NC0002468_SARP_Rev0_Narrative_20161201

SITE ANALYSIS AND REMOVAL PLAN
DAN RIVER STEAM STATION
REVISION 0
Prepared for
('DUKE
�7 ENERGY...
Duke Energy
550 South Tryon Street
Charlotte, North Carolina 28202
December 2016
Prepared by
IT
amec
�C
foster
wheeler
��O�Ii1/1/111�
Amec Foster Wheeler Environment & Infrastructure, Inc. oa�`�N CAAtoe�'or
r
Project No. 7810140065.09 o�`�'Q°••°* 6!'`•Z{ '
w
A i `� ��AL •s.
�III�/IsrltN�t`3�Q �l6

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

i

EXECUTIVE SUMMARY
Amec Foster Wheeler Environment and Infrastructure, Inc. (Amec Foster Wheeler) has
prepared this Site Analysis and Removal Plan (Removal Plan) in support of the proposed
closure of the Coal Combustion Residuals (CCR) Basins/surface impoundments (ash
management facilities) at the Dan River Steam Station located on the north side of the Dan
River in Eden, North Carolina. The purpose of this Removal Plan is to seek the North Carolina
Department of Environmental Quality’s (NCDEQ) concurrence with the Duke Energ y Carolinas,
LLC (Duke) plan for closure of the ash management facilities located at Dan River Steam
Station. This Removal Plan is submitted to NCDEQ on behalf of Duke. The work to be
performed in support of the closure of the ash management facilities is summarized in this
document, which is consistent with the requirements of the Hazardous and Solid Waste
Management System: Disposal of Coal Combustion Residuals from Electric Utilities Rule (CCR
Rule) (EPA, 2015) and the North Carolina Coal Ash Management Act (CAMA). This Removal
Plan is based on engineering and environmental factors minimizing the impacts to communities
and managing cost. The Drawing Set presented herein is subject to change in response to
actual site conditions encountered as work progresses. The closure option entails excavation of
CCR within the ash management facilities and placement in an on-site or an off-site permitted
landfill.
Duke is in the process of decommissioning the coal-fired generating facility at the Dan River
Steam Station property. Dan River Steam Station ash management facilities include the Primary
Ash Basin and Secondary Ash Basin. In addition to these ash basins, Duke will close two dry
CCR storage areas known as Ash Fill 1 and Ash Fill 2 (also referred to as Ash Stack 1 and Ash
Stack 2). Duke intends to construct a landfill on the Dan River Steam Station Property in the
footprint of Ash Fill 1. The estimated CCR volume in Ash Fill 1 is approximately 795,000 cubic
yards (CY) (approximately 950,000 tons-assuming a density of approximately 1.2 tons/CY). The
majority of Ash Fill 1 CCR will be placed in an off-site landfill, making way for construction of the
on-site landfill. The remaining CCR from the Primary Ash Basin, Secondary Ash Basin, and Ash
Fill 2 will be placed in the on-site landfill. The estimated CCR volume in the Primary Ash Basin
is approximately 1,012,000 CY (1,215,000 tons). The estimated CCR volume in the Secondary
Ash Basin is approximately 324,000 CY (390,000 tons). The estimated CCR volume in Ash Fill 2
is approximately 345,000 CY (415,000 tons).
Assessment activities for the Dan River facility were performed by HDR Engineering Inc. of the
Carolinas (HDR) and were reported in a Comprehensive Site Assessment (CSA) Report dated
August 14, 2015, a Corrective Action Plan (CAP) Part 1 dated November 12, 2015, and a CAP
Part 2 dated February 10, 2016. Assessment work included a source area assessment in the
Primary and Secondary Ash Basins, Ash Fills 1 and 2, and a total of nine ash basin and storage
area water seeps. Source area impact delineation including the collection of samples in
surrounding soil, partially weathered rock (PWR), bedrock, surface water, sediment and
groundwater. Results of assessment identified the following constituents of interest (COIs) in
soil: arsenic, boron, chromium, cobalt, iron, manganese, selenium and vanadium. Soil impacts
were delineated at the Dan River Steam Station with the exception of COIs in off-site areas
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

ii

north and east of Ash Fill 1. Beneath the basins, soil appeared to be limited to the uppermost
soil sample. COIs identified in groundwater included: antimony, arsenic, boron, cobalt, iron,
manganese, selenium, sulfate, thallium, total dissolved solids (TDS), and vanadium. Source
area groundwater impacts were generally found to be limited in extent, with the exception of Ash
Fill 1 where impacts extended vertically and horizontally north of the storage area. Groundwater
and surface water interaction was also identified east of the Secondary Cell. Surface water
COIs included copper, lead, aluminum, and arsenic in the eastern unnamed tributary that flows
into the Dan River. HDR attributed the source of copper to an off-site source, while remaining
COIs were likely attributable to the Dan River Steam Station.
Groundwater trend analysis was performed under the existing condition and excavation
scenario. Model results indicated that antimony, boron, cobalt, sulfate, thallium, and vanadium
would be greater than the 2L Standard and/or IMAC; and hexavalent chromium would be
greater than the DHHS HSL at the Dan River interface for both the existing condition and
excavation scenario. Several of the metals identified above the criteria were also reported
above the criteria in the background data set used. Models indicated that COI concentrations
would not be effectively reduced under the excavation scenario for the modeled period (2015 to
2115). Arsenic and selenium concentrations were predicted to be below the respective 2L
Standards at the Dan River interface for both the existing condition scenario and the excavation
scenario. Boron and sulfate were reduced to below the respective standard or IMAC under the
modeled excavation scenario.
Groundwater and surface water interaction modeling was performed by HDR to estimate
groundwater flow and constituent loading into adjacent surface water bodies. Mixing model
results predicted that water quality standards would be attained at the edge of the mixing zone
for all compounds with the exception of localized arsenic exceedances in the eastern unnamed
tributary that flows into the Dan River. In the Dan River, modeled calculated results were less
than the acute, chronic, and human health 2B Standards at the edge of the mixing zones.
A preliminary geotechnical evaluation was performed and is presented in this Removal Plan.
The results of the investigations indicate that the subsurface materials primarily consist of, from
top to bottom, CCR (within the ash management facilities) or Dike Fill (at the perimeters of the
ash management facilities), and Foundation Soils (residual soils consisting primarily of alluvium,
residuum, saprolite) sitting on bedrock. A PWR zone was encountered at the transition between
the residuum and the bedrock.
The closure of the ash management facilities will entail the following activities. CCR will be
excavated and placed in an off-site landfill while the on-site landfill is constructed. Once the on-
site landfill is operational, remaining CCR will be placed in the on-site landfill. The excavated
surface will be stabilized with permanent vegetation and will be maintained throughout the post-
closure period. This Removal Plan also presents a summary of the engineering evaluation and
analyses performed and a Construction Quality Assurance (CQA) Plan.
Ash Management Facilities closure will require several permits and are summarized in this
Removal Plan. The primary and Secondary CCR basins were operated as an integral part of the
facilities' wastewater and stormwater management system. Description of the existing
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

iii

stormwater and wastewater management facilities, as well as, provisions for stormwater and
wastewater management during and after CCR basin closure are provided in this removal plan.
An ash basin Post-Closure Operations Maintenance and Monitoring Plan is included with this
Removal Plan. Post-Closure groundwater monitoring requirements will be established in the
Groundwater Monitoring Plan, and will be submitted under separate cover as part of ongoing
CSA and CAP activities. This Removal Plan identifies estimated schedule milestones related to
basin closure and post-closure activities.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

iv

LIST OF ACRONYMS AND ABBREVIATIONS
Acronym/
Abbreviation Definition
CAMA Coal Ash Management Act
CAP Corrective Action Plan
CCP Coal Combustion Products
CCR Coal Combustion Residuals
CFR Code of Federal Regulations
COI Constituent of Interest
CPT Cone Penetrometer Testing
CQA Construction Quality Assurance
CSA Comprehensive Site Assessment
EPA United States Environmental Protection Agency
GQS Groundwater Quality Standards
fs Sleeve friction
H&H Hydrology and Hydraulic
IMACs Interim Maximum Allowable Concentrations
Kd Partition Coefficient
MCL Maximum Contaminant Level
NCAC North Carolina Administrative Code
NCDEQ North Carolina Department of Environmental Quality
NPDES National Pollutant Discharge Elimination System
POG Protection of Groundwater
PWR Partially Weathered Rock
qt Tip resistance
RCRA Resource Conservation and Recovery Act
Rf Friction ratio
SCM Site Conceptual Model
SPLP Synthetic Precipitation Leaching Procedure
SPT Standard Penetration Test
SSI Statistically Significant Increase
SWS Solid Waste Section
TCLP Toxicity Characteristic Leaching Procedure
TDS Total Dissolved Solids
Tsf
USGS
Tons per square foot
United States Geological Survey

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

v

RECORD OF REVISION
Revision
Number
Revision
Date
Section
Revised
Reason for
Revision Description of Revision
0 12/2016 N/A N/A Initial Issue
1
2

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

vi

TABLE OF CONTENTS
EXECUTIVE SUMMARY ............................................................................................................. i
LIST OF ACRONYMS AND ABBREVIATIONS ......................................................................... iv
RECORD OF REVISION ........................................................................................................... v

1. INTRODUCTION ............................................................................................................. 1
1.1 Site Analysis Removal Plan Objectives .............................................................................. 1
1.2 Report Organization ............................................................................................................ 1
2. GOVERNING REGULATIONS ........................................................................................ 2
2.1 Federal CCR Rules ............................................................................................................. 2
2.2 North Carolina ..................................................................................................................... 2
3. FACILITY DESCRIPTION AND EXISTING SITE FEATURES ........................................ 4
3.1 Surface Impoundment Description ...................................................................................... 4
3.1.1 Site History and Operations ................................................................................... 4
3.1.2 Estimated Volume of CCR Materials in Impoundments ........................................ 5
3.1.3 Description of Surface Impoundment Structural Integrity ...................................... 6
3.1.4 Sources of Discharges into Surface Impoundments.............................................. 9
3.1.5 Existing Liner System ............................................................................................ 9
3.1.6 Inspection and Monitoring Summary ..................................................................... 9
3.2 Site Maps .......................................................................................................................... 14
3.2.1 Summary of Existing CCR Impoundment Related Structures ............................. 14
3.2.2 Receptor Survey .................................................................................................. 17
3.2.3 Existing On-Site Landfills ..................................................................................... 18
3.3 Monitoring and Sampling Location Plan ........................................................................... 18
4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL
INVESTIGATIONS ........................................................................................................ 20
4.1 Hydrogeology and Geologic Descriptions ......................................................................... 20
4.1.1 Regional Geologic Setting ................................................................................... 20
4.1.2 Regional Hydrogeologic Setting........................................................................... 21
4.2 Stratigraphy of the Geologic Units Underlying Surface Impoundments ........................... 22
4.3 Hydraulic Conductivity Information ................................................................................... 22
4.4 Geotechnical Properties .................................................................................................... 23
4.4.1 Fill Material ........................................................................................................... 23
4.4.2 Ash ....................................................................................................................... 24
4.4.3 Residual Soils ...................................................................................................... 24
4.5 Chemical Analysis of Impoundment Water, CCR Materials and CCR Affected Soil ........ 25
4.5.1 Source Area(s) Characterization.......................................................................... 27
4.5.2 Soil, PWR and Bedrock Assessment ................................................................... 28
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

vii

4.5.3 Surface Water and Sediment Assessment .......................................................... 30
4.6 Historical Groundwater Sampling Results ........................................................................ 31
4.7 Groundwater Potentiometric Contour Maps ..................................................................... 34
4.8 Figures: Cross Sections Vertical and Horizontal Extent of CCR within the Impoundments
.......................................................................................................................................... 35
5. GROUNDWATER MODELING ANALYSIS................................................................... 36
5.1 Site Conceptual Model Predictions ................................................................................... 36
5.2 Groundwater Chemistry Effects ........................................................................................ 38
5.3 Groundwater Trend Analysis Methods .............................................................................. 38
6. BENEFICIAL USE AND FUTURE USE ........................................................................ 44
6.1 CCR Material Use ............................................................................................................. 44
6.2 Site Future Use ................................................................................................................. 44
7. CLOSURE DESIGN DOCUMENTS .............................................................................. 45
7.1 Engineering Evaluations and Analyses ............................................................................ 45
7.1.1 Freeboard During Dam Decommissioning ........................................................... 45
7.1.2 Stormwater Management During Interim Conditions ........................................... 46
7.1.3 Stormwater Management During Final Conditions .............................................. 46
7.2 Removal Plan Drawings .................................................................................................... 46
7.3 Construction Quality Assurance and Control Plan ............................................................ 47
8. MANAGEMENT OF WASTEWATER AND STORMWATER ........................................ 48
8.1 Stormwater Management .................................................................................................. 48
8.2 Wastewater Management ................................................................................................. 49
9. DESCRIPTION OF FINAL DISPOSITION OF CCR MATERIALS ................................. 50
10. APPLICABLE PERMITS FOR CLOSURE .................................................................... 51
10.1 Decommissioning Request and Approval ......................................................................... 51
11. POST-CLOSURE MONITORING AND CARE .............................................................. 52
11.1 Groundwater Monitoring Program ..................................................................................... 52
12. PROJECT MILESTONES AND COST ESTIMATES ..................................................... 53
12.1 Project Schedule ............................................................................................................... 53
12.2 Closure and Post-Closure Cost Estimate ......................................................................... 53
13. REFERENCED DOCUMENTS ...................................................................................... 54

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

viii

Tables
Table 2-1 Federal CCR Rule Closure Plan Requirements, Summary and Cross
Reference Table
Table 2-2 North Carolina CAMA Closure Plan Requirements, Summary and Cross
Reference Table
Table 3-1 Estimated Volume and Weight of CCR Materials
Table 4-1 Hydrostratigraphic Layer Properties - Horizontal Hydraulic Conductivity
Table 4-2 Hydrostratigraphic Layer Properties - Vertical Hydraulic Conductivity

Figures
Figure 1 Site Vicinity Map
Figure 2 Site Aerial Map – CCR Units
Figure 3 Site Aerial Map – Landfill Units

Appendices
Appendix A Ash Inventory Calculation
Appendix B Tables, Select Figures, Boring Logs, CPT Logs, and Laboratory Test Reports
from Phase 2 Reconstitution of Ash Basin Design Report
Appendix C Drawings - Dan River Dam Decommissioning Plan
Appendix D Select Tables and Figures from the Comprehensive Site Assessment Report,
Dan River Steam Station Ash Basin, August 14, 2015 (HDR, 2015a); the
Corrective Action Plan Part 1, Dan River Steam Station Ash Basin, November 12,
2015 (HDR, 2015b); and the Corrective Action Plan Part 2, Dan River Steam
Station Ash Basin, February 10, 2016 (HDR, 2016)
Appendix E Engineering Evaluations and Analyses - Dan River Decommissioning Plan
Appendix F Construction Quality Assurance Plan - Dan River Decommissioning Plan
Appendix G Post-Closure Operations Maintenance and Monitoring Plan
Appendix H Closure and Post-Closure Cost Estimates (to be added at a later date)

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

1
1. INTRODUCTION
Amec Foster Wheeler has prepared the following Site Analysis and Removal Plan (Removal
Plan) for the Duke Energy (Duke) Dan River Steam Station. The Dan River Steam Station is
located on the north side of the Dan River in Eden, Rockingham County, North Carolina,
approximately 35 miles north of Greensboro, North Carolina. The project location from a
regional context is illustrated on Figure 1.
Duke is in the process of decommissioning the coal-fired generating facility at the Dan River
Steam Station property. Ash management facility closure is being undertaken as part of the
overall station decommissioning efforts. Specifically, the Dan River Steam Station ash
management facilities include two ash basins known as the Primary Ash Basin and the
Secondary Ash Basin and two dry ash storage areas known as Ash Fill 1 and Ash Fill 2 (also
referred to as Ash Stack 1 and Ash Stack 2). The ash management facilities are shown on
Figure 2.
Duke intends to close the Primary and Secondary Ash Basins as well as Ash Fill 1 and Ash Fill
2. Both basins will be closed by removal of the coal ash for transport to an on-site or an off-site
landfill. The purpose of this document is to present the plan and objectives to achieve closure for
the Dan River Steam Station ash management facilities and meet the requirements of applicable
Federal and State rules.
1.1 Site Analysis Removal Plan Objectives
This Removal Plan has been prepared to address closure through ash removal and placement
in an on-site landfill containment system in accordance with applicable regulations, including the
Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals from
Electric Utilities Rule (CCR Rule) (EPA, 2015) and the North Carolina Coal Ash Management
Act (CAMA) for closure of CCR surface impoundments.
1.2 Report Organization
Although the Dan River CCR surface impoundments are specifically subject to the closure
requirements set out in Part II, Sections 3.(b) and 3.(c) of CAMA (and not N.C.G.S. § 130A-
309.214), for purposes of consistency with the closure plans for those non-high-priority Duke
facilities to which N.C.G.S. § 130A-309.214 applies, this Removal Plan is structured to follow
generally the closure plan elements set forth in N.C.G.S. § 130A-309.214(a)(4).
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

2
2. GOVERNING REGULATIONS
2.1 Federal CCR Rules
The CCR Rule was published in the Federal Register on April 17, 2015. These rules regulate
CCR as a nonhazardous waste under Subtitle D of the Resource Conservation and Recovery
Act (RCRA). The effective date of the rule is October 19, 2015.
Written closure plan requirements are defined in Federal CCR Rule §257.102(b)(1)(i-vi) and are
summarized in Table 2-1. Table 2-1 provides a cross reference between each regulatory closure
plan requirement and the corresponding Removal Plan section(s) where that requirement is
addressed.
The Federal CCR Rules also require that a history of construction be developed for each CCR
unit as described in Federal CCR Rule §257.73(c)(1)(i-xii). Federal CCR Rule § 257.105, record
keeping requirements, requires the history of construction be maintained in a written operating
record and be made available on a publicly accessible internet site. A History of Construction
Report (Amec Foster Wheeler, 2016c) has been developed to serve the purposes of being a
primary source of information reported in the Removal Plan and to satisfy these record keeping
requirements.
2.2 North Carolina
In August of 2014, the North Carolina General Assembly passed Senate Bill (S.B.) 729 known
as CAMA, which lists specific regulatory requirements for CCR surface impoundment closure.
For the Dan River Steam Station, “surface impoundment” as defined in N.C.G.S. §130A-
309.201(6) was interpreted to include only the Primary Ash Basin and Secondary Ash Basin.
However, closure of Ash Fill 1 and Ash Fill 2 will be implemented in conjunction with ash basin
closure. The CAMA closure plan requirements are summarized in Table 2-2 for reference.
CAMA deems Dan River a “high priority” site and specifically requires closure by August 1,
2019; however, dam decommissioning and final grading of the former ash basin areas and
completion of corrective action to restore groundwater quality, if needed, as provided in
N.C.G.S. § 130A-309.204, may extend beyond this date.)
The closure plan requirements are set out for non-high-priority sites in N.C.G.S. § 130A-
309.214(a)(4) and summarized in Table 2-2 of this document for reference. Although not
specifically applicable to Dan River, which is a high-priority site required to close pursuant to
Part II, Sections 3.(b) and 3.(c) of CAMA, this Removal Plan relies on N.C.G.S. § 130A-
309.214(a)(4) of solely to inform its organization. Specifically, this Removal Plan includes the
following:
 Facility description
 Site maps
 Hydrogeologic, geologic, geotechnical characterization results
 Groundwater potentiometric maps and extent of contaminants of concern
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

3
 Groundwater modeling
 Description of beneficial reuse plans
 Removal Plan drawings, design documents, and specifications
 Description of the construction quality assurance and quality control program
 Description of wastewater disposal and stormwater management provisions
 Description of how the final disposition of CCR will be provided
 List of applicable permits to complete closure
 Description of post-closure monitoring and care plans
 Estimated closure and post-closure milestone dates
 Estimated costs of assessment, corrective action, closure and post-closure care
 Description of future site use
In addition to the closure pathway and closure plan requirements, CAMA outlined groundwater
assessment and corrective action requirements summarized as follows:
 Submit Groundwater Assessment Plans by December 14, 2014;
 Within 180 days of Groundwater Assessment Plan approval, complete groundwater
assessment and submit a Groundwater Assessment Report;
 Provide a corrective action plan (if required) within 90 days (and no later than 180 days)
of Groundwater Assessment Report completion.
The groundwater assessment and corrective action activities for the Dan River Steam Station
facility are in progress and being developed by HDR Engineering Inc. of the Carolinas (HDR).
The Comprehensive Site Assessment (CSA) Report for the Dan River Steam Station was
completed on August 14, 2015 and is herein referenced as CSA Report (HDR, 2015a).
Information from the CSA Report has been incorporated into this Removal Plan. HDR noted that
a CSA Report supplement will be developed following a second groundwater sampling event.
Duke received permission from NCDEQ to submit a Corrective Action Plan (CAP) in two
phases. The first phase, herein referenced as the CAP Part 1 (HDR, 2015b), was submitted on
November 12, 2015 and includes background information, a brief summary of the CSA findings,
a description of site geology and hydrogeology, a summary of the previously completed receptor
survey, a description of NCAC Subchapter 2L Groundwater Standards (2L Standards) and
NCAC Subchapter 2B Surface Water Standards (2B Standards) exceedances, proposed site-
specific groundwater background concentrations, a detailed description of the site conceptual
model, and groundwater flow and transport modeling. The second phase, “CAP Part 2” (HDR,
2016), was submitted on February 10, 2016 and included the risk assessment, alternative
methods for achieving restoration, conceptual plans for recommended corrective actions,
implementation schedule, and a plan for future monitoring and reporting.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

4
3. FACILITY DESCRIPTION AND EXISTING SITE FEATURES
3.1 Surface Impoundment Description
3.1.1 Site History and Operations
The Dan River Steam Station located on the Dan River near Eden, in Rockingham County,
North Carolina began commercial operation as a coal-fired power generation facility with two (2)
coal-fired units, Unit 1 and Unit 2 coming online in 1949 and 1950, respectively. By 1955, a third
coal-fired unit was added. By 1968, the Steam Station also had three (3) smaller combustion
turbines in operation.
By April 1, 2012, the three (3) coal-fired units and three (3) smaller combustion turbine units
were retired. By December 2012, the new Dan River Combined Cycle Plant was constructed on
the property just north of the former Steam Station. By the end of 2012, the new Combined
Cycle Plant that burns natural gas came online. Decommissioning of the remaining Steam
Station components is currently under progress.
CCR material consisting primarily of fly ash and bottom ash (hereafter referred to as “ash”) was
produced and disposed of at the Dan River Steam Station facility until the coal-fired units were
retired in 2012. CCR material created during operation of the coal-fired facility was deposited
within ash basins by hydraulic sluicing operations.
Initial operation of the Dan River Steam Station began in 1949. Ash from operations from 1949
to 1956 went into a Lay of Land Area (LOLA). Few documents exist detailing this operation,
however, the first purpose-built ash basin was constructed over that preexisting LOLA. It was
constructed in 1956 for the purpose of receiving hydraulically sluiced fly ash and bottom ash for
storage and disposal. Several modifications to the basin were made, which included the
development of the Primary Ash Basin and Secondary Ash Basin. These ash basins are located
east of the plant site and adjacent to the Dan River as shown on Figure 2. In addition, on-site
ash management facilities include two dry ash storage areas located to the north (uphill) of the
ash basins and known as Ash Fill 1 and Ash Fill 2 also shown on Figure 2.
The primary construction history of the on-site ash management facilities is summarized below:
 1949 to 1956: Ash from the plant went into a LOLA
 1956: The first ash basin was constructed to an approximate crest elevation of 523.5 feet
by constructing earth fill around the basin perimeter. This first basin was built over the
previous LOLA
 1968 – 1969: The ash storage basin was expanded to the current footprint and the
embankments were raised to an approximate elevation of 530 feet.
 1976 – 1977: The intermediate dike was constructed to stage sluicing by subdividing the
basin into the Primary and Secondary Ash Basins. The Intermediate Dike and new Primary
Ash Basin embankments were constructed to approximate elevation 540 feet.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

5
 1980: dikes, referenced as the dredge dikes, were constructed north of the Primary and
Secondary Ash Basins, creating a dredge basin and two dry storage areas known as Ash
Fill 1 and Ash Fill 2.
 2011: Inverted rock filters were installed along portions of the Primary and Secondary
Basin embankments.
 April 1, 2013: Sluicing ceased when the coal-fired generation of electricity at Dan River
was ended.
 February 2014: The 48-inch diameter storm water pipe underneath the Primary Ash Basin
failed. Both storm water pipes passing beneath the Primary Ash Basin were subsequently
grouted. The embankment was lowered at a location on the north side of the Primary Ash
Basin during response efforts related to the pipe collapse. The lowered area was rebuilt
in July and August of 2014 to elevation 532 feet, eight feet lower than the design crest
elevation of elevation 540 feet.
 August 2016: The Secondary Ash Basin operating water level was lowered to elevation
515 feet. This was accomplished through dredging ash from the Secondary Ash Basin
into a dredge cell located in the Primary Ash Basin.
3.1.2 Estimated Volume of CCR Materials in Impoundments
Historical and current topographic and bathymetric data was utilized to estimate top of ash and
bottom of ash grades for the Primary and Secondary Ash Basins, Ash Fill 1, and Ash Fill 2, and
quantity of soil stockpile on Ash Fill 1. AutoCAD Civil 3D was used to estimate in-situ volumes
of ash and soil stockpile.
The material in the Primary and Secondary Ash Basins generally consists of sluiced fly ash and
bottom ash, while the material in Ash Fills 1 and 2 includes ash placed as fill, cover soils, and
additional soil stockpiled on top of Ash Fill 1. The complete Ash Inventory Calculation is
included as Appendix A and summarized below:

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

6

Table 3-1 Estimated Volume and Weight of CCR Materials
Location Estimated CCR Volume
(cy)
Estimated Moist Weight*
(tons)
Ash Fill 1 795,406 954,487
Ash Fill 2 345,490 414,588
Subtotal Ash Fills 1,140,896 1,369,075

Primary Ash Basin 1,012,267 1,214,720
Secondary Ash Basin 323,871 388,645
Subtotal Ash Basin 1,336,138 1,603,365

Totals 2,477,034 2,972,440
Notes:
* – Estimated Moist Weight is calculated using a factor of 1.2 tons/cubic yard to account for moisture content in ash.
Maintenance dredging of the Secondary Ash Basin was completed in on June 28, 2016 with an
estimated 41,588 cubic yards (CY) of ash moved to the Primary Ash Basin.
3.1.3 Description of Surface Impoundment Structural Integrity
In late 2014, Amec Foster Wheeler completed field investigations, data review and analyses for
the Dan River Primary Ash Basin and Secondary Ash Basin, associated dams (including the
Intermediate Dike), and associated outlet structures. The structural integrity evaluation for the
current conditions of these features is contained in the Dan River Steam Station Phase 2
Reconstitution of Ash Basin Design Report (Amec Foster Wheeler, 2016d). Note that North
Carolina Dam Safety identifies the Primary Ash Basin as State ID ROCKI-237 and the
Secondary Ash Basin as State ID ROCKI-238. The Intermediate Dike does not have a State ID.
Key findings from the Dan River Steam Station Phase 2 Reconstitution of Ash Basin Design
Report are summarized below:
 Geotechnical analyses indicate:
o Results of liquefaction screening level analyses indicated that the Primary and
Secondary Ash Basin foundations would not be subject to liquefaction based on the
estimated seismicity for the design seismic event with a 2,500 year return period.
o Liquefaction screening results indicated that zones of impounded ash fill within the
ash basins exhibit liquefaction factors of safety less than 1.1, and are therefore
potentially susceptible to liquefaction based on the estimated seismicity for the
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

7
design seismic event with a 2,500 year return period. Of particular note are zones of
ash fill at depths of 24 to 34 feet below the ground surface located underneath the
1977-era expansion embankment fill.
o Liquefaction screening results indicated that zones within the Secondary Ash Basin
embankment exhibit liquefaction factors of safety less than 1.1. Therefore, the
embankment materials are potentially susceptible to liquefaction based on the
estimated seismicity for the design seismic event with a 2,500 year return period.
The susceptible zones are composed of embankment fill at depths ranging from 19
to 30 feet below the ground surface.
o The Secondary Ash Basin embankment was further evaluated for liquefaction
susceptibility using the computer program FLAC Version 7. In addition to the
potentially liquefiable embankment soils identified in the liquefaction screening
analyses, the FLAC analyses indicated liquefaction in the foundation soils. FLAC
results indicate that a 5 to 10-foot layer of foundation soils (sandy alluvial soils)
immediately above the PWR may be subject to concentration of seismic cyclic
stresses high enough to indicate liquefaction of these materials. This is due to the
relatively high contrast in the shear wave velocity from the foundation soils to the
underlying PWR and rock.
o For the static, steady-state seepage load case, slope stability factors of safety
meeting or exceeding the required value of 1.5 were calculated for the Primary Ash
Basin, the Intermediate Dike and the Secondary Ash Basin based on the water levels
existing in August 2016.
o For the flood surcharge load case, slope stability factors of safety meeting or
exceeding the required value of 1.4 were calculated for the Secondary Ash Basin
based on the water levels existing in August 2016. This load case was not
considered applicable to the Primary and Intermediate embankments.
o For the temporary loading case, slope stability factors of safety meeting or exceeding
the required value of 1.3 were calculated for the Primary Ash Basin, the Intermediate
Dike, and the Secondary Ash Basin Dam based on application of a uniform
surcharge load of 1,000 pounds per square foot.
o For the rapid drawdown load case, slope stability factors of safety meeting or
exceeding the required minimum value of 1.2 were obtained for the models
representing the Primary Ash Basin, the Intermediate Dike and the Secondary Ash
Basin, with the exception of the downstream slope of Section E-E in the Secondary
Ash Basin. The factor of safety for the downstream slope of Section E-E is 1.15.
Given the very conservative peak flood river level that was used, this factor of safety
is judged to meet the required criterion of 1.2.
o For the pseudo-static load case, slope stability factors of safety meeting or
exceeding the required minimum value of 1.0 were obtained for the Primary Ash
Basin. Conventionally, the pseudo-static analysis is performed only if liquefaction of
the soil profile is not anticipated, otherwise a post-seismic analysis is performed. As
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

8
requested by Duke, however, the pseudo-static analyses were performed for the
Intermediate Dike and the Secondary Ash Basin where there is a potential for
liquefaction. For these pseudo-static analyses, 80 percent of full static undrained
shear strengths were used for non-liquefiable soils, and the undrained residual shear
strengths were used for liquefiable soils. Considering the pseudo-static analyses
performed for the post-liquefaction condition uses both a seismic load and undrained
residual shear strengths for liquefied materials, the resulting factor of safety is
considered to be very conservative.
o The results of the post-seismic analyses meet or exceed the required minimum value
of 1.2 for the models representing the Primary Ash Basin, the Intermediate Dike, and
the Secondary Ash Basin. Based on the results of dynamic deformation analysis for
Section C-C using FLAC software, the magnitude of expected deformations should
be acceptable and the dams should perform adequately during the design
earthquake and maintain containment.
o Provided the Primary and Secondary Ash Basin water levels remain at or near the
August 2016 levels of 502.5 and 515 feet, respectively, the groundwater levels within
the dam structures should not support concerns regarding seepage issues such as
internal erosion, piping, or heave associated with the dam structures themselves.
Piping along conduits penetrating the dam structures of ash basins should be
considered an ongoing concern and monitored appropriately.
 Structural analyses indicate:
o The riser for the Primary Ash Basin was not evaluated since failure of the riser would
not result in discharge of ash from the basins. Water is not impounded in the Primary
Ash Basin and any discharge through the outlet pipe enters the Secondary Ash
Basin.
o The Secondary Ash Basin riser appeared to satisfy the criteria for moment
equilibrium for the unusual load Operational Basis Earthquake (OBE) condition, but
failed to satisfy criteria for moment equilibrium for the extreme load Maximum Design
Earthquake (MDE) condition. The riser at the Secondary Ash Basins appeared to
satisfy criteria for sliding stability for the OBE and MDE conditions. The riser at the
Secondary Ash Basin appeared to satisfy criteria for floatation for the usual load,
OBE, and MDE conditions. Under the MDE condition, the risers at the Secondary
Ash Basin appeared to have overturning issues.
o The riser and the stop logs for the riser at the Secondary Ash Basin were not
evaluated for strength due to lack of information regarding the reinforcing steel within
the concrete members.
 Hydrologic and Hydraulic analyses indicate:
o The previous analyses performed in 2014 for the Primary and Secondary Ash Basins
were updated in January 2015 using more recent topographic data. The more recent
topographic data indicated that a portion of the crest of the Primary Ash Basin dam
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

9
was at elevation 532 feet, the same as used in the 2014 analysis. The more recent
topographic data indicated the lowest crest elevation of the Secondary Ash Basin
dam wass at elevation 528.52 feet, which wass lower than the design elevation (530
feet) used in the 2014 analysis. Note, this topographic data also indicated the
majority of the crest elevations exceed 529 feet.
o The Primary Ash Basin will have 0.4 feet of freeboard to the locally lowered dam
section at elevation 532 feet based on the hydraulic capacity analysis and will safely
pass the inflow design flow (IDF) storm (3/4 Probable Maximum Precipitation). Since
the remainder of the dam crest is at an approximate elevation 540 feet, it will shield
the peak water surface from direct wind, and it is likely that wind-generated wave
runup and setup will not be a factor.
o The Secondary Ash Basin will have 5.56 feet of freeboard to the current top of dam
elevation of 528.52 feet, with the stop log elevation lowered to 515.5 feet based on
the hydraulic capacity analysis and will safely pass the (IDF) storm (3/4 Probable
Maximum Precipitation). Since the Secondary Ash Basin is partially shielded from
direct wind action by the Primary Ash Basin Dike and the Ash Stack (dry ash storage
areas), it is likely that wind-generated wave runup and setup will not be a factor.
o Both the Primary and Secondary Ash Basins discharge 80 percent of the inflow from
the design storm within 15 days of the peak for the design storm.
Tables and select figures (Figures 3 through 15) from the Phase 2 Reconstitution of Ash Basin
Design Report have been included as Appendix B.
3.1.4 Sources of Discharges into Surface Impoundments
The ash basins were operated as an integral part of the site’s wastewater treatment system.
During operation of the Dan River Steam Station coal-fired units, the ash basin received
variable inflows from the ash removal system, station yard drain sump, stormwater flows, and
other permitted flows. The coal ash was sluiced to the southwest corner of the Primary Basin on
a variable basis. For the purpose of surface water management, Ash Fill 1and Ash Fill 2 are
located within the ash basin system. Stormwater runoff from the ash fills is contained within the
overall ash stormwater system and flows to the Secondary Ash Basin.
3.1.5 Existing Liner System
Based on historical information, no liner system was installed under the Dan River Steam
Station ash management facilities, i.e. the Primary Ash Basin, Secondary Ash Basin, Ash Fill 1,
and Ash Fill 2.
3.1.6 Inspection and Monitoring Summary
Weekly, monthly and annual inspections of the ash management facilities (Primary Ash Basin,
Secondary Ash Basin, Ash Fill 1, and Ash Fill 2) at the Dan River Steam Station have been
initiated in response to the North Carolina CAMA and CCR Rule effective in 2015.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

10
Independent third-party inspections are performed once every year. This was previously
required every 5 years; however, in a letter dated August 13, 2014, NCDEQ required these
inspections to be increased to annually at Duke’s 14 coal ash impoundment facilities in North
Carolina. These inspections are to promote structural integrity and the design, operation, and
maintenance of the surface impoundment in accordance with generally accepted engineering
standards. Inspection reports are to be submitted to NCDEQ within 30 days of the completion of
the inspection.
Annual inspections are performed to gather information on the current condition of the dams
and appurtenant works. This information is then used to establish needed repairs and repair
schedules, to assess the safety and operational adequacy of the dam, and to assess
compliance activities with respect to applicable permits, environmental and dam regulations.
Annual inspections include an evaluation of previous repairs.
Annual inspections for the Dan River Steam Station Ash Basin dams were performed on
December 11, 2014 (AMEC, 2014), November 3, 2015 (Amec Foster Wheeler, 2016a), and May
5, 2016 (Amec Foster Wheeler, 2016b). The annual inspections included observations of the
ash basin dams, discharge towers and drainage pipes. In addition to the field observations of
the physical features of the impoundments, the annual inspections included a review of
available design documents and other inspection records.
The 2014, 2015, and 2016 annual inspections did not identify any features or conditions in the
ash basin dams, their outlet structures or spillways that indicate an imminent threat of
impending failure hazard. The annual inspections review of critical analyses indicated the
design conforms to current engineering state of practice to a degree that no immediate actions
are required other than the recent and ongoing surveillance and monitoring activities already
being conducted. The annual inspection reports noted some deficiencies that may require
remedial action and/or secondary investigations, which are part of an ongoing comprehensive
engineering review by Duke.
A general summary of the observations, recommendations and planned actions from the annual
inspections include:
 Continued management of the Vegetation Management Implementation Program (VMIP)
to restore and maintain vegetative ground cover that may have been interrupted by
recent construction and investigation work.
 Continued management of animal burrows on the dams as part of CCR unit routine
maintenance.
 The reinforced concrete discharge pipe (RCP) of the Secondary Ash Basin should be
repaired. This was completed in 2016 (Duke Work Order No.: 5809304).
The external slopes of both the Primary and Secondary Ash Basin dams were evaluated for
stability during the Phase 2 Reconstitution of Ash Basin Design, completed in late September
2015 (Revision 0 final report dated June 30, 2015). Duke lowered the Secondary Ash Basin
operating water level to elevation 515 in August 2016 and relevant analyses were updated and
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

11
incorporated in a revised Phase 2 Reconstitution of Ash Basin Design Report (Revision 1,
December, 2016). The revised report concluded the following:
 Screening level analyses for liquefaction potential, augmented by more sophisticated
evaluations (2-dimensional finite difference modeling using the computer program FLAC)
identified three areas of concern:

1. Saturated embankment fill materials in the Secondary Ash Basin Dam: The
screening analysis reported in 2015 indicated that liquefaction of the embankment fill
materials may result in significant embankment deformations. In August 2016, Duke
lowered the Secondary Ash Basin operating water levels. Liquefaction susceptibility
was revaluated with the computer program FLAC Version 7, which uses a two-
dimensional, finite-difference analysis to evaluate the dynamic response, liquefaction
potential, and permanent displacements of the cross section during the design-level
seismic shaking at the site. Results indicated that localized zones in the
embankment and foundation soils would experience liquefaction during the design-
level seismic shaking. However, results indicated the estimated deformations were
acceptable and that the there is no potential for release of impounded ash materials
due to the design seismic event.

2. Impounded ash underlying and therefore providing foundation support for the portion
of the Primary Ash Basin Dam constructed as a vertical expansion of the basin circa
1977: It should be noted that this material is unsaturated by the current water level of
502.5 feet but would be saturated if the water level in the basin were to rise.

3. Although not specifically studied, liquefaction of the sluiced ash within the interior of
the basin would be anticipated for the design seismic event.

 Slope stability analyses were performed for cases modeling required loading conditions
with results as follows:

1. The slope stability analyses for the Primary Ash Basin Dam indicate slope stability
factors of safety that meet the recommended criteria based on August 2016 water
levels within the basin.

2. The slope stability analyses for the Secondary Ash Basin Dam indicate slope stability
factors of safety that meet the recommended criteria based on August 2016 water
levels within the basin.

3. The slope stability analyses for the river bank slopes generally indicate factors of
safety that suggest sloughing and surficial failures are likely, particularly for the
slopes of steeper inclinations. The types of failures indicated should not pose an
immediate threat to the stability of the overall dams, but would eventually result in
some form of destabilization of the dams. Duke constructed a project in 2016
stabilizing river bank slopes adjacent to a portion of the Secondary Ash Basin with a
rip-rap buttress.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

12
4. Slope stability analyses of the Intermediate Dike generally indicate acceptable
performance with the exception of the post-seismic load case.

As described in the Phase 2 Reconstitution of Ash Basin Design Report (Amec Foster Wheeler,
2016d), due to space limitations downstream of the Secondary Ash Basin Dam, practical means
of improving the slope stability factors of safety are limited. Potential courses of action included
lowering the water level in the secondary basin, installing additional piezometers in the
Secondary Dam to gather data for revised analyses, and accelerating removal of pond ash.
Duke has lowered the operating water level in the Secondary Ash Basin to 515 feet and this
water level has been incorporated into analyses with satisfactory results. No additional
recommendations for action prior to basin decommissioning were presented.

The annual inspections also included a few specific observations and recommendations for
each dam as follows:
 Primary Ash Basin Dam
1. A masonry (brick) facing has been built against the grout plug at the outlet end of the
48‐inch‐diameter drainage pipe. Amec Foster Wheeler observed the bottom two rows
of bricks were slightly damp. The brick facing should continue to be monitored and
the cause of the moisture evaluated if the condition continues.
Status: Repairs were completed in the fall of 2015. Polyurethane foam and a metal
plate were installed at the outlet end of the pipe.
2. Drawings reviewed by Stantec (who conducted third-party inspections summarized in
the 2014 annual inspection report) indicated the original ash basin decant structure
and outlet pipe were originally constructed along the southern portion of the eastern
dam in the Primary Ash Basin. The drawings have the structure labeled as
“abandoned;” however, no other documentation reviewed confirmed this
abandonment or how it was accomplished. It is understood that Duke has located the
abandoned structure and plans on further investigating its condition to confirm the
abandonment. The construction activities should be well documented to permanently
close this issue.
Status: Initial results of geophysical survey performed by Duke indicated that the
discharge pipe was buried too deep to safely excavate and/or abandon properly.
Piezometers labelled ROCKI-237-200 and ROCKI-237-201 were installed in the
vicinity and are monitored monthly to identify any abrupt changes in water levels in
the vicinity of this pipe. In 2016 Duke developed and implemented a plan to
excavate, locate, and abandon the discharge pipe in-place.
 Secondary Ash Basin Dam
1. Stantec observed a possible seepage area, approximately 2‐feet in diameter, on the
downstream side of the embankment east of the Secondary Ash Basin. No flow was
apparent and no buildup of sediment was observed. Soft soil was determined to be
approximately 3‐inches in depth. This condition was also observed by Amec Foster
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

13
Wheeler during the annual inspection on November 11 & 12, 2014. The wet area
appeared to result from seepage originating from the riprapped slope above the wet
area. This wet area should continue to be monitored
Status: On-going monitoring. Included in the weekly inspection.
2. The elevated water level at Environmental Monitoring Well MW 21‐D should be
further investigated to determine if artesian conditions occur at the toe of the
Secondary Ash Basin Dam.
Status: The water level in this monitoring well has been evaluated. This monitoring
well extends into underlying rock resulting in the higher water levels. It is not
believed to represent the conditions in the soil above the rock.
3. Video inspection of the 36-inch reinforced concrete discharge pipe (RCP) of the
Secondary Ash Basin noted a crack approximately 30 feet above the downstream
toe about 150-200 feet north of the intersection of the Intermediate Dike with
Primary and Secondary Ash Basin Dams. The crack had been filled with bentonite
cement slurry at the time of inspection.
Status: Completed as part of Phase 2 work and as a yearly inspection item. The
discharge pipe was repaired in 2016 per Duke Work Order No. 5809304.
Note that these recommendations have been subsequently addressed or continue to be
monitored through the routine inspections of the dams described below.
Weekly ash basin inspections include observation of downstream slopes, toes, abutment
contacts and adjacent drainageway(s); spillway(s) and associated structure(s); upstream slopes
and shorelines; and, other structures and features of the dams.
Monthly inspections of the ash basins include the weekly monitoring elements with the addition
of piezometer and observation well readings; water level gauges/sensors; and, visual
observations and documentation of slopes and benches.
Daily inspections of the ash management facilities are not routinely required. However, on a
case-by-case basis, the Ash Basin facilities may be inspected daily beginning at such times, and
continued for the duration as specified by Plant Management. Such daily inspections might be
initiated, for example, during a repair activity on the dam or in response to a specific imposed
regulatory agency requirement.
Special inspections of the ash basins may be performed during episodes of high-flow,
earthquake, emergency, or other special events. Visual inspections are performed after a heavy
precipitation event when accumulation of 4 inches of rainfall or greater occurs within a 24-hour
period. An internal inspection will be performed after an earthquake event if the seismic event
was felt at the station or measured by the U.S. Geological Survey was greater than a Magnitude
3 and with an epicenter within 50 miles of the dam. A special inspection would also be
performed during an emergency, such as when a potential dam breach condition might be
identified or when construction activities (e.g., basin clean-out) are planned on or near the dam.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

14
They are also made when the ongoing surveillance program identifies a condition or a trend that
appears to warrant special evaluation.
3.2 Site Maps
3.2.1 Summary of Existing CCR Impoundment Related Structures
3.2.1.1 Primary Ash Basin
The Primary Ash Basin is located along the Dan River and is the western-most basin (Figure 2).
Based on review of available information, this ash basin has a surface area of approximately 27
acres and a total storage volume on the order of 477 acre-feet. The dam has a 15-foot wide
crest at approximate elevation 540 feet with 2H:1V exterior and interior slopes that are primarily
grassed covered. Adjacent to the river, the embankments have riprap slope protection extending
upslope from the toe to approximate elevation 512. In addition, there is a rock-fill berm designed
with a top elevation of 503 feet located along the western portion of the southerly downstream
toe of the Primary Ash Basin embankment. The southern toe of the embankment is accessible
by driving along a roadway, however only on the western portion. The eastern portion of the
southern toe of the embankment is not accessible and covered with mature trees, thick brush,
and adjacent to a steep-slope riverbank. The maximum embankment height is on the order of
50 feet. The dam was not designed with internal drainage or toe drains. The crest of the dike
and the intermediate bench on the southern embankment slope are paved with an aggregate
road. The overall length of crest (excluding the Intermediate Dike length) is on the order of
4,000 feet.
The Primary Ash Basin drains to the Secondary Ash Basin through a reinforced concrete outlet
structure located at the northeast corner of the Primary Ash Basin. This structure consists of a
vertical square riser with stop logs on two-sides and a pipe connecting the vertical riser to the
Secondary Ash Basin. A detail of the Primary Ash Basin outlet structure from the Phase 2
Reconstitution of Ash Basin Design Report (Amec Foster Wheeler, 2016d) has been included as
Figure 14 in Appendix B.
There are two (2) stormwater pipes that pass underneath the ash basins to convey surface
runoff collected outside of the basins to the river. Shown on Appendix C, Drawing
DNR_C999.001.003 (Dan River Decommissioning Plan Drawings), a 48-inch diameter storm
water pipe (culvert) passes underneath the Primary Ash Basin. Also shown on Appendix C,
Drawing DNR_C999.001.003, a 42-inch/36-inch-diameter storm water pipe is located east of the
48-inch pipe and approximately underneath the Intermediate Dike between the Primary and
Secondary Basins.
In February 2014, the collapse of the 48-inch stormwater pipe passing underneath the Primary
Ash Basin resulted in the release of ash and water to the Dan River. Duke has since plugged
portions of the two (2) stormwater pipes passing underneath the basins by grouting them in
place to an extent adequate to prevent further release into the Dan River. The Primary Ash
Basin has been drained and contains free water only at low levels near the outlet structure.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

15
Piezometers are in place around the Primary Ash Basin as shown on Appendix C, Drawings
DNR_C999.001.002 and DNR_C999.001.003. Based on historic piezometer readings, the
phreatic surface within the Primary Ash Basin embankment ranges from approximately 32 to 36
feet below the crest, or at elevation 504 to 508 feet, which places the phreatic surface within five
(5) to ten (10) feet of the bottom of the structure, at the centerline of the cross section of the
embankment. One (1) piezometer located near the toe of the Primary Ash Basin embankment
indicated the phreatic surface on the order of 18 feet below the ground surface or at elevation
484 feet.
The ash within the Primary Ash Basin has been covered with spray-applied stabilizers, and
there is vegetation growing over much of the ash. The Primary Ash Basin is currently holding
water at estimated elevation 510 to 515 feet. During response efforts for the February 2014
incident, a portion of the crest of the Primary Ash Basin embankment on the north side of the
ash basin was lowered to elevation 532 feet, eight (8) feet lower than the design crest elevation
of 540 feet.
3.2.1.2 Secondary Ash Basin
The Secondary Ash Basin is located along the Dan River and is the eastern most ash basin
(Figure 2).
Based on review of available information, this ash basin has a surface area of approximately 12
acres and a total storage volume on the order of 187 acre-feet. The dam has a 15-foot wide
crest at approximate elevation 530 feet with 2 horizontal to 1 vertical (2H:1V) exterior and
interior slopes that are primarily grass covered. There is thick growth of cat tails around the
shoreline that extends well into the ash basin on the western and northern sides. Significant
portions of the southern (along the Dan River) and eastern exterior embankment slopes are
covered with riprap. The crest of the dike is paved with an aggregate road. The southern toe of
the embankment (along the Dan River) is not accessible by driving. The eastern and southern
portions of the toe of the embankment are difficult to access due to steep slopes, and the area
beyond the toe is covered with mature trees and vegetation and is bordered by a steep-slope
riverbank. The maximum embankment height is on the order of 40 feet. The dam was not
designed with internal drainage or toe drains. The overall length of crest along the south and
east sides excluding the Intermediate Dike is on the order of 1,300 feet. This crest length does
not include the ash basin perimeter to the north and northeast that was created by grading of
existing ground, therefore not requiring embankment fill during construction.
The Secondary Ash Basin outlet is a four (4)-sided, reinforced concrete outlet structure located
at the southeast corner of the basin. This structure consists of a vertical riser with stop logs on
four sides and a pipe connecting the vertical riser to the outlet at the Dan River. A detail of the
Secondary Ash Basin outlet structure from the Phase 2 Reconstitution of Ash Basin Design
Report (Amec Foster Wheeler, 2016d) has been included as Figure 15 in Appendix B. The
Secondary Ash Basin contains free water and historically had an operating water level around
elevation 522.5 feet. Piezometers are in place around the southern side of the Secondary Ash
Basin as shown on Appendix C, Drawings DNR_C999.001.002 and DNR_C999.001.003. Based
on historic piezometer readings, the phreatic surface within the Secondary Ash Basin
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

16
embankment ranges from approximately 15 to 20 feet below the crest or at elevation 505 to 515
feet, which places the phreatic surface within 5 to 10 feet of the bottom of the structure at the
centerline of the profile. Hand auger borings advanced near the toe of the Secondary Ash Basin
embankment indicated a phreatic surface on the order of 14 feet below the ground surface.
In 2016, dredging was performed in the Secondary Ash Basin. The dredge spoils were placed in
the Primary Ash Basin. The operating water level in the Secondary Ash Basin was subsequently
lowered to elevation 515 feet.
3.2.1.3 Intermediate Dike
The Intermediate Dike’s western (Primary Ash Basin side) and eastern (Secondary Ash Basin
side) embankment slopes are grass covered. There is thick growth of cat tails along the eastern
slope shoreline. The eastern toe of the slope is covered with riprap. The crest of the
Intermediate Dike is paved with an aggregate road. Piezometers are present along the
Intermediate Dike as shown on Appendix C, Drawings DNR_C999.001.002 and
DNR_C999.001.003.
3.2.1.4 Ash Fill 1
Ash Fill 1 is a benched, dry stack feature located just north of the Secondary Ash Basin that
comprises a surface area of approximately 20 acres. Two (2) soil stockpiles were placed on top
of the ash in Ash Fill 1 as shown on Appendix A, Figure 1. The thickness of the northern-most
soil stockpile is on the order of 10 to 20 feet and the thickness of the southern-most soil
stockpile is on the order of 38 feet. At its highest point (the crest of the northern-most soil
stockpile), Ash Fill 1 has an elevation of approximately 648 feet. An aggregate road
encompasses most of the perimeter toe and the middle bench of Ash Fill 1 as shown on Figure
2. The surface and side slopes of Ash Fill 1 are soil covered and vegetated with grass. Several
groundwater observation wells and monitoring wells exist (or existed) in and around Ash Fill 1
as shown on Appendix C, Drawings DNR_C999.001.002 and DNR_C999.001.003.
Groundwater observation wells within the landfill footprint have been abandoned.
Two (2) soil stockpiles were removed in the 1st and 2nd quarters of 2016. Ash removal is
ongoing. The soil was and the ash is being shipped to the existing Maplewood Landfill located in
Jetersville, Virginia.
3.2.1.5 Ash Fill 2
Ash Fill 2 is a dry stack feature located just east of Ash Fill 1 as shown on Figure 2. Ash Fill 2 is
approximately 14 acres in area. Ash Fill 2 is covered on its top surface with gravel and crushed
rock as it is commonly used as a parking lot during site construction activities. Ash Fill 2 has a
top surface elevation of approximately 582 to 585 feet. The top of Ash Fill 2 can be accessed by
two (2) aggregate paths at the southern and western corners of Ash Fill 2 as shown on Figure 2.
The side slopes of Ash Fill 2 are soil covered and vegetated with grass. Several groundwater
observation wells and monitoring wells exist in and around Ash Fill 2 as shown on Appendix C,
Drawings DNR_C999.001.002 and DNR_C999.001.003.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

17
3.2.2 Receptor Survey
Duke submitted a receptor survey to the NCDEQ in September 2014, and a supplemental
receptor survey in November 2014 (HDR 2014a and 2014b, respectively). According to HDR,
the purpose of the receptor survey was to identify the exposure locations that are critical to be
considered in the groundwater transport modeling and human health risk assessment. In the
survey HDR identified properties and receptors within a 0.5-mile radius of the on-site ash
basins. The results of the survey are summarized in this section.
Properties identified within a 0.5-mile radius of the on-site ash basins compliance boundary
include:
 North and northwest - residential properties
 Northeast - two industrial properties one of which has a wastewater treatment plant
discharging into the Dan River
 South - One residence across the Dan River
 Southeast - Undeveloped property and farmland (across the Dan River)
The following receptors were identified within a 0.5-mile radius of the ash basin compliance
boundary:
 Three water supply wells located more than 2,000 feet away from the Dan River ash
basin compliance boundary found to be either upgradient or across the Dan River from
the ash basin system
 One private water supply spring, not currently in use
 No public water supply wells or wellhead protection areas were identified within a 0.5-
mile radius of the ash basin compliance boundary
 No water supply wells (including irrigation wells and unused or abandoned wells) were
identified within the ash basin potential area of interest
 Several unnamed tributaries were identified adjacent to or downgradient of the site
HDR concluded that no information gathered as part of the assessment (HDR, 2015a)
suggested that water supply wells or springs located within the 0.5-mile radius of the
compliance boundary are impacted by the Dan River ash basin system.
The identified water supply wells are shown on a USGS receptor map included as Figure 4-1 of
the CSA Report (Appendix D). Figures 4-2 through 4-6 of the CSA Report (Appendix D) illustrate
an aerial receptor map, ash basin underground features map, ash storage area underground
features map, aerial map of surface water bodies, and surrounding property owners map,
respectively.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

18
3.2.3 Existing On-Site Landfills
One closed land clearing and inert debris (LCID) Landfill (Permit No. 79-B) exists on the
property just west of the Dan River Combined Cycle facility as shown on Figure 3. The Dan
River LCID Landfill was permitted in January 1983 to receive waste insulation (including
asbestos), scrap wood, metal, and rock. The need for the on-site LCID Landfill was primarily
due to the Rockingham County Landfill ceasing to accept asbestos. Permit conditions included
double-bagging (polyethylene within canvas bags) any assumed asbestos-containing material,
and covering immediately with six (6) inches of soil. The Dan River LCID Landfill was officially
closed in August 2005. Closure consisted of a 12-inch thick final cover with grading, fertilization,
and seeding.
Duke began the process of designing and permitting an on-site landfill within the footprint of Ash
Fill 1 in 2014. The on-site landfill will be the final destination for ash from the Primary Ash Basin,
Secondary Ash Basin, Ash Fill 1 (except for the ash hauled to an off-site landfill), and Ash Fill 2.
The NCDEQ issued the landfill permit to construct 7906-INDUS-2016 on October 26, 2016 and
construction began in November 2016. Construction of the first of three landfill cells is
anticipated to be completed, and the permit to operate issued, in mid-2017.
3.3 Monitoring and Sampling Location Plan
Discharge from the ash basin system is currently permitted by the NCDEQ’s Division of Water
Resources (DWR) under the National Pollutant Discharge Elimination System (NPDES) Permit
NC0003468. In accordance with this NPDES permit, surface water samples are collected from
Outfalls 001 and 002 and groundwater samples are collected from the following compliance
monitoring wells: MW-20S, MW-20D, MW-21S, MW-21D, MW-22S, MW-22D and MW-23D. The
location of NPDES outfall and NDPES groundwater compliance wells are depicted on CSA
Report, Figure 2-7 (Appendix D).
CAMA also requires a schedule for continued/interim groundwater monitoring at the site. The
current plan includes one additional interim groundwater sampling in 2015. The purpose of this
interim sampling will be to evaluate seasonal fluctuations in Constituent of Interest (COI)
concentrations, and to provide additional data for statistical analysis of site-specific background
concentrations. Thereafter groundwater monitoring is to be performed twice yearly for the
Constituents for Detection and Assessment Monitoring detailed under CCR Rule Part 257
Appendices III and IV. These constituents are summarized in CSA Report, Table 16-1 (Appendix
D). Groundwater sampling locations, as summarized in CSA Report, Table 16-2 (Appendix D)
will include:
 Background Wells: GWA-1S, GWA-1D, GWA-9S, GWA-9D, GWA-14S, GWA-14D, MW-
23D, MW-23BR, BG-5S and BG-5D.
 Downgradient Ash Basin Wells: MW-21S, MW-22D, GWA-5BR, MW-22S, MW-22D, MW-
22BR, AB-30S, AB-30D, and AB-30BR
 Downgradient Ash Storage Area (Ash Fills 1 and 2) Wells: GWA-10D, GWA-10D, GWA-
11S and GWA-11D.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

19
The location of the CAMA monitoring wells, the approximate ash basin waste boundary, and the
compliance boundary are depicted on CSA Report, Figure 6-2 (Appendix D).
In accordance with NCDEQ 15A NCAC 02L Groundwater Rules, the results of the groundwater
monitoring are to be compared to the NCDEQ 2L Standards, Interim Maximum Allowable
Concentrations (IMACs), and where NCDEQ standards do not exist the U.S. EPA Maximum
Contaminant Levels (MCLs). Assessment monitoring with potential implementation of corrective
action measures may be required for COIs with a Statistically Significant Increase (SSI) over
background. If an SSI over background is not found monitoring is to continue for the active life
of the CCR and post-closure period. Remedy completion is achieved once COI concentrations
are at or below the associated standards at all compliance points for a period of three years.
It is important to note that HDR has plans for the installation of additional assessment wells on
the site as part of a supplemental CSA Report. As a result, compliance monitoring sampling
locations may be modified following analysis and interpretation of additional data.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

20
4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL
INVESTIGATIONS
4.1 Hydrogeology and Geologic Descriptions
4.1.1 Regional Geologic Setting
North Carolina is divided into distinct regions which are portions of three physiographic
provinces: the Atlantic Coastal Plain, Piedmont, and Blue Ridge (Fenneman, 1938).

Illustration 1-Generalized Geologic Map of North Carolina, showing major geologic regions and the locations of
Triassic basins and sub-basins (Reid and Milici, 2008)
The Dan River Steam Station is located within the Piedmont Province. The Piedmont is bound
to the east and southeast by the Atlantic Coastal Plain and to the west by the escarpment of the
Blue Ridge Mountains, having a width of 150 to 225 miles (LeGrand, 2004). The topography of
the Piedmont region is characterized by low, rounded hills and long, rolling, northeast-southwest
trending ridges (Heath, 1984). Stream valley to ridge relief in most areas can range from 75 to
200 feet. The Piedmont region rises from an elevation of 300 feet above mean sea level along
the Coastal Plain boundary, to an elevation of 1,500 feet at the base of the Blue Ridge
Mountains (LeGrand, 2004).
Located within the Piedmont Province are two exposed rift basins that form two subparallel belts
striking north-easterly, mainly across North Carolina (Olsen Et al., 1991). The eastern belt
includes the broad Deep River basin and two small outliers, the Ellerbe basin in North Carolina
and the Crowburg basin in South Carolina. The western belt includes the narrow Dan River
basin and a small southerly outlier, the Davie County basin. The rift basins were formed
approximately 220 million years ago during the Triassic Period as the supercontinent Pangea
broke apart.
Sedimentation from runoff coming from the highlands deposited sand and silt and mud and
created alluvial fans at the base of streams coming off the highlands. This deposition
accumulated and formed the mudstones, siltstones, and sandstones found in the Dan River
Dan River Steam Station
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

21
basin. Thayer (Thayer, 1970; cited in Olsen Et al., 1991) recognized a three-part stratigraphy for
the Dan River basin, dividing the rocks of the Dan River Group (in ascending stratigraphic order)
into the Pine Hall Formation, the Cow Branch Formation, and the Stoneville Formation. In
general, Triassic basins display an overall tripartite stratigraphy consisting of a lower sequence
of mainly reddish-brown, arkosic, coarse-grained sandstone and conglomerate, a middle
sequence of mostly gray to black fossiliferous siltstone, carbonaceous shale, and thin coal beds,
and an upper sequence of mainly reddish-brown siltstone, arkosic sandstone, pebbly
sandstone, minor red and gray mudstone, and conglomerate.
4.1.2 Regional Hydrogeologic Setting
The groundwater system within the Piedmont region should be viewed as a two-unit system.
The first unit, the regolith (encompassing residuum, saprolite, and weathered rock), contains
and transports water through primary pore spaces in the soil and between rock particles. The
second unit, the bedrock, has very limited pore spaces. Instead, water flows through and is
stored in secondary conduits. These secondary conduits are sheet-like openings formed along
rock fractures (Heath, 1980). A transition zone between the saprolite and bedrock is also
common within the regolith of the Piedmont region. This transition zone will typically consist of
partially weathered rock of the parent bedrock (Daniel and Dahlen, 2002).
Depending on the parent material and degree of weathering, the regolith can range in porosity
between 20 and 30 percent, while the bedrock porosity is only 0.01 to 2 percent (Heath, 1984).
Thus, the regolith serves as the principal storage reservoir for the underlying bedrock during
recharge events (LeGrand, 2004). Hydraulic conductivities are similar in both the regolith and
fractured bedrock and can range from 0.004 to 3.5 feet per day1 (Heath, 1984). Fracture
intensity, orientation, and aperture will dictate the hydraulic conductivity of the underlying
bedrock.
Conceptually, the groundwater system in the Piedmont region is one in which the saprolite acts
as a groundwater storage unit and bedrock functions as the main supply or transport unit and
each unit functions are distinctly separate. Whereas Coastal Plain units typically serve as both,
the regolith serves as a storage reservoir due to its high porosity and low yield, while the
fractured bedrock serves as the main groundwater transport unit due to its low porosity and high
yield. (Heath, 1984).
Groundwater will flow in the direction of high to low hydraulic head. Given that the topography of
the Piedmont is predominantly composed of rounded hills and valleys, the water table closely
mimics the land surface with less relief (LeGrand, 1988). Thus, topographic divides also serve
as groundwater divides, with groundwater continuously flowing from ridge to valley, and,
ultimately discharging at the nearest perennial stream. Locally, regolith and bedrock conditions
and topography directly influence the hydraulic parameters of the groundwater system. Flow
rates can differ from basin to basin by orders of several magnitudes (LeGrand, 2004).
Additionally, Triassic Units in North Carolina often contain dikes and sills. These structural
features weather differently and have been known to control groundwater flow horizontally and
vertically at sites.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

22
4.2 Stratigraphy of the Geologic Units Underlying Surface Impoundments
Stratigraphy at the site was interpreted based on a review of historical boring logs, borings
completed during recent site characterization activities, and available dam construction records.
Representative boring logs and a plan showing boring locations from the Phase 2
Reconstitution of Ash Basin Design Report (Amec Foster Wheeler, 2016d) are included in
Appendix B for reference. The primary units identified at the site are: fill material (generally
borrowed from one area of the site and distributed to other areas), ash, alluvium, residuum
(residual soils), saprolite, partially weathered bedrock, and competent bedrock.
Beneath the fill and ash material and outside of areas where no construction activities were
performed, the surficial unit consists of alluvial deposits or residuum. Thickness of the alluvial
material, defined as soil material that has been deposited by fluvial processes, ranges from
approximately 4 to 30 feet. Beneath the alluvium, residuum, defined as soil material that has
been weathered in place from the parent bedrock, is present. Residuum thickness ranges from
approximately 3 to 12 feet. Saprolite was generally encountered below the residuum layer, and
the thickness of this layer ranges from approximately 1 to 25 feet. The saprolite transitions to
bedrock through a zone of partially weathered rock, interpreted to range in thickness from
approximately 0.3 to 45 feet. Bedrock in this area has been classified by field descriptions as
dark gray to black siltstone/shale and gray fine-grained sandstone and greywacke with intense
fracturing. The elevations of contact between the saprolite and the bedrock/foundation unit
varied across the site.
4.3 Hydraulic Conductivity Information
Based on the CSA Report (HDR, 2015a), the groundwater system in the natural materials at
Dan River is an unconfined, connected aquifer system without confining layers. The
groundwater system is divided into two layers, the shallow aquifer and the bedrock aquifer,
which distinguish the flow layers within the connected aquifer system. This description of the
groundwater system is consistent with the regional hydrogeologic setting described in Section
4.1.2.
Hydraulic conductivity of the hydrostratigraphic layers at Dan River were developed utilizing
data collected during the investigation for the CSA Report and applicable historic data. The
hydraulic conductivity was determined by in-situ permeability testing, including falling head,
constant head, and packer testing; slug tests in monitoring wells; and laboratory testing of
undisturbed samples of the hydrostratigraphic units.
A detailed review of the methods used to determine the hydraulic conductivities of the
hydrostratigraphic units at the Dan River Steam Station can be found in Section 11.2 and
Appendix G of the CSA Report (HDR, 2015a). Tables 4-1 and 4-2 below provide a summary of
the horizontal and vertical hydraulic conductivities adopted from the CSA Report (HDR, 2015a).

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

23

Table 4-1 Hydrostratigraphic Layer Properties - Horizontal Hydraulic Conductivity

H ydrostratigraphic
Unit N Geometric
Mean
(cm/sec)
Geometric
Mean +
1SD
(cm/sec)
Geometric
Mean -
1SD
(cm/sec)
Geometric
Median
(cm/sec)
Minimum
(cm/sec) Maximum
(cm/sec)
Ash 8 2.3E-04 3.2E-03 1.7E-05 3.2E-04 4.0E-06 1.2E-02
Fill 3 4.7E-04 2.8E-03 7.9E-05 2.4E-04 1.2E-04 3.5E-03
Alluvium (S) 3 3.2E-05 2.1E-04 7.9E-05 1.8E-05 1.2E-04 2.6E-04
M1 3 7.6E-05 5.0E-03 1.2E-06 2.9E-04 7.0E-07 2.2E-03
M2 11 2.1E-05 2.9E-04 1.5E-06 2.7E-05 4.6E-07 8.0E-04
Transition Zone (TZ) 20 2.0E-04 1.2E-03 3.3E-05 1.5E-04 8.5E-06 4.4E-03
Bedrock (BR) 50 1.1E-04 5.9E-04 2.1E-05 1.4E-04 7.4E-07 1.6E-03

Table 4-2 Hydrostratigraphic Layer Properties - Vertical Hydraulic Conductivity

H ydrostratigraphic
Unit N Geometric
Mean
(cm/sec)
Geometric
Mean +
1SD
(cm/sec)
Geometric
Mean -
1SD
(cm/sec)
Geometric
Median
(cm/sec)
Minimum
(cm/sec) Maximum
(cm/sec)
Ash 7 4.4E-05 4.0E-04 4.9E-06 4.9E-05 2.2E-06 4.7E-04
Fill 3 6.2E-07 1.5E-06 2.6E-07 8.8E-07 2.3E-07 1.2E-06
Alluvium (S) 4 4.3E-07 2.6E-06 6.9E-08 4.6E-08 4.6E-08 3.5E-06
M1 6 3.7E-06 6.0E-05 2.3E-07 6.2E-06 3.0E-08 4.8E-05
M2 7 8.5E-07 1.0E-05 7.2E-08 6.0E-07 4.3E-08 4.8E-05
Transition Zone (TZ) 0 - - - - - -
Bedrock (BR) 0 - - - - - -
4.4 Geotechnical Properties
The geotechnical properties of the stratigraphic layers present at Dan River Steam Station
Primary and Secondary Ash Basins are described in the following sections. Representative
boring logs, a plan showing boring locations, and laboratory test reports supporting the
geotechnical property descriptions are based largely on information from the Phase 2
Reconstitution of Ash Basin Design Report (Amec Foster Wheeler, 2016d) and are included in
Appendix B for reference.
4.4.1 Fill Material
As reported in the Phase 2 Reconstitution of Ash Basin Design Report (Amec Foster Wheeler,
2016d), the embankments consisted of fill soils that were placed during various site grading
activities since plant construction. Embankment soils were mostly clayey sand (SC) and sandy
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

24
lean clays (CL) with occasional silty sand (SM) and sandy silt (ML) soils. The embankment soils
were typically a medium plasticity, with fines contents (percent passing No. 200 sieve) between
30 and 60 percent. The embankment soils were derived from on-site excavated residual soils
and saprolite. Embankment fill consistency ranged from firm to hard with Standard Penetration
Test (SPT) blow counts (N-values) ranging from 5 to over 30 blows/foot. The transition from fill
to underlying natural materials was sometimes difficult to distinguish due the similarity of fill to
its parent material. Results of Cone Penetrometer Test (CPT) soundings (AMEC, 2013)
advanced in and around the ash basins indicate measured tip resistance (qt) ranged from 10 to
50 tons per square foot (tsf) and sleeve friction (fs) ranged from 1 to 2 (tsf). CPT results
indicated friction ratios (Rf) greater than 2 indicating fill soils were cohesive.
4.4.2 Ash
Amec Foster Wheeler (2015) reported that ash was encountered within the footprint of the CCR
units, and beneath portions of the Primary Ash Basin upper embankment fill and the
Intermediate Dike. The ash was generally described as a silty sand (SM) or sandy silt (ML)
material based on visual observation and laboratory testing. Ash was generally gray, non-
plastic, with fines contents between 30 and 95 percent, which is consistent with fly ash and
bottom ash materials. The ash below the groundwater table had moisture contents between 35
and 70 percent and was soft, with typical SPT blow counts equal to 4 blows/foot or less (AMEC,
2013). The ash above the groundwater table wass generally moist to wet, with typical moisture
contents measured between 25 and 50 percent, and was firm or stiff in consistency, with typical
SPT blow counts from 5 to 15 blows/foot (AMEC, 2013). Results of CPT soundings (AMEC,
2013) advanced in and around the ash basins indicated qt was generally low and ranged from
10 to 20 tsf. Measured fs was consistently less than 0.5 tsf. CPT results indicated a Rf generally
less than 2 indicating the ash was not cohesive.
4.4.3 Residual Soils
Beneath the embankment and ash fill soils and in areas undisturbed by construction activities,
residual soils consisting of alluvium, residuum, saprolite, partially weathered rock, and bedrock
were encountered (AMEC 2013, 2014).
The alluvial soils were typically encountered below the embankment fill. The alluvial soils
typically consisted of interbedded sandy lean clay (CL), clayey sand (SC), and silty sand (SM).
Some gravel seams were also encountered within the alluvium. The SPT N-values obtained in
the alluvial material ranged from 9 to 30 blows/foot. Results of CPT soundings (AMEC, 2013)
advanced in and around the ash basins in areas potentially characterized as alluvium, indicated
measured qt ranging from 40 to 70 tsf and f s ranging from 1.0 to 1.5 tsf. CPT results indicated Rf
less than 2 indicating alluvium was not cohesive.
The residual soils typically consisted of sands, silts and clays with some sand and trace rock
fragments (AMEC 2013, 2014). The residual soil was typically medium dense or very stiff to
hard in consistency with typical SPT blow counts ranging from 16 to over 30 blows/foot. CPT
soundings advanced in and around the ash basins (AMEC, 2013) indicated measured qt ranged
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

25
from 10 to 120 tsf and fs ranged from 0.5 to 4 tsf. CPT results indicated most Rf greater than 2,
although some were less than 2, indicating residual soil was predominantly cohesive.
A partially weathered rock (PWR) zone was encountered at the transition between the residuum
and the rock. The weathered rock was typically hard with SPT blow counts of 100 or more
blows/feet.
When encountered, the weathered rock typically transitioned to a sound or competent bedrock.
Drilling refusal was typically encountered in the bedrock and required coring to advance
subsurface explorations. Bedrock classified as a moderately hard to hard, light gray to gray,
siltstone and sandstone.
4.5 Chemical Analysis of Impoundment Water, CCR Materials and CCR Affected
Soil
N.C.G.S. §130A-309.211 directs owners of CCR surface impoundments in North Carolina to
conduct groundwater monitoring, assessment, and remedial activities, as necessary. Duke
submitted a Groundwater Assessment Work Plan in September 2014 and subsequently
submitted the Revised Groundwater Assessment Work Plan for the Dan River Steam Station to
the NCDEQ on December 30, 2014. The Work Plan was approved by NCDEQ on February 16,
2015. The CSA was performed by HDR in order to define the extent of impacts in soil and
groundwater that were attributable to CCR source areas. The CSA Report was submitted to
NCDEQ on August 14, 2015 (HDR, 2015a) and included the following activities:
 Installation of soil boring and monitoring wells in order to collect and analyze chemical,
physical, and hydrogeologic data for subsurface materials within and beyond the waste
boundary and Compliance Boundary
 Evaluation of laboratory data to refine the Dan River Steam Station Site Conceptual
Model (SCM)
 Update the September 2014 receptor survey
 Completion of a screening-level risk assessment
Because impacts to groundwater were identified in the CSA, N.C.G.S. §130A-309.211 (b)
required the implementation of corrective action for the restoration of groundwater quality in
accordance with Subchapter L of Chapter 2 of Title 15A of the North Carolina Administration
Code (15A NCAC 02L) and required Duke to submit a CAP. Duke and the NCDEQ mutually
agreed to a two-part CAP submittal. The CAP Part 1 (HDR, 2015b) submitted to the NCDEQ on
November 12, 2015 provided the following information:
 Background information
 A summary of the CSA findings
 A description of the site geology and hydrogeology
 A summary of the previous receptor evaluation results
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

26
 A summary of the COI exceedances and distribution
 The development of proposed soil and groundwater provisional background
concentrations
 A detailed description of the SCM
 The results of the groundwater flow and fate and transport model
 The results of the groundwater to surface water interaction model
The CAP Part 2 (HDR, 2016) submitted to the NCDEQ on February 10, 2016 provided the
following information:
 A description of groundwater, surface water and soil exceedances of the associated
standard or screening levels;
 A refined SCM;
 A refined groundwater flow and fate and transport model;
 A refined groundwater to surface water model;
 The results of the site geochemical model;
 The results of the risk assessment;
 An evaluation of methods for achieving groundwater quality restoration;
 A discussion of the conceptual plan(s) for recommended proposed corrective action(s);
 A schedule for proposed corrective action implementation; and,
 A plan for monitoring and reporting on proposed corrective action effectiveness.

Assessment work documented in the CSA Report (HDR, 2015a) included a source area
assessment in the Primary and Secondary Ash Basins, Ash Fills 1 and 2, and a total of nine ash
basin and storage area water seeps. Assessment activities included the collection of multiple
media samples following the installation of soil borings and monitoring wells in addition to
collection of grab samples in order to determine the presence or absence of COIs associated
with CCR activities. Source area media sampled included ash matrix from both the basin and
storage areas, surface water, ash pore water, and seep water. Soil, PWR, bedrock, surface
water, sediment, and groundwater were also sampled to determine the presence/absence of
COIs that may have migrated from source areas and to determine to what extent impacts were
present.
The following subsections summarize the assessment work conducted by HDR at the Dan River
Steam Station to define contaminates in the source area and assess how the source area is
impacting surrounding media. Groundwater is independently discussed in Section 4.6.
Groundwater modeling is discussed in Section 5.1.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

27
4.5.1 Source Area(s) Characterization
Included in this section are the results of the CCR unit source area characterization, as
presented by HDR in the CSA Report (HDR, 2015a), CAP Part 1 (HDR, 2015b), and CAP Part 2
(HDR, 2016). Source area media sampled by HDR included ash samples, ash basin surface
water, pore water, soils and sediments, surface water, and areas of wetness (AOWs).
Ash Basin and Ash Storage Area Ash Characteristics
HDR installed nine borings / monitoring wells (AB-5D, AB-10D, AB-15D, AB-20S, AB-25BR, AB-
35BR, MW-308BR, MW-311BR, and MW-314BR) within the ash basin waste boundary of both
the Ash Basin Primary and Secondary Basins, and collected 23 ash samples in May and June
2015. Eight borings / monitoring wells (AS-4D, AS-8D/BR, MW-301BR, MW-303BR, MW-
306BR, MW-315BR, and MW-318D) were installed in Ash Fills 1 and 2 and 16 ash samples
were collected between March and May 2015. Boring and monitoring well assessment locations
are depicted on CSA Figure 7-1 (Appendix D).
Ash samples were collected to a maximum depth of 42 feet (ft) below ground surface (bgs) in
the ash basins and a maximum depth of 76.5 ft bgs in the Ash Fill Areas. The laboratory
analysis suite performed on ash samples is summarized in CSA Tables 7-1 and 8-1 (Appendix
D). Results of the ash samples compared to the NCDEQ Preliminary Soil Remediation Goals
(PSRGs) for Industrial Health (IH) and Protection of Groundwater Standards (POG) are
summarized in CSA Tables 7-2.1 and 7-2.2 (Appendix D).
Based on a review of laboratory analytical results of ash samples collected from the ash basin
and ash storage areas, HDR identified the following COIs in ash: arsenic, barium, boron, cobalt,
iron, manganese, selenium, and vanadium.
Seventeen (17) of the 39 ash samples (from both the ash basins and storage areas) were
submitted for Synthetic Precipitation Leaching Procedure (SPLP) analysis to determine the
potential leachability of metals from ash samples into surrounding media. Results of the ash
sample SPLP analysis compared to the NCDEQ 2L Standards and where a 2L Standard does
not exist the NCDEQ IMACs are summarized in CSA Table 7-8 of the CSA Report (Appendix D).
Based on the SPLP analysis results, HDR indicated that the following COIs have the potential to
leach from the ash surface: antimony, arsenic, barium, beryllium, chromium, cobalt, iron, lead,
manganese, selenium, thallium, and vanadium.
Summary of Ash Pore Water Characteristics
As part of the CSA activities, HDR installed five monitoring wells (AB-5S, AB-10S, AB-10SL, AB-
15S, and AB-25S) in the ash basin and collected a total of nine pore water samples in the
Primary and Secondary Ash Basin Basins in June and September 2015. Pore water laboratory
analysis was performed as summarized in CSA Table 7-3 (Appendix D). The monitoring well
locations are depicted on CSA Figure 7-1 (Appendix D).
Results of the ash basin pore water analysis were compared to the 2L Standards and IMACs
and are summarized in CSA Table 7-5 (Appendix D).
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

28
From the results, HDR identified the following COIs in ash pore water: antimony, arsenic,
barium, boron, chromium, cobalt, iron, lead, manganese, nickel, sulfate, thallium, TDS, and
vanadium.
Summary of Ash Basin Surface Water Characteristics
HDR collected a total of four surface water samples (SW-1 and SW-9) from within the ash basin
in May and September 2015. Surface water laboratory analysis was performed as summarized
in CSA Table 7-3 (Appendix D). The locations of these samples are depicted on CSA Figure 7-1
(Appendix D).
Results of the ash basin surface water analysis compared to NCDEQ 2B Standards for surface
water and wetlands are summarized in CAP Part 2 Table 2-4 (Appendix D).
HDR identified the following COIs in surface water within the basin: aluminum, arsenic, copper,
manganese and zinc.
Summary of Areas of Wetness (AOW) Characteristics
AOWs were sampled in May, September, and November 2015 as part of the CSA activities.
AOW samples were collected at locations S-1 through S-4 and S-6 to evaluate potential
exceedances in the eastern unnamed tributary. The location of each sample is depicted on CAP
Part 2 Figure 2-1 (Appendix D). The results of the area of wetness sample analysis were
compared to 2L Standards or IMAC and are summarized in CAP Part 2 Table 2-12 (Appendix
D).
HDR reported the following COIs in the AOW samples: arsenic, cobalt, iron, lead, manganese,
and vanadium.
Summary of NCDEQ March 2014 Sampling
In July and September 2015, HDR collected four water samples coincident with historic NCDEQ
sample locations INFSW009, CCSW001, CCSW002, and/or DRRC001. Results of the sample
analysis were compared to 2L Standards for groundwater or 2B Standards for surface water,
and are summarized in CAP Part 2 Table 2-13 (Appendix D).
According to HDR, COIs at NCDEQ sample locations included: aluminum, cobalt, copper, iron,
lead, manganese, mercury, and vanadium.
4.5.2 Soil, PWR and Bedrock Assessment
Included in this section are a summary of the results of the background soil assessment and the
results of the media analysis surrounding the known source areas as presented in the CSA
Report (HDR, 2015a), the CAP Part 1 (HDR, 2015b), and the CAP Part 2 (HDR, 2016). Media
samples that were collected by HDR included soil, PWR, and bedrock.
Summary of Background Soil Assessment Results
As summarized in the CAP Part 1 (HDR, 2015b), HDR selected boring locations to represent
background soil conditions that included: BG-1D, BG-5S/D, GWA-9S/D, GWA-12S/D, and SB-1
through SB-3. HDR used the 95% upper tolerance limit (UTL) to calculate Proposed Provisional
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

29
Background Concentrations (PPBCs) from a total of 23 soil samples collected from the
aforementioned borings. Samples were collected between 0 and 5 feet below ground surface
(bgs). PWR and bedrock samples were not included in soil background statistics (HDR, 2015b).
The calculation method followed USEPA’s ProUCL Technical Guidance, Statistical Software for
Environmental Applications for Data Sets with and without Nondetect Observations (2013). Soil
PPBCs are presented in CAP Part 1 Table 2-9 which is included in Appendix D.
Summary of Soil Assessment Results
In March through June 2015, HDR installed borings and monitoring well locations on the site to
assess if source areas have impacted surrounding soil. Boring locations BG-1D, BG-5D, SB-1,
SB-2, and SB-3 were installed to establish background concentrations of constituents in soil.
Locations AB-10D, AB-15D, AB-25BR, AB-30D, AB-35BR, AB-10D, AS-12S, MW-310BR, MW-
311BR, and MW-314BR were installed through the Primary and Secondary Ash Basin to collect
soil beneath the basins to determine if impacts are present or absent and to what lateral/vertical
extent beneath the basins. Locations AS-2D, AS-4D, AS-6D, AS-8D, MW-303BR, MW-315BR,
and MW-318BR were installed through the Ash Fills 1 and 2 to collect soil beneath the storage
areas to determine if impacts were present or absent and to what lateral/vertical extent beneath
the storage areas. Finally, GWA-10D, GWA-11D, GWA-12D, GWA-12S, GWA-14S, GWA-15D,
GWA-1D, GWA-2D, GWA-3D, GWA-4D, GWA-5BR, GWA-6S, GWA-7S, GWA-8D, GWA-9D,
MW -22BR, and MW-317BR were installed within and outside of the compliance boundary to
collect soil to determine if impacts are present or absent and to what lateral/vertical extent. CSA
Figure 8-1 (Appendix D) depicts the location of each of these boring and monitoring well
locations.
During the soil assessment a total of 107 soil samples were collected, 23 of which were
considered to be background soil sample locations. Sampling intervals/purpose in addition to
selected laboratory analysis for soil samples are summarized in CSA Tables 8-1 and 8-2
(Appendix D). Soil sample results were compared to PSRGs POG and are summarized in CSA
Tables 8-3 and 8-5 (Appendix D).
In the CAP Part 1 (HDR, 2015b), HDR reported that soil analytical results revealed
concentrations of arsenic, chromium, iron, manganese and selenium above the PSRGs POG
beneath the ash basins, beneath the ash storage areas, beyond the waste boundary, and at or
beyond the compliance boundary. HDR further indicated that with the exception of selenium,
these COIs were also reported in one or more of the background soil boring locations at
concentrations exceeding the PSRGs POG. HDR reported that all six COIs with concentrations
exceeding the PSRGs POG will be considered for corrective action in soil.
In the CAP Part 2 (HDR, 2016), HDR concluded that where soil impacts were identified beneath
the ash storage areas and ash basins, the vertical extent was limited to the uppermost soil
sample collected beneath the ash/soil interface.
Summary of PWR and Bedrock Characteristics
In the CAP Part 1 (HDR, 2015b), HDR reported that PWR and bedrock samples were collected
from rock cores at the request of NCDEQ. In order to analyze samples for ash-related
constituents as unconsolidated material, PWR and bedrock samples were pulverized as part of
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

30
the CSA activities. Sampling intervals/purpose and selected laboratory analysis for PWR and
bedrock samples were summarized in CSA Tables 8-1 and 8-2 with sample locations depicted
on Figure 8-1 (Appendix D). PWR and bedrock sample results compared to the NCDEQ PSRGs
for IH and POG are summarized in CSA Tables 8-4 and 8-6 (Appendix D).
Results reported in the CSA (HDR, 2015a) for the PWR and bedrock analysis indicated that with
the exception of barium, all of the COIs identified in PWR and bedrock were consistent with the
background locations where rock was obtained at concentrations exceeding the applicable soil
standards.
HDR stated in the CAP Part 1, that PWR and bedrock data were not representative of in-situ
PWR/bedrock conditions. According to HDR, hydraulic and geochemical properties of the
PWR/bedrock were changed following pulverization. It was for this reason that HDR indicated
further evaluation of constituents in the solid PWR and bedrock matrix would not be conducted
and no COIs were identified for corrective action.
4.5.3 Surface Water and Sediment Assessment
Summary of Surface Water Characteristics
In May and June, 2015 (Round 1) and September, 2015 (Round 2), HDR collected surface
water samples from the Dan River and two unnamed tributaries located on the eastern and
western sides of the site that discharge to the river. Surface water samples including SW-2
through SW-8, and SW-10 through SW-13 are depicted on CAP Part 2 Figure 2-1 (Appendix D).
Surface water laboratory analysis was performed for the same analytes as ash basin surface
water samples and are summarized in CSA Table 7-3 (Appendix D). Surface water results were
compared to 2B Standard and applicable USEPA National Recommended Water Quality Criteria
and are summarized CAP Part 2 Table 2-11 (Appendix D).
The analysis, particularly in Round 2, focused on the eastern unnamed tributary as it was
determined that there is a hydraulic connection between the ash storage basin and the tributary
from earlier CSA activities. The surface water analysis indicated exceedances of 2B Standards
in the eastern unnamed tributary and, as a result, the following compounds were identified as
COIs:
 Copper in SW-3, SW-6, and SW-13
 Lead in SW-11, SW-12, SW-3, and SW-8
 Aluminum in SW-4, SW-12, and SW-13
 Arsenic in SW-10 (in Round 2 only) and SW-3 (in Round 1 only)
Summary of Sediment Characteristics
Between May and July 2015, HDR collected sediment samples coincident with surface water
sample locations in the western unnamed tributary and in the Dan River (SW-3, SW-4, SW-6,
and SW-7). Three additional sediment samples (S-1 through S-3) were collected from the
eastern unnamed tributary. Background sediment samples were also collected in the western
unnamed tributary (SW-5) and in the Dan River (SW-8). No background samples were collected
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

31
in the eastern unnamed tributary. Sediment samples were analyzed for the same analytes as
soil samples and are summarized in CSA Table 8-2 (Appendix D). CSA Figure 9-1 (Appendix D)
depicts the location of each of the sediment samples locations.
Sediment sample results were compared to NCDEQ PSRGs for IH and PGS are summarized in
CSA Table 9-1 (Appendix D). According to the CSA, arsenic, cobalt, iron, manganese, and
vanadium were identified as COIs in sediment. HDR concluded that with the exception of
arsenic, the COIs detected in sediment were also reported in the background sediment sample
locations at concentrations exceeding the applicable soil standards. As a result, only arsenic
was considered as a COI for corrective action in sediment in the CAP Part 1 (HDR, 2015b).
4.6 Historical Groundwater Sampling Results
Included in this section is a summary of groundwater assessment activities performed by HDR
on and in the vicinity of the Dan River Steam Station. Beginning in February 2015, HDR
installed a total of 78 groundwater monitoring wells at the site. HDR collected two rounds of
groundwater samples from monitoring wells installed upgradient, within, and downgradient of
the source area. Background wells were sampled four times in order to generate the data
necessary for PPBC development. The results of groundwater sampling indicated that the
extent of groundwater impacts needed to be refined in the following areas:
 Vertically in the vicinity of Ash Fill 1
 Horizontally and vertically north of Ash Fill 1
 At the groundwater-surface water interface north of the Secondary Cell
In order to understand the extent of groundwater impacts in these areas, 13 additional wells
were planned for installation in the first quarter of 2016. Available monitoring well construction
details including total depth and screening intervals are included in CSA Tables 10-6 and 10-7
(Appendix D).
The following sections provide a summary of the groundwater monitoring well installation and
assessment of analytical results including background groundwater and source area samples,
i.e. ash basin and ash storage areas.
Tables comparing groundwater results to the associated criteria and/or standards are provided
in CAP Part 2 Tables 2-4 through 2-9 (Appendix D). Areas with exceedances of the 2L
Standards, IMACs, or North Carolina Department of Health and Human Services (DHHS)
Health Screening Levels (HSL) are depicted on CAP Part 2 Figure 2-5 (Appendix D).
It should be noted that following the CSA activities, several monitoring wells in source areas
including AS-4D, AS-6D, AS-0D, GWA-2S/D, GWA-3S/D, MW-303BR, and MW-306BR were
abandoned by HDR due to planned ash removal activities at the Dan River Steam Station.
Summary of Background Groundwater Monitoring Wells
For the CSA, a total of four rounds of groundwater samples were collected from background
monitoring wells in June, September, November, and December 2015. Shallow background
groundwater samples were collected from compliance monitoring well BG-5S and CSA
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

32
monitoring well GWA-12S. Deep background groundwater samples were collected from CSA
monitoring wells BG-1D, BG-5D, BG-12D, and MW-23D. Bedrock background groundwater
samples were collected from MW-23BR. BG-1D was installed as a background well during the
CSA, however, the well was dry and could not be sampled during assessment activities.
Groundwater sample results were compared to the 2L Standards, IMACs, or DHHS HSL. CSA
Figure 10-8 (Appendix D) depicts the location of each monitoring well. Background groundwater
sample results are summarized CAP Part 2 Table 2-5 (Appendix D).
Antimony, chromium, cobalt, iron, manganese, thallium, vanadium, hexavalent chromium, and
pH were reported at concentrations greater than the 2L Standards, IMACs, or DHHS HSLs.
HDR concluded in the CAP Part 2 that further evaluation of background sample results and
PPBCs would be provided in subsequent reports.
In addition to performing an on-site background groundwater evaluation, HDR also compared
site groundwater (Round 1) to published regional groundwater values and constituent
concentrations from private wells located between two and ten miles from the Dan River Steam
Station waste boundary. The background groundwater concentrations for the Dan River Steam
Station Site are presented in the CAP Part 1 Table 2-2 (Appendix D).
Summary of Groundwater Assessment Results Upgradient of the Ash Basin and Ash
Storage Area
During Round 1 and 2 groundwater sampling events, samples were collected from the following
wells located upgradient of the ash basin and ash storage areas: GWA-12D/12S, GWA-6S,
GWA-7D/7S, GWA-8D/8S, GWA-9D/9S, MW-12/12D, MW-20D, MW-20S, and OW-310D. CAP
Part 2 Figure 2-1 depicts the location of these wells. Groundwater analytical results compared to
the 2L Standards, IMACs, or DHHS HSL are presented in CAP Part 2 Table 2-6.
The results of the sampling identified the presence of the following COIs upgradient of the ash
basin and ash storage areas: antimony, beryllium, cobalt, iron, manganese, and vanadium
(HDR, 2016).
Summary of Groundwater Assessment Results beneath the Ash Basin
To evaluate groundwater beneath the ash basins, HDR collected groundwater from monitoring
wells installed within the footprint of the Primary and Secondary Ash Basins and associated
dams in June and September 2015, Round 1 and Round 2, respectively. Ash basin monitoring
wells included: AB-5S/D, AB-10S/SL/D, AB-25S/D/BR, AB-30S/D/BR, AB-35BR, MW-308BR,
MW -310BR, MW-311BR, MW-314BR, and MW-22BR. Additionally, to supplement groundwater
quality data, HDR also sampled ten existing groundwater monitoring wells located within the ash
basin system and associated dams. These monitoring wells included: MW-9, MW-9D, MW-10,
MW -10D, MW-11, MW-11D, MW-22S/D, OW-308D, and OW-310D. CSA Figures 10-8 and 10-
63 (Appendix D) depict ash basin groundwater monitoring well locations and the groundwater
result exceedances for Round 1, respectively. Groundwater analytical results compared to the
2L Standards, IMACs, or DHHS HSL are presented in CAP Part 2 Table 2-10 (Appendix D).
The COIs identified in groundwater beneath the ash basins included antimony, arsenic, boron,
cobalt, hexavalent chromium, iron, manganese, and vanadium (HDR, 2016).
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

33

Summary of Groundwater Assessment Results Downgradient of the Ash Basin and Ash
Storage Areas
To evaluate potential impacts from the ash basin and ash storage areas on groundwater quality
beyond the waste boundary, HDR installed and sampled 27 groundwater monitoring wells
(shallow, deep, and bedrock) downgradient of the ash basin and ash storage areas, and
collected groundwater samples in June and September 2015, Round 1 and Round 2,
respectively. Downgradient wells included GWA-1S/D, GWA-2S/D, GWA-3S/D, GWA-4S/D,
GWA-5BR, GWA-6S/D, GWA-7S/D, GWA-8S/D, GWA-9S/D, GWA-10S/D, GWA-11S/D, GWA-
12S/D, MW-317BR, GWA-14S/D, and GWA-15D. HDR noted that GWA-10S was dry during
Round 1 and was not sampled. CSA Figures 10-8 and 10-63 (Appendix D) depict groundwater
monitoring well locations beyond the waste boundary and the groundwater result exceedances
for Round 1, respectively. Groundwater analytical results compared to the 2L Standards, IMACs,
or DHHS HSL are presented in CAP Part 2 Table 2-9 (Appendix D).
The COIs identified in groundwater beyond the waste boundary included arsenic, cobalt, iron,
manganese, sulfate, TDS and vanadium (HDR, 2016).
Summary of Groundwater Quality Standard Exceedances
HDR compared COIs identified during Round 1 and Round 2 groundwater sampling events to
PPBCs to determine if the COIs were naturally occurring or attributable to ash handling activities
at the Dan River Steam Station. The results of the comparison are provided in CAP Part 2 Table
2-10 (Appendix D). Areas of exceedances of COIs attributable to ash handling activities at the
Dan River Steam Station are depicted on CAP Part 2 Figure 2-5 (Appendix D). COIs identified
by HDR in groundwater that were being evaluated for corrective action include: antimony,
arsenic, boron, cobalt, iron, manganese, selenium, sulfate, thallium, TDS, and vanadium.
Summary of Groundwater Geochemistry
The ash storage area and ash basin system are subject to different processes including
precipitation and process water infiltration that promote leachate migration into underlying soil
and groundwater. HDR identified that the distribution and concentrations of COIs that result from
the leaching process are controlled by a number of factors. These factors include how dissolved
phase concentrations are transported through soil/rock media, the composition of the soil/rock
media in the flow path, and the geochemical conditions present along flow paths. To understand
geochemical effects at the Dan River Steam Station, HDR evaluated cations/anions, redox
potential, solute speciation, and sorption in subsurface groundwater or soil. The results of these
evaluations are summarized in the following subsections.

pH, Dissolved Oxygen (DO), and Oxidation-Reduction Potential (ORP)
Field measurements indicate that pH in groundwater at the Dan River Steam Station ranges
from 4.77 to 11.44 standard units (SU). Background and upgradient wells indicated pH ranges
between 6.89 and 7.45 SU and 5.39 and 7.81 SU, respectively. Within the ash basin materials,
pH ranged from 6.46 to 8.61 SU. ORP readings collected during sampling indicated reducing
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

34
(negative values) and oxidizing (positive values) across the site. Both reducing and oxidizing
conditions were observed in ash pore water. Oxidizing conditions were generally observed in
the three flow layers identified beneath the Dan River Steam Station, with the exception of
several areas located directly beneath the ash basins and storage areas, and in the deep flow
layer located outside of the Dan River Steam Station waste boundary. Background wells
consistently reported oxidizing conditions.
At the site, the primary redox are oxic and mixed (anoxic). HDR reported DO levels that
exceeded the threshold of 0.5 mg/L in 52 percent (%) of the samples collected. Predominant
redox processes are oxygen reduction of iron or manganese couples. According to HDR, under
these conditions, metals species arsenic (V), selenium (VI), and manganese (IV) would be
expected. Approximately 72% from wells across the site were found to be suboxic or oxic,
where reduced species of metals like arsenic (III) are less likely to be present (HDR, 2016).

Cations/Anions
Using Piper diagrams to graphically depict the distribution of major cations and anions in
groundwater samples from the Dan River Steam Station, HDR found that groundwater and
surface water was predominantly rich in calcium, magnesium, and bicarbonate. Downgradient
monitoring wells differed with calcium, magnesium, and sulfate-rich geochemical composition.
Finally, Piper diagrams plots indicated that mixing of ash basin pore water and groundwater was
likely occurring.

Solute Speciation
As part of on-site assessment activities, select groundwater and pore water monitoring wells
were sampled for chemical speciation analyses of arsenic (III), arsenic (V), chromium (VI), iron
(II), iron (III), manganese (II), manganese (IV), selenium (IV), and selenium (VI). Speciation
analysis indicated that redox conditions are reflected in the speciation of redox-sensitive
species. Reduced arsenic (III), iron (II), manganese (II), and selenium (IV) were observed in the
14 samples analyzed for solute speciation with the exception of one non-detect for selenium
(IV). Two of three samples indicated arsenic (III) as the dominant species. Because arsenic (III)
tends to react less than arsenic (V) with aquifer media, oxidation of arsenic would improve
sorption and attenuation of arsenic. In summary, the results indicate there are significant
concentrations of reduced species of COIs in wells at the site. Therefore, HDR concluded that
consideration of speciation is necessary in evaluation of corrective measures (HDR, 2015b).
4.7 Groundwater Potentiometric Contour Maps
HDR generated potentiometric surface maps from data collected from shallow “S”, deep “D”,
and bedrock “BR” groundwater monitoring wells installed on the site. Based on CSA results,
HDR reported that the undisturbed, native material groundwater system is consistent with a
regolith-fractured rock system. This system was characterized as being an unconfined,
connected aquifer system. Regolith was characterized as the alluvium, residuum, and saprolite
hydrostratigraphic units. These units in combination with ash and fill material represented the
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

35
shallow and deep aquifer for the Dan River Steam Station. PWR (or transition zone) and
bedrock hydrostratigraphic units were identified to represent the bedrock aquifer. Potentiometric
contour maps for the flow layers are presented in CAP Part 1 Figures 3-3 through 3-5 (Appendix
D).
HDR reported that, in general, the shallow and deep potentiometric surfaces flow from the north
toward the Dan River which are south and southeast of the site. An area north of Ash Fill 1 was
noted as an exception to the shallow and deep potentiometric surface. In this area, groundwater
elevation data indicated the presence of a groundwater divide in the vicinity of MW-12 and
GWA-1. Localized groundwater north of the divide was found to flow away from the Dan River
Steam Station site and toward the unnamed tributary to the east.
HDR reported that groundwater flow in the bedrock hydrostatic units were consistent with the
shallow and deep units and generally flowed in a south-southeasterly direction.
As reported in the CAP Part 2 (HDR, 2016), average horizontal hydraulic gradients were
calculated for the Round 1 and 2 sampling events as follows:
 Shallow Aquifer: Round 1 – 0.030 feet/foot; Round 2 – 0.029 feet/foot
 Deep Aquifer: Round 1 - 0.029 feet/foot; Round 2 – 0.029 feet/foot
 Bedrock Aquifer: Round 1 - 0.037 feet/foot; Round 2 – 0.035 feet/foot
According to HDR, the vertical hydraulic gradient was generally downward across the site, with
16 of the 20 well pairs ranging between -0.002 feet/foot and -1.864 feet/foot. Four of the 20 well
pairs exhibited an upward gradient ranging between 0.051 feet/foot and 0.333 feet/foot in close
proximity to the ash storage areas and ash basin (HDR, 2016).
4.8 Figures: Cross Sections Vertical and Horizontal Extent of CCR within the
Impoundments
Cross sections illustrating the vertical and horizontal extent of CCR material within the
impoundments were developed as part of the CSA Report (HDR, 2015a) and are shown in
Figures 11-1 through 11-5 (included in Appendix D).

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

36
5. GROUNDWATER MODELING ANALYSIS
5.1 Site Conceptual Model Predictions
HDR developed a SCM in accordance with ASTM standard guidance document E1689-95
(Reapproved 2014) using the following criteria:
 Identification of potential contaminants
 Identification and characterization of the source contaminants
 Delineation of potential migration pathways through environmental media
 Establishment of background areas
 Environmental receptor identification and discussion
 Determination of system boundaries
A schematic representation of the SCM is included as CAP Part 2, Figures 3-1 and 3-2
(Appendix D). Below is a summary of the SCM results for each of the criterion.
Potential Contaminants
Sections 4.5 and 4.6 of this Removal Plan summarize the results of CSA activities for the Dan
River Steam Station and present the results of the potential contaminants for the site. These
potential contaminants were identified by HDR as COIs for multiple media including soil,
groundwater, surface water, and sediment.
Source Area Characterization and Contaminants
The primary source areas at the site are defined as the CCR units, namely Primary and
Secondary Ash Basins and the Ash Fill 1 and Ash Fill 2. Source area contaminants from ash,
ash basin water, pore water, and AOWs are summarized in Section 4.5.1.
In the CAP Part 2, HDR reported that ash within the basins was encountered at depths ranging
between 17 and 45 feet below ground surface (bgs). In Ash Fill 1, ash was encountered from 10
to 80 feet bgs (HDR, 2016). Finally, in Ash Fill 2, ash was encountered from 2 to approximately
27 feet bgs (HDR, 2016). A geologic cross-section illustrating the vertical and horizontal extent
of source area is shown in CAP Part 2 Figure 3-2 (Appendix D).
COI Delineation
As discussed in Sections 4.5 and 4.6 of this Removal Plan, the results of the CSA indicate that
COIs at the Dan River Steam Station are present beneath the CCR units as well as
downgradient and east of the Secondary Cell.
HDR indicated that soil was delineated on the site with the exception of COIs in off-site areas
north and east of Ash Fill 1. Beneath the basins, soil was delineated to the uppermost soil
sample beneath the ash for COIs including arsenic, boron, chromium, cobalt iron, manganese,
selenium, and vanadium. The impacted soil beneath the ash could also be considered a
potential secondary source. As a result, HDR recommended that soils left onsite after
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

37
excavation be assessed for COIs and the data added to the fate and transport model. If data
indicates a modification to the CAP is required, Duke will prepare and submit a revised CAP.
Additional assessment is being conducted by HDR to further delineate soil impacts at the site
and will be reported under separate cover.
In groundwater, HDR reported that the approximate extent of impacts is limited to beneath the
ash basin and ash storage areas with the exception of the following areas:
 Vertically beneath Ash Fill 1
 Horizontally and vertically north of Ash Fill 1
 East of Secondary Cell where groundwater and surface water interaction has been
observed
COIs identified in groundwater that are being evaluated for corrective action include: antimony,
arsenic, boron, cobalt, iron, manganese, selenium, sulfate, thallium, TDS, and vanadium.
As discussed in Section 4.7, the groundwater system is divided into three layers: shallow, deep,
and bedrock. Groundwater generally flows from the north/northwest to the south/southeast,
towards the Dan River. Groundwater north/northeast of Ash Fill 1 flows to the eastern unnamed
tributary which ultimately discharges to the Dan River. Groundwater in bedrock flows in the
same general direction as shallow and deep layers. Finally, the Dan River serves as the lower
hydraulic boundary for shallow, deep, and bedrock groundwater.
COIs identified in surface water (SW-3) collected from the unnamed tributary to the Dan River
were, according to HDR, similar to COIs identified in groundwater monitoring wells located
between the eastern unnamed tributary and the Secondary Cell. Aluminum, copper, and lead
were identified as COIs in surface water samples collected from Dan River. HDR attributed the
source of copper to an off-site source.
Background Areas
Background monitoring wells were installed in areas to the north, northwest, and west of
portions of the Dan River Steam Station. The results of the background groundwater
assessment are discussed in Section 4.6 of this Removal Plan.
Receptors
In September and November 2014, Duke conducted and updated a receptor survey of the area
within a 0.5 of the Compliance boundary. The results of the survey are summarized in Section
3.2.2 of this Removal Plan. Receptors are depicted on CAP Part 2 Figure 3-3.
System Boundaries
The property boundary, as well as waste and compliance boundaries for the Dan River Steam
Station, are depicted based on the SCM in CAP Part 2 Figure 2-1 (Appendix D). The site is
bounded by a hydrologic divide to the north of Ash Fill 1, the Dan River to the south/southeast,
and an unnamed tributary to the east and South Edgewood Road to the west. HDR reported
that bedrock beneath the site impedes vertical migration of COIs at depth.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

38
5.2 Groundwater Chemistry Effects
The objective of the geochemical modeling for the Dan River Steam Station was to describe the
expected partitioning of COIs between the aqueous and solid phases (i.e., between
groundwater and soil and between ash pore water and ash), and to anticipate changes in phase
distributions given variations in DO, pH, and TDS. COIs evaluated for the geochemical modeling
included: antimony, arsenic, boron, chromium, cobalt, iron, manganese, pH, selenium, sulfate,
TDS, thallium, and vanadium.
Evaluations of COIs were performed for each monitoring well using the United States
Geological Survey PHREEQC (v3.3.3.) geochemical speciation code (Parkhurst and Appelo
2013) and PhreePlot (Kinniburgh and Cooper 2011). Model input parameters included the
concentration of the COIs, ORP, alkalinity, sodium, and other ions in groundwater for 78
monitoring wells at the site. Simulations were performed to predict geochemical speciation for
COIs in the presence of adsorption to soils and response to changes in DO, pH, and TDS.
Hydrous ferric oxides (HFO) represented weak binding sites and hydrous aluminum oxides
(HAO) represented strong binding sites.
HDR provided the following geochemical modeling observations:
 Because redox conditions varied widely across the site, equilibrium was not achieved or
data are not representative of the conditions sampled. HDR recommended that
additional groundwater results be added to the model to further refine the model and to
confirm findings if data is not representative of actual groundwater conditions.
 The limited solubility of arsenic, chromium, cobalt and selenium in site groundwater was
confirmed by geochemical modeling.
 pH, Eh and TDS should be further evaluated to address monitoring natural attenuation
(MNA) or remediation options including, but not limited to, capping and pH adjustment.
Remediation by capping could be further modeled to assess impacts microbial
mechanisms and/or secondary metal reductions.
 Soil sorptive capacity for COIs such as boron were lower than COIs such as arsenic.
5.3 Groundwater Trend Analysis Methods
COIs under the influence of certain physical and geochemical processes may leach and migrate
into groundwater. In order to evaluate COI migration and predict potential impacts that could
result following closure of the CCR units at the site, HDR performed modeling of groundwater
flow, COI fate and transport, and groundwater to surface water mixing.
Groundwater models were run to simulate groundwater elevations in the ash and underlying
groundwater flow layers and to simulate COI concentrations at the compliance boundary or
other downgradient locations of interest over time for closure scenarios.
The University of North Carolina at Charlotte (UNCC) developed a site-specific, 3-D, steady-
state groundwater flow and fate and transport model for the Dan River Steam Station using
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

39
MODFLOW (Niswonger et. al., 2011) and MT3DMS (Zheng and Wang, 1999). The model
domain included the site, a section of the Dan River, and site features relevant to the
assessment of groundwater. The model domain was bounded by the following hydrologic
features:
 The northern shoreline of the Dan River along the station
 The unnamed tributary to the east
 The groundwater boundary along a topographic divide to the north
 The unnamed tributary to the west
Initially, as part of the CAP Part 1 (HDR, 2015b), groundwater elevations and COI
concentrations were evaluated for each of the closure scenarios using a 12 model layer divided
among the hydrostratigraphic units detailed in Section 4.7. COI velocity and flow direction to
potential off-site receptors were simulated by assigning geologic units, hydrologic features, and
flow boundaries within the COI source areas.
For the site, a laboratory determination of the partition coefficient (Kd) was performed by UNCC
on soil samples collected during the CSA. Soil samples were tested in flow-through columns to
measure sorption of COIs at varying concentrations. Twelve column tests and 22 batches were
tested. The resulting Kd data was used as input parameters to evaluate fate and transport
through the subsurface. Sorption studies on soil samples obtained during the CSA indicated that
Kd values for COIs in native soil surrounding the ash basins and ash storage areas are higher
than the values used in modeling.
Subsequent to the submittal of the CAP Part 1, UNCC and Geochemical, LLC recalculated Kd
values using linear Freundlich isotherm. Use of the refined COI Kd values in the fate and
transport model resulted in improved model calibration of source concentrations to measured
concentrations in downgradient wells. Additionally, the model was refined to incorporate PPBCs.
Finally, the refinements were made to better represent measured source area pore water
concentrations.
Two closure scenarios were modeled for the Dan River Steam Station. The existing conditions
scenario assumed ash sources were left in place. The excavation scenario assumed accessible
ash was removed from the site. No modifications were made to the previously modeled existing
conditions scenario hydrogeologic parameters or structure between each modeling phase.
Existing Conditions Scenario
One of the purposes of modeling the existing conditions scenario was to predict when steady-
state concentrations would be achieved at the compliance boundary. The model was calibrated
for steady-state groundwater flow conditions and transient transport of COIs under existing
conditions. The simulation revealed that COI concentrations remained the same or increased
initially with source concentrations held at their constant value over time. Concentrations and
discharge rates were found to remain constant thereafter. According to HDR, the existing
conditions scenario represented the most conservative case in terms of groundwater
concentrations onsite and offsite, with COIs discharging to surface water at steady-state.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

40
Areas close to the compliance boundary were predicted to reach steady-state concentrations
sooner than areas further away from the compliance boundary. Sorptive COIs were predicted to
remain transient for a longer period of time as their peak breakthrough concentrations travel at
rates less than groundwater pore velocity.
Excavation Scenario
The excavation scenario assumed water and/or ash would be removed from the CCR units and
transported offsite. The model did not account for backfilling of excavation areas and the
constant concentration of COIs in the source areas above and below the water table being
removed. An assumed recharge rate of 6.5 inches per year was used. The simulation revealed
that COIs already present in groundwater continued to migrate downgradient as water infiltrated
and recharged the aquifer. COIs also moved through the saturated zone beneath the source
areas at rates dependent on physical and geochemical interactions of the COI and groundwater.
If the area became unsaturated, COIs were observed to decrease over time without a
contributing source. COI migration slowed relative to pore water velocity with sorptive COIs
attenuated by site materials.
Summary of Groundwater Modeled Scenario Predictions
A summary of the modeled results for both scenarios at the Compliance Boundary as presented
in the CAP Part 2 is provided in the table below.
Constituent
(Standard)
Flow
Layer
Existing Conditions Excavation Scenario
Year 0 Year 100 Year 0 Year 100
Antimony
IMAC
(1 µg/L)
Shallow + + + +
Deep + + + +
Bedrock + + + +
Arsenic
2L
(10 µg/L)
Shallow - - - -
Deep - - - -
Bedrock - - - -
Boron
2L
(700 µg/L)
Shallow - + - -
Deep - + - -
Bedrock - + - -
Chromium Shallow - - - -
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

41
Constituent
(Standard)
Flow
Layer
Existing Conditions Excavation Scenario
Year 0 Year 100 Year 0 Year 100
2L
(10 µg/L)
Deep + - + -
Bedrock - - - -
Cobalt
IMAC
(1 µg/L)
Shallow + + + +
Deep + + + +
Bedrock + + + -
Hexavalent
Chromium
NCDHHS HSL
(0.07 µg/L)
Shallow + + + +
Deep + + + +
Bedrock + + + +
Selenium
2L
(20 µg/L)
Shallow - - - -
Deep - - - -
Bedrock - - - -
Sulfate
2L
(250,000 µg/L)
Shallow - + - -
Deep + + + -
Bedrock + + + -
Thallium
IMAC
(0.2 µg/L)
Shallow - + - +
Deep - + - +
Bedrock + + + +
Vanadium
IMAC
(0.3 µg/L)
Shallow + + + +
Deep + + + +
Bedrock + + + +
Notes:
“+” indicates that concentration of a given COI has exceeded its applicable 2L Standard, IMAC or NCDHHS HSL.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

42
“-“ indicates that concentration of a given COI is below its applicable 2L Standard, IMAC or NCDHHS HSL.
Year 0 represents initial concentrations observed in 2015.
Year 100 represents the observed 100 year post implementation of each scenario.
Based on the model prediction results, the CAP Part 2 (HDR, 2016) provided the following
observations:
 A CAP may be approved by the NCDEQ without requiring groundwater remediation to
the 2L Standards if seven requirements are met (15A NCAC 02L. 0106[k]). One
requirement is that the 2L Standards must be met at a location no closer than one year
time to travel upgradient of an existing or foreseeable receptor. The Dan River is the
receptor for the site. To evaluate this requirement, HDR and UNCC conducted particle
tracking for the existing conditions scenario using monitoring well data from onsite wells.
Results indicated that four of the seven shallow wells, six of the seven deep wells, and
four of the five bedrock wells did not meet the condition criteria for these respective
groundwater flow layers.
 Under the existing conditions and excavation scenarios, the model predicted that
antimony, boron, cobalt, sulfate, thallium, and vanadium would be greater than the
respective 2L Standard or IMAC at the Dan River interface for groundwater flow layers.
Hexavalent chromium was predicted to be greater than the DHHS HSL at the Dan River.
Background concentrations used for modeling antimony, cobalt, thallium and vanadium
also exceeded the applicable groundwater standard at Dan River.
 Refined model predictions did not reveal that COI concentrations would be effectively
reduced by ash removal under the excavation scenario. The COIs that were predicted to
be greater than the respective standard or screening level will remain above for the
modeled period (2015 to 2115).
 Arsenic and selenium concentrations were predicted to be below the respective 2L
Standards at the Dan River interface for both the existing condition scenario and the
excavation scenario.
 The model predicted that COIs like boron and sulfate, with low Kd values, rapidly and
nearly completely reduce to below the respective standard or IMAC under the
excavation scenario.
Groundwater to Surface Water Interaction Modeling
As part of the CAP Part 1 (HDR, 2015b), a simulation model was performed to estimate
groundwater flow and constituent loading to the adjacent downgradient unnamed tributaries and
to the Dan River. For the groundwater-surface water interaction simulation, fate and transport
output data were applied using a Mixing Model Approach. River flow data from the USGS (or
other suitable gauges) were used to design upstream river design flows and constituent
compliance with 2B Standards. The groundwater to surface water mixing model calculations
were commensurate with the observed concentrations at surface water sample location SW-3
near the mouth of the unnamed east tributary and at surface water locations SW-6 and SW-7 in
the Dan River adjacent to the site. Differences in model outputs were attributed to the use of
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

43
maximum observed groundwater concentrations in mixing model calculations. The mixing model
results predicted that water quality standards would be attained at the edge of the mixing zone
for all compounds with the exception of arsenic. Arsenic concentrations were calculated in the
eastern unnamed tributary to be above the human health standard 2B Standard at surface
water sample location SW-3.
For the CAP Part 2, HDR refined the groundwater-surface water interaction model by using the
following:
 Using revised Kd values
 Additional COIs were added based on the results of Round 2 groundwater sampling or
as requested by NCDEQ
 Updated groundwater flux data
 Round 2 groundwater results
For the refined model implementation, groundwater-surface water interactions were completed
using groundwater model output and a surface water mixing model approach. This was done to
evaluate potential surface water impacts of COIs in groundwater as they discharge to surface
water bodies adjacent to the Dan River Steam Station. Results of the groundwater model-
calculated and surface water sample concentrations indicated that the 2B Standards were met
for all COIs except for arsenic in the unnamed tributary, which exceeded the standard for human
health. This conclusion was based on an average surface water concentration of 11.3 µg/L (from
SW -3, SW-4, SW -10, SW-11, SW-1, and SW-13). HDR concluded that this was a localized
condition as model results for surface water at locations SW-4, SW-11, SW-12, and SW-13 in
the eastern unnamed tributary were less than the human health 2B Standard. In the Dan River,
modeled calculated results were less than the acute, chronic, and human health 2B Standards
at the edge of the mixing zones.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

44
6. BENEFICIAL USE AND FUTURE USE
6.1 CCR Material Use
Duke regularly considers CCR beneficial use in an environmentally responsible manner for ash
that is produced at its plants or needs to be removed from existing ash basins. Duke has a team
dedicated to identifying beneficial use opportunities and evaluating their feasibility. Consistent
with North Carolina CAMA requirements, Part III, Section 4.(e), Duke issued a request for
proposals to conduct a beneficial use market analysis, study the feasibility and advisability of
installing existing beneficiation technologies, and examine innovative technologies.
Duke completed a 4,000 ton beneficial use pilot with Roanoke Cement Company, LLC (RCC) in
2016 and is in on-going negotiations with RCC for a long-term agreement to utilize small-scale
CCR quantities.
At this time, no large-scale CCR beneficial use opportunities have been identified for the Dan
River Steam Station. In light of the August 1, 2019 CAMA closure deadline and the large
investment that would be required, large-scale beneficiation is unsupportable on the basis of
economic and business criteria. However, the final closure design does consider long-term
reclamation of CCR should feasible beneficial uses be identified in the future. This does not
necessarily change the general design but considers reclamation as part of the overall site
planning and permitting.
6.2 Site Future Use
There is currently no planned future use for the ash basin areas. The closure design provides
for removal and decommissioning of the dams and regrading the ash basin areas to balance
earthwork cut and fill and provide for storm water management. After ash and dam removal, the
ash basin area will be stabilized with permanent vegetation (consisting of grasses) and will be
maintained throughout the post-closure period.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

45
7. CLOSURE DESIGN DOCUMENTS
Closure design consists of disposing impounded CCR materials into a lined landfill facility and
decommissioning the existing dams associated with the ash basins such that the dams may be
removed from the state dam inventory and jurisdiction of dam safety regulations. The two dams
to be decommissioned as part of the closure process are the Dan River Primary Ash Basin Dam
(NC State ID ROCKI-237) and the Dan River Secondary Ash Basin Dam (NC State ID ROCKI-
238). Following removal of CCR materials, grades will be established which will prevent future
impounding of runoff and restore gravity flow from upstream tributary areas across the existing
basin footprint and into the Dan River.
Ash basin closure design has been developed and documented through engineering
evaluations and analyses, drawings, specifications, and a construction quality assurance plan.
The closure design documents are summarized in the following sections.
7.1 Engineering Evaluations and Analyses
Engineering evaluations and analyses for ash basin closure focus on stormwater management.
Geotechnical stability analyses are not necessary to support ash removal and dam
decommissioning and are not be provided. Furthermore, results of existing geotechnical stability
analyses (Amec Foster Wheeler, 2016d) indicate that the ash basin dams will satisfy
geotechnical stability criteria during ash and dam removal. Engineering analyses are included in
Appendix E and summarized below.
7.1.1 Freeboard During Dam Decommissioning
The existing ash basin embankments and outlet structure will be lowered as CCR removal
progresses. Adequate freeboard will be maintained during dam decommissioning activities. The
freeboard requirements during dam decommissioning were specified based on the calculation
titled “Primary (NC State ID ROCKI-237-H) and Secondary (NC State ID ROCKI-238-H) Ash
Ponds – Hydrologic and Hydraulic (H&H) Analysis” dated January 30, 2015 which was
developed as part of the “Duke Energy Coal Combustion Residual Management Program
Reconstitution Design of Ash Basins – Dan River Steam Station” (Amec Foster Wheeler,
2016d). Based on this calculation, the design storm is the ¾ probable maximum precipitation
(PMP), 6-hour event with a resulting peak stormwater storage volume of 33 acre-feet into the
Primary Ash Basin and 65 acre-feet into the Secondary Ash Basin (total of 98 acre-feet). The
approximate surface area is 12.0 acres for the Primary Ash Basin and 8.9 acres for the
Secondary Ash Basin (total of 20.9 acres). The minimum freeboard requirements for several
scenarios were estimated as follows and include one foot of additional freeboard:
 Primary Ash Basin and Secondary Ash Basin are not hydraulically linked (except for the
existing pipe and culvert system from the Primary Ash Basin to the Secondary Ash
Basin):
o Primary Ash Basin freeboard = 33 ac-ft / 12.0 ac + 1 = 4 ft
o Secondary Ash Basin freeboard = 65 ac-ft / 8.9 ac + 1 = 10 ft
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

46
 Primary Ash Basin and Secondary Ash Basin are excavated such that a consistent
ash/water surface elevation is maintained across both basins:
o Ash Basin freeboard = 98 ac-ft / 20.9 ac + 1 = 6 ft
Note that freeboard is measured as the difference between the lowest point on the dam crest
and the average elevation of material (CCR or water) within the basin.
7.1.2 Stormwater Management During Interim Conditions
The existing ash basin embankments will be lowered during removal of CCR materials. A
section of embankment approximately 10-feet in height will temporarily remain upon completion
of CCR removal. Four sediment basin outlets will be installed along the southern edge of the
ash basin footprint to discharge water from the remaining impounded area to the Dan River. The
interim graded condition will be utilized during fine-grading within the ash basin footprint and
establishment of vegetation within the newly graded area.
Proposed stormwater channels, culverts, and downdrains were designed for capacity and lining
stability for a 2-year, 24-hour design storm assuming interim conditions consisting of newly
graded tributary drainage areas and channels temporarily stabilized with erosion control matting
or riprap.
7.1.3 Stormwater Management During Final Conditions
The remaining 10-foot high section of embankment and four temporary sediment basins will be
removed upon stabilization of the tributary drainage area such that water will not be impounded
within the abandoned ash basin footprint. Stormwater flows will discharge to the Dan River at
four gabion downdrains coinciding with the location of the temporary sediment basins.
Proposed stormwater channels, culverts, and downdrains were designed for capacity and lining
stability for a 100-year, 24-hour design storm assuming final conditions consisting of grassed
tributary drainage areas and channels permanently stabilized with grass or riprap.
7.2 Removal Plan Drawings
Removal Plan drawings have been developed to support the Decommissioning Plan for
submittal to the NCDEQ Division of Energy Mineral and Land Resources, Safe Dams Program
(Dam Safety). These Removal Plan drawings are provided in Appendix C and include the
following:
DNR-C999.001.001 COVER SHEET
DNR-C999.001.002 SITE AERIAL
DNR-C999.001.003 SITE EXISTING CONDITIONS
DNR-C999.001.004 ASH BASIN EXISTING CONDITIONS
DNR-C999.001.005 ASH BASIN CONDITIONS PRIOR TO CLOSURE
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

47
DNR-C999.001.006 DEMOLITION PLAN
DNR-C999.001.007 ASH BASIN INTERIM CONDITIONS
DNR-C999.001.008 ASH BASIN PROPOSED CLOSURE GRADES
DNR-C999.001.009 ASH BASIN PROPOSED STORMWATER PLAN
DNR-C999.001.010 EXISTING ASH BASIN PIPE PROFILES
DNR-C999.001.011 GENERAL DETAILS 1
DNR-C999.001.012 GENERAL DETAILS 2
DNR-C999.001.013 GENERAL DETAILS 3
DNR-C999.001.014 GENERAL DETAILS 4
7.3 Construction Quality Assurance and Control Plan
Construction quality assurance and control requirements for ash basin closure construction are
defined in the Construction Quality Assurance (CQA) Plan provided in Appendix F. The CQA
Plan outlines the responsibilities and authorities for monitoring and testing activities, sampling
strategies, and reporting requirements.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

48
8. MANAGEMENT OF WASTEWATER AND STORMWATER
8.1 Stormwater Management
The Primary and Secondary Ash Basins were operated as an integral part of the facilities’ waste
water and stormwater management system. Existing site conditions are illustrated in the
Decommissioning Plan Drawings, Drawing DNR-C999.001.003, included in Appendix C and
general site conditions are illustrated in Figure 2. The Primary and Secondary Ash Basin are
located downhill, and as a result, down gradient of a tributary area including the Combined
Cycle Plant, Ash Fill 1, and Ash Fill 2. Historically, stormwater from portions of the upgradient
watershed were conveyed underneath the Primary Ash Basin through a 48-inch diameter culvert
and a 36-inch diameter culvert. In 2014, the 48-inch stormwater culvert failed and both of these
culverts have been plugged. Stormwater at the 48-inch stormwater plugged culvert is pumped to
a sedimentation basin that discharges into a settling pond through stormwater Outfall SW009.
Stormwater at the inlet of the 36-inch stormwater plugged culvert is pumped into the Secondary
Ash Basin and discharged through its outlet structure to the Dan River (Industrial Wastewater
NPDES Outfall 002). Stormwater from the Ash Fill 1 and Ash Fill 2 areas flows to a localized
area between the ash fills where it is conveyed through a pipe into the Secondary Ash Basin
and discharged through its outlet structure to the Dan River (Industrial Wastewater NPDES
Outfall 002). Stormwater from the yard sump, power house sump, and coal yard that were
traditionally pumped to the Primary Ash Basin are currently being rerouted to the west through
the existing service water settling basin and a permitted stormwater outfall.
During Ash Basin closure construction, stormwater will be managed in accordance with
Decommissioning Plan Drawings (Appendix C) and an NPDES permit for construction activities.
Engineering analyses and design for stormwater management and erosion and sediment
control measures during construction (interim) and final conditions are described in Section 7.1
and provided in Appendix E. Details of the stormwater management plans are provided in the
Removal Plan Drawings, Drawings DNR-C999.001.005 and DNR-C999.001.009, and
accompanying detail sheets. Upon closure construction, stormwater from areas upgradient of
the ash basin areas will be conveyed in a controlled and stable manner across the former ash
basin area to discharge into the Dan River. Furthermore, stormwater from within the ash basin
areas will be conveyed and controlled in a stable manner, also discharging to the Dan River.
Duke is authorized to discharge stormwater to receiving waters designated as the Dan River in
accordance with NPDES Permit NCS000572. NPDES Permit NCS000572 has been modified to
incorporate new outfalls namely Outfall SW009 and SW010, created as part of
decommissioning of the former coal-fired steam plant and other construction activities on the
site. The Duke Coal Combustion Products (CCP) Closure Team will coordinate with Duke CCP
Environmental Permitting and Compliance Specialists for any NPDES Industrial Stormwater
Permit modifications.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

49
8.2 Wastewater Management
The Primary and Secondary Ash Basins were operated as an integral part of the facilities’ waste
water and stormwater management system. Existing site conditions are illustrated in the
Decommissioning Plan Drawings, Drawing DNR-C999.001.003, included in Appendix C.
General site conditions are illustrated in Figure 2. Waste water from various sources associated
with the coal-fired plant including the coal yard, yard sump, powerhouse sump, and wastewater
were historically pumped to the ash basins and discharged through the Secondary Ash Basin
outlet structure to the Dan River (Industrial Wastewater NPDES Permit NC0003468 Outfall 002).
As part of the coal-fired plant decommissioning, these sources will be managed through interim
treatment methods until they are removed.
Ash basin closure plans are to remove ash from the ash basins, Ash Fill 1, and Ash Fill 2 to an
on-site landfill to be constructed in the current Ash Fill 1 location. Ash will be removed offsite
until the landfill is operational. Surface water from Ash Fills 1 and 2 is conveyed to the
Secondary Ash Basin through a pipe. Therefore, contact water management will be required
during landfill construction and ash removal from Ash Fills 1 and 2. In addition, wastewater
treatment will be required for dewatering the ash basins prior to transporting ash to the on-site
landfill. Duke is currently evaluating treatment methods, plans to provide for waste water
treatment, and permit conditions to support ash removal. The Duke CCP Closure Team will
coordinate with Duke CCP Environmental Permitting and Compliance Specialists for any
NPDES Wastewater Permit modifications.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

50
9. DESCRIPTION OF FINAL DISPOSITION OF CCR MATERIALS
Duke intends to construct a landfill on Dan River Steam Station property to store CCR currently
located in the Primary Ash Basin, Secondary Ash Basin, Ash Fill 1, and Ash Fill 2. The proposed
landfill will be constructed to enable transfer of ash from the ash basins to a lined facility by
August 1, 2019 as required by the North Carolina CAMA of 2014. The proposed landfill will be
constructed in the footprint of Ash Fill 1. To allow for landfill construction and reduce double-
handling of material, Duke intends to remove some of the ash (from Ash Fill 1) by rail to the
existing Maplewood Landfill in Jetersville, Virginia.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

51
10. APPLICABLE PERMITS FOR CLOSURE
Implementation of the Dan River ash basin closure will require several permits issued by
regulatory authorities. Below is a list of the applicable permits required for closure:
 Dam Breach Approval for Decommissioning Dam Structures
 Discharge Permits for Wastewater and Stormwater
 Solid Waste Permits for Landfills
 Erosion and Sedimentation Control Permits
 Section 401/404 Water Quality certification if applicable
Note that air permits or air permit modifications are not anticipated for the ash basin closure.
The Title V air permit for operating the Dan River Steam Station was rescinded when the plant
was retired in 2012.
10.1 Decommissioning Request and Approval
The plans, specifications, design data, and calculations for decommissioning of the Primary and
Secondary Ash Basin dam structures (ROCKI-237 and ROCKI-238) will be prepared and
submitted to the Dam Safety Section of the NCDEQ Division of Energy, Mineral and Land
Resources as part of the dam breach permit application (Decommissioning Plan).
The Decommissioning Plan and accompanying design package consisting of drawings,
engineering analyses, technical specifications, and a CQA Plan will be submitted for approval
separately from this Removal Plan. Decommissioning Plan drawings, engineering analyses, and
CQA Plan were summarized in Section 7.0 and provided for reference in Appendices C, E, and
F respectively.
The drawings provide grading plans to be implemented for the removal of CCR materials. The
drawings also establish final grades after the dams are breached. The design package also
provides sequencing of construction activities, controls and restrictions on dewatering, and dam
breach sequencing and restrictions. The intent of the dewatering restrictions is to control the
rate of drawdown as well as maintaining dewatering levels during the project. The purpose of
the dam breach restrictions is to maintain adequate freeboard during construction for
containment of CCR materials and precipitation during construction.
Following review of the Decommissioning Plan by the Dam Safety Section, an approval to
breach the dams will be issued by the Director of the Division of Land Resources with any
applicable stipulations. Once the dams are breached under the supervision of a professional
engineer, as-built drawings, engineer’s certification, and the owner’s certification will be
prepared and submitted to the Dam Safety Section. Subsequently, the dams will be inspected
by the NCDEQ Land Quality Section to confirm that the as-built drawings are accurate. An
approval will be granted by the Division of Energy, Mineral and Land Resources and the dams
will be removed from the state dam inventory.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

52
11. POST-CLOSURE MONITORING AND CARE
The Post-Closure Operations Maintenance and Monitoring (OM&M) Plan is provided as
Appendix G. The default post-closure period is 30 years, however opportunities to modify and
reduce the post-closure period for various requirements including groundwater and surface
water monitoring are possible. The Post-Closure OM&M Plan addresses the following:
 Description of the closure components
 Regular inspections and maintenance of the stormwater and erosion control measures
 Post-closure inspection checklist to guide post-closure inspections
 Continuation of the groundwater and surface water monitoring and assessment program
 Provide means and methods of managing affected groundwater and stormwater
 Maintaining the groundwater monitoring system
 Facility contact information
 Description of planned post-closure uses
11.1 Groundwater Monitoring Program
Post-closure groundwater monitoring requirements will be established in the Groundwater
Monitoring Plan, and submitted under separate cover. The CSA Report (HDR, 2015a) provides
an interim groundwater monitoring plan to bridge the gap between completion of CSA Report
activities and implementation of the pending Groundwater Monitoring Plan and CAP. Two
comprehensive sampling events and two background-only sampling events were conducted in
2015. There have been two comprehensive sampling events so far in 2016.
The proposed constituents and parameters for the interim groundwater monitoring plan are
listed in Table 16-1 of the CSA Report, and the proposed sampling locations are presented in
Table 16-2 of the CSA Report. The interim groundwater monitoring plan includes sampling
background wells during the additional interim groundwater sampling event in 2015.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

53
12. PROJECT MILESTONES AND COST ESTIMATES
12.1 Project Schedule
The North Carolina CAMA requires closure by August 1, 2019. The CAMA-defined closure
definition of dewatering to the maximum extent practicable and removing and transferring CCR
to a landfill or structural fill is demonstrated in the proposed schedule. The CAMA defined
closure definition for providing corrective action to restore groundwater quality (if needed) is not
addressed in the schedule included herein. Groundwater assessment and corrective action is
currently ongoing and the need and timeframe for restoring groundwater quality is currently
unknown.
Anticipated closure activities and milestones include the following items:
 Removal Plan Submittal (milestone)
 Removal Plan Concurrence (milestone)
 Dam Decommissioning Plan Submittal (milestone)
 Dam Decommissioning Plan Approval (milestone)
 Start Date of Ash Removal (milestone)
 Removal of Ash: beginning with removal of Ash Fill 1 ash followed by ash basin and Ash
Fill 2 ash and includes activities necessary to dewater, excavate, and remove CCR
material from the ash basins and dispose the CCR material in a permitted landfill facility
 Completion of Ash Removal (milestone)
 Dam Decommissioning Construction: including activities necessary to remove the dams
and grade the former ash basin area consistent with Dam Decommissioning Plans
 Dam Decommissioning Certification – Agency Review
 Dam Decommissioning Letter Issued (milestone)
 Beginning of Post-Closure Care Period
12.2 Closure and Post-Closure Cost Estimate
Duke is preparing closure and post-closure care cost estimates at a level of detail and from the
perspective that sufficient funding will be set aside in a financial assurance mechanism for a
third-party (other than the owner) to complete the scope of work. The cost estimates will be
included as Appendix H of this Removal Plan at a later date.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

54
13. REFERENCED DOCUMENTS
ASTM. 2104. Standard Guide for Developing Conceptual Site Models for Contaminated Sites
(E1689-95). ASTM International. Reapproved 2014.

AMEC Environment and Infrastructure, Inc. 2013. Interpretation & Analysis Report – DRAFT,
Ash Basin Closure – Conceptual Design, December, 2013.

AMEC Environment and Infrastructure, Inc. 2014. 2014 Annual Ash Basin Dam Inspection,
December 22, 2014.

Amec Foster Wheeler, Environment and Infrastructure, Inc. 2016a. Dan River Steam Station
Coal Combustion Residuals (CCR) Annual Surface Impoundment Report, Revision 1,
February 12, 2016.

Amec Foster Wheeler, Environment and Infrastructure, Inc. 2016b. Dan River Steam Station
Coal Combustion Residuals (CCR) Annual Surface Impoundment Report, Revision 0,
July 25, 2016.

Amec Foster Wheeler, Environment and Infrastructure, Inc. 2016c. Dan River Steam Station
Coal Combustion Residuals (CCR) History of Construction, Revision 0, October 12,
2016.

Amec Foster Wheeler, Environment and Infrastructure, Inc. 2016d. Dan River Steam Station
Phase 2 Reconstitution of Ash Basin Design, Final Report Submittal, Revision 1 (Draft),
December 2016.

Aquaveo, MT3DMS, Groundwater Modeling System.

Daniel, C.C., III, and Dahlen, P.R., 2002, Preliminary Hydrogeologic Assessment and Study
Plan for a Regional Ground-Water Resource Investigation of the Blue Ridge and
Piedmont Provinces of North Carolina: U.S. Geological Survey Water Resources
Investigations Report 02-4105, 60 p.

Duke Energy Corporation, 2014. Emergency Action Plan (EAP) Duke Energy Dan River
Steam Station, Revision No. 1, July 31, 2014.

Fenneman, N.M. 1938, Physiographic Divisions of the United States: Assoc. Am. Geographers
Annals, vol 18, no. 4, 290 p.

Heath, R.C., 1980, Basic Elements of Ground-Water Hydrology with Reference to Conditions in
North Carolina: U.S. Geological Survey Water Resources Open-File Report 80-44, 86 p.

Heath, R.C., 1984, Ground-water Regions of the United States: U.S. Geological Survey Water
Supply Paper 2242, 78 p.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

55
HDR Engineering, Inc. 2014a, Dan River Steam Station – Ash Basin Drinking Water Supply
Well and Receptor Survey. [Online] URL: http://portal.ncdenr.org/web/wq/drinking-water-
receptor-surveys

HDR Engineering, Inc. 2014b, Dan River Steam Station – Ash Basin Supplement to Drinking
Water Supply Well and Receptor Survey. [Online] URL:
http://portal.ncdenr.org/web/wq/drinking-waterreceptor-Surveys

HDR Engineering, Inc. 2015a, Comprehensive Site Assessment Report, Dan River Steam
Station Ash Basin, August 14, 2015.

HDR Engineering, Inc. 2015b, Corrective Action Plan Part 1, Dan River Dan River Steam
Station Ash Basin, November 12, 2015.

HDR Engineering, Inc. 2016, Corrective Action Plan Part 2, Dan River Dan River Steam Station
Ash Basin, February 10, 2016.

Kinniburgh, D.G., and Cooper, D.M., 2011. PhreePlot – Creating graphical output with
PHREEQC. Available at http://www.phreeplot.org/, original date June 2011, last updated
December 31, 2015.

LeGrand, H.E., 1988, Region 21, Piedmont and Blue Ridge, p.201-208, in Black, W.,
Rosenhein, J.S., and Seaber, P.R., eds., Hydrogeology: Geological Society of America,
The Geology of North America, v. O-2, Boulder, Colorado, 524p.

LeGrand, H.E., 2004, A Master Conceptual Model for Hydrogeological Site Characterization in
the Piedmont and Mountain Region of North Carolina, A Guidance Manual.

Olsen, P.E., Froelich, A. J., Daniels, D.L., Smoot J.P., and Gore, P.J. W., 1991, Rift Basins of
Early Mesozoic Age, in Horton, W., ed., Geology of the Carolinas, University of
Tennessee Press, Knoxville, p. 142-170.

Parkhurst, D.L., and C.A.J Appelo. 2013. Description of input and examples for PHREEQC
version 3 – A computer program for speciation, batch-reaction, one-dimensional
transport, and inverse geochemical calculation: U.S. Geological Survey Techniques and
Methods, book 6, chap. A43, 497 p. [Online] URL: http://pubs.usgs.gov/tm/06/a43/.

Pollock, D. 2012. MODPATH: A Particle-Tracking Model for MODFLOW. U.S. Geological
Survey Office of Groundwater.

Niswonger, R.G., Panday, S., and Ibaraki, M. 2011. MODFLOW_NWT, A Newton formulation
for MODFLOW2005: U.S. Geological Survey Techniques and Methods 6-A37, 44p.

Reid, J.C., Milici, R.C., 2008, Hydrocarbon Source Rocks in the Deep River and Dan River
Triassic Basins, North Carolinas: U.S. Geological Survey Open-File Report 2008-11008,
28 p.

State of North Carolina Department of Environment and Natural Resources Division of
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

56
Water Quality, “NPDES NC 0003468”, March 1, 2013.

State of North Carolina Department of Environment and Natural Resources Division of
Water Quality, “NPDES NC003468”, Renewal, March 2006.

State North Carolina General Assembly, General Statues, Chapter 143. State
Departments Institutions and Commissions. (Regulation may be viewed at http:
http://www.ncga.state.nc.us/gascripts/statutes/StatutesTOC.pl?Chapter=0143

State of North Carolina Administrative Code (NCAC), Title 15A, Chapter 2. Environment
and Natural Resources: Environmental Management. (Regulation may be viewed
at http://reports.oah.state.nc.us/ncac.asp?folderName=\Title 15A - Environment
and Natural Resources\Chapter 02 - Environmental Management

North Carolina Senate Bill 729, General Assembly of North Carolina Session 2013,
“Governor’ Coal Ash Action Plan”, May 15, 2014.

North Carolina Department of Environment and Natural Resources. 2013a. 15A NCAC 2B
.0200s. Classifications and Water Quality Standards Applicable to the Surface Waters
and Wetlands of North Carolina. NC and EPA Combined Surface Water Quality
Standards and Criteria Table. May 15. [Online] URL:
http://portal.ncdenr.org/web/wq/ps/csu/swstandards

North Carolina Department of Environment and Natural Resources. 2013b. 15A NCAC 02L.
Groundwater Rules. Groundwater Standards Table. April 1. [Online]
URL:http://portal.ncdenr.org/web/wq/ps/csu/gwstandards#4

North Carolina Department of Environment and Natural Resources. 2013c. 15A NCAC 02L.
Groundwater Rules. Interim Maximum Allowable Concentrations (IMACs) Table. April 1.
[Online] URL: http://portal.ncdenr.org/web/wq/ps/csu/gwstandards#4

North Carolina Department of Environment and Natural Resources. 2015. NPDES Permit for
Dan River Steam Station. [Online] URL:
http://portal.ncdenr.org/c/document_library/get_file?uuid=38c490a7-5b93-4540-a593-
d8ae3014d724&groupId=38364

State of North Carolina, DENR, “2014 Dam Inventory, portal.ncdenr.org/web/dams”.

USEPA, April 17, 2015, Hazardous and Solid Waste
Management System; Disposal of Coal Combustion Residuals from Electric
Utilities.

U.S. Environmental Protection Agency PA’s ProUCL Technical Guidance, Statistical Software
for Environmental Applications for Data Sets with and without Nondetect Observations,
2013.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

57
Venkatakrishnan, R. and Gheorghiu, F. 2003. Conceptual groundwater flow models identified in
Triassic Basins, eastern United States: EGS-AGU-EUG Joint Assembly, Abstract from
Meeting, Held in Nice, France, 6-11 April 2003, Abstract #8569.

Waterloo Hydrogeologic, Visual MODFLOW 2011.1 (flow engine USGS MODFLOW 2005).

Zheng, C. and P. Wang. 1999. MT3DMS, A modular three-dimensional multi-species transport
model for simulation of advection, dispersion and chemical reactions of contaminants in
groundwater systems, Documentation and Users Guide, U.S. Army Engineer Research
and Development Center Contract Report SERDP-99-1, Vicksburg, MS, 202 p.

Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

TABLES

Revision 0 December 2016
Table 2-1: Federal CCR Rule Closure Plan Requirements
Summary and Cross Reference Table
Site Analysis and Removal Plan - Dan River Steam Station
Duke Energy
No.Description Corresponding
Closure Plan Section
i.Narrative description of how CCR unit will be closed (in accordance with this section)All Chapters
ii.If closure is through the removal of CCR from the unit, description of procedures to remove CCR and decontaminate CCR unit (in accordance with (c))7
iii.If closure by leaving CCR in place, description of final cover system (in accordance with (d)), methods & procedures used to install final cover, and also discussion of how final cover will achieve performance standards (in accordance
with (d))NA
iv.Estimate of maximum inventory of CCR ever on site over active life of CCR unit 3.1.2
v.Estimate of largest area of CCR unit ever requiring a final cover (in accordance with (d)) at any time during active life of CCR unit NA
vi.Schedule for completion of all activities necessary to satisfy closure, including estimate of year in which all closure activities will be completed. Sufficient information to describe sequential steps of closure, including:12.1
a.Obtaining approvals and permits 10
b.Dewatering and stabilization phases 7
c.Installation of final cover system 7
d.Estimated timeframes to complete each step/phase 10
Note:If closure exceeds timeframes in (f)(1), closure plan must include site specific info./factors/considerations to support time extension.
Federal Register Vol. 80 No. 74 Part 2 (April 17, 2015)/40 CFR Part 257: Environmental Protection, Beneficial Use, Coal Combustion Products, CCRs, Coal Combustion Waste, Disposal, Hazardous Waste, Landfill, Surface Impoundments
40 CFR §257.102 (b)(1) (i. - vi) Closure Plans for all impoundments shall include all of the following:
1 OF 1
Revision 0 December 2016
Table 2-2: NC CAMA Closure Plan Requirements
Summary and Cross Reference Table
Site Analysis and Removal Plan - Dan River Steam Station
Duke Energy
No.Description Corresponding Closure
Plan Section
1 Site history and history of site operations, including details on the manner in which coal combustion residuals have been stored and disposed of historically.3.1.1
2 Estimated volume of material contained in the impoundment.3.1.2
3 Analysis of the structural integrity of dikes or dams associated with impoundment.3.1.3
4 All sources of discharge into the impoundment, including volume and characteristics of each discharge.3.1.4
5 Whether the impoundment is lined, and, if so, the composition thereof.3.1.5
6 A summary of all information available concerning the impoundment as a result of inspections and monitoring conducted pursuant to this Part and otherwise available. 3.1.6
1 All structures associated with the operation of any coal combustion residuals surface impoundment located on the site. For purposes of this sub-subdivision, the term "site" means the land or waters within the property boundary of the
applicable electric generating station. 3.2.1
2 All current and former coal combustion residuals disposal and storage areas on the site, including details concerning coal combustion residuals produced historically by the electric generating station and disposed of through transfer to
structural fills. 3.2.1
3 The property boundary for the applicable site, including established compliance boundaries within the site.3.3
4 All potential receptors within 2,640 feet from established compliance boundaries. 3.2.2
5 Topographic contour intervals of the site shall be selected to enable an accurate representation of site features and terrain and in most cases should be less than 20-foot intervals.3.3
6 Locations of all sanitary landfills permitted pursuant to this Article on the site that are actively receiving waste or are closed, as well as the established compliance boundaries and components of associated groundwater and surface water
monitoring systems.3.2.3
7 All existing and proposed groundwater monitoring wells associated with any coal combustion residuals surface impoundment on the site.3.3
8 All existing and proposed surface water sample collection locations associated with any coal combustion residuals surface impoundment on the site.3.3
1 A description of the hydrogeology and geology of the site.4.1
2 A description of the stratigraphy of the geologic units underlying each coal combustion residuals surface impoundment located on the site. 4.2
3 The saturated hydraulic conductivity for (i) the coal combustion residuals within any coal combustion residuals surface impoundment located on the site and (ii) the saturated hydraulic conductivity of any existing liner installed at an
impoundment, if any. 4.3
4
The geotechnical properties for (i) the coal combustion residuals within any coal combustion residuals surface impoundment located on the site, (ii) the geotechnical properties of any existing liner installed at an impoundment, if any, and (iii)
the uppermost identified stratigraphic unit underlying the impoundment, including the soil classification based upon the Unified Soil Classification System, in-place moisture content, particle size distribution, Atterberg limits, specific gravity,
effective friction angle, maximum dry density, optimum moisture content, and permeability.
4.4
5 A chemical analysis of the coal combustion residuals surface impoundment, including water, coal combustion residuals, and coal combustion residuals-affected soil. 4.5
6 Identification of all substances with concentrations determined to be in excess of the groundwater quality standards for the substance established by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code, including
all laboratory results for these analyses.4.6
7 Summary tables of historical records of groundwater sampling results.4.6
8 A map that illustrates the potentiometric contours and flow directions for all identified aquifers underlying impoundments (shallow, intermediate, and deep) and the horizontal extent of areas where groundwater quality standards established
by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code for a substance are exceeded.4.7
9 Cross-sections that illustrate the following: the vertical and horizontal extent of the coal combustion residuals within an impoundment; stratigraphy of the geologic units underlying an impoundment; and the vertical extent of areas where
groundwater quality standards established by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code for a substance are exceeded.4.8
d.
1
An account of the design of the proposed Closure Plan that is based on the site hydrogeologic conceptual model developed and includes (i) predictions on post-closure groundwater elevations and groundwater flow directions and velocities,
including the effects on and from the potential receptors and
(ii) predictions at the compliance boundary for substances with concentrations determined to be in excess of the groundwater quality standards for the substance established by Subchapter L of Chapter 2 of Title 15A of the North Carolina
Administrative Code.
5.1
2 Predictions that include the effects on the groundwater chemistry and should describe migration, concentration, mobilization, and fate for substances with concentrations determined to be in excess of the groundwater quality standards for
the substance established by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code pre- and post-closure, including the effects on and from potential receptors.5.2
3 A description of the groundwater trend analysis methods used to demonstrate compliance with groundwater quality standards for the substance established by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code
and requirements for corrective action of groundwater contamination established by Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative Code.5.3
Part II. Provisions for Comprehensive Management of Coal Combustion Residuals
§ 130A-309.214(a)(4) Closure Plans for all impoundments shall include all of the following:
a. Facility and coal combustion residuals surface impoundment description. – A description of the operation of the site that shall include, at a minimum, all of the following:
b. Site maps, which, at a minimum, illustrate all of the following:
The results of groundwater modeling of the site that shall include, at a minimum, all of the following:
c. The results of a hydrogeologic, geologic, and geotechnical investigation of the site, including, at a minimum, all of the following:
1 OF 2
Revision 0 December 2016
Table 2-2: NC CAMA Closure Plan Requirements
Summary and Cross Reference Table
Site Analysis and Removal Plan - Dan River Steam Station
Duke Energy
No.Description Corresponding Closure
Plan Section
e.A description of any plans for beneficial use of the coal combustion residuals in compliance with the requirements of Section .1700 of Subchapter B of Chapter 13 of Title 15A of the North Carolina Administrative Code (Requirements for
Beneficial Use of Coal Combustion By-Products) and Section .1205 of Subchapter T of Chapter 2 of Title 15A of the North Carolina Administrative Code (Coal Combustion Products Management).6.1
f.All engineering drawings, schematics, and specifications for the proposed Closure Plan. If required by Chapter 89C of the General Statutes, engineering design documents should be prepared, signed, and sealed by a professional
engineer.7.1, 7.2
g.A description of the construction quality assurance and quality control program to be implemented in conjunction with the Closure Plan, including the responsibilities and authorities for monitoring and testing activities, sampling
strategies, and reporting requirements. 7.3
h.A description of the provisions for disposal of wastewater and management of stormwater and the plan for obtaining all required permits. 8
i.
A description of the provisions for the final disposition of the coal combustion residuals. If the coal combustion residuals are to be removed, the owner must identify (i) the location and permit number for the coal combustion residuals
landfills, industrial landfills, or municipal solid waste landfills in which the coal combustion residuals will be disposed and (ii) in the case where the coal combustion residuals are planned for beneficial use, the location and manner in
which the residuals will be temporarily stored. If the coal combustion residuals are to be left in the impoundment, the owner
must (i) in the case of closure pursuant to sub-subdivision (a)(1)a. of this section, provide a description of how the ash will be stabilized prior to completion of closure in accordance with closure and post-closure requirements
established by Section .1627 of Subchapter B of Chapter 13 of Title 15A of the North Carolina Administrative Code and (ii) in the case of closure pursuant to sub-subdivision (a)(1)b. of this section, provide a description of how the ash
will be stabilized pre- and post-closure. If the coal combustion residuals are to be left in the impoundment, the owner must provide an estimate of the volume of coal combustion residuals remaining.
9
j.A list of all permits that will need to be acquired or modified to complete closure activities.10
k.
A description of the plan for post-closure monitoring and care for an impoundment for a minimum of 30 years. The length of the post-closure care period may be (i) proposed to be decreased or the frequency and parameter list
modified if the owner demonstrates that the reduced period or modifications are sufficient to protect public health, safety, and welfare; the environment; and natural resources and (ii) increased by the Department at the end of the
post-closure monitoring and care period if there are statistically significant increasing groundwater quality trends or if contaminant concentrations have not decreased to a level protective of public health, safety, and welfare; the
environment; and natural resources. If the owner determines that the post-closure care monitoring and care period is no longer needed and the Department agrees, the owner shall provide a certification, signed and sealed by a
professional engineer, verifying that post-closure monitoring and care has been completed in accordance with the post-closure plan. If required by Chapter 89C of the General Statutes, the proposed plan for post-closure monitoring
and care should be signed and sealed by a professional engineer. The plan shall include, at a minimum, all of the following:
11
1 A demonstration of the long-term control of all leachate, affected groundwater, and stormwater.11
2 A description of a groundwater monitoring program that includes (i) post-closure groundwater monitoring, including parameters to be sampled and sampling schedules; (ii) any additional monitoring well installations, including a map with the
proposed locations and well construction details; and (iii) the actions proposed to mitigate statistically significant increasing groundwater quality trends. 11.1
l.An estimate of the milestone dates for all activities related to closure and post-closure. 12.1
m.Projected costs of assessment, corrective action, closure, and post-closure care for each coal combustion residuals surface impoundment. 12.2
n. A description of the anticipated future use of the site and the necessity for the implementation of institutional controls following closure, including property use restrictions, and requirements for recordation of notices documenting
the presence of contamination, if applicable, or historical site use.6.2
§ 130A-309.214(b)(3) No later than 60 days after receipt of a proposed Closure Plan, the Department shall conduct a public meeting in the county or counties proposed Closure Plan and alternatives to the public.
§ 130A-309.214(d) Within 30 days of its approval of a Coal Combustion Residuals Surface Impoundment Closure Plan, the Department shall submit the Closure Plan to the Coal Ash Management Commission.
2 OF 2
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

FIGURES
PREPARED
BY
DATE CHECKED
BY
DATE JOB NUMBER FIGURE 17810-14-0065
Rockingham County
NN OO RR TT HH CC AA RR OO LL II NN AA
MS 12/12/2016 KD 12/12/2016
SITE VICINITY MAPDUKE ENERGY DAN RIVER STEAM STATIONROCKINGHAM COUNTY, NORTH CAROLINA
NORTH CAROLINA
Project Location (Rockingham County)
¯
0 12,0006,000
Feet
Do
c
u
m
e
n
t

P
a
t
h
:

F
:
\
A
M
E
C
_
P
r
o
j
e
c
t
s
\
2
0
1
4
\
7
8
1
0
-
1
4
-
0
0
6
5
\
G
I
S
\
M
X
D
s
\
7
8
1
0
-
1
4
-
0
0
6
5
.
0
9
.
0
3
\
F
i
g
-
1
_
S
i
t
e
_
V
i
c
i
n
i
t
y
_
M
a
p
2
.
m
x
d
)*
Service Layer Credits: Sources: Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO,
NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong),
swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community
Copyright:© 2013 National Geographic Society, i-cubed
¯
LEGEND
APPROXIMATE CCR UNIT BOUNDARIES
APPROXIMATE DUKE PROPRETY BOUNDARY
ASH FILL 2
ASH FILL 1
PRIMARYASH BASIN
SECONDARYASH BASIN
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus
DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the
GIS User Community
SITE AERIAL MAP- CCR UNITS
DUKE ENERGY CAROLINAS, LLC
DAN RIVER STEAM STATION
ROCKINGHAM COUNTY, NORTH CAROLINA
F:
\
A
M
E
C
_
P
r
o
j
e
c
t
s
\
2
0
1
4
\
7
8
1
0
-
1
4
-
0
0
6
5
\
G
I
S
\
M
X
D
s
\
7
8
1
0
-
1
4
-
0
0
6
5
.
0
9
.
0
3
\
F
i
g
u
r
e
2
_
D
a
n
R
i
v
e
r
.
m
x
d
,

U
s
e
r
:

m
a
d
d
i
s
o
n
.
s
u
t
t
o
n
;

C
h
e
c
k
e
d

b
y
:

K
D

D
a
t
e
:

1
2
/
1
2
/
2
0
1
6
PROJECT NO:7810-14-0065 FIGURE NO:2
Note: This figure is for reference only.
¯
0 750 1,500 Feet
LEGEND
APPROXIMATE CCR UNIT BOUNDARIES
APPROXIMATE DUKE PROPERTY BOUNDARY
DAN R
I
V
E
R

Ash Fill 2
Ash Fill 1
Primary
Ash Basin
Secondary
Ash Basin
Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus
DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the
GIS User Community
SITE AERIAL MAP - LANDFILL UNITS
DUKE ENERGY CAROLINAS, LLC
DAN RIVER STEAM STATION
ROCKINGHAM COUNTY, NORTH CAROLINA
F:
\
A
M
E
C
_
P
r
o
j
e
c
t
s
\
2
0
1
4
\
7
8
1
0
-
1
4
-
0
0
6
5

D
a
n

R
i
v
e
r

P
r
o
p
o
s
e
d

L
a
n
d
f
i
l
l
\
G
I
S
\
M
X
D
s
\
L
A
N
D
F
I
L
L
U
N
I
T
S
.
m
x
d
,

U
s
e
r
:

m
a
d
d
i
s
o
n
.
s
u
t
t
o
n
;

D
a
t
e
:

6
/
3
0
/
2
0
1
6

8
:
0
2
:
5
9

A
M
,

C
h
e
c
k
e

b
y
:

S
S

D
a
t
e
:

1
0
/
8
/
2
0
1
5
PROJECT NO:7810-14-0065 FIGURE NO:3Note: This figure is for reference only.
¯
0 500 1,000 Feet
LEGEND
LCID LANDFILL
PROPOSED CCR LANDFILL LOW
PROPERTY LINE
DAN R
I
V
E
R

Closed LCID Landfill
(Permit No. 79-B)
Proposed CCR Landfill
Limit of Waste
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Dan River Steam Station Site Analysis and Removal Plan
Revision 0

APPENDICES