NC0004987_Comments on Draft Permit 2016_20160622

�' DUKE Harry Sideris
Senior Vice President
ENERGY. Environmental,Health and Safety
Duke Energy
526 South Church Street
Charlotte,NC 28202
Mailing Address:
Mail Code EC13K/P.O.Box 1006
June 22, 2016
North Carolina Department of
Environmental Quality
Division of Water Resources
Attn: Wastewater Permitting
1617 Mail Service Center RECEIVEDINCDEQIDWR
Raleigh, NC 27699-1617
JUN 2 4 2016
Subject: Comments on the DRAFT NPDES Permit Water Quality
Marshall Steam Station Permitting Section
Permit No.: NC0004987
Catawba County
Wastewater Permitting Staff:
Duke Energy Carolinas, LLC submits the following comments on the draft National Pollutant Discharge
Elimination System Permit for Marshall Steam Station, issued for public comment by the North Carolina
Department of Environmental Quality("NCDEQ")on May 17, 2016. Duke Energy appreciates NCDEQ's
efforts to develop the Draft Permit, which addresses novel issues associated with surface impoundment
decommissioning. Duke Energy continues to work toward closing Marshall's surface impoundments,
and finalizing this wastewater permit is a critical step to advance that process by authorizing decanting
and dewatering. The company further agrees with the conclusion stated in the draft permit that
discharges from the facility's outfalls will not cause contravention of the state water quality standards in
the receiving waters. In addition to these general comments, Duke Energy offers the following
comments on specific provisions of the Draft Permit:
1. Comments on Draft Permit Section A. (2.) Effluent Limitations and Monitoring Requirements
(Outfall 002-normal operations)
• In the DRAFT Permit, the monitoring frequency for arsenic and mercury is "weekly," in contrast
to the "quarterly" monitoring frequency in the current permit. Historical monitoring data do
not indicate that the discharge from Outfall 2 has caused problems with arsenic and mercury in
the receiving stream, and the reasonable potential analysis("RPA") demonstrates the discharge
will not cause contravention of the water quality criteria for either of these constituents. Given
that more frequent monitoring is not necessary to address an immediate concern, Duke Energy
requests the sampling frequency be returned to "quarterly". If NCDEQ feels that more frequent
monitoring is needed, Duke Energy would not object to "monthly" sampling.

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• The DRAFT Permit requires chronic toxicity testing"monthly"during normal operations,
contrasted with"quarterly" in the current permit. Historical data do not indicate that chronic
toxicity is a concern during normal operations,and Duke Energy requests that the monitoring
frequency be changed to a"quarterly" requirement during normal operations.
• Duke Energy requests that the language in Note 2 be clarified to state that continuous
monitoring of Total Suspended Solids("TSS") is only required when decanting via pumps.As
written,the permit could be interpreted to require continuous TSS monitoring during normal
operations not involving pumping from the ash basin.
• Duke Energy requests re-insertion of Note 2 from the existing permit related to TSS.The existing
footnote reads: "A total suspended solids average of 40 mg/L is permitted provided the
Permitee can demonstrate that the difference between the monthly average of 20 mg/L and 40
mg/L is the result of the concentration of total suspended solids in the intake water."
• Duke Energy requests that language on page 5 be amended as follows: "The facility is allowed
to drawdown the wastewater in the ash pond settling basin to no less than three feet above the
ash at the pump intake location under this section. Lowering the level below the three feet
mark triggers the limits and conditions in Section A.(3)of this permit." Without this
clarification,the permit could be misinterpreted to prevent Duke from ever undertaking the
work authorized in Section A.(3).
• Duke Energy requests that the language on page 5 be clarified to state that the zero discharge
limits on fly ash and bottom ash transport water only applies to fly ash and bottom ash
transport water generated after November 1, 2018 and January 31,2021. Fly ash and/or
bottom ash transport water generated prior to these dates and stored in the ash basins is
classified as"legacy wastewater" under the Steam Electric Effluent Limitations Guidelines(ELG)
Rule. As stated in the rule, legacy wastewater is not subject to the same limits. We believe the
intent of the permit is to allow continued discharges from the ash basin after the effective dates
but to require zero discharge of new fly ash transport water after 2018 and of bottom ash
transport water after 2021. To address this concern, Duke Energy suggests either adding
additional definitions to Section A.(10.)or making the following clarifications on page 5:
o The zero discharge limit of fly ash transport water only applies to fly ash transport water
generated after November 1, 2018.
o The zero discharge limit of bottom ash transport water only applies to bottom ash
transport water generated after January 31,2021.
2. Comments on Draft Permit Section A.(3) Effluent Limitations and Monitoring Requirements
(Outfall 002-dewatering phase)
• The DRAFT Permit sets a flow limit at 1.0 million gallons per day(MGD). Duke Energy requests
the flow limit be removed and only require monitor and report. Flows during dewatering will be
lower than flows during decanting,for which Section A.(2)does not set a daily limit. Dewatering
is already subject to a limit on drawdown of 1 ft/week for dam safety purposes.

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3. Comments on Draft Permit Section A.(7.) Effluent Limitations and Monitoring Requirements
(Internal Outfall 004)
• As written,the Discharge Limitation on Total Mercury in this section is not subject to Note 4,
probably due to a typographical error. Duke Energy requests the addition of a Note 4
superscript to the total mercury limits in the permit limit table to clarify that limits on total
mercury are also effective on January 31, 2021.
4. Comments on Draft Permit Sections A.(8.)and A.(9.) Effluent Limitations and Monitoring
Requirements(Outfall 101 and 102)
• Duke Energy requests that Note 3 be amended to state that a measurement of pH lower than
6.0 or higher than 9.0 is not a violation of the permit limits. As a result of the
hydrogeochemistry involved in the migration of ash basin seepage through groundwater,the pH
of water measured at Outfalls 101 and 102 will not always be representative of the seep flow
discharge from the ash basin. Water in the ash basin consistently discharges between 6.0 and
9.0, but natural conditions, including contributions from stormwater, in the vicinity of the ash
basin can result in lower pHs measured at the Outfalls. As long as discharges from the ash basin
at Outfall 002 remain between 6.0 and 9.0, lower pHs at Outfalls 101 and 102 could be
considered unrepresentative samples.
• Similarly, Duke Energy requests that a note be added to state that TSS levels due to conditions
of the sampling area (sediment entrainment)should be considered an unrepresentative sample
since a seep flow from the Ash Basin would not carry TSS levels in excess of 30 mg/I.
• Duke Energy requests the removal of the monitoring and reporting requirements for Total Iron,
Total Manganese and Conductivity.There are no surface water quality standards associated
with these parameters;therefore, it is unnecessary to conduct monitoring and report for these
parameters.
S. Comments on Draft Permit Section A.(10.)ADDITIONAL CONDITIONS AND DEFINITIONS
• Duke Energy requests the inclusion of the following statement based on the historical
permitting of non-chemical metal waste without limits for copper and iron: "Non-chemical
metal cleaning wastewater will be treated as'low volume waste' subject only to TSS and oil and
grease limits based on the historical permitting of non-chemical metal cleaning wastewater."
6. Comments on Draft Permit Section A.(17.) Chronic Toxicity Pass/Fail Permit Limit
• The DRAFT Permit establishes the chronic toxicity effluent concentration of 23%for Outfall 002,
changed from 12%in the current permit. Duke Energy requests this to be changed to 18%
based on the instream wastewater concentration (IWC) reported in the Fact Sheet and the
minimum flow release of Cowens Ford dam of 80 cubic feet per second (cfs). See additional
comments on the minimum flow release below.
• The DRAFT Permit establishes the chronic toxicity requirement for dewatering and references
Part I,Section A.(17.),which sets a chronic toxicity effluent concentration of 23.0%. The RPA
for dewatering was conducted at a flow of 1.0 MGD and the DRAFT Permit sets a flow limit of
1.0 MGD.Therefore,the chronic toxicity effluent concentration for dewatering should be set at

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an appropriate level based on RPA calculations(Ex. 2.0%based on a flow of 1.0 MGD and a
7010s of 80 cfs or 3.7%based on a flow of 2.0 MGD and a 7010s of 80 cfs).
7. Comments on Draft Permit Section A.(30.)Seep Pollutant Analysis
• Duke Energy appreciates that the approach of this section is based on the model developed for
the Riverbend NPDES permit. However,the circumstances at Marshall are different because,as
stated in the Draft Permit, Marshall's two existing seeps,5-1 and 5-2, have been designated as
Effluent Channels,and both are included as outfalls in the draft permit. Because water quality
standards do not apply in Effluent Channels,as stated in 1SA NCAC 2B.0200,there is no need to
determine compliance with water quality standards in the channels themselves. Because both
discharge to the Catawba River,the RPA performed for the permit should be sufficient to
demonstrate that water quality standards in the receiving stream are not contravened,as
required in subparagraph 3. As a result,there is no further work to be done with respect to the
existing seeps required by Section A.(30). Duke Energy proposes to revise this section so that it
applies only to New Identified Seeps,as follows:
The facility has identified two previously unpermitted seeps(all non-engineered)from the ash settling
basin,S-1 and 5-2, the locations of which are identified on the attached map. On May 4,2016,DWR
representatives delineated Effluent Channels at the Marshall Steam Station for both seeps, in accordance
with the requirements of 15A NCAC 02B.0228. Both Effluent Channels discharge to the Catawba River.
An RPA performed for this permit demonstrates that water quality standards in the Catawba River will
not be contravened by these existing seepage flows.
Table 1.Seep Coordinates and Assigned Outfall Numbers
Seep ID Latitude Longitude Outfall Number
•
S-1 35036'71" 80057'62" 101
5-2 35042'56" 80021'56" 102
New Identified Seeps
If new seeps are identified that meet the definition of a point source and discharge to waters of the
state, the facility shall follow the following procedures. The facility shall determine within 90 days from
the date of discovery if a seep meets the state water quality standards established in 15A NCAC 2B.0200
and submit the results of this determination to the Division. If the standards are not contravened, the
facility shall conduct monitoring for the parameters specified in A. (8.)and A. (9.). In accordance with
ISA NCAC 028.0205, water quality standards will not be considered violated when values outside the
normal range are caused by natural conditions.
If any of the water quality standards are exceeded, and values outside the normal range are not caused
by natural conditions, the facility shall implement one of the following options within the prescribed time
frame. The facility shall:
1) If the seep itself is within a jurisdictional water as set forth in a final Jurisdictional
Determination issued by the United States Corps of Engineers,submit a complete application
as applicable for a 404 Permit(within 30 days after determining that a water quality
standard is exceeded)to pump the seep discharge to one of the existing outfalls, install a
pipe to discharge the seep to the Catawba River, or install an in-situ treatment system. The
facility shall complete the installation of the pump,pipe, or treatment system within 180

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days from the date of the 404 permit receipt(or determining no 404 permit is required)and
begin pumping/discharging or treatment.
2) Demonstrate through modeling that the decanting and dewatering of the ash basin will
result in the elimination of the seep and submit the modeling results to the Division. Within
180 days from the completion of the dewatering the facility shall confirm that the seep flow
ceased. If the seep flow continues, the facility shall choose one of the other options in this
Special Condition.
3) Demonstrate within 30 days of determining that a water quality standard is exceeded that
the seep is discharging through the designated"Effluent Channel"and the water quality
standards in the receiving stream are not contravened.
8. Comments on Attachment 1:Groundwater Monitoring Plan
• Please add the following clarifying language to the permit:
"3(h).The provisions of sections 3(f)and 3(g)apply only to the sampling events described in 3(b)
above. The reporting requirements for any sampling events other than those described in 3(b)
above shall be in accordance with the general provisions of 15A NCAC 02L."
• Additionally, Duke requests that the GW59CCR form submittal date be 60 days after sampling in
lieu of 45 days.
9. Comments on Fact Sheet
• The Fact Sheet states that the summer 7010 flow of 60 cubic feet per second(cfs) is based on
the minimum release from the dam that regulates the receiving water body(Cowens Ford).
However, based on the issued Catawba-Wateree operating license,the minimum release from
Cowens Ford is 80 cfs and the minimum average daily release requirement is 311 cfs. In the
recently issued permit for McGuire Nuclear Station,the 7010 was set at 80 cfs. In addition,the
IWC reported in the Fact Sheet is 18%,which corresponds to a flow of 11.44 MGD and 7010 of
80 cfs. Duke request the 7010 reflect the minimum release from Cowan's Ford Dam stated in
the current Catawba-Wateree operating license.
Duke Energy welcomes any further discussion on our comments or the Draft Permit. If you have any
questions,please contact Shannon Langley at(919)546-2439 or at Shannon.Lanalev@duke-energvcom.
Harry Sideris
Duke Energy
Senior Vice President Environment, Health&Safety

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cc: Rick Roper,Duke Energy,'Station Manager
Jim Wells, Duke Energy,VP EHS CCP
Richard Baker,Duke Energy,EHS CCP
Scott LaSala,Duke Energy,Marshall Plant Environmental Coordinator