Oil and gas drillers ran afoul of regulators on average 2.5 times a day in three energy-intensive states for mistakes such as wastewater spills, well leaks or pipeline ruptures during the boom in hydraulic fracturing.

Online records in West Virginia, Pennsylvania and Colorado showed regulators issued 4,600 citations from 2009 to 2013, the Natural Resources Defense Council said Thursday in a report. The report excluded violations in 33 other states with drilling because such records aren’t available on the Internet.

“It’s extremely difficult for the public to get this kind of information,” said Amy Mall, an author of the report for the New York-based environmental advocate. “The companies are violating the law too often, and we need policy solutions to increase transparency and to change the consequences for not complying” with the rules, she said.

Hydraulic fracturing has sparked a production boom in long- bypassed energy states such as Pennsylvania, site of the first U.S. oil well. The technique lets producers break apart the underground shale formations and free trapped oil or gas. Each job can entail millions of gallons of water mixed with sand and chemicals.

The industry says the practice is safe, and that fracking itself hasn’t caused chemical contamination of water supplies.

Violations Tabulated

The NRDC report tabulated citations issued by inspectors for breaching rules adopted to make sure wells are constructed soundly and the wastewater is handled safely. Because of the way inspectors categorize the violations, it’s difficult to tell if any one issue was tied directly to fracking, Mall said.

The vast majority of violations—about 4,000—were in Pennsylvania. West Virginia and Colorado combined had about 600.

In addition, 1,933 spills were reported in Colorado, which are listed separately from the violations.

The number of violations or spills isn’t necessarily a sign of deficiencies, and show that states are ready to act when necessary, said Jon Haubert, a spokesperson for Coloradans for Responsible Energy Development, an industry-backed group.

“People in Colorado have an assurance, because we have such tight regulation and enforcement,” Haubert said. “In Colorado you aren’t seeing an increase in spills, you are seeing an increase in the reporting of spills, and I would argue that’s a good thing.”

Paperwork ‘Issues’

The report doesn’t categorize the infractions, but lists examples such as poor well construction and a ruptured pipeline.

“A fair amount of these ‘violations’ involve paperwork and other administrative issues,” said Steve Everley, a spokesperson for Energy in Depth, part of the Independent Petroleum Association of America. “Those are things that certainly should be corrected, but it’s pretty dishonest of NRDC to suggest errors that accountants can fix are the same thing as imminent environmental threats.”

Chesapeake Energy Corp. had the most violations listed in the NRDC report, followed by Cabot Oil & Gas Corp. While both companies have large operations in Pennsylvania, neither is the biggest producer in the state.

Voice mail messages and e-mails to both Chesapeake and Cabot weren’t immediately returned.

Pressure from groups such as the NRDC for more disclosures about fracking comes as drillers grapple with a drop in oil and gas prices, and increasing regulation from the federal government for production on federal lands. Oil prices dropped about 50 percent in the past year through Wednesday, while gas fell 39 percent.