Geothermal resources are underground reservoirs of hot water or steam created by heat from Earth’s interior. Geothermal steam and associated geothermal resources include (1) all products of geothermal processes, including indigenous steam, hot water, and hot brines, (2) steam and other gases, hot water, and hot brines resulting from water, gas, or other fluids artificially introduced into geothermal formations, (3) heat or other associated energy found in geothermal formations, and (4) any byproducts (see 43 CFR 3200.1) of the above resources. Geothermal steam and hot water are naturally discharged at Earth’s surface in the form of hot springs, geysers, mud pots, and steam vents. As an energy source, geothermal resources of hot water or steam are extracted and supplied to steam turbines that generate electrical energy. Geothermal resources also include subsurface areas of hot, dry rock (BLM and USFS 2008a). The BLM field offices in the Bighorn Basin are responsible for supervising and managing all exploration, development, and production operations on any federal geothermal leases in the Planning Area.
Energy derived from geothermal sources is considered a renewable energy resource. Geothermal energy is classified as a renewable energy source because the water used for geothermal energy is replenished by rainfall and the heat and steam harvested for geothermal energy is continuously produced inside Earth.
There are three geothermal areas in the Planning Area, although none is considered viable for use to generate electricity (with current technology and market conditions), and the BLM has not issued federal geothermal leases (BLM 2008d). The Cody Hydrothermal System extends from the DeMaris Hot Springs 1 mile west of Cody to the Horse Center anticline 7 miles south of Cody. The Cody Hydrothermal system reaches maximum temperatures of 113°F to 131°F at depths of 853 to 1,640 feet. The Thermopolis Hydrothermal System extends east from the Hamilton Dome oil field area about 15 miles to the Warm Springs oil field area. This area reaches temperatures between 115°F and 176°F and is used by several private residences and commercial entities. Water from this system surfaces naturally at Hot Springs State Park, but is not used for municipal heating purposes in the nearby town of Thermopolis. The Bighorn Basin area produces high-temperature water in some of its aquifers because of the thickness of the overlaying sedimentary rock layer; the highest temperature measured in the basin was 306°F at a recorded depth of 23,081 feet (BLM 2009b).
The USGS has not identified any conventional (hydrothermal) geothermal resources in the Planning Area capable of generating electricity (USGS 2008b). In addition, the USGS reports geothermal resource occurrence as low for the entire Planning Area, with the exception of the thermal springs near Thermopolis, which the USGS ranks as moderately low. It should be noted, however, that at an average depth of 6.5 kilometers (approximately 21,000 feet), all of the lands in the Planning Area have temperatures in excess of 150 degrees Celsius (°C) (approximately 300°F), sufficiently hot for hot- and moderate-temperature hydrothermal systems, but at depths currently uneconomical for development (BLM 2008c). Known geothermal resources being exploited by the public or by individuals are primarily on private or state‐owned lands in the Planning Area.
The Final Programmatic EIS for Geothermal Resources in the Western United States (BLM and USFS 2008a) describes the Bighorn Basin as having “potential” for geothermal resource development. The BLM is aware of a low to moderate potential for some level of interest in Bighorn Basin geothermal resources over the next 10 to 20 years.
Due to current policy direction guiding the development of renewable energy resources on public lands, there could be increased interest in geothermal development in the Planning Area. The American Reinvestment and Recovery Act of 2009 provides for $350 million in new investment in geothermal energy for research on technology, exploration, development techniques, and geothermal resource assessments (DOE 2009). Should geothermal leasing begin in the Bighorn Basin at some level, the CYFO and WFO would likely be able to accommodate some geothermal resource development over the next planning cycle (BLM 2009b). The BLM would work carefully to ensure that interests in geothermal development in the Bighorn Basin would not adversely affect the geothermal resource at Thermopolis, which the community holds in high regard.
Readers can find additional information and related studies on geothermal resources and development potential in the Reasonable Foreseeable Development Scenario for Geothermal, Bighorn Basin Planning Area (BLM 2009j).
Management challenges are most apparent near the natural hot springs at Thermopolis. The management challenge would be to ensure that any potential geothermal development did not deplete water or heat from the system and therefore adversely affect the Thermopolis hot springs, the local tourism based economy, or the quality of life of local residents. The BLM would take care to consider the views of local, state, and national communities, and use the best available scientific information, before considering geothermal leasing in this area.