Duke Energy and the Florida Department of Environmental Protection are determining how to best limit or remove contamination from coal ash stored at Duke's Citrus County plant after high levels of heavy metals were found in groundwater samples taken at the site.
In a report from June obtained last week, Geosyntec Consultants documented excessive amounts of arsenic, lithium, molybdenum and other contaminants in several samples taken in May 2018, October 2018 and March 2019 from monitoring wells surrounding the coal plants on Duke's Crystal River Energy Complex.
Reports like Geosyntec’s are required by federal law and propose remedies once a significant quantity of harmful substances is detected in groundwater from the storage of coal ash. Coal ash is the waste left behind after coal is burned to produce power.
Geosyntec Consultants' coal ash report for Duke Energy's Crystal River Energy Complex.
Geosyntec told Duke in its report the company must, “as soon as feasible,” select a solution to curb the inflow of contaminants, and must hold a public meeting at least 30 days prior to choosing a plan.
The report does not endorse a specific means of remediating the pollution, instead highlighting options available to the company to either control the contamination at its source and/or remove it from the groundwater.
Source-control measures suggested include: installation of a final cover system for the ash; excavation of the ash for reuse; or excavation and disposal of ash off-site.
For controlling the contamination in groundwater, the consultants suggested: in-situ chemical immobilization; preventing the migration of affected groundwater; withdrawing affected groundwater for treatment; permeable reactive barriers; phytoremediation, or the usage of plants to remove contamination; or monitored natural attenuation — keeping an eye on the problem and seeing whether it gets better with time.
“We are working diligently to further explore the feasibility of the various options as quickly as possible,” Duke spokeswoman Paige Sheehan said. “Our goal is to bring well-researched potential correction actions to the regulator and the public.”
Duke is federally mandated to maintain the monitoring wells to measure whether groundwater at various depths is being contaminated due to storage of coal ash at the site.
"A dense network of monitoring wells also tells us that people and the environment remain well protected from our operations," Sheehan said.
Dee Ann Miller, a Florida Department of Environmental Protection spokeswoman, said there are no public lots or wells downstream of Duke's coal-ash stores.
"Due to the location of Duke Energy’s Crystal River Energy Complex, there are no downgradient residential properties or public water supply wells that might be impacted," she said.
In between nine and 16 of the total 26 tested wells in 2018 and 2019, Geosyntec reported arsenic levels as high as 79.8 micrograms per liter (ug/L), lithium as high as 502 ug/L and molybdenum up to 338 ug/L, according to Geosyntec’s report.
Maximum groundwater contaminant levels set by the U.S. Environmental Protection Agency for arsenic, lithium and molybdenum are 10, 40 and 100 ug/L, respectively.
Sheehan said the findings “are exactly what you’d expect under a coal-ash facility like ours at Crystal River.”
“Very importantly, the impacted groundwater is highly localized and remains on plant property and in very close proximity to the landfill,” she added.
Miller corroborated that the contaminants were found close to Duke's coal ash landfill and have not traveled off the complex.
Geosyntec also recorded high amounts of radium in wells, but concluded they were natural.
“The constituents you find in coal ash are also naturally occurring in soil and dirt, so that means we also find them in nature,” Sheehan noted.
Sheehan said Duke’s two remaining coal-fired units (two others were recently retired) on the local complex produce both a finer fly ash, which is filtered out through smokestacks; and a coarser bottom ash, which forms at the bottom of the furnace.
Coal ash is either sold to be reused in ready-mix concrete, or compacted on 62 acres of a 100-acre landfill a few thousand feet west of Duke’s natural gas plant on the 4,730-acre complex, of which 1,462 acres are developed, according to Geosyntec.
In 2015, Duke pleaded guilty to federal environmental crimes and agreed to pay $102 million in connection to a 2014 coal-ash spill that impacted 70 miles of a river shared by North Carolina and Virginia.
Duke, a Charlotte-based company, announced in July it had restored a significant portion of the Dan River bottom in accordance with a legal agreement that followed the incident.
Geosyntec stated Duke had installed a total 26 monitoring wells in 2015, 2016, 2018 and 2019 to capture groundwater as it flows from the northeast to the southwest, through its local complex and coal ash deposit.
Geosyntec reported that much of the chemicals’ concentrations were found in wells along the northern, southwestern and southern edges of Duke's landfill.
Miller said more sampling of areas north of the landfill needs to be done to confirm if the lithium and arsenic there are coming from either Duke's coal ash or from somewhere off the complex.
Monitoring wells farther west of Duke’s coal ash landfill, nearer the Gulf of Mexico, did not show excessive contamination, according to Geosyntec.
“We feel very confident that the Gulf is well protected from operations,” Sheehan said. “Groundwater monitoring data shows the impact to groundwater is very localized around the landfill and we do not expect any appreciable migration to the Gulf.”