NC0000396_Supplemental Information_20171207

DUKE
Garry A. Whisnant
ENERGY®
Plant General Manager
PROGUSS
Asheville Steam ElectncPlant
Certified Mail. 7016 2140 0001 0231 0671
Duke Energy Progress
ASVL PLT / 200 CP&L Dr
Arden, NC 28704
File- 12520A
o 828-687-5201
f 828-687.5204
December 7, 2017
garry whisnant@ duke -energy com
Mr Jeff Poupart
NCDENR, Division of Water Resources
1617 Mail Service Center
Raleigh, NC 27699-1617
RECEIVE®I®ENROWR
DEC 112017
Subject- Duke Energy Progress, Inc
deter Resources
Asheville Steam Electric Generating Plant
Permitting Section
Supplemental to NPDES Permit Renewal Application
NPDES Permit No NC0000396
Buncombe County
Dear Mr Poupart:
Duke Energy Progress, LLC (Duke) is submitting supplemental information in support of the Asheville
Steam Electric Plant's NPDES permit renewal application This submittal is in addition to the previous
renewal application and permit modification requests submitted Please see Table 1 for submittal history.
Duke is requesting that the information provided in all of these submissions be included during the permit
renewal process
Information is provided for a modified process flow path to Outfall 001, removal of the 1982 ash basin,
and options for closure of the 1964 ash basin. Revised site and flow diagrams are attached
We appreciate your attention to these requests and look forward to finalizing the NPDES permit for the
Asheville Steam in the near future Should you have any quesfmons regarding this letter or require
additional information, please contact Ms Tina Woodward at [phone] or at
Tina.Woodward@Duke-Energy com
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 then a are significant penalties for submitting false information, including the possibility of
fines and imprisonment for knowing violations
Sincerely,
4A-rA 11Z4
Garry Whmsnant
Plant Manager
Asheville Steam Plant

Duke Energy Progress, Inc
Asheville Steam Electric Generating Plant
Supplemental to NPDES Pernmt Renewal Application
NPDES Permit No NC0000396
Buncombe County
Table 1 - NPDES Permit No. NC000396 Submittal History
Date
Title/Activity
06/11/2010
Submitted to DEQ Permit Renewal Application
09/29/2010
Sent requested 2007-2008 Environmental Monitoring Report for Lake Julian
to DEQ.
05/13/2011
Received DEQ approval to relocate outfall 001
11/01/2011
Administrative update to permit application six (6) chemical additions
10/11/2012
Administrative update to permit application one (1) chemical addition
07/30/2014
Submitted to DEQ update to renewal application
02/04/2015
Submitted to DEQ Chemical characterization of water for dewater of the ash
basins
07/22/2015
Submitted to DEQ notice of pending wastewater treatment facility - Wetlands
Demolition
02/01/2016
Submitted to DEQ notice of pending wastewater treatment facility - Removal
of Duck Pond and Installation of Filters
09/28/2016
DEQ Effluent Channel Visit
12/01/2016
Submitted to DEQ Supplemental to Permit Renewal Application
Enclosures -
Supplemental Information Package
Attachment A — 1982 Ash Basin Dam Breach Letter
Attachment B — NPDES Outfalls
Attachment C — Process Flow Diagrams
Attachment D — Flow, Sources of Pollution, and Treatment Technologies
cc: Sergei Chernikov
Complex NPDES Permit Supervisor
1617 Mail Service Center
Raleigh, NC 27699-1617
Landon Davidson
Asheville Regional Office Supervisor
2090 U.S Highway 70
Swannanoa, NC 28778

Duke Energy Progress, LLC.
Asheville Steam Electric Plant
NPDES Permit # NC0000396
Supplemental Information Package
Introduction and Background
Duke Energy Progress, LLC.
Asheville Steam Electric Plant
NPDES PERMIT # NC0000396
Supplemental Information Package
Duke Energy Progress, LLC. (Duke) is submitting this additional supplemental information in support of the
pending NPDES permit renewal for the Asheville Steam Electric Plant (Plant) This submittal is intended to
provide alternatives for closure of the 1964 ash basin that will be necessary to comply the Federal Coal
Combustion Residual (CCR) rule, the North Carolina Coal Ash Management Act of 2014, HB 630 of 2016
and the Senate Bill 716: Mountain Energy Act of 2015.
Supplemental information is also provided for the following:
1. Removal of the former 1982 ash basin as a wastewater treatment structure.
2. A modified process flow path to Outfall 001.
3. Clarification to the Steam Electric Effluent Limitation Guidelines
4. A discussion on the dewatering of the 1964 basin.
In total, there will remain two final outfalls to waters of the State: Outfalls 001 and 002. The process flows
to Outfall 001 have changed and these changes have been documented with the Division of Water
Resources, NPDES regulatory permitting agency as described below. There are no changes to Outfall
002; therefore, that outfall is not discussed in this supplemental information packet. (See attachment B
entitled NPDES Outfalls)
Revised site and flow diagrams are included in Attachment C
Removal of the former 1982 Ash Basin from the NPDES Program
The 1982 Ash Basin was constructed in 1982 with the establishment of a dam (BUNCO -089) in the valley
adjacent to the 1964 Ash Basin. The 1982 Ash Basin reached capacity in 2007, and an ash excavation
plan was developed to increase ash storage capacity. The excavated ash was transported to the Asheville
Regional Airport (Airport) for the airport's taxiway infrastructure. The 1982 Ash Basin has been dewatered,
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Duke Energy Progress, LLC
Asheville Steam Electric Plant
NPDES PERMIT p NC0000396
Supplemental Information Package
and approximately 4.1 million tons of ash have been excavated and transported to the Airport for a
structural fill project in accordance with the Asheville Plant's ash reuse permit (Distribution of Residual
Solids (503 Exempt) Permit Number WQ0000020).
Ash placement at the last structural fill project (Airport Area III) was completed on July 17, 2015. Loading
and transportation of ash from the 1982 Ash Basin to the R&B Landfill in Homer, GA began on October 15,
2015 and to the onsite landfill at the Rogers Energy Complex (Cliffside) on February 29, 2016.
Excavation of the 1982 Ash Basin was completed on September 30, 2016, and the Basin was turned over
for dam decommissioning and the construction of a natural gas combined cycle plant after an independent
qualified professional engineer concluded that primary source ash had been removed from the basin as
verified by visual observation methods in accordance with Duke Energy's Coal Combustion Residual (CCR)
Removal Verification Procedure.
All former water inflows into the 1982 Ash Basin were re-routed to the open water area in the 1964 Basin.
Stormwater that collected naturally on the 1982 basin or water from a Department of Transportation (DOT)
culvert has been rerouted via underdrains to facilitate the construction of the combined cycle plant On
August 23, 2017, the engineer of record determined the basin had been filled to the prescribed level and
the embankment lowered in general accordance with the approved plans. The 1982 Ash Basin Dam
Breach Letter is included as attachment A.
For these reasons, Duke is requesting the removal of the 1982 ash basin from the permit.
Outfa11001 Current Condition
The 1964 Ash Basin Dam (BUNCO -097) was constructed in 1964 to serve as a wastewater treatment
facility for the treatment of ash sluice water. The surface area of the basin is approximately 45 acres. The
basin does not retain a permanent pool with the exception of a three -acre unlined retention pond known as
the open water area.
All ash wastes are expected to be removed completely from the 1964 ash basin by applicable regulatory
deadlines. The Plant's remaining ash basin (hereinafter referred to as the 1964 ash basin), is located east
of the French Broad River, south of the plant and discharges into the French Broad River. With the
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Duke Energy Progress, LLC
Asheville Steam Electric Plant
NPDES PERMIT # NC0000396
Supplemental Information Package
approval of the North Carolina Department of Environmental Quality (NC DEQ), Duke relocated treated
waters from the former 1982 ash basin and lined rim ditch to a downstream outfall location (Outfall 001) on
the French Broad River. The relocation of Outfall 001 was necessary to allow for enhancement to the dam
of the 1964 ash basin to meet current engineering standards.
Production ash is sluiced to a concrete rim ditch system that is located within the footprint of the 1964 Ash
Basin The rim ditch system also receives plant stormwater drainage and low volume wastewater. CCR
are dredged from the rim ditch, dewatered, and transported off-site.
Historically, the wastewater from the rim ditch process was treated in the lined rim ditch system, then
routed to the open water area, and decanted to a settling pond outside of the 1964 Ash Basin. The settling
pond serves as the monitoring point for Outfall 001 of the Plant's NPDES permit. Water discharge from this
settling pond is routed directly to the French Broad River through a permitted outfall.
During 2016, wastewater flows and treatment were adjusted to facilitate the excavation of the 1982 Ash
Basin. The center pond filters were constructed at the end of the rim ditch and commissioned to replace
the treatment provided by the open water area. Infrastructure was developed to dewater the open water
area to the head of the rim ditch, and subsequently, the low volume waste and stormwater that flowed into
the 1982 Ash Basin and pumped to the rim ditch was re-routed to the open water area.
The ash basin and/or rim ditch provides treatment by sedimentation and neutralization to the plant's waste
streams. Water leaves the rim ditch via weirs and curtains to the lined center pond where a skimmer pulls
water into 1 of 4 filter trains and flows via either the 1964 ash pond or direct discharge to a lined stilling
pond, where the discharge Is treated by an automated pH system, where it is then discharged by overflow
to a pipe that coveys it to the French Broad River. Toe drains from the 1964 basin are currently collected
and pumped to the rim ditch and flow through the treatment system to outfall 001 and the French Broad
River. Duke Energy has requested that the toe drains be Included In the reissued permit as separate
outfalls. If they are Included as such In the new permit, upon permit Issuance, toe drain flows may be
released to the French Broad River.
Flue Gas Desulfurization Blowdown (Low Volume Waste)
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November 2017

Duke Energy Progress, I.I.C.
Asheville Steam Electric Plant
NPDES PERMIT # N00000396
Supplemental Information Package
This system is currently discharging to the Metropolitan Sewerage District (MSD) from the waste water
treatment building. The Flue Gas Desulfurization (FGD) system directs flue gas into an absorber where a
limestone (calcium carbonate) slurry is sprayed. Sulfur dioxide in the flue gas reacts with the limestone to
produce calcium sulfate (gypsum). This system reclaims any unreacted limestone slurry to be reused in
the absorber. A small blowdown stream is used to maintain the chloride concentration in the reaction tank.
The blowdown stream is passed through a clarifier to remove solids and reduce the chloride concentration
in the waste stream Chemicals are used to adjust pH and to aid solids removal in the clarifier. The waste
stream enters a weir box and is discharged into a connection to MSD.
1964 Ash Basin Pre -closure Wastewater
Duke Energy is in the process of excavating ash from the 1964 ash basin which will continue through plant
retirement no later than January 31, 2020 and subsequent closure. It is anticipated that interstitial water will
be encountered early in the process as portions of the 1964 ash basin are being excavated. Duke Energy
plans to place the interstitial water discovered within the 1964 basin into the Rim Ditch and treat as
necessary to ensure compliance with permit limits prior to discharging through Outfall 001. It is Duke
Energy's understanding that this activity is permitted under North Carolina's NPDES wastewater permit
program, because the contents of this basin is regulated as a wastewater until leaving the treatment basin
for disposal or beneficial use. Prior to moving the wastewater into the rim ditch, Duke will assure that (i) all
NPDES permit terms and conditions are being met; and (ii) any necessary dam safety approvals are
secured and that the work is being done in accordance with applicable dam safety guidelines and
requirements
For these reasons, Duke is requesting that the proposed intra basin wastewater handling be
permitted under North Carolina's NPDES wastewater permit program.
Steam Electric Effluent Limitation Guidelines Clarification
On December 1, 2016, Duke Energy submitted a justification for the appropriate applicability dates for
compliance with the 2015 revisions to the Steam Electric Effluent Limitation Guidelines (2015 ELG Rule) for
the Plant. The justification demonstrated that the appropriate applicability date to comply with the more
stringent best available technology (BAT) limits for flue gas desulfurization (FGD) wastewater and bottom
ash transport water (BATW) was January 31, 2020. However, on September 18, 2017, U.S. EPA issued a
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Duke Energy Progress, I.I.C.
Asheville Steam Electric Plant
NPDES PERMIT # NC0000396
Supplemental Information Package
final rule postponing the earliest compliance date for the more stringent BAT limits for BATW and FGD
wastewater until November 1, 2020 (82 Fed. Reg. 43,494 (Sept. 18, 2017)).
As a result of this final rule, Duke request an applicability date of November 1, 2020 for the no
discharge limit of bottom ash transport water and the limits for arsenic, mercury, nitrate/nitrite and
selenium for FGD wastewater.
1964 Water Treatment Options - Post Asheville Coal Fired Plant Closure
The 1964 Ash Basin is currently void of free-standing water, except for the small open water area
(described above). Stormwater and wastewater flows into the open water area are captured and pumped
to the head of the rim ditch wastewater treatment system within the footprint of the 1964 Ash Basin.
As noted above, the settling treatment provided by the open water area was replaced by a filtration
system. The filtration system meets existing permit requirements as it relates to the treatment previously
provided by the open water area. The treated wastewater continues to flow to the permitted NPDES Outfall
001. The open water area is used for retention of the 1964 Basin and the low volume stormwater and
wastewater flows.
Contact and interstitial water from the 1964 Ash Basin excavation will also be pumped to the rim ditch
wastewater treatment system, including filtration until station retirement and demolition of the rim ditch.
In order to facilitate compliance with the NPDES permit, Duke Energy has developed two options to
accomplish dewatering and ultimately closure of the 1964 ash basin. Flow diagrams and Form 2C tables for
the preferred options are included in Attachments C and D, respectively.
Option A - Onsite Treatment Only
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Duke Energy Progress, LLC.
Asheville Steam Electric Plant
NPDES PERMIT # NC0000396
Supplemental Information Package
Option A involves the installation of two fully redundant treatment trains. Each treatment train would treat
400 to 500 gpm flows, removing suspended solids and associated metals. One treatment train could be
eliminated in the future once LVWS is eliminated by demolition, which is tentatively scheduled for August
2021. This option will also include a lined settling basin (side hill basin) to segregate the LVWS that is a
non -CCR waste stream from the 1964 basin. This option may also require a tank by the treatment plant to
equalize interstitial water and 1964 basin stormwater flows as described in Option B.
Option B - Hybrid Option that includes onsite treatment as well as Low Volume Wastes and incidental
stormwater disposal to the MSD
Option B includes development of a single 400 to 500 gpm mobile treatment system for placement inside or
outside the basin. This system would remove suspended solids and associated metals from post
operational flows and dewatering flows from the contractor's water management sumps. A tank, of
approximately 200,000 -gallon capacity may be needed to equalize flows to the treatment system. A
dedicated lined equalization basin within the 1964 Basin (side hill basin) would be used to settle out
suspended solids and to equalize flow for direct discharge to the MSD, should a modified SIU permit be
acceptable to MSD.
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Duke Energy Progress, LLC
Asheville Steam Electric Plant
NPDES PERMIT # NC0000396
Supplemental Information Package
List of Attachments:
Attachment A -1982 Ash Basin Dam Breach Letter
Attachment B — NPDES Outfalls
Attachment C — Process Flow Diagrams -
— Current State
— Option A
— Option B
Attachment D — Form 2C - Item II - A Flow, Sources of Pollution, and Treatment Technologies
— Current State
— Option A
— Option B
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Attachment A - 1982 Ash Basin Dam Breach Letter

September 7, 2017 amec
foster`�"y
Mr. Michael G Clough, REwheelerLead Engineer
Duke Energy
400 South Tryon Street
Charlotte, North Carolina 28202
Subject.- 1982 Ash Basin Dam Breach Letter
Asheville Steam Electric Generating Plant
Amec Foster Wheeler Project No • 7810160620
Dear Mr. Clough:
Duke Energy Progress is in the process of breaching the Asheville Steam Electric Generating
Plant -1982 Basin Dam (BUNCO -089) according to the plans approved in February 2016 by
North Carolina Department of Environmental Quality — Dam Safety Division. On August 23,
2017, Amec Foster Wheeler representative (Luke Williams, engineer of record) visited the site
and observed that the basin had been filled to the prescribed level and the embankment lowered
in general accordance with these approved plans As such the structure will not impound water
of sufficient volume to be subject to the Emergency Action Plan requirements
Additional work to fulfill the remaining requirements of the approved breach plans are still
ongoing (ditches, final grading, topsolling, etc ). Once this work is completed, as -constructed
plans will be submitted for fulfillment of decommissioning the dam
If you have any questions regarding this submittal do not hesitate to contact us.
Sincerely,
Amec Foster Wheeler Environment & Infrastructure, Inc.
Luke C. Williams P.E.
Senior Consultant
Jill Heimburg, PE
Senior Engineer 2/ Project Manager
Amec Foster Wheeler Environment & Infrastructure Inc
2801 Yorkmont Road, Suite 100 Registered in North Carolina
Charlotte, North Carolina 28208 Engineering and Land Surveying License No F-1253
704-357-8600 Geology License No C-247
amecfw com

Attachment B - WPDES Outfalls