Down a dirt road in northwest Oklahoma, only a few hundred yards from where the city of Enid draws its drinking water, a company injects the toxic byproduct of oil production deep underground.

That close proximity violates a state rule meant to protect public groundwater supplies from oil field wastewater, which can be saltier than the sea and laden with toxic metals. Injection operations are banned within a half-mile of public water wells unless regulators hold a hearing to ensure that such activity will not pollute the water. 

But in 2018, without a hearing, state regulators approved this injection well, an apparatus that applies pressure to dispose of wastewater down a steel tube. And in the years since, the well, named the Flying Monkey, has repeatedly failed structural integrity tests, signaling a potential leak.

The Frontier and ProPublica mapped every injection well in the state to determine how close they are to public water wells. We identified at least 114 injection wells in communities across Oklahoma — including the Flying Monkey and two others in Enid — that are located within a half-mile of a public water supply well. More than 300,000 Oklahomans live in communities that rely on these water wells, according to our analysis.

Sources: Oklahoma Corporation Commission, Oklahoma Department of Environmental Quality, Oklahoma Water Resources Board

The city of Enid has complained to the state about the threat to its water. In Oklahoma and beyond, toxic oil field fluid has spread underground and threatened municipal supplies. Midland, Texas, is still cleaning up groundwater polluted by a leaking injection well more than two decades ago. 

But Enid officials are powerless under state law to pass their own rules governing these wells. And so they are appealing to the same Oklahoma agency that had approved the Flying Monkey to now revoke the permit that allows the well to inject wastewater. The city is also asking the state to impose stronger protections against pollution from injection, as more oil and gas companies seek permission to drill wells that dispose of their wastewater nearby. It’s a rare example of pushback against one of Oklahoma’s most powerful industries. 

The Oklahoma Corporation Commission, which is responsible for ensuring that industry operations do not pollute groundwater, has approved thousands of orders for waivers or adjustments to state rules in recent years, according to the agency’s administrative court database. These include nearly 400 orders granting exceptions to injection regulations alone since 2022, agency records show. 

The agency has repeatedly declined to punish oil and gas companies for causing widespread pollution, according to an earlier investigation by ProPublica and The Frontier. The news outlets also found that the agency chose not to pursue stronger rules for wastewater injection following industry opposition. In response to that reporting, the agency told the news outlets that the state is committed to “doing the right thing, holding operators accountable, protecting Oklahoma and its resources, and providing fair and balanced regulation.”

Enid’s case will be heard in the agency’s administrative law court later this year. Neither city leadership nor their attorney agreed to be interviewed before the matter is resolved. The Oklahoma Corporation Commission declined to comment for this story, citing the ongoing case, as did the Flying Monkey’s current operator, BCE-Mach III Midstream Holdings LLC. 

Ben Ezzell, a former Enid city commissioner, said he hopes the state recognizes that the community is asking for “reasonable” protections against catastrophic long-term damage to its water supplies. 

“It’s ultimately all one big aquifer,” he said. “You can’t just pee in part of the pool. If any of the aquifer is tainted, all of the aquifer will be tainted.”

Skirting State Laws 

A row of hulking grain elevators sits just outside Enid’s main commercial district, evidence of the prolific local farm economy that earned the city of 50,000 the nickname “Queen Wheat City.” But in the heart of downtown, a large art deco building gestures at one of Enid’s other vital, long-standing industries: It was once the office for Continental Resources, now the world’s largest private oil company.

Although Continental outgrew Enid more than a decade ago, pumpjacks pulling up oil still seesaw up and down near town. Oil production inevitably means wastewater. And dozens of injection wells west of Enid blast the industry’s byproduct underground in the same area where many of the city’s water wells are located.

The nation’s bedrock water protection law — the Safe Drinking Water Act — singles out oil and gas injection of wastewater as a particularly urgent threat to drinking water. And it requires oil states to draft specific regulations to protect public water wells. 

Oklahoma, however, has not always followed its own rules. In 2018, a small company called Hinkle Oil & Gas applied for a permit for an injection well — the Flying Monkey — less than a quarter-mile from two of the city’s water wells, according to publicly available data. 

But on its application, the company had checked a box attesting that the injection well was not within a half-mile of a public water supply well — the distance that, under state rules, should have triggered a hearing to evaluate the Flying Monkey’s pollution threat. “This was demonstrably false,” Enid’s lawyers wrote in a September 2025 court filing. 

The commission approved Hinkle’s application for the well without a hearing, giving the company the green light to inject more than 800,000 gallons of wastewater into the earth each day. Hinkle declined to answer questions about the Flying Monkey. The commission did not respond to questions about whether it verified the distance before approving the permit. Nor did it respond to The Frontier and ProPublica’s offer to show agency officials our mapping of the 114 injection wells across the state that are located within a half-mile of a public water supply well. 

Later in 2018, Hinkle transferred the well to another small company, which applied for a new permit to convert the Flying Monkey to a commercial well to dispose of the wastewater produced by other oil companies, too. By approving the permit, the city contends, regulators allowed the company to violate another state rule meant to protect public water wells from commercial disposal sites. The new company’s application also failed to acknowledge the close proximity of the public water supply well. The company has since filed for bankruptcy.

Both of thesepermits were ultimately signed by Patricia Downey, the manager of the agency’s underground injection control program, and read: “decision without hearing.” Downey did not respond to any questions sent directly to her, including whether she knew about the Flying Monkey’s proximity to public water wells.

In the last five years, the state has shut down the Flying Monkey repeatedly — for months at a time — for failing mechanical tests required by the state that evaluate the well’s structural integrity. Failing these tests can indicate a problem with the well that may be allowing wastewater to escape. The well has failed five of these tests since 2021, including one in March due to a leak in the well’s tubing that the company had reported to the agency, according to state records. The agency’s report about the March incident does not reference an investigation into whether the leak reached nearby groundwater. The agency typically notes when an investigation is conducted. It did not answer questions about whether it investigated the well for potential pollution.

In the court filing last fall, Enid’s lawyers described this pattern of violations as “a significant compliance red flag, especially given the well’s immediate proximity to Enid’s public supply well.” The city wants the state to terminate the Flying Monkey’s permit. After a period of inactivity last year, the well began injecting wastewater again last summer, only to be shut down again this March. State records indicate that the Flying Monkey’s operator, BCE-Mach III Midstream Holdings, repaired the tubing leak in April, and the well’s status is listed as active; the company declined to comment.  

Neither the company’s nor the commission’s court filings include responses to Enid’s accusations. In June, BCE-Mach III Midstream Holdings refiled a permit application for the Flying Monkey, acknowledging the proximity of the city’s water supply wells.

Close by the Flying Monkey, another wastewater injection well — Estill #8 —sits roughly a quarter-mile from three of Enid’s water wells. 

In its application, submitted in August 2012, an affiliate of the U.S. Energy Development Corp. acknowledged the proposed injection well’s proximity to the city’s water supply but subsequently urged state regulators to approve an emergency order to allow the well to begin injecting wastewater immediately. Waiting for the required hearing, the company wrote, would result in “irreparable financial harm” because any delay would deprive it of a way to get rid of the wastewater generated by its nearby oil wells. In general, oil companies want their wastewater disposal sites to be as close as possible to their producing wells to reduce the cost of transporting the fluid. The commission approved the emergency order on a temporary basis while it considered whether to issue a permanent permit, and the well began injecting wastewater in November 2012. 

In February of the following year, the company returned to the commission to renew its request to continue injecting without a standard hearing. The commission approved the second request in March and two weeks later authorized the well’s official permit without a hearing. The commission did not answer questions about the permitting process for Estill #8.

The well has been operating ever since, injecting more than 12 million gallons of wastewater into the earth last year. (A third injection well also operates within a quarter mile of a city water well, but that one was permitted in the 1970s, before modern regulations were established.) The state has tested these injection wells every few years and has not identified problems with either one.

Enid’s Quiet Battle

In this arid part of Oklahoma, where surface water is scarce, Enid has become a vital source of drinking water for a dozen smaller, more rural communities as well as Vance Air Force Base. Even after the recent completion of a 70-mile, $400 million pipeline to bring water from Kaw Lake, Enid will continue to rely heavily on its groundwater wells. 

“In the 21st century, water is going to be the new gold,” Frank Baker, an Enid city commissioner, said in an interview. 

Driven by increasing concern over water scarcity and the potential for contamination, the city’s effort to protect its water has stretched for two years but has received scant attention around town. The issue hasn’t previously been covered in the media. The City Council hasn’t discussed it in public meetings. And few follow the obscure quasi-judicial system of the Oklahoma Corporation Commission. 

If residents knew how close injection wells operate to their drinking water supply, they would be concerned, said Elizabeth Betchan, a barista at a downtown coffee shop. “I would feel more comfortable if there was more of a buffer there,” she said. 

Enid is asking regulators to impose a ban on oil and gas wastewater injection within a half-mile of its water wells, with no possibility of exceptions. It also wants the state to require additional testing, pollution monitoring and mechanical safety measures for wells within 1 mile of an Enid water well, according to its application to state regulators. 

“I think a mile is probably too close,” said Eddie Mack, a retired manager of a rural water district who also served on Enid’s planning commission.

Pollution from high-pressure wastewater injection can radiate much farther than a mile. Oil companies have acknowledged that their injection wells can impact one another’s operations that were 3 miles apart, according to agreements between companies on how to respond in such scenarios. The Frontier and ProPublica identified more than 400 wastewater injection wells across Oklahoma that are within 1 mile of a public water supply well. 

Regulations for this issue vary widely among oil states. Colorado and Ohio set a minimum buffer of 1,000 feet between injection wells and public water supplies. Many states do not have fixed setbacks, instead relying on belowground geological evaluations to ensure that injected fluid does not contaminate aquifers. 

A leak from one injection well can cause severe pollution that lasts decades. That’s what happened more than 20 years ago in Midland, Texas, which has no fixed buffer requirement between injection wells and public water wells. After the company responsible went bankrupt, cleanup fell to the city, which has spent millions of dollars trying to stop the pollution from spreading, according to an investigation by Inside Climate News. 

But Enid’s bid to protect its groundwater faces numerous obstacles. 

Five companies have formally opposed the city’s request for stronger rules to protect its groundwater. Those include Flying Monkey owner BCE-Mach III Midstream Holdings, Estill #8 owner U.S. Energy Development Corp. and two others — D&B Operating and Royalty Energy Development LLC — that have pending applications for new injection wells near Enid. Neither of the latter two companies responded to requests for comment.

Matthew Allen, an attorney representing U.S. Energy Development Corp., argued in a May procedural hearing that the city’s proposed changes would “significantly increase the regulatory burden” and costs to companies. He also said that the administrative court was the incorrect venue for the city to pursue such a significant change. Neither Allen nor other company representatives responded to requests for comment. 

Kaylee Davis-Maddy, Enid’s attorney, emphasized during the hearing that the city was not trying to establish a statewide rule. Rather, she said, Enid wants the rules to apply within a geographic boundary to protect its freshwater. Davis-Maddy declined to be interviewed.

Enid has to bring its appeal to the state agency in large part due to a 2015 law that forbids cities and counties from establishing their own regulations on oil and gas operations. 

That matters because even if the administrative law judge sides with Enid, such a decision must be approved by the regulatory agency’s three elected commissioners. Right now, two of them are former state legislators who in the past have opposed efforts by Oklahoma municipalities to restrict oil and gas operations.

Before winning election to the commission in 2024, Brian Bingman served in the state Senate, where, as the Senate president pro tempore, he was the lead author of the bill to ban local governments from regulating the oil and gas industry. Kim David, another commissioner, voted for the bill as a state senator. All three commissioners were elected with significant financial support from the oil and gas industry. Neither Bingman nor David responded to requests for comment. 

At the time the preemption law passed, several local governments were considering restrictions on hydraulic fracturing amid a wave of earthquakes caused by oil and gas injection. The legislation mandated that any regulation of the industry be approved by the corporation commission. 

The state Supreme Court upheld the law in its 2022 decision nullifying a requirement by the city of Norman, about 20 miles south of Oklahoma City, that oil and gas companies maintain extra liability insurance.

“Municipalities no longer possess a broad police power to regulate oil and gas,” the court wrote in its unanimous decision.