NC0024406_1_FINAL_CSA Supplement 2 Report_20160811

Comprehensive Site Assessment
Supplement 2
Belews Creek Steam Station Ash Basin
Site Name and Location
Groundwater Incident No.
NPDES Permit No.
Date of Report
Permittee and Current Property Owner
Consultant Information
Latitude and Longitude of Facility
Belews Creek Steam Station
3195 Pine Hall Road
Belews Creek, NC 27009
Not Assigned
NC0024406
August 11, 2016
Duke Energy Carolinas, LLC
526 South Church St.
Charlotte, NC 28202-1803
704.382.3853
HDR Engineering, Inc. of the Carolinas
440 South Church St, Suite 900
Charlotte, NC 28202
704.338.6700
36016' 55"N, 80°03' 35 "W
This document has been reviewed for accuracy and quality
commensurate with the intended application.
Al
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'''••.,;RAMC �S S..•••
Malcolm F. Schaeffer, L.G.
Senior Geologist

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
TABLE OF CONTENTS
Table of Contents
Page
ExecutiveSummary ................................................................................................................... 1
Section1 — Background............................................................................................................. 3
1.1 Purpose of CSA Supplement.......................................................................................
3
1.2 Site Description............................................................................................................
4
1.3 History of Site Groundwater Monitoring........................................................................
6
1.3.1 NPDES Sampling.................................................................................................
7
1.3.2 Solid Waste Landfill Monitoring.............................................................................
7
1.3.3 CSA Sampling......................................................................................................
8
1.3.4 Post-CSA Sampling..............................................................................................
9
1.3.5 NCDEQ Sampling.................................................................................................
9
Section 2 — CSA Review Comments.........................................................................................12
2.1 NCDEQ General Comments and Responses..............................................................12
2.2 NCDEQ Site -Specific Comments and Responses......................................................12
2.2.1 Bedrock Lithology at Background Well Locations.................................................12
2.2.2 Assessment of Area of Wetness Location S-9.....................................................14
2.2.3 Middleton Loop Road Cross-Section....................................................................16
2.3 Errata..........................................................................................................................16
Section 3 — Additional Assessment...........................................................................................17
3.1 Additional Assessment Activities................................................................................17
3.1.1 Well Installation....................................................................................................17
3.1.2 Well Gauging and Sampling.................................................................................20
3.2 Additional Assessment Results...................................................................................20
3.2.1 Groundwater Flow Direction.................................................................................21
3.2.2 Sampling Results.................................................................................................21
Section 4 — Background Concentrations...................................................................................27
4.1 Methodology...............................................................................................................27
4.2 Observation for Background Wells..............................................................................29
Section 5 — Anticipated Additional Assessment Activities..........................................................30
5.1 Proposed Additional Assessment Monitoring Wells.....................................................30
5.2 Implementation of the Effectiveness Monitoring Plan..................................................31
Section 6 — Recommendations and Conclusions......................................................................32

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
TABLE OF CONTENTS
FIGURES
1-1 Site Location Map
1-2 Sample Location Map
1-3 NCDEQ Water Supply Well Sampling
2-1 Background Well Location Map
3-1 Potentiometric Surface - Shallow Flow Layer
3-2 Potentiometric Surface - Deep Flow Layer
3-3 Potentiometric Surface - Bedrock Flow Layer
3-4.1 Antimony Isoconcentration Contour Map - Shallow Wells (S)
3-4.2 Antimony Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.3 Antimony Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.4 Arsenic Isoconcentration Contour Map - Shallow Wells (S)
3-4.5 Arsenic Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.6 Arsenic Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.7 Beryllium Isoconcentration Contour Map - Shallow Wells (S)
3-4.8 Beryllium Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.9 Beryllium Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.10 Boron Isoconcentration Contour Map - Shallow Wells (S)
3-4.11 Boron Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.12 Boron Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.13 Chloride Isoconcentration Contour Map - Shallow Wells (S)
3-4.14 Chloride Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.15 Chloride Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.16 Hexavalent Chromium Isoconcentration Contour Map - Shallow Wells (S)
3-4.17 Hexavalent Chromium Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.18 Hexavalent Chromium Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.19 Chromium (Total) Isoconcentration Contour Map - Shallow Wells (S)
3-4.20 Chromium (Total) Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.21 Chromium (Total) Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.22 Cobalt Isoconcentration Contour Map - Shallow Wells (S)
3-4.23 Cobalt Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.24 Cobalt Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.25 Iron Isoconcentration Contour Map - Shallow Wells (S)
3-4.26 Iron Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.27 Iron Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.28 Manganese Isoconcentration Contour Map - Shallow Wells (S)
3-4.29 Manganese Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.30 Manganese Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.31 Selenium Isoconcentration Contour Map - Shallow Wells (S)
3-4.32 Selenium Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.33 Selenium Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.34 Sulfate Isoconcentration Contour Map - Shallow Wells (S)
3-4.35 Sulfate Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.36 Sulfate Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.37 Total Dissolved Solids Isoconcentration Contour Map - Shallow Wells (S)
3-4.38 Total Dissolved Solids Isoconcentration Contour Map - Deep Wells (D and BRU)
3-4.39 Total Dissolved Solids Isoconcentration Contour Map - Bedrock Wells (BR)
3-4.40 Thallium Isoconcentration Contour Map - Shallow Wells (S)
3-4.41 Thallium Isoconcentration Contour Map - Deep Wells (D and BRU)

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
TABLE OF CONTENTS
3-4.42 Thallium Isoconcentration Contour Map — Bedrock Wells (BR)
3-4.43 Vanadium Isoconcentration Contour Map — Shallow Wells (S)
3-4.44 Vanadium Isoconcentration Contour Map — Deep Wells (D and BRU)
3-4.45 Vanadium Isoconcentration Contour Map — Bedrock Wells (BR)
3-5.1 Site Cross Section Locations
3-5.2 Cross Section A -A' (1 of 4)
3-5.3 Cross Section A -A' (2 of 4)
3-5.4 Cross Section A -A' (3 of 4)
3-5.5 Cross Section A -A' (4 of 4)
3-5.6 Cross Section B-B' (1 of 4)
3-5.7 Cross Section B-B' (2 of 4)
3-5.8 Cross Section B-B' (3 of 4)
3-5.9 Cross Section B-B' (4 of 4)
3-5.10 Cross Section C-C' (1 of 4)
3-5.11 Cross Section C-C' (2 of 4)
3-5.12 Cross Section C-C' (3 of 4)
3-5.13 Cross Section C-C' (4 of 4)
3-6.1 Piper Diagram — Background Groundwater, Porewater, Areas of Wetness, Ash Basin
Water, and Surface Water
3-6.2 Piper Diagram — Shallow Groundwater, Porewater, Areas of Wetness, Ash Basin
Water, and Surface Water
3-6.3 Piper Diagram — Deep Groundwater, Porewater, Areas of Wetness, Ash Basin Water,
and Surface Water
3-6.4 Piper Diagram — Bedrock Groundwater, Porewater, Areas of Wetness, Ash Basin
Water, and Surface Water
TABLES
1-1 Well Construction Information
1-2 NPDES Historical Data
1-3 Range of 2L Groundwater Standard Exceedances from NPDES Sampling
2-1 Responses to General NCDEQ Comments
2-2 Total and Effective Porosity and Specific Storage by Flow Layer
3-1 Round 5 Analytical Results of Groundwater Monitoring
3-2 Round 5 Analytical Results of Porewater Monitoring
3-3 Round 5 Analytical Results of Ash Basin Surface Water Locations
3-4 Round 5 Analytical Results of Surface Water Locations
3-5 Round 5 Analytical Results of Areas of Wetness
3-6 Summary of Groundwater Elevations
3-7 Summary of Cation -Anion Balance Differences
APPENDICES
A Background Monitoring Well Boring Logs
B Monitoring Well Boring Logs and Core Photos
C Field Sampling Forms and Slug Test Report
D Laboratory Report, Chain -of -Custody Forms, and Validation Report

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
EXECUTIVE SUMMARY
Executive Summary
Duke Energy Carolinas, LLC (Duke Energy) owns and operates the Belews Creek Steam
Station (BCSS), located on Belews Lake in Stokes County, North Carolina (Figure 1-1). BCSS
began operation in 1974 and operates two coal-fired units. Coal combustion residuals (CCR)
and other liquid discharges from BCSS's coal combustion process have been disposed in the
ash basin since its construction. In 1983, BCSS converted to dry handling of fly ash with
disposal in on -site landfills; bottom ash is sluiced to the ash basin and fly ash is sluiced to the
ash basin on start-up and in emergency situations. Discharge from the ash basin is permitted by
the North Carolina Department of Environmental Quality (NCDEQ)' Division of Water
Resources (DWR) under the National Pollutant Discharge Elimination System (NPDES) Permit
NC0024406.
This Comprehensive Site Assessment (CSA) Supplement 2 report addresses the following:
• Summary of groundwater, porewater, ash basin surface water, surface water, and area
of wetness (AOW) monitoring data through May 2016;
• Responses to NCDEQ review comments pertaining to the CSA;
• Findings from assessment activities conducted since submittal of the CSA report,
including additional assessment previously proposed in the CSA;
• Update on the development of provisional background groundwater concentrations; and
• Description of planned additional source area assessment activities.
Boron, the primary site -derived constituent in groundwater, was detected at concentrations
greater than the 15A NCAC (North Carolina Administrative Code) 02L.0202 Groundwater
Quality Standards (2L Standards or 2L) beneath and downgradient (south-southeast) of the ash
basin, ash basin dike, west of the ash basin, and south of the ash basin in the vicinity of the
Pine Hall Road Landfill. Boron has been detected in groundwater beyond the compliance
boundary downgradient of the ash basin dam as well as adjacent to the structural fill.
Groundwater monitoring results from Round 5 of CSA well sampling and NPDES groundwater
monitoring data are presented herein. Updated summary tables, isoconcentration maps, cross
sections, and graphical representations of the data are included.
Presentation of site -specific proposed provisional background concentrations (PPBCs) was
included in the Corrective Action Plan (CAP) Part 1 report and should be refined as more data
becomes available and pending input from NCDEQ. With refinement of the PPBCs, the
evaluation of whether the presence of constituents of interest (COls) downgradient of the source
areas is naturally occurring or potentially attributed to the source areas can be advanced in
more detail.
The following conclusions and recommendations are offered:
' Prior to September 18, 2015, the NCDEQ was referred to as the North Carolina Department of Environment and
Natural Resources (NCDENR). Both naming conventions are used in this report, as appropriate.

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
EXECUTIVE SUMMARY
• The conclusion from the groundwater chemical signature evaluation is that water supply
wells in the vicinity of the BCSS facility are not impacted by CCR releases from the ash
basin.
• Groundwater monitoring results from Round 5 of sampling, including data from additional
assessment groundwater monitoring wells, indicate consistency with previous sampling
results, specifically the extent of impact to groundwater from ash basin -related
constituents (e.g., boron).
• Groundwater exceedances of the 2L Standard for boron, sulfate, and total dissolved
solids (TDS) were observed in wells GWA-23S/D and exceedances for boron in AOW S-
9, indicating ash -related impacts from the structural fill prior to capping in 2012.
• Groundwater exceedances of the 2L Standard, Interim Maximum Allowable
Concentration (IMAC) established by NCDEQ pursuant to 15A NCAC 2L.0202(c), and/or
North Carolina Department of Health and Human Services (DHHS) Health Screening
Level (HSL) (hexavalent chromium only) for antimony, arsenic, boron, chloride, cobalt,
chromium, hexavalent chromium, iron, manganese, selenium, thallium, TDS, and
vanadium were observed in GWA-20S/D/BR and GWA-27S/D/BR and are being
evaluated as part of ongoing field investigations.
• Refinement of PPBCs should be conducted once the minimum number (e.g., eight) of
viable observations per background well are available.
• Groundwater exceedances of the 2L Standard, IMAC, and/or NCDHHS HSL for
antimony, chromium, cobalt, hexavalent chromium, iron, manganese, and vanadium
were observed in monitoring wells between the ash basin and Middleton Loop Road and
west of Middleton Loop Road. The observed concentrations of these constituents in
some wells were higher than in wells in downgradient or background locations; however,
further evaluation is necessary to assess their presence as potentially source -related or
naturally occurring once additional data is available.
• Additional monitoring wells should be installed to refine the vertical and horizontal
delineation of groundwater exceedances near the chemical pond, west of the area
downgradient of the accelerated remediation "area of interest," or AOI, northwest of the
ash basin and dike, northwest and downgradient of GWA-19S/D, north and northeast of
the abandoned voluntary well MW-103S/D, and southeast of the ash basin.
• Additional evaluation of groundwater results from GWA-22D will be considered with MW-
201 BR results upon review of Round 6 sampling data.
• Additional assessment activities in the Structural Fill area are recommended to identify
the source of exceedances indicated in GWA-23S/D.
• Duke Energy will implement the effectiveness monitoring plan in accordance with
recommendations provided in the CAP Part 2 report as well as subsequent discussions
with NCDEQ.

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 1 — BACKGROUND
Section 1 — Background
Duke Energy Carolinas, LLC (Duke Energy) owns and operates the Belews Creek Steam
Station (BCSS), located on Belews Lake in Stokes County, North Carolina (Figure 1-1). BCSS
began operation in 1974 and operates two coal-fired units. Coal combustion residuals (CCR)
and other liquid discharges from BCSS's coal combustion process have been disposed in the
ash basin since its construction. In 1983, BCSS converted to dry handling of fly ash with
disposal in on -site landfills; bottom ash is sluiced to the ash basin and fly ash is sluiced to the
ash basin on start-up and in emergency situations. Discharge from the ash basin is permitted by
the North Carolina Department of Environmental Quality (NCDEQ )2 Division of Water
Resources (DWR) under the National Pollutant Discharge Elimination System (NPDES) Permit
NCO024406.
The Comprehensive Site Assessment (CSA) report for BCSS was submitted to NCDEQ on
September 9, 2015. Given the compressed timeframe for submittal, certain information was not
included in the CSA report because the data was not yet available. Thus, Duke Energy
committed to providing this information after submittal of the CSA report. In addition, NCDEQ's
review of the CSA report led to requests for additional information. As such, CSA Supplement 1,
submitted to NCDEQ on February 18, 2016 as an appendix to the Corrective Action Plan (CAP)
Part 2, provided information to address the temporal constraints, information requested by
NCDEQ subsequent to submittal of the CSA report, additional data validation reporting, and a
response to site -specific NCDEQ comments obtained during in -person meetings.
1.1 Purpose of CSA Supplement
The purpose of this CSA Supplement 2 is to provide data obtained during additional well
installation and sampling conducted between March and May 2016. These activities were
conducted to refine the understanding of subsurface geologic/hydrogeologic conditions and the
extent of impacts from historical production and storage of coal ash. This CSA Supplement 2
was prepared in coordination with Duke Energy and NCDEQ as a result of requests for
additional information and areas identified additional assessment. It includes the following
information:
• A brief summary and update of groundwater sampling data from the NPDES, CSA, and
post-CSA monitoring well sampling events;
• A brief summary of results of NCDEQ water supply well sampling activities;
• A summary of NCDEQ comments on the CSA report and responses to those comments;
• A description of additional assessment activities conducted since submittal of the CSA
report and the findings of those assessment activities;
• An updated approach for the refinement of proposed provisional background
concentrations (PPBCs) for groundwater at the BCSS site; and
• A description of additional planned assessment activities.
2 Prior to September 18, 2015, the NCDEQ was referred to as the North Carolina Department of Environment and
Natural Resources (NCDENR). Both naming conventions are used in this report, as appropriate.

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 1 — BACKGROUND
As a complement to the CSA report and the CSA Supplement 1, this CSA Supplement 2
provides an updated evaluation of the extent of impacts from the ash basin and related ash
storage facilities based on existing CSA groundwater monitoring wells, monitoring wells installed
subsequent to submittal of the CSA report (herein referred to as additional assessment wells),
and some voluntary, compliance, and Pine Hall Road Landfill monitoring wells. Additional
assessment groundwater monitoring wells are shown on Figure 1-2 with green text labels.
Site Description
The BCSS site is located on the north side of Belews Lake on Pine Hall Road in Belews Creek,
Stokes County, North Carolina. The BCSS site occupies approximately 700 acres and is owned
by Duke Energy. BCSS, one of Duke Energy's largest coal -burning power plants in the
Carolinas, is a two -unit coal-fired electricity generating plant with a current net capacity of 2,240
megawatts (MW). The station began commercial operations in 1974 with Unit 1 (1,120 MW)
followed by Unit 2 (1,120 MW) in 1975. Cooling water for BCSS is provided by Belews Lake, a
man-made lake formed by Duke Energy.
The BCSS ash basin is located across Pine Hall Road, northwest of the station, and consists of
a single cell impounded by an earthen dam located on the north end of the ash basin. The ash
basin was constructed from 1970 to 1972 and has a surface area of approximately 283 acres.
The full pond elevation of the BCSS ash basin is approximately 750 feet. Coal ash residue from
the coal combustion process was disposed in the ash basin prior to 1983. In 1983, BCSS
converted to dry handling of fly ash with disposal of fly ash in Pine Hall Road Landfill. Bottom
ash has continued to be sluiced to the ash basin, and fly ash is sluiced to the ash basin during
startup or maintenance activities.
The Pine Hall Road Landfill was permitted in 1983 under NCDEQ Solid Waste Permit No. 8503
to accept only fly ash from BCSS operations. The original landfill was unlined and was permitted
with a soil cap 1-foot thick on the side slopes and 2-feet thick on flatter areas. The Phase 1
Expansion, permitted in 2003, was also unlined but with a synthetic cap system to be applied at
closure. Ash disposal was halted after exceedances of 2L Standards were observed in
groundwater monitoring wells near the landfill. Duke Energy installed an engineered cap as a
corrective action measure, following NCDEQ approval of the closure plan in December 2007.
The engineered cap consists of a 40-mil low -density polyethylene geomembrane, a geonet
composite, 18 inches of compacted soil, and 6 inches of vegetative soil cover over a 37.9-acre
area; an adjacent 14.5-acre area had additional soil cover applied and was graded to improve
surface drainage. The cap was substantially completed in December 2008.
The Craig Road Landfill was permitted in 2007 under NCDEQ Solid Waste Permit No. 8504 to
accept coal ash, wastewater treatment sludge, and off -spec FGD residue (gypsum) generated
from BCSS operations. Phase 1 of the landfill was constructed with an engineered liner system
and the waste boundary contains an area of approximately 32.4 acres. Phase 1 began
accepting waste in February 2008. Phase 2 of the landfill was constructed with an engineered
liner system and the waste boundary contains an area of approximately 34.7 acres. Placement
of a protective cover layer of approximately 137,000 tons of bottom ash on top of the Phase 2

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 1 — BACKGROUND
liner system began on June 11, 2013. Phase 2 of the landfill received a Permit to Operate
January 16, 2014 and started receiving waste on June 13, 2014.
The FGD Residue Landfill was permitted for operation in 2008 under the NCDEQ Solid Waste
Permit No. 8505 to receive FGD residue (gypsum) and wastewater treatment clarifier sludge
produced at the BCSS. Waste disposal began in April 2008. The landfill has an engineered liner
system consisting of a leachate collection system, underlain by an HDPE geomembrane liner,
underlain by a geo-synthetic clay liner. The landfill covers an area of approximately 24 acres
and is located on the south side of Belews Lake, approximately one-half mile north of the Craig
Road Landfill.
An unlined structural fill comprised of compacted fly ash was constructed southeast of the ash
basin. The ash structural fill is located south of the Pine Hall Road topographic divide, and
therefore, groundwater flow beneath the fill is away from the ash basin towards Belews Lake.
This structural fill was constructed under the NCDEQ Division of Waste Management structural
fill rules found in 15A NCAC 13B .1700. The Notification of the Beneficial Use Structural Fill was
submitted by Duke Energy to NCDEQ on May 7, 2003. Approximately 968,000 cy of ash were
placed within the structural fill from February 2004 to the last ash placement in July 2009. An
engineered cap similar to that previously described for the Pine Hall Road Landfill was
constructed over the structural fill in 2012. The structural fill is currently used as an
equipment/material staging area and for overflow parking. Per the approved Work Plan, ash
used in the structural fill was not considered part of the source area and was not evaluated
during the CSA.
The location of the ash basin, the site landfills, and the structural fill are shown on Figure 1-1
Topography at the BCSS site ranges from an approximate high elevation of 878 feet southeast
of the ash basin near the intersection of Pine Hall Road and Middleton Loop Road to an
approximate low elevation of 646 feet at the toe of the earthen dike located at the north end of
the ash basin. Middleton Loop Road and Pine Hall Road are located approximately along
topographic divides. Topography to the west of Middleton Loop Road and north of the earthen
dam and natural ridge generally slopes downward toward the Dan River, which is located
approximately 2,000 feet north of the Ash Basin Compliance Boundary. Topography to the
south and east of Pine Hall Road generally slopes downward toward Belews Lake. An unnamed
stream channel extends from the base of the ash basin dam and flows approximately 4,400 feet
northwest to the Dan River. The elevation at the discharge point of the tributary to the Dan River
is approximately 578 feet. The elevation of Belews Lake is approximately 725 feet. A site layout
map is included as Figure 1-2.
The groundwater system in the natural materials (alluvium, soil, soil/saprolite, and bedrock) at
the BCSS site is consistent with the Piedmont regolith-fractured rock system and is an
unconfined, connected system of flow layers. In general, groundwater within the shallow and
deep layers (S and D wells) and bedrock layer (BR wells) flows from the groundwater divide
along Pine Hall Road, located south, southeast, and east of the ash basin and south of the Pine
Hall Road Landfill to the north toward the Dan River.

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 1 — BACKGROUND
The source areas at BCSS are defined as the ash basin, the chemical pond located within the
southern portion of the ash basin, and the closed Pine Hall Road Landfill. Source
characterization was performed to identify physical and chemical properties of ash, ash basin
surface water, ash porewater, and ash basin areas of wetness (AOW).
The compliance boundary for groundwater quality at the BCSS site is defined in accordance
with Title 15A NCAC 02L .0107(a) as being established at either 500 feet from the waste
boundary or at the property boundary, whichever is closer to the waste boundary. As described
in the CSA report, analytical results for groundwater samples were compared to the North
Carolina Groundwater Quality Standards, as specified in 15A NCAC 2L.0202 (2L Standards or
2L) or Interim Maximum Allowable Concentration (IMAC) established by NCDEQ pursuant to
15A NCAC 2L.0202(c), or North Carolina Department of Health and Human Services (DHHS)
Health Screening Level (HSL) (hexavalent chromium only) for the purpose of identifying
constituents of interest (COls). The IMACs were issued for certain constituents in 2010, 2011,
and 2012; however, NCDEQ has not established a 2L Standard for those constituents as
described in 15A NCAC 2L.0202(c). For this reason, the IMACs noted in this document are for
reference purposes only.
Areas of 2L Standard, IMAC, or NCDHHS HSL exceedances are limited to within or directly
adjacent to the sources. The limited downgradient extent of impacts indicates that physical and
geochemical processes (i.e., dispersion and sorption) beneath the BCSS site reduce the lateral
migration of COIs. The approximate vertical extent of groundwater impacts is generally limited
to the shallow and deep flow layers. In accordance with LeGrand's slope -aquifer system
characteristic of the Piedmont, whereby groundwater from shallow, deep, and bedrock flow
layers discharges into surficial waterbodies, groundwater at the BCSS site discharges into the
Dan River north of the groundwater/topographic drainage divide along Pine Hall Road and
south, southeast, and east of this divide towards Belews Lake.
1.3 History of Site Groundwater Monitoring
Monitoring wells were installed by Duke Energy in 2006 as part of the voluntary monitoring
system for groundwater for the ash basin. Eight voluntary groundwater monitoring wells were
sampled twice each year by Duke Energy from November 2007 until May 2010 and the
analytical results were submitted to NCDEQ DWR. Two of the voluntary monitoring wells (MW-
102S and MW-102D) were recently abandoned during reinforcement construction activities at
the ash basin dam. The voluntary monitoring wells are not included in compliance monitoring
and have not been sampled routinely since 2010. As required by the North Carolina Coal Ash
Management Act of 2014 (CAMA), additional monitoring wells were installed and sampled in
2015 and 2016.
Construction details for voluntary monitoring wells are provided in Table 1-1. The location of the
ash basin voluntary and compliance monitoring wells, the approximate ash basin waste
boundary, and the compliance boundary are shown on Figure 1-2.
As described in Section 1.2, the compliance boundaries for groundwater quality at the BCSS
site are defined in accordance with Title 15A NCAC 02L .0107(a) as being established at either

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 1 — BACKGROUND
500 feet from the waste boundaries or at the property boundary, whichever is closer to the
waste boundary. After additional review, Duke Energy is aware that the compliance boundaries
currently depicted need to be revised to accurately reflect Duke Energy property ownership. The
current property depiction was obtained from county GIS records and shows certain areas
consisting of rights -of -ways as not being owned by Duke Energy. Duke Energy is in the process
of revising these areas and will submit revised compliance boundary figures to NCDEQ for
approval.
1.3.1 NPDES Sampling
NPDES compliance monitoring wells (compliance wells) were installed in 2010. Compliance
groundwater monitoring, as required by the NPDES permit, began in January 2011. From
January 2011 through May 2016, compliance groundwater monitoring wells at the BCSS site
have been sampled three times per year, resulting in 17 total sampling events during that time.
A review of the NPDES compliance well sampling results indicates the following:
• Boron exceeded the 2L Standard once in compliance well MW-200D over the period of
monitoring.
• Chromium exceeded the 2L Standard once in compliance well MW-202D over the period
of monitoring. However, the turbidity in this monitoring well during the chromium
exceedance was reported at 513 nephelometric turbidity units (NTU), which may have
affected the chromium result.
• Iron and manganese have intermittently exceeded the 2L Standards in compliance wells
screened in the shallow and deep flow layers located across the site during the NPDES
sampling period. However, these exceedances may be attributable to naturally occurring
conditions and require additional evaluation as site -specific PPBCs are refined.
• Thallium exceeded the 2L Standard in three samples at compliance wells MW-200S,
MW-200D, and MW-201 D over the period of monitoring.
• TDS exceeded the 2L Standard once in compliance monitoring well MW-200D over the
period of monitoring.
Historical analytical results and a summary of the range of exceedances within the NPDES
groundwater monitoring program are provided in Tables 1-2 and 1-3, respectively.
1.3.2 Solid Waste Landfill Monitoring
Groundwater monitoring is conducted at the three permitted BCSS landfills (Pine Hall Road,
Craig Road, and FGD Residue) in accordance with NCDEQ Solid Waste permit requirements.
Monitoring is performed twice per year based on an established scheduled at each landfill.
Summary information for each landfill is provided below.
Pine Hall Road Landfill — the groundwater monitoring system currently consists of 13
monitoring wells, and two surface water sample locations. Twelve wells are screened in
the residual soil/saprolite layer and one well (MW-1 D) is screened in fractured bedrock.
Groundwater monitoring wells MW-1, MW-2, MW-3, MW-4, and MW-5 were installed in
1989. Monitoring well MW-3 was installed to monitor background groundwater quality.
The initial groundwater sampling was performed at these wells in October 1989.

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 1 — BACKGROUND
Monitoring wells MW-6, MW2-7, MW2-9, OB-4, OB-5, and OB-9 were installed, and
monitoring was initiated, as part of the site investigation for the Phase 1 Expansion and
subsequent investigation of groundwater exceedances from 2000 to 2004. Monitoring
wells MW-1 D and MW-7 were installed after installation of the engineered cap in 2008.
Groundwater monitoring at the Pine Hall Road Landfill is performed in April and October
of each year.
Craig Road Landfill — the groundwater monitoring system currently consists of 17
monitoring wells, six surface water sample locations, and three leachate sample
locations. Monitoring well CRW-10 was installed to monitor background water quality.
Monitoring wells were installed to monitor the transition zone (TZ) between the
saprolite/partially weathered rock zone and bedrock. The initial groundwater sampling
event was performed in January 2007 prior to initial placement of waste in February
2008. Groundwater monitoring at the Craig Road Landfill is performed in January and
July of each year.
• FGD Residue Landfill — the groundwater monitoring system currently consists of 12
monitoring wells, one surface water sample location, and one leachate sample location.
Wells BC-23A and BC-28 were installed to monitor background groundwater quality. The
monitoring wells were installed to monitor groundwater quality in the residual
soil/saprolite layer. The initial groundwater sampling event was performed in November
2007 prior to initial waste placement in April 2008. Groundwater monitoring at the FGD
Residue Landfill is performed in May and November of each year.
The location of the assessment wells at the Pine Hall Road Landfill and the landfill compliance
boundary are shown on Figure 1-2. The Craig Road Landfill and the FGD Residue Landfill are
located on the south side of Belews Lake, hydraulically isolated from the ash basin and Pine
Hall Road Landfill; as such, those monitoring wells are not shown.
1.3.3 CSA Sampling
The CSA for the BCSS site began in January 2015 and was completed in September 2015.
Seventy soil/ash and rock borings (for groundwater monitoring wells) were installed as part of
this assessment to characterize the ash, soil, rock and groundwater at the BCSS site. One
comprehensive round of sampling and analysis was included in the CSA report and included
sampling of soil, groundwater, ash basin surface water, and surface water locations at the Dan
River and Belews Lake (Figure 1-2). In addition, hydrogeological evaluation testing was
performed on newly installed wells.
The following constituents were reported as COls in the CSA report:
Soil: arsenic, barium, cobalt, iron, manganese, selenium, and vanadium.
Groundwater: antimony, arsenic, beryllium, boron, cadmium, chloride, chromium3,
cobalt, hexavalent chromium, iron, manganese, pH, selenium, sulfate, thallium, total
dissolved solids (TDS), and vanadium.
Surface water: chloride, copper, manganese, lead, TDS, and thallium.
3 Unless otherwise noted, references to chromium in this document should be assumed to indicate total chromium.

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 1 — BACKGROUND
Horizontal and vertical delineation of source -related soil impacts was presented in the CSA
report. Where soil impacts were identified beneath the ash basin (beneath the ash/soil
interface), the vertical extent of contamination was generally limited to the soil samples collected
just beneath the ash.
Groundwater impacts at the BCSS site attributable to ash handling and storage were delineated
during the CSA activities with the following areas requiring refinement:
• Horizontal extent west toward Middleton Loop Road from the ash basin dam and
downgradient (north) of the ash basin dam.
• Horizontal and vertical extent in the area of AOW sample location S-9 in the drainage
south of Pine Hall Road and adjacent to the ash structural fill.
1.3.4 Post-CSA Sampling
Four additional rounds of groundwater sampling of the CSA wells, surface water locations, and
AOWs have occurred since submittal of the CSA report. Round 2 of groundwater monitoring
occurred in September 2015 and was reported in the Corrective Action Plan (CAP) Part 1 report
(submitted on December 8, 2015). Rounds 3 and 4 of groundwater monitoring occurred in
November and December 2015 and results were reported in the CSA Supplement 1 as part of
the CAP Part 2 report (submitted on March 4, 2016). Round 5 of groundwater monitoring was
conducted between March and April 2016, and is the focus of the data evaluation presented in
Section 3 of this CSA Supplement 2.
1.3.5 NCDEQ Sampling
Section § 130A-309.209 (c) of CAMA indicates that NCDEQ requires sampling of water supply
wells to evaluate whether the wells may be adversely impacted by releases from CCR
impoundments. NCDEQ required sampling of all drinking water receptors within 0.5 mile of the
CSS compliance boundary in all directions, since the direction of groundwater flow had not been
determined at BCSS at the time of the sampling. Between March and December 2015, NCDEQ
arranged for independent analytical laboratories to collect and analyze water samples obtained
from wells identified during the Drinking Water Well Survey4, 5 if the owner agreed to have their
well sampled. The NCDEQ-directed water supply well sampling consisted of collection and
analysis of the following:
• A total of 34 samples collected from 34 water supply wells within 0.5 mile of the BCSS
compliance boundary; and
A total of 11 samples collected from background water supply wells located within a 2- to
10-mile radius of the BCSS site boundary.
The locations of the private water supply wells identified within 0.5 mile of the BCSS compliance
boundary, including NCDEQ-directed sampling locations with updated analytical results
provided to Duke Energy, are shown on Figure 1-3.
4 HDR. 2014a. Belews Creek Steam Station Ash Basin Drinking Water Supply Well and Receptor Survey. NPDES
Permit NCO024406 September 30, 2014.
5 HDR. 2014b. Belews Creek Steam Station Ash Basin. Supplement to Drinking Water Supply Well and Receptor
Survey. NPDES Permit NC0024406. November 6, 2014.

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 1 — BACKGROUND
The results of water supply well testing conducted by the NCDEQ in the vicinity of the BCSS
facility indicated that boron was detected in 3 of the 34 NCDEQ-sampled water supply wells
within 0.5 mile of the compliance boundary and in none of the background well samples
collected by NCDEQ and Duke Energy. Arsenic was below the drinking water standard in 27 of
the 34 NCDEQ-sampled water supply wells. In general, pH was below the state and federal
drinking water standard range in 20 of the 34 NCDEQ-sampled water supply wells and in
NCDEQ- and Duke Energy -sampled background wells. This result is not unexpected, based on
a study published by the United States Geological Survey6 and additional North Carolina -
specific studies' showing that groundwater pH in the state is commonly below the Maximum
Contaminant Level (MCL) range of 6.5 to 8.5 Standard Units. None of the NCDEQ-sampled
water supply well results were above Federal primary drinking water standards (MCLs), with the
exception of the pH and arsenic results noted above.
Boron is a naturally occurring compound, usually found in various inorganic forms in sediments
and sedimentary rocks. Boron presents in water, soil, and air originates from both natural and
anthropogenic sources.
Natural weathering of boron -containing rocks is thought to be the primary source of boron
compounds in water and soil. Releases to air from oceans, volcanoes, and geothermal steam
are other natural sources of boron in the environment.
Human causes of boron contamination include releases to air from power plants, chemical
plants, and manufacturing facilities. Fertilizers, herbicides, and industrial wastes are among the
sources of soil contamination. Contamination of water can come directly from industrial
wastewater and municipal sewage, as well as indirectly from air deposition and soil runoff.
Borates in detergents, soaps, and personal care products can also contribute to the presence of
boron in water. Boric acid and its sodium salts are registered for use as pesticides$.
"Do Not Drink" letters were issued by the DHHS for 3 water supply wells at BCSS. Two letters
were issued for vanadium, though these were based on the now -outdated screening level, and
those "Do Not Drink" warnings have been lifted for vanadium. One letter was issued for iron.
Based on data obtained during the NCDEQ water supply well sampling, Duke Energy used a
multiple -lines -of -evidence approach to evaluate whether the presence of constituents in water
supply wells near BCSS are the result of migration of CCR-impacted groundwater. This
approach consisted of a detailed evaluation of groundwater flow and groundwater chemical
signatures.
The results of the groundwater flow evaluation confirmed that the source of groundwater for the
water supply wells is upgradient of the ash basin, and supplied by recharge falling on areas not
6 Chapman, M.J., Cravotta III, C.A., Szabo, Z. and Linsay, B.D. 2013 Naturally occurring contaminants in the
Piedmont and Blue Ridge crystalline -rock aquifers and Piedmont Early Mesozoic basin siliciclastic-rock aquifers,
eastern United States, 1994-2008 (Scientific Investigations Report No. 2013-5072). U.S. Geological Survey.
Briel, L.I. 1997. Water quality in the Appalachian Valley and Ridge, the Blue Ridge, and the Piedmont physiographic
rovinces, eastern United States (Professional Paper No. 1422-D). U.S. Geological Survey.
USEPA Office of Water. January 2008. Health Effects Support Document for Boron. Document Number EPA-822-
R-08-002.
IN

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 1 — BACKGROUND
impacted by coal ash. The groundwater flow directions for the site is consistent with the slope -
aquifer system and show that groundwater flow is away from off -site water supply wells and
toward the Dan River, Belews Lake, or the ash basin. A groundwater divide coincident with Pine
Hall Road exists and the groundwater flow direction across most of the site is north toward the
Dan River. South of the road, the flow direction is to the south, southeast, and east toward
Belews Lake. Thus, groundwater flow from areas associated with the ash basin, ash landfills,
and the ash storage area is laterally away from the water supply wells within the transition zone
and overlying saprolite and soil limiting the impact of coal ash related constituents in bedrock as
shown by analytical data and supported by groundwater modeling. Although not mounding, but
due to the narrow ash basin rim, there is evidence of groundwater flow northwesterly across the
topographic divide of Middleton Loop Road near the west abutment of the Ash Basin Dam.
There are no water supply wells down gradient of this area.
The results of the groundwater chemical signature evaluation indicate that constituent
concentrations in the water supply wells are generally consistent with background levels,
including boron and sulfate. Further, the different constituent clustering patterns from the
porewater wells and the water supply wells indicate that the source water for the water supply
wells is not CCR-impacted groundwater. The conclusion from the groundwater chemical
signature evaluation is that water supply wells in the vicinity of the BCSS facility are not
impacted by CCR releases from the ash basin.
is

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 2 — CSA REVIEW COMMENTS
Section 2 — CSA Review Comments
Representatives of NCDEQ's Central Office and Winston-Salem Regional Office (WRO) met
with Duke Energy and HDR on October 23, 2015 to present their review comments to the CSA
report. Comments were organized in two categories: general comments applicable to all Duke
Energy Carolinas CSA reports regardless of site and site -specific comments applicable to
BCSS.
NCDEQ General Comments and Responses
General comments applicable to the CSA reports, and responses to the comments, are
presented in Table 2-1.
NCDEQ Site -Specific Comments and Responses
Site -specific comments and responses were included in the CSA Supplement 1, which was
submitted to NCDEQ on February 18, 2016 as part of the CAP Part 2 report. Additional
information requests were received during a meeting on May 6, 2016 in NCDEQ's Winston-
Salem office and are addressed within this sub -Section.
2.2.1 Bedrock Lithology at Background Well Locations
During the May 6, 2016 meeting, NCDEQ requested that the bedrock lithologies in background
wells for the Belews Creek Ash Basin, Pine Hall Road Landfill, Craig Road Landfill, and the
FGD Residue Landfill be identified. Locations of the background wells are shown on Figure 2-1
and the following table provides the bedrock lithologies for the background wells. Appendix A
includes the monitoring well boring logs for the background well locations referenced.

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 2 - CSA REVIEW COMMENTS
Belews Creek Ash Basin Background Wells - D and BR Background Wells
Well #
Ground
Elevation
(ft)
Depth to
Refusal
(ft)
Depth of
Well (ft)
Bedrock Lithology
Depth
(ft) From
Depth
(ft) To
Screened
Interval -
Depth (ft)
Remarks
BG-113
805.63
40.0
57.0
Quartz -Feldspar Gneiss
42.0
57.0
47.0 - 52.0
BG-1S is Adjacent Shallow
Background Well
BG-2D 809.95 65.0 80.0
Mica Schist
65.0
68.5
BG-2S is Adjacent Shallow
Background Well
Hornblende Schist
68.5
80.0
70.0- 75.0
BG-2BR 810.05 65.0 129.5
Mica Schist
65.0
68.5
BG-2S is Adjacent Shallow
Background Well
Hornblende Schist
68.5
80.0
Mica Schist
80.0
86.0
80.5 - 85.5
Augen Gneiss
86.0
129.5
BG-3D 841.72 56.0 71.0
Mica Gneiss
56.0
66.8
62.0 - 67.0
BG-3S is Adjacent Shallow
Background Well
Quartz -Feldspar Gneiss
66.8
71.0
MW-202D 790.78 79.0 89.2
Gneiss
79.0
89.2
84.0 - 89.0
MW-202S is Adjacent Shallow
Background Well
MW-202BR 786.87 81.0 130.5
Schistose Mica Gneiss
81.0
83.0
MW-202S is Adjacent Shallow
Background Well
Quartz -Feldspar Gneiss
83.0
86.0
Schistose Mica Gneiss
86.0
97.0
Quartz -Feldspar Gneiss
97.0
100.5
98.0-103.0
Flaser Gneiss
100.5
101.5
Schistose Mica Gneiss
101.5
117.8
Flaser Gneiss
117.8
121.7
Quartz -Feldspar Gneiss
121.7
130.5
Pine Hall Road Landfill Background Well
MW-3 47.8 47.8 37.0-47.0 Screened inSaprolite
Craig Road Landfill Background Well
CRW-17 832.02 47.2 47.2 29.0 - 39.0 Formerly CRHS-44. Screened in
Saprolite
FGD Residue Landfill Bankground Well
BC-23A
1863.79 (1)1
85
1 102.7
1 Quartz -Feldspar Gneiss
85.0
102.7
76.7 - 101.7
Screened in Saprolite and Bedrock
BC-28
1818.09 (1)1
55
1 60
1 Biotite Gneiss
55
60
43.2 - 58.2
Screened in Saprolite and Bedrock
Wells listed in the table above are screened in the deep and bedrock layers except as noted. Wells BG-1S, BG-2S, BG-3S, MW-202S, MW-3,
and CRW-17 are background wells screened in the saprolite layer (Swells) with no information on bedrock lithology provided on the boring
logs.
The main rock types underlying the BCSS ash basin and three landfills are mica schist (some
layers garnet -rich), schistose mica gneiss, mica gneiss, augen gneiss, flaser gneiss, quartz -
feldspar gneiss, and biotite gneiss (all sedimentary in origin) with interlayered hornblende
schist/gneiss (volcanic in origin). The rocks have been metamorphosed to the sillimanite/kyanite
zone of amphibolite grade. The mica schist is coarse -grained, well -foliated, "button" schist
composed of muscovite and quartz with pinhead garnets. Interlayered with the "button" schist
are thin layers of mica schist (non -"buttoned") and fine- to medium -grained schistose mica
gneiss and mica gneiss. The augen gneiss is a fine- to medium -grained rock with a well -
developed foliation wrapping around conspicuous pods or "eyes" of feldspar. They are
comprised primarily of quartz, feldspar, and mica. The flaser gneiss consists of small lenses of
granular materials (quartz -feldspar -mica) separated by wavy ribbons and streaks of finely
crystalline, foliated materials (primarily muscovite). The quartz -feldspar gneiss is a medium- to
coarse -grained, foliated, normally mica -poor rock, although some massive, less foliated
varieties have up to 15% muscovite. The hornblende schist/gneiss is a fine- to coarse -grained,
dark colored rock composed primarily of hornblende, pyroxene, biotite, and plagioclase. It is
semi -massive to well -foliated and occurs in layers up to 15 feet thick.
13

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 2 — CSA REVIEW COMMENTS
All the rock types are interlayered and the felsic rocks grade laterally into each other. The
contacts of the hornblende schist/gneiss with the felsic rocks are generally sharp. The
compositional layering is parallel to the strongly developed foliation. The orientation of the
foliation is relatively consistent throughout the area (—N72E; 67SE). The presence of "button"
schist, augen gneiss, and flaser gneiss indicates that the rocks have been strongly deformed
and sheared, probably during at least two episodes of isoclinal folding ("buttons" are formed by
the intersection of two, nearly parallel, foliation surfaces). The deformation was primarily ductile,
although the presence of layers of flaser gneiss suggests that some of the deformation occurred
under semi -brittle to brittle conditions.9 Additional information on the site geology is presented in
the BCSS CSA report.
The primary, secondary, and trace minerals and their chemical formulas of the felsic-rich rocks
(quartz -feldspar gneiss, gneiss, biotite gneiss augen gneiss, schistose mica gneiss, flaser
gneiss, and mica schist) and mafic-rich rocks (hornblende schist) are presented in the following
table.
Metasedimentary Felsic Rocks'
Primary Minerals
Chemical Formula
Secondary and
Trace Minerals
Chemical Formula
quartz
Si02
chlorite
(Mg,AI,Fe)12[(Si,AI)80201(OH)16
plagioclase
Na[AlSi308]-Ca[Al2Si2O8]
garnet (almandine)
Fe3+2Al2Si3012
othoclase
(K,Na)[AISi30$]
garnet (spessartine)
Mn3Al2Si3012
muscovite
K2AI4[Si6A12020](OH,F)4
epidote
Ca Fe+3A120*0H1Si20711Si041
biotite
I K2(Mg,Fe+2)6-4(Fe+3,AI,Ti)0_2[Si6_5AI2_3020](OH,F)4
staurolite
(Fe +2,Mg)2(AI,Fe+3)906[SiO4]4(O,OH)2
kya n ite
AI2Si O5
magnetite
Fe+2Fe2+304
pyrite
FeS2
sericite
K2A141S'3AlC j0j (C H)2
hematite
Fe203
Mafic Metavolcanic Rocks - Hornblende Gneiss/Schist2
plagioclase
Na[AISi3091-Ca[Al2Si20$1
chlorite
(Mg,AI,Fe)12[(Si,AI)80201(OH)16
hornblende
(Na,K)o_1Ca2(Mg,Fe+2,Fe+3,AI)jSi6_7Al2-10221(OH,F)2
tremolite
Ca2(Mg,Fe+2)5[Si8022](OH,F)2
pyroxene (augite)
(Ca,Na,Mg,Fe+',Mn,Fe+3,AI,Ti)2[(Si,AI)206]
epidote
Ca Fe+'A120*0H1Si2o711Sio41
pyroxene (diopside)
Ca(Mg,Fe)[Si206]
sericite
K2AI4[Si3A1010](OH)2
biotite
K2(Mg,Fe+2)6.4(Fe+3,AI,Ti)0_2[Si6.5AI2.3020](OH,F)4
apatite
Ca5(PO4)3(OH,F,CI)
pyrite
FeS2
zircon
Zr[SiO4]
quartz
I Si02
Reference for Chemical Formulas: Deer, W. A., R. A. Howie, and J. Zussman. 1966. An Introduction to the Rock -Forming Minerals: John Wiley and
Sons, Inc., New York, N.Y., 528p.
From Petrographic Descriptions of Felsic Rock in Appendix A - CSA Supplement 1 in the Belews Creek CAP 1 Report.
2From Petrographic Descriptions of Mafic Metavolcanic Rocks of Similar Metamorphic Grade in Appendix A- CSA Supplement 1 in Buck CAP 1 Report.
2.2.2 Assessment of Area of Wetness Location S-9
To address the extent of exceedances near AOW S-9, monitoring wells GWA-23S and GWA-
23D were installed and sampled as part of the Round 5 sampling event. Groundwater
monitoring well pair GWA-23S/D was installed in April 2016, approximately 450 feet west of the
9 Schaeffer, M. F. 2001. Groundwater characterization of a site in the Milton belt, North Carolina: 9t" Clemson
Hydrogeology Symposium, April 13, 2001, P. 14-18.
HDR Engineering of the Carolinas, Inc. 2015. Belews Creek Steam Station Comprehensive Site Assessment Report
dated September 9t"
14

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 2 — CSA REVIEW COMMENTS
Structural Fill and approximately 300 feet north of S-9 (Figure 1-2). The well pair was installed
to provide additional data on groundwater concentrations in the area west of the structural fill
after exceedances of groundwater standards were measured at S-9. Exceedances for boron,
manganese, and uranium were measured in S-9 during the March 31, 2016 sampling event.
Location S-9 also had measured groundwater exceedances during sampling performed in
Round 1 and Round 2.
Groundwater samples collected from GWA-23S/D measured exceedances for boron, cobalt,
iron, manganese, sulfate, TDS, vanadium, and pH in samples collected after installation in April
2016. The installed depths of the well screens are provided below.
GWA-23S
GWA-23D
Top of Casing (feet)
811.79
811.57
Groundwater Elevation (feet)
786.57
786.64
Screen Length (BGS - feet)
15
5
Top of Screen (BGS - feet)
24.40
56.61
Bottom of Screen (feet)
39.40
61.61
Top of Screen (elevation — feet)
787.39
754.96
Bottom of Screen (elevation — feet)
772.39
749.96
The ash basin full pond elevation is 750 feet. The surveyed water elevation in the Chemical
Treatment Pond in April 2014 was 772.0 feet. A pond depth survey performed by HDR in June
2014 measured an approximate maximum depth of 15 feet below the pond water surface. If the
water surface was at or near the April 2014 elevation of 772 feet, the corresponding elevation
would be 757 feet. The water elevation in this pond has been lowered and the surveyed
elevation in April 2016 was approximately 760.4 feet.
Concentrations of the constituents in GWA-23S and GWA-23D are similar, indicating that the
concentrations are from the same source. The lowest elevation of the screen in GWA-23S is
772.39 feet, approximately 12 feet above the pond elevation for the Chemical Treatment Pond
(760.4 feet) and approximately 22.4 feet above the ash basin full pond elevation (750 feet).
The elevation differences indicate that the source of the exceedances in GWA-23S is not the
ash basin. Although the screen elevation for GWA-23D is lower than the Chemical Treatment
Pond area historical elevation (754.96 feet to 749.96 feet), based on the similar nature of the
exceedances, it is likely that the same source is the cause of the exceedances in both GWA-
23S and GWA-23D. Additional evidence is noted in comparison of the analytical results for
boron, sulfate, and TDS between monitoring wells GWA-9S/D, located in the earthen dike for
the Chemical Treatment Pond area, and the results for these constituents in GWA-23S/D. See
Table 3-1.
Table 3-5 also provides the analytical results for S-9 for a March 31, 2016 sampling event. The
approximate elevation for S-9 is 792 feet, which is above the elevation of the ash pond and the
Chemical Treatment Pond.

Duke Energy Carolinas, LLC I CSA Supplement 2
Belews Creek Steam Station Ash Basin FN
SECTION 2 — CSA REVIEW COMMENTS
The groundwater flow maps for the shallow and deep flow layers show a distinct groundwater
drainage divide along Pine Hall Road between the ash basin and GWA-23S/D and S-9, further
indicating that the exceedances are not related to the ash basin (Figures 3-1 and 3-2). Only
nine of 18 bedrock monitoring wells were measured for water level on May 9, 2016 by Duke
Energy. Therefore, a representative bedrock potentiometric flow map could not be developed
(Figure 3-3). The data is consistent with a drainage divide along Pine Hall Road, and a
drainage divide is expected within the slope -aquifer system as clearly identified in the shallow
and deep flow layers.
The exceedances in GWA 23S/D are consistent with constituents associated with coal ash and
a potential source could be the nearby structural fill. The fill was operated from approximately
2003-2004 until ash placement was completed in 2009. An engineered cover system, similar to
that used in landfills, was constructed over the fill in 2012. As the structural fill was constructed
under the NCDEQ Division of Waste Management (DWM) structural fill rules found in 15A
NCAC 13B .1700, Duke Energy has notified DWM of these exceedances.
2.2.3 Middleton Loop Road Cross -Section
At the request of the NCDEQ Winston-Salem office, an additional cross-section along Middleton
Loop Road has been produced. This cross-section, C-C' is included on Figures 3-5.10, 3-5.11,
3-5.12, and 3-5.13.
Errata
Editorial comments and corrections to the CSA report were included in the CSA Supplement 1,
which was submitted to NCDEQ on February 18, 2016 as part of the CAP Part 2 report. Since
the issuance of the CAP Part 2 report, additional evaluation of site data has occurred, resulting
in refinement by flow layer of total porosity, secondary (effective) porosity, and specific storage
for the lower hydrostratigraphic units (deep transition zone) and bedrock), as provided in Table
2-2.

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
Section 3 — Additional Assessment
Additional assessment activities identified in the CSA report were addressed and the findings
are discussed in the following section.
Additional Assessment Activities
Additional assessment activities included monitoring well installation and sampling, as
discussed below.
3.1.1 Well Installation
Additional monitoring wells were installed to refine understanding of groundwater flow direction
and extent of exceedances at BCSS. Refinement of exceedances focused primarily on the
extent of COI exceedances between the ash basin and Middleton Loop Road and west of
Middleton Loop Road; and the extent of boron near AOW S-6 and the extent of boron, cobalt,
sulfate, and TDS near AOW S-9. Additional assessment was also requested to be performed to
refine the delineation of horizontal and vertical exceedances in the area downgradient of the
2.23 acre tract of property (e.g., the accelerated remediation "area of interest" AOI). To address
the extent of exceedances between the ash basin and Middleton Loop Road and west of
Middleton Loop Road, monitoring wells GWA-24S/D, GWA-18S/D, GWA-16BR, GWA-91BR,
GWA-25BR, and GWA-26S/D/BR were installed. To address the extent of exceedances near
AOW S-6, monitoring wells MW-201 BR and GWA-22D were installed. To address the extent of
exceedances near AOW S-9, monitoring wells GWA-23S/D were installed. To address the
extent of exceedances within the AOI, monitoring wells GWA-19S/D, GWA-20S/D/BR, GWA-
21 S/D, and GWA-27S/D/BR were installed.
Subsequent discussions with Duke Energy and NCDEQ resulted in the installation of additional
monitoring wells beyond described above. A summary of those additional assessment wells and
installation dates, as well as the purpose for installation, is provided in the table below.
Boring /Well I Installation Purpose for Installation
Identification I Date I
AB-1 BR
AB-4BRD
Res u Its
5/3/2016 NCDEQ requested these monitoring I Not installed in time for sampling
wells to refine the vertical extent of inclusion during the Round 5
exceedances. samDlino event
4/21 /2016
MW-201BR 4/21/2016 Additional bedrock groundwater
monitoring well at location of
compliance monitoring well MW-201
to refine the understanding of
groundwater quality in bedrock
between the northeast portion of the
active basin and the offsite water
I suDDly wells.
Not installed and developed in
time for sampling inclusion during
the Round 5 sampling event
Concentrations of hexavalent
chromium and vanadium
exceeded applicable criteria
17

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
Boring /Well
Installation
Purpose for Installation
Results
Identification
Date
GWA-9BR
5/11/2016
NCDEQ requested this monitoring
Not installed in time for sampling
well to refine understanding of
inclusion during the Round 5
groundwater quality between the
sampling event
southwestern portion of the active
basin and the offsite water supply
wells.
GWA-16BR
4/5/2016
NCDEQ requested this monitoring
Monitoring well inadvertently not
well at location of assessment
sampled during the Round 5
monitoring wells GWA-16S/D to
sampling event by Duke Energy
refine the understanding of
groundwater quality in bedrock
between the western portion of the
active basin and the offsite water
supply wells.
3/23/2016
GWA-18S
Monitoring wells installed to refine
Water level was not measured
understanding of groundwater
during the 5/9/2016 depth to water
elevations as well as horizontal and
measurement event.
vertical extent of boron and TDS
Concentrations of cobalt, iron,
reported in wells and AOWs in area
manganese, and vanadium
well nests.
exceeded the applicable criteria.
Water level measured and used
GWA-18D
3/23/2016
for contouring of deep flow layer.
Concentrations of hexavalent
chromium and vanadium
exceeded the applicable criteria.
Not installed in time for sampling
GWA-18SA
5/25/2016
inclusion during the Round 5
sampling event
GWA-19S
3/16/2016
Water level measured and used
for contouring of shallow flow
layer. Concentrations of beryllium,
boron, cobalt, manganese,
selenium, and thallium exceeded
the applicable criteria
Water level was inadvertently not
GWA-19D
3/15/2016
measured by Duke Energy during
the 5/9/2016 depth to water
measurement event.
Concentrations of chromium,
cobalt, iron, manganese, and
vanadium.
GWA-19SA
5/25/2016
Not installed in time for sampling
inclusion during the Round 5
sampling event
Not sampled during the Round 5
GWA-20S
3/19/2016
sampling event(dry)
GWA-20D
3/19/2016
Water level measured and used
for contouring of deep flow layer.
Concentrations of boron, chloride,
cobalt, iron, manganese, and TDS
exceeded the applicable criteria

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
Boring /Well
Installation
Purpose for Installation
Results
Identification
Date
GWA-20SA
5/23/2016
Not installed in time for sampling
inclusion during the Round 5
sampling event
Water level measured and used
GWA-21S
3/8/2016
for contouring of shallow flow
layer. Concentrations of beryllium,
cobalt, and manganese exceeded
applicable criteria.
Water level measured and used
GWA-21D
3/7/2016
for contouring of deep flow layer.
Concentrations of hexavalent
chromium, cobalt, and
manganese exceeded applicable
criteria.
Not installed in time for sampling
GWA-20BR
6/1/2016
inclusion during the Round 5
sampling event
GWA-22S
5/10/2016
Exceedance of the 2L Standard for
Not installed in time for sampling
boron was measured at CSA AOW
inclusion during the Round 5
location S-6, which is east of the
former ash basin discharge structure
sampling event
GWA-22D
5/11/2016
Not installed in time for sampling
that drains to Belews Lake and is
inclusion during the Round 5
near the compliance boundary.
sampling event
Monitoring wells installed to refine
understanding of concentrations at
AOW S-6.
GWA-23S
4/7/2016
CSA AOW location S-9 exhibited 2L
Water level measured and used
Standard or IMAC exceedances for
for contouring of shallow flow
boron, cobalt, sulfate, and TDS.
layer. Concentrations of boron,
These monitoring wells were
cobalt, iron, manganese, sulfate,
installed to refine understanding of
and TDS exceeded applicable
groundwater elevations and
concentrations in this area.
criteria.
Water level measured and used
GWA-23D
4/14/2016
for contouring of deep flow layer.
Concentrations of boron, cobalt,
iron, manganese, sulfate, TDS,
and vanadium exceeded
applicable criteria
GWA-24S
3/30/2016
NCDEQ requested this well to refine
Not sampled during the Round 5
understanding of exceedances at
AOW 003 reported as well as at
sampling event(dry)
GWA-24D
3/30/2016
Water level measured and used
GWA-1S/D. Monitoring wells
for contouring of deep flow layer.
installed to refine understanding of
Concentrations of hexavalent
concentrations at AOW 003.
chromium, cobalt, and
manganese exceeded applicable
criteria.
GWA-25BR
4/26/2016
NCDEQ requested these monitoring Not installed in time for sampling
wells to refine understanding of inclusion during the Round 5
groundwater concentrations sampling event
GWA-26S
between the Pine Hall Road Landfill Not installed in time for sampling
4/30/2016
and offsite water supply wells. inclusion during the Round 5
sampling event
19

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
Boring /Well
Installation
Purpose for Installation
Results
Identification
Date
I
GWA-26D
5/4/2016
Not installed in time for sampling
inclusion during the Round 5
sampling event
Not installed in time for sampling
GWA-26BR
5/4/2016
inclusion during the Round 5
sampling event
Not installed in time for sampling
GWA-27S
5/16/2016
Monitoring wells installed to refine
understanding of horizontal and
inclusion during the Round 5
vertical extent of boron and TDS
reported in wells and AOWs in area
sampling event
GWA-27D
5/17/2016
Not installed in time for sampling
well nests and to refine groundwater
inclusion during the Round 5
flow direction.
sampling event
GWA-27BR
512112016
Not installed in time for sampling
inclusion during the Round 5
sampling event
Monitoring well logs and core photos, field sampling and slug test records, and analytical
laboratory reports are included in Appendices B, C, and D, respectively.
Several monitoring wells exhibit pH results of 9 or above, which is indicative of cement leakage
beyond the borehole seal. In addition, several monitoring wells were sampled with turbidity
greater than 10 NTU. The evaluation of groundwater quality data obtained from these wells
during Round 5 sampling must be qualified and further evaluated. The additional assessment
wells were installed by North Carolina -licensed drillers according to construction standards
described in 15A NCAC 2C.0107.
3.1.2 Well Gauging and Sampling
Round 5 of groundwater, ash basin surface water, surface water, AM and ash basin water
sampling activities was completed between March 29 and April 28, 2016. Groundwater
analytical parameters and methods for Round 5 were consistent with those used during
previous sampling events, as presented in previous reports. A total of 81 groundwater and ash
porewater monitoring wells were sampled during the Round 5 event. Sample locations are
depicted on Figure 1-2.
3.2 Additional Assessment Results
Findings and results from Round 5 of sampling and analysis and additional assessment
activities are presented below. Note that the Round 3 and 4 monitoring events focused on
sampling of background wells only. Therefore, groundwater elevation and analysis results are
compared to data previously obtained during Round 1 and 2 monitoring events. A summary of
the analytical results is presented in Tables 3-1, 3-2, 3-3, 3-4, and 3-5 for groundwater,
porewater, ash basin surface water, surface water, and AOWs, respectively. A summary of
groundwater elevations measured during the Round 1 through 5 gauging events is presented in
Table 3-6.
20

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
3.2.1 Groundwater Flow Direction
On May 9, 2016, monitoring wells were manually gauged from the top of the PVC casing using
an electronic water level indicator accurate to 0.01 foot. Groundwater elevations were generally
higher than those measured during Rounds 1 and 2, which is likely attributable to seasonal
variation of the water table. Groundwater flow direction was consistent with flow directions
identified in Rounds 1 and 2, and generally flows from the vicinity of the ash basin north-
northwest toward Dan River. South, southeast, and east of Pine Hall Road, groundwater flows
toward Belews Lake. Groundwater elevations and inferred contours for the shallow, deep, and
bedrock flow layers are depicted on Figures 3-1, 3-2, and 3-3, respectively. These groundwater
flow directions are consistent with interpretations made in the CSA report.
3.2.2 Sampling Results
3.2.2.1 SUMMARY OF ROUND 1 AND 2 GROUNDWATER SAMPLING RESULTS
As previously mentioned in Section 1.3.2, the following COls were identified in groundwater as
a result of sampling conducted during the CSA: antimony, arsenic, beryllium, boron, cadmium,
chloride, chromium3 , cobalt, hexavalent chromium, iron, manganese, pH, selenium, sulfate,
thallium, TDS, and vanadium. The list of COls resulting from Round 5 of groundwater sampling
is consistent with the exception of cadmium, which did not have exceedances during the Round
5 sampling event.
3.2.2.2 ROUND 5 POREWATER SAMPLING RESULTS
A total of 9 porewater wells were sampled in March and April 2016 as part of the Round 5
sampling event. The analytical results for the porewater well samples are presented in Table 3-
2. Concentrations of antimony, arsenic, beryllium, boron, chloride, hexavalent chromium, cobalt,
iron, manganese, nickel, selenium, sulfate, TDS, thallium, and vanadium that exceed the
applicable 2L Standard or IMAC were detected in porewater samples collected during the
Round 5 sampling event. The range and number of exceedances of each COI in porewater are
listed below.
• Antimony: 9.8 pg/L to 10.1 pg/L; 3 exceedances/9 samples (3/9)
• Arsenic: 17.2 pg/L to 147 pg/L; 7/9
• Barium: no exceedances in porewater
• Beryllium: 4.1 pg/L; 1/9
• Boron: 746 pg/L to 2 1, 100 pg/L; 6/9
• Cadmium: no exceedances in porewater
• Chloride: 534,000 pg/L to 614,000 pg/L; 2/9
• Chromium: no exceedances in porewater
• Hexavalent chromium: 0.13 pg/L to 1.6J pg/L; 4/9
• Cobalt: 3.2 pg/L to 271 pg/L; 3/9
• Iron: 483 pg/L to 132,000 pg/L; 7/9
• Manganese: 111 pg/L to 10,400 pg/L; 5/9
• Mercury: no exceedances in porewater
• Nickel: 174 pg/L; 1/9
• Selenium: 36.4 pg/L to 205 pg/L; 3/9
21

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
• Sulfate: 637,000 tag/L; 1/9
• TDS: 558,000 tag/L to 1,170,000 tag/L; 4/9
• Thallium: 1 fag/L to 1.9 fag/L; 2/9
• Vanadium: 0.31 fag/L to 930 fag/L; 8/9
• Zinc: no exceedances in porewater
3.2.2.3 ROUND 5 GROUNDWATER SAMPLING RESULTS
A total of 72 groundwater monitoring wells were sampled during March and April 2016 as part of
the Round 5 sampling event. The analytical results for the groundwater monitoring well samples
are presented on Table 3-1. In general, the COls identified during Round 5 groundwater
sampling are consistent with the results obtained during Rounds 1 and 2. A summary of Round
5 sampling results per COI identified during the CSA is as follows:
Antimony: 1.2 fag/L to 10.1 tag/L; 5 exceedances/74 samples (5/74)
o No exceedances of antimony were detected in wells screened within the shallow
flow layer; however, antimony exceeded the IMAC in two wells (GWA-1D and
GWA-11 D) screened within the deep flow layer and in three bedrock flow layer
wells (AB-4BR, BG-2BR and GWA-16BR). Antimony was detected above the
IMAC in background well BG-2BR, indicating that antimony may be present as a
naturally occurring constituent. In general, total and dissolved concentrations
were consistent in each sample.
• Arsenic: 16.8 fag/L to 70 fag/L; 3/74
o Arsenic exceeded the 2L Standard in wells MW-103S and AB-3D, which are both
located north of the ash basin. Arsenic also exceeded the 2L Standard in well
AB-9BR, which is located between the chemical pond and the ash basin. In
general, total and dissolved concentrations were consistent in each sample.
• Barium: No exceedances in groundwater
• Beryllium: 4.8 fag/L to 7.3 fag/L; 4/74
o Beryllium exceeded the IMAC in four wells (GWA-11S, GWA-19S, GWA-21S,
and GWA-7S), all screened within the shallow flow layer. No exceedances of
beryllium were detected in wells screened within the deep and bedrock flow
layers.
• Boron: 703 fag/L to 13,100 tag/L; 9/74
o Boron exceeded the 2L Standard in several wells screened within the shallow
and deep flow layers located north of the ash basin and west of the structural fill.
No exceedances of boron were detected in wells screened in the bedrock flow
layer. In general, total and dissolved concentrations were consistent in each
sample.
0 Cadmium: No exceedances in groundwater

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
• Chloride: 279,000 pg/L to 504,000 pg/L; 6/74
o Chloride exceeded the 2L Standard in several wells screened in the shallow and
deep flow layers located north and northwest of the ash basin. No exceedances
of chloride were detected in wells screened in the bedrock flow layer.
• Chromium: 10.6 pg/L to 51.4 pg/L; 9/74
o Chromium exceeded the 2L Standard in several wells screened in in the shallow
flow layer located north, west, and southwest of the ash basin. Chromium
exceeded the 2L Standard in three wells (GWA-1 D, GWA-11 D, and GWA-19D),
all screened in the deep flow layer northwest of the ash basin. Only one bedrock
flow layer well (GWA-16BR) exhibited an exceedance of chromium. The
dissolved concentrations were significantly lower than the total concentrations in
most of the shallow and deep flow layer wells indicating that these exceedances
may be turbidity -derived. In general, the total and dissolved concentrations in the
bedrock flow layer were consistent in each sample.
• Hexavalent Chromium: 0.078 pg/L to 2.8 pg/L; 32/74
o Hexavalent chromium exceeded the DHHS HSL in several wells screened in the
shallow flow layer located downgradient and sidegradient of the ash basin and
located downgradient of the structural fill. Hexavalent chromium also exceeded
the DHSS HSL in the deep flow layer wells with higher frequency across the
BCSS site than the shallow flow layer wells. Exceedances in the bedrock flow
layer were less frequent and generally restricted to wells east and northeast of
the ash basin and west and southwest of the ash basin. Note that dissolved
phase analyses for hexavalent chromium were not performed on groundwater
samples.
• Cobalt: 2.1 pg/L to 108 pg/L; 31 /74
o Cobalt exceeded the IMAC in several wells screened in the shallow flow layer
located north and west of the ash basin and south and southeast of the chemical
pond. Concentrations were generally the highest north and northwest of the ash
basin. Cobalt exceedances in the deep flow layer wells north of the ash basin
exhibited higher concentrations than were observed in the shallow flow layer. No
exceedances of cobalt were detected in wells screened within the bedrock flow
layer. Total and dissolved concentrations were generally consistent in each
sample.
• Iron: 308 pg/L to 84,000 pg/L; 21/74
o Iron exceeded the 2L Standard in several wells screened in the shallow flow
layer located north, east, and west of the ash basin. Exceedances of iron were
also exhibited in the shallow layer in wells northwest and southeast of the ash
landfill area. Exceedances of iron in the deep flow layer were more frequent
along the northwestern and northern portions of the ash basin as well areas
23

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
west, north and northeast of the structural fill. An exceedance of iron in the
bedrock flow layer was limited to one well (GWA-16BR) located southwest of the
ash basin. Total and dissolved concentrations were generally inconsistent for a
majority of samples in the shallow and deep flow layer.
• Manganese: 308 pg/L to 84,000 tag/L; 35/74
o Manganese exceeded the 2L Standard in the shallow and deep flow layers in
wells across the BCSS site. The frequency of exceedances and concentrations
were generally consistent in both the shallow and deep flow layer. No
exceedances of manganese were detected in the bedrock flow layer. Total and
dissolved concentrations were generally consistent across the sample set except
for shallow flow layer well AB-2S which exhibited total and dissolved
concentration of 555 pg/L and 73 pg/L, respectively.
Mercury: No exceedances in groundwater
Nickel: No exceedances in groundwater
• Selenium: 24.8 pg/L to 55.5 pg/L; 3/74
o Selenium exceeded the 2L Standard in GWA-10S and GWA-19S two wells
screened within the shallow flow layer and in AB-1 D screened within the deep
flow layer. There were no exceedances for selenium in wells screened within the
bedrock flow layer. The wells screened in the shallow flow layer were located
west of the ash basin. Total and dissolved concentrations were generally
consistent across the sample set.
• Sulfate: 313,000 pg/L to 881,000 pg/L; 2/74
o Sulfate exceeded the 2L Standard in one well (GWA-23S) screened within the
shallow flow layer and one well (GWA-23D) within the deep flow layer. These
wells are located sidegradient and west of the structural fill. No exceedances for
sulfate were detected in wells screened within the bedrock flow layer.
• Thallium: 0.22 tag/L to 1.5 pg/L; 5/74
o Thallium exceeded the IMAC in GWA-6S, GWA-10S, GWA-11S, and GWA-19S
wells screened within the shallow flow layer. Three of these wells are located
northwest of the ash basin. Thallium exceeded the IMAC in one well (MW-103D)
screened within the deep flow layer. There were no exceedances for thallium in
wells screened within the bedrock flow layer.
TDS: 554,000 pg/L to 1,230,000 pg/L; 8/74
o TDS exceeded the 2L Standard in GWA-23S, AB-1 S, and A13-3S screened within
the shallow flow layer and GWA-20D, GWA-23D, AB-1 D, AB-21D, and AB-3D
screened within the deep flow layer. All of these wells are located north of the

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
ash basin and west of the structural fill. No TDS concentrations were detected in
wells screened within the bedrock flow layer.
• Vanadium: 0.34 pg/L to 13.3 pg/L; 43/74
o Vanadium exceeded the IMAC in the shallow, deep and bedrock layers in wells
across the BCSS site, including background wells. Total and dissolved
concentrations were generally consistent across the sample set.
• Zinc: No exceedances in groundwater.
The pH was measured outside of the range specified in 2L (6.5-8.5 SU) in the shallow, deep,
and bedrock flow layers across the BCSS site. However, as discussed in Section 1.3.4, this can
be expected in the Piedmont Province of North Carolina.
The horizontal extent of exceedances is presented in the form of isoconcentration figures
(Figures 3-4.1 through 3-4.45). The vertical extent of boron is presented on applicable cross
sections (Figures 3-5.1 through 3-5.13). In addition, cross sections show hydrostratigraphic
layers, rock lithology, rock core recovery (REC) and rock quality designation (RQD; a measure
of rock mass discontinuities/fracturing) in response to comments received from NCDEQ.
The following monitoring wells were sampled with turbidity greater than 10 NTU during Round 5:
• AB-1 S (32.1 NTU)
• A13-2S (685 NTU)
• GWA-12S (29.6 NTU)
• GWA-2S (75.25 NTU)
• MW-104D (41.22 NTU)
Given that high turbidity can result in increased COI concentrations, groundwater quality data
obtained from these wells during Round 5 sampling must be qualified.
3.2.2.4 ROUND 5 GROUNDWATER RESULTS WEST OF MIDDLETON LOOP ROAD
To address the extent of exceedances between the ash basin and Middleton Loop Road and
west of Middleton Loop Road, monitoring wells GWA-24D, GWA-18S/D, and GWA-16BR were
installed and sampled as part of the Round 5 sampling event. The following exceedances of the
2L Standard, IMAC, or DHHS HSL were observed in one or more wells: antimony, chromium,
cobalt, hexavalent chromium, iron, manganese, and vanadium. Monitoring wells GWA-24S,
GWA-913R, GWA-2513R, and GWA-26S/D/BR were sampled as part of the Round 6 sampling
event for this evaluation; however, Round 6 sampling results were not available in time for
inclusion in this report.
3.2.2.5 ROUND 5 GROUNDWATER RESULTS OF AREA OF INTEREST
To address the extent of exceedances within the AOI, monitoring wells GWA-19S/D, GWA-20D,
and GWA-21 S/D were installed and sampled as part of the Round 5 event. Monitoring wells
GWA-20S/BR and GWA-27S/D/BR were sampled as part of the Round 6 sampling event for this
evaluation and preliminary lab reports (i.e., prior to complete data validation) were utilized as
part of the accelerated remediation effort at the BCSS site with the following observations:

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 3 — ADDITIONAL ASSESSMENT
• Exceedances between the ash basin and the 2.23-acre parcel (not owned by Duke
Energy) — Boron exceedances were observed in shallow and deep wells located
between the ash basin and the 2.23-acre parcel not owned by Duke Energy (GWA-20S
and GWA-20D), but not in the bedrock well GWA-20BR. Arsenic was reported above the
2L Standard in the deep and bedrock wells at this location. Other indicator constituents
such as chloride and TDS were reported at concentrations that exceeded 2L Standards
in the shallow and deep wells, but not in the bedrock well.
• West of the 2.23-acre parcel (on Duke Energy property) — Boron exceeded the 2L
Standard in the deep well (GWA-27D); however, boron did not exceed the 2L Standard
in the shallow well (GWA-27S) and was not detected in the bedrock well (GWA-27BR).
Chloride and TDS were also reported at concentrations that exceeded the 2L Standards
in the deep well (GWA-27D), but not in the shallow or bedrock wells at this location.
• Further west-southwest of GWA-27S/D/BR — Boron and selenium exceedances of the
2L Standards were observed in GWA-19S. Exceedances of the 2L Standards in GWA-
19D included iron and chromium, which were not reported at higher concentrations
upgradient between this well pair and the ash basin, and could have been a result of
turbidity. No field parameter data were available for the GWA-19D sample as part of this
evaluation.
• GWA-10S — Selenium exceeded the 2L Standard at this location in March and May
2016, but not in July and October 2015.
• Other constituents, such as antimony, beryllium, chromium, cobalt, hexavalent
chromium, iron, manganese, thallium, and vanadium exceeded the 2L Standard, IMAC,
or DHHS HSL in wells within the AOI. pH values were measured above 10 SU in wells
GWA-10D, GWA-16D, GWA-16BR, and GWA-27BR.
3.2.2.6 COMPARISON OF POREWATER AND GROUNDWATER RESULTS
Based upon review of data collected during Round 5 sampling, there was no discernable trend
in comparison of the COI concentrations in the porewater versus COI concentrations for
groundwater in wells screened within the shallow flow layer. However, the majority of
groundwater COls that are likely attributable to the source areas at the BCSS site were
observed in the general areas: north, northwest, and west of the ash basin, west of the
structural fill, and beneath the chemical pond and the ash basin.
Piper diagrams presented in the CSA report provided evidence of mixing ash basin porewater
and groundwater, and Round 5 analytical results are consistent with previous presentations. In
general, the ionic composition of groundwater and surface water at the BCSS site is
predominantly rich in calcium/magnesium. Piper diagrams with cation -anion balance differences
< 10% are presented in Figures 3-6.1 through 3-6.4. In addition, overall cation -anion balance
differences are summarized in Table 3-5.
26

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 4 — BACKGROUND CONCENTRATIONS
Section 4 — Background Concentrations
Presentation of site -specific PPBCs was included in the CAP Part 1 report and is pending
refinement as the required minimum number of additional sampling results become available.
Regulations providing North Carolina groundwater quality standards are provided in T15A
NCAC 02L .0202. Section (b)(3) of the regulation provides that:
Where naturally occurring substances exceed the established standard, the standard shall
be the naturally occurring concentration as determined by the Director.
The reference background concentrations determined by the methodology described below will
be submitted to the NCDEQ DWR as the proposed naturally occurring site background
concentrations for the specific constituents. A site -specific report documenting the procedures,
evaluations, and calculation will be prepared and submitted to DEQ.
4.1 Methodology
As stated in the USEPA (USEPA 2009) (Unified Guidance):
The Unified Guidance recommends that a minimum of at least 8 to 10
independent background observations be collected before running most
statistical tests. Although still a small sample size by statistical standards, these
levels allow for minimally acceptable estimates of variability and evaluation of
trend and goodness -of fit. However, this recommendation should be considered
a temporary minimum until additional background sampling can be conducted
and the background sample size enlarged.10
One the required minimum number of samples are available, HDR will calculate PPBCs utilizing
the appropriate methods in the Unified Guidance, the USEPA ProUCL software, and guidance
found in the North Carolina Division of Water Quality (NCDWQ) technical assistance document
Evaluating Metals in Groundwater at DWQ Permitted Facilities.
This process will also follow HDR's proposed method to establish reference background
concentrations for constituents according to the Environmental Protection Agency's Hazardous
and Solid Waste Management System; Disposal of Coal Combustion Residuals from Electric
Utilities; Final Rule (EPA CCR)." The proposed method will be developed in consultation with
Synterra, Duke Energy's groundwater assessment consultant for Duke Energy Progress sites,
to ensure consistency in approach.
10 U.S. Environmental Protection Agency (USEPA) Unified Guidance (USEPA 2009), 5.2.1 Selecting Monitoring
Constituents and Adequate Sample Sizes
11 HDR modified its earlier methods to establish reference background concentration so that both state and federal
regulations are comparable. Having similar processes to address the two sets of regulations will minimize confusion.
27

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 4 — BACKGROUND CONCENTRATIONS
As recommended by the USEPA Unified Guidance, HDR will calculate the 95 percent upper
prediction limits (UPL95) as the proposed reference background concentration value for each
constituent at the BCSS site.12
HDR will calculate UPL95 values for each of the constituents using their respective
concentrations observed in the samples taken from the set of site -specific background wells
once a minimum of eight observations per constituent are available. Samples will not be used to
develop reference background concentrations whenever turbidity is 10 NTU or greater. Only
non -filtered results will be utilized. HDR will review and evaluate the corresponding filtered
results; however, they will not be used for compliance purposes at this time.
The data across the background wells will be pooled prior to estimating the reference
background concentration using the UPL95.
When implementing this approach, HDR will consider that the background wells are screened in
different hydrostratigraphic units (shallow, transition zone, or bedrock). While there are
differences as described, the fundamental assumption will be that the constituent concentrations
sampled at these background wells, when pooled, will serve as an estimate of overall well field
conditions for a given constituent. HDR will test this assumption using statistical methods and if
distinct sub -groups exist, separate background concentrations for each distinct sub -group of
wells by hydrostratigraphic unit (shallow, transition zone, and bedrock) will be calculated.
The methodology used to calculate upper prediction limits (UPLs) for the constituents will be
generally completed in three parts as follows:
1. Analyze Preliminary Data
2. Determine Differences Across Sub -Groups
3. Develop Background Threshold Values (UPLs)
Part 1 of the process includes the preliminary data analyses used to assess and transform the
data where necessary such that the data can be used to calculate UPLs. Statistical methods will
used to evaluate outliers, serial correlation, seasonality, spatial variability, trends, and
appropriateness of the period of record (sampling period).
Part 2 of the process includes describing the approach to test for sub -group differences. Types
of sub -groups to test include seasonal sub -groups (winter, spring, summer, and fall) and well
class sub -groups (bedrock, shallow, or deep). If the groups are statistically different after testing,
the same steps described in Part 1 can be applied to the partitioned data to better understand
the distribution of the samples within a sub -group for each constituent. The reference
12 There are different methods that can be used to estimate the reference background concentrations such as the
UPL and the upper tolerance limit (UTL). HDR selected the UPL as it is the statistic recommended by the USEPA
Unified Guidance (page 2-15). The Unified Guidance recommends the UPL over the UTL for the following reasons,
(1). The ability to estimate a UTL which can control for Type I error rates when simultaneously testing an exact
number of multiple future or independent observations is not as precise as when estimating the appropriate UPL. (2)
The mathematical underpinnings of UPLs under re -testing strategies are well established, while those for re -testing
with tolerance limits are not. Re -testing strategies are now encouraged and sometimes required under assessment
monitoring situations. (3) Statistically, the two limits are similar, especially under normal assumptions.
28

Duke Energy Carolinas, LLC I CSA Supplement 2 ���
Belews Creek Steam Station Ash Basin
SECTION 4 — BACKGROUND CONCENTRATIONS
background concentration values using the UPL95 for a constituent will be produced for each
sub -group of samples, provided the sub -groups represent distinct populations.
Part 3 of the process involves describing the statistical analyses and presenting the resulting
background threshold values (UPLs) for each constituent.
Observation for Background Wells
Currently, the BCSS site has the following number of usable observations at background wells
for implementation of the background concentration methodology described in Section 4.1:
• BG-1S (CSA Monitoring Well) — 0 observations
• BG-1 D (CSA Monitoring Well) — 6 observations
• BG-2S (CSA Monitoring Well) — 6 observations
• BG-21D (CSA Monitoring Well) — 6 observations
• BG-2BR (CSA Monitoring Well) — 6 observations
• BG-3S (CSA Monitoring Well) — 5 observations
• BG-31D (CSA Monitoring Well) — 5 observations
• MW-202BR (CSA Monitoring Well) — 6 observations
• MW-202S (Compliance Monitoring Well) — 19 observations
• MW-202D (Compliance Monitoring Well) — 14 observations
• BC-23A (FGD Landfill Monitoring Well) — 3 observations
• BC-28 (FGD Landfill Monitoring Well) — 3 observations
• CRW-17 (Craig Road Landfill Monitoring Well) — 2 observations
• MW-3 (Pine Hall Road Landfill Monitoring Well) — 2 observations
It is expected that with interim monitoring implementation, the BCSS site will have the
appropriate number of data points to perform the calculation of UPL95s. HDR is considering
alternatives that will provide the required number of sample events and will provide an update
on that evaluation at a later date.

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 5 — ANTICIPATED ADDITIONAL ASSESSMENT ACTIVITIES
Section 5 — Anticipated Additional Assessment
Activities
Anticipated additional assessment activities are summarized below.
Proposed Additional Assessment Monitoring Wells
Based on review of site information and analytical data available at this time, there are several
locations at the site where additional groundwater assessment is warranted to refine delineation
of the vertical extent of groundwater impacts associated with potential coal ash -related
constituents. The following wells are currently planned for installation during Fall of 2016:
Proposed Additional
Location
Purpose
Approximate
Monitoring Wells
Monitoring Well
Depth(s) (ft.) i
A13-913RD
On dike at chemical
Evaluate possible extent of I
200
pond
exceedances in bedrock at AB-
9. This will also provide
additional BR data in south end
of ash basin.
_
GWA-1 BR
Northwest of dike
_
Evaluate possible extent of
125
exceedances downgradient and
West of accelerated
northwest of the dike.
Evaluate possible extent of
100
GWA-19BR
remediation area
exceedances at GWA-10 and
Northwest of ash
GWA-19 locations.
Evaluate possible extent of
125
GWA-20BR
basin
exceedances in bedrock at
GWA-20. This will also provide
additional BR data in south end
of ash basin.
GWA-24BR North of dike
Well will add additional BR well
75
to improve site characterization
data.
GWA-30S/D Northwest of dike
Evaluate possible extent of
50
exceedances west of GWA-
1S/D and northwest of dike.
80
GWA-31S/D Northwest and
Evaluate possible extent of
30
downgradient of
exceedances downgradient of
GWA-19S/D
GWA-19S/D.
50
GWA-32S/D North-northeast of
Evaluate possible extent of
50
abandoned voluntary
exceedances near previous
wells MW-103S/D
MW-103 location.
80
MW-104BR Southeast side of ash
Evaluate possible extent of
130
basin
exceedances southeast of the
ash basin and add additional
BR well to improve site
i characterization data.
30

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 5 — ANTICIPATED ADDITIONAL ASSESSMENT ACTIVITIES
Implementation of the Effectiveness Monitoring Plan
The effectiveness monitoring plan proposed in CAP Part 2 provided detailed information
regarding field activities to be performed during collection of groundwater, surface water, and
AOW samples associated with the ash basin, the chemical pond located within the southern
portion of the ash basin, and the closed Pine Hall Road Landfill at BCSS. The monitoring plan is
intended to evaluate the effectiveness of proposed corrective actions and address the need to
evaluate baseline conditions and seasonal variation in groundwater, surface water, and AOWs
at the BCSS site.
Duke Energy will implement the effectiveness monitoring plan in accordance with
recommendations provided in the CAP Part 2 report as well as subsequent discussions with
NCDEQ.

Duke Energy Carolinas, LLC I CSA Supplement 2 ��
Belews Creek Steam Station Ash Basin
SECTION 6 — RECOMMENDATIONS AND CONCLUSIONS
Section 6 — Recommendations and Conclusions
The following findings and conclusions have been developed from the information presented in
this CSA Supplement 2 report:
• The conclusion from the groundwater chemical signature evaluation is that water supply
wells in the vicinity of the BCSS facility are not impacted by CCR releases from the ash
basin.
• Groundwater monitoring results from Round 5 of sampling, including data from additional
assessment groundwater monitoring wells, indicate consistency with previous sampling
results, specifically the extent of impact to groundwater from ash basin -related
constituents (e.g., boron).
• NCDEQ requested installation of additional monitoring wells AB-1 BR, GWA-9BR, GWA-
16BR, GWA-24S/D, GWA-25BR, and GWA-26S/D/BR, which were completed.
• Groundwater exceedances of the 2L Standard for boron, sulfate, and TDS were
observed in wells GWA-23S/D and exceedances for boron in AOW S-9, indicating ash -
related impacts from the structural fill prior to capping in 2012.
• Groundwater exceedances of the 2L Standard, IMAC, or DHHS HSL for antimony,
arsenic, boron, chloride, cobalt, chromium, hexavalent chromium, iron, manganese,
selenium, thallium, TDS, and vanadium were observed in GWA-20S/D/BR and GWA-
27S/D/BR and are being evaluated as part of ongoing field investigations.
Based on the conclusions presented above, the following recommendations are offered:
• Refinement of PPBCs should be conducted once the minimum number (e.g., eight) of
viable observations per background well are available.
• Groundwater exceedances of the 2L Standard, IMAC, and/or NCDHHS HSL for
antimony, chromium, cobalt, hexavalent chromium, iron, manganese, and vanadium
were observed in monitoring wells between the ash basin and Middleton Loop Road and
west of Middleton Loop Road. The observed concentrations of these constituents in
some wells were higher than in wells in downgradient or background locations; however,
further evaluation is necessary to assess their presence as potentially source -related
and/or naturally occurring once additional data is available.
• Additional monitoring wells should be installed to refine the vertical and horizontal
delineation of groundwater exceedances near the chemical pond, west of the AOI,
northwest of the ash basin and dike, northwest and downgradient of GWA-19S/D, north
and northeast of the abandoned voluntary well MW-103S/D, and southeast of the ash
basin.
• Additional evaluation of groundwater results from GWA-22D will be considered with MW-
201 BR results upon review of Round 6 sampling data.
• Additional assessment activities in the Structural Fill area are recommended to identify
the source of exceedances indicated in GWA-23S/D.
• Duke Energy will implement the effectiveness monitoring plan in accordance with
recommendations provided in the CAP Part 2 report as well as subsequent discussions
with NCDEQ.

Figures

Tables

Appendix A
Background Monitoring Well
Boring Logs
F-j

al
Appendix B
Monitoring Well Boring Logs
Core Photos
F-j

Appendix C
Field Sampling Forms
Slug Test Report
F-j

Appendix D
Laboratory Report and
Chain -of -Custody Forms
Validation Report