NC0038377_Responses to Comments_20211215

Responses to Comments for Mayo Steam Electric Generating Plant
09/17/2021
Comments from SELC
Comment: The Agency must establish Best Available Technology (BAT) standards for
Mayo's coal ash landfill leachate (BPJ BAT)
Response: The Technology -based limits are already incorporated into the permit. The
effluent limitations in the permit are established in accordance with the existing federal
and state rules and regulations. EPA has recently updated 40 CFR 423 for Power Plants
in 2015 and then again in 2020. EPA conducted extensive data gathering and analysis
and established Technology Based Effluent Limitations (TBELs) for numerous
parameters in various waste streams generated by Power Plants.
The EPA decided that TBELs for all parameters of concern are not necessary because
"Effluent limits and monitoring for all pollutants of concern is not necessary to ensure
that the pollutants are adequately controlled because many of the pollutants originate
from similar sources, have similar treatabilities, and are removed by similar
mechanisms. Because of this, it may be sufficient to establish effluent limits for one
pollutant as a surrogate or indicator pollutant that ensures the removal of other
pollutants of concern." The EPA established TBEL limitations for two parameters of
concern in the landfill leachate: TSS and Oil and Grease.
At this time, the DWR has no capacity to develop their own BPJ BAT in according with
the EPA guidance. This effort would be enormous in nature and will require full time
commitment from numerous existing staff members and require expertise in economics
beyond what exists in the DWR. For example, EPA has the Engineering and Analysis
Division that employs approximately 40 experts. They develop Effluent Guidelines, this
Division spent 10 years to develop the latest update to the Power Plant Guidelines and
then an additional 5 years to make subsequent adjustments to the Final Rule.
In 2014, the DWR attempted to develop their own BPJ BAT for Duke Energy Riverbend
permit by using a very simplified procedure. SELC was critical of DWR's effort for not
adhering to the EPA BPJ BAT guidance.
Therefore, the DWR has to rely on the EPA capacity and expertise in developing Effluent
Guidelines. In addition, the new EPA administrator made a commitment to update the
Power Plant Guidelines by the end of the 2022. When the new update is finalized, the
DWR will incorporate newly promulgated TBELs into the Duke permits.
The suggestion to use membrane filtration is ill-advised because it will generate liquid
waste that has to be disposed somewhere off -site at the hazardous waste landfill. The
utilization options for such a waste are very limited and some facilities have to ship
liquid hazardous waste to Texas. DWR disagrees with SELC position that 2020 changes
to the rule represent a "rollback". In fact, the 2020 update tightened 4 FGD limits and
relaxed 3 FGD limits. These changes went through the public vetting process which
SELC was afforded the opportunity to comment on at that time.
Furthermore, the existing Mayo Plant is one of the most advanced facilities in the USA,
it uses cooling towers and Zero Liquid Discharge for treating FGD waste. The facility
currently meets all the water -quality based limits.
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