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“The whole neighbourhood of Mount Saint Helena is full of sulphur and of boiling springs … and Calistoga itself seems to repose on a mere film above a boiling, subterranean lake.”

— Robert Louis Stevenson, “Silverado Squatters”

Gone are the steaming marshlands where, for generations, a series of small hot springs sent ethereal mists rising along the north end of the Napa Valley.

The land once known as the Springs Grounds today sits dry and partially developed with resorts and other uses in Calistoga. But beneath the surface, the scalding mineral water remains.

Calistogans have been tapping into the area’s geothermal aquifer for 150 years — filling spa pools with the heated fluids, bottling mineral waters for sale and in latter times drawing crowds to watch forceful geysers, one of which still regularly erupts from subterranean pressures.

The hot springs constitute both a natural wonder and a major piece of the town’s history. Without them, said Calistoga Mayor Chris Canning, “we wouldn’t be here.”

“Long before we had a wine industry, we had a spa industry,” said Canning, who doubles as executive director of the chamber of commerce.

Today the town of 5,200 is home to the largest hot springs resort area in the state, if not the nation. And town leaders point to new signs of economic progress, including the recent $23 million expansion of the Indian Springs Resort and the efforts underway to build two other luxury resorts in town.

The first attempt to commercialize the geothermal resource came when pioneer millionaire Samuel Brannan built an expansive 19th century resort at the Springs Grounds, which includes today’s Indian Springs Resort on Lincoln Avenue.

In 1862 Brannon held a gala opening for his destination, which included a hotel, cottages, steam rooms, mud baths, dance pavilion and racehorse track.

The developer later promoted the construction of a railroad from the Vallejo area that made it easier for his guests to travel to what was then a remote part of the state.

‘Calistoga of Sarafornia’

Brannan, whose early moneymaking ventures included selling high-priced goods to Gold Rush prospectors, reportedly had grasped Calistoga’s potential after visiting spa resorts in Europe and in Saratoga, N.Y. (Once when tipsy, he sought to say that he would replicate Saratoga in California, but instead he blurted that he would build the “Calistoga of Sarafornia.” Locals insist this slip of the tongue gave the town its name.)

The draw for visitors then was the same as it is today: the hot mineral waters and volcanic mud baths.

Native Americans are believed to have bathed in the surface springs for centuries, using the water and mud to relieve aches and pains.

The minerals in the water have “a natural calming element,” said Michael Lennon, general manager of the Calistoga Spa Hot Springs, a hotel and spa that includes four different hot pools fed by the underground aquifer.

“It will start to help you relax.”

Though scalding hot, the geothermal aquifer is classified by scientists as low to moderate temperature.

“We’re right at boiling which, compared to The Geysers, is pretty cool, believe it or not,” said Dean Enderlin, a geologist and fourth-generation Calistogan.

The surface temperature is typically near 212 degress Fahrenheit, but beneath the surface the water averages about 302 degrees.

The source that heats the water is believed to lie far beneath the surface from a magma chamber or chambers linked to past volcanic activity. A 1986 study for the state Energy Commission suggested that the intense heat boils water deep underground and sends it rising toward the surface via an earthquake fault zone that runs along the upper Napa Valley

Enderlin said the hot water becomes trapped beneath impermeable rocks but can rise when movement in the fault lines breaks the rocks.

Measure ground movements

The makeup of the underground system isn’t fully understood, said Shaul Hurwitz, a research hydrologists with the U.S. Geological Survey. What is known, he said, is that Calistoga lies less than 20 miles southeast of The Geysers, “which is probably the biggest geothermal field in the world.”

In 2009, Hurwitz joined professors and grad students from UC Berkeley for research at Calistoga’s Old Faithful Geyser of California. There they used sophisticated equipment to measure ground movement during eruptions.

“That was kind of a warm-up,” Hurwitz explained. The team went on to conduct similar experiments at Yellowstone National Park’s Old Faithful Geyser and in Chile as part of their research to better understand the activity of the nearly 1,000 natural geysers worldwide.

Brannan’s ownership of the Calistoga resort ended in the 1870s after he went through a divorce that drained his finances. He was forced to sell the property to former governor Leland Stanford.

When author Robert Louis Stevenson visited the town around 1880, he stayed at Brannan’s former resort, which by then had become the more modest “Springs Hotel” and cottages. By this time the town’s resort business had shriveled and would remain nearly dormant for decades before blossoming again in the 1920s.

A new type of transportation gets some credit for the revival.

“The advent of the automobile made more remote locations accessible,” said Enderlin, who also is a volunteer for the town’s Sharpsteen Museum.

By the time the tourists returned, Calistogans had managed to drill a number of wells, greatly increasing their ability to tap into the hot waters beneath them for various uses, including spas, mineral water bottling operations and a winery that sought water for washing wine barrels and tanks.

But the drilling occasionally created violent reactions when dissolved chemicals in the heated water caused the eruption of geysers.

“It’s kind of like shaking a champagne bottle and popping the cork,” Enderlin said.

The first such well was likely drilled during Brannan’s time in the late 1860s, according to a 1981 study by two geologists with what was then known as the California Division of Mines and Geology, now the California Geological Survey.

The drill rig reached a depth of 65 feet “when the boring instruments were blown out with tremendous force high into the air, as if some unseen power beneath was resenting the intrusion of mortals upon his domain,” according to an 1871 article in Bancroft’s “Tourist Guide.”

“The workmen ran for their lives and could not be induced to resume operations on any terms.”

Regular eruptions

Winery owner Ephriam Light had another well drilled in town around 1914. It resulted in a geyser that became known for its regular eruptions, resulting in benches being set up for viewing, according to the 1981 study.

And in 1928 a local well driller working at what is now the Indian Springs Resort on Lincoln Avenue had his equipment sent skyward by a geyser whose force was “estimated to be about one thousand pounds per square foot,” according to a 1946 book by resident I. C. Adams. Despite efforts to cap it, the geyser erupted continuously for several days.

“After much publicity in bay-area papers, the Springs Grounds was the goal of thousands of motorists for several days,” Adams wrote.

Finally the town’s firefighters succeeded in pumping enough cold water down the well to cool it and enable it to be capped off.

Only one erupting geyser remains in the valley today. The Old Faithful Geyser of California lies in the valley with expansive views of Mount St. Helena and rugged bluffs to the east known as the Palisades. More than 90,000 people visited the geyser in the past 12 months, said Koray Sanli, president and CEO of the company that owns the land.

In the middle of April, the geyser was spouting more than 30 feet in the air, with each eruption lasting about a minute. The interval between eruptions was roughly 5 to 10 minutes, but the timing can be affected by heavy rain and earthquakes, Sanli said.

“This place also has a reputation of being an earthquake predictor,” he said.

Exhibits include a 1992 Press Democrat story about a scientific study of how the eruption interval changes before a quake. The day before the August 2014 Napa quake, Sanli said, the interval between eruptions stretched to as long as one hour and 45 minutes.

Study questioned

In their 1981 study, the state geologists said the geyser resulted from a well drilled around 1915. Sanli, who took over the property about a year ago, questioned the accuracy of that statement and said he believed the geyser was a completely natural phenomenon.

But he added, “Even if drilled, at the end of the day it became one of the three old faithful geysers in the world,” adding it was so designated by the National Geographic Society. The other two are Yellowstone’s Old Faithful and the Pohuto Geyser in New Zealand.

During the 1920s, the Springs Grounds in the southern part of town essentially dried up, possibly due to the wells that tapped into the hot water.

A significant amount of water has been extracted over the decades. The California Energy Commission estimated in 1986 that Calistoga’s spas and mineral bottling water companies drew more than 55 million gallons a year from the geothermal aquifer.

Even so, the authors predicted the underground reservoir still had a usable life of 100 years.

Since that time, the town’s two remaining bottling companies have greatly reduced their extractions.

The Calistoga Mineral Water Company still removes a limited amount of water but bottles it elsewhere, said Canning, and the Crystal Geysers Water Co. bottles water in Calistoga that it hauls in from outside the town.

The 1986 study noted that the geothermal fluids typically contain high concentrations of boron, chloride and fluoride, plus low concentrations of sulfate, iron and bicarbonate. All those minerals have an incredible ability to crystallize into jagged clumps within the water pipes.

Change piping

John Merchant, owner of Indian Springs, said his staff has to change piping from their wells every five to eight months. The resort cuts up the partially clogged pipes and sells pieces to guests as curiosity items.

At the nearby Calistoga Hot Springs Resort, the owners have done a complete renovation in the past four years, said Lennon, the general manager.

“We still are genuine to what people used to come to Calistoga for,” he said, which includes spa treatments and the chance to relax in and by the heated waters.

Hotel guests and day users can enjoy the resort’s four linked pools, through which the heated water flows and gradually cools.

It first enters a jacuzzi pool kept at 104 degrees Fahrenheit, then flows into a soaking pool, a lap pool and finally a children’s wading pool.

In Calistoga, the challenge isn’t in heating the water but in making it sure it’s cool enough for the swimmers.

Al Derrick, a volunteer at the town’s museum, said that also was the case in the 1940s, when he and other high school students went together to swim on the former Springs Grounds at Pacheteau Baths, now part of the Indian Springs Resort.

The main pool got topped off in the spring, but the heated mineral waters still needed time to cool, Derrick recalled.

“We had to wait a week after they filled it.”

You can reach Staff Writer Robert Digitale at 521-5285 or robert.digitale@pressdemocrat.com. On Twitter @rdigit

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