But Duke University professor Avner Vengosh, who did research for the study, told The Associated Press in October that the proximity of the coal pits to the water was still "on the table" as a possible factor in water contamination.
"The most import thing is to make sure the industry, the coal ash issue, is not off the table," Vengosh said. "Groundwaters near coal ash ponds are contaminated. We see evidence for that. But the issue with hexavalent chromium, we're finding, is unrelated and much larger than we thought."