CHARLESTON, W.Va. -- Federal regulators this week backed off any separate enforcement action at a huge Raleigh County coal slurry impoundment, but disputed West Virginia's conclusion that the facility used "the most conservative design" and that concerns about the site are unfounded.

The U.S. Office of Surface Mining Reclamation and Enforcement concluded that state officials had acted properly in policing the Brushy Fork impoundment, in part because the West Virginia Department of Environmental Protection has promised more stability testing at the site just upstream from Whitesville.

Roger Calhoun, director of the OSM Charleston field office, said impoundment owner Alpha Natural Resources is going to drill deeper into the impoundment to test whether solid particles inside it appear likely to liquefy.

Also, Calhoun said, Brushy Fork will be one of 10 slurry impoundments around the state targeted in a new OSM study of whether coarse coal waste used in dams is properly compacted to ensure the structures are stable. That study, based on citizen group recommendations, is meant partially to spot-check testing already done by industry consultants.

"Trust, but verify," Calhoun said. "The design assumes certain parameters. It's a good thing to verify the parameters you have assumed in that design."

On Monday, Calhoun had issued a ruling that drops -- at least for the moment -- any potential for the OSM to take separate federal enforcement action at the 750-foot-tall dam, which Alpha acquired when it bought Massey Energy two months ago.

OSM officials had launched one of their more detailed investigations in years, responding to complaints from citizen activist Joe Stanley and other coalfield residents who have for years worried about Brushy Fork's safety.

Generally, the OSM is supposed to resolve questions about potentially improper DEP actions within 10 days -- thus the name of the "10-day notice" issued to state regulators. However, the OSM and the DEP have gone back and forth several times since January, without federal officials reaching a final decision.

OSM officials already had pushed the DEP to add new limits to control any potential impacts on the Brushy Fork impoundment from surface-mine blasting at Alpha's nearby Bee Tree Mine, which has been the site of repeated citizen protests.

The U.S. Office of Surface Mining Reclamation and Enforcement concluded that state officials had acted properly in policing the Brushy Fork impoundment, in part because the West Virginia Department of Environmental Protection has promised more stability testing at the site just upstream from Whitesville.

Roger Calhoun, director of the OSM Charleston field office, said impoundment owner Alpha Natural Resources is going to drill deeper into the impoundment to test whether solid particles inside it appear likely to liquefy.

Also, Calhoun said, Brushy Fork will be one of 10 slurry impoundments around the state targeted in a new OSM study of whether coarse coal waste used in dams is properly compacted to ensure the structures are stable. That study, based on citizen group recommendations, is meant partially to spot-check testing already done by industry consultants.

"Trust, but verify," Calhoun said. "The design assumes certain parameters. It's a good thing to verify the parameters you have assumed in that design."

On Monday, Calhoun had issued a ruling that drops -- at least for the moment -- any potential for the OSM to take separate federal enforcement action at the 750-foot-tall dam, which Alpha acquired when it bought Massey Energy two months ago.

OSM officials had launched one of their more detailed investigations in years, responding to complaints from citizen activist Joe Stanley and other coalfield residents who have for years worried about Brushy Fork's safety.

Generally, the OSM is supposed to resolve questions about potentially improper DEP actions within 10 days -- thus the name of the "10-day notice" issued to state regulators. However, the OSM and the DEP have gone back and forth several times since January, without federal officials reaching a final decision.

OSM officials already had pushed the DEP to add new limits to control any potential impacts on the Brushy Fork impoundment from surface-mine blasting at Alpha's nearby Bee Tree Mine, which has been the site of repeated citizen protests.

Calhoun said Tuesday his staff still believes solid coal waste within an upstream portion of the impoundment has shown a potential to liquefy. DEP officials, though, convinced the OSM that the company was taking appropriate steps to avoid that and to minimize any consequences should this "liquefaction" actually occur, Calhoun said.

Areas where waste has shown a high potential to liquefy are in an upstream area "being developed for future additional phases and do not serve as the load-bearing portion of the dam," Calhoun said in a three-page decision letter.

While state regulations don't specify such language, Calhoun said the DEP "is acting reasonably in its interpretation that the area being developed does not have to meet the same standards as the dam already approved as long as any failure in the construction area would not compromise the structural integrity of the dam at the currently approved slurry level," Calhoun wrote.

Tom Clarke, director of the DEP's Division of Mining and Reclamation, said the upstream development at Brushy Fork is not only legal, but also involves "very conservative design elements that will protect public safety and the environment."

However, Calhoun said this upstream construction "by its very nature is not the most conservative approach to dam construction" and that elevated liquid pressures showing up in company tests "are an indication of elevated risks."

Alpha officials did not respond to a request for comment.

Stanley said he had hoped the OSM would take federal enforcement action at the site.

"I'm disappointed, to say the least, that they didn't take a tougher stance on this," Stanley said.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.