SOIL BTV MEMO FINAL REDUCED_20171006

Lip
synTerra
TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.21
To: Ryan Czop (Duke Energy)
Cc Kathy Webb (SynTerra)
From: Chris Suttell (SynTerra) CTS
Subject: Background Threshold Values for Soil
Cliffside Steam Station - Mooresboro, NC
An updated background soil dataset was provided to the North Carolina Department of
Environmental Quality (NCDEQ) for Cliffside Steam Station (Cliffside) 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 for a constituent was
computed to be either:
It? The highest value, or
N 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:
0 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
Cliffside Steam Station Page 2 of 4
,47 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
0 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 Cliffside 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 Cliffside 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 BG -1S(3.5-5) , BG -1S (8.5-10), MW -30S (4-5), MW -30S (9-10), MW -30S (19-20), and MW -
30S (28-29) - samples were analyzed for total organic carbon only;
01 GWA-10D- collected immediately adjacent to the waste boundary at Units 1-4 basin;
0 GWA-31D (7), GWA-31D (8.7), and GWA-31BR - collected immediately downgradient
of the waste boundary at Unit 5 basin, adjacent to a road and parking lot;
0 MW -38D (33.5-35) - collected downgradient of Unit 5 Inactive Ash Basin and adjacent to
the Broad River;
0' GWA-31) (48.5-50) - collected downgradient of Unit 5 Inactive Ash Basin;
0 GWA -12BRU (20-23.5) - collected at a location immediately downgradient of Units 1-4
Inactive Ash Basin and near the Broad River at a depth potentially close to the water
table;
E7 GWA -21BRU (5) - collected at a location potentially downgradient of a basin adjacent to
the Broad River where there is potentially significant fluctuations of water levels by a
discharge point. Sample depth may be immediately above the water table;
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Background Threshold Values- Soil September 5, 2017
Cliffside Steam Station
Page 3 of 4
h GWA-22S (3-5) - collected at a location side gradient of the Active Ash Basin and
adjacent to the Broad River. Collected at a depth within the screened interval of the
well;
`7 GWA-27D (13.5-15) and GWA-27D (24.9) - collected at a location downgradient of and
adjacent to the impoundment. Collected at a depth within the screened interval of the
well;
h MW-40BRU (3.5-5) - collected at a location downgradient of and adjacent to the Unit 5
Inactive Ash Basin and near the Broad River. Collected at a depth within the screened
interval of the well; and,
'47 GWA-61) (28.5-30) - collected at a location immediately downgradient of and the Unit 5
Inactive Ash Basin and near the Broad River. Collected at a depth which may be close to
the water table.
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 resultant
background dataset satisfies the minimum requirement of 10 samples to use formal statistics to
derive BTVs for all constituents except antimony and thallium. 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). In their July 7, 2017 letter, NCDEQ identified selenium as also having reporting
limits above the PRSG; however, the revised dataset for selenium contains 10 valid samples.
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.
BTVs were calculated using formal UTL statistics for constituent datasets meeting the minimum
requirement of 10 samples. PBTVs for antimony and thallium 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. Antimony and thallium datasets were
comprised of less than 10 valid samples. Therefore, PBTVs for antimony, and thallium were
computed. BTVs and PBTVs for constituents in site soil are provided in Table 2.
Additional soil samples will be collected to satisfy the minimum number of soil samples and for
analysis of 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
antimony and thallium 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.
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Background Threshold Values- Soil
Cliffside Steam Station
LIST OF FIGURES:
Figure 1 Background Soil Sample Location Map
LIST OF TABLES:
Table 1 Background Dataset for Soil
Table 2 Background Threshold Values for Soil
September 5, 2017
Page 4 of 4
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Background Threshold Values - Soil
Cliffside Steam Station
FIGURE
September 5, 2017
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LEGEND
• ; -, � O PROPOSED ADDITIONAL BACKGROUND
SOIL SAMPLE LOCATION
EXISTING BACKGROUND �� ` 4 �• _ . ® LOCATION- OSAMPLE
-ACCEPTED BYNC EQ
u ► ! r v r WASTE BOUNDARY
COMPLIANCE BOUNDARY
NOTES:'
2014 AERIAL ORTHOPHOTOGRAPHY OBTAINED FROM USDA NRCS y
GEOSPATIAL DATA GATEWAY . =
(https://gdg.sc.egov.usda.gov/GDGOrder.aspx). �-
DRAWING HAS BEEN SET WITH A PROJECTION OF NORTH ;
CAROLINA STATE PLANE COORDINATE SYSTEM FIPS 3200
(NAD83/2011).
« / DUKE POWER CLIFFSIDE PLANT
BOUNDARY
y
400 200 0 400 800 FIGURE 1
�. GRAPHIC SCALE IN FEET BACKGROUND SOIL
148 RIVER STREET, SUITE 220 SAMPLE LOCATION
PHONE [phone]AR0LINA 29601 CLIFFSIDE STEAM STATION
wwws nterro .com
Terra CHECKED BY: M. YOU°BLOOD DATE 08/08/2017 MOORESBORO, NORTH CAROLINA
PROJECT MANAGER: C. SUTTELL
P:\Duke Energy Progress.1026\00 GIS BASE DATA\Cliffside\Mapdocs\Background\Figure 1- Background Sail Sample Locations—ol

Background Threshold Values - Soil
Cliffside Steam Station
TABLES
September 5, 2017
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TABLE 1
BACKGROUND UNSATURATED SOIL DATA SUMMARY
CLIFFSIDE STEAM STATION
DUKE ENERGY CAROLINAS, LLC, MOORESBORO, NC
Analytical Parameter
pH
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chloride
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrate
tN)
(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
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 (3.5-5)
2/23/2015
5.4 j
26100
3 U
60.9
3 U
0.54
0.14 U
179
314 U
36.4
7.5
15.1
35900
24.1
3400
75.2
0.0088 j
0.6 U
11.3
31.4 Uj
2920
104
4.4
314 U
59.7
69.3
BG -1D (8.5-10)
2/23/2015
5.7 j
9490
1.4
57.7
13.3 U
1.2
0.13 U
26.5 U
267 U
21.9
8.1
23.7
17400
10.3
3520
64.7
0.0087 U
2.7 U
8
26.7 Uj
3440
1.4
71.2
7.6
267 U
0.7 j
31
92.3
BG -2D (3.5-5)
2/23/2015
5.5 j
30600
3.5 U
108
69.4 U
0.92
0.17 U
130
353 U
84
15.2
31.5
61500
18.9
7920
234
0.012 U
0.97
20.4
35.3 Uj
5830
1.8 j
179
1.1
353 U
110
86.9
3G -2D (8.5-10)
2/23/2015
5.2 j
18200
3.3 j
131
18.4 j-
0.91
0.38 U
186 j
85.5
22
13.5
39100
19.5
4940 j
591 j
0.011 j-
0.64 Uj
19.7 j-
31 Uj
3350
3.1 j
320 U
3.2 Uj
75.7
30 j -
BG -2D (18.5-20)
2/23/2015
5.5j
9980
3.4j
98.4
21.7
0.65
0.5 U
48.9
400 U
109
19.3
10.4
22000
15.1
3060
415
0.013 U
0.83 U
17.1
40 Uj
2430
8.3
52.1 j+
0.83 U
400 U
60.1
25.7
BG -2D (28.5-30)
2/23/2015
5.7 j
12700
3.5
148
16.9 U
1.3
0.16 U
38.7
330 U
71.2
25.6
11.9
16600
11
4810
517
0.01 U
0.68 U
22
33 Uj
3580
1.3 j
77.7
0.9
330 U
52.9
34.4
MW -30D (3.5-5.5)
2/23/2015
5.9 j
25200
3.2 j
78.5
3.9 U
0.62
0.19 U
220
394 U
79.9
7.3
12.4
48500
26.7
5080
145
0.013 U
0.78 U
18.9
39.4 Uj
3380
2.2 j
125
1.1
394 U
97.8
38.2
MW -30D (8.5-10)
2/23/2015
6 j
18900
2.4j
37.7
4.1 U
0.42
0.49 U
93.1
48.1
3.3j
11.9
27300
19.9
1930
89
0:034
0.82 U
8.1
39.6 Uj
1890
88.5
1.6
70.3
22.9
MW -30D (18.5-20)
2/23/2015
5 j
10000
3.5 j
34.3
4.7 U
0.82
0.23 U
46.9 U
488 U
80.6
2.4 j
19.3
60600
26
793
215
0.016 U
0.94 U
16.4
48.8 Uj
596
154
0.94 U
488 U
125
19
MW -30D (28.5-30)
2/23/2015
6.1 j
13300
3.6 j
142
27.3 j
1
0.27
385 U
88.6
36.1
24.6
38700
30.1
7800
979
0.012 U
7.7 U
44.6
38 Uj
6920
5.1
77iU
7.7 U
1 j
93.8
72.7
MW -32D (3.5-5)
3/4/2015
5.2 j
25900
3.8
50.1
30.1 U
0.5 j
0.14 U
242
317 U
79.8
5.7
16.6
48700
24
2150
148
0.038
0.48 j+
11.2
31.7 Uj
1670
1.6 j
113
1.4
204 j
96.7
22.9
MW -32D (8.5-10)
3/4/2015
6j
19000
1.9j
56.5
30.6 U
0.34
0.15 U
98.8
309 U
50.5
6.7
14.6
44800
27.6
2470
107
0.0099 U
0.39j
10
30.9 Uj
1920
126
2
309 U
74.5
27.5
MW -32D (18.5-20)
3/4/2015
5.9 j
8000
1.7
26.3
3.3 U
0.14
0.16 U
§130
321 U
3.7
3.2
3h
2760
7.2
61.7
62
0.0065j
0.67 U
6.2
32.1 Uj
120
2
66.6 U
13.3
321 U
4.3
MW -32S (22.5-24)
3/12/2015
6.3j
27500
200
38.9 U
1.6
0.47 U
148 j+
387 U
116
33.8
25.6
46400
13.6
11700
910
0.013 U
7.8-U
49.2
38.7 Uj
8100
83.6
1.4 j+
387 U
90.1
159
MW -42D (28.5-30)
2/23/2015
6.6j
19800
1.8
195
4 Uj
1.3
0.19 U
83-7
423 U
85.4
13.1
12
21600
6.4
13300
321
0.014 U
0.81 Uj
40.1
42.3 Uj
9000
1.1j
95.8
7.1
423 U
0.89j
50.9
53.2
GWA-25D (8.5-10)
5/11/2015
5.1 j
15800
5.6 U
80
14 U
0.48
0.67 U
140 U
268 U
28.3
11.8
24.5
23500
8.1
3780
254
0.0089 U
2:8-U
11.4
26.8 Uj
6150
281 U
2.8 U
268 U
51.4
65.7
Prepared by:JHG Checked by: CJS
Notes:
54 Indicates value omitted from dataset.
Indicates data removed /identified as an outlier.
Not applicable
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 - concentration not detected at or above the adjusted reporting limit.
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TABLE 2
BACKGROUND THRESHOLD VALUES FOR SOIL
CLIFFSIDE STEAM STATION
DUKE ENERGY CAROLINAS, LLC, MOORESVILLE, NC
Parameter
Reporting Unit
PSRG Protection of
Groundwater
BTV
pH*
S. U.
NE
4.7 - 6.7
Aluminum
mg/kg
NE
36,464
Antimony
mg/kg
0.9
NA
Arsenic
mg/kg
5.8
4.88
Barium
mg/kg
580
233
Beryllium
mg/kg
63
38.9
Boron
mg/kg
45
1.82
Cadmium
mg/kg
3
ND
Calcium
mg/kg
NE
304
Chloride
mg/kg
NE
ND
Chromium
mg/kg
360,000
109
Cobalt
mg/kg
0.9
59.5
Copper
mg/kg
700
34.7
Iron
mg/kg
150
75,162
Lead
mg/kg
270
38.1
Magnesium
mg/kg
NE
25,562
Manganese
mg/kg
65
1518
Mercury
mg/kg
1
0.016
Molybdenum
mg/kg
NE
0.97
Nickel
mg/kg
130
66.2
Nitrate (as N)
mg/kg
NE
ND
Potassium
mg/kg
NE
18,460
Selenium
mg/kg
2.1
12
Sodium
mg/kg
NE
194
Strontium
mg/kg
NE
14.1
Sulfate
mg/kg
NE
ND
Thallium
mg/kg
0.28
NA
Vanadium
mg/kg
6
142
Zinc
mg/kg
1200
214
Prepared by: LWD Checked by: TME
Notes:
* - Upper and lower threshold values calculated for parameter
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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