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Wine Country, Geothermal Energy & The Golden Gate Bridge In One Day

Updated: May 17, 2021

Saucalito, California

May 17, 2021

Yesterday was quite an adventure. I started off in Vacaville and headed into the Wine Country of Napa and Sonoma. It reminded me of a Sunday drive on the Brew Ridge Trail, the horse country around Middleburg and the drive around St. Michael's on the Eastern Shore -- folks getting away from the city for the day. The roads were busy and the parking lots of the wineries were crowded.

The Geysers provided a flashback to my career. In the 1990s, I had conducted due diligence into acquiring the geothermal power plants being sold by PG&E as part of their divesiting their generation assets. Unfortunately, Calpine had a right of first refusal so any offer we would have made would have been topped by them.

Later at DOE, I was point on an effort by the Bottle Rock power plant to borrow money to redevelop their geothermal resource. Worst private equity investment I ever saw. They had sunk tens of millions of dollars into the above ground equipment only to realize the real problem was the geothermal resource. I don't think they banked on anyone at DOE having a clue as to what a losing proposition they had for us. I turned them down and wished them luck.

I returned to the Golden Gate Bridge when there was a bit of break in the clouds. Just enough to get some better photos than I had taken previously.

Enjoy the photos and a bit of history about Geyserville and The Geysers.

Geyserville is the home of Dreaming Tree wine which is owned in whole or in part by Dave Matthews. Unfortunately there is no vineyard to visit which makes me think that Dreaming Tree must buy its grapes from others in the area.

And, yes, The Dreaming Tree is a DMB song:

Geyserville (formerly Clairville) is an unincorporated community and census-designated place (CDP) in Sonoma County, California, USA. Located in the Wine Country, Geyserville has a small selection of restaurants, bed and breakfasts, and wineries. Geyserville is located on California State Route 128, close to US Route 101. The population was 862 at the 2010 census.


Geyserville, located on the Rancho Tzabaco Mexican land grant, owes its foundation to the discovery in 1847 of a series of hot springs, fumaroles, and steam vents in a gorge in the mountains of Sonoma County, California, between Calistoga and Cloverdale. This complex, which became known as The Geysers, soon became a tourist attraction, and a settlement grew up to provide accommodation and serve as a gateway to The Geysers. It was initially known as Clairville but subsequently renamed Geyserville. After the San Francisco and North Pacific Railroad was extended to Cloverdale in the 1870s, its trains stopped in Geyserville.


According to the United States Census Bureau, the CDP covers an area of 4.6 square miles, all of it land.


At the 2010 census Geyserville had a population of 862, although the official sign at the entrance to the town says "1,600" on August 8, 2014. The population density was 187.9 people per square mile. The racial makeup of Geyserville was 609 (70.6%) White, 5 (0.6%) African American, 7 (0.8%) Native American, 14 (1.6%) Asian, 0 (0.01%) Pacific Islander, 192 (22.3%) from other races, and 35 (4.1%) from two or more races. Hispanic or Latino of any race were 328 people (38.1%).

The census reported that 98.5% of the population lived in households and 1.5% lived in non-institutionalized group quarters.

There were 298 households, 108 (36.2%) had children under the age of 18 living in them, 169 (56.7%) were opposite-sex married couples living together, 26 (8.7%) had a female householder with no husband present, 22 (7.4%) had a male householder with no wife present. There were 22 (7.4%) unmarried opposite-sex partnerships, and 2 (0.7%) same-sex married couples or partnerships. 51 households (17.1%) were one person and 14 (4.7%) had someone living alone who was 65 or older. The average household size was 2.85. There were 217 families (72.8% of households); the average family size was 3.17.

The age distribution was 201 people (23.3%) under the age of 18, 71 people (8.2%) aged 18 to 24, 213 people (24.7%) aged 25 to 44, 293 people (34.0%) aged 45 to 64, and 84 people (9.7%) who were 65 or older. The median age was 39.9 years. For every 100 females, there were 116.0 males. For every 100 females age 18 and over, there were 122.6 males.

There were 325 housing units at an average density of 70.8 per square mile (27.4/km2), of which 58.4% were owner-occupied and 41.6% were occupied by renters. The homeowner vacancy rate was 1.7%; the rental vacancy rate was 0%. 55.7% of the population lived in owner-occupied housing units and 42.8% lived in rental housing units.


Geyserville Avenue carries the designation of California State Route 128 until it routes along U.S. Route 101 to the north. The Northwestern Pacific right-of-way is expected to be reactivated for Sonoma–Marin Area Rail Transit service when the line is rebuilt to Cloverdale, but Geyserville is not planned to receive a stop.

On the trip I have been to El Dorado but I'll have to wait for another day to shout "Eureka!"

The Geysers is the world's largest geothermal field, containing a complex of 18 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains approximately 70 miles north of San Francisco, California. It is a steam dominated resource meaning that there is no pumping or flow of liquid water in front of the steam turbines. Most other geothermal power plants in California use "dual flash" or "binary cycle" technology.

The Geysers produced about 20% of California's renewable energy in 2019.


For about 12,000 years, Native American tribes built steambaths at the Geysers and used the steam and hot water for healing purposes and cooking. When European Americans first entered the area, six Indian tribes inhabited the area around the Geysers, three bands of Pomo people, two bands of Wappo people, and the Lake Miwok people.The Wappo also collected sulfur which they called te'ke and a Wappo village, named tekena'ntsonoma (teke sulphur + nan well containing water + tso ground + no'ma village) was located about 12 miles southeast of Cloverdale and on the present-day Sulphur Creek. Today, Calpine Corporation generates power at the site and no Native American groups receive direct financial benefits from the operation.

The Geysers were first seen by European Americans and named in 1847 during John Fremont's survey of the Sierra Mountains and the Great Basin by William Bell Elliot who called the area "The Geysers," although the geothermal features he discovered were not technically geysers, but fumaroles.

Between 1848 and 1854, Archibald C. Godwin developed The Geysers into a spa named The Geysers Resort Hotel, which attracted tourists including Ulysses S. Grant, Theodore Roosevelt and Mark Twain. The resort declined in popularity in the mid 1880s, and rebranded itself to appeal to lower-income people. In 1938, the main building was destroyed in a landslide although the bar/restaurant, small cabins and the swimming pool stayed open, despite another fire in March 1957, until about 1979. In 1960, Pacific Gas and Electric began operation of their 11-megawatt geothermal electric plant at the Geysers. Unocal Corporation dismantled the remains of the resort in 1980.

Five of the Geysers facilities were damaged in the Valley Fire of September 2015, suffering "severe" damage to their cooling towers. The main power houses were not damaged. The Kincade Fire was reported burning at John Kincade Road and Burned Mountain Road in The Geysers, at 9:27 PM on October 23, 2019. The fire started at 9:24 PM during an extreme wind event, and subsequently burned 77,758 acres until the fire was fully contained on November 6.

The Geysers Geothermal Power Development project was designated as a California Historic Civil Engineering Landmark by the San Francisco Section of the American Society of Civil Engineers in 1976.

Geothermal development

The Geysers is the world's largest geothermal field spanning an area of around 30 square miles in Sonoma, Lake and Mendocino counties in California, centered in the area of Geyser Canyon and Cobb Mountain. Power from The Geysers provides electricity to Sonoma, Lake, Mendocino, Marin, and Napa counties. It is estimated that the development meets 60% of the power demand for the coastal region between the Golden Gate Bridge and the Oregon state line. Unlike most geothermal resources, the Geysers is a dry steam field which mainly produces superheated steam.

Steam used at The Geysers is produced from a greywacke sandstone reservoir, capped by a heterogeneous mix of low permeability rocks and underlain by a silicic intrusion. Gravity and seismic studies suggest that the source of heat for the steam reservoir is a large magma chamber over 4 miles beneath the surface, and greater than 8 miles in diameter.

The first geothermal wells drilled in Geyser Canyon were the first in the Western Hemisphere. The first power plant at the Geysers was privately developed by the owner of The Geysers Resort and opened in 1921, producing 250 kilowatts of power to light the resort. In 1960, Pacific Gas and Electric began operation of their 11-megawatt plant at the Geysers. The original turbine lasted for more than 30 years and produced 11 MW net power.

By 1999 the steam to power extraction had begun to deplete the Geysers steam field and production began to drop. However, since October 16, 1997, the Geysers steam field has been recharged by injection of treated sewage effluent, producing approximately 77 megawatts of capacity in 2004. The effluent is piped up to 50 miles (80 km) from its source at the Lake County Sanitation waste water treatment plants and added to the Geysers steam field via geothermal injection. In 2003, the City of Santa Rosa and Calpine Corporation partnered on constructing a 42-mile pipeline that became known at the Santa Rosa Geysers Recharge Project (SRGRP). Since 2003, SRGRP has delivered approximately 11 million gallons per day of tertiary treated wastewater to replenish The Geysers’ geothermal reservoir. In 2004, 85% of the effluent produced by four waste-water treatment plants serving 10 Lake County communities was diverted to the Geysers steam field. Injecting treated water into the Geysers field increases the amount of power that can be generated.

The injection of wastewater to the Geysers protects local waterways and Clear Lake by diverting effluent which used to be put into surface waters, and has produced electricity without releasing greenhouse gases into the atmosphere.

Geothermal power stations

Calpine owns 19 existing units, most of which were acquired from PG&E and Unocal Geothermal in 1999. NCPA Units 1-4 are jointly owned by the Northern California Power Agency (NCPA) and Silicon Valley Power. Bottle Rock is wholly owned by Bottle Rock Power LLC, a joint-venture between U.S. Renewables Group and Riverstone Holdings.

In addition, Ormat owns the plans for a new 30 MW geothermal power station at the vacant Calpine 15 site that were acquired through a merger with U.S. Geothermal in 2018. The plans were previously developed by Ram Power before being sold to U.S. Geothermal in 2014.

A steam pipe valve

Here's an article from Calpine's perspective:

Amid the Mayacamas Mountains in northwest California sits the world’s largest geothermal field: The Geysers.

Since 1960, steam from the 45 square mile field spanning Lake and Sonoma counties has been extracted to drive turbines and generate baseload renewable electricity.

Fifty years later, Houston-based Calpine Corporation operates 15 geothermal plants at The Geysers.

These plants generate up to 725 megawatts (MW) of clean energy daily, enough to power a city the size of San Francisco, making Calpine America’s largest geothermal power producer. “We are the largest independent wholesale power company in the United States in terms of power produced. Yet we have the smallest greenhouse gas footprint,” says Mike Rogers, Calpine’s regional vice president at The Geysers.

Renewable energy: 24/7

Rogers anticipates that The Geysers - and Calpine - will continue to provide sustainable and reliable power as The Golden State works towards its goal of generating 33 percent of its electricity from renewable sources by 2020.

“The around-the-clock availability of geothermal energy sets it apart from other renewable resources and makes The Geysers an environmentally-valuable baseload generation asset,”

he says. Baseload power plants generate energy at a constant rate and meet a given region’s continuous energy demand.

A new report by The American Council On Renewable Energy (ACORE) highlights the importance of geothermal power in California. In 2009, the state produced 13,023 gigawatt hours of energy through geothermal resources, more than any other renewable except hydropower.

Despite the rise of geothermal power production in California, Calpine’s road to success at The Geysers has not been a straight one.

Five years ago, sinking fuel prices and a $22 billion debt caused Calpine to file for Chapter 11. But the company is now on solid footing after employing some innovative financing techniques and securing longer-term power contracts.

A first: Wastewater to clean energy

Calpine’s re-emergence has enabled the company to focus on developing innovative geothermal technologies at The Geysers.

In the late 1990s, Calpine teamed with Lake County Sanitation District and Northern California Power Agency to build a 29-mile pipeline that currently pumps eight million gallons of recycled wastewater each day to recharge naturally-occurring steam reservoirs beneath the earth’s surface.

In 1989, Calpine purchased an interest in a 20 gigawatt facility at The Geysers. Within 10 years the company bought nearly all plants. Now, the Geysers operation provides 24 percent of California’s renewable energy, 40 percent of America’s geothermal power and employs 350 workers.

According to Rogers, the project had two distinct advantages: providing “an environmentally-sound wastewater discharge solution for neighboring cities, while also increasing the long-term productivity of The Geysers’ resource.”

Its success led to Calpine’s next wastewater recycling effort. “Soon thereafter, we developed a similar project with the City of Santa Rosa,” Rogers says.

The Santa Rosa project boosted geothermal energy production at The Geysers by about 85 MW and has a significant environmental impact for the city. The recharge pipeline “uses an average of 12 million gallons of wastewater a day,” notes Rogers.

Two projects, one goal: geothermal expansion

Rogers sees significant potential for expansion of geothermal energy at The Geysers as the company works on two projects partially financed by the Department of Energy’s Geothermal Technologies Program (GTP): an innovative exploration project and an Enhanced Geothermal System (EGS) demonstration.

In the exploration project - a portion of which received $5 million in Recovery Act funds -

Calpine and Lawrence Berkeley National Laboratory are partnering to create a 3-dimensional geologic model of Caldwell Ranch in Sonoma County that could reveal details about new steam reservoirs. This tool could be pivotal in future exploration to characterize geothermal resources.

After the model is built, Calpine seeks to re-open selected wells. The wells will then be deepened for injection and stimulated using treated wastewater from a new connection to the available Santa Rosa Geysers Recharge Pipeline.

“Steam from these wells would be piped to Calpine’s proposed Units 25 and 27, or the existing Eagle Rock Power Plant for use in electric generation,” Rogers says of the well project.

Calpine is also working on an Enhanced Geothermal Systems (EGS) project at the northwest Geysers with subsidiary CPN Wild Horse, Lawrence Berkeley National Laboratory and the U.S. Geological Survey.

The project – which received almost $5.5 million from GTP in 2008 – includes injecting cold water into one well and producing high temperature steam in the other.

The two projects illustrate Calpine’s commitment to geothermal technology, Rogers says. “Our research programs with Lawrence Berkeley National Laboratory exemplify Calpine’s diligence in expanding the potential of geothermal energy in our nation’s clean energy future.”

Back to the Golden Gate Bridge.

I started to walk across the bridge. I was doing ok until the chain link fence on the water side stopped about 1/3 mile into my walk. For some reason, that fence was my security blanket. Perhaps I will try again today?

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