United States Office of Ground Water EPA/816-R-99-014r
Environmental and Drinking Water (4601) September 1999
Protection Agency
The Class v Underground Injection
Control Study
Volume 18
Geothermal Direct Heat Return Flow
Wells
-------
Table of Contents
Page
1. Summary 1
2. Introduction 2
3. Prevalence of Wells 3
4. Injectate Characteristics and Injection Practices 5
4.1 Injectate Characteristics 5
4.2 Well Characteristics 12
4.3 Well Siting 12
4.4 Well Operation 15
5. Potential and Documented Damage to USDWs 15
5.1 Injectate Constituent Properties 15
5.2 Observed Impacts 16
6. Best Management Practices 16
7. Current Regulatory Requirements 17
7.1 Federal Programs 18
7.1.1 SDWA 18
7.1.2 Geothermal Steam Act 19
7.2 State and Local Programs 21
Attachment A: State and Local Program Descriptions 24
References 41
September 30, 1999
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GEOTHERMAL DIRECT HEAT RETURN FLOW WELLS
The U.S. Environmental Protection Agency (USEPA) conducted a study of Class V
underground injection wells to develop background information the Agency can use to evaluate
the risk that these wells pose to underground sources of drinking water (USDWs) and to
determine whether additional federal regulation is warranted. The final Class V Underground
Injection Control (UIC) Study consists of 23 volumes and five supporting appendices. Volume 1
provides an overview of the study methods, the USEPA UIC Program, and general findings.
Volumes 2 through 23 present information summaries for each of the 23 categories of wells that
were studied (Volume 21 covers 2 well categories). This volume, which is Volume 18, covers
Class V geothermal direct heat return flow wells.
1. SUMMARY
Geothermal fluids are used to heat individual homes and/or communities or to provide
heat to greenhouses, aquaculture, and other commercial and industrial processes in several
(primarily western) states. Following use of geothermal fluids for such heating application,
some facilities use geothermal direct heat return flow wells to return these geothermal fluids to
the subsurface.
The temperature and chemical characteristics of geothermal fluids used for heating vary
substantially from site to site. At some sites, the geothermal fluids are of drinking water quality
and, in fact, are used as drinking water and not reinjected. More commonly, concentrations of
some constituents exceed maximum contaminant levels (MCLs) or health advisory levels
(HALs). Available data indicate that arsenic, boron, sulfate, and fluoride exceed primary MCLs
or HALs and that total dissolved solids (TDS), chloride, iron, manganese, and sulfate exceed
secondary MCLs. TDS concentrations are generally <10,000 mg/1 except in the comparatively
rare situations where high temperature geothermal fluids used for power production are also used
for heating.
When geothermal fluids used for heating are reinjected into the subsurface following use
(rather than discharged to surface water or used for drinking, irrigation, or livestock watering),
they typically are reinjected into the same hydrothermal formation from which they were
produced. In addition, the composition of the geothermal fluids normally does not change
appreciably as a result of use for heating, although traces of pump lubricating oil may be added
in some cases.
No documented cases of USDW contamination by geothermal direct heat return flow
wells have been reported. In addition, the wells typically are not vulnerable to receiving
accidental spills or other illicit discharges, because the geothermal fluids are handled in closed
piping systems. Typically, the geothermal fluids are produced from a well, passed through a
heat exchanger, and injected down another well.
September 30, 1999
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The survey results indicate that there are 31 documented geothermal direct heat return
flow wells and another 17 more wells estimated to exist. Although these wells exist in as many
as 11 states, more than 80 percent of the documented wells are in only five states: Oregon (8),
Nevada (7), Utah (4), New Mexico (4) and Idaho (3). All of the 17 estimated wells are in
Oregon, but Alaska also indicated the potential presence of these wells without providing an
estimated number.
Individual permits are required for geothermal direct heat return flow wells in all five of
the states that have most of these wells. In Idaho, an individual permit is not required if the well
is <18 feet deep, but all of the geothermal direct heat return flow wells are substantially deeper
than 18 feet. Individual permit requirements, which also apply in California, are similar in many
respects to those for Class II wells. Further, for wells located on federal land, Bureau of Land
Management (BLM) approval of well drilling, testing, and abandonment is also required by
regulations promulgated under the Geothermal Steam Act of 1970.
2. INTRODUCTION
The existing UIC regulations in 40 CFR 146.5 (e) define Class V wells to include
"injection wells associated with the recovery of geothermal energy for heating, aquaculture, and
the production of electric power." Geothermal injection wells are most commonly associated
with electric power generation. However, Class V injection wells also include wells used in
association with recovery of geothermal energy sources for purposes other than electric power
production. These injection wells are the subject of this information summary. Often referred to
as "direct heat" applications, these non-power applications use low to moderate temperature
(50°C-150°C) geothermal fluids to heat individual homes and/or communities and provide heat
to greenhouses, aquaculture, and other commercial and industrial processes (food dehydration,
laundries, gold mining, milk pasteurizing, etc.) (USDOE, 1996). Applications that tap the
energy in ground water at "normal" temperatures are not included here; rather, they are
considered in the heat pump and air conditioner return flow well category. Similarly, geothermal
wells with down-hole heat exchangers used in direct heat applications are not included here
because they are closed loop systems that are not injection wells subject to USEPA's Class V
UIC regulations.
Following heat extraction, the spent (cooled) geothermal fluids can be reinjected, usually
into the source reservoir.1 Underground injection of spent geothermal fluids occurs for various
reasons including: subsidence prevention, water and heat conservation, maintenance of aquifer
water and pressure levels, disposal of effluent, and legal (e.g., water rights) and regulatory
requirements. In many cases, regulatory requirements provide the principal stimulus for
geothermal fluid reinjection because surface discharge, where permitted, is generally less costly
than injection (Culver, 1988, 1989). For example, in 1990, the city of Klamath Falls, Oregon
implemented a ban on surface disposal of geothermal fluids which resulted in an increase in
1 Discharge to surface water or use for other purposes, such as drinking water and live stock
watering, in lieu of injection is common in some areas. Such discharges and uses are not covered in this
document.
September 30, 1999
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subsurface injection. In contrast, there are an estimated 5,000 users of geothermal heat from the
Madison formation in South Dakota, but no reported geothermal injection wells in South Dakota,
because surface discharge is allowed (Geo-Heat Center, 1998a).
3. PREVALENCE OF WELLS
For this study, data on the number of Class V geothermal direct heat return flow wells
were collected through a survey of state and USEPA Regional UIC Programs. The survey
methods are summarized in Section 4 of Volume 1 of the Class V Study. Table 1 lists the
numbers of Class V geothermal direct heat return flow wells in each state, as determined from
this survey. The table includes the documented number and estimated number of wells in each
state, along with the source and basis for any estimate, when noted by the survey respondents. If
a state is not listed in Table 1, it means that the UIC Program responsible for that state indicated
in its survey response that it did not have any Class V geothermal direct heat return flow wells.
As shown in Figure 1, geothermal resources with sufficient temperature for development
of direct heat applications occur primarily in the western United States, but some are located in
the eastern United States as well. Where geothermal resources are developed for direct heat
applications, injection of the spent geothermal fluid appears to be used relatively infrequently.
For example, a 1988 study reported that of 1,030 identified direct heat use applications, only 17
used injection wells. The other direct use applications employ surface disposal methods (i.e,
release into trenches, ponds, streams, etc.) to dispose of spent geothermal fluids (Culver, 1988).
There are an estimated 48 UIC Class V geothermal direct heat return flow wells in the
United States, as indicated in Table 1. The majority of the 31 documented wells are located in a
few western states: Oregon (8), Nevada (7), New Mexico (4), Utah (4), and Idaho (3). The
additional 17 wells are believed to occur in Oregon. Direct heat return flow wells are also
reported in Florida (in the Central District of the Florida Department of Environmental
Protection), Michigan (based on the 1987 Report to Congress on Class V wells), Louisiana, and
California.2
Use of geothermal energy sources for direct heat applications has been increasing about 5
percent per year on a heat energy basis (Fortuna, 1999). If this trend continues, the number of
direct heat return flow wells would be expected to increase as well, but not necessarily by the
same amount, because: (1) not all geothermal fluids extracted for heating are reinjected; (2)
some uses may involve closed loop systems; and (3) expanded use of geothermal fields that
already have injection wells may not require additional wells.
2 In Louisiana, the one documented well, which was drilled in 1957 for disposal of fluids from a
geothermal spa, is inactive, based on an inspection conducted in December, 1998 by the Louisiana
Department of Natural Resources, Office of Conservation.
September 30, 1999
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Table 1. Inventory of Direct Heat Geothermal Return Flow Wells in the U. S.
State
Documented
Number of Wells
Estimated Number of Wells
Number
Source of Estimate and Methodology1
USEPA Region 1 - None
USEPA Region 2 - None
USEPA Region 3 - None
USEPA Region 4
FL
1
Unknown
N/A
USEPA Region 5
MI
2
NR
N/A
USEPA Region 6
LA
NM
1
4
1
4
N/A
N/A
USEPA Region 7 - None
USEPA Region 8
UT
4
4
Best professional judgement.
USEPA Region 9
CA
NV
1
7
1
7
N/A
N/A
USEPA Region 10
AK
ID
OR
NR
3
8
NR
3
25
State indicates that these wells may exist in AK, but none
are reported.
N/A
Data collected by Calvin Terada, Region 10, per telephone
conversations with state personnel.
All USEPA Regions
All states
31
48
Total estimated number counts the documented number
when the estimated is NR.
1 Unless otherwise noted, the best professional judgement is that of the state or USEPA Regional staff completing the survey
questionnaire.
N/A Not available.
NR Although USEPA Regional, state and/or Territorial officials reported the presence of the well type, the
number of wells was not reported, or the questionnaire was not returned.
Unknown Questionnaire completed, but number of wells is unknown.
September 30, 1999
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Figure 1. Geothermal Resources in the U.S.
Souica: ESEJ, 1995
Temperature Above 10013 (212V)
Temperature Below 100 IS (212 T)
I I Are a S uitable for O eothenn al H e at P um ps (entire U.S.)
Source: Geo-Heat Center, 1998b
4. INJECTATE CHARACTERISTICS AND INJECTION
PRACTICES
4.1 Injectate Characteristics
This section presents data on the chemical characteristics of geothermal fluids associated
with direct heat applications. In general, the chemical characteristics of the injected fluids are
very similar to those of the produced fluids and the receiving formation, which normally is also
the producing formation. The available data provide information on the characteristics of the
produced geothermal fluids, the injected fluids, and the receiving formation, depending on the
site. Changes in chemical characteristics may occur when the produced geothermal fluids are
exposed to atmospheric conditions (e.g., pressure, sunlight), but are generally minor. Data
presented below on the characteristics of injected geothermal fluids as well as the quality of the
water in the formation, are organized by state.
September 30, 1999
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New Mexico. Table 2 presents the results of six samples collected in 1982 and 1983 that
indicate the characteristics of the geothermal fluids produced from three wells at New
Mexico State University (NMSU) and the characteristics of the fluids in the formation at
the point of injection. As shown, these data indicate that IDS, arsenic, chloride, iron,
and manganese concentrations in the produced (and reinjected) fluids exceed drinking
water standards or HALs. The data also show that concentrations of these constituents in
the receiving formation generally are similar to those in the injected fluids. One
exception is arsenic, which is present below the HAL in the receiving formation at one
injection well.3
Idaho. Table 3 presents water quality data for the geothermal system in and around
Boise. The data in column 1, which are based on information compiled by the U. S.
Geological Survey over a period of several years, indicate the range of concentrations
observed in geothermal production wells throughout the area. Columns labeled 1, 3, and
4 each provide data for a sample collected during well installation that indicate the
characteristics of the fluids in the formation at the point of injection. As shown, these
data indicate that arsenic and fluoride concentrations exceed drinking water standards or
HALs. Exceedences are also indicated for lead and iron. In general, these data also
indicate that water quality of the injected fluids and the receiving formations are
comparable.
Oregon. Table 4 provides data on the water quality characteristics of geothermal fluids
around Klamath Falls, Oregon. Data compiled for more than 100 geothermal wells over
a period of several years indicate that the concentrations of boron, iron, and sulfate in the
geothermal fluids typically exceed drinking water standards or HALs. Data from specific
injection and production wells indicate that the concentrations of arsenic routinely exceed
HALs in produced (and then injected) fluids and the receiving formation. In addition,
TDS concentrations sometimes exceed secondary drinking water standards in some
produced (and then injected) fluids and the receiving formation. It appears that
manganese and fluoride concentrations may sometimes exceed drinking water standards
as well.
Nevada. Data on the water quality characteristics of five geothermal direct heat sites
with injection wells are presented in Table 5. As shown, the concentrations of TDS,
arsenic, and boron routinely exceed drinking water standards or HALs both in the
injected fluid and the receiving formation. Data for the Peppermill Hotel Casino show a
noteworthy difference in characteristics for the injectate and receiving formation, because
the geothermal fluids are produced from a formation
3 At NMSU, the production wells are located in the lower Santa Fe group in a zone of geothermal
upflow from the underlying limestone formation while the primary injection well (GD-2) is located in the
outflow plume of the geothermal system in the upper Santa Fe. Thus, injection occurs "downstream" of
the production wells and into the same geothermal system despite the difference in the depth of the wells.
September 30, 1999
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Table 2. Injectate and Formation Characteristics at New Mexico State University
Constituents
IDS
pH (Std. units)
Arsenic
Barium
Bicarbonate (HCOj'1)
Boron
Cadmium
Calcium
Chloride
Chromium
Copper
Fluoride
Iron
Lead
Magnesium
Manganese
Mercury
Nitrate (NCV1)
Potassium
Selenium
Silica (SI02)
Silver
Sodium
Sulfate (SO/2)
Drinking Water Health Ac
Standards* Levels
mg/1
500
6.5-8.5
0.05
2
-
-
0.005
-
250
0.1
1.3
4.0
0.3
0.015
-
0.05
0.002
10
-
0.05
-
0.1
-
500/250
P/S mg/1
S
S
P 0.002
P 2
--
0.6
P 0.005
--
S
P 0.1
P
P
S
P
--
S
P 0.002
P
--
P
--
S 0.1
-
P/S
University of New Mexico, Las Graces
Concentrations in mg/1 unless otherwise noted
i ** Production Wells Injection Wells
PG-1
(1)
860ft
2000
7.95
C 0.002
N <0.4
612.6
N 0.10
N <0.005
138
590.6
N <0.05
1.31
0.28
<0.005
19
0.06
N <0.0002
0.02
57.9
0.002
92
N <0.05
488.0
285
PG-2
(1)
505ft
1980
8.36
0.013
508.9
0.23
188
610
1.31
0.55
21
1.05
51
57.5
450
226.2
PG-3 NMSU #4
(1) (1)
870 ft 607 ft
2010
6.8 7.37
0.003
<0.4
547.9
0.09
<0.005
138 131.7
546 391.4
<0.05
<0.10
1.52
3.95
<0.005
17.4 23
0.16
<0.0002
0.01
52 33.6
0.002
60.9
<0.01
488 321.4
147.5
GD-2 LRG - 3648
468ft
1948
7.65
<0.001
0.08
422.2
0.30
<0.005
130
573.7
<0.002
1.29
1.28
0
36.0
0.09
<0.0002
0.01
43.8
<0.001
23.2
0.05
427.6
315.0
(2)
840ft
1787
7.8
0.001
0.09
494.2
0.30
<0.005
114.5
440.3
<0.002
0.55
6
0.005
36.6
0.13
<0.0002
0.02
34.8
0.001
36
0.05
386.2
280.0
* Drinking Water Standards: P= Primary, S= Secondary
** Health Advisory Levels: N=Noncancer lifetime, C= Cancer Risk
Sources:
(1) Cunniff, Houghton & Clanton, 1982, except TDS values, which are from reference (2).
(2) NMSU, 1983.
September 30, 1999
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Table 3. Constituent Data from Selected Geothermal Wells in Idaho
Constituents
Sampling Date
Well Completion Date
Well Depth (ft.)
IDS
pH (Std. units)
Aluminum
Arsenic
Boron
Cadmium
Calcium
Chloride
Chromium
Copper
Fluoride
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Nitrate (NO/1)
Total NO2 * NO3 as N
Phosphorus
Potassium
Silica (SI02)
Silver
Sodium
Sulfate (SCV2)
Zinc
Gross Alpha (pCi/L)
Gross Beta (pCi/L)
Drinking Water Health Advisory
Standards** Levels ***
mg/1
-
-
-
500
6.5-8.5
0.05-0.2
0.05
-
0.005
-
250
0.1
1.3
4.0
0.3
0.015
-
0.05
0.002
0.1
10
-
-
-
-
0.1
-
500/250
5
15
-
P/S mg/1 N/C
-
-
-
S
S
S
P 0.002 C
0.6 N
P 0.005 N
-
S
P 0.1 N
P
P
S
P
-
S
P 0.002 N
P 0.1 N
P
-
-
-
-
S 0.1 N
-
P/S
S 2 N
P 15 C
-
Boise, Idaho Geothermal Wells
Concentrations in mg/1 unless otherwise noted
(1) (2) (3)
4/24/98 1/8/87
4/9/98 12/13/86
3200 2300
254-330 270.3
8.3 8.3
1.680
0.0048
0.08 -0.09 0.09
ND
1.6-5.5 1.77
7.2-8.7 7.31*
<0.0005
ND
12-19 16.2 14.0
0.871
ND
ND-0.13 0.27
ND
ND
0.01 0.011
0.8-1.6 1.11
55-80 85.0* 115
ND
80-89 64.0
21-24 20.3* 18
0.004
(4)
2152
0.01
0.31
0.001
3.2
6.85
0.05
0.01
16.9
0.02
0.05
0.5
0.01
0.001
0.006
0.8
52.4.
0.001
88
22
0.004
<0.8
1.3
* Sample exceeded recommended holding time before analysis.
** Drinking Water Standards: P= Primary, S= Secondary
*** Health Advisory Levels: N=Noncancer lifetime, C= Cancer Risk
(1) USGS Database Range of concentrations from Boise geothermal aquifer. Montgomery Watson, 1998.
(2) Julia Davis Park Injection Well. Montgomery Watson, 1998.
(3) V. A. Medical Center Injection Well. Montgomery, 1987.
(4) Capital Mall Exploratory Well # 1. Anderson, 1981
September 30, 1999
-------
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at a depth of about 750 feet bgs while injection is into an aquifer 2,500 to 3,000 feet bgs
(Land, 1999b). At some locations in Nevada, higher temperature geothermal resources
that are used for power production are also used for direct heat applications. Data for
two of these sites (Amor II and Brady) provided in the electric power geothermal
injection well information summary show that concentrations of dissolved constituents
are generally several times greater in high temperature geothermal fields than in the
lower temperature geothermal resources represented in Table 5 below. At one or both of
these sites, fluoride, iron, and manganese concentrations also exceed drinking water
standards or HALs.
Table 5. Constituent Data for Selected Geothermal Wells in Nevada
(concentrations in mg/1 unless otherwise specified)
Constituent
IDS
EC
pH
Arsenic
Barium
Boron
Cadmium
Calcium
Chloride
Chromium
Copper
Fluoride
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Nitrate
Potassium
Selenium
Silica
Silver
Sodium
Sulfate
Zinc
Drinking Water Health Ad
Standards * Levels
me/1
500
-
6.5-8.5
0.05
2
-
0.005
250
0.1
1.3
4.0
0.3
0.015
-
0.05
0.002
10
0.05
-
0.10
500/250
5
P/S me/1
S
S
P 0.002
P 2
0.6
P 0.005
S
P 0.1
P
P
S
P
-
S
P 0.002
P
P
-
S 0.1
P/S
S 2
Warren
Estates
** Injectate
N/C 5/13/96
1,002
1,350
7.98
C 0.11
N 0
N 0
N 0
0
0
N 0
0
5.2
0
0
0
0
0
N 0
0
0
0
0
N 0
0
0
N 0
12/10/96
1,016
1,450
8.09
0.14
0
2.1
0
28
51
0
0
4.6
0.28
0
0.3
0.13
0.05
0
<0.1
8
0
105
0
280
510
0
Virginia Lake Townhouse Century Wellness Center
Injectate
11/19/92
694
890
8.20
0.077
0.03
1.1
<0.1
18.8
34
<0.05
<0.02
2.8
0.07
0.003
0
0.9
0.02
<0.0005
<0.1
7.7
<0.001
90
<0.02
193
266
<0.02
3/25/96
761
1,082
8.14
0.091
0.04
1.1
0
21
30
0
0.01
2.64
0.03
0
0
0
0.03
0
0
8
0
84
0
204
0
0.01
Formation
10/10/85
618
0
8.40
0.16
0
0.9
0
20
36
0
0
0.4
0.03
0
0
0.2
0.2
0
<0.1
6
0
47
0
185
300
0
Injectate
12/4/95
596
850
8.22
0.087
0
1.2
0
16
27
0
0
2.6
0
0
0
0.4
0
0
0
3.6
0
52
0
240
250
0
12/10/96
587
850
8.15
0.13
0
1.2
0
14
27
0
0
2.3
0
0
0
0.51
0
0
0
3.4
0
56
0
140
260
0
Peppermill Hotel Casino
Injectate
11/20/92
681
935
8.17
0.19
0.04
1.3
<0.01
21
36
<0.05
0.05
2.1
0.09
0.005
0
0.4
0.03
<0.0005
<0.1
7.3
<0.001
0
<0.02
176
294
0.21
12/24/98
672
930
7.15
0.11
0
0.81
0
17
29
0
0
2.1
0
0
0
0.42
0
0
<0.2
7.1
0
79
0
180
300
0
Formation
3/1/89
1,148
0
8.50
0.16
0
2 9
0
15
50
0
0
3.6
1.12
0
0
1.0
0.05
0
0
7.9
0
0
0
315
509
0
9/1/89
1,365
0
7.30
0.077
0
4.0
0
43
157
0
0
14
2.2
0
0
2.5
0.38
0
0
15
0
0
0
550
694
0
Caliente
Formation
8/1/96
505
740
7.75
0.036
0
1.4
<0.001
43
66
0.029
0.02
1.2
0.06
0.005
0
15
0.01
0
0.4
7.9
0
43
<0.001
100
62
0.088
* Sample exceeded recommended holding time before analysis.
** Drinking Water Standards: P= Primary, S= Secondary
Source: Land, 1999a
September 30, 1999
10
-------
California. Though direct heat uses of geothermal resources occur in several parts of the
state, injection is only reported to occur at one location. Data available shown in Table 6
indicate that concentrations of TDS and sulfate exceed secondary drinking water
standards while boron concentrations exceed HALs in both the injected fluids and the
receiving formation.
Table 6. Constituent Data for Selected Geothermal Wells in Susanville, California
(concentrations in mg/1 unless otherwise noted)
Drinking Water Health Advisory
Standards (MCLs) Levels (HALs)
mg/1 P/S* mg/1 N/C*
EC**
pH*** 6.5-8.5 S
Temp. (°C)
TDS 500 S
Calcium
Magnesium
Sodium
Potassium
HCO3
C03
SO4 500/250 P/S
Chloride 4 P -
Boron - 0.6 N
Fluoride 4/2 P/S
SiO,
* P=primary, S= secondary, N=non-cancer, C=cancer
** electrical conductivity, micromhos/cm
*** standard units
Source: GeothermEx, 1984
Injection Well
(sample from
the well on
10/25/82)
1180
8.73
728
20.4
0.42
227.0
3.2
30.3
4.2
321.0
128.0
2.8
6
Production Wells
Susan 1
(11/23/80)
1129
8.91
73
886
30.0
0.35
245.0
6.8
0.0
12.2
379.0
127.0
2.5
0.00
83
Susan 1
(10/27/81)
1400
8.40
77
949
28.0
0.06
240.0
7.0
32.9
0.0
450.0
130.0
2.4
2.20
73
Naef
(4/17/84)
1200
8.90
66
906
26.0
0.12
260.0
4.6
29.0
10.0
380.0
140.0
o o
J.J
2.10
66
These data, in combination with data for higher temperature geothermal resources
provided in Volume 17, show that chemical characteristics of injected geothermal fluids vary
considerably depending on the nature of the geothermal resource. They also show that the
concentrations of some constituents such as TDS, arsenic, and boron, based on available data,
exceed drinking water standards or HALs in both the injected fluids and the receiving
formations. Injectate may also contain traces of lubricants from equipment (e.g., oil lubrication
of the bearings in a lineshaft pump), but no data were found to quantify the effect (if any) on
injectate quality.
September 30, 1999
11
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4.2 Well Characteristics
Geothermal injection wells used in various direct heat applications are generally 200 feet
to 2,000 feet deep, although some (see Figure 2) are deeper. The wells are typically constructed
with a single casing cemented to the top of the injection zone and a screen or a perforated liner
installed in the injection zone. In the example shown in Figure 2, a surface casing is also used
for this relatively large diameter well. In the example shown in Figure 3, no surface casing was
used.
The specific well designs and materials used for direct heat injection wells vary
depending upon the chemical nature of the geothermal resource, well depth, and the geology of
the injection zone (USEPA, 1987). In general terms, there is a correlation between the chemical
characteristics of geothermal fluids and the reservoir depth and temperature. Lower temperature
fluids from shallower depths are typically less corrosive than fluids found at greater depth and
higher temperature (U.S. House of Representatives, 1992). The choice of well casing materials
is highly dependent upon the geothermal fluid chemistry. Standard carbon steel pipe may be
used with non-aggressive waters, while corrosion-resistant alloys may be necessary when
corrosive fluids are injected. Similarly, casing and piping thickness vary according to the area's
geologic structural stability and expected length of heating operations. In addition, casing
selection and related design features also are affected by geothermal formation pressure. In
general, geothermal formation pressures associated with direct heat applications are much lower
than in the higher temperature resources used for power production, but in some cases are still
high enough for the injection well to have artesian or "near artesian" flow when the well is
initially drilled. For example, injection wells in Boise have demonstrated artesian flow, and a
3,400 feet injection well in Louisiana showed a static water level 69 feet below ground surface
(Montgomery Watson, 1998; Turcan, 1959).
4.3 Well Siting
Siting of direct heat return flow wells is normally governed by geothermal reservoir
management considerations. Specifically, the injection wells need to be sited where the cooled
fluid will be returned to a location that does not cause a drop in temperature at the production
wells. In the example shown in Figure 3, the well was drilled to a depth of nearly 1,000 feet to
ensure that the geothermal injection zone did not overlie a potable water aquifer and that the
injection horizon would be located within the outflow from the geothermal reservoir system.
Analysis of temperature logs, water chemistry, and lithology information led to the conclusion
that injection should occur in approximately the 370 feet to 470 feet interval. Thus, the lower
500 feet of the well were backfilled and then sealed with a cement plug (Cunniff, 1983).
In addition, land surface considerations typical for any well (e.g., access for maintenance)
also apply. Because injected geothermal fluids are delivered to the wells in a closed pipeline
system, well siting is not expected to affect injectate quality.
September 30, 1999 12
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Figure 2. Example of a Direct Heat Return Flow Well ~ Boise, ID
(Depths in feet below ground surface)
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
oftnn
^ouu
3000
3200
S-aSStSS
y//y/y////f/,
p^%g
;|^|^|
:^tlll
'/^'/4'///'//,
'/ /' / v/x/'1' y
^0J&
0^/1^
'•ftyy///f/.
•///'•///<
p/ t/'f '^ ,''''/
s^K'^
sSssK?
^ ••
C^ftC^"^
•/V'v'VsCt
A ""T A ' o A '
^,f '.^''.^
:"°vj?di°=.
f^Ci^0^.
,-{j a r>*T£ a
'-^y^T?.-iy
-, ".. "..' -
— Sand and gravel f3§"
v^ ;
— Interbedded sand, silt, clay, t;
and minor gravel layers @
86'-95' 122'-130' 145'- 155'
165'-192',231'-245',465'-495',
508'-525', 542'-572, 586'-642,
652'-670, and 679'-704'
— Silt, sandy silt, siltstone,
and claystone
— Siltstone/basalt ash clay
and silty clay
— Basalt and altered
— Silty sand, sandy clay, •;
and clay ^
^
I
— Rhyolite
— Sandstone
1 rl 1
— Rhyolite with sand and
gravel interbeds
— Sand and gravel
! ! 1
i II
1 1 1
i II
1 II
L II
1 II
L II
1. II
L II
1 II
1
•~xj»- 24" Bore Hole
.- :> v^ 20"OD Casing
^ \ 0.375" Wall Thickness (to 71')
^ "^ Portland Cement
•y — 16" OD Casing
A 0.375" Wall Thickness (to 307')
\ 18 1/2" Bore Hole
* Halliburton Light Cement
: « 14 3/4" Bore Hole
* 12" OD Casing, 0.375" Wall Thickness
Centralizers at 1 00' Intervals
s
i!
J Class G Cement
55
^
8" OD Casing 0 322" Wall Thickness1
MHI oiot rerroratea witn io
Perforations per Foot at 1/4"x3", . . .
Centralizers at 100' Intervals
Shale Baskets at 2360, 2465, 2545,
2625 3015 3145 and 3200
« 11" Bore Hole
Source: Montgomery Watson, 1998.
September 30, 1999
13
-------
Figure 3. Example of a Direct Heat Return Flow Well ~ New Mexico
(Depths in feet below ground surface)
50
TOO
150
200
250
300
350
40O
450
500
550
600
650
700
750
800
850
900
950
foSM
o °°s 6 .0
r! "* ^ * ^ •,
-: ->f * s«
;; v;,\;
OoJVf" s-A)
&:3%
Hull ..^.^1', ,f.
>~ >\V
"' V^
"x ,i-^ ,\
*^
<
'^A^4
^^%^
•-'•'- '/•».-
88
mill
— ouiiauesaiiu
— Big gravel
c .
j
— Red clay and gravel
— Medium sand and gravel
— Red clay
— Medium sand and gravel
— Sand, clay and gravel
— Sandy clay, sand and gravel
— Hard rock with sandy clay
— Cemented gravel
— Clay
— Cemented gravel
— Sand
— Cemented gravel
V'
-
V
/•
te
?
1
i
\A; \^
v*\
— lA
?:
//
^,
//
/
\
\ Cement 348' to top
/,
/
* ^^.J_.___, 316 SS .060 slot screen
p^ Blank 8 5/8"casing
IL r. i r, •!• 1
316 SS .060 slot screen
— Jetted sample 468'
bacK Tilled pilot / 1 16
486' to 520
bacK IHIeu pilul 0 \U
520'to99f
* rn QQV
Source: NMSU, 1983.
September 30, 1999
14
-------
4.4 Well Operation
Prior to being placed in operation, the integrity of the casing and overall well
construction may be tested by a variety of means. Testing may include an evaluation of the
cement job (e.g., cement bond log) and a pressure test of the well casing. Monitoring and
periodic testing may also be performed as part of on-going well operation, depending onsite
conditions and requirements. On-going (e.g., daily, weekly) monitoring of injection pressures
and flow rates is often conducted as part of well operation to collect data that will aid in the
management of the geothermal reservoir, especially where flow rates and pressures vary
seasonally with changes in the demand on the direct heat system.4 Periodically (e.g., every five
years), well operation may be temporarily suspended for pressure testing of the casing if the well
passes through a USDW and corrosion is a potential concern due to the characteristics of the
geothermal fluids.
The injections wells are operated as part of an integrated fluid extraction, heat recovery,
and injection cycle. Throughout this cycle, the fluids are handled in closed piping systems and
so are generally not vulnerable to receiving accidental spills or other illicit discharges. Injection
wells used in association with district heating systems, however, are potentially vulnerable to
contamination, because each customer is a potential point of contamination if they modify their
piping to allow waste water from other sources, such as shallow ground water cooling wells or
back up boiler systems, to be pumped into the geothermal fluid flow (Johnson, 1999).
5. POTENTIAL AND DOCUMENTED DAMAGE TO USDWs
5.1 Injectate Constituent Properties
The primary constituent properties of concern when assessing the potential for Class V
geothermal direct heat return flow wells to adversely affect USDWs are toxicity, persistence, and
mobility. The toxicity of a constituent is the potential of that contaminant to cause adverse
health effects if consumed by humans. Appendix D of the Class V Study provides information
on the health effects associated with contaminants found above drinking water standards or
HALs in the injectate of geothermal direct heat return flow wells and other Class V wells.
Persistence is the ability of a chemical to remain unchanged in composition, chemical
state, and physical state over time. Appendix E to the Class V Study presents published half-
lives of common constituents in fluids released in geothermal direct heat return flow wells and
other Class V wells. All of the values reported in Appendix E are for ground water. Caution is
advised in interpreting these values, because ambient conditions have a significant impact on the
persistence of both inorganic and organic compounds. Appendix E also provides a discussion of
the mobility of certain constituents found in the injectate of geothermal direct heat return flow
wells and other Class V wells.
4 At some sites, system demand is less dependent on seasonal temperatures, as in the case of the
onion dehydration plants that have year-round, 24-hours a day operation.
September 30, 1999 15
-------
Based on the information presented in Section 4.1, the concentrations of arsenic, boron
fluoride, and sulfate in injected geothermal fluids exceed drinking water standards or HALs.
Chloride, iron, manganese, and TDS have been measured above secondary drinking water
standards in some injected geothermal fluids. In general, these constituents are persistent and
mobile following injection to approximately the same extent as they were before extraction,
because the spent (injected) geothermal fluids are injected into the producing formation.
5.2 Observed Impacts
None of the states that reported having direct heat return flow wells (see Table 1)
indicated that this type of injection well is known to have contributed to the contamination of a
USDW. A study of injection attempts in Susanville, California found that injectate fluids
reached the surface during the initial mechanical integrity testing (MIT) of a direct heat return
flow injection well. It is not clear from the available information whether the leak, which was
caused by an improperly cemented seal on the new well, resulted in release to subsurface
formations other than the intended injection zone (Culver, 1990a). Corrosion in wells associated
with direct heat applications has also been documented (Lund, 1990). Much of the study on
corrosion in direct heat applications has focused on components other than injection well casing,
such as distribution piping and down-hole heat exchangers. While far less of a problem than
with electric power geothermal injection wells, some geothermal fluids are sufficiently corrosive
that they may cause well failures unless appropriate precautions are taken during well design and
operation.
6. BEST MANAGEMENT PRACTICES
Several best management practices (BMPs) can be implemented to provide increased
protection of USDWs (when present) and, in many cases, also provide improved safety and cost
performance for direct heat return flow wells. The following discussion is neither exhaustive nor
represents a USEPA preference for the stated BMPs. Each state, USEPA Region, and federal
agency may require certain BMPs to be installed and maintained based on that organization's
priorities and site-specific considerations.
Siting of direct heat return flow wells to enhance protection of USDWs (if present) and
operation of the heat recovery system is improved by careful investigation and understanding of
the geothermal resource. Through investigation, operators gain the necessary conceptual and
physical understanding of the resource area. Knowledge of the hydrogeological, structural, and
chemical nature of the resource aids in siting decisions and well design. Hydrogeological
information is important for predicting the flow of the injected water once it enters the
subsurface. Understanding existing flow rate, direction, and volumes gives insight into how
injected fluids behave and travel in the formation. For example, small geothermal sources that
are characterized by high transmissivity may not permit effective injection without excessive
thermal breakthrough (Culver, 1988). Techniques such as injectivity, transmissivity, and tracer
testing can be used to acquire information beneficial to siting decisions.
September 30, 1999 16
-------
Well life and operation are improved if well design and material selection include
consideration of factors such as how the well will be operated, the nature of the formations that
the well is drilled through, and the corrosion potential of the geothermal fluids. If well operation
results in alternating periods of use and disuse, thermal expansion/contraction of well casing may
cause a fracturing in the cement seals in unconsolidated formations and, thus, allow interzonal
fluid migration. Placing a cement seal above the perforations in the injection well, and using
bentonite filling (rather than cement) can reduce the potential for fluid movement in the borehole
in applications where changes in well casing temperatures are anticipated (Culver, 1990b).
Various constituents found in geothermal fluids, including air, oxygen, carbon and
carbon oxides, sulfur-containing gases, hydrogen, and metal halides, may cause corrosion of
direct heat return flow wells (METALogic NV, 1998). Thus, corrosion potential is site specific.
Although in general, corrosion problems increase with increasing fluid solids content and
temperature. Most direct heat return flow wells are constructed with steel casing, but stainless
steel well screens are sometimes used. Stainless steel may be used to resist the corrosive effects
of some geothermal fluids. In other situations, stainless steel may be used to withstand repeated
acidizing of a well (to remove deposits from the screen).
After the well is constructed, initial pressure testing of the casing and a survey of the
cementing integrity (e.g., cement bond log) serve to verify that the well construction was
accomplished as planned. On-going monitoring of injection flow rates and pressures both
provides data for use in managing the geothermal reservoir and for checking the proper operation
of the well. Periodic re-testing of casing and cementing integrity provides added assurance that
fluids continue to be injected into the intended formation.
As indicated in Section 4, injection wells used in association with district heating systems
are potentially vulnerable to contamination because each customer is a potential point of
contamination. Monitoring of the chemical composition of the fluid flow can help guard against
such potential contamination. In Boise, for example, geothermal water has high fluoride levels.
Therefore, a protocol for testing fluoride levels in water being injected has been developed as the
first step to detect unauthorized waste flows being added to the spent geothermal fluids
(Johnson, 1999).
7. CURRENT REGULATORY REQUIREMENTS
Several federal, state, and local programs exist that directly manage or regulate Class V
geothermal direct heat return flow wells. On the federal level, management and regulation of
these wells fall primarily under the UIC program authorized by the Safe Drinking Water Act
(SDWA). In addition, the BLM has enacted regulations under the authority of the Geothermal
Steam Act to control the use of geothermal resources on federal lands. Some states and localities
have used these authorities, as well as their own authorities, to extend the controls in their areas
to address concerns associated with geothermal direct heat return flow wells.
September 30, 1999 17
-------
7.1 Federal Programs
7.1.1 SDWA
Class V wells are regulated under the authority of Part C of SDWA. Congress enacted
the SDWA to ensure protection of the quality of drinking water in the United States, and Part C
specifically mandates the regulation of underground injection of fluids through wells. USEPA
has promulgated a series of UIC regulations under this authority. USEPA directly implements
these regulations for Class V wells in 19 states or territories (Alaska, American Samoa, Arizona,
California, Colorado, Hawaii, Indiana, Iowa, Kentucky, Michigan, Minnesota, Montana, New
York, Pennsylvania, South Dakota, Tennessee, Virginia, Virgin Islands, and Washington, DC).
USEPA also directly implements all Class V UIC programs on Tribal lands. In all other states,
which are called Primacy States, state agencies implement the Class V UIC program, with
primary enforcement responsibility.
Geothermal direct heat return flow wells currently are not subject to any specific
regulations tailored just for them, but rather are subject to the UIC regulations that exist for all
Class V wells. Under 40 CFR 144.12(a), owners or operators of all injection wells, including
geothermal direct heat return flow wells, are prohibited from engaging in any injection activity
that allows the movement of fluids containing any contaminant into USDWs, "if the presence of
that contaminant may cause a violation of any primary drinking water regulation ... or may
otherwise adversely affect the health of persons."
Owners or operators of Class V wells are required to submit basic inventory information
under 40 CFR 144.26. When the owner or operator submits inventory information and is
operating the well such that a USDW is not endangered, the operation of the Class V well is
authorized by rule. Moreover, under section 144.27, USEPA may require owners or operators of
any Class V well, in USEPA-administered programs, to submit additional information deemed
necessary to protect USDWs. Owners or operators who fail to submit the information required
under sections 144.26 and 144.27 are prohibited from using their wells.
Sections 144.12(c) and (d) prescribe mandatory and discretionary actions to be taken by
the UIC Program Director if a Class V well is not in compliance with section 144.12(a).
Specifically, the Director must choose between requiring the injector to apply for an individual
permit, ordering such action as closure of the well to prevent endangerment, or taking an
enforcement action. Because geothermal direct heat return flow wells (like other kinds of Class
V wells) are authorized by rule, they do not have to obtain a permit unless required to do so by
the UIC Program Director under 40 CFR 144.25. Authorization by rule terminates upon the
effective date of a permit issued or upon proper closure of the well.
Separate from the UIC program, the SDWA Amendments of 1996 establish a
requirement for source water assessments. USEPA published guidance describing how the states
should carry out a source water assessment program within the state's boundaries. The final
guidance, entitled Source Water Assessment and Programs Guidance (USEPA 816-R-97-009),
was released in August 1997.
September 30, 1999 18
-------
State staff must conduct source water assessments that are comprised of three steps.
First, state staff must delineate the boundaries of the assessment areas in the state from which
one or more public drinking water systems receive supplies of drinking water. In delineating
these areas, state staff must use "all reasonably available hydrogeologic information on the
sources of the supply of drinking water in the state and the water flow, recharge, and discharge
and any other reliable information as the state deems necessary to adequately determine such
areas." Second, the state staff must identify contaminants of concern, and for those
contaminants, they must inventory significant potential sources of contamination in delineated
source water protection areas. Class V wells, including geothermal direct heat return flow wells,
should be considered as part of this source inventory, if present in a given area. Third, the state
staff must "determine the susceptibility of the public water systems in the delineated area to such
contaminants." State staff should complete all of these steps by May 2003 according to the final
guidance.5
7.1.2 Geothermal Steam Act
The BLM regulates use of geothermal resources on federal lands administered by the
Department of the Interior or the Department of Agriculture, on lands conveyed by the U.S.
where geothermal resources were reserved to the U.S., and on lands subject to Section 24 of the
Federal Power Act, as amended (16 U.S.C. 818) with concurrence from the Secretary of Energy.
Guidance on geothermal classification, leasing, exploration, operations, and resource protection
and utilization is provided in 43 CFR parts 3200, 3210, 3220, 3240, 3250, and 3260. The BLM
can issue geothermal resource operational orders, under the Geothermal Steam Act of 1970, for
nationwide requirements; notices to lessees for statewide or regional requirements; and other
orders and instructions specific to a field or area. The BLM can also issue permit conditions or
approval and verbal orders.
Permitting Requirements
In order to use federal lands for access to geothermal resources, a site license and
construction permit must be issued before starting any site activities. A plan showing the
proposed site plans and a draft of a proposed site license agreement must be submitted to BLM.
The BLM reviews these materials and decides on the issuance of a permit and license to proceed
with work.
To get approval for drilling operations and well pad construction the following must be
submitted to BLM: a completed drilling permit application, a completed operations plan, a
complete drilling program, and an acceptable bond. A drilling program describes the
operational aspects of the proposed drilling, completion, and testing of the well. The drilling
program requires numerous items, including the casing and cementing program, the circulation
media (mud, air, foam, etc.), a description of the logs that will be run, and a description and
5 May 2003 is the deadline including an 18-month extension.
September 30, 1999 19
-------
diagram of the blowout prevention equipment that will be used during each phase of the drilling.
An operations plan describes how to drill and test for the geothermal resources.
Within 30 days of completion of the well, a geothermal well completion report (form
3260-4) must be submitted to BLM.
Operational Requirements
The rules establish general standards that apply to drilling operations. They include
meeting all environmental and operational standards, preventing unnecessary impacts to surface
and subsurface resources, conserving geothermal resources and minimizing waste, protecting
public health, safety and property, and complying with the requirements of the Act;
implementing regulations; Geothermal Resource Operational Orders; notices to lessees; lease
terms and stipulations; approved plans and permits; conditions of approval; verbal orders from
BLM which will be confirmed in writing; other instructions from BLM; and any other applicable
laws and regulations (43 CFR 3200.4). Federal regulations 43 CFR subparts 3260 through 3267
establish permitting and operational procedures for drilling wells, conducting flow tests,
producing geothermal fluids, and injecting fluids into a geothermal reservoir. Also included in
these regulations are redrilling, deepening, plugging back and other well re-work operations.
BLM operational requirements for drilling include: keeping the wells under control at all
times, conducting training during operation to ensure trained and competent personnel can
perform emergency procedures effectively, and using properly maintained equipment and
materials. Other requirements include employing sound engineering principles using all
pertinent data, selecting drilling fluid types and weights, providing a system to control fluid
temperatures, providing blowout prevention equipment, and providing a casing and cementing
program.
Mechanical Integrity Testing
Generally, BLM requires that wells be tested once every two years unless problems have
occurred with a well. Casing failures or other problems can lead to orders from BLM specifying
more frequent MIT.
BLM also may specify particular types of MITs, such as hydraulic pressure tests and
electronic casing log tests, or approve other methods proposed by operators on a case-by-case
basis. Hydraulic pressure tests require a bridge plug to be placed as close as possible to the
injection zone and the casing tested to a surface pressure of 1,000 psi or 200 percent of the
maximum injection pressure, whichever is greater. However, the test pressure is not to exceed
70 percent of the minimum internal yield. If pressure declines more than 10 percent in 30
minutes, corrective action must be taken to identify and correct the cause of the pressure loss.
Electronic casing log tests are run every two years and require injection well casing thickness to
be no less than 75 percent of new nominal wall thickness. If the well fails this test, it must be
placed out of service until BLM approves reactivation.
September 30, 1999 20
-------
Financial Responsibility
Before initiating any operation, operators are required to deposit a security or personal
bond, subject to approval by BLM.
Plugging and Abandonment
In order to abandon a well, a notice that documents the proposed plugging and
abandonment program must be approved before closure begins. The local BLM office must also
be notified before beginning abandonment so that they can witness the closure. Furthermore, a
well abandonment report must be submitted to BLM within 30 days after completion of
abandonment. The abandonment report includes a description of each plug, including the
amount and type of cement used, the depth that the drill pipe or tubing was run to set the plug,
the depth to the top of the plug, if the plug was verified, whether pressure testing or tagging was
used, and a description of the surface restoration procedures.
Geothermal Resources Operational Order Number 3, effective February 1, 1975, states
specific requirements for well plugging and abandonment. Cement used to plug any geothermal
well, except for surface plugging, must be placed into the well hole by pumping through a drill
pipe or tubing. Plugging cement should consist of a high temperature resistant admix, unless
waived by the Site Supervisor. In uncased portions of the well, as well as in production
perforations, cement plugs must be placed to protect all subsurface mineral resources including
fresh water aquifers. These plugs must extend a minimum of 100 feet below and, if possible,
100 feet about the aforementioned zones. Intervals of the hole not filled with cement must be
filled with good quality heavy mud. All open annuli extending to the surface must be plugged
with cement and the innermost casing string which reaches ground level must be cemented or
concreted to a minimum depth of 50 feet measured from 6 feet below ground level. All casing
strings must be cut off at least 6 feet below the ground level and capped by welding a steel plate
on the casing stub. The surface area must be restored as specified by the site supervisor.
7.2 State and Local Programs
As discussed in Section 3 above, more than 85 percent of the documented wells and more
than 90 percent of the estimated wells under either state or federal jurisdiction are located in six
states: New Mexico, Utah, California, Nevada, Idaho, and Oregon. Attachment A of this volume
describes how each of these states regulate direct heat return flow wells.
Individual permits are required for geothermal direct heat return flow wells in all states.
The individual permit requirements are, in most cases, similar to those for Class II wells. The
states' requirements include detailed siting and construction requirements, monitoring and other
operating requirements, mandatory MIT, detailed requirements for plugging and abandonment,
and financial responsibility requirements. In several of these states, the state agency responsible
for regulating geothermal direct heat return flow wells also has jurisdiction over other natural
resources, such as oil and gas, and is separate from the state's Class V UIC program.
September 30, 1999 21
-------
In addition to the USEPA Regional oversight of Class V wells in this Direct
Implementation state, California issues individual permits to geothermal direct heat
return flow wells under the authority of its Public Resources Code and regulations
governing geothermal resources. A detailed permit application allowing for case-by-case
permitting decision is required. The state specifies, in regulations and permit conditions,
requirements for well construction, operation, MIT, plugging and abandonment, and
financial responsibility.
Idaho is a Primary State for UIC Class V wells. The state issues individual permits for
direct heat return flow wells under its UIC Class V program as well as its authority over
geothermal resources. Permits are based on extensive background information, and
specify well location and construction. Wells are required to supply information on the
impact of injection on the geothermal reservoir and on other natural resources. Plugging
and abandonment must be approved in advance.
New Mexico is a Primacy State for UIC Class V wells, but has delegated authority over
direct heat return flow wells to the Oil Conservation Division (OCD). The OCD,
working with the State Engineer, issues individual permits for direct heat return flow
wells under the authority of the state's Geothermal Resources Act, using a proposed rule
as additional guidance on siting and construction, operating requirements, annual MIT,
required plugging and abandonment plans, and financial responsibility.
Nevada issues individual permits to direct heat return flow wells under its authority as a
UIC Class V Primacy State. In addition, the State Engineer and Division of Minerals
also permit direct heat return flow wells under their authority over geothermal resources.
Detailed siting and construction standards, operating requirements, requirements for
plugging and abandonment, and financial responsibility are found in both the UIC
regulations and the regulations governing geothermal resources. Direct heat return flow
wells in the state must satisfy both sets of standards.
Oregon is a Primary State for UIC Class V wells. The state, through the Water
Resources Department, regulates direct heat return flow wells under its water resource
regulations pertaining to either low temperature or high temperature geothermal
production and disposal. The state geologist within the Department of Geology and
Mineral Industries also permits all geothermal wells. Such wells also must meet
construction standards, operating requirements, MIT requirements every five years, and
must follow specified plugging procedures.
Utah is a Primary State for UIC Class V wells. Utah's Division of Water Rights (DWR)
issues individual permits to direct heat return flow wells under its authority over
geothermal energy production found in the state's water rights code. DWR's jurisdiction
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is intended to eliminate duplication of regulation, particularly with the state's Class V
UIC program and Bureau of Pollution Control. The DWR applies detailed well siting
and construction requirements; requires testing and monitoring of injection operations,
individual MIT; sets stringent plugging and abandonment requirements; and requires
bonds for financial responsibility.
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ATTACHMENT A
STATE AND LOCAL PROGRAM DESCRIPTIONS
This attachment describes the control programs in the states in which direct heat return
flow wells are most prevalent, namely California, Idaho, Nevada, New Mexico, Oregon, and
Utah. In combination, these states have all but 4 of the 31 documented wells in the national
inventory.
California
USEPA Region 9 directly implements the UIC program for Class V injection wells in
California. At the state level, the California Department of Conservation, Division of Oil, Gas,
and Geothermal Resources (CDOG) is the state agency with direct responsibility for geothermal
direct heat return flow wells under Chapter 4 of Division 3 of the California Public Resources
Code (PRC) (Sections 3700 - 3776). The Department has enacted state-wide geothermal
regulations in Title 14, Chapter 4, Subchapter 4 of the California Code of Regulations (CCR).
The PRC explicitly covers "any special well, converted producing well or reactivated or
converted abandoned well employed for reinjecting geothermal resources or the residue thereof
(3703 PRC). The regulations define an injection well as "a service well drilled or converted for
the purpose of injecting fluids" (1920.1(e) CCR). They also specify that injection wells may be
used for the disposal of waste fluids, the augmentation of reservoir fluids, pressure maintenance
of reservoirs or for any other purpose authorized by CDOG. New wells may be drilled and/or
old wells may be converted for water injection or disposal service (1960 CCR).
Under California's Water Quality Control Act (WQCA), the state is divided into nine
regions, and Regional Water Quality Control Boards, which are organizations separate from
CDOG, are delegated responsibilities and authorities to coordinate and advance water quality
(Chapter 4 Article 2 WQCA). A Regional Board can prescribe requirements for discharges
(waste discharge requirements or WDRs) into the waters of the state, including ground water6
(13263 WQCA). A WDR can pertain to injection wells (13263.5 and 13264(b)(3) WQCA) and
at least one Regional Board has issued a WDR for geothermal wells.
Permitting
Under the state geothermal regulations, injection well operators must file a Notice of
Intent to Drill, post a bond or surety prior to injection operations, and pay an application fee
(3724 PRC, 1931 CCR). Operations may not commence until the CDOG reviews and approves
the application (3724.3 PRC; 1931 CCR). Applicants must provide a letter setting forth the
entire plan of operations that includes analysis of reservoir conditions, method of injection (i.e.,
through casing, tubing, or tubing with a packer), source of injection fluid, and estimates of the
daily amount of water to be injected. The application must include a map of the well field along
6 The WQCA defines "waters of the state" as "any surface or ground water, including saline waters,
within the boundaries of the state."
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with one or more cross sections showing the wells involved and a copy of any environmental
documents created in support of the operations. Notice is also required when operators convert
an existing well to an injection or disposal well, even if there will be no change in mechanical
condition as a result of the conversion. In addition, applicants must provide chemical analyses
of injectate and injection zone fluids. Finally, the application must contain copies of the letter of
notification sent to neighboring operators, if required by CDOG (3724, 3724.1 PRC). Officials
set permit conditions on a case-by-case basis.
Regional Water Quality Control Boards can include special monitoring and reporting
requirements in a Waste Discharge Requirement's monitoring and reporting program (3724
PRC).
Siting and Construction
The CDOG's geothermal regulations contain specifications for well construction. All
wells must be cased in a manner that protects or minimizes damage to the environment, surface
and ground waters, geothermal resources, life, health, and property (1935 CCR). Conductor pipe
must be cemented with sufficient cement to fill the annular space from the shoe to the surface
(1935.1 CCR). Surface casing must provide for control of formation fluids, protection of ground
water, and prevention of blowouts. However, the specific requirements regarding length of
casing and cementing point may be waived or modified for low-temperature geothermal wells
(1935.2 CCR). Intermediate casing must be cemented solid to the surface whenever possible
(1935.3 CCR). Similarly, production casing may be set above or through the injection zone and
cemented above the objective zones (1935.4 CCR). The specific casing design criteria are
determined on a case-by-case basis, depending on the hydrogeological conditions at each well
field (3740 PRC).
State regulations also contain standards for blowout prevention. Each well must be
equipped with blowout prevention equipment (BOPE) that includes high temperature-rated
packing units and ram rubbers. This equipment must have a working-pressure rating equal to or
greater than the lesser of (a) a pressure equal to the depth of the BOPE anchor string in meters
multiplied by 0.2 bar per meter, (b) a pressure equal to the rated burst pressure of the BOPE
anchor string, or (c) a pressure equal to 138 bars (2,000 psi). The state generally prohibits
drilling in unstable geothermal areas, including areas with fumaroles, geysers, hot springs, and
mud pots. However, if drilling in these areas is approved, drilling operations must be monitored
by state officials until the surface casing has been cemented and the BOPE has been pressure-
tested satisfactorily (1941-1942.2 CCR).
Operating Requirements
Completed and operating geothermal injection wells must be maintained and tested to
prevent loss of or damage to life, health, property, and natural resources. All surface and
wellhead equipment and pipeline, and subsurface casing and tubing must be examined
periodically for corrosion. Operators must show "complete" casing integrity upon completion of
a new injection well, when converting a production well to an injection well, or when
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reactivating an idle well. The geothermal regulations also require monitoring of injection well
operations on a "continuing" basis to establish that all injectate is confined to the intended
injection zone. CDOG staff (well supervisors) conducts onsite inspections periodically to note
surface conditions and determine remedial action needed to address problems, if any. Operators
must examine, document, and report injection pressures to CDOG, and CDOG may rescind
injection approval if it appears damage is being done (1966 CCR).
Mechanical Integrity
Casing integrity tests must be performed within 30 days after injection starts and every
two years thereafter, unless otherwise specified by CDOG. State regulations mandate the use of
MITs to prevent damage to life, health, property, and natural resources; to protect geothermal
reservoirs from damage; and to prevent the infiltration of detrimental substances into
underground or surface water suitable for agricultural, industrial, municipal, or domestic use.
Casing tests must be performed, which may include spinner surveys, wall thickness, pressure,
and radioactive tracer tests. Cementing tests are also required, which may include tests on
cementing of the casing, pumping of plugs, hardness of plugs, and depths of plugs. Finally,
regulations require equipment testing of gauges, thermometers, surface facilities, lines, vessels,
and BOPE. The CDOG well supervisor is delegated authority to require "such tests or remedial
work as in his or her judgment are necessary" to prevent damage "or to prevent the infiltration of
detrimental substances into underground or surface water ..." and therefore may determine the
type and frequency of these tests on a case-by-case basis (1954 CCR).
Financial Responsibility
Operators must file an individual indemnity bond that secures the state against all losses,
charges, and expenses incurred from assuring compliance with the state's geothermal resources
regulations. The bond must be filed with CDOG at the time operators file the Notice of Intent to
Drill. Bonds must be executed by the owner, as principal, and by an authorized surety company,
as surety, on condition that the principal named in the bond will comply with all the provisions
of the state's geothermal regulations. The bond's language must substantially conform to the
language provided in California's Public Resources Code, Chapter 4, §3725. Operators may
choose to file an individual indemnity bond of $25,000 for each well drilled, redrilled, deepened,
maintained, or abandoned; or they may file a blanket bond of $100,000 to cover all operations
statewide. Individual and blanket bonds may be terminated and canceled after the wells have
been properly abandoned (3725.5 PRC). Liability for individual wells covered under a blanket
bond may be terminated by consent of the CDOG supervisor (3725 and 3728 PRC).
Plugging and Abandonment
Under the geothermal requirements of PRC, an operator must file for and obtain written
approval to abandon, specifying the proposed method of abandonment. Furthermore, the
operator must file the request at least 10 days before the proposed abandonment (3747 PRC).
Unless otherwise approved, no person shall remove the casing from a geothermal injection well
without first giving written notice to the state of the intention to do so. The notice shall be given
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at least 10 days before the proposed removal (3751 PRC). Within 60 days after the completion
of abandonment of any well, the owner or operator of the well must provide a written report of
completion. The CDOG well supervisor, in turn, must furnish the owner/operator with a written
final approval of abandonment or disapproval (3748 PRC).
The regulations provide detailed requirements for plugging and abandonment. They
include, for cased wells (including injection wells) a requirement that cement plugs must extend
from the bottom of the geothermal zone or perforations to 30 meters over the top of the zone or
perforations. Cement plugs must be placed from 15 meters below to 15 meters above liner tops.
The requirements also address casing salvage, plugging of stubs and laps, shoe plugs, bridge
plugs, surface plugs, and other specifications (1980 - 1981.2 CCR).
Idaho
Idaho is a UIC Primacy State for Class V wells and has promulgated regulations for all
types of Class V wells. Geothermal wells used for direct heat are regulated in the Administrative
Rules of the Idaho Water Resource Board (WRB), specifically, the Rules for the Construction
and Use of Injection Wells (IDAPA 37 Title 03, Chapter 03) and Drilling for Geothermal
Resources (IDAPA 37, Title 03, Chapter 04).
Permitting
Construction and use of deep injection wells (>18 feet) requires a permit (IDAPA
37.03.03.025.03(c)). Construction and use of shallow injection wells (<18 feet) is authorized by
rule only if all required inventory information is submitted, and use of the well will not endanger
USDWs or violate the state's water quality standards (IDAPA37.03.03.025.03(d)). Construction
and use of geothermal production, exploration, or injection wells is authorized by permit
(IDAPA 37.03.04.025.02).
Permit applications should include, but not be limited to, the following information: maps
of the well area, locations of other drainage wells, construction information for the well, quantity
and general character of the injected fluids, geologic and physical characteristics of the injection
zone and confining beds, contingency plans to cope with well failures, and proof that the
applicant is financially responsible, such as through a performance bond, to abandon the well
properly (IDAPA 37.03.03.035).
Permits may be in effect for Class V wells for no longer than 10 years (IDAPA
37.03.03.040.07).
Siting and Construction
Class V wells requiring a permit may be required to be located at a minimum distance
from a point of diversion for beneficial use that may be harmed from accidental or unauthorized
injection, as determined by the Director. These requirements may be waived if the applicant can
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demonstrate that any springs or wells in the calculated perimeter of the perched water zone will
not be contaminated by the applicant's well (IDAPA 37.03.03.050.03).
Owners or operators of a proposed injection well must submit the following information
to the WRB: existing reservoir conditions, method of injection, source of injection fluid,
estimate of daily amount of material to be injected, zones or formations affected, and analysis of
fluid to be injected and of the fluid from the intended zone of injection (IDAPA 37.03.01.040).
Injection wells must be constructed to prevent the entrance of any fluids other than
specified in the permit, as well as to prevent waste of fluids or movement of fluids from one
aquifer to another (IDAPA 37.03.03.045.04.d).
Wells shall be located more than 100 feet from the boundary of the parcel of land on
which the well is situated, or more than 100 feet from a public road. This requirement may be
waived or modified by the WRB upon written request. Modifications may be made by giving
consideration to factors such as topographic, geologic, hydrologic characteristics of the area,
minimizing well interference, minimizing interference with multiple uses of the land, and
protection of the environment (IDAPA 37.03.04.025.05).
Wells must be cased in a manner that protects or minimizes damage to the environment,
usable ground waters, geothermal resources, life, health, and property. Specifications for casing
strength may be determined by the WRB on a well-by-well basis. The permanent wellhead
completion equipment must be attached to the production casing or to the intermediate casing if
production casing does not reach the surface. All casing reaching the surface must provide
adequate coverage for blow-out prevention equipment, hole protection control, and protection
for natural resources. Sufficient casing must be run to reach a depth below all known and
reasonably estimated ground water levels to prevent blow-outs or uncontrolled flows. Detailed
requirements for conductor pipe, surface casing, production casing and intermediate casing are
included in the regulations (IDAPA 37.03.04.025.06).
Operating requirements
For each well requiring a permit, the quality of injected fluids must either meet MCLs or
other drinking water standards, or meet the concentration of chemical contaminants in receiving
waters, whichever standard is less stringent. BMPs may be required to reduce coliform
concentration in injectate. Monitoring for coliform may be required.
All injection wells authorized by rule must meet drinking water standards at the point of
injection, and must not cause a violation of drinking water standards (IDAPA 37.03.03.050).
The owner/operator of a proposed injection well shall provide the WRB with information
necessary for the evaluation of the impact of such injection on the geothermal reservoir and other
natural resources. This information may include existing reservoir conditions, method of
injection, source of injection fluid, estimates of daily amount of material to be injected, zones or
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formations affected, and analysis of fluid to be injected and of fluid from the intended zone of
injection (IDAPA 37.03.04.040.01).
Mechanical Integrity
An owner or operator who proposes to drill or modify an injection well or convert a
producing or idle well to an injection well must demonstrate by means of a test that casing has
"complete" integrity (IDAPA method approved by the Director).
To establish integrity of annular cement above the shoe of the casing, the owner or
operator must make sufficient surveys within 30 days after injection has started to prove that all
injected fluid is confined to the intended zone of injection. Thereafter surveys shall be made at
least every two years or more often if necessary. The WRB may grant a waiver from such tests
(IDAPA 37.03.04.040).
The injection well owner/operator must develop approved procedures to detect
constructional or operational failure in a timely fashion, and have contingency plans to cope with
well failure (IDAPA 37.03.03.045.05(c)).
Financial Responsibility
The injection well owner/operator shall maintain financial responsibility to insure that the
injection operation is abandoned as prescribed (IDAPA 37.03.03.045.06.(f)). Owners/operators
must file with the Director a bond no less than $10,000 indemnifying the State of Idaho
providing sufficient security conditioned upon the performance of the duties required by the
regulations and the proper abandonment of the well (IDAPA 37.03.04.025.04).
Plugging and Abandonment
A notice of intent to abandon a geothermal resource well must be filed with the WRB
five days prior to abandonment procedures (IDAPA 37.03.04.045.01). All wells shall be
monumented with a four inch diameter pipe, ten feet in length of which four feet shall be above
ground. The remainder shall be embedded in concrete. Good quality heavy drilling fluid shall
be used to replace any water in the hole and to fill all portions of the hole not plugged with
cement. All open annuli shall be filled solid with cement to the surface. A minimum of one
hundred feet of cement shall be emplaced straddling the interface or transition zone at the base of
the ground water aquifers (IDAPA 37.03.04.045.02). The state has prepared "General
Guidelines for Abandonment of Injection Wells." The guidelines are not mandatory, and explain
that because the final abandonment procedure must be specific to the well, it must be approved
prior to abandonment.
Casing should be pulled. If it cannot be pulled, the casing should be cut a minimum of
two feet below the land surface, and a cement cap should be placed at the top of the
casing after plugging the well, with at least two feet of soil covering the filled hole/cap.
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• If the casing is left in place, it should be perforated and cement containing up to 5%
bentonite may be pressure-grouted to fill the hole. Coarse bentonite chips or pellets may
be used. A screen may be used if the well extends into the aquifer.
If the well extends into the aquifer, a clean pit-run gravel or road mix can be used to fill
the bore hole up to ten feet below the top of the saturated zone, or ten feet below the
casing, whichever is deeper, and cement grout or bentonite clay used to the surface.
• The abandonment process must be witnessed by an IDWR representative.
Nevada
Nevada is a UIC Primacy State for Class V wells in which the Division of Environmental
Protection (DEP) administers the UIC program. Direct heat return flow wells must satisfy
Nevada's UIC program requirements. Geothermal wells also must satisfy special requirements
pertaining to geothermal resources under the Division of Mineral's regulations.
UIC Statutes and Regulations
Nevada Revised Statutes (NRS) §§ 445A.300 - 445A.730 and regulations under the
Nevada Administrative Code (NAC) §§ 445A.810 - 445A.925 establish the state's basic
underground injection control program. The injection of fluids through a well into any waters of
the state, including underground waters, is prohibited without a permit issued by DEP (445A.465
NRS), although the statute allows both general and individual permits (445A.475 NRS and
445A.480 NRS). Furthermore, injection of a fluid that degrades the physical, chemical, or
biological quality of the aquifer into which it is injected is prohibited, unless the DEP exempts
the aquifer and the USEPA does not disapprove the exemption within 45 days after notice of it
(445A.850 NRS). The statute defines geothermal wells used in heating as Class V wells
(445A.849 NRS).
Regulations, particularly Chapter 445A NAC, "Underground Injection Control," define
and elaborate these statutory requirements. First, they provide that any federal, state, county, or
municipal law or regulation that provides greater protection to the public welfare, safety, health,
and to the ground water prevails within the jurisdiction of that governmental entity over the
Chapter 445A requirements (445A.843 NAC).
Permitting. The UIC regulations specify detailed information that must be provided in
support of permit applications, including proposed well location, description of geology,
construction plans, proposed operating data on rates and pressures of injection, analysis of
injectate, analysis of fluid in the receiving formation, proposed injection procedures, and
corrective action plan (445 A.867 NAC). The DEP may, however, modify the permit application
information required for a Class V well.
Siting and Construction. The state specifies, among other siting requirements, that the
well must be sited in such a way that it injects into a formation separated from any USDW by a
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confining zone free of known open faults or fractures within the area of review. It must be cased
from the finished surface to the top of the injection zone and cemented to prevent movement of
fluids into or between USDWs (445A.908 NAC).
Operating Requirements. Monitoring frequency for injection pressure, pressure of the
annular space, rate of flow, and volume of injected fluid is specified by the permit for Class V
wells. Analysis of injected fluid must be conducted with sufficient frequency to yield
representative data.
Mechanical Integrity. MIT is required once every 5 years, by a specified method.
Financial Responsibility. Class V geothermal injection wells are charged fees by DEP.
Fees are lower if the wells discharge less than 250,000 gallons daily (445 A. 872 NAC). Class V
geothermal injection wells also are specifically required to satisfy bonding requirements, and
must be covered by a bond either equal to the estimated cost of plugging and abandonment of
each well or, if approved by DEP, a sum not less than $50,000 to cover all injection wells of the
permit applicant in the state. However, these bonding requirements may be waived or reduced
by DEP upon receipt of adequate proof of financial responsibility (445A.872.3 NAC).
Plugging and Abandonment. A plugging and abandonment plan and cost estimate must
be prepared for each well, and reviewed annually. Before abandonment, a well must be plugged
with cement in a manner that will not allow the movement of fluids into or between USDW
(445A.923 NAC).
Regulations on Geothermal Resources
In addition to Nevada's requirements pertaining to underground injection wells,
geothermal wells used for direct heat also must satisfy regulations of the State Engineer and the
Division of Minerals (DOM). These requirements are found in Chapter 534A NAC,
"Geothermal Resources."
These regulations define a geothermal injection well as any well used to dispose of fluids
derived from geothermal resources into an underground reservoir (534A.061 NAC). They
further divide geothermal wells into three categories based on the use of the geothermal
resource. A geothermal well is considered a commercial well if it is primarily used to provide
geothermal resources on a commercial basis for purposes other than the generation of power
(534A. 170.2 NAC).
Permitting Requirements. The state requires a permit to drill or operate an individual
geothermal well. Geothermal operators are required to file a Notice of Intention to Drill with the
State Engineer, including descriptions of the purpose, location, estimated depth, casing, blowout
protection, and drilling rig. The application must include information concerning well
ownership, including the name of the land owner where the well will be sited, the name of the
geothermal resource owner, and the name and address of the well operator and drilling
contractor. Each permit application must include the appropriate financial assurance bond.
September 30, 1999 31
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Finally, the permit must include a description of the location by the quarter section, section,
township, and range. If the area has not been mapped, the application must state the location by
distance and direction from an established landmark. Operators may also apply to permit wells
for an entire project area, and must submit all the information required for individual permits
(534A.190 and 534A.193 NAC).
In addition to geothermal well permit requirements that address production and injection
wells alike, applications for geothermal injection wells must contain additional information for
permit approval. This includes a description of the casings in the wells or proposed wells; the
proposed method for testing the casings before injection; the estimated maximum injection
pressure and temperature; and a description of the proposed pipelines, metering equipment, and
safety devices used to prevent accidental pollution (534A. 196 NAC).
Siting and Construction. Injection wells may not be drilled within 100 feet of the
boundary of the land on which the well is sited (except for non-profit organizations) or a public
road, street or highway. Exceptions to these regulations may be granted by DOM after
considering such factors as the topographic, hydrologic and geologic characteristics of the area;
characteristics of the reservoir; protection of the environment; and any existing rights. All wells
must be cased in a manner that minimizes damage to the environment, ground and surface
waters, geothermal resources, and property. Completion equipment for the well must be
attached to the surface casing, and all casing reaching the surface must provide adequate
anchorage for blowout protection equipment. Also, surface casing must provide for control of
formation fluids and protection of fresh water. The annular space must be filled by circulating
cement up the annulus to the surface. If the cement does not circulate or falls back, the casing
must be cemented at the surface (534A.200, 534A.260, 534A.430 NAC) .
Operating Requirements. Unless otherwise approved, all geothermal fluids must be
reinjected into the same reservoir from which they originated. Operators must take all necessary
precautions to keep wells under control and operating safely at all times (534A.270, 534A.420
NAC).
Industrial geothermal well operators must complete monthly reports of production and
temperature, based on continuous metering of rate of flow of water, steam, and pressure and
temperature of fluids (534A.400, 534A.410, 534A.460 NAC). The injection of fluid for
recharging, to maintain pressure, or for the disposal of water, must be reported in writing to
DOM (534A.570 NAC). The owner or operator must notify DOM of the start date of injection
before beginning injection, and notify DOM of discontinuation of injection within 10 days of
discontinuation (534A.570 NAC).
Mechanical Integrity Testing. Nevada geothermal regulations do not specify MIT.
However, the code states that all equipment used or purchased for development and production
of geothermal resources must meet the minimum standards generally accepted for geothermal
well equipment. DOM may require additional testing or repairs to prevent waste and damage to
the environment.
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Financial Responsibility. In addition to small annual fees, Nevada also requires operators
to provide a sufficient bond of at least $10,000 per well to indemnify the state against costs of
enforcing its geothermal regulations. Liability ceases upon proper well abandonment. Operators
may also file blanket bonds of at least $50,000 to cover all wells to be operated statewide.
Bonds must be in cash, issued by a surety authorized to do business in Nevada, or in the form of
a savings or time certificate of deposit. If the certificate is used, it must be issued by a bank or
savings and loan association operating in Nevada, and payable to the State of Nevada. Operators
who deposited a surety bond guaranteeing performance with the federal government for wells
drilled on federal land must file a copy of the bond with DOM (534A.250 NAC).
Plugging and Abandonment. Operators must file a request to abandon a well with DOM,
including a detailed statement of the proposed abandonment activities. Cement used to plug the
well, except for surface plugging, must be placed in the hole by pumping through drill pipe or
tubing. The cement mix must be able to withstand high temperatures. Cement plugs must be
placed in the uncased portion of wells to protect all subsurface resources. The plug must extend
a minimum of 100 lineal feet above the producing formations and 100 lineal feet below the
producing formations, or to the total depth drilled, whichever is less. Where there is an open
borehole, a cement plug must be placed in the deepest casing string.
If there is a loss, or anticipated loss, of drilling fluids into the formation or if the well has
been drilled with air or another gaseous substance, a permanent bridge plug must be set at the
casing shoe and capped with a minimum of 200 lineal feet of cement. Cement plugs must also
be placed across perforations, extending 100 lineal feet below, or to the total depth drilled,
whichever is less, and 100 lineal feet above the perforations. If a cement retainer is used to plug
perforations, it must be placed a minimum of 100 lineal feet above the perforations. DOM must
approve cutting and recovering the casing. All annular spaces extending to the surface must be
plugged with cement, and the innermost string of casing that reaches ground level must be
cemented to a minimum depth of 50 feet below the top of the casing. Any interval not cemented
must be filled with good quality heavy drilling fluids. Finally, the surface should be restored as
near as practicable to its original condition, including cutting all casing strings below ground
level, capping casing strings by welding a steel plate on the stub, and removing all structures and
other facilities (534A.490 NAC).
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New Mexico
New Mexico is a UIC Primacy State for Class V wells.7 Direct heat return flow wells are
principally regulated by OCD under a delegation of responsibility under the Geothermal
Resources Act, rather than the UIC program. The OCD and the New Mexico State Engineer
Office (SEO) acting jointly issue permits for direct heat return flow wells. OCD and SEO use
Proposed Draft Rule 21 (PD 21), October 6, 1997 (which has not yet been finally promulgated)
as guidance.
Permitting
Under PD 21, an approved discharge permit is required prior to injection. PD 21
specifies detailed information that must be included in support of the discharge permit
application, including maps showing the location of the proposed wells; proposed maximum and
average injection pressures, rates and injection volume; appropriate geological data (i.e.,
structure of the area; injection zone interval including lithologic detail, name, thickness and
depth); proposed stimulation program; proposed injection procedure; proposed construction
procedures, including a cementing and casing program; logging procedures; deviation checks;
and a drilling, testing, and coring program; and a closure plan including a cost estimate sufficient
to plug and abandon the well and close the facility in a manner that protects public health and the
environment (PD 21.B).
Siting and Construction
Casing must be designed to prevent corrosion, loss of disposal fluids, and contamination
of fresh water resources. A minimum of one casing string must be set below all fresh water
bearing strata and cemented to the surface. All intermediate casing strings must be cemented to
the surface. All cement tops and cement integrity must be verified by logging (PD 21 .B. 15).
Appropriate logs must be kept and tests conducted during the drilling and construction of new
wells and submitted to OCD for review prior to well injection. (PD 21.E.l.o)
Operating Requirements
There must be an approved discharge permit prior to injection. Specific operating
requirements, which are separate from permit application requirements, such as boundary
markings, injection pressure, flow rate, flow volume, and annulus pressure, are described in
PD 21. The concentration of the injectate must be 10,000 mg/1 or less TDS. The maximum
injection pressure at the wellhead shall not initiate new fractures or propagate existing fractures
in the confining zone, or cause the movement of injection or formation fluids into ground water
7 The state defines "ground water" as "interstitial water which occurs in saturated earth material and
which is capable of entering a well in sufficient amounts to be utilized as a water supply" (20-6-2-1-
1101 .V NMAC). The state seeks to protect ground water "which has an existing concentration of
10,000 mg/1 or less TDS, for present and potential future use as domestic and agricultural water supply"
(20-6-2-III-3101 .A NMAC).
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having 10,000 mg/1 or less TDS. Injection between the outermost casing and the well bore is
prohibited in a zone other than the injection zone (PD 21.E. 1). Continuous monitoring and
recording devices must be installed and mechanical charts made of injection pressure, flow rate,
flow volume, and annular pressure. Continuous hydrogen sulfide monitoring devices also must
be installed to protect public health. These devices must be checked and readings recorded daily
(PD 21.F). Monthly and quarterly reports must be provided to OCD.
In addition to requirements under the Geothermal Resources Act, the New Mexico
Environmental Department (NMED) requires the discharger to submit a contingency plan for
NMED approval which addresses and outlines corrective action measures to be implemented
should the system fail or the discharge result in ground water contamination.
Mechanical Integrity
Under PD 21, a well has mechanical integrity if there is no detectable leak in the casing,
tubing, or packer while operating at maximum operating temperature and pressure; and no
detectable conduit for fluid movement out of the injection zone through the well bore or vertical
channels adjacent to the well bore (PD 21 .D. 1). Mechanical integrity tests are required prior to
commencing injection and at least once yearly during operation (PD 21.D.2).
Financial Responsibility
Financial assurance in the form of a Plugging and Abandonment Bond and Safety Bond
in the amount of the estimated closure cost described in the permit application must be submitted
toOCD(PD21.C).
Plugging and Abandonment
Notification to OCD is required 30 days prior to the cessation of operations. Closure
shall be in accordance with the approved closure plan and any modifications or additional
requirements made by OCD to protect public health and the environment. Prior to the release of
the financial assurance covering the facility, OCD will inspect the site to determine that closure
is complete (PD 21.H.I).
Oregon
Oregon is a UIC Primacy State for Class V wells. Under the statutory authority of
Chapter 552 of the Oregon Revised Statutes, two state agencies have promulgated rules for
geothermal wells used for direct heat. The Water Resources Department (WRD) has
promulgated Division 210 of the Administrative Regulations (OAR) (690-210-0005 et seq.),
which includes well construction standards and Division 230 (690-230-0005 et seq.), which
includes standards and procedures for low-temperature geothermal production and injection
wells and effluent disposal systems. The Department of Geology and Mineral Industries
(DGMI) has promulgated Division 20 (632-020-0005 et seq.), which includes geothermal
regulations covering re-injection of geothermal fluids into underground reservoirs to ensure that
the re-injection will not be detrimental to the beneficial uses of waters of the state. However,
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compliance also is required with Water Resources Department rules (632-020-0005(1) and (3)
OAR).
Permitting
A permit to drill or operate any geothermal injection well is required from the State
Geologist under the rules of the DGMI. The application for the permit must include an injection
plan, map of the area, injection fluid characteristics, characteristics of the injection zone,
hydrology of the area, estimated impacts of the injection, and proposed equipment and design
(OAR 632-020-0155). WRD also permits on an ad hoc basis.
Siting and Construction
WRD applies general standards for well construction by rule (OAR 690-200-0005 to
0110) as well as special standards (OAR 690-230-0005 to 0140) on an ad hoc basis.
WRD requires wells to be constructed in a manner that protects ground water8 from
contamination, waste, loss of artesian pressure, and substantial thermal alteration (OAR 690-
230-0030 (2)). Well construction standards include detailed requirements regarding materials
used and methods for drilling and construction (OAR 690-210).
Low temperature geothermal production and injection wells must be constructed in
conformance with WRD's rules in OAR 690-200-0005 to 690-225-0110 (Well Construction and
Maintenance, Well Driller Licensing, Well Construction Standards, Abandonment of Wells) with
specific modifications described in OAR 690-230-0005 to 690-230-0140.
No low temperature geothermal wells with an injection rate of less than 15,000 gpd can
be located within 75 feet of any geothermal production well using the same ground water
reservoir unless both wells are owned by the same person (OAR 690-230-0040).
The owner of any low-temperature injection well having an injection rate of greater than
15,000 gpd must have a separation distance between production and injection wells that is
adequate to protect production wells from substantial thermal interference (OAR 690-230-0045).
An injection plan must be filed with WRD (OAR 690-230-0110 and 0115). Well "start
card" and well logs must be filed by the well driller identifying the intended use of the well
(OAR 690-230-0050). All wells may be inspected during and following construction.
8 The state's rules on ground water quality protection provide that all ground waters shall be
protected from pollution that could impair existing or potential beneficial uses for which the natural
quality of the ground water is adequate.
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Operating Requirements
Adequate well-head protection equipment to insure public safety and the protection of
ground water resources must be installed on any low-temperature injection or production well
when the temperature of the fluid being withdrawn from the well bore exceeds 150 degrees F.
Wells must be pump tested (<15,000 gpd for 1 hour, >15,000 gpd for 4 hours). Water well
reports must include the temperature of fluid as measured at the discharge point at the beginning
and end of the timed production test, as well as the maximum fluid temperature attained during
the test (OAR 690-230-0070).
Procedures required to inject effluent into a low temperature injection well must not
cause failure of the well casing and/or seal materials or other components of well structure,
including movement, displacement, or fracturing of overburden.
Mechanical Integrity
All injection wells must be tested for mechanical integrity at least once every five years
to determine there is no leak in the casing, and that there is no fluid movement into a USDW
other than that from which the fluid was produced. The state must witness MITs (OAR 632-
020-0157).
Financial Responsibility
There are no financial responsibility requirements.
Plugging and Abandonment
The owner/operator must give notice of at least 24 hours before the proposed date for
commencement of abandonment procedures. Detailed plugging procedures are specified in the
regulations at OAR 632-020-0125.
City of Klaniath Falls, Oregon
An example of local regulation of direct heat return flow wells is provided by the City of
Klamath Falls, one of the state's local communities that regulates geothermal wells and
resources within and adjacent to the city. Klamath Falls' City Code provides for the
conservation and beneficial management of geothermal resources and thermal ground waters, so
as to assure their continued availability and productivity (8.250.1). Other sub-purposes include
minimization of the potential for damage to or degradation of geothermal resources and thermal
ground waters and protection of the subsurface environment during development and utilization
of geothermal resources (8.250).
Prior to constructing, installing, or altering a well within the city limits, an application for
a well permit must be submitted to the city's Geothermal Data Center. Permits will be granted
based on several criteria, including, but not limited to, the estimated hydrological impacts of the
proposed well's operation on the reservoir and surrounding wells, the adequacy of provisions for
September 30, 1999 37
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environmental protection and public safety, and the compliance of the proposed well and its use
with all applicable city laws, ordinances, and regulations. The ordinance is also intended to be
compatible with all pertinent state regulatory requirements (8.276).
The City Manager may attach conditions to the well permits as necessary to ensure the
conservation and protection of geothermal resources, and/or their efficient utilization. Such
conditions may include restrictions on hours of well operations, well design requirements above
and beyond state requirements, restrictions on pumping, heat exchanging, storage and/or
injection operations, or requirements for scientific sampling, testing or monitoring (8.280).
Once the well has been completed or altered, the owner/operator must provide a well
completion inspection and report assuring compliance with the city ordinance and registration
with the Geothermal Data Center (8.284).
Utah
Utah is a UIC Primacy State for Class V wells. Utah's DWR has primary regulatory
authority among state agencies over wells used for geothermal energy production under Chapter
R655 of the Utah Administrative Code (UAC), "Water Rights." Geothermal injection wells are
defined as any special wells, converted producing wells, or reactivated abandoned wells used to
maintain geothermal reservoir pressure, provide new material, or re-inject any material medium,
residue, or by-product of geothermal resource exploration/development.
Permitting Requirements
Any person or operator who wishes to construct an injection well must submit an
application form to DWR. This requirement extends to modifying an existing injection well and
converting another well type to an injection well (even in cases where mechanical condition does
not change). The application must contain information detailing location, elevation, and layout;
lease identification and well number; a list of tools and equipment to be used; expected depth
and geologic characteristics; drilling, mud, casing, and cementing plans; logging, coring, and
testing plans; waste disposal plans; environmental considerations; and emergency procedures.
Information contained in permit applications may be shared with other state agencies having
interest in or jurisdiction over injection issues. To the extent possible, DWR will eliminate
duplicative application efforts with other interested agencies, including the Bureau of Pollution
Control. DWR conditions permits on a case-by-case basis (UAC R317-7-6 thru R317-7-9).
Siting and Construction
Injection wells used in geothermal operations must be located more than 100 feet from
the boundary of the parcel on which the well is situated. In addition, injection wells must be
more than 100 feet from a public road, street, or highway dedicated prior to the commencement
of drilling. The State Engineer must approve all well spacing proposals, giving consideration to
topographic characteristics of the area, hydrogeological characteristics, well interference,
economic considerations, and environmental protection. Regulations also allow DWR to
approve directional drilling for parcels of one acre or more whose surface is unavailable for
September 30, 1999 38
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drilling. In such cases, the surface well location may be on another property that may or may not
be contiguous to the property containing the geothermal resource (UAC R655-1-2.4.1 through
2.4.5).
Regulations governing well construction require that all wells be cased in a manner that
protects or minimizes damage to the environment, usable ground waters, geothermal resources,
life, health, and property. Permanent wellhead completion equipment must be attached to the
production casing or to the intermediate casing if production casing does not reach the surface.
Casing strength specification is determined on a case-by-case basis. All casing reaching the
surface should provide adequate anchorage for blowout protection equipment, hole pressure
control, and protection of natural resources. In addition, casing should reach below all known or
reasonably estimated ground water levels to prevent blowouts or uncontrolled flows (UAC
R655-1-2.7).
Operating Requirements
Operators must conduct MIT upon completion of a new well or before converting a
production well to injection, showing that the casing has "complete" integrity (UAC R655-1-
5.2.1). Testing must be completed within 30 days after injection operations commence, and
thereafter every two years. The test must prove that all injected fluid is confined to the intended
injection zone. Operators must notify DWR 48 hours prior to testing. In addition, operators
must test for corrosion of well materials. Other regulations require operators to provide reports
of injection operations by the tenth day of each month (UAC R655-1-5.2).
Mechanical Integrity Testing
Testing is required at the discretion of DWR to prevent damage to life, health, property,
and natural resources; to protect geothermal reservoirs; or to prevent the infiltration of
detrimental substances into underground or surface waters suitable for beneficial uses. The
regulations list the various tests that are required, including casing tests, cementing tests, and
equipment tests (UAC R655-1-7.3).
Operators must conduct casing integrity testing upon completion of a new well or before
converting a production well to injection, showing that the casing has "complete" integrity (UAC
R655-5.2.1). Testing must be completed within 30 days after injection operations commence,
and thereafter every two years. The test must "prove that all injected fluid is confined to the
intended zone of injection." Operators must notify DWR 48 hours prior to testing should the
department wish to observe the testing. In addition, operators must test for corrosion of well
materials. Other regulations require operators to provide monthly reports of injection operations
(UACR655-1-5.2.2).
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Financial Responsibility
Utah requires owners to file a bond with DWR indemnifying the state against costs of
enforcing its geothermal regulations and the improper abandonment of any permitted wells. The
amount of the bond will not be less than $10,000 for each individual well, or $50,000 for
statewide operations. These bonds remain in force for the life of the well(s) and will not be
released until properly abandoned or substituted by another bond. Any person who acquires
ownership or operation of any well is subject to the bonding requirements and must tender his
own bond, or assume responsibility under an existing blanket bond (UAC R655-1-2.3).
Plugging and Abandonment
Utah's regulations pertaining to plugging and abandonment of injection wells specify that
the actions taken must block interzonal migration of fluids that may contaminate fresh water and
other natural resources; prevent damage to geothermal resources; prevent reservoir energy loss;
and protect life, health, the environment, and property (UAC R655-1-6.1). Written notification
is required 5 days before abandonment efforts commence, as well as a history of well operations
within 60 days of abandonment completion (UAC R655-1-6.2 (b) and (n)). All abandoned wells
must be monumented by 4-inch diameter pipe 10 feet in length, of which 4 feet are above
ground. Name, number, and location of the well shall appear on the monument. When filling the
wells, operators should use good quality heavy drilling fluid to replace any water in the hole and
to fill all portions of the hole not plugged with cement (UAC R655-1-6.2 (d)). All cement plugs
should be pumped into the hole through drill pipe or tubing, and all open annuli should be filled
solid with cement to the surface. A minimum of 100 feet of cement should be emplaced
straddling the interface or transition zone at the base of ground water aquifers (UAC R655-1-
6.2(g)). In addition, 100 feet of cement should straddle the placement of the shoe plug on all
casings, including conductor pipe. Other requirements include a surface plug of neat cement or
concrete mix in place from the top of the casing to at least 50 feet below the top of the casing
(UAC R655-l-6.2(i)). All casing should be cut off at least 5 feet below land surface and cement
plugs should extend 50 feet over the top of any liner installed in the well (UAC R655-1-
6.2(j),(k)); (UAC R655-1-6.1- R655-1-6.2).
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