The company agrees that monitoring is important, says Bob Sullivan, a senior vice president at Ormat Technologies. But Sullivan doesn’t believe there’s a need to drill expensive deep wells solely to keep track of water pressures and chemistry. He says the hot zone can be monitored by taking working wells off line periodically to gather measurements.

It’s not as if the water is removed permanently from the geothermal zone. It’s put back after its heat has been used to create electricity — but not in the same spot it came from.

The geothermal zone can be looked at as an underground river that starts west of the town and flows eastward until it hits the surface at a lower-elevation spot called Big Hot Springs in the Hot Creek Gorge.

Ormat essentially pumps hot water from this “river” and then returns it, cooler, through a well further downstream.

What has people concerned is the distance between where the water is removed and where it is returned. It’s possible that removing that water could cause a pressure drop in the geothermal zone that might then draw down water from the cold water reservoir, says Bill Evans, a research chemist with the U.S. Geological Survey in Menlo Park, Calif. Or, it might cause steam and other gases to shoot up into the cold water aquifer, potentially contaminating it. That scenario, Evans says, is less likely.

Ormat would increase the amount of pumping by about 50 percent overall but double the amount from wells in the area that the water district says are most sensitive. The water coming up would be much hotter than the current flow, allowing Ormat to double its power output to about 60 megawatts. The plant’s power flows off to homes and industries in Southern California and San Francisco.

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