Mt Princeton Hot Springs Geothermal Area
Geothermal Area Profile
|Exploration Region:||Rio Grande Rift|
|GEA Development Phase:||Phase II - Resource Exploration and Confirmation|
|Mean Reservoir Temp:||160°C433.15 K
|Estimated Reservoir Volume:|
|Mean Capacity:||10 MW10,000 kW
|USGS Mean Reservoir Temp:||95°C368.15 K
|USGS Estimated Reservoir Volume:||1 km³|||
|USGS Mean Capacity:||5 MW|||
The hydrothermal system consists of a highly permeable sedimentary reservoir, the heat and fluid of which are sourced in the fault system that extends into the underlying Precambrian basement. Two major springs, Mt. Princeton and Hortense hot springs, comprise the surface expressions of this hydrothermal system. Temperatures as high as 84 °C have been measured at Hortense Hot Spring , reportedly making it the hottest natural spring in Colorado . Heat flow values as high as 378 mW m-2  have been measured at the Mount Princeton Hot Springs geothermal area.
History and Infrastructure
Operating Power Plants: 0
|No geothermal plants listed.|
|Add a new Operating Power Plant|
Developing Power Projects: 0
|No geothermal projects listed.|
|Add a new Developing Power Project|
Power Production Profile
|Gross Production Capacity:|
|Net Production Capacity:|
|Power Purchasers :|
Since 2007 Mt. Princeton Geothermal, LLC has been assessing the area for its geothermal energy production potential. The company has conducted several preliminary scientific surveys, and is currently in the pre-development stages of constructing an anticipated 10 MW power plant at a site located near Mount Princeton Hot Springs (fig. 1b). Much of the scientific data used by Mt. Princeton Geothermal, LLC in the site evaluation has been collected by the Colorado School of Mines (CSM), Colorado Geological Survey (CGS), and Dewhurst Group, LLC .
Electrical infrastructure is suitable for the construction of a geothermal power plant. Prospective power plant sites are located about 2 miles from a 12.5 kV substation and 115 kV transmission line, which are capable of transmitting the anticipated 10 MW of power. The proximity of this infrastructure is anticipated to result in significant reductions in future development costs . Locations for electrical transmission lines and substations in the Mount Princeton vicinity are depicted in figure 2. Geothermal electricity production at the Mount Princeton Hot Springs area would supply power to the Sangre de Cristo Electric Association via these transmission lines .
Regulatory and Environmental Issues
Due to a post-1980s decline in interest, research, and development of geothermal technologies in the United States, federal and Colorado state regulatory officials have not recently been acquainted with permitting and regulatory procedures pertaining to closed-cycle geothermal power systems. Currently, the United States Forest Service (USFS) and Bureau of Land Management (BLM) classify geothermal resources as a mineral rights, while the Colorado Division of Water Resources (CDWR) is regulates geothermal resources as water resources   . Until recently these problems resulted in confusion pertaining to federal vs. state jurisdiction on geothermal operations, significantly impeding geothermal development in Colorado. In 2011, however, a press release from the BLM and Colorado Department of Natural Resources (CDNR) announced a memorandum of understanding (MOU) between the two agencies. The MOU outlined a joint effort to facilitate communication regarding leasing, permitting, and administration of geothermal resources in Colorado .
Geothermal resources at the Mount Princeton Hot Springs area are located beneath federal, state, and private surface estates. . However, subsurface hydrothermal resources are subject to both state jurisdiction  and federal mineral rights law. In many cases the federal government holds the title to subsurface mineral estate , even if the surface estate is privately owned. Such cases are termed “split estate” lands, and are the result of the Southern Homestead Act of 1866 . This type of geothermal resource may be exploited with proper CDWR permitting and state or federal leases, regardless of which entity owns the surface estate. However, exploratory or development activities on surface estates under which the geothermal resources are privately owned, require explicit permission from land owners .
Different regulatory and permitting procedures apply to the development of a geothermal resource depending on whether the resource is classified as tributary or non-tributary . Groundwater is considered to be tributary if it is determined to be hydrologically connected to a natural surface stream . CRS§ 37-90 mandates that tributary waters be considered a public resource, and therefore may only be appropriated by private land owners or lease holders subject to regulations and permits administered by the State Engineer and CDWR  . Alternatively, groundwater resources deemed non-tributary are considered subject to statutes associated with land ownership rights  . Most water resources in Colorado, including those in the Mount Princeton Hot Springs area, are considered tributary waters  .
Water resource use is classified as either consumptive or non-consumptive use. In this context, consumptive water use is equated with the depletion of water resources. Because closed-loop, binary geothermal power plants re-inject 100% of the water pumped from the production well, water exploitation for geothermal electricity production at the Mount Princeton Hot Springs area would be classified as non-consumptive  .
Mt. Princeton Geothermal, LLC anticipates having initiated Colorado’s first commercial geothermal electricity production within the next few years. These plans include the completion of state and federal regulatory and permitting procedures, confirmative geophysical testing, and the construction of a 10-15 MW binary power plant .
Held and Henderson (2012) outline three stages for the geothermal power plant development process currently being undertaken by Mt. Princeton Geothermal, LLC. Stage I includes land acquisition and preliminary geophysical and geochemical surveys. The company is currently in stage II, which consists of drilling deep wells for resource confirmation testing, and borehole geophysical surveys. Stage III will include acquiring permits, drilling production and injection wells, and power plant development and construction  .
Mt. Princeton Geothermal, LLC is currently (as of 2014) preparing to drill two to three additional 300-400 m thermal gradient holes, and one slim hole for reservoir flow tests in target areas delineated using previous magnetotelluric (MT) surveys. These wells are supplementary to several shallow thermal gradient holes that already exist in the area. Temperature gradients measured in the newly drilled wells will be used to infer the depths at which the target reservoir temperatures (120-150 °C) will be reached, and will serve as a basis for drilling confirmation test wells .
First Discovery Well
|Initial Flow Rate:||
|Flow Test Comment:|
In the 1970s three exploration firms—Occidental Oil, AMAX, and Petro-Lewis—began surveying the Mount Princeton Hot Springs area for the purpose of geothermal resource assessment. These activities included deep and shallow temperature gradient measurement, geologic mapping, and geophysical surveys . AMAX Exploration drilled 31 temperature gradient wells in the area , but reconnaissance activity in the area stagnated significantly due to complications in obtaining geothermal leases from the USFS . Global declines in oil prices also contributed substantially to a reduction in interest and investments in renewable energy sources .
In 1971 Zohdy et al. (1971) measured groundwater resistivity in locations approximately 7 km north of the Mount Princeton Hot Spring. The survey included measurement of both vertical electrical soundings (VES) and dipole electrical soundings (DES), and was conducted primarily to validate the thickness of the valley-fill aquifer indicated previously by an associated gravity survey .
Case and Sikora (1984) conducted gravity and aeromagnetic surveys in the upper Arkansas River Valley (UARV) region, including the Mount Princeton Hot Springs geothermal area. Results yielded gravity and magnetic lows corresponding with the Mt. Princeton Batholith, and a density contrast of -0.5 g/cm3 of the adjacent valley-fill sediments relative to the batholith .
Academic field work conducted between 2008 and 2010 for a geophysics field camp in the UARV consisted of several geophysical reconnaissance studies. The surveys, which were the collaborative efforts of the Colorado School of Mines (CSM), Boise State University (BSU), and Imperial College-London (ICL), characterize the geological, hydrogeological, and geothermal conditions of the Mount Princeton Hot Springs geothermal area. In 2008 the field camp study recorded temperature, natural gamma ray counts, and resistivity in two wells on either block of one of several normal faults in the area. A temperature of 63 °C was measured at a depth of 18 m on the footwall. Significantly lower temperatures recorded in the well on the hanging wall fault block substantiate previous studies attributing the source of thermal waters to fault conduits. Two-dimensional deep seismic reflection surveys conducted in a transect through the Mount Princeton Hot Springs geothermal area yielded results that validate previously inferred stratigraphic and structural characteristics of the UARV .
Blum et al. (2009) summarize the geophysical reconnaissance completed for the Upper Arkansas River Valley (UARV) and Mount Princeton Hot Springs geothermal area. This research, part of the Colorado School of Mines and Boise State University geophysics field camp, includes gravimetric, electromagnetic (EM), ground penetrating radar (GPR), DC resistivity, well logging, vertical seismic profiling (VSP), self-potential (SP), and deep reflection seismic surveys . The continuation of this research in the UARV is presented in Batzle et al. (2008, 2009, & 2010)  .
In 2009 Mt. Princeton Geothermal, LLC drilled five temperature gradient holes in the Mount Princeton Hot Springs area, delineating the western margin of the temperature anomaly .
Richards et al. (2010) provide interpretations of geoelectrical data collected for the CSM-BSU-ICL geophysics field camps. Self-potential and DC resistivity surveys were conducted to identify subsurface fluid-flow patterns within the geothermal system. Researchers collected 2700 SP measurements and produced 12 resistivity profiles, each approximately 1.3 km in length. Equilibrium temperature data from wells and shallow (30±5 cm) holes was correlated to geoelectrical data. Self-potential data was interpreted by comparing results to 6 generalized geothermal groundwater flow patterns and their associated self-potential signatures .
Magnetotelluric (MT) surveys were conducted by Dewhurst Group, LLC in 2011 and 2012 in conjunction with the exploratory efforts of Mt. Princeton Geothermal, LLC. These surveys yielded results indicative of 150 °C waters at depths of 760-1,070 m. Additionally, the results are consistent with the inference of a normal, listric fault control on upward fluid flow .
Lamb et al. (2012) present an overview of 3D seismic refraction surveys conducted by the CSM-BSU-ICL geophysics field camps in an area between the Hortense and Mount Princeton hot springs (fig. 1b). Refractive methods were useful in delineating both the water table and boundary between bedrock and overlying sediments. Refraction tomography was also correlated with self-potential and resistivity data to locate stratigraphic offset within bedrock units, and hence map probable fault locations and geometries .
Well Field Description
Well Field Information
|Number of Production Wells:|
|Number of Injection Wells:|
|Number of Replacement Wells:|
|Average Temperature of Geofluid:|
|Sanyal Classification (Wellhead):|
|Reservoir Temp (Geothermometry):||140°C413.15 K
|Reservoir Temp (Measured):|
|Sanyal Classification (Reservoir):|
|Depth to Top of Reservoir:|
|Depth to Bottom of Reservoir:|
|Average Depth to Reservoir:|
To date, production and injection wells at the Mt. Princeton Hot Springs geothermal area have not yet been developed. The anticipated layout, orientations, and depths of prospective production and injection wells constitute proprietary information of Mt. Princeton Geothermal, LLC.
Research and Development Activities
In 2009 Mt. Princeton Geothermal, LLC completed the drilling of five temperature gradient holes in the area. Currently the company is awaiting the geophysical confirmation of the Mount Princeton Hot Springs area as a proven geothermal reservoir and economical resource. Legal permitting, and hence the development of a geothermal power plant, is dependent on this confirmation. A magnetotelluric (MT) survey completed in 2012 by Dewhurst Group, LLC was conducted to both estimate resource depths and validate the structural characteristics of the reservoir host and boundary rocks. Results from this survey were used to delineate target drill sites in a sparsely populated area approximately 2.4 km northeast of the Chalk Cliffs. Although the results of the MT survey increased confidence in the resource, completion of additional thermal gradient wells and deep reservoir test wells to further minimize uncertainty is pending  . Mt. Princeton Geothermal, LLC has recently acquired an exploratory lease of approximately 3,700 acres of land from the Colorado State Land Board in an effort to advance the exploration process .
Technical Problems and Solutions
Because the Mount Princeton Hot Springs geothermal area has not yet undergone development, no technical problems have been encountered.
Geology of the Area
|Moeck-Beardsmore Play Type:|
|Modern Geothermal Features:||Hot Springs|||
|Relict Geothermal Features:||Hydrothermal Alteration|||
|Host Rock Age:|
|Host Rock Lithology:|
|Cap Rock Age:|
|Cap Rock Lithology:|
The Mount Princeton Hot Springs geothermal area is located between Salida and Buena Vista in Chafee County, Colorado, approximately 12 km southwest of Buena Vista. The area is bounded by the Sawatch Range to the west and the upper Arkansas River Valley (UARV) and Mosquito-Ten Mile Range to the east. Mt. Princeton itself is located on the western margin of the UARV  (figs. 1 & 3).
The western margin of the UARV is bounded by the Precambrian igneous and metamorphic core of the Sawatch anticline, which is topographically expressed as the mountainous range in the area. This range exhibits several tall peaks including Mt. Princeton, a Tertiary intrusive peak which reaches 4,328 m above sea level. The rocks of these Tertiary intrusive peaks, including those of Mt. Princeton, cut through the Precambrian basement . The eastern side of the UARV abuts the southern extension of the Mosquito-Ten Mile Range. The Mosquito-Ten Mile Range near Mt. Princeton comprises Precambrian basement overlain by Tertiary volcanic and pyroclastic flows. Figures 1d and 3 display generalized geologic cross sections.
The UARV is the northern extension of the Rio Grande Rift zone , which resulted from the westward movement of the Colorado Plateau. Beginning in mid-Tertiary time, this westward movement produced an area of extension and crustal thinning . The area of the UARV near Mt. Princeton is a narrow, north-trending, down-dropped trough which exhibits steeply-dipping normal faults at its boundaries. Although the western edge of the UARV is characterized by a relatively simple narrow fault area, the edge of the valley abutting the Mosquito-Ten Mile Range is a much more complex array of parallel normal faults demonstrating significant displacement . The western margin of the UARV, marked by the northwest trending Sawatch Range normal fault system, hosts a geometric segment boundary. This boundary appears in the form of an en echelon step near the Chalk Cliffs. The boundary is a zone of highly fractured and hydrothermally-altered quartz monzonite. This area is outlined in figure 1b.
The stratigraphy of the area around the Mount Princeton Hot Springs geothermal area consists primarily of the Dry Union formation, which overlies a layer of igneous extrusive rocks and the Precambrian granitic basement. Interpreted seismic sections are presented in figures 1d and 3. During the period of its subsidence, the UARV was filled with sediments derived primarily from the Sawatch Mountains. The majority of these sediments are fluvial in origin, with some beds including significant volumes of volcanic ash. Toward the south end of the valley, near Droney Gultch, the top 80 m of the Dry Union formation are exposed and may be measured. The Dry Union formation consists primarily of poorly consolidated sandstone, pebble beds and mudstone beds as thick as 2000 m in parts of the valley .
Rhyolitic lavas derived from the Mount Princeton eruption underlie the Dry Union formation throughout the UARV. The base of this lava is glassy; indicating that it cooled quickly, while lava in the upper interval exhibits an aphanitic texture. A stratigraphic column produced in the Hecla Junction area (approx. 18 km southeast of Mt. Princeton) is provided in figure 4 .
Interest in the hydrothermal system at the Mount Princeton Hot Springs area was initially focused upon the area at the base of Mount Princeton itself, and at the base of the Chalk Cliffs (fig. 1b). The most prominent surface expressions of this hydrothermal system, the Mount Princeton and Hortense hot springs , are located within 1 km of one another, and at the surface range in temperature from 50 to 84 °C . Heat flow values at these sites range from 100 to 378 mW m-2  (fig. 5), and subsurface temperatures within the reservoir are estimated at 200 °C . Discharge measurements at the Mount Princeton and Hortense hot springs yield ranges of 250-400 and 23-33 gpm, respectively .
Hydrothermal fluids are heated in the fractured crystalline basement, and are transported upward into the overlying valley-fill sediments via a system of intersecting faults . Resistivity profiles conducted 7 km north of the Mount Princeton Hot Springs yielded thickness measurements of these sediments of approximately 1400 m . Temperatures within this valley-fill aquifer have been estimated using Si, Na-K, and Na-K-Ca geothermometry methods. Silica geothermometer results indicated a range of 97 to 118°C, Na-K geothermometers yielded a range of 132 to 150 °C, and Na-K-Ca geothermometry methods suggested a range of 168 to 188 °C .
DC resistivity and self-potential data collected for the purposes of delineating prevalent groundwater flow patterns within faults in the crystalline basement suggested the existence of a dextral fault zone (Fault B) just south of the Chalk Cliffs (fig. 6). Several low resistivity and high self-potential anomalies are consistent with both the fault orientation and its associated thermal anomalies. Similar methods yield results that suggest upwelling just east of the Chalk Cliffs in a system of tensile fractures (Fault A) characteristic of extensional strain (fig. 6). Geoelectrical data coupled with finite element solutions yield upward groundwater flux values of 4±1×103 m3/day at Fault B and 2±1×103 m3/day at Fault A. Additional evidence of vertical flow of thermal groundwater is found south of the Chalk Cliffs, in a fractured quartz monzonite aquifer. Here, a temperature of 67 °C was measured at a depth of 149 m .
Active hydrothermal alteration is observed in the surface hot spring systems, and is evidenced by the presence of calcium zeolite, leonhardite, chlorite, illite, epidote, calcite, and fluorite. The most prevalent alteration has occurred at the Chalk Cliffs (fig. 6) and in the Mount Princeton Quartz Monzonite. Alteration at these localities is zeolitic, resulting in the conversion of biotite to chlorite; hornblende to calcite, orthoclase to sericite; and plagioclase to albite . This zeolitization suggests reservoir temperatures of 145 to 220 °C at depths between 140 and 1,800 m, values which substantiate geothermometric estimations .
Heat is sourced in the faulted and fractured crystalline basement, and is subjected to advective and convective upward transport into the overlying Cenozoic sedimentary reservoir via the Sawatch Fault System  . More specifically, Olson and Dellachaie (1976) postulate that fluid is sourced in fractures that extend to depths of 3 km, and that regional heat energy anomalies are traced to mafic intrusions beneath the southern San Luis Valley (southern CO and northern NM) .
|Brine Constituents:||Na, SO4, HCO3|||
The Colorado Geological Survey (CGS) provides measurements of total dissolved solids (TDS) from springs and wells at the Mount Princeton Hot Springs geothermal area (table 1). Detailed chemical analyses of the wells and springs in the area conducted by AMAX Exploration, Inc. can be retrieved from Olson & Dellechaie (1976) . The CGS also conducted an isotopic analysis of the thermal waters in an effort to determine their origins and ages . Concentrations of oxygen-18, deuterium and tritium measured for this study in the Mount Princeton and Hortense hot springs are given in table 2. Negative signs for O18 and 2H express the divergence of concentrations from Standard Mean Ocean Water (SMOW). These data indicate: 1.) a groundwater age (time of presence within the aquifer) of less than 10 years, 2.) that significant mixing occurs between shallow ground water and upwelling hot water, 3.) that no magmatic water is present in the system, and 4.) that recharge is controlled explicitly by local precipitation (virtually no meteoric water from other regions enters the system) . Spring and well waters in the Mount Princeton Hot Springs geothermal area are predominantly basic, exhibiting pH levels ranging from 7.6 to 9.6 .
NEPA-Related Analyses (0)
Below is a list of NEPA-related analyses that have been conducted in the area - and logged on OpenEI. To add an additional NEPA-related analysis, see the NEPA Database.
CSV No NEPA-related documents listed.
Exploration Activities (12)
Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI. Add a new Exploration Activity
- R.H. Pearl, J.K. Barrett. 1976. Geothermal resources of the Upper San Luis and Arkansas valleys, Colorado. Epis, R.C. & Weimer, R.I., editors. (!) : Colorado School of Mines: Studies in Colorado Field Geology, Professional Contributions. 439-445p.
- J. Held, F. Henderson. 01/04/2014. A.T. Ochsner (Personal Communication, 2014). Personal Communication sent to A.T. Ochsner.
- U.S. Geological Survey. 2008. Assessment of Moderate- and High-Temperature Geothermal Resources of the United States. USA: U.S. Geological Survey. Report No.: Fact Sheet 2008-3082.
- Richards, K., Revil, A., Jardini, A., Henderson, F., Batzle, M., & Hass, A.. 2010. Pattern of shallow ground water flow at Mount Princeton Hot Springs, Colorado, using geoelectrical methods.. Journal of Volcanology and Geothermal Research. 198:217-232.
- T. Blum, K. van Wijk, L. Liberty, M. Batzle, R. Krahenbuhl, A. Revil, R. Reynolds. 2009. Characterization of a geothermal system in the Upper Arkansas Valley. In: Society of Exploration Geophysicists International Exposition and Annual Meeting (SEG Houston, 2009); 2009/01/01; Houston, Texas. Online: Society of Exploration Geophysicists International Exposition and Annual Meeting (SEG Houston, 2009); p. 1289-1293
- Batzle, M., Raynolds, B., Jakubowicz, H., Collins, G., van Wijk, K., Liberty, L., et al. (Colorado School of Mines, Boise State University, and Imperial College-London). 2010. Characterization of the Upper Arkansas Basin, Chaffee County, Colorado. Golden, Colorado: Colorado School of Mines, Boise State University, and Imperial College-London.
- J.S. Crompton. 1976. An active seismic reconnaissance survey of the Mount Princeton area, Chaffee County, Colorado [Thesis]. [Golden, Colorado]: Colorado School of Mines.
- Paul Morgan. 2012. Colorado thermal spring water geothermometry (public dataset). Denver, Colorado. Colorado Geological Survey. 0p.
- H.J. Olson, F. Dellechaie. 1976. The Mount Princeton geothermal area, Chaffee County, Colorado. Epis, R.C. & Weimer, R.I., editors. (!) : Colorado School of Mines: Studies in Colorado Field Geology, Professional Contributions. 431-438p.
- Interpretive geothermal heat flow map of Colorado. [Map]. Place of publication not provided. (!) . 2007. Available from: http://geosurvey.state.co.us/SiteCollectionDocuments/EnergyResources/Geothermal/LoRes_Plate1_Interpretitive_Geothermal_Heat_Flow_Map.pdf.
- 2010. Energy Now. (!) : Chaffee County, CO.
- F.C. Healy. 1980. Geothermal energy potential in Chaffee County, Colorado. (!) : Colorado Geological Survey Open File. Report No.: 80-10.
- P. Morgan. 2012. Geothermal regulations in Colorado---land ownership is the key. Geothermal Resources Council- Transactions. 36:1233-1237.
- J. Held, F. Henderson. 2012. New developments in Colorado geothermal energy projects. Geothermal Resources Council- Transactions. 36:679-684.
- M.D. Detsky. 2010. Getting into hot water: the law of geothermal resources in Colorado. The Colorado Lawyer. (!) .
- Vanessa Delgado, Todd Hartman. 2011. Bureau of Land Management, Colorado collaborate to advance efficient geothermal development. Memorandum sent to NEWS RELEASE.
- R. Waskom, M. Neibauer. Glossary of water terminology [Internet]. 8-Jan-14. Colorado State University and Colorado Water Institute. [updated 2014/04/04;cited 2014/04/04]. Available from: http://www.ext.colostate.edu/pubs/crops/04717.html
- P. Morgan. 2013. Analysis of borehole temperature data from the Mt. Princeton Hot Springs area, Chaffee County, Colorado (abstract only). In: 2013 AAPG Rocky Mountain Section Meeting, Official Meeting Program. AAPG Rocky Mountain Meeting; 1/08/11; Salt Lake County, Utah. Online: AAPG Rocky Mountain Meeting; p. 60
- Zohdy, A.A., Hershey, L.A., Emery, P.A., & Stanley, W.D.. 1971. Resistivity sections, Upper Arkansas River Basin, Colorado. (!) : U.S. Geological Survey Open-File Report. Report No.: 71-002.
- J.E. Case, R.F. Sikora. 1984. Geologic interpretation of gravity and magnetic data in the Salida region, Colorado. (!) : U.S. Geological Survey Open-File Report. Report No.: 84-372.
- Batzle, M., Li, Y., Krahenbuhl, R., van Wijk, K., Liberty, L. (Colorado School of Mines and Boise State University). 2008. Characterization of the Upper Arkansas Basin, Chafee County, Colorado. Golden, Colorado: Colorado School of Mines.
- Batzle, M., Krahenbuhl, R., Revel, A., Jakubowicz, H., Wood, S., van Wijk, K., Liberty, L. (Colorado School of Mines, Boise State University, and Imperial College-London). 2009. Characterization of the upper Arkansas Basin, Chaffee County, Colorado. Golden, Colorado: Colorado School of Mines.
- A.P. Lamb, L.M. Liberty, K. van Wijk, A. Revil, C. Diggins. 2012. Near-Surface imaging of a hydrogeothermal system at Mount Princeton, Colorado using 3D seismic, self-potential, and dc resistivity data. Society of Exploration Geophysicists-The Leading Edge. 31(1):70-74.
- Richard Howard Pearl. 1979. Colorado's Hydrothermal Resource Base - An Assessment. Denver, Colorado: Colorado Geological Survey in Cooperation with the U.S. Department of Energy. Report No.: Resource Series 6.
- D.H. Knepper. 1974. Tectonic analysis of the Rio Grande Rift Zone, central Colorado [Dissertation]. [Golden, Colorado]: Colorado School of Mines.
- R.H. Pearl. 1979. Colorado's hydrothermal resource base---an assessment. (!) : Colorado Geological Survey Resource Series.
- R.H. Pearl. 1972. Geothermal resources of Colorado. (!) : Colorado Geological Survey Special Publication.
- J.K. Barrett, R.H. Pearl. 1978. An appraisal of Colorado's geothermal resources. (!) : Colorado Geological Survey Bulletin.
List of existing Geothermal Resource Areas.
Some of the content on this page was part of a case study conducted by: UND Team 2