The records also show that 13 of the 18 expired since Governor John Kasich took office in 2011, and have until now gone unnoticed, spurring accusations of corruption from environmental groups.

Several holders of expired permits provided funds to Kasich’s 2010 gubernatorial campaign, Ohio campaign finance records show.

That included more than $US35,000 from employees of Murray Energy and its subsidiaries and $US22,000 from executives of Oxford Mining, both of which were found to be operating with expired permits.

However, a quirk of Ohio law may clear those companies operating with expired permits.

The pollution-discharge permits state what pollutants each mining operation, coal preparation plant, storm water facility or coal waste storage area can release under state and federal clean water laws.

Environmentalists contend delayed permit renewals allow mining companies to avoid modernising cleanup technologies as required under the federal Clean Water Act.

“We can’t afford to be the next West Virginia or North Carolina,” Sierra Club Ohio Chair Robert Shields said. “We want to stop a spill before it happens, and we want to ensure that our water is safe to drink and brush our teeth with.”

Ohio EPA spokesman Chris Abbruzzese said renewing permits was a complicated process.

He said 14 of the permits were in the process of gaining updated approvals.

The federal EPA has the power to impose penalties on Ohio for extended delays in reissuing permits through its state grant program.

Abbruzzese dismissed all claims of corruption, saying that under Ohio law if a company applied for a renewal six months before its permit expired, it could operate under that expired permit indefinitely.

State records show Murray Energy’s Ohio Valley Coal has run its Powhatan No. 6 mine in Belmont County under an expired permit for nearly nine years.