NC0004961_Comments on Draft Permit_20150504

jDUKE Harry K.Sideris
CENERGY® Environmental,
Vice President
ental,Health&Safety
526 South Church Street
Mail Code EC3XP
Charlotte,NC 28202
[phone]
May 4, 2015 RECEIVEDIDENRIDWR
MAY - 72015
North Carolina Department of
Water Quality
Environment and Natural Resources permitting Sectio►'
Wastewater Permitting
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Comments on the draft NPDES Permit for Riverbend Steam Station
Permit No.: NC0004961
Attention Wastewater Permitting:
The North Carolina Department of Environment and Natural Resources (NCDENR) Division of Water
Resources (the Division) issued a draft National Pollutant Discharge Elimination System (NPDES) Permit
for the Duke Energy Riverbend Steam Station on March 6, 2015. Duke Energy Carolinas LLC (Duke
Energy) commends NCDENR for developing the draft permit and recognizing the existing discharges
from the facility's outfalls will not cause contravention of the state water quality standards or EPA
criteria. Duke Energy continues to work as quickly as possible to close the ash basins and finalizing this
wastewater permit is a critical step to advance the ash basin closure process. In order to facilitate the
closure process, Duke Energy needs permit conditions that are reasonable while ensuring the discharges
will not adversely affect water quality. Duke Energy, therefore, respectfully submits the following
comments on the draft permit.
Outfall 001
Historically, the once-through cooling water was discharged through Outfall 001. With the station no
longer generating electricity, the discharges through this outfall will primarily consist of water from the
plant chiller system. The permit imposes temperature monitoring and a downstream temperature limit,
as well as monthly flow monitoring.
Recommended changes
1. Duke Energy requests the removal of the downstream temperature limit and the temperature
monitoring requirement for Outfall 001. The Riverbend Steam Station retired on April 1, 2013
and ceased the discharge of once-through cooling water. The station will not be contributing

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heat to the receiving waterbody through any of the discharges. Any increase in the downstream
temperature will be due to ambient conditions outside the control of the station.
2. Duke Energy requests the Fact Sheet be updated to reflect the current wastestreams discharged
through this outfall,which is primarily water from the plant chiller system.
Comments on the Development of the Technology Based Effluent Limits(TBELs)
The permit establishes technology based effluent limits (TBELs)for arsenic, selenium and nitrate/nitrite
as N on Outfall 002 (ash pond discharge), Outfall 002 (dewatering) and Outfall 010 (combined seep
outfall). The TBELs for arsenic and selenium were based on an evaluation of the effluent data from the
ash basin discharges from Belews Creek,Allen and Marshall Steam Stations. The limits for nitrate/nitrite
as N were based on the proposed EPA Steam Electric Effluent Limitation Guidelines (ELG) because the
Division did not have any long-term nitrate/nitrite data.
The NPDES regulations at 40 CFR §125.3(c)(2) require permit writers developing TBELs to consider the
following:
• The appropriate technology for the category class of point sources of which the applicant is a
member, based on all available information.
• Any unique factors relating to the applicant.
The regulations also require that, in setting TBELs, the permit writer consider several specific factors
established in §125.3(d), to select a model treatment technology and derive effluent limitations on the
basis of that treatment technology.That process and the factors considered by the permit writer are the
same factors required to be considered by EPA in developing effluent guidelines. For establishing best
available technology(BAT) requirements for toxic and non-conventional pollutants,the following factors
must be considered:
— The age of equipment and facilities involved,
— Process employed,
— Engineering aspects of the application of various types of control techniques,
— Process changes,
— The cost of achieving such effluent reductions,and
— Non-water quality environmental impacts(including energy requirements).
Based on the information published by the Division, there was no indication that any of these factors
were considered in establishing the TBELs.
Furthermore, the Fact Sheet states "The existing federal regulations require the development of
Technology Based Effluent Limits (TBELs) for the parameters of concern." In Duke Energy's opinion,
however, the permit writer has the discretion to choose whether or not to impose BPJ limits. This
opinion is supported by a recent court ruling in Tennessee. The state court affirmed a 2013 decision of

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the Tennessee Board of WaterTVA's Quality,Oil, and Gas(the Board) holdingthat NA s Bull Run Fossil Plant is
not required to have "BPJ" permit limits beyond what the 1982 Effluent Limitations Guidelines require.
The Board ruled against claims that more permit limits were required. The Board stated the permit
complies with the 1982 ELG rules, and "[b]ecause the 1982 ELG for power plants governs, a Best
Professional Judgment (BPJ) analysis was not required." The Board further stated, when EPA set the
1982 rules, EPA considered setting numeric limits for metals but decided not to because they were
"present in amounts too small to be effectively reduced"'.
In addition, it is stated in EPA's NPDES Permitting Manual (September 2010), regarding situations in
which case-by-case TBELs are necessary, "The permit writer should make sure that the pollutant of
concern is not already controlled by the effluent guidelines and was not considered by EPA when the
Agency developed the effluent guidelines.i2 Since EPA considered setting numeric limits for metals, the
Division is not obligated to establish TBELs for these parameters.
The Division's decision to propose TBELs on FGD wastewater, and seeps appears to be dictated by a
memorandum from James A. Hanlon to EPA Water Division Directors for its Regions: Memorandum,
James A. Hanlon to Water Division Directors, Regions 1-10, "National Pollutant Discharge Elimination
System (NPDES) Permitting of Wastewater Discharges from Flue Gas Desulfurization (FGD) and Coal
Combustion Residuals (CCR) Impoundments at Steam Electric Power Plants" (June 7, 2010). It is
important to note the Hanlon memorandum is guidance and not legally binding, as stated in Section VI
of the memo. Furthermore, the guidance does recommend establishing TBELs for FGD wastewater;
however, the guidance recommends establishing limits for coal combustion leachate (i.e. ash basin
seeps) based on water quality based effluent limits (WQBELs)not TBELs3.
Furthermore, the Riverbend Steam Station retired on April 1, 2013.The proposed ELG rule,therefore, is
not expected to be applicable to Riverbend Steam Station. Under the proposed ELG rule, the water
remaining in the ash basin would be classified as legacy wastewater and EPA did not propose any limits
on legacy wastewater.
Mercury Limits at Outfall 002.and Outfall 010
The permit imposes TBELs for mercury at the combined Outfall 010(combined ash basin seeps),Outfall
002 (ash basin discharges),Outfall 002(dewatering)and Outfall 011 (Former Stormwater Outfall 1).
These limits are based on the statewide mercury total maximum daily load (TMDL).
1
In the Matter of Tennessee Clean Water Network v. Tennessee Dept.of Environment and Conservation,Case No.
WPC10-0116(Tenn. Dept.of Env.and Conservation Dec. 17,2013).
2 Refer to EPA's NPDES Permit Writers'Manual,September 2010,Section 5.2.3.2"Identifying the Need for Case-
by-Case TBELs"p.5-45—46.
3 Refer to Attachment B,"Water Quality-Based Effluent Limits Coal Combustion Waste Impoundments",of the
James Hanlon memorandum,June 7,2010.

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Recommended Changes
3. Duke Energy requests a 5-year compliance schedule to comply with the mercury limit. With the
limits being newly proposed, a compliance schedule should be included to allow for the design,
evaluation, budget,and construction of a treatment system to meet the limits.
Outfall 002 Ash Pond Discharge
As stated above, the permit establishes TBELs for arsenic, selenium, and nitrate/nitrite as N on Outfall
002 (Ash Pond Discharge). The proposed TBELs are effective 4.5 years from the effective date of the
permit. In the interim, temporary best professional judgment (BPJ) limits are imposed, which were
derived by multiplying the proposed TBELs by 5.
Due to the lack of long-term data,the Division based the nitrate/nitrite as N limits on the proposed ELG
rule. The nitrate/nitrite limits proposed in the ELG rule were specific to FGD wastewater, and were
based on data collected immediately following the FGD wastewater treatment systems at Belews Creek
and Allen Steam Stations, which were not associated with the ash basin discharge. Furthermore, the
nitrate/nitrite limits proposed in the ELG rule were based on only 10 observations (5 observations from
both Belews Creek and Allen Steam Stations)1. EPA, therefore, did not have sufficient long-term data to
develop the limits for nitrate/nitrite in the proposed ELG rule. Since Riverbend has never had a FGD
scrubber,there is no technical basis for establishing nitrate/nitrite as N limits on the ash basin discharge.
In addition,there are additional sources of nitrate/nitrite into the ash basin that were not accounted for
in the development of the limit,such as:
— Goose droppings,
— Algae blooms due to nutrient inputs from stormwater runoff,and
— Input of sanitary waste treatment systems to the ash basin.
Recommended Changes
4. Duke Energy requests the removal of the TBELs from Outfall 002, given the reasonable potential
analysis (RPA) concluded that the discharge is not expected to violate applicable water quality
criterion and the TBELs were not developed in accordance with 40 CFR 125.3(d).The Riverbend
Steam Station has ceased electric generation and discharges from the ash pond have
significantly reduced, as stated in the Fact Sheet. In fact, there have not been any discharges
from Outfall 002 since April 2014. Bottom and fly ash is no longer discharged to the pond and
the station has never had a FGD scrubber. Therefore, the revisions proposed in the ELG rule,
with the possible exception of combustion residual leachate, are not expected to apply to
1 Observations at Allen included the average of four 24-hour composite samples collected from 8/3/10-8/6/10,and
four 24-hr composite samples collected on 10/5/10, 11/1/10, 12/6/10 and 1/12/11.
Observations at Belews Creek included the average of four 24-hour composite samples collected from 6/8/10–
6/11/10,and four 24-hr composite samples collected on 10/6/10, 11/3/10, 12/8/10 and 1/17/11.

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Riverbend Steam Station. Furthermore, there is no technical justification for the nitrate/nitrite
limits at Riverbend Steam Station. In the proposed ELG rule, these limits were applied
specifically to the FGD wastewater stream and only proposed for the chemical precipitation
followed by biological treatment model technology.
5. If the TBELs are applied, Duke Energy requests the specific model technology used to derive the
TBELs that were applied to Outfall 002 (ash basin discharge). In the event the model technology
is installed and the limits imposed are not achieved, Duke Energy would like to have the option
of requesting a less stringent limit as allowed under the Clean Water Act §402(o)2(E). Duke
Energy, also, requests inclusion of clarifying language in the permit authorizing the removal of
free water above the settled ash layer including, but not limited to, decanting, controlled
pumping and/or normal operation. It is Duke Energy's understanding, based on conversations
with Division staff that the permit as drafted allows for the discharge of free water above the
settled ash layer in the ash basin by removal of stop logs, sections of riser and/or controlled
pumping through the permitted Outfall 002. The discharge of this water would only be subject
to the limits imposed on Outfall 002 (ash basin discharge). Only the removal of interstitial water
from the secondary ash basin would be subject to the Outfall 002 (dewatering) limits. Interstitial
water is defined as entrapped water (i.e., water occupying the pore space within the ash and
below the ash surface). In addition, stormwater collected in the ash basin would be permitted
under Outfall 002 (Ash Pond Discharge).
6. Duke Energy requests the title for the ash basin discharge outfall to be revised to "Outfall 002
(discharges from the ash basin associated with normal operations, decanting and/or
stormwater)".This will be necessary to avoid confusion between the two outfalls.
7. Duke Energy would also like to request the language in the Fact Sheet be updated to reflect
current discharges to the ash basin. These would consist of stormwater from roof drains and
paving, treated groundwater, coal pile runoff, track hopper sump (groundwater), turbine and
boiler room sumps,general plant/trailer sanitary wastewater, and stormwater from pond areas,
upgradient watershed and miscellaneous stormwater flows.
Outfall 002 Dewatering
The permit establishes TBELs for arsenic, selenium, and nitrate/nitrite as N on Outfall 002 (Dewatering).
Again, the arsenic and selenium TBELs were based on an evaluation of the effluent data from the ash
basin discharges from Belews Creek, Allen and Marshall Steam Stations and the limits for nitrate/nitrite
as N were based on the proposed ELG rule.
Comments on the Definition of Dewatering
The permit does not clearly define dewatering. Based on discussion with Division staff, the limits for
dewatering do not apply to the removal of free water(i.e. decanting) above the settled ash layer by the
removal of stop logs, sections of riser and/or controlled pumping through the permitted outfall flow.

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The limits only apply to the removal of interstitial water. Interstitial water is defined as entrapped water
(i.e., water occupying the pore space within the ash and below the ash surface). Dewatering would also
not apply to stormwater collected in the ash basin during dewatering activities.
Comments on the proposed limits for nitrate/nitrite as N
Due to the lack of long-term data, the Division based the nitrate/nitrite as N limits on the proposed ELG
rule. As stated above, the nitrate/nitrite limits in the proposed ELG rule only applied to the internal
outfall from the FGD wastewater system and the proposed limits were only based on 10 observations(5
observations from both Belews Creek and Allen). Riverbend has never had a FGD Scrubber; therefore,
there is no technical basis for establishing nitrate/nitrite as N limits on dewatering.
Also, the same possible sources of nitrate/nitrite in the ash basin would apply to the dewatering
process. These other sources were not accounted for in the TBELs.
Recommended Changes
8. Duke Energy requests clarifying language in the permit that"dewatering limits" are applicable to
removal of interstitial water only, based on discussions with Division staff. The following
language is recommended:
"The limits for dewatering do not apply to the removal of free water (i.e.
decanting) above the settled ash layer by removal of stop logs, sections of riser
and/or pumping through the permitted outfall flow path. The limits only apply
to the removal of interstitial water and removal of interstitial water is
authorized by this permit. Interstitial water is defined as entrapped water (i.e.,
water occupying the pore space within the ash and below the ash surface).
Interstitial wastewater would be generated through mechanical movement of
ash such as through dredging, and excavating trenches within the ash and
discharge would generally occur by controlled pumping. Stormwater collected in
the ash basin during dewatering activities would not be subject to the
dewatering limits."
9. Duke Energy requests the inclusion of clarifying language in the permit that the dewatering
limits would only apply to the removal of interstitial water generated by dewatering activities
occurring in the secondary ash basin. Dewatering activities in the primary ash basin would not
be subject to the dewatering limits unless this water is discharged directly to waters of the state.
10. Duke Energy requests the title for the dewatering outfall to be revised to"Outfall 002(discharge
of interstitial water due to dewatering)". This will be necessary to avoid confusion between the
two outfalls.

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11. Duke Energy requests the removal of the TBELs from Outfall 002 (Dewatering) due to the fact
the TBELs were not developed in accordance with 40 CFR 125.3(d), the proposed ELG rule did
not include limits on dewatering and insufficient data exists to develop TBELs. This is especially
true for the nitrate/nitrite as N limits. There is no technical justification for these limits at
Riverbend Steam Station. In the proposed ELG rule, these limits were applied specifically to the
FGD wastewater stream and presumably because EPA favors biological treatment. Given the
RPA concluded that the discharge is not expected to violate applicable water quality criterion for
arsenic, selenium or nitrate/nitrites, water quality will not be adversely impacted by the
dewatering process.
12. If the Division is bound to develop TBELs for the dewatering process, Duke Energy request
interim limits for a period of 4.5 years to further evaluate the characteristics of the dewatering
waste stream and evaluate, budget and design a treatment technology. Since the dewatering
waste stream is similar to the ash basin discharge (Outfall 002), the interim limits should be 5
times the limits in the draft permit. This would allow Duke Energy to further evaluate the
dewatering stream while still working towards removing all the ash from the site by August 1,
2019.
13. If the TBELs are applied, Duke Energy requests the specific model technology used to derive the
TBELs that were applied to Outfall 002 (dewatering). In the event the model technology is
installed and the limits imposed are not achieved, Duke Energy would like to have the option of
requesting a less stringent limit as allowed under the Clean Water Act§402(o)2(E).
Outfall 010 combined seep
Comments on the proposed limits for Arsenic,Selenium and Nitrate/Nitrite as N
Similar to Outfall 002, the permit establishes TBELs for arsenic, selenium, and nitrate/nitrite as N on
Outfall 010 (combined seep outfall).Again,the arsenic and selenium TBELs were based on an evaluation
of the effluent data from the ash basin discharges from Belews Creek,Allen and Marshall Steam Stations
and the limits for nitrate/nitrite as N were based on the proposed ELG rule.
The proposed ELG rule classifies seeps from the ash basin as combustion residual leachate, specifically
impoundment leachatel. Under all the preferred options presented in the ELG rule, combustion residual
leachate would only be limited by total suspended solids (TSS) and oil and grease (O&G). In fact, EPA did
not even identify nitrate/nitrite or selenium as pollutants of concern for impoundment leachate in their
1 Refer to Fed. Reg./Vol. 78, No. 110/Friday,June 7, 2013/p. 34533§423.11(r) "The term combustion residual
leachate means leachate from landfills or surface impoundments containing residuals from the combustion of
fossil or fossil-derived fuel. Leachate includes liquid, including any suspended or dissolved constituents in the
liquid, that has percolated through or drained from waste or other materials placed in a landfill, or that pass
through the containment structure(e.g., bottom, dikes, berms) of a surface impoundment. Leachate also includes
the terms seepage, leak,and leakage,which are generally used in reference to leachate from an impoundment."

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analysis for the proposed ELG rule'. Furthermore, the Hanlon memo describes a reasonable potential
approach for establishing limits for seeps based on water quality, not technology.
The nitrate/nitrite limits proposed in the ELG rule were based on data collected immediately following
the FGD wastewater treatment systems at Belews Creek and Allen Steam Stations and were not
associated with the ash basin discharge or ash basin seeps. The FGD treatment systems at Belews Creek
and Allen require denitrification, in order to remove selenium from the FGD wastewater stream. There
are, however, additional sources of nitrate/nitrite into the ash basin and potentially into the seeps that
are unrelated to the FGD wastewater discharge,such as:
— Goose droppings,
— Algae blooms due to nutrient inputs from stormwater runoff,and
— Input of sanitary waste treatment systems to the ash basin.
Furthermore, the nitrate/nitrite limits established for Outfalls 010 is extremely low and unnecessary.
The EPA 2013 Proposed Reissuance of the NPDES Multi-Sector General Permit for Stormwater
Discharges Associated with Industrial Activity proposed a benchmark for nitrate/nitrate of 0.68 mg/L,
which is 5 times the monthly average limit in the draft permit.
Comments on the Implementation
The permit needs to state the methodology to calculate the concentration for the combined seeps to be
reported in the discharge monitoring reports (DMR).A flow-weighted average concentration is the most
appropriate methodology.This methodology is represented by the following formula.
C _rn(Ci x Qi)
En Qi
Where,
C= Flow-weighted average concentration of combined seeps or toe drains.
n= Number of seeps or toe drains sampled.
Ci =Concentration of the parameter for each seep or toe drain in micrograms per liter.
Qi= Flow of each seep or toe drain in liters.
Recommended Changes
14. Appendix A of the draft permit proposes that 12 identified seep locations be classified
collectively and permitted as Outfall 010 (combined seep outfall). Duke Energy will be further
classifying seeps into non-engineered seeps at locations where the seepage emerges from
1 Refer to Section 6.7.3 of the Technical Development Document for the Proposed Effluent Limitations Guidelines
and Standards for the Steam Electric Power Generating Point Source Category, April 2013. Nitrites/nitrates as N
were not listed as a pollutant of concern for landfill leachate or impoundment leachate. Selenium was listed as a
pollutant of concern for landfill leachate but not impoundment leachate.

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natural or residual material and engineered seeps. Duke Energy requests the seeps listed and
updated in the Discharge Identification Plan (DIP) referenced in Appendix B be used as the
official seep identification with regards to official location and type (non-engineered seeps and
engineered seeps, i.e. toe drains). It would be anticipated that the seepage flows and water
quality would be inherently different at these two types of features. Duke Energy, therefore,
believes it is appropriate that the seeps be grouped into two outfalls: one for engineered seeps
and one for non-engineered seeps. The same permit limits and conditions applied to Outfall 010
should be applied to engineered seeps.
15. Duke Energy requests the removal of the TBELs from Outfall 010 due to the fact the TBELs were
not developed in accordance with 40 CFR 125.3(d), the proposed ELG rule did not include limits
on arsenic, selenium, or nitrate/nitrate and insufficient data exists to develop TBELs. The data
used to derive the limits were based on other waste streams not specific to ash basin seeps;
therefore, the limits are not technically justified. Furthermore, the RPA incorporated a 357%
increase in the flow as a safety factor. This added conservatism ensures the ash basin seeps are
not and will not adversely affect water quality. Additionally, the Division assumed the seeps
reach the surface water; however, to be considered a point source discharge, the Clean Water
Act requires a discernible, confined and discrete conveyance, in which pollutants are discharged
to navigable waters.The TBELs,therefore, should be removed from the permit and doing so will
not adversely affect water quality.
16. In lieu of TBELs, Duke Energy requests the Division to adopt a similar process as with new seep
identification to evaluate the constituent concentration and flow. If the concentration of any
parameter exceeds the concentrations in Table 1 of the permit or the total flow of all seeps is
determined to be in excess of 0.5 MGD, the Division should calculate reasonable potential to
determine if water quality based effluent limits (WQBELs) are necessary. If so, a formal
modification of the permit can be conducted to incorporate the WQBELs in the permit. This
approach would be consistent with the Hanlon memo.
17. If the Division is bound to develop TBELs for the seeps, Duke Energy requests a 5-year
compliance schedule. The permit states the limits can be met by installing a treatment system,
re-routing the discharge to the existing treatment system, or discontinuing the discharge. The
Fact Sheet, however, states it will be time-consuming and ineffective to re-route the seeps back
to the ash basin. Given these conflicting statements, a compliance schedule is necessary to
evaluate, budget,design and construct the treatment system or eliminate the discharge.
18. Duke Energy requests the inclusion of the methodology for determining the concentration to be
reported in the DMR for Outfall 010. Duke Energy recommends the following approach.

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C _E7(Ci x Qi)
Qi
Where,
C= Flow-weighted average concentration of combined seeps or toe drains.
n = Number of seeps or toe drains sampled.
Ci=Concentration of the parameter for each seep or toe drain in micrograms per liter.
Qi = Flow of each seep or toe drain in liters.
Sem Pollutant Analysis
The permit requires the facility to continue to implement the Plan for Identification of New Discharges
to determine if new seeps have emerged. New seeps identified must have the flow calculated and
sampled for parameters listed in the permit.
Comments on the identification of new seeps
The permit does not clearly define a seep or how the seep should be identified. It should be recognized
that a wet spot near the ash pond dike is not necessarily a seep from the ash basin and warrant the flow
to be calculated and samples collected. Seeps can emerge due to several factors that are
inconsequential to the ash basin, such as:
— Natural springs,
— Fluctuation in water level of the adjacent water body,
— Naturally formed wetlands,
— Intermittent and ephemeral streams,and
— Stormwater drainage.
Furthermore, a discernible, confined and discrete conveyance from the seep to waters of the state or
U.S. should be present to classify the seep as a new discharge.
Comments on the Table 1 Parameters
The parameters listed in Table 1 of the permit include the daily maximum concentrations of the TBELs
for arsenic, selenium and nitrate/nitrite as N as opposed to multiplying the highest baseline seep
concentration by 10,as with the other parameters.As stated above,there is no technical justification for
these concentrations to be used as screening values. This is especially true for the nitrate/nitrite
screening value, which was based on the proposed ELG rule specific to FGD wastewater, not ash basin
discharge or discharges from ash basin seeps.

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Comments on Notification
The notification requirements for newly identified seeps are not clear in the permit. It is stated in the
permit that newly identified seeps must be reported to the "Division of Water Resources within 5 days
of detection (location only, sampling results shall be submitted within 30 days of sampling) for
administrative inclusion in Appendix A". It is not clear whether the deadlines refer to calendar or
business days. The wording regarding the reporting of the location only and sampling results should
clearly indicate the deadlines. In addition, the permit is unclear on when samples must be collected
from the newly identified seep.
Recommended Changes
19. Duke Energy requests the inclusion of clarifying language in the permit defining a seep that
warrants further evaluation. Duke Energy requests the following clarifying language be included
in the permit:
"Seepage is considered to be the movement of wastewater from the ash basin
through the ash basin embankment, the embankment foundation, the
embankment abutments, through residual material in areas adjacent to the ash
basin, or through the bottom of the ash basin. Therefore, a seep is defined in
this permit as an expression of seepage at the ground surface above the
ordinary high water mark of any waters of the state. Only seeps that have the
presence of a discernible, confined and discrete conveyance to the surface
water will be considered a new seep warranting further evaluation of flow and
pollutant characterization."
20. Duke Energy requests the screening value of nitrate/nitrite removed from Table 1.There was no
baseline data collected and the screening concentration imposed is based on samples collected
from the discharge of FGD wastewater treatment systems, not ash basin discharge or ash basin
seeps. Furthermore, there are natural sources of nitrate/nitrite that are unrelated to the ash
basin. Therefore, there is no technical justification for the inclusion of nitrate/nitrite as N in
Table 1.
21. Duke Energy requests the screening values for arsenic and selenium be revised to be 10 times
the baseline concentration as with the other parameters. Again, the screening values were
based on the TBELs imposed on Outfall 002. These values, however, were not derived in
accordance with 40 CFR 125.3(d)and were not based on data collected from ash basin seeps.
22. Duke Energy requests the inclusion of clarifying language on the notification requirements for
newly identified seeps.The following language is recommended:
"New seeps identified through the seep survey or otherwise discovered or
reported to the permittee shall have their flow calculated, and be sampled for

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parameters indicated in Table 1. The location(s) of the seep shall be reported to
Division of Water Resources within 5 business days. Samples of the seep shall be
collected within 10 business days of identification and the sampling results shall
be submitted within 30 days of sampling for administrative inclusion in Appendix
A."
Outfall 011--Former Stormwater Outfall 1
Outfall 011 is the former Stormwater Outfall 1,which consists of discharges of stormwater,groundwater
flow and wastewater from a 10,000 gallon oil separator tank. The wastewater permit lists this outfall as
a former stormwater outfall, but this outfall was also listed in the draft stormwater NPDES permit for
Riverbend. Duke Energy will be requesting the removal of this outfall from the stormwater NPDES
permit.
Recommended Changes
23. Duke Energy requests the removal of the monitor and report requirements for arsenic,
selenium, mercury, nitrate/nitrite as N, total phosphorus and total nitrogen on Outfall 011. This
outfall predominately consists of stormwater flow, groundwater infiltration and the discharge
from a 10,000-gallon oil water separator. The RPA incorporated a 278% safety factor for flow
and concluded the discharges will not violate surface water quality standard. This added
conservatism ensures the discharge from Outfall 011 have not and will not adversely affect
water quality.
24. Duke Energy requests the removal of the turbidity requirements for Outfall 011. With the low
flow,obtaining an acceptable sample to measure turbidity will be extremely difficult. Also,given
the extremely low flow of this discharge, the likelihood the effluent is contributing to an
increase in turbidity in the receiving water body is extremely low.
25. Duke Energy requests the revision of the oil and grease (O&G) limits for Outfall 011 to equal the
(O&G) limits in the current ELG, which are a monthly average of 15 mg/L and a daily maximum
of 30 mg/L.There was no justification stated for the lower limits in the permit or Fact Sheet.
26. Duke Energy requests the revision of the total suspended solids (TSS) limits for Outfall 011 to
equal the TSS limits in the current ELG, which are a monthly average of 30 mg/L and a daily
maximum of 100 mg/L. There was no justification for the lower limits in the permit or Fact
Sheet.
27. Duke Energy requests the removal of footnote 2 from Outfall 011. There are no copper and iron
limits imposed on this outfall and there are no chemical metal cleaning wastewater discharged
to this outfall.

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Outfall 002A(Yard Sumo Overflow)
28. Duke Energy requests the removal of the copper and iron limits on Outfall 002A. There was no
justification within the permit or Fact Sheet for these limits. The Fact Sheet states that limits
were developed in accordance with 40 CFR 423, but 40 CFR 423 only applies copper and iron
limits to chemical metal cleaning wastewater and metal cleaning wastewater. Chemical metal
cleanings do not go to this sump and an overflow would be low volume wastewater.
Nonchemical Metal Cleaning Wastewater
The permit defines chemical metal cleaning wastewater and metal cleaning wastewater, but does not
define nonchemical metal cleaning wastewater. The permit only applies limits for chemical cleaning
wastewater to Outfall 002 (ash basin discharge and dewatering)and Outfall 002A(yard sump over flow),
but no limits are applied for metal cleaning wastewater or nonchemical metal cleaning wastewater.
29. Duke Energy requests the inclusion of language defining nonchemical metal cleaning
wastewater as low volume wastewater and only subject to the low volume wastewater limits of
O&G and TSS. In the proposed ELG rule, EPA acknowledged the conflicting guidance given
historically on nonchemical metal cleaning wastewater and proposed to exempt stations from
the proposed revisions to the nonchemical metal cleaning limitation.Given the previous permits
for Riverbend only applied limits for chemical metal cleaning, Riverbend should qualify for this
exemption.
Chronic Toxicity
The permit contains conflicting effluent concentrations at which the conduct the chronic toxicity test
should be conducted. On page 8 of 15,the effluent chronic toxicity is listed at 2.7%; however,for
footnote 4 under Outfall 002(ash basin discharge) page 4 of 15 and (dewatering), page 5 of 15,the
effluent concentration is listed as 10%.
Duke Energy welcomes any further discussion on our comments or the draft permit. If you have any
questions, please contact Richard Baker at 704 382-7959 or at [e-mail].
Sincerely,
arry K. deris
Duke Energy
Senior Vice President, Environmental, Health&Safety