_Cliffside Unit 5 CBE - Closure Plan_20200107

�> DUKE
ENERGY,
December 30, 2019
Ms. Sheila Holman
Assistant Secretary for Environment
North Carolina Department of Environmental Quality
1611 Mail Service Center
Raleigh, North Carolina 27699-1611
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
526 S. Church Street
Mail Code. EC3XP
Charlotte, NC 28202
[phone]
Subject: Submittal of Ash Basin Closure Plan and Corrective Action Plan Update
Rogers Energy Complex (Cliffside)
Dear Ms. Holman:
In accordance with the requirements of N.C.G.S. §§ 130A-309.21 1 (b) and .214(a)(4), Duke
Energy provides the following documents: (1) a plan for basin closure by excavation, and (2) a
corrective action plan (CAP) for the Cliffside site, which will address groundwater impacts within
9 years of full-scale operation, regardless of the specific closure method.
Closure by Excavation
The enclosed excavation plan is in response to NCDEQ's April 1 order requiring excavation of
the Cliffside coal ash basins. After regulatory approval, excavating the basin ash would require
8 years to move the ash to a new lined landfill within plant property. The landfill would be
located next to the existing lined landfill south of McCraw Road and rise about 170 feet above
the road.
Continuing to Protect Water Resources
Robust scientific study, conducted under the direction of NCDEQ, demonstrates that drinking
and recreational water supplies around the Cliffside facility are well -protected from coal ash
impacts and will only continue to improve during and after closure. Ongoing research and
monitoring also provide a detailed understanding of groundwater conditions at the site,
indicating that the impact is highly localized and will be addressed through the planned
corrective action approach. The CAP designed for Cliffside will achieve groundwater
remediation through a combination of strategically placed groundwater extraction wells coupled
with clean water infiltration wells, the installation of Tree WeIITM technology, and installation of a
groundwater collection.
Prior to submission, the closure plan was reviewed by the National Ash Management Advisory
Board (NAMAB), which consists of nationally and internationally recognized and published
experts with practical experience working with and for the private sector, federal government,
and academia. NAMAB helped develop the guiding principles for safe basin closure and their
feedback is incorporated herein.
Duke Energy remains committed to safely and permanently closing basins in ways that continue
to protect people and the environment and welcomes the opportunity to work constructively with
NCDEQ to move forward.

Ms. Sheila Holman
December 30, 2019
Submittal of Ash Basin Closure Plan and Corrective Action Plan Update
Rogers Energy Complex (Cliffside)
Page 2
mcere
Paul Draovitch
Senior Vice President
Environmental, Health & Safety
Enclosure:
• Corrective Action Plan Update
• Closure by Excavation Closure Plan

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Duke Energy Cliffside Steam Station
Inactive Unit 5 Ash Basin
COAL COMBUSTION RESIDUALS SURFACE IMPOUNDMENT
CLOSURE PLAN (Closure by Excavation)
Revision 0
Prepared for
DUKE
ENERGY.,
400 South Tryon Street
Charlotte, North Carolina 28202
Prepared by
Wood Environment & Infrastructure Solutions, Inc.
2801 Yorkmont Road, Suite 100
,.�''A C A R'''�,
Charlotte, North Carolina 28208 ,
Revision Issue Date
December 18, 2019
Wood EMS Project No. 7812190194
�7
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
TABLE OF CONTENTS
EXECUTIVE SUMMARY............................................................................................................. iv
1. INTRODUCTION...............................................................................................................1
1.1 Background.........................................................................................................................1
1.2 Closure Plan Objectives...................................................................................................... 1
1.3 Report Organization............................................................................................................ 2
2. GOVERNING LAWS.........................................................................................................2
3. FACILITY DESCRIPTION AND EXISTING SITE FEATURES.........................................3
3.1 Surface Impoundments Description.................................................................................... 3
3.1.1
Site History and Operations................................................................................... 3
3.1.2
Estimated Volume of CCR in Surface Impoundments...........................................3
3.1.3
Description of Surface Impoundment Structural Integrity......................................3
3.1.4
Sources of Discharges into Surface Impoundments..............................................4
3.1.5
Existing Surface Impoundment Liner System........................................................4
3.1.6
Inspection and Monitoring Summary..................................................................... 5
3.2 Site Maps............................................................................................................................ 5
3.2.1
Existing Surface Impoundment Related Structures...............................................5
3.2.2
Receptor Survey....................................................................................................6
3.2.3
Existing On -Site Landfills.......................................................................................6
3.3 Monitoring and Sampling Location Plan............................................................................. 6
4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL
INVESTIGATIONS............................................................................................................ 6
4.1
Background......................................................................................................................... 6
4.2
Hydrogeology and Geologic Descriptions........................................................................... 6
4.3
Stratigraphy of the Geologic Units Underlying Surface Impoundments ............................. 7
4.4
Geotechnical Properties...................................................................................................... 7
4.4.1 CCR Within Basin..................................................................................................7
4.4.2 Liner Material Properties........................................................................................7
4.4.3 Subsurface Soil Properties....................................................................................7
4.4.4 CCR Basin Dam Soil Properties............................................................................ 7
4.5
Chemical Analysis of Impoundment Water, CCR and CCR-Affected Soil .......................... 8
4.6
Historical Groundwater Sampling Results.......................................................................... 8
4.7
Groundwater Potentiometric Contour Maps....................................................................... 8
4.6
Estimated Vertical and Horizontal Extent of CCR within the Impoundments ..................... 8
5. GROUNDWATER MODELING ANALYSIS......................................................................8
5.1 Site Conceptual Model Predictions..................................................................................... 9
5.2 Groundwater Chemistry Effects.......................................................................................... 9
5.3 Groundwater Trend Analysis Methods................................................................................ 9
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
6. BENEFICIAL USE AND FUTURE USE...........................................................................9
6.1 CCR Use............................................................................................................................. 9
6.2 Site Future Use................................................................................................................... 9
7. CLOSURE DESIGN DOCUMENTS..................................................................................9
7.1 Engineering Evaluations and Analyses.............................................................................. 9
7.2 Closure Plan Activities...................................................................................................... 10
7.3 Design Drawings............................................................................................................... 11
7.4 Description of the Construction Quality Assurance Plan .................................................. 11
8. MANAGEMENT OF WASTEWATER AND STORM WATER........................................12
8.1 Anticipated Changes in Wastewater and Stormwater Management ................................ 13
8.2 Wastewater and Stormwater Permitting Requirements.................................................... 14
9. DESCRIPTION OF FINAL DISPOSITION OF CCR.......................................................14
10. APPLICABLE PERMITS FOR CLOSURE.....................................................................14
11. DESCRIPTION OF POST -CLOSURE MONITORING AND CARE................................14
11.1 Groundwater Monitoring Program..................................................................................... 15
12. PROJECT MILESTONES AND COST ESTIMATES......................................................15
12.1 Project Schedule............................................................................................................... 15
12.2 Closure and Post -Closure Cost Estimate......................................................................... 15
13. REFERENCED DOCUMENTS.......................................................................................17
Tables
Table 2-1 NC CAMA Closure Plan Requirements Summary and Cross Reference Table
Table 4-1 Summary of Typical Geotechnical Measured Properties
Table 10-1 Unit 5 Inactive Ash Basin - Regulatory Permits, Approvals, or Requirements for
Basin Closure by Excavation
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
Figures
Figure ES-1 Current Condition View
Figure ES-2 Post -Closure Condition View
Figure 1-1 Vicinity Map and Site Plan
Figure 3-1 Existing Conditions Plan
Appendices
Appendix A Estimated Volume of CCR in Impoundment
Appendix B Geotechnical Data and Properties
Appendix C Engineering Evaluations and Analyses
Appendix C1 - Stormwater
Appendix C2 - Geotechnical
Appendix C3 - Soil Quantities
Appendix D Inactive Unit 5 Ash Basin Closure Plan Drawings
Appendix E Excavation and Sampling Plan for Closure by Excavation Areas
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
EXECUTIVE SUMMARY
As required by the North Carolina Department of Environmental Quality's (NCDEQ) April 1, 2019
"Coal Combustion Residuals Surface Impoundment Closure Determination," (Closure
Determination) Duke Energy has prepared this Closure Plan to describe the closure of the Inactive
Unit 5 Ash Basin at Rogers Energy Complex (Cliffside Station). This plan details closure by
excavation of the Inactive Unit 5 Ash Basin (U513) and placement of the excavated coal
combustion residuals (CCR) in the permitted, on -site CCR landfill. The excavation of CCR and
the closure of the U513 will be in accordance with applicable provisions of the North Carolina Coal
Ash Management Act of 2014, as amended (CAMA), (codified at N.C.G.S. § 130A-309.200 et
seq.), and the federal Disposal of Coal Combustion Residuals from Electric Utilities rule (CCR
Rule) (codified at 40 C.F.R. § 257.50 et seq.).
Cliffside Station is located at 573 Duke Power Road, Mooresboro, North Carolina. The Station is
approximately 55 miles west of Charlotte and about 1 '/2 miles south of the town of Cliffside, North
Carolina. The Station is situated along the southern bank of the Broad River in Rutherford and
Cleveland Counties and is approximately 1,000 acres in area. Cliffside Station consists of two
coal and natural gas fired electric generating units with a combined generating capacity of 1,387
megawatts.
CCR was previously collected from the generating units and conveyed by hydraulic methods for
disposal within permitted basins located on the station site. CCR is currently collected from the
generating units and conveyed by pneumatic (dry) handling methods into storage silos, loaded
into trucks and then transported for disposal within the on -site CCR landfill.
Cliffside Station historically operated three unlined impoundments, the Active Ash Basin (AAB),
Unit 5 Inactive Ash Basin (U5B), and Units 1-4 Inactive Ash Basin. The approximately 86-acre
AAB was constructed in 1980. The approximately 46-acre U513 was constructed in 1970. Units
1-4 Inactive Ash Basin was closed in March 2018 by removal of CCR and is not covered in this
closure plan.
The U513 includes two dams known as the Inactive Ash Basin Unit 5 Main Dam (RUTHE-070) and
Inactive Ash Basin Unit 5 Saddle Dam (RUTHE-072). The Inactive Unit 5 Ash Basin was
constructed in 1969 and 1970 and retired in 1980. Storm water drainage is currently released
through a primary discharge outlet located at the Main Dam to the Broad River.
The U513 is unlined and contains up to 92 feet of ash. Based on CCR Inventory Data provided by
Duke as of July 31, 2019, the U513 is estimated to contain 1.96 million cubic yards of CCR, or
approximately 2.36 million. The estimates are approximate because they are based on assumed
pre -basin grades.
Closure activities for the Basins have already begun with the initiation of decanting under the
Special Order by Consent (SOC). Upon approval of the Closure Plan by NCDEQ additional
actions will commence, including finalization of detailed designs, dewatering and removal of
interstitial water, contracting and detailed planning for the closure work, expansion of the existing
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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CCR landfill, excavation of the CCR, final grading of the site and landfill, and development of
storm water features and vegetative covers.
Figures ES-1 and ES-2 illustrate the current state, and post -closure state of the U513 as detailed
by this Closure Plan.
Figure ES-1 Current View Figure ES-2 Post Closure View
The U5B CCR will be removed to a new lined landfill on the Station property, located adjacent to
the current landfill south of McCraw Road. The landfill would rise approximately 170 feet above
McCraw Road. Post -excavation, the U5B site will resemble the land's valley shape before the
basin was created. Soil will be graded to restore contours for stormwater flows, then planted with
native grasses for erosion control. The existing U513 dam will be partially removed, and
stormwater flows will then make their way to the Broad River.
This document also includes a description of the Post -Closure Plan, which will describe the
inspection, monitoring, and maintenance activities required to be performed throughout the 30-
year post -closure care period for the closed basins at the Cliffside Station.
This document summarizes properties of the site, as well as geotechnical properties of CCR and
natural soils to support engineering analyses of the closure design. These analyses indicate that
closure by excavation, as detailed in the Closure Plan, meets regulatory requirements for the
stability of the site, management of storm water run-off, and access for effective maintenance
over the post -closure care period. The U5B dam is proposed to be removed or breached as part
of closure and removed from the state's regulatory jurisdiction inventory.
In accordance with the requirements of N.C.G.S. § 130A-309.21 1 (b)(1), Duke Energy separately
submitted an updated Corrective Action Plan (CAP) in parallel with this Closure Plan; the updated
CAP is herein incorporated in its entirety by this reference. Neither the updated CAP nor its
content is the work product of Wood. Although the Closure Plan contains references to the
updated CAP, all specific relevant details to groundwater and related actions are found in the
updated CAP itself and not in this Closure Plan.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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As detailed in the updated CAP, Duke Energy (i) will complete ash basin closure; and (ii) intends
to implement a groundwater extraction system. The CAP provides that these corrective action
measures will most effectively achieve remediation of the groundwater through the installation of
groundwater extraction wells northeast of the U5 Inactive Ash Basin saddle dam. Significantly,
groundwater modeling simulations indicate (i) these measures will control COI at or beyond the
compliance boundary, and (ii) at such time the site -specific considerations detailed within the CAP
have been satisfied, including, but not limited to, securing all required state approvals, installing
the necessary equipment, and commencing full-scale system operation, COI migration will be
contained within the compliance boundary.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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1. INTRODUCTION
1.1 Background
The primary objective of this Closure Plan is to address the closure of the U513 at the Cliffside
Station which is a coal and natural gas fired electricity -generating facility owned and operated by
Duke Energy. The Station is located on the Broad River approximately 55 miles west of Charlotte
and about 1 '/2 miles south of the town of Cliffside, North Carolina. The power plant is situated on
the south side of the Broad River and straddles the Cleveland/Rutherford County line. Cliffside
Station is a two -unit, 1,387 megawatt, coal and natural gas fired power generation facility that
began commercial operation in 1940 with Units 1-4. Units 1-4 were retired on October 1, 2011. In
1972, Unit 5 began commercial operation and is still in operation. Duke completed the
modernization project with the addition of Unit 6, which began commercial operation in December
2012. CCR have historically been managed in the Station's on -site basins. Cliffside Station
ceased all waste flows to the basins in 2019.
Figure 1-1 presents a Vicinity Map and Site Plan of the Cliffside Station.
Duke Energy uses three facilities to manage CCR at the Cliffside Station that include the following
earthen embankment dams regulated by NCDEQ:
1. Active Ash Basin Downstream Dam (State ID CLEVE-049);
2. Active Ash Basin Upstream Dam (State ID CLEVE-050);
3. Unit 5 Inactive Ash Basin Main Dam (State ID RUTHE-070); and
4. Unit 5 Inactive Ash Basin Saddle Dam (State ID RUTHE-072).
As further discussed in Section 2 below, the closure method mandated by order of the NCDEQ
for the U513 is closure by excavation.
1.2 Closure Plan Objectives
The objective of this Closure Plan is to address the closure by excavation of CCR from the U513
as directed by order of NCDEQ. Duke Energy does so without prejudice of its position that closure
by excavation is neither necessary nor appropriate for the USB. Duke Energy also notes that
approval from NCDEQ is required to proceed and develop the additional details as described
further within this Closure Plan to complete the necessary working documents to complete the
closure actions. Duke Energy submits this Closure Plan with the knowledge that other details will
follow, as necessary. This Closure Plan describes and communicates the key actions and
activities necessary to close the AAB in accordance with the requirements for written Closure
Plans for CCR surface impoundments presented in N.C.G.S. §130A-309.214(a)(4). Planned
closure activities include:
• Decanting the Basin;
• Construction and operation of a water management system to manage discharges in
compliance with the NPDES permit during closure;
• Dewatering to support safe excavation of CCR from the basin;
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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Wood E&IS Project No. 7812190194
• Excavation of the CCR and establishing post -excavation final grades using soil fill where
required;
• Lowering and removal of the U5B Main dam;
• Expansion of the on -site CCR landfill to permanently store the excavated CCR,
• Modification of the discharge channel downstream of the Main Dam; and
• Restoration of disturbed areas.
1.3 Report Organization
This Closure Plan is structured to follow the requirements provided in CAMA (N.C.G.S. § 130A-
309.214(a)(4)).
2. GOVERNING LAWS
In August 2014, the North Carolina General Assembly enacted CAMA, which contains specific
statutory requirements applicable to the Basins. Subsequently, in July 2016, the North Carolina
General Assembly enacted H.B. 630, Session Law 2016-95, which provides that impoundments
be classified as "low -risk" if, by certain deadlines, the owner has established permanent
alternative water supplies, as required, and has rectified any deficiencies identified by, and has
otherwise complied with requirements of, any dam safety order. NCDEQ determined that Duke
Energy met these criteria on November 14, 2018, and officially classified the U5B at Cliffside
Station as "low -risk."
On April 1, 2019, NCDEQ issued its Closure Determination mandating that the U513 be closed by
excavation of the CCR. A closure plan is required for each CCR surface impoundment regardless
of the risk classification. CAMNs closure plan requirements and cross-referenced sections of this
Closure Plan are summarized in Table 2-1. On April 26, 2019, Duke Energy filed a Petition for
Contested Case Hearing before the North Carolina Office of Administrative Hearings appealing
this determination and on May 24, 2019 Duke Energy filed amended petitions in the case. The
petitions allege that in issuing its Closure Determination, NCDEQ failed to (i) follow the mandatory
process and procedure outlined in CAMA and (ii) consider or apply the scientific and engineering
evidence submitted and available to it in reaching its decision to require the most expensive
closure method available despite scientific and engineering evidence demonstrating the
availability of less expensive and more rapid closure options that would continue to fully protect
human health and the environment. Certain decisions by the administrative law judge in that case
are currently under appeal to the North Carolina Superior Court.
In addition to the closure plan requirements, CAMA sets out groundwater assessment and
corrective action requirements. A Comprehensive Site Assessment (CSA) report update was
submitted to NCDEQ in January 2018. Duke Energy intends that an updated CAP will be
submitted in parallel with this Closure Plan to NCDEQ in December 2019.
In addition to the above requirements, National Pollutant Discharge Elimination System (NPDES)
permit program compliance, SOC (which commits Duke Energy to initiate and complete decanting
of the Basins by dates certain) compliance, dam safety approvals for modifications to regulated
Basin dams, and environmental permitting requirements must be considered as part of closure.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
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Wood E&IS Project No. 7812190194
3. FACILITY DESCRIPTION AND EXISTING SITE FEATURES
3.1 Surface Impoundments Description
This section provides details on the Inactive Unit 5 Ash Basin at the Cliffside Station.
3.1.1 Site History and Operations
Figure 1-1 shows locations of the plant and the CCR facilities. Figure 3-1 presents overall existing
conditions including topography and bathymetry of the USB. The U513 addressed within this
closure plan is described below:
Inactive Unit 5 Ash Basin (Dam ID: RUTHE-070 and RUTHE-072):
The U513 is located on the western portion of the site, west and southwest of coal-fired Unit 5 and
Unit 6. The Main Dam (Dam ID - RUTHE-070) and Saddle Dam (Dam ID - RUTHE-072) are the
principal embankments which form the Basin. The Main Dam is approximately 1,460 feet long at
the crest and the Saddle Dam is about 590 feet long at the crest. A smaller, non -regulated
containment dike exists along the eastern border of the basin adjacent to the plant access road
and is referred to as the Roadway Embankment. The dams and dike were constructed in 1969
and 1970 in advance of Unit 5 operations. The U513 received sluiced CCR from Unit 5 starting in
1972 until it was retired in 1980 when it reached capacity. The U513 currently receives stormwater
from a localized drainage area. A majority of the eastern side of the U513 is currently used as a
lay down yard for equipment and materials.
3.1.2 Estimated Volume of CCR in Surface Impoundments
Based on CCR inventory data provided by Duke as of July 31, 2019, the approximate volume of
CCR in the U513 is listed in the table below. To compute the estimated mass of CCR in place an
assumed density of 1.2 tons per CY was used, which is the Duke Energy fleet wide assumption.
See Appendix A for the Estimated Volume of CCR in Impoundment calculation.
Impoundment
Estimated CCR Volume
Estimated CCR Weight
(CY)
(Tons)
Inactive Unit 5
1,960,000
2,352,000
Ash Basin
3.1.3 Description of Surface Impoundment Structural Integrity
The purpose of this section is to summarize the Basin's structural integrity evaluations based on
current existing information. This section includes the geotechnical, and hydrology and hydraulics
(H&H) capacity analyses results. In summary, the structural integrity of the Basin and subsequent
dam inspection reports meets the regulatory requirements of EPA's CCR Rule (40 § CFR 257.73).
Duke Energy's certifications of these requirements are available on Duke Energy's publicly -
accessible CCR Rule Compliance Data and Information website.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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• Slope stability
For the U5B Main and Saddle Dams, slope stability analysis results for the existing conditions
global factors of safety for static long-term maximum storage pool, static maximum surcharge
pool, sudden drawdown conditions, and pseudo -static seismic conditions meet regulatory and
programmatic criteria.
• Liquefaction conditions (where susceptible) and Liquefaction potential
In 2016, Wood performed a screening level liquefaction analysis for the U513 dams. Based on the
screening analyses, the U513 dams and their foundation soils are not liquefaction -susceptible.
Based on the conditions encountered in the borings performed for this project, ground motions of
the design seismic event (2,500-year return period) were calculated and analyzed for evaluation
of liquefaction potential. The analysis was performed using the methodology from Idriss and
Boulanger (2014). The results of this analysis do not indicate the potential to trigger liquefaction
or cyclic softening within granular soils in the embankments, or below the embankments for the
U5B dams.
• Hydrology and hydraulics (H&H) capacity analyses
Hydrologic analysis performed by Wood following the 2016 construction of alternate spillway for
the U513 show that the U513 is capable of conveying the inflow design flood event while maintaining
adequate freeboard. This study also indicates that the spillway system for the U513 is capable of
removing 80 percent of the detained storm volume within 15 days following the design storm peak
[6 hour 3/4 probable maximum precipitation (PMP)], as required by the North Carolina Dam Safety
Rules.
Per direction from NCDEQ, additional hydrologic modeling was conducted to evaluate whether
the existing U513 and spillway system could convey the spillway design flood (SDF) generated
during the full PMP event without overtopping the dam. The evaluation involved incorporation of
updated drainage area characteristics. The evaluation showed that the U5B and existing spillway
system was capable of conveying the SDF generated during the full PMP without overtopping the
dam. This analysis is in Appendix C.
3.1.4 Sources of Discharges into Surface Impoundments
Process flows no longer discharge into the U513. Process flows are directed toward newly -
constructed holding and auxiliary basins. The Cliffside Station currently employs a dry ash
handling system transporting CCR by truck to the on -site industrial landfill.
Currently, the U513 receives only stormwater runoff.
3.1.5 Existing Surface Impoundment Liner System
The U513 located at the Cliffside Station does not include a geomembrane or clay liner system
and is considered to be unlined. The U513 was constructed directly on top of the historical ground
surface.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
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3.1.6 Inspection and Monitoring Summary
Weekly Basin inspections have been on -going since 2014, and include observation of upstream
slopes and shorelines, crest, downstream slopes, toes, abutment contacts and adjacent drainage
way(s), spillway(s) and associated structure(s), and other structures and features of the dams.
Monthly inspections of the U513 include the weekly monitoring elements with the addition of
piezometer and observation well readings and water level gauges/sensors.
Daily inspections of the basins are not routinely required, however, on a case -by -case basis, the
basins may be inspected daily beginning at such times and continued for the duration as specified
by plant management. Such daily inspections might be initiated during a repair activity on the dam
or in response to a specific imposed regulatory agency requirement.
The U513 is inspected annually by an independent third -party consultant. In a letter dated August
13, 2014, NCDEQ requires these inspections to be conducted annually at all of Duke Energy's
CCR impoundments in North Carolina. These inspections are intended to confirm adequacy of
the design, operation, and maintenance of the surface impoundments in accordance with
accepted engineering standards. Reports are to be submitted to the NCDEQ within 30 days of
the completion of the inspection.
The results of the annual inspections are used to identify needed repairs, repair schedules, to
assess the safety and operational adequacy of the dam, and to assess compliance activities
regarding applicable permits, environmental and dam regulations. Annual inspections are also
performed to evaluate previous repairs. The annual inspections of the dikes have been ongoing
since 2009, with 5-year inspections conducted between 1979 and 2009.
The 2015 through 2019 annual inspections did not identify features or conditions in the U513 dams,
or their outlet structures or spillways that indicate an imminent threat of impending failure hazard.
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 underway.
Special, episodic inspections of the Basins may be performed during episodes of earthquake,
emergency, or other extraordinary events. Visual inspections are performed after a heavy
precipitation event when accumulation of four inches of rainfall or greater occurs within a 24-hour
period. An internal inspection will be performed if an earthquake is felt locally or detected by the
US Geological Survey measuring greater than a Magnitude 3 and with an epicenter within 50
miles of the dams. 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 cleanout) are planned on or near the dams. Special inspections are also conducted when
the ongoing surveillance program identifies a condition or a trend that warrants special evaluation.
3.2 Site Maps
3.2.1 Existing Surface Impoundment Related Structures
A site map showing property boundary, location of the Cliffside Station and Basins with their
boundaries, topographic contours, and bathymetric contours are shown on Figure 3-1.
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Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
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Wood E&IS Project No. 7812190194
3.2.2 Receptor Survey
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
3.2.3 Existing On -Site Landfills
There is an on -site industrial landfill at the Cliffside Station, as identified in the table below. Figure
1-1 shows locations of this landfill.
Landfill
Permit Number
Comment
Rogers CCP Landfill
8106-INDUS-2009
Active
3.3 Monitoring and Sampling Location Plan
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
Locations of the existing groundwater monitoring wells are shown in the Closure Plan Drawings,
Appendix D, but the CAP should be consulted for details of well locations, names, and status.
4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL
INVESTIGATIONS
4.1 Background
An overall boring and existing monitoring well location plan indicating the locations of recent and
historical borings, monitoring wells, and piezometers is shown on in the drawings included in
Appendix D.
This chapter summarizes the site geology and hydrogeology; site stratigraphy of the geologic
units underlying the surface impoundments, hydraulic conductivity of CCR and the soils
underlying the surface impoundment, geotechnical properties of the CCRs and the uppermost
stratigraphic unit under the surface impoundment, and CCR and CCR affected soils.
4.2 Hydrogeology and Geologic Descriptions
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
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4.3 Stratigraphy of the Geologic Units Underlying Surface Impoundments
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
4.4 Geotechnical Properties
This section summarizes the geotechnical conditions and properties found from investigations
performed within the U513 and U5B Main and Saddle Dam areas. The presented information was
obtained from previous geotechnical investigations at the site and recent investigation activities
conducted to support the Closure Plan development. The geotechnical conditions within the U5B
generally consist of CCR (interbedded layers of fly ash and bottom ash) placed in the basin
primarily by hydraulic sluicing underlain by residual soil, saprolite, partially weather rock (PWR),
and bedrock.
For the purposes of discussion of the geotechnical properties of the materials, the saprolite
material is described as partially weathered rock. General properties of the various materials
encountered within and surrounding the U5B are described below. A range of measured material
properties of laboratory tests performed by Wood, AECOM, HDR, and SynTerra for the
subsurface explorations completed within the U513 is presented in Table 4-1. Appendix B of this
Closure Plan presents boring and laboratory information collected at the site used for the analyses
and development of this document.
4.4.1 CCR Within Basin
The CCR within the U5B consists primarily of alternating layers and mixtures of bottom ash and
fly ash. Bottom ash consists of moist, gray to dark gray, fine to coarse silty sand (SM). Fly ash
obtained consists of very loose, wet, and gray to dark gray silt (ML) material.
4.4.2 Liner Material Properties
The U513 is unlined so there are no associated material properties.
4.4.3 Subsurface Soil Properties
Subsurface residual soil (including saprolite) consists of very loose to very dense and soft to hard;
moist to wet; fine to coarse; brown, orange, gray, tan, yellow and red silty sand or clayey sand
with some plastic soil.
4.4.4 CCR Basin Dam Soil Properties
The embankment fills are predominately classified as silty sand (SM) with some layers of sandy
silt (ML) also encountered. The consistency of the silty sand fill materials ranged from loose to
medium dense.
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4.5 Chemical Analysis of Impoundment Water, CCR and CCR-Affected Soil
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
4.6 Historical Groundwater Sampling Results
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
4.7 Groundwater Potentiometric Contour Maps
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
4.8 Estimated Vertical and Horizontal Extent of CCR within the Impoundments
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
5. GROUNDWATER MODELING ANALYSIS
In accordance with the requirements of N.C.G.S. § 130A-309.21 1 (b)(1), Duke Energy
separately submitted an updated Corrective Action Plan (CAP) in parallel with this Closure Plan;
the updated CAP is herein incorporated in its entirety by this reference. Neither the updated
CAP nor its content is the work product of Wood. Although the Closure Plan contains references
to the updated CAP, all specific relevant details to groundwater and related actions are found in
the updated CAP itself and not in this Closure Plan.
Among other areas, the updated CAP evaluates the extent of, and remedies for, constituents of
interest (COI) in groundwater associated with the Unit 5 Inactive Ash Basin, focusing on
constituent concentrations detected above the applicable 02L Standards, Interim Maximum
Allowable Concentrations, or approved background threshold values north and northeast of the
Unit 5 Inactive Ash Basin. In addition, the updated CAP considers the federal groundwater
corrective action requirements at 40 C.F.R. §§ 257.96-.98.
As detailed in the updated CAP, Duke Energy (i) will complete ash basin closure; and (ii) intends
to implement a groundwater extraction system. The CAP provides that these corrective action
measures will most effectively achieve remediation of the groundwater through the installation of
groundwater extraction wells northeast of the U5 Inactive Ash Basin saddle dam. Significantly,
groundwater modeling simulations indicate (i) these measures will control COI at or beyond the
compliance boundary, and (ii) at such time the site -specific considerations detailed within the CAP
have been satisfied, including, but not limited to, securing all required state approvals, installing
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the necessary equipment, and commencing full-scale system operation, COI migration will be
contained within the compliance boundary.
5.1 Site Conceptual Model Predictions
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
5.2 Groundwater Chemistry Effects
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
5.3 Groundwater Trend Analysis Methods
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
6. BENEFICIAL USE AND FUTURE USE
6.1 CCR Use
At this time, Duke Energy has not identified a beneficial use of CCR from the U513 at Cliffside
Station.
6.2 Site Future Use
At this time Duke Energy has not identified any future use of the land reclaimed by the dewatering
and excavation of the USB.
7. CLOSURE DESIGN DOCUMENTS
7.1 Engineering Evaluations and Analyses
Engineering evaluations and analyses to support closure of the U513 at the Cliffside Station, as
detailed in this Closure Plan, are provided in Appendix C.
The U513 will be fully removed down to grade. Based on the final post closure configuration and
absence of engineered fill features, no geotechnical calculations have been included for the
Closure Plan (approval stage) design. A permit to construct application with associated
geotechnical and hydrogeologic analyses has been prepared and submitted to NCDEQ Solid
Waste Section for expansion of the CCR landfill into Phases III and IV. Dam removal related
calculations will be included in the dam modification permit applications.
Safe and effective access to the U513 is critical to CCR excavation and the completion of closure.
Access road locations into or across the U513 for excavation cannot be reliably established until
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detailed phasing of closure is developed, and a contractor is selected to complete the work. A
variety of mitigation techniques can be applied, such as installation of a geogrid and crushed
stone aggregate, placement and spreading of dry CCR over the basin surfaces to establish
access, and use of low ground pressure or light weight construction equipment.
Areas for stockpiling or conditioning of CCR are generally needed. These areas must be
established within the limits of the CCR unit and require placement or stacking of CCR excavated
from other areas of the U51B. They can be established in areas where all or most of the CCR has
been removed, or on areas where a significant depth of CCR remains in place. Sluiced CCR
forming the foundation of stockpiles or conditioning areas may be subject to bearing capacity or
slope failures from the additional vertical compressive stress imparted by the stacked CCR and
hauling equipment.
During excavation of CCR, interim or temporary excavated CCR slopes are commonly created.
These slopes vary in height and the duration they will have to stand. Some slopes are subject to
potential loading from hauling or stockpiling operations. The location and geometry of such slopes
cannot be established during design. These elements depend on the means and methods
employed by the construction contractor, site conditions, schedule and other site conditions.
Excavation in a deep valley fill creates significant safety risks that need further evaluation and will
require the means and methods inputs from a contractor to fully address before closure
excavation work commences. A detailed phasing and excavation plan will be developed after this
Closure Plan is approved by NCDEQ.
7.2 Closure Plan Activities
The primary activities associated with closure by excavation are as follows:
• Decant by using floating pumps, screened intakes, and pumping through the discharge
pipe outlets.
• Construction and operation of a temporary water management system (WMS) to
manage all discharges in compliance with the NPDES permit during closure.
• Dewater the CCR to the extent necessary to allow for access, CCR excavation, and
conditioning (drying) prior to placement in the on -site landfill.
• Start CCR excavation from the U51B, with sequencing determined for optimal
progression. Manage and control of dust -generating activities through specific site
planning and mitigation. Construct landfill cells in coordination with CCR excavation.
Place the excavated CCR in the on -site landfill after conditioning, and compact.
Instrumentation and monitoring requirements to be developed prior to construction will
be followed to verify construction phase stability. Construction dewatering to be used
as needed to provide stable work areas and slopes.
• Maintain required hydrologic/hydraulic storage capacity throughout the excavation
process and progressively breach the U51B Main Dam as excavation advances.
• Complete closure by excavation verification. Grade the area to promote positive
drainage and seed for vegetative growth.
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• Sequence final dam breach with construction of proposed stormwater detention basins
and inflow design flood management.
Additional information and details pertaining to the closure design are provided in the Closure
Plan drawings, which are presented in Appendix D.
7.3 Design Drawings
The Closure Plan drawings presented in Appendix D include the following:
• Cover sheet
• General notes
• Existing conditions plan with aerial photograph
• Existing conditions plan with topography
• Exploration location plan
• Demolition plan
• Estimated bottom of CCR contour plans
• Final grading plan
• Final grading profiles, cross -sections and details
• Excavation plan
• Excavation profiles and details
• Closure details
• Stormwater management — ditch details
• Erosion and Sediment Control Details
These Closure Plan drawings will be further developed and refined to develop construction level
drawings during subsequent stages following NCDEQ approval of the Closure Plan. In addition,
supplemental drawing sets will be prepared on an as needed basis to support dam modification
and/or decommissioning permits, erosion and sediment control permits, NPDES permit
modifications, and other related permits.
Once the excavation grades shown on the Closure Plan drawings or the actual ash soil interface
with residual soil material (where it differs from the drawings) have been achieved the procedures
described in the Duke Energy Excavation Soil Sampling Plan (Appendix E) will be followed to
confirm that the closure by excavation has been achieved.
7.4 Description of the Construction Quality Assurance Plan
A Construction Quality Assurance (CQA) Plan will be developed following NCDEQ approval of the
Closure Plan for the USB. The CQA Plan will be prepared to address G.S. §130A-
309.214(a)(4)(g). Its purpose is to describe the CQA program to be adhered to in execution of
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closure activities at the Cliffside Station. The CQA Plan will present the roles and responsibilities
for monitoring and testing activities and presents guidance on the methodology to be used for
evaluating whether the construction has been performed in accordance with the approved Closure
Plan. The CQA Plan will also detail the material testing frequencies; methods for transportation,
handling, and storage of materials; test methods and verifications; manufacturer, field, and
laboratory testing; field activities for construction monitoring and oversight; and reporting and
documentation requirements. Technical specifications to be developed as part of the construction
level design packages for contractor bidding and will present specific material properties and
specifications.
The CQA Plan will address materials and CQA activities associated with the following
components:
• Earthwork
■ CCR Excavation
■ Structural Soil Fill
• HDPE Piping
• Vegetation
• As -Built Conditions
• Record Documentation Report
8. MANAGEMENT OF WASTEWATER AND STORM WATER
The Cliffside Station manages wastewater and stormwater under the NPDES permit issued by
the NCDEQ. Permit number NC0005088, effective September 1, 2018 through August 31, 2023,
authorizes six discharge points into the Broad River. Outfalls 002B, 002C are for emergency
overflows that are unlikely to happen. Outfalls 104 and 106 are constructed seep discharges.
Outfall 002 is the associated outfall for the AAB discharges. Outfall 005 is associated with the
water management system treated discharge effluent. The treated wastewater from the U513 will
be discharged through NPDES Outfall 005. All discharges are to be conducted in accordance
with NPDES permit NC0005088. The stormwater from the power station area is sent to the new
water management system where it also is treated and then discharged through NPDES outfall
005. Other stormwater outfalls associated with industrial activities are discharged in accordance
with Industrial Storm Water permit NCS000571.
The U513 has historically collected the wastewater from plant operations and stormwater runoff
before discharging it through the basins' outlet structures. All power station stormwater (contact
water) is now routed to the new WMS and no longer discharges into the USB. Stormwater that
falls directly onto or in the surrounding area of the USB, runs through a vegetated area and then
discharges out storm water outfall SW009, which is regulated by permit NCS000571. Stormwater
that accumulates elsewhere on the Cliffside Station property that does not enter the Basins is
regulated per NCS000571.
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The U51B currently has the capacity to contain the PMP storm event by maintaining the water
surface level elevation at or below El. 764.87 ft, which provides a minimum freeboard of 0.13 ft.
As part of the closure, the U5B Main Dam will be removed by excavating an engineered breach.
Under this post closure condition, there will be increased flow downstream of the U5B Main Dam
compared to the existing conditions. Additional stormwater retention capacity will need to be
developed following dam removal or the existing downstream culverts will need to be retrofitted
to increase their conveyance capacities. The closure design proposed herein provides additional
storage capacity following breach of the U513 Main Dam using detention basins as described
further below. The concept designs for these proposed basins were based on limiting post -closure
downstream stormwater flows to less than or equal to existing stormwater flows.
Wastewater from the U513 will be pumped, treated and discharged in two phases; the (very limited)
Decanting phase and Dewatering phase. U513 does not currently have a significant amount of
ponded water. The U513 will advance into the Dewatering phase to remove interstitial water.
During this phase, additional physical -chemical treatment processes will be added to the WMS
as necessary to maintain compliance with the requirements of the discharge permit. During
Dewatering phase, the Cliffside Station WMS will have a designed flow rate of 250 to 400 gpm.
Dewatering is performed to remove the interstitial or pore water from the CCR to facilitate
excavation, to access in -place CCR or to establish safe slopes prior to and after CCR excavation.
It is anticipated that performance criteria will be established in the construction -level
documentation to identify required vertical and horizontal limits of interstitial water removal at
critical locations and for critical conditions during closure.
Excavated CCR will likely have to be conditioned (dried) prior to placement into the landfill as part
of closure. Consideration of required conditioning and management of contact water during
excavation will be included in the development of closure phasing and landfill fill placement.
The proposed post -closure grades restore the historical flows from the surrounding landscape
and route flow toward the Downstream Dam and the Broad River. Up to and including the last
phase of closure before the U513 dams are breached, the U5B will maintain the capacity to contain
the required storm size/flows functioning as a detention basin.
The detention basin design criteria will be further refined for the construction -level documents
based on actual field elevations reached in the excavated areas and discussions with NCDEQ
with regards to the embankment heights, which will follow NCDEQ approval of this Closure Plan.
The designs for the detention basins are conceptual level at this time. These concept designs for
the detention basin are based conservatively on 100-year storms. Appendix C presents the
results of the closure stormwater management calculations.
8.1 Anticipated Changes in Wastewater and Stormwater Management
Closure of the AAB has necessitated changes in the management of a number of wastewater and
process streams. Wastewater and process streams previously discharging to the AAB have been
rerouted to the new holding and auxiliary basins as separate treatment systems.
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The company will obtain necessary permit coverage for any flows associated with post closure
conditions as plans are finalized. A WMS will be utilized such that the permit terms can be met
throughout the duration of dewatering, closure and post -closure timeframes
Erosion and Sediment Control Plans for different phases of the construction will be developed as
part of the construction level packages and formal Erosion and Sediment Control Plan permit
submittal. The details for the erosion and sediment control measures depicted on the drawings in
this Closure Plan submittal will be re-evaluated after the specific construction phasing is
established, which will follow NCDEQ approval of this Closure Plan. In addition, erosion and
sediment control measures may be installed and removed in phases as stabilization is achieved.
8.2 Wastewater and Stormwater Permitting Requirements
Additional information on required permits is described in Section 10
9. DESCRIPTION OF FINAL DISPOSITION OF CCR
CCR will be dispositioned by placement into an approved and permitted lined on -site CCR landfill.
Vegetation encountered or removed during the progression of the work will be managed in
accordance with state regulations for handling and disposal.
10. APPLICABLE PERMITS FOR CLOSURE
Refer to Table 10-1 for detailed information on the potential and applicable permitting needed to
perform closure by excavation. Development of permitting package submittals and/or regulatory
approval requests would follow NCDEQ approval of the Closure Plan.
11. DESCRIPTION OF POST -CLOSURE MONITORING AND CARE
A post -closure Plan will be developed following NCDEQ approval of the Closure Plan for the
Closure by Excavation Plan for the U513 closures at the Cliffside Station. The purpose of the post -
closure Plan will be to provide a description of the inspection, monitoring, and maintenance
activities required to be performed throughout the 30-year post -closure care period for the closed
USB.
The post -closure Plan will be developed to meet the requirements of CAMA (G.S. §130A-
309.214(a)(4)(k)). The items that will be included in the post -closure Plan for the U513 include:
• Name, address, phone number, and email address of the responsible office or person;
• Means and methods of managing affected groundwater and stormwater;
• Maintenance of the groundwater monitoring systems;
• Regular inspection and maintenance of the final cover system;
• Groundwater and surface water monitoring and assessment program (included as part of
the CAP);
• Post -closure inspection checklist to guide post -closure inspections;
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• Description of planned post -closure uses; and
• Financial assurance estimates for post -closure operations and maintenance and remedial
action.
11.1 Groundwater Monitoring Program
This information is included as part of the CAP being prepared separately by SynTerra for Duke
Energy and is being submitted in parallel to this Closure Plan. The CAP is herein incorporated by
this reference, but its content is not the work product of Wood.
12. PROJECT MILESTONES AND COST ESTIMATES
12.1 Project Schedule
A Closure project high level milestone schedule has been prepared by Duke Energy and is
provided below. The schedule defines the following anticipated activities and milestones:
Engineering, decanting, dewatering Ongoing
Submit plan and design for landfill expansion construction permit Ongoing
Start landfill expansion construction Q4-2021
Start CCR excavation Q4-2021
Complete CCR excavation Q4-2028
Complete final closure and cover system of new landfill Q4-2029
Site final grading and vegetative cover Q4-2030
It should be noted that CCR excavation will not be completed by the CAMA 2029 deadline at
N.C.G.S. § 130A-309.214(a)(3). A detailed construction schedule will be developed following
NCDEQ approval of this Closure Plan.
12.2 Closure and Post -Closure Cost Estimate
Cost estimates for closure and post -closure of the Basins at Cliffside Station were developed by
Duke Energy and provided to Wood. These cost estimates are not a work product of Wood. These
are Class 5 estimates as the detailed and final design is not developed at this stage of the closure
project. Following approval of this Closure Plan by NCDEQ and further development of the project
plans and engineering designs the cost estimate will be refined and updated.
The cost to complete the closure by excavation, including the landfill expansion, is estimated to
be $87 million.
The cost to perform the 30-year post -closure activities and monitoring is estimated to be $43
million.
The cost estimates prepared by Duke Energy includes the following major activities:
• Mobilization and Site Preparation
• Dewatering, earthwork, and subgrade preparation
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• CCR excavation
• Stormwater management, erosion and sediment control, and site restoration
• Engineering support (design and CQA)
• Post closure — groundwater monitoring
• Post closure — operations and maintenance
• Contingency
Corrective action costs are included as part of the CAP being prepared separately by SynTerra
for Duke Energy and is being submitted in parallel to this Closure Plan. The CAP is herein
incorporated by this reference, but its content is not the work product of Wood.
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13. REFERENCED DOCUMENTS
Idriss and Boulanger, CPT and SPT Based Liquefaction Triggering Procedures, Report
UCD/CGM- 14/01, Department of Civil and Environmental Engineering, University of
California, Davis, CA, April 2014.
NCDEQ, 2009. Industrial Solid Waste Landfill Facility Permit No. 8106, Issued June 24, 2009.
NCDEQ, 2015. Permit No. NCS000571 to Discharge Stormwater under the National Pollutant
Discharge Elimination System. September 30, 2015.
NCDEQ, 2018. Permit No. NC0005088 to Discharge Wastewater under the National Pollutant
Discharge Elimination System. July 13, 2018.
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TABLES
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Table 2-1: NC CAMA Closure Plan Requirements
Summary and Cross Reference Table
Duke Energy, Rogers Energy Complex - Cliffside Steam Station
No.
Description
Corresponding
Closure Plan Section
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:
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.
7.1
6
JA 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
b. Site maps, which, at a minimum, illustrate all of the following:
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.
3.3
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
c. The results of a hydrogeologic, geologic, and geotechnical investigation of the site, including, at a minimum, all of the following:
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

Table 2-1: NC CAMA Closure Plan Requirements (continued)
Summary and Cross Reference Table
Duke Energy, Rogers Energy Complex — Cliffside Steam Station
Corresponding
No.
Description
Closure Plan Section
d.
The results of groundwater modeling of the site that shall include, at a minimum, all of the following:
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
1
(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
5.1
Carolina Administrative Code.
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
2
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
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
3
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
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
e
(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
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
g
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
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
i
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
9
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.
j.
A list of all permits that will need to be acquired or modified to complete closure activities.
10
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
k
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
11
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:
1
A demonstration of the long-term control of all leachate, affected groundwater, and stormwater.
11.1
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
2
the proposed locations and well construction details; and (iii) the actions proposed to mitigate statistically significant increasing groundwater quality trends.
11.2
I.
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
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
n
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.

Table 4-1. Summary of Typical Geotechnical Measured Properties
Properties
CCR/Ash within Ash Basin
Foundation Soil (Residual) below Ash Basin
Embankment Soil
Foundation Soil (Alluvial)
below Embankment Dams
Foundation Soil (Residual) below
Embankment Dams
Partially Weathered
Rock (PWR)
Soil Type
Silt (ML) -Fly Ash,
Silty Sand (SM) - Bottom Ash
Silty Sand (SM),
Clayey Sand (SC)
Predominantly Silty Sand (SM orSilty
SP), or Sand y Silt (ML), Lean Clay
(CL), and Fat Clay (CH)
Sand (SM and SP-SM),
Silt (ML and MH)
Silty Sand (SM) and
Clayey Sand (SC)
Breaks down to Silty Sand
(SM) with rock fragments
Color
Grayto Dark Gray
Y
Brown, Tan, White, Olive, Red, Gray, Yellow
y'
Brown, Orange, Red, Gray, Tan
g Y'
Brown, Tan, Red, Gray
y
Brown, Gray, Tan, Orange, Red, Yellow
y' g
White, Brown, Gray,
Multicolor
Plasticity
Non Plastic
Non Plastic to Very Plastic
Non Plastic to Very Plastic
Non plastic to Very Plastic
Non plastic to Medium Plastic
Non Plastic
Liquid Limit
Non Plastic
NP - 47%
NP - 60%
NP - 64
NP - 42
Non Plastic
Plasticity Index
Non Plastic
NP - 21%
NP - 30%
NP - 28
NP - 16
Non Plastic
Representative
Range
Geometric
Mean
Representative Range
Geometric Mean
Representative Range
Natural Moisture Content (%)
15%- 81%
54%
15%- 26%
19%
5%- 54%
20%- 26%
14%- 38%
12%- 17%
Fines Content
14%-99%
65%
16%-44%
25%
2%-83%
7%-91%
17%-43%
14%-22%
Clay Content
1%-28%
11%
4%-37%
9%
3%-44%
8%-25%
Moist Unit Weight - ym (pcf)
-
-
-
-
-
-
98 -104 pcf
-
Dry Unit Weight - yd (pcf)
-
-
-
-
81-114 pcf
104 pcf
2.63 - 2.73 pcf
-
Specific Gravity
2.05 - 2.61
2.3
2.55 - 2.70
2.65
2.65 - 2.76
2.68
--
2.63 - 2.71
Horizontal Hydraulic Conductivity (cm/sec)
-
Vertical Hydraulic Conductivity (cm/sec)
1.5E-07 - 3.82E-04
1.03E-04
3.0E-06 -1.3E-04
4.8E-OS
1.0E-07 - 8.6E-05
5.5E-06 - 5.2E-05
Notes:
' Data obtained from laboratory tests conducted by AECOM, Wood/Amec Foster Wheeler, and HDR performed on materials obtained from within the Ash Basins and associated dams.

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
Table 10-1. Inactive Unit 5 Ash Basin - Regulatory Permits, Approvals, or Requirements
for Basin Closure by Excavation
Permit/Approval
Type of
Regulatory
General Permit
Regulating
Existing
Name or Subject
Agency
Permit No.
Approval
pp
Comments
(if applicable)
Mechanism or
Not Required
Permit modification likely due
Permit
to the increased heavy
Air Quality
NCDEQ
modification
equipment vehicle traffic and
likely
potential dust generated
during closure activities
Rutherford or
A local building permit is
Building Permit
Cleveland
New Permit
required for installation of
County
construction trailers
Modification or abandonment
of CAMA program monitoring
CAMA
NCDEQDWR
N/A
Written NCDEQ
wells require the approval of
Monitoring Plan
approval
the Division of Water
Resources (DWR)
CCR
US EPA
Required postings to Public
Impoundment
CCR Rule
Self -Regulating
Record
Closure
CCR
Maintain CCR GW monitoring
Impoundment
US EPA
Self -Regulating
network and requirements as
Monitoring
CCR Rule
stated in 257.90 - 257.98
Network
Clean Water Act
NCDEQ
Potential
If work is needed that
401
physically impacts WOTUS
Clean Water Act
USACE
Potential
If work is needed that
404
physically impacts WOTUS
Cutting Trees
Permitting is required to
Certificate of
modify or abandon wells and
Dam Safety
NCDEQ
RUTHE-070
Approval to
instrumentation on regulatory
RUTHE-072
Modify
dams through the Division of
Energy, Mineral, and Land
Resources (DEMLR)
Inactive Unit 5 Ash Basin Main
Certificate of
Dam - Permitting is required
Dam Safety
NCDEQ
RUTHE-070
Approval to
to modify the dam in
Modify
accordance with the Dam
Safety Law of 1967, 15A NCAS
wood.

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
Permit/Approval
Type of
Regulatory
General Permit
Regulating
Existing
Name or Subject
Agency
Permit No.
Approval
pp
Comments
(if applicable)
Mechanism or
Not Required
02K.0201 (b)(2); an
application must be filed with
the Division of Energy,
Mineral, and Land Resources
(DEMLR)
Inactive Unit 5 Ash Basin
Saddle Dam - Permitting is
required to remove the dam
Certificate of
in accordance with the Dam
Dam Safety
NCDEQ
RUTHE-072
Approval to
Safety Law of 1967, 15A NCAS
02K.0201 (b)(2); an
Modify
application must be filed with
the Division of Energy,
Mineral, and Land Resources
(DEMLR)
Utilization of or modification
to state or federal highways
DOT - General
to transport CCR will require
consultation or notification to
relevant DOT agency
Temporary access or driveway
Driveway Permit
NCDOT
permits as needed
Land disturbance activities
outside of the Basin will
exceed one acre, therefore in
conformance with 15A NCAC
Erosion and
NCDEQ
04, an E&SC Permit is
Sediment
Mooresville
New Permit
required from Land Quality
Control (E&SC)
Regional Office
prior to commencement of
construction in those areas.
Note that land disturbance
includes tree clearing and
grubbing and vehicular wheel
or tracking as disturbance.
Removal from or import of
material could be restricted
Fire Ants
Restriction not
depending on the potential
likely
for fire ants and geographic
regions involved
wood.

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
Permit/Approval
Type of
Regulatory
General Permit
Regulating
Existing
Name or Subject
Agency
Permit No.
Approval
pp
Comments
(if applicable)
Mechanism or
Not Required
Flood Damage Prevention
Ordinance of Person County,
Article 3 General Provisions,
Section C, requires a
Floodplain
Rutherford
Floodplain Development
Development
County
New Permit
permit prior to any
development activities within
FEMA mapped Special Flood
Hazard Areas for the Flood
Insurance Rate Maps
Permits are required to
construct any water supply
well or water well system
Large Capacity
New Permit
with a design capacity equal
Water Supply
NCDEQ
possible
to or greater than 100,00
Well
gallons per day - for
dewatering outside of the
Basin
Multi -State
If movement of CCR will cross
Not required
state lines, multi -state
Agreement
regulations might apply
NPDES (National
Pollutant
Permit
Modification of NPDES may
Discharge
NCDEQ
NC0005088
modification
be necessary if new source or
Elimination
likely
outfall is created.
System)
NPDES (National
Pollutant
Revision to existing sitewide
Discharge
Permit revision
permit or new permit may be
Elimination
NCDEQ
NCS000571
likely
required for access roads,
System)
Industrial
staging areas, etc.
Stormwater
NPDES (National
Pollutant
Permit required for
Discharge
NCDEQ
NCO005088
New Permit
temporary and permanent
Elimination
possible
System)
stormwater rerouting.
Stormwater
wood.

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
Permit/Approval
Type of
Existing
General Permit
Regulating
Permit No.
Regulatory
Comments
Name or Subject
Agency
Approval
pp
(if applicable)
Mechanism or
Not Required
Removal from or import of
vegetated material could be
Noxious Weeds
restricted depending on the
vegetation and geographic
regions involved
Railroad
Construction activities
Easement,
adjacent to tracks/ballast or a
Access, or
new railroad crossing require
Crossing Permit
an agreement or permit
SPCC (Spill
In accordance with the
Federal Water
Prevention
Modification of
Pollution Control Act (Clean
Control and
NCDEQ
existing plan
Water Act) of 1974, Title 40,
Countermeasure
Code of Federal Regulations,
Plan
Part 112.
Federal and/or state
regulations may apply
including agency consultation
and performing site -specific
Threatened or
surveys within the proper
Endangered
NCDEQ
survey period (e.g., flowering
Species
And EPA
period for listed plant) to
determine if Threatened or
Endangered Species or their
habitat exist within the limits
of disturbance
Solid Waste
8106-
Existing CCR Landfill
Permit to
NCDEQ
permit
INDUS-2009
Expansion
Construct
Solid Waste
8106-
Existing CCR Landfill
Permit to
NCDEQ
Permit
INDUS-2009
Expansion
Operate
wood.

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
FIGURES
wood.

Project Location
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n 7
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wood* JOB NUMBER 7812-19-0194 FIGURE 1-1

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LICENSURE: NCENG:F-1253 NCGEOLOGY:C-247 ISSUED FOR PERMITTING - NOT RELEASED FOR CONSTRUCTION
I \� \ \ \\ \\ \ SEAL
C? SCALE: AS SHOWN DES: VMO
NOTE: / I yF \ DUKE
1. THE "APPROXIMATE LIMITS OF ASH BASIN FACILITY BOUNDARY" AND THE "APPROXIMATE LIMITS OF CCR BOUNDARY" ARE BASED ON AERIAL PHOTOGRAPHY, /i /�\ \\ \ \ \ \ DWG TYPE: DWG DFTR : VMO/ANE
TOPOGRAPHIC MAPPING, AND OTHER HISTORICAL DRAWINGS AND INFORMATION AND SHOULD BE CONSIDERED APPROXIMATE. THE "APPROXIMATE LIMITS OF / /� �\ \X \ \ \ +
ASH BASIN FACILITY BOUNDARY" INCLUDES THE CONTAINMENT DAMS AND DIKES WHILE THE "APPROXIMATE LIMITS OF CCR BOUNDARY" EXCLUDES THOSE / 6 �/\I \ \ \ \ JOB NO: 7812-19-0194 CHKD: KRD
STRUCTURES AND IS BASED ON UPDATED TOPOGRAPHIC MAPPING, REPORTED OPERATIONAL LEVELS, AND SUBSURFACE DATA COLLECTED WITHIN THE BASIN. CY
IT SHOULD BE NOTED THAT THE DETERMINATION OF THE ACTUAL LATERAL EXTENT OF THE CCR MATERIALS WILL TAKE PLACE PRIOR TO AND/OR DURING �` v / 1 CR-C - p \\ �\ d \❑ NOT FOR ENE R Y® DATE: OCTOBER 15, 2019 ENGR: JB
IMPLEMENTATION.
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CON
STRUCTION NSTRUCTION
P?Q �\/ \\ II �— \�\ �\\\\ FILENAME: FIGURE 3-1 U5.dwg APPD: JB
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0
/ \\ ( \\ I I / 0 q \ \\ \ \ Q DWG SIZE DRAWING NO. REVISION
REFERENCES:
1. ASH BASIN FACILITY BOUNDARIES, BORING LOCATIONS, PIEZOMETER LOCATIONS, AND SEEP LOCATIONS PROVIDED BY DUKE ENERGY. \ \\ \\ 1 IIII\ /) \1 \ ANSI D
2. EXISTING TOPOGRAPHIC INFORMATION WAS PRODUCED FROM PHOTOGRAMMETRIC METHODS FROM AERIAL PHOTOGRAPHY OBTAINED ON JULY 31, 2015 BY f l FIGURE 31 WSP. / \ \I II \ \\ i / / \ 22" x34" ----
/ \ REV DATE JOB NO. PROJECT TYPE DES DFTR CHKD ENGR DESCRIPTION
INCHES 1 2 3 TENTHS 10 20 30 4 5 I I 1 7 8 9 1 0
I I I I I
Plotted By: Bell, Josh Sheet Set: 7812190194 — Unit 5 Inactive Ash Basin Layout:.005 EXISTING CONDITIONS —TOPOGRAPHIC October 15, 2019 04: 12: 50pm Q: \Duke\CliffSide\7812190194 — Cliffside Closure Plan\Exhibit\FIGURE 3-1 U5.dwg

Duke Energy Coal Combustion Residuals Management Program December 18, 2019
Cliffside Steam Station— Inactive Unit 5 Ash Basin CAMA Closure Plan (Closure by Excavation)
Revision 0
Wood E&IS Project No. 7812190194
APPENDICES
wood.