HF Lee - GW BTV TM FINAL_20170905

41P
synTerra
TECHNICAL MEMORANDUM
Date: September 5, 2017 File: 1026.04
To: Ryan Czop (Duke Energy)
Cc: Kathy Webb (SynTerra)
From: Judd Mahan (SynTerra)
Subject: Background Threshold Values for Groundwater
H.F. Lee Energy Complex— Goldsboro, NC
An updated background groundwater dataset was provided to the North Carolina Department
of Environmental Quality (NCDEQ) for H.F. Lee Energy Complex (H.F. Lee) 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) after October 31, 2017. BTVs for soil are provided under separate cover.
The revised background groundwater dataset provided to NCDEQ on May 26, 2017 addressed
comments provided in a letter by NCDEQ (Zimmerman to Draovitch, April 28, 2017). NCDEQ
requested Duke Energy collect at least 10, rather than the previously planned eight, valid
samples from background monitoring wells prior to determination of BTVs for constituents
within each flow system. For groundwater datasets with less than 10 valid samples available
for determination of BTVs, no formal upper tolerance limit (UTL) statistics will be run and the
provisional BTV (PBTV) for a constituent and groundwater flow system will be computed to be
either:
ill The highest value, or
0 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.
NCDEQ requested that the updated background groundwater dataset exclude data from the
background data set due to one or more of the following conditions:
01 Sample pH is greater than or equal to 8.5 standard units (S.U.) unless the regional
DEQ office has determined an alternate background threshold pH for the site;
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Background Threshold Values for Groundwater September 5, 2017
H.F. Lee Energy Complex Page 2 of 3
0 Sample turbidity is greater than 10 Nephelometric Turbidity Units (NTUs);
,67 Result is a statistical outlier identified for background sample data presented to
NCDEQ on May 26, 2017;
0 Sample collection occurred less than a minimum 60 days between sampling events;
and
0 Non -detect results are greater than 2L/IMAC.
Additional site -specific requirements related to the groundwater background dataset for H.F.
Lee as outlined in the July 7, 2017 NCDEQ letter, such as exclusion of data not approved by
NCDEQ, have been incorporated into the groundwater 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).
GROUNDWATER BACKGROUND DATA
The current background monitoring well network consists of wells installed within three flow
zones — surficial, Black Creek, and Cape Fear. Well locations are presented on Figure 1.
Background datasets provided to NCDEQ on May 26, 2017 were revised based on input from
NCDEQ in the July 7, 2017 letter. The revised background datasets for each flow system
utilized to statistically determine naturally occurring concentrations of inorganic constituents in
groundwater are provided in Table 1. The following sections summarize the refined
background datasets along with the results of the statistical evaluations for determining BTVs.
SURFICIAL
Seven wells — AMW-11S, AMW-12S, AMW-13S, AMW-17S, CCR-100S, IMW- 01S, and IMW-
03S — monitor background groundwater quality within the surficial flow zone. The CCR-100S
location was not included in the NCDEQ approved background location list of July 7, 2017.
However, in follow-up correspondence on August 14, 2017, NCDEQ concurred that this
surficial flow zone background well was appropriate for use in development of BTVs. Samples
collected less than 60 days between sampling events, statistical outliers, and invalid data were
omitted prior to statistical determinations. The updated background dataset for the surficial
flow zone meets the minimum requirement of 10 samples for all constituents. The revised
surficial flow zone background dataset is presented in Table 1. BTVs were calculated for
constituents monitored within the surficial flow zone using formal UTL statistics. BTVs for the
surficial flow zone are presented in Table 2.
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Background Threshold Values for Groundwater September 5, 2017
H.F. Lee Energy Complex Page 3 of 3
BLACK CREEK
As discussed between Duke Energy, NCDEQ and SynTerra, sampling of monitoring wells from
the Black Creek flow zone have not indicated exceedances for arsenic or boron, the primary
constituents that occur at levels greater than background at H.F. Lee. Additionally, the Black
Creek is limited in both horizontal and vertical extent. It has been been identified only in wells
at the east side of the active basin. Only one well - AMW-17BC - monitors background
groundwater quality within the Black Creek flow zone. Due to these factors, statistical
determination of background concentrations for constituents in the Black Creek flow zone is not
anticipated as a requirement for completion of the CSA.
The AMW-17BC location was not included in the NCDEQ approved background location list of
July 7, 2017. However, in follow-up correspondence on August 14, 2017, NCDEQ concurred
that this Black Creek flow zone background well was appropriate for use in development of
BTVs. Currently, two valid samples have been collected from AMW-17BC. The background
groundwater dataset for the Black Creek flow zone does not meet the minimum requirement of
10 samples. Table 1 presents the revised background dataset for the Black Creek flow zone. No
formal UTL statistics were performed and PBTVs were not computed with only two valid
samples. For the purposes of comparison, the 2L/IMAC will be relied upon until sufficient data
is available to develop BTVs.
CAPE FEAR
Seven wells - AMW-11BC, AMW-12BC, AMW-13BC, AMW-16BC, IMW- 0113C, IMW- 02BC and
IMW- 03BC - monitor background groundwater quality within the Cape Fear flow zone. In the
July 7, 2017 letter, NCDEQ identified AMW-16BC as a location potentially in contact with Black
Creek flow zone. Review of boring logs indicates this location is within the Cape Fear flow
zone and is thus included in the Cape Fear background dataset. Samples collected less than 60
days between sampling events, statistical outliers, and invalid data were omitted prior to
statistical determinations. The updated background dataset for the Cape Fear flow zone meets
the minimum requirement of 10 samples for all constituents. The revised Cape Fear flow zone
background dataset is presented in Table 1. BTVs were calculated for constituents monitored
within the Cape Fear flow zone using formal UTL statistics and are presented in Table 2.
LIST OF FIGURES:
Figure 1 Well Location Map
LIST OF TABLES:
Table 1 Background Groundwater Results through March 2017
Table 2 Background Threshold Values for Groundwater
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MEMO \ HF Lee \ Groundwater \ HF Lee - GW BTV TM_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
H.F. Lee Energy Complex
FIGURE
P:\Duke Energy Progress.1026\Statistics—CAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ HF Lee \ Groundwater \ HF Lee - GW BTV TM_FINAL.docx

Background Threshold Values for Groundwater September 5, 2017
H.F. Lee Energy Complex
TABLES
P:\Duke Energy Progress.1026\Statistics—CAMA\Background Determinations for NCDEQ July 72017\BTV TECH
MEMO \ HF Lee \ Groundwater \ HF Lee - GW BTV TM_FINAL.docx

TABLE 1
UPDATED BACKGROUND GROUNDWATER ANALYTICAL RESULTS THROUGH MARCH 2O17
H.F. LEE ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, GOLDSBORO, NC
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TABLE 1
UPDATED BACKGROUND GROUNDWATER ANALYTICAL RESULTS THROUGH MARCH 2O17
H.F. LEE ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, GOLDSBORO, NC
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Preoared bv: JHG Checked bv: RHJ
Notes:
S4 - Indicates value omitted from dataset.
- Indicates parameter not measured or analyzed.
®Indicates data removed due to out as an outlier
- Indicates data removed due to autocorrelation
< concentration not detected at or above the adjusted reporting limit. pCbI_ - picocuries per liter
mg - N/L - Milligrams nitrogen per liter S.U. - Standard Unit
mg/L - Milligrams per liter ug/L - Micrograms per Liter
NE - Not established
NTU - Nephelometric turbidity unit
' - Interim Maximum Allowable Concentrations (IMACs) of the 15A NCAC 02L Standard, Appendix 1, April, 1, 2013.
- Hexavalent chromium does not have a NC 21JIMAC standard; therefore, the NC 2L standard for Intel chromium is relied upon as a surrogate.
e - Target analyte detected in method blank at or above the reporting limit. Target analyte concentration in sample is less than 1OX the concentration in the method blank. Analyte concentration in sample could be due to blank contamination.
82 - Target analyte was detected in blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit Analyte concentration in sample is valid and may be used for compliance purposes.
83 - Target analyte was detected in Continuing Calibration Blank(s) at a concentration greater than 1/2 the reporting limit but less than the reporting limit. Analyte concentration in sample is valid and may be used for compliance purposes.
CL - The continuing calibration for this compound is outside of Pace Analytical acceptance limits. The results may be biased low.
D3 - Sample was diluted due to the presence of high levels of non -target analytes or other matrix interference.
D6 - The relative percent difference (RPD) between the sample and sample duplicate exceeded laboratory control limits.
H - Sample analyzed past the recommended holding time.
L3 - Analyte recc,ery in the laboratory control sample (LCS) exceeded quality control (QC) limits. Analyte presence below reporting limits in associated samples. Results unaffected by high bias.
Ml - Matrix spike recovery was high: the associated Laboratory Control Spike (LCS) was acceptable.
M2 - Matriz spike recovery was Low: the associated Laboratory Control Spike (LCS) was acceptable.
M4 -The spike recovery value was unusable since the analyte concentration In the sample was disproportionate to the spike level. The associated Laboratory Control Spike recovery was acceptable.
M6 - Matrix spike and Matrix spike duplicate recovery not evaluated against control limits due to sample dilution.
NI - This sample was inadvertently collected with sample running through the flow cell and should be considered invalid based on possible contamination from the Now cell.
Rl - Relative Percent Difference (RPD) value was outside control limits.
S - Associated calibration check did not meet specified criteria.
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TABLE 2
GROUNDWATER BACKGROUND THRESHOLD VALUES
H.F. LEE ENERGY COMPLEX
DUKE ENERGY PROGRESS, LLC, GOLDSBORO, NC
Parameter
Reporting Unit
NCAC 02L Standard
Background Threshold Values
Surficial
Cape Fear
pH*
S.U.
6.5-8.5
3.4 - 6.8
5.3 - 8.3
Alkalinity
mg/L
NE
73.9
219
Aluminum
pg/L
NE
1059
264
Antimony
pg/L
1A
1
1
Arsenic
pg/L
10
1
1.42
Barium
pg/L
700
641
342
Beryllium
pg/L
4A
1
1
Bicarbonate
mg/L
NE
73.9
219
Boron
pg/L
700
50
256
Cadmium
pg/L
2
1
1
Calcium
mg/L
NE
11.2
30.8
Carbonate
mg/L
NE
5
5
Chloride
mg/L
250
19
72
Chromium (VI) 1
Ng/L
10
0.354
0.15
Chromium
pg/L
10
1
1
Cobalt
Ng/L
1A
13.7
8.97
Copper
pg/L
1000
4.39
1
Iron
pg/L
300
6320
11600
Lead
pg/L
15
2.61
1
Magnesium
mg/L
NE
6.55
6.94
Manganese
pg/L
50
1140
1560
Mercury
pg/L
1
0.05
0.05
Methane
pg/L
NE
16.7
7701
Molybdenum
pg/L
NE
1
10.9
Nickel
pg/L
100
9.81
15.3
Nitrate + Nitrite
mg-N/L
NE
11
0.953
Potassium
mg/L
NE
4.95
5.2
Selenium
pg/L
20
1
1
Sodium
mg/L
NE
12.5
102
Strontium
pg/L
NE
119
133
Sulfate
mg/L
250
54.7
23
Sulfide
mg/L
NE
0.1
0.1
TDS
mg/L
500
163
385
Thallium
pg/L
0.2°
0.2
0.2
TOC
mg/L
NE
1.5
1.7
Vanadium
pg/L
0.3"
0.471
2.78
Zinc
pg/L
1000
20.9
8
Radium (Total)
pCi/L
NE
23.4
3.01
Uranium (Total)
Ng/ml-
NE
0.002
0.0004
Prepared by: LWD Checked by: TCP
Notes:
* - Upper and lower tolerance limits calculated for parameter
A - Interim Maximum Allowable Concentrations (IMACs) of 15A NCAC .021- Standard, Appendix 1, April 1, 2013
pg/L - micrograms per liter
pg/mL - micrograms per milliliter
t - Provisional; dataset contains less than 10 valid samples
- Hexavalent chromium does not have a NC 2UIMAC standard; therefore, the NC 2L standard for total chromium is relied upon as a surrogate.
mg - N/L - Milligrams nitrogen per liter
mg/L - milligrams per liter
NE - Not Established
pCi/L - picocuries per liter
Radium (Total) - Radium-226 and Radium-228 combined
S.U. - Standard Unit
TDS - Total Dissolved Solids
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