Duke Mayo Gyp Pad Additional Assessment Work Plan

4� DUKE
ENERGY
February 13, 2020
North Carolina Department of Environmental Quality
Water Quality Regional Operations
3800 Barrett Drive
1628 Mail Service Center
Raleigh, North Carolina 27699
Attn: Mr. Eric Rice (submitted electronically)
Re: Mayo Steam Electric Plant Gypsum Pad Storage Area
Additional Groundwater Assessment Work Plan
Mayo Steam Electric Plant
10660 Boston Road
Roxboro, North Carolina 27574
Dear Mr. Rice:
2500 Fairfax Road
Greensboro, North Carolina 27407
336-215-4576
Duke Energy is submitting the attached Additional Assessment Work Plan for the Gypsum Pad
Storage Area (GPSA) at the Mayo Steam Electric Plant for your review.
The initial assessment Work Plan for the GPSA was submitted to the Division Raleigh Regional
Office on May 15, 2019, subsequently approved on June 14, 2019.
Initial assessment efforts indicate the presence of CCR related constituents in groundwater
proximate with the GPSA. Two monitoring well clusters are proposed for installation to further
characterize the GPSA on the northwest side. Like the Coal Pile Storage Area (GPSA), the
GPSA is bound on the northwest by internal plant roadways, multiple rail lines, multiple utilities,
and ultimately the ash basin. The southeast area of the GPSA is constrained by plant roads,
underground utilities, overhead conveyors, and ultimately the powerhouse. The CPSA is
adjacent to the southwestern side of the GPSA. The Conceptual Site Assessment for the CPSA
and GPSA will be combined and completed as one report since source characterization
potentially overlaps the area between the areas.
Upon concurrence with this Work Plan, Duke Energy will pursue receipt of necessary permits
for the installation of 6 proposed groundwater monitoring wells, soil investigation, and perform
associated sampling and analysis.
If you need additional information regarding this submittal do not hesitate to call or email, 336-
215-4576 or [e-mail].
Mayo Steam Electric Plant - Page I of 2

Respectfully submitted,
K-`64
Kimberlee Witt, PE
Environmental Services
Attachments: Work Plan for Additional Assessment — Gypsum Pile Storage Area, Mayo Steam
Electric Plant, SynTerra February 2020
ecc: Coal Ash War Room - NCDEQ
Rick Bolich - NCDEQ
Eric Smith — NCDEQ
Scott Vinson - NCDEQ
Steve Lanter — NCDEQ
Eric Rice - NCDEQ
John Toepfer - Duke Energy
Ed Sullivan — Duke Energy
Jerry Wylie — SynTerra
Peggy Altman - SynTerra
Mayo Steam Electric Plant - Page 2 of 2

,(VIP
synTerra
WORK PLAN FOR ADDITIONAL ASSESSMENT
GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
10660 BOSTON ROAD
ROXBORO, NC 27574
FEBRUARY 2020
PREPARED FOR
/DUKE
ENERGY
PROGRESS
DUKE ENERGY PROGRESS, LLC
Jerry/A. ylie, NOG 1425
Project Manager
P--r �, —�� —
Peggy W. Altman
Project Hydrogeologist

Work Plan for Additional Assessment - Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
TABLE OF CONTENTS
SECTION
PAGE
1.0
INTRODUCTION.........................................................................................................1-1
1.1
Regulatory Background...........................................................................................1-1
1.2
Site Description.........................................................................................................1-2
1.3
Initial Assessment Results.......................................................................................1-3
2.0
GYPSUM STORAGE PAD AREA ASSESSMENT OBJECTIVES ......................
2-1
2.1
Soil Assessment.........................................................................................................
2-1
2.2
Groundwater Assessment.......................................................................................
2-1
2.3
Monitoring Well Assessment Procedures.............................................................
2-2
LIST OF FIGURES
Figure 1 Site Location Map
Figure 2 Proposed Additional Monitoring Well and Soil Boring Locations
LIST OF TABLES
Table 1
Groundwater Analytical Results
Table 2
Soil Analytical Results
Table 3
Soil Sample Analytical Methods
Table 4
Proposed Soil Samples and Monitoring Wells
Table 5
Groundwater Analytical Methods
Page i

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
1.0 INTRODUCTION
Duke Energy Progress, LLC (Duke Energy) owns and operates the coal-fired Mayo
Steam Electric Plant (Mayo, Plant, or Site) located in a rural area approximately 10 miles
north of the City of Roxboro in Person County, North Carolina (Figure 1). Duke Energy
owns the site property, which is roughly bisected by US Highway 501, encompasses 460
acres, and includes the power plant, ash basin, material storage, industrial landfill and
other operational features associated with coal-fired power generating facilities. Mayo
began operations in 1983 with a single coal-fired unit.
This work plan describes activities proposed for further assessment of groundwater and
soil around the Mayo gypsum pad storage area (GPSA). Duke Energy submitted a
Work Plan for the initial evaluation of the GPSA on May 15, 2019 that was approved by
the NCDEQ Raleigh Regional Office (RRO) on June 14, 2019. The initial assessment
effort conducted in the third quarter of 2019 indicated the presence of constituents
(metals, other inorganics) in groundwater proximate with the GPSA. Initial assessment
data indicate the area northeast of the GPSA to be evaluated further (Figure 2).
Initial groundwater assessment indicates that groundwater flow, as anticipated, moves
beneath the GPSA, approximately from south-southwest to north-northeast. Detections
of constituents in downgradient locations (GYP-1 and GYP-5 wells) indicate the need
for additional assessment north-northeast of these areas to horizontally delineate
constituent occurrence. Proposed groundwater and soil assessment activities for the
GPSA are described herein.
1.1 Regulatory Background
In 2014, The North Carolina General Assembly passed the Coal Ash Management Act
(CAMA). CAMA required owners of a coal combustion residual (CCR) surface
impoundment to conduct detailed assessment of Site groundwater within and around
the CCR surface impoundment.
As indicated in a letter from the North Carolina Department of Environmental Quality
(DEQ) dated September 8, 2017 (Zimmerman to Sullivan), it is understood that in
addition to CAMA requirements, Duke Energy is also bound by the rules and
requirements of the NC General Statutes and NC Administrative Code 02L. These
provide requirements for the assessment and abatement of soil and groundwater
impacts resulting from Site activities. Therefore, Duke Energy is required to assess soil
and groundwater in areas where there is a potential for groundwater impact, identified
as primary and secondary sources.
Page 1-1

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
1.2 Site Description
Detailed descriptions of the Site operational history, the Site conceptual model, physical
setting and features, geology/hydrogeology, and results of the findings of the
Comprehensive Site Assessment (CSA) and other CAMA-related works are
documented in full in the following documents:
• Comprehensive Site Assessment Report —Mayo Steam Electric Plant
(SynTerra, September 2, 2015)
• Corrective Action Plan Part 1— Mayo Steam Electric Plant (SynTerra,
December 1, 2015)
• Corrective Action Plan Part 2— Mayo Steam Electric Plant (SynTerra,
February 2, 2016)
• Comprehensive Site Assessment Supplement 1 —Mayo Steam Electric Plant
(SynTerra, July 7, 2016)
• Comprehensive Site Assessment Update —Mayo Steam Electric Plant
(SynTerra, October 31, 2017)
• Corrective Action Plan Update —Mayo Steam Electric Plant (SynTerra,
December 31, 2019)
The GPSA at Mayo Plant is not discussed in detail in the documents described above.
The unit is located in the central portion of the Plant south of the ash basin (Figure 1).
The GPSA is approximately two acres and was put into operation in May 2009 to
contain and temporarily store synthetic gypsum generated by the Plant's flue gas
desulfurization (FGD) scrubbing process. Improvements to the GPSA were installed in
2016 including a synthetic liner under the gypsum storage area footprint, lining of
stormwater discharge conveyances, and pavement of surrounding gravel areas. The
GPSA is bounded to the north and east by internal Plant access roads and buildings as
well as the Plant railroad line. The GPSA is bounded to the west and south by the coal
pile and internal Plant access roads.
The GPSA appears to be positioned in a separate flow regime from the ash basin area.
Hydrogeological interpretation based on previous Site assessment activities indicates
that a groundwater divide is present roughly correlated with the ridge upon which the
Plant railroad is constructed. Groundwater flows to the west and north on the west side
of the ridge, and groundwater flows to the east towards Mayo Reservoir on the east
side of the ridge. The GPSA does not appear to be coincident to nor flow into the ash
basin. However, given its historical use and the potential for CCR impacts from this
Page 1-2

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
unit, groundwater and soil assessment will be conducted as required by 02L.
Groundwater flow will be further evaluated as part of this proposed assessment work.
1.3 Initial Assessment Results
Initial assessment data indicate groundwater concentrations of sulfate, total dissolved
solids (TDS), strontium, and selenium greater than regulatory comparison criteria
(Standards or CAMA Background Threshold Value for groundwater, whichever is
greater) in the vicinity of the GPSA (Table 1). Additionally, there are occurrences of
unsaturated soil concentrations of chromium that are greater than the regulatory
comparison criteria (Standards or CAMA Background Threshold Value for soil,
whichever is greater) at three locations GYP-1, GYP-3, and GYP-5 (Table 2).
Page 1-3

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
2.0 GYPSUM STORAGE PAD AREA ASSESSMENT OBJECTIVES
Objectives of the additional GPSA assessment activities presented in this work plan
include the following:
• Further characterize and delineate constituent concentrations in groundwater
and soil in the area north-northeast, and downgradient, of the GPSA.
• Refine the understanding of groundwater flow direction in the GPSA.
2.1 Soil Assessment
Soil samples will be collected during assessment activities and analyzed for inorganic
parameters consistent with assessment of areas used for coal and CCR management
(Table 3).
GPSA soils will be sampled and analyzed for metals and inorganic parameters to
determine if they are a source that may leach into underlying groundwater in excess of
NC 02L standards or BTVs. Soil samples will be collected during well drilling and
installation activities. The proposed locations of the monitoring wells are included in
Figure 2. Proposed locations are approximate and may vary slightly based on field
observations and locations of underground utilities, which will be determined prior to
initiation of boring activities.
Soil samples will be collected from the near ground surface (two to three feet) and at
approximately two to five-foot intervals to the top of the groundwater table or bedrock,
whichever is encountered first. An additional soil sample will be collected below the
water table within the new well screen intervals. SPLP samples will be collected at a
frequency of two per well cluster location with one unsaturated sample collected from
near ground surface (two to three feet) and a saturated sample collected two to three
feet below the water table (Table 4).
2.2 Groundwater Assessment
The extent of groundwater impact in the GPSA will be assessed by installing
groundwater monitoring wells and collecting/analyzing representative groundwater
samples from newly completed and existing wells.
Proposed Assessment Locations
Two monitoring well clusters are proposed for installation to further characterize GPSA
groundwater conditions at the proposed locations shown in Figure 2.One monitoring
well cluster could include one, two, or three individual monitoring wells depending on
Site conditions. If saturated conditions are present, a well will be installed in the
Page 2-1

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
surficial, transition zone, upper bedrock flow zones. Well locations may be modified
slightly based on field constraints (e.g. underground utility locations, rig stability).
Proposed locations GYP-6 and GYP-7 are located downgradient from the GPSA and
assessment activities in these locations are integral to defining the extent of
groundwater impact in the area of the GPSA.
2.3 Monitoring Well Assessment Procedures
Well installation procedures and well construction materials and lengths will be
consistent with CAMA assessment activities in accordance with the approved Proposed
Groundwater Assessment Work Plan (Rev. 1) (SynTerra, 2014). During borehole
installations, SynTerra will describe soil and rock cuttings. Those descriptions will
include lithology, color, and the type of soil or rock. The proposed monitoring wells
would be constructed in accordance with NCAC Title 15A, Subchapter 2C, Section .0100
Well Construction Standards. The proposed wells would consist of 2-inch diameter
schedule 40 polyvinyl chloride flush -joint threaded casings and prepacked well screens.
Shallow wells are proposed to be installed so that the top of the screened interval is
positioned approximately five feet below the water table, where practical, to avoid
potential issues such as biofouling and introduction of artificial redox conditions, which
are common among monitoring wells with screened intervals that bracket the water
table.
The primary drilling technology for soil sampling, well drilling, and well installation
will either be rotary sonic drilling or a combination of air rotary and hollow stem auger
drilling. Anticipated well depths are provided in Table 4. After well installation is
complete, monitoring wells will be developed to remove drilling fluids and solids that
might have been introduced into the surrounding formation and sand pack during well
installation. Well development helps establish interaction of the well with surrounding
groundwater. The location and elevation of each newly installed well will be
determined by survey. The newly installed wells will also be slug tested to evaluate
hydraulic properties of the groundwater flow system at each location.
Groundwater samples will be analyzed for field parameters (e.g., pH, conductivity, and
turbidity) and inorganic constituents consistent with ongoing CAMA assessment
activities (Table 5). Groundwater samples will be collected using low -flow sampling
techniques and procedures outlined in the Low Flow Sampling Plan, Duke Energy
Facilities, Ash Basin Groundwater Assessment Program, North Carolina, June 10, 2015.
Samples would be collected at a frequency no less than 60 days between monitoring
events.
Page 2-2

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
FIGURES

,f
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ASH BASIN COMPLIANCE
DUKE ENERGY PROGRESS BOUNDARY
PROPERTY LINE
60' RIGHT-OF-WAY NORTH CAROLINA-VIRGINIA STATE LINE
HALIFAX COUNTY (APPROXIMATE)
--------------
• PERSON COUNTY FERSON COUNTY
♦����
It
/ / ♦ T _
FGD -�APPROXIMATE ASH BASIN
i `. ♦ WASTE BOUNDARY FGD
RIGHT-OF-WAY i � ♦ ♦ r�
100' RAILROAD ��� r� r - +; I SETTING
RIGHT-OF-WAY ♦ � BASIN
CCP MONOFILL APPROXIMATE 1981
� : ♦11 C&D LANDFILL
r PONDS AREA (CLOSED)
III >
11 ♦ ��
f r\
ill �f11 / �'
LINED RETENTION
BASIN AREA
APPROXIMATE FUTURE ASH BASIN POWER PLANT
WASTE BOUNDARY
` I . GYPSUM STORAGE
n♦ `♦ 1�1 COAL PAD AREA
♦ r - - — .. .. J •�` ♦` STORAGE
♦ l PILE
�• . AREA
po
� L
r.
2019 USGS TOPOGRAPHIC MAP, CLUSTER SPRINGS q 4' qA
QUADRANGLE, QUAD ID: 36078E8, OBTAINED FROM THE USGS STORE AT
https://store.usgs.gov/map-locator.
tn
DUKE PERSON FIGURE 1
COUNTY SITE LOCATION MAP
ENERGY WORK PLAN FOR ADDITIONAL ASSESSMENT
PROGRESS WINSTON-SALEM GYPSUM PAD STORAGE AREA
RA`EIGH • MAYO STEAM ELECTRIC PLANT
10 ROXBORO, NORTH CAROLINA
CHARLOTTE •
DRAWN BY: A. ROBINSON DATE: 06/02/20T9 GRAPHIC SCALE
REVISED BY: A. RO OBINSBINSON DATE: 02/06/2020 1,000 0 1,000 2000,
synTerra CHECKED BY: P. ALTMAN DATE: 02/06/2020
APPROVED BY: J. WYLIE DATE: 02/06/2020
www.synterracorp.com PROJECT MANAGER: J. WYLIE NFEET

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LINED
RETENTION
BASIN
AREA
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ASH
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s�j•PSB-18 �
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APPROXIMATE FUTURE
i BASIN WASTE BOUNDARY
(SEE NOTE 2)
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CPA-4D �� CPA SBA
CPA-12D/BR
CPA-11 BR
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LEGEND
PROPOSED MONITORING WELLAND SOIL BORING
LOCATION
!;
(APPROXIMATE)
MONITORING WELL LOCATION (APPROXIMATE) -PENDING
SURVEY RESULTS
EXISTING MONITORING WELLAND SOIL BORING
LOCATION
aj
�-O '�• •e ASH BASIN WASTE BOUNDARY
7
— - — COMPLIANCE BOUNDARY
GENERALIZED GROUNDWATER FLOW DIRECTION
'' - lam,►'
NOTES:
1. COAL PILE DRAINAGE SYSTEM CONSTRUCTION FEATURES PROVIDED BY DUKE
ENERGY PROGRESS.
\\ ` 2. AREA OF INVESTIGATION THAT DETERMINED SETTLED CCR MATERIAL IS NOT
PRESENT IN THIS AREA OF THE ASH BASIN. A FUTURE REPRESENTATIVE ASH BASIN
WASTE AND COMPLIANCE BOUNDARY IS INCLUDED IN THE MAYO NPDES PERMIT
NCO038377 PART I, 5.A.(18.) ATTACHMENT B FIGURE 1.1 DATED JULY 13, 2018.
• 3. NATURAL RESOURCES TECHNICAL REPORT (NRTR) PREPARED BYAMEC FOSTER
1 • i WHEELER INC., JUNE 17, 2015.
`S * 4. WSP SURVEY CONDUCTED APRIL 17, 2014.
5. FLOOD INSURANCE BOUNDARIES PROVIDED BY FEMA, PERSON COUNTY FLOOD
INSURANCE STUDY, EFFECTIVE NOVEMBER 17, 2017
HTTP S://MS C. FE MA. GOWP O RTAL).
6. ALL BOUNDARIES ARE APPROXIMATE.
0 -, %A _ 41111111110-
4f DUKE
ENERGY
PROGRESS
GRAPHIC SCALE
120 0 120 240
(IN FEET)
DRAWN BY: A. ROBINSON DATE: 06/06/201;
REVISED BY: A. ROBINSON DATE: 02/11/2020
CHECKED BY: P. ALTMAN DATE: 02/11/2020
APPROVED BY: J. WYLIE DATE: 02/11/2020
PROJECT MANAGER: J. WYLIE
7. MAYO PLANT PROPERTY BOUNDARY PROVIDED BY DUKE ENERGY PROGRESS.
8, AERIAL PHOTOGRAPHY OBTAINED FROM ESRI ONLINE ON JUNE 10, 2019. AERIAL
WAS COLLECTED ON FEBRUARY 6, 2017.
9. DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH CAROLINA STATE PLANE
COORDINATE SYSTEM FIPS 3200 (NAD83).
FIGURE 2
PROPOSED ADDITIONAL MONITORING WELL
AND SOIL BORING LOCATIONS
WORK PLAN FOR ADDITIONAL ASSESSMENT
GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
ROXBORO, NORTH CAROLINA

Work Plan for Additional Assessment — Gypsum Pad Storage Area February 2020
Mayo Steam Electric Plant
TABLES

TABLE 1
GROUNDWATER ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
FIELD PARAMETERS
WATER QUALITY PARAMETERS
SELECTED 40CFR257 APPENDIX III CONSTITUENTS plus Sr
pH
Temperature
Specific
Conductance
Dissolved
Oxygen
Oxidation Reduction
Potential
Eh
Turbidity
Alkalinity
Bicarbonate
Alkalinity
Sulfide
Total Organic
Carbon
Total Suspended
Solids
Boron
Calcium
Chloride
Strontium
Sulfate
Total Dissolved
Solids
Reporting Units
S.U.
Deg C
Nmhos/cm
mg/L
mV
mV
NTUs
mg/L
mg/L
mg/L
mg/L
mg/L
pg/L
mg/L
mg/L
Ng/L
mg/L
mg/L
15A NCAC 02L Standard
6.5-8.5
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
700
NE
250
NE
250
500
2019 Updated BTV (Transition Zone)
5.6-6.6
NE
NE
NE
NE
NE
NE
302
302
0.1
2
NE
50
59
39
390
8
430
2019 Updated BTV (Bedrock Zone)
5.1-7.2
NE
NE
NE
NE
NE
NE
240
221
0.2
1
NE
50
73
41
418
130
470
Sample ID
Sample Collection Date
Analytical Results
Analytical Results
Analytical Results
GYP-01BR
09/19/2019
7.6
19
963
3.15
173
378
26.0
NA
NA
<0.1
NA
NA
<50
130
NA
851
NA
NA
GYP-01D
09/19/2019
6.3
20
2277
0.76
240
445
9.2
103
103
<0.1
1.5
10
238
329
160
1210
980
1910
GYP-01D
11/19/2019
6.1
16
2097
1.99
279
484
1.9
104
104
<0.1
1.3
6
221
314
150
1170
950
1870
GYP-02BR
09/18/2019
7.5
24
916
0.29
-160
45
7.7
197
197
<0.1
1.7
11
<50
87.1
48
2470
210
621
GYP-02BR
11/19/2019
7.2
15
915
0.31
228
433
2.2
208
208
0.13
1.3
<5
<50
79.2
147
2410
180
583
GYP-03BR
09/18/2019
7.6
22
2197
4.33
179
384
9.2
123
123
<0.1
0.75 j
12
49.465 j
417
160
1580
990
1880
GYP-03BR
11/19/2019
7.6
18
2077
4.15
226
431
6.1
111
111
<0.1
0.7
6
45.734 j
393
150
1590
960
1850
GYP-03D
09/18/2019
6.3
20
2209
0.27
165
370
7.0
75.7
75.7
<0.1
0.61 j
12
27.411 j
328
200
1290
1000
1910
GYP-03D
11/19/2019
6.4
18
1929
0.37
255
460
6.2
85
85
<0.1
0.768
12
<50
293
180
1160
850
1730
GYP-04D
09/18/2019
8.5
21
1543
0.29
15
220
7.6
55.7
40.7
<0.1
1.9
10
432
295
23
852
820
1310
GYP-04D
11/19/2019
8.3
19
1881
0.36
231
436
3.2
27.3
25.3
<0.1
1.6
<5
777
432
40
1060
1100
1780
GYP-05BR
09/19/2019
6.2
17
959
0.40
202
407
6.5
98.5
98.5
<0.1
2.7
25
<50
121
56
617
300
694
GYP-05BR
11/18/2019
6.3
15
926
6.47
263
468
9.7
98.4
98.4
<0.1
2.4
21
<50
119
59
627
310
770
GYP-05D
09/19/2019
6.1
17
976
0.31
206
411
4.6
82.8
82.8
<0.1
2.9
23
<50
120 M4
166
693
310
714
GYP-05D
11/18/2019
6.2
16
953
1.06
292
497
9.6
87.2
87.2
<0.1
2.7
12
<50
124
67
733
320
799
Notes:
0 - Bold highlighted concentration indicates exceedance of the 15A NCAC 02L .0202 Standard or the IMAC. (Effective date for 15A NCAC 02L .0202 Standard and IMAC is April 1, 2013)
0 - Bold highlighted concentration indicates exceedance of the 2019 Updated Background Threshold Values for Mayo Steam Electric Plant. (Calculated using data from background groundwater samples collected from April 2010 to December 2018)
0 - Turbidity of Sample ? 10 NTUs
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013
< - concentration not detected at or above the adjusted reporting limit.
^ - Federal MCL
B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes.
Deg C - Degrees Celsius
DO - Dissolved oxygen
Eh - Redox Potential
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M1 - Matrix spike recovery was high: the associated Laboratory Control Spike (LCS) was acceptable.
M4 - The spike recovery value was unusable since the analyte concentration in the sample was disproportionate to the spike level.
mg - N/L - Milligrams nitrogen per liter
mg/L - Milligrams per liter
mV - Millivolts
NA - Not available or Not Applicable
NE - Not established
NTU - Nephelometric turbidity unit
ORP - Oxidation -Reduction Potential
P4 - Sample field preservation does not meet EPA or method recommendations for this analysis.
pCi/L - picocuries per liter
RO - The data are unusable. The sample results are rejected due to serious deficiencies in meeting QC criteria. The analyte may or may not be present in the sample.
S.U. - Standard Unit
U - Analyte was analyzed for, but not detected above the MDC.
pm - Microns
Ng/L - Micrograms per liter
pg/mL - micrograms per milliliter
Nmhos/cm - Micro mhos per centimeter
Prepared by: GRK Checked by:Tr
Page 1 of 4

TABLE 1
GROUNDWATER ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
INORGANIC PARAMETERS (TOTAL CONCENTRATION)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium (VI)
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Selenium
Sodium
Thallium
Vanadium
Zinc
Reporting Units
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
mg/L
pg/L
pg/L
pg/L
pg/L
mg/L
pg/L
mg/L
pg/L
pg/L
pg/L
15A NCAC 02L Standard
NE
1*
10
700
4*
2
10
10
1*
1000
300
15
NE
50
1
NE
100
NE
20
NE
0.2*
0.3*
1000
2019 Updated BTV (Transition Zone)
692
1
1
68
1
1
1.28
6
1
5
1356
1
14
448
0.2
1
5
4
1
53
0.2
5.8
15
2019 Updated BTV (Bedrock Zone)
574
1
1
97
1
1
0.36
7
5
5
3771
1
15
548
0.2
17
6
11
2
117
0.2
4.4
35
Sample ID
Sample Collection Date
Analytical Results
GYP-01BR
09/19/2019
438
0.553 j
0.672 j
60
<1
<1
NA
1.36
<1
0.871 j
199
<1
25
413
<0.05
4.23
0.721 j
19.4
<1
38.3
<0.2
2.66
3.718 j
GYP-01D
09/19/2019
383
<1
<1
45
<1
0.546 j
0.061
1.36
0.634 j
5.12
360
0.467 j
95.3
134
<0.05
3.76
2.58
11.3
33
80.3
0.1 j
1.88
15
GYP-01D
11/19/2019
115
<1
<1
41
<1
0.643 j
<0.025
0.624 j
0.882 j
2.44
128
<1
90.3
223
<0.05
1.38
2.63
11
31.6
81.1
<0.2
1.42
13
GYP-02BR
09/18/2019
385
<1
1.38
61
<1
<1
<0.025
1.5
0.525 j
0.476 j
788
<1
43.8
124
<0.05
17.1
1.85
12.1
<1
39.8
<0.2
0.966
2.921 j
GYP-02BR
11/19/2019
31
<1
1.77
52
<1
<1
<0.025
0.358j
<1
<1
525
<1
1 40.6
115
<0.05
18.1
1.39
11.4
<1
37.9
<0.2
0.432
4.4023
GYP-03BR
09/18/2019
138
<1
<1
52
<1
<1
0.59
1.29
0.348 j
0.351 j
83
<1
71.7
1030
<0.05
8.49
1.21
15.2
3.12
38.1
<0.2
0.998
2.15 j
GYP-03BR
11/19/2019
93
0.419 j
0.335 j
45
<1
<1
2.9
3.39
<1
0.811 j
75
<1
67
592
<0.05
8.55
1.7
19
2.61
40.9
<0.2
1.04
4.578 j
GYP-03D
09/18/2019
159
<1
<1
81
<1
<1
<0.025 P4,RO
1.77
2.71
0.628 j
229
<1
115
1600
<0.05
7.88
22.9
10.4
10.6
65
<0.2
1.16
3.918 j
GYP-03D
11/19/2019
144
<1
<1
72
<1
<1
<0.025
2.12
4.22
0.442 j
283
<1
90.5
1880
<0.05
8.02
35.2
11.3
5.51
47.4
<0.2
1.07
10
GYP-04D
09/18/2019
303
<1
0.462 j
57
<1
<1
1.9
2.97
0.58 j
1.19
338
<1
34.1
455
<0.05
38.7
1.23
14.3
7.39
28.4
<0.2
3.71
1.814 j
GYP-04D
11/19/2019
87
<1
0.378 j
61
<1
<1
0.94
1.42
0.444 j
0.52 j
103
<1
35.3
428
<0.05
12.1
0.792 j
13.7
224
23.4
<0.2
2.14
2.568 j
GYP-05BR
09/19/2019
102
<1
<1
18
<1
<1
<0.025
1.32
<1
5.71
190
<1
32
52
<0.05
1.46
2.8
4.73
20.6
35.5
<0.2
1.32
<5
GYP-O5BR
11/18/2019
159
<1
<1
20
<1
<1
<0.025 P4,RO
1.38
<1
1.82
360
<1
31.4
35
<0.05
1.12
2.73
4.59
20.5
34.8
<0.2
1.33
8
GYP-05D
09/19/2019
1360
<1
<1
53
<1
<1
0.057
7.09
0.814 j
1.83
1490
0.46 j
35.4
76
<0.05
1.21
14.76
4.08
26.4
34.8
<0.2
4.79
4.045 j
GYP-05D
11/18/2019
786
<1
<1
50
<1
<1
0.043
3.21
0.381LJ
1.06
912
<1
35.4
48
<0.05
1.04
2.67
3.96
26.7
35.4
<0.2
2.89
6
Notes:
0 - Bold highlighted concentration indicates exceedance of the 15A NCAC 02L .0202 Standard or the IMAC. (Effective date for 15A NCAC 02L .0202 Standard and IMAC is April 1, 2013)
0 Bold highlighted concentration indicates exceedance of the 2019 Updated Background Threshold Values for Mayo Steam Electric Plant. (Calculated using data from background groundwater samples collected from April 2010 to December 2018)
0 - Turbidity of Sample ? 10 NTUs
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013
< - concentration not detected at or above the adjusted reporting limit.
^ - Federal MCL
B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes.
Deg C - Degrees Celsius
DO - Dissolved oxygen
Eh - Redox Potential
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M1 - Matrix spike recovery was high: the associated Laboratory Control Spike (LCS) was acceptable.
M4 - The spike recovery value was unusable since the analyte concentration in the sample was disproportionate to the spike level.
mg - N/L - Milligrams nitrogen per liter
mg/L - Milligrams per liter
mV - Millivolts
NA - Not available or Not Applicable
NE - Not established
NTU - Nephelometric turbidity unit
ORP - Oxidation -Reduction Potential
P4 - Sample field preservation does not meet EPA or method recommendations for this analysis.
pCi/L - picocuries per liter
RO - The data are unusable. The sample results are rejected due to serious deficiencies in meeting QC criteria. The analyte may or may not be present in the sample.
S.U. - Standard Unit
U - Analyte was analyzed for, but not detected above the MDC.
pm - Microns
Ng/L - Micrograms per liter
pg/mL - micrograms per milliliter
pmhos/cm - Micro mhos per centimeter
Prepared by: GRK Checked by: CMH
Page 2 of 4

TABLE 1
GROUNDWATER ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
INORGANIC PARAMETERS (DISSOLVED CONCENTRATION WITH FILTER SIZE 0.45pm)
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Reporting Units
pg/L
pg/L
pg/L
pg/L
pg/L
mg/L
pg/L
pg/L
pg/L
pg/L
pg/L
mg/L
pg/L
pg/L
pg/L
pg/L
15A NCAC 02L Standard
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
2019 Updated BTV (Transition Zone)
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
2019 Updated BTV (Bedrock Zone)
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
NE
Sample ID
Sample Collection Date
Analytical Results
GYP-01BR
09/19/2019
KIA
MNNNNM_NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
GYP-01D
09/19/2019
<1
44
<1
241
0.485 j
NA
0.362 j
0.457 j
2.1
<10
<1
NA
111
<0.05
4.76
2.42
GYP-01D
11/19/2019
<1
41
<1
232
0.456 j
326
<1
0.536 j
1.09
3.6 j
<1
93.3
147
<0.05
1.25
1.93
GYP-02BR
09/18/2019
1.27
60
<1
<50
<1
NA
<1
0.335 j
<1
277
<1
NA
119
<0.05
16.5
1.09
GYP-02BR
11/19/2019
1.72
52
<1
<50
<1
79.8
<1
<1
<1
447
<1
40.8
113
<0.05
18.1
1.22
GYP-03BR
09/18/2019
<1
49
<1
46.277 j
<1
NA
0.809 j
<1
<1
<10
<1
NA
982
<0.05
6.32
0.603 j
GYP-03BR
11/19/2019
<1
44
<1
46.787 j
<1
407
3.21
<1
<1
<10
<1
69.4
535
<0.05
7.69
0.611 j
GYP-03D
09/18/2019
<1
77
<1
17.605 j
<1
NA
0.549 j
2.03
<1
36
<1
NA
1170
<0.05
5.3
20.9
GYP-03D
11/19/2019
<1
79
<1
<50
<1
342
<1
2.19
<1
120
<1
118
925
<0.05
3.33
19.2
GYP-04D
09/18/2019
0.497 j
53
<1
424
<1
NA
3.14
<1
<1
<10
<1
NA
389
<0.05
36.9
0.648 j
GYP-04D
11/19/2019
<1
64
<1
811
<1
446
1.34
<1
0.335 j
<10
<1
36.3
425
<0.05
12.5
0.632 j
GYP-05BR
09/19/2019
<1
17
<1
<50
<1
NA
<1
<1
0.449 j
31 B2
<1
NA
44
<0.05
1.48
2.49
GYP-OSBR
11/18/2019
<1
17
<1
<50
<1
NA
<1
<1
0.503 j
6.314 j
<1
NA
21
<0.05
0.855 j
1.07
GYP-05D
09/19/2019
<1
43
<1
<50
<1
NA
0.506 j
<1
<1
<10
<1
NA
10
<0.05
1.01
2.5
GYP-05D
11/18/2019
<1
44
<1
<50
<1
NA
<1
<1
<1
<10
<1
NA
9
<0.05
0.953 j
1.98
Notes:
0 - Bold highlighted concentration indicates exceedance of the 15A NCAC 02L .0202 Standard or the IMAC. (Effective date for 15A NCAC 02L .0202 Standard and IMAC is April 1, 2013)
0 Bold highlighted concentration indicates exceedance of the 2019 Updated Background Threshold Values for Mayo Steam Electric Plant. (Calculated using data from background groundwater samples collected from April 2010 to December 2018)
- Turbidity of Sample > 10 NTUs
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013
< - concentration not detected at or above the adjusted reporting limit.
^ - Federal MCL
B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes.
Deg C - Degrees Celsius
DO - Dissolved oxygen
Eh - Redox Potential
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M1 - Matrix spike recovery was high: the associated Laboratory Control Spike (LCS) was acceptable.
M4 - The spike recovery value was unusable since the analyte concentration in the sample was disproportionate to the spike level.
mg - N/L - Milligrams nitrogen per liter
mg/L - Milligrams per liter
mV - Millivolts
NA - Not available or Not Applicable
NE - Not established
NTU - Nephelometric turbidity unit
ORP - Oxidation -Reduction Potential
P4 - Sample field preservation does not meet EPA or method recommendations for this analysis.
pCi/L - picocuries per liter
RO - The data are unusable. The sample results are rejected due to serious deficiencies in meeting QC criteria. The analyte may or may not be present in the sample.
S.U. - Standard Unit
U - Analyte was analyzed for, but not detected above the MDC.
pm - Microns
pg/L - Micrograms per liter
pg/mL - micrograms per milliliter
pmhos/cm - Micro mhos per centimeter
Prepared by: GRK Checked by: CMH
Page 3 of 4

TABLE 1
GROUNDWATER ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
INORGANIC PARAMETERS (DISSOLVED CONCENTRATION WITH FILTER SIZE 0.45pm)
RADIONUCLIDES
OTHER PARAMETERS
Potassium
Selenium
Sodium
Strontium
Thallium
Vanadium
Zinc
Radium-226
Radium-228
Total Radium
Uranium-238
Total Uranium
Carbonate Alkalinity
Reporting Units
mg/L
pg/L
mg/L
pg/L
pg/L
pg/L
pg/L
pCi/L
pCi/L
pCi/L
pg/L
pg/mL
mg/L
15A NCAC 02L Standard
NE
NE
NE
NE
NE
NE
NE
NE
NE
5^
NE
0.03^
NE
2019 Updated BTV (Transition Zone)
NE
NE
NE
NE
NE
NE
NE
NE
NE
35
NE
0.0010
10
2019 Updated BTV (Bedrock Zone)
NE
NE
NE
NE
NE
NE
NE
NE
NE
5
NE
0.0026
10
Sample ID
Sample Collection Date
Analytical Results
Analytical Results
Analytical Results
GYP-01BR
09/19/2019
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
GYP-01D
09/19/2019
NA
30.8
NA
1220
<0.2
1.12
9
0.246 U
0.517
0.763
0.00107
0.00107
<5
GYP-01D
11/19/2019
11.3
28.7
82.8
1200
<0.2
1.14
12 B2
0.574
0.667
1.241
0.00101
0.00101
<5
GYP-02BR
09/18/2019
NA
<1
NA
2500
<0.2
0.33
<5
1.15
0.397 U
1.547
0.00194
0.00194
<5
GYP-02BR
11/19/2019
11.4
<1
38.5
2440
<0.2
0.523
2.356 j,B2
1.44
0.415 U
1.855
0.00194
0.00194
<5
GYP-03BR
09/18/2019
NA
3.01
NA
1520
<0.2
0.904
<5
2.77
0.854
3.624
0.0189
0.0189
<5
GYP-03BR
11/19/2019
19.8
2.52
43.3
1670
<0.2
0.941
3.831j,B2
3.11
0.702
3.812
0.027
0.027
<5
GYP-03D
09/18/2019
NA
12.1
NA
1310
<0.2
0.904
<5
0.602
0.0078 U
0.6098
0.000493
0.000493
<5
GYP-03D
11/19/2019
10.2
10.3
55.4
1360
<0.2
0.927
5 B2
0.493
0.281 U
0.774
0.000393
0.000393
<5
GYP-04D
09/18/2019
NA
8.42
NA
857
<0.2
3.52
<5
0.579
0.73 U
1.309
0.00296
0.00296
15
GYP-04D
11/19/2019
14.2
229
24.4
1120
<0.2
1.93
2.789j,B2
1.28
0.391 U
1.671
0.00069
0.00069
<5
GYP-05BR
09/19/2019
NA
20.5
NA
619
<0.2
0.958
<5
0.301 U
0.397 U
0.698
0.000397
0.000397
<5
GYP-OSBR
11/18/2019
NA
19.5
NA
602
<0.2
1.03
<5
0.478
0.319 U
0.797
0.000277
0.000277
<5
GYP-05D
09/19/2019
NA
26.8
NA
694
<0.2
1.19
<5
0.863
0.416 U
1.279
0.000361
0.000361
<5
GYP-05D
11/18/2019
NA
26.3
NA
711
<0.2
1.25
<5
0.587
0.151 U
0.738
0.000373
0.000373
<5
Notes:
0 - Bold highlighted concentration indicates exceedance of the 15A NCAC 02L .0202 Standard or the IMAC. (Effective date for 15A NCAC 02L .0202 Standard and IMAC is April 1, 2013)
0 Bold highlighted concentration indicates exceedance of the 2019 Updated Background Threshold Values for Mayo Steam Electric Plant. (Calculated using data from background groundwater samples collected from April 2010 to December 2018)
- Turbidity of Sample > 10 NTUs
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April 1, 2013
< - concentration not detected at or above the adjusted reporting limit.
^ - Federal MCL
B2 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes.
Deg C - Degrees Celsius
DO - Dissolved oxygen
Eh - Redox Potential
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M1 - Matrix spike recovery was high: the associated Laboratory Control Spike (LCS) was acceptable.
M4 - The spike recovery value was unusable since the analyte concentration in the sample was disproportionate to the spike level.
mg - N/L - Milligrams nitrogen per liter
mg/L - Milligrams per liter
mV - Millivolts
NA - Not available or Not Applicable
NE - Not established
NTU - Nephelometric turbidity unit
ORP - Oxidation -Reduction Potential
P4 - Sample field preservation does not meet EPA or method recommendations for this analysis.
pCi/L - picocuries per liter
RO - The data are unusable. The sample results are rejected due to serious deficiencies in meeting QC criteria. The analyte may or may not be present in the sample.
S.U. - Standard Unit
U - Analyte was analyzed for, but not detected above the MDC.
pm - Microns
pg/L - Micrograms per liter
pg/mL - micrograms per milliliter
pmhos/cm - Micro mhos per centimeter
Prepared by: GRK Checked by: CMH
Page 4 of 4

TABLE 2
SOIL ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
Percent
Moisture
Percent
Solids
pH
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride
Chromium
Cobalt
Copper
Fluoride
Reporting Units
%
%
S.U.
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
PSRG Protection of Groundwater
NE
NE
NE
110000
0.9
5.8
580
63
45
3
NE
NE
3.8
0.9
700
6000
Provisional Background Threshold Values
NE
NE
5.2-7.6
46946
0.7
4.5
616
1
13
0.03
4830
42
77.4
44.2
124
NE
2019 Updated Background Threshold Values
NE
NE
4.7-8.3
50978
0.6
3.9
598
2
16
0.60
8769
312
440.0
81.7
216
NE
Sample ID
Depth
Interval
(FEET BGS)
Sample
Collection
Date
Analytical Results
GYP-SB-01 (2-3)
2 - 3
07/11/2019
NA
87.4
7.3
30000
<0.5
0.82
65
0.43
<2.5
<0.13
9200
5.4 j
48
7.1
32
3.4
GYP-SB-01 (7-8)
7 - 8
07/11/2019
NA
89.5
7.4
22000
<0.53
0.54
94
0.45
<2.6
0.075 j
2900
6.2 j
71
9.3
31
4
GYP-SB-01 (12-13)
12- 13
07/11/2019
NA
89.2
6.7
26000
<0.49
1.2
100
0.46
<2.4
0.082 j
3300
8.3 j
78
8.6
34
2.1
GYP-SB-01 (17-18)
17- 18
07/12/2019
NA
77.2
5.3
74000
<0.63
2.2
130
0.73
<3.2
0.061 j
1000
22
53
11
220
<1.3
GYP-SB-01 (22-23)
22- 23
07/12/2019
NA
84.7
6.1
51000
<0.53
1.1
180
0.68
<2.7
0.84
4700
11 j
100
22
130
<1.2
GYP-SB-01 (27-28)
27 - 28
07/12/2019
NA
96.1
8.2
20000
<0.46
0.72
98
0.27
<2.3
1.1
24000
3 j
55
8.9
55
<1
GYP-SB-01 (34-44)
34 - 44
07/24/2019
NA
72.5
7.3
12000
<0.53
0.95
81
0.22 j
<2.7
0.98
2500
26
25
9.7
68
NA
GYP-SB-01 (89-104)
89 - 104
07/19/2019
NA
99.3
9.3
3400
<0.42
2.5
21
0.11 j
<2.1
0.56
4700
<10
0.93
2.7
7.8
NA
GYP-SB-02 (2-3)
2 - 3
06/24/2019
NA
72.6
5.9
19000
<0.62
0.52 j
120
0.4
<3.1
0.19
2800
4.8 j
87
12
39
NA
GYP-SB-02 (103-118)
103 - 118
06/27/2019
NA
82.3
8.1
17000
<0.58
0.37 j
63
<0.29
<2.9
0.041 j
15000
27
85
16
42
NA
GYP-SB-03 (2-3)
2 - 3
07/01/2019
NA
85.8
5.6
20000
<0.57
0.6
96
0.43
<2.8
0.073 j
1200
5.1 j
83
14
36
<1.2
GYP-SB-03 (7-8)
7 - 8
07/01/2019
NA
84.6
5.7
23000
<0.57
0.64
91
0.48
<2.9
<0.15
870
17
70
9.6
31
<1.2
GYP-SB-03 (12-13)
12- 13
07/01/2019
NA
84.5
7.5
44000
<0.56
0.86
290
1.8
<8.4
0.08 j
1600
4.3 j
85
79
110
6.7
GYP-SB-03 (17-18)
17 - 18
07/01/2019
NA
90.9
7.2
23000
<0.51
0.48 j
180
0.55
<5.1
0.081 j
1500
7.7 j
63
16
37
5.3
GYP-SB-03 (22-23)
22 - 23
07/01/2019
NA
54.9
6.8
43000 M
<0.84 M
0.96
260
0.8
<8.7
0.18 j
4600
29
410
35 M
50
5.8
GYP-SB-04 (2-3)
2 - 3
06/24/2019
NA
93.8
7.0
22000
<0.51
0.76
120
0.24 j
<5.1
0.09 j
5600
2.1 j
63
18
62
NA
GYP-SB-04 (7-8)
7 - 8
06/24/2019
NA
83.4
7.5
23000
<0.56
0.51 j
140
0.35
<5.6
0.091 j
7000
<12
77
21
64
NA
GYP-SB-05 (2-3)
2 - 3
07/11/2019
NA
85.4
6.3
27000
<0.54
0.57
120
0.64
<2.7
0.091 j
2400
14
57
11
26
1.1 j,M
GYP-SB-05 (7-8)
7 - 8
07/10/2019
NA
80
5.8
18000
<0.6
0.45 j
99
0.48
<3
0.079 j
1500
13
61
10
23
<1.3
GYP-SB-05 (12-13)
12 - 13
07/10/2019
NA
81.8
6.0
31000
<0.59
0.7
130
0.53
<3
0.05 j
1300
10 j
180
15
34
1.5
GYP-SB-05 (17-18)
17- 18
07/10/2019
NA
77.4
5.6
35000
<0.62
1.4
110
0.64
<3.1
0.036 j
760
8.3 j
84
8.4
30
3.2
GYP-SB-05 (44-54)
44 - 54
07/25/2019
NA
85.8
6.0
16000 M
<0.52 M
1.8
120
0.33
<2.4
0.11 j
3100 M
2.9 j
150
11
22
NA
GYP-SB-05 (75-80)
75 - 80
07/17/2019
NA
96.2
8.8
3800 M
<0.44
<0.44
20
0.086 j
<2.4
0.066 j
6400 M
I <10
22
2.3
12
<1
Prepared by: GRK Checked by: CMH
Notes•
0 - Bold highlighted concentration indicates exceedance of the Inactive Hazardous Sites Branch PSRG Table (May 2019) for Protection of Groundwater
< - concentration not detected at or above the adjusted reporting limit.
B - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample is less than 1OX the concentration in the method blank. Analyte concentration in sample could be due to blank contamination.
bgs - below ground surface
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M - Matrix spike / matrix spike dup failure.
mg/kg - milligrams per kilogram
NA - Not available or Not Applicable
NE - Not established
S.U. - Standard Unit
Page 1 of 2

TABLE 2
SOIL ANALYTICAL RESULTS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameters
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrate
(as N)
Potassium
Selenium
Sodium
Strontium
Sulfate
Thallium
Total
Organic
Carbon
Vanadium
Zinc
Reporting Units
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
PSRG Protection of Groundwater
150
270
NE
65
1
7.1
130
NE
NE
2.1
NE
1500
1438
0.28
NE
350
1200
Provisional Background Threshold Values
82634
16
47958
1894
0.1
4.5
71
0.33
21421
2.9
833
69
14
0.41
NE
188
340
2019 Updated Background Threshold Values
85345
16
51829
2985
0.1
12.0
193
31.20
20393
2.9
1496
95
362
0.85
NE
207
326
Sample ID
Depth
Interval
(FEET BGS)
Sample
Collection
Date
Analytical Results
GYP-SB-01 (2-3)
2 - 3
07/11/2019
27000 B
7.4
5800
280
<0.084
0.51 j
24
NA
2300
<1.3
110 j
28
900
0.12 j
1850
33
49
GYP-SB-01 (7-8)
7 - 8
07/11/2019
25000 B
7.5
7200
450
<0.081
<2.1
31
NA
4100
<1.4
230 j
21
200
0.17
6460
34
75
GYP-SB-01 (12-13)
12- 13
07/11/2019
25000 B
7.7
6800
390
<0.083
<2
28
NA
3900
<1.3
190 j
19
140
0.18
4730
39
72
GYP-SB-01 (17-18)
17- 18
07/12/2019
63000 B
18
9400
360
0.035 j
<2.5
34
NA
6100
<1.6
180 j
14
100
0.38
1740
98
190
GYP-SB-01 (22-23)
22- 23
07/12/2019
54000 B
8.5
27000
1700
<0.092
<2.1
70
NA
8300
<1.4
270
46
67
0.32
670
100
280
GYP-SB-01 (27-28)
27 - 28
07/12/2019
28000 B
3.7
10000
1100
<0.078
<1.9
24
NA
7600
<1.2
130 j
38
72
0.26
7700
42
150
GYP-SB-01 (34-44)
34 - 44
07/24/2019
15000
8.7
4800
540
<0.11
0.68 j
12
0.19 j
3000
<1.4
96 j
19
260
0.17
3670
39
90
GYP-SB-01 (89-104)
89 - 104
07/19/2019
10000
12
1600
800
<0.078
3.2
0.58 j
0.2
1300
<1.1
77 j
28
17
0.068 j
1180
5.7
370
GYP-SB-02 (2-3)
2 - 3
06/24/2019
24000
5
9900
660
<0.11
<2.5
35
0.15 j
5500
<1.6
120 j
26
350 M
0.17
2580
43
93 B
GYP-SB-02 (103-118)
103 - 118
06/27/2019
23000
1 0.89
18000
410
<0.097
<2.3
37
<0.24
5200
<1.5
300
54
140
0.084 j
<998
56
59 B
GYP-SB-03 (2-3)
2 - 3
07/01/2019
26000
4.8
8400
580
<0.093
<2.3
33
NA
3200
<1.5
140 j
15
320
0.14 j
1230
45
81
GYP-SB-03 (7-8)
7 - 8
07/01/2019
20000
7.9
5400
270
<0.09
0.58 j
19
NA
2500
<1.5
180 j
8
94
0.11 j
2360
38
46
GYP-SB-03 (12-13)
12- 13
07/01/2019
67000
3.7
19000
1500
<0.098
1.2 j
66
NA
6700
0.56 j
1200
22
<12
0.23
1140
130
170
GYP-SB-03 (17-18)
17 - 18
07/01/2019
33000
3.1
11000
620
<0.085
0.64 j
34
NA
7900
<1.3
310
13
49
0.19
<998
69
85
GYP-SB-03 (22-23)
22 - 23
07/01/2019
66000 M
4.7
26000 M
1500 M
<0.13
2.5 j
120
NA
12000 M
<2.2
490
28
130
0.34
<998
150
180
GYP-SB-04 (2-3)
2 - 3
06/24/2019
32000
3.3
17000
560
<0.086
0.83 j
38
0.21
6500
<1.3
150 j
54
61
0.14
1570
62
84 B
GYP-SB-04 (7-8)
7 - 8
06/24/2019
35000
1.8
19000
710
<0.097
0.61 j
54
<0.24
1 9200
<1.5
120 j
53
20
0.19
<998
62
110 B
GYP-SB-05 (2-3)
2 - 3
07/11/2019
31000 B
6.8
7400
960
<0.09
<2.2
32
NA
4500
<1.4
130 j
28
420
0.16
2840
42
79
GYP-SB-05 (7-8)
7 - 8
07/10/2019
25000 B
8.2
6300
800
<0.1
<2.4
30
NA
3100
<1.6
100 j
17
170
0.12 j
1000
39
67
GYP-SB-05 (12-13)
12- 13
07/10/2019
37000 B
4.9
12000
760
<0.095
<2.4
60
NA
4400
<1.5
370
18
200
0.15
940
62
85
GYP-SB-05 (17-18)
17- 18
07/10/2019
31000 B
6.8
5300
270
<0.099
<2.5
30
NA
3000
<1.6
190 j
13
48
0.18
420 j
49
58
GYP-SB-05 (44-54)
44 - 54
07/25/2019
23000 M
7.8
13000 M
810 M
<0.092
1.5 j
54
0.93
7700
<1.3
87 j
20
13
0.4
890
52 M
88
GYP-SB-05 (75-80)
75 - 80
07/17/2019
6500 B,M
0.93
3300 M
330 M
<0.085
0.61 j
12
NA
2600 M
<1.1
36 j
25 M
36
<0.11
5940
0.7 j
26
Prepared by: GRK Checked by: CMH
Notes•
- Bold highlighted concentration indicates exceedance of the Inactive Hazardous Sites Branch PSRG Table (May 2019) for Protection of Groundwater
< - concentration not detected at or above the adjusted reporting limit.
B - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample is less than 1OX the concentration in the method blank. Analyte concentration in sample could be due to blank contamination.
bgs - below ground surface
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
M - Matrix spike / matrix spike dup failure.
mg/kg - milligrams per kilogram
NA - Not available or Not Applicable
NE - Not established
S.U. - Standard Unit
Page 2 of 2

TABLE 3
SOIL SAMPLE ANALYTICAL METHODS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELETRIC PLANT
DUKE ENERGY PROGRESS LLC, ROXBORO, NC
INORGANIC COMPOUNDS
UNITS
METHOD
Aluminum
mg/kg
EPA 6010D
Antimony
mg/kg
EPA 6020B
Arsenic
mg/kg
EPA 6020B
Barium
mg/kg
EPA 6010D
Beryllium
mg/kg
EPA 6010D
Boron
mg/kg
EPA 6010D
Cadmium
mg/kg
EPA 6020B
Calcium
mg/kg
EPA 6010D
Chloride
mg/kg
EPA 9056A
Chromium
mg/kg
EPA 6010C
Cobalt
mg/kg
EPA 6020A
Copper
mg/kg
EPA 6010C
Iron
mg/kg
EPA 6010C
Lead
mg/kg
EPA 6020B
Magnesium
mg/kg
EPA 6010D
Manganese
mg/kg
EPA 6010C
Mercury
mg/kg
EPA 7471B
Molybdenum
mg/kg
EPA 6010D
Nickel
mg/kg
EPA 6010C
Nitrate as Nitrogen
mg/kg
EPA 9056A
pH
S.U.
EPA 9045D
Potassium
mg/kg
EPA 6010D
Selenium
mg/kg
EPA 6020B
Sodium
mg/kg
EPA 6010D
Strontium
mg/kg
EPA 6010C
Sulfate
mg/kg
EPA 9056A
Thallium
mg/kg
EPA 6020B
Total Organic Carbon
mg/kg
EPA 9060
Vanadium
mg/kg
EPA 6020B
Zinc
mg/kq
EPA 6010C
Prepared by: RBI Checked by: SRW/TCP/VTV
Notes•
1. Soil samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA Method 9045,
as noted above.
2. Soil samples collected from near ground surface (2 to 3ft) and from just above water table (field determined) in
each boring will also be analyzed for leaching potential using SPLP Extraction Method 1312 in conjunction with USEPA
Methods 6010/6020.
3. Analytical methods and reporting limits as presented were developed for CSA field implementation in 2015.
Analytical methods and reporting limits are updated periodically and applied as appropriate.
mg/kg - Milligrams per kilogram
S.U. - Standard Unit
Page 1 of 1

TABLE 4
PROPOSED SOIL SAMPLES AND MONITORING WELLS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Monitoring
Estimated Well
Soil Sample ID
Well ID
Depth
(Estimated Depth
Comments
(feet bgs)
Interval in feet bgs)
--
--
GYP-SB6 (2-3)
Near -surface unsaturated soil sample (water table —10 feet bgs)
--
--
Continue soil sampling at 5' intervals until the bottom of unconsolidated material is
GYP-SB6 (Various)
reached. (i.e., 7-8', 12-13', 17-18', etc.)
GYP-6S
20
GYP-SB6 (15-16)
Soil sample from shallow well screened interval
GYP-6D
40
GYP-SB6 (35-36)
Soil sample from deep well screened interval
Rock sample from bedrock well screened interval
GYP-6BR
90
GYP-SB6 (85-86)
--
--
GYP-SB7 (2-3)
GYP-SB7 (Various)
Near -surface unsaturated soil sample (water table —10 feet bgs)
--
--
Continue soil sampling at 5' intervals until the bottom of unconsolidated material is
reached. (i.e. , 7-8', 12-13', 17-18', etc.)
GYP-7S
20
GYP-SB7 (15-16)
Soil sample from shallow well screened interval
GYP-7D
40
GYP-SB7 (35-36)
Soil sample from deep well screened interval
GYP-713R
90
GYP-SB7 (85-86)
Rock sample from bedrock well screened interval
Prepared by: PWA Checked by: GRK
Notes:
Estimated well and soil sample depths based on data from the previously installed gypsum pad storage area wells.
Number of soil samples is approximate. A shallower water table will result in fewer samples, and a deeper water table will result in additional samples.
SynTerra recommends each well screen be submerged beneath the water table and have a length of at least 10 feet.
Not applicable
Approximately
bgs - below ground surface
Page 1 of 1

TABLE 5
GROUNDWATER ANALYTICAL METHODS
WORK PLAN FOR ADDITIONAL ASSESSMENT GYPSUM PAD STORAGE AREA
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS LLC, ROXBORO, NC
PARAMETER RL UNITS METHOD
FIELD PARAMETERS
H
NA
S.U.
Field Water Quality Meter
Specific Conductance
NAPS/Cm
Field Water Quality Meter
Temperature
NA
°C
Field Water Quality Meter
Dissolved Oxygen
NA
m /L
Field Water Quality Meter
Oxidation Reduction Potential
NA
mV
Field Water Quality Meter
Eh
NA
mV
Field Water Quality Meter
Turbidity
NA
NTU
Field Water Quality Meter
INORGANICS
Aluminum
0.005
m /L
EPA 200.7 or 6010D
Antimony
0.001
m /L
EPA 200.8 or 6020B
Arsenic
0.001
m /L
EPA 200.8 or 6020A
Barium
0.005
m /L
EPA 200.7 or 6010C
Beryllium
0.001
m /L
EPA 200.8 or 6020A
Boron
0.05
m /L
EPA 200.7 or 6010C
Cadmium
0.001
m /L
EPA 200.8 or 6020A
Chromium
0.001
m /L
EPA 200.8 or 6010C
Cobalt
0.001
m /L
EPA 200.8 or 6020A
Copper
0.001
m /L
EPA 200.8 or 6020B
Hexavalent Chromium
0.000025
m /L
EPA 218.7
Iron
0.01
m /L
EPA 200.7 or 6010C
Lead
0.001
m /L
EPA 200.8 or 6020A
Manganese
0.005
m /L
EPA 200.7 or 6010C
Mercury
0.000
m /L
EPA 245.1 or 7470A
Molybdenum
0.001
m /L
EPA 200.8 or 6020B
Nickel
0.001
m /L
EPA 200.8 or 6020B
Selenium
0.001
m /L
EPA 200.8 or 6020A
Strontium
0.005
m /L
EPA 200.7 or 6010C
Thallium low level
0.0002
m /L
EPA 200.8 or 6020A
Vanadium low level
0.0003
m /L
EPA 200.8 or 6020A
Zinc
0.005
m /L
EPA 200.7 or 6010C
RADIONUCLIDES
Radium 226
1
O/L
EPA 903.1 Modified
Radium 228
1
O/L
EPA 904.0/SW846 9320 Modified
Uranium 223, 234, 236, 238
Varies by Isotope
/mL
SW846 3010A/6020B
Total Uranium
NA
/mL
Calculated
ANIONS/CATIONS
Alkalinity as CaCO3
5
m /L
SM 2320B
Bicarbonate
5
m /L
SM 2320
Calcium
0.01
m /L
EPA 200.7
Carbonate
5
m /L
SM 2320
Chloride
0.1
m /L
EPA 300.0 or 9056A
Magnesium
0.005
m /L
EPA 200.7
Potassium
0.1
m /L
EPA 200.7
Sodium
0.05
m /L
EPA 200.7
Sulfate
0.1
m /L
EPA 300.0 or 9056A
Sulfide
0.1
m /L
SM4500S2-D
Total Dissolved Solids
25
m /L
SM 2540C
Total Organic Carbon
0.1
m /L
SM 5310C/EPA9060A
Total Suspended Solids
2.5
m L
SM 2450D
Prepared by: RBI Checked by: SRW/TCP
Notes:
1. Select constituents will be analyzed for total and dissolved concentrations.
2. Analytical methods and reporting limits as presented were developed for CSA field implementation in 2015. Analytical methods and reporting limits are updated
periodically and applied as appropriate.
OC - Degrees Celsius
pS/cm - micro -Siemens per centimeter
mg/L - Milligrams per liter
my - Millivolts
NA - Not analyzed
NTU - Nephelometric turbidity unit
pCi/L - picocuries per liter
RL - reporting limit
S.U. - Standard Unit
pg/mL - micrograms per milliliter
Page 1 of 1