Allen- SOIL BTV MEMO_FINAL

TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.17
To: Sean DeNeale (Duke Energy)
Cc Kathy Webb (SynTerra)
From: Chris Suttell (SynTerra) =S
Subject: Background Threshold Values for Soil
Allen Steam Station — Belmont, NC
An updated background soil dataset was provided to the North Carolina Department of
Environmental Quality (NCDEQ) for Allen Steam Station (Allen) 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 60
days from receipt of the NCDEQ letter for facilities submitting Comprehensive Site
Assessments (CSAs) later than October 31, 2017. BTVs for groundwater are provided under
separate cover.
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 samples prior to the determination of BTVs for each constituent. For soil
datasets with less than 10 valid samples available for BTV determination, no formal upper
tolerance limit (UTL) statistics could be run and the provisional BTV (PBTV) for a constituent
was computed to be either:
h The highest value, or
h 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.
Soil samples meeting the following criteria are considered valid for use in statistical
determinations of BTVs:
h Sample was collected from a location that is not impacted by coal combustion
residuals or coal associated materials;
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Background Threshold Values- Soil September 5, 2017
Allen Steam Station Page 2 of 3
0 Sample was collected from a depth not less than 0.5 feet below ground surface;
0 Sample was collected from a location that is not impacted by other potential
anthropogenic sources of constituents; and
h 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 Allen 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 soil 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 Allen Plant during the 2015
Comprehensive Site Assessment (CSA). 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 foot 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 the
following samples are not appropriate for use in determining BTVs:
1611 GWA-15D — collected immediately adjacent to the waste boundary west of the ash
storage area and according to the boring log, was collected in fill material, and
h GWA-51) — collected immediately adjacent to the waste boundary east of the ash basin
and was collected in fill material.
Prior to statistical determinations, the background soil dataset was re -screened for outliers to
adjust for the removal samples from the dataset. An updated background soil dataset
identifying valid samples and statistical outliers are presented as Table 1. Currently, the
background dataset satisfies the minimum requirement of 10 samples to use formal statistics to
derive BTVs for all constituents except antimony, arsenic, boron, molybdenum, selenium,
sodium and thallium. The dataset for arsenic and selenium contains zero valid samples. The
background soil dataset for antimony and thallium included laboratory reporting limits above
the NCDEQ IHSB Preliminary Soil Remediation Goals (PSRG) Protection of Groundwater
standards (dated October 2016). NCDEQ requires that the analytical practical quantitation limit
(PQL) for antimony and thallium be less than the PSRG Protection of Groundwater for the data
to be valid for calculating BTVs.
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Memos \ 2017-09 \ Allen- SOIL BTV MEMO_FINAL.docx

Background Threshold Values- Soil September 5, 2017
Allen Steam Station Page 3 of 3
BTVs were calculated using formal UTL statistics for constituent datasets meeting the minimum
requirement of 10 samples. Arsenic, boron, molybdenum, selenium and sodium datasets
contain less than 10 valid samples. Antimony, and thallium have zero valid samples; therefore,
PBTVs are not presented for these consitutents. PBTVs for arsenic, boron, molybdenum and
sodium were determined 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.
Therefore, the PBTV for arsenic, boron, molybdenum and sodium were computed. BTVs and
PBTVs for constituents in site soil are provided in Table 2.
Additional soil samples will be collected at locations approved by NCDEQ to satisfy the
minimum number of soil samples and provide antimony and thallium by a method whereby
the PQL is below the PSRG Protection of Groundwater values. Once the planned additional
samples are included in the dataset, the dataset will be screened for outliers and BTVs
computed. Sampling and analysis of additional background soil samples is not complete at this
time. Therefore, as previously stated, PBTVs for arsenic, boron, molybdenum and sodium were
computed and are provided in Table 2. Boring logs and analytical data for subsequent
collection of background soil samples 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
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Memos \ 2017-09 \ Allen- SOIL BTV MEMO_FINAL.docx

Background Threshold Values- Soil
Allen Steam Station
FIGURE
September 5, 2017
P: \ Duke Energy Carolinas \ 17.ALLEN \ 05.EHS CAMA Compliance Support \ Assessment \ Background \ Soil \ Tech
Memos \ 2017-09 \ Allen- SOIL BTV MEMO_FINAL.docx

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Background Threshold Values- Soil
Allen Steam Station
TABLES
September 5, 2017
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Memos \ 2017-09 \ Allen- SOIL BTV MEMO_FINAL.docx

TABLE 1
BACKGROUND UNSATURATED SOIL DATA SUMMARY
ALLEN STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELMONT, NC
Prepared by: JHG Checked by: CJS
Notes:
54 - Indicates values omitted from dataset.
--- - Not applicable; non -detect concentration greater than PSRG Protection of Groundwater; value omitted
- Indicates data removed /identified as an outlier
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
j- - Estimated concentration, biased low.
j+ - Estimated concentration, biased high.
mg/kg - milligrams per kilogram
NE - Not established
PSRG Protection of Groundwater - NCDEQ IHSB Preliminary Soil Remediation Soil Remediation Goals Table - October 2016
S.U. - Standard Units
U - Results not detected at concentrations which equal the laboratory's method reporting limit.
P:\Duke Energy Carolinas\17.ALLEN\05. EHS CAMA Compliance Support\Assessment\Background\Soil\Tech Memos\2017-09\Tables\Table 1 -Allen Soils Page 1 of 1
Analytical Parameter
pH
Aluminum Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride Chromium
Cobalt
Copper
Iron
Lead
Magnesium Manganese
Mercury
Molybdenum
Nickel
�asN)
Potassium Selenium
Sodium
Strontium
Sulfate
Thallium Vanadium
Zinc
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
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
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
BG -1D (1.0-2.0)
4/27/2015
5.8
15300
---
---
20.5
0.32 U
15.8 U
0.76 U
462
305 U
15.2
13.3
8.1
35100
10.9
297
340
0.074
3.2 U
2.2
30.5 U
162 j
---
316 U
3.3
305 U
---
78.1
10.1
BG -1D (9.0-10.5)
4/27/2015
5.5
6450
---
---
42.8
0.61
16.9 U
0.81 U
169 U
357 U
4.6
---
26.7
53600
7.1
433
293
0.016
3.4 U
1.7 U
35.7 U
339 U
---
339 U
3.4 U
357 U
---
343
14.7
BG -1D (19.0-20.5)
4/28/2015
5.3
4990
---
---
46.2
0.36
15.5 U
0.74 U
155 U
304 U
14.7
14.5
11.9
27600
7.6
903
436
0.0094 U
3.1 U
1.8
30.4 U
752
---
310 U
3.1 U
304 U
---
68.1
13.2
BG -1D (45-50)
5/1/2015
5.7 j
20100
---
---
203
0.91
23.4 j+
0.92 U
245
363 U
6.2
18.7
29
33600
6.9 j
10000
1060
0.011 U
3.8 U
5.3
36.3 Uj
10100
---
384 U
10.1
363 U
---
79.3
88.2
BG -2D (1.0-2.5)
5/14/2015
5 j
29280
---
---
216
0.38 j
21.8 U
1 U
127 j
423 U
6.7
5.6 j
34.3
51300
6.3 j
10400
627
0.026
4.4 U
2.2 U
42.3 Uj
9740
---
436 U
3.9 j
423 U
---
81.6
64.4
BG -2D (8.5-10.0)
5/14/2015
5.4 j
17800
---
--- 1
208
0.35 116.1
U
0.77 U
195
315 U 1
3.1
9.7 1
3.2
23100
1 3.6 j
8930
1 587
0.0082 j
3.2 U
1.4 j
31.5 Uj
8720
---
322 U
5.5
315 U
---
49
59.4
BG -2D (18.0-20.0)
5/14/2015
6 j
15500
---
---
233
0.95
17.6 U
0.84 U
1260
336 U
2.7
19.4
55.7
32400
3.9 j
9490
1340
0.011 U
3.5 U
1.8 U
33.6 Uj
7790
---
351 U
i6..7
336 U
---
77.5
64.3
BG -3D (1-2.5)
2/23/2015
5.1 j
11800
---
3.4 Uj
229
0.85
17.2 U
0.11 j
517
345 U
30.9
19.8
31.2
24900
6.1
4780
712
0.017
3.4 U
53.5
34.5 Uj
3370
---
344 U
12
345 U
---
48.5
52.3
BG -3D (13.5-15)
2/23/2015
5.4j
8570
---
3 U
109
0.36 Uj
3-6
0.35
59.8
311 U
1.7
28.5
10.3
13600
33-6
4890
962
0.0071j
OAU
2.1
31.1 Uj
5220
---
33.3j
1.5
311 U
---
40.9
36.4
BG -3D (18.5-20)
2/23/2015
6-9-1
2500
---
1.2 U
26.3
0.071 j
341
0.14 U
773
291 U
7.6
3.9
18.2
6400
1.7
1160
172
0.01 U
8-69
0.78
29.1 Uj
1110
1.2 U
59.3-U
1.3
291 U
---
15.3
16.8
GWA-14D(10.0-12.0)
6/9/2015
5.1
11200
---
---
84.3
0.46 U
23.1 U
1.1 U
231 U
437 U
4.9
5.7 j
30.3
34700
5.8 j
2680
501
0.014 U
4.6 U
5.1
43.7 U
2430
---
461 U
4.6 U
437 U
---
89.8
23.9
GWA-8D (38.5-40)
2/18/2015
6.2
12100j+
---
3.7 U
136
1.3
41.3
0.18 U
373 U
372 U
43.3
32.6
59.5
44300 j+
3.3
3090
1190
0.01 U
875TH
20&8
37.2 Uj
2150
---
74641
7.5 U
372 U
---
90
23.2
GWA-8D (48.5-50)
2/18/2015
5.9
17200 j+
---
3.6 U
211
1.5
42:5
0.18 U
365 U
375 U
48A
39.8
53.8
43000 j+
4.8
6490
1280
0.01 U
7-.344
59,6
37.5 Uj
4440
---
73841
7.3 U
375 U
---
89.9
72.3
Prepared by: JHG Checked by: CJS
Notes:
54 - Indicates values omitted from dataset.
--- - Not applicable; non -detect concentration greater than PSRG Protection of Groundwater; value omitted
- Indicates data removed /identified as an outlier
j - Estimated concentration above the adjusted method detection limit and below the adjusted reporting limit.
j- - Estimated concentration, biased low.
j+ - Estimated concentration, biased high.
mg/kg - milligrams per kilogram
NE - Not established
PSRG Protection of Groundwater - NCDEQ IHSB Preliminary Soil Remediation Soil Remediation Goals Table - October 2016
S.U. - Standard Units
U - Results not detected at concentrations which equal the laboratory's method reporting limit.
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TABLE 2
BACKGROUND THRESHOLD VALUES FOR SOIL
ALLEN STEAM STATION
DUKE ENERGY CAROLINAS, LLC, BELMONT, NC
Parameter
Reporting Unit
PSRG Protection of
Groundwater
BTV
pH*
S. U.
NE
4.3 - 6.8
Aluminum
mg/kg
NE
26,991
Antimony
mg/kg
0.9
NA
Arsenic
mg/kg
5.8
3.7t
Barium
mg/kg
580
233
Beryllium
mg/kg
63
1.3
Boron
mg/kg
45
23.4t
Cadmium
mg/kg
3
0.368
Calcium
mg/kg
NE
1,192
Chloride
mg/kg
NE
ND
Chromium
mg/kg
360,000
93.6
Cobalt
mg/kg
0.9
48.6
Copper
mg/kg
700
78.4
Iron
mg/kg
150
69,316
Lead
mg/kg
270
12.3
Magnesium
mg/kg
NE
15,100
Manganese
mg/kg
65
1786
Mercury
mg/kg
1
0.0233
Molybdenum
mg/kg
NE
4.6t
Nickel
mg/kg
130
9.08
Nitrate (as N)
mg/kg
NE
ND
Potassium
mg/kg
NE
13,742
Selenium
mg/kg
2.1
NA
Sodium
mg/kg
NE
461t
Strontium
mg/kg
NE
24.9
Sulfate
mg/kg
NE
ND
Thallium
mg/kg
0.28
NA
Vanadium
mg/kg
6
132
Zinc
mg/kg
1,200
112
Prepared by: LWD Checked by: CJS
Notes:
* - Upper and lower threshold values calculated for parameter
t - Indicates value is provisional; dataset contains less than 10 valid samples
mg/kg - milligrams per kilogram
NA - Not applicable; dataset contains zero valid samples
ND - Not Detected
NE - Not Established
S.U. - Standard Unit
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TABLE 2 - Allen Soil BTVs Page 1 of 1