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Bulletin

fifteen dollars

28 GRC Bulletin l www.geothermal.org

Nevada Geothermal Update - 30 Years of Power Production

by Lisa ShevenellATLAS Geosciences Inc.

Chair 2015 GRC Annual Meeting Committee

IntroductionNevada recently exceeded 30 years of

geothermal power generation with 2014 production of 2.742 million net MWh at 16 geothermal fields, enough to power 247,000 Nevada households. Production from these fields contributes significantly to the renewable portfolio standard of 25% by 2025. Geothermal accounted for 6% of Nevada’s total energy capacity in 2014, accounting for 50% of the non-hydro renewable energy capacity state-wide (10% and 66%, respectively for Northern Nevada; PUCN Docket No. 15-03042, Tables 5.1 and 5.2).

Although geothermal leasing and drilling activity has slowed in Nevada since a recent (somewhat artificial) boom ended around 2010, various trends have stabilized and there have been significant successes and promise for future development. The successes include an increase of the total geothermal power production capacity in Nevada by over 350 MW since 2005 at seven separate new geothermal production areas and expansions at five additional fields. Nevada has the most development of low temperature resources in the U.S, beginning in 1984 with the 107°C Wabuska resource, to the latest plant, the Don A Campbell 129°C resource, both Ormat Nevada Inc. installations. Additionally, Nevada boasts the first, and only, hybrid geothermal-solar power plant in the world, commissioned at the Stillwater geothermal area in 2011 by Enel Green Power North America. At San Emidio, U.S. Geothermal

replaced their existing 3.6 MW plant with a new, more efficient 11.75 MW power plant (8.6 MW net) that utilizes the existing, proven geothermal reservoir, demonstrating a significant technology development.

Two new power plants were constructed in 2014 at blind geothermal systems: Don A Campbell (formerly Wild Rose) and McGinness Hills, both Ormat facilities. McGinness Hills phase I (30 MW) went into operation in 2012, but experienced such success in the development of the field that Ormat added an additional 42 MW to the project in 2015. This brought the project capacity to 72 MW, one of the largest fields developed in Nevada (A GRC Fieldtrip will visit the McGinness Hills geothermal power plant, September 23-25 after the GRC Annual Meeting). The first phase of the Don A Campbell project came online in late 2013, both under budget and ahead of schedule, delivering power from its new 22.5 MW facility. the second phase is currently under construction, slated to be commissioned in early 2016. Both these projects helped to increase total geothermal production capacity for the state to approximately 610 MW, second only to California in installed capacity in the U.S.

All existing power projects are plotted on the map at Figure 1 and summarized in Table 1, which shows that 44% of the existing power plants in Nevada are “blind” geothermal systems. Producing systems through 2002 are summarized in Garside et al. (2002), with newer power generation facilities summarized here.

July/August 2015 29

Figure 1. Geothermal power plants in Nevada.

Table 1. Geothermal power projects in Nevada.

30 GRC Bulletin l www.geothermal.org

TrendsGeothermal development began in Nevada

in the mid-1980s with the commissioning of the Wabuska plant in Lyon County, rapidly increasing as 12 power plants were brought on-line into 1993. No additional capacity was added from the mid-nineties until the mid-2000’s when the Galena 1 power plant came on–line at Steamboat in 2005, followed by Galena 2 and Galena 3 (Burdette) in 2007 and 2008 (Table 1) (A GRC Fieldtrip will visit the Steamboat geothermal complex on September 20 just before the GRC Annual Meeting). Following a regulation change in BLM leasing in 2007, a considerable increase in lands leased and power installed ensued (Figure 2; Table 2). While power generation continued to increase through 2014 as previously leased and drilled properties came into production, land leasing dropped precipitously following 2010 in terms of acres leased, parcels sold and lease revenues generated (Table 2).

According to the Geothermal Energy Association (GEA), at the end of 2014, 23 projects were in various stages of development in Nevada, which could result in the construction of up to 85 MW of additional power generation capacity over the next 5 to 10 years (GEA, 2015). Many new companies entered the geothermal industry in Nevada in 2007-2010, many of which were later acquired by other companies, or have since been disbanded, in part resulting in the significant reduction in lands leased following the 2008-2010 peak.

A similar peak in drilling of geothermal production wells occurred (Figure 3), although with a longer sustained period of drilling activity and decline by 2014, which still exceeds the numbers of wells drilled in the 1990’s. A comparison shows the steady increase in geothermal activity between 2007 and 2009 (Table 3) based on permit data from the Nevada Division of Minerals.

Table 3. Number of permits issued and wells drilled by year in Nevada. Number of wells drilled include production, injection and observation wells drilled at a geothermal prospect or production area. Wells drilled were not necessarily permitted in the same year.

Source data at: http://www.blm.gov/nv/st/en/prog/minerals/leasable_minerals/geothermal0/ggeothermal_leasing.html

Table 2.

Trend in net output of geothermal power in Nevada from 1985 through 2014.

Figure 2:

Number of production wells drilled by year in Nevada.

Figure 3:

July/August 2015 31

Recent SuccessesThe new power plant areas summarized here

are for those that began commercial operation in 2010 or afterward, as noted in Table 1. Much of the content below of these recent power plant installations is summarized from Shevenell and Reid (2015).

Blue Mountain (Faulkner 1)The Blue Mountain project is a blind

geothermal system that was originally located during gold exploration drilling that encountered high temperature water (up to 88°C) (Parr and Percival, 1991). Maximum temperatures encountered at the site are 416°F (213°C) at approximately 2,000 feet (610 m) (Niggemann et al., 2009; Benoit 2013). Faulkner 1 was commissioned in January 2010, although the project initially had difficulties attaining contracted power outputs. This resulted in some financial restructuring in 2012, in part as a result of the lower power output than plant capacity, requiring a revised reinjection strategy to meet loan covenants. As a result of the debt restructuring, Alternative Earth Resources began operating the Faulkner 1 power plant, under contract to Blue Mountain Power LLC, through its subsidiary Nevada Geothermal Operating Company LLC. During this restructuring, the plant began to shift injection locations to avoid injection returns that cooled the geothermal fluids in the production zone too quickly. A revised and recalibrated GeothermEx reservoir model using production data indicates that the re-distribution of injection to 3 wells would allow for contracted power requirements to be met for the remaining 17 years of the plant.

As of June 2015, Baseload Clean Energy Partners (BCEP; subsidiary of AltaRock Energy Inc.) was in the midst of acquiring the 49.5-MW Faulkner 1 geothermal power plant from EIG Global Energy Partners, acquiring 100% of Blue Mountain’s equity and debt (http://geothermalresourcescouncil.blogspot.com/2015/05/usa-nevada_38.html). AltaRock plans to use a multi-zone stimulation process along with power plant improvements to increase power output to approach the design capacity of the power plant.

Hazen (Patua)Gradient Resources Inc. conducted exploration

and confirmation drilling and performed assessments on the Patua geothermal property for several years. This area has long been known as a geothermal resource area and includes 13 hot springs that range in temperature from 82 to 204°F (28 to 96°C). In 1962, Magma Power drilled three wells from 300 to 750 ft (91 to 230 m), recording a maximum temperature of 270°F (132°C). In 2008 and 2009, Vulcan conducted an extensive exploration program that included well drilling (including core), geological, geochemical, and geophysical surveys, and well discharge testing.

The power plant itself is located on private property, but wells are located on federal lands under BLM lease in Churchill and Lyon Counties. The Patua Project is proceeding in phases, the first being a 30 MW power plant under a Power Purchase Agreement (PPA) with Sacramento Municipal Utility District (SMUD). Initial construction work at the Patua site began in Q3 2011 (as did Phase II drilling of gradient holes), with commercial operations beginning in December 2013 from a resource with drilled temperatures of up to 208°C (Peterson et al., 2013).

Jersey ValleyThe Jersey Valley geothermal area is located

at the base of the western flank of the Fish Creek Range at the northern end of Dixie Valley. Early temperature estimates using silica and Na-K-Ca geothermometers suggested reservoir temperatures of 142°C and 182°C, respectively (Mariner et al., 1974). Ormat Nevada Inc. began drilling in this area in 2007, after which a 20-year Power Purchase Agreement (PPA) with NV Energy was established. Ormat proceeded to drill three observation wells in 2007, two production wells in 2008, four production wells in 2009, one production well in 2010 and one injection well in 2011. On February 1, 2011, Ormat announced the completion of the new 15 MW-capacity power plant at Jersey Valley (GRC Bulletin 40(2): 2011). Details of the exploration and development of the Jersey Valley property to locate the 165°C resources can be found in Drakos et al. (2010).

32 GRC Bulletin l www.geothermal.org

McGinness HillsOrmat Nevada Inc. has been actively engaged

in geothermal development drilling at the McGinness Hills property in Lander County since 2009. Precious metal exploration focused by surface sinter identified an otherwise blind geothermal system. Drilling of seven thermal gradient wells and two observation wells encountered hot water with high geothermometer temperatures, leading to a November 2009 announcement of a 20-year Power Purchase Agreement (PPA) between Ormat and NV Energy. Five production wells were drilled in 2010 and three in 2011, and one injection well was drilled in 2012. Construction of a 30 MWe (net) plant began in 2010 and continued through 2012. Commercial production at the McGinness Hills 168°C (460 m depth) resource commenced June 15, 2012. This air-cooled binary power plant, with a 36 MW (net) capacity, has been providing energy to the NV Energy transmission system since July 2012. Five of the wells drilled have very high flow rates of 2,350 gpm each (8,900 l/min), which are only limited by pump capacity (Nordquist and Delwiche, 2013, Table 1). New wells drilled in 2013 included two production wells drilled to depths of approximately 5000 ft (1,524 m) and one observation well of approximately 4000 ft (1,219 m). Additional production wells led to the commissioning of phase 2 of the McGinness Hills project in 2015, providing 42 MW of additional capacity from the resource (www.ormat.com/news/latest-items/mcginness-hills-phase-2-geothermal-power-plant-begins-commercial-operation). (A GRC Fieldtrip will visit the McGinness Hills geothermal power plant, September 23-25 after the GRC Annual Meeting).

Salt Wells (Eightmile Flat)On March 20, 2007, Enel North America, Inc.

(a subsidiary of Enel S.p.A., Italy) purchased AMP Resources, LLC from AMP Capital Partners and a minority investor. In April 2009, Enel North America inaugurated its new 18 MW gross-capacity binary geothermal power plant at Salt Wells from a shallow (150 m) 140°C resource, bringing the power plant facility to two binary power units. Enel continued active drilling at Salt Wells with three additional observation wells and one production

well drilled in 2012 and a new production well to the south end of their field in 2013, discontinuing use of the production well in the northernmost part of the field (Hinz et al., 2014). (A GRC Fieldtrip will visit the Salt Wells geothermal power plant, September 23-25 after the GRC Annual Meeting).

San EmidioIn 2007, U.S. Geothermal, Inc. (USG) acquired

the Empire geothermal power plant and 28,358 acres of geothermal leases and ground-water rights. U.S. Geothermal had plans to develop a 35 MW power project for the San Emidio resource that called for the construction of twin binary-cycle plants, with the anticipation that the current well field could provide approximately 75% of the geothermal fluid requirement for one of the binary plants. An expanded production and injection well field could be drilled to provide the balance of the needed geothermal fluid for the second phase, to make it a 27 MW development (U.S. Geothermal, Inc. www.usgeothermal.com and Nevada Geothermal Update, Nevada Division of Minerals, May 2008). The development was planned in two stages: repower and expansion. During the first stage, the existing 3.6 MW plant was replaced with a new, more efficient 11.75 MW power plant (8.6 MW net) that utilizes the existing, proven geothermal reservoir. The second stage requires drilling new production wells and the construction of an upgraded transmission line to allow for increased power production. This expansion is expected to produce an additional 26 MW.

The new Phase I 8.6 MW power plant is a water cooled facility constructed to replace the original plant using no additional wells. This new unit uses the cost-efficient working fluid R134a, which is non-flammable, non-toxic and non-corrosive, reducing capital and operating costs. The plant initially experienced several operational and mechanical issues including defective capacitors, the mechanical failure of the 2,500 horsepower process pump, and excessive vibration in the turbine gear box. These were all subsequently resolved.

Commercial operations began in May 2012, and the new San Emidio plant is projected to generate approximately 75,000 MWh of electrical power each year under a 25 year Power Purchase Agreement

July/August 2015 33

with Sierra Pacific Power. The old unit that this plant replaces, generated approximately 23,000 MWh annually over 20 years (since 1987). Hence, the new, more efficient TAS unit is producing more than double the power output of the aging unit, while using no additional wells. Drilling for Phase II began in September 2013.

StillwaterIn 2004, AMP Resources, LLC, purchased the

Stillwater Power Plant and associated geothermal resources from Stillwater Holdings, LLC. In August 2005, AMP Resources applied to the Nevada Public Utilities Commission (PUC) for a permit to construct a 37 MW binary geothermal power plant adjacent to the existing Stillwater power plant. In May 2006, the PUC approved a permit to build a 26 MW power plant to replace the existing Stillwater plant, online since 1989. Enel North America subsequently acquired the Stillwater property from AMP Resources, and in April 2009, Enel North America, Inc. inaugurated its new 47.2 MW gross-capacity Stillwater binary plant.

In 2011, Enel commissioned the first hybrid geothermal-solar power plant in the world, with plant capacities of 24 MW (solar) and 33.1 MW (geothermal) (www.enelgreenpower.com/en-GB/ena/).

In March 2012, Enel Green Power expanded the capacity of the Stillwater solar power plant from 24 MW to 26 MW (89,000 solar panels). Enel subsequently won the 2012 GEA Technology Advancement Award for its unique contributions to advancing geothermal power production. The Enel geothermal-solar hybrid unit has the advantages of increased power production from the solar plant during times of decreased efficiency in geothermal power production around mid-day in the summer months. When the solar unit produces less power in the winter months, geothermal power production is more efficient. This allows the hybrid plant to better follow the power-demand load.

Tuscarora (Hot Sulphur Springs)The geothermal area includes six springs, one

geyser, and one fumarole. These occur in a narrow zone approximately 3 km long within a small accommodation zone in a broad step-over between two west-dipping range-front faults (Dering and

Faulds, 2012). Waters from the hot springs were analyzed and subsurface temperatures of 442°F and 333°F (228°C and 167°C) were indicated by the Na-K-Ca and silica geothermometers, respectively. In 2003-2004 Earth Power Resources, which had the lease on the resource rights at that time, discovered a geothermal resource over 330°F (166°C) between depths of 2,950 and 3,810 feet (900 and 1,161 m). Eventually, this lease was transferred to TG Power LLC.

In 2007, TG Power LLC began to move forward with the development of a 48 MW-net power plant at Hot Sulphur Springs. Ormat ultimately acquired the leases to the property and drilled 3 production wells in 2010 for the planned 18 MW water-cooled binary plant. Work continued through 2011 and achieved commercial production in the first quarter of 2012.

The success of the Tuscarora project is the result of years of work by several private companies followed by the successful development by Ormat. Earth Power Resources signed a PPA with NV Energy but did not demonstrate commercial viability and sold the project to TG Power in 2006. TG Power drilled a production hole in 2007 but ran out of money and sold the project to the Energy Investment Fund in 2008. After the passage of Nevada’s AB522 bill in 2009, Ormat became interested in Tuscarora and developed a commercially viable project in 2012. (www.elkocountynv.net/meetings/board_of_commissioners/docs/Ormat.pdf).

Don A. Campbell (Wild Rose)Ormat initially developed the blind geothermal

project at Wild Rose, located in Gabbs Valley approximately 22 miles (35 km) west of Gabbs, Nevada. This resource is also known as the Don A. Campbell project (after the late long time Ormat employee and a pioneer in the exploration, development and reservoir management of geothermal resources) and Deadhorse Wells by the BLM. This system is apparently associated with a series of synthetic and antithetic NE-striking, moderately to steeply dipping normal faults linked to dextral faults in the east-central part of the Walker Lane Belt (Orenstein and Delwiche, 2014).

34 GRC Bulletin l www.geothermal.org

Resource development for the first phase includes a 15-35 MW net (up to 40 MW gross) geothermal power plant and electrical substation, which includes construction and operation of a 22-mile (35 km), 120-kV generation-tie to Highway 261, along with a switching station. In 2010, anomalously high temperatures up to 267°F (130°C) were encountered at depths within 200 ft (61 m) of the surface. One observation well was completed in 2011, and one injection, one observation, and three production wells were completed in 2012 to depths of 1,500 to 1,800 ft (457 to 549 m) (permitted depths). By the end of 2012, all wells required to operate the power plant had been drilled.

In April 2013, Ormat entered into a 20-year Power Purchase Agreement (PPA) with Southern California Public Power Authority (SCPPA) to deliver electricity from their new 19 MW (net; 22.5 MW gross) power plant. The binary, air-cooled power plant came into commercial operation in December 2013 ahead of schedule and below budget, producing from a low temperature (260°F; 127°C) resource for power generation (Orenstein and Delwiche, 2014). SCPPA is reselling the produced power to the Los Angeles Department of Water and Power (LADWP) and Burbank Water and Power (BWP). The power is transmitted to LADWP and BWP through NV Energy’s transmission system. In March, 2015, Ormat entered into a 20-year Power Purchase Agreement (PPA) with Southern California Public Power Authority for phase 2 of this project. Commercial operation of a new 22.5 MW facility is expected in the first quarter of 2016 (www.ormat.com/news/latest-items/ormat-signs-power-purchase-agreement-second-phase-don-campbell-geothermal-plant-ne).

Current ActivityOn-going work to expand the Nevada

geothermal resource base continues, some results of which will be presented at the 2015 GRC Annual Meeting. These on-going projects are summarized below.

Regional AssessmentsFaulds et al. (2015) initiated an integrated

geologic, geochemical, and geophysical study of a 240 by 400-km area across central Nevada as part of the DOE sponsored Play Fairway Analysis program. The primary goal of this study is to produce a new geothermal potential map, including 11 geologic parameters to identify geothermal play fairways that will assist in predicting the locations of blind or hidden geothermal systems. The preliminary model demonstrates that several geologic, geophysical and geochemical parameters are positively correlated with highly favorable geothermal areas. The resultant model successfully combines multiple data sets into a new geothermal favorability map for Nevada.

Kirby, et al (2015) compiled fluid geochemistry from producing geothermal systems at Tuscarora and Beowawe, produced water from the Blackburn oil field, and thermal springs throughout central Nevada. Heat-flow across the area is generally greater than 85 mW/m2, suggesting a broad zone of high geothermal potential. Preliminary results suggest that there is potential for temperatures in excess of 180°C at depths below 3 kilometers within the carbonate aquifer. In addition to the known, producing fields at Beowawe and Tuscarora, geothermal fluids from the Mary’s River area and Ruby Valley also suggest elevated geothermometry warranting more detailed evaluations.

Gwynn (2015) is evaluating the geothermal potential of laterally extensive, deep sedimentary formations in eastern Nevada by re-evaluating over 260 wells with nearly 500 bottom-hole temperatures and drill stem tests. These sedimentary units may have temperatures exceeding 150°C and have suitable porosity and permeability that occur in basins with large accumulations of overlying sediments that insulate the reservoir rocks. Data presented include numerous temperature logs and basin depths in six eastern Nevada counties. Preliminary results indicate that heat flow in the Eureka Low ranges up to 140 mW/m2 in Steptoe Valley, with both Steptoe Valley and Railroad Valley warranting more detailed evaluation of the geothermal potential of deep sedimentary units.

July/August 2015 35

Site-Specific Assessments

Black Warrior (North Valley)The Black Warrior geothermal system lies 20

km east of the south end of Pyramid Lake in the Truckee Range of northwestern Nevada. This blind geothermal system was discovered by shallow temperature gradient drilling (100-600 m, max temp: 128°C) by Phillips Petroleum Company in the 1980s and observed with a 2-m shallow temperature survey circa 2011. The structural framework is characterized by north-northeast-striking, moderately to steeply west-dipping normal faults that terminate and step in the vicinity of the thermal anomaly. This suggests two possible favorable structural settings: (1) a fault termination of the southeastern range-front fault with accompanying horse-tail splaying, producing an area with abundant closely spaced faults and high fracture permeability; and/or (2) a fault step-over in a broad left-step of the major normal faults, whereby many closely-spaced minor faults provide hard linkage and a zone of high fracture permeability. In either case, the study area lies in a favorable setting for geothermal activity and may host a robust geothermal system at depth (Sadowski and Faulds, 2015).

Buffalo ValleyMolisee and Bell (2015) report on their

characterization of the structural setting at Buffalo Valley hot springs. Their work includes geologic mapping at 1:24,000 scale, slip and dilation tendency analysis of faults mapped proximal to Buffalo Valley hot springs (BVHS), and shallow temperature surveys. Results indicate that a geothermal system is located within a right-step in the Fish Creek mountains western range-bounding fault, with smaller faults forming at least one fault intersection. Although anomalies from the temperature surveys were small, results indicate geothermal upwelling is primarily controlled by a fault intersection rather than dilation of individual faults.

FallonOver the last three years, exploration drilling

or re-drilling of six wells has been conducted by the Navy Geothermal Program Office on the southeastern portion of the Naval Air Station Fallon Mainside installation. In general, the deeper (>1524 m) resource with maximum measured temperatures up to 214°C cannot maintain sufficient flow rates for commercial viability of power generation. Based on these results, the Navy has decided to focus future development efforts on the shallower (<1524 m), lower temperature resource for direct use or low temperature binary generation. The shallower, targeted horizon is capable of sustaining pumping rates of 3000 gpm (Blake et al., 2015).

A DOE-funded project to initiate a field laboratory dedicated to research on enhanced geothermal systems (EGS) as part of the FORGE (Frontier Observatory for Research in Geothermal Energy) program has recently been set up at Fallon. The initial phase of this work will focus on fully characterizing the field laboratory to include technical and logistical tasks that will demonstrate site viability for progression to Phase 2 (Faulds et al., 2015).

San EmidioDiPippo and Kitz (2015) discuss the newly

installed (2012) power plant at San Emidio that increased the resource capacity by approximately 8 MW while using approximately the same inlet flow rate as the original 3.8 MW power plant. For the first time, this new plant uses a water-cooled, supercritical cycle using R134a as the working fluid. The new power plant was designed to be much more efficient than the original plant and was designed to yield 9.1 MW, which was ultimately exceeded during testing. This success story at San Emidio is compared to new power plants at Neal Hot Springs and Raft River in their 2015 GRC Annual Meeting paper.

StillwaterWendt et al. (2015) present model validation

using operational data from the first-in-the-world hybrid plant consisting of a medium-enthalpy geothermal power plant and solar photovoltaic plant at Stillwater. These authors have developed

36 GRC Bulletin l www.geothermal.org

models to predict the performance of the hybrid plant in order to optimize performance at Stillwater and assist in improved plant designs for the future. Preliminary model results indicate that various control system and hardware modifications could improve the underperforming solar array performance by up to 15%.

SummaryAlthough overall numbers of geothermal

leases and wells drilled in Nevada have been declining since 2010, development has proceeded at many sites on previously explored, leased and drilled properties. Drilled production wells have apparently been more successful, as 186 MW of new electrical generation capacity has been brought on-line since 2010, even as numbers of production wells drilled per year decreased. Successes include developing increased efficiency power plants (i.e., San Emidio), construction of new power plants in blind geothermal areas (e.g., McGinness Hills, Wild Rose), field expansions (e.g., Desert Peak, Steamboat, Stillwater), and commissioning of the first hybrid solar-geothermal power plant in the world (e.g., Stillwater).

AcknowledgementsThe author thanks Josh Nordquist of Ormat and

Richard Perry and Lowell Price of Nevada Division of Minerals for reviewing this document and providing useful comments, and Jack McGinley for providing NV Energy power statistics.

ReferencesBenoit, D. (2013). An Empirical Injection Limitation

in Fault-Hosted Basin and Range Geothermal Systems. Geothermal Resources Council Transactions 37: 887-894.

Blake, K., A. Tiedeman, A. Sabin, M. Lazaro, D. Meade, W. Huang. (2015). Naval Air Station Fallon Mainside: An Update of Geothermal Exploration. Geothermal Resources Council Transactions 39: (in press)

BLM (2015), Prior Sales and Results, http://www.blm.gov/nv/st/en/prog/minerals/leasable_minerals/geothermal0/ggeothermal_leasing/prior_sales.html

Dering, G. and Faulds, J. (2012), Structural Controls of the Tuscarora Geothermal Field, Elko County, Nevada: Geothermal Resources Council Transactions 36: 41-46.

DiPippo, R. and K. Kitz. (2015). Geothermal Binary Power Plants at Raft River, San Emidio and Neal Hot Springs: Part 1 - Plant Descriptions and Design Performance Comparison. Geothermal Resources Council Transactions 39: (in press)

Drakos, P., Spielman, P., and Bjornsson, G. (2010), Jersey Valley exploration and development: Geothermal Resources Council Transactions 25: 751-759.

GEA. (2015), 2014 Annual U.S. & Global Geothermal Power Production Report - April 2015: Geothermal Energy Association, 21 p. http://geo-energy.org/reports/2015/2015%20Annual%20US%20%20Global%20Geothermal%20Power%20Production%20Report%20Draft%20final.pdf

Faulds, J.E., N.H. Hinz, M.F. Coolbaugh, L.A. Shevenell, D.L. Siler, C.M. Depolo, W.H. Hammond, C. Kreemer, G. Oppliger, P. Wannamaker, J. Queen, C. Visser. (2015a). Integrated Geologic and Geophysical Approach For Establishing Geothermal Play Fairways and Discovering Blind Geothermal Systems in the Great Basin Region, Western USA: A Progress Report. Geothermal Resources Council Transactions 39: (in press)

Faulds, J.E., N.H. Hinz, Nicholas, D. Blankenship, A. Sabin, and M. Kennedy. (2015b). Geologic Setting of the Proposed Fallon Forge Site, Churchill County, Nevada: Suitability for EGS Research. Geothermal Resources Council Transactions 39: (in press)

Garside, L.J., L.A. Shevenell, J.H. Snow, and R.H. Hess. (2002). Status of Nevada Geothermal Resource Development - Spring 2002. Geothermal Resources Council Transactions 26: 527-532.

Gwynn, M. (2015). Geothermal Potential in the Basins of East-Central and Southeastern Nevada. Geothermal Resources Council Transactions 39: (in press)

Hinz, N.H., Faulds, J.E., and Coolbaugh, M. (2014), Association of Fault Terminations with Fluid Flow in the Salt Wells Geothermal Field, Nevada, USA: Geothermal Resources Council Transactions 38: 3-10.

Kirby, S., S. Simmons, M. Gwynn, R. Allis, and J. Moore. (2015). Comparisons of Geothermal Systems in Central Nevada: Evidence for Deep Regional Geothermal Potential Based on Heat Flow, Geology, and Fluid Chemistry. Geothermal Resources Council Transactions 39: (in press)

Mariner, R.H., Rapp, J.B. , Willey, L.M., and Presser, T.S. (1974). The chemical composition and estimated minimum thermal reservoir temperatures of the principal hot springs of northern and central Nevada: U.S. Geological Survey Open File Report 74-1066, 35 p.

Molisee, D.D., and J.W. Bell. (2015). Structural Constraints of Buffalo Valley Hot Springs, North-Central Nevada. Geothermal Resources Council Transactions 39: (in press)

Moulding, A., and T., Brikowski. (2015). Influence of Continuously Variable Permeability and Basin Rock Properties on Three Dimensional Heat and Mass Balance Models of Basin & Range Geothermal Systems. Geothermal Resources Council Transactions 39: (in press).

Niggemann, K., Samuel, A., Morriss, A. V., and Hernández, R. (2009), Foamed cementing geothermal 13 3/8-in. intermediate casing – NGP #61-22: Geothermal Resources Council Transactions 33: 217-222.

Nordquist, J. and Delwiche, B. (2013). The McGinness Hills Geothermal Project: Geothermal Resources Council Transactions 37: 57-64.

Orenstein, R and Delwiche, B. (2014). The Don A. Campbell Geothermal Project: Geothermal Resources Council Transactions 38: 91-97.

Parr, A. J., and Percival, T. J. (1991). Epithermal Gold Mineralization and a Geothermal Resource at Blue Mountain, Humboldt County, Nevada: Geothermal Resources Council Transactions 15: 35-39.

Peterson, N., J. Combs, L. Bjelm, S. Garg, B. Kohl, C. Goranson, R. Merrill, P. van de Kamp, A. Lamb, A. Sadowski, and J. Faulds. (2013). Integrated 3D Modeling of Structural Controls and Permeability Distribution in the Patua Geothermal Field, Hazen, NV. Stanford Geothermal Workshop 2013, 11 p.

Public Utility Commission of Nevada (2015). PUCN Docket No. 15-03042, Tables 5.1 and 5.2

Wind Energy Foundation. (2015). Powering up Nevada – A Report on the Economic Benefits of Renewable Electricity Development. A Renewable America - Wind Energy Foundation, January 2015, 28 p.

Sadowski, A. and J. Faulds. (2015). The Structural Controls of the Black Warrior Blind Geothermal System, Truckee Range, Washoe-Churchill Counties, NV, USA. Geothermal Resources Council Transactions 39: (in press)

Shevenell, L., and A. Reid (2015). Geothermal Energy, in The Nevada Mineral Industry 2013 (ed. J. Muntean). Nevada Bureau of Mines and Geology MI-2013, p. 117-131. http://pubs.nbmg.unr.edu/The-NV-mineral-industry-2013-p/mi2013.htm

Wendt, D.S., G.L. Mines, C.S. Turchi, G. Zhu, S. Cohan, L. Angelini, F. Bizzarri, D. Consoli, and A. De Marzo. (2015). Stillwater Hybrid Geo-Solar Power Plant Analyses. Geothermal Resources Council Transactions 39: (in press) n

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Please note: There will be four fieldtrips from the GRC Annual Meeting including two that will visit some of the Nevada geothermal power plants mentioned in this article.

On Sunday, September 20, there will be a half day trip to the Ormat Steamboat Geothermal Plant Complex. After the GRC Annual Meeting from Wednesday-Friday, September 23-25, there will be a two day excursion to the McGinness Hills and Salt Wells Geothermal Power Plants.

Sign up when you register for the GRC Annual Meeting. Registration is now open! – more information at www.geothermal.org