NC0038377_Wastewater Permit App_20160815

4
DUKE
ENERGY®
August 15, 2016
Sergei Chernikov, PhD.
North Carolina Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: NPDES Wastewater Permit Application Submittal 98
Duke Energy Progress, LLC.
Mayo Electric Generating Plant
Permit #: NCO038377
Person County
Dear Dr. Chernikov,
Harry K. Sideris
Senior Vice President
Environmental, Health & Safety
526 S. Church Street
Mail Code: EC3XP
Charlotte, NC 28202
[phone]
RECEIVEDINCDEQIDWR
AUG 18 2016
Water Quality
permitting Section
Duke Energy Progress, LLC (Duke) is submitting herewith three copies of supplemental
information in support of the NPDES renewal application submitted in September 2011 for the
subject facility. This update is in addition to the previous updates and requests submitted dated
October 15, 2014, October 31, 2014, December 22, 2014, February 4, 2015, July 22, 2015 and
July 5, 2016. Please include this supplemental information and the information in the previous
submittals in your review.
This submittal is intended to provide an update of modifications that will be necessary to comply
with recently enacted laws and regulations including the Federal Steam Electric Effluent
Guidelines (ELG), Federal Coal Combustion Residual (CCR) rule, the North Carolina Coal ash
Management Act of 2014 and HB 630 of 2016. Specific permit requests from Duke Energy are
identified in bold throughout this submittal.
With numerous federal and state requirements to coordinate and implement in a short time for
the site, planning and sequencing of work are paramount and dynamic. As such, final scope and
sequence for all work is not complete at this time. Where scope is still not finalized, Duke has
provided a range of options that are being evaluated and provided various alternate scenarios in
an attempt to limit the number of subsequent submittals necessary. As there are no requests for
new external outfalls to waters of the United States and all proposed modifications contained
herein are internal to our wastewater process flows, it is Duke's belief that the information
provided in this submittal is of sufficient detail to allow for review and issuance or renewed
NPDES permit for the Mayo plant. This is consistent with the guidance received from DEQ staff
in a meeting on November 20, 2015 and follow up correspondence dated January 11, 2016 and
January 28, 2016.

Mayo Plant NPDES application update #8
NC0038377
Person County
Page 2of16
1. Duke intends to construct a new retention basin to treat low volume waste, monofill
leachate, cooling tower blowdown, treated domestic sewage, various unit wash
waters and coal pile runoff as a replacement of the ash basin. CAMA 2014 and the
Federal CCR will prohibit continued wastewater flows to the existing ash basin at Mayo.
Projects are nearly completed to convert ash handling of all ash (both bottom ash and fly
ash) to 100% dry handling and disposal systems at Mayo. All other wastewater inputs to
the current ash basin must be redirected and handled in another manner. Duke intends to
construct a lined, retention basin to handle all wastewater flows currently directed to the
active ash basin. Monofill leachate will also be directed to this basin. Cooling tower
blowdown flows will be routed to the retention basin with the alternate cooling tower
blowdown line directed to outfall 002.
Additionally, the retention basin will have a cell where various vacuumed sediments and
solids can be decanted prior to disposal of materials into the Mayo CCR monofill.
Periodically, any accumulated solids in the retention basin will be disposed of in the
facility's onsite landfill or another approved disposal facility. The retention basin will be
approximately 7 acres in area and have the capability to have addition of flocculent and
pH adjustment chemicals.
A holding basin will be constructed for high volume flows such as air heater washes,
process washes, etc. The holding basin will have a chemical feed system for adjusting
pH and polymer addition to enhance settling. Once acceptable, the holding basin
contents will be transferred to the primary basin in the retention basin. The holding basin
will be designed for batch processing.
Duke requests that ELG limits associated with landfill leachate and coal pile runoff
be applied at the discharge point from this basin. An aerial photo with planned
locations of the basin can be found in Attachment 1.
As requested, available sampling data from the monofill leachate is provided in
Attachment 2.
2. Duke is constructing a new FGD settling basin to replace the existing basin. The
existing FGD settling basin is located partially within the ash basin and must be replaced
in accordance with applicable federal regulations. Duke intends to construct a new basin
for FGD blowdown flows. The potential location of this basin is shown in attachment 1.
The discharge flows from this basin will serve as the input to the Vapor Compression
Evaporator and there will be no typical discharge from this basin. An emergency
overflow will be constructed in the basin to allow for controlled release in the event of

Mayo Plant NPDES application update #8
NC0038377
Person County
Page 3 of 16
meteorological event in excess of a design storm. It is anticipated that any releases from
this basin would be very infrequent. Duke requests that an emergency overflow to
Mayo creek be permitted as part of the renewal. Duke also requests that FGD basin
overflow be listed as a contributing flow to outfall 002. The final location where the
overflow will need to be directed will depend on the final location where the FGD basin
is constructed. As this is for an emergency overflow and not anticipated to be used with
any regularity, Duke requests that both potential pathways be permitted to avoid a need
for a major modification soon after this permit is issued. Duke will remove the request
for the flow path not utilized in a future renewal.
3. Duke intends to redirect monofill leachate to the ash basin, upon permit issuance.
Upon permit issuance with monofill leachate sown as a contributing flow to outfall
002, Duke will redirect this flow into the existing ash basin. The flow is currently sent
to the Vapor Compression Evaporator however sampling data (attached) confirms the
flow of leachate is suitable to be released through outfall 002 currently upon permit
coverage. Duke requests that monofill leachate be listed as a contributing flow to
outfall 002 upon permit reissuance.
4. To facilitate ongoing work and required wastewater reroutes, the sampling point for
NPDES outfall 002 will be moved. The discharge will still be to the same cove of the
Reservoir but the sampling and flow measurement location will be moved further
southeast within the effluent channel as shown on the drawing found in attachment 1.
5. Duke requests specific permit authorization that upon ceasing flows to the ash
basin, decanting and dewatering of the basin through existing NPDES outfall 002
can occur. Specific authorization for decanting and dewatering is a condition currently
in the NPDES permit at Sutton and Marshall. Duke requests specific authorization
that the ash basin may be decanted and dewatered and clarity on what the permit
limits associated with that activity will be. A characterization of the ash basin
interstitial water has been previously provided. This submittal was dated July 22, 2015.
Current plans are for decanting and dewatering to occur through NPDES outfall 002 to
Mayo Reservoir.
6. Duke requests that existing outfalls SW outfall 004, 005, 006 (a -e) be included in the
NPDES wastewater permit. Characterization of outfalls 004 and 005 was included in
the December 22, 2014 submittal primarily related to seep monitoring. Outfall 004 and

Mayo Plant NPDES application update #8
NC0038377
Person County
Page 4 of 16
005 samples were included in Table 2 of the report. There is periodic and documented
groundwater flow observed from outfall 004 and 005 that is not associated with storm
water. As such, Duke requests inclusion of these flows in the NPDES wastewater permit.
Future plans call for the flows from outfall 004 and outfall 005 to be piped and released
through NPDES outfall 002 as part of ongoing wastewater re -direction projects.
Outfalls006 (a) (b) (c) (d) and (e) are located in the area of the cooling tower. A number
of these points are subject to having minor flows associated with cooling water spray
from the cooling tower. As such, Duke requests that these flows remain in the NPDES
permit.
7. Duke plans to construct a yard sump which will direct flows to the new retention
basin. This sump is being constructed with redundancy built in but in the case of a
failure, overflows from the sump would be released to the Reservoir through outfall
002. This yard sump would discharge only in emergency situations or in the event of an
equipment failure. Duke requests that potential overflows from the yard sump be
listed in either the NPDES permit or NPDES fact sheet as a potential contributing
flow to NPDES outfall 002.
8. Duke requests that internal outfall 009 remain in the permit. Even though current
flows from the FGD system are processed through the Vapor Compression evaporator
system, Duke requests the option to discharge these flows at a future date should a new
technology for treating the wastewater to permit limits become a viable alternative. Duke
anticipates Steam Electric Effluent Limits Guidelines to be applied to this internal outfall.
9. Monofill leachate
Currently, leachate from the monofill is sent to the FGD pond where it is then
evaporated. Duke intends to install an option to redirect flows of monofill leachate to
the newly constructed retention basin upon completion. Duke requests that ELG
limits associated with leachate be applied after treatment after the retention basin.
Results from previous leachate sampling events are included in this submittal and can be
found in Attachment 2. Upon permit issuance but prior to construction of the lined
retention basin, Duke intends to release leachate flows through outfall 002 via the
existing ash basin.
10. Area of wetness (AOW) Permit coverage Disposition — Duke has evaluated the list of
AOW's submitted to the DEQ for pen -nit coverage. Based upon further review, Duke
withdraws requests for coverage from areas previously identified at S4, S5, S6, S7

Mayo Plant NPDES application update #8
NCO038377
Person County
Page 5 of 16
and S9. This request is based on location of the respective AOW's and/or review of
sampling data that confirms the lack of pollutants associated with plant activities
being released to Waters of the State from these points. Duke requests that DEQ
provide concurrence or acknowledgement of this request in the NPDES Fact Sheet
for the permit.
Duke requests permit coverage for AOW's identified as Sl, SIA, S2, S2A, S2B, S8
and S10. All of these points commingle below the ash basin dam at the point identified
as "S-3". Consequently, Duke requests effluent channel designation for all AOW's
to the point identified as S3 on our AOW map. In addition, for locations S1, SIA,
S2, S2A, S213, S8 and S10 there may be some small-scale treatment installed to achieve
appropriate treatment criteria including TSS, pH, and Oil & Grease, if necessary.
11. CWA Section 316(b) alternate schedule. Duke requests an alternate schedule for
compliance with Section 316(b) of the Clean Water Act. Specifics of the request can
be found in Attachment 3.
12. Duke has included a process flow diagram of the future wastewater flows on the site
to help with visualizing these changes. This can be found in Attachment 4.
We appreciate your attention to these requests and look forward to finalizing the NPDES permit
for the Mayo plant in the near future. Should you have any questions regarding this letter or
require additional information, please contact Mr. Shannon Langley at [phone] or at
[e-mail].
"I cert, 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 nay 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,
Harry Sideris
SVP - Environmental, Health & Safety
Enclosures

Mayo Plant NPDES application update #8
NCO038377
Person County
Page 6of16
Duke Energy cc: Tom Copolo, Shannon Langley, Bert Lea, Rob Miller, Jake Muessen, Heath Slade

Attachment 1
Proposed Retention Basin, FGD blowdown and
NPDES outfall 002 relocation locations
Mayo NPDES permit Application update
August 15, 2016
NCO038377

Approximate relocated
- sample point for
outfall 002
b� �8' � CSS Iti' PLi 1=3
Y^d'9
100. 4.

Attachment 2
Untreated Monofill leachate data
Mayo NPDES permit Application update
August 15, 2016
NCO03 83 77

TABLE 8
LEACHATE FIELD AND ANALYTICAL RESULTS
MAYO CCP LANDFILL PHASE 1 - PERMIT NO. 7305
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Sample Date: April 6, 2016 Laboratory Certificate Codes:
SynTerra Corporation Field #5591
Field Sampling performed by SynTerra Corporation Duke Energy Analytical Laboratory #248
Parameter
SWS ID
Units
Certificate Code
Sample Location
RDL
SWSL
7305 L-1
Field pH
320
SU
5,591
7.9
-
NE
Specific Conductance
323
umho/cm
5,591
305
-
NE
Temperature
325
°C
5,591
14
-
NE
Arsenic
14
µ9/L
248
14.7.
1
10
Barium
15
µ9/L
248
61
5
100
Boron
428
µg/L
248
1,270
50
NE
Cadmium
34
µg/L
248
< 1
1
1
Chloride
455
µg/l_
248
39,000
1,000
NE
Chromium
51
µg/L
248
26
5
10
Copper
54
µg/L
248
< 5
5
10
Fluoride
312
µg/L
248
180
100
2,000
Iron
340
µg/L
248
416
10
300
Lead
131
ltg/L
248
< 1
1
10
Manganese
3.42
lig/L
248
8
5
50
Mercury
132
µg/L
248
< 0.05
0.05
0.2
Nickel
152
µg/L
248
34
5
50
Nitrate (as Nitrogen)
303
ltg/L
248
630
23
10,000
Selenium
183
µg/L
248
1.7
1
10
Silver
184
µg/L
248
< 5
5
10
Sulfate
315
µg/L
248
130,000
2,000
250,000
Total Dissolved Solids
311
µg/L
248
330,000
25,000
NE
Zinc
213
ltg/L
248
204
5
10
Prepared by: BDW Checked by: TCP
Notes:
1. = - Concentrations are equal to or greater than the SWSL.
2. Bold concentrations are equal to or greater than the 15A NCAC 2B Standard (for pH bold indicates a measurement outside of the range).
3. Concentrations presented in micrograms per liter (jig/Q.
4. SWS ID is the Solid Waste Section Identification Number.
5. RDL is the laboratory reporting limit.
6. SWSL is the Solid Waste Section Limit. NCDEQ defines the SWSL as the lowest amount of analyte in a sample that can be quantitatively determined
with suitable precision and accuracy.
7. Grayed values indicate values that equal or are greater than the SWSL.
8. Qualifiers in non -italicized text are laboratory data qualifiers or "flags". "U" is used to identify results not detected at concentrations which equal the
laboratory's method detection limit (MDL). "J" is used to identify estimated concentrations which equal or are greater than the MDL but are less than
the laboratory's method reporting limit (MRL).
9. SU indicates Standard Units.
10. MA/cm indicates micromhos per centimeter.
11. NE indicates not established.
12. According to the Constituent Look -up webpage on the NCDEQ Division of Waste Management webpage, there is no SWSL for chloride associated
with CAS number 16887-08-6, which is the CAS reported by the laboratory for the analyses completed. Therefore, the SWSL listed is for the chloride
with CAS number SW301 as specified on the Constituent Look -up webpage.
13. Analytical results obtained from Electronic Data Deliverable (EDD) provided by Duke Energy on May 17, 2016.
P:\Duke Energy Progress. 1026\05.MAYO\17. 2016 Well Samping Monofill\APRIL 2016 SOLID WASTE PERMIT REPORT\Table 8 - Leachate Field and Analytical
Results.xlsx Page 1 of 1

Attachment 3
Clean Water Act Section 316(b) Alternate Schedule
Mayo NPDES permit Application update
August 15, 2016
NCO03 83 77

Alternate Schedule Request §316(b) of the Clean Water Act
Mayo Generation Station
Final regulations to establish requirements for cooling water intake structures at existing
facilities were published in the Federal Register on August 15, 2014 (i.e. regulations
implementing §316(b) of the Clean Water Act) with an effective date of October 14, 2014. Per
§125.91(a)(1)-(3) Applicability, the Mayo Generating Station (Mayo) is subject to the
requirements at § 125.94 through § 125.99 (316(b) requirements) based on the following:
— The facility is defined as an existing facility;
The facility has a point source discharge;
The facility uses a cooling water intake with a design intake flow (DIF) of greater than 2
million gallons (MGD) to withdraw water from waters of the U.S.; and
— Twenty-five percent or more of the water withdraws on an actual intake flow basis are
exclusively used for cooling purposes.
Per §125.98(b) Permitting requirements, 316(b) requirements are implemented through the
NPDES permit. For Mayo, the NPDES permit proceedings had begun prior to the effective date
of the rule. Therefore, 40 C.F.R §125.98(g) Ongoing permitting proceedings, applies, which
states:
"... whenever the Director has deterinined that the information already submitted by the
owner or operator of the facility is sufficient, the Director may proceed with a
determination of BTA standards for impingement mortality and entrainment without
requiring the owner or operator of the facility to submit the information required in 40
CFR 122.21(r).."
Mayo was not subject to the remanded 316(b) Phase II Rule because the station employs a
close -cycle recirculation cooling water system; therefore, no information related to 316(b) has
been previously submitted. As stated in the preamble to the rule, "In such circumstances where
permit proceedings have already begun prior to the effective date of the rule, these facilities will
still need to submit the appropriate permit application materials found at § 122.21(r) permit
applications during their next application." 1
Furthermore, the regulation states the owner of a facility whose current effective permit
expires after July 14, 2018, must submit the above information when applying for a subsequent
permit and the owner of a facility whose current effective permit expires on or before July 14,
2018 may request an alternate schedule for the submission of the above information. As allowed
under §125.95(a)(2), Duke Energy would like to request an alternate schedule for the submission
179 fed. Reg. 48358 (15 August 2014)

of the applicable 316(b) information for Mayo Generating Station. Per §122.21(r)(1)(ii), the
following information must be submitted for all existing facilities:
§122.21(r)(2) Source Water Physical Data
§122.21(r)(3) Cooling Water Intake Structure Data
§122.21(r)(4) Source Water Baseline Biological Characterization Data
§122.21(r)(5) Cooling Water System Data
§ 122.21(r)(6) Chosen Method(s) of Compliance with Impingement Mortality Standard
§ 122.21(r)(7) Entrainment Performance Studies
§122.21(r)(8) Operational Status
The actual intake flow (AIF), as well as the design intake flow (DIF), for Mayo is less than 125
million gallons per day (MGD); therefore, the additional information requirements under
§ 122.21(r)(1)(ii)(B) Existing facilities greater than 125 MGD AIF are not applicable to Mayo.
Duke Energy is not planning on collecting any new biological data on the source water or
conducting irnpingement or entrainment studies at the cooling water intake structure and has not
been requested to do so by North Carolina Department of Environmental Quality (NCDEQ).
Existing biological data will be used to complete §122.21(r)(2) Source Water Physical Data and
§122.21(r)(4) Source Water Baseline Biological Characterization Data. Furthermore, with the
station utilizing mechanical draft cooling towers and withdrawing make-up cooling water from
an impoundment created for the purpose of serving as part of the cooling water system, Duke
intends to demonstrate the existing technologies at Mayo meet the best technology available
(BTA) standard for both impingement and entrainment mortality.

Attachment 4
Future condition Flow diagram
Mayo NPDES permit Application update
August 15, 2016
NCO038377

Mayo Steam Station
August 2016NPDES
Planned Water Schematic Flow Diagram Post ash basin usage'
permit application update
,
FIGURE 1
Gypsum & Limestone Pile
Runoff
15
Coal Pile Runoff.
Holding Basin
Potable Water from City
Potable & Sanitary 4
Sewage Treatment
of Roxboro
Systems
S
Monofill leachate
Misc. Low Volume
Secondary Containment
17
7
T
for Anhydrous Ammonia
I
Tanks
Oily Waste Treatment
Crutchfield Branch
Note. Leachate directed
to ash basin prior to
t
Iretention
Water Storage
Ion Exchange
Condensate Storage
completion of lined
basin
AOW's and dam drainage
=6
Storm Water
Raw Water Treatment
5
1
Outfall 002
3
1
Mayo Reservoir
Intake Structure
Fire Protection
Water Redirects Sump
Retention Basin
10 1110
Outfall 002
Outfall 001
/-
Evaporation
12
2
26
Cooling Towers
18
�Tl
Misc. Equipment Heat
14
Exchangers
9
Condensers
Boiler & Turbine
Industrial Stormwater
13 Alternate
16
Note 1: Monofill leachate will be redirected to outfall 002 upon receipt of NPDES permit renewal

I Storm Water I
I Groundwater I
Potential Dust
Suooression Irriaation
Mayo Steam Station
Water Schematic Flow Diagram
FIGURE 2
I Storm Water I
Groundwater F P Outfall 004
Potential Dust
Future condition upon
completion oflined
retention basin and
relocation of outfall 002
sampling point. Until that
time flows are directed
towards Mayo reservoir
Outfall 005
I Storm Water I
Switchyard Runoff to Outfalls 006a, b, c, d, and
006a 110 e
Potential Cooling Tower
Drift
NPDES Permit application
update August 2016 ,
Future condition upon
completion oflined
retention basin and
relocation of outfall 002
sampling point. Until that
time flows are directed
Outfall 002 I- -1 Mayo Reservoir