Asheville- SOIL BTV MEMO_Final

TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.102
To: John Toepfer (Duke Energy)
Cc Kathy Webb (SynTerra)
From: Todd Plating (SynTerra)
Subject: Background Threshold Values for Soil
Asheville Steam Electric Plant — Arden, NC
An updated background soil dataset was provided to the North Carolina Department of
Environmental Quality (NCDEQ) for Asheville Steam Electric Plant (Asheville) 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:
t0 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:
t' 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
Asheville Steam Electric Plant Page 2 of 3
0 Sample was collected from a depth not less than 0.5 feet below ground surface;
,07 Sample was collected from a location that is not impacted by other potential
anthropogenic sources of constituents; and
t7 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 Asheville 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 Asheville 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:
0 MW -08 and MW -09 - collected at or immediately adjacent to the waste boundary.
17 CB -08, MW -03, MW -05 and MW -07 - collected downgradient of a site impacted area.
E7 MW-13SB (22-22.5) - collected three feet below water table
Additionally, the sample collected from MW -12 was eliminated due to proximity to the waste
boundary. After these samples were removed from the dataset, the remaining background soil
dataset was re -screened for outliers prior to statistical determinations. A revised background
soil dataset identifying valid samples and statistical outliers are presented as Table 1. The
background dataset satisfies the minimum requirement of 10 samples to use formal statistics to
derive BTVs for all constituents except antimony, selenium and thallium. The background soil
dataset for antimony, selenium 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, selenium, and thallium be less than the PSRG Protection of Groundwater
for the data to be valid for calculating BTVs.
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Background Threshold Values- Soil September 5, 2017
Asheville Steam Electric Plant Page 3 of 3
BTVs were calculated using formal UTL statistics for constituent datasets meeting the minimum
requirement of 10 samples. Currently, there are no valid samples for antimony and thallium
and PBTVs could not be computed at this time. The PBTV for selenium was 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. PBTVs and BTVs for
constituents in site soil are provided in Table 2.
Additional soil samples will be collected at locations approved by DEQ to satisfy the minimum
number of soil samples and provide antimony, selenium and thallium by a method whereby the
PQL will be below the PSRG Protection of Groundwater values. Once planned additional
samples are included in the dataset, the dataset will be screened for outliers and BTVs
computed. The sampling of additional background soil samples are not complete at the time.
Therefore, as previously stated, PBTVs for selenium, was computed and is 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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Background Threshold Values- Soil
Asheville Steam Electric Plant
FIGURE
September 5, 2017
P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ Asheville \ Soil \ Asheville- SOIL BTV MEMO.docx

Background Threshold Values- Soil
Asheville Steam Electric Plant
TABLES
September 5, 2017
P:\Duke Energy Progress.1026\Statistics_CAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ Asheville \ Soil \ Asheville- SOIL BTV MEMO.docx

TABLE 1
UNSATURATED BACKGROUND SOIL DATA SUMMARY
ASHEVILLE STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ARDEN, NC
Analytical Parameter
pH
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrate
(as N)
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
CB -01 SB (7-8)
04/10/2015
5.8
14100
---
<2.9
57.2
0.63
<14.3
<0.34
<143
<292
14.3
18
17.1
23400
8.8
1780
279
<0.0094
<2.9
6.9
<29.2
1730
---
<286
<2.9
<292
---
27.3
77.3
CB -01 SB (30-31)
04/10/2015
5.8
10900
---
2.4
30.1
0.94
<14.9
<0.72
<149
<300
12
32.6
41.6
31700
4.6
1920
434
<0.0096
<3
4.9
<30
755
3.3
<298
<3
<300
---
44.6
51.8
CB -09 SB (1-2)
04/12/2015
5.2
16800
---
2.3
49.7
0.56
<17.9
<0.43
<179
<348
38.8
20.3
13.5
40300
27.5
326
599
0.06
<3.6
2
<34.8
290
---
<358
2.1
<348
---
55.9
10.7
CB -09 SB (25-27)
04/12/2015
5.6
12900
---
<3.1
75
1
<15.3
<0.37
<153
<303
45.1
23.7
25.6
40700
16.5
4430
1010
<0.01
<3.1
11.9
<30.3
4660
---
<307
<3.1
<303
---
65.2
54.7
GW -01 SB(1-2)
04/25/2015
7.8
21400
---
3.7
157
1.2
31.4
0.51
8500
<311
28.7
18.6
48.5
33000
48.7
7490
486
---
<3.1
15.5
<31.1
4750
---
<313<311
---
39.9
206
MW-11SB(1.5-2)
02/04/2015
7.2
18100
---
1.4
112
0.51
20.4
<0.31
975
<247
18.5
10.1
5.9
20900
7.3
5470
190
0.018
<5.2
13.6
<24.7
4470
1.6
<515
3.6
<247
---
26
62.4
MW-13SB(1.5-2)
01/29/2015
6.9
12700
---
<2.5
36.3
0.4
36.4
<0.3
664
<248
41.7
11
21.4
36200
12.7
622
215
0.041
<0.5
3.3
<24.8
372
---
<501
1.8
<248
---
45
10.7
MW-13SB (14.5-15)
01/29/2015
6.3
32700
---
<2.5
172
0.89
36.2
<0.3
271
<248
34.2
9.4
11.6
39200
12.2
4890
226
0.016
<5.1
15.5
<24.8
4490
2.4
<506
<5.1
<248
---
48.7
116
MW-14SB(1.5-2)
02/03/2015
6.4
21000
---
2.2
113
0.72
31.1
<0.3
167
<248
36.1
31.8
66.2
32200
12.1
4840
616
0.011
<5
16.4
<24.8
3790
2.9
<503
<5
<248
---
41.5
85.6
MW -22 (1-2)
06/23/2015
5.7
15100
---
3
112
0.92
<14.7
<0.71
330
<297
17.7
9.7
9.4
17600
11.8
1740
716
0.035
<2.9
9.6
<29.7
1330
---
<294
3.4
<297
---
25.6
33.3
MW-23BR(2-3)
06/14/2015
4.7
13900
---
---
60.5
0.62
<15.7
<0.75
218
<300
17.8
4.1
8.3
20800
10
1720.
70.4
0.039
<3.1
4.9
<30
1070
---
<313
3.5
<300
---
26.9
31
MW-24SB(1-2)
05/04/2015
6.4
21500
---
4.6
125
1.9
36.6
<0.84
1020
<333
48.6
40.2
33.8
35100
37.5
5430
728
0.03
<7
21.9
<33.3
3900
7
1 <349
6.8
<333
---
66.4
101
Prepared by: LWD Checked by: TDP
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.
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
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TABLE 2
BACKGROUND THRESHOLD VALUES FOR SOIL
ASHEVILLE STEAM ELECTRIC PLANT
DUKE ENERGY PROGRESS, LLC, ARDEN, NC
Parameter
Reporting Unit
PSRG Protection of
Groundwater
BTV
pH*
S. U.
NE
3.4 - 8.9
Aluminum
mg/kg
NE
33,951
Antimony
mg/kg
0.9
NA
Arsenic
mg/kg
5.8
5.06
Barium
mg/kg
580
220
Beryllium
mg/kg
63
1.96
Boron
mg/kg
45
36.6
Cadmium
mg/kg
3
ND
Calcium
mg/kg
NE
1,295
Chloride
mg/kg
NE
ND
Chromium
mg/kg
360,000
64.88
Cobalt
mg/kg
0.9
49.62
Copper
mg/kg
700
76.6
Iron
mg/kg
150
53,379
Lead
mg/kg
270
71.04
Magnesium
mg/kg
NE
9,673
Manganese
mg/kg
65
1,228
Mercury
mg/kg
1
0.07
Molybdenum
mg/kg
NE
ND
Nickel
mg/kg
130
27.6
Nitrate (as N)
mg/kg
NE
ND
Potassium
mg/kg
NE
4,750
Selenium
mg/kg
2.1
7t
Sodium
mg/kg
NE
ND
Strontium
mg/kg
NE
7.76
Sulfate
mg/kg
NE
ND
Thallium
mg/kg
0.28
NA
Vanadium
mg/kg
6
82.8
Zinc
mg/kg
1,200
218.5
Prepared by: JHG Checked by: MCM
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 - Asheville Soil Background Threshold Values.xlsx Page 1 of 1