ERWIN -- The stated purpose of Thursday night's Nuclear Regulatory Commission (NRC) public meeting here was to discuss the federal agency's Aug. 2 decision to grant a 25-year renewal of Nuclear Fuel Services' (NFS) operating license.

Plenty of other questions and comments were directed toward NRC officials, however, about the 120-foot-deep sinkhole that recently appeared on the grounds of Love Chapel Elementary School in Erwin -- and about the potential environmental implications if similar sinkholes should appear on the property of NFS, less than one mile away from the school.

NRC officials assured citizens present that testing done on the NFS property indicates that the possibility of sinkholes appearing there is not likely.

But those assurances didn't do much to convince opponents of the NFS operation that the sinkholes cannot happen at NFS, given the topography of the area.

The Erwin community is noted for its karst topography. Karst topography is typically characterized by numerous caves, sinkholes, fissures, and underground streams.

Karst topography usually forms in regions of plentiful rainfall, where bedrock consists of carbonate-rich rock, such as limestone, gypsum, or dolomite that is easily dissolved.

Limestone rock, with its high calcium carbonate content, is prevalent throughout much of the Erwin area.

The rock can be dissolved by the acids produced by organic materials, resulting in channels and caves that are susceptible to collapse from the surface.

Dye samples were placed in the groundwater collected at the bottom of the Love Chapel school sinkhole. The groundwater, which lies uphill (up-gradient) from NFS, migrated to a spot along the Linear Trail in Erwin near the Nolichucky River and the NFS plant site.

Another sinkhole opened about 300 feet from the school in December 2011.

"Now that yet another sinkhole has opened in Erwin, and the dye poured into the sinkhole found its way rather quickly to surface water next to the Linear Trail, is the NRC convinced yet that the groundwater flow in our karst topography is changing?" Jonesborough resident Linda Cataldo Modica asked officials.

She questioned the data collected by NRC that supports the contention that sinkholes are unlikely to form on the NFS property.

"Had NRC done its research right, might you have already found that karst topography is no place to site a nuclear waste dump like NFS?" she asked.

Modica said she was "more than a little disappointed" with the NRC environmental assessment conducted prior to granting the 25-year license extension to NFS.

She added that previous surveys of the property show faults, fracture zones and features "indicative of karst topography."

"We are concerned about sinkholes. We are also concerned about NFS' groundwater contamination," she said.

"People are concerned about the groundwater contamination that NFS has already caused."

NFS officials have said that two sinkholes that recently formed in Erwin (discussed above) have no connection to the operation at the plant.

James Park, an NRC project manager, pointed out on a overhead map display what he said was a "transition zone" showing two other kinds of rock formations in the area of NFS.

He said that, based on information available to the NRC, "We are not aware of any sinkholes that have formed on the NFS site."

Kevin Ramsey, acting chief of the NRC's Fuel Manufacturing Branch, Division of Fuel Cycle Safety and Safeguards, said the agency has already evaluated the potential impact of earthquakes and flooding on the NFS site.

"We're going to follow up on sinkholes," Ramsey said. "My personal opinion is the consequences of a sinkhole will not be any worse than the consequences of an earthquake or a flood."

NFS manufactures uranium fuel for the U.S. Navy's nuclear-powered submarines and surface ships.

The site in Unicoi County is near the Nolichucky River, about 28 miles upstream from Greeneville. Drinking water for Greeneville and Jonesborough is drawn from the river.

John Kinneman, director of the NRC Division of Fuel Cycle Safety and Safeguards, said that NFS "has drilled a number of holes at the site" over the years.

"That provides a great deal of information NFS is taking a look at," he said.

Ramsey said earlier in the meeting that the NRC staff has determined that the significance of environmental impacts from the license renewal would be minor and "not detectable."

One exception, which could fall into the "moderate" category, includes groundwater and soils.

The NRC's definition of "moderate" is "environmental effects are sufficient to alter noticeably, but not destabilize, important attributes of the resource."

Barbara O'Neal, of the Erwin Citizens Awareness Network (ECAN), voiced to NRC officials her concern about possible radioactive groundwater contamination.

"Watching this issue unfold with the sinkhole at Love Chapel school, and having read all the of the environmental reports that the NRC has released on NFS through the years, I don't believe I've ever read anything about an accident scenario involving a sinkhole or any mention of sinkholes," she said.

Two separate samplings by private entities have shown high-enriched uranium in the Nolichucky River, O'Neal said, including one 95 river miles downstream.

"The state gave NFS only three years on their (National Pollution Discharge Elimination System Permit) and the state has yet to approve the renewal of their hazardous waste permit," O'Neal said.

NRC officials at the meeting said all questions asked by citizens will be answered. No time frame was specified.