For those who haven’t spent time in California’s Central Valley, it may come as a surprise to learn that the same landscape that produces nearly half of the United States’ fruit, vegetables, and nuts is also home to active oil fields. Drive through these farm fields, particularly in Kern Country, two hours north of Los Angeles, and you’ll see bobbing oil derricks scattered throughout the acres of nut orchards, vineyards, and farms growing crops that include carrots, potatoes, and tomatoes.

Oil drilling began here in the 1870s. And because of the geology, when this oil is extracted, it brings large volumes of water out with it. The question of what to do with this water—often called “produced” water—which contains salts, oil, and other contaminants, is a question at the center of a controversy in the drought-plagued state. More specifically, should it be irrigating crops?

Recycling wastewater for agricultural irrigation here is not new. The practice has been going on for at least 20 years; in some places it dates back to the 1980s. But it has come under increasing scrutiny as the impacts of fracking elsewhere in the country have heightened public concern about the way oil and gas drilling can impact water quality. While there’s no fracking in the Central Valley districts using this water, there are concerns about chemical contaminants—both those that occur naturally and those that might result from the oil extraction process, which uses numerous chemicals to maintain the wells.

At the same time, California’s epic drought has increased farmers’ interest in using this water. Last week, a coalition of environmental and health advocacy groups delivered a petition with some 350,000 signatures to California Jerry Brown and the California Water Resources board asking the state to stop this practice until it can be proven safe. On the same day, California’s major agricultural trade organizations signed a letter opposing a state Senate bill that would increase regulation of this water. And it seems that many major Central Valley agricultural producers wish questions about this issue would just go away.

“We understand that there are a lot of folks concerned,” California Water Resources Board deputy director John Bishop told Civil Eats. “That’s why we have requirements on any water that’s being used,” said Bishop, explaining that this water must be tested to meet certain standards and that the Central Valley Water Quality Control Board has convened a Food Safety panel to look into these issues. “We take it seriously, ” he said “We’re concerned about any discharge that would impact any beneficial use of water.”

“I think it’s not as big issue as some people think it is,” said California Farm Water Coalition executive director, Mike Wade. “[Irrigation water has] been monitored for a long time by the agencies responsible for water quality, and the [water] districts are going beyond those requirements.”

But, says Environmental Working Group’s California director of governmental affairs Bill Allayaud, “We’re saying not so fast. We’re saying we don’t know for sure, so prove it’s safe. ”

“Our message is it’s the government’s job to do this testing and it should stop this practice until they can show it’s safe,” said Adam Scow, California director for Food and Water Watch.

Kern County almond farmer Tom Frantz agreed. “I have personally seen oil field wastewater” he told Civil Eats. “You can smell the oil in the water.” This practice is “threatening my groundwater,” he added. “The produce itself is just now being tested. That’s a big unknown.”