CANADYS -- State investigators have concluded that particles in well water near a South Carolina Electric & Gas coal-fired power plant probably are made of lignite, a geologic precursor of coal that has been found underground before in the area.

Technicians with the state Department of Health and Environmental Control took new samples late last year after an initial sampling effort failed to identify the particles. They sent the samples to the University of South Carolina's Electron Microscopy Center for analysis and consulted with a federal government geologist.

"We relied on multiple lines of evidence," said David Baize, DHEC assistant bureau chief, adding that the SCE&G coal plant wasn't the source of the particles. "It's not physically possible (for materials, such as coal) to move through the formations."

Residents in the area have found black particles in their well water for years and long wondered whether the coal plant was the source. The plant's history of air and groundwater pollution fueled these concerns; records show the facility's massive coal ash ponds have leached arsenic and other toxic chemicals into shallow aquifers, despite SCE&G's efforts to contain these chemicals.

In response to these concerns, Post and Courier Watchdog worked with College of Charleston geologists to analyze dark black particles in residents' water. Tests showed the particles had similar chemical characteristics to loose chunks of coal found just outside the plant. Officials with SCE&G have strenuously denied any connection between the particles in the well water and coal used at the plant.

Officials with DHEC tested wells in the fall but said they didn't have the equipment and expertise to identify the particles. They did a second round of sampling in December and sent particles to USC for analysis. They began to focus on lignite.

Lignite is an ancient plant material that over long periods of time becomes more like coal. It's used in some coal plants, but SCE&G said it has never used lignite at any of its coal plants. Lignite has a lower carbon content than other forms of coal, making it less efficient to burn.

Baize said DHEC analyzed samples from five homes near the plant and determined that some particles were 28 to 78 percent carbon and had a chemical makeup consistent with lignite.

Officials also consulted with Frank Chappelle, a U.S. Geological Survey geologist, who noted that a well drilled eight miles north of the area found lignite in what's known as the "Black Mingo" formation between 300 to 500 feet below the surface.

Baize said a longtime well-driller in the area also has found what he described as "woody" materials in deeper aquifers. "Based on the evidence, lignite is the most likely answer," Baize said. The agency has determined that the water itself in the area is free from any chemical contamination but that some of the homes may have copper and lead in their plumbing systems. He said the agency is encouraging residents to use filters to keep sediment out of their drinking water.

"We feel vindicated that testing has determined, conclusively, that the black particles in the water are in no way associated with the operation of our Canadys Station," said Scott Grigg, the power company's supervisor of public affairs.

Residents in the area remain skeptical about the DHEC results and frustrated by the particles. "Last week, I went out to the washing machine, and it filled up with that coal dust," said Raymond Lewis, a longtime resident.

Two environmental groups found 31 coal ash pits across the country, including three in South Carolina, that should be added to an existing federal roster of polluting ash dumps.

Read their report, Out of Control: Mounting Damages From Coal Ash Waste Sites (142 page PDF)