Mayo - GW BTV Tech Memo_20171005

TECHNICAL MEMORANDUM
Date: August 4, 2017 File: 1026.105
To: Kimberlee Witt (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Jerry Wylie (SynTerra)
Subject: Background Threshold Va ues for Groundwater
Mayo Steam Electric Plant — Roxboro, NC
An updated background groundwater dataset was provided to the North Carolina Department
of Environmental Quality (NCDEQ) for Mayo Steam Electric Plant (Mayo) on May 26, 2017.
Additionally, the revised Statistical Methods for Developing Reference Background Concentrations for
Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR Engineering, Inc.
and SynTerra Corporation, May 2017) was provided to NCDEQ. On July 7, 2017, NCDEQ
provided a response letter (Zimmerman to Draovitch, July 7, 2017) for each Duke Energy coal
ash facility that identified soil and groundwater data appropriate for inclusion in the statistical
analysis to determine background threshold values (BTVs) for both media. As outlined in the
NCDEQ July 7, 2017 letter, Duke Energy is required to provide BTVs for both media within 30
days from receipt of the NCDEQ letter for facilities submitting Comprehensive Site
Assessments (CSAs) by October 31, 2017, and 60 days from receipt of the NCDEQ letter for all
other facilities. The background threshold values for soil are provided under separate cover.
The revised background groundwater dataset provided to NCDEQ on May 26, 2017 addressed
comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ
requested Duke Energy collect at least 10, rather than the previously planned eight, valid
samples from background monitoring wells prior to determination of BTVs for constituents
within each flow system. For groundwater datasets with less than 10 valid samples available
for determination of BTVs, no formal upper tolerance limit (UTL) statistics will be run and the
provisional BTV (PBTV) for a constituent and groundwater flow system will be computed to be
either:
y The highest value, or
,07 If the highest value is above an order of magnitude greater than the geometric mean
of all values, then the highest value should be considered an outlier and removed
from further use and the PBTV is computed to be the second highest value.
NCDEQ requested that the updated background groundwater dataset exclude data from the
background data set due to one or more of the following conditions:
P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH
MEMO \ Mayo \ Groundwater \ Mayo - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater August 4, 2017
Mayo Steam Electric Plant Page 2 of 3
h Sample pH is greater than or equal to 8.5 standard units (S.U.) unless the regional
DEQ office has deteremined an alternate background threshold pH for the site;
h Sample turbidity is greater than or equal to 10 Nephelometric Turbidity Units
(NTUs);
47 Result is a statistical outlier identified for background sample data collected through
second quarter 2017;
47 Sample collection occurred less than a minimum 60 days between sampling events;
and
h Non -detected results are greater than 2L/IMAC.
Additional site -specific requirements related to background groundwater dataset for Mayo
groundwater as outlined in the July 7, 2017 NCDEQ letter have been incorporated into the
groundwater background dataset.
This technical memorandum summarizes the revised background groundwater datasets and
statistically determined BTVs. Statistical determinations of BTVs were performed in accordance
with the revised Statistical Methods for Developing Reference Background Concentrations for
Groundwater and Soil at Coal Ash Facilities (statistical methods document) (HDR Engineering, Inc.
and SynTerra Corporation, May 2017).
GROUNDWATER BACKGROUND DATA
The current background monitoring well network consists of wells installed within three flow
zones — surficial, transition zone, and bedrock. Well locations are presented on Figure 1.
Background datasets provided to NCDEQ on May 26, 2017 were revised based on input from
NCDEQ in the July 7, 2017 letter. The revised background datasets for each flow system used to
statistically determine naturally occurring concentrations of inorganic constituents in
groundwater are provided in Table 1. The following sections summarize the refined
background datasets along with the results of the statistical evaluations for determining BTVs.
SURFICIAL
One well, MW-12S, monitors background groundwater quality within the surficial (saprolite)
flow zone. In the July 7, 2017 letter, NCDEQ retained MW-12S in the background dataset.
Eleven samples have been collected from MW-12S since June 2015. Samples collected less than
60 days between sampling events, statistical outliers, and invalid data have been omitted from
use in statistical determinations which has resulted in six valid samples for the surficial flow
zone. Additional samples will be collected from MW-12S to achieve the minimum requirement
of 10 valid samples to determine BTVs. The surficial flow zone background dataset is presented
in Table 1. PBTVs for constituents within the surficial flow zone were computed to be either
the maximum value, or, if the maximum value was above an order of magnitude greater than
the geometric mean of all values, the second highest value. PBTVs for the surficial flow system
P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH
MEMO \ Mayo \ Groundwater \ Mayo - GW BTV MEMO_FINAL.docx

Background Threshold Values for Groundwater August 4, 2017
Mayo Steam Electric Plant Page 3 of 3
are provided in Table 2. Additional analytical data will be submitted to the NCDEQ Regional
Office if received and processed in sufficient time for review prior to the preparation of the
updated CSA report.
TRANSITION ZONE
Two wells, BG-02 and MW-12D, monitor background groundwater quality within the transition
zone. NCDEQ indicated in the July 7, 2017 letter that these two transition zone background
wells were retained for use in development of BTVs. The transition zone background
groundwater dataset meets the minimum requirement of 10 samples for all constituents except
radionuclides (radium-226, radium-228, uranium-233, uranium-234, uranium-236, and
uranium-238). Table 1 presents the revised background dataset for the transition zone. PBTVs
for radionuclides were computed to be either the maximum value, or, if the maximum value
was above an order of magnitude greater than the geometric mean of all values, the second
highest value. BTVs were calculated for all remaining constituents monitored within the
transition zone using formal UTL statistics. PBTVs and BTVs for the transition zone are
presented in Table 2.
BEDROCK
Three wells - BG-01, MW-13BR, and MW-14BR - monitor background groundwater quality
within the fractured bedrock. In the July 7, 2017 letter, NCDEQ recommended that a fourth
well (MW-10BR) be removed from the background dataset. Additionally, NCDEQ identified
four samples collected from BG-01 and two samples collected from MW-13BR that were
collected less than 60 days between sampling events and are not appropriate for use in
statistical determinations. Prior to statistical determinations, the background bedrock dataset
was re -screened for outliers to adjust for the removal of MW-10BR from the dataset. A revised
background dataset including updated outliers is presented in Table 1. The background
bedrock dataset satisfies the minimum requirement of 10 samples to use formal UTL statistics to
derive BTVs for each constituent monitored within fractured bedrock. BTVs for fractured
bedrock are presented in Table 2.
LIST OF FIGURES
Figure 1- Background Groundwater Sample Locations - Mayo Steam Electric Plant
LIST OF TABLES
Table 1- Background Groundwater Results Through April 2017 - Mayo Steam Electric Plant
Table 2 - Groundwater Background Threshold Values - Mayo Steam Electric Plant
P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017 \ BTV TECH
MEMO \ Mayo \ Groundwater \ Mayo - GW BTV MEMO_FINAL.docx

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BACKGROUND GROUNDWATER
148 RIVER STREET, SUITE 220
GREENVILLE, SOUTH CAROLINA 29601
PHONE[phone]
SAMPLE LOCATIONS
MAYO STEAM ELECTRIC PLANT
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TABLE 1
BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameter
pH
Turbidity
Alkalinity
Aluminum
Antimony
Arsenic
Barium
Beryllium
Bicarbonate
Boron
Cadmium
Calcium
Carbonate
Chloride
Chromium (VI)
Chromium
Cobalt
Copper
Iron
Reporting Units
S.U.
NTUs
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
mg/L
ug/L
ug/L
mg/L
mg/L
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
15A NCAC 02L Standard
6.5-8.5
NE
NE
NE
1.
10
700
4*
NE
700
2
NE
NE
250
10
10
1*
1000
300
Sample ID
Sample
Collection Date
Field Parameters
Analytical Results
Surficial
MW-125
09/10/2015
5.8
6.31
13
98
<1
<1
19
<1
13
<50
<1
1.77
<10
3.1
---
3.23
1.02
<1
108
14W-125
5-7
6-9
42
464
<4
F4
4-6
<4
42
<50
<1
4,56
<-10
33
0-943
7-.4-7
-4
�4
346
MW-12S
01/07/2016
5.8
9.89
11.1
220
<1
<1
11
<1
11.1
<50
<1
1.96
<5
3.1
0.038
1.43
<1
<1
178
MW-12S
04/06/2016
5.8
7.42
10.2
566
<1
<1
12
<1
10.2
<50
<1
1.19
<5
3.3
0.058
<1
<1
<1
338
MW-12S
07/11/2016
4.9
9.82
12.8
392
<1
<1
13
<1
12.8
<50
<1
2.89
15
2.9
0.045
<1
<1
1.9
385
P4W-i-25
r.S
9,24
9i
284
-4
<1
4-2
�4
gi
-.50
<1
4si6
<i
3-2
04.6
�4
F4
�4
24G
MW-125
11/04/2016
5.6
9.12
9.2
200
<1
<1
11
<1
9.2
<50
<1
1.14 B1
<5
3.1
0.088
<1
<1
1.08
245
A4W-i-25
63
9: }7
4-3
324
<1
<1
8
�4
13
<-50
�4
2-1-2
�-5
2-2
0-.%
-�4
--4
2:22
327
MW-12S
02/01/2017
6.5
8.53
361
<1
i:79
11
<1
ts,a
<50
11
7-.B7-B2
<5
1.61
1 -
9,46
1 3240
Transition Zone
__
___
___
<0.5
<5
67.7
---
---
<50
<0.08
---
---
32.9
---
7.5
--
<5
312
---
<5
---
<5
152
<0.5
<5
53.4
---
---
<50
<0.08
---
---
35.3
---
5.9
--
<5
460
--
<5
759
BG-02
04/10/2013
6.3
8.5
---
226
<1
<1
66
---
---
<50
<1
---
---
28
---
<5
<5
646
---
<50
<1
---
---
30
---
<5
---
<5
1130
BG-02
11/13/2013
6.4
9.5
---
384
<1
<1
62
---
---
<50
<1
---
---
29
---
<5
<5
841
---
<50
<1
---
---
28
---
<5
---
<5
943
BG-02
07/18/2014
6.4
7.71
---
355
<1
<1
65
---
---
<50
<1
---
---
30
---
<5
<5
1010
-
---
233
<1
<1
61
---
---
<50
<1
---
---
30
---
<5
---
<5
647
BG-02
04/13/2015
6.3
7.09
259
136
<1
<1
54
<1
259
<50
<1
57
<5
28
---
<5
<1
<5
435
BG-02
07/07/2015
6.5
8.51
225
193
<1
<1
54
<1
225
<50
<1
56.1
15
30
---
<5
<1
<5
467
BG-02
9/11/2015
6.4
6.88
220
82
<1
<1
50
<1
220
<50
<1
50.6
<10
32
-58
4.05
<1
<1
244
8G-92
12,109120156+i
S24
257-14
H00
60
10-2
257
KB
F0.88
<-5
29,7
<6.03
<B,SB
11
450
BG-02
01/08/2016
6.4
1.98
263
80
<1
<1
58
<1
263
<50
<1
57.3
<5
33
<0.03
<1
<1
1.21
471
BG-02
04/04/2016
6.4
2.71
303
65
<1
<1
65
<1
303
<50
<1
59.2
<5
30
<0.03
<5
<1
<5
585
BG-02
07/13/2016
6.2
3.4
302
58
<1
<1
59
<1
302
<50
<1
59.9
<5
30
<0.03
<5
<1
<5
484
66-102
6
2A
257
451
F4
<4
59
F4
257
<56
E4
S"
<5
33
<&.03
F4
F4
<4
553
BG-02
11/02/2016
6.3
5.07
240
59
<1
<1
48
<1
240
<50
<1
51.3
<5
34
<0.03
<1
<1
<1
213
BG-02
01/30/2017
6.6
9.68
228
82
<1
<1
43
<1
228
<50
<1
50 B2
<5
33
0.055
<1
<1
<1
184
MW-12D
06/24/2015
6.2
4.02
53
184
1.63
<1
26
<1
53
<50
<1
12.6
<10
4
---
<1
437
<1
326
MW-12D
09/10/2015
6.2
3.88
57
220
<1
<1
20
<1
57
<50
<1
11.7
<10
4.1
---
1.1
<i
<1
277
MW-12Lo
64
8,08
533
450
<65
<8.5
20
<-92
53-2
F50
0,099
44.5
<-5
3.7
0-64-P41
46
G,51
F4
280
MW-12D
01/07/2016
6.1
9.26
13.1
678
<1
<1
22
<1
13.1
<10
<1
11.1
<5
4.5
0.12 Ml
2.91
<1
1.14
968
MW-12D
04/05/2016
5.9
9.9
55.1
370
<1
<1
21
<1
55.1
<50
<1
11.4
<5
4.5
0.6
1.64
<1
<1
385
MW-12D
07/11/2016
5.7
9.35
56.3
155
<1
<1
17
<1
56.3
<50
<1
11.5
<5
4.4
0.73
1.19
<1
<1
223
M,.-12D
63
9.2
5-3.5
254
<-1
�4
46
<1
MW-12D
11/04/2016
6.3
9.09
55
272
<3
<1
16
<1
55
<50
<1
10.6 Bl
<5
4
0.64
1.92
<3
<S
405
,-..--ao
6.4
&.42
54-.9
415
<4
F4
44
<1
54A
<3B
<1
4B3$2
<3
3.8
B�9
439
«
«
243
MW-12D
03/28/2017
5.9
5.7
54.3
140
<1
<1
15
<1
54.3
<50
<1
12.1
<5
4.3
0.63
1.25
<1
1.24
242
P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\TM Tables\Table 1 Page 1 of 4

TABLE 1
BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameter
Lead
Magnesium
Manganese
Mercury
Methane
Molybdenum
Nickel
Nitrate + Nitrite
Potassium
Selenium
Sodium
Strontium
Sulfate
Sulfide
TDS
Thallium
TOC
Vanadium
Zinc
Radium (Total)
Uranium (Total)
Reporting Units
ug/L
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
mg-N/L
mg/L
ug/L
mg/L
ug/L
mg/L
mg/L
mg/L
ug/L
mg/L
ug/L
ug/L
pCi/L
ug/mL
ISA NCAC 02L Standard
15
NE
50
1
NE
NE
100
NE
NE
20
NE
NE
250
NE
500
0.2-
NE
0.3-
1000
NE
NE
Sample ID
Sample
Collection Date
Analytical Results
Saprolite
MW-12S
09/10/2015
<1
0.723
253
<0.05
12
<1
2.98
0.7
1.53
<1
5.43
23
1.4
<0.1
55
<0.2
0.633
<0.3
64
---
---
MW--f
":- - t"2915
�4
4.792
4sz!
<0.05
F1B
F4
5.41.
Q-Am
-1.4
F4
5,48
21
1.3
�41
26
<8.2
0.519
0.313
79
MW-12S
01/07/2016
<i
0.753
68
<0.05
<10
<1
1.6
0.599
1.58
<1
4.76
18
1.4
<01
35
<0.2
1.6
<0.3
157
---
---
MW-12S
04/06/2016
<1
0.749
24
<0.05
<10
<1
<1
0.798
1.22
<1
5.49
17
1.2
<0.1
29
<0.2
0.522
0.408
43
3.537
0.000367
MW-12S
07/11/2016
<i
0.694
34
<0.05
'10
<1
1.16
0.566
1.89
<1
4.34
21
1.6
<0.1
43
<0.2
2
0.974
227
2
0.00035
MWc-12S
-�F
9.fi4
14
<0.05
-.48
�4
-4
&756
4:.36
-�4
478
16
i:1
-.0.1
52
F8-2
4463
0-411
-140
2.56
0-00035
MW-125
11/04/2016
<S
0.661 el
19
<0.05
'10
<1
1.19
0.739
1.35
<1
4.85 B2
16
0.89
<0.1
52
<0.2
0.53
0.593
73
2
0.00035
MW-
-4
"-'Z
22
10.05
<A-+4s
493
4-22
4.41-9
233
F4
4-46
44
23
�4
57
<-9-2
3i
4.698
64- 2
4i4
&-9�8
MW-125
02/01/2017
244
211
<0.05
36-N-2
3.15
3.03
<0.01
3.78
<1
25
1.6
<0.1
85
10.2 B5
i4
90
2
0.000262
Transition Zone
<10
---
---
7.2 B
---
367 B
<0.1
---
---
<30
BG-02
11 03 2011
<5
---
36.7
<0.2
---
---
5.2
---
---
<10
---
---
6.9
---
341
<0.1
---
---
<10
BG-02
04/04/2012
<5
---
27
<0.2
---
<5
---
---
<10
---
---
7.5
---
412
<0.1
---
---
<10
BG-02
07/09/2012
<5
---
54.9
<0.2
---
---
<5
---
---
<10
---
---
7.7
---
382
<0.1
---
---
<10
BG-02
11/05/2012
<5
---
43.7
<0.2
---
<5
---
---
<10
---
---
8.3
---
389
<0.1
---
---
'10
BG-02
04/10/2013
<1
---
111
0.18
---
---
15
---
---
<1
---
---
5.4
---
430
<0.2
---
---
<5
---
<5
<1
---
---
5.2
---
430
<0.2
---
---
<5
BG-02
11/13/2013
<1
---
177
0.11
---
---
<5
---
---
<1
---
---
5.2
---
360
<0.2
---
---
<5
BG-02
04/01/2014
<1
---
226
0.06
---
---
<5
<1
---
---
4.8
---
450
BG-02
07/18/2014
<1
---
244
0.08
---
---
<5
---
---
<1
---
---
4.9
---
400
<0.2
---
---
5
BG-02
11/12/2014
<1
---
180
<0.05
---
<5
---
---
<1
---
---
5
---
370
<0.2
- -
---
8
BG-02
04 13 2015
<I
11.8
150
0.06
---
<1
<5
---
3.27
<1
49.7
---
4.8
---
380
<0.2
---
--
11
BG-02
07/07/2015
<1
12
135
<0.05
---
<1
<5
---
3.61
<1
48.2
---
5.1
---
370
<0.2
---
5.88
15
BG-02
9/11/2015
<1
10.6
130
<0.05
400
<1
2.87
0.019
3.56
<1
44.6
291
5.4
<0.1
330
<0.2
1.4
4
23
SG-D2
4
42.3
200
<0.2
660
0:74
0-.82
<-&.&2
K
- 0,5
54-.3
390
34
-.04
344
- 0.4
4:4
S:8
1-2
BG-02
01/08/2016
<3
12.6
196
<0.05
477
<1
<I
<0.01
3.4
<1
50.6
350
5.5
<0.1
370
<0.2
1.3
4.2
<5
BG-02
04/04/2016
<1
13.9
237
<0.05
1130
<1
<5
---
3.34
<1
56
391
4.9
<0.1
360
<0.2
1.8
5
<5
7.07
0.00117
BG-02
07/13/2016
<1
13.5
207
<0.05
2260
<1
<5
<0.01
3.23
<1
53.3
374
4.9
<0.1
370
<0.2
1.6
4.79
<5
7.52
0.001068
BG-02
E1
434
494
---0:05
1670
-.4
`4
<0.&1
3,34
<4,
S'.
378
S6
- 0.4
370
47 6
5,34
K
4.994
0�BB944
BG-02
11/02/2016
<1
10.8
131
<0.05
1120 N2
<1
<1
0.02
3.48
<1
45.3
320
5.6
<0.1
330 Hl
<0.2
1.4
3.63
<5
3.36
0.001005
BG-02
01/30/2017
<1
10.6
104
<0.05
801 N2
<1
<3
<0.01
3.48
<1
44 62
287
5.6
<0.1
320
<0.2
1.4
4.14 62
<5
2
0.001076
MW-12D
06/24/2015
<3
3.44
683
<0.05
<10
1-7i
2.5
0.08
1.6
<1
8.98
95
0.96
<0.1
120
<0.2
0.396
0.719
<5
MW-12D
09/10/2015
<1
3.04
218
<0.05
<10
<1
1.35
07664
1.41
<1
9.03
85
0.99
<0.1
100
<0.2
1.7
0.637
9
Mw-:4P
E44
3-24
460
<8.2
F40
0.8
34
04-5
<-5
<-B.5
956
85
-4
<04
422
�1
F4
F4
<-18
MW-12D
01/07/2016
<1
3.28
131
<0.05
<10
<1
2.23
0.139
1.39
<1
8.76
87
1.1
<0.1
82
<0.2
0.184
1.65
5
MW-12D
04/05/2016
<1
3.27
100
<0.05
<10
<1
1.49
0.146
1.42
<1
9.35
92
1.1
<0.1
120
<0.2
0.314
1.06
<5
9
0.000383
MW-12D
07/11/2016
<i
3.16
81
<0.05
17.9
<1
1.23
0.176
1.36
<1
9.26
88
1.1
<0.1
98
<0.2
0.276
0.898
6
3.62
0.0002419
MW-429
-�4
3$2
64
.4-05
4 -.4
E4
2.02
048
4,34
<4
9-05
83
14
<-9.4
400
F0-2
0-289
4-43
5
349
0-.000255
MW-12D
11/04/2016
<1
2.97 Bl
56
<0.05
28.5 N2
<1
1.37
0.166
1.37
<1
8.39 B2
85
1.1
<0.1
110
<0.2
0.171
1.25
<5
1.659
0.000318
M --a9
E-4
26
96
<-0-05
74-N2
F4
1 1..62
0-19
4-22
<4
838-132
83
4
<-0-4
440
<9:2-BS
0?66
0474
K143�
0�00296
MW-121)
03/28/2017
<1
3.2
45
<0.05
<10
<1
1.29
0.19
1.41
<1
9.26
85
1.1
<0.1
10.2
96
0.192 B3
0.805
<5
1.68
0.000273
P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\TM Tables\Table 1 Page 2 of 4

TABLE 1
BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameter
pH
Turbidity
Alkalinity
Aluminum
Antimony
Arsenic
Barium
Beryllium
Bicarbonate
Boron
Cadmium
Calcium
Carbonate
Chloride
Chromium (VI)
Chromium
Cobalt
Copper
Iron
Reporting Units
S.U.
NTUs
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
mg/L
ug/L
ug/L
mg/L
mg/L
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
15A NCAC 02L Standard
6.5-8.5
NE
NE
NE
1*
10
700
4*
NE
700
2
NE
NE
250
10
SO
1*
1000
300
Sample ID
Sample
Collection Date
Field Parameters
Analytical Results
Bedrock
BG-01
11/3/2011
5.5
3.84
-
216
<0.5
c5
95.4
-
-
<50
0.2
-
-
13.1
-
7.9
-
<5
261
BG-01
04/04/2012
5.6
9.52
-
191
<0.5
<5
93
-
-
<50
0.12
-
-
14.3
-
6.7
-
<5
388
BG-01
07/09/2012
5.3
9.32
-
478
<0.5
<5
101
-
-
<50
0.13
-
-
14.6
-
20
-
<5
640
BG-01
11/05/2012
5.4
9.45
-
465
<0.5
<5
101
-
-
<50
0.089
-
-
13.4
-
<5
-
<5
526
BG-01
04/10/2013
5.2
9.05
-
202
<1
<1
97
-
-
<50
<1
-
-
13
-
7
-
<5
323
BG-01
07/09/2013
5.4
8.95
-
383
<1
<1
97
-
-
<50
<1
-
-
13
-
<5
-
<5
488
BG-01
11/13/2013
5.5
8.2
-
339
<1
<1
95
-
-
<50
<1
-
-
12
-
<5
-
<5
412
BG-01
04/01/2014
5.4
8.2
-
202
<1
<1
90
-
-
<50
<1
-
-
12
-
<5
-
<5
290
BG-01
07/18/2014
5.5
6.68
-
245
<1
<1
93
-
-
<50
<1
-
-
12
-
<5
-
<5
325
BG-01
11/12/2014
5.5
9.96
-
332
<1
<1
95
-
-
<50
<1
-
-
12
-
<5
-
<5
466
BG-01
04/13/2015
5.5
6.9
49.8
392
<1
<1
90
<1
49.8
<50
<1
12.5
<5
11
-
<5
<1
<5
409
BG-01
07/07/2015
5.6
10
4B.3
418
<3
<1
97
<1
48.3
<50
<1
13.1
<5
11
-
<5
<1
<5
557
BG-01
09/10/2015
5.3
7.83
54
276
<1
<1
91
<1
54
<50
<1
12.8
<10
11
-
<1
<1
<1
300
BG--91
6:9
449
52-1
33
F}
E4
99
<1
52-1
FSg
<4
12:8-B2
<-5
42
-
<5
F4
<-5
45
BG-94
S.i
9i
528
259
<-49.5
<g5
94
<0.2
523
FSG
6,473
i-r6
<-5
404
0-31
1
E65
E}
350
BG-01
O1/08/2016
5.1
5.78
51.1
227
<1
<1
87
<1
51.1
<50
<1
12.6
<5
12
0.2
<1
<1
<1
272
BG-01
04/04/2016
5.5
4.3
53
177
<1
<1
88
<1
53
<50
<1
12.1
<5
11
0.19 M1
<5
<1
<5
190
BG-01
07/13/2016
5.0
3.84
53.1
66
<1
<1
86
<1
53.1
<50
<1
12.3
<5
12
0.23
<5
<1
<5
89
BG-04
5.6
9.49
529
275
«
F}
99
<1
529
<39
<1
4-2
<6
44
&3
E4
-4
-�1
336
BG-01
11/02/2016
5.5
2.98
52.8
48
<3
<1
90
<1
52.8
<50
<1
12.4
<5
11
0.23
<1
<1
<1
50
BG 04
136
4.37
52:8
234
<1
F4
87
<1
528
F59
<1
4.-2
<-5
975
0-29
F4
F4
i-.32
290
BG-01
03/28/2017
5.4
0.47
53
218
<1
<1
B7
<1
53
<50
<1
12.9
<5
11
0.25
<1
<1
<1
137
MW-13BR
06/23/2015
7.2
2.22
210
37
<1
<1
40
<1
210
<50
<1
75.2
<10
46
-
<1
1.19
<1
1130
MW-13BR
09/08/2015
6.9
7.55
230
143 B1
<1
<1
51
<1
230
<50
<1
73
<10
43
-
<1
<1
<1
2400
rnr-mrt
-7.0
6.5
2479
i-74
<4
F4
45
.4
2449
FSB
F}
42.7
<-}9
447
- g,@3
416 3
<-}
4-.2
249G
MW-13BR
O1/07/2016
7.3
7.79
223 M1
230
<3
<1
42
<1
223
<50
<1
73.3
<5
45
<0.03
7.65
<1
<1
2550
MW-13BR
04/05/2016
7.1
9.05
217
97
<1
<1
35
<1
217
<50
<1
70.8
<5
43
<0.03
<1
1.01
<1
1750
MW-13BR
07/11/2016
7.0
8.8
211
407
<1
<1
29
<1
211
<50
<1
70.2
<5
40
<0.03
4.51
4.92
1.95
1330
Mart
F4
4767
1 2 -6
434
<1
F4
38
F4
216
E50
�4
69-7
<-5
38
<9.&3
2.G2
1.17
.4
2529
MW-13BR
11/08/2016
6.9
9.9
221
102
<1
<1
35
<1
221
<50
<1
67
<5
37
0.18
3.58
2,92
<1
2430
MA-4-38R
1-9
9-13
233
91
<i
F4
31
F4
243
<30
<4
65
<3
34
0-26
27
2-.91
-�1
2928
MW-14BR
03/12/2015
6.7
35
96
589
<1
<1
30
<1
96
<50
<1
19.5
<10
9.3
-
<1
1.41
4.5
907
MW-14BR
09/09/2015
6.9
3.36
160
61
<1
1.8
42
<1
160
65
<1
20.2
<10
11
-
<1
1.09
<1
2730
MW-449R
14
2.37
380
74
<1
-4
22
-4
4949
KO
E4
43:4
<-1B
44
1-9,93
E4
F4
E4
3g6
MW-14BR
O1/07/2016
6.7
2.45
94.8
163
<1
<1
17
<1
94.8
<50
<1
13
<5
13
<0.03
<1
<1
1.21
96
MW-14BR
04/05/2016
6.7
2.45
104
225
<1
<1
19
<1
104
<50
<1
13
<5
13
<0.03
<1
<1
1.87
89
MW-14BR
07/11/2016
6.7
1.34
130
58
<1
<1
22
<1
130
<50
<1
14.4
<5
13
<0.03
<1
<1
1.58
37
MW-44BR
6.7
5.69
439
59
<1
�4
26
�4
130
<-5g
<1
<i
14
8&3
<4
<1
4.43
56
MW-14BR
11/08/2016
7.0
3.74
136
129
<1
<1
28
<1
136
<50
<1
16.2
<5
13
<0.025
<1
1.14
1.97
172
MW-14BR
02/02/2017
6.7
1.14
121
63
<1
<1
19
<1
121
<50
<1
28.9
<5
13
0.067
<1
<1
1.36
37
Prepared by: LyV D Checked by:
Notes;
54
- Indicates value omitted from dataset
Indicates Parameter not measured or analyzed.
- Indicates data removed /identifed as an outlier.
- Indicates data removed due to autocorrelation.
mg - N/L - Milligrams nitrogen per liter pCi/L - picocuries per liter
mg/L - Milligrams per liter S.U. - Standard Unit
NE - Not established ug/L - Micrograms per liter
NTU - Nephelometric turbidity unit ug/mL - micrograms per milliliter
< - concentration not detected at or above the reporting limit.
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013.
B1 - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample was greater than 1OX the concentration in the method blank. Analyte concentration in sample is not affected by blank contamination.
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.
B5 - Target analyte was present in blank(s) above the method detection limit but less than the reporting limit. Data is valid for compliance purposes.
HS - Results are from sample aliquot taken from VOA vial with headspace (air bubble greater than 6 mm diameter).
P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\TM Tables\Table 1 Page 3 of 4

TABLE 1
BACKGROUND GROUNDWATER RESULTS THROUGH APRIL 2017
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Analytical Parameter
Lead
Magnesium
Manganese
Mercury
Methane
Molybdenum
Nickel
Nitrate + Nitrite
Potassium
Selenium
Sodium
Strontium
Sulfate
Sulfide
TDS
Thallium
TOC
Vanadium
Zinc
Radium (Total)
Uranium (Total)
Reporting Units
ug/L
mg/L
ug/L
ug/L
ug/L
ug/L
ug/L
mg-N/L
mg/L
ug/L
mg/L
ug/L
mg/L
mg/L
mg/L
ug/L
mg/L
ug/L
ug/L
pCi/L
ug/mL
15A NCAC 02L Standard
1s
NE
50
1
NE
NE
SOO
NE
NE
20
NE
NE
250
NE
Soo
0.2*
NE
0.3-
1000
NE
NE
Sample ID
Sample
Collection Date
Analytical Results
Bedrock
BG-01
11/03/2011
<5
-
6.9
<0.2
-
-
6.2
-
-
<10
--
-
<5
-
106
<0.1
-
-
<10
-
-
BG-01
04/04/2012
<5
-
11.6
<0.2
-
-
<5
-
-
<10
-
-
<5
-
107
<0.1
-
-
<10
-
---
BG-01
07/09/2012
<5
-
21.6
<0.2
-
-
9.4
-
-
<10
-
-
2
-
128
<0.1
-
-
<10
-
-
BG-01
11/05/2012
<5
-
55.6
<0.2
-
-
<5
-
-
<10
-
-
<2
-
123
<0.1
-
-
11.6
-
--
BG-01
04/10/2013
<1
-
15
<0.05
-
-
<5
-
-
<1
-
-
0.44
-
130
<0.2
-
-
7
-
-
BG-01
07/09/2013
<1
-
48
<0.05
-
-
<5
-
-
<1
-
-
0.52
-
130
<0.2
-
-
12
-
---
BG-01
11/13/2013
<1
-
27
<0.05
-
-
<5
-
-
<1
-
-
0.51
-
130
<0.2
-
-
30
-
-
BG-01
04/01/2014
<1
-
14
<0.05
-
-
<5
-
-
<1
-
-
0.4
-
140
<0.2
-
-
29
-
--
BG-01
07/18/2014
<1
-
15
<0.05
-
-
<5
-
-
<1
-
-
0.46
-
140
<0.2
-
-
16
-
-
BG-01
11/12/2014
<1
-
25
<0.05
-
-
<5
-
-
<1
-
-
0.51
-
120
<0.2
-
-
34
-
---
BG-01
04/13/2015
<1
3.35
35
<0.05
-
<1
<5
-
1.4
<1
12.4
-
0.32
-
130
<0.2
-
-
29
-
-
BG-01
07/07/2015
<1
3.63
23
<0.05
-
<1
<5
-
1.5
<1
11.8
-
0.32
-
130
<0.2
-
4.94
50
-
--
BG-01
09/10/2015
<1
3.41
26
<0.05
16
<1
1.78
0.645
1.38
<1
11.6
172
0.37
<0.1
120
<0.2
0.913
3.93
17
-
-
SG- 1
1- 33r2015
-4
3-18
7
E8-BS
F4
F5
___
4-5
�1
}4-.882
449
G-.
-
44-0
E42
___
34
.5
BG-Pl
G-4-3
3-28
18
2
HG
<-9-5
1:9
0=66
.5
F9,5
42-.2
189
<.1
<-4.1
118
<-G-1
1
43
14
BG-01
01/08/2016
<1
3.36
11
<0.05
<10
<1
1.24
0.643
1.39
<1
11.9
166
0.24
<0A
130
<0.2
0.558
3.94
<5
-
-
BG-01
04/04/2016
<1
3.2
12
<0.05
<10
<1
<5
-
1.36
<1
11.5
167
0.25
<0.1
130
<0.2
0.738
3.94
7
5.25
0.00035
BG-01
07/13/2016
<1
3.09
7
<0.05
<10
<1
<5
0.827
1.28
<1
11.9
177
0.23
<0.1
140
<0.2
0.723
3.58
<5
2.29
0.00035
BG-947
^^��6
-�1
3-21
43
<8.85
HG
F4
1-46
0>828
4-.32
<4
44-4
472
G32
�1
4730
<0-2
14-667
4i9
26
3.876
G-GBG35
BG-01
11/02/2016
<1
3.18
8
<0.05
<10 N2
<1
1.82
0.811
1.31
<1
11.4
183
0.26
<0.1
110 H1
<0.2
0.565
3.82
<5
6.24
0.00035
86-41
F4
3.49
13
<4.9.5
F10N2
E4
1-6
G-4G9
4-:33
F4
1i3
474
G-26
<-G.-i
449
<8.2
G3493
4�..485
<5
2
B�GG35
BG-01
03/28/2017
<1
3.28
10
<0.05
<10
<1
1.41
0.834
1.38
<1
12.5
173
0.25
<0.1
120
<0.2
0.64 B3
4
<5
2.862
0.00035
MW-13BR
06/23/2015
<1
13.1
474
<0.05
<10
8.28
<1
<0.01
5.49
<1
25.7
418
18
G fS
370
<0.2
0.9
0.361
36
4.22
0.00035
MW-13BR
09/08/2015
<1
12.9
630
<0.05
<10
5.17
<3
<0.01 M2
5.31
<1
24.8
430
12
<0A
360
0,§38
0.859
0.465
99
-
--
*W-z-..ort
�4
4-3.5
548
<-G.95
<-}0
5-46
7-9-7
--G-G-1
5-49
�4
233
416
14
�2
330
-18:2
&761
G.429
54
MW-13BR
01/07/2016
<3
12.9
519
<0.05
25:9
5.81
4.98
<0.01
5.12
<1
23.7
389
15
<0.1
330
<0.2
0.647
<0.3
37
-
---
MW-13BR
04/05/2016
<1
12.9
481
<0.05
27
4.3
<3
<0.01
4.72
<1
20.8
393
17
<0.1
340
<0.2
0.733
<0.3
9
5.65
0.00644
MW-13BR
07/11/2016
<1
13
348
<0.05
543
3.2
2.82
<0.01
4.72
<1
19.4
380
18
<0.1
330
<0.2
0.594
0.871
23
3.103
4:00203
-art
�4
32-.7
432
<8.65
135
2.98
448
<B-Gk
4i8
�4
484
381
36
<-G4
330
<9-2-B2
G{45
.9-.3
38
68-.2
0.000601
MW-13BR
11/08/2016
<3
12.3
471
<0.05
993-N2
2.85
2.26
<0.01
4.46
<1
17.3
374
15
<0.1
310
<0.2
0.574
0.38
6
1.392
0.000569
-art
-�1
42
421
<8.85
55-42
2-5
4.39
F8-&1
443
<4
36n8
353
43
194
320
0,458
G.4G6
<3
2-.141
B�GB617
MW-14BR
03/12/2015
<1
2.96
544
<0.05
<10
14
<3
0.039
4.08
<1
33
149
12
H
190
<0.2
1.3
1.29
10
-
-
MW-14BR
09/09/2015
<1
3.07
648
<0.05
13
27.3
<1
0.011 M2
6.56
<1
60.2
167
27
<0.1
260
<0.2
1.3
0.469
<5
-
-
MW-i481t
-4
249
3G4
EBBS
<49
6:62
F4
G312
5.75
F4
413
141
19
-.494
24-9
E42
4E22
4-82
.5
MW-14BR
01/07/2016
<1
2.36
199
<0.05
<10
4.56
<3
0.384
4.49
<1
37.4
131
10
<0.1
ISO
<0.2
0.855
2.45
<5
-
-
MW-14BR
04/05/2016
<1
2.36
196
<0.05
<10
5.06
<3
0.346
4.06
<1
38.4
134
9.9
<0A
200
<0.2
0.873
2.86
<5
3.999
0.000391
MW-14BR
07/11/2016
<1
2.51
247
<0.05
<10
8.07
<1
0.157
5.18
<1
47.9
140
11
<0.1
200
<0.2
0.84
2.48
11
1.947
0.000606
MW-34BR
E4
2s17
322
8-Gs
<10
9 17
F4
G4.91
7-.+3
E1
468
12
-.49-.1
230
�2
G.4387
2-.07
7
3
448g464
MW-14BR
11/08/2016
<1
2.64
385
<0.05
12�2-N2
10.7
<3
0.187
6.78
<1
49.9
158
9.6
<0.1
220
<0.2
0.785
1.56
6
2.07
0.000539
MW-14BR
02/02/2017
<3
13.1
96
<0.05
<10 N2
5.04
<3
0.291
4.04
<1
38.4
150
8.6
<0A
200
<0.2
0.832
2.07
<5
2
0.00.355
Prepared by: LWD Checked by:
Notes:
54 - Indicates value omitted from dataset.
Indicates parameter not measured or analyzed.
Indicates data removed /identified as an outlier.
- Indicates data removed due to autocorrelation.
mg - N/L - Milligrams nitrogen per liter pCi/L - picocuries per liter
mg/L - Milligrams per liter S.U. - Standard Unit
NE - Not established ug/L - Micrograms per liter
NTU - Nephelometric turbidity unit ug/ml- - micrograms per milliliter
< - concentration not detected at or above the reporting limit.
* - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013.
Bl - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample was greater than 1OX the concentration in the method blank. Analyte concentration in sample is not affected by blank contamination.
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.
B5 - Target analyte was present in blank(s) above the method detection limit but less than the reporting limit. Data is valid for compliance purposes.
HS - Results are from sample aliquot taken from VOA vial with headspace (air bubble greater than 6 mm diameter).
P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\TM Tables\Table 1 Page 4 of 4

TABLE 2
GROUNDWATER BACKGROUND THRESHOLD VALUES
MAYO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ROXBORO, NC
Parameter
Reporting Unit
NCAC 02L Standard
Background Threshold Values
Surficialt
Transition Zone
Bedrock
pH*
S.U.
6.5-8.5
4.9 - 6.5
5.7 - 6.6
5.0 - 7.3
Alkalinity
mg/L
NE
13
302
223
Aluminum
pg/L
NE
566
489
551
Antimony
pg/L
1A
ND
ND
ND
Arsenic
pg/L
10
ND
ND
ND
Barium
pg/L
700
19
62
97
Beryllium
Ng/L
4A
ND
ND
ND
Bicarbonate
mg/L
NE
13
302
223
Boron
pg/L
700
ND
ND
ND
Cadmium
pg/L
2
ND
ND
1
Calcium
mg/L
NE
3
59
73
Carbonate
mg/L
NE
ND
ND
ND
Chloride
mg/L
250
3
33
43
Chromium (VI)
pg/L
10
0.1
1
0.3
Chromium
Ng/L
10
3
6
7
Cobalt
Ng/L
1A
1
ND
1
Copper
Ng/L
1000
2
ND
5
Iron
Ng/L
300
385
1301
3359
Lead
pg/L
15
ND
ND
ND
Magnesium
mg/L
NE
0.8
14
13
Manganese
Ng/L
50
253
297
544
Mercury
pg/L
1
ND
0.2
ND
Methane
Ng/L
NE
12
2238
ND
Molybdenum
pg/L
NE
3
ND
13
Nickel
Ng/L
100
3
5
5
Nitrate + Nitrite
mg-N/L
NE
0.8
0.3
1
Potassium
mg/L
NE
4
4
7
Selenium
pg/L
20
ND
ND
ND
Sodium
mg/L
NE
5
53
61
Strontium
pg/L
NE
25
391
418
Sulfate
mg/L
250
2
8
18
Sulfide
mg/L
NE
ND
ND
ND
TDS
mg/L
500
85
430
340
Thallium
pg/L
0.2A
ND
ND
ND
TOC
mg/L
NE
2
2
1
Vanadium
Ng/L
0.3A
1
6
6
Zinc
pg/L
1000
227
11
42
Radium (Total)
pCi/L
NE
4
9t
8
Uranium (Total)
Ng/mL
NE
0.0004
0.001t
0.006
Prepared by: JHG / LWD Checked by: JAW / RKD
Notes:
Surticial (Saprolite) background wells: MW-12S
Transition Zone background wells: BG-2 and MW-12D
Bedrock background wells: BG-1, MW-13BR, and MW-14BR
t - Indicates value is provisional; dataset contains less than 10 valid samples
TDS - Total Dissolved Solids
Radium (Total) - Radium-226 and Radium-228 combined
Uranium (Total) - Uranium-233, Uranium-234, Uranium-236, and Uranium-238 combined
S.U. - Standard Unit
pg/L - micrograms per liter
mg/L - milligrams per liter
pCi/L - picocuries per liter
pg/mL - micrograms per milliliter
* - Upper and lower tolerance limits calculated for parameter
A - Interim Maximum Allowable Concentrations (IMACs) of 15A NCAC .02L Standard, Appendix 1, April 1, 2013
ND - Not Detected
NE - Not Established
P:\Duke Energy Progress. 1026\Statistics_CAMA\Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Mayo\Groundwater\TM Tables\TABLE 2 - Mayo GW BG
Threshold Values Page 1 of 1