When Tom Frantz looks eastward from his small Kern County almond grove, the farmer sees a bank of low hills rising from the Central Valley floor and, eventually, building into the large peaks of the southern Sierra Nevada. Frantz has these mountains to thank for his livelihood, since the snowmelt that runs off the peaks eventually sinks into the ground and, over time, descends into the natural underground reservoirs of the Central Valley. In drier years, Frantz gets most of his water from wells that tap into this aquifer.  

But the water, Frantz says, is being poisoned. In these foothills, hundreds of deep holes bored into the ground are being used as disposal sites for water containing high levels of dangerous toxins — including arsenic, thallium and benzene. Some of the injection wells are illegal, though many are permitted by the Environmental Protection Agency. The agency allows oil drilling operations in California to annually dispose billions of gallons of toxic wastewater that spills from their wells during their drilling operations.

Legal or not, such disposal of poisoned water into the earth could come back to haunt our society, warn scientists.  

“We’re intentionally contaminating aquifers that today are not designated for human consumption,” says Mark Williams, professor of hydrology at the University of Colorado. “But 20 or 50 years from now we’re going to want that water.”

But it isn’t just our future water supply that is threatened.

“The very same aquifers that oil and gas companies are dumping wastewater into are being drawn upon now for irrigation,” says Patrick Sullivan, climate media director with the Center for Biological Diversity.

He says more than 500 injection wells, mostly in the San Joaquin Valley, have been investigated for illegally contaminating aquifers protected by the Safe Drinking Water Act. Hollin Kretzmann, a staff attorney with the same group, says there are at least 100 water supply wells within a mile of several wastewater injection wells in the San Joaquin Valley alleged to be unsafe.

The fate that Frantz fears seems already to have been realized on another nearby property. Here, farmer Mike Hopkins had to remove 3,500 dead or dying cherry trees in 2013 after they were apparently poisoned by tainted groundwater. A test of Hopkins’ wellwater showed it contained chemicals associated with oil well wastewater. A wastewater injection operation at work just yards from Hopkins’ property was named as the culprit.

The farmer is currently a plaintiff in an ongoing lawsuit alleging that state officials – including Gov. Jerry Brown – conspired to allow the continuation of illegal wastewater injection, even after a state employee demanded stricter scrutiny of the activity. According to the lawsuit, that employee was fired in 2011 and replaced with an official more lenient toward oil companies.

But UC Davis professor of hydrogeology Graham Fogg is not entirely convinced that pumping wastewater into the earth is the environmental time bomb others say it is. He says the great depth of most wastewater injection wells – sometimes more than a mile – makes them secure disposal sites.

However, Fogg does agree that, over time, effects of this practice could begin to surface.

“If you keep injecting into the deep aquifers, and I mean for like decades or centuries, could there be a longer-term effect? Well, that’s not impossible,” Fogg says.

When it comes to water under the earth’s surface, much remains unknown. For one thing, the speed at which subterranean water migrates seems to be anyone’s guess. Moreover, whether it will migrate at all is a valid question in some regions. That’s because rock layers, called aquicludes, can act as impermeable barriers that separate underground reservoirs.

But in regions shaken by seismic activity — like much of California — many aquicludes have been broken apart, says Timothy Krantz, a professor of environmental studies at the University of Redlands.  

In fact, Williams says that the process of injection itself can shatter the rock. “So, you’re essentially creating pipes for the water to move through the ground,” he says.

Krantz says there is no question that there will be intermingling between aquifers designated for drinking and those now used now for wastewater disposal.

“That’s how groundwater works,” he says. “It doesn’t just sit there or sink into the bowels of the earth. It moves down-gradient toward sea level.”

In the western Sierra Nevada foothills, that means the water will cross some of the most fertile farmland in America.

Frantz feels certain that his farm is one of many that will eventually be destroyed by a slow but steady downhill migration of tainted water.

“I don’t know if the water I’m pumping from my well today was snow in the mountains 100 years ago, 300 years ago or 15 years ago,” Frantz says. “But it will eventually get here. It’s a time bomb that will affect lots of land.”

The culprits, he speculates, may never face consequences.

“By the time our groundwater is ruined, the oil companies won’t even be here anymore,” says Frantz.