The report, which was released in September by researchers from the Nicholas School of the Environment at Duke University and the Department of Geological and Environmental Sciences at Appalachian State University, collected samples of the soil and used physical observations, optical point counting analysis and trace element analyses to study them.
The concentrations of toxic metals in the site's coal ash were discovered to be 10 to 30 times the baseline soil concentrations in North Carolina.
The chemicals in the coal ash also exceeded the EPA's threshold guidelines for ecological standards, which may pose human and environmental health concerns, according to the study.
Vengosh spoke at a September panel hosted by Safe Housing for Chapel Hill, where he explained both the report and the dangers of coal ash in residential areas.
"Coal ash is not defined as a hazardous waste, but by all means of scientific criteria, it is hazardous material — it cannot be part of our life," he said during the panel.
Over the past 30 years, scientists have also found that people living in close proximity to coal-fired power plants had higher rates of all-cause and premature mortality, according to a study from Dr. Julia Kravchenko, an associate professor of surgery at Duke University, and Herbert Kim Lyerly, a distinguished professor of immunology at the Duke University School of Medicine.
Their study, which included an analysis of 113 peer-reviewed articles on the subject, found the elevated health risk may be associated with exposure to air pollutants from plant emissions and a spectrum of radioactive isotopes and heavy metals in coal ash.
The study suggested more studies on the health impacts of coal-burning power plants in North Carolina to profile the severity of cumulative impacts of different air, water and soil contaminants.
Kravchenko, who also spoke at the September panel, said the coal ash at 828 Martin Luther King Jr. Blvd. should be removed before further development.
"The ground, the surface, should be clean," she said. "Before doing something — a playground, an apartment complex or just some rest area — everything should be removed."
She said the issue is that there are still not many studies in communities located near areas at a higher risk of coal ash exposure. The waste has very different version-specific components based on geographic area, she added.
Because of this, it is important to test a specific area's soil and look at its contaminants to make projections about how it would impact the health of surrounding communities, Kravchenko explained.
To get the day's news and headlines in your inbox each morning, sign up for our email newsletters.
"I think everyone can agree that coal ash itself can be toxic to humans in certain conditions," Hemminger said. "We have a very different site here than the ones they are talking about in most of their articles."
She said Hart & Hickman deemed digging up the coal ash and transporting it elsewhere hazardous to the health and safety of community members. Capping and containing the ash is the best option moving forward, and there are people who know how to do it well, she said.
Still, a report from Earthjustice, a nonprofit public-interest environmental law organization, said the cap-in-place method leaves coal ash sites permanently vulnerable due to floods or cap failure during extreme storms.
Removal of coal ash, in contrast, typically mitigates risks of both groundwater pollution and catastrophic spills, according to the report.
The report stated that different closure approaches result in different outcomes for environmental, economic and public health in each community.
Quantifying different approaches is important to help inform public officials, regulators and residents as the appropriate method is chosen, the Earthjustice report also stated.
Hemminger said the Town has been transparent about what it has learned, followed the science, hired reputable firms for the investigation and worked closely with the North Carolina Department of Environmental Quality.
"We've been working towards solutions for this site and will continue to do so," she said.
@DTHCityState | firstname.lastname@example.org
CORRECTION: A previous version of this article incorrectly stated information from a risk assessment by Hart & Hickman. The article has been updated to more reflect accurately reflect the report. The Daily Tar Heel apologizes for this error.