HomeMy WebLinkAboutRoxboro WAB - CBE - Closure Report_20200107f
� 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
(980) 373-0408
Subject: Submittal of Ash Basin Closure Plan and Corrective Action Plan Update
Roxboro Steam Electric Plant
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 Roxboro 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 Roxboro coal ash basins. After regulatory approval, excavating the basin ash would require
15 years to move the ash to a new lined landfill within plant property. The landfill would be
located in the prior footprint of the East Ash Basin adjacent to Dunnaway Road, rising about 180
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 Roxboro 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 CAP
approach. The West Ash Basin is currently in compliance with state groundwater standards at
the compliance boundary. The CAP designed for Roxboro will achieve groundwater standards
at the East Ash Basin through a combination of strategically placed groundwater extraction
wells coupled with clean water infiltration wells.
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
Roxboro Steam Electric Plant
Page 2
SizDraovi
Pach
Senior Vice President
Environmental, Health & Safety
Enclosure:
• Corrective Action Plan Update
• Closure by Excavation Closure Plan
wood.
DUKE ENERGY
ROXBORO STEAM ELECTRIC PLANT
COAL COMBUSION RESIDUALS SURFACE
IMPOUNDMENT CLOSURE PLAN
CLOSURE BY EXCAVATION
WEST ASH BASIN (WAB) AND FGD BASINS
CLOSURE PLAN REPORT
Final Submittal
Prepared for
(, DUKE
ENERGY.
550 South Tryon Street
Charlotte, North Carolina 28202
Final Revision 0
Issue Date: December 18, 2019
Prepared by
Wood Environment & Infrastructure Solutions, Inc.
4021 Stirrup Creek Drive, Suite 100
Durham, North Carolina 27703
Project No. 7812190186
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Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
TABLE OF CONTENTS
EXECUTIVE SUMMARY............................................................................................................v
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 FEATURES DESCRIPTION ........................3
3.1 Surface Impoundment Description...................................................................................... 3
3.1.1
Site History and Operations................................................................................... 3
3.1.2
Estimated Volume of CCR in Impoundment..........................................................5
3.1.3
Description of Surface Impoundment Structural Integrity......................................5
3.1.4
Sources of Discharges into Surface Impoundments..............................................6
3.1.5
Existing Liner System............................................................................................7
3.1.6
Inspection and Monitoring Summary.....................................................................7
3.2 Site Maps............................................................................................................................ 8
3.2.1
Existing CCR Impoundment Related Structures....................................................8
3.2.2
Receptor Survey.................................................................................................... 8
3.2.3
Existing On -Site Landfills.......................................................................................8
3.3 Monitoring and Sampling Location Plan............................................................................. 8
4. RESULTS OF HYDROGEOLOGIC, GEOLOGIC, AND GEOTECHNICAL
INVESTIGATIONS..........................................................................................................8
4.1 Background......................................................................................................................... 8
4.2 Hydrologic and Geologic Descriptions................................................................................ 9
4.3 Stratigraphy of the Geologic Units Underlying Surface Impoundments ............................. 9
4.4 Geotechnical Properties...................................................................................................... 9
4.4.1 CCR within Ash Basins and FGD Basins..............................................................9
4.4.2 Liner Material Properties......................................................................................10
4.4.3 Subsurface Soil Properties..................................................................................10
4.5 Chemical Analysis of Impoundment Water, CCR, and CCR Affected Soil ....................... 10
4.6 Historical Groundwater Sampling Results........................................................................ 10
4.7 Groundwater Potentiometric Contour Maps..................................................................... 10
4.8 Estimated Vertical and Horizontal Extent of CCR within the Impoundments ................... 11
5. GROUNDWATER MODELING ANALYSIS...................................................................11
5.1 Site Conceptual Model Predictions................................................................................... 12
5.2 Groundwater Chemistry Effects........................................................................................ 12
5.3 Groundwater Trend Analysis Methods.............................................................................. 12
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
6. BENEFICIAL USE AND FUTURE USE........................................................................12
6.1 CCR Use........................................................................................................................... 12
6.2 Site Future Use................................................................................................................. 12
7. CLOSURE DESIGN DOCUMENTS..............................................................................12
7.1 Engineering Evaluations and Analyses............................................................................ 12
7.2 Closure Plan Activities...................................................................................................... 13
7.3 Design Drawings............................................................................................................... 14
7.4 Description of Construction Quality Assurance and Plan ................................................. 14
8. MANAGEMENT OF WASTEWATER AND STORMWATER........................................15
8.1 Anticipated Changes in Wastewater and Stormwater Management ................................ 16
8.2 Wastewater and Stormwater Permitting Requirements.................................................... 16
9. DESCRIPTION OF FINAL DISPOSITION OF CCR......................................................17
10. APPLICABLE PERMITS FOR CLOSURE....................................................................17
11. DESCRIPTION OF POST -CLOSURE MONITORING AND CARE...............................17
11.1 Groundwater Monitoring Program..................................................................................... 17
12. PROJECT MILESTONES AND COST ESTIMATES.....................................................18
12.1 Project Schedule............................................................................................................... 18
12.2 Closure and Post -Closure Cost Estimate......................................................................... 18
13. REFERENCED DOCUMENTS......................................................................................19
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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
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Tables
Table 2-1 NC CAMA Closure Plan Requirements Summary and Cross Reference Table
Table 4-1 Summary of Typical Geotechnical Index Properties
Table 10-1 Regulatory Permits, Approvals, or Requirements for Basin Closure by
Excavation
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
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 Borrow Soil Quantities
Appendix D Closure Plan Drawings
Appendix E Excavation Soil Sampling Plan
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
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 West
Ash Basin (WAB) and Flue Gas Desulfurization (FGD) Basins at the Roxboro Steam Electric
Plant. This plan details closure -by -excavation of the WAB and FGD Basins (collectively, Basins),
and placement of the excavated coal combustion residuals (CCR) in a proposed expansion to the
existing permitted on -site lined landfill. Closure of the WAB includes the Southern Extension
Impoundment (SEI) area of the WAB. The excavation of CCR and the closure of the WAB 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.).
The Roxboro Plant is owned and operated by Duke Energy Progress (Duke Energy) and is located
in Person County, approximately 5 miles southeast of Semora, North Carolina. The Roxboro
Plant consists of four coal-fired electric generating units with a combined generating capacity of
2,422 megawatts. The first generating unit (Unit 1) at the Roxboro Plant site went into service in
1966.
Duke Energy has historically operated impoundments at the Roxboro Plant site for storing CCR,
including the WAB, FGD Basins and the East Ash Basin (EAB). It should be noted that a separate
Closure Plan has been prepared for closure of the EAB. The WAB was formed by construction
of the EAB Main Dam (regulated by NCDEQ as PERSO-038) around 1973. In 1986, The WAB
Main Dam was raised by 13 feet to the current maximum height of 70 feet. Raising of the WAB
Main Dam also included construction of WAB Dike No. 1 (regulated by NCDEQ as PERSO-039),
saddle dikes and extension of the existing discharge outlet channel (also referred to as the
"western discharge canal"). The WAB closure area includes the Southern Extension
Impoundment (SEI) area of the WAB.
The FGD Basins (also referred to as FGD Ponds) are located within the WAB for storage of wet
sluiced FGD process residuals (also CCR). Construction for the current configuration of the FGD
Basins (regulated by NCDEQ as PERSO-040, 041, and 042) was completed in 2009, and the
FGD Basins have a total surface area of approximately 26.6 acres. The FGD Basins are
constructed on CCR deposits and are located on the northwest side of the WAB near the WAB
Main Dam.
The area enclosed by the CCR boundary of the WAB is estimated to be approximately 225 acres,
which includes approximately 42 acres for the SEI area of the WAB. Based on a topographic
survey performed in April 2014 and other data, bathymetric survey performed in January 2015,
and production data thru July 2019, the WAB closure area is estimated to contain approximately
10.81 million cubic yards of CCR or approximately 12.97 million tons. This estimate includes CCR
contained within the FGD Basins and the SEI area of the WAB.
Closure activities for the Basin have already begun with the initiation of decanting under the
Special Order by Consent (SOC). Upon approval of a Closure Plan by NCDEQ, additional actions
will commence, including finalization of the detailed designs, dewatering and removal of interstitial
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
water, contracting and detailed planning for the closure work, removal and disposal of CCR from
the SEI area of the WAB, excavation of CCR from the Basin, excavation and removal of CCR
from the FGD Ponds, removal of the FGD Pond dikes and related facilities, construction of
additional industrial landfill capacity to permanently store the excavated CCR, breaching and
partial removal of the WAB Main Dam, complete removal of WAB Dike No. 1, and restoration of
disturbed areas.
Figures ES-1 and ES-2 illustrate the current state, and post -closure state of the Basins as detailed
by this Closure Plan.
Figure ES-1 Current View
Figure ES-2 Post Closure View
The Basin CCR will be removed to a new lined landfill expansion within the Station property,
located partially within the prior footprint of the EAB, adjacent to Dunnaway Road. The landfill
would rise approximately 180 feet above Dunnaway Road. Post -excavation, the Basin 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 Basin
Dam will be removed, allowing Hyco Lake to reach back into the footprint.
This document also includes a description of the Post -Closure Care Plan, which provides a
description of the inspection, monitoring, and maintenance activities required to be performed
throughout the 30-year post -closure care period for the closed Basins at the Roxboro Plant.
This document provides a summary of 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 this Closure Plan, meets regulatory
requirements for the stability of the site, management of surface water run-off, and access for
effective maintenance over the post -closure care period.
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.
As detailed in the updated CAP, Duke Energy has begun to implement, and will continue
implementing, source control measures at the site, including (i) complete decanting of the East
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Ash Basin and West Ash Basin to lower the hydraulic head within the basins and decrease
hydraulic gradients, reducing groundwater seepage velocities and COI transport potential; and (ii)
complete closure of the East Ash Basin and West Ash Basin. In addition, Duke Energy intends to
implement a robust active groundwater remediation program that includes extraction and
treatment at the East Ash Basin, and a combination of groundwater extraction and clean water
infiltration at the gypsum storage area and dry fly ash handling area. The CAP provides that these
corrective action measures will most effectively achieve remediation of the groundwater through
the installation of (i) extraction wells in the area of the unnamed pond north of the East Ash Basin;
(ii) extraction wells on the northeast side of the East Ash Basin; (iii) extraction wells in the
comingling zone near the dry fly ash handling area; and (iv) extraction wells and clean water
infiltration wells in the area between the gypsum storage area/dry fly ash handling area and Intake
Canal. Significantly, groundwater modeling simulations indicate (i) these measures will address
COI at or beyond the East Ash Basin 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 at or beyond the East Ash Basin compliance boundary will meet the
remedial objectives in nine years. Critically, as discussed above, the model indicates that COI
concentrations currently meet the 02L Standards at and beyond the West Ash Basin compliance
boundary.
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1. INTRODUCTION
1.1 Background
The Roxboro Plant is located in Person County, approximately 5 miles southeast of Semora, North
Carolina and consists of four coal-fired electric generating units with a combined generating
capacity of 2,422 megawatts. The first generating unit (Unit 1) at the Roxboro Plant site went into
service in 1966. CCR has historically been managed in the Roxboro Plant's on -site West Ash
Basin (WAB), East Ash Basin (WAB) and the Flue Gas Desulfurization (FGD) Basins (also
referred to as FGD Ponds). The Roxboro Plant ceased all waste flows to the WAB in 2019 with
exception of FGD Basins (pending NPDES permit approval). The CCR boundary for WAB
includes the Southern Extension Impoundment (SEI) area.
Figure 1-1 presents a Vicinity Map and Site Plan of the Roxboro Plant.
For this Closure Plan, Duke Energy uses three facilities to manage CCR at the Roxboro Plant
that include dams and dikes regulated by the NCDEQ:
1. The West Ash Basin Main Dam (NCDEQ ID: PERSO-038);
2. The West Ash Basin Dike No. 1 (NCDEQ ID: PERSO-039); and
3. The FGD Basins including the FGD West Settling Pond Dikes (NCDEQ ID: PERSO-040),
FGD East Settling Pond Dikes (NCDEQ ID: PERSO-041), and FGD Forward Flush Pond
Dikes (PERSO-042).
As further discussed in Section 2 below, the closure method mandated by order of the NCDEQ
for the Basins 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 Basin
and FGD Ponds as directed by order of NCDEQ. Wood understands Duke Energy does so
without prejudice of its position that closure by excavation is not necessary for either the Basin or
FGD Ponds. 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 Basins 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::
• Removal and disposal of CCR from the SEI area of the WAB;
• Decanting the WAB;
• Excavation and removal of CCR from the FGD Ponds;
• Demolition, excavation and removal of the FGD Pond dikes and related facilities;
• Construction and operation of a temporary water management system to manage
discharges in compliance with NPDES permit during closure;
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• Dewatering to support safe excavation of CCR from the Basins;
• Excavation and removal of CCR from the WAB and establishing post -excavation final
grades using soil fill where required;
• Construction of CCR landfill expansion capacity to permanently store the excavated CCR;
• Breaching and removal of the WAB Main Dam;
• Complete removal of WAB Dike No. 1 including discharge outlet features; and
• Restoration of disturbed areas.
1.3 Report Organization
This document is structured to follow the requirements provided in 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 CCR Basins. Subsequently, in July 2016, the North
Carolina General Assembly enacted House Bill 630, 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 WAB as "low -risk."
On April 1, 2019, NCDEQ issued its Closure Determination mandating that the WAB be closed by
excavation of the CCR pursuant to N.C.G.S. § 130A-309.214(a)(3)a. A closure plan is required
for each CCR surface impoundment regardless of the risk classification. The CAMA 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 report was submitted to
NCDEQ in September 2015, with supplemental reports submitted August 2016 and October 2017.
The Corrective Action Plan (CAP) Part 1 was submitted December 2015 and the CAP Part 2 was
submitted February 2016. Duke Energy intends that an updated CAP will be submitted in parallel
with this Closure Plan.
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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
CCR basin dams, and environmental permitting requirements must be considered as part of
closure.
3. FACILITY DESCRIPTION AND EXISTING FEATURES DESCRIPTION
3.1 Surface Impoundment Description
This section provides details on the CCR-related features for the WAB Closure Plan at the
Roxboro Plant.
3.1.1 Site History and Operations
Figure 1-1 presents a Vicinity Map and Site Plan for the Roxboro Plant and Figure 3-1 presents
an Existing Conditions Plan for the WAB, FGD Basins and other site features.
For this Closure Plan, CCR facilities located on -site include the WAB and FGD Basins as
described in more detail below:
West Ash Basin (WAB Main Dam NCDEQ ID: PERSO-038 and Dike No. 1 ID: PERSO-039)
The WAB is situated southwest of the Roxboro Plant generating units. The surface area enclosed
within the CCR boundary for WAB is estimated to be approximately 225 acres, which includes the
SEI area of the WAB. The WAB is unlined and is located in a former valley area of Sargents
Creek drainage basin. The WAB was operated at a normal pond level of Elevation 463 feet.
The WAB Main Dam was constructed in 1973 with an earth -fill embankment and a central low
permeability earth core. The original structural height of the dam was about 70 feet with a crest
at Elevation 457 feet. In 1986, the dam was raised by 13 feet to the current crest level at Elevation
470 feet. The WAB Main Dam has a "Large Size" and "High Hazard" classification under the
regulations of NCDEQ, Division of Energy, Mineral and Land Resources, Land Quality Section,
Dam Safety Program. The North Carolina Dam Identification Number for the WAB Main Dam is
PERSO-038. Additionally, the 1986 modifications included construction of four new containment
dikes (Nos. 1, 2, 3, and 4) and an excavated outlet channel. The modifications provided additional
storage capacity and changed the internal circulation to increase ash retention/settling time.
The WAB Dike No. 1 (also referred to as the "Filter Dike") is constructed of rock fill, primarily
excavated from the nearby outlet channel (western discharge canal). The embankment design
includes provisions for a sand filter blanket on the upstream slope below a layer of rock fill;
however, the sand filter blanket has not been observed during field investigations. The original
crest of the embankment is at Elevation 473 feet, and the maximum structural height is
approximately 50 feet. Two discharge outlet structures were originally installed for the basin, both
located within WAB Dike No. 1. These discharge outlet structures have been abandoned and
grouted closed and replaced with a new spillway system. The WAB Dike No. 1 has a "Large Size"
and "High Hazard" classification under the regulations of NCDEQ, Division of Energy, Mineral and
Land Resources, Land Quality Section, Dam Safety Program. The North Carolina Dam
Identification Number for WAB Dike No. 1 is PERSO-039.
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The SEI area of the WAB constitutes a ponded area within the CCR boundary of the WAB, which
is located south and upstream of WAB Dike No. 1. The estimated surface area for the SEI area
of the WAB is around 42 acres.
Stormwater and other discharges from within the WAB currently flow through the western
discharge canal into the Heated Water Discharge Pond and are finally released to the Hyco
Reservoir through NPDES Outfall 003.
The WAB historically accepted bottom ash and fly ash generated from operation of the Roxboro
Plant conveyed via wet sluicing methods, along with various other waste water streams. The
WAB has received fly ash, bottom ash, CCR transport water, coal pile runoff, stormwater runoff,
cooling tower blowdown, and low volume wastewater.
The Plant converted from wet to dry CCR handling system. During 2019, modifications were
completed to re -direct plant stormwater, wastewater and process flows; therefore, those flows to
the WAB have ceased.
The stormwater outflow from part of the EAB currently discharges into the WAB through existing
culvert pipes located under Dunnaway Road.
Flue Gas Desulfurization (FGD) Basins (West Settling Pond NCDEQ ID: PERSO-040, East
Settling Pond ID: PERSO-041 and Forward Flush Pond ID: PERSO-042
Wastewater from Roxboro Plant Flue Gas Desulfurization (FGD) equipment operations is
currently conveyed to the FGD Ponds, then is released to the Bioreactor facility for treatment
before being discharged to western discharge canal. The Roxboro Plant is currently planning to
cease discharge of FGD wastewater flow into the FGD Basins following receipt of NPDES permit
approval.
The FGD Ponds are constructed on top of CCR deposits located entirely within the CCR boundary
of the WAB. Construction of the FGD West Settling Pond and FGD Forward Flush Pond was
completed in 2008. The FGD Ponds were temporarily shut down for improvements, which was
completed in 2011. The FGD Pond containment dikes have "Medium Size" and "High Hazard"
classification under the regulations of NCDEQ, Land Quality Section, Dam Safety Program.
The FGD West Settling Pond and portions of the FGD Forward Flush Pond containment dikes
are constructed of compacted fly ash material, with portions of the FGD Flush Pond dikes
constructed of compacted soil. The FGD East Settling Pond containment dike was constructed
on the east side of the FGD West Settling Pond and the north side of the FGD Flush Pond dikes.
The north and east containment dikes of the FGD East Settling Pond were constructed of
compacted soil. The outer perimeter of the FGD Pond dikes have topsoil and grass vegetation for
erosion protection on the exterior slopes. A liner system on the interior slopes and bottom of each
pond area consists of a geosynthetic clay liner (GCL) and a surface liner of 60-mil-thick, linear
low -density polyethylene (LLDPE). The design crest level for the dikes for the West Settling Pond
and Forward Flush Ponds is at Elevation 506 feet. The design crest level for the East Settling
Pond dike is at Elevation 500 feet.
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3.1.2 Estimated Volume of CCR in Impoundment
wood.
Based on CCR inventory data provided by Duke Energy as of July 31, 2019 and upon surface
comparison calculations, comparing the approximate pre -development topography to recent
topographic and bathymetric surveys, the approximate volume of CCR in the Basins, including
the FGD Pond areas is listed in the table below.
During 2016, field investigations were performed for the purpose of estimating the extent of CCR
material present within the SEI area of the WAB. The estimated volume of CCR for the SEI area
of the WAB is included in the estimate provided below.
To compute the estimated volume of CCR in place an assumed density of 1.2 tons per cubic yard
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 (CY)
Estimated CCR Weight
Description
(Tons)
West Ash Basin
(WAB)
10,811,667
12,974,000
(Notes 1 & 2)
SEI Area of the WAB
Included in estimate above.
Included in estimate above
Totals
10,811,667
12,974,000
Table Notes:
1. The WAB Estimated CCR includes the CCR contained within the FGD Basins.
2. The WAB Estimated CCR is based on updated CCR Inventory Data provided by
Duke Energy as of July 31, 2019.
3.1.3 Description of Surface Impoundment Structural Integrity
The purpose of this section is to summarize the structural integrity evaluations for the WAB based
on current existing information. This section includes the geotechnical, and hydrology and
hydraulics 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 257.3). Duke Energy's certifications of these requirements are available on Duke Energy's
publicly accessible CCR Rule Compliance Data and Information website.
• Slope stability
For the WAB Main Dam embankment, Dike No. 1, and FGD Basin enclosure dikes, the 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 criteria. Slope stability results under the loading
conditions mentioned above met regulatory requirements.
• Liquefaction conditions (where susceptible) and Liquefaction potential
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A liquefaction screening analysis was performed for the site including the WAB Main Dam, Dike
No. 1, and the FGD Pond areas. Based on the evaluation of the available borings, the Seismic
Site Classification for subsurface conditions to 100 feet below the foundation level of the dikes
was determined to be C for the WAB Main Dam and Dike No. 1. The FGD Basins are constructed
on sedimented CCR with a depth of up to approximately 85 feet; therefore, Site Class E was
selected for analysis of this area.
Based on the conditions encountered in the borings performed for this project, ground motions
for the design seismic event (2,500-year return period) are calculated not to trigger liquefaction
or cyclic softening within granular soils below the embankments for the WAB Main Dam and Dike
No. 1 (i.e., factors of safety above 1.1). For the FGD Pond dikes, the conclusion of liquefaction
potential analyses is that global failure of the FGD Pond dikes is unlikely during the design seismic
event. Shallow surficial sloughing may occur on the downstream slopes and near/outside the toe
of the FGD Pond dikes, which could be considered as maintenance issues.
• Hydrology and Hydraulics (H&H) Capacity Analyses
WAB Main Dam and Dike No. 1: H&H analyses were performed to evaluate whether the existing
Ash Basin and discharge outlet could safely pass a design storm for the full Probable Maximum
Precipitation (PMP) storm event without overtopping the dam. This analysis was based on a
design flood for a site specific PMP storm event as developed by Applied Weather Associates
(AWA). It is assumed that the existing 10-foot diameter culvert under Dunnaway Road will be
placed into service prior to closure of the WAB. Thus, for this analysis, inflow was assumed from
the EAB to be through the 10-foot culvert and the two existing 30-inch diameter culverts under
Dunnaway Road. The results for the additional H&H analyses indicate that the WAB can contain
and safely pass the full site specific PMP with 0.9 feet of freeboard (peak elevation 469.1).
FGD Basins: H&H analyses were performed to evaluate whether the existing FGD Basins could
safely pass a design storm for the full PMP storm event without overtopping the dam. This
analysis was based on a design flood for a site specific PMP storm event as developed by Applied
Weather Associates (AWA). Based on the results for the analyses, the existing conditions for the
FGD Ponds will safely contain the design storm event (back-to-back PMP storm events) without
an uncontrolled discharge and are compliant with North Carolina Dam Safety Regulations.
3.1.4 Sources of Discharges into Surface Impoundments
Process flows are no longer discharged into the WAB. The Roxboro Plant currently employs a dry
ash handling system transporting CCR to the on -site landfill.
Stormwater flows from the EAB into the WAB through existing culvert pipes located under
Dunnaway Road.
The FGD Basins currently receive process water from plant scrubber equipment operations,
which is released to the Bioreactor facility for treatment before being discharged to the western
discharge canal. The FGD Basins are perched and have no watershed other than direct rainfall.
The Roxboro Plant is currently planning to cease discharge of FGD wastewater flow into the FGD
Basins following receipt of NPDES permit approval.
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3.1.5 Existing Liner System
The WAB does not include a geomembrane or clay liner system and is considered to be unlined.
The WAB was constructed directly on top of the historical ground surface.
The interior slopes and bottom of the FGD Basins are lined with a geosynthetic clay liner (GCL)
and a 60-mil-thick LLDPE liner.
3.1.6 Inspection and Monitoring Summary
Weekly inspections of the Basins 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 Basins include the weekly monitoring elements with the addition of
piezometer and observation well readings, 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 Basins are 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. Historically, independent inspections of the WAB Main Dam
have performed by an independent third -party consultant on a 5-year and annual basis between
1998 and 2013.
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.
Review of current annual inspection reports did not identify features or conditions in the CCR
Basin 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
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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 CCR Impoundment Related Structures
A site map showing property boundary, location of the Roxboro Plant, WAB and FGD Basins with
their boundaries and topographic and bathymetric contours are shown on Figure 3-1.
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 are currently three existing permitted landfills on site, which are identified in the table below,
along with the status (active/closed). The existing landfills are shown on the attached Figure 3-
1, and described in more detail in Section 3.1.1 of the separate EAB Closure Plan. The CCR
contained within the landfill is not subject to this Closure Plan.
Landfill
Permit Number
Comment
On -site Industrial Landfill
7302-INDUS-1988
Active
LCID Landfill
1979 C&D Landfill
73D-LCID-2002
73-A
Non-CCR, Active
Non-CCR, Inactive
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.
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, piezometers and Cone Penetration Test (CPT) sounding
locations is shown on the drawings included in Appendix D. In addition, the available boring logs
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and records for subsurface exploration are provided in the Wood, Geotechnical Data Report —
Final Rev. 0, Roxboro Steam Station — West Ash Basin, July 1, 2019 (Wood, 2019d), which is
included in Appendix B.
This section 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; and geotechnical properties of the CCRs and the uppermost stratigraphic
unit under the surface impoundment.
4.2 Hydrologic 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 the CAP content is not the work product of Wood.
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 provides a summary of geotechnical conditions and properties found from
investigations performed within the WAB for the WAB Main Dam, WAB Dike No. 1, and FGD Pond
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 WAB 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. Explorations in the FGD Basins area
encountered embankment fill underlain by CCR, residual soils, and PWR.
General properties of the various materials encountered within and surrounding the WAB are
described below. The results of available laboratory tests performed on samples from the
subsurface explorations completed within the WAB area were reviewed, and the range of
measured material properties was evaluated to select representative material properties. The
results of available laboratory tests performed on samples from the subsurface explorations
completed within and surrounding the WAB were reviewed, and the range of representative
material properties is summarized in Table 4-1.
4.4.1 CCR within Basins
The CCR within the WAB consists primarily of bottom ash and fly ash. Other CCR such as slag
are also typically encountered. The bottom ash is generally described as very loose to loose,
moist to wet, dark gray to gray material, and typically classified as silty sand (SM). The fly ash is
generally described as very soft to soft, moist to wet, light to medium gray material, and typically
classified as sandy silt and silt (MIL).
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The CCR within the FGD Basins consists primarily of residue from FGD blowdown. When
excavated, this material will be placed in the on -site landfill.
4.4.2 Liner Material Properties
The WAB is unlined so there are no associated material properties. The FGD Basins are lined
with a geosynthetic clay liner (GCL) and a 60-mil-thick LLDPE geomembrane.
4.4.3 Subsurface Soil Properties
Alluvium: Alluvial soil is typically encountered beneath the sluiced CCR. The alluvium generally
consists of very loose to loose, wet, silty fine sand (SM) or soft to firm, wet, fine sandy silt
(ML). The soil colors encountered ranged from gray to dark gray, green, brown and
black. Alluvium may not be encountered in excavated areas.
Residuum: The residuum (including saprolite) is the next layer encountered and generally was
found to consist of soft to hard sandy lean clays (CL) and sandy silts (ML), or loose to dense silty
sands (SM) and clayey sands (SC). The soil colors encountered ranged from gray to dark gray,
green, brown and black. The saprolite layers typically were sampled as sandy silt (ML) or silty
sand (SM).
PWR: Partially Weathered Rock (PWR) is typically encountered below the residuum for the Basin.
PWR primarily consists of wet, light gray to reddish brown to light brown mottled sand (SP), silty
sand (SM), sandy non -plastic silt (ML), sand with clay (SP-SC), lean clay (CL), and weathered
meta -quartz diorite, meta-granodiorite, and meta-diabase bedrock.
Bedrock: Bedrock is typically encountered below the PWR for the Basin. The bedrock primarily
consists of dark greenish gray, very strong, coarse grained, massive Meta -Quartz diorite, and
black and white, strong, fine to coarse grained Meta-Diabase bedrock.
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.
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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-309.211(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.
The updated CAP evaluates the extent of, and remedies for, constituents of interest (COI) in
groundwater associated with the East Ash Basin and gypsum storage area, focusing on
constituent concentrations detected above the applicable 02L Standards, Interim Maximum
Allowable Concentrations, or approved background threshold values beyond the basin's
compliance boundary. Importantly, constituent concentrations in groundwater associated with the
West Ash Basin are less than applicable regulatory standards at and beyond the compliance
boundary. Accordingly, groundwater corrective action under North Carolina's 02L standards is not
required for this basin. In addition to the state's corrective action requirements, 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 has begun to implement, and will continue
implementing, source control measures at the site, including (i) complete decanting of the East
Ash Basin and West Ash Basin to lower the hydraulic head within the basins and decrease
hydraulic gradients, reducing groundwater seepage velocities and COI transport potential; and (ii)
complete closure of the East Ash Basin and West Ash Basin. In addition, Duke Energy intends to
implement a robust active groundwater remediation program that includes extraction and
treatment at the East Ash Basin, and a combination of groundwater extraction and clean water
infiltration at the gypsum storage area and dry fly ash handling area. The CAP provides that these
corrective action measures will most effectively achieve remediation of the groundwater through
the installation of (i) extraction wells in the area of the unnamed pond north of the East Ash Basin;
(ii) extraction wells on the northeast side of the East Ash Basin; (iii) extraction wells in the
comingling zone near the dry fly ash handling area; and (iv) extraction wells and clean water
infiltration wells in the area between the gypsum storage area/dry fly ash handling area and Intake
Canal. Significantly, groundwater modeling simulations indicate (i) these measures will address
COI at or beyond the East Ash Basin 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 at or beyond the East Ash Basin compliance boundary will meet the
remedial objectives in nine years. Critically, as discussed above, the model indicates that COI
concentrations currently meet the 02L Standards at and beyond the West Ash Basin compliance
boundary.
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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 Basins at Roxboro
Plant.
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 WAB.
7. CLOSURE DESIGN DOCUMENTS
7.1 Engineering Evaluations and Analyses
Engineering evaluations and analyses to support closure of the Basins at the Roxboro Plant, as
detailed in this Closure Plan, are provided in Appendix C.
The FGD Basins will be fully removed and the waste material will be placed in a permitted solid
waste facility approved to receive the waste stream. Decommissioning of the FGD Basins will be
completed before proceeding with WAB closure.
Geotechnical calculations for the proposed landfill expansion design will be performed separately
as part of its permit application, which will follow NCDEQ approval of this Closure Plan. Dam
removal -related calculations will be included in the dam modification permit applications, which
will follow NCDEQ approval of this Closure Plan.
Safe and effective access to the Basin is critical to CCR excavation and the completion of closure.
Access road locations into or across the Basin cannot be reliably established until 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
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aggregate, placement and spreading of dry CCR over the Basin surface 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 will be established
within the closure limits of the Basin and require placement or stacking of CCR excavated from
other areas of the WAB. 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 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. However, the proposed excavation and sampling plan for closure by
excavation areas is included in Appendix E.
7.2 Closure Plan Activities
The primary activities associated with closure by excavation are as follows:
• Remove and dispose of CCR from within the SEI area of the WAB.
• Reduce free/surface water volume via discharge to the existing NPDES-permitted Outfall
003.
• Decant by using floating pumps, screened intakes, and pumping.
• Construction and operation as necessary of a temporary water management system
(WMS) to manage all discharges in compliance with the NPDES permit during closure.
• Dewater the CCR to allow access for CCR excavation and conditioning (drying) prior to
placement in the proposed on -site landfill.
• Start CCR excavation from the basin, 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 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 hydraulic storage capacity though the excavation process and
progressively breach the WAB Main Dam and Dike No.1 as excavation progresses.
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• Complete closure by excavation verification. Grade the area to promote positive drainage.
• Sequence final dam breach for the WAB Main Dam and complete removal for the WAB
Dike No. 1 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 can be found in Appendix D.
7.3 Design Drawings
The Closure Plan drawings found in Appendix D include the following:
• Cover sheet
• General notes
• Existing conditions plan with aerial photograph
• Existing conditions plan with topography
• Subsurface exploration location plan
• Estimated bottom of CCR plan
• Demolition plan
• Final grading plan
• Final surface water management plan
• Site cross sections
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 have been achieved, the
procedures described in the Duke Energy Excavation Soil Sampling Plan (Appendix E) will be
followed to confirm that closure by excavation has been achieved.
7.4 Description of Construction Quality Assurance and Plan
A Construction Quality Assurance (CQA) Plan will be developed following NCDEQ approval of the
Closure Plan for closure of the Basins at the Roxboro Plant. The CQA Plan will be prepared to
address N.C.G.S. §130A-309.214(a)(4)(g), and its purpose is to provide a description of the CQA
program to be adhered to in execution of closure activities. The CQA Plan will present a
description of the roles and responsibilities for monitoring and testing activities and provides
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
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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
o CCR Excavation
o Soil Fill
• HDPE Piping
• Vegetation
• As -Built Conditions
• Record Documentation Report
8. MANAGEMENT OF WASTEWATER AND STORMWATER
The Roxboro Plant manages wastewater under NPDES Permit NC0003425. The permit
authorizes two discharge points into the Hyco Reservoir.
The Roxboro Plant manages stormwater under NPDES Permit NCS000581. The facility is
permitted to discharge stormwater to the Hyco Reservoir.
Process flows no longer discharge into the WAB at the Roxboro Plant. Process flows are directed
toward newly -constructed lined retention basins. The WAB will continue to operate during closure
to meet the NPDES permit discharge requirements as it goes through decanting and dewatering.
The WAB must also continue to safely pass the PMP to meet dam safety requirements.
Decanting of the WAB will be performed to drawdown the existing free/standing water using
floating pumps, screened intakes, and pumping. The pumping system is expected to draw down
the stored water after storm events, route it through the WMS, if necessary, and discharge the
water via the permitted outfall. When dewatering of the CCR begins, all discharge flows are
anticipated to be routed through the WMS and meet the permitted discharge limits.
The WAB currently has the capacity to contain the PMP storm event by maintaining the water
surface level at or below the crest level for the WAB Main Dam at Elevation 470.0 feet, which
provides a minimum freeboard of 0.9 feet. As part of the closure, the WAB Main Dam will be
partially removed by excavating an engineered breach in the embankment along with lowering
the crest level along the entire length of the dam. In addition, WAB Dike No. 1 will be completely
removed for closure resulting in run-on flow being redirected toward the WAB Main Dam
engineered breach. Under this post -closure condition, there will not be a net increase in flow
downstream of the WAB Main Dam within the receiving body of water compared to the existing
conditions. No additional stormwater retention capacity will be needed following the planned dam
breaching and removal.
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Dewatering will be performed to remove the interstitial water from the CCR to facilitate excavation
and access to in -place CCR. Along with other factors, dewatering will be used to facilitate 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.
Wastewater from the WAB will be pumped, treated as needed and discharged in two phases: the
decanting phase and dewatering phase. In the decanting phase, free water above the settled
CCR layer will be removed from the basins without the mechanical disturbance of the CCR. For
the decanting phase, the Roxboro water management process has a designed flow rate of 1250
gpm. Following the decanting phase and as the Closure Plan schedule dictates, the WAB site will
advance into the dewatering phase to remove interstitial water from the Basin. D uring this phase,
additional physical -chemical treatment processes may be added to the WMS as necessary to
maintain compliance with the requirements of the discharge permit. During dewatering phase, the
designed flow rate may drop to 250-400 gpm.
The post -closure grades restore the historical flows from the surrounding landscape and route
that flow toward the breached WAB Main Dam. Up to and including the last phase of closure
before the WAB dam is breached, the WAB will maintain the capacity to contain the run-on from
the required storm size/flows.
Detention basin requirements and 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, which will follow NCDEQ approval of this Closure Plan. Appendix C1 presents the
results of the post -closure stormwater management calculations. Detailed stormwater design for
the proposed landfill expansion will be developed as part of its permit process and is not covered
herein.
8.1 Anticipated Changes in Wastewater and Stormwater Management
Wastewater and process streams from the Roxboro Plant previously discharging to the WAB have
been rerouted to a new lined retention basin. The FGD Basins still receive process streams,
which will be rerouted when NPDES permit approval is received.
A temporary WMS will be utilized as necessary such that the permitted NPDES effluent discharge
limits, or other limits as directed by the NCDEQ, will be met throughout the duration of dewatering
and closure.
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. 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.
December 18, 2019
FINAL Rev. 0 16
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Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
9. DESCRIPTION OF FINAL DISPOSITION OF CCR
CCR will be dispositioned by placement into an approved and permitted, lined on -site CCR landfill
expansion. Duke Energy intends to laterally expand the existing on -site industrial landfill (NCDEQ
Permit 7302-INDUS-1988) to accommodate CCR in completion of the NCDEQ-mandated closure
by excavation. A permit application for construction of the on -site landfill will be prepared and
submitted to NCDEQ Division of Waste Management following approval of this Closure Plan.
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/approval
needed to implement this Closure Plan. 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 closure
of the WAB. 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 WAB.
The post -closure care plan will be developed to meet the requirements of N.C.G.S. §130A-
309.214(a)(4)(k). The items that will be in the Post -Closure Care plan for the Roxboro site 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
CAP);
• Post -closure inspection checklist to guide post -closure inspections;
• 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.
December 18, 2019
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Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
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 Q4-2020
Start new landfill expansion construction Q4-2021
Start CCR excavation Q1-2023
Complete CCR excavation Q4-2035
Complete final closure and cover system of landfill Q4-2036
Site final grading and vegetative cover Q4-2037
It should be noted that NCDEQ approval of this Closure Plan by March 31, 2020 will allow
completion of the CCR excavation actions 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 Basin at Roxboro Plant was 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 is estimated to be $507 Million.
The cost to perform the 30-year post -closure activities and monitoring is estimated as $67 Million
The cost estimates include the following major activities:
• Mobilization and Site Preparation
• Dewatering, earthwork, and subgrade preparation
• 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.
December 18, 2019
FINAL Rev. 0 18
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Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
13. REFERENCED DOCUMENTS
(Amec, 2013). Amec, 2013 Five-year Independent Consultant Dam Inspection, Duke Energy
Progress — Roxboro Electric Plant, Person County, North Carolina, October 23, 2013.
(Amec, 2015). Amec Foster Wheeler, Report of Tail Risk Liquefaction Study (ROX-601), West Ash
Pond FGD Pond Area, Roxboro Steam Station, Person County, North Carolina, December
1, 2015.
(Amec, 2015a). Amec Foster Wheeler, Summary of FGD Pond Slope Stability Factors of Safety,
Roxboro Steam Station, Person County, North Carolina, December 30, 2015.
(Amec, 2016). Amec Foster Wheeler, Re-evaluation of Liquefaction Potential, Roxboro FGD
Ponds, Roxboro Steam Station, Person County, North Carolina, February 5, 2016.
(Amec 2016a). Amec Foster Wheeler, Report of Ash Extent Exploration (Issue ROX-134),
Former Part of the West WAB, November 14, 2016.
(Wood, 2019). Wood E&IS, Roxboro East and West Ash ponds H&H Update, Summary of
Supporting H&H Analyses, Duke Energy — Roxboro Steam Station, November 5, 2019.
(Wood, 2019a). Wood E&IS, Roxboro East FGD Settling Pond H&H Update, Summary of
Supporting H&H Analyses, Duke Energy — Roxboro Steam Station, Person County, North
Carolina, April 26, 2019.
(Wood, 2019b). Wood E&IS, Roxboro West FGD Settling Pond H&H Update, Summary of
Supporting H&H Analyses, Duke Energy — Roxboro Steam Station, Person County, North
Carolina, April 26, 2019.
(Wood, 2019c). Wood E&IS, Roxboro FGD Forward Flush Pond H&H Update, Summary of
Supporting H&H Analyses, Duke Energy — Roxboro Steam Station, Person County, North
Carolina, April 26, 2019.
December 18, 2019
FINAL Rev. 0 19
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Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
FIGURES
2 3
4
5
6 7
8
ROX-FIG . 1-1 WAB CBE
REV. 0
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Environment & Infrastructure Solutions
4021 STIRRUP CREEK DRIVE, SUITE 100
PERSON COUNTY, NORTH CAROLINA
DURHAM NC 27703
TEL: (919) 381-9900
VICINITY MAP AND SITE PLAN
FAX: (919) 381-9901
LICENSURE:
FOR
NCENG:F-1253
ISSUED FOR REVIEW
t s
NC GEOLOGY: C-247
SEAL
SCALE: AS SHOWN DES: IL
DUKEDWG TYPE: DWG DFTR SM
rmba,B
JOB NO: 7812190186 CHKD: AP
ENERGY®
KiM1 H,
NOT FOR
DATE: 12/18/2019 ENGR: SA
CONSTRUCTION
FILENAME: ROX-FIG. 1-1 WAB CBE.dwg APPD: CK
SITE VICINITY MAP - 1" = 5 MILES
DWG SIZE DRAWING NO. REVISION
MAP SOURCE: ESRI WORLD TOPOGRAPHIC BASEMAP
ANSI D FIGURE 1-1 0
0 12/18/2019 7812190186 DESIGN PLAN JL SM AP SA CK ISSUED FOR REVIEW
22"x34"
REV DATE JOB NO. PROJECT TYPE DES DFTR CHKD ENGR APPD DESCRIPTION
TENTHS 10 20
30 4
5
6 7
8
9 10
INCHES 1 2 3
Plotted By: Markham, Steven Sheet Set: 7812190186 — Roxboro CAMA Closure Plans Layout: OVERALL SITE EXISTING CONDITIONS — AERIAL December 18, 2019 08:47:45am Q: \Duke Energy\Roxboro\7812190186 — CAMA Closure Plan\Exhibit\FIG. 1-1 WAB\ROX—FIG. 1-1 WAB CBE.dwg
2 3 4 5 6 7 8
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Plotted By: Markham, Steven Sheet Set: 7812190186 - Roxboro CAMA Closure Plans Layout: EXISTING CONDITIONS PLAN December 18, 2019 08: 59: 25am Q: \Duke Energy\Roxboro\7812190186 - CAMA Closure Plan\Exhibit\FIG. 3-1 WAB\ROX_FIG. 3-1 WAB CBE.dwg
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
TABLES
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WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 2-1: NC CAMA Closure Plan Requirements
Summary and Cross Reference Table
Duke Energy, Roxboro Steam Electric Plant
Corresponding
No.
Description
Closure Plan
Section
Part II. Provisions for Comprehensive Management of Coal Combustion Residuals §
130A-309.214 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:
Site history and history of site operations, including details on the manner in
1
which coal combustion residuals have been stored and disposed of
3.1.1
historically.
2
Estimated volume of material contained in the impoundment.
3.1.2
3
Analysis of the structural integrity of dikes or dams associated with
3.1.3
impoundment.
4
II sources of discharge into the impoundment, including volume and
3.1.4
characteristics of each discharge.
5
Whether the impoundment is lined, and, if so, the composition thereof.
3.1.5
A summary of all information available concerning the impoundment as a
6
result of inspections and monitoring conducted pursuant to this Part and
3.1.6
otherwise available.
b. Site maps, which, at a minimum, illustrate all of the following:
All structures associated with the operation of any coal combustion residuals
surface impoundment located on the site. For purposes of this sub-
1
subdivision, the term "site" means the land or waters within the property
3.2.1
boundary of the applicable electric generating station.
All current and former coal combustion residuals disposal and storage areas
on the site, including details concerning coal combustion residuals produced
2
historically by the electric generating station and disposed of through transfer
3.1.1
Ito structural fills.
3
The property boundary for the applicable site, including established
3.1.1
compliance boundaries within the site.
4
All potential receptors within 2,640 feet from established compliance
3 2 2
boundaries.
Topographic contour intervals of the site shall be selected to enable an
5
accurate representation of site features and terrain and in most cases should
3.2.1
be less than 20-foot intervals.
Locations of all sanitary landfills permitted pursuant to this Article on the site
6
that are actively receiving waste or are closed, as well as the established
3.2.3
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compliance boundaries and components of associated groundwater and
surface water monitoring systems.
7
All existing and proposed groundwater monitoring wells associated with any
3.2.1
coal combustion residuals surface impoundment on the site.
All existing and proposed surface water sample collection locations
8
associated with any coal combustion residuals surface impoundment on the
3.2.1
site.
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.
4.2
2
A description of the stratigraphy of the geologic units underlying each coal
4.3
combustion residuals surface impoundment located on the site.
The saturated hydraulic conductivity for (i) the coal combustion residuals
within any coal combustion residuals surface impoundment located on the
3
site and (ii) the saturated hydraulic conductivity of any existing liner installed
4.4
at an impoundment, if any.
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
4
impoundment, including the soil classification based upon the Unified Soil
4.4
Classification System, in -place moisture content, particle size distribution,
Atterberg limits, specific gravity, effective friction angle, maximum dry density,
optimum moisture content, and permeability.
A chemical analysis of the coal combustion residuals surface impoundment,
5
including water, coal combustion residuals, and coal combustion residuals-
4.5
affected soil.
Identification of all substances with concentrations determined to be in excess
of the groundwater quality standards for the substance established by
6
Subchapter L of Chapter 2 of Title 15A of the North Carolina Administrative
4.6
Code, including all laboratory results for these analyses.
7
Summary tables of historical records of groundwater sampling results.
4.6
A map that illustrates the potentiometric contours and flow directions for all
identified aquifers underlying impoundments (shallow, intermediate, and
8
deep) and the horizontal extent of areas where groundwater quality standards
4.7
established by Subchapter L of Chapter 2 of Title 15A of the North Carolina
Administrative Code for a substance are exceeded.
Cross -sections that illustrate the following: the vertical and horizontal extent o
the coal combustion residuals within an impoundment; stratigraphy of the
geologic units underlying an impoundment; and the vertical extent of areas
9
where groundwater quality standards established by Subchapter L of Chapter
4.8
2 of Title 15A of the North Carolina Administrative Code for a substance are
exceeded.
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
1
(i) predictions on post -closure groundwater elevations and
5.1
groundwater flow directions and velocities, including the effects on
and from the potential receptors and
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(ii) predictions at the compliance boundary for substances with concentration
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.
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
2
standards for the substance established by Subchapter L of Chapter 2 of Title
5.2
15A of the North Carolina Administrative Code pre- and post -closure,
lincluding the effects on and from potential receptors.
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 Administrativ
3
Code and requirements for corrective action of groundwater contamination
5.3
established by Subchapter L of Chapter 2 of Title 15A of the North Carolina
Administrative Code.
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
6.1
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).
f.
All engineering drawings, schematics, and specifications for the proposed Closure
Plan. If required by Chapter 89C of the General Statutes, engineering design
7.1, 7.2, 7.3
documents should be prepared, signed, and sealed by a professional engineer.
g.
A description of the construction quality assurance and quality control program to
be implemented in conjunction with the Closure Plan, including the responsibilities
7.3
and authorities for monitoring and testing activities, sampling strategies, and
reporting requirements.
h.
A description of the provisions for disposal of wastewater and management of
8
stormwater and the plan for obtaining all required permits.
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
9
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.
j.
A list of all permits that will need to be acquired or modified to complete closure
10
activities.
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)
11
proposed to be decreased or the frequency and parameter list modified if the
owner demonstrates that the reduced period or modifications are sufficient to
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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:
1
A demonstration of the long-term control of all leachate, affected
11.1
groundwater, and stormwater.
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
2
a map with the proposed locations and well construction details; and (iii) the
11.1
actions proposed to mitigate statistically significant increasing groundwater
Iquality trends.
I. An estimate of the milestone dates for all activities related to closure and post-
12.1
closure.
m. Projected costs of assessment, corrective action, closure, and post -closure care
12.2
for each coal combustion residuals surface impoundment.
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
6.2
restrictions, and requirements for recordation of notices documenting the presence
of contamination, if applicable, or historical site use.
§ 130A-309.212(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-309.212(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.
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Table 4-1: Summary of Typical Materials Properties
Duke Energy, Roxboro Steam Electric Plant
Table 4.1: Summary of Typical Material Properties
Fill Soil covering CCR within the CCR
Compacted CCR within the CCR
Sedimented CCR within the CCR
Foundation Soil (Residual) below the
Weathered Rock (WR) below theFill
Soil within the Embankment
Foundation Soil (Residual) below the
Properties
Embankment Dikes and the CCR
Basins
Basins'
Basins'
CCR Basins
Dikes
Embankment Dikes
Basins
Silt/Sandy Silt (ML) - Predominantly
Silty Sand (SM) - Predominantly
Breaks down to Sandy Silt and
Soil Type
CL, SM, ML, and SC
Bottom Ash, Silt, Sandy Silt (ML) -
SC, SM, ML, CL, CH
silty sand with rock fragments -
SM, SC, GW
SC, SM, CL, ML
Fly Ash
Predominantly Fly Ash
Weathered Gneiss
Gray to dark gray, green, brown, and
Gray, light green, brown, and
Color
Dark gray, tan, and brown
g y
Gray to dark gray, black
y g y
Gray to dark gray, black
y g y
Gray, black, and brown
y
Tan, green, brown, gray to dark gray
g g y g y
black
orange
Plasticity
NP to 20 - 30
Predominantly Non Plastic
Predominantly Non Plastic
NP to 14 - 35
**
NP - 22
NP - 36*
Liquid Limit
NP to 36 - 59
Predominantly Non Plastic
Predominantly Non Plastic
NP to 24 - 46
**
NP - 40
NP - 113*
Plasticity Index
NP to 16 - 28
Predominantly Non Plastic
Predominantly Non Plastic
NP to 7 - 22
**
NP - 18
NP - 77*
Representative
Representative
Representative
Representative
Geometric Mean
Geometric Mean
Geometric Mean
Geometric Mean
Representative Range
Range
Range
Range
Range
Natural Moisture Content(%)
8%-63%
25%
5%-52%
26%
12%-98%
49%
8%-72%
20%
**
18%-41%
7%-44%
Fines Content
6%- 68%
27%
12%- 69%
42%
27%- 90%
55%
6%- 68%
27%
**
**
**
Clay Content
2%- 54%
20%
1%- 20%
6%
3%- 29%
10%
2%- 54%
20%
**
**
**
Blow Count - Uncorrected N Value (bpf)
4 - 72
17
2 - 58
17
WOR - 27
4
0 - 80
23
50/0" - 50/5"
4 - 48
4 - 26
Moist Unit Weight
**
**
92 - 93 pcf
92 pcf
52 - 100 pcf
83 pcf
**
**
**
97 - 140 pcf
113 -139 pcf
Dry Unit Weight
**
**
68 - 70 pcf
69 pcf
30 - 74 pcf
55 pcf
**
**
**
69 - 116 pcf
86 - 121 pcf
Specific Gravity
**
**
2.1
*
1.9 - 2.3
2.1
**
**
**
**
**
Horizontal Hydraulic Conductivity (cm/sec)
**
**
**
**
**
**
**
**
**
**
**
Vertical Hydraulic Conductivity (cm/sec)
**
**
**
**
**
**
**
**
**
**
6.0E-08 -1.6E-06
Notes:
Outlier values were not inlcuded in the table above. For additional laboratory testing information, see attached Appendix
NP: Non -Plastic
pcf: Pounds per Cubic Foot (Ib/ft)
bpf: blows per foot
WOH: Weight of hammer
WOR: Weight of Rods
*Only one lab test available
**No lab data available
1Data used to differentiate between compacted ash and sedimented ash was obtained from lab tests and boring logs from the 2015 and 2016 Amec Foster Wheeler, Geotechnical Investigation of West Ash Bain
Wood Environment & Infrastructure Solutions, Inc.
Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 10-1: Regulatory Permits, Approvals, or Requirements for WAB Closure by
Excavation
Duke Energy, Roxboro Steam Electric Plant
Permit/Approval
General Permit
Regulating
Existing
Type of Regulatory
Name or Subject
Agency
Permit No.
Approval
Comments
(if applicable)
Mechanism or Not
Required
Permit modification likely
due to the increased
Air Quality
NCDEQ
Permit modification
heavy equipment vehicle
likely
traffic and potential dust
generated during closure
activities
Person
A local building permit is
Building Permit
County
New Permit
required for installation
of construction trailers
Modification or
abandonment of CAMA
CAMA Monitoring
Written NCDEQ
program monitoring
Plan
NCDEQ
DWR approval
wells require the
approval of the Division
of Water Resources
DWR
CCR
Impoundment
US EPA
Self -Regulating
Required postings to
Closure
CCR Rule
Public Record
CCR
Maintain CCR GW
Impoundment
US EPA
Self -Regulating
monitoring network and
Monitoring
CCR Rule
requirements as stated
Network
in 257.90 - 257.98
Clean Water Act
401
Clean Water Act
404
Cutting Trees
Permitting is required to
modify or abandon wells
Certificate of
and instrumentation on
Dam Safety
NCDEQ
Approval to Modify
regulatory dams through
the Division of Energy,
Mineral, and Land
Resources DEMLR
WAB Dam - Permitting is
required to modify the
Dam Safety
NCDEQ
PERSO-035
Certificate of
dam in accordance with
Approval to Modify
the Dam Safety Law of
1967, 15A NCAS
02K.0201 (b)(2); an
Wood Environment & Infrastructure Solutions, Inc.
Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 10-1: Regulatory Permits, Approvals, or Requirements for WAB Closure by
Excavation
Duke Energy, Roxboro Steam Electric Plant
Permit/Approval
General Permit
Regulating
Existing
Type of Regulatory
Name or Subject
Agency
Permit No.
Approval
Comments
(if applicable)
Mechanism or Not
Required
application must be filed
with the Division of
Energy, Mineral, and
Land Resources
(DEMLR)
FGD Settling Pond Dam
- Permitting is required
to remove the dam in
accordance with the
Dam Safety Law of
Dam Safety
NCDEQ
PERSO-36
Certificate of
1967, 15A NCAS
Approval to Modify
02K.0201 (b)(2); an
application must be filed
with the Division of
Energy, Mineral, and
Land Resources
DEMLR
FGD Flush Pond Dam -
Permitting is required to
remove the dam in
accordance with the
Dam Safety Law of
Dam Safety
NCDEQ
PERSO-37
Certificate of
1967, 15A NCAS
Approval to Modify
02K.0201 (b)(2); an
application must be filed
with the Division of
Energy, Mineral, and
Land Resources
DEMLR
Utilization of or
modification to state or
federal highways to
DOT - General
transport CCR will
require consultation or
notification to relevant
DOT agency
Temporary access or
Driveway Permit
NCDOT
driveway permits as
needed
Wood Environment & Infrastructure Solutions, Inc.
Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 10-1: Regulatory Permits, Approvals, or Requirements for WAB Closure by
Excavation
Duke Energy, Roxboro Steam Electric Plant
Permit/Approval
General Permit
Regulating
Existing
Type of Regulatory
Name or Subject
Agency
Permit No.
Approval
Comments
(if applicable)
Mechanism or Not
Required
Land disturbance
activities outside of the
WAB will exceed one
acre, therefore in
conformance with 15A
NCAC 04, an E&SC
Erosion and
NCDEQ and
Permit is required from
Sediment Control
Person
New Permit
Land Quality prior to
(E&SC)
County
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
Fire Ants
Restriction not likely
restricted dependent on
the potential for fire ants
and geographic regions
involved
Flood Damage
Prevention Ordinance of
Person County, Article 3
General Provisions,
Section C, requires a
Floodplain
Person
New Permit
Floodplain Development
Development
County
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
Large Capacity
system with a design
Water Supply Well
NCDEQ
New Permit possible
capacity equal to or
greater than 100,00
gallons per day - for
dewatering outside of
the WAB
Wood Environment & Infrastructure Solutions, Inc.
Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 10-1: Regulatory Permits, Approvals, or Requirements for WAB Closure by
Excavation
Duke Energy, Roxboro Steam Electric Plant
Permit/Approval
General Permit
Regulating
Existing
Type of Regulatory
Name or Subject
Agency
Permit No.
Approval
Comments
(if applicable)
Mechanism or Not
Required
If movement of CCR will
Multi -State
Not required
cross state lines, multi -
Agreement
state regulations might
apply
NPDES (National
Modification of NPDES
Pollution
Discharge
NCDEQ
NCO038377
Permit modification
may be necessary if new
Elimination
likely
source or outfall is
System)
created.
NPDES (National
Revision to existing
Pollution
sitewide permit or new
Discharge
Elimination
NCDEQ
Permit revision likely
permit may be required
System) Industrial
for access roads, staging
Stormwater
areas, etc.
NPDES (National
Pollution
Permit required for
Discharge
NCDEQ
New Permit possible
temporary and
Elimination
permanent stormwater
System)
rerouting.
Stormwater
Removal from or import
of vegetated material
could be restricted
Noxious Weeds
dependent on the
vegetation and
geographic regions
involved
Railroad
Construction activities
Easement,
adjacent to tracks/ballast
Access, or
or a new railroad
Crossing Permit
crossing require an
agreement or permit
In accordance with the
SPCC (Spill
Federal Water
Prevention Control
Modification of
Pollution Control Act
and
NCDEQ?
existing plan
(Clean Water Act) of
Countermeasure)
1974, Title 40, Code of
Plan
Federal Regulations,
Part 112.
Wood Environment & Infrastructure Solutions, Inc.
Duke Energy —Roxboro Plant wood.
WAB Coal Combustion Residuals Surface Impoundment Closure Plan (Excavation)
Table 10-1: Regulatory Permits, Approvals, or Requirements for WAB Closure by
Excavation
Duke Energy, Roxboro Steam Electric Plant
General Permit I Regulating
Name or Subject I Agency
Permit/Approval
Existing Type of Regulatory
Permit No. Approval
(if applicable) Mechanism or Not
Required
Comments
Threatened or
Federal and/or state
Endangered
regulations may apply
Species:
including agency
Candidate
consultation and
Conservation
performing site -specific
Agreement
surveys within the proper
Avian Protection
NCDEQ
survey period (e.g.,
Plan(s)
And EPA
flowering period for listed
Bird and Bat
plant) to determine if
Conservation
Threatened or
Strategies
Endangered Species or
Eagle
Conservation Plan
their habitat exist within
Eagle Take Permit
the limits of disturbance
Solid Waste
Permit to
NCDEQ
Permit
Landfill expansion
Construct
Solid Waste
Permit to Operate
NCDEQ
Permit
Landfill expansion