The Western San Juan Mountains: Their Geology, Ecology, and Human History

8. Energy Resources

CHAPTER 8 ENERGY RESOURCES T. L. BRITT AND J. M. HORNBECK The scenic San Juan Skyway route lies in a relatively energy-poor corridor between two major oil- and gas-producing basins, the Paradox Basin to the west and the San Juan Basin to the south. Prolific oil fields associated with Pennsylvanian-age (300 million years) algal and oolitic carbonate reservoirs of the Paradox Basin are located 25 miles west ofCortez. The eastern edge ofthese productive Pennsylvanian trends is defined by drilling east and north of the town of Dolores, where both Ismay and Desert Creek test wells have been completed as producers. A few miles south ofDurango is the northern margin of the San Juan Basin gas field, a huge natural-gas deposit second in size, within the lower fortyeight states, only to the Hugoton Field ofOklahoma, Kansas, and Texas. This basin is, among other distinctions, the world's largest area of coal-seam gas production, and development of this resource is expected to continue for several more years. East from Cortez approximately 20 miles, a series of small, shallow Cretaceous Dakota Sandstone oil and gas pools have been developed within the Mancos River valley. Coal deposits underlie a large part of Montezuma and La Plata Counties, but thickness, mining costs, and transportation have restricted their economic development to small local markets. Recently, however, coal from the Durango area has been sold as far away as central Arizona, and production is increasing. 96 Energy Resources 97 The Skyway route also skirts the southeastern end of the Uravan mineral belt, a large uranium/vanadium district with myriad individual mines and mills (now abandoned or inactive). Minor uranium/vanadium deposits lie in the Placerville district, which is bisected by the Skyway route, and these also are inactive. Geothermal resources in the form of warm springs are present along U.S. Highway 550 between Durango and Ouray and in the Rico area. Cooling Tertiary intrusive rocks in the San Juan Mountains heat the water. A few of these sites have been turned into commercial spas, delighting tourists and locals alike. URANIUM RESOURCES The Skyway route traverses a section of the Colorado Plateau that played a pivotal role in the development ofnuclear power. This area provided some of the earliest enriched radium for experimental purposes and, later, uranium for the early U.S. atomic bomb effort. In fact, one of the most common uranium oxide minerals, carnotite , was discovered in 1895 and described from a site in Sinbad Valley, Utah, about 60 miles northwest of Placerville, Colorado. Recognition of carnotite, a powdery, yellow potassium uranyl vanadate (approximately K10, 2U03 V10S 3H10), as a possible source of radium sparked the first of three'mining booms in this portion of the Colorado Plateau. The initial boom, called the Radium Era, lasted from 1900 to 1924 and produced about 200 grams of radium, which sold for about $100,000 per gram. This metallic radium was used for medical and scientific research as well as some industrial applications. Though local legend ascribes the radium originally identified by the Curies in 1898 to ores from this area, it seems more probable that they used Czechoslovakian materials in their initial work and finally isolated the element in 1910 using American ores (Smith 1960). During the Radium Era, carnotite ore averaging less than 2 percent U308 (extremely high grade by current standards) was not considered worth milling, and most ofit was discarded on the mine dumps. Early exploration focused primarily on shallow, oxidized ores containing minerals of the carnotite group. These enriched high-grade uranium ores were handpicked at the mines and 98 The Western San juan Mountains D Colorado 1hc:rmal spins! ';,7 8 Fig. 8.1 Distribution of energy resources in and around the San Juan Skyway. hauled by burro, freight wagon, and truck to Placerville, where they were shipped by narrow-gauge rail to Salida, Colorado, and then on to New Jersey by standard rail. Nearly all ofthe significant uranium mines from this era lay within the Uravan mineral belt (Fig. 8.1), located approximately 40 miles northwest ofPlacerville, but some production came from smaller deposits in the Placerville district just north and east of the townsite. The Radium Era suffered a fatal blow when higher-grade deposits were discovered in the Belgian Congo in 1915. The second mining boom, the Vanadium Era, occurred from 1909 to about 1945. Whereas the Radium Era began slowly...