SAN FRANCISCO (KPIX 5) — Every day oil companies in California dump millions of gallons of wastewater underground.

Most of it is getting injected deep under the Central Valley, which also happens to be the state’s agricultural heartland.

Now we’re learning some farmers, like Mike Hopkins, suspect that wastewater might be what’s killing their crops, and impacting our food supply.

The problem he says began about eight years ago when the leaves of his newly planted cherry orchard started turning brown. Soon the almond trees followed.

“We started doing water tests, soil tests, tissue tests, digging holes, trying to find out where the problem was,” he said.

The water tests provided a clue.

“It had more contaminants in it, chlorides, boron, not at toxic levels, but levels that were harmful to the trees,” said Hopkins.

His irrigation water contained the very same salty compounds found in the wastewater produced by dozens of nearby oil wells.

On average, 10 barrels of wastewater come up with each barrel of oil and most of it is injected back into the ground.

State regulators told Hopkins the wastewater injection well right across the street from his farm couldn’t be to blame, because it was abandoned years ago. But it turns out abandoned wells can be a problem.

“That acts as essentially a chimney,” said Patricia Oliver, who is suing the oil companies involved on Hopkins’ behalf.

According to the lawsuit, abandoned injection wells reach into the same area deep underground where dozens of other active wells are injecting wastewater.

When pressure builds in the injection zone the wastewater can push up through an abandoned well if it’s not properly sealed and leak into the fresh water zone above it.

“Nobody is testing the water wells nearby, even though the Division of Oil and Gas knows there are multiple farmers complaining,” said Oliver.

In an email to KPIX one of the oil companies involved, San Joaquin Facilities Management, blamed the drought and Big Ag irrigation practices for the problem, telling us, “There is no evidence that San Joaquin’s injected water escaped the zone into which it was injected.”

Three other oil companies said they can’t comment because of pending litigation.

The Division of Oil and Gas that oversees the drilling, operation and abandonment of oil wells and injection wells also turned down our request for an interview, sending us instead to the State Water Resources Control Board.

Jonathan Bishop is the department’s chief deputy director.

His agency is assisting the Division of Oil and Gas, also known as DOGGR, in a federally mandated review of hundreds of injection wells that the U.S. Environmental Protection Agency has determined could potentially be contaminating California’s drinking water supplies.

“We did a first cut review and identified a number of wells that needed further study,” said Bishop.

Dozens of injection wells were found in violation.

The well near Hopkins’ farm was not on the list, but DOGGR confirms it was never capped.

And Bishop told us, “There is a theoretical potential that an abandoned well that perforates down into the oilfield might have some cross connection with a water zone.”

He says so far no wells used for irrigation or drinking have been found to be contaminated.

But the review process, scheduled to be completed this month, is way behind target.

And all the geological and mechanical surveys to make sure the injection wells are safe are being done by the oil companies.

We asked if that is a little like the fox watching the hen house.

Bishop’s response was, “Well, that is what we have been doing for 50 years, it’s the way our regulatory scheme works.”

Back at the farm, attorney Patricia Oliver predicts things are just going to get worse.

She says with no help from the state, or from the federal EPA, her client had no choice but to sue.

“We all know what we face with the current administration trying to take away any power the EPA has,” she said.

Meanwhile Mike Hopkins has planted pistachios on the field where his cherry trees once blossomed. They’re sturdier plants, but he doesn’t hold out much hope they’ll survive either. And once his almond trees stop producing he says he’ll pull those too.

“This is a small orchard but we have neighbors who are much larger that are going through the same problem. Once we get to a point where everybody is complaining, it’s probably going to be too late,” said Hopkins.

This is the full statement provided to KPIX from officials with San Joaquin Facilities Management: