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Environment » Air, Water & Land Quality » Solid Waste » Water Related Issues

Water Related Issues

Duke Energy is committed to the safety and well-being of our employees, our communities and the environment. We operate all our facilities, including our ash ponds and landfills, in compliance with local, state and federal environmental regulations.

Surface Water

Water is discharged from ash ponds into surface waters (lakes or rivers). These discharges are regulated by each state under the National Pollution Discharge Elimination System (NPDES) permitting program. The characteristics of the water that is discharged into surface waters must comply with the limits that are specified in a facility’s NPDES permit. Those limits are established by the authorized state at levels that it considers protective of human health and the environment, based on rigorous analysis.

The NPDES limits vary from facility to facility and from state to state based on the characteristics of the discharge and the receiving body of water. Duke Energy samples its discharges according to the frequencies specified in the NPDES permits for those substances with permit limits. We then submit the data to the state regulatory authority to demonstrate compliance with the NPDES permit. Some substances that have no permit limits are sampled at different frequencies.

NPDES permits must be renewed every five years. As part of its permit renewal application, Duke Energy must complete an extensive analysis and characterization of its discharges and submit that information to the state regulatory authority, which uses the information to establish the limits in the new permit.


We monitor the groundwater around our active ash ponds regularly to ensure the protection of public health and safety. The company has installed groundwater-monitoring wells around all active ash ponds, except for the Edwardsport facility in Indiana where the existing generating units will soon be retired and the ash ponds closed. We take samples several times a year and share the data with the appropriate state agencies.

  • We own the majority of land around our active facilities; therefore, few public or private groundwater wells or residents are located near the ash ponds.
  • Most of the constituents we monitor are nontoxic and do not have health-based drinking water standards. For example, we monitor manganese because of an aesthetics-based secondary drinking water standard for the smell and color of the water. There is no drinking water standard established for some constituents, such as boron.
  • It is important to conduct extensive scientific studies to ensure that we fully and accurately understand any potential impacts from the ash ponds.
  • If initial monitoring reveals a potential trend of elevated constituents, we notify the appropriate state agencies and increase the number of monitoring wells. The data from these additional wells helps us identify the location, flow and source of the elevated constituents, and gather data on naturally occurring levels.
  • Where needed, we work collaboratively with experts and authorities to pursue transparent, responsible and practical solutions.

Utility Industry Action Plan

In 2007, Duke Energy formally adopted the voluntary Utility Industry Action Plan for the Management of Coal Combustion Products (CCPs). Per the action plan, Duke Energy samples groundwater around its coal ash ponds at least twice each year for CCP-related substances that have primary drinking water standards, regulatory-established maximum concentration levels (MCLs) or other state standards, and that may reasonably be expected to migrate from the coal ash pond to groundwater based on site-specific factors.

If an exceedance of a groundwater standard is detected and the cause of the exceedance can be reasonably attributed to be the ash pond, Duke Energy will consult with the state regulatory authority to determine what, if any, additional groundwater monitoring should be performed to assess the cause of the exceedance. In the event that additional monitoring is performed, and that monitoring confirms a CCP-related exceedance of one or more MCLs or other standards, Duke Energy will work with the state regulatory authority to develop a response plan to address the situation. The objective is to prevent any detected contaminants from migrating off the power plant site and negatively impacting groundwater off-site.