The state’s environmental protection agency has let more than 500 pollution control permits expire, potentially threatening rivers, groundwater and air quality across South Carolina.

Officials with the S.C. Department of Health and Environmental Control are scrambling to address the backlog of permits, many of which need to be updated with tighter pollution limits.

DHEC officials said late Tuesday that 503 of the state’s 3,693 active permits have expired. The bulk of the expired permits are for water and air pollution discharges, according to data released by DHEC. Many have expired in the past three to five years, but others date to the early 2000s. One land disposal permit for a trailer park expired in 1994, agency records show.

“I’m stunned,” said Rep. James Smith, a Richland County Democrat who has tangled with DHEC over pollution discharges. “What are they doing over there?”

DHEC director Catherine Templeton blamed the backlog on the agency’s previous administration, which she said did not see the need to process permits as an urgent matter. She acknowledged that shrinking budgets contributed to the backlog, but said the issue is broader than that. The agency’s attitude was “we’ll get to it, but it’s no big deal.”

“This is not just a concern, it’s a priority” to resolve, Templeton said Tuesday. “This is absolutely unacceptable.”

Cutting down on the backlog can’t be fixed overnight, but Templeton said the agency will make the matter a higher priority than in the past. She took office in March. She has asked DHEC staff for plans to resolve the problem.

The backlog is significant because, in some cases, industries, power companies and businesses have continued to discharge pollution at higher levels than would have been allowed if new, up-to-date discharge permits had been issued by DHEC.

The expired permits include one for a Lexington County sewage dump that has leaked toxins into groundwater near Pelion and another for an Horry County power plant that discharges into the Waccamaw River west of Myrtle Beach. Residents in Chester County also have complained recently about a sludge disposal permit that has expired.

Frank Holleman, an attorney with the Southern Environmental Law Center, said DHEC’s failure to issue a water pollution discharge permit for Santee Cooper’s power plant in Conway is an example of the larger problem. Holleman’s group sued DHEC on Tuesday over its failure to issue a new permit for the state-owned power company’s Grainger coal-fired power plant.

Records show the five-year permit for the company’s Grainger coal plant expired Sept. 30, 2006. A new permit with stricter controls on mercury, copper and arsenic was proposed but never issued, Holleman said.

“This ties into DHEC failing to do its job across the board,” he said.

The federal law that set up discharge permits “is designed to eliminate and reduce pollution,” Holleman said. “Polluters are supposed to use new technology that becomes available to reduce pollution. That is the whole point.”

Federal and state laws allow companies to legally discharge pollution within certain limits or if it is treated. But those permits expire and many are supposed to be re-examined every five years. Until they are reissued, the old permit limits stay in effect.

Former DHEC director Earl Hunter told The (Charleston) Post and Courier that budget cuts had made it difficult to process many permits. Data released by the agency Tuesday show other states in the Southeast region also have permit backlogs.

Either way, reducing the backlog in South Carolina is important, said former DHEC wastewater regulator Andy Yasinsac.

“Commonly, DHEC will require some pollutant to be limited that previously had not been recognized that needs limits,” he said. “The idea is you have reduced pollutants going into the water.”

The issue of expired permits recently prompted an email to Templeton from Dave Cole, who is battling the disposal of human sludge on a field near his home in the Chester area between Charlotte and Columbia. Cole wrote an email last month to complain about the agency’s inaction.

Cole told The State that DHEC’s failure to make a decision has denied the public a right to formally ask for stricter limits on the disposal.

“They’ve denied the community a voice,” Cole said. “It’s outrageous.”

Yasinsac said he’s particularly concerned that the agency has failed for about three years to decide on a new land discharge permit for the C.E. Taylor sewage dump near Pelion. The sprawling dump is one of the largest sewage disposal grounds in the Carolinas. It has been in existence for more than two decades. It sits atop a slick of contaminated groundwater in a rural area where people drink from wells. Some private wells have shown unsafe levels of nitrates, pollutants that can sicken babies.

Many people in the Pelion area have called on DHEC to deny a new permit for the sewage dump or at the very least, include stricter limits on the disposal. Templeton said a decision on the C.E. Taylor permit is expected later this week. The Taylor permit expired in 2009, records show.

The law center’s Conway suit was filed in state court in Columbia on behalf of the Southern Alliance for Clean Energy and the Waccamaw Riverkeeper. It asks the court to order DHEC to make a decision on the permit for Santee Cooper. It also said DHEC gave special treatment to a fellow state agency in not issuing a permit. Santee Cooper, which is state owned, expressed concern about the cost of a tougher permit, the suit said.

Full list of expired DHEC permits