History of Development at the Geysers Geothermal Field, California

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This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Geothermal Resources Council, Monograph on The Geysers Geothermal Feld, Special Report No. 17,1991 HISTORY OF DEVELOPMENT AT THE GEYSERS GEOTHERMAL FIELD, CALIFORNIA James B. Koenig GeothermEx, Inc., 5221 Central Avenue, Suite201 Richmond, Calfonah 94804 INTRODUCTION LOCATION AND DESCRIPTION - empty into San Francisco Bay. Some tributaries flow all The Geysers - the world’s largest developed geother- year; others are seasonal, becoming dry or almost dry in mal field - is located in mountainous terrain of the Mayaca- summer and early fall. masRange,about75miles (120km)northofSanFrancisco, There are two climatic seasons: a hot, dry summer and in Sonoma and Lake Counties, California (Figure 1).This a cool, wet winter. Average temperature varies greatly part of the northern Coast Ranges is characterized by with elevation. Summer temperatures occasionally reach narrow, linear, northwest-trending ridges and valfeys. or exceed 100°F (38°C);freezing temperatures and even Ridge tops commonly reach,over 3,000 feet (900 meters) snowfalls are experienced in winter months. The change above sea level; valley floors typically are 1,000 to 1,600 between rainy and dry seasons is often abrupt, usually feet (300 to 500 m) in elevation. The-highest point within occurring in May and again in October. the geothermal field is Cobb Mountain, at 4,722 feet (1,440 Amounts of annual precipitation also vary with local m) elevation. elevation, ranging in average between 35 and over 80 To the south, elevations decline and the terrain becomes inches (90 to over 200 an).This falls almost entirely be- gentler. Broad valleys open southward towards San Fran- tween the months of October and April, and peaks during cisco Bay. To the north, the rugged terrain increases in the winter months of December through March. average elevation. Clear Lake, located some dozen miles (20 km) north of The Geysers, is the largest permanent SETTLEMENT AND HUMAN ACTIVITY body of water in the region. Its elevation is 1,325 feet (400 m) above sea level. Mount Konocti, on the southwest edge Because of its rugged terrain, this part of the California of the lake, has an elevation of 4,200 feet (1,280 m). There Coast Ranges was not settled extensively during the several areas of flat to gently rolling terrain near the Spanish occupation in the eighteenth and early nineteenth southern margins of the lake. centuries. Large land grants were made to settlers in the Hydrologically, The Geysers region is drained by fertile Napa and Santa Rosa valleys, some distance to the tributaries of the Russian River, and Clear Lake empties south. The brush-covered, poorly accessible uplands were via Cache Creek. Tributary streams generally follow the left to hunters and mineral prospectors. northwest-southeast grain of the country, cutting south- Mercury ore was discovered in the 1850s. An extensive ward or northward through narrow gaps in the ridges to mining industry developed in the Mayacamas Range in join larger tributary streams and eventually to join either the latter half of the nineteenth century, supplying mer- the Russian River in its course to the Pacific Ocean, or to cury to the mines of the Sierra Nevada foothills for use in 7 History of Development at The Geysers Geothermal Field Mendo .--- e Heo/ds bur g Sonoma Co. '. Napa Co. -; i n SCALE IN MILES Figure 1. Location of The Geysers geothermal field. a James B. Koenig The earliest known photograph of The Geysers geothermal field, Sonoma County, California, taken on December 17,1909 by Gerald A. Waring of the US. Geological Survey near the southern entrance to the field. The photo was included in Mr. Waring's publication SprinSs of California, 7915, U.S. Geological Survey Water Supply Paper 338. The steam in the photo is from fumaroles. Notice the thermally-altered terrain. (US. I Geological Survey) the recovery of gold by amalgamation. The Mayam power generation first began, was less than 100. And Range continued to produce mercury episodically into the within the 100 square mile (250 square km) area that 196Os,when environmental and economic considerations includes the neighboring small towns of Cobb and Mid- closed the last of the operations. Over 100 years of mmry dletown, population was under 2,500. Even today, the production earned the Mayacmas Range the rating as the year-round population of this region is not over 5,000 largest mercury-producing district in North America, and persons. possibly in the western hemisphere. Since 1960,and especially since the early 70s, increasing In addition to mining and sport hunting, the Mayacmas numbers of persons in the region have earned their living region became famous for its remation activities. Spas directly or indirectly from the geothermal field. Geother- existed at the numerous thermal springs from the 1860s mal activity now rivals recreation and agriculture as one onwards, and boating and bathing flourished in Clear of the principal tax bases of the area. Lake. However, the steepness of the terrain and the mag- nesian serpentinite soils limited agriculture to certain valley areas, especially near Clear Lake where the soils pre- THERMAL FEATURES OF THE GEYSERS dominantly are volcanic, and where fruit orchards and AND VICINITY vineyards were established. It is widely recognized that The Geysers is a misnomer; Roads either followed the topographic grain,generally at the time of its discovery in 1847 by William Bell Elliott, northwest-southeast, or took erratic and complex courses of the JohnC. Fremont expedition, them were widespread of switchbacks amss the ridges and canyons. There were areas of fumaroles, mud pots and steaming ground, and no major settlements in the immediate Geysers area. To the minor hot springs in the canyon of Big Sulphur Creek, but south, communities in the Napa and Santa Rosa valleys nogeysers. These fumarolesand mud pots were sufficient- prospered and grew. Small resort communities and fm- ly impressive that this 1847 survey party referred to the ing towns dotted the shores of Clear Lake. However, area as both "The Geysers" and "The Gates of Hell." This within the 20 square mile (50 square km) area of the latter designation apparently reflected the popular im- geothermal field, the permanent population in 1960,when agination of the time; the devil and his abode were per- 9 History of Development at The Geysers Geotheimal Field ceived almost everywhere at The Geysers ("Devil's Pul- pit," "Devil's Toll Gate," "Devil's Laboratory," etc.). Thdsprings are common through this part of the northem Coast Ranges, and thermal activity is especially intense at Calistoga, 20 miles (35km) to the southeast, and at Sulphur Bank on the eastern margin of Clear Lake. other thermal springs are the sites of old resorts, among them Siegler Springs, Howard Springs and Wilbur Springs. This widespread and intensive thermal activity usually is described in relation to the episodes of Late Tertiary and Quaternary volcanism that helped to shape the region. Nowhere, however, was thermal activity as widespread, intensive or high temperature as at The Geysers. E.T. Allen and A.L. Day, in their 1927 Carnegie Institution report, "Steam Wells and Other Thermal Activity at The Geysers, California," described a 5 mile (8 km)thermally active zone along Big Sulphur Cdc: beginning in the upper reaches of the Big Sulphur Canyon and extending to the west of The Geysers, this zone was characterized by patches ofsteaming ground and fumaroles. Allen and Day noted that intense hydrothermal alteration had led to the Traveling to The Geysers Resort by stagecoach. (Geothermal formation of extensive suites of secondary sulfate, oxide, Resources council) and silicate minerals. The ground in these areas was bleached tan or white, or was stained yellow by sulfur. The pervasive smell of rotten eggs indicated the discharge of in the late 185Os, ultimately becoming capable of accom- H2S-rich gases. modating over 200 guests. People traveled by train to Healdsburg or Calistoga and then by stagecoach over twisting, dusty (or muddy, depending upon the season) DEVELOPMENT AS A SPA roads. After the automobile had gained acceptance, a gaso- The heyday of recreational spas in the United States line pump was installed at the resort for the convenience was the last three decades of the nineteenth century and of daring motorists. the first decade of this century. Mineral springs and wells One early visitor, California state geologist W.H. Brew- were prized for their supposed therapeutic value in the er, in 1861 described the trip by horseback before the road years before antibioticsand vitamin pills. When the waters was completed. The trail, he said, was so hard, "charges at were not only mineralized, but also naturally hot and the hotel so extortionate", and the fumaroles and springs found in an area of scenic beauty, their popularity was so overrated, that the trip was hardly worth the effort.

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