One of the state environmental protection agency’s biggest critics praised the department’s director Wednesday for tackling a backlog of expired pollution discharge permits the agency has let build up over the years.

Ann Timberlake, director of the Conservation Voters of South Carolina, said she’s glad to see that agency director Catherine Templeton is trying to fix the problem.

Templeton said this week that the S.C. Department of Health and Environmental Control has more than 500 expired permits – a backlog that sparked a lawsuit Tuesday and produced a flurry of questions about how the buildup will affect rivers, groundwater and air in South Carolina. Templeton said easing the backlog is a priority.

“I want to thank Catherine Templeton for insisting that DHEC act on expired permits for allowable pollution discharges,’’ Timberlake said. “That’s moving the ball forward. We’ve got to do that.’’

Timberlake made her remarks at the group’s annual Green Tie luncheon, which recognizes state policymakers for their efforts to protect the environment.

Wednesday’s luncheon, held at 701 Whaley in Columbia, drew about 400 people, including some of the state’s top policymakers, business people and conservation leaders. The Conservation Voters, now in its 10th year, represents state environmental groups on legislative issues.

At the luncheon, the group honored state Rep. Laurie Funderburk, D-Kershaw; departing state Rep. Paul Agnew, D-Abbeville; and state Sen. Ray Cleary, R-Georgetown, for their conservation efforts. The group also recognized former Department of Natural Resources board chairman Mike McShane and former U.S. Sen. Fritz Hollings, D-S.C., for the work they had done to protect the environment.

Timberlake has been a leading critic of DHEC and missteps the agency has made. She and her group coordinated efforts several years ago to reform DHEC, which critics say has been too slow to react to environmental threats in South Carolina. The agency drew particular criticism from Timberlake and the Conservation Voters in 2007, when DHEC failed to inform legislators about the extent of groundwater pollution from a leaking nuclear waste dump in Barnwell County. Her organization was a leader in the reform argument after The State newspaper published a series of articles in 2008 about agency shortcomings.

Templeton, who took office at DHEC last spring, was initially a source of complaints after she laid off nine DHEC coastal division employees, presided over the departure of numerous agency veterans and brought in a team of highly paid advisers.

But since then, Templeton has led efforts to clean up a polluted Columbia neighborhood, tackle the state’s obesity problem and reduce spending. DHEC is the state’s chief environmental protection and public health agency, and one of its largest, regulating everything from pollution discharges to hospital expansions.

Templeton, who attended Wednesday’s luncheon, said this week she was surprised to learn DHEC had such a backlog of expired permits. She acknowledged part of that relates to shrinking agency budgets, but also said the agency has not considered clearing the backlog a priority.

Allowing a company to continue operating on an expired permit many times allows it to operate with looser pollution limits. New permits often contain stricter controls on contaminants that are released to the environment.

“It could be bad for the environment,’’ Templeton said this week. “My hope is I’m blustering for no reason and there’s not been one harmful molecule of anything because of this. But my problem is, ‘How do you know?’”