Tour the Geysers geothermal field

On an overcast morning early last month, a group of 15 people met in tiny Middletown in Lake County for a unique experience — a tour of the rarity that is the power-producing Geysers geothermal field.

The Geysers, covering 45 miles within the Mayacamas Mountains, is home to the largest complex of geothermal power plants on Earth.

Calpine Corporation, which hosts these tours, is the biggest geothermal power producer in the United States. Calpine owns 13 geothermal power plants at The Geysers and can generate up to 725 megawatts of energy around the clock.

The tours, which include touring a Calpine power plant, will restart in April, but they do fill up. So be advised — on Jan. 3, tickets will open for the 2022 tours.

Our tour group was met at the visitor center by Danielle Matthews Seperas, Calpine’s director of government and community affairs, and Tim Conant, Calpine geothermal mechanical engineer. We boarded the small tour bus, with borrowed hard hats in hand, and headed up Highway 175.

Just past the village of Anderson Springs, we started uphill through hairpin turns to The Geysers geothermal field. The mountains retain much of their magnificent beauty and grandeur, with mixed evergreen forests and California chaparral and woodland, after making a comeback from recent wildfires such as 2015’s Valley fire that burned more than 76,000 acres and nearly 2,000 structures and the Kincade fire in 2019 that was similarly devastating.

Our first stop was the Sonoma Overlook. The dips, peaks and dramatic crags of the Mayacamas Mountains are more pronounced after the Valley fire exposed so much of the mountains’ countenance.

“On clear days, you can see the ocean from here,” Seperas said.

“This stop is also known as ‘Little Alaska,’ since it gets so cold and windy in winter,” Conant added. We were driving over 24-inch effluent pipes that originated in Santa Rosa, he said. A maze of monster-size 48-inch pipes, made of carbon steel, ran up the side of the road.

Next up was the Burned Mountain fumaroles, openings in the Earth’s crust that emit steam and gases. Here we were reminded that Earth has a fire in its belly — water meets the super-heated rock below the surface, and steam rises up through the fumaroles and all along both sides of the road.

It was surprising to learn that a perennial native grass, geysers dicanthelium, thrives in the sulfuric, heated environment here. This area proves too hot for most plants to handle; however, this hardy grass has found a way to make use of the hot steam vents.

After the grass seeds have dispersed, the plants germinate at high temperatures. Other flora that have evolved to thrive in the greenish serpentine and red volcanic rock soils of The Geysers’ ridges include glandular western flax, snow mountain buckwheat and Morrison’s jewel flower, which pay no heed to the low calcium and high heavy metals of these unique soils.

A history of electricity

The first electricity was generated at The Geysers in the 1920s, when John C. Grant used a small steam-engine generator to produce the electricity. He acquired a lease for The Geysers Resort and hoped to generate electrical power from steam to sell to Healdsburg and Cloverdale.

Beginning in the 1950s, the rocky outcrops at The Geysers sported a crazy-quilt of steam-drilling companies. Today, the Calpine Corporation is the predominant drilling company, with about 300 employees.

During the 1970s and 1980s, the water in Earth’s reservoir proved to have limits, forcing out some drilling companies. Steam pressure to the power plants decreased, as more steam was directed to the power plants than could be replaced in The Geysers natural reservoirs.

In a win-win to allow for a continued abundance of steam to flow and to solve Lake and Sonoma counties’ wastewater dilemmas, two large-scale wastewater injection projects were created. In 1990, Geysers operators, Lake County and the California Energy Commission collaborated to identify a source of wastewater from Lake County. The project is called the Southeast Geysers Effluent Pipeline and now includes 40 miles of pipeline to deliver effluent to The Geysers.

The second effluent project, the Santa Rosa Geysers Recharge Project, brings wastewater from the vicinity of Santa Rosa to The Geysers via a 42-mile pipeline.

Roughly 20 million gallons of reclaimed water each day is injected into The Geysers reservoir. The intense heat of the reservoir rocks underground converts that water to steam to help replace the initial reservoir steam going to the power plants.

How it works

Geothermal power plants are ingeniously designed to harness pressurized steam taken from the naturally occurring steam field reservoirs 5 to 10 miles beneath the Earth’s surface. The subterranean magma chamber heats groundwater to boiling, forcing up the steam.

The steam is captured through insulated steel pipelines, then it rushes into powerful turbines, allowing it to expand then drive generators to create green, renewable energy for homes and businesses in Northern California.

The Geysers satisfies the power needs of much of Mendocino, Sonoma and Lake counties, along with a share of Marin and Napa counties, too.

Riding up the mountain, it’s easy to imagine being conveyed up here in the good old days by way of stage coach, keeping a watchful eye out for Black Bart who, it is said, was known to hide out here. Instead of rustic campgrounds or a quaint hotel, we are looking at impressive and powerful equipment designed for the 21st century. The streamlined, modern power plants are humming with computers and equipment which requires specialized training to operate.

During the tour, we got whiffs of the rotten egg smell of sulfur, wafting through the air high in the mountains and present in the geothermal field. Conant said he’s used to the odor of sulfur and can no longer detect it.

“I learned about a Geysers tour through a UC Davis class I was taking many years ago,” Conant said. “On that tour, I learned that it’s a beautiful place to work. It was sunny with patches of snow when I first came up.”

Healing waters

Although the Geysers’ name implies that water erupts from a column beneath the Earth, no actual geysers exist in The Geysers geothermal field. The Geysers got its name from early explorers who noted the fumarolic activity, with steam rising from the area’s hot springs.

Born around a million years ago, The Geysers holds layers of rock, including graywacke, serpentinite and argillite, which sit above magma layered with fractures, allowing water to heat up naturally to create hot springs and fumaroles.

Archaeologists have determined that over 12,000 years ago, the trails open to Southern, Eastern and Central Pomo Indians as well as the Northern and Western Wappo and the Lake Miwok people crisscrossed The Geysers. While some trails led them to fumaroles and healing hot springs, others guided them to favored hunting and gathering places.

The eastern section of The Geysers, called Castle Rock Springs, was favored by the Lake Miwok people for its hot springs. Wappo lands included the area of The Big Geysers, where they took advantage of the hot springs adjacent to Big Sulphur Creek, and where, later, The Geysers Resort Hotel was built.

The Wappo people also collected sulfur salt here, mixing it with ash from burnt cow parsnip stems, more than likely as a medicine. Each group spoke a different language and held their own belief systems. The Geysers was used as a gathering place and spiritual oasis for millennia. Some native people built willow huts over steam jets where they sat for medicinal purposes.

In the 1840s, the first tourists began camping at The Geysers and 1854, construction of the Geysers Resort Hotel began. Hot springs like Harbin Hot Spring became popular for a time, with tourists coming to “take on the waters.”

The Calpine Geothermal Visitor Center in Middletown is a great educational destination in itself, but it’s currently only open on tour days. The center’s interactive displays interpret the geothermal energy process, the geology and history of The Geysers. Perhaps the biggest highlight is the real-time and historic seismic data on display and the interactive topographical model portraying Calpine’s wells, power plants and steam injection pipelines.

The Geysers and Calpine’s Geothermal Visitor Center are highly engaging places that honor the unique history of the area and of geothermal power, part of the stories of Lake and Sonoma counties.