers are dominated by
hydrogen sulfide, ammonia and carbon dioxide, with significant
boron.
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3.3.2 Potential Water Pollutants
As described above, pollutants within The Geysers area are
anticipated to be boron (or some compound of boron), ammonia and
hydrogen sulfide. Chloride is a possible pollutant in areas
outside The Geysers. Arsenic, mercury and radon are in low
concentrations. Carbon dioxide will evolve from many surface
and groundwaters.
3-3.3 Potential Pollution Mechanisms and Pathways
It is believed that all pollutants derive from attack of
thermal waters on country rock. Possibly some carbon dioxide,
ammonia, boron and sulfur derive from the magma believed to
underlie the region at depth; but there are no isotope data to
support this possibility. However, attack by hot water is a
convincing mechanism, and a magmatic source is not needed.
Mixing of thermal and cool surficial waters can account for
reduced levels of boron, carbon dioxide, ammonia and sulfur com-
pounds noted in many areas. Chloride is derived from a suite of
Mesozoic age rocks believed to have residual quantities of
connate water. Chloride is relatively rare in Franciscan rocks
of The Geysers area.
Therefore, it is quite reasonable to suppose that these
pollutants circulate through fractured bedrock in thermal
waters, and that all groundwaters in the region might contain
quantities of any or all of these substances. The nearly total
absence of wells drilled into Franciscan bedrock, other than at
The Geysers, makes it difficult to test this hypothesis. When
thermal water rises from fractured bedrock into the relatively
thin alluvium, it may issue as mineralized springs or it may mix
with cool surficial or unconfined groundwater, thereby diluting
these pollutants. Regional anomalies of pollutants are sus-
pected .
3.3.4 Level of Potential Pollution
All fluid produced from geothjermal wells is either a)
evaporated to the atmosphere, or b) reinjected into deep wells
in the geothermal field. Therefore, no additional pollution of
surface or groundwaters is expected from routine geothermal
operations. If there are abnormal conditions (accidents, earth-
quakes, etc.), pollutants may be discharged onto the surface.
As described earlier, the pollutants include boron, hydrogen
sulfide (which will volatilize to over 85%), ammonia (largely
volatilized), and very minor quantities of other substances.
Discharges of drilling muds (see section 3.2.1) may add
trace amounts of other substances to surface waters (Table 3.5).
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The relative impermeability of Franciscan rock at the
surface tends to preclude significant recharge of pollutants to
the ground water regime. In any event, these pollutants issued
from the subsurface in that area, and their return to depth
could not be considered detrimental.
3.4 SEISMICITY
A study of seismicity of The Geysers must include seismic
activity across a wider area of northern California, to deter-
mine the location of faults that might have seismic effects on
operations at The Geysers and to determine relative seismic
hazards.
3.4.1 Summary of Baseline Seismicity and Seismic Risk
Baseline data come from the USGS (National Center for
Earthquake Research [NCER]); the University of California,
Berkeley (U.C.B.), Seismograph Station; and the California
Division of Mines and Geology. These include seismic records,
microseismic surveys, strong-motion accelerograph records,
compilations of epicenters, compilations of historical seis-
micity, projections of maximum acceleration, maximum magnitude
and maximum intensity to be encountered, and maps of active or
Quaternary faults.
The lack of population in the Mayacmas Mountains relative
to the adjoining alluviated valleys makes it difficult to eval-
uate historical reports of earthquakes. Do fewer reports mean
fewer events or fewer persons to report events? This question
is discussed below.
Earthquake hazards consist of two distinct classes of
ground movement: vibrational and permanent. The degree of
these hazards varies geographically as a function of seismic
potential and near-surface geologic conditions. Seismic risk
(the probability of property loss or human injury) is a function
of both the naturally occurring seismic hazards and the earth-
quake resistance of manmade works. Where there are no manmade
structures, seismic risk is vanishingly small. Prediction of
seismic risk means prediction of all of the following: the
location, magnitude and frequency of earthquakes; vibratory
motion in rock; the response of unconsolidated earth materials
to these rock motions; and the response of manmade structures to
resultant ground-surface motions.
Hazard elements to be discussed are: a) seismic potential
(earthquake location, magnitude and frequency of occurrence); b)
vibratory rock and ground motion; and c) permanent ground mo-
tions including faulting, liquefication, landsliding, differen-
tial settlement and lurch-cracking.
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Since 1855, more than 140 earthquakes have been felt in the
Santa Rosa-Sonoma Valley-Clear Lake region. While some ten of
these did significant damage in Santa Rosa and Sonoma Valleys,
only one was destructive in The Geysers region itself. This was
the great 1906 (M = 8^) earthquake, caused by rupture along the
San Andreas Fault. Modified Mercalli (MM) intensity ranged from
about VII to IX in the Santa Rosa Valley, reaching IX in the
city of Santa Rosa due to soft, saturated ground conditions
there. In the Mayacmas Mountains, MM intensity was about VI to
VII, with very minor damage reported from The Geysers. Around
Clear Lake, damage was confined to alluviated areas along the
north and west shores: MM intensity VII prevailed in the area
from Kelseyville to Upper Lake, as evidenced by fallen chimneys;
fissures were reported in alluvial ground south of Kelseyville.
Damage to any given type of structure in The Geysers-Clear Lake
region was controlled by shallow ground conditions, being mini-
mal on bedrock and maximal on water-saturated unconsolidated
alluvium.
Other than the 1906 event, no shock in the region has been
of sufficient magnitude to cause significant damage in The
Geysers area. The largest had a magnitude estimated to have
been near 5, and produced intensity VII (fallen chimneys) at
Upper Lake and along the Russian River from Healdsburg to Ukiah;
these places are located beyond the margins of The Geysers
geothermal area, and on alluvium. Maximum MM intensity within
The Geysers area probably did not exceed VI on alluvium and V on
bedrock for any of these other shocks.
In 1969 two earthquakes with magnitudes 5.6 and 5.7 oc-
curred on the southern end of the Healdsburg Fault on the north
side of Santa Rosa. They caused substantial damage to buildings
in Santa Rosa, but not within The Geysers area.
Frequency of occurrence of strong ground shaking (inten-
sities VI, VII and VIII) has been nearly as great in Santa Rosa
Valley as in the entire San Francisco Bay region. For The
Geysers area, data are more sparse, reflecting thinner settle-
ment. Probably, however, recurrence of strong shaking is lower
than at Santa Rosa. This reflects a) greater distance from
major active faults, and b) shallow bedrock.
If the last 160 years are fairly representative of long-
term seismicity of the Bay region, we should expect potentially
damaging ground shaking (intensity VII or greater) about once
every 30 years on the average in alluviated portions of the
region. On bedrock ,within The Geysers region, the "30-year
intensity" is probabl^ about VI; intensity VII or greater may be
expected about once every century; and intensity VIII or more,
which may be damaging to modern structures, about once in three
centuries. However, the seismic record is short relative to
long-term variations of regional crustal strain, and instru-
mental magnitudes are available only since 1932.
165
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The greater San Francisco Bay region, extending from Monte-
rey Bay on the south to Ukiah on the north and east to Vaca-
ville, is one of the most seismically active areas of Califor-
nia. Seismicity was much higher in this region during the
nineteenth century than it has been in the twentieth: since the
great 1906 earthquake a few moderate (magnitude less than 6.0)
and no major shocks have occurred; however, between 1836 and
1906 there were five major (magnitude probably greater than
7.0), and a number of moderate shocks.
Table 3.5 shows that for the period 1932 to 1971 seismicity
(per unit area) of the Santa Rosa 1° by 2° Sheet is similar to
that of the larger central Coast Range zone for magnitudes 6 and
greater. Therefore, the long-term unit area seismicity of the
two regions should be similar. From this, it is concluded that
the recurrence intervals for the central Coast Range for 1810-
1931 are a reasonably good indicator of future seismicity af-
fecting the study region. Geodetic and geologic data suggest a
recurrence interval of from 100 to 400 years for magnitude 8 or
greater earthquakes at any place along the San Andreas Fault.
This is in satisfactory agreement with the seismicity data.
Earthquake epicenter maps have been compiled by U.C.B. and
the USGS. The accuracy of U.C.B. epicenters in this area is
probably better than ±5 km (3 mi) for magnitude 3% or greater
shocks; however, before 1963, when the U.C.B. seismography
network was greatly improved, accuracy probably improved from
about ±20 km (12 mi) in 1910 to ±10 km (6 mi) in 1962. For this
reason, one cannot see distinct clustering of epicenters along
any active faults.
Immediately following the Santa Rosa earthquakes in 1969,
NCER of USGS extended its dense Bay Area seismograph network
into the Santa Rosa Valley area. This yielded a better corre-
lation between epicenters and the mapped traces of the Rodgers
Creek-Healdsburg Fault Systems (Fig. 3.1). This correlation
appears because of the relatively high accuracy and precision of
the NCER data: epicenters are accurate to better than ±2 km
(1.2 mi).
Both the USGS and U.C.B. data indicate a lack of seismicity
along the San Andreas Fault; this is characteristic of the fault
northward from the Santa Cruz Mountains to Point Arena. Crustal
strain apparently is still low there, but geodetic measurements
at Fort Ross and Point Reyes indicate that strain is now accum-
ulating along the San Andreas Fault.
The NCER data show high microseismicity in The Geysers
geothermal field, but epicenter locations do not resolve spe-
cific active faults. It seems safe to say that seismicity there
is produced by microfracturing throughout the geothermal field.
This probably is the result of low-level strain release which is
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TABLE 3.5 EARTHQUAKE RECURRENCE INTERVALS FOR THE CENTRAL COST RANGE
Average Recurrence Intervals (yrs)
Earthquake Data Set Recurrence
Parameters* 1.000 km 12.000 km2
Region Area (km2) Period (years) a b TM: 6 7 6 7 8
Santa Rosa Sheet 12,000 1944-1971 1.42 0.72 720 3600 60 300 1500
Central Coast
Ranges 33,000 1932-1961 2.83 0.90 370 2960 32 250 2000
Central Coast
Ranges 37,000 1810-1931 0.84 0.53 216 735 18 62 210
*Parameters of the equation log N = a-b M;
'a* is normalized on an annual and per 1000 km^ basis.
^magnitude
-------
localized by high temperature and pore pressure in the geother-
mal system. To the east in the Clear Lake area, microseismicity
is much lower than in The Geysers area. Nearly one half of all
microearthquakes in this area occurred in a two-day-long swarm
located under the south flank of Mount Konocti and 1.6 km (1 mi)
west of the trace of the Konocti Bay Fault. As all of these
shocks had a similar focal mechanism with modal plans paralleling
the fault, the shocks may have occurred on that fault. There-
fore, it is concluded that the Konocti Bay Fault is seismically
active. Otherwise, epicentral data does not delineate faults in
the Clear Lake area.
Geologic mapping by various workers indicates that the
Collayomi Fault is potentially active (displaces Quaternary
features) in Cobb Valley northeast of The Geysers. Data on this
are fragmentary.
Maximum shaking in rock commonly is specified in terms of
maximum credible and maximum probable accelerations. Maximum
credible acceleration at any given place is defined as the
maximum acceleration that could reasonably be expected to occur,
given the known geologic framework. Thus it is based entirely
on the location, length and relative recentness of faults in the
region surrounding a site under consideration. Maximum probable
acceleration at a site is derived from statistical analysis of
the recorded seismicity of the surrounding region.
Shaking is not completely described by maximum accelera-
tion; one also needs to know its duration and spectral character
(the distribution of amplitude relative to vibrational period).
Spectral shapes appropriate for rock can be computed and scaled
to fit maximum acceleration values from existing accelerograms.
It is both realistic and practical to use maximum probable
acceleration in regions where the spatial and temporal distribu-
tion of destructive earthquakes is not well understood. Of
course, most areas fall into this category, the present one
included. In other words, where seismicity is largely known in
a statistical way, it is sensible to predict ground motion in a
probabilistic manner.
Only three major (more than a few kilometers in length)
active faults are known to lie within 65 km (40 mi) of The
Geysers. Faulting beyond this distance is not capable of pro-
ducing significant damage. The three faults are, from west to
east, the San Andreas, Healdsburg-Rodgers Creek, and Mayacmas
Faults. The first two are proven seismically active; the Mayac-
mas Fault appears to creep (aseismic slippage), but no earth-
quakes are known to have occurred on it. In addition, there is
evidence that the Collayomi Fault may be active, but its extent
and recentness of movement are unknown. Other, shorter faults
may be active or potentially active, particularly in The Geysers
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region. However, except for the Konocti Bay Fault, there is no
clear evidence for their activity. At an arbitrary location,
accelerations induced by earthquakes on shorter faults, many of
which are unknown, may exceed those from events on major faults.
Maximum credible bedrock acceleration may be estimated from
the length of and distance from a given fault. Empirical data
relate rupture length and magnitude. Assuming that the entire
mapped length of an active fault may rupture during a single
event, one can estimate the maximum credible magnitude of earth-
quakes on particular faults. In this way, we estimate Q% on the
San Andreas Fault, 7^ on the Healdsburg-Rogers Creek Fault, and
6% on the Mayacmas Fault. From empirical curves relating peak
rock acceleration, earthquake magnitude, and distance from the
causative fault, we find that maximum credible bedrock acceler-
ation in the study region varies from about 0.7 g (acceleration
of gravity) adjacent to active faults down to about 0.2 g south
of Lower Lake.
Duration of strong shaking for these maximum credible
events varies from about 20 seconds for M = 6H to 40 seconds for
M =
Maximum probable acceleration is derived by simply assuming
that all earthquakes are randomly distributed, implicitly on
unknown faults. Using magnitude- frequency parameters for 1810-
1930 in the central Coast Range, maximum probable bedrock accel-
eration per 100 years is about 0.26 g in this area. This has a
63% chance of being exceeded in any 100-year interval, or 30% in
50 years. Design to this value would not be "conservative," in
the engineering sense of the term.
A more conservative design might use the 200-year maximum
probable bedrock acceleration, with a 30% chance of being ex-
ceeded in any 100-year interval (or 15% in 50 years); this is
0.42 g.
However, we expect most of the larger earthquakes to be
associated with the Healdsburg or San Andreas Faults, located
far beyond the region of expected geothermal development.
Therefore, the accelerations given above are really too high for
the given time periods, but by an unknown amount. A more sophi-
sticated analysis, as outlined above, would certainly give
smaller values of acceleration in the area of concern.
Liquefaction, differential settlement, lurch cracking,
surface faulting, and landsliding comprise the various types of
permanent ground deformation, or ground failure. All but fault-
ing result from ground shaking; faulting is the proximate cause
of ground shaking. Strictly speaking, liquefaction is a cause,
rather than a manifestation, of ground failure.
169
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Although permanent ground deformations may locally do
serious damage to building foundations, ground shaking will
cause more widespread and greater total depth damage.
Liquefaction is defined as the transformation of a granular
material from a solid into a liquefied state as a consequence of
increased pore-water pressures. Liquefaction may be an impor-
tant problem where the groundwater table in alluvial areas is
generally not more than 3 to 6 m (10 to 20 ft) deep. It may
also occur in water-saturated fills, such as are often con-
structed for drilling pads and power plant facilities in the
Mayacmas Mountains.
Landslides and land slumps are frequently triggered by
strong ground shaking. In the Mayacmas Mountains extensive
areas are underlain by melange deposits of the Franciscan For-
mation which are particularly prone to landsliding, even without
earthquake shaking. Of course, these same areas are subject to
additional landslide potential under earthquake loading. There-
fore, slope-stability studies for siting geothermal facilities
should include analysis of the effect of earthquake shaking.
Failure by liquefaction imay be a problem in saturated
alluvium or fills which contain much silt to sand-sized ma-
terial. Good drainage may practically eliminate potential
problems in such fills.
3.4.2 Potential Induced Seismicity
Seiymicity may be induced by greatly changing pore pres-
sures OJL fluids in rocks, through processes of extraction and
reinjection. This is most typical in areas (a) of unconsoli-
dated sediments and (b) where intensive pressure is used to
extract and inject fluid.
Neither criteria applies to The Geysers. In The Geysers
area., rocks are solid, brittle and well compacted. Steam is
produced without pumping, and steam condensate is injected under
hydrostatic head, again without pumping. A hydrostatic column
of, say, 1,500 m (5,000 ft) in a reinjection well may exert a
pressure some 140 kg/sq cm (2,000 psig) greater than is the
steam pressure within the reservoir. This pressure differential
is believed to be insufficient to fracture reservoir rocks
further than they are already fractured.
Currently, 18,000,000 Ipd (4,700,000 gpd) of reinjectant
are being disposed of via six wells, whose depths range from 721
to 2,452 m (2,364 to 8,045 ft). Injection rates of 4,540 1pm
(1,200 gpm) per well produce no back-pressure at the well bead.
Injection levels are generally deeper than or equal to produc-
tion depths. Injected water is not known to communicate with
shallow groundwaters.
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monit°nng of seismicity and triangulation surveys
(Chasteen, 1975) has produced no information suggesting changes
in seismicity. NO evidence suggests that brittle limits of
formation rock are being reached by hydrostatic injection.
3.5 SUBSIDENCE
Subsidence often accompanies withdrawal of fluid (oil, gas,
steam, water) from unconsolidated or poorly consolidated aqui-
fers. Geothermal field subsidence has occurred at Wairakei, New
Zealand.
In addition to being dense and brittle, rocks of the Fran-
ciscan Formation at The Geysers are well indurated and devoid of
intergranular pores. Fractures are random but pervasive, and
may be subject to periodic sealing with silica, calcite and
zeolite minerals, followed by renewed tectonic fracturing.
3.5.1 Baseline Data
Three types of data are being collected regarding possible
subsidence: horizontal triangulation, precise vertical level-
ing, and net changes in gravity field with time. Interpretation
of these data is complicated greatly by tectonic activity: it
is widely agreed that this part of the Mayacmas Mountains has
been uplifted by up to 910 m (3,000 ft) in Quaternary time.
Seismic data (see section 3.4.2) suggest that tectonism is
continuing.
USGS is conducting precise leveling and triangulation
surveys, in the search for tectonic, induced seismic and sub-
sidence effects. To date nothing is known to indicate sub-
sidence. Gravity surveys over a 15-year period across The
Geysers field suggest very tentatively that mass is not being
lost from the field as rapidly as production withdrawals of
steam would predict. This may reflect (a) inadequate measure-
ments, (b) natural recharge, (c) tectonic uplift or (d) some
unknown factor. Nothing suggests subsidence.
3.5.2 Potential Subsidence
On the basis of the above (sections 3.5 and 3.5.1), no
subsidence is anticipated. If it occurs, it may be difficult ta
distinguish from tectonic effects. In any case, it is unlikely
to have much effect upon the rugged, mountainous, uninhabited
area of the geothennal field. It is especially difficult to see
how it could cause pollutants to enter the local surface or
groundwaters.
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3.6 POLLUTION CONTROL TECHNOLOGY
3.6.1 Current Practices
The principal pollution control practice is reinjection of
condensate into the deep reservoir. There is no intentional
water discharge to surface or shallow groundwaters.
Additionally, no discharges of drilling fluids are per-
mitted. All fluids are either evaporated to dryness or trucked
to certified disposal sites. Only nontoxic materials (rock
cuttings) are allowed to dry for use as fill. No permanent
spoil banks are allowed. Sumps for temporary storage of dril-
ling fluid are either plastic- or clay-lined, to prevent measur-
able percolation into bedrock.
Siting requirements for roads, wells and plants are very
rigorous, to minimize runoff of silt-laden waters.
Accidental discharges of waters from tanks, sumps or other
sources do occur, but control of these discharges is reasonably
good.
Prior to 1972, yolatiles (water vapor, hydrogen sulfide,
carbon dioxide, ammonia, etc.) were liberated to the atmosphere.
The emission of hydrogen sulfide to the atmosphere from geother-
mal power production at The Geysers rose from 30 Ib/hr in 1960
to 1,670 Ib/hr in 1975 (Leibowitz, 1977).
Blowouts of geothermal wells may cause atmospheric and/or
ground water pollution. Up to 50% of the wells drilled at The
Geysers are sited on old landslides (Bacon, 1976), which aggra-
vates the blowout problem, since well casings may be sheared by
reactivated landslides. Many of the old landslides have tempo-
rarily stabilized; however, each wet winter season charges the
slopes and slides with high moisture which can cause renewed
slide activity.
Union Oil Company well No. GDC 65-28, completed in 1968 on
the upper part of a large landslide, blew out in March 1975.
Bacon (1976) believes this event may be directly related to
renewed movement of the slide. After the blowout Union Oil
initiated a program to rework their early wells and bring them
up to present well completion and engineering standards in order
to prevent this type of blowout.
3.6.2 Anticipated Technology
It is anticipated that discharge requirements set by the
state ARE and the local APCD for hydrogen sulfide for each plant
and for wells being tested will be complied with in the future
by designing new plants with hydrogen sulfide controls and by
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installing retrofit abatement systems in preexisting plants.
Research by PG&E (Allen and McCluer, 1975) has indicated that
the following methods are practicable for hydrogen sulfide
abatement:
1) Direct injection of sulfur dioxide into cooling waters
to oxidize hydrogen sulfide to sulfur by the Glaus
reaction: 2H2S + SO2 -> 3S + 2H2O.
2) Simultaneous injection of sulfur dioxide and air.
3) Addition of a metal catalyst, iron, to the cooling
waters, to promote direct oxidation of hydrogen sul-
fide to elemental sulfur: 2H2S + 02 -> 2S + 2H2
-------
Other than condensate reinjection and hydrogen sulfide
abatement, no additional treatment is anticipated.
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REFERENCES
Allen, G. w. and H. K. McCluer. Abatement of Hydrogen Sulfide
Emissions from The Geysers Geothermal Power Plant; in
Second United Nations Symposium on the Development and Use
of Geothermal Resources, v. 3, p. 1313-1316, 1975.
Anderson, S. O. Environmental Impacts of Geothermal Resource
Development on Commercial Agriculture: A Case Study of
Land Use Conflict; in Second United Nations Symposium on
the Development and Use of Geothermal Resources, Proceed-
ings, v. 3, p. 1317-1322, 1975.
Bacon, C. F. The Recent Blowout of a Geothermal Well at The
Geysers Geothermal Field; in Geothermal Environmental
Seminar - 1976, Lake County, California, F. L. Tucker and
M. S. Anderson, eds., 1976.
Budd, C. F. Steam Production at The Geysers Geothermal Field;
in Geothermal Energy, P. Kruger and C. Otte, eds., Stanford
University Press, p. 129-144, 1973.
California Department of Water Resources. Lake County Investi-
gation Bulletin 14, 197 p., 1957.
Castrantas, H. M., T. A. Turner and R. W. Rex. Hydrogen Sulfide
Abatement in Geothermal Steam; in Geothermal Environmental
Seminar - 1976, Lake County, California, F- L. Tucker and
M. S. Anderson, eds., 1976.
Chasteen, A. J. Geothermal Steam Condensate Reinjection; in
Second United Nations Symposium on the Development and Use
of Geothermal Resources, Proceedings, v. 3, p. 1335-1336,
1975.
Finney, J. P. Design and Operation of The Geysers Power Plant;
in Geothermal Energy, P. Kruger and C. Otte, eds., Stanford
University Press, p. 145-162, 1973.
economics, Inc. Baseline Geotechnical Data for Four Geothermal
Areas. U.S. Environmental Protection Agency, Office of
Research and Development, in press.
175
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Hearn, B. C., J. M. Donnelly and F. E. Goff. Geology and Geo-
chronology of the Clear Lake Volcanics, California; in
Second United Nations Symposium on the Development and Use
of Geothermal Resources, Proceedings, v. 1, p. 423-428,
1975.
Leibowitz, L. P. Projections of Future Hydrogen Sulfide Emis-
sions and Geothermal Power Generation: The Geysers Region,
California; in Geothermal: State of the Art, Geothermal
Resources Council, Transactions, 1977.
Reed, M. J. and G. E. Campbell. Environmental Impact of De-
velopment in The Geysers Geothermal Field, USA; in Second
United Nations Symposium on the Development and Use of
Geothermal Resources, Proceedings, v. 3, p. 1399-1410,
1975.
Roberson, C. E. and H. C. Whitehead. Ammoniated Thermal Waters
of Lake and Colusa Counties, California. USGS Water Supply
Paper 1535-A, 11 p., 1961.
Upson, J. E. and F. Kunkel. Ground Water of the Lower Lake-
Middletown Area, Lake County, California. USGS Water
Supply Paper 1297, 83 p., 1955.
Weres, 0. Environmental Implications of the Exploitation of
Geothermal Brines; in Geothermal Environmental Seminar
-1976, Lake County, California, F. L. Tucker and M. S.
Anderson, eds.7 1976.
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SECTION FOUR
KLAMATH FALLS
4.1 INTRODUCTION
4.1.1 Summary
Some 400 shallow wells are used for space heating at the
Klamath Falls and Klamath Hills thermal areas. Of these, only a
handful produce geothermal fluid to the surface; the remainder
utilize heat-exchanging with cool meteoric water in the well
bore. Well depth averages about 150 m (500 ft); deepest wells
reach 550 m (1,800 ft).
Recorded temperatures reach 113°C (235°F); water geothermo-
metry suggests 140°C (280°F) to possibly over 150°C (300°F) as
the temperature of a deeper (1 km [0.6 mi]) reservoir.
Consumed heat is equivalent to 5.6 MW average annual use,
with peak demand reaching 56 MW.
Water chemistry is relatively benign, with TDS of 500 to
1,000 ppm, moderate (50 ppm) chloride, low boron and fluoride
(about 1 ppm each), and no reported toxic substances. The
system is not gassy.
The area exhibits low seismicity, and appears to have
little potential for induced seismicity as a result of field
production. Subsidence is not recognized.
4.1.2 Background
Data for this study come from many sources. Principal
among these are reports by the USGS and the Oregon State Engi-
neer's Office. These are supplemented by brief reports by the
Oregon Department of Geology and Mineral Industries, and by
fragmentary data from private sources, researchers at Oregon
State University and Oregon Institute of Technology (OIT), and
company records of GeothermEx, Inc.
These data mainly deal with surface geology and hydrology,
the shallow groundwater system, utilization of thermal water at
Klamath Falls, and results of exploration for geothermal re-
sources. There are limited data on water chemistry and seis-
micity.
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Data are lacking on the deep geothermal system: its chem-
istry, enthalpy, state, extent and producibility. Data are
scarce concerning possible subsidence, induced seismicity and
likely pollutants from a geothermal system.
A canvass of wells is presently being conducted by the USGS
and OIT. However, very little is known other than well loca-
tions, depths and temperatures.
4.2 GEOTHERMAL SYSTEM
4.2.1 Definition of System
Klamath Falls, a city of nearly 20,000 inhabitants, is
located in the southern part of Klamath County in southern
Oregon (Fig. 4.1) within a large, compound graben known as the
Klamath Basin. The basin contains numerous thermal springs and
areas of thermal wells, the most significant of which are:
1) a 5-km (3-mi) long northwest trending zone of thermal
springs and wells within Klamath Falls city;
2) a 5-km (3-mi) long northwest trending zone of thermal
wells on the southwest flank of the Klamath Hills,
some 19 km (12 mi) south of Klamath Falls;
3) a stream canyon at Olene Gap, about 13 km (8 mi)
southeast of Klamath Falls, the site of thermal
springs and wells, and
4) the east side of Eagle Point, a peninsula in Klamath
Lake 24 km (15 mi) northwest of Klamath Falls, the
site of thermal springs.
Mildly thermal waters are found at several other places in
the Klamath Basin. All told, these form a discontinuous and
en-echelon, principally northwest trending zone of thermal
waters nearly 48 km (30 mi) long. Indeed, possible structural
extensions of the Klamath Basin in northern California are
indicated by occasional thermal wells.
By far the most important of these thermal anomalies are
those at Klamath Falls and Klamath Hills, with those at Klamath
Falls being better known and more extensively developed. Mani-
festations include thermal springs (Klamath Falls, Olene and
Eagle Point) at temperatures from about 32°C (90°F) (Eagle
Point) to near boiling (Klamath Falls); shallow thermal wells
(Klamath Falls, Klamath Hills, Olene and elsewhere) producing
water just above ambient nonthermal groundwater temperatures
(16°C [60°F]) or higher to as high as 113°C (235°F) (Klamath
Falls); and a few shallow wells that produce steam (Klamath
Falls).
178
-------
If 'Sp^-x-^f <££ *$m^
g ' / - £.y,Vs. 4: '^^r'^^v?^
"
Ay- IV-i....' ""^ '• "-''Jr,'''
'-Mi -^>^?
:•••> ^.."-W^iW
KLAMATH
MTNS.
CALIFORNIA
KLAMATH
FALLS
N
Figure 4.1 Physiography of Klamath Falls,
Oregon vicinity (modified from
Raisz, 1955)
179
-------
Altogether, at least 400 features produce thermal fluid,
the majority of them only slightly above ambient nonthermal
groundwater temperatures. Most wells with temperatures above
60°C (140°F) are in Klamath Falls city or suburbs. At least
three wells with temperatures to 82°C (180°F) are located not
farther than about 1.6 km (1 mi) from a major fault zone
(Sammel, 1976).
The association of these thermal features with faults of
the Basin and Range type (normal, down on the valley side)
suggests that deep convective circulation of meteoric water is
the source of heat for the geothermal system. Nothing clearly
suggests a magmatic heat source.
Fluid chemistry (silica concentration, sodium-potassium-
calcium ratios) is suggestive of a reservoir temperature of
about 14p°C (280°F) which would be inadequate for generation of
electricity. Temperatures this high have not been encountered
in drilling to date; therefore, the depth to waters of this
temperature is unknown. Speculation suggests about 1 km (3,300
ft) to the high temperature reservoir, with convective circu-
lation reaching perhaps 3 to 4 km (10,000 to 13,000 ft) along
major faults. This assumes a conductive gradient of perhaps
35°C per km (1°F per 100 ft), which is "normal" for most areas
of the western United States. In the event of higher than
normal gradients, convective circulation might be shallower.
Wells in the Klamath Falls area commonly are less than 210
m (700 ft) deep, with many wells being less than 75 m (250 ft),
especially along fault scarps. The wells producing wet steam
are less than 46 m (150 ft) in depth, along the trace of a fault
in the center of Klamath graben. Apparently, steam has col-
lected there as the result of boil-off from a deeper hot water
aquifer.
The deepest thermal wells are those at OIT campus, which
reach to 550 m (1,800 ft) in depth, and have a temperature of
88°C (190°F). Deep oil tests elsewhere in the region may have
as high or higher temperatures, but do not involve the geo-
thermal convective system. A geothermal test hole near the
Klamath Hills geothermal zone was drilled to more than 1,700 m
(5,500 ft) by Thermal Power Company in 1976. Although no tem-
perature logs or chemical analyses are available to the public,
it is believed that the hole did not encounter the geothermal
aquifer sought.
Reservoir fluid probably is hot water. However, it is pos-
sible that steam is ascending from greater depths, perhaps as
boil-off from a still deeper hot water aquifer, and mixing with
descending cool meteoric water. This is based principally on
the relatively dilute chemical character of the hot water as
known.
180
-------
Chemically (Table 4.1), the cool ground and surface waters
are calcium magnesium bicarbonate, with very low TDS (often less
than 100 ppm). Chloride, sulfate, boron and fluoride are pres-
ent at less than 1 ppm. With increasing temperature, waters
show:
1) increased TDS, commonly reaching 500-700 ppm, and
occasionally exceeding 1,000 ppm;
2) increase of chloride and especially sulfate relative
to bicarbonate;
3) increase of sodium relative to calcium, and absolute
drop in magnesium, probably as a result of fixation in
clay minerals;
4) only a mild increase in boron and fluoride, with
values rarely exceeding 1 ppm of either.
The system does not appear to be very gassy, although gas
analyses are almost nonexistent.
The Klamath Hills system appears similar, except that
sulfate values appear to be lower than at Klamath Falls.
Crude calculations based on mixing variable fractions of
low TDS, calcium magnesium bicarbonate water with hotter, more
concentrated geothermal waters lead to the conclusion that true
reservoir equilibrium temperature in the Klamath Hills system
may be above 150°C (300°F). This is compatible with a 55°C per
km (2°F per 100 ft) gradient to 3 km (10,000 ft).
Presently, about 500 hundred homes, offices, commercial
buildings, schools, churches and greenhouses are heated by
geothermal water from the shallow system from some 400 separate
shallow wells (Lund, et al. 1975). Well water ranges from 38°
to 110°C (100° to 230°F) in temperature as produced. The energy
consumption from this system is equivalent to 5.6 MW average
annual use, with a peak load equivalent to 56 MW. Although it
is widely believed that the system has the capacity to produce
far more than this, there is no factual basis for making a
quantitative estimate.
Well costs averaging about $10,000 have kept many home-
owners and small businessmen from installing geothermal well
systems. However, rising fuel costs have heightened interest in
such systems and increased utilization can be anticipated in
coming years.
181
-------
TABLE 4.1
CHEMICAL ANALYSES OF WATERS FROM SPRINGS AND WELLS
KLAMATH BASIN, OREGON
co
to
Name of Spring or Well
Eagle Point Spring
Shell Rock Spring
Cabin Spring
Hummingbird Spring
Neubert Spring
Well, 98.6 feet deep
OIT Well #6
Mer-Bell-Dairy
J. E. Erlcson
Oregon Water Corp.
Keno Spring
Alfred Jacobson
Weyerhaeuser Well /M
U. S. Air Force
Dave O'Connor
0. H. Osborn
Anderson Well
Abe Boehm
Liskey Well
Tulana Farms Spring
Sample
Location
T, R, Sec.
36-7-23dca
38-8-27
37-8-26
37-9-6bcd
37-9-7adc
37-9-9dcc
38-9-20adb
38-9-28ccc
38-9-28cdc
38-9-30acb
38-12-14
39-9-34
39-9-18
40-7-llccc
40-9-23bab
40-9-27cda
40-9-27
40-9-28aca
40-9-34aca
41-8-5cbb
Date
of
Sample
4-6-75
8-6-75
8-5-72
4-2-75
8-6-75
8-6-75
3-31-75
1-24-55
1 19-55
8-8-75
1-0-16-75
5-20-74
10-11-73
5-27-74
5-7-74
5-31-74
11-8-75
5-30-74'
5-9-74
8-8-75
Temp . ,
°C
85
7
11
11
10
10
79
81
83
15
11
30
22
15
24
90
27
25
93
13
PH
8.3
6.4
5.5
8.3
8.2
6.8
8.2
8.8
8.7
8.0
7.7
7.6
8.3
8.6
7.6
9.5
8.0
7.1
8.9
6.9
Specific
Conduc-
tance
Umho/ctn
305
110
-
135^
160
150
1050
1160
1230
250
100
290
200
340
260
920
450
2700
1030
115
TDS
Evapo-
ration
_
_
_
-
158
—
—
-
72
—
^
_^
-
286
_
724
_
(continued)
-------
TABLE 4.1 (continued)
00
U)
Name of Spring or Well
Eagle Point Spring
Shell Rock Spring
Cabin Spring
Hummingbird Spring
Neubert Spring
Well, 98.6 feet deep
OIT Well #6
Mer-Bell-Dairy
J. E. Ericson
Oregon Water Corp.
Keno Spring
Alfred Ja'cobson
Weyerhaeuser Well #4
U. S. Air Force
Dave O'Connor
0. H. Osborn
Anderson Well
Abe Boehra
Liskey Well
Tulana Farms Spring
Si02
38
32
29
18
21
24
31
81
. 87
27
40
65
16
31
42
90
41
100
90
24
Na
62
5.9
5.9
8.0
7.0
7.6
195
213
221
22
4.1
69
32
17
32
140
88
480
200
5.7
K
5.7
1.5
1.6
1.2
1.2
1.3
3.9
4.2
4.4
-
3.0
12
3.3
1.6
8.1
4.1
2.5
18
4.0
1.2
Ca
0.6
8.1
11.2
9.2
10.6
12.1
24.2
23
25
14.4
7
160
10
24
12
15
5.0
180
15
9.2
Mg
0.1
3.9
5.1
6.5
8.2
7.2
0.1
0
0
0.8
6.2
2.4
1.9
17
6.6
0
0.1
47
0.1
4.9
HC03
136
50
94
84
96
94
44
32
32
-
73
160
115
200
130
37
165
1460
48
60
C03
0
0
0
0
0
0
0
8
8
-
0
0
4.5
3
0
9
6.0
1
2
0
so4
<2
<2
<1
<2
<2
<2
400
403
1.2
0.4
13
4
2.3
14
270
36.2
300
360
2
^
Cl
16
<1
<2
1
1
1
58
54
56
4.5
1.8
7.9
4
2.3
9.1
56
23
170
59
_
F
.75
.10
.10
.10
.10
.11
1.45
1.2
1.6
.01
.08
.10
.11
0
0
1.5
.40
.20
1.5
.07
B
.14
.05
.10
.07
.05
.05
1.0
.96
.91
—
.05
.50
.09
0.9
0
.77
.15
1.4
.65
.05
(continued)
-------
TABLE 4.1 (continued)
00
Name of Spring or Well Na:K
Eagle Point Spring
Shell Rock Spring
Cabin Spring
Hummingbird Spring
Neubert Spring
Well, 98.6 feet deep
OIT Well #6
Mer-Bell-Dairy
J. E. Ericson
Oregon Water Corp.
Keno Spring
Alfred Jacobson
Weyerhaeuser Well 04
U. S. Air Force
Dave O'Connor
0. H. Osborn
Anderson Well
Abe Boehm
Liskey Well
Tulana Farms Spring
18.51
6.70
6.30
9.95
9.96
1.70
85.1
86.50
76.80
16.98
2.32
9.78
16.40
18.07
6.72
7.88
59.70
45.35
75.00
8.10
Na:Ca
180.99
12.70
0.90
1.15
1.10
1.51
14.05
16.20
15.40
2.66
1.02
.75
5.58
1.23
4.65
2.21
30.80
4.65
16.13
1.08
Na+K
Ca4MR
149.60
.82
.50
.55
.61
1.08
14.12
16.40
15.61
1.33
.59
.81
4.51
.60
2.80
2.49
30.71
3.32
14.81
.65
\tJLi
Total
Alk.
.40
.07
.10
.04
.04
.04
4.53
4.63
-
—
.06
.17
.12
.04
.24
4.19
.46
.40
3.64
.06
Cl
S04
21.70
1.36
-
1.35
1.35
2.72
.39
.36
.35
10.0
12.18
1.64
2.71
2.71
1.76
.56
1.72
1.53
.52
.50
•- J.OUJ.C IUH.J.UH —
Cl Cl
F B
11.45
5.42
-
5.42
4.94
39.40
21.44
24.10
18.80
239.50
21.85
42.20
19.78
-
-
20.01
32.80
455.48
18.40
7.83
34.87
6.80
-
7.63
7.63
_
17.70
17.16
18.78
-
10.97
4.82
13.56
.08
-
22.19
46.91
37.05
28.17
6.10,
HC03
B
172.31
177.38
269.60
340.56
333.47
-
7.80
7.39
7.80
—
259.50
56.76
235.52
400.08
-
10.06
194.20
185.11
15.40
212.85
Alk
SO/,
53.61
19.71
-
62.02
37.06
72.39
.09
.08
.07
-
200.10
9.70
23.55
69.54
7.31
.13
3.72
3.83
.14
9.72
-------
4.2.2 Potential Pollutants
The principal pollutant is heat; this is derived from all
wells, whether heat-exchangers (see 4.2.1, above) or direct
consumers of geothermal fluid. Those holes involving heat-ex-
change do not discharge any mineralized water, as none is pro-
duced from the wells. Only those few holes consuming geothermal
reservoir fluid have any geothermal discharge.
4.3 WATER POLLUTION POTENTIAL
4.3.1 Summary of Baseline Water Characteristics
Klamath Basin groundwaters fall into two main chemical
groups. Cool wells and springs are of the calcium magnesium'
bicarbonate type with low TDS (about 55 ppm). The second type
of water, occurring in warm and hot wells and springs, mostly
within the basins of the Klamath graben, is sodium bicarbonate
chloride sulfate water with TDS averaging 700 ppm (and reported
as high as 4,000 ppm). Boron and fluoride concentrations in-
crease with temperature. For a detailed discussion of water
characteristics of Klamath Basin, refer to Geonomics (in press).
Water pollution data are very scarce, incomplete and prob-
ably meaningless. They show principally that pulp; and paper
operations at Klamath Falls and agricultural irrigation dis-
charge more pollutants and possibly toxic substances than the
geothermal system can be shown to contain. Among these indus-
trial and agricultural wastes are pesticide residue, various
phosphate fertilizers, and sulfate and chloride ions. Partial
analyses of water from Klamath Lake and Klamath River show
indications of these.
4.3.2 Potential Water Pollutants
The principal pollutants from this discharge are chloride
ions (perhaps 50 to 60 ppm, Table 4.1) and boron, with about 1
ppm on the average. In comparison, local cool surface waters
average less than 1 ppm boron and 1 to 10 ppm chloride.
Other polluting constituents are not recognized from the
scattering of partial chemical analyses available to this study.
However, no data are available concerning metals or other trace
element contents of these waters. When these additional data
are obtained,the pollution potential may be altered.
185
-------
4.3.3 Potential Pollution Mechanisms and Pathways
Direct discharge from thermal wells goes into local surface
waters. Most wells do not directly produce the reservoir fluid,
but utilize heat-exchanging in the well with cool, meteoric
water supplied through the municipal water system. The heated
municipal water is discharged to the sewer system when depleted
of its heat. Those wells (principally OIT and Klamath Hills)
consuming reservoir fluid at the surface, dispose of the heat-
depleted fluid in a similar manner.
4.3.4 Level of Potential Pollution
No reason is seen for an increase in pollutants, unless
either:
1) New wells are allowed to discharge to the surface
instead of being heat-exchanged with cool meteoric
water; or
2) Wells are drilled into deeper aquifers (perhaps 900 m
[3,000 ft] or deeper).
The latter seems unlikely in the near future, because of
the cost of the deeper drilling, and the general lack of inter-
est in exploration for a deep geothermal aquifer for generation
of electricity. If it occurs, new studies of chemistry, heat
content and pollutants will be required.
4.4 SEISMICITY ,
4.4.1 Summary of Baseline Seismicity and Seismic Risk
Throughout the Pacific Northwest, including Klamath Basin,
very few seismograph stations operated until the year 1962.
Earthquakes of magnitudes smaller than 4% or 5 either were not
recorded at all, or were not recorded at sufficient stations to
permit instrumental location of epicenters and determination of
magnitude. Thus, nearly all pre-1962 shocks were located using
felt-reports, which are highly dependent upon the distribution
of population and time of day of occurrence. Also, the "size"
of these events was based on a crude, graduated rating of
effects.
Therefore, the earthquake history of this region is poorly
known as to the occurrence of noninstrumental epicenter location
and size of smaller shocks (M^5). For this reason, correlation
of seismicity with particular faults, and determination of mag-
nitude-frequency curves for various areas, cannot be done with
much confidence.
186
-------
Most of Oregon, and adjacent parts of Idaho, Nevada and
California, form a large region of low seismicity in comparison
with many parts of the western United States. Historically, no
major, destructive earthquakes have occurred in Oregon, nor has
any instance of surface faulting been reported. Moderate seis-
micity characterizes the Portland-Willamette Valley area of
northwestern Oregon; however, the rest of the state exhibits
lower or negligible seismicity. Slight seismicity has been
reported near Klamath Falls, but not elsewhere in Klamath Basin.
Berg and Baker (1963) reported five small shocks, with intensity
IV, at Klamath Falls during the years 1947 to 1951.
Earthquake risk is poorly known because of the extremely
low seismicity and inadequate reporting. Couch and Lowell
(1971) have analyzed earthquake occurrence in Oregon, and de-
scribed the seismicity of several physiographic provinces. One
of the provinces is the Basin and Range, which includes Klamath
Basin.
Very limited data suggest a rate of energy release of 8.8 x
1016 ergs/yr for the period 1870 to 1970 (Couch and Lowell,
1971); this figure is probably too low, due to the lack of
shocks being reported between 1870 and 1906. In any case, this
rate of energy release is equivalent to the occurrence of one
M~3.3 earthquake per year per 10,000 sq km (3,900 sq mi); or to
one shock of M~5 per 50 years per 10,000 sq km (3,900 sq mi).
Clearly, this area has exhibited very low seismicity compared to
the seismicity of central coastal California, which may be
expressed as ten M~5 shocks per 50 years per 10,000 sq km (3,900
sq mi).
Based upon the above data, the maximum probable earthquake
acceleration per 100 years at a given site in the Klamath Basin
is expected to be about 0.07 g. Therefore, earthquake risk to
well-engineered facilities in this area is quite low in com-
parison with many other areas.
No individual faults are mapped as presently active or as
disturbing late Quaternary deposits. However, fault movement
was intense in Pliocene and early Pleistocene time, and the
potential for renewed movement may exist.
4.4.2 Potential Induced Seismicity
Seismicity may be induced by change of pore pressures,
resulting from (a) withdrawal of fluid from rocks that are
poorly consolidated, with abundant pore space, or (b) injection
of fluid under high pressure into brittle rocks of limited
porosity. Neither condition is recognized at Klamath Falls.
Withdrawal is limited to a few wells on the OIT campus and
at Klamath Hills. Other wells involve in situ heat-exchanging,
187
-------
without production of fluid from the geothermal reservoir. No
injection takes place.
Unless the conditions of utilization change radically,
induced seismicity is not anticipated.
4.5 SUBSIDENCE
Subsidence is reported from many localities where fluid
(oil, gas, steam, water) is produced from poorly consolidated
rocks or sediments. The case at the Wairakei, New Zealand,
geothermal field is well known.
4.5.1 Baseline Data
There has been no systematic attempt to collect data from
leveling or triangulation surveys to determine if subsidence is
occurring at Klamath Falls.
4.5.2 Potential Subsidence
If production of geothermal fluid increases, or continues
for a very long time at its limited rate, some surface sub-
sidence may be noted. Production currently is limited to a few
hundred liters per minute along the Klamath Hills and on the OIT
campus. Some declines in static and pumped water levels have
been reported informally at OIT, but no quantification has been
possible. At these production levels, it may be decades before
ground subsidence is recognized.
4.6 POLLUTION CONTROL TECHNOLOGY
4.6.1 Current Practices
Pollution appears so minimal, that nothing is done at
present to control it. Probably the single most significant
indirect control mechanism is the practice of heat-exchanging in
all but a handful of the 400 thermal wells in Klamath Falls and
Klamath Hills, thus preventing discharge of any geothermal
fluid.
4.6.2 Anticipated Technology
Changes'in practice are not anticipated. Perhaps in future
years it will be necessary to ensure that all nonthermal aqui-
fers are cased and cemented off from the thermal aquifers in
every well. However, the value to be gained from this may be
minimal, as the thermal water is of relatively good quality.
188
-------
REFERENCES
Berg, J. W. and C. D. Baker. Oregon Earthquakes, 1841-1958.
Seis. Soc. Amer. Bull. v. 53, p. 95-108, 1963.
Couch, R. W. and R. P. Lowell. Earthquakes and Seismic Energy
Release in Oregon. Oregon Dept. Geol. and Min. Industries,
Ore Bin, v. 33, No. 4, p. 61-84, 1971.
Geonomics, Inc. Baseline Geotechnical Data for Four Geothermal
Areas in the United States. United States EPA, Environ-
mental Monitoring and Support Laboratory, Las Vegas,
Nevada, in press.
Lund, J. W., G. G. Culver and L. S. Svanevik. Utilization of
Intermediate-temperature Geothermal Water in Klamath Falls,
Oregon; in Second United Nations Symposium on the Develop-
ment and Use of Geothermal Resources, Proceedings, v. 2, p.
2147-2154, 1975.
Raisz, E. Landform Map of Oregon. State Department of Geol.
and Min. Ind., Portland, Oregon, 1955.
Sammel, E. A. Hydrologic Reconnaissance of the Geothermal Area
Near Klamath Falls, Oregon. USGS Open File Report WRI
76-127, 1976.
189
-------
SECTION FIVE
RIO GRANDE RIFT ZONE
5.1 INTRODUCTION
For discussion purposes the Rio Grande Rift divides con-
veniently into four parts, each with distinctive geothermal
features and energy potential (Fig. 5.1). In "downstream"
order these parts are:
1) the San Luis Basin,
2) the Jemez (Valles Caldera) area,
3) the Socorro-La Jencia Basin, and
4) the southern Rio Grande Rift area.
These areas represent markedly different levels of geother-
mal potential and consequently different levels of potential
environmental impact resulting from development.
The baseline data report of this series (Geonomics, in
press) described the climatology, geology, hydrology and seis-
mology of the Rio Grande Rift in general. That study has led us
to focus on the Jemez (Valles Caldera) area. Consequently, more
detailed baseline data for the Jemez area will be developed
here, with emphasis on potential environmental impacts.
The Jemez River Basin includes both the Union Oil Company's
announced geothermal discovery (in the Valles Caldera) and the
hot dry rock experiment being carried out nearby by the Los
Alamos Scientific Laboratory, University of California (LASL).
From the standpoint of anticipating the potential environmental
impact of geothermal development, sufficient data exist only for
the Jemez area. Either the hot dry rock experiment or the Union
Oil Company field could become operational geothermal energy
sources within a few years. The need to understand the environ-
mental impact of these operations could become urgent within a
relatively short time; whereas the environmental impact of geo-
thermal development in the other areas lies years to decades in
the future. Therefore, we have focused only on the Jemez area
in this report.
190
-------
COLORADO
108°
I06e
32
36°-
^^*
Z
o
N
34°—
o:
<
_
!
.
o i
1
i rf
I i I
JemeZ .JemezX
Area-* Springs
y|
*/ALBUOUE
il
*/
~ o J
If *
• SOCORRO
J
/
fl
n
f
I
\
. 1
— v — i r
] San Luis
J •* — Basin
' SANTA FE
ROUE
Socorro La
— Jenica Basin
Southern
Rio Grande
« — Rift Area
\LAS CRUCES
\
\
MEXICO
'0 TEXAS
— 1
•
-36°
to
X
UJ
1-
— 34°
i
—
1
-i — 32°
>° 104° N
*-o 1
108° IUO~ 1
0 25 50 75 100 125 150 mlln '
6 50 100 150 200 Mlomitars
Figure 5.1 Thermal areas of the Rio Grande Rift in New Mexico
191
-------
The Jemez area includes the high mountains of the rela-
tively young Valles Caldera and some smaller and older volcanic
structures (including the Toledo Caldera) and their related
valleys, plus the plateaus and river valleys adjacent to the
principal volcanic pile (Fig. 5.2).
Fig. 5.3 shows the thermal features of the area. Warm and
hot springs occur at more than 20 places within the area.
Carbon dioxide and hydrogen sulfide discharge from many of the
springs and an extensive solfataric area within the caldera.
Two wells drilled outside the caldera during the search for
oil and gas found hot water and, in I960, Westates Petroleum
Company drilled a wildcat well in the solfataric area in Alamo
Canyon of the Valles Caldera and found steam.
The San Luis Basin represents a not unusual enigma—just
enough thermal activity to make it a possible target, but not
enough activity to make it a high priority target for explora-
tion.
The Socorro-La Jencia area excites the imagination, because
it may be underlain by a large magma body.
The Southern Rio Grande Rift area exhibits many surficial
thermal features that constitute attractive potential targets
for geothermal exploration.
5.1.1 Summary
The Jemez area of the Rio Grande Rift is the only area in
the Rift for which sufficient data are available to assess the
potential subsurface environmental impacts of geothermal devel-
opment.
The Valles Caldera dominates the area and is the apparent
center of geothermal activity. Within the caldera Union Oil
Company has six production wells. West of the caldera LASL is
conducting the hot dry rock experiment using two wells drilled
deep into the underlying granite, where rock temperatures are
200°C (392°F). Water circulating through hydraulically produced
fractures from the injection well to the production well has
been warmed to more than 100°C (212°F) during short tests.
The geothermal features occur entirely within the Jemez
River Basin. The warm and hot waters outside the caldera are
mixtures of circulating shallow groundwater and "deep thermal
ground water" from the caldera.
Potential pollutants due to production of thermal fluids
include arsenic, boron, fluoride and hydrogen sulfide. Injec-
tion of waste fluids into wells within the caldera should remove
any hazard; release at the surface would be hazardous.
192
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VALLES
CALDERA
JEMEZ RIVER
BASIN
107° Aftef Traln«r(l974)
Figure 5.2 General features of the Jemez area
193
-------
„ r m ^^P1^!'1 &
VALLES CALDERA AREA
^LuQU^fa|tf^^x^-Mg£g '£>&
' J ^^—,
-35° 18'56"|
»
r~
O 0
20 kilometers
•
20 miles
•v. . *aL^aiMUsy .. .1
By R.M. Colprtts,Jr. 6/77 "in'
After Summers, W.K. (1976) -^
«.
g
Figure 5.3 The Jemez River Basin
194
-------
Waters circulating in the hot dry rock experiment will have
compositions similar to those observed in granite terrains and
TDS should be well within the federal and state quality stand-
ards for potable water.
Distinguishing environmental changes created by development
of the geothermal resources from changes due to natural phenom-
ena or to other activities of man will be difficult.
Seismic effects of hydraulic fractures at the land surface
are negligible. Deformation within the caldera is primairly by
creep, so the seismic effects of steam production should be
minimal.
Subsidence could become evident in the caldera if the
pressure head in the caldera fill sediment decreases.
5.2 GEOLOGIC SETTING
5.2.1 Topography and Drainage
The Jemez Mountains dominate the Jemez area (Figs. 5.3 and
5.4). They are a great pile of igneous rocks rising from dis-
sected plateaus to peaks over 3,100 m (10,000 ft) above sea
level. Valles Caldera lies within these towering peaks, a
roughly circular depression about 19 to 24 km (12 to 15 mi)
across.
The Jemez River drains Valles Caldera and empties into the
Rio Grande about 10 km (6 mi) north of the community of Ber-
nalillo. It is the only major stream draining the area of
discharging thermal water in this volcanic field. All the
smaller streams in the caldera area drain into the Jemez River.
The Rio Chama drains the north flank of the area and the Rio
Puerco drains the west flank of the Sierra Nacimiento.
The floor of the Valles Caldera lies 150 to 610 m (500 to
2,000 ft) below the caldera rim and is crumpled into numerous
smaller valleys and peaks. Most of the peaks result from resur-
gent emplacement of rhyolite after the caldera floor collapsed.
Between and below the peaks are high mountain valleys with
perennial streams. San Antonio Creek drains the northern and
western parts of the caldera. The East Fork of the Jemez River
drains the southeastern and southern part of the caldera.
Sulphur Creek and Redondo Creek drain the western interior of
the caldera, including the solfataric areas where most of the
drilling for steam has been concentrated.
Most of the domed mountains follow the ring fractures
within the caldera wall (Kudo, 1974). Redondo Peak rises from
the caldera floor inside the ring fractures to an altitude of
3,432 m (11,254 ft) and is the highest peak in the region.
195
-------
o
o
o
So
10
10
ByR.M.Colpi»1»,Jr.6/77 "to
20 kilometers W.K.Summers 8 Assoc. -°
after Oane,C.H.a Bochman,G.O.(l965) 5-
, 20 miles
U>
Figure 5.4 Geology of the Jemez area
(legend to this figure is on following
page)
-------
EXPLANATION
Quoternary
QT I Quaternary-Tertiary
I T I Tertiary
M
Mesozoic
p€
P Paleozoic
Pre-CamDrian
Quaternary-Tertiary
Basalt Flows
Tertiary 8 Cretaceous
Intrusions
m
,-Xv
Calderos
HH Debris field related to
Ji the VallesCaldera
contact
fault
/* diKe
Figure 5.4 (continued)
197
-------
5.2.2 Physiography and Geomorphology
In geologic terms the Jemez Mountains are young. The
oldest basalts of this complex volcanic pile appear to be of
early Pliocene age with one member dated by the potassium-argon
method to be at least 8.5 million years old (Kudo, 1974). Two
periods of caldera formation followed these early flows, the
latest about 1.1 million years ago (Kudo, 1974).
Ross, et al. (1961) describe the Jemez as "a maturely
eroded, central mountainous mass surrounded by more youthfully
dissected plateaus and mesas." The gentle slopes of the mesas
and plateaus surrounding the Valles Caldera are deceptive, for
deep canyons with steep walls cut them into numerous smaller
sections. Best known of these gorges is San Diego Canyon,
through which the Jemez River flows away from the caldera and
south to San Ysidro where it is joined by the Rio Salado. Hot
springs have built the famous Soda. Dam across the Jemez River in
San Diego Canyon south of the caldera. Reagan (1903) believed
the series of breached travertine dams showed that San Diego
Canyon was cut by the river as it continued to erode a channel
through a series of uplifts.
5.2.3 Soils and Vegetation
Most of the soils in the area developed basically in place
from the volcaT _c rocks of the pile, although the lower mesas
down by Jemez Pueblo and San Ysidro contain Tertiary and Quater-
nary sediments of more varied composition. All but the steepest
canyon walls support vegetative cover, including forests in the
high plateaus and mountains. Greasewood, cacti and native
grasses characterize the lower elevations with willows and
cottonwoods along the rivers. Mixed conifer forests of aspen,
gambel oak, pine, spruce and fir cover the higher mountains.
5.2.4 Structure
The Valles Caldera lies across the Jemez Fault (Fig. 5.4),
a northeast trending fault which has been called the western
margin of the Rio Grande Depression (Ross, et al. 1961). Our
broader interpretation of the rift zone puts the western bound-
ary along the Nacimiento Fault (Fig. 5.9), which trends north-
south west of the Jemez Plateau and separates the Rio Grande
Rift from the San Juan Basin. As Fig. 5.4 shows, numerous
smaller faults criss-cross the Jemez area. Most trend north to
northeast, but a few trend northwest. Many follow an en-echelon
pattern similar to those associated with the rift in other
areas. The Valles Caldera and the volcanic pile around the
caldera cover many suspected faults.
Ross, et al. (1961) suggested that the Jemez Fault may have
continued into the caldera, where the post-caldera graben aligns
198
-------
Su99ested extension of the Jemez Fault. Besides that
\al faults break UP the dome within the
al ' i970)' The ring faults along which ««
have been covered by younger volcanics and
« ™™ flth' et al* (1970) found exposures that indicate
a»«»ff J+"?,^8 Z°ne 3 ^ 5 km (2 to 3 mi) wide around the
"moat" of the Valles Caldera.
^ T7 9reatj-er thickness of volcanics toward the east side of
tne Valles Caldera, compared with thickness of volcanics to the
west, plus displacement along the major fault zones, led Ross,
et al. (1961) to suggest that "volcanism in the Jemez Mountains
is related to the initiation of faulting in the Rio Grande
Depression."
5.2.5 Heat Flow
Heat flow values of about 5 HFU (1 HFU = 10~6 cal/cm2/sec)
occur on the west side of the caldera (Blair, et al. 1976).
Reiter, et al. (1976) measured heat flows ranging from 3.8 HFU
to 10.0 HFU for ten intervals in four drill holes west of the
caldera, and thermal gradients ranging from 23.1°C/km to
273.8°C/km (100°F/mi to 488°F/mi) for 26 intervals in 13
holes. The wide variation among values within a hole compli-
cates use of these data, but even the low heat flow calculated
at 3.8 HFU exceeds the world average heat flow of 1.5 HFU
(Blair, et al. 1976).
Reiter, et al. (1976) suggest that magmatic sources asso-
ciated with the young resurgent domes in Valles Caldera could
account for the unusually large heat flow of the area.
5.2.6 Stratigraphy and Paleography
Rocks of Precambrian Age —
Rocks of Precambrian age crop out in parts of the Jemez
River Basin and have been found at depth in several drill holes.
Fig. 5.5 shows contours on the surface of the rocks of Precam-
brian age. This map was modified from Cordell (1976) on the
strength of additional data from the well log library of the
petroleum section of the New Mexico State Bureau of Mines and
Mineral Resources. Precambrian rocks in this area generally are
called granite although many of them are metamorphic rocks.
Tester (1974) reports granites, granodiorites , monzonites,
quartz monzonites, gneisses, schists and amphibolites encoun-
tered in the Precambrian section of the granite test holes of
LASL's hot dry rock project.
Rocks of Paleozoic Age
Rocks of Paleozoic age in the Jemez area are mostly sedi-
mentary strata of Pennsylvanian and Permian age. Smith, et al.
(1970) include Mississippian age rocks in their undivided Car-
199
-------
to
20 kilometers
20 miles
00 Q -100(12000 .
By RM.Co»pitfs,Jr. 6/77
IW.K. Summers 8 Atscc.
Modified offer Corddl (1976)
EXPLANATION
Altitude of
the top of
Pre-Cambrian (ft.)
Pre-Cambrion
outcrop
Stratigraphic
control
points
Well log from
O NM8MMR
Well log library
107° 00
+4000
35? 18' 56"
106° 14*05"
Figure 5.5 Relief of the rocks of Precambrian
age in the Jemez area
200
-------
boniferous unit, but most other workers cite Magdalena Group
strata of Pennyslvanian age directly overlying Madera Limestone
(Purtyman, 1973). The Sandia Formation locally includes a lower
limestone and upper clastic unit of sandstone, shale and lime-
stone. The Madera Limestone contains gray shales and a few
sandstones interbedded in the lower dark gray limestone, with
limestone and arkosic limestone alternating with gray and red
arkosic shale above it (Purtymun, 1973). Trainer (1974) found
as much as 300 m (1,000 ft) of Magdalena Group rocks. Permian
rocks in the area include sandstone, siltstone and shale redbeds
assigned to the Abo and Yeso Formations and totalling up to 366
m (1,200 ft) (Trainer, 1974).
Rocks of Mesozoic Age—
Rocks of Mesozoic age in the Jemez River Basin include the
Chinle Formation of Triassic age, the Morrison, Todilto and
Entrada Formations of Jurassic age, and the Mancos Shale and
Dakota Sandstone of Cretaceous age (Smith, et al. 1970). Renick
(1931) measured sections of the rocks of Mesozoic age. His
sections suggested a total thickness of 1,500 m (5,000 ft), but
since he continually notes that these formations have highly
variable thickness, that number is little better than a guess.
Test holes at the LASL's hot dry rock project and some test
wells in the caldera went from Abiguiu Tuff of early Tertiary
age directly into Abo Formation (Purtymun, 1973). The rocks of
Mesozoic age occur only in the western part of the area; over
the remainder of the area they were eroded away before the rocks
of early Tertiary age were deposited.
Rocks of Tertiary Age—
Renick (1931) found 250 m (820 ft) of Nacimiento Formation
and 35 m (115 ft) of Wasatch Formation to be of Eocene age, and
at least 460 m (1,500 ft) of Santa Fe Formation to be of Miocene
to Pliocene age. These formations all consist of sedimentary
rocks, mostly soft shales and sandstones of gray, tan and buff
colors, although the Santa Fe commonly is red and tan. Other
formation names have been used by other authors in different
parts of the map area for similar sedimentary strata. Smith, et
al. (1970) mapped the main caldera area, and their stratigraphic
descriptions include the El Rito, Galisteo, Zia Sand and Santa
Fe Formations, which contain sand, silt, clay, sandstone, shale,
siltstone and conglomerate of red, tan, gray and buff colors.
These rocks, of highly variable thicknesses, are interbedded
with volcanic and volcanic-derived units which range from basal-
tic to rhyolitic in composition and also have variable thick-
nesses. Most of these volcanic beds belong to the Keres Group
of Bailey, et al. (1969), who state that the lenticular nature
of the formations in this group make its maximum actual thick-
ness no more than 915 m (3,000 ft).
The Keres Group occurs mostly in the southern Jemez Moun-
tains and represents a pre-caldera phase of volcanism (Kudo,
1974).
201
-------
Rocks and Sediments of Quaternary-Tertiary Age—
Several pediments, terraces and older alluvium deposits,
and the Polvadera Group of volcanic rocks show Pliocene to early
Pleistocene ages. The Polvadera Group consists of "the sequence
of basaltic, andesitic, dacitic, and rhyolitic rocks that form
part of the central and most of the northern Jemez Mountains"
(Bailey, et al. 1969). The lenticular nature of formations in
the group allovfl a maximum thickness in one place of 1,070 m
(3,500 ft) (Bailey, et al. 1969). Kudo (1974) points out that
Santa Ana Mesa and Cerros de Rio Basalts southeast of the Jemez
Mountains also erupted during the time of the Polvadera Group,
and volcaniclastics accumulated between and around volcanic
units.
Rocks and Sediments of Quaternary Age—
The Tewa Group volcanics represent the last stages of
volcanism in the Jemez Mountains and include the famous Bande-
lier Tuff, the Cerro Toledo Rhyolite, the Cerro Rubio Quartz
Latite, and the yalles Rhyolite (Bailey, et al. 1969). The
oldest formation in the Tewa Group is the Bandelier Tuff of
early Pleistocene age, and the Bandelier Tuff is divided into
two members, each having a basal pumice bed overlain by ash-flow
tuff (Kudo, 1974). According to Ross, et al. (1961) the Bande-
lier Rhyolite Tuffs
"erupted from the crest of the Valles Range from
centers now obscured, poured down valleys in the
higher mountainous terrain, and spread out as broad
coalescing fans on the gentler surrounding slopes...
They cover an area of nearly 1,040 sq km (400 sq mi),
locally attain a thickness of 300 m (1,000 ft), and
represent the accumulation of more than 200 cu km (50
cu mi) of ash and pumice."
The explosive eruption of each member of this voluminous
formation produced caldera collapse. The Toledo Caldera re-
sulted from the first period of eruption of Bandelier Tuff. The
Valles Caldera formed about 1.1 million years ago. The tuff
from the second eruption partially obscures the Toledo Caldera
(Kudo, 1974).
After each eruption, rhyolitic magmas rose along the ring
fractures of the caldera and formed volcanic domes (Kudo, 1974).
Within the Valles Caldera, renewed magmatic activity created the
resurgent dome we call Redondo Peak (Ross, et al. 1961). Tuffa-
ceous sediments deposited in lakes during several stages in the
calderafs history lie interbedded with rhyolites of the Tewa
Group (Ross, et al. 1961). Other Quaternary units include
alluvium, landslike deposits, terrace gravels, fan deposits and
caldera fill (Smith, et al. 1970).
202
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5.2.7 Water Bearing Characteristics
With the exception of the rocks of Precambrian age at the
site of the hot dry rock experiments, we lack detailed quanti-
tative measurements of the water bearing or water yielding
characteristics of the rocks in the Jemez area. Most of the
rocks in the area are of moderate to low hydraulic conductivity
and yield water to wells or springs at some place in the area,
but many wells yield less than 40 1pm (10 gpm).
Water in the Precambrian basement occurs in fractures, so
the concentration of fracturing controls the amount of water
available from these rocks (Trainer, 1974). In the hot dry rock
project on the Jemez Plateau, Purtymun, et al. (1974) found
permeabilities that ranged from 5.3 x 10"16 sq cm (5.4 x 10~8
darcys), determined from water level decay over a period of
months, to 1.4 x 10~12 sq cm (1.4 x 10~4 darcys) determined from
pressure decay after repressurization of a hydraulic fracture,
and said these permeabilities indicate the basement at the site
is "dry" for project purposes.
The Paleozoic strata carry water in fractures, intergran-
ular pores, and solution channels (Trainer, 1974 and Renick,
1931). Locally the hydraulic conductivity of these rocks could
be greater than 30 m/d (100 ft/d), but the average hydraulic
conductivity is undoubtedly much lower, possibly in the range of
0.03 to 0.2 m/d (0.1 to 0.5 ft/d).
The brittle sandstones and siltstones of Mesozoic age yield
water to wells primarily from fractures. Tests of cores from
wells elsewhere in New Mexico suggest that these brittle rocks
have an interstitial hydraulic conductivity that is very low,
whereas pumping tests of wells that tap fractures indicate an
average hydraulic conductivity in the range of 0.3 to 2 m/d (1
to 5 ft/d).
The Tertiary valley fill tested near Los Alamos appears to
have hydraulic conductivity ranging from 0.3 to 7.6 m/d (1 to 25
ft/d). Where these deposits are thick (2,070 m [6,800 ft]),
they yield as much as 3,800 1pm (1,000 gpm) to wells (Purtymun
and Johansen, 1974).
Quaternary sediments have the best water bearing character-
istics among the rocks of the Jemez River Basin. In the high
country all the materials with a granular nature, including
broken rock and soil, become important water bearing units
because they accept infiltrating water and transmit part of it
downward (Trainer, 1974).
203
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5.3 HYDROLOGIC SETTING
5.3.1 Introduction
The Jemez River Basin (Fig. 5.3), an area of about 2,700 sq
km (1,040 sq mi), and a sub-basin of the Rio Grande Basin, con-
tains 'all the thermal features of the Jemez area. It is the
primary hydrologic entity that will be impacted by geothermal
development. We have, therefore, concentrated our attention on
the hydrology of this basin.
5.3.2 Climate
The Jemez River Basin map covers a large range of altitudes
and the climate varies accordingly. The immediate area of
interest around the Valles Caldera has a more restricted range
of climatic variation.
Climatoloqical Data—
Climatological data have been collected at 32 stations in
the map area by the U.S. Weather Bureau. Of these, 28 have one
year or more of precipitation data, 14 also have temperature and
potential evapotranspiration data. LASL installed a weather
station at the site of the dry hot rock project in December
1975.
Annual Means—
Annual mean precipitation at stations in the Jemez Basin
ranges from 170 mm (6.73 in.) at San Ysidro, altitude 1,700 m
(5,500 ft) to 634 mm (24.94 in.) at Jemez Springs, altitude
1,900 m (6,230 ft). These numbers represent the total monthly
mean precipitation recorded at the stations. Fig. 5.6 shows the
linear trend obtained when these mean annual precipitation data
are plotted versus the altitude of the stations.
Mean annual potential evapotranspiration ranges from 544 mm
(21.43 in.) at Lee Ranch, altitude 2,651 m (8,691 ft), to 1,056
mm (41.58 in.) at Pena Blanca, altitude 1,595 m (5,230 ft).
Fig. 5.7 shows the linear trend obtained when annual potential
evapotranspiration data are plotted versus altitude.
Mean annual deficit ranges from 93 mm (3.56 in.) at Lee
Ranch, altitude 2,651 m (8,691 ft), to 873 mm (34.38 in.) at
Pena Blanca, altitude 1,595 m (5,230 ft).
Mean annual surplus ranges from 0.5 mm (0.02 in.) at Berna-
lillo, altitude 1,539 m (5,045 ft), to 157 mm (6.20 in.) at Wolf
Canyon, altitude 2,501 m (8,200 ft).
Monthy Variation During an Average Year—
• Table 5.1 gives the monthly percentage of the annual total
and cumulative percent of mean monthly precipitation for five
204
-------
altitude
(ft)
npoo
Jemez Basin Area Rio Grande Rift, N.M.
10,000
9,000
O
apoo
7,000
O
O
0
I QG>
© t
O
O
Stations with more than
D30 years annual
record
O 30 years or less of
annual record
(using sum of monthly
means, over bottom
figures, where there's
a choice)
epoo
O
0
0
00
0
Q
10
20 30
Precipitation (in)
40
50
Figure 5.6 Relation of annual mean precipitation to altitude
205
-------
altitude
(ft)
iipoo
icpoo
Jemez Basin Area Rio Grande R'rft, N.M.
9000
epoo
O
D
©
Stations with more than
CD 30 years annual
record
0 30 years or less of
annual record
7000
0
0
O
6,000
a
m
5,000
Q
10
20 30
evapotranspiration (in)
40
50
Figure 5.7 Relation of annual mean potential evapotranspiration
to altitude
206
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TABLE 5.1 CUMULATIVE PERCENT OP MEAN MONTHLY PRECIPITATION FOR STATIONS
IN THE JEMEZ AREA
Station Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Total
Lee Ranch monthly 4.0 8.0 7.1 4.7 7.3 7.0 17.8 15.9 13.2 5.8 4.5 4.7 100.0
(86911)
cumulative 4.0 12.0 19.1 23.8 31.1 38.1 55.9 71.8 85.0 90.8 95.3 100.0
Jemez Springs monthly 4.9 5.4 5.9 5.8 6.7 7.1 16.3 17.4 9.9 9.7 4.6 6.1 99.8
(6230')
cumulative 4.9 10.3 15.2 22.0 28.7 35.8 52.1 69.5 79.4 89.1 93.7 99.8
Bernalillo monthly 4.9 4.9 6.0 5.2 6.5 4.9 15.6 17.1 13.0 11.6 4.5 5.6 99.8
10 (50451)
cumulative 4.9 9.8 15.8 21.0 27.5 32.4 48.0 65.1 78.1 89.7 94.2 99.8
Pena Blanca monthly 5.9 4.0 5.1 4.7 4.6 7.4 10.1 19.3 15.4 11.4 3.2 9.0 100.1
(52301)
cumulative 5.9 9.9 15.0 19.7 24.3 31.7 41.8 61.1 76.5 87.9 V,i.l 100.1
Wolf Canyon monthly 6.8 7.7 8.4 6.5 6.2 5.4 15.8 14.6 9.0 7.6 5.0 6.8 99.8
(8220')
cumulative 6.8 14.5 22.9 29.4 35.6 41,0 56.8 71.4 80.4 88.0 93.0 99.8
-------
stations in the Jemez area. The figures show a "wet" period of
July, August and September over the area, followed closely by a
"dry" period in November, December and January.
5.3.3 Stream Flow
The Jemez River and its tributaries are gaining, effluent
streams, from the headwaters down to about the Jemez Pueblo
where the river begins to flow over the Tertiary-Quaternary
valley fill. From about Zia Pueblo to its confluence with the
Rio Grande, the Jemez River is a losing stream. The Rio Salado,
which drains the Sierra Nacimiento and the southwestern part of
the Jemez River Basin, is an intermittent stream.
The USGS gages stream flow in the Jemez River Basin at four
locations (Table 5.2).
Separation of the flow duration curves for the Rio Guada-
lupe and the Jemez River near Jemez into surface runoff and
groundwater components (under the assumption that both distri-
butions are log normal) suggests that the mean annual base flow
due to groundwater discharge is about 45 and 240 Ips (1.6 and
8.4 cfs) or 0.08 and 0.19 Ips/sq km (0.007 and 0.017 cfs/sq mi)
respectively; whereas the surface runoff is about 960 and 1,700
Ips (34 and 61 cfs) or 1.59 and 1.42 Ips/sq km (0.145 and 0.130
cfs/sq mi) respectively.
5.3.4 Groundwater
Flow Systems—
Local, intermediate and regional flow systems can be iden-
tified in the Jemez River Basin. The local flow systems are
recharged nearby and discharge the water to springs and head-
water streams such as the San Antonio Creek and Rio Cebolla.
Intermediate systems underflow these local systems to discharge
to the Rio Guadalupe or the Jemez River. Thus, we expect that
the volume of groundwater discharging should increase down-
stream. This expectation is supported by the observed increase
in the groundwater component estimated from the stream flow
duration curves. The regional flow system involves the movement
of groundwater from the recharge area within the Jemez River
Basin to the Rio Grande. That such underflow occurs is diffi-
cult to prove systematically but it exists by inference. The
Jemez River becomes influent near San Ysidro. Titus (1961)
showed through water table contours that this water moves about
due south toward the Rio Grande. Clearly any part of the ground-
water underflow that had not discharged to the Jemez River must
also then move toward the Rio Grande.
Recharge—
Groundwater recharge has not been quantified, but based on
the apparent groundwater discharge estimated from the stream
208
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TABLE 5.2 STREAM GAGING STATION IN THE JEMEZ RIVER BASIN
to
o
vo
Number
08-3215.00
08-3230.00
08-3290.00
08-3290.00
Station
Name
Jemez River below
East Fork, near
Jemez Springs
Rio Guadalupe at
Box Canyon, near
Jemez
Jemez River near
Jemez
Jemez River below
Jemez Canyon Dam
Gage
altitude
(ft)
6703
6016
5622
5096
Drainage
area
(mi2)
173
235
470
1083
Years
of
record
1949-1950
1951-1957
1958-
1958-
1936-1940
1949-1950
1953-
1936-1937
1943
Discharge
Mean/area
Mean (cfs) (cfs/mi2)
28.4 .164
36.3 .154
69.2 .147
54.8 .051
-------
flow duration curves, we believe that the average recharge upon
the area is larger than 0.2 Ips/sq km (0.02 cfs/sq mi). Assum-
ing 80% of the area above the gaging station on the Jemez River
near Jemez Springs is recharge area, more than 6.4 mm/yr (0.25
in./yr) of the precipitation becomes recharge.
Recharge estimates can also be based on the relationship:
R = Pj (P-i)/100
where:
R = average annual recharge,
P = average annual precipitation,
j = a terrain constant, and
i = annual precipitation that must be exceeded for recharge
to occur.
Assuming j = 0.5, i = 6, and this relationship, we see that
recharge can be expected to range from about 5 mm/year (0.2
in./year) at low altitudes to about 64 mm/year (2.5 in./year) at
the highest altitudes. So we have still further reason for
believing that significant underflow to the Rio Grande occurs.
Discharge—
Groundwater discharge occurs to the atmosphere via evapo-
transpiration, to springs and streams, and as underflow to the
Rio Grande. Discharge to wells within the basin serves for
domestic and stock use and probably represents only a very small
part of the total ground water discharged from the basin.
5.3.5 Water Chemistry
Our knowledge of the chemical characteristics of the water
of the Jemez River Basin derives from analyses of water from
comparatively few sources, albeit some of these sources have
been sampled many times. Detailed chemical analyses of thermal
and nonthermal groundwater as well as analyses of surface water
can be found in the following publications. Summers (1976)
compiled the available analyses of thermal water. Kelly and
Anspach (1913), Clark (1929) and Renick (1931) presented a few
chemical analyses of water from nonthermal wells, springs and
streams.
The LASL program has generated analyses from multiple
sources (Purtymun, et al. 1974; Purtymun, et al. 1975; Purtymun,
et al. 1976; and Pettitt, 1976). In addition to the LASL staff
investigation, the USGS has briefly studied the water chemistry
of the area (Trainer, 1974 and 1975, and Hiss, et al. 1975).
Despite these efforts the data are insufficient to predict
the chemical characteristics of the ground water at any point in
210
-------
the flow continuum. The data are sufficient to permit some
generalizations about the chemical characteristics of the flow
systems and the impact of the geothermal features on these
systems.
Groundwater in the Jemez River Basin exhibits principal
ion concentrations that are typical of groundwater flow in
silicate rocks. Exceptions can be attributed to the concen-
trating effects of evapotranspiration in the discharge areas, to
the presence of carbonates in the flow continuum, to the mixing
of thermalwater from depths, to the reduction of hydrogen
sulfide to sulfuric acid, and to exchange reactions brought on
by locally higher temperatures.
Groundwater discharging from local flow systems with
obviously short flow paths (e.g., wells in recharge areas,
springs, and the base flow of streams in the headwater area) has
the following characteristics:
1) low TDS (less than 250 mg/1),
2) relatively large ratio of silica to TDS (more than
0.25), and
3) calcium and bicarbonate ions as other principal con-
stituents .
As the length of the flow paths increases, the TDS concen-
tration increases, the ratio of silica to TDS decreases, and the
ratios of calcium plus magnesium to the sum of all cations and
bicarbonate plus carbonate to the sum of all anions (expressed
as equivalents per million) decrease with increasing TDS.
For very long flow paths in silicate rocks the TDS concen-
tration approaches that of brines and the principal ions are
sodium and chloride.
Along the Rio Salado flood plain, groundwater discharges by
evapotranspiration to the atmosphere so the groundwater sig-
nificantly increases in dissolved solids. Gypsum and calcite
precipitate, and are washed away during floods, so that the
sodium and chloride ions build up; concentrations in excess of
2,000 mg/1 of these ions are common. TDS in the stream flow
exceed 10,000 mg/1.
The chemical characteristics of the groundwater in the
Jemez River Basin above the Rio Salado depart from those ex-
pected in silicate rock terrain for several reasons. Of these
perhaps the most important is the mixing of a geothermal fluid
that includes carbon dioxide and hydrogen sulfide with the
circulating groundwater (Trainer, 1975). At Sulphur Springs
the result is a low flow acid (pH~2) spring. Elsewhere
211
-------
warm and hot waters generally tend to be relatively rich in
silica, sodium and potassium ions because these constituents are
more soluble at higher temperatures. !As a result thermal waters
contain these constituents in greater proportion than nonthermal
waters.
In the upper Jemez River Basin the TDS of both thermal and
"cool" waters range upwards from about 100 mg/1, and all the
thermal waters and some of the cool waters contain silica,
sodium and potassium ions in anomalous concentrations.
Some analyses of cool surface stream waters are presented
in Table 5.3. These stream water analyses would be representa-
tive of cool groundwater in this area since the streams are
influent at low flow. Chemical analyses of some representative
thermal and cool groundwaters are presented in Table 5.5.
However, the water chemistry discussions here are based on the
much more extensive sample of water analyses included in the
references mentioned at the beginning of this section. There-
fore, some of the features or characteristics discussed may not
be illustrated by these representative analyses shown in Tables
5.3 and 5.4.
On the assumption that the water obtained from the granite
of Precambrian age from the LASL well GT-2 represented the
thermal groundwater flowing from the caldera, Trainer estimated
that the water discharging from the hot and warm springs con-
sisted of a mixture of about one to two parts nonthermal ground-
water to one part of deep thermal groundwater, whereas the two
cool waters he examined showed ten to 60 parts nonthermal ground-
water to one part of deep thermal groundwater.
The shortage of detailed data plus the natural mixing of
thermal and nonthermal groundwater combine to make predictions
of the impact of geothermal development extremely difficult.
5.4 GEOTHERMAL DEVELOPMENT
Through 1975 the Union Oil Company drilled 16 wells in the
Valles Caldera, six of which produced hot water or steam with
temperatures reported to be as high as 260°C (500°F). The wells
range in depth from 1,830 to 2,745 m (6,000 to 9,000 ft). Stone
and Mizell (1977) state that Union would need to prove 30-year
production capacity from their wells to attract a 55 MW electric
generating complex. However, Union Oil Company has not an-
nounced the total proven capacity of the wells, nor has the
company released data on the character of the fluids.
The LASL hot dry rock experiment involves two holes, each
3,050 m (10,000 ft) deep, that are separated at the surface by
about 76 m (250 ft). Water under high pressure is utilized in a
212
-------
TABLE 5.3 CHEMICAL ANALYSES OF SURFACE WATERS IN THE UPPER JEMEZ
RIVER BASIN (Pettit, 1976)
Location
Sulphur Creek
above San Antonio
Creek (P)
Jemez River
below
Battleship Rock fJI
San Antonio Creek
above
Sulphur Creek fN)
Rio Guadalupe
above
Jemez River (Q)
Date of Collection (1975)
Chemical Analysis fag/11
Silica .(Si02)
Calcium (Ca)
Magnesium (Mg)
Sodium (Na)
to Carbonate (CO.)
H
w Bicarbonate (HC03 as CaCOj)
Sulfate (S04)
Chloride (Cl)
Fluoride (P)
Nitrate (N)
Total dissolved solids
Total hardness (as CaC03)
Specific conductance (ymho/cm)
nil
P"
Temperature (*C)
Discharge estimated (1/s)
9/30
32
26
5
15
0
20
61
19
0.2
<0.1
184
88
260
8 A
• U
S
30
12/8
34
33
3
18
0
14
34
37
0.2
<0.1
240
96
340
79
t *
0
30
5/28
33
13
4
7
0
38
14
3
0.3
0.1
98
48
140
6
.
9/30
49
14
2
14
0
62
9.7
7
0.7
0.1
144
46
165
9
340
12/8
53
14
2
15
0
60
13
4
0.9
0.1
144
44
180
1
450
5/28
42
14
4
6
0
56
8.0
<1
0.5
0.1
136
54
150
B fl
6
.
9/30
51
22
3
15
0
96
4.9
3
1.1
0.1
194
68
190
8n
. II
8
90
12/8
60
14
2
17
0
58
6.4
3
1.1
0.1
148
42
170
«l
• j
0
110
5/28
17
23
2
11
0
68
10
<1
0.2
0.2
152
68
140
7 ft
« • o
6
.
9/30
30
41
9
14
4
156
2.6
4
0.5
0.1
182
140
330
84
• ^
13
140
12/8
27
50
6
16
5
163
7.2
4
0.7
<0.1
176
148
340
8*
• i*
6
230
-------
TABLE 5.4 CHEMICAL ANALYSES OF THERMAL WATERS IN
THE UPPER JEMEZ RIVER BASIN (Pettit, 1976)
Location
San Antonio
Warm Springs
(RV-1)
San Antonio
Hot Springs
(RV-2)
Spence Spring
(RV-4)
b Collected R. L. Borton, SEO, flow 0.6 i/s.
c Collected R. L. Borton, SEO, flow 1.0 £/s.
d Collected R. L. Borton, SEO.
McCauley Spring
(RV-5)
Date of Collection (1975)
Chemical Analysis (mg/1) :
Silica (SiO )
2
Calcium (Ca)
Magnesium (Mg)
Sodium (Na)
Carbonate (COs)
Bicarbonate (HC03 as CaC03)
Sulfate (SOi^)
Chloride (Cl)
Fluoride (F)
Nitrate (N)
Total dissolved solids
Total hardness (as CaC03)
Specific conductance (ymhos/cm)
PH
Temperature (*C)
8/14b
97
6
<1
27
0
58
10
6
1.3
0.8
244
18
120
7.6
38
8/12
83
6
<1
22
0
56
7.0
14
0.9
0.3
166
16
195
7.5
41
9/24°
65
7
2
49
0
120
15
8
0.6
<0.1
242
26
290
8.0
41
12/9
68
7
2
49
0
128
16
10
0.7
0.1
258
28
280
8.3
40
9/24d
53
10
4
19
0
76
3.5
4
0.8
0.3
154
40
170
7.9
32
12/9
59
10
5
20
0
74
5.0
4
1.0
<0.1
148
44
170
8.0
30
-------
process known as hydraulic fracturing to create cracks in hot
granite (otherwise, it has a very low hydraulic conductivity).
ine iractures serve two purposes:
1) they provide communication between the wells, and
2) they expose a large heat-exchange surface of rock with
a temperature of 204°C (400°F). In a 20-hour exper-
iment in early June 1977 cold water was pumped down
one hole at 60 to 70 bars (900 to 1,000 psi). It
circulated through the crack system, was heated, and
flowed into the second hole. Water discharged from
the second hole at temperatures of 129°C (265°F).
Thus for the Jemez area the impact of two distinctly dif-
ferent efforts must be assayed. Information about the con-
ventional field is remarkably sparse. LASL, on the other hand,
has made extensive studies and has gathered extensive data for
the purpose of appraising environmental impacts.
Fig. 5.8 is a simplified cross section through the caldera
that shows the relationship of the salient features of the area.
We have inferred the water table, but its shape must be essen-
tially as shown or the streams at higher altitudes would not be
gaining streams. The shape of the water table near the Rio
Grande derives from a map by Purtymun and Johansen (1974).
The flow of groundwater in the Jemez River Basin (as well
as the groundwater flow in the Puerco Basin and the Rio Grande
Basin generally) is southerly (i.e., normal to the plane of the
section in Fig. 5.8). Thus a comparison of this section of the
map with the geologic map (Fig. 5.4) and the location of thermal
features (Fig. 5.3) suggests that the thermal fluids are all
derived from the Valles Caldera. The high heat flow on the west
is not so much due to more heat on the west side, but to the
greater thickness of groundwater bearing rocks on the east, so
that the heat is swept away by the large influx of groundwater.
The lack of heat indication on the north edge of the caldera is
probably due in part to the sweep of the groundwater flow
system that carries the heat via mass transfer from north to
south.
For the most part the discharging heat is carried in water
that underflows the local and intermediate flow systems, sur-
facing only at windows in the local flow systems.
The moderately warm springs near the confluence of the Rio
Salado and the Jemez River may indeed be the discharge region
for the intermediate flow that underflows the Rio Guadalupe
local flow systems. i
215
-------
• Jemez River Basin
Caldero-
4-10,000
Redondo Peak
Nociemento
WATER
TABLE
1
Thermal fluids
Temperature
. 200C
-2POO
-4000
P«
£ \ Approximate equivalent altitude
of •hot-dry rock experiment
BHT~40Cft- 200eC
Figure 5.8 Simplified cross section through the Valles Caldera
and GT-1. The surface trace of the section is
perpendicular to the Rio Grande .
216
-------
5.5 WATER POLLUTION POTENTIAL
5.5.1 Caldera Area
Only two partial analyses of water from test wells in the
caldera are available. These analyses are of the steam con-
densates from one of the early test wells drilled near Sulphur
Springs. These analyses both show 24 mg/1 fluoride but rela-
tively low dissolved solids (2,970 and 1,700 mg/1).
The water of the hot springs in the Jemez area generally
contains more than 2 mg/1 fluoride and more than 4 mg/1 boron.
Spectrographic analyses of the water from Soda Dam Hot Springs
and Jemez Spring indicate arsenic concentrations ranging from
0.3 to 13 mg/1. We conclude, therefore, that fluoride, boron
and arsenic concentrations in the effluent from the steam wells
are likely to be potential pollutants in this area.
The TDS concentration of the thermal waters of the Jemez
area are almost all less than 10,000 mg/1 and generally less
than than 4,000 mg/1.
Throughout the area hydrogen sulfide and carbon dioxide
discharge with the thermal waters. The hydrogen sulfide could
oxidize to sulfuric acid and pose a gas and liquid emission
problem.
•".5.2 Hot Dry Rock Experiment
Presumably, the native water in the granite will be similar
to the vater in the caldera, but since the program calls for the
circulation of "cool" water from the surface through the frac-
tured rocks, the native water should not pose a problem. How-
ever, the circulating water should react with the hot rock and
increase its TDS content.
According to Pettitt (1976),
"The mineral composition of the granite
comprising the downhole reservoir contains
mostly iron, potassium, sodium, calcium and
magnesium as hydrated oxides of aluminum and
silica, pure quartz, and some carbonates.
Dissolved material brought to the surface will
resemble the products of the natural weathering
of granite, and should not be objectionable. An
important part of the program is directed toward
controlling the dissolution and reprecipitation
of such minerals. Present estimates indicate a
total dissolved solids content of less than 500
ppm for fluids circulating in a 200°C (392°F)
reservoir with dissolved silica (Si02) as
major component."
217
-------
5.6 SEISMICITY
Historic seismicity and seismic risk along the Rio Grande
Rift and in the Jemez Valles Caldera region in general are
discussed in Geonomics (in press). LASL seismologists have
studied the seismic characteristics of the Fenton Hill site (and
hence of the surrounding area) since 1973 and results from this
program are discussed below.
Fig. 5.9 shows the locations of microearthguake epicenters
in north-central New Mexico, September 1973 through December
1975. This map shows a lower rate of occurrence of microearth-
guakes around the Fenton Hill site. According to Pettitt
(1976):
"An estimate of seismic risk from natural
events can be made from the microearthguake
recording carried out since September 1973.
Because of the moderate levels and sporadic
nature of earthquake activity in New Mexico, one
must exercise caution in extrapolating the
results to too small an area or too long a time
interval. Fig. [5.10] shows a plot of cumula-
tive number versus magnitude for all earthquakes
detected since September 1, 1973 within 225 km
(140 mi) of Los Alamos (an included area of
160,000 sq km [61,500 sq mi]). An extrapolation
of these data using the fitting b = 0.77 slope
projects the maximum probable earthquake for
this area per century to be a magnitude 6.6
event. Because the slopes of such curves may be
biased by observational selection effects,
giving rise to incomplete coverage of the smal-
ler events, some investigators prefer to impose
the slope constraint of b = 1.0 on the data.
When this is done, the present seismicity rates
correspond to a maximum probable earthquake per
century with a local magnitude of 5.6, in close
agreement with similar instrumental studies of
other parts of the state. The 5.6 local magni-
tude projection is, however, somewhat smaller
than projections (-6.0) made on the basis of
historical damage reports.
Although considerable caution must be
exercised when making long-term projections for
areas much smaller than that considered above,
the observed distribution of seismicity in the
Jemez region indicates that local magnitude >1
earthquakes are almost completely absent from
the central part of the Jemez Mountains. The
explanation of this phenomenon is probably the
218
-------
Figure 5.9
Locations of microearthquake epicenters in north-
central New Mexico, September 1973-December 1975
LOON
Figure 5.10
Magnitude-frequency relationship for all earth-
quakes within 225 km of Los Alamos,
September 1973-December 1975
219
-------
same as that proposed for a similar situation in
the Yellowstone Caldera complex: that strain
energy at shallow depths is being relieved by
creep rather than by brittle failures. This
interpretation is supported by data on tectonic
and geologic structure, historical earthquake
records, and other geophysical evidence includ-
ing gravity, aeromagnetic, and high heat flow
data."
The on-site seismographs have operated throughout LASL's
hydraulic fracturing experiment, and according to Pettitt
(1976), no surface seismic activity associated with the frac-
turing experiment has been detected by the equipment, but anal-
ysis of downhole signals associated with the hydraulic frac-
turing shows that these nanoearthquakes have magnitudes of -6 to
-3. More than two years of monitoring microearthquakes by
LASL seismologists has led them to the conclusion that the.
Nacimiento Fault System is a seat of continuing but moderate
activity.
5.7 SUBSIDENCE
We can only speculate about the subsidence potential in the
Jemez area. At the hot dry rock site the rocks have sufficient
strength to preclude subsidence. Within the caldera, however,
sedimentary fill may compact if the pressure head is reduced.
Presently no data are available to the public which would allow
estimates of the magnitude of this potential problem.
5.8 CONCLUSION
The subsurface environmental impact of geothermal devel-
opment in the Jemez area will be restricted to the effects of
effluent disposal. One well in the caldera system was drilled
as a reinjection well (Summers, 1976). If the waste effluent
from field development is indeed injected into the well, the
impact of the effluent will be negligible except when the pro-
ducing wells are free flowed during their drilling and produc-
tion. The effect of the discharge will depend in large part on
the state of the Jemez River Basin at the time of discharge. If
the basin discharges flood water from spring runoff or summer
storms, the concentration of offensive components in the dis-
charging effluent would not be detectable. However, at low base
flow the concentrations of arsenic, boron and fluoride in the
effluent could raise the concentrations in the Jemez River to
levels that exceed present state and federal standards.
220
-------
REFERENCES
Bailey, R. A., R. L. Smith and C. S. Ross. Stratigraphic Nomen-
clature of Volcanic Rocks in the Jemez Mountains, New
Mexico. USGS Bull. 1274-P, 19 p., 1969.
Blair, A. G., J. w. Tester and J. J. Mortensen. LASL Hot-dry-
rock Geothermal Project, July 1, 1975-June 30, 1976. Los
Alamos Scientific Laboratory, LA-6525-PR, 238 p.
Clark, J. D. The Saline Springs of the Rio Salado, Sandoval
County, New Mexico. University of New Mexico, Bull. 163,
Chem. Ser., v. 1, No. 3, 1929.
Cordell, Lindrith. Aeromagnetic and Gravity Studies of the Rio
Grande Graben in New Mexico Between Belen and Pilar. New
Mexico Geol. Soc., Spec. Pub. No. 6, p. 62-70, 1976.
Dane, C. H. and G. O. Bachman. Geologic Map of New Mexico.
USGS, scale 1:500,000, 2 sheets, 1965.
Geonomics, Inc. Baseline Geotechnical Data for Four Geothermal
Areas in the United States. EPA, Environmental Monitoring
and Support Laboratory, Las Vegas, Nevada, in press.
Hiss, W. L., F. W. Trainer, B. A. Black and D. R. Posson.
Chemical Quality of Ground Water in the Northern Part of
the Albuguergue-Belen Basin, Bernalillo and Sandoval
Counties, New Mexico. New Mexico Geol. Soc., Guidebook
26th Field Conf., p. 219-235, 1975.
Kelly, C. and E. V. Anspach. A Preliminary Study of Waters of
the Jemez Plateau, New Mexico. University of New Mexico,
Bull., Chem. Ser., v. 1, No. 1, 1913.
Kudo, A. M. Outline of the Igneous Geology of Jemez Mountains
Volcanic Field. New Mexico Geol. Soc., Guidebook 25th
Field Conf., p. 287-289, 1974.
Pettitt, R. A. Environmental Monitoring for the Hot Dry Rock
Geothermal Energy Development Project, Annual Report for
the Period of July 1975-June 1976. Los Alamos Scientific
Laboratory, LA-6504-SR, 92 p., 1976.
Purtvmun, W. D. Geology of the Jemez Plateau West of Valles
Caldera. Los Alamos Scientific Laboratory, LA-5124-MS, 13
p., 1973.
221
-------
Purtymun, W. D. and S. Johansen. General Geohydrology of the
Pajarito Plateau. New Mexico Geol. Soc., Guidebook 25th
Field Conf., p. 347-349, 1974.
Purtymun, W. D., F. G. West and W. H. Adams. Preliminary Study
of the Quality of Water in the Drainage Area of the Jemez
River and Rio Guadalupe. Los Alamos Scientific Laboratory,
LA-5595-MS, 26 p., 1974.
Purtymun, W. D., W. H. Adams and J. W. Owens. Water Quality in
Vicinity of Fenton Hill Site, 1974. Los Alamos Scientific
Laboratory, LA-6093, 1975.
Purtymun, W. D., W. H. Adams, A. K. Stoker and F. G. West. Water
Quality in Vicinity of Fenton Hill Site, 1974. Los Alamos
Scientific Laboratory, 1976.
Reagan, A. B. Geology of the Jemez-Albuquerque Region, New
Mexico. Am. Geologist, v. 31, No. 21, p. 67-111, 1903.
Reiter, M., C. Weidman, C. L. Edwards and H. Hartman. Subsur-
face Temperature Data in Jemez Mountains, New Mexico. New
Mexico Bureau of Mines and Mineral Resources Circ. 151, 16
p., 1976.
Renick, B. C. Geology and Ground Water Resources of Western
Sandoval C inty, New Mexico. USGS Water Supply Paper 620,
117 p., 1931.
Ross, C. S., R. L. Smith and R. A. Bailey. Outline of the
Geology of the Jemez Mountains, New Mexico. New Mexico
Geol. Soc., Guidebook 12th Field Conf., p. 139-143, 1961.
Smith, R. L., R. A. Bailey and C. S. Ross. Geologic Map of the
Jemez Mountains, New Mexico. USGS Map 1-571, 1970.
Stone, W. J. and N. B. Mizell. Geothermal Resources of New
Mexico a Survey of Work to Data. New Mexico Bureau of
Mines and Mineral Resources Open File Report 73, 117 p.,
1977
Summers, W. K. Catalog of Thermal Waters in New Mexico. New
Mexico Bureau of Mines and Mineral Resources Hydrologic
Report 4, 80 p., 1976.
Tester, J. W. Proceedings of the NATO-CCMS Information Meeting
on Dry-hot-rock Geothermal Energy. Los Alamos Scientific
Laboratory, LA-5818-C, NATO CCMS Report No. 38, 40 p.,
1974.
222
-------
Titus, F. B., Jr. Ground Water Geology of the Rio Grande Trough
in North-central New Mexico, with Sections on the Jemez
Caldera and the Lucero Uplift. New Mexico Geol. Soc.,
Guidebook 12th Field Conf., p. 186-192, 1961.
Trainer, F. W. Ground Water in the South-western Part of the
Jemez Mountains Volcanic Region, New Mexico. New Mexico
Geol. Soc., Guidebook 25th Field Conf., p. 337-345, 1974.
Trainer, F. W. Mixing of Thermal and Nonthermal Waters in the
Margin of the Rio Grande Rift, Jemez Mountains, New Mexico.
New Mexico Geol. Soc., Guidebook 26th Field Conf., p.
213-218, 1975.
Tuan, Yi-Fu, C. E. Everard and J. G. Widdisor. The Climate of
New Mexico. New Mexico State Planning Office, Santa Fe,
New Mexico, 169 p., 1969.
223
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APPENDIX A
ABBREVIATIONS AND CHEMICAL SYMBOLS
ABBREVIATIONS
acre-ft
APCD
ARB
atm
BTU
°C
cal
Cal Tech
cfs
cm
cu
d
ERDA
emp
EPRI
°F
ft
g
9
gpd
gpm
ha
ha-m
HFU
hr
in.
J
JTU
KGRA
kg
kH
km
kW
kW.hr
LASL
1
Ib
—acre-feet
—Air Pollution Control District
—California Air Resources Board
—atmosphere
—British Thermal Unit
—degrees Celcius
—calorie
—California Institute of Technology
—cubic feet per second
—centimeter
—cubic
—day
—U.S. Energy Research and Development
Administration
-U.S.* Environmental Protection Agency
—equivalence per million
—Electric Power Research Institute
—degrees Fahrenheit
-feet
—acceleration of gravity
—grams
—gallons per day
—gallons per minute
—hectare
—hectare-meter
—heat flow unit
—hour
—inch
—joule
—Jackson turbidity unit
—Known Geothermal Resource Area
—kilogram
—transmissivity i
—kilometer
-kilowatt
—kilowatt-hour
—Los Alamos Scientific Laboratory
-liter
—pound
224
-------
ABBREVIATIONS (continued)
Ipd
1pm
Ips
Isd
m
M
MM
md
md-ft
mg
mg/1
mgal
mm
msl
mv
MW
MWe
NCPA
NCER
NIDWR
ohm-m
OIT
oz
pCi/1
PG&E
ppm
psi
psia
psig
SDG&E
sec
sq
TDS
U.C.B.
USER
USDA
USGS
USPHS
U.C.R.
Mmho/cm
P
<|>ch
-liter per day
-liter per minute
-liter per second
-land-surface datum
-meter
-Richter magnitude
—Modified Mercalli intensity
-millidarcy
• -mi Hi dar cy- feet
—milligram
—milligram per liter
—milligal
—millimeter
—mean sea level
—millivolt
—megawatt
—megawatt (electricity)
—Northern California Power Administration
—National Center for Earthquake Research
—National Interim Drinking Water Regulations
—ohm-meter
—Oregon Institute of Technology
—ounce
—picocurie per liter
—Pacific Gas and Electric Company
—parts per million
—pounds per square inch
—pounds per square inch absolute
—pounds per square inch gage
—San Diego Gas and Electric
—second
—square
—total dissolved solids
—University of California, Berkeley
—U. S. Bureau of Reclamation
—U. S. Department of Agriculture
—U.S. Geological Survey
—U.S. Public Health Service
—University of California, Riverside
—micro mho per centimeter
—density
—specific capacitance
CHEMICAL SYMBOLS
Ac
Al
Am
—Actinium
—Aluminum
—Americium
Cd
Ca
Cf
—Cadmium
—Calcium
—Californium
225
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CHEMICAL SYMBOLS (continued)
Sb
Ar
As
At
Ba
Bk
Be
Bi
B
Br
Er
Eli
Fm
F
Fr
Gd
Ga
Ge
Au
Hf
He
Ho
H
In
I
Ir
Fe
Kr
La
Lr
Pb
Li
Lu
Mg
Mn
Md
Hg
Mo
Nd
Ne
Np
Ni
Nb
N
No
Os
—Antimony
—Argon
—Arsenic
—Astatine
—Barium
—Berkelium
—Beryllium
—Bismuth
—Boron
—Bromine
—Erbium
—Europium
—Fermium
—Fluorine
—Francium
—Gadolinium
—Gallium
—Germanium
—Gold
—Hafnium
—Helium
—Holmium
—Hydrogen
—Indium
—Iodine
—Iridium
—Iron
—Krypton
—Lanthanum
—Lawrencium
—Lead
—Lithium
—Lutetium
—Magnesium
—Manganese
—Mendelevium
—Mercury
—Molybdenum
—Neodymium
—Neon
—Neptunium
—Nickel
—Niobium
(Columbium)
—Nitrogen
—Nobelium
—Osmium
C
Ce
Cs
Cl
Cr
Co
Cu
Cm
Dy
Es
P
Pt
Pu
Po
K
Pr
Pm
Pa
Ra
Rn
Re
Rh
Rb
Ru
Sm
Sc
Se
Si
Ag
Na
Sr
S
Ta
Tc
Te
Tb
Tl
Th
Tm
Sn
Ti
W
U
V
Xe
Yb
Y
—Carbon
—Cerium
—Cesium
—Chlorine
—Chromium
—Cobalt
—Copper
—Curium
—Dysprosium
—Einsteinium
—Phosphorus
—Platinum
—Plutonium
—Polonium
—Potassium
—Praese-
odymium
—Promethium
—Protac-
tinium
—Radium
—Radon
—Rhenium
—Rhodium
—Rubidium
—Ruthenium
—Samarium
—Scandium
—Selenium
—Silicon
—Silver
—Sodium
—Strontium
—Sulfur
—Tantalum
—Technitium
—Tellurium
—Terbium
—Thallium
—Thorium
—Thulium
—Tin
—Titanium
—Tungsten
—Uranium
—Vanadium
—Xenon
—Ytterbium
—Yttrium
226
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CHEMICAL SYMBOLS (continued)
—Oxygen Zn —Zinc
— Palladium Zr — Zirconium
NH3 — Ammonia
»TTT +
NH4 — Ammonium
HCO3" — Bicarbonate
H3B03 —Boric Acid
CaC03 — Calcium Carbonate
CO2 — Carbon Dioxide
CO — Carbon Monoxide
C03"2 — Carbonate
C2H6 — Ethane
H2 — Hydrogen
HF — Hydrogen Fluoride
H2S — Hydrogen Sulfide
CH4 — Methane
NO3" — Nitrate
NO2- — Nitrite
N2 — Nitrogen
02 —oxygen
PO4~3 — Phosphate
H3PO4 — (Ortho) Phosphoric Acid
Sio2 —Silica Dioxide
NaCl — Sodium Chloride
S04"2 — Sulfate
SO2 —Sulfur Dioxide
227
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APPENDIX B
EXPLANATION FOR DESCRIPTION OF WELLS TABLES
Map Number; Number on maps in this report.
State Number; The wells are identified according to their
location in the rectangular system for the subdivision of
public land. The identification consists of the township
number, north or south; the range number, east or west; and
the section number. The section is further subdivided into
sixteen 40-acre tracts lettered consecutively (excepting
I and O), beginning with A in the northeast corner of the
section and progressing in a sinusoidal manner to R in the
southeast corner. Wells within the 40-acre tract are
numbered sequentially.
Owner or Name; The apparent owner or user,
local name of the well is given.
In some cases, the
Ownership;
F Federal Government
N Corporation or company, churches, lodges and other non-
profit, nongovernment groups
P Private
S State agency
W Water district
Water Use:
G Geothermal <
H Domestic
N Industrial, including mining
Well Use:
H Heat reservoir
O Observation
P Oil or gas
R Recharge
R Recreation
U Unused
Z Other
T Test hole
U Unused or abandoned
W Withdraw water
Z Destroyed
Diameter; Inside diameter of the well, in inches; nominal
Inside diameter, in inches, of the innermost casing at the
surface for drilled cased wells.
Deepest Depth; Depth,
"drilled hole.
in feet below land-surface datum, of
Depth Cased; Length of casing, in feet below land-surface datum
or to the top of the perforated or screened interval.
228
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Depth of Well; Depth, in feet below land-surface datum, is
defined as the bottom of the perforated or screened inter-
val or the drilled depth.
Altitude of Isd; Altitude of land-surface datum, in feet, above
or below (-) mean sea level. Land-surface datum is an
arbitrary plane closely approximating land surface at the
time of the first measurement and used as the plane of
reference for all subsequent measurements.
Water Level; Depth to water, in feet, above (+) or below land-
surface datum;
F Flows, head unknown
D Dry
Date Measured; Month and year of the water level measurement.
Yield of Well; In gallons per minute.
229
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APPENDIX C
U.S.-METRIC CONVERSION TABLE
U.S. CUSTOMARY
U.S. EQUIVALENT
inch (In)
inch
foot (ft)
yard (yd)
mile (mi)
square foot (sq ft)
square yard (sq yd)
acre
acre
square mile (sq mi)
gallon
acre-foot (acre-ft)
acre-foot/acre
cubic feet (cu ft)
cubic mile (cu mi)
gallons per second
gallons per minute (gpm)
gallons per day (gpd)
gallons per minute/foot
(gpm/ft)
gallons per day/ft
(gpd/ft)
18.2 gpd/sq ft @ 60°F
•pounds per hour
cu ft per sec (cfs)
Length
0.083 ft
0.083 ft
0.33 yd, 12 in
3 ft, 36 in
5,280 ft, 1,760 yd
Area
144 in
1,294 sq in, 9 sq ft
43,560 sq ft, 4,840 sq yd
43,560 sq ft, 4,840 sq yd
640 acres
Volume
4 quarts
325,850.28 gallons
Flow Rate
METRIC EQTTTVAT.FNT
25.4 millimeters (mm)
2.54 centimeters (cm)
0.3048 meter (m)
0.9144 m
1.609 kilometer (km)
0.0929 sq m
0.836 sq m
4,047 sq m
0.4046 hectare (ha)
2.59 sq km
3.785 liters (1)
0.12335 hectare-
meter (ha-m)
0.3048 ha-m
0.02832 cubic meter
(cu m)
4.1655 cu km
3.785 liters per
second (Ips)
3.785 liters per
minute (1pm)
3.785 liters per
day (Ipd)
12.418 Ipm/m
12.418 Ipd/m
9.66 x 10~k cm/sec @ 20°C
1.262 x 10"1* kg/sec
28.32 Ips
230
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APPENDIX C. (continued)
U.S. CUSTOMARY U.S. EQUIVALENT METRIC EQUIVALENT
Miscellaneous
°F 9/5(°C) + 32
1.12°F/mi l°C/km
l°F/mi 0.8939°C/km
°C ' (°F - 32)(5/9)
pounds per square inch (psi) 0.7031 g/sq cm
pounds per square inch (psi) 0.0689 bar
British Thermal Unit (BTU) 1,055 joules (J)
BTU/lb 2,325.84 J/kg
ounce 28.35 g
pound 0.4536 kg
ton 0.907 metric ton
231
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APPENDIX D
GLOSSARY
alluvium: Relatively unconsolidated detrital material (clay,
silt, sand, gravel) deposited in comparatively recent geo-
logic time by flowing water.
aquiclude: Relatively impermeable strata that absorbs water
slowly and functions as a boundary of an aquifer. It does
not transmit groundwater quickly enough to supply a well
or spring. Clay or shale beds and faults often act as
aquicludes.
aquifer: A body of rock or sediment that contains sufficient
saturated permeable materials to conduct groundwater and
yield significant quantities of groundwater to wells and
springs.
aquitard: Confining strata that retards the flow of water, but
does not prevent flow to or from an adjacent aquifer.
artesian water: Groundwater confined under hydrostatic pres-
sure. Water in an artesian well rises above the level of
the water table under artesian pressure, but does not
necessarily reach the land surface. The term is sometimes
restricted to mean only a flowing artesian well.
Bouguer anomaly: A gravity value calculated by allowing for the
attraction effect of topography, but not for that of iso-
static compensation.
brine: A solution containing more than 3.5% total dissolved
solids (35,000 mg/1). This is the approximate TDS of sea-
water .
caprock (geothermal): A relatively impermeable rock layer over-
lying a hot water or steam reservoir which prevents the
heat or fluid from directly migrating or dissipating upward
to the surface.
clast: A rock fragment produced by mechanical weathering (dis-
integration) of a larger rock mass.
232
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conductive heat flow: Heat transfer from a higher temperature
to a lower temperature region by molecular impact (vibra-
tion) without transfer of matter itself.
convective heat flow: Mass transfer of heat due to tempera-
ture-caused density gradients, e.g., circulation of hot
water in a convecting geothermal reservoir.
connate water: Water trapped, at the time of deposition, in the
interstices of a sedimentary or extrusive igneous rock.
contour line: A line that passes through all consecutive points
of equal value for a parameter which is variable, e.g.,
topographic elevation, ground water level, or temperature.
craton: A part of the earth's crust which has attained stabil-
ity, and which has been little deformed for a prolonged
period.
deuterium: The hydrogen isotope that occurs in water and has
twice the mass of ordinary hydrogen. It is also called
heavy hydrogen and its chemical symbol is "D"-
diktytaxitic: Rock texture of some olivine basalts in the
Pacific northwest, characterized by numerous jagged, ir-
regular vesicles bounded by crystals.
effluent: Flowing forth or out, emanating: a) a surface stream
that flows out of a lake or larger stream, b) a liquid
discharged as waste.
electrical resistivity survey: A geophysical exploration tech-
nique where electric current is artificially introduced
into the ground and the distribution of current below the
surface is measured by electrodes separated by increasing
increments. Depths to geologic interfaces may be deter-
mined by plotting apparent resistivity versus electrode
separation.
eutrophication: The artificial or natural enrichment of a lake
by an influx of nutrients required for the growth of
aquatic plants.
fault: A surface or zone of rock fracture along which there has
been displacement, from a few centimenters to hundreds of
kilometers in scale. Faults are classified according to
the relative motion of the rock on each side of the frac-
ture zone, or fault plane. These classifications are
illustrated below in the diagrams of fault types.
233
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NORM*L REVERSE STRIKE - SLIP ROTATIONAL TRANSFORM
fault scarp: A fairly steep slope or cliff formed directly by
movement along one side of a fault and representing the
exposed surface of the fault plane before modification by
erosion and weathering.
fumarole: A volcanic vent from which gases and vapors are
emitted; it is characteristic of a late stage of volcanic
activity.
geomorphology: The science of the earth's surface; specifically
the classification, description, origin, and development of
present land forms and their relationships to underlying
structures.
geosyncline (variety eugeosyncline, miogeosyncline): Often an
elongate crustal depression or basin, often subsiding,
where thousands of meters of sediment accumulate, usually
in some phase of a marine environment.
geothermal gradient (temperature gradient): The rate of in-
crease of temperature in the earth with depth. The average
gradient is approximately 1°C per 30 m (2°F per 100 ft).
geothermal water: "Strictly defined, any spring, [ground] or
well water whose average temperature is noticeably above
the mean annual temperature of the air at the same locality
may be classed as thermal. Among European springs that are
developed commercially, only those whose temperature is
higher than about 20°C (68°F) are classed as thermal. In
the United States, only those springs are called thermal
whose temperature is at least 8°C (15°F) above the mean
annual temperature of the air at their localities. In
areas where the mean annual air temperature is low, some
springs that do not freeze in winter because of natural
protective conditions are considered to be thermal; in
tropical areas some springs that are only a few degrees
warmer than the temperature of the air may be considered
thermal." (Thermal Springs of the United States and Other
Countries of the World—a Summary, G. A. Waring, USGS Prof.
Paper 492, 1965). The definition used for Imperial Valley
geothermal water is somewhat different—see section 2.3.
234
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geothermometry (geologic thermometry): 1) The science of the
earth s heat; 2) a mineral or mineral assemblage whose
characteristics are fixed within known thermal limits thus
allowing conclusions about temperatures during process of
formation; e.g., .sodium, potassium and calcium concen-
trations in natural waters may be used to predict the last
temperature of water-rock equilibration.
graben: A crustal block that is bounded by faults on its long
sides, the block being downdropped in relation to the
surrounding land.
groundwaten Subsurface water, especially that contained in a
saturated zone, or strata, including underground streams.
horst: A crustal block that is bounded by faults on its long
sides, the block being uplifted in relation to the sur-
rounding land.
hydraulic gradient: In an aquifer, the rate of change of pres-
sure head (height of a column of water that the pressure
can support) per unit of distance of flow at a given point
and in a given direction. It is usually expressed in
meters per kilometer or feet per mile.
hydrologic budget (variety water budget): An accounting of the
inflow to, outflow from, and storage in, a hydrologic unit,
e.g., drainage basin, aquifer, or reservoir; the relation-
ship between evaporation, precipitation, runoff, and change
in water storage, is implied.
hydrology: The science that deals with all properties of water
(liquid and solid) on, under and above the earth's surface.
hydrothermal: Pertaining to heated water (or aqueous solution)
or products resulting from heated water, i.e., alteration
of rocks or minerals by reaction of hydrothermal water.
igneous rock: A rock that solidified from molten or partly
molten material, i.e., from a magma. Intrusive (plutonic) -
usually having visible crystal components, and formed deep
under the earth's surface, e.g., granite, diorite, gabbro,
peridotite. Extrusive (volcanic) - an igneous rock that
solidified on or near the surface, e.g., rhyolite, andes-
ite, basalt; (lava flows).
inflow: The act or process of flowing in, e.g., the flow of
water into a drainage basin.
inlier: An area or group of rocks surrounded by outcrops of
younger rocks.
235
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intensity (of an earthquake): A subjective measurement rating
the severity of ground motion at a specific site during an
earthquake. The Modified Mercalli scale uses Roman num-
erals from I to XII, to describe the motion that was felt
and the damage to man-made structures. Intensity at a
point depends not only upon the strength of an earthquake
(the earthquake magnitude), but also upon the distance to
the earthquake epicenter and the geologic and soil condi-
tions at the point.
intrusion: The injection of magma into preexisting rock, re-
sulting in plutpns, batholiths and laccoliths (large
scale); stocks, dikes and sills (small scale).
isotherm: A line connecting points of equal temperature.
isotope ratios: Isotope abundances given as a ratio relative to
a standard rather than an absolute. Different ratios can
indicate changes in environment or origin for a given
chemical element. The standard is often Standard Mean
Ocean Water (SNOW). Some common ratios are defined as
follows:
6018(in °/00) = bamPle - 1 | 1000
I '018/016}
Standard
-]
Similar definitions exist for ratios of deuterium (D)
to hydrogen (H) and for C14 to C12
juvenile water: Water derived directly from a magma, reaching
the earth's surface for the first time.
Langelier-Ludwig diagram: A diagram representing groupings of
chemical composition of aqueous solutions.
lithic fragment: A fragment from a preexisting rock mass,
.usually used in describing a medium-grained sedimentary
rock or certain types of volcanic deposits.
mafic: Generally igneous or volcanic rocks, containing iron,
magnesium and other dark-colored minerals.
magnetic survey: Measurement of a component or element of the
geomagnetic field at different locations. It is usually
made to map either the broad patterns of the earth's main
field or local anomalies due to variation in rock magneti-
zation. It is often conducted as an aeromagnetic survey.
236
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magnetotellunc survey (MT): An electromagnetic method in which
natural electric and magnetic fields are measured; usually
two-dimensional horizontal electric field and three-dimen-
sional magnetic field components are recorded.
magnitude (earthquake): A measure of the strength of an earth-
quake or the strain energy released by it, as determined by
seismologist C.F. Richter, who first applied it to southern
California earthquakes. For that region he defined local
magnitude as the logarithm, to the base 10, of the ampli-
tude in microns of the largest trace deflection that would
be observed on a standard torsion seismograph (static
magnification = 2,800, period =0.8 sec, damping constant =
0.8) at a distance of 100 km (62.2 mi) from the epicenter.
Magnitudes determined at teleseismic distances using the
logarithm of the amplitude to period ratio of body waves
are called body-wave magnitudes and using the logarithm of
the amplitude of 20-sec period surface waves are called
surface-wave magnitudes. The local body-wave and surface-
wave magnitudes of an earthquake will have somewhat differ-
ent numerical values.
melange: A mixture of rock materials derived from more than one
depositional realm, usually sheared and deformed. It is a
mappable body, sometimes several kilometers in length.
o
metamorphic rock: Rock resulting from once solid, preexisting
rock subjected to extreme heat, pressure, or chemical
changes. e.g., slate, schist, gneiss, quartzite, marble,
serpentine.
o
meteoric water: Water of atmospheric origin (e.g., rain).
microearthquake: An earthquake having a magnitude of two or
less on the Richter scale (cutoff may vary accoridng to
user).
Mohorovicic discontinuity (Moho): A sharp seismic-velocity
discontinuity that separates the earth's crust from the
subjacent mantle. Its depth varies from 5-10 km (8-16 mi)
beneath the ocean floor to about 35 km ( 25 mi) below the
continents.
nanoearthquake: An earthquake having a magnitude of zero or
less on the Richter scale (cut off may vary according to
user.)
noncondensible gas: A gas that is not easily condensed by
cooling, i.e., a substance that remains in the gas phase in
geothermal processes.
237
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outflow: The act or process of flowing out, e.g., groundwater
seepage and stream water flowing out of a drainage basin.
pediment: Gently inclined erosion surface carved in bedrock,
with a thin veneer of alluvium derived from the upland
masses and in transit across the,surface. Pediments occur
between mountain fronts and valley floors.
percent reactance: The ratio of one anion species to the total
anion species, expressed in milliequivalents. per liter, and
similarly for cation species. For example, if a water
contains 0.8 meq/1 calcium and the sum of all the cation
species is 13.7 meq/1 then the percent reactance calcium
would be 0.8/13.7 or 6%. This expression provides a method
of "normalizing" chemical analyses for data having a wide
range of concentrations.
perched water table: Unconfined groundwater separated from an
underlying main body of groundwater by an aquiclude and an
unsaturated zone.
permeability: Ability of a rock, sediment or soil to transmit a
fluid without impairment of the structure of the medium. A
measure of the relative ease of fluid flow under unequal
pressure. The customary unit of measurement is the darcy.
It is equivalent to the passage of one cubic centimeter of
fluid of one centipore viscosity flowing in one second
under a pressure differential of one atmosphere through a
porous medium having a cross-sectional area of 1 sq cm
and a length of 1 cm.
porosity (effective): The ratio of the continuous void space
(through which water can move) to total volume, measured at
a point in a flow system.
radiometric age-dating: A method of absolute age determination
based on nuclear decay of natural elements. Calculating an
age, in years, for geologic materials by measuring the
presence of short-life radioactive elements, e.g., carbon-
12/carbon-14, or by measuring the presence of a long-life
radioactive element and its decay product, e.g., potassium-
40/argon-40.
recharge: The processes involved in the absorption and addition
of water to the zone of saturation.
reinjection well: A well in which fluid is introduced; often
used to dispose of waste liquid or possibly to replace
groundwater removed from strata which might subside if the
water were permanently removed.
238
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rift zone: A system of crustal fractures, usually producing a
valley or graben-like depression.
sag pond: A small body of water in a depression formed because
active or recent fault movement has impounded drainage.
salinity: .Total quantity of dissolved salts in water, measured
by weight in parts per thousands or parts per million (ppm)
with the following qualifications: all carbonate has been
converted to oxide, bromide and iodide to chloride, and all
organic matter completely oxidized.
sedimentary rock: A rock resulting from the consolidation of
loose organic or inorganic fragmental material that has
accumulated in layers, i.e. 1) clastic sediments, e.g.
shale, sandstone, conglomerate; 2) chemical sediments
precipitated from solution, e.g. gypsum, salt, carbonate;
or 3) organic sediments consolidated from the remains or
secretions of plants or animals, e.g. some limestones.
seismic survey: A geophysical prospecting technique that uti-
lizes a seismic source such as a thumper or dynamite, and
sensitive detection instruments to record travel times.
Interpretation of this data allows the location of geologic
structures such as faults and thickness of lithologic
units.
sparker survey: A seismic survey in which an electrical dis-
charge in water is the energy source (also called exploding
wire).
solfataric activity: A late or decadent type of volcanic activ-
ity characterized by the emission of sulfurous gases from
the vent.
specific yield: The ratio of the volume of water a given mass
of saturated rock or soil will yield by gravity to the
volume of that mass.
Stiff diagram: A closed polygon representing the chemical char-
acteristics of a substance. Distinctions between substan-
ces can be easily observed by comparison of the different
polygonal shapes for each substance.
subduction zone: A region where one crustal block descends
beneath another by folding or faulting or both.
temperature gradient: See geothermal gradient.
transmissivity: In an aquifer, the rate at which water of the
prevailing viscosity is transmitted through a unit width
under a unit hydraulic gradient.
239
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trilateration: A method of surveying where the lengths of the
three sides of a series of touching or overlapping trian-
gles are measured (usually by electronic methods) and the
angles are computed from the measured lengths.
underflow: The flow of water through the soil or a subsurface
stratum, or under a structure.
volcanic rock (extrusive): A rock formed from a magma at or
near the earth's surface. Usually fine-grained, sometimes
solidifying as ejected from a volcano (see extrusive
igneous rock).
water budget: See hydrologic budget.
240
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/» TECHNICAL REPORT DATA
(nease read Instructions on the reverse before completing)
2.
3. RECIPIENT'S ACCESSION NO.
|4. TITLE AND SUBTITLE
GEOTHERMAL ENVIRONMENTAL IMPACT ASSESSMENT
Subsurface Environmental Assessment for Four Geothermal
Systems
6. PERFORMING ORGANIZATION CODE
. REPORT DATE
November 1978
7. AUTHOR(S)
|8. PERFORMING ORGANIZATION REPORT NO.
Subir Sanyal and Richard Weiss
|9. PERFORMING ORGANIZATION NAME AND ADDRESS
Geonomi cs, Inc.
3165 Adeline Avenue
Berkeley, CA 94703
10. PROGRAM ELEMENT NO.
1NE624
11. CONTRACT/GRANT NO.
Contract #68-03-2468
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency—Las Vegas, NV
Office of Research and Development
Environmental Monitoring and Support Laboratory
Las Vegas, NV 89114
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES For further information contact Donald B. Gilmore, Project Officer,
(702)736-2969, ext. 241, in Las Vegas, NV.
16. ABSTRACT
This is the second in a series of reports concerning the environmental assessments of
effluent extraction, energy conversion, and waste disposal in geothermal systems.
This study involves the subsurface environmental impact of the Imperial Valley and
The Geysers, California; Klamath Falls, Oregon; and the Rio Grande Rift Zone,
New Mexico.
17.
KEY WORDS AND DOCUMENT ANALYSIS
la.
DESCRIPTORS
Groundwater
(.IDENTIFIERS/OPEN ENDED TERMS
Geothermal
Energy Conversion
Imperial Valley, CA
The Geysers, CA
Klamath Falls, OR
Rio Grande Rift Zone, NM
c. COSATI Held/Croup
08H
|18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport/
UNCLASSIFIED
258
20 SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
A12
EPA Form 2220-1 (R«v. 4-77) PREVIOUS COITION is OBSOLETE
4 U.S. 6PO: 1979-634-147/2084
------- |