Marshall Soil Background Tech Memo_REV1_20170526_20170526

F)�
Technical Memorandum
Date: Friday, May 26, 2017
Project: Marshall Steam Station
To: Tyler Hardin
From: Chad Hearn
Subject: Quantification of Valid Background Soil Samples for Statistical Calculations — Revision 1
The purpose of this revised technical memorandum (TM) is to address the North Carolina Department of
Environmental Quality's (NCDEQ's) requirement identified below. In addition, this revised TM provides the
basis for evaluation of soil samples proposed for use in determining site -specific background
concentrations using statistical methods for the Marshall Steam Station (MSS) as originally presented in
the TM dated December 20, 2016.
Following submittal of the TM dated December 20, 2016, Duke Energy submitted the Statistical Methods
for Developing Reference Background Concentrations for Groundwater and Soil at Coal Ash Facilities
(Background Methodology) to DEQ on January 20, 2017. NCDEQ subsequently requested additional
information regarding the Background Methodology via a letter dated April 28, 2017. As part of the April
28, 2017 letter, NCDEQ requested the following information:
Provide up-to-date digital spreadsheets of raw background soil data for each facility by May 26,
2017. Any soil data collected since submittal of the Comprehensive Site Assessments (CSAs)
should be included in the table and existing soil data should be reviewed to identify any quality
control issues (i.e., sampling intervals, corresponding boring sample ID, etc.) along with
identification of outliers and revised accordingly.
The up-to-date raw background soil data for background determinations at MSS are provided in Table 1
of this revised TM. Note the remainder of the requirements in the April 28, 2017 NCDEQ letter are
addressed in a revision to the Background Methodology under separate cover.
The soil samples evaluated herein were principally collected during CSA fieldwork conducted between
May and July 2015, and in March 2017. The locations of soil samples to be evaluated for use in the
background determinations are shown on Figure 1.
Viability of samples for use in developing background concentrations was evaluated using the following
criteria:
• Soil sample is collected from a location that is not impacted by coal combustion residuals or coal -
associated materials;
• Soil sample is collected from a location that is not impacted by other potential anthropogenic
sources of constituents;
• Soil sample is collected from the unsaturated zone, above the maximum groundwater elevation
measured in shallow wells during seven well gauging events conducted between July 2015 and
September 2016; and
0 Soil sample collected from a location not impacted by periodic flooding.

F)�
A total of 46 soil samples were collected at Marshall during CSA activities. Of these 46 samples, 7
samples satisfy the four criteria listed above and are considered viable samples for use in statistical
calculations. These samples were collected from the following locations on -site: BG-3D is located beyond
the compliance boundary northeast of the ash basin; GWA-1 BR is located at the southern end of the ash
basin dam; GWA-4D is located beyond the compliance boundary northwest of the ash basin; GWA-5D is
located near the compliance boundary north of the ash basin; and MW-14BR located within the
compliance boundary of the Dry Ash Landfill (Phase 1). Four additional soil samples were collected in
March 2017 from borings advanced to install additional monitoring wells GWA-2DA and GWA-14S. The
GWA-2DA boring is located adjacent to existing upgradient well GWA-2D. GWA-14S is located offsite,
upgradient, and to the northwest of the ash basin system. Note that viable samples collected from borings
near the waste boundary or down -gradient of ash management areas were collected at least one foot
above the maximum measured groundwater elevation and are assumed to have not been impacted by
groundwater migrating from ash sources.
Soil sampling data used in this evaluation, including the range of groundwater elevations for shallow wells
in each well cluster and analytical results per well are provided in Table 1. Note that laboratory reporting
limit for antimony, arsenic, boron, selenium, and thallium exceeded the North Carolina Protection of
Groundwater (POG) Preliminary Soil Remediation Goals, as revised in October 2016.

OQO
OQ
�e
�S
GWA-4S
GWA-4D
GWA-3S
GWA-14S GWA-3 D
GWA-14D`
BG-1BRA
DUKE ENERGYPRQPERTY — �s.�� BG-1D
\paps BG_1S
Apq �
4
�
INDUSTRIAL LANDFILL #1 ,GWA-8S � GWA-8D
PERMIT NO. 1812
(PHASE I CELL 1-4) /
I
MW-4 GWA-55 - BG-3BR BG-31)
MW-4D GWA-5D o
AB-175 ��`��v '
M W -3
AB-185 AB-16S ASBESTOS
AB-18D LANDFILL AL-3S
AL-3BR -0,
AB-16D mw- AL-3D
' ASH BASIN OLU } M W-6
AL-41)- (VOLUNTARY)
GWA-9BR AL-4BR DRY ASH LANDFILL
*-13S (PHASE II)
M W-13D AB-155
AB-15SL
AB-20S AB-15D
AB-15BR AL-2S
'O'AB-20D AL-2BRLL AL-2BR
GWA-13S
GWA-13 DA
ST f A� PIA IV T RpAD
GWA-12S
GWA-12D
GWA-12BR
M
M
MW-1"1S
MW-11D
AB-13D
AB-13S
AB-14S Q�
AB-14D
AB- S
AB-7D
ASH BASIN
AB-6BRA AB-
AB-6D
AB-6S
O
MS-16
FGD RESIDUE
LANDFILL
PERMIT NO. 1809
0
C- M S-15
O
M S-14
1�k
ipIppow
MS-13
M 5-12
GWA-2DA�
GWA-25
GWA-2D
M W -2 O
AB-12S
AB-12BR -CAB-12SL
AB-12D
AB-SBR
AB-5D
AB-5S
MW-5
O
AB-10S
�}AB-10SL
AB-10BR AB-10D
AB-21S
AB-21D
AB-4S
AB-4 ❑
CAB-4SL
AB-3S
AB-3D
NOTES:
1. PARCEL DATA FOR THE SITE WAS OBTAINED FROM DUKE ENERGY REAL ESTATE AND ISAPPROXIMATE.
2. ASH BASIN WASTE BOUNDARY AND LANDFILL/STRUCTURAL FILL BOUNDARIES ARE APPROXIMATE. SCALE (FEET)
3. THE COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO THE DEFINITION FOUND IN 15A NCAC 02L.0107 (a). 250' 0 250' 500'
4. EXISTING MONITORING WELL LOCATIONS PROVIDED BY DUKE ENERGYAND WSP.
5. EXSITING SHALLOW MONITORING WELLS (S) ARE SCREENED ACROSS THE SURFICIAL WATERTABLE. V, = 500'
6. EXSITING DEEP MONITORING WELLS (D) ARE SCREENED IN THE TRANSITION ZONE BETWEEN COMPETENT BEDROCKAND THE REGOLITH.
7. EXISTING BEDROCK MONITORING WELLS (BR) ARE SCREENED ACROSS WATER BEARING FRACTURES IN COMPETENT BEDROCK.
8. TOPOGRAPHY DATA FOR ONSITE WAS OBTAINED FROM WSP (JULY2015).
9. TOPOGRAPHY DATA FOR OFFSITE WAS OBTAINED FROM NCDOT GEOGRAPHIC INFORMATION SYSTEM (GIS) WEB SITE (DATED 2007).
10. AERIAL PHOTOGRAPHY WAS OBTAINED FROM WSP DATED APRIL 2014.
11. HYDROGRAPHY WAS OBTAINED FROM THE PROVISIONAL JURISDICTIONAL WATERS MAP(USACE APPROVAL PENDING), PROVIDED BY AMEC FOSTER WHEELER, DATED MAY29, 2015.
0 AB-11S
AB-11D
GWA-6S
GWA-6D
GWA-7S
GWA-7D
'-14BR
MW-14D
MW-14S
AL-lS
-1BR `0�- AL-lD
�BG-2S
BG-2BR
0
a
z
z
D
GWA-10S
GWA-10D.ri�E
GWA-15S
�w-
GWA-11BR
v
1 0 B-1
GWA-11D
WA-11S
DRY ASH LANDFILL
,WHATE 1)
ACTIVE ASH BASIN
GWA-1S
GWA-11),jj�
GWA-1BR
RNEM
1l f, . 1,
LAKE NORMAN
ELEVATION 760 FT (APPROXIMATE)
AB-1BR
ii�AB-1D
AB-1S
MW-7S MW-10S
MW-7D MW-10D
-0� MW-8S
M W-8 D
M W-9S
C AB-25 MW-9D
AB-2 D
,p
LEGEND:
-�- -
DUKE ENERGY PROPERTY BOUNDARY
ASH BASIN WASTE BOUNDARY
LANDFILL/STRUCTURAL FILL BOUNDARY
LANDFILL COMPLIANCE BOUNDARY
ASH BASIN COMPLIANCE BOUNDARY
ASH BASIN COMPLIANCE BOUNDARY COINCIDENT
WITH DUKE PROPERTY BOUNDARY
STREAM
WETLAND AREA
ASH BASIN COMPLIANCE
GROUNDWATER MONITORING WELL
ASH BASIN VOLUNTARY
GROUNDWATER MONITORING WELL
CSA GROUNDWATER MONITORING WELL
EXISTING LANDFILL GROUNDWATER MONITORING
WELL (ASH LANDFILLS AND FGD RESIDUE LANDFILL)
POST-CSA ADDITIONAL ASSESSMENT
GROUNDWATER MONITORING WELL
ABANDONED MONITORING WELL
MONITORING WELL LOCATION MAP
CAMA, NPDES AND LANDFILL PROGRAMS
DUKE ENERGY CAROLINAS, LLC
MARSHALL STEAM STATION ASH BASIN
CATAWBA COUNTY, NORTH CAROD NA
DATE
FIGURE
MAY 2017

Table 1. Marshall Steam Station Soil Background Analytical Results
Analyte
Aluminum
Antimony
Arsenic
Barium
Boron
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Strontium
Thallium
Vanadium
Zinc
Calcium
Chloride
Magnesium
Nitrate
Potassium
Sodium
Sulfate
pH (field)
Total
Organic
Carbon
Result Unit
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mglkg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mglkg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
Std. Units
mg/kg
NCDEQ Industrial Health PSRG
100000
94
3
44000
46000
460
200
100000
70
9400
100000
800
5200
8
1200
4400
1200
100000
2.4
1200
70000
NS
NS
NS
100000
NS
NS
NS
NS
NS
NCDEQ Protection of Groundwater PSRG
NS
0.9
5.8
580
45
63
3
360000
0.9
700
150
270
65
1
NS
130
2.1
NS
0.28
6
1200
NS
NS
NS
NS
NS
NS
NS
NS
NS
Sample Name
Sample Date
Range of Depth -
to -Water (ft)
BG-3D(1-2)
6/9/2015
22.87-30.03
34100
a.7-U
8.4
649
57.3 U
1.3
0.69 U
420
27.4
50.2
37600
11.1
243
0.05
1 2.9 U
237
6.7
213
57-U
81.9
59.2
1660
278 U
1 29200
2Z8 UJ
7470
286 U
278 U
6.1 J
605 J
BG-31)(10-12)
6/9/2015
22.87-30.03
29600
53U
5.7
1030
52.9 U
0.34
0.63 U
406
28
29.8
34300
3.2 J
412
0.0085 U
2.6 U
267
3.7 J
200
5:3-U
83.3
72.4
10300
262 U
36700
26.2 UJ
25500
204 J
262 U
7.5 J
363 J
GWA-iBR(8-10)
6/26/2015
41.29-43.69
10700
67.1
5.7 U
128
14.3 U
1.9
0.69 U
6
9_1
20.3
16000
14.5
529
0.01
2.9 U
5.3
5.7-U
19.8
5.7-U
30.4
70.9
755
302 U
2970
30.2 UJ
1840
287 U
302 U
5.8 J-
723 U
GWA-iBR(14-15.5)
6/26/2015
41.29-43.69
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
902 U
GWA-1BR(18-20)
6/26/2015
41.29-43.69
12800
6,2-U
6.2 U
118
15.5 U
1.4
0.74 U
13.4
7_t
21.4
18100
17.7
192
0.0097 J
3.1 U
9.5
6:2-14
12.2
6:2-U
46.7
62.8
408
297 U
2900
29.7 UJ
2060
310 U
297 U
7 J-
2580
GWA-2DA(3-5)
3/13/2017
20*
27500
2.9 U
11
159
6.6 U
2.2
0.17 U
10.8
22.6
30.2
38900
13.2
361
0.0074 J
0.66 U
11.1
0.92 J
3.1
4."
97
46.2
369
63.1 U
8300
6.3 UJ
8210
330 U
91.4
4.7 J
-
GWA-2DA(8-10)
3/13/2017
20*
38400
24`U
1.2 J
270
7.2 U
2.9
0.16 U
16
16.7
83.2
33400
10.1
734
0.0072 J
0.72 U
14.3
1.2 J
6
0.78 J
112
71.5
267
59.7 U
16100
6 UJ
12900
360 U
79
4.8 J
-
G WA-4D(52-53)
5/19/2015
54.64-56.11
18900 J+
6-UJ
6 UJ
345 J+
59.8 U
1.8 J-
0.72 UJ
15
23.2 J-
215 J-
42300 J-
3.7 J-
810 J-
0,0098 U
3 UJ
7.1 J-
61Jd
16.5
6-U
128 J-
70.1 J-
1160
293 UJ
11100 J-
29.3 UJ
9920 J-
299 U
293 UJ
6.2 J
759 U
GWA-513(27.5-29.0)
7/1/2015
31.05-32.38
23000
7-8U
7.9 U
490
19.7 U
2.6
0.94 U
1 3.1
8.3
7.3
31500
1 9.3
509
1 0,013 U
3.9 U
4.5
7-.9-11
60.7
Z.Bkl
67.7
101
260
384 U
11100
384 UJ
14000
394 U
384 UJ
5.8 J
931 U
GWA-14S(3-5)
3/9/2017
43*
1890
.
.
23.
4
2.6
183000
1235.5
34
064JU
2.7
1J
135
34
330.8
73
.
5.1.4J
2
5.6 UJ
33902
5566..1 U
5.2 J
-
9
0.087
90GWA-14S(8-10)
6.3 UJ
2720
UU
5J
51 J3/9/2017
-
MW-14BR(31.5-33.0)
7/10/2015
34.72-36.24
34400
6,50-U
6.50 U
828
3.30 U
6.3
0.78 U
61.9
16.8
104
50400
26.7
421
0.01 U
3
45.2
6bU
19.1
6b"
128
101
412.00J
329.00U
12300
32.90 UJ
10800
212
329.00 U
6.00 J
794 U
Total Number of Viable Soil Samples >>
12
11
0
11
11
11
11
11
11
11
11
11
11
11
11
11
11
6
11
1
11
11
11
11
11
11
11
11
11
11
8
General Notes:
Depth -to -Groundwater data was collected in: 7/15, 9/15, 11/15, 12/15, 4/16, 6116, and 9116 (month/yr)
*Approximate depth to water measurement provided based on depth to water observed when advancing the boring and installing the GWA-2DA and GWA-14S monitoring wells.
"Strike-throughs" indicate samples that are not included in the viable sample count due to the method detection limit (MDL) for the non -detect result being greater than the North Carolina Protection of Groundwater (POG) Preliminary Soil Remediation Goal (PSRG) for that constituent.
mg/kg - milligrams per kilogram
NA- Not analyzed or not reported by analytical laboratory
Std. Units - pH units
Comparison Criteria:
NS - No applicable standard for this parameter
Shading indicates exceedance of either applicable criteria.
bold - indicates exceedance of NCDEQ
Industrial Health Based PSRG
Italio'underlfne- indicates exceedance of
NCDEQ Protection of Groundwater PSRG
North Carolina Department of Environmental Quality Division of Waste Management Soil Remediation Goals Table (October 2016) - Preliminary
Industrial Health Based Soil Remediation Goal (PSRG) and Protection of Groundwater PSRG.
**Note: No PSRG for Total Chromium is currently available, as a sunogate the PSRG for Trivalent Chromium was used for comparison purposes only.
Qualifier Notes:
U -- Not detected above the reporting detection limit.
J - Estimated Concentration
J+- Estimated concentration, biased high.
J--Estimated concentration, biased low.