NC0004979_Comments on Draft Permit_20150504

Harry K.Sideris
• (' DUKE Senior Vice President
Environmental,Health&Safety
ENERGY® 526 South Church Street
Mail Code EC3XP
Charlotte,NC 28202
[phone]
RECEIVEDIDENR/DWR
May 4,2015
MAY - 72015
North Carolina Department of Water Quality
Environment and Natural Resources permitting Sectior
Wastewater Permitting
1617 Mail Service Center
Raleigh, NC 27699-1617
Subject: Comments on the draft NPDES Permit for Allen Steam Station
Permit No.: NC0004979
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 Allen 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.
Comments on the Development of the Technology Based Effluent Limits ITBELs)
The permit establishes technology based effluent limits (TBELs) for arsenic, selenium and nitrate/nitrite
as N on internal Outfall 005 (FGD wet scrubber wastewater to the ash settling basin), Outfall 010
(combined seep outfall) and Outfall 011 (Toe Drains effluent). 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 case-by-case TBELs to
consider the following:

• Page I2
• 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 require that, in setting case-by-case 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
the Tennessee Board of Water Quality,Oil, and Gas (the Board) holding that TVA'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"1.
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
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).

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Agency developed the effluent guidelines."' Since EPA considered setting numeric limits for metals in
the 1982 ELG rule,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 water quality based effluent limits (WQBELs), not
TBELs,for coal combustion leachate (i.e. ash basin seeps)2.
Mercury Limits on Outfall 002.Outfall 010 and Outfall 011
The permit imposes TBELs for mercury at the combined Outfall 010(combined ash basin seeps),Outfall
011 (toe drain effluent) and Outfall 002(ash basin discharges).These limits are based on the statewide
mercury total maximum daily load(TM DL).
Recommended Changes
1. 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 005(treated FDG wet scrubber wastewater to ash settling basin)
As stated above, the permit establishes TBELs for arsenic, selenium, and nitrate/nitrite as N on the
internal Outfall 005 (treated FDG wet scrubber wastewater to ash settling basin). 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. If the Division has determined the FGD wastewater
treatment systems at Belews Creek and Allen Steam Station represent BAT for FGD wastewater, the
limits should be based on the 95th and 99th percentiles of the effluent data collected from the internal
outfalls at Belews Creek (Outfall 002) and Allen (Outfall 005) Steam Stations. For example, this analysis
would yield the following TBELs for selenium3.
Parameter 95th percentile 99th percentile
1 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.
2 Refer to Attachment B,"Water Quality-Based Effluent Limits Coal Combustion Waste Impoundments",of the
James Hanlon memorandum,June 7,2010.
3 The 95th and 99th percentiles were calculated from effluent data collected from the internal FGD outfall at Belews
Creek(Outfall 002)and Allen(Outfall 004)from April 2010 to March 2015.

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Selenium ((.tg/L) 23 99
If this analysis resulted in a limitation less than 10 .tg/L, the ability of the analytical method would need
to be evaluated to determine whether commercial laboratories could consistently detect the parameter
at or below the permit limit.
Due to the lack of long-term data,the Division based the nitrate/nitrite limits on the proposed ELG rule.
It should be noted, however, the nitrate/nitrite limits proposed in the ELG were only based on 10
observations (5 observations from both Belews Creek and Allen Steam Stations)'. These observations
were based on samples collected between June 2010 and January 2011 from the effluent immediately
following the FGD wastewater treatment systems. EPA, therefore, did not even have sufficient long-
term data to develop the limits for nitrate/nitrite in the proposed ELG rule.
In addition, the removal of nitrates/nitrites is only a co-benefit of the removal of selenium in the
anaerobic biological reactor and appears to only have been included in the proposed ELG rule to favor
anaerobic biological treatment over other selenium removal treatment technologies. In fact, EPA did not
derive limits for nitrates/nitrites for the other considered model technologies for the treatment of FGD
wastewater,such as chemical precipitation or vapor-compression evaporation.
These issues were the subject of numerous comments on the nitrate/nitrite limits in the proposed ELG
rule, in addition to the following:
— Analytical detection method: The method detection limit for nitrates/nitrites can be
affected by chlorides in the wastewater.This was not considered in the proposed ELG rule.
— Changes in the ORP can affect the ability of the treatment system to remove nitrate/nitrite.
— The analysis for the ELG rule did not consider removals for stations that have higher
selenium and nitrogen levels than Belews Creek and Allen. The treatment systems at Belews
Creek and Allen target selenium removal but not nitrogen removal, and both plants have
low selenium and nitrate/nitrite levels in their influent compared to the industry.
Recommended Changes
2. Duke Energy requests the removal of TBELs from Outfall 005. EPA is under a court-order to
finalize the ELG rule by September 30, 2015. The final ELG rule is expected to impose limits on
the internal outfall of the discharge of FGD wastewater; however, EPA proposed three
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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treatment options for FGD wastewater with each option imposing different limitations. Given
the difficulty, cost and time in developing TBELs on a case-by-case basis in accordance with 40
CFR 125.3(d), it would be reasonable to remove the TBELs and incorporate the limitations and
the implementation schedule established under the final ELG rule. This would avoid any issues
with anti-backsliding and conflicts with North Carolina General Statute§ 150B-19.3.
3. If the Division is bound to impose TBELs for this permit issuance, Duke Energy requests the
inclusion of language in the permit allowing the TBELs to be revised, if less stringent limits are
imposed in the final ELG rule. This is especially prudent given the issues associated with the
development of the TBELs noted above (i.e. lack of adherence to 40 CFR 125.3(d)).The receiving
water body, Lake Wylie, is in attainment for all parameters limited in the permit and the
reasonable potential analysis(RPA)concluded the discharges will not cause contravention of the
state water quality standards or EPA criteria; therefore, revising these limits to match the final
ELG rule will not impair the water quality or the designated use of the water body. To
accomplish this, Duke Energy recommends making the effective date of the TBELs to coincide
with the effective date of the final ELG rule with compliance required 4.5 years from the
effective date. It is anticipated the ELG rule will be effective in 1st quarter 2016. In addition,
Duke Energy requests an Outfall 005 (post-ELG rule) be created to serve as a "placeholder" to
incorporate the limitations in the final ELG rule into the permit.
4. If the TBELs are applied, Duke Energy requests the specific model technology used to derive the
TBELs that were applied to Outfall 005. 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). If the Division has determined
the FGD wastewaters treatment systems at Belews Creek and Allen Steam Stations represents
BAT, the limits should be based on the 95`h and 99th percentiles of the effluent data from the
internal FGD wastewater outfalls at Allen and Belews Creek Steam Stations. If this analysis
resulted in a limitation less than 10 µg/L, the ability of the analytical method would need to be
evaluated to determine whether commercial laboratories could consistently detect the
parameter at or below the permit limit.
Outfall 010(combined seeps)and Outfall 011(combined toe drains'
Comments on the proposed limits for Arsenic,Selenium and Nitrate/Nitrite as N
Similar to Outfall 005, the permit establishes TBELs for arsenic, selenium, and nitrate/nitrite as N on
Outfall 010 (combined seep outfall) and Outfall 011 (toe drains effluent). 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.

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The proposed ELG rule classifies seeps and toe drains from the ash basin as combustion residual
leachate, specifically impoundment leachate'. 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 analysis for the proposed ELG rule2. 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.
In addition, the nitrate/nitrite limits established for Outfalls 010 and 011 are 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 _E'(Ci x Qi)
Qi
Where,
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."
2 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. Nitrite/nitrate as N was
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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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.
Comments specific to Outfall 011 Toe Drain Effluent
In addition to the limits discussed above, the permit imposes limits for copper and iron during chemical
metal cleaning on Outfall 011 (toe drain effluent). The toe drains are engineered drains designed to
protect dam stability. The discharge from the toe drains primarily consist of rainfall that has percolated
through the ash basin dike into the internal drainage system. The copper and iron limits, therefore,
during chemical metal cleanings are unnecessary for this outfall.The likelihood of any constituent from a
chemical metal cleaning is very low. In addition, there is no clear residence time between the time a
chemical metal cleaning occurs and the time any constituent would potentially appear in the toe drain
effluent to determine when sampling should occur.
Furthermore,the permit imposes turbidity limits on Outfall 011 (Toe Drain effluent). Due to the low flow
of the toe drains, approximately 0.0091 million gallons per day(MGD), it will be very difficult to collect a
suitable sample for turbidity analysis. In addition,the flow from the toe drains represents approximately
0.05%of the ash pond discharge. Assuming the discharge from the toe drain reaches surface water, any
contribution of turbidity from the toe drain discharge will have no effect on the turbidity of the receiving
water body. It is,therefore,unnecessary to sample this effluent for turbidity.
In addition,the permit requires flow from Outfall 011 to be measured on a weekly basis as compared to
flow being measured on a monthly basis from Outfall 010. Measurement of flow on a weekly basis is
unnecessary given the expected low flow of this outfall.
Recommended Changes
5. Appendix A of the draft permit proposes that 7 identified seep locations be classified collectively
and permitted as Outfall 010 (combined seep outfall) and 2 toe drains be permitted as Outfall
011. Duke Energy will be further classifying seeps into non-engineered seeps at locations where
the seepage emerges from 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(Outfall 011).
6. Duke Energy requests the removal of the TBELs from Outfall 010 and 011 due to the fact the
TBELs were not developed in accordance with 40 CFR 125.3(d), the proposed ELG rule did not

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include limits on arsenic, selenium, or nitrate/nitrate, EPA recommends a reasonable potential
approach based on water quality 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 for the seeps was conducted at a
flow rate of 83 times the measured flow rate of the seeps and a 110% safety factor was
incorporated in the RPA for the toe drains.This added conservatism ensures the ash basin seeps
and toe drains are not and will not adversely affect water quality. Additionally, the Division
assumed the seeps and toe drains 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.
7. 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 or
toe drains is determined to be in excess of 0.5 MGD, the Division should calculate reasonable
potential to determine if 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.
8. If the Division is bound to develop TBELs for the seeps and toe drains, 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.
9. If the TBELs are imposed, Duke Energy requests the specific model technology used to derive
the TBELs that were applied to Outfall 010 (combined seeps) and Outfall 011 (combined toe
drains). 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).
10. Duke Energy requests the copper and iron limits during chemical metal cleanings on Outfall 011
removed from the permit. These limits are unnecessary, and there is insufficient information of
the residence time for any chemical metal cleaning wastewater to potentially be present in the
toe drain effluent.
11. Duke Energy requests the turbidity limit on Outfall 011 is removed from the permit. Given the
low flow, collecting a suitable sample of the toe drain effluent to monitor turbidity will be
difficult and the likelihood the effluent is affecting the turbidity in the receiving water body is
extremely low.

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12. Duke Energy requests the monitoring frequency for flow for Outfall 011 be revised from weekly
to monthly to coincide with the monitoring frequency for Outfall 010.
13. Duke Energy request the inclusion of language that allows the monitoring frequency for Outfall
011 reduced to semi-annually after the first year of monitoring,similar to Outfall 010.
14. Duke Energy requests the inclusion of the methodology for determining the concentration to be
reported in the DMR for Outfall 010 and Outfall 011. Duke Energy recommends the following
approach.
C _rn(Ci x Qi)
rn 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.
Seep 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.

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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.
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
15. 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."
16. 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.

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17. 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 005. 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.
18. 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
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 002A(Coal Yard Sumo Overflow)and Outfall 002B(Power House Sumo Overflow)
19. Duke Energy requests the removal of the copper and iron limits on Outfall 002A and Outfall
002B in the final permit. The permit imposes a copper limit of 1.0 mg/L and iron limit of 1.0
mg/L on Outfall 002A and Outfall 002B. 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. As stated in the Fact Sheet, chemical metal
cleanings do not go to this sump and on overflow would be low volume wastewater.
Dewatering
20. Duke Energy 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 flow path. As further discussed with Division staff, Duke
Energy will submit interstitial data to request authorization to conduct interstitial dewatering
activities. Interstitial water should be defined in the permit 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.
Nonchemical Metal Cleaning Wastewater

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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), Outfall 002A (coal yard sump over flow), Outfall 002B
(Power House Sump Overflows)and Outfall 011 (Toe Drains Effluent), but no limits are applied for metal
cleaning wastewater or nonchemical metal cleaning wastewater.
21. 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 Allen only applied limits for chemical metal cleaning,Allen should qualify for this exemption.
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,
Harry K.Sideris
Duke Energy
Senior Vice President, Environmental, Health&Safety