The Hoosier Environmental Council said it would continue its legal challenge against Duke Energy Corp., despite the company agreeing to rethink a plan to close two potentially toxic coal ash ponds along the Ohio River.

The HEC opposes Duke Energy’s 2016 plan to close coal ash impoundments, also known as coal ash ponds, at its Gallagher Generating Station in Floyd County that involved leaving about 3 million tons of coal ash in place in unlined landfills.

The HEC argued the 2016 plan violated state and federal laws by allowing the coal ash, which contains toxic chemicals and heavy metals, to threaten human health and the environment by being in permanent contact with groundwater.

“Compounding the environmental threat from Duke’s coal ash at the Gallagher site is the fact that the contaminated groundwater flows into the Ohio River, spreading the pollution to surface waters,” said Dr. Indra Frank, HEC’s environmental health director. “What’s more, increasingly severe storm events resulting from climate change are increasing the risk of leaving coal ash in flood-prone areas, like the location of the Gallagher ash ponds.”

Duke Energy submitted the plan believing four out of the seven impoundments would be regulated under state regulations instead of the U.S. Environmental Protection Agency’s stricter 2015 Coal Combustion Residuals Rule, which sets rules for coal ash impoundments, including requirements on structural integrity, groundwater monitoring, record keeping and other criteria.

The plan was approved by the Indiana Department of Environmental Management in 2019, and the HEC appealed the decision to the Office of Environmental Adjudication, which upheld IDEM’s decision.

The HEC asked the Marion County Superior Court to review the OEA’s decision.

The EPA in January 2022 claimed the impoundments would need to comply with the federal rule, and Duke Energy withdrew its plan in April. The company said it would submit a new one to the state.

The HEC said it will continue to appeal the OEA’s decision on the original plan.

“Duke Energy’s decision to withdraw its unlawful Closure Plan for the coal ash ponds at Gallagher indicates it no longer believes it can reasonably defend its unsupported reading of the federal coal ash rule,” said Kim Ferraro, HEC’s senior staff attorney. “Whether the company’s pending revision of its closure plan will comply with the federal rule and be sufficiently protective of public health and groundwater quality remains to be seen, which is why HEC is continuing its legal challenge against the OEA’s decision to uphold IDEM’s wrongful approval of Duke’s now withdrawn Closure Plan.”

Duke Energy said its new plan to close the coal ash impoundments will involve a below-ground slurry wall and a synthetic liner cover that will minimize the amount of groundwater mixing with the coal ash. The company will also monitor groundwater for at least 30 years.

The company has not said when it will submit the new plan to IDEM for approval.