Roxboro - BTV Soil Tech Memo_FINAL_20170804

TECHNICAL MEMORANDUM
Date: August 4, 2017 File: 1026.107
To: Kimberlee Witt (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Craig Eady (SynTerra) CL -
Subject: Background Threshold Values for Soil
Roxboro Steam Electric Plant — Semora, NC
An updated background soil dataset was provided to the North Carolina Department of
Environmental Quality (NCDEQ) for the Roxboro Steam Electric Plant (Roxboro) 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 groundwater are provided under
separate cover.
The updated background soil datasets provided to NCDEQ on May 26, 2017 incorporated
comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ
requested that Duke Energy collect a minimum of 10, rather than the previously planned eight,
valid background soil samples prior to the determination of BTVs for each constituent. For soil
datasets with less than ten valid samples available for BTV determination, no formal upper
tolerance limit (UTL) statistics will be run and the provisional BTV (PBTV) for a constituent will
be computed to be either:
'47 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.
P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ Roxboro \ Soil \ Roxboro - BTV Soil TM_FINAL.docx

Background Threshold Values- Soil August 4, 2017
Roxboro Steam Electric Plant Page 2 of 3
Soil samples meeting the following criteria are considered valid for use in statistical
determinations of BTVs:
47 Sample was collected from a location that is not impacted by coal combustion
residuals or coal associated materials;
0 Sample was collected from a depth not less than 0.5 feet below ground surface;
1' Sample was collected from a location that is not impacted by other potential
anthropogenic sources of constituents; and,
Sample is collected from the unsaturated zone, greater than one foot (ft) above the
seasonal high water table elevation.
Additional site -specific requirements related to the Roxboro background soil dataset as outlined
in the July 7, 2017 NCDEQ letter have been incorporated into the soil 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).
SOIL BACKGROUND DATA
Soil samples were collected from soil borings conducted at the Roxboro Plant during the 2015
Comprehensive Site Assessment. Background soil sample locations are presented in Figure 1.
The background dataset provided to NCDEQ on May 26, 2017 included pooled soil samples
collected from multiple depth intervals. Only samples collected from background locations at
depth intervals greater than one ft above the seasonal high water table were included in the
dataset. The background soil dataset has been further revised from the May 26, 2017 submittal
based on input from NCDEQ in the July 7, 2017 letter. NCDEQ determined samples collected
from the depth interval 0-2 ft below ground surface at the following locations: MW-07, MW-08,
MW-10BR, MW-13BR, MW-15BR, MW-16BR, and MW-18BR do not meet NCDEQ IHSB
Guidance requirements and were deemed too shallow (included sampled soil less that 0.5
below ground surface); therefore, are not appropriate for use in determining BTVs.
The background soil dataset included laboratory reporting limits for antimony and thallium
above the NCDEQ IHSB Preliminary Soil Remediation Goals (PSRG) Protection of
Groundwater values (dated October 2016). NCDEQ resquested the values for antimony and
thallium be reported below the PSRG Protection of Groundwater values.
Prior to statistical determinations, the background soil dataset was re -screened for outliers to
adjust for the removal of samples from the dataset. A revised background dataset including
updated outliers is presented in Table 1. Currently, the background dataset does not satisfy the
P:\Duke Energy Progress. 1026\Statistics—LAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ Roxboro \ Soil \ Roxboro - BTV Soil TM_FINAL.docx

Background Threshold Values- Soil
August 4, 2017
Roxboro Steam Electric Plant
Page 3 of 3
minimum requirement of 10 samples to use formal statistics to derive BTVs. Therefore, PBTVs
for soil constituents 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 soil constituents are provided in Table 2.
Additional soil samples were collected on July 19, 2017 to satisfy the minimum number of soil
samples and to provide values for antimony and thallium below the PSRG Protection of
Groundwater values. The analysis of the additional background soil samples are not complete
at the time of this technical memo. Therefore, as previously stated, PBTVs for soil constituents
were computed and are provided in Table 2. Boring logs associated with the additional soil
samples are included in Attachment 1. 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.
LIST OF FIGURES
Figure 1- Background Soil Sample Location Map
LIST OF TABLES
Table 1- Background Unsaturated Soil Data Summary
Table 2 - Background Threshold Values for Soil
LIST OF ATTACHMENTS
Attachment 1- Soil Boring Logs (Additional Samples)
P:\Duke Energy Progress. 1026\Statistics—LAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ Roxboro \ Soil \ Roxboro - BTV Soil TM_FINAL.docx

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FIGURE 1
IN FEET BACKGROUND SOIL
148 RIVER STREET, SUITE 220
GREENVILLE, SOUTH CAROLINA 29601 SAMPLE LOCATIONS
PHONE[phone] ROXBORO STEAM ELECTRIC PLANT
)mTerm Hnaw MANAGER:
co
e;�' DROECT MANAGERNC. EADY DATE: 07/27/2017 SEMORA, NORTH CAROLINA
CHECKED BY: A. LEFITZ

TABLE 1
BACKGROUND UNSATURATED SOIL DATA SUMMARY
ROXBORO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, SEMORA, NC
Analytical Parameter
pH
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
itrate N)
(asReporting
Potassium
Selenium
Sodium
Strontium
Sulfate
Thallium
Vanadium
Zinc
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
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
NE
0.9
5.8
580
63
45
3
NE
NE
360000
0.9
700
150
270
NE
65
1
NE
130
NE
NE
2.1
NE
NE
NE
0.28
6
1200
Sample ID
Sample
Collection Date
Analytical Results
MW-08 (14-16)
04/27/2015
7.6
4110
---
<5.2
49.3
0.23 j
<13.1
<0.63
1830
<263
0.82 j
4.6 j
2.4
10200
<5.2
2910
222
<0.0086
<2.6
1.4
<26.3
836
---
221 j
13.7
<263
---
21.6
41.4
MW-08(21-23)
04/27/2015
7.3
14800
---
<5.7
128
1.1
<14.2
<0.68
11200
<283
17.4
15.3
0.78j
20500
6
14300
496
<0.0092
<2.8
31.7
<28.3
5680
---
211j
97.2
<283
---
43.1
78.6
MW-13BR (22-24)
03/04/2015
8.0
6730
---
<1.2
102
0.14
9.2
<0.14
3890
<299
8.7
8.1
41
13100
<1.2
4020
132
<0.01
<0.6
4.4
<29.9
2320
<1.2
389
13.2
<299
---
59.3
25.1
MW-14BR (1-1.25)
02/25/2015
4.8
11000
---
<1.2
71.3
0.14 j
<3.1
<0.15
593
<300
4.1
5.3
11.1
16100
4.8
4960
79.4
0.011
<0.62
3.4
<30
1110
<1.2
183
20.4
<300
---
45.2
26.6
MW-14BR(31-31.5)
02/25/2015
8.8
8590
---
<1
170
0.11j
<2.6
<0.12
2810
<254
9
8.6
23.1
12600
<1
6490
238
<0.0084
<0.51
6.5
<25.4
4830
<1
383
22.4
<254
---
31
37.9
MW-14BR(37.5-38)
02/25/2015
8.0
12300
---
<1.1
198
0.25
<2.8
<0.13
6340
<286
54
15.8
17.7
15200
<1.1
13100
290
<0.0089
<0.55
53.7
<28.6
3860
<1.1
174
57.5
<286
---
33.3
49.6
MW-17 (29-31)
04/21/2015
8.4
8530
---
<5.1
84.3
0.32
17.9
<0.61
5300
<250
4.8
5.7
5.7
19800
<5.1
5920
315
<0.0081
<2.5
7.9
<25
857
---
183 j
18.8
<250
---
23
56.4
MW-18 (31-33)
05/16/2015
7.3
3420
---
---
31.3
0.221
<15
<0.72
581
<292
1.9
<6
4.8
7000
<6
686
353
<0.0092
<3
<1.5
<29.2
731
---
222 j
8
<292
---
3.1 j
18.7
MW-18 (37-38)
05/16/2015
7.3
3600
---
---
18.4
0.18 j
<15.3
<0.73
670
<296
1.31
<6.1
22.4
3410
<6.1
708
175
<0.0098
<3.1
<1.5
<29.6
486
---
<306
6.7
<296
---
<6.1
16.2
Prepared by: JHG Checked by: CDE
Notes:
54 = Indicates values omitted from dataset.
--- = Value removed; non -detected concentration exceeding PSRG Protection of Groundwater
= Indicates data removed/identified as an outlier
< = concentration not detected at or above the adjusted reporting limit.
I = Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
mg/kg = milligrams per kilogram
NA = Not analyzed
NE = Not established
PSRG Protection of Groundwater = NCDEQ IHSB Preliminary Soil Remediation Soil Remediation Goals Table - October 2016
S.U. = Standard Units
P:\Duke Energy Progress. 1026\Statistics_CAMA\Preliminary Background Determinations for NCDEQ July 7 2017\BTV TECH MEMO\Roxboro\Soil\Tables\TABLE 1 - Roxboro BG Soil Dataset_Highlighted Outliers Page 1 of 1

TABLE 2
BACKGROUND THRESHOLD VALUES FOR SOIL
ROXBORO STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, SEMORA, NC
Parameter
Reporting Unit
PSRG Protection of
Groundwater
BTVt
pH*
S.U.
NE
7.3 - 8.4
Aluminum
mg/kg
NE
14800
Antimony
mg/kg
0.9
NA
Arsenic
mg/kg
5.8
6
Barium
mg/kg
580
198
Beryllium
mg/kg
63
1
Boron
mg/kg
45
18
Cadmium
mg/kg
3
0.7
Calcium
mg/kg
NE
11200
Chloride
mg/kg
NE
300
Chromium
mg/kg
360,000
17
Cobalt
mg/kg
0.9
16
Copper
mg/kg
700
41
Iron
mg/kg
150
20500
Lead
mg/kg
270
6
Magnesium
mg/kg
NE
14300
Manganese
mg/kg
65
496
Mercury
mg/kg
1
0.01
Molybdenum
mg/kg
NE
3
Nickel
mg/kg
130
35
Nitrate (as N)
mg/kg
NE
30
Potassium
mg/kg
NE
5680
Selenium
mg/kg
2.1
1
Sodium
mg/kg
NE
389
Strontium
mg/kg
NE
97
Sulfate
mg/kg
250
300
Thallium
mg/kg
0.28
NA
Vanadium
mg/kg
6
59
Zinc
mg/kg
1200
79
Prepared by: JHG Checked by: CDE / LWD
Notes:
S.U. = Standard Unit
mg/kg = milligrams per kilogram
* = Upper and lower threshold values calculated for parameter
t = Indicates value is provisional; dataset contains less than 10 valid samples
NE = Not Established
NA = Not applicable; dataset contains zero valid samples
P:\Duke Energy Progress.1026\Statistics_CAMA\Preliminary Background Determinations for NCDEQ July 7 2017\BTV TECH
MEMO\Roxboro\Soil\Tables\TABLE 2 - Roxboro Soil Background Threshold Values Page 1 of 1

Background Threshold Values- Soil
August 4, 2017
Roxboro Steam Electric Plant
ATTACHMENT 1
SOIL BORING LOGS (ADDITIONAL SAMPLES)
P: \ Duke Energy Progress.1026 \ Statistics_CAMA \ Background Determinations for NCDEQ July 7 2017\BTV TECH
MEMO \ Roxboro \ Soil \ Roxboro - BTV Soil TM_FINAL.docx

PROJECT: Roxboro Station
WELL / BORING NO: BGSB-112
PROJECT NO: 1026.107
STARTED: 7/19/17 COMPLETED: 7/19/17
DRILLING COMPANY: Geologic Exploration
NORTHING: 993900.7 EASTING: 1986193.02
DRILLING METHOD: GeoProbe
G.S. ELEV: ft M.P. ELEV: NA ft
BOREHOLE DIAMETER: 3 IN
DEPTH TO WATER: NA ft TOC TOTAL DEPTH: 20.0 ft BGS
NOTES:
LOGGED BY: A. Lefitz CHECKED BY: E. Yurkovich
w v
❑
v
= 0
Q O
r
co
DESCRIPTION
w
a
g
<
O^
U a
W"
U)
z
OJ ❑
m0
❑ E
a s
WELL
CONSTRUCTION
ML
Moderately stiff to loose, orange brown, clayey silt, dry,
saprolite to partially weathered rock.
5
ML
Moderately stiff to loose, orange brown, clayey silt, dry,
saprolite to partially weathered rock. Increase in
partially weathered rock with depth.
10
Moderately dense, dry, partially weathered rock with
clay lenses.
15
Moderately dense, dry, partially weathered rock with
clay lenses. Relic structure present.
20
25
30
35
40
45
Coordinates obtained with hand held GPS unit.
f CLIENT: Duke Energy Progress, LLC.
ra PROJECT LOCATION: Semora, NC
148 River Street, Suite 220
48 R
���.ra Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 1

PROJECT: Roxboro Station
WELL / BORING NO: BGSB-14
PROJECT NO: 1026.107
STARTED: 7/19/17 COMPLETED: 7/19/17
DRILLING COMPANY: Geologic Exploration
NORTHING: 996082.78 EASTING: 1984658.36
DRILLING METHOD: GeoProbe
G.S. ELEV: ft M.P. ELEV: NA ft
BOREHOLE DIAMETER: 3 IN
DEPTH TO WATER: NA ft TOC TOTAL DEPTH: 10.0 ft BGS
NOTES:
LOGGED BY: A. Lefitz CHECKED BY: E. Yurkovich
w v
❑
v
= 0
Q O
co
D
DESCRIPTION
w
a
g
<
O^
U a
W"
U)
z
OJ ❑
m0
❑ E
a s
WELL
CONSTRUCTION
ML
Soil with vegetation and mulch, sandy silt, moist to d
ML
Loose to moderately dense, orange brown, sandy silt
with clay lenses, moist to dry.
CL
Stiff, orange brown clayey silt to silty clay, dry.
5
Light gray brown, saprolite to partially weathered rock
with relic structure observed.
10
15
20
25
30
35
40
45
Coordinates obtained with hand held GPS unit.
f CLIENT: Duke Energy Progress, LLC.
ra PROJECT LOCATION: Semora, NC
148 River Street, Suite 220
48 R
���.ra Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 1

PROJECT: Roxboro Station
WELL / BORING NO: BGSB-18
PROJECT NO: 1026.107
STARTED: 7/19/17 COMPLETED: 7/19/17
DRILLING COMPANY: Geologic Exploration
NORTHING: 986646.49 EASTING: 1982285.21
DRILLING METHOD: GeoProbe
G.S. ELEV: ft M.P. ELEV: NA ft
BOREHOLE DIAMETER: 3 IN
DEPTH TO WATER: NA ft TOC TOTAL DEPTH: 13.0 ft BGS
NOTES:
LOGGED BY: A. Lefitz CHECKED BY: E. Yurkovich
W
❑Q
U
= O
O
U)
DESCRIPTION
w
a
<LU
O^
U)
Oz
❑a
0
E❑ s
WELL
CONSTRUCTION
5
SM
Light orange brown, loose, silty sand with rock and
some clay lenses, dry.
10
SM
Light gray, silty sand. Saprolite to Partially weathered
rock. Geoprobe refusal at 13 feet below ground
surface.
15
20
25
30
35
40
45
Coordinates obtained with hand held GPS unit.
f CLIENT: Duke Energy Progress, LLC.
ra PROJECT LOCATION: Semora, NC
48 R
148 River Street, Suite 220
���.ra Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 1

PROJECT: Roxboro Station
WELL / BORING NO: BGSB-2
PROJECT NO: 1026.107
STARTED: 7/18/17 COMPLETED: 7/18/17
DRILLING COMPANY: Geologic Exploration
NORTHING: 987877.39 EASTING: 1976136.75
DRILLING METHOD: GeoProbe
G.S. ELEV: ft M.P. ELEV: NA ft
BOREHOLE DIAMETER: 3 IN
DEPTH TO WATER: NA ft TOC TOTAL DEPTH: 8.5 ft BGS
NOTES:
LOGGED BY: A. Lefitz CHECKED BY: E. Yurkovich
v
=
co
w
a
O^
a
U)
z
OJ
❑ E
WELL
CONSTRUCTION
w v
0
Q O
DESCRIPTION
g
U
❑
a s
❑
r
<
W"
m0
Dense, orange brown, sandy silt, moist to dry. At 4.5
ML
feet below ground surface, white, silty, saprolite to
J.
partially weathered rock, dry.
5
White, silty, saprolite to partially weathered rock.
Geoprobe refusal at 8.5 feet below ground surface.
10
15
20
25
30
35
40
45
Coordinates obtained with hand held GPS unit.
f CLIENT: Duke Energy Progress, LLC.
ra
48 RPROJECT LOCATION: Semora, NC
148 River Street, Suite 220
���.ra Greenville, South Carolina 29601
Phone:[phone] PAGE 1 OF 1