Marshall CBE - Closure Plan - Appendix A_20200107

APPENDIX A
ESTIMATED VOLUME OF CCR IN IMPOUNDMENT

AECOM
Job Duke Energy — Marshall Closure
Description Estimated Volume of CCR
in Impoundment
Project No. 60432116 / Sheet 1 of 3
60603377
Computed by MSR Date 9/20/19
Checked by RJB Date 9/20/19
The purpose of these calculations is to estimate the quantity of the coal combustion residual
(CCR) located within the Ash Basin at the Duke Energy Marshall Steam Station (MSS), located in
Catawba County, North Carolina. These calculations have been developed independent of past
calculations/estimates prepared by others, and the actual volume of CCR within the Ash Basin
will vary from that presented previously. This variability is primarily due to the differences in
data sources/references used in the calculations. These volume estimates will be refined if
more accurate data is collected throughout the design process.
APPROACH
CCR Quantity within the Ash Basin
The approximate pre -development topography (see Figure A-1), which is based on the Duke
Energy drawing No. M-1 entitled "Plant Marshall -Unit 1&2 Site Plan", was compared to
existing topography (see Figure A-2) using AutoCAD Civil 3D version 2018 (AutoCAD). The
quantity of CCR within the Ash Basin was subsequently calculated, using AutoCAD Civil 3D,
as the volume differential between the pre -development topographic contours and the
existing topographic contours, within the Ash Basin Waste Boundary (see Figure A-3). The
quantity of CCR within the Ash Basin Waste Boundary was calculated to be approximately
14,320,000 cubic yards (CY).
However, this initial estimated quantity of CCR within the Ash Basin does not account for
areas within the Ash Basin Waste Boundary that are not comprised of CCR (i.e., free water
areas and fill used to construct the FGD Constructed Wetlands Treatment Area). Currently,
there is no bathymetry data for these free water areas, as the bathymetry data referenced
above (and used in the CCR quantity calculation) is only representative of the bathymetry
contours within the Active Ash Basin area. The free water areas and volumes within the Ash
Basin Waste Boundary, outside of the Active Ash Basin area, are estimated as follows:

I_a141•7►i
Job Duke Energy — Marshall Closure
Description Estimated Volume of CCR
in Impoundment
60432116 /
Project No. 60603377
Computed by MSR
Checked by RJB
Sheet 2 of 3
Date 9/20/19
Date 9/20/19
Free Water Area
Surface Area (SF)
Volume (CY)
Pond adjacent to Coal Pile
75,000
20,000
Nursery Pond
60,000
20,000
Pond west of Asbestos Landfill
25,000
10,000
Pond north of 1804 Landfill (Phase II)
140,000
40,000
Total Free Water Volume
90,000
1. The free water areas provided were calculated using AutoCAD and are approximate.
2. Due to the lack of bathymetry data in each of the specified free water areas, an average water
depth of eight feet was assumed.
In addition, borrow soil fill was placed within the Ash Basin Waste Boundary in order to
construct the FGD Constructed Wetlands Treatment Area. Based on soil boring data,
AECOM assumed an average depth of 18 feet of borrow soil fill is present above the CCR in
this area. Utilizing AutoCAD, the portions of the FGD Constructed Wetlands Treatment
Area, located within the Ash Basin Waste Boundary, were estimated to occupy an area of
approximately 480,000 SF. This equates to a borrow soil fill volume within the Ash Basin
Waste Boundary of approximately 320,000 CY.
The free water volume (90,000 CY) and clean fill volume (320,000 CY) within the Ash Basin
Waste Boundary were subtracted from the initial estimated quantity of CCR within the Ash
Basin (14,320,000 CY), equating to a final estimated volume of CCR within the Ash Basin of
approximately 13,910,000 CY, or 16,692,000 tons (using an assumed conversion rate of 1.2
tons/CY).
I 4M01141Lill ML1I
Based on the calculations described above, the total quantity of CCR within the Ash Basin at
the MSS is estimated to be approximately 13,910,000 CY, or 16,692,000 tons. It is noted
that based on estimates of net CCR disposal rates into the Ash Basin since the dates of the
above mentioned surveys, Duke Energy has reported an in -place CCR tonnage of 16,840,000
tons (14,033,000 CY), as of July 31, 2019, with no additional CCR being disposed of in the
Ash Basin.

AECOM
Job Duke Energy — Marshall Closure Project No. 60432116 / Sheet 3 of 3
60603377
Description Estimated Volume of CCR Computed by MSR Date 9/20/19
in Impoundment Checked by RJB Date 9/20/19
III. ATTACHMENTS
Attachment A: Figures
- Figure A-1— Pre -Development Topography
- Figure A-2 — Existing Topography
- Figure A-3 — In -Place CCR Isopach Map

ATTACHMENT A
Figures

FIGURE A-1
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— 800 - PRE -DEVELOPMENT MAJOR TOPOGRAPHIC CONTOUR
PRE -DEVELOPMENT MINOR TOPOGRAPHIC CONTOUR
ASH BASIN WASTE BOUNDARY (APPROXIMATE)
NOTES
BASIS OF BEARINGS: NC GRID NAD83/2011. ELEVATIONS ARE BASED ON NAVD88.
2. (10-FOOT) CONTOURS WERE DIGITIZED BY AMEC FOSTER WHEELER FROM HISTORICAL TOPOGRAPHY (REFERENCE 1).
3. A DATUM SHIFT OF -0.72 FEET WAS APPLIED TO CONVERT ELEVATIONS FROM NGVD 29 TO NAVD88.
4. THIS IS AN ACCURATE REPRESENTATION OF THE CONTOURS SHOWN IN REFERENCE 1 AND IS AN APPROXIMATION OF
THE BOTTOM OF ASH POND CONTOURS (I.E., PRE -DEVELOPMENT TOPOGRAPHY) BASED ON THE INFORMATION
AVAILABLE TO AECOM.
REFERENCES
DRAWING NO. M-1 ENTITLED "PLANT MARSHALL-UNIT 1&2 SITE PLAN" PREPARED BY DUKE POWER COMPANY, REV. 14,
DATED FEBRUARY 3, 1988. VERTICAL DATUM CONVERTED FROM NGVD29 TO NAVD88.
2. THE CURRENT ASH BASIN WASTE BOUNDARY PRESENTED IN THIS FIGURE IS BASED ON THE "2018 COMPREHENSIVE
SITE ASSESSMENT UPDATE" PREPARED BY SYNTERRA FOR DUKE ENERGY AND SUBMITTED TO NCDEQ (NPDES PERMIT
NO. NC0004987) ON JANUARY 31, 2018.
IN
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TITLE
L=com
PRE -DEVELOPMENT TOPOGRAPHY
MARSHALL STEAM STATION
CLOSURE BY EXCAVATION CLOSURE PLAN
CATAWBA COUNTY. NORTH CAROLINA
FOR ISSUED FOR APPROVAL
�
DUKE
ENERGYC
SCALE: 1 "=500'
DES:
MSR
DWG TYPE:.DWG
DFTR:
MSR
JOB O 819
DATE: 09-20
ENGR:
JB
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FILENAME:
FIGURE A-1 PRE
-DEVELOPMENT TOPOGRAPHY. DWG
APPD:
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6INCHES j 2 3 ITENTHS 1'0 20 30
0 500 1000 1500
GRAPHIC SCALE (IN FEET)
DWG SIZE I DRAWING NO. I REVISION
ANSI I
22.0"x34.0" FIGURE A-1 A
10

Existing Topography
FIGURE A-
REV. A
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f v+• „ .. - FGD CONSTRUCTED '
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}
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' ■ ♦♦♦ w1♦♦� � ` . x •�'Y -yam '� ` 0, � ♦ ♦ � • _ ,
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• BASINS ♦♦♦ f. '. COAL i i `~
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MARSHALL STEAM STATIONIlL
f . `" �� S.
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fhT T,. �d. y 4
0 IN 1 2 3 TENTHS 10 20 30 4 5
1 1
LEGEND
ASH BASIN WASTE BOUNDARY (APPROXIMATE)
------------- EXISTING SITE FEATURE (APPROXIMATE)
PROPERTY BOUNDARY
INDUSTRIAL LANDFILL (ILF) PHASE BOUNDARY (APPROXIMATE)
IN -PLACE CCR MATERIAL THICKNESS
NUMBER
MINIMUM DEPTH (FT)
MAXIMUM DEPTH (FT)
AREA (SF)
COLOR
1
0.00
10.00
2432684.65
2
10.00
20.00
2751742.64
0
3
20.00
30.00
2701533.60
4
30.00
40.00
2678238.70
5
40.00
50.00
1596709.72
6
50.00
60.00
741432.37
7
60.00
70.00
555413.54
8
70.00
80.00
230378.43
9
80.00
90.00
47654.70
NOTES
1. IN -PLACE CCR MATERIAL DEPTHS ARE BASED ON A COMPARISON BETWEEN PRE -DEVELOPMENT TOPOGRAPHY AND EXISTING
TOPOGRAPHY WITHIN THE ASH BASIN WASTE BOUNDARY AND THE STRUCTURAL FILL ACCESS ROAD, UTILIZING AUTOCAD CIVIL 3D
VERSION 2018.
REFERENCES
1. THE ASH BASIN WASTE BOUNDARY; THE PERIMETERS OF THE 1804 LANDFILL (PHASES I AND II), STRUCTURAL FILL, FGD LANDFILL,
ASBESTOS LANDFILL, AND DEMOLITION LANDFILL; PRESENTED IN THIS FIGURE ARE BASED ON THE "2018 COMPREHENSIVE SITE
ASSESSMENT UPDATE" PREPARED BY SYNTERRA FOR DUKE ENERGY AND SUBMITTED TO NCDEQ (NPDES PERMIT NO. NC0004987) ON
JANUARY 31, 2018.
2. THE PERIMETER OF THE STRUCTURAL FILL ACCESS ROAD PRESENTED IN THIS FIGURE IS BASED ON THE "MARSHALL STEAM STATION
STRUCTURAL FILL CLOSURE REQUIREMENT AND RECORDATION (RECORD NUMBER: 006021 MS)" LETTER SUBMITTED TO THE NORTH
CAROLINA DEPARTMENT OF ENVIRONMENT, HEALTH AND NATURAL RESOURCES BY DUKE POWER ON JULY 8, 1998.
3. THE PERIMETER OF THE INDUSTRIAL LANDFILL PRESENTED IN THIS FIGURE WAS PROVIDED BY DUKE ENERGY.
4. THE PROPERTY BOUNDARIES PRESENTED IN THIS FIGURE ARE BASED ON THE CATAWBA COUNTY GIS, THE TOPOGRAPHIC SURVEY
PERFORMED BY WSP IN APRIL 2014 AND SUBMITTED TO DUKE ENERGY IN JULY 2015, AND THE "BOUNDARY SURVEY OF PROPERTY TO
BE ACQUIRED FROM DELMAR SHERRILL AND GEORGE C. SHERRILL" DATED JANUARY 27, 2016.
5. THE AERIAL PHOTOGRAPH WAS OBTAINED FROM BING (MICROSOFT CORPORATION, 2018).
0 500 1000 1500
GRAPHIC SCALE (IN FEET)
AECOM
TITLE
IN -PLACE CCR MATERIAL
ISOPACH MAP
MARSHALL STEAM STATION
CLOSURE BY EXCAVATION CLOSURE PLAN
CATAWBA COUNTY, NORTH CAROLINA
FOR
ISSUED FOR APPROVAL
rftDUKE
�
ENERGY®
SCALE: 1 : =500'
DES:
MSR
DWG TYPE:.DWG
DFTR:
MSR
JOB NO: 60572849
CHKD:
RJB
DATE: 09-20-19
ENGR:
JB
FILENAME:
APPD:
JB
DWG SIZE
DRAWING NO.
REVISION
ANSID
22.0"x34.0"
FIGURE A- 3
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