Despite its prevalence as a construction material in North Carolina, state records show a conspicuous absence of coal ash being used as structural fill in the Triangle, one of the fastest-growing and most construction-intensive regions of the the state.
Most of the 70-plus structural fill sites documented by the N.C. Department of Environment and Natural Resources are in rural areas, such as Halifax, Cumberland, Brunswick, Iredell and Nash counties.
The agency lists a pair of projects in Orange County and one in Durham County, but they were not completed or records are unavailable.
One project was a UNC-Chapel Hill pilot study in 1992 to assess the feasibility of using 500 to 600 tons of coal ash as a substitute for lime on agricultural fields at a farm that grew soybeans.
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The university has no records of the study and none of the employees from that time still work for UNC’s Energy Services department, said UNC spokeswoman Susan Hudson.
One condition of the state’s approval for the project was that UNC would submit a report on the pilot project, but DENR does not have a copy on file.
The UNC ash came from the campus co-generation power plant that burns coal as one of its fuel sources. The ash is temporarily stored on site in a silo and trucked away for reuse as structural fill, as concrete or for other uses, Hudson said.
DENR also lists Duke University as designating 4,000 to 5,000 tons of coal ash to be used as structural fill for the Science Research Center, Law School Addition, Public Policy Building, Medical Science Research Building and for utility trenches.
However, Duke spokesman Keith Lawrence said veteran employees on facilities projects do not recall ash being used for structural fill. “As best as we can determine, there is no indication that the ash was actually used as material,” Lawrence said.
Lawrence said the university does not have the time and resources to manually search its paper records, which are archived off-site, to confirm the employees’ recollections about the ash.
Duke had been burning coal on campus since the 1920s and converted the power plant to burn natural gas in 2011. The plant produces steam to heat Duke’s buildings, sterilize surgical equipment and maintain proper humidity for artwork and lab research.