DEQ Strengthens Air Quality Permits for 2 Duke Energy Facilities that will Reduce Overall Emissions

The North Carolina Department of Environmental Quality’s Division of Air Quality (DAQ) is issuing permit modifications to two Duke Energy facilities for the replacement of their coal units with gas turbines, after substantially strengthening the permits based on public feedback.

Division staff thoroughly reviewed public comments following two public hearings on the draft air quality permits. In response, the final air quality permits add new emissions limits and testing and reporting requirements, along with other revisions designed to ensure the facilities adhere to all applicable state and federal rules.

Duke Energy plans to retire coal-fired boilers at two power plants: Duke Energy Progress, LLC - Roxboro Steam Electric Plant in Person County, and Duke Energy Carolinas, LLC - Marshall Steam Station in Catawba County. These units would be replaced with new natural gas-fired turbines. The transition away from burning coal at both facilities will reduce overall emissions of air pollution, particularly nitrogen oxides (NOx) and sulfur dioxide (SO₂). Both permits contain requirements to comply with federal greenhouse gas standards for new sources.

After two coal boilers at Marshall Steam Station are retired, the facility will emit 1,981 fewer tons of NOx and 1,196 fewer tons of SO₂ each year. Retiring the six coal boilers at the Roxboro facility will lead to 4,130 fewer tons of NOx and 3,675 fewer tons of SO₂ each year. Emissions of fine particulate matter, carbon monoxide and toxic air pollutants, such as sulfuric acid, arsenic and a variety of heavy metals would also see substantial decreases.

The final air quality permits require that each new turbine be equipped with low-nitrogen oxide burners and be controlled by an oxidational catalyst and a selective catalytic reduction system. The facilities would also be required to continuously monitor emissions of several criteria air pollutants. Both plants would be subject to recordkeeping and reporting requirements and regular inspections.

Air dispersion modeling reviewed by DAQ demonstrated that emissions of toxic air pollutants at both facilities are not expected to cause an exceedance of any acceptable ambient level. The final permits include conditions that ensure ambient levels of all pollutants beyond both facilities’ fence lines comply with emission standards, including applicable health-based standards.

DAQ held a public hearing on each draft permit and public comment periods to solicit feedback from North Carolinians. Division staff thoroughly reviewed every comment received. In response to these public comments, the final permits were strengthened in the following ways:

Marshall Steam Station Changes:

• Added Prevention of Significant Deterioration Avoidance limitations and conditions for four additional pollutants: fine particulate matter, coarse particulate matter, SO₂ and sulfuric acid.
• Added a requirement that Duke Energy notify DAQ when commercial operation of the gas-fired turbines has begun, which will trigger a requirement to retire the coal units.
• Added more stringent reporting and recordkeeping requirements related to ancillary equipment at the site.
• Additional minor clarifications and updates.

Copies of Marshall Steam Station’s final permit, final permit review, hearing officer’s report, permit application, and one-page project fact sheet are available online.

Roxboro Steam Electric Plant Changes:

• Added a testing requirement for sulfuric acid and a conditional testing requirement for SO₂.
• Clarified that the required testing for particulate matter must include condensable particles in addition to filterable particles.
• Added more stringent reporting and recordkeeping requirements related to ancillary equipment at the site.
• Added a condition to subject the facility to New Source Performance Standards for Stationary Combustion Turbines and Stationary Gas Turbines, Subpart KKKKa, should the U.S. Environmental Protection Agency finalize that rule in the future.
• Additional minor clarifications and updates.

Copies of Roxboro Steam Electric Plant’s final permit, final permit review, hearing officer’s report, permit application, and one-page project fact sheet are available online.

If you need this information in Spanish or another language, please call 919-707-8446 or email Shawn.Taylor@deq.nc.gov.