NC0005088_Report_20190529

Rogers Energy Complex
DUKE'E- 573 Duke Power Road
ENERGY® Mooresboro,
North Carolina 28114
828 657 2000
May 22, 2019
Sergei Chernikov, Ph.D. RECEIVED/N�bE61/p
wR
NC Division of Water Resources
Water Quality Permitting Section - NPDES M4r •9 •
%1119
1617 Mail Service Center
Raleigh, North Carolina 27699-1617 PeWat! tlatity
milting Section
Subject: NPDES Wastewater Permit
Rogers Energy Complex
Permit #NC0005088
Thermal Model Verification Study Plan
Dear Dr. Chernikov:
Part I A. (27) d) of NPDES permit NC0005088 requires after 12 months of temperature data are
collected that a report be submitted to the Division to verify the CORMIX model assumptions
and predictions. Part I A. (27) e) requires the permittee to perform an assessment to verify that
the mixing zone does not prevent the passage of aquatic organisms around the mixing zone.
That part also requires submission of a study plan prior to performing the assessment.
To address these two permit conditions, the attached study plan has been developed. As
outlined in this plan, the approach is to use biodegradable dye in the discharge from Outfall 005
and measure the downstream dye concentrations to understand the plume concentration levels.
While the plume temperatures near the outfall will be measured, the temperature will likely
dissipate quickly. Therefore, a dye study is necessary to measure the plume dilution further
downstream.
Outfall 005 began to discharge on April 1, 2019. Therefore, the 12 months of temperature data
collection will be completed on March 31, 2020. A report using this study and the collected
temperature data will be compiled and submitted to your office by September 1, 2020.
Your review and concurrence of the attached study plan is requested. Should you have
questions or require additional information, please contact Robert Wylie at 704-382-4669.
Sincerely,
ati
David P. Barnhardt
General Manager II, Rogers Energy Complex
Fossil/Hydro Operations - Carolinas Coal Generation
Attachment: REC Outfall 005 Thermal Model Verification Study Plan
USPS 70171450000038768443

Water Environment Consultants
s P.O. Box 2221
r L---� ✓ Mount Pleasant, SC 29461
843-375-9022
May 21, 2019
Mr. Robert Wylie
Environmental Project Manager
Duke Energy Corporation
526 South Church Street
Charlotte, North Carolina 28202
PROJECT: Rogers Energy Complex Thermal Model Verification Study Plan
Dear Mr. Wylie:
Under contract with Duke Energy Corporation (Duke) and in support of the Rogers Energy Complex's
NPDES permit (NC0005088), Water Environment Consultants (WEC) developed a thermal model
verification Study Plan for the North Carolina Department of Environmental Quality (NCDEQ)to review.
The goal of the Study Plan is to document the data collection effort necessary to verify and/or adjust the
previously approved Outfall 005 CORMIX model predictions with field measurements. The enclosed
Study Plan outlines WEC's methodology for determining channel geometry,flow, and dilution
downstream of Outfall 005 in the Broad River.
So the field work may be performed this summer, WEC recommends that Duke provide the attached
Study Plan to NCDEQ as soon as possible in order to obtain any comments and approval.
Sincerely,
--541/4, 41g
John K. Durkee, P.E.
Principal
Enclosure:Attachment A
Water Environment Consultants I www.water-ec.com

ATTACHMENT A - REC Outfall 005 Thermal Model Verification Study Plan
Introduction
Water Environment Consultants (WEC) prepared this Study Plan for Duke Energy Corporation (Duke)and
the North Carolina Department of Environmental Quality(NCDEQ) in support of NPDES permit
(NC0005088)for Duke's Rogers Energy Complex (REC) located in Mooresboro, North Carolina.
Previously, the NCDEQ-approved "desktop" CORMIX model completed by WEC showed that the
applicable instream temperature standards will be met at a relatively short distance downstream of
Outfall 005 (including both the 89.6°F maximum temperature requirement [15A NCAC 02B .0211 Fresh
Surface Water Quality Standards for Class WS-IV Waters], and the requirement of no more than a 5.04°F
rise above the natural water [also per 15A NCAC 02B .0211]). The worst-case,winter model showed
compliance with the 5.04°F "delta-T" instream standard, and both standards were modeled at worst-
case 7Q10 low-flow ambient conditions. While neither of these conditions will occur during the field
study, given the regulatory timeframe, performing the work during low-flow spring/summer conditions
as close to 7Q10 as possible is preferred.
The permit requires field verification of the modeling prediction used to set the 100°F daily maximum
temperature limit at Outfall 005. Parts I.A.27.d and I.A.27.e of the permit state:
After 12 months of temperature data are collected, the permittee shall submit a report to the
Division to verify the CORMIX model predictions. The report shall include field verification of
assumptions used in the model and a summary of temperature data for effluent, upstream and
downstream...
Once during the permit term, the permittee shall perform an assessment to verify that the
mixing zone does not prevent the passage of aquatic organisms around the mixing zone.A study
plan shall be submitted to the Division prior to commencement of the study...
This Study Plan details the data collection effort in the following sections:
• Ambient Currents,Water Depths, and Temperature
• Elevation Survey
• Outfall Characteristics
• Ambient Dilution Study
• Thermal Plume Monitoring
• CORMIX Modeling
WEC will generate a CORMIX dilution and temperature model using the measured field data. The
resulting mixing zone dimensions and thermal plume will be compared to those previously approved by
NCDEQ. Based on the comparison,the worst-case winter model will be adjusted, if necessary,to ensure
the instream requirements are being met.
A-1

Ambient Currents, Water Depth, and Temperatures
WEC will use a Sontek RiverSurveyor-M9 to collect detailed water depths and current velocities in the
Broad River. The RiverSurveyor is an Acoustic Doppler Current Profiler(ADCP), equipped with a
differential GPS to provide horizonal positioning data. The ADCP instrument measures depths and
currents through the water column as it traverses the river perpendicular to the shoreline,thereby
providing a two-dimensional cross-section of current velocities. The instrument also measures water
temperatures at the surface. WEC will make several transects across the Broad River at and
downstream of Outfall 005, as preliminarily shown in Figure 1.
Since it's rare the river stage matches 7Q10 conditions, WEC will perform the field measurements in the
low-flow, spring/summer months of 2019,when conditions are as close to 7Q10 as possible. At the
conclusion of field data collection, WEC will post-process the data to determine a mean channel
geometry and depth-averaged current velocities. Measurements across several transects will be used to
calculate the instantaneous river flow rate, and this information, along with data from a nearby USGS
station(s)will be used to refine the CORMIX input geometry, including estimating the river depth and
width at 7Q10 conditions.
St*
.a...
•
Legend )11
Outfall 005
Feet
Transeds A 0 250 500 750 1 000
Figure 1. Preliminary field measurement transect layout
A-2

Elevation Survey
In addition to the ADCP instrument, WEC will measure water surface elevation at various points using a
Trimble Geo 7x Centimeter Edition GPS. The GPS is capable of measuring with a vertical accuracy of±0.1
foot and will be used to convert measured water depths to bottom elevation relative to the North
American Vertical Datum of 1988 (NAVD88).
Outfall Characteristics
Previous model inputs of the outfall structure discharge were based on design drawings, maximum flow
rate, and CORMIX geometrical restrictions (e.g. outfall "channel" depth to width ratio). WEC will
observe the constructed outfall structure and measure characteristics for slope,geometry, and depth.
These measurements will be used to adjust the model's input for discharge channel geometry.
Ambient Dilution Study
To the CORMIX model,the ambient temperature is less important than the ambient flow because
temperature changes within the region of interest are primarily driven by mixing and not heat exchange
with the atmosphere. Temperatures will still be measured as part of the field verification. Dilution,
however,will be the primary measurement.
To better determine instream mixing,WEC will conduct a dye tracer study using Rhodamine WT dye.
The dye will be injected into the wastewater discharge at a constant rate, under constant discharge flow
conditions. Cyclops-7 loggers with rhodamine sensors will be deployed to continuously measure the dye
concentration. A fluorometer will be utilized to measure the concentration at the outfall and
downstream within the Broad River at regularly spaced transects (see Figure 1). The CORMIX model
assumes a Gaussian distribution across the plume, and the concentration at the edge of the plume is
0.37 times the centerline concentration.This definition will be used to set the outer edge of the
measured plume width and for comparison to modeled plume width and the plume width that allows
safe passage. Any mixing provided by the confluence of Suck Creek into the Broad River will be
measured.
WEC will measure dye concentrations at 1-foot depth increments until the dye is vertically mixed, at
which measurements will be made one foot below the water surface. WEC will use the resulting data to
generate two-dimensional plots of the dye concentration for comparison to the CORMIX model
predicted dilutions.
Thermal Plume Monitoring
Though the dye measurements will provide more detailed mixing information,WEC will also measure
the instream temperature from the outfall and downstream until the difference between the discharge
and ambient temperatures is 0.5°F. Based on the difference between the discharge and ambient
temperatures on the study date, several transects near the outfall will likely be required.
A-3

CORMIX Modeling
Utilizing the bathymetric and river velocity data collected in the field,WEC will determine a
representative cross-sectional channel geometry within the plume length that is more accurate than the
previous desktop estimate. WEC will set up and run a CORMIX(Version 11.0) model to include the new
model inputs, ambient flow, and the outfall discharge's flow and temperature on the field measurement
day. Model inputs will be adjusted, to the extent possible,to match the measured data.
The CORMIX model will be used to predict the dilution and temperature plume from the discharge
during the worst-case conditions (i.e. 6.0 MGP discharge, 7010 river flow, 100°F discharge temperature)
that were previously used to set the daily maximum permit limitation. The new, resulting mixing zone
dimensions will be compared to those from the previous model to ensure the 89.6°F and 5.04°F "delta-
T" instream requirements are still being met at a relatively short distance downstream from the outfall.
WEC will model the field measurement day's conditions using temperature units for comparison as well.
The results will be compared to the thermal plume monitoring data as well as the dilution model results
to ensure they are consistent with respect to dilution from mixing only and not from evaporative
temperature loss.
A-4

fDUKE Paul Draovitch
Senior Vice President
`a ENERGY® Environmental,Health&Safety
526 S.Church Street
Mail Code:EC3XP
Charlotte,NC 28202
[phone]
May 22, 2019
Wastewater Branch
Water Quality Permitting Section
Division of Water Resources RECEIVED/NCDE9/DW1?
1617 Mail Service Center
Raleigh, NC 27699-1617 MAY 2 9 2019
Subject: Delegation of Signature Authority Water Quality
Permitting Section
Buck Combined Cycle
NPDES Permit Number NC0004774
Rowan County
To Whom It May Concern:
Duke Energy Carolinas, LLC, submits this correspondence as a revision to documentation for your
records of designation of duly authorized representatives ("Delegated Authorities")for the NPDES Permit
for Buck Combine Cycle. We are requesting the removal of Henry Botkins Jr. as the delegated Authority,
effective June 1, 2019. By notice of this letter, I hereby delegate signatory authority to the following
individuals for all permit applications, discharge monitoring reports, and other information relating to the
operations at the subject facility as required by all applicable federal, state, and local environmental
agencies specifically with the requirements for signatory authority as specified in 15A NCAC 2B.0506.
Name: Kristopher C Eisenrieth
Title: General Manager II
Mailing Address: 1385 Dukeville Road
Salisbury NC 28146
Physical Address:
(if different)
Email Address: [e-mail]
Office Phone: [phone]
Mobile Phone: [phone]
Should you have any questions regarding this letter or require additional information,please contact Ms.
Elizabeth Glenn at [e-mail] or 980-373-0530.
I

Buck Combined Cycle
NC0004774
Rowan County
Page 2 of 2
"I 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."
Sinc rely,
RECENED/NCUEQ/DWR
CJL
Paul Draovitc MAY 29 1019
SVP - Envir mental, Health & Safety Water Quality
Permitting Section
cc: Mooresville Regional Office -Water Quality Permitting Section
A