Cerro Prieto, the world’s third-largest geothermal field

Eighteen miles southeast of Mexicali

Who among us has not twitched a little during this, the year of California’s power crisis, upon hearing Tales of the End Time of the Fossil Fuel. For more than a billion years, the planet’s organic matter has laid down its life to form combustible sumps of oil, gas, and coal. And now, petroleum engineers predict, the cache is dwindling — lo, accelerating its dwindling — as we dig and siphon more of that cache every day. Here is the prognosis again, in case you missed it. At present rates of consumption, recoverable world coal reserves will last no more than 1000 years. U.S. coal reserves will last us 275 years. Recoverable world oil and natural gas reserves will last between 100 and 200 years. U.S. oil and gas reserves, between 50 and 75; that is, without Alaska and without West Coast offshore drilling. Such temporal abstractions leave most Americans unmoved. What drives us is not the reckoning with what’s left but the challenge of getting at it. That we’re good at. From oil rigs crowding the Gulf of Mexico to vast coal-mine pits in the Midwest, we have a century-long record of developing technology to recover what’s recoverable with scant development of renewable sources like solar power.

For the moment, let’s forget technology and its hold upon us. In terms of supply alone, there is one energy source — renewable and recoverable — whose reserves dwarf projections for oil, gas, and coal: geothermal energy, which exists as heat, hot water, and steam buried in the earth. In the upper six miles of rock beneath the contiguous United States, there is approximately 6000 times the energy contained in the world’s oil reserves. Six thousand times more. Since geothermal energy has no CO2 emissions and is almost entirely renewable, this may as well be forever. The multiple reaches its apogee because water, the conveyor of geothermal heat, is self-renewing.

What is San Diego’s connection to the heat beneath? Beyond the gentle mountains of our coastal range lies the Colorado Desert and its centerpiece, the Imperial Valley. Underneath the Valley’s half-million acres, which on the surface is a below-sea-level, furnace-hot, irrigated paradise for agriculture, there’s a reclusive geologic giant, water boiling deep in the cauldron of the Salton Trough, hot enough to supply an epoch of energy needs. The trick is, of course, to get the heat out. Plumbing the trough’s depths are three multiplant geothermal-power operations — one east of Holtville on the Valley’s East Mesa, going toward Yuma; one in Heber, south of El Centro; and one north of Westmorland, a gull’s quick commute from the Salton Sea. Groundwater a mile down, heated by the magma, is brought to the surface and sent through an intestinal array of pipes, pressures, and processes that spin turbines and generate volts. Once spent, the geothermal fluid, or brine, is returned to its underground reservoir via injection wells, a cyclical dance that on a grander scale might make the Saudis nervous. But geothermal production is hardly full-blown. The Valley is making 540 megawatts of electricity, enough to power 540,000 homes. Valley generators do not sell to San Diego Gas and Electric — still, at 2.5 people per home, 540 megawatts represents nearly half of San Diego County’s residents. Twelve percent of California’s electricity comes from renewables like small hydroelectric, biomass, wind, solar, and geothermal. The fossil fuels rule now, but the renewables are the future.

Eighteen miles southeast of Mexicali, Mexico, is Cerro Prieto, the world’s third-largest geothermal field. Its three plants make 600 megawatts of electricity for northern Baja. I received permission by phone to visit the plant from a woman at the visitors’ center who said, “Please come. A man will show you around.” I sent a letter, outlining my journalistic business, and a geologist friend and I drove the 135 miles. At the plant gate, we were pointed from one guard-in-a-little-house to another with ¿Qué quieren ustedes? until we were told the interview and tour were canceled. Back home I got a terse e-mail from the woman saying that according to Mexico City headquarters, Comisión Federal de Electricidad, access to control rooms and wellheads was denied. Since then I’ve learned the probable reason: The state-owned electric utility rarely monitors its pollution. Apparently Cerro Prieto’s energy jefes don’t want any journalist investigating the plant, especially now that Baja is exporting power to the United States.


Sergio Cabañas is a solemn-faced man with distinctive wisps of gray in a black mustache. He’s formal and confessional, moving easily from one temper to the other. An environmental engineer with Covanta Energy in Heber, he is also a son of the border. Cabañas, like much of the Imperial Valley’s history, embodies that memorable line of poet Guillermo Gómez-Peña: “The border is the juncture, not the edge.” Born in San Diego, Cabañas was raised in Mexicali, Mexico’s ever-booming Valley border town. Owning dual citizenship, he returned for high school to Calexico, Mexicali’s sister city on this side. (Partaking of each other’s name exemplifies juncture.) Cabañas describes himself then as “miserable,” because he didn’t fit in. There was a backlash from “my own people. I was not a lowrider; I was not a cholo.” He was more dedicated to study than, as he says, some of his Chicano brothers “over here.” Disgruntled, he enrolled in Mexico City’s Universidad Nacional Autónoma de México, one of the oldest and largest schools in the Americas. With a degree in biochemistry, Cabañas returned to Mexicali just in time for (what seems) the peso’s decennial devaluation: A cousin working at Vons in Calexico was making more money than he was as a freelance chemist.

In the late 1970s, the bilingual Cabañas again studied biochemistry, this time at San Diego State, for two reasons. He needed to take additional courses in California to have his Mexico degree recognized for employment here, and he hoped to get up to speed with biochemistry’s newest technology. He half-smiles, remembering the atomic absorption machine at State, “right out of a movie and a mad scientist’s lab.” But, to continue, he needed a school loan. With a large check in hand he asked his counselor, “What do I do with this?” Pay for your books, tuition, rent, he was told. In class, when Cabañas saw the girls at State, he thought he’d “died and gone to heaven.” In Mexico, students dress formally for class; in San Diego, both sexes sometimes show up in bathing suits. The shock of easy money and drafty clothing was too much. “That first year, I used to sit down and cry,” he remembers. “Did I make a mistake by leaving Mexico?”

In 1982, with a U.S. degree in biochem, he was drawn once more to the Valley. His father was ill in Mexicali, and the economy had buoyed. He got a job in an agricultural laboratory in Brawley, testing the chemicals in ag soils and the deep-seated brine being brought up by the fledgling geothermal industry. “Man, we made money in that lab, left and right, running silicas, irons, you name it.” With reservoir research bubbling, Cabañas eventually became head chemist for San Diego Gas and Electric’s only foray into geothermal energy, a small experimental plant, now an abandoned hulk (For Sale) down the road from Heber’s two plants. He worked for Magma Power Company at two projects in the East Mesa and since 1988 has worked at Ogden Geothermal, which earlier this year changed its name to Covanta.

In a spare office of a nondescript, well-insulated metal building, Cabañas recounts the history of the Valley’s geothermal plants, which, after decades of experimental development, became commercially viable in 1979. Engineers at first sent the fluid directly into a turbine, with limited success. Because the Imperial Valley geothermal brine is highly mineralized, silica (the most abundant mineral), calcium carbonate (the material of seashells), and other minerals stuck to the turbine blades as well as stuck to and clogged — like the buildup of plaque from bad cholesterol on our arterial walls — the well pipes themselves. Weighed down with gunk, the turbine blades eventually slowed and inevitably needed replacing.

Next, the geothermal industry developed “flash” technology, which is still employed at one of Heber’s plants. Flashing occurs when the highly pressurized hot water is brought up a production well and its pressure is suddenly lowered inside a separator, or flash tank. The lower pressure causes part of the water to flash, that is, to boil, or rapidly vaporize, and turn to steam. Routed into the turbine, the steam then drives the blades. Brine is often flashed twice. The first flash takes place in a high-pressure separator, and the second flash occurs in a low-pressure separator. After two cycles, called “dual-flash,” the spent brine is routed out of the plant and injected into the ground.

In 1993, Covanta decided to change one of its plants from a flash system to a binary, or heat-exchange, system and contracted Ormat, an Israeli company, to build the new operation. Binary technology provides greater efficiency than flashing. Now, instead of flashing the brine, the process transfers, or exchanges, the heat from the brine to another liquid, isopentane, which, at 82 degrees Fahrenheit, converts to a gas. The function recalls those standing steam radiators in old hotel rooms: Pipes full of hot brine heat the isopentane that flows around those pipes and then, as a gas, the isopentane is pulled through the turbine. There are two advantages to this new technology. One, the hot geothermal fluid can easily boil the isopentane. Two, the turbine blades, turned by the gas, do not corrode.

Covanta’s two plants — dual-flash and binary — are fed by 25 production wells. In a full-windowed room that looks onto the 12-acre dual-flash plant (the room is “decorated,” as geothermal engineers seem destined to do, with aerial photos of geothermal facilities), plant manager Byron Jensen says there is a 4000- to 6000-foot “optimal” range underground from which Covanta gets fluid at around 330 degrees. The original wells drilled by Chevron in the 1980s were deep — some down to 10,000 feet. Chevron drilled with “an oil-field mentality,” Jensen says. Mentality as in rapacious and random. Modern drilling technology is to go straight down or go straight down, then angle toward the source, termed directional drilling. The point is to go “as shallow as you can get away with,” Jensen says. For brine close to the surface, the company uses a slotted liner, a pipe with an angled cut at the bottom that sucks up fluid from only one point. “It’s cheaper, it’s faster, and it works better.” The other kind of pipe is perforated, that is, punctured with inch-wide holes. These holes allow fluid to leach in over less saturated expanses of the reservoir rock.

Because the land on top of the reservoir is 95 percent cultivated, engineers have perfected directional drilling. A whipstock bit permits a drill by minute turns to go in any direction. Later, to observe a directional well, Cabañas has my friend and me stand above one such well on an iron-grate platform. The heat wafts up in moiré patterns. Sun above and heat below, there’s no escape. Luckily these beefy pipes are wrapped with insulation like those pudgy blankets that enclose hot-water heaters. Hot is key. The higher the temp, the less the silica will crystallize. Cabañas reads from a metal plaque, fence-wire-tied to the fence: “This is Heber Geothermal Unit Number 7,” he says. “The total perforation [pipe punctured with inch-wide holes] is 5444 feet. At 3557 feet all the way to 5444 feet, the pipe is trying to pull in water. At 1137 feet the pipe starts going in a new direction,” angling toward its target. Before us is a temperature meter with a glass face and a dial. A needle quivers yet holds its point at 300 degrees.

Covanta’s computerized control room stands watch before the new 40-acre binary plant. Shift supervisor Jorge Nozot and control operator Manuel Mendoza monitor a bank of computers that display an elegant, neon-colored flow chart. The visual tracking system shows the heat-exchange system. The diagramming is complex, but the color coding helps us follow two routes. In red courses the ever-new brine, coming in, circulating, and being returned to the earth. In green runs the forever-cycling isopentane. Like Cabañas, Nozot reads the dial aloud: “We’re pulling in 15,000 gallons of fluid per minute from 11 production wells at 328 degrees Fahrenheit.”

Outside on a walking tour, we follow Mendoza as he hollers, points, waves us past the recycling, metamorphic journeys of fluid and gas. A geothermal plant resembles the dense circuitry of a silicon chip, but writ large. It is formally intoxicating, this terracing and tracking-back-upon-itself complexity of pipes and ducts, turbines and vents, pumps and tanks and smokestacks, in diameters from three inches to six feet, in harsh browns and harsher rusts. (Some readers know the 3D Pipes of Microsoft’s screen saver, an apt if hyperbolical depiction.) Pipes in the fields (we view them later on a driving tour) are simpler to grok. From multiple wellheads scattered over a two-mile radius, these pipes, some as large as tractor tires, run parallel to the Valley’s irrigation ditches. At Heber there are more than 50 miles of pipe, painted green where they pass through fields and brown where they hug dirt and paved roads.

A troop of Dick Nixons, we stoop-shoulder behind Mendoza through the screaming hiss, the nagging whine, the sibilant whistling — from where, I’m not sure: vented steam? escaping gas? pipes wearing thin? “We don’t want to expose that isopentane to the atmosphere,” Mendoza yells over the noise. “It’s bad, man.” Bad as in explosion and fire. The smallest of the straight-then-right-angled pipes is one that channels water to thousands of sprinkler heads, poised to flood the works “in case of emergency.” Mendoza asks if we want to taste the brine, then fetches us a Styrofoam cupful. It’s as salty as beer nuts and gray like the hard water from a desert hot spring.

Cabañas drives us to lunch on roads aligned ruler-straight to utility wires, irrigation canals, corn rows. Beneath us is the largest concentration of hot-water reservoirs in America. And yet the monotony of the farmland and the relentlessness of the sun preoccupies us until, strangely, our senses find the singularities. On this spring day the pithy smell of onions floats in from the fields. From Cerro Prieto a soft wind delivers the faint malodor of hydrogen sulfide, or rotten eggs. Wafting by from lowing feedlots is the reek of cow dung. Pure sights abound. On a telephone line a kestrel waits for a rat’s dash beside the concrete-V irrigation ditch. The canal at regular intervals is stanched by trapezoidal sluice gates with screw-turn handles to divert water into the fields. The rushing, clear, abundant water in these ditches seems flagrantly detached from, sumptuously superior to, the heat.

An unexpected curve in the road signals Camacho’s Mexican Restaurant, shaded by a grove of tamarisk. Food arrives, and Cabañas tosses his foil-wrapped tortilla to the side, yet another heat source whose release he won’t bother with. He digs into a platter of beans and rice, enchiladas with cheese, and albóndigas (meatballs). About us are signed photos of the Blue Angels who train in nearby Seeley, photocopied news stories about Camacho’s staying power (serving tamales since 1946), and the wiped-clean sheen of checkerboard vinyl tablecloths. Tables for four or more. None for two; intimacy is less important. In California’s poorest county, where unemployment averages 25 percent, in one of California’s three hottest counties, where temperatures pass 100 degrees 110 days a year, this is a land of sticking together. Like the minerals in the brine. Like the immigrants who forged a trail across the Valley in 1849.

We huddle closer. Cabañas says, after moving back and forth from border towns to San Diego, “The Valley is my home now.” In Mexicali, where he grew up, things are going well, he notes. These days the U.S.-financed maquiladoras employ thousands of young Mexican women, chiefly for the dexterity of their hands. They’ve supercharged Mexicali’s economy. Cabañas lists the benefits: child care, doctor and nurse on staff, free bus rides to and from work, air conditioning, the highest minimum wage in Mexico. In one generation, such work is transforming the Mexican female from housebound daughter to independent woman. Some contend that the greedy are exploiting their labor. For Cabañas, at 46, his life a testament, the border encourages work and engenders opportunity. A juncture, not an edge.


The Imperial Valley is the midriff sink of the Colorado Desert, which runs 164 miles from the San Gorgonio Pass to the Colorado River delta at the northern end of the Gulf of California. The desert is part of the Salton Trough, a peculiar geological feature, something no one expects to be that low — well below sea level — and that close to the coastal mountains, whose erosion would normally fill it with deposits faster than those deposits themselves would erode. No, the Salton Trough is sinking faster than it’s filling. And to understand the sinking — and the consequent heating of the groundwater in the geothermal reservoir — one needs a quick tour of plate tectonics. Providing this is University of San Diego hydrothermal geochemist Anne Sturz. As head of the college’s Marine and Environmental Studies program, she describes her research calling as “hot-rock, hot-water analysis.”

The theory of plate tectonics holds that the earth is covered by 20 or so rigid crustal plates, oceanic and continental, that make up the lithosphere. These massive slabs move relative to one another atop the magma’s roof, the asthenosphere, whose consistency, Sturz says, is like “very hot Silly Putty.” At junctions where the plates meet, they create “hot spots,” or spreading zones. Locally, in geologic terms, our “hot spot” is the zone between the East Pacific Rise (the eastern edge of the vast Pacific Plate) and the continental North American Plate. South of Baja’s tip and next to mainland Mexico is a trench, which for 14 million years has been pulled apart by the movement of crustal plates. It is this widening trench that has pushed Baja California away from Mexico and allowed ocean water into the divide, creating the Gulf of California. At the northern end of the Gulf and under the Salton Trough, the rifting continues as well, an inch or two per year.

Though the East Pacific Rise is pulling away from the North American Plate under the Gulf of California, the cause of their separation is located more than 8000 miles away, one-third of the globe’s circumference. There, near the Philippines, the western edge of the Pacific Plate is being dragged down into the mantle. Sturz clears a corner of her desk to show how this happens. She touches the edges of two sheets of paper, then pulls the opposite edge of one piece off the desk’s edge, thus opening a gap between the sheets. She notes that geologists aren’t sure whether the plate is going down into the mantle by its own weight or by convection currents — “sort of like boiling oatmeal,” she says — an abyssal churning by which an opening to the mantle causes more heat to rise and, in turn, more plate to melt.

Illustrating the tensional pull-apart features of the Salton Trough, Sturz gathers opposing sides of her floor-length denim dress on her lap. She pulls and a basin forms. She skews the pulled area, and the basin gets a tad deeper. Her point: The more the plates stretch apart diagonally, the deeper they yield to the hot rock in the asthenosphere. More gap also means more upwardly mobile heat.

Sedimentation has also helped form the trough. This terrestrial phenomenon is limned in William deBuys’s magnificent Salt Dreams: Land & Water in Low-Down California: “When one gazes into the Grand Canyon and wonders where the content of such a mighty rent in the earth’s crust might have gone, the answer, simply, is downstream. The soils of the Imperial Valley, the clays beneath the Salton Sea, the plain on which Mexicali sprawls, and all the salinizing fields southward, down to the mudflats at tidewater and the sea bottom off San Felipe — all these are the anti-Canyon of North America.”

As quakes inched the trough downward and northward, four to five million years of Colorado River deposits inched up a delta, cordoning off a large northern bay from the Gulf of California. In the trough north of the delta, marine sediments were already present. River deposits continued to bed. And, owing to the buildup of the delta itself, at least four epochal floods of the Colorado River occurred, diverting the river into the trough and creating a freshwater lake each time. Lacustrine deposits from those lakes — the most recent, occupied by native peoples beginning in 1100 A.C.E., was Lake Cahuilla — also joined the layering of sediments. (It’s easy to find remains of Lake Cahuilla’s wave-cut shoreline by walking the higher east or west edges of the Imperial Valley: The ground is littered with tiny coiled shells, or mollusks, once windrowed onto an ancient shore.) Finally, because the Colorado River delta in prehistoric time seldom rose higher than 13 feet above sea level (today it’s about 40), marine water overtopped the delta as often as the Colorado River flooded in.

Further complicating the trough is the force of volcanism. When plates pull apart and the pressure that’s created between them subsides, the new disposition causes rocks to melt. (Heat always moves from hotter to colder regions.) After rocks melt, their melt rises and, on occasion, forms volcanoes. Evidence of volcanism in the trough are the 10,000-year-old rhyolite domes at Red Hill, on the south end of the sea. Fine-grained rhyolite often shows flow lines etched by its volcanic origin. Nearby Red Hill is Obsidian Butte. That shiny black rock is also known as volcanic glass.

For several million years, volcanic rock as well as marine, deltaic, and lacustrine sediments have compacted, under great pressure and heat, to form the trough’s prevailing rock, sandstone. Sandstone (sand bonded by silica) continues to circulate the ancient water of the Gulf of California. It’s four miles deep now, and the upper mile makes up the geothermal reservoir. Sealing the reservoir is an impermeable lid of hardened clay, which means neither sea nor river nor irrigation nor rainwater percolates down. The water underneath the clay has remained and keeps moving because the sandstone is both porous and permeable. Though Salton Trough sandstone is made of coarse grains that are compressed, the rock is also a sponge. “Put water on it,” one reservoir engineer told me, “and the rock will absorb it in ten minutes.”

Sturz: “Porosity is the holes, the voids, between all the little particles of rock. Permeability is the interconnectedness of those holes. If, for example, you have basalt that’s got a bunch of holes in it from gas bubbles but each individual hole is not connected to the others, it has high porosity but no permeability. Sandstone is made of little grains that may be next to each other but [preserves] spaces in between, so it has high porosity. Sandstones make good reservoirs because they have high porosity and high permeability.”

Finally, there’s more to add about the active faulting of the Salton Trough. The San Andreas Fault ends on the northeast side of the Valley; the San Jacinto fault zone (a more active system) runs partway along the western edge. (Every day, Cabañas told me, the Valley has earthquakes, though most are minor and barely register in one’s feet.) With a phalanx of smaller faults like the Imperial Fault in the Valley itself, the San Andreas is the largest fracture in a system of many faults that connect and parallel their way down to the Gulf of California, where the Gulf’s sea-floor spreading, in turn, activates all of them. The plates continue to strike-slip northward at the same time they help spread and lower the Valley. Such a seismic history, according to Sturz, actually makes the Salton Trough a graben, or a fault-bounded basin. (San Diego, the coastal range, and Baja California have split off from the North American Plate. San Diego’s terra firma is now part of the Northern Pacific Plate, headed toward San Francisco: Arrival time, about 12 million years.) Because of this seismicity, there are more fractures in the trough’s sandstone and in the rock beneath the sandstone. Increased faulting increases permeability.


Another day, still in spring, my friend and I drive the drag-strip-straight Forrester Road, north from Heber, bypassing El Centro and Brawley, through Westmorland and its lone stop light, where irrigation-equipment trucks deepen the chuckholes with each rumbling stop. We pass fields of carrots and lettuce and onions; melons and sorghum and wheat; sugar beets and Bermuda grass; the Valley’s king crop, alfalfa, to feed the cows, and on by interposing red, white, purple rows of larkspur. Farmworkers stoop in hives of labor, boxing cabbage, their site “factories in the fields,” as journalist Carey McWilliams once named them. Flocks of redwing blackbirds race in mad clusters from crop to crop. We pass unchained stacks of field irrigation pipe, their ends T’ed with pipe stubs and topped with brass impulse sprinklers. Along the way the air is ripe with the tang of fertilizer and ammonia, then a swampy humidity from the approaching Salton Sea. Faint, in the low dusky distances, the color of tofu, are the Valley’s west and east rises, the Fish Creek Mountains and the Chocolate Mountains. Irrigation and aridity, sky and sand, people and their absence — the contrasts invite, seduce, enthrall.

We arrive at CalEnergy’s geothermal operation, to speak with Cabañas’s counterpart, land manager Vince Signorotti. The youthful, affable Signorotti began his sojourn in geothermal by working 12 years for Unocal in the Geysers project, a plant in Northern California that generates electricity by using only dry steam from the geysers. He landed in the Imperial Valley in 1988, thinking he’d stay a few years. He hoped to be transferred out of the heat, but, he says, things seldom go as planned. Like Cabañas, Signorotti moved laterally to the Magma Power Company, then stayed on following a hostile takeover in 1993 of Magma by CalEnergy. (He was the only one of 36 who was retained.) Signorotti is in charge of CalEnergy’s 3000 owned acres. He’s also in charge of 20,000 acres of land whose subsurface mineral rights CalEnergy leases from vegetable growers or the Imperial Irrigation District, which owns the land under the sea. There is a distinction between what’s on top and what’s below, but typically when one leases mineral rights, Signorotti says, the law allows one “reasonable use of the surface to develop those minerals.”

Because his manner is easy and his explanations unscientific (he often stops and simplifies the recondite language of geothermalese), the company recently “anointed” him its spokesman. He’s plied a tide of reporters this year. They’ve called wanting to know how the small operators — from which, according to a 1978 government mandate, the utilities must purchase power and from which California gets 30 percent of its electricity — are handling the power crisis. Just fine, he tells them, despite Southern California Edison’s overdue bill of $120 million. From November 2000 until late March, Edison did not pay CalEnergy for its product. In April, a judge freed CalEnergy from its contract with Edison. CalEnergy began selling, at a better rate, to El Paso Merchant Energy and, as far as Signorotti knows, the volts stayed in California. In June, Edison filed suit against CalEnergy to force them to honor the 30-year contract. In late June, CalEnergy agreed with Edison on a payment schedule (with interest) for Edison’s $120 million debt. In exchange, CalEnergy began selling its power to the utility at a price guaranteed by the old contract.

About 30 percent of the reservoir CalEnergy taps lies under the Salton Sea and must be got at directionally. As world fluids go, Signorotti says, this brine is unique because most geothermal fields lie within volcanic rock, not young sediments. Another anomaly, this fluid is hotter than most, up to 600 degrees. And it is sodden with salt: brine from the Salton Sea reservoir contains 25 to 30 percent dissolved solids, whereas the Heber fluid is salty but only at 8 to 10 percent. (One geologist told me, “Imagine a mariner who doesn’t clean his tools. The salt is going to corrode them. Now imagine the Salton Sea reservoir, seven times saltier than seawater, corroding them.”) Heber’s and Holtville’s brine is not really brine, Signorotti says. “It’s drinking water by comparison.” In the Salton Sea fluid, silica, chlorides (calcium and sodium), and zinc are suspended. In fact, almost every element of the 88 that occur in nature (some in infinitesimal quantities) can be detected here.

Early on, engineers at Magma Power found that even steam drawn off the Salton Sea brine contained enough silica to gum up the turbine. A desalinizing discovery came in 1980 when chemist John Featherstone observed silica attaching itself to previously precipitated crystals of silica. Featherstone added these crystals to the brine in a crystallizer — before the brine was flashed — and this crystallized silica pulled out much of its cousin, the brine’s silica. The brine’s solids were reduced by half.

One by-product of a long-term contract is money up front to buy the expensive alloys that Signorotti says CalEnergy must use on its pipes. He draws a diagram of what’s called “standard well-drilling technology.” To bring material to the surface, one must “put a straw in the reservoir.” This is accomplished by a series of progressively narrower straws, or concentric casings, fitted one inside the other, to a depth, on average, of 2000 feet. After the outer casing is set, the next “string of tubing,” say 300 feet worth, is sunk deeper and cemented to the tube around it. Imagine each smaller straw being held in place by the slightly wider straw above it. The last straw, at 9 5/8 inches in diameter, is made with titanium and runs $1000 a foot. There might be 1000 feet of titanium pipe, a $1 million straw. At the bottom of the production well is a “shoe” that sits on top of the reservoir. The pipe is not perforated, as it is in the Heber field. Instead, the pipe is slot-cut at the bottom where the boiling brine rushes in.

The brine’s Jekyll-and-Hyde character comes clear when Signorotti hoists a ravaged chunk of 18-inch pipe for our inspection. This 3/4-inch-thick, carbon-steel pipe spent years in a production well before it was replaced. On one side there’s a small tear-shaped hole where the fluid wore the steel away. On the opposite side is an elegant excrescence of silica, as large and warty as a witch’s nose, bonded to the pipe. A mad element, this silica — eating the steel away and cementing itself to it, driven by an impulse to make whatever it touches (both or either, depending on its mood) porous and rigid.

For an overlook of the Unit Number 3 plant, making 50 megawatts, Signorotti takes us aloft onto the turbine deck. We climb the steel-grid stairways, stand on gratings that vibrate, their platforms sawtooth-cut to grip our shoes. A turbine buzzes and whistles and whines in front of us. The giant tank, its girth bolt-stitched, is like a hot dog on steroids. “Inside it,” Signorotti shouts, “is a seven-stage turbine. There are seven sets of separate turbine blades. They appear in descending order on either side of a shaft. So they’re larger on the outside — smaller, smaller, smaller, smaller, smaller — to where the turbine blades in the center are probably about 30 inches. It’s a dual-inlet turbine; it accepts standard-pressure steam and low-pressure steam.” This turbine is whirring at 3600 revolutions per minute. It drives a generator at 60 cycles per second and produces alternating current.

My friend and I lean close to hear Signorotti’s descriptions. (Loud noises make good neighbors, another kind of intimacy in the desert.) I suggest a camera crew should videotape the Unit Number 3 plant we’re standing on and, in the distance, the Vonderahe Number 1 plant, its cooling-tower plumes of hoary steam above the Salton Sea’s glittering blue. Between the plants is the bucolic scene of a field and a farmer, dust rising from his tractor wheels as he plows.

“People think that industry and agriculture can’t coexist,” Signorotti says. “We’ve proven them wrong. They’re preparing this field for another crop, melons, I believe. They just harvested an absolutely gorgeous stand of bell peppers.” California’s renewable abundance is suddenly clear: The twin fertilities, steam and sun, netherworld and ethereal, combine and flourish on the Valley floor. I recall that more than 40 percent of the entire U.S. winter crop is grown in these fields, let alone the year-round spectacles of strawberries flowering, of wheat stalks rustling. The bounty of food and the electricity to light that bounty in supermarkets and kitchens is overpowering — what the Joads felt when they reached Tehachapi Pass and beheld the Central Valley.

What’s it like, I ask, to be up here in August, with the temperature over 100, radiating from all this steel?

Signorotti says he’s seen the gauge hit 124 degrees in August. And that was in the shade. “So, up here, without any shade, in the direct sun, the temperature would exceed 140.” One hundred forty degrees is the hottest we can bear. But, for plant brine, that’s a too-cool, dysfunctional temp. It needs to go underground, for reheating, on the periphery of the earth’s burning core.


The ubiquity of water. It is the last juncture — especially water in the desert — I am trying to grasp. Think of lettuce: leafy green vascular tissue tumescent with bound water. Beneath the Colorado Desert, Miocene water (14 million years old) is trapped between one-half and four miles down; water is trapped in the hardened clay of the capping layer above the reservoir; water is trapped in the Salton Sea from the great floods of 1905–1907; water is trapped via canals from the Colorado River to irrigate the fields. Water is its entrapment, its embayment. But water will insinuate itself into anything that will contain it. We may harness it to power turbines, to irrigate crops, to bulk lemonade. But that’s not water’s purpose. Water’s purpose is to be on its way elsewhere as much as it is to be here, escaping and trapped.

The Salton Trough is a “ready-made geothermal system,” says geologist Alex Schreiner, who today runs a geothermal consulting business, after working at CalEnergy for 11 years. He tells me by phone from his home in Ridgecrest, California, that in addition to the reservoir’s high porosity and high permeability, there’s a third component in the makeup of the reservoir system. Storability. In the trough’s landlocked basin, water has encased itself in a geological matrix where it also stores itself away from the evaporative atmosphere. Schreiner calls the reservoir a “huge pile of sand, some 20,000 feet of it.” But it’s also “like an aquifer with lots of water moving quickly from one place to another.” It’s been stored there all that time because of the self-cementing nature of the clay on top. Nothing gets in, next to nothing (except the piped-up brine) gets out. By water’s design.

Capping the reservoir, clay, silt, and fine particles from ocean, lake, and river deposits have built up on the surface. Two theories exist as to why this cap is so highly impermeable and why it keeps re-cementing itself.

One idea is simple depositional order: As settling occurs, the finer lake sediments, or clay-size particles, remain on top; the less fine river deposits sink a bit deeper; and the coarser-grained ocean sediments go deeper still. The clay is nonporous and nonpermeable because sand in same-sized granules has been packed very tight in clearly defined layers. Such uniformity sounds common but it is not, for there are few assemblages as erosionally well-tiered as the Salton Trough.

The other idea is that the 1000-foot clay cap seals itself with the help of frequent earthquakes. Whenever the trough fractures, steam rushes up and into the cracks to cause a hydrothermal-chemical reaction that glues the clay shut. Once the water cools and begins evaporating, the moistened solids that the steam leaves behind seal themselves.

If sandstone has sand, what does clay have? The finest of soil particles, no more than two microns in size, clay is composed of dried-up silicates. But, like Jell-O, the silicates are also bound by water. Thus, when clay is slaked by water it becomes plastic. For potters, cool, wet clay becomes pottery when fired. Above a geothermal reservoir, heated then cooled clay becomes an impermeable cap whose plasticity is latent. In a sense, the clay that tops the reservoir is like a giant earthenware lid. The lid is regularly cracked by quakes but remoistened and reheated by the saline boiling and rising beneath it, then (in equal intensity) rehardened by the cooling temperature settling in from above.

Hot water escapes at one place on the surface: a playground of mud pots and mud volcanoes on the southeast edge of the Salton Sea, near Niland, California. At two locations, one can see what Schreiner calls the cap’s “modeling clay.” Gray-green mud gurgles and bubbles in little pools or pots; in more robust spew, the mud mounds and clumps into mini–volcano cones. Anne Sturz, who’s been monitoring mud-pot activity for ten years, has written that the pots are “a geochemical indicator…between the deep-seated geothermal reservoir and the surface structures.” The earth is venting. In micro-miniature. Revealing its clayey hand.

The mud pots are, according to Sturz’s research, a viscous mix of clay, water from two recent El Niño storms, irrigation runoff, CO2 degassing, some leaky brine, magma heat, and surface reshuffling from the 1992 Landers earthquake. Sturz calls the leaky brine the big relational question between depth and surface. She’s convinced, though, there’s a simple answer. The “plumbing system” of the clay cap leaks. Sturz and her students have documented traces of brine minerals on the surface. “It’s not a straight pipe but a convoluted system” of pipes, she says. The Fahrenheit temperature of the deep brine is 300; the mud-pot muddy water is 60. The water from the reservoir “has ample time to cool off [as it rises], but it still retains its chemical character.”

Is this why, I ask, despite all that roiling hot water underground, there are no hot springs or geysers in the Imperial Valley?

Sturz says that any fluid below must take a long, tortuous route to come close to the surface. Even if steam reached an opening, the clay, like a guardian angel, would cool it off. Thus, there’s no blow. When Yellowstone’s Old Faithful stops spouting, its plumbing refills with groundwater, reheats geothermally, boils, and blows once more, every 40 to 80 minutes. Forbidding such spectacle, the lid of the Salton Trough is screwed on tight.

“Every time we have an earthquake,” Sturz says, “I run out there expecting to see geysers.”

Really, I say.

“No,” she teases, “that’s an exaggeration. But it’s possible. If the cracks crack enough, water will rise to the surface very quickly, at its greater-than-boiling temperature, and flash into steam. That’s why the geothermal companies are in business, because that’s exactly what they do. They have very controlled geysers. It wouldn’t surprise me, terribly, to see a naturally occurring geyser — if earthquake activity would rupture that capping unit sufficiently. Much to my vast disappointment too, since I always think that those things are geoadventurism.”

What else, I wonder, is the planet — and our energy futures — made of but geoadventurism.

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