APPENDIX V: 

REASONABLY 

FOREESEABLE 

DEVELOPMENT 

SCENARIO FOR 

GEOTHERMAL 

DEVELOPMENT 
This Page Intentionally Left Blank 
Jarbidge Draft RMP/EIS Appendix V 

APPENDIX V: REASONABLY FORESEEABLE 

DEVELOPMENT SCENARIO FOR GEOTHERMAL 

DEVELOPMENT 

REASONABLY FORESEEABLE DEVELOPMENT SCENARIO 

FOR 

GEOTHERMAL DEVELOPMENT 

IN THE 

JARBIDGE FIELD OFFICE 

Prepared by: Karen Porter, BLM Idaho State Office Geologist
 

Prepared by: ____signed copy on file____________ Date: __11/6/2009____ 

Reviewed by: 

Reviewed by: ____signed copy on file_____________ Date: __11/3/2009____ 

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Appendix V Jarbidge Draft RMP/EIS 

SUMMARY 

Based on the geology of the Jarbidge Field Office (i.e., the planning area), the presence of 

numerous hot springs and wells in several locations and a Known Geothermal Resource Area 

(KGRA), and a review of the available data collected and technical reports written on the area, it 

has been determined that the lands within the planning area have some level of potential for the 

discovery and/or development of a geothermal resource for both indirect use (i.e., commercial 

generation of electricity) and direct use (i.e., use of the resource for other purposes). The lands 

east of the Bruneau River and west of the Saylor Creek Air Force Range are determined to have 

high geothermal potential, based on the determination of high heat flow and the inclusion of 

most of those lands in the Bruneau KGRA. Lands situated north of the numerous faults that trend 

northwest from roughly the Balanced Rock area to the Bruneau KGRA have been determined to 

have medium potential, while lands situated south of these faults have been determined to have 

low potential, based on currently available information. These conclusions are described in more 

detail in the Geothermal Potential Report prepared for the area (BLM, 2009). 

Based on the geothermal potential for the planning area, it is reasonable to assume that a 20-MW 

power plant would be developed over the 20-year life of the plan. This development would 

disturb between approximately 185 and 230 acres cumulatively, including the construction of 

drill pads to support the drilling of 20 temperature-gradient wells and 10 production and injection 

wells, road construction, power plant development, and pipeline and transmission line 

construction. Much of this disturbance would be reclaimed after each phase of development, 

such that once the power plant is operational, the actual disturbance would be considerably less 

than the cumulative total. Surface disturbances for direct use are expected to be much less than 

those anticipated for indirect use. 

INTRODUCTION 

This report, describing a Reasonably Foreseeable Development Scenario (RFDS), accompanies 

the Geothermal Potential Report (BLM, 2009) prepared for the planning area. The RFDS 

describes the anticipated level of exploration and development activity associated with 

geothermal leasing. These projections are necessary for assessing the anticipated impacts of 

geothermal development-related activity in the Environmental Impact Statement (EIS) for the 

Jarbidge Resource Management Plan (RMP); for determining which lands within the planning 

area will be available for geothermal leasing; and for determining what stipulations may be 

necessary to attach to leases in order to protect surface resources. These anticipated impacts are 

for the BLM-administered public lands described above during the next 20 years (2009-2029). 

DESCRIPTION OF GEOLOGY 

The geology of the planning area is described in detail in the Geothermal Potential Report 

prepared for the area (BLM, 2009). The planning area lies within the Snake River Plain 

physiographic province and is entirely covered by Cenozoic volcanic deposits, with Quaternary 

lake deposits found overlying the volcanics in the northwest corner of the planning area. The 

August 2010 A-188 
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planning area is dominated by the Owyhee Plateau, a broad volcanic upland considered to be a 

continuation of the eastern Snake River Plain. These volcanic rocks, consisting of multiple sheets 

of welded ash-flow tuff, rhyolite, and finally basalt, were erupted from the Bruneau-Jarbidge 

eruptive center starting 11 million years ago (Bonnichsen, 1982). The silicic rocks (ash-flows 

and rhyolites) of this sequence are loosely termed the Idavada Volcanics. The Idavada volcanic 

sequence is considered the most important aquifer in the area and has the known capacity to act 

as a reservoir for thermal water (Chapman & Ralston, 1970 and Young & Whitehead, 1975). The 

sequence is 3,000 feet thick or more and is exposed or underlies all of the planning area. 

In the northern portion of the planning area, a series of northwest-trending en echelon normal 

faults, down dropped to the north, propagate across the Bruneau Desert from roughly the 

Balanced Rock area (also known as the Blue Gulch area) to the Bruneau Hot Springs area 

(Malde et al, 1963 and Jenks et al, 1998). High heat flow values are found in springs and wells 

drilled for agricultural and domestic uses in these two areas, although no exploration drilling for 

geothermal testing has been performed (Blackwell, 1975 and Brott et al., 1976). 

PAST AND PRESENT GEOTHERMAL ACTIVITY 

BLM records indicate that there has never been a geothermal lease issued in the planning area. 

There is a KGRA, the Bruneau KGRA, located in the extreme northwest corner of the planning 

area (T 7 S, R 6 E, sections 14, 15, 21, 22, 23, 26, 27, and 28; 5,120 acres). The KGRA was 

established in 1975 due to overlapping nominations of those lands for geothermal leasing and an 

analysis of the available geothermal indicia at the time. A lease sale was held after the 

establishment of the KGRA, but records indicate the offered parcel(s) did not receive any bids. 

While there are no deep (over 5,000 feet) wells drilled for geothermal resources, there are 

numerous water wells drilled on private lands with temperatures between 20 and 50°C in the 

planning area (Smith et al., 1980). Most of these are concentrated in the Bruneau area; however 

there are 15 to 20 wells on private lands in the Blue Gulch area, located northwest of Balanced 

Rock (T 9-10 S, R 12-13 E), with temperatures between 25 and 35°C. There is also a cluster of 

warm wells (approximately 25°C) in the Glenns Ferry area. Most of the wells in the planning 

area are used for agricultural (irrigation) purposes; however, a few utilize the heat source for 

direct uses such as heating a greenhouse and aquaculture. Most of the wells are less than 1,000 

feet deep. 

REASONABLY FORESEEABLE DEVELOPMENT SCENARIO 

GENERAL ASSUMPTIONS
 

The general assumptions and descriptions of the phases of development that follow are based on 

the geothermal potential in the Jarbidge Field Office. This Reasonably Foreseeable Development 

Scenario (RFDS) was adapted from the Final Programmatic Environmental Impact Statement 

(PEIS) for Geothermal Leasing in the Western US, released in October 2008 (BLM & USFS, 

2008), and applied to the local conditions and mineral potential of the planning area. The RFDS 

primarily describes the development of the resource for the commercial generation of electricity, 

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Appendix V Jarbidge Draft RMP/EIS 

termed “indirect use”; however, geothermal resources also can be utilized directly. Direct uses 

are briefly described at the end of this RFDS. 

Based on the geothermal potential for the planning area, it is reasonable to assume that a total of 

20 MW of power would be developed over the life of the plan. The most likely location for this 

development is in or near the Bruneau KGRA, determined to have high potential for geothermal 

resources, but there is a possibility that the area designated as having moderate potential may 

encounter exploration activities and possible development as well. 

During the life of the plan, it is assumed that exploration activities would include geophysical 

exploration and drilling of up to 20 temperature gradient wells. Existing roads would be used for 

access as much as possible; however, given the scarcity of roads in the area, it is assumed that up 

to 1 mile of temporary access road may be required per well on average. This disturbance would 

be reclaimed and the holes plugged immediately after data and samples are collected. 

Once an area is determined to have potential for commercial geothermal development, largediameter production wells would be drilled, for further flow testing and for possible future use in 

production. Assuming the eventual development of a 20-MW resource, approximately 10 largediameter wells would be drilled: half of these would be production wells, and half would be used 

as injection wells. These wells would likely be concentrated within a 9 to 16 square-mile area. 

Construction of well pads would be required. The average well pad is approximately 3.5 acres in 

size. After drilling is completed, the well pad would be reclaimed by blending the well pad 

material into the surrounding landscape and re-seeding with an approved seed mix. 

Additional disturbance would be anticipated if a site is developed. This would include 

construction of a power plant, which would disturb approximately 10 additional acres for a 20­

MW plant. Pipelines, needed to convey the geothermal fluid from the producing well to the plant 

and from the plant back to injection wells, would be placed approximately 2 feet above the 

ground. It is assumed that approximately 1 mile of pipeline would be required per well. 

Transmission lines are also needed, to carry the electricity from the plant to the power grid (140 

kV or greater). The proposed Gateway West transmission line is within 2 to 5 miles of the 

Bruneau KGRA. It is assumed that between 0.25 miles and10 miles of line would be required. 

Table 1 provides the estimated acreage of land disturbance that would be anticipated for 

exploration and development of a geothermal resource, over the life of the RMP. The actual area 

of disturbance varies depending upon site conditions and the size of power plant being 

constructed. Acreages are not provided for the Reclamation and Abandonment phase since this 

phase involves the return of previously disturbed lands to their existing conditions. Much of the 

land would be reclaimed after each phase of the initial exploration, drilling, and construction. For 

example, once wells are drilled, the well pad would be reduced to a minimum size and the pad 

reclaimed. Therefore, the actual amount of land occupied during the utilization phase would be 

less than the total cumulative acreage. A typical development generally requires several leases or 

the use of private or other adjacent lands. The details of each phase of development are described 

in the section following the table. 

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Table 1. Surface Disturbance Anticipated for Geothermal Resource Development during the Life of 

the Jarbidge RMP (assuming a 20-MW Power Plant) 

Development Phase Disturbance Estimate 

Exploration 

Geologic mapping negligible 

Soil surveys 30 square feet A 

Gravity and magnetic surveys negligible 

Seismic surveys negligible 

Resistivity surveys negligible 

Shallow temperature measurements negligible 

Road/access construction for temperature gradient wells 80 acres 

Temperature gradient well pads 5 acres B 

Total Exploration Disturbance 85 acres 

Drilling and Utilization 

Drill pads 35 acres C 

Road improvement/construction 20 acres D 

Power plant 10 acres E 

Pipelines 30 acres F 

Transmission lines 5-50 acres G 

Well workovers, repairs and maintenance negligible H 

Total Development and Utilization Disturbance 100-145 acres 

Total Cumulative Distance Approximately 185-230 acres A

 Calculated assuming 10 soil gas samples, at a disturbance of less than three square feet each. B Calculated assuming an area of disturbance of up to 0.25 acre per well and 20 wells. C

 Calculated assuming a 20-MW power plant requires about 10 well pads, at 3.5 acres (approx. 400’ x 400’) each, to 

support 5 production wells and 5 injection wells. Does not assume multiple wells located on a single well pad. D

 Assumes 0.5 miles of road per well (10 wells). Estimates 30-foot wide surface disturbance for an 18-20 foot road 

surface, including cut and fill slopes and ditches. 

E

 Based on average of 5 acres of disturbance per 10-MW power plant. F

 Pipelines from well to plant assumed to be 1 mile on average, for a total of 10 miles of pipeline in length, with a 25-

foot-wide disturbance corridor. 

G Transmission lines assumed to be 1 to 10 miles long, 40-foot-wide construction corridor. H

 Disturbance would be limited to previously disturbed areas around the well(s). 

TYPICAL PHASES IN GEOTHERMAL DEVELOPMENT 

This RFDS for geothermal resource use describes four sequential phases: (1) exploration, (2) 

drilling, (3) field development and utilization, and (4) reclamation, plugging, and abandonment. 

The success or failure of each phase affects the implementation of subsequent phases and, 

therefore, subsequent environmental impacts. The general assumptions and descriptions of the 

geothermal development are intended to be used in support of the Jarbidge RMP revision, to 

analyze future environmental impacts that may result from the issuance of Federal geothermal 

leases, and to identify areas that may require additional stipulations to the standard lease form to 

protect other resources, if those lands are nominated for leasing in the future. These anticipated 

impacts are for the BLM-administered public lands described above during the next 20 years 

(2009-2029). The EIS written in association with the RMP revision analyzes the leasing 

decision; however, additional site-specific NEPA analysis will be conducted for each phase of 

geothermal resource development activity. Additional Conditions of Approval may be developed 

and attached to these permitted activities. 

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Appendix V Jarbidge Draft RMP/EIS 

Phase One: Geothermal Resource Exploration 

Before geothermal resources are developed, a geothermal resource developer explores for 

evidence of geothermal resources on leased or unleased land. Exploration activities may involve 

some ground disturbance but does not include the direct testing of geothermal resources or the 

production or utilization of geothermal resources. Exploration operations include, but are not 

limited to, conducting geophysical and/or geochemical surveys, and drilling temperature gradient 

wells. A geothermal lease is not required to conduct exploration activities; however, an 

exploration permit is required from BLM (see 43 CFR 3250 for regulations pertaining to 

geothermal exploration operations). 

Usually, the first, on-the-ground step in exploration is to conduct geophysical prospecting or 

surveying. This exploration method consists of collecting and interpreting electrical, 

gravitational, magnetic, thermal, and/or seismic data to identify underground structures favorable 

for the occurrence of a geothermal resource. Geophysical surveying is a relatively inexpensive 

method of indirectly exploring the sub-surface of a relatively large area for a mineral resource, 

and results in relatively minor disturbance to surface resources. Once the data are compiled, 

geologists and geophysicists examine the data and make inferences about where the higher 

temperature anomalies may occur and whether other geologic conditions, such as porosity and 

faulting, are present. These conditions can indicate the location of potential underground 

geothermal reservoirs capable of supporting commercial uses. 

Resistivity surveys involve laying out long cables (up to 1,000 feet or more) on the land surface, 

or setting up equipment repeatedly in small areas (a few tens of square feet at the most for each 

measuring site). Minor, temporary disturbances are associated with each site for the burial of 

sensors. 

While not widely used for geothermal surveys, seismic surveys have the greatest impact on the 

local environment. These surveys typically involve setting up an array of geophones and creating 

a pulse or series of pulses of seismic energy. The pulse is created either by detonating a small 

charge below the ground surface (requires drilling a narrow “shot hole”, usually by hand) or by a 

vibroseis truck that is driven through the survey area. Data is transmitted from the geophones to 

a central location. The geophones may be installed on the ground’s surface, in small excavations 

made specifically for burying the geophones, and/or in existing wells. These surveys are 

typically undertaken over the course of a few days. No road building is required for this type of 

activity. 

Geochemical surveying, such as collecting and analyzing water samples from hot springs, can 

also be used to determine the subsurface characteristics of a particular area. In some cases, gas 

collectors may be installed to measure soil gases. These collectors have partially buried sensors 

and may disturb small areas of less than three square feet. 

Access requirements for geophysical and geochemical surveying can generally be met by the use 

of existing roads or trails, cross-country travel using all-terrain vehicles, or by foot. While very 

little surface disturbance is associated with these surveys, the survey crew, usually consisting of 

two to four personnel, may be walking or moving through a fairly large area for several days. 

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The second step of the exploration phase is to drill temperature gradient wells. A gradient well 

can provide additional information to determine a more precise location of higher-than-normal 

temperature gradients; however, the geothermal resource is not directly accessed or utilized. 

Temperature gradient wells can be drilled using a truck-mounted rig, and range from 200 feet to 

over 4,000 feet deep. Figure 1 is a photograph of a typical drill rig used to drill a temperature 

gradient well. The number of gradient wells drilled also varies, depending on the geometry of the 

system being investigated and the anticipated size of the geothermal reservoir. Geologists 

examine either rock fragments or long cores of rock that are brought up from the bottom of the 

well as it is being drilled. Water samples are taken from any groundwater encountered during 

drilling. Temperatures are measured at various depths. Both well temperatures and the results of 

rock sample analyses are used to determine if additional drilling is worthwhile to identify the 

presence and characteristics of an underground geothermal reservoir. After collecting the desired 

samples and data, the wells are plugged and abandoned in accordance with State and Federal 

requirements. 

Figure 1. Typical Drill Rig for Drilling Temperature Gradient Wells 

Most temperature gradient wells are drilled with a small rotary rig (often truck-mounted), similar 

to that used for drilling water wells, or a diamond-coring rig, similar to that used for geologic 

sampling in mineral exploration and civic works projects. The mast of the drill rig is 

approximately 60 feet tall. Support equipment is needed, including water trucks, tanks for mixing 

and holding drilling fluids, personnel and supply transport vehicles, and sometimes a backhoe for 

earthmoving activities needed to prepare the drilling site. During exploration, a driller is not 

permitted to produce any fluids out of, or inject any fluids into the well; therefore, the site may 

also host a sump or tanker truck. Additionally, a diesel generator may also be used at the site to 

power equipment. A temperature gradient drilling operation can be run by about three on-site 

personnel and others traveling to the site periodically with materials and supplies. 

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Temperature-gradient well drilling requires road access. Whenever possible, a driller would 

access the temperature gradient well site using existing roads. When existing roads are not 

available, temporary access roads may need to be constructed for the truck-mounted rig to reach 

the site, possibly disturbing 1 acre (for 0.25 miles of 30-foot wide road) to 6 acres (1.5 miles). 

Given the road density in the planning area, it is assumed that an average of 1 mile (4 acres) of 

temporary access road would be required per temperature gradient well. 

Drilling a temperature-gradient well generally does not require construction of a well pad or 

earth-moving equipment unless the site is steeply sloping. Preparing the site for drilling may 

include leveling the surface and clearing away vegetation. The well site itself involves 

excavation of a small cellar (typically less than 3 feet square and less than 3 feet deep) to allow 

the conductor casing to be set beneath the rig. It is assumed that 0.25 acres of disturbance would 

occur per drill site. Drilling takes from several days to several weeks per hole. Several 

temperature gradient wells are usually drilled to determine both the areal extent of the 

temperature anomaly and where the highest temperature gradient occurs. It is assumed that 20 

wells would be drilled over the life of the plan. 

Temperature gradient wells are not intended to directly contact the geothermal reservoir, and 

therefore produce no geothermal fluids. In areas of known artesian pressures, any drilling 

expected to penetrate the groundwater table would be required to include blow-out prevention 

equipment. In cases where a temperature gradient well does penetrate a geothermal zone, any 

release of geothermal fluids at the surface is likely to be minimal due to the small well diameters 

and the use of blow-out prevention equipment. 

Drilling fluids may include drilling mud (bentonite clay, activated montmorillonite clay and 

crystalline silica-quartz), drilling mud additives (caustic soda, sodium bicarbonate, or anionic 

polyacrylamide liquid polymer), cement (Portland cement and calcium chloride), fuel (diesel), 

lubricants (usually petroleum-based) and coolants. The specific fluids and additives depend on a 

variety of factors, including the geologic formations being penetrated and the depth of the well. 

Releases of drilling muds are not permitted. Sump and tanker trucks are required to capture all 

fluids. The risk of spills of other fluids is similar to that of any other project involving the use of 

vehicles and motorized equipment. 

All surface disturbances would be reclaimed to the satisfaction of BLM. Once drilling is 

completed, the temperature gradient well would be plugged and abandoned in accordance with 

BLM and State requirements. Site reclamation includes removing all surface equipment and 

structures; re-grading the site to blend into the surrounding landscape and prevent erosion; and 

replanting vegetation with a seed mix approved by BLM, to facilitate natural restoration of the 

site. 

Phase Two: Drilling Operations 

Once exploration has indicated a viable prospect and necessary leases have been secured, the 

drilling of large-diameter wells can proceed, in accordance with 43 CFR 3260 regulations. 

Unlike temperature gradient wells, these wells tap the geothermal resource and are capable of 

being fitted for production; however, they are initially used to test the reservoir for commercial 

development. Multiple wells may be drilled per lease. Each well requires an approved 

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Geothermal Drilling Permit. A Drilling Plan and an Operations Plan are also required (one Plan 

can be submitted for multiple wells). NEPA analysis is conducted to determine whether the 

drilling locations are appropriate and whether Conditions of Approval, attached to the Drilling 

Permit, are required in addition to the lease stipulations. A bond is required. Drilling operations 

include drilling large-diameter production wells, flow testing of the wells, producing geothermal 

fluids for chemical evaluation, and injecting fluids back into the geothermal reservoir. This 

would also involve the construction of sumps or pits on the well pad, to hold excess geothermal 

fluids. It could involve development of minor infrastructure to conduct such operations. 

Access roads capable of supporting large drill rigs would be required. It is assumed that 0.5 miles 

of new road would be constructed per well on average (total of 5 miles). Depending on the type 

and use-intensity of the road, the areas of surface disturbance is about 30-feet wide for an 18-20 

foot wide road surface, including cut and fill slopes and ditches. 

Construction of a well pad is required for drilling a production well. The size of the well pad is 

dependent upon site conditions and on the number of wells per pad, but they are typically about 

3.5 acres (400 x 400 feet) for one well. The well pad needs to be of sufficient size to safely 

accommodate drilling activities and various temporary support facilities such as generators, mud 

tanks, cement tanks, trailers for the drillers and mud loggers, housing trailers, and storage sheds. 

Each well pad would be fenced around the perimeter to prevent access by unauthorized persons, 

wildlife, or livestock during the duration of the drilling operation. If the drilling site is not 

located on level ground, minor cut and fill may be required. Gravel may be required to stabilize 

roads and pads and provide for drainage. 

After a well pad has been constructed and support facilities have been assembled, production 

wells would be drilled using a geothermal (or oil and gas) drill rig (Figure 2). Production-size 

wells can be over 2 miles (10,560 feet) deep. The wells narrow (telescope) in diameter from 30 

inches at the surface to 12 inches at the bottom of the well. In order to drill these deep holes, a 

large drilling rig would be erected. The top of the drill rig derrick could be as much as 155 feet 

above the ground surface, and the rig floor could be at least 25 feet above the ground surface. 

These rigs are typically equipped with diesel engines, fuel and drilling mud storage tanks, mud 

pumps, and other ancillary equipment. Blow-out prevention equipment would be utilized while 

drilling to prevent uncontrolled flow at the surface if a pressurized thermal pocket is 

encountered. 

Getting the rig and ancillary equipment to the site may require 15 to 20 trips by full-sized tractortrailers, with a similar amount for de-mobilizing the rig. There would be 10 to 40 daily trips for 

commuting and hauling in equipment. Drilling operations would likely occur 24 hours a day and 

seven days a week. It takes approximately one month to drill one well. A drilling operation 

generally has from 10 to 15 people on site at all times, with more people coming and going 

periodically with equipment and supplies. 

Geothermal fluid production and associated waste production (drill cuttings and waste drilling 

mud) is likely to occur for short periods, as wells are tested to determine reservoir characteristics. 

Excess geothermal fluids are either re-injected into a previously drilled well, if available, or are 

stored in temporary pits or sumps, generally lined with a synthetic liner (permeability less than 

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Appendix V Jarbidge Draft RMP/EIS 

10-7 cm/sec) or an impermeable clay liner. The water in the pit is left to evaporate and any sludge 

is removed and properly disposed of. The rate of fluid production from a geothermal reservoir is 

unknown until the development testing phase is completed. 

Figure 2. Typical Drill Rig for Drilling Production Wells 

During the initial stages of testing, one well is likely to be tested at a time. If testing is successful 

and the well and reservoir are sufficient for development, wellheads, valves, and control 

equipment would be installed on top of the well casing so that the wells can be utilized for 

production. The size of the well pad would be reduced to the minimum necessary for production, 

and the area reclaimed. If a production well is unsuccessful, it may be used for injection of fluids 

from other wells. If not necessary for either production or injection, the well would be plugged 

and abandoned in accordance with State and Federal requirements, and the site would be 

reclaimed by recontouring the well pad and seeding with an approved seed mix. Those roads that 

are no longer needed would be reclaimed. 

Phase Three: Field Development and Utilization 

Utilization of the geothermal resource is the final phase of development, if a viable reservoir is 

determined and a power purchase agreement can been secured. Utilization requires the applicant 

to secure a site license and construction permit from BLM, in accordance with regulations at 43 

CFR 3270. An EIS may be required for the construction of a power plant on Federal lands. 

It is likely that the existing production wells would be used, although additional drilling to 

expand and develop the well field may be required. The number of wells is dependent upon the 

geothermal reservoir characteristics and the planned power generation capacity. For example, a 

50-MW (net) power plant could require up to 25 production wells and 10 injection wells. Based 

on the geothermal potential in the planning area, it is assumed that a 20-MW power plant would 

be developed, with 5 production wells and 5 injection wells. The utilization phase could last 

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from 10 to 50 years and involves the operation and maintenance of the geothermal field(s) and 

generation and sale of electricity. 

Additional infrastructure would be needed for commercial operations, including construction of a 

power plant, installation of production and injection pipelines, and installation of transmission 

lines. It is assumed that no new access roads would be required, beyond the roads constructed for 

the production well drilling. 

Geothermal resources can be classified as low temperature (less than 90°C, or 194°F), moderate 

temperature (90 to 150°C, or 194 to 302°F), and high temperature (greater than 150°C, or 

302°F). While at one time only the highest temperature resources were used for generating 

electrical power, emerging technologies and demand for alternative energy sources are proving 

that moderate and even lower temperature resources can be used for electrical generation. 

Moderate to high temperature reservoirs, with adequate flow rates and fracture systems, are 

currently suitable for the commercial production of electricity. While there are several types of 

power plants that harness geothermal resources, the most likely type of plant used for moderate 

temperature resources is a binary-cycle plant. These modular plants use the geothermal resource 

that has been pumped to the surface to heat a secondary “working fluid” such as isobutene or 

isopentane that has a lower boiling point than water. As the working fluid boils, it expands and 

turns a steam turbine, producing electricity. The geothermal fluid and the working fluid never 

come in contact with each other, nor are they exposed to the environment (closed loop system). 

The geothermal fluid is re-injected back into the geothermal zone via injection wells, while the 

working fluid is cooled, condensed, and recycled. 

Binary plants are by far the most common type of power plant used today, as they can operate 

with lower water temperature (74 to 182° C, or 165 to 360°F) than flash or steam plants, produce 

few air emissions, are quiet, and result in a low impact to the environment once constructed. 

They can be constructed off-site (e.g., Ormat’s plants are manufactured in Israel), transported to 

a site, and erected fairly easily, and they can be expanded as a well field is developed. In this 

sense, they are modular units. Generally, the final permanent surface disturbance required for all 

related production wells, the power plant, and surface facilities is about 1 acre per Megawatt of 

power produced. 

A 50-MW plant would utilize a site area of up to 20 to 25 acres to accommodate all the needed 

equipment, including the power plant itself, space for pipelines geothermal fluids and reinjection, 

space for moving and storing equipment, and buildings needed for various purposes (power plant 

control, fire control, maintenance shop, etc.). The power plant itself would occupy an estimated 

25% of this area for a water-cooled plant, or about 50% for an air-cooled plant. Where 

topography permits, the power plant could be situated to be less visible from nearby roads, trails, 

scenic vistas, or scenic highways. The site of the plant requires reasonable air circulation to 

allow for efficient operation of the plant’s condensers. A smaller, 20-MW plant would typically 

require approximately 5 to 10 acres for the entire complex. Figure 3 shows what a recently 

constructed 10-MW power plant looks like. 

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Appendix V Jarbidge Draft RMP/EIS 

Figure 3. 10-MW Power Plant at US Geothermal Inc’s Raft River Site (from US Geothermal Website) 

A pipeline system would be needed to connect each of the production wells and injection wells 

to the power plant. Pipelines are usually 24 to 36 inches in diameter and are typically constructed 

on supports above the ground surface, resulting in little if any surface impact to the surrounding 

area once construction is complete and the corridor has been revegetated. The pipelines typically 

have a few feet of clearance underneath them, allowing small animals to easily cross their path. 

Every 100 to 200 feet or so, the pipeline may have an expansion loop, or U-shaped bends, to 

allow for expansion due to heating and cooling. Pipelines transporting hot fluids to the plant are 

wrapped in insulation, whereas injection pipelines are generally not. Where feasible, the pipeline 

may parallel the access roads and existing roads to the power plant. The pipelines are typically 

painted to blend in with the surrounding environment. For the planning area, it is assumed that 

the pipeline to each well would be approximately 1 mile long on average, with a corridor width 

of about 25 feet. Once the pipeline is constructed, these corridors would be reclaimed. 

Transmission lines would be required to carry power from the plant to the electric grid. It is 

assumed that in the planning area, these lines would be from 1 to 10 miles in length, with a 

corridor width of approximately 40 feet. Wooden poles would most likely support them, and 

about 5 acres could be disturbed per mile of transmission line. 

The number of people required for routine operation of a power plant is typically three per shift; 

however, additional personnel may be on site during the day for maintenance and management 

of the facility and monitoring fluids and power production. Activities associated with operation 

and maintenance of the facility and energy production would not generally involve additional 

ground-disturbing activities. 

Using data from other areas of geothermal development, it appears that production of geothermal 

fluids can be expected to vary widely from 1 to 6 million gallons per well, per day. Assuming 5 

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million gallons per day per well as an average production figure, a geothermal field with 5 

producing wells would produce 25 million gallons of fluid per day. Geothermal fluids produced 

are re-injected back into the geothermal reservoir via injection wells. Binary power plants utilize 

a closed loop system; therefore, well production and injection wells operate with no fluid loss. 

The routinely used chemicals for a binary geothermal plant include the hydrocarbon working 

fluid (such as iso-butane or n-pentane) and the lubricating oil used in the downhole pumps. 

While downhole scaling may be a problem for flash or steam plants, it does not occur in binary 

plants because they are liquid dominated systems. Therefore, there is no need for scale-inhibiting 

chemicals or any other chemicals with a binary plant. 

Phase Four: Reclamation and Abandonment 

This phase involves abandoning the well after production ceases and reclaiming all disturbed 

areas in conformance with BLM and State standards. Abandonment includes plugging and 

capping the wells and reclaiming the well site. Reclamation also includes removing the power 

plant and all surface equipment and structures, regrading the site and access roads to 

predisturbance contours, and replanting native or appropriate vegetation to facilitate natural 

restoration. 

RFDS FOR DIRECT USE 

Low temperature geothermal resources are increasingly being used for a wide variety of 

applications across the Western US, including in the planning area and nearby. These direct uses 

include: 

 Agricultural uses, such as controlling environmental conditions for growing crops, 

flowers, or trees; 

 Aquacultural uses, such as controlling environmental conditions for raising fish or other 

animals; 

 Direct heating and cooling systems for buildings; 

 Public safety uses, such as eliminating ice and snow on public sidewalks; 

 Public health uses through food processing, such as dehydration, washing, and 

processing; and 

 Recreational uses, such as hot tubs, steam baths, and mud baths. 

Use of the geothermal resource for these activities on Federal lands requires a direct use 

geothermal lease, in accordance with regulations at 43 CFR 3205. 

Surface disturbances for direct use are generally much less than for indirect use since direct uses 

are more likely to be located near existing communities with less of a need for new access roads. 

Also, since direct use applications utilize the geothermal energy on-site, there is no need for the 

construction of electrical equipment and transmission lines, except for bringing in electricity 

from the existing grid to the facility being constructed. Surface disturbances can still be expected 

for well pad development, site access, and construction of the facility utilizing the resource, 

although in some cases the facility may already exist and may simply be shifting its heat source 

to geothermal. 

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Appendix V Jarbidge Draft RMP/EIS 

TYPICAL PHASES IN DIRECT USE GEOTHERMAL DEVELOPMENT 

Phase One: Exploration 

Existing direct use applications are largely co-located with, and draw directly from, existing 

surface geothermal manifestations such as hot springs, eliminating the need for most exploration 

activities. Exploration activities in the past have often been limited to water temperature and 

chemistry analysis. 

Looking to the future, it is likely that most direct use applications will not be able to draw from 

existing surface manifestations as they have in the past. Surface manifestations such as naturally 

occurring hot springs have become increasingly sought after with increases in population in the 

Western US, increased recreational use, and more stringent regulations preserving such resources 

for their recreational, cultural, or scenic value. In such cases where surface manifestations are not 

nearby or are not being utilized directly, exploration activities similar to those described above 

for indirect use would also apply for direct use. 

Phase Two: Drilling 

In applications where a surface manifestation is used directly, the resource development phase 

involves installing piping into that manifestation to withdraw the hot water. For applications 

requiring the drilling of a well, drilling activities would be similar to those described above under 

Phase Two for indirect use, although the well would not be as deep, likely only one well would 

be drilled, and the volume of fluid would not be as great as for indirect use. 

Phase Three: Utilization 

The utilization phase typically lasts for several decades or longer. Activities associated with the 

production phase are generally limited to maintenance and repair activities of all components of 

the collection, distribution and injection/use/disposal system. 

As described above for indirect use, the drilling of production wells may be necessary. Drilling 

activities would be similar to that discussed above in the drilling phase, although it is likely that 

only one production well and one injection well would be required. Some applications may inject 

the post-use geothermal fluids back into the ground, in which case an injection well would be 

drilled and connected via piping to the application. In other applications where the spent 

geothermal fluids are discharged to a surface water body or used for some other purpose, then 

discharge piping, collection systems or distribution systems may need to be constructed. For 

such systems where the waters are not reinjected into the geothermal reservoir but are rather 

discharged or otherwise used, treatment systems may need to be installed to reduce levels of any 

naturally occurring but toxic chemicals present within the geothermal waters, such as mercury, 

arsenic, and boron, to meet applicable health or environmental standards. Operation and 

maintenance of existing facilities and production of geothermal energy also takes place during 

the production phase. Activities associated with operation and maintenance and energy 

production would involve managing waste generated by daily activities, managing geothermal 

water, landscaping, and maneuvering construction and maintenance equipment and vehicles 

associated with these activities. 

August 2010 A-200 
Jarbidge Draft RMP/EIS Appendix V 

Phase Four: Reclamation and Abandonment 

As described above for indirect use, this phase involves abandoning the well after production 

ceases and reclaiming all disturbed areas in conformance with BLM and State standards. 

Abandonment includes plugging, capping, and reclaiming the wells. Reclamation includes 

removing all surface equipment and structures, regrading the site to blend into the surrounding 

landscape, and replanting native or appropriate vegetation. 

LITERATURE CITED 

BLM. (2009). Geothermal potential of the Jarbidge Field Office. Boise, ID: USDOI Bureau of 

Land Management, Idaho State Office. 

BLM and USFS. (2008). Final Programmatic Environmental Impact Statement for Geothermal 

Leasing in the Western United States. Washington, DC: USDOI Bureau of Land 

Management and USDA United States Forest Service. 

Blackwell, D. D. (1975). Report on reconnaissance heat flow and geothermal gradient study in 

north central Owyhee County, Idaho (M-102). Department of Energy. 

Bonnichsen, B. (1982). The Bruneau-Jarbidge eruptive center, southwestern Idaho. In B. 

Bonnichsen & R. M. Breckenridge (Eds.), Cenozoic Geology of Idaho (Bulletin 26, pp. 

237-254). Moscow, ID: Idaho Bureau of Mines and Geology. 

Brott, C. A., Blackwell, D. D., & Mitchell, J. C. (1976). Geothermal investigations in Idaho: 

Heat flow in the Snake River Plain region, southern Idaho. Idaho Department of Water 

Resources Water Information Bulletin No. 30 Part 8. 

Chapman, S. L., & Ralston, D. R. (1970). Ground-water resource of the Blue Gulch area in 

eastern Owyhee and western Twin Falls Counties, Idaho. Idaho Department of Water 

Administration Water Information Bulletin No. 20. 

Jenks, M. D., Bonnichsen, B., & Godchaux, M. M. (1998). Geologic map of the Grand ViewBruneau Area, Owyhee County, Idaho (Technical Report 93-2). Moscow, ID: Idaho 

Geological Survey. 

Malde, H. E., Powers, H. A., & Marshall, C. H. (1963). Reconnaissance geologic map of westcentral Snake River Plain, Idaho. USGS Miscellaneous Geologic Investigations Map I373. 

Smith, R. H., Berry, G. W., & Grim, P. J. (1980). Geothermal Resources of Idaho map (Plate 1) 

in Geothermal investigations in Idaho: Potential for direct heat application of 

geothermal resources. Idaho Department of Water Resources Water Information Bulletin 

No. 30 Part 9. 

Young, H. W., & Whitehead, R. L. (1975). Geothermal investigations in Idaho: An evaluation of 

thermal water in the Bruneau-Grand View area, southwest Idaho. Idaho Department of 

Water Resources Water Information Bulletin No. 30 Part 2. 

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