NC0039586_Modification Request_20210310

In) DUKE Kim E.Maza
Vice President
ENERGY, Harris Nuclear Plant
5413 Shearon Harris Rd
New Hill,NC 27562-9300
FEB 2 4 2021
Serial: RA-21-0080 ` ,c
Certified Mail Number: 7014 2120 0003 3196 7224RECEI v GD
Return Receipt Requested MAR 1 0 2021
Mr. Danny Smith, Director
NC DEQ Division of Water Resources NCDEQ/DWR/NPDES
512 N. Salisbury Street
Raleigh, NC 27604
Subject: Duke Energy Progress, LLC (Duke Energy)—Shearon Harris Nuclear Power Plant
NPDES Permit No. NC0039586, Wake County
Clarifications to Mixing Zone Modeling &Analysis
Dear Mr. Smith:
The 2016 NPDES Permit for Duke Energy's Shearon Harris Nuclear Power Plant(HNP) included new
effluent limits for copper and zinc at Outfall 006,which discharges into Harris Lake. This permit,
effective September 1, 2016,required compliance with these new limits by September 30, 2021. In
accordance with the strategy outlined in the Corrective Action Plan(CAP), submitted to NC DEQ's
Division of Water Resources(DWR) in September 2017,Duke Energy has expanded sampling and
effluent characterization, employed water chemistry management strategies,and completed specialized
testing and site-specific engineering studies.
In August 2020, as part of these compliance activities,Duke Energy submitted the results of a Mixing
Zone Study(Study), completed at the request of DWR. The Study used EPA guidance and national best
practices to complete hydrodynamic modeling of mixing zones, evaluate acute and chronic mixing zone
boundaries, and calculate dilution effects. In November,Duke Energy and DWR held a video conference
call to address DWR questions about the Study.
At this meeting,DWR raised two questions regarding the CORMIX hydrodynamic model and
recommended additional modeling runs to validate results. Although originally requesting additional
review time,DWR confirmed by email on December 11th,that their review was complete, and they had
no additional questions or concerns. After performing the requested additional modeling runs,responses
to DWR's two inquiries were detailed in the enclosed Technical Memorandum(TM).
Duke Energy trusts DWR is satisfied with the responses and supplemental modeling provided in
the TM. Duke Energy requests the Study be approved, and the conclusions implemented to
remove the copper and zinc limits from Outfall 006 within NPDES Permit No. NC0039586.
Duke Energy respectfully requests the removal of copper&zinc limits associated with Part I
(A)(6) Effluent Limitations and Monitoring Requirements (Outfall 006) and the compliance
language and date of September 30, 2021 as addressed in Part I (A)(9) Schedule of
Compliance (Outfall 006). A check for$1,030 made payable to NC DEQ DWR for the major
permit modification processing fee is enclosed. Duke Energy remains committed to continued
compliance at HNP and requests DWR issue an appropriate permit revision as soon as
practicable but prior to the current NPDES permit expiration date of August 31, 2021.

NC DEQ Division of Water Resources
Serial: RA-21-0080 / Page 2
l certify, under penalty of law, that this document and all attachments were prepared under my
direction or supervision in accordance with a system designed to assure that qualified personnel
properly gather and evaluate the information submitted. Based on my inquiry of the person or
persons who manage the system, or those persons directly responsible for gathering the
information, the information submitted is, to the best of my knowledge and belief, true, accurate,
and complete. I am aware that there are significant penalties for submitting false information,
including the possibility of fines and imprisonment for knowing violations.
Sincerely,
RECEIVED
Kim E. Maza MAR 1 0 2021
Vice President, Harris Nuclear Plant
Duke Energy Progress, LLC
NCDEQ/DWR/NPDES
Enclosures: Check for Major Permit Modification Processing Fee
Technical Memorandum, Clarifications to Mixing Zone Modeling &Analysis,
February 12, 2021
cc: Mr. Sergei Chernikov, Environmental Engineer III, NPDES Industrial Permitting
Certified Mail Number: 7014 2120 0003 3196 7262
Return Receipt Requested
Mr. Scott Vinson, Water Resources Regional Supervisor
Certified Mail Number: 7014 2120 0003 3196 7279
Return Receipt Requested
Ms. Cyndi Karoly, Chief, Water Sciences Section, NC DEQ DWR
Certified Mail Number: 7014 2120 0003 3196 7286
Return Receipt Requested
Mr. David Hill, Environmental Specialist II, NPDES Industrial Permitting
Certified Mail Number: 7014 2120 0003 3196 7231
Return Receipt Requested
Mr. Nick Coco, Environmental Engineer, NPDES Permitting
Certified Mail Number: 7014 2120 0003 3196 7248
Return Receipt Requested
NCDEQ DWR Central Files
Certified Mail Number: 7014 2120 0003 3196 7255
Return Receipt Requested

NC DEQ Division of Water Resources
Serial: RA-21-0080
Enclosures
Harris Nuclear Plant
NPDES Permit No. NC0039586
Check for Major Permit Modification Processing Fee
Submittal of Technical Memorandum, Clarifications to Mixing Zone Modeling &Analysis
(46 pages including cover)

1
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JTechnical Memorandum
aco s.
111 Coming Road,Suite 200
Cary,North Carolina 27518
+1.919.859.5000
+1.919.859.5151(fax)
www.jacobs.com
Subject Shearon.Harris Nuclear Plant-Permit NC#0039586 "'.•.:
Clarifications to Mixing Zone Modeling&Analysis r'�t'CARQ s`•.,L• 3
Project Name Shearon Harris Nuclear Plant NPDES Permit Assistance s' �; SSAp.'',
1
Project No. D33934.02 3 s
Date February 11,2021 i y'y%
Prepared for Duke Energy Progress, LLC(Duke Energy) • ,e,%., INet y ,r'
Prepared by Jennifer Bell,PE-CH2M HILL North Carolina,Inc.(Jacobs) •'"•.,y�,.E•• L � . �:,.
Brad Paulson—Jacobs � R L. '��
Executive Summary
In July 2019,as a response to Duke Energy's submittal of a Water Effect Ratio Study,the North Carolina
Division of Water Resources(DWR)requested that a dye dispersion study or dilution modeling be
completed to augment the WER Study results and further inform the development of permit limits for Total
Recoverable Copper at Outfall 006 of the Shearon Harris Nuclear Plant(HNP)discharging into Harris
Lake.Accordingly, Duke Energy conducted a mixing zone study following U.S. Environmental Protection
Agency(EPA)guidance and using the Cornell Mixing Zone Expert System(CORMIX).
The results of that study,submitted in August 2020, indicated significant dilution effects occur at Outfall
006.Within the model, the least favorable of eight seasonal cases predicted a dilution factor of 15.3(or
6.5% Instream Water Concentration [IWC])at the acute mixing zone boundary, equivalent to an allowable
daily maximum of 166.1 pg/L for Total Recoverable Copper.
After reviewing the Mixing Zone Study, DWR had two questions regarding the CORMIX model:
1. Is the modeling algorithm for a"Heated Discharge"different than what is used for the
"Conservative Pollutant"option? s
2. What is the sensitivity of the model to variations in Reservoir levels?
Responses to these two inquiries are detailed in this.Technical Memorandum(TM)and were confirmed
with additional CORMIX model runs. In both cases, the model results reaffirmed the conclusion that,
when dilution effects are considered, the maximum predicted copper concentration at Outfall 006
(calculated by DWR Reasonable Potential Analysis spreadsheets)is less than half of the allowable limit.
TABLE 1.
Dilution Factors& Equivalent Copper Effluent Limits from Additional CORMIX Cases
CORMIX- Daily Monthly
Calculated Maximum Average ;
Dilution Factor (Acute) (Chronic)
Results from Original CORMIX Model in Mixing Zone Study 15.3 166.1 pg/L 166.1 pg/La
Results Using"Conservative Pollutant"Option 15.3 166.1 pg/L 166.1 pg/La
Results Using Minimum(10"'percentile)Reservoir Water Levels 15.0 163.0 pg/L 163.0 pg/La 1
Maximum Values at Outfall 006—Jan 2016 to July2020
63.5 pg/L 32.7 Ng/L
3
a The resulting calculated limit for monthly average exceeds the calculated limit for daily maximum(or acute conditions).Therefore,
the acute condition governs and the Daily Max and Monthly Average limits are equivalent.
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..Jacobs Shearon Harris Nuclear Plant-Permit NC#0039586
Clarifications to Mixing Zone Modeling&Analysis
1. Introduction
Duke Energy conducted a mixing zone study evaluating the dilution provided for the discharge from
Outfall 006 from Shearon Harris Nuclear Plant(HNP) into Shearon Harris Reservoir under National
Pollutant Discharge Elimination System (NPDES) Permit No. NC0039586, effective September 1, 2016.
Prior to initiating modeling, a plan for the Mixing Zone Study was submitted to DWR on November 15,
2019,which included proposing using CORMIX for dilution modeling. Email approval of the study plan
was received from DWR with the following recommendations:
• Ambient data collected since 2017 needs to include seasonal measurements of velocity,
temperature, and density at the site of discharge and anticipated plume; and
• The thermocline should be sufficiently characterized and modeled as a boundary condition where
appropriate.
Both ambient current and seasonal density gradients were addressed and incorporated into the modeling
approach. CORMIX modeling results and mixing zone analysis were summarized in the Mixing Zone
Study(Study), dated August 14, 2020, which was submitted concurrently with the Year 4 Activities
Report for the Corrective Action Plan, dated August 19, 2020.
Duke Energy requested the opportunity to discuss both the Study and the conclusions summarized in the
Year 4 Activities Report with DWR and to address any questions or concerns.A video conference call
was held on November 2, 2020,with Duke Energy, DWR, and Jacobs personnel. Meeting minutes for this
video conference are included as Attachment A.
While DWR expressed confidence in the overall approach and information they had reviewed,two
specific questions were raised by David Hill regarding the CORMIX model:
1. Is the modeling algorithm for a"Heated Discharge"different than what is used for the
"Conservative Pollutant"option, and how are the predicted dilution factors and plume dimensions
affected?
2. What is sensitivity of the model results to variations in key input parameters such as reservoir
levels?
Responses to these two inquiries are detailed in the following sections and were evaluated with additional
CORMIX model runs.A representative sample of the validating runs was selected for each section and
output data included as Attachment B and Attachment C, respectively.
2. Temperature Dispersion Versus Conservative Constituent Dilution
In accordance-with-the-approved-study-plan,—the-CORMIXhydrodynamie-modeling system-(EORMIX-1
module)was used to calculate the dilution and associated plume dimensions for a range of effluent and
ambient conditions. CORMIX is an EPA-supported empirical modeling system based on experimentally
derived curve-fit equations that predict dilution and verify the accuracy of theoretical models. The model
emphasizes prediction of the near-field geometry and dilution, although it also predicts the behavior of the
discharge plume beyond initial mixing (e.g., in the far-field).
2.1 CORMIX Pollutant Types
The inputs for'pollutant type' in CORMIX allow for five types of pollutant discharges(described in Section
4.3.1 of the CORMIX User Manual [Doneker and Jirka, 2007]). Specifically, these pollutant types are as
follows:
1. Conservative Pollutant—no decay or growth processes occur; pollutant of concern can be in
any unit of concentration (e.g., pg/L, °C, ppm, or%)
2. Non-conservative Pollutant—first-order decay or growth processes occur; pollutant of concern
can be in any unit of concentration (e.g., pg/L, °C, ppm, or%)
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Shearon Harris Nuclear Plant-Permit NC#0039586 7
Clarifications to Mixing Zone Modeling&Analysis Jacobs
3. Heated Discharge—capable of modeling heat loss to the atmosphere using a specified surface
heat exchange coefficient,which is a function of wind velocity and ambient receiving water
temperature; discharge dilution/concentration is shown in terms of thermal properties or"heat
concentration"(shown as°C)
4. Brine Discharge—discharge density greater than ambient density(e.g., desalination by-
product); may also include a pollutant concentration of interest(conservative/non-
conservative/heated discharge)
5. Sediment Discharge—discharge density greater than ambient density with settling particles
(e.g., discharge with suspended sediments); may also include a pollutant concentration of interest
(conservative/non-conservative)
The two pollutant types directly applicable to effluent at Outfall 006 are 1) 'conservative pollutant' (i.e.,
effluent properties considered in the Study, such as zinc and copper concentrations or hardness—do not
experience decay in freshwater) and 3) 'heated discharge'.
2.2 Selection of a "Pollutant Type"for HNP's Outfall 006
In modeling Outfall 006 (or any freshwater discharge) in CORMIX, thermal data—both effluent and
ambient—is essential to predict discharge behavior, as temperature is equivalent to relative density,
which governs hydrodynamics.Whether using pollutant TYPE 1 or TYPE 3 in the CORMIX model, the
same thermal input is required, and all versions of Outfall 006 have a discharge which is"heated"
(warmer than ambient temperatures).
The only meaningful distinction between the"conservative pollutant"and"heated discharge"options is
that the latter has the added functionality of modeling atmospheric heat loss, if applicable, using a surface
heat exchange coefficient(based on wind velocity and ambient water temperatures). This functionality is
more useful when looking at far-field effects(i.e.,when the plume behavior is impacted by ambient
conditions more than initial discharge velocity) or where a shallow discharge allows for significant plume-
surface interaction with a high heat exchange coefficient.
For purposes of the Study, only near-field effects were evaluated, and surface heat losses were not
expected to be impactful at Outfall 006, considering its depth and the presence of a thermocline in
Summer and Fall. However, unless a non-conservative property is being evaluated, Jacobs typically
defaults to the'Heated Discharge'type when generating new model scenarios. In general,this is a more
robust option in the event that surface heat-losses do impact an analysis.
•
2.3 Concurrence from CORMIX Software Developer
As mentioned above, in the absence of atmospheric heat losses, both the"conservative pollutant"and
"heated discharge" options are essentially identical in their predictive algorithms. In theory, if a model is
run with a surface heat exchange coefficient of zero (or near zero), or if a predicted discharge plume does
not come in contact with the surface, CORMIX results—including centerline dilution and plume geometry
—from either pollutant type should be fully identical.
To confirm our understanding of the CORMIX model algorithms and Pollutant Type functionality, Jacobs
reached out to the software developer(MixZon, Inc.)on November 9, 2020. Senior Software Engineer Adi
S. Ramachandran explained, "assuming all CORMIX model input parameters are the same, CORMIX
should predict the same flow class [and thereby provide the same predictions]when specified as using
the'Conservative Pollutant'vs 'Heated Discharge' pollutant options." He further noted that—due to the
ability of the"Heated Discharge" option to model atmospheric heat loss—results CAN vary in cases
where there is a"loss of buoyancy in a positively buoyant surfacing plume due to ... surface heat
exchange, mainly in the buoyant spreading regions of the prediction."
2.4 Validation of Study Model Results Using the"Conservative Pollutant"Type
To further validate the assertion that in the absence of atmospheric heat losses"conservative pollutant"
and"heated discharge" produce identical results, CORMIX cases from the Study were rerun using the
TYPE 1 "Conservative Pollutant"option using copper concentration as the material of interest, rather than
temperature. For the Summer/Fall cases (Cases 3a, 3b, 4a, and 4a),where the thermocline"traps"the
CH2M HILL North Carolina, Inc. Page 3

Shearon Harris Nuclear Plant-Permit NC#0039586
Jacobs Clarifications to Mixing Zone Modeling&Analysis
plume and prevents any surface interaction,the output data showed 100%identical plume data and
dilution factors, as expected.Output for the modified Case 4a, using the"Conservative Pollutant"type, is
included in Appendix B as a representative sample of these validating model runs.
For the Winter/Spring cases(Cases la, 1 b, 2a, and 2a),where the plume is exposed to the surface(and
potential atmospheric heat loss),output data was nearly identical. Output used in the Study (all near-field
predictions)was the same for both"Conservative Pollutant"and"Heated Discharge"options. The
anticipated mathematical variations in output-due to the difference in treatment of surface heat losses-
were almost undetectable and statistically meaningless (i.e.,within the ability of the model to resolve). For
example, in Case la,the first difference in predicted dilution is notable at a location 1717 m from Outfall
006,where the pollutant TYPE 1 option predicted dilution of 54.4 and the TYPE 3 option predicted 54.5.
3. Parametric Evaluation of Changing Reservoir Levels
As with any computer model, simplifying assumptions were made to provide input values to CORMIX that
simulate effluent properties and ambient conditions at Outfall 006.These model inputs and assumptions
are detailed in Section 3 of the Study TM, including their source and/or basis for their selection.
In accordance with DWR's recommendations, seasonal variations for temperature profiles and effluent
flow velocities were captured by running separate model cases for each season and utilizing average or
maximum values, as appropriate. Model sensitivity to these key input parameters can be seen in the
variation of predicted dilution factors at the acute mixing zone boundary, ranging from 15.3.to 27.2.
For most other inputs, however, static values were selected to best reflect"typical"or"most probable"
conditions at Outfall 006.Water depth is an example of this kind of static variable. During the video
conference call in November 2020, DWR requested a parametric evaluation be performed to illustrate the
model's sensitivity to changes in static inputs, recommending reservoir levels be examined.
3.1 Historic Shearon Harris Reservoir Levels
In the Stud water depthp (detailed in Section 3.2)were calculated using the Shearon Harris
Y� p parameters
Reservoir normal pool elevation of 220 ft(National Geodetic Vertical Datum [NGVD]). To establish an
appropriate range of elevations to use in the requested parametric evaluation, historical data from
reservoir level meters in the HNP Primary and Secondary Intake Pumping Station were analyzed.
The table below shows the low(10th percentile), high (90t percentile), and median daily reservoir levels
for the six-year period from January 2015 to November 2020.A copy of the complete data set is included
as Attachment D.
TADJ..E 2,
Summary of Daily Reservoir Levels from January 2015 to November 2020
Case 1: Case 2: Case 3:, Case 4
Winter Spring Summer. Fall Year
Dec-Feb Mar-May Jun-Aug: Sep-Nov Round
Low Water Level 217.5 ft NGVD 219.8 ft NGVD 219.0 ft NGVD 218.0 ft NGVD 218.8 ft NGVD
(10th percentile)'
High Water Level 221.0 ft NGVD 220.9 ft NGVD 220.5 ft NGVD 220.7 ft NGVD 220.8 ft NGVD
(90th percentile)
Median Level 220.3 ft NGVD 220.3 ft NGVD 219.8 ft NGVD 2197 ft NGVD. 220.0 ft NGVD
(50th percentile)
As shown here, Shearon Harris Reservoir levels have been historically stable over the past six years,
even in periods of extreme drought. While this supports the use of the normal pool elevation (220 ft
NGVD) in the original Study, a parametric evaluation which explores sensitivity to a-2 ft/+lft variability is
helpful in validating the model and clarifying predicted behavior.
Case 4a(Fall season, Maximum Day discharge)was selected for the parametric evaluation, as it was the
most restrictive model scenario, predicting the least dilution in the acute mixing zone.Additionally, a Fall
Page 4 CH2M HILL North Carolina,Inc.

Shearon Harris Nuclear Plant-Permit NC#0039586 7
Clarifications to Mixing Zone Modeling&Analysis „Jacobs
or Summer case is expected to be more sensitive to changes in water level, as the CORMIX model
predicts the discharge plume is trapped by the thermocline, restricting the volume available for dispersion.
Of the two seasons with "stratified"conditions, Fall had the greatest pool variability, according to the
historic level data
3.2 Input Parameters Affected by Pool Elevation
In the parametric evaluation, two input values were recalculated to adjust for changes in pool elevation:
• Height/Depth at Discharge Location (Ho)—height to the water surface measured from the
reservoir floor(sediment bottom); calculated as the difference between pool elevation and
estimated bottom elevation at Outfall 006(175 ft NGVD from available bathymetric survey data)
• Height of Thermocline(HINT)—height to the thermocline measured from reservoir floor;
calculated by deducting the depth to the thermocline(estimated to be 5 m [16 ft] below the water
surface)from the total Height at Discharge Location (HD)
The calculated input values used in the revised model runs for the parametric evaluation are shown in
bold below.
TABLE 3.
Summary of Revised CORMIX Model Input Parameters
Normal Pool Level Low Water Level High Water Level
Median—All Seasons 10"'Percentile for Fall 90th Percentile for Fall
Reservoir Pool Elevation 220 ft NGVD 218 ft NGVD 221 ft NGVD
Estimated Bottom Elevation at Discharge 175 ft NGVD 175 ft NGVD 175 ft NGVD
Height/Depth at Discharge(Ho) 45 ft(13.7 m) 43 ft(13.1 m) 46 ft(14.0 m)
Height of Thermocline(HINT) 29 ft(8.7 m) 27 ft(8.1 m) 30 ft(9.0 m)
3.3 Parametric Evaluation Results and Conclusions
Case 4a (Fall Season, Max Day Discharge)was modified to reflect alternative scenarios with low and high
water conditions. Output for the Low Water Level variation of Case 4a is included in Appendix C. The
CORMIX model results are summarized below for the original and alternative scenarios.As described in
Section 3.1, the results confirm the plume is impacted by the thermocline, which acts as an upper
boundary. Compared to the original Study Case 4a, the low water scenario further restricts the vertical
movement of the plume, slightly expanding the width and reducing predicted dilution by less than 2%.
Conversely, the high water scenario raises the thermocline, allowing for a slight increase in vertical
movement and narrower plume. The impact on dilution was negligible for the high water scenario.
TABLE 4.
CORMIX Case 4a(Original &Variations) Results at EPA-defined Acute Mixing Zone Boundary
CORMIX Radial Horizontal Plume Centerline Equivalent Effluent Limit
Case 4a Distance a Distance a Width Dilution Factor IWC Acute Copper(Daily Max)
Original Study 175.5 ft 278.1 ft 15.3 6.54% 166.1 pg/L -
High Water Level 177 ft 175.6 ft 277.0 ft 15.3 6.54% 166.1 pg/L -
Low Water Level 175.9 ft 279.6 ft 15.0 6.67% 163.0 pg/L -1.9%
Notes:
a The radial distance is a vector distance from the center of the port,while the horizontal distance reflects the x-direction only(plan
view,looking down at the surface of the waterbody)
For purposes of dilution at an acute mixing zone boundary, the Low Water Level Case 4a represents a
"worst-case of the most conservative case"scenario. Notably, the predicted dilution factor at the acute
mixing zone boundary of 15.0 is equivalent to an effluent limit of 163.0 pg/L, which is greater than double
the maximum value measured at Outfall 006.
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,Jac®bs Shearon Harris Nuclear Plant-Permit NC#0039586
Clarifications to Mixing Zone Modeling&Analysis
4. References
Doneker, R.L., and G.H Jirka. 2007. CORMIX User Manual. A Hydrodynamic Mixing Zone Model and
Decision Support System for Pollutant Discharges into Surface Waters. EPA-823-K-07-001. December
2007.
Duke Energy. 2020. Corrective Action Plan for Copper and Zinc for Harris Nuclear Plant NPDES Permit,
Year 4 Activities Report. Submitted to North Carolina Department of Environmental Quality on August 27,
2020.
Page 6 CH2M HILL North Carolina, Inc.

Attachment A
Meeting Minutes: Overview of Year 4 Activities
and Mixing Zone Study — November 2, 2020

Jacobs
MEETING MINUTES
Corrective Action Plan (CAP) for Copper and Zinc for
Harris Nuclear Plant NPDES Permit —
Overview of Year 4 Activities and Mixing Zone Study
MEETING DATE/TIME: Monday,November 2, 2020 (2:00-3:00 pm EDT)
LOCATION: Microsoft Teams Meeting
INVITEES: David Hill/DEQ Bob Wilson/Duke Energy-HNP
Nick Coco/DEQ Don Safrit, PE/Duke Energy
Sergei Chernikov/DEQ Cynthia Winston/Duke Energy
Min Xiao/DEQ
Julia Byrd/DEQ
Jennifer Bell, PE/CH2M HILL North Carolina, Inc. (Jacobs)
Jaime Robinson/Jacobs
Brad Paulson/Jacobs
Meeting Minutes
Following introductions, Don Safrit opened the call with a safety moment regarding working safely at
home. Don then began discussing the slide deck shared with the group.
1) Review of Compliance Action Plan(CAP)schedule for NPDES permit compliance:
Duke's progress along the CAP timeline was discussed, leading up to discussion of the mixing zone
study. In mid-2019, Duke presented results of the Copper WER study and DEQ responded with a
request that dilution effects be considered. No additional discussion occurred.
2) Mixing Zone Study Results:
— Brad-Paulson-then began an overview of the mixing zone study_methodology used,_including
application-of-CORMIX—Brad reviewed-the-available-dat-a-and-parameters used-in-the-model,.
including accounting for seasonality.
David Hill provided initial DEQ comments on the modeling:
• The field data used in the model were fine.
• David raised a question regarding the use of the"heated discharge" option when running
the CORMIX models. He assumed this was done because Duke is also interested in thermal
impacts of the discharge. Brad stated that he would take a closer look at the"heated
discharge" option and potential impacts on the mixing zone results.
• David also asked whether a sensitivity analysis could be performed on key parameters.
• One key parameter identified by David was Reservoir levels.A parametric evaluation of
water levels and their effect on the mixing zone was recommended.
• David requested that a revised report be issued.
CH2M HILL NORTH CAROLINA,INC. 1
IS WHOLLY-OWNED BY JACOBS,INC.

MEETING MINUTES-
CAP FOR COPPER AND ZINC FOR HARRIS NUCLEAR PLANT NPDES PERMIT
OVERVIEW OF YEAR 4 ACTIVITIES AND MIXING ZONE STUDY
Don followed up with a reminder that Duke is not looking for details now and is looking forward to
receiving detailed feedback from DEQ in the near future.Jennifer Bell added that the modeling
approach looked at the most conservative scenarios and that the team is ready to evaluate
sensitivity.
3) Application of Mixing Zone Results to Water Quality Criteria:
Jennifer Bell reviewed Duke's recommended approach for incorporating mixing zone results into the
calculation of water quality criteria.Once a mixing zone is defined,water quality criteria are
calculated at the edge of the mixing zone. Hardness data are incorporated as well. NCDEQ does not
have written guidance and Duke evaluated potential water quality criteria using EPA and Wisconsin
guidance.No further discussion was had.
4) Next Steps Forward:
Don Safrit stated that Duke is receptive to refining the findings and then determining outcomes of
an evaluation of appropriate water quality criteria.Don asked that DEQ provide written comments
so that this can be resolved expeditiously ahead of or in parallel with the permit renewal process.
Duke understands that DEQ cannot provide additional feedback on water quality criteria until
comments on mixing zone study are addressed.
David Hill stated that DEQ aims to provide written mixing zone study comments within 30 days.
Duke will plan to address those comments within the following 30 days.
David Hill asked if other DEQ industrial permitting staff had comments or questions. None were
provided.This concluded the call.
Copies of PowerPoint Slides have been included as an attachment to these Meeting Minutes
CH2M HILL NORTH CAROLINA,INC. 2
IS WHOLLY-OWNED BY JACOBS,INC.

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Correcti •v•e Action Plan (CAP) for Copper and Zinc
Overview of Year 4 CAP Activities and Mixing Zone Study
November 2, 2020
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Corrective Action Plan (CAP) for Copper and Zinc for Harris Nuclear Plant NPDES Permit—
Overview of Year 4 Activities and Mixing Zone Study
HNP Copper& Zinc—
Permit Obligations 8, Compliance
• HNP Discharge Point into Harris Reservoir(Class WS-V)
• Revised Surface Water Standards for Copper&Zinc in 2015
• New NPDES Permit Limits in Outfall 006 in 2016
(September 2021 compliance deadline)
— Limits based upon state level defaults
Review of CAP Schedule and (limited availability of historic and/or site-specific information)
Previously Completed Activities ---Overview of Year 4 CAP Activit ee•a,ua Pdixlny Zone Study ;:, Daily Max Monthly Average
1(Acute) (Chronic)I'
November 2,2020 ii�W. ''clL,,Lp4Pe,rw�11211l�r I' !`11V�WiJu�l�„IJ�uL. aji, �.w1u'iW{�.Ih „'�h ILL.z,/
Zinc 126 pg/L 126 pg/L
fai. DUKE
ENERGY
JACOBS-
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2 3
Schedule of Compliance From WER to Mixing Zone Study
September 1.2016 sep19966e91,2017 Sep[embnl.2lI Sepbplher 1,2019 Se66e•6ber1,2020 September 1.2021 _
t f • t • • May 2019—WER Study Results and proposed copper WER
NPDES Cutective Year 2Report Year 2Report Year• Deadline to submitted to DEQ
Permit Issued - Aehon Plan S •F urtneevery 0•Dlw..n rn.,.rle,v.wn Rport Achl ve
Rep. a a Compliance 1 W values n • June 2019—Duke Energy met with DEQ to discuss Copper WER
ease V.ER pon['ummws
IsaaN ZmesbavPWuea
Study
Effluent Chanctulzatlon A r�
_ • July 2019-DEQ provided written comments on the proposed Copper
Submit
Permit
WER,requesting that dilution effects be considered and that
• .WER d•ed°°"�,uumned 5�6 additional rounds of WER testing be performed..'
i • November 2019—Mixing Zone Study Plan submitted to DEQ
Copper Mixing Zone Study Submit
oea�a.a�•�.�a•�� MWn92one • January2020—DEQ responded to the MixingZone StudyPlan,
•vkNes:.:PmPe.nl2°, 1 xingz.. P
""• r�Stud
requesting incorporation of velocity,temperature,and density at the
€il�iil nR41a�1'��'' site of discharge and anticipated plume and modeling of thermocline
71i�l ��
as a boundary condition
ONyProceetl • Januaryto April 2020— Zone Studycompleted using
d Requeed �
�1 VA�L�++ p Mixing P
,4171 Q � II� CORMIX dilution model
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Corrective Action Plan (CAP) for Copper and Zinc for Harris Nuclear Plant NPDES Permit—
9verview of Year 4 Activities and Mixing Zone Study
Mixing Zone Study
• The purpose of the Mixing Zone Study is to
account for dilution effects as effluent mixes with
reservoir water at the discharge point ,Agtblenc
DEQ suggested study to determine test ,�,..yt 3k'tx• y
concentrations for further WER study , v
�,p �,y — Study conducted using EPA and other State r :4 �''-t
�' guidance;results used for calculation of
Mixing Zone Study �� '/I permit limits « ,cif. � z'
and Dilution Modeling -, r t�
Mixing is impacted by: w
C•de. _.\of Year 4 CAP Act _ c riixing,t3 i..�,:_, Optfall 1 L
— Outfall(discharge)configuration
— Effluent characteristics(discharge rate,2020
November 2, '''.sti+
density,etc.) r�; � �, o
— Receiving water characteristics(ambient -
farwa Z.Nn Ate, ,
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density stratification,velocity,etc.) ate
ENERGY • Use of CORMIX mixing zone expert system:
- EPA-developed modeling system;nearly 30
years of use&continually updated
JACOBS' _ Approved for use by DEQ >DUKE
— Appropriate for application in lakes/reservoirs T ENERGY.
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Defining the "Mixing Zone" Seasonal reservoir data used to determine
, "worst case" mixing conditions
• North Carolina rules allow mixing zones _but provi
de little specificity for
determining characteristics ! ,r , • . v, ;ry ;,'-:.•,--
• EPA created the Technical Support Document( in 1991 for 1+ ) 1"'" '-t,I t7 -•-vsa.m.
regulating toxic substances such as copper;includes guidance on
mixing zones: : i .
- Significant overall detail for establishing mixing zo es;general in nature
- Provides guidance for acute mixing zone definition • ! .� -
- No specific guidance for chronic mixing zones d r
• Wisconsin developed detailed mixing zone rules and guidance: ;
- Chronic mixing zone for lakes based on edge of discharge-induced mixing M . , ,a,.., 1 R_ M.
- Includes a default dilution ratio for chronic mixing f 10:1 f� """'
.•may
DUKE V Source:Duke Energy,Environmental Monitoring Reports for 2016-2018 ,DUKE
ENERGY. ENERGY.
8 9

Corrective Action Plan (CAP) for Copper and Zinc for Harris Nuclear Plant NPDES Permit- _
Overview of Year 4 Activities and Mixing Zone Study
Seasonal reservoir data used to determine g"worst case" mixing conditions Acute Mxin Z•
one Results
CORMIX Effluent .: Seasonal Effluent
Case No. ,'Flow(mgd) Scenario Temperature Ambient Tempera reI CORMIX Radial Horizontal Dilution Plume Travel
_ �.. •s Case No. Distanceerft.Distancerft,.Facto,r„ yOWC Width;MILL i mm,
01a Max day:17.17 Winter Unstratified
alb MMA:14.86 (Dec-Feb) 18.1°C t00°� 01a 25.2 3.97% 265 8.8
02a Max day:22.02 Spring 27 3°C Linear Stratification 01 b 173 ft 27.2 3.68% 286 1.0
02b MMA:15.86 (Mar-May) Surface:23.5°C Bottom:14.0°C 02a 16.8 5.95% 227 5.4
03a Max day:17.89 Summer 02b 20.5 4.88% 293 7.5
03b MMA:tars (Jun-Aug) 32.6°C Two-Layer Stratification 177 ft
Constant at surface(0-5 m):29.5°C 03a 15.4 6.49% 334 8.9
04a Max day:19.10 Fall Linear decrease from(5 m):26.0°C
29.6°C to bottom 14 m 16.0°C 5.92%
04b MMA:14.81 (Sep-Nov) (- )� 03b 16.9 363 11.0
176 ft
• Effluent temperatures based on the 9041-percentile of DMR data(Jan
04a 15.3 6.54% 278 7.2
2016-Aug 2019) 04b 17.0 5.88% 322 9.2
• Reservoir temperatures measured at E2 monitoring station,located
0.75 miles S/SE of discharge (.DUKE - ( DUKE
ENERGY. 4t ENERGY.
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Chronic Mixing Zone Results:
Edge of Discharge-Induced Mixing
CORMIX Radial Horizontal Dilution Plume
Case No. Distance,ft Distance;ft Factor IWC Width,ft,.
01a 565 564 92.3 1.08% 1,234
01b 494 493 91.1 1.10% 1,111
02a 756 755 82.8 1.20% 1,919 Application of Study Results �-3 � :.
02b 556 555 79.1 1.26% 1,518 to Cu and Zn Limits -__'
Ca i,iia.,`r ear4 CAP_Actiuit es anL Nlndng 2:coe„7,i�;... -
03a 594 594 55.4 1.81% 1,496
03b 500 500 54.7 1.83% 1,319 November z,2020
04a 647 647 61.9 1.62% 1,593 etas DUKE
04b 509 509 58.8 1.70% 1,327 ' ENERGY.
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ct' ENERGY.
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I
Corrective Action Plan (CAP)for Copper and Zinc for Harris Nuclear Plant NPDES Permit—
Overview of Year 4 Activities and Mixing Zone Study
Adjusting Effluent Limits for Dilution Hardness Characterization
J
• Once a"mixing zone"is defined,required Wate Quality Criteria(WQC)' Default(25 mg/L as CaCO3)used in calculating HNP original limits
The Dilution Factor(DF)quantifies how•we _ than at the of 44 mg/L
are evaluated at the mixing zone boundary,rather —
"end-of-pipe" Used monthly average median Effluent Hardness
II mid"effluent and lake/ so
reservoir water are at the zone boundary E 55 r''
50 --r • r -'-„ 1 •..
•
• WQC are recalculated based on mixed/combin_d water hardness at the
zone boundary ` ••`T i� ?, . ,
• Background Concentration should be considere 35 a` • �' �'I
• 30 i =r
° SclieGulegsAutdownsofH�
Permitted effluent limits=(WQC x DF)—Concentration in Lake m 25
s1 0� �1 ,0 ••0 ; ,�9 •.1 '` ' ti� �o .rye
0. 31, o°` •ar PQ` )J OZ` ��° PQ �J� OZ ��° Q` )J
f�
• Ambient25mL reservoirforur Hardnessosesofthe Mixing Y V ENERGY,
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"Worst Case" Dilution Factors & Zinc Characterization -
Revised Effluent Limits Maximum Daily Values
• Zinc values t o w substanially lower after change of corrosion inhibitors
Total Recoverable Metals Limits for Outfall 006
Acute Zone:EPA Guidance; Acute Zone:n/a 200 _
Current Chronic Zone:WiDNR Edge Chronic Zone:
2021 of Discharge-Induced Mixing WIDNR Default = 180
Limits from CORMIX � of DF=10 � 160 • - --
Dan), 126 pg1L 177 ft DF=15.3
140
ax
Zn
r same=z5.g/L
eye 126 ygrl_�.. 500 ft DF=.54.7 -< < 100 —
la r mc",w:i
0
p 50 0
°ate wa10 5 pall-,,:‘ 177 ft DF=15.3 trt-A ,i );
CLI
Monthty '`= i fi H 20 t' %01' m o o •-,
Average� .4f 500 ft DF=54.7 { i,_ - - 0 '°®,.0�00 e,• 6 °jO„q�$.R, � . ,
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