NC0004987_Responses to Comments 3-2-2022_20220302

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Responses to Comments for Marshall Steam Station
03/02/2022
Comments from SELC
I.A. DEQ Must Strengthen Relaxed Monitoring Requirements in the Draft Permit.
Response: The existing monitoring frequency is sufficient to evaluate compliance of the
facility with the water quality standards and permit conditions. The frequency is
established in accordance with the DWR policy. Reduction in the monitoring frequency
does not violate anti -backsliding provision, the Division has routinely reduced
monitoring frequencies since the early 1970s when NC NPDES program was
authorized by the EPA. The established frequency is consistent with other Duke
permits and has been approved by the EPA.
The enforcement of daily maximum and monthly average limitations is not prevented
by using Monthly, Quarterly, or even Annual Monitoring. The DWR has been enforcing
such limits since 1972.
I.B. DEQ Must Amend Weakened and Eliminated Effluent Limitations in the
Draft Permit.
Response: The need for water quality based effluent permit limits is determined based
on the results of the reasonable potential analysis (RPA). The RPA procedure utilized
by the Division is conducted in accordance with the EPA's regulation (40 CFR
122.44(d)(1)). When the permitting authority determines, using procedures in
paragraph (d) (1) (ii) of this section, that a discharge causes, has the reasonable
potential to cause, or contributes to an in -stream excursion above the allowable
ambient concentration of a State numeric criteria within a State water quality
standard for an individual pollutant, the permit must contain effluent limits for that
pollutant. Permit limits are added only if the results of the RPA indicate the potential
for exceeding the water quality standards, and are not arbitrarily assigned. However,
absence of permit limits does not allow the facility to violate instream water quality
standards.
When the RPA indicates no potential to violate water quality standards for a particular
parameter, the limit for this parameter is eliminated from the permit. This procedure
is conducted in accordance with EPA guidance, it does not violate anti -backsliding
provisions of the Clean Water Act, and has been consistently implemented for decades
with the EPA approval.
II.A. Site -Specific TBELs Must Be Based on the Best Available Technology.
and
II.B. The Draft Permit Fails to Limit Known Constituents of Coal Ash Waste
Using the Best Available Technology
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
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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 the 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 and SELC was afforded the opportunity to comment on at that time.
III. The Reasonable Potential Analysis is Flawed
Response: The Division conducted EPA -recommended analyses to determine the
reasonable potential for toxicants to be discharged at levels exceeding water quality
standards/EPA criteria by this facility. For the purposes of the RPA, the background
concentrations for all parameters were assumed to be below detection level. The RPA
uses 95% probability level and 95% confidence basis in accordance with the EPA
Guidance entitled "Technical Support Document for Water Quality -based Toxics
Control." The RPA included evaluation of dissolved metals' standards, utilizing a default
hardness value of 25 mg/L CaCO3 for hardness -dependent metals. This analysis has
been approved by the EPA, including the use of the default hardness value.
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The Division conducted a new RPA analysis using 8.1 MGD flow, the results remained
the same for majority of the parameters with the exception of Arsenic. Therefore, the
Division will re -instate the Arsenic limits to Outfall 002.
The assumptions regarding background concentration of the pollutants being below
detection level have been confirmed by the long term instream monitoring. The permit
requires monthly upstream and downstream monitoring near the ash pond discharge.
The upstream site (Station 15.9) is approximately 1 mile upstream of the discharge and
downstream location (Station 14) is approximately 1 mile downstream of the discharge.
These monitoring stations have been established through the BIP monitoring program,
which was required to maintain the 316(a) temperature variance and have been in place
for decades. The current monitored parameters are: As, Cd, Cr, Cu, Hg, Pb, Se, Zn, Br,
Total Hardness as CaCO3) and Total Dissolved Solids (TDS).
The concentrations of the following measured parameters upstream are either below
detection level (As, Cd, total Cr, Pb, Se, and Zn) or very well below water quality
standards (Cu and Hg). When the RPA was conducted, state did not establish criterion
for Br.
It is very important to emphasize that concentrations of the measured parameters
downstream are also either below detection level (As, Cd, Pb, Se, Zn) or well below water
quality standards (Cu, Hg, Br, and TDS). It means that the existing permit limitations
are sufficient to maintain water quality standards.
Furthermore, there is additional evidence to suggest that instream water quality is well
protected by the existing discharge limitations. The permit requires fish tissue
monitoring for As, Se, and Hg near the ash pond discharge once every 5 years. This
frequency is consistent with EPA guidance. During the last permit cycle sunfish and
bass tissues were analyzed for these trace elements. The results were below action
levels for Se and Hg (10.0 pg/g - Se, 0.40 pg/g - Hg, NC) and screening value for As
(1.20 - pg/g, EPA). These results are consistent with the previous monitoring results.
IV. DEQ Must Address Unpermitted Discharges of Contaminants Through
Groundwater
Response: Duke is conducting site remediation actions that include dewatering of ash
pond and ash excavation. If these action will not address miniscule discharges from
the two seeps, the Division will address this issue.
V. DEQ Continues to Misapply the Turbidity Standard at Marshall
Response: The permit turbidity conditions have been developed by the Division and
approved by the EPA, they are consistently used for all Duke Permits. The correction
of instream turbidity requirement will be made to change the limit from 50 NTU to 25
NTU.
Most importantly, the instream monitoring indicates that downstream turbidity
concentrations are below 10 NTU. Therefore, the facility discharge does not cause
violation of turbidity standard (25 NTU).
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The Division does not have any evidence to suggest that discharge from Outfall 005
exceeds 25 NTU. Historically, discharges from unlined ash ponds were well below 25
NTU and the new Lined Retention Basin has no physical properties that would change
such trend. Hence, addition of the turbidity monitoring to Outfall 005 is not justified.
The Division will continue to evaluate the station's compliance with the water quality
standard through instream monitoring.
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