Geysers-area quakes up 30% since start of wastewater use
While taking blame for tremors, power companies dispute residents' complaints of damage to homes
ANDERSON SPRINGS - Glinda Addington's 1920s home perched above a stream in a narrow, tree-lined canyon in western Lake County is picture-postcard pretty with its rock-studded foundation, flower garden and Victorian-influenced architecture.
But upon closer inspection, there are cracks in its foundation and concrete porch, cracks she and other Anderson Springs residents believe were caused by hundreds of earthquakes generated every year by The Geysers' geothermal energy plants.
The number of small quakes in Anderson Springs has jumped 30 percent since November, one month before Calpine began injecting millions of gallons of Santa Rosa wastewater deep into the underground steam fields at The Geysers, 2½ miles away from Addington's home.
During the first seven months of injection, The Geysers experienced 574 earthquakes of magnitude 1.5 or greater. During the same period last year, there were 451 quakes of similar size, according to the U.S. Geological Survey.
Anderson Springs residents have grown accustomed to the frequent shaking. Last year, there were close to 4,500 earthquakes of magnitude 0.9 or larger at The Geysers, making it one of the most seismically active areas in California, said David Oppenheimer, a USGS seismologist. Nearly all are "micro-quakes," the vast majority of which are too small to be felt, he said.
But Addington and other residents are concerned about the growing frequency of earthquakes at The Geysers. They want the power companies responsible for the quakes to help them repair the damage and take measures to prevent temblors in the future.
"I've had this house too long to watch it crumble," Addington said.
Calpine Corp. and the Northern California Power Agency, which operate geothermal plants at The Geysers, take responsibility for the earthquakes but not the damage.
"We just don't see there is any earthquake damage," said Calpine senior geoscientist Mitch Stark.
Calpine owns 19 of the 21 power plants operating at The Geysers, home to the world's largest underground steam fields in the fault-lined, rugged mountains bordering Anderson Springs.
In December, Santa Rosa and three other cities began pumping 11 million gallons of wastewater daily to The Geysers. There, it is injected one to two miles underground to replenish the steam fields. The superheated vapor spins turbines at the surface, where it is turned into electricity.
Calpine admits micro-quakes - those of less than magnitude 3.0 - are caused both by the extraction of steam from the earth and injection of water back into the ground to recharge the dwindling steam supply. Both processes cool the magma-heated rock miles beneath the surface, causing it to shrink, which triggers earthquakes as the rock adjusts, Oppenheimer said.
"We recognize we do cause quakes," Stark said.
But Calpine denies the quakes are responsible for the damage to Anderson Springs homes. The damage could be attributed to the fact many of the homes are older and are settling naturally as they age, Stark said.
"We've had no earthquake damage to anything at our facilities," Stark said.
There are good reasons employees at the power plants don't feel as many quakes as Anderson Springs residents, said Jeff Gospe, a part-time Anderson Springs resident.
For one, those facilities are newer and more solid than most Anderson Springs homes, which were largely built in the 1950s before earthquakes were a regular occurrence, Gospe said. In the 1960s, power companies started tapping The Geysers for energy.
In addition, the power plants are high in the mountains while Anderson Springs is in the valley below, closer to the earthquakes' epicenters, Gospe said.
"Part of why we're being affected so much is they're very, very shallow" earthquakes, he said.
As a result, a 2.0 quake, which normally goes unnoticed by most people, feels like a "a truck backing up and knocking into the house," said Gospe, an executive with a Santa Rosa business consulting firm.
Oppenheimer agreed shallow quakes, such as the ones in Anderson Valley, can feel much stronger than quakes deep underground.
Gospe also said the small quakes could trigger larger ones, like a 4.4 magnitude temblor that hit in February. The strongest recorded earthquake in the area was a 4.6 in 1982.
Stark, however, said there is no evidence that will occur, based on The Geysers' earthquake history. There has been no increase in the number of stronger quakes since the Santa Rosa wastewater injections began in December, Stark said.
The number of quakes of magnitude 3.0 and higher has remained relatively steady over the years, averaging about 20 a year, Oppenheimer said.
There were nine quakes of magnitude 3.0 or larger in the seven-month period after the start of wastewater injections at The Geysers, unchanged from the same period a year ago, the USGS said.
While small quakes can trigger larger quakes, it is doubtful they would ever cause a temblor larger than magnitude 5.0 in Anderson Springs because there are no major faults in the area, Oppenheimer said. The size of faults determine the maximum size of earthquakes, he said.
"You can't get large earthquakes in small faults," Oppenheimer said.
Power companies have been generating electricity at The Geysers for more than 40 years.
Quake activity rose as steam production climbed, spiking in the mid-1980s when steam production reached an all-time high. But seismic activity tapered off as the geothermal field was depleted of steam, Stark said. At that time, there were almost a dozen companies, including PG&E and Calpine, competing for the steam, he said.
"There were too many straws in the glass," he said.
Quake activity surged in 1997, when power companies began injecting 8 million gallons of Lake County water and treated effluent into the steam fields daily. The injections, coupled with heavy rainfall, caused earthquake activity to jump more than 40 percent to roughly 1,000 temblors a year between magnitude 1.5 and 3.0, Calpine said.
Calpine bought most of the plants and consolidated production in 1999.
Today, about 25 million gallons of water is injected into The Geysers each day, Stark said. As a result of 19 million gallons of wastewater from Sonoma and Lake counties, electricity production at The Geysers has rebounded to almost 1,000 megawatts, less than half what it was at its peak in 1987. The wastewater injections are expected to hold Calpine's energy production steady, Stark said.
The debate over potential and real damage is part of discussions between the energy producers, Lake County officials, state officials and Anderson Springs residents.
Stark said Calpine wants to contribute to the community, but it won't admit causing damage to homes.
Despite the problems, no one has ever formally submitted a claim to Calpine or sued the company, although Gospe has threatened to do so.
"I don't think it's worth it," said Allen Clay, a longtime Anderson Springs resident and a former Geysers engineer. A lawsuit would not stop energy production or earthquakes, he said.
"You've just got to deal with it. It's part of life," Clay said. "They're not killing anybody. It's just aggravating."