Bradley Report (April 2016)

■F T
REPORT ON
www.haleyaldrich.com
EVALUATION OF WATER SUPPLY WELLS IN THE VICINITY OF
DUKE ENERGY COAL ASH BASINS IN NORTH CAROLINA
by Haley & Aldrich, Inc.
Boston, Massachusetts
for Duke Energy

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
List of Tables
List of Figures
List of Acronyms
iv
1.
Introduction
1
1.1 CURRENT CAMA STATUS
1
1.2 APPROACH TO EVALUATION OF WATER SUPPLY WELLS
2
1.3 REPORT ORGANIZATION
3
2.
Sources of Data
5
2.1 NCDEQ WATER SUPPLY WELL DATA
5
2.2 NCDEQ RECONNAISSANCE OR BACKGROUND WATER SUPPLY WELL DATA
5
2.3 DUKE ENERGY BACKGROUND WATER SUPPLY WELL DATA
6
2.4 PER -FACILITY MONITORING WELL DATA
6
2.5 REGIONAL BACKGROUND WATER SUPPLY WELL DATA
6
2.6 DATA MANAGEMENT
6
3.
Water Supply Well Evaluation
8
3.1 SCREENING LEVELS
8
3.2 SCREENING LEVELS FOR VANADIUM AND HEXAVALENT CHROMIUM
8
3.3 SCREENING METHODOLOGY
9
3.4 CCR RULE CONSTITUENTS
9
4.
STATISTICAL EVALUATION OF BACKGROUND
11
4.1 BACKGROUND DATASETS
11
4.2 INITIAL STATISTICAL EVALUATION
12
4.2.1 Regional Water Supply Well Data
12
4.2.2 Facility Monitoring Well Data
12
4.3 RAW DATA EVALUATION
12
4.4 TESTING OF STATISTICAL ASSUMPTION
13
4.5 BTV ESTIMATE
14
4.6 FACILITY -SPECIFIC APPLICATION
15
5.
Groundwater Flow Evaluation
16
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6. Groundwater Characteristics Evaluation 17
6.1 EVALUATION APPROACH
17
6.2 CCR -RELATED CONSTITUENTS SCREENING FOR SIGNATURE DEVELOPMENT
18
6.3 DATA ANALYSIS METHODS
18
6.3.1 Box Plot
18
6.3.2 Correlation Plot
18
6.3.3 Piper Plot
19
6.4 DATA SYNTHESIS
19
7. Summary of Results
20
7.1 AVAILABLE DATA
20
7.2 RISK-BASED SCREENING EVALUATION
21
7.3 BACKGROUND EVALUATION
22
7.4 GROUNDWATER FLOW EVALUATION
22
7.5 GROUNDWATER CHARACTERISTICS EVALUATION
22
7.6 CONCLUSIONS
23
8. References
24
Tables
Figures
Appendix A
—Allen Steam Station
Appendix B —
Belews Creek Steam Station
Appendix C —
Buck Steam Station
Appendix D
— Cliffside Steam Station
Appendix E —
Marshall Steam Station
Appendix F —
Mayo Steam Electric Plant
Appendix G
— Roxboro Steam Electric Plant
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List of Tables
Table No. Title
1 Summary of NCDEQ and Duke Energy Water Supply Well and Background Well
Samples and Well Counts
2 Summary of Screening Values
3 Statistical Summary of NCDEQ-Sampled Water Supply Well Data
4 Summary of NCDEQ-Sampled Water Supply Well Data Screening
5 Statistical Summary of NCDEQ-Sampled Background Water Supply Well Data
6 Summary of NCDEQ-Sampled Background Water Supply Well Data Screening
7 Statistical Summary of Duke Energy -Sampled Background Water Supply Well
Data
8 Summary of Duke Energy -Sampled Background Water Supply Well Data
Screening
9 Summary of Available Background Data for Groundwater
10 Comparison of Background Threshold Values
List of Figures
Figure No. Title
1 North Carolina Department of Environmental Quality: Draft Ash Basin Risk
Classification Map
2 Example Box Plot and Piper Plot
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List of Acronyms
2L Standards North Carolina Groundwater Quality Standards as specified in Title 15A NCAC.0202L
BTV Background Threshold Value
CAMA North Carolina Coal Ash Management Act of 2014
CAP Corrective Action Plan
CC Confidence Coefficient
CCR Coal Combustion Residuals
CSA Comprehensive Site Assessment
EDF Empirical Distribution Function
GOF Goodness -Of -Fit
HDR HDR, Inc.
IID Independent, Identically Distributed
IQR Interquartile Range
IMAC Interim Maximum Allowable Concentrations
IQR Interquartile Range
KM Kaplan -Meier
µg/L Micrograms per Liter
MCL Maximum Contaminant Level
MDL Method Detection Limit
NCAC North Carolina Administrative Code
NCDEQ North Carolina Department of Environmental Quality
ND Non -Detect
NCDHHS North Carolina Department of Health and Human Services
Q -Q Plot Normal Quantile -Quantile Plot
ROS Robust Regression on Order Statistics
RSL Risk -Based Screening Level
SCM Site Conceptual Model
SMCL Secondary Maximum Contaminant Level
S -W Shapiro -Wilk
TDS Total Dissolved Solids
UPL95 95% Upper Prediction Limit
USEPA U.S. Environmental Protection Agency
USGS U.S. Geological Survey
UTL95-95 Upper Tolerance Limit with 95% confidence and 95% coverage
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1. Introduction
This document was prepared to supplement previous work completed by Duke Energy to meet the
requirements of the North Carolina Coal Ash Management Act of 2014 (CAMA, 2014) for its coal -fueled
generating stations. Duke Energy owns and operates, or has operated 14 coal -fueled electric generating
facilities in the state of North Carolina. Figure 1 shows the locations of the Duke coal -fueled fleet in
North Carolina.
1.1 CURRENT CAMA STATUS
The CAMA is primarily administered by the North Carolina Department of Environmental Quality
(NCDEQ). The CAMA requires the NCDEQ to, as soon as practicable, but no later than January 31, 2016,
prioritize for the purpose of closure and remediation coal combustion residuals (CCR) surface
impoundments, including active and retired sites, based on these sites' risks to public health, safety, and
welfare, the environment, and natural resources.
On 31 January 2016, NCDEQ released draft proposed risk classifications for Duke Energy's coal ash
impoundments in North Carolina in the document "Coal Combustion Residual Impoundment Risk
Classifications, January 2016" (NCDEQ, 2016). Four of the facilities were ranked High risk, per the
CAMA. Four facilities (or portions thereof) were ranked Intermediate risk based on the position of ash
impoundments in the 100 -year flood level (see below for the exception to this basis). Six facilities (or
portions thereof) were ranked Low to Intermediate risk, and three facilities (or portions thereof) were
ranked Low risk.
The Low to Intermediate risk classification is not specified in the CAMA; for those facilities with this
"interim" classification, a final Low risk or Intermediate risk classification will need to be made at the
end of the public review process. The following facilities have draft NCDEQ Low to Intermediate
classifications:
• Allen Steam Station (Allen)
• Belews Creek Steam Station (Belews Creek)
• Buck Steam Station (Buck)
• Cliffside Steam Station (Cliffside) — [one ash basin; two ash basins are classified as Low risk]
• Marshall Steam Station (Marshall)
• Roxboro Steam Electric Plant (Roxboro) — [one ash basin; another ash basin is classified as Low
risk, and one former impoundment area is classified as Intermediate risk as it was identified
after the site investigation was completed]
The primary basis for the Low to Intermediate risk classification was stated by NCDEQ as the current
"uncertainty related to site conditions that may relate to potential impacts to up -gradient and side -
gradient well users." The most cited information needs in the document included incomplete
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background concentration determination, and incomplete capture zone modeling for the water supply
wells in the vicinity of each facility.
In addition to the six facilities listed above, this report also includes an evaluation of:
• Mayo Steam Electric Plant (Mayo)
Mayo is classified as Low risk; by including it in this report, all Low to Intermediate risk and all Low risk
ash basins are evaluated using the approach identified below.
1.2 APPROACH TO EVALUATION OF WATER SUPPLY WELLS
There is not a single metric that can be used to identify if a well has been impacted by a release from a
coal ash management unit. This is due in large part to the fact that all of the constituents that are
present in coal ash and that could be released to groundwater are naturally occurring. The challenge is
to understand these background conditions, and in that context evaluate whether there has been an
impact from a release of constituents from coal ash.
Based on our understanding of the behavior of constituents that can be released from coal ash into
groundwater, the U.S. Environmental Protection Agency (USEPA) has identified those constituents that
are considered together to be indicators of a potential release from coal ash; these are identified as the
Appendix III constituents in the Hazardous and Solid Waste Management System; Disposal of Coal
Combustion Residuals from Electric Utilities (CCR Rule; USEPA, 2015a). Of these, boron and sulfate are
the most common constituents used to evaluate the potential for an impact in groundwater. These
constituents move with groundwater flow unlike other constituents whose movement is impeded by
chemical or physical interactions with soil and weathered rock.
Constituent concentrations alone are not sufficient to identify whether impact has occurred. There
must also be a transport pathway from the coal ash management unit of interest to the specific well or
wells of interest. For an exposure pathway to be complete, the following conditions must exist (as
defined by USEPA (1989)):
1) A source and mechanism of chemical release to the environment;
2) An environmental transport medium (e.g., water);
3) A point of potential contact with the receiving medium by a receptor; and
4) A receptor exposure route at the contact point (e.g., ingestion).
Thus, to understand if a particular well or wells have been impacted by a release from a coal ash
management unit, the following are needed:
• An evaluation of the magnitude of concentrations of the constituents in the well;
• An evaluation of those detected constituents in relation to background concentrations in
groundwater;
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• Consideration of the information available on the potential for there to be a complete transport
pathway between a coal ash management unit and a well; and
An evaluation of the potential correlation between the co -presence and concentration of
constituents considered to be indicators of a release from a coal ash management unit.
The purpose of this document is to provide the NCDEQ with additional information needed to develop a
final risk classification for the Duke Energy ash basins under the CAMA requirements. A technical weight
of evidence approach has been used to evaluate the available data for these facilities to determine
whether or not the local water supply wells sampled by NCDEQ in the vicinity of these facilities may be
impacted by a release from an ash basin or coal ash management area. This report provides technical
evaluations for each of the seven facilities in four important assessment areas:
1) An evaluation of the data collected by NCDEQ for local private and public water supply wells,
and "reconnaissance" or background water supply wells, with respect to groundwater standards
and screening levels, and evaluation of background water supply well data collected by Duke
Energy with respect to the same screening levels;
2) Additional statistical analysis of regional background groundwater data (NCDEQ and Duke
Energy data), and facility -specific background groundwater data;
3) Amore comprehensive evaluation of groundwater flow with respect to local water supply wells,
including a water supply well capture zone analysis (where appropriate); and
4) A detailed comparison of facility -specific coal ash groundwater chemistry, background
groundwater chemistry (both regional and facility -specific), and local water supply well
chemistry.
1.3 REPORT ORGANIZATION
This report provides an overview of the four-part evaluation process used for each of the seven (7)
facilities. This report is divided into eight sections:
• Section 2 describes the sources of data used in the evaluation.
• Section 3 describes the methods used to conduct the standards-based and risk-based screening
of the water supply well data.
• Section 4 provides the methods used to conduct the statistical evaluation of the background
groundwater data and the development of the background threshold values.
• Section 5 provides an overview of the groundwater flow evaluation.
• Section 6 describes the methods used to conduct the groundwater chemistry analysis.
• Section 7 summarizes the results for the facilities evaluated.
• Section 8 provides the references used.
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The appendices provide the details of the evaluation for each of the facilities:
A. Allen
B. Belews Creek
C. Buck
D. Cliffside
E. Marshall
F. Mayo
G. Roxboro
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2. Sources of Data
Data used in this analysis include:
1) Local water supply well data collected by NCDEQ in the vicinity of the seven Duke Energy
facilities.
2) "Reconnaissance" or background water supply well data collected by NCDEQ in the environs of
the Duke Energy Allen, Buck, and Marshall facilities.
3) Background water supply well data collected by Duke Energy in the environs, within 2 to 10
miles, of each of the seven facilities.
4) On-site monitoring well data collected by Duke Energy and their site investigation lead
contractors, HDR, Inc. (HDR), and Synterra Corporation (Synterra).
Each of these is discussed below.
2.1 NCDEQ WATER SUPPLY WELL DATA
The CAMA (2014) requires that "all drinking water supply well within one-half mile down -gradient from
the established compliance boundary of the impoundment" be identified (§130A-309.209. (c)). At the
request of NCDEQ, a receptor survey was conducted by Duke Energy at each facility for the purpose of
identifying drinking water wells within a 0.5 -mile (2,640 -foot) radius of each facility's ash basin(s)
compliance boundary. Using this information, NCDEQ offered to sample water supply wells within a
1,000 foot radius, and subsequently within a 1,500 radius of the ash basin(s)' compliance boundary,
referred to here as the "local" area. Table 1 provides a summary by facility of the number of wells
sampled by NCDEQ and the number of sample results. (See Section 2.6 below for how the data were
summarized for this analysis.)
The NCDEQ provides a "Water Well Testing Information" webpage here: http://deg.nc.gov/news/hot-
topics/coal-ash-nc/well-water-testing-information
The NCDEQ publicly available local water supply well data are posted here:
https://ncdenr.s3.amazonaws.com/s3fs-public/document-
library/Ful I%20Wel l%20Water%20Testi ng%20Results%20For%20Posting%208.20.pdf
NCDEQ provided Duke Energy with an Excel version of the most recent data, dated 2016-03-08. These
data were used in this analysis. The local water supply well data were evaluated by facility in each of the
appendices to this report.
2.2 NCDEQ RECONNAISSANCE OR BACKGROUND WATER SUPPLY WELL DATA
In what it describes as a reconnaissance study, NCDEQ collected 24 water samples from 24 water supply
well locations in the vicinity of three of the Duke Energy facilities: Allen (seven [7] locations), Buck
(seven [7] locations), and Marshall (ten [10] locations), as shown on Table 1.
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NCDEQ provides the following description: "The study provides a limited evaluation of the distribution
of metals and other parameters that may be naturally occurring in the groundwater, and provides data
for staff to develop a better understanding of background concentrations of metals and other
parameters in areas that are not hydraulically connected to groundwater beneath Duke Energy's coal-
fired power plant facilities."
The NCDEQ background water supply well data are publicly available at: http://deg.nc.gov/news/hot-
topics/coal-ash-nc/coal-ash-news (note, as of this writing, some of the links are not functional).
In October 2015, NCDEQ provided Duke Energy with Excel versions of 16 of the 24 analytical results
posted on the website. The Excel versions were used in this evaluation and supplemented with the
missing results that are available in PDF on the website.
2.3 DUKE ENERGY BACKGROUND WATER SUPPLY WELL DATA
Duke Energy developed a background water supply well dataset by offering to sample private drinking
water wells for facility employees, contractors, and others associated with Duke Energy, if their well was
located generally between 2 miles and 10 miles of each facility.
Table 1 shows the number of background water supply wells/samples from those wells.
2.4 PER -FACILITY MONITORING WELL DATA
Monitoring well data are available for each of the seven facilities included in this analysis. The data
include samples from ash porewater wells, and groundwater monitoring wells screened at various
depths in upgradient (background), downgradient, and lateral or side gradient locations. The specifics of
each dataset are provided in the Appendices.
The background monitoring well data are referred to as the "facility -specific background monitoring well
data" or "facility -specific background data."
2.5 REGIONAL BACKGROUND WATER SUPPLY WELL DATA
The background water supply well data collected by NCDEQ and Duke Energy are referred to for each
facility as "regional background water supply well data" or "regional background data" to distinguish
these data from the "facility -specific background monitoring well data."
After statistical evaluation, as described in Section 4 and in each of the appendices, confirmed that it
was appropriate, the NCDEQ background water supply well data and the Duke Energy background water
supply well data were combined into one dataset each for Allen, Buck, and Marshall, as indicated on
Table 1.
2.6 DATA MANAGEMENT
The data for this analysis were managed in an EQuIS database. Where there were multiple results for a
single well in the NCDEQ-sampled local water supply well dataset, a representative value was identified
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to be used in the evaluation, which is defined as the maximum of the detected values if the analytical
results are detected values. If the analytical results are all not detected, the lowest reporting limit is
defined as the representative value.
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3. Water Supply Well Evaluation
Analytical data for the local and regional background water supply wells for each of the facilities were
compared to screening levels and standards, as described below.
3.1 SCREENING LEVELS
The screening levels used in this evaluation are provided on Table 2. They are from both State and
Federal (USEPA) sources, as follows:
• 2L Standards: NCAC. 2013. 15A NCAC 02L.0202. Groundwater Standard (2L), Classifications
and Water Quality Standards Applicable to Groundwaters of North Carolina. North Carolina
Administrative Code. April 1, 2013. These values include Interim Maximum Allowable
Concentrations (IMAC). Available at:
httD://Dortal.ncdenr.ora/c/document library/Ret file?uuid=laa3fal3-2cOf-45b7-ae96-
5427fb1d25b4&2rouDld=38364
• Federal Drinking Water Standards: Maximum Contaminant Levels (MCLS) and Secondary
Maximum Contaminant Levels (SMCLs). USEPA. 2012. 2012 Edition of the Drinking Water
Standards and Health Advisories. Spring 2012. Available at:
http://water.epa.gov/drink/contaminants/index.cfm. Note that the MCLs are enforceable
standards for public drinking water supplies, and that the SMCLs are not enforceable standards.
NCDHHS Screening Levels: NCDHHS. 2015. DHHS Screening Levels. Division of Public Health,
Epidemiology Section, Occupational and Environmental Epidemiology Branch. North Carolina
Department of Health and Human Services. April 24, 2015. Available at:
http://portal.ncdenr.org/c/document library/get file?p I id=1169848&folderld=24814087&na
me=DLFE-112704.PDF. Note that these screening levels have been developed for water supply
well sampling near coal ash facilities, and do not apply to other areas of the state, or to drinking
water supplies.
• USEPA Risk -Based Screening Levels (RSLs): USEPA. 2015b. USEPA Risk -Based Screening
Levels. November 2015. Available at: http://www2.epa.gov/risk/risk-based-screening-table-
generic-tables. The RSLs are purely risk-based levels, derived using standard default exposure
parameters that do not take into consideration treatment technologies or regulatory issues.
3.2 SCREENING LEVELS FOR VANADIUM AND HEXAVALENT CHROMIUM
The analysis provided in this report and its appendices uses the currently available IMAC for vanadium
(0.3 micrograms per liter [µg/L]) and NCDHHS screening level for hexavalent chromium (0.07 µg/L).
These are the values used by the NCDHHS to issue "Do Not Drink" letters to the majority of water supply
well owners, both local to each facility and regionally for those background water supply wells sampled
by NCDEQ. However, NCDEQ announced that it has changed those values and has rescinded many of
the "Do Not Drink" letters sent to residents due to the change. Because the updated values have not
been published, they have not been incorporated into the analysis in this report. However, to account
for the change, the discussion of the results for each facility does not focus on these two constituents.
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3.3 SCREENING METHODOLOGY
The analytical results for each well for all three water supply well data sets described in Section 2 are
compared to each of these four types of screening levels.
I SOURCES OF DATA I SCREENING LEVELS I
1) NCDEQ Water Supply Well Data
2) NCDEQ Reconnaissance or Background Well
Data
3) Duke Energy Background Water Supply Well
Data
1) 2L Standards (including IMACs)
2) Federal Drinking Water Standards
3) DHHS Screening Levels
4) USEPA Risk -Based Screening Levels (RSLs)
The screening comparisons are presented by facility in each of the appendices to this report. Each of
the screening tables provides the analytical data by well location and by constituent. Each row presents
the analytical data from one well sample. The constituents have been organized in columns left to right
based on the constituents required for groundwater monitoring under the federal CCR Rule (USEPA,
2015a) (see Section 3.4, below). Thus, Appendix III (Detection Monitoring) constituents are listed first,
followed by Appendix IV (Assessment Monitoring) constituents, followed by all others. In the "All
Others" category, vanadium has been listed first — the remaining constituents are presented by
alphabetical order.
The four sets of screening levels are listed at the top of each table in the appendices. There are four
screening tables for each set of water supply well data for each facility; each of the tables provides the
results of screening using one set of screening levels. For example:
• The first table presents the results of the comparison to 2L groundwater standards/IMAC;
• The second table presents the results of the comparison to federal MCLS/SMCLs;
• The third table presents the results of the comparison to NCDHHS screening levels; and
• The fourth and last table presents the results of the comparison to USEPA RSLs.
Yellow highlighting is used to indicate results that are above the applicable screening level; gray
highlighting is used to indicate that the detection limit for a non -detect result is above the applicable
screening level.
3.4 CCR RULE CONSTITUENTS
The constituents identified for Detection Monitoring and Assessment Monitoring under the CCR Rule
were identified by USEPA as part of the six-year long rule-making process that culminated in the 2015
Final Rule (USEPA, 2015a).
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The constituents included on the NCDEQ private well sampling analyte list that are also identified for
detection monitoring in the CCR Rule are: boron, calcium, chloride, pH, sulfate, and total dissolved
solids (TDS). These are constituents that are considered to be indicators of potential releases from a
coal ash management unit. The presence of these constituents in groundwater is not enough to
conclude that there has been a release from a coal ash management unit; it is the magnitude of the
concentrations, the potential correlations between the constituent concentrations, and importantly the
information on the hydrogeology of an area that are used to make such a determination.
The constituents identified by USEPA in Appendix IV for Assessment Monitoring are those that USEPA
has identified as constituents most likely to be present in groundwater at levels that may present a risk
to human health or the environment if there has been a release from a coal ash management unit. The
Appendix IV constituents included in the NCDEQ private well sampling are:
Antimony
Cadmium
Mercury
Arsenic
Chromium
Molybdenum
Barium
Cobalt
Selenium
Beryllium
Lead
Thallium
The Appendix IV constituents were identified by USEPA using a very conservative national risk
assessment evaluating potential impacts of ash management units on groundwater (USEPA, 2015c).
This is not to say that all of these constituents would be present at concentrations above screening
levels in all locations if there has been a release from an ash management unit — only that there is the
potential for release of these constituents that could result in concentrations in groundwater above
screening levels. This potential is the basis for the development of the Appendix IV list. The USEPA risk
assessment considered many other constituents, as shown in the table from the Executive Summary of
the risk assessment:
Table ES -1. List of Chemical Cotistiltrietits Evaluated iti the CCR Risk Assessment
■ Aluminum
a Cadmium
■ Iron
■ Molybdenurn
Strontium
■ Ammonia
■ Calcium
■ Lanthanum
■ Nickel
■ Sulfate
■ Antimony
■ Chloride
■ Lead
■ Nitrate J Nitrite
■ Sulfide
■ Arsenic
■ Chromium
■ Lithium
a 'Selenium
Thallium
■ Barium
E Cobalt
■ Magnesium
. Silicon
Uranium
■ Beryllium
■ Copper
■ Manganese
. Silver
■ Vanadium
■ Baron
■ Fluoride
■ Mercury
■ Sodium
■ Zinc
Most notably, vanadium was evaluated quantitatively but was not included in Appendix IV based on the
national risk assessment results.
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4. STATISTICAL EVALUATION OF BACKGROUND
It is important to note that all of these constituents are naturally present in our environment, as shown
by work conducted by the U.S. Geological Survey (USGS, 2014), and they are also naturally occurring in
groundwater (USGS, 2011).
Applicable statistical analysis method(s) were chosen to perform background statistical evaluations of
selected constituents for each facility. The ultimate purpose of the statistical evaluations conducted for
each facility in each appendix to this report is to develop a Background Threshold Value (BTV) for a
subset of constituents for each facility. The subset of constituents was defined first by whether "Do Not
Drink" letters were issued for those constituents, and second by the needs of the groundwater
chemistry evaluation, which is the fourth component of this evaluation.
This statistical plan refers to the USEPA "Unified Guide" (USEPA, 2009) for additional details of the
methods that have been chosen for estimating BTVs. An overview of the process is provided here. The
BTV value for each dataset is estimated for selected constituents at each facility by using a stepwise
approach outlined below.
1) Initial evaluation of background input data sources.
2) Raw data evaluation by descriptive statistics, histograms, outlier tests, and trend tests.
3) Testing of statistical assumptions of the input data by checking for independent, identically
distributed (IID) measurements and goodness -of -fit (GOF) distribution tests.
4) Selection of an appropriate parametric or non -parametric analysis method to estimate
constituents BTVs.
5) Summarizing the statistical analysis results and drawing conclusions.
4.1 BACKGROUND DATASETS
Two or three background groundwater datasets are available for each facility.
• As described in Section 2.2, NCDEQ collected 24 water samples from 24 regional background
water supply well locations in the vicinity of three of the Duke Energy facilities: Allen (seven [7]
locations), Buck (seven [7] locations), and Marshall (ten [10] locations).
• As described in Section 2.3, Duke Energy developed a regional background water supply well
data set for each of its facilities by offering to sample private drinking water wells for facility
employees, contractors, and others associated with Duke Energy, if their well was located
generally between 2 miles and 10 miles of each facility.
As described in Section 2.4, monitoring well data for upgradient/background locations are
available for each of the seven facilities included in this analysis.
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4.2 INITIAL STATISTICAL EVALUATION
For three facilities, two regional background water supply well datasets are available (Allen, Buck, and
Marshall). For all of the facilities, there are multiple sets of data for the facility specific monitoring wells
are available. Before combining data within each of these groups, an initial statistical evaluation was
performed to check the homogeneity of variance assumption for the multiple groups of wells using
Levin's test. The test examines if the differences in sample variances occurred because of random
sampling. This evaluation is conducted to identify any significant variations between the groups to
determine the need for excluding the data.
Note that the original focus of the background evaluation was on vanadium and hexavalent chromium,
as these were the two constituents for which the majority of the "Do Not Drink" letters were issued.
This statistical analysis was begun prior to the lifting of the "Do Not Drink" letters, however, the use of
these two constituents for the purpose of determining whether the datasets can be combined is
appropriate. Data sources were tested for statistical variations as described in the following sections.
4.2.1 Regional Water Supply Well Data
The regional background groundwater data for Allen, Buck, and Marshall regional wells include the data
provided by both NCDEQ and Duke Energy. The background groundwater data for remaining facilities'
regional background water supply wells included only the data provided by Duke Energy. The data
provided by NCDEQ and Duke Energy were collected in similar environs of the Allen, Buck, and Marshall
facilities. However, before combining the two data sources, the NCDEQ and Duke Energy data were
tested for homogeneity of variance assumption using Levine's test. If the variances are concluded to be
homogenous by Levine's test then the two datasets were combined. If not, the NCDEQ dataset would
be omitted from further analysis (because the NCDEQ regional background water supply well dataset is
smaller than the corresponding Duke Energy dataset); however this was not the case.
4.2.2 Facility Monitoring Well Data
The background groundwater data for each facility consists of data from facility -specific background
monitoring wells screened in different subsurface groundwater formations. Before combining the
facility -specific background monitoring wells into one dataset as one group, the test for homogeneity of
variance assumption was tested using Levine's test. If the variances are concluded to be homogenous
by Levine's test then the datasets were combined. If not, the datasets were omitted from further
analysis.
4.3 RAW DATA EVALUATION
The next step is to compute and tabulate the descriptive statistics for each facility dataset for each
selected constituent. The most common descriptive statistics are: number of observations, number of
detects, percentage of non -detects (ND), minimum ND concentration, maximum ND concentration,
mean concentration, median concentration (50th percentile), 95th percentile, variance, standard
deviation, and coefficient of variation. Although statistics computed using discrete data sets of small
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sizes (e.g., < 8) are generally not used to make decisions, facility -specific knowledge and limited
statistical evaluation, can be used to evaluate such datasets.
Next, visual plots such as histograms and probability plots are developed to examine the data closely
and visually determine if there are extreme outliers in the dataset. If extreme outliers are visually
identified, then outlier tests using Rosner's and Dixon's outlier tests were performed to confirm the
outliers at a 5% significant level. The presence of outliers in the computation of the various decision
statistics can lead to incorrect conclusions. The decision to include or not include outliers in statistical
computations is decided by the project team based on constituent and facility -specific knowledge. In
some cases, decision statistics are computed with and without the outliers to evaluate the influence of
outliers on the decision making statistics. If the presence of an outlier is confirmed, and if there is
enough evidence to remove the outlier, then the outlier is removed from further statistical analysis.
Where applicable, time series plots were also developed for each constituent for each facility by using
all wells in the same plot or as single well plots to examine any temporal trend.
4.4 TESTING OF STATISTICAL ASSUMPTION
After performing the initial statistical evaluation and removing the potential outliers, two critical
statistical assumptions are tested for: independent, identically distributed (IID) measurements, and test
for normality.
In general, the groundwater monitoring program is designed to have IID measurements for statistical
analysis, which is generally satisfied in designing and carrying out the monitoring program. The
groundwater samples are not statistically independent when analyzed as aliquots or splits from a single
physical sample. Therefore, split sample data were removed from the dataset. In case of a duplicate
sample, the maximum detected value or minimum ND value is selected. For a small fraction of non -
detects in a sample (10-15% or less) censored at a single reporting limit, simple substitution methods
can be utilized by substituting each non -detection with an imputed value of the method detection limit
(MDL). However, more complicated situations arise when there is a combination of multiple MDLs
(detected values intermingled with different non -detection levels), or the proportion of non -detections
is larger. For complicated situations, strategies such as Kaplan -Meier (KM), Cohen's Method, Robust
Regression on Order Statistics (ROS), and Parametric Regression on Order Statistics are utilized. The
substitution will depend on the data distribution and site conditions.
For the normality assumption, the data is first tested for normal distribution with histograms, probability
plots and GOF tests statistics for each constituent for each dataset for each facility. If the data appeared
to be skewed, then the data are transformed to test for log -normal and Gamma distributions. The GOF
statistics tests are generated using the USEPA ProUCL software (USEPA, 2013), which tests for normal,
lognormal, and gamma distributions to establish the appropriate distribution. The GOF test statistics for
normal and lognormal distributions is based on Normal Quantile -Quantile (Q -Q) plot and Shapiro -Wilk
(S -W) Tests. The GOF test statistics for a gamma distribution are based upon the Empirical Distribution
Function (EDF). The two EDF tests incorporated in ProUCL are the K -S test and the A -D test. If the Q -Q
plot and the values of the GOF test statistics suggest the data follow a certain distribution, then
parametric methods are utilized to estimate the BTV value. If the normality assumption is not met, then
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the data are considered as distribution free, and non -parametric statistical methods are used to
estimate BTV values.
A common difficulty in checking for normality among groundwater measurements is the frequent
presence of non -detect values, known in statistical terms as left -censored (positively skewed)
measurements. The magnitude of these sample concentrations is unknown and they fall somewhere
between zero and the detection or reporting limit. Many positively skewed data sets follow a lognormal
as well as a gamma distribution. It is well-known that for moderately skewed to highly skewed data
sets, the use of a lognormal distribution tends to yield inflated and unrealistically large values of the
decision statistics especially when the sample size is small (e.g., <20-30). It is observed that the use of a
gamma distribution tends to yield reliable and stable results to a practical merit. If the GOF statics are
inconclusive then non -parametric methods are utilized.
4.5 BTV ESTIMATE
In this step, an appropriate parametric or non -parametric test method to estimate BTVs was selected
based on conclusions from the above sections. When selecting parametric methods or non -parametric
methods, it is implicitly assumed that the background data set used to estimate BTV's represent
unimpacted single statistical population that are free from outliers. However, since outliers are
inevitable in most environmental data (high percent of NDs), when present, outliers were treated on a
facility -specific basis using all existing knowledge about the facility, groundwater conditions and
reference areas under investigation as discussed in the previous section. The BTV's for the constituents
were estimated using ProUCL by using one of the following methods.
• Parametric or non -parametric 95% Upper Prediction Limits (UPL95)
Parametric or non -parametric Upper Tolerance Limits with 95% confidence and 95% coverage
(UTL95-95)
A prediction interval is the interval (based upon background data) within which a newly and
independently obtained (future observation) site observation (e.g., onsite, downgradient well) of the
predicted variable (e.g., boron) falls with a given probability (or Confidence Coefficient (CC)). A UPL95
represents that statistic such that an independently collected new/future observation from the
population will be less than or equal to the UPL95 with a CC of 0.95. It is noted that the use of a UPL95
to compare many observations may result in a higher number of false positives; that is the use of a
UPL95 to compare many observations just by chance tends to incorrectly classify observations coming
from the background population as coming from the impacted site locations.
A tolerance limit is a confidence limit on a percentile of the population rather than a confidence limit on
the mean. A UTL95-95 represents that statistic such that 95% observations (current and future) from
the target population will be less than or equal to the UTL95-95 with a CC of 0.95. A UTL95-95
represents a 95% UCL of the 95th percentile of the data distribution. A UTL95-95 is designed to
simultaneously provide coverage for 95% of all potential observations (current and future) from the
background population with a CC of 0.95. A UTL95-95 can be used when many (unknown) current or
future onsite observations need to be compared with a BTV. For moderately to highly skewed data sets
(high percentage of NDs), upper limits using KM estimates in gamma upper concentration limit and UTL
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equations provide better results, if the detected observations in the left -censored data set follow a
gamma distribution.
The nonparametric upper limits (e.g., UTLs, UPLs) are computed by the higher order statistics such as
the largest, the second largest, the third largest, and so on of the background data. The order of the
statistic used to compute a nonparametric upper limit depends on the sample size, coverage probability,
and the desired CC. In practice, non -parametric upper limits do not provide the desired coverage to the
population parameter (upper threshold) unless the sample size is large.
4.6 FACILITY -SPECIFIC APPLICATION
In each appendix to this report, these statistical methods were used to develop a regional background
groundwater BTV for specific constituents using the NCDEQ and/or the Duke Energy water supply well
data, and a facility -specific background groundwater BTV for the same constituents using the facility
upgradient/background monitoring well data. The results are provided in each appendix, and the
detailed statistical evaluations are provided as attachments to each appendix.
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S. Groundwater Flow Evaluation
The groundwater flow evaluations were conducted for this report by the companies that have been the
lead investigators on each site for Duke Energy under the CAMA program:
• HDR, Inc. (HDR) is the lead investigator for Allen, Belews Creek, Buck, Cliffside, and Marshall.
• SynTerra Corporation (SynTerra) is the lead investigator for Mayo and Roxboro.
The sections on groundwater flow provided in each appendix succinctly summarize the wealth of
information collected during the CAMA program on the hydrogeology of each site, information that has
been included in the following reports:
• Comprehensive Site Assessment (CSA);
• Corrective Action Plan, Part 1 (CAP -1); and
• Corrective Action Plan, Part 2 (CAP -2).
While the purpose of the CAMA program groundwater investigation is to evaluate the impact the ash
basins and other ash management areas on groundwater at and downgradient of these units, these data
have been used in this report to evaluate groundwater flow with respect to the location of the water
supply wells within the vicinity of each facility, which are upgradient and in some cases side gradient.
A detailed site conceptual model (SCM) is presented for each facility. The generalized SCM is a slope -
aquifer system typical of the Piedmont Province where a surface drainage basin is contained within one
or more adjacent topographic divides, located along ridge tops serving as the upper hydraulic
boundaries and with a stream, river, or lake serving as the lower hydraulic boundary. Detailed plan
views and cross-sections are used to localize the area of groundwater impact at the facility, as defined
by the locations where boron, the leading coal ash indicator, is present above the 2L standard.
It should be noted that all of the groundwater investigations at each of the facilities have been
conducted under the conditions where the local water supply wells have been active and in normal
operation. Thus the water level measurements and the interpretations of groundwater flow reflect the
combined impact this active pumping condition may have on groundwater flow.
A groundwater model has been developed for each site, and where the model has been sufficiently
developed, reverse particle tracking has been used in a well capture zone analysis to delineate well
capture zones for the active water supply wells near each of these facilities: Belews Creek, Cliffside,
Marshall, Mayo, and Roxboro. These models have simulated active pumping and were conducted to
simulate a time frame of water supply well usage starting with the first date that the ash basin(s) were
in operation.
Details on these evaluations are provided in the appendices.
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6. Groundwater Characteristics Evaluation
The objective of the groundwater characteristics evaluation is to understand, from the groundwater
chemistry perspective, whether the CCR -impacted groundwater at each facility has resulted in the water
quality exceedances reported in the local water supply wells. The following provides a summary of the
methods applied to the groundwater characteristics evaluation for each of the facilities.
6.1 EVALUATION APPROACH
The evaluation consists of the following two key steps:
• Identify site-specific CCR -related signature constituents that can effectively serve as indicators
to evaluate the extent of the CCR -impacted groundwater.
• Compare the absolute and relative abundance of major common constituents and signature
constituents among various well groups to determine whether CCR -impacted groundwater at
the site has resulted in the water quality exceedances found in the local water supply wells.
The approach taken to address these two steps follows:
Screen the geochemical and transport behaviors of typical CCR -related constituents to establish
candidate constituents for further evaluation.
• Assess the presence and magnitude of candidate constituents in the groundwater beneath the
site as a result of a release from the ash basin system by comparing the concentration
magnitude of these constituents in the four major well groups below:
— Ash basin porewater monitoring wells;
— Other facility monitoring wells, including wells screened in the shallow flow layer
(shallow wells), wells screened in the transition zones (deep wells), and bedrock wells;
— Local water supply wells (data from NCDEQ); and
— Regional background wells (data from NCDEQ and/or from Duke Energy).
Note that the wells in a major group may be further divided into multiple subgroups in order to
evaluate the spatial trends of the groundwater data; for example, the facility bedrock wells may
be further divided into two subgroups based on the groundwater flow direction in the bedrock
unit: (a) facility bedrock wells that are likely to be within the area of CCR -impacted groundwater,
and (b) facility bedrock wells that are likely to be outside of this area.
• Identify useful reduction -oxidation (redox) sensitive constituents that can also serve as an
indicator or a signature for CCR -impacted groundwater by comparing the concentration
magnitude of dissolved oxygen, iron, and manganese, among various well groups.
• Select effective constituents that can differentiate the site -related impacts and background
conditions to serve as signature constituents to assess the potential relationship between the
facility CCR -impacted groundwater and the local water supply wells.
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• Compare the relative abundance patterns of major cations and anions in groundwater among
various well groups to assess the data clustering pattern and correlation among various well
groups.
• Apply the site-specific geochemical principles and the knowledge of the groundwater flow field,
which have been developed and documented in the CSA and CAP reports and summarized for
each facility in this report, to coherently interpret the groundwater data trends and to verify or
reject the connection between the CCR -impacted groundwater and the water quality
exceedances found in the local water supply wells.
6.2 CCR -RELATED CONSTITUENTS SCREENING FOR SIGNATURE DEVELOPMENT
The first step for the identification of the CCR -impacted signature constituents is to identify the
constituents that have the following characteristics:
• They are recalcitrant to degradation and transformation under site-specific conditions.
• They are very soluble and subject to little sorption.
• During the transport process, the constituents of interest are not likely subject to a mechanism
that can increase or decrease their concentrations.
• Their concentrations or values are substantially different from the background concentrations or
values.
6.3 DATA ANALYSIS METHODS
Three types of data visualization techniques were used to evaluate the data for the constituents
identified as useful or key indicator constituents. Each facility -specific appendix identifies how these
tools are used to evaluate the site-specific data.
6.3.1 Box Plot
The comparisons of the concentration magnitude among different well groups for various potential
indicators were made using the box plots produced by the ProUCL software (USEPA, 2013). An example
box plot (also commonly known as a "box and whiskers plot") is shown in Panel (a) of Figure 2, which
defines the various components of the box plot. The location of the upper whisker is the lesser of 1.5
times the interquartile range (IQR) above the 75 percentile or the maximum value; the location of the
lower whisker is the greater of 1.5 times the IQR below the 25 percentile or the minimum value. The
analyses include both detected and non-detected values.
6.3.2 Correlation Plot
The constituents found to be signature indicators of CCR -impacted groundwater can be used to
generate correlation plots to further evaluate the relationships among various data groups. To create a
correlation plot, different data groups can be plotted using different symbols with the concentrations of
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one constituent on the x-axis and the concentrations of the other constituent on the y-axis. The
clustering patterns or trends will illustrate the correlations among data groups.
6.3.3 Piper Plot
Piper plots have been frequently used to assess the relative abundance of general cations (sodium,
potassium, magnesium, calcium) and anions (chloride, sulfate, bicarbonate and carbonate) in
groundwater and to differentiate different water sources in hydrogeology (Domenico and Schwartz,
1998). Groundwater resulting from different water sources or in different geologic units may exhibit
distinct clustering patterns on a piper plot. Because calcium and sulfate are common coal ash
constituents, it is expected that CCR -impacted groundwater may show a different clustering pattern
than the background groundwater or the groundwater that has not been impacted by CCR.
An example figure is shown in Panel (b) of Figure 2, which compares the general water chemistry among
the porewater in an ash basin, surface water in the ash basins, and groundwater in the bedrock wells for
an example site. The piper plot consists of three subplots: a cation composition trilinear plot in the
lower left corner, an anion composition trilinear plot in the lower right corner, and a diamond plot in
between. The red lines on each subplot show how to read the meanings of a data point in a subplot.
For example, in the cation subplot, the data point of AB -4S shows about 37 percent of the total cation
charges from sodium and potassium, approximately 40 percent from calcium, and about 26 percent
from magnesium. In the anion subplot, the data point of SW-AB1 shows about 37 percent of the total
anion charges from sulfate, approximately 25 percent from chloride and nitrate related anions (NO2-
and NO3-), and 38 percent from carbonate (C032-) plus bicarbonate (HCO3-) anions. In the diamond
subplot, the data point of AB-7BRU shows about 68 percent of the total anion charges from chloride,
nitrate related anions, and sulfate, and approximately 48 percent of the total cation charges from
calcium and magnesium.
The piper plots for this evaluation were generated using the GW_Chart program developed by the USGS
(Winston, 2000).
6.4 DATA SYNTHESIS
The groundwater characterization uses the results of these analyses in concert with the groundwater
flow information and the background statistics to determine if the local water supply wells may be
impacted by a release of constituents from the ash basins and coal ash management facilities at each
location.
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7. Summary of Results
The NCDEQ classified six of the Duke Energy ash basins as Low to Intermediate risk. The primary basis
for this classification was stated as the current "uncertainty related to site conditions that may relate to
potential impacts to up -gradient and side -gradient well users." When finalizing the classifications, a
decision must be made by NCDEQ to classify these ash basins as Low or as Intermediate risk. The
NCDEQ cited a lack of information as the basis for the Low to Intermediate classification. The most cited
information needs in the document included incomplete background concentration determination, and
incomplete capture zone modeling for the water supply wells in the vicinity of each facility.
Duke Energy commissioned Haley & Aldrich, Inc. (Haley & Aldrich) to conduct a detailed evaluation of
available facility data for the sites classified Low to Intermediate. The purpose of the study was to
evaluate whether or not the ash basins and other coal ash management areas at each facility may
impact off-site local water supply wells.
The results of an initial evaluation of the local water supply well data collected by NCDEQ in the vicinity
of each of the Duke Energy facilities was conducted by Haley & Aldrich, and was presented to the
NCDEQ in December 2015 (Haley & Aldrich, 2015). This report supplements and expands on that initial
evaluation, and provides technical evaluations in four important assessment areas: 1) an evaluation of
the private and public water supply well data collected by the NCDEQ with respect to groundwater
standards and screening levels; 2) additional statistical analysis of regional background groundwater
data, and facility -specific background groundwater data; 3) a more comprehensive evaluation of
groundwater flow with respect to local water supply wells, including a water supply well capture zone
analysis; and 4) a detailed comparison of facility -specific coal ash groundwater chemistry, background
groundwater chemistry (both regional and facility -specific), and water supply well chemistry. This
report addresses the following facilities: Allen, Belews Creek, Buck, Cliffside, Marshall, Roxboro, and
Mayo. The draft NCDEQ classification for Mayo is Low, but has been included in this report so that it
addresses all sites with draft classifications of Low to Intermediate, and Low.
7.1 AVAILABLE DATA
The data used in the analysis came from several sources. The local water supply well data were
provided directly to Duke Energy by the NCDEQ in March 2016. These data included results for the
water supply wells sampled within 1,500 feet of the ash basin(s) compliance boundary for each facility.
In October 2015, NCDEA provided "reconnaissance" or background water supply well data collected in
the vicinity of the Allen, Buck, and Marshall facilities. Regional background water supply well data are
also available from Duke Energy for samples collected within a 2- to 10 -mile radius of each facility.
Groundwater monitoring well data for each facility were also used in the analysis.
Table 1 provides a summary of the sample count used in this analysis for the local water supply wells
and the regional background water supply wells.
Water supply wells constructed in the Piedmont province of North Carolina are predominantly deep
bedrock wells. Typically in the Piedmont, private water supply wells are assumed to be open boreholes
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installed within the upper 100 feet of bedrock; however, most are generally less than 250 feet deep with
yields of 10 to 20 gallons per minute (Daniel and Dahlen, 2002). Therefore, the facility -specific data for
bedrock and deep wells were the focus of the comparative analysis of local water supply wells and
facility -specific information.
7.2 RISK-BASED SCREENING EVALUATION
Local water supply well data and the background data from both NCDEQ and Duke were compared to
the following (Table 2):
• North Carolina Statute 15A NCAC 02L.0202 (2L Standard) groundwater standards, and IMACs;
• Federal Safe Drinking Water Act MCLS and SMCLs;
• NCDHHS screening levels; and
• USEPA RSLs.
The detailed screening tables for each of the seven facilities are provided in the appendices, by facility.
Table 3 provides a statistical data summary and Table 4 provides a summary of the screening results for
all of the local water supply well data available for all of the Duke Energy facilities in North Carolina.
Tables 5 and 6 provide the same information, respectively, for the NCDEQ-sampled regional background
wells. Tables 7 and 8 provide the same information, respectively, for the Duke Energy -sampled regional
background wells.
The analysis provided in this report uses the currently available IMAC for vanadium (0.3 µg/L) and
NCDHHS screening level for hexavalent chromium (0.07 µg/L); however, NCDEQ announced that it has
changed those values and has rescinded many of the "Do Not Drink" letters sent to residents due to the
change. Because the updated values have not been published, they have not been incorporated into
the analysis in this report. However, to account for the change, the discussion of the results for each
facility does not focus on these two constituents.
The concentrations of boron and the other potential coal ash indicators were low and generally not
above screening levels in the local water supply wells sampled by NCDEQ, nor in the regional
background wells. The exception to this is pH. pH was below the drinking water standard range in
approximately half of the NCDEQ-sampled water supply wells, both local and regional background.
These results are not unexpected, based on a study published by the USGS (Chapman, et al., 2013) and
additional North Carolina specific studies (Briel, 1997) showing that groundwater pH in the state is
commonly below the MCL range of 6.5 to 8.5.
Table 9 provides background groundwater data available from the literature for the constituents
included in this evaluation.
When looking at the local water supply well data, it is clear that there are very few results above
regulatory levels or risk-based screening levels (with the earlier caveat about the lifting of the "Do Not
Drink" letters for hexavalent chromium and vanadium). The water supply well sampling conducted by
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NCDEQ within the 0.5 -mile radius of Duke Energy ash basins included over 14,200 chemical analyses of
samples from 347 wells. Only 1.38% of the results were above an MCL; the vast majority of these were
due to pH readings outside the federal drinking water range, and these values are generally consistent
with background in North Carolina, as noted above. When pH is not considered, only 0.16% of the
results are above an MCL. Only 1.15% of the individual results are above a secondary federal drinking
water standard (aluminum, iron, and manganese); these SMCLs are based on aesthetics and most of the
results are below USEPA's risk-based screening levels.
7.3 BACKGROUND EVALUATION
The constituents present in coal ash and, therefore, in the groundwater impacted by coal ash, are
naturally occurring in our environment. Therefore, it is important to consider the water supply well data
in the context of background concentrations of the detected constituents. The background water supply
well data collected by Duke Energy and by the NCDEQ (where available) for each facility are referred to
as "regional" background to distinguish it from the "facility -specific" background groundwater data
collected from monitoring wells located in upgradient locations at each facility. A detailed statistical
analysis of regional background groundwater data and facility -specific background groundwater data
was conducted to develop "background threshold values" or point descriptors of background for specific
constituents to compare to the data for the NCDEQ-sampled local water supply wells. The comparison
indicates that constituent concentrations in the water supply wells are generally consistent with both
regional and facility -specific background concentrations (including vanadium and hexavalent chromium).
Table 10 provides a summary of the regional and facility -specific BTVs for bedrock groundwater,
calculated for each of the seven facilities included in this analysis. The results are generally similar
between the two datasets for each facility, and across facilities, and represent regional and local natural
variability in groundwater.
7.4 GROUNDWATER FLOW EVALUATION
A comprehensive evaluation of groundwater flow was conducted with specific emphasis on evaluating
flow directions with respect to the locations of the ash basin(s) and other coal ash management areas
and the local water supply wells at each facility. The results for all facilities demonstrate that
groundwater flow at each site is predominantly in directions away from areas where water supply wells
are located and towards the local groundwater discharge features, whether they be a river or lake. In all
cases the detailed groundwater models support these flow directions.
The water supply well capture zone analyses conducted for each facility (where appropriate) using
reverse particle tracking also indicates that groundwater utilized by water supply wells near the coal ash
impoundments is not impacted by the coal ash sources.
7.5 GROUNDWATER CHARACTERISTICS EVALUATION
These conclusions about groundwater flow and the lack of impact on the local water supply wells are
confirmed by the detailed characterization of groundwater chemistry at each facility. Data for facility -
specific groundwater, regional background groundwater, and local water supply well water were
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included in the evaluations. The analyses included evaluation of CCR indicators, redox conditions, and
correlation evaluations. The results of the chemical correlation analyses indicate that, based on the
differences in clustering patterns of constituents from the ash basin porewater wells and the local water
supply wells, the source water for the local water supply wells is not CCR -impacted groundwater.
The graphical results from these seven facility evaluations allow for easy comparison of the ash
porewater well results between facilities, and easy comparison of the local water supply well results
between facilities. The correlations between the ash indicators boron and sulfate, and between the
major groundwater ions (calcium, magnesium, chloride, sulfate, etc.) for the ash porewater wells are
strikingly similar between facilities. These same comparisons are also strikingly similar between all of
the facilities' local water supply wells. Moreover, the patterns between the two groups of data, ash
porewater wells and local water supply wells, are distinctly different in the correlation plots. This
comparison between facilities further supports the conclusion that CCR -impacted groundwater is not
impacting the local water supply wells.
7.6 CONCLUSIONS
Therefore, the evaluations performed for all 7 of these facilities support a Low risk classification under
CAMA:
• Allen Steam Station
• Belews Creek Steam Station
• Buck Steam Station
• Cliffside Steam Station
• Marshall Steam Station
• Mayo Steam Electric Plant
• Roxboro Steam Electric Plant
These results confirm the Low risk classification proposed by NCDEQ for Mayo, and the specific ash
basins at Cliffside and Roxboro.
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8. References
1. Briel, L.I. 1997. Water quality in the Appalachian Valley and Ridge, the Blue Ridge, and the
Piedmont physiographic provinces, eastern United States (No. 1422-D). US Geological Survey.
2. CAMA. 2014. North Carolina Coal Ash Management Act. Senate Bill S729v7. Available at:
http://www.ncleg.net/Sessions/2013/BiIIs/Senate/PDF/S729v7.PDF
3. Chapman, M.J., Cravotta III, C.A., Szabo, Z. and Lindsay, B.D. 2013. Naturally occurring
contaminants in the Piedmont and Blue Ridge crystalline -rock aquifers and Piedmont Early
Mesozoic basin siliciclastic-rock aquifers, eastern United States, 1994-2008 (No. 2013-5072).
U.S. Geological Survey.
4. Daniel, C.C. III and Dahlen, P. 2002. Preliminary Hydrogeologic Assessment and Study Plan for a
Regional Ground -Water Resource Investigation of the Blue Ridge and Piedmont Provinces of
North Carolina. USGS Water Resources Investigation Report 02-4105.
5. Domenico, P.A. and Schwartz, F.W. 1998. Physical and chemical hydrogeology (Vol. 44). New
York: Wiley.
6. Haley & Aldrich. 2015. Evaluation of NC DEQ Private Well Data. December 2015.
7. NCAC. 2013. 15A NCAC 02L.0202. Groundwater Standard (2L), Classifications and Water
Quality Standards Applicable to Groundwaters of North Carolina. North Carolina Administrative
Code. April 1, 2013. Available at:
http://Portal.ncdenr.org/c/document library/Ret file?uuid=laa3fa13-2cOf-45b7-ae96-
5427fb1d25b4&arouDld=38364
8. NCDEQ. 2016. Coal Combustion Residual Impoundment Risk Classifications. North Carolina
Department of Environmental Quality. January 2016. Available at:
https://ncdenr.s3.amazonaws.com/s3fs-public/document-
library/1.29.16 Coal%20Combustion%2OResidual%201mpoundment%20CIassifications.pdf
9. NCDHHS. 2015. DHHS Screening Levels. Division of Public Health, Epidemiology Section,
Occupational and Environmental Epidemiology Branch. North Carolina Department of Health
and Human Services. April 24, 2015. Available at:
http://Portal.ncdenr.org/c/document library/get file?p I id=1169848&folderld=24814087&na
me=DLFE-112704.PDF
10. USEPA. 1989. Risk Assessment Guidance for Superfund, Volume 1: Human Health Evaluation
Manual, Part A. EPA/540/1-89/002. Office of Emergency and Remedial Response, Washington,
DC. December.
11. USEPA. 2009. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified
Guidance. U.S. Environmental Protection Agency. March 2009. EPA 530/R-09-007.
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12. USEPA. 2012. 2012 Edition of the Drinking Water Standards and Health Advisories. Spring
2012. Available at: http://water.epa.gov/drink/contaminants/index.cfm
13. USEPA. 2013. Statistical Software ProUCL 5.0.00 for Environmental Applications for Data Sets
with and without Nondetect Observations. Software: http://www2.epa.gov/land-
research/proucl-software, and User's Guide: http://www2.epa.gov/sites/production/files/2015-
03/documents/proucl v5.0 user.PDF
14. USEPA. 2015a. Coal Combustion Residual (CCR) Rule (Hazardous and Solid Waste Management
System; Disposal of Coal Combustion Residuals From Electric Utilities; FR 80(74): 21302-
21501, April 19, 2015. Available at: http://www.gpo.gov/fdsys/pl<g/FR-2015-04-17/PDF/2015-
nn7S7 PnF
15. USEPA. 2015b. USEPA Risk -Based Screening Levels. November 2015. Available at:
http://www2.epa.gov/risk/risk-based-screening-table-generic-tables.
16. USEPA. 2015c. Human and Ecological Risk Assessment of Coal Combustion Residuals. U.S.
Environmental Protection Agency, Office of Solid Waste and Emergency Response, Office of
Resource Conservation and Recovery. Final. December 2014. EPA-HQ-RCRA-2009-0640-11993.
Available at: http://www.regulations.gov
17. USGS. 2011. Trace Elements and Radon in Groundwater Across the United States, 1992-2003.
Scientific Investigations Report 2011-5059. Available at:
http://water.usgs.gov/nawqa/trace/pubs/sir20ll-5059/
18. USGS. 2014. Smith, D.B., Cannon, W.F., Woodruff, L.G., Solano, Federico, and Ellefsen, K.J.,
Geochemical and mineralogical maps for soils of the conterminous United States. U.S.
Geological Survey. Open -File Report 2014-1082. Available at:
http://dx.doi.org/10.3133/ofr20141082
19. Winston, R.B. 2000. Graphical User Interface for MODFLOW, Version 4 (Open -File Report 00-
315). U.S. Geological Survey. Software:
http://water.usgs.gov/nrp/gwsoftware/GW Chart/GW Chart.html
APRIL 2016 25 %UICH

Page 1 of 1
Table 1
Summary of NCDEQ and Duke Energy Water Supply Well and Background Well Samples and Well Counts
Water Supply Well Evaluation
Duke Energy
April 2016
Station
Number of NCDEQ
Private Wells (a)
NCDEQ (b)
Background
Duke Energy (c)
Background
Combined
Background
Allen
124
7
16
23
Belews Creek
34
0
11
11
Buck
89
7
17
24
Cliffside
22
0
9
9
Marshall
39
10
29
39
Mayo
3
0
14
14
Roxboro
15
0
1 26
1 26
Notes:
DEQ- Department of Environmental Quality.
NC - North Carolina.
(a) - NCDEQ Water Supply Well data. Data from NCDEQ document submittal from March 15, 2016.
(b) - NCDEQ Background data. Accessed December 14, 2015.
http://porta I. ncden r.org/c/document_l ibra ry/get_file?uuid=lb4291cf-958f-4b7e-a272-fb7ab6O8a 158&groupld=14
(c) - Duke Energy Background data. Duke employee private well survey within 2-10 miles from identified facility.
Haley & Aldrich, Inc.
Table 1 -2016 -04 -Data Audit.xlsx APRIL 2016

Page 1 of 2
Table 2
Summary of Screening Values
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 2_2016-04_Screening Levels.xlsx APRIL 2016
15A NCAC 02L.0202
Federal
DHHS
Tap Water
Groundwater Standard
MCL/
Screening
RSL
Constituents Units
a
SMCL b
Level c
2015 d
Boron ug/L
700
NS
700
4000
Calcium ug/L
NS
NS
NS
NS
Appendix III (e)
Chloride mg/L
250
*250
250
NS
pH su
6.5-8.5
6.5-8.5
NS
NS
Sulfate mg/L
250
*250
250
NS
Total Dissolved Solids m /L
500
*500
NS
NS
Antimony ug/L
1
6
1
7.8
Arsenic ug/L
10
10
10
0.052
Barium ug/L
700
2000
700
3800
Beryllium ug/L
A4
4
4
25
Cadmium ug/L
2
5
2
9.2
Appendix IV (f)
Chromium ug/L
10
100
10
22000
Cobalt ug/L
Al
NS
1
6
Lead ug/L
15
15
15
15
Mercury ug/L
1
2
1
5.7
Molybdenum ug/L
NS
NS
18
100
Selenium ug/L
20
50
20
100
Thallium u /L
0.2
2
0.2
1 0.2
Aluminum ug/L
NS
*50 to 200
3500
20000
Copper mg/L
1
1.3
1
0.8
Hexavalent Chromium ug/L
NS
NS
0.07
44 (g)
Iron ug/L
300
*300
2500
14000
Magnesium ug/L
NS
NS
NS
NS
Manganese ug/L
50
*50
200
430
Nickel ug/L
100
NS
100
390
Potassium ug/L
NS
NS
NS
NS
Sodium ug/L
NS
NS
20000
NS
Constituents Not
Strontium ug/L
NS
NS
2100
12000
Identified in the
Vanadium ug/L
A0.3
NS
0.3
86
CCR Rule
Zinc mg/L
1
*5
1
6
Alkalinity mg/L
NS
NS
NS
NS
Bicarbonate mg/L
NS
NS
NS
NS
Carbonate mg/L
NS
NS
NS
NS
Total Suspended Solids mg/L
NS
NS
NS
NS
Turbidity NTU
NS
NS
NS
NS
Temperature °C
NS
NS
NS
NS
Specific Conductance umhos/cm
NS
NS
NS
NS
Dissolved Oxygen mg/L
NS
NS
NS
NS
Oxidation Reduction Potential mV
I NS
NS
I NS
NS
Haley & Aldrich, Inc.
Table 2_2016-04_Screening Levels.xlsx APRIL 2016

Page 2 of 2
Table 2
Summary of Screening Values
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
A - Denotes IMAC value.
* - Denotes SMCL value.
°C - Degrees Celsius.
CCR - Coal Combustion Residual.
DEQ - Department of Environmental Quality.
DHHS - Department of Health and Human Services.
HI - Hazard Index.
IMAC - Interim Maximum Allowable Concentration.
MCL - Maximum Contaminant Level.
mg/L - milligrams/liter.
mV - millivolts.
NA - Not Available.
NC - North Carolina.
NS - No standard Available.
NTU - Nephelometric Turbidity Units.
RSL- Risk Based Screening Level.
SMCL - Secondary Maximum Contaminant Level.
su - Standard units.
USEPA - United States Environmental Protection Agency.
ug/L - micrograms/liter.
umhos/cm - micromhos/centimeter.
USGS - United States Geological Survey.
(a) - Classifications and Water Quality Standards Applicable to Groundwaters of North Carolina. North Carolina Administrative Code. April 1, 2013.
http://portal.ncdenr.org/web/wq/ps/csu/gwstandards
(b) - USEPA 2012 Edition of the Drinking Water Standards and Health Advisories. Spring 2012. http://www.epa.gov/sites/production/files/2015-09/documents/dwstandards2012.pdf.
(c) - DHHS Screening Levels. Department of Health and Human Services, Division of Public Health, Epidemiology Section, Occupational and Environmental
Epidemiology Branch. http://Porta1.ncdenr.org/c/document_library/get_file?p_l_id=1169848&folderld=24814087&name=DLFE-112704.pdi
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tapwater. HI = 1.
http://www.epa.gov/risk/risk-based-screen ing-table-generic-tables
(e) - The CCR Rule lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(f) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(g) - Alternative screening level calculated for hexavalent chromium using RSL calculator (http://epa-prgs.ornl.gov/cgi-bin/chemicals/csl_search) and
current dose -response data from the USEPA's Integrated Risk Information System. Available at: http://www.epa.gov/IRIS/. The RSL for
hexavalent chromium is not a drinking water standard, and the basis of the draft oral cancer toxicity value used in the calculation of the RSL
has been questioned by USEPA's Science Advisory Board; therefore, RSL for Chromium (IV) is based on the noncancer values developed by USEPA.
Haley & Aldrich, Inc.
Table 2_2016-04_Screening Levels.xlsx APRIL 2016

Page 1 of 2
Table 3
Statistical Summary of NCDEQ-Sampled Water Supply Well (d) Data
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 3_2016-04_NCDEQ Data Supply Well Statistical Summary.xlsx SUMMARY Percentiles APRIL 2016
Frequency of
Frequency of
Range of Detected
Mean
10th
25th
50th
75th
90th
Detection
Constituents
Units
Detection (a)
Detect
Percentile
Percentile
Percentile
Percentile
Percentile
PercentConcentrations
Constituents Listed in Appendix III Detection Monitorin of the CCR Rule b'
Boron
ug/L
97 / 368
26%
5 - 690
50.57 5
5
5
12.45
50
Calcium
ug/L
366 / 368
99%
1,340 - 246,000
18,465 4,964
7,208
12,200
20,925
31,940
Chloride
mg/L
363 / 368
99%
0.92 - 335
10.13 1.57
2.3
4.29
8.4
19.03
pH
su
368 / 368
100%
2.13 - 9.4
6.553 5.87
6.2
6.5
6.9
7.409
Sulfate
mg/L
239 / 368
65%
0.15 - 711
20.17 2
2
2.5
6.575
18.85
Total Dissolved Solids
mg/L
364 / 367
99%
25 - 2040
139.1 59
81
109
1 147.5
201.6
Constituents Listed
in Appendix
IV Assessment Monitorin of the CCR Rule c'
Antimony
ug/L
37 / 368
10%
0.031 - 1.87
0.243 0.4
0.5
0.5
0.5
0.832
Arsenic
ug/L
77 / 368
21%
0.1 - 108
4.06 0.5
0.5
0.5
0.5
2.06
Barium
ug/L
362 / 368
98%
0.46 - 400
39 5.5
11.9
25.15
47.7
79.9
Beryllium
ug/L
17 / 368
5%
0.04 - 0.78
0.24 0.2
0.2
0.2
0.2
0.4
Cadmium
ug/L
32 / 368
9%
0.063 - 1.4
0.247 0.08
0.08
0.08
0.08
0.159
Chromium
ug/L
245 / 368
67%
0.176 - 22.1
2.499 0.5
0.515
1.105
2.6
5
Cobalt
ug/L
67 / 368
18%
0.03 - 12
1.301 0.227
0.5
0.5
0.5
1
Lead
ug/L
318 / 368
86%
0.073 - 75.5
1.991 0.1
0.23
0.52
1.4
3.128
Mercury
ug/L
25 / 368
7%
0.017 - 0.12
0.0484 0.0594
0.2
0.2
0.2
0.2
Molybdenum
ug/L
144 / 368
39%
0.064 - 20.2
1.991 0.387
0.5
0.5
1.1
4.23
Selenium
ug/L
39 / 368
11%
0.164 - 3.4
1.049 0.5
0.5
0.5
0.5
1.73
Thallium
u /L
13 368
4%
0.057 - 0.24
0.117 0.1
0.1
0.1
0.1
0.2
Constituents Not Identified in the CCR RuIE
Vanadium
ug/L
270 / 368
73%
0.197 - 26.5
6.572
1
1
4
8.2
12
Aluminum
ug/L
129 / 368
35%
2.2 - 5,000
195.2
10
10
10
25.18
109.3
Copper
mg/L
328 / 368
89%
0.00019 - 29
0.181
0.0011
0.0027
0.00764
0.0231
0.0709
Iron
ug/L
171 / 368
46%
14.5 - 18,200
869.9
50
50
50
188.3
1016
Hexavalent Chromium
ug/L
265 / 365
73%
0.033 - 22.3
1.659
0.03
0.081
0.62
1.9
4.72
Magnesium
ug/L
366 / 368
99%
372 - 61,200
4,655
1,300
2,123
3,455
5,193
7,141
Manganese
ug/L
304 / 368
83%
0.49 - 1010
34.49
0.5
0.84
2.77
14.7
47.78
Nickel
ug/L
168 / 368
46%
0.18 - 15
1.55
0.5
0.5
0.5
1.2
3.26
Potassium
ug/L
367 / 368
100%
96.1 - 21,200
2187
953.8
1,300
1,800
2,405
3,500
Sodium
ug/L
368 / 368
100%
570 - 370,000
11,388
4,207
5,578
7,435
9,643
16,430
Strontium
ug/L
365 / 368
99%
9.7 - 3,400
140.9
38.03
60
98.6
168.3
263.6
Zinc
mg/L
317 / 368
86%
0.00212 - 5.26
0.135
0.005
0.00975
0.025
0.0662
0.238
Alkalinity
mg/L
359 / 366
98%
1.4 - 376
54.01
16.05
28.5
42.4
61.95
89.8
Bicarbonate
mg/L
345 / 356
97%
1.23 - 317
52.73
13.35
26.9
41.85
61.18
89.75
Carbonate
mg/L
2/ 354
1%
6- 42.6
24.3
1
5
5
5
5
Total Suspended Solids
mg/L
59 / 367
16%
0.4 - 363
16.7
1
2.5
2.5
2.5
5
Turbidity
NTU
104 / 367
28%
0.15 - 210
11.16
1
1
1
1
3.68
Temperature
°C
366 / 366
100%
7.4 - 28.3
18.01
15.6
16.8
17.8
19.1
21
Specific Conductance
umhos/cm
367 / 367
100%
4.5 - 1,770
174.3
64
92.2
134.5
197.3
280.8
Dissolved Oxygen
mg/L
367 / 367
100%
0.01 - 13
5.532
1.258
4.005
5.91
7.4
8.3
Oxidation Reduction Potential
mV
328 328
100%
1 - 774.7
1 211.5
1 112.9
1 166.8
1 203.2
1 246.5
1 300.4
Total Number of Analyses:1
14,274
Haley & Aldrich, Inc.
Table 3_2016-04_NCDEQ Data Supply Well Statistical Summary.xlsx SUMMARY Percentiles APRIL 2016

Page 2 of 2
Table 3
Statistical Summary of NCDEQ-Sampled Water Supply Well (d) Data
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
°C - Degrees Celsius.
mg/L - milligrams/liter.
mV - millivolts.
NTU - Nephelometric Turbidity Units.
su - standard units.
ug/L - micrograms/liter.
umhos/cm - micro mhos/centimeter.
CCR - Coal Combustion Residual.
DEQ- Department of Environmental Quality.
NC - North Carolina.
(a) - Frequency of Detection: number of detects / total number of results,
(b) - The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(c) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV)
(d) - NCDEQ Water Supply Well data. Data from NCDEQ document submittal from March 15, 2016,
Haley & Aldrich, Inc.
Table 3-2016-04—NCDEQ Data Supply Well Statistical Summary.xlsx SUMMARY Percentiles APRIL 2016

Page 1 of 2
Table 4
Summary of NCDEQ-Sampled Water Supply Well (h) Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 4_2016-04_NCDEQ Data Supply Well Screen Summary.xlsx SUMMARY APRIL 2016
Frequency of
Frequency of
Range of Detected
Frequency Detected Above:
Frequency of Reporting Limits Above:
Frequency of
Detection
Detects Below All
Constituents
Units
Detection (g)
percent
Concentrations
2L (a)
DHHS (b)
MCL (c)
RSL (d)
2L (a)
DHHS (b)
MCL (c)
RSL (d)
Screening Levels
Constituents Listed in Appendix III Detection Monitoring)
of the CCR Rule e'
Boron
ug/L
97 / 368
26%
5 - 690
0
0
0
0
0
0
97
Calcium
ug/L
366 / 368
99%
1,340 - 246,000
--
--
--
--
--
--
--
--
--
Chloride
mg/L
363 / 368
99%
0.92 - 335
1
1
1
0
0
0
362
pH
su
368 / 368
100%
2.13 - 9.4
173
--
173
0
--
0
195
Sulfate
mg/L
239 / 368
65%
0.15 - 711
5
5
5
0
0
0
234
Total Dissolved Solids
mg/L
364 / 367
99%
25 - 2040
7
--
7
0
--
0
--
357
Constituents Listed in Appendix IV Assessment Monitoring) of the CCR Rule f
Antimony
ug/L
37 / 368
10%
0.031 - 1.87
2
2
0
0
8
8
0
0
35
Arsenic
ug/L
77 / 368
21%
0.1 - 108
7
7
7
77
0
0
0
290
0
Barium
ug/L
362 / 368
98%
0.46 - 400
0
0
0
0
0
0
0
0
362
Beryllium
ug/L
17 / 368
5%
0.04 - 0.78
0
0
0
0
0
0
0
0
17
Cadmium
ug/L
32 / 368
9%
0.063 - 1.4
0
0
0
0
0
0
0
0
32
Chromium
ug/L
245 / 368
67%
0.176 - 22.1
8
8
0
0
4
4
0
0
237
Cobalt
ug/L
67 / 368
18%
0.03 - 12
27
27
--
2
9
9
--
2
40
Lead
ug/L
318 / 368
86%
0.073 - 75.5
6
6
6
6
0
0
0
0
312
Mercury
ug/L
25 / 368
7%
0.017 - 0.12
0
0
0
0
0
0
0
0
25
Molybdenum
ug/L
144 / 368
39%
0.064 - 20.2
--
1
--
0
--
1
--
0
143
Selenium
ug/L
39 / 368
11%
0.164 - 3.4
0
0
0
0
0
0
0
0
39
Thallium
ug/L
13 368
4%
0.057 - 0.24
1
1
0
1
28
28
0
28
12
Constituents Not Identified in the CCR Rule
Vanadium
ug/L
270 / 368
73%
0.197 - 26.5
263
263
--
0
86
86
--
0
7
Aluminum
ug/L
129 / 368
35%
2.2 - 5,000
--
1
57
0
--
0
3
0
72
Copper
mg/L
328 / 368
89%
0.00019 - 29
4
4
3
4
0
0
0
0
324
Iron
ug/L
171 / 368
46%
14.5 - 18,200
67
17
67
1
1
0
1
0
104
Hexavalent Chromium
ug/L
265 / 365
73%
0.033 - 22.3
--
243
--
0
--
35
--
0
22
Magnesium
ug/L
366 / 368
99%
372 - 61,200
--
--
--
--
--
--
--
--
--
Manganese
ug/L
304 / 368
83%
0.49 - 1010
33
14
33
5
0
0
0
0
271
Nickel
ug/L
168 / 368
46%
0.18 - 15
0
0
--
0
0
0
--
0
168
Potassium
ug/L
367 / 368
100%
96.1 - 21,200
--
--
--
--
--
--
--
Sodium
ug/L
368 / 368
100%
570 - 370,000
28
--
0
--
340
Strontium
ug/L
365 / 368
99%
9.7 - 3,400
1
--
0
--
0
--
0
364
Zinc
mg/L
317 / 368
86%
0.00212 - 5.26
10
10
1
0
0
0
0
0
307
Alkalinity
mg/L
359 / 366
98%
1.4 - 376
--
--
--
--
--
--
--
--
--
Bicarbonate
mg/L
345 / 356
97%
1.23 - 317
Carbonate
mg/L
2 / 354
1%
6 - 42.6
Total Suspended Solids
mg/L
59 / 367
16%
0.4 - 363
Turbidity
NTU
104 / 367
28%
0.15 - 210
Temperature
°C
366 / 366
100%
7.4 - 28.3
Specific Conductance
umhos/cm
367 / 367
100%
4.5 - 1,770
Dissolved Oxygen
mg/L
367 / 367
100%
0.01 - 13
Oxidation Reduction Potential
mV
328 / 328
100%
1 - 774.7
--
--
--
--
--
--
Total Number of Analyses:1
14,274
1 Total Number of Exceedances:
614
639
360
96
136
171
4
320
4,478
Haley & Aldrich, Inc.
Table 4_2016-04_NCDEQ Data Supply Well Screen Summary.xlsx SUMMARY APRIL 2016

Page 2 of 2
Table 4
Summary of NCDEQ-Sampled Water Supply Well (h) Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
°C - Degrees Celsius.
CCR - Coal Combustion Residual.
RSL - Risk Based Screening Level.
mg/L- milligrams/liter.
DEQ- Department of Environmental Quality.
SMCL -Secondary Maximum Contaminant Level.
mV - millivolts.
DHHS - Department of Health and Human Services.
USEPA - United States Environmental Protection Agency.
NTU - Nephelometric Turbidity Units.
HI - Hazard Index.
No Standard Available.
su - standard units.
[MAC - Interim Maximum Allowable Concentration,
ug/L - micrograms/liter.
MCL - Maximum Contaminant Level.
umhos/cm - micro mhos/centimeter.
NC - North Carolina.
(a) - Classifications and Water Quality Standards Applicable to Groundwaters of North Carolina. North Carolina Administrative Code. April 1, 2013
http://portal.ncdenr.org/web/wq/ps/csu/gwstandards
(b) - DHHS Screening Levels. Department of Health and Human Services, Division of Public Health, Epidemiology Section, Occupational and Environmenta
Epidemiology Branch. http://portal.ncdenr.org/c/document_library/get file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(c) - USEPA 2012 Edition of the Drinking Water Standards and Health Advisories. Spring 2012,
http://water.epa.gov/drink/contaminants/index.cfm
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tap water. HI = 1
http://www.epa.gov/reg3hwmd/risk/human/rb-concentration tabla/GenericTables/index.htm
(e) - The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III)
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(f) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(g) - Frequency of Detection: number of detects / total number of results
(h) - NCDEQ Water Supply Well data. Data from NCDEQ document submittal from March 15, 2016,
Haley & Aldrich, Inc.
Table 4_2016-04_NCDEQ Data Supply Well Screen Summary.xlsx SUMMARY APRIL 2016

Page 1 of 2
Table 5
Statistical Summary of NCDEQ-Sampled Background Water Supply Well Data
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 5_2016 -04 -DEQ Bkg Well Statistical Summary.xlsx APRIL 2016
Frequency of
Frequency of
Range of Detected
Mean
10th
25th
75th
90th
Constituents
Units
Detection (a)
Detection
Concentrations
Detect
Percentile
Percentile
Median
Percentile
Percentile
Percent
Constituents Listed in Appendix III Detection Monitorin of the CCR Rule b
Boron
ug/L
6 / 24
25%
5.3 - 135
30.08
5
5
5
5.075
11.41
Calcium
ug/L
24 / 24
100%
1,680 - 74,200
24,238
8,227
10,700
17,900
31,400
55,880
Chloride
mg/L
24 / 24
100%
1.6 - 38
6.667
1.73
1.975
4.1
7.675
12.11
pH
su
24 / 24
100%
5.15 - 7.85
6.532
6.033
6.215
6.545
6.878
7.169
Sulfate
mg/L
17 / 24
71%
2.1 - 186
22.52
2
2
4.55
13.73
30.36
Total Dissolved Solids
m /L
23 24
96%
51 - 373
153.7
79.9
87.25
109
166.5
336.6
Constituents Listed in Appendix IV Assessment Monitorin of the CCR Rule c
Antimony
ug/L
0 / 24
0%
NA
NA
0.5
0.5
0.5
0.5
0.5
Arsenic
ug/L
2 / 24
8%
4.4 - 4.4
2.62
0.5
0.5
0.5
0.5
0.5
Barium
ug/L
24 / 24
100%
0.89 - 77.3
26.05
5.36
12.63
22.35
33.48
58.11
Beryllium
ug/L
0 / 24
0%
NA
NA
0.2
0.2
0.2
0.2
0.2
Cadmium
ug/L
0 / 24
0%
NA
NA
0.08
0.08
0.08
0.08
0.08
Chromium
ug/L
18 / 24
75%
0.51 - 5
1.37
0.5
0.508
0.805
1.45
1.9
Cobalt
ug/L
0 / 24
0%
NA
NA
0.5
0.5
0.5
0.5
0.5
Lead
ug/L
18 / 24
75%
0.12 - 3.2
0.603
0.1
0.115
0.24
0.58
0.888
Mercury
ug/L
0 / 24
0%
NA
NA
0.2
0.2
0.2
0.2
0.2
Molybdenum
ug/L
6 / 24
25%
0.58 - 4.9
2.523
0.5
0.5
0.5
0.52
2.66
Selenium
ug/L
2 / 24
8%
0.52 - 0.72
0.62
0.5
0.5
0.5
0.5
0.5
Thallium
u /L
0 24
0%
NA
NA
0.1
0.1
0.1
0.1
0.1
Constituents Not Identified in the CCR Rule
Vanadium
ug/L
19 / 24
79%
1 - 23.7
5.784
1
1.15
2.85
5.3
11.38
Aluminum
ug/L
5 / 24
21%
12.1 - 213
85.72
10
10
10
10
60.55
Copper
mg/L
21 / 24
88%
0.001 - 0.0161
0.00537
0.001
0.00185
0.0028
0.00758
0.011
Iron
ug/L
6 / 24
25%
57.5 - 1,340
335.6
50
50
50
51.88
164
Hexavalent Chromium
ug/L
12 / 24
50%
0.14 - 4.5
1.187
0.247
0.6
0.6
0.918
1.5
Magnesium
ug/L
24 / 24
100%
808 - 28,800
7172
2,109
2,858
5,165
8,238
14,550
Manganese
ug/L
16 / 24
67%
0.5 - 271
25.03
0.5
0.5
0.785
8.9
22.5
Nickel
ug/L
6 / 24
25%
0.53 - 1.8
1.038
0.5
0.5
0.5
0.508
0.97
Potassium
ug/L
24 / 24
100%
265 - 3,450
1906
1,010
1,253
1,880
2,428
3,203
Sodium
ug/L
24 / 24
100%
4,610 - 29,900
10,375
6,491
6,785
8,300
9,603
19,920
Strontium
ug/L
24 / 24
100%
12.2 - 1150
238.6
78.03
98.4
147.5
214.8
516.8
Zinc
mg/L
17 / 24
71%
0.0051 - 0.147
0.0209
0.005
0.005
0.00735
0.0137
0.0281
Alkalinity
mg/L
24 / 24
100%
7.4 - 226
79.86
34.19
48.03
66.1
90
166.2
Bicarbonate
mg/L
23 / 24
96%
7.4 - 226
81.04
25.03
46.63
66.1
90
166.2
Carbonate
mg/L
0/ 24
0%
NA
NA
5
5
5
5
5
Total Suspended Solids
mg/L
4 / 24
17%
4.2 - 20.6
10.38
2.5
2.5
2.5
2.5
5.07
Turbidity
NTU
4 / 24
17%
2 - 10.6
4.675
1
1
1
1
2.63
Temperature
°C
24 / 24
NA
15.25 17.68
16.59
16.01
16.37
16.51
16.86
17.18
Specific Conductance
umhos/cm
24 / 24
NA
0.053 0.9
0.26
0.0912
0.116
0.188
0.295
0.563
Dissolved Oxygen
mg/L
24 / 24
NA
0.32 9.86
3.291
0.604
1.553
3.025
4.335
5.488
Oxidation Reduction Potential
mV
24 / 24
NA
-63 241
134.6
46
110.5
146.5
177
198.3
Total Number of Analyses:
936
Haley & Aldrich, Inc.
Table 5_2016 -04 -DEQ Bkg Well Statistical Summary.xlsx APRIL 2016

Page 2 of 2
Table 5
Statistical Summary of NCDEQ-Sampled Background Water Supply Well Data
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
°C - Degrees Celsius. CCR - Coal Combustion Residual.
mg/L - milligrams/liter. DENR - Department of Environment and Natural Resources.
mV - millivolts. DEQ- Department of Environmental Quality.
NTU - Nephelometric Turbidity Units. NC - North Carolina.
su - standard units.
ug/L - micrograms/liter.
umhos/cm - micromhos/centimeter.
(a) - Frequency of Detection: number of detects / total number of results.
(b) - The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(c) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
Haley & Aldrich, Inc.
Table 5_2016 -04 -DEQ Bkg Well Statistical Summary.xlsx APRIL 2016

Page 1 of 2
Table 6
Summary of NCDEQ-Sampled Background Water Supply Well Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 6_2016 -04 -DEQ Bkg Well Screen Summary.xlsx APRIL 2016
Frequency of
Frequency of
Range of Detected
Frequency Detected Above:
Frequency of Reporting Limits Above:
Frequency of
Constituents
Units
Detection (g)
Detection
Percent
Concentrations
2L (a)
DHHS (b) MCL (c)
RSL (d)
2L (a)
DHHS (b)
MCL (c)
RSL (d)
Detects Below All
Screening Levels
Constituents Listed in Appendix III Detection Monitoring)
of the CCR Rule e
Boron
ug/L
6/ 24
25%
5.3 - 135
0
0
0
0
0
0
6
Calcium
ug/L
24 / 24
100%
1,680 - 74,200
--
--
--
-
-
--
--
Chloride
mg/L
24 / 24
100%
1.6 - 38
0
0
0
0
0
0
24
pH
su
24 / 24
100%
5.15 - 7.85
12
--
12
--
-
--
--
Sulfate
mg/L
17 / 24
71%
2.1 - 186
0
0
0
0
0
0
17
Total Dissolved Solids
mg/L
23 24
96%
51 - 373
0
0
0
-
0
23
Constituents Listed in Appendix IV(Assessment Monitoring)
of the CCR Rule f
Antimony
ug/L
0/ 24
0%
NA
0
0
0
0
0
0
0
0
0
Arsenic
ug/L
2/ 24
8%
4.4 - 4.4
0
0
0
2
0
0
0
22
0
Barium
ug/L
24 / 24
100%
0.89 - 77.3
0
0
0
0
0
0
0
0
24
Beryllium
ug/L
0/ 24
0%
NA
0
0
0
0
0
0
0
0
0
Cadmium
ug/L
0/ 24
0%
NA
0
0
0
0
0
0
0
0
0
Chromium
ug/L
18 / 24
75%
0.51 - 5
0
0
0
0
0
0
0
0
18
Cobalt
ug/L
0/ 24
0%
NA
0
0
-
0
0
0
--
0
0
Lead
ug/L
18 / 24
75%
0.12 - 3.2
0
0
0
0
0
0
0
0
18
Mercury
ug/L
0/ 24
0%
NA
0
0
0
0
0
0
0
0
0
Molybdenum
ug/L
6 / 24
25%
0.58 - 4.9
--
0
--
0
--
0
--
0
6
Selenium
ug/L
2/ 24
8%
0.52 - 0.72
0
0
0
0
0
0
0
0
2
Thallium
I ug/L
1 0 24
1 0%
1 NA
1 0
0
0
0
1 0
0
0
0
1 0
Constituents Not Identified
in the CCR Rule
Vanadium
ug/L
19 / 24
79%
1 - 23.7
19
19
--
0
5
5
--
0
0
Aluminum
ug/L
5 / 24
21%
12.1 - 213
--
0
3
0
--
0
0
0
2
Copper
mg/L
21 / 24
88%
0.001 - 0.0161
0
0
0
0
0
0
0
0
21
Iron
ug/L
6/ 24
25%
57.5 - 1,340
1
0
1
0
0
0
0
0
5
Hexavalent Chromium
ug/L
12 / 24
50%
0.14 - 4.5
--
12
--
0
--
11
--
0
0
Magnesium
ug/L
24 / 24
100%
808 - 28,800
--
--
--
--
--
--
--
--
--
Manganese
ug/L
16 / 24
67%
0.5 - 271
0
1
0
0
0
0
0
0
15
Nickel
ug/L
6 / 24
25%
0.53 - 1.8
0
0
--
0
0
0
--
0
6
Potassium
ug/L
24 / 24
100%
265 - 3,450
--
--
Sodium
ug/L
24 / 24
100%
4,610 - 29,900
3
0
21
Strontium
ug/L
24 / 24
100%
12.2 - 1150
0
--
0
--
0
--
0
24
Zinc
mg/L
17 / 24
71%
0.0051 - 0.147
0
0
0
0
0
0
0
0
17
Alkalinity
mg/L
24 / 24
100%
7.4 - 226
--
--
--
--
--
--
--
--
--
Bicarbonate
mg/L
23 / 24
96%
7.4 - 226
Carbonate
mg/L
0 / 24
0%
NA
Total Suspended Solids
mg/L
4 / 24
17%
4.2 - 20.6
Turbidity
NTU
4 / 24
17%
2 - 10.6
Temperature
C
24 / 24
NA
15.25 - 17.68
Specific Conductance
umhos/cm
24 / 24
NA
0.053 - 0.9
Dissolved Oxygen
mg/L
24 / 24
NA
0.32 - 9.86
Oxidation Reduction Potential
I mV
24 24
NA
-63 - 241
Total Number of Analyses:
936
Total Number of Exceedances:
32
35
16
2
5
16
0
22
249
Haley & Aldrich, Inc.
Table 6_2016 -04 -DEQ Bkg Well Screen Summary.xlsx APRIL 2016

Page 2 of 2
Table 6
Summary of NCDEQ-Sampled Background Water Supply Well Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
°C - Degrees Celsius.
mg/L - milligrams/liter.
CCR - Coal Combustion Residual.
mV - millivolts.
DENR - Department of Environment and Natural Resources.
NTU - Nephelometric Turbidity Units.
DEQ - Department of Environmental Quality.
su - standard units.
DHHS - Department of Health and Human Services.
ug/L- micrograms/liter.
HI - Hazard Index.
umhos/cm - micromhos/centimeter.
IMAC - Interim Maximum Allowable Concentration.
MCL- Maximum Contaminant Level.
NC - North Carolina.
RSL - Risk Based Screening Level.
SMCL -Secondary Maximum Contaminant Level.
USEPA - United States Environmental Protection Agency.
--- No Standard Available.
(a) - Classifications and Water Quality Standards Applicable to Groundwaters of North Carolina. North Carolina Administrative Code. April 1, 2013.
http://portal.ncdenr.org/web/wq/ps/csu/gwstandards
(b) - DHHS Screening Levels. Department of Health and Human Services, Division of Public Health, Epidemiology Section, Occupational and Environmental
Epidemiology Branch. http://portal.ncdenr.org/c/document_library/get_file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(c) -USEPA 2012 Edition of the Drinking Water Standards and Health Advisories. Spring 2012.
http://water.epa.gov/drink/contaminants/index.cfm
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tap water. HI = 1.
http://www.epa.gov/reg3hwmd/risk/human/rb-concentration —table/Generic—Tables/index.htm
(e) - The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(f) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV)
(g) - Frequency of Detection: number of detects / total number of results.
Haley & Aldrich, Inc.
Table 6_2016 -04 -DEQ Bkg Well Screen Summary.xlsx APRIL 2016

Page 1 of 2
Table 7
Statistical Summary of Duke Energy -Sampled Background Water Supply Well Data
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 7_2016 -04 -Duke Bkg Well Statistical Summary.xlsx APRIL 2016
Frequency of
Frequency of
Range of Detected
Mean
10th
25th
50th
75th
90th
Constituents
Units
Detection (a)
Detection
Concentrations
Detect
Percentile
Percentile
Percentile
Percentile
Percentile
Percent
Constituents
Listed in Appendix III Detection Monitorin of the CCR Rule
b
Boron
ug/L
39 / 198
20%
5.1 928 96.69 5
5.6
50
50
50
Calcium
ug/L
198 / 198
100%
14 195,000 22,946 3,273
7,485
13,750
29,975
53,360
Chloride
mg/L
66 / 66
100%
0.62 290 24.39 1.6
2.9
6.3
12.5
31.5
pH
su
65 / 65
100%
4.54 11.7 7.245 6.508
6.9
7.31
7.73
8.06
Sulfate
mg/L
63 / 66
95%
0.26 170 11.17 0.43
1.325
5.2
12.75
19.5
Total Dissolved Solids
mg/L
50 / 50
100%
42 760 198.4 65.5
96.25
140
200
439
Constituents Listed
in Appendix
IV Assessment Monitorin of the CCR Rule
c
Antimony
ug/L
100 / 198
51%
0.5 1.5 0.976 0.551
0.94
1
1.035
1.15
Arsenic
ug/L
27 / 198
14%
0.52 14.1 2.65 0.5
0.5
1
1
1.003
Barium
ug/L
176 / 198
89%
0.47 486 47.89 5
6.2
20
57.5
116.9
Beryllium
ug/L
7 / 198
4%
0.2 0.5 0.349 0.2
0.2
1
1
1
Cadmium
ug/L
8 / 198
4%
0.01 - 1.17 0.284 0.08
0.08
1
1
1
Chromium
ug/L
32 / 198
16%
0.5 157 11.28 0.5
0.5
5
5
5
Cobalt
ug/L
21 / 198
11%
0.58 25.9 3.47 0.5
0.5
1
1
1
Lead
ug/L
113 / 198
57%
0.12 73.2 3.009 0.2
0.643
1
1.303
3.09
Mercury
ug/L
1 / 198
1%
0.27 0.27 0.27 0.05
0.05
0.05
0.2
0.2
Molybdenum
ug/L
49 / 198
25%
0.52 10.8 2.438 0.5
0.5
1
1
1.891
Selenium
ug/L
10 / 198
5%
0.59 1.7 1.188 0.5
0.5
1
1
1
Thallium
ug/L
3 / 198
2%
0.18 0.554 0.363 0.1
0.1
0.2
0.2
0.2
Constituents
Not Identified in the CCR Rule
Vanadium
ug/L
107 / 198
54%
0.318 112
6.035
0.3
0.471
1
2.638
8.782
Aluminum
ug/L
98 / 198
49%
5 32,200
725.6
5
6
10
21.75
79.02
Copper
mg/L
131 / 198
66%
0.0011 - 0.992
0.0445
0.00227
0.005
0.005
0.0214
0.0619
Iron
ug/L
131 / 198
66%
10 45,000
1,410
10
18.25
50
300.8
2,059
Hexavalent Chromium
ug/L
72 / 128
56%
0.033 73.5
1.656
0.03
0.03
0.115
0.6
1.29
Magnesium
ug/L
197 / 198
99%
14.2 46,300
5,244
800.6
1,868
3,520
5,928
11,880
Manganese
ug/L
130 / 198
66%
0.56 4,820
124.9
2.37
5
7
34.53
103.7
Nickel
ug/L
39 / 198
20%
0.53 380
14.02
0.5
0.575
5
5
5
Potassium
ug/L
198 / 198
100%
123 32,700
2,344
535.5
1,113
1,720
2,518
3,912
Sodium
ug/L
198 / 198
100%
763 200,000
15,777
4,377
5,960
8,460
11,775
21,450
Strontium
ug/L
193 / 194
99%
0.88 2,210
175.2
26.39
55.35
107
190
354.8
Zinc
ug/L
155 / 198
78%
5 2,990
143.7
5
6
16.35
61.65
233.9
Alkalinity
mg/L
NA
NA
NA
NA
NA
NA
NA
NA
NA
Bicarbonate
mg/L
NA
NA
NA
NA
NA
NA
NA
NA
NA
Carbonate
mg/L
NA
NA
NA
NA
NA
NA
NA
NA
NA
Total Suspended Solids
mg/L
8 / 72
11%
5 - 970
135.3
5
5
5
5
5
Turbidity
NTU
NA
NA
NA
NA
NA
NA
NA
NA
NA
Temperature
C
NA
NA
NA
NA
NA
NA
NA
NA
NA
Specific Conductance
umhos/cm
NA
NA
NA
NA
NA
NA
NA
NA
NA
Dissolved Oxygen
mg/L
NA
NA
NA
NA
NA
NA
NA
NA
NA
Oxidation Reduction Potential
I mV
I NA
I NA
I NA
I NA
I NA
I NA
I NA
I NA
I NA
Total Number of Analyses:
1 5,393
Haley & Aldrich, Inc.
Table 7_2016 -04 -Duke Bkg Well Statistical Summary.xlsx APRIL 2016

Page 2 of 2
Table 7
Statistical Summary of Duke Energy -Sampled Background Water Supply Well Data
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
"C - Degrees Celsius.
BTV - Background Threshold Value.
mg/L- milligrams/liter.
CCR - Coal Combustion Residual.
mV - millivolts.
DENR- Department of Environment and Natural Resources.
NTU - Nephelometric Turbidity Units.
DEQ - Department of Environmental Quality.
su - standard units.
DHHS - Department of Health and Human Services.
ug/L- micrograms/liter.
HI - Hazard Index.
umhos/cm - micromhos/centimeter.
IMAC- Interim Maximum Allowable Concentration.
KM - Kaplan -Meier
MCL- Maximum Contaminant Level.
NC- North Carolina.
RSL - Risk Based Screening Level.
SMCL - Secondary Maximum Contaminant Level.
USEPA - United States Environmental Protection Agency.
USL - Upper Simultaneous Limit
WH - Wilson Hilferty.
(a) - Frequency of Detection: number of detects / total number of results.
(b) - The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(c) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV)
Haley & Aldrich, Inc.
Table 7_2016 -04 -Duke Bkg Well Statistical Summary.xlsx APRIL 2016

Page 1 of 2
Table 8
Summary of Duke Energy -Sampled Background Water Supply Well Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Table 8 -2016 -04 -Duke Bkg Well Screen Summary.xlsx APRIL 2016
Frequency of
Frequency of
Range of Detected
Frequency Detected Above:
Frequency of Reporting Limits Above:
Frequency of
Constituents
Units
Detection (g)
Detection
Percent
Concentrations
2L (a)
DHHS (b)
MCL (c)
RSL (d)
2L (a)
DHHS (b)
MCL (c)
RSL (d)
Detects Below All
Screening Levels
Constituents Listed in Appendix III I Detection Monitoring)
of the CCR Rule e
Boron
ug/L
39 / 198
20%
5.1 - 928
1
1
--
0
0
0
--
0
38
Calcium
ug/L
198 / 198
100%
14 - 195,000
--
--
--
--
--
-
--
-
--
Chloride
mg/L
66 / 66
100%
0.62 - 290
2
2
2
--
0
0
0
--
64
pH
su
65 / 65
100%
4.54 - 11.7
7
--
7
--
0
-
0
--
58
Sulfate
mg/L
63 / 66
95%
0.26 - 170
0
0
0
--
0
0
0
--
63
Total Dissolved Solids
mg/L
50 / 50
100%
42 - 760
5
--
5
--
0
--
0
--
45
Constituents
Listed in Appendix IV Assessment Monitoring)
of the CCR Rule f
Antimony
ug/L
100 / 198
51%
0.5 - 1.5
51
51
0
0
0
0
0
0
49
Arsenic
ug/L
27 / 198
14%
0.52 - 14.1
1
1
1
27
0
0
0
171
0
Barium
ug/L
176 / 198
89%
0.47 - 486
0
0
0
0
0
0
0
0
176
Beryllium
ug/L
7/ 198
4%
0.2 - 0.5
0
0
0
0
0
0
0
0
7
Cadmium
ug/L
8/ 198
4%
0.01 - 1.17
0
0
0
0
0
0
0
0
8
Chromium
ug/L
32 / 198
16%
0.5 - 157
3
3
2
0
0
0
0
0
29
Cobalt
ug/L
21 / 198
11%
0.58 - 25.9
15
15
--
2
0
0
--
0
6
Lead
ug/L
113 / 198
57%
0.12 - 73.2
5
5
5
5
0
0
0
0
108
Mercury
ug/L
1/ 198
1%
0.27 - 0.27
0
0
0
0
0
0
0
0
1
Molybdenum
ug/L
49 / 198
25%
0.52 - 10.8
--
0
--
0
--
0
--
0
49
Selenium
ug/L
10 / 198
5%
0.59 - 1.7
0
0
0
0
0
0
0
0
10
Thallium
ug/L
3/ 198
1 2%
1 0.18 - 0.554
2
2
0
2
0
0
0
0
1
Constituents Not Identified in the CCR Rule
Vanadium
ug/L
107 / 198
54%
0.318 - 112
107
107
--
1
52
52
--
0
0
Aluminum
ug/L
98 / 198
49%
5 - 32,200
--
3
31
2
--
0
0
0
67
Copper
mg/L
131 / 198
66%
0.0011 - 0.992
0
0
0
1
0
0
0
0
130
Iron
ug/L
131 / 198
66%
10 - 45,000
50
16
50
2
0
0
0
0
81
Hexavalent Chromium
ug/L
72 / 128
56%
0.033 - 73.5
--
61
--
1
--
13
--
0
11
Magnesium
ug/L
197 / 198
99%
14.2 - 46,300
--
--
--
--
--
--
--
--
--
Manganese
ug/L
130 / 198
66%
0.56 - 4,820
40
13
40
7
0
0
0
0
90
Nickel
ug/L
39 / 198
20%
0.53 - 380
1
1
--
0
0
0
--
0
38
Potassium
ug/L
198 / 198
100%
123 - 32,700
--
--
--
--
--
--
--
--
--
Sodium
ug/L
198 / 198
100%
763 - 200,000
--
24
--
--
--
0
--
--
174
Strontium
ug/L
193 / 194
99%
0.88 - 2,210
--
1
--
0
--
0
--
0
192
Zinc
ug/L
155 / 198
78%
5- 2,990
5
5
0
0
0
0
0
0
150
Alkalinity
mg/L
NA
NA
NA
--
--
--
--
--
--
--
--
--
Bicarbonate
mg/L
NA
NA
NA
--
--
--
--
--
--
--
--
--
Carbonate
mg/L
NA
NA
NA
--
--
--
--
--
--
--
--
--
Total Suspended Solids
mg/L
8 / 72
11%
5 - 970
--
--
--
--
--
--
--
--
--
Turbidity
NTU
NA
NA
NA
--
--
--
--
--
--
--
--
--
Temperature
°C
NA
NA
NA
--
--
--
--
--
--
--
--
--
Specific Conductance
umhos/cm
NA
NA
NA
--
--
--
--
--
--
--
--
--
Dissolved Oxygen
mg/L
NA
NA
NA
--
--
--
--
--
--
Oxidation Reduction Potential
mV
NA
NA
NA
--
--
-
--
--
--
--
--
--
Total Number of Analyses:
1 5,393
Total Number of Exceedances:
295
311
143
50
52
65
0
171
1,645
Haley & Aldrich, Inc.
Table 8 -2016 -04 -Duke Bkg Well Screen Summary.xlsx APRIL 2016

Page 2 of 2
Table 8
Summary of Duke Energy -Sampled Background
Water Supply Well Data Screening
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
°C - Degrees Celsius.
BTV - Background Threshold Value.
KM - Kaplan -Meier.
mg/L- milligrams/liter.
CCR - Coal Combustion Residual.
MCL - Maximum Contaminant Level.
mV - millivolts.
DENR - Department of Environment and Natural Resources.
NC - North Carolina.
NTU - Nephelometric Turbidity Units.
DEQ- Department of Environmental Quality.
RSL- Risk Based Screening Level.
su - standard units.
DHHS - Department of Health and Human Services.
SMCL - Secondary Maximum Contaminant Level.
ug/L - micrograms/liter.
HI - Hazard Index.
USEPA - United State --- No Standard Available.
umhos/cm - micromhos/centimeter.
IMAC - Interim Maximum Allowable Concentration.
--- No Standard Available.
(a) - Classifications and Water Quality Standards Applicable to Groundwaters of North Carolina. North Carolina Administrative Code. April 1, 2013.
http://portal.ncdenr.org/web/wq/ps/csu/gwstandards
(b) - DHHS Screening Levels. Department of Health and Human Services, Division of Public Health, Epidemiology Section, Occupational and Environmenta
Epidemiology Branch. http://portal.ncdenr.org/c/document_library/get file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pd
(c) - USEPA 2012 Edition of the Drinking Water Standards and Health Advisories. Spring 2012.
http://water.epa.gov/drink/contaminants/index.cfrr
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tap water. HI = 1
http://www.epa.gov/reg3hwmd/risk/human/rb-concentrationtable/Generic Tables/i ndex.htrr
(e) -The CCR Rule (FR80(74):21302-21501; April 17, 2015) lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pd
(f) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV)
(g) - Frequency of Detection: number of detects / total number of results
Haley & Aldrich, Inc.
Table 8_2016 -04 -Duke Bkg Well Screen Summary.xlsx APRIL2016

Page 1 of 1
Table 9
Summary of Available Background Data for Groundwater
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
USGS
North Carolina
Private Wells
mg/L- milligrams/liter.
DEQ- Department of Environmental Quality.
USGS (c)
USGS (c)
USGS (c)
USGS (c)
USGS (c)
USGS (c)
NC Private Well Water
NC Private Well Water
umhos/cm - micromhos/centimeter.
USGS - United States Geological Survey.
Range of County
Range of County
Constituents Units
1992-2003
cn
30 Percentile
1992-2003
m
25 Percentile
1992-2003
Median
1992-2003
n
75` Percentile
1992-2003
m
90 Percentile
1992-2003
Maximum
Averages
1998-2010 d
Averages
2010(d)
Boron ug/L
8.5
17
35
82
220
3400
NA
NA
Calcium ug/L
NA
NA
NA
NA
NA
NA
NA
NA
Appendix III (a)
Chloride mg/L
NA
NA
NA
NA
NA
NA
NA
NA
pH su
NA
NA
NA
NA
NA
NA
5.36-8.32
5.02-8.36
Sulfate mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Total Dissolved Solids mg/L
NA
NA
NA
I NA
NA
NA
NA
NA
Antimony ug/L
< 1
< 1
< 1
< 1
< 1
6.3
NA
NA
Arsenic ug/L
0.079
0.23
0.79
3.0
7.4
550
0.83-10
2.44-13.06
Barium ug/L
9.0
24
54
120
220
5100
50.00-1,607.60
50.00-3,351.22
Beryllium ug/L
< 1
< 1
< 1
< 1
< 1
18
NA
NA
Cadmium ug/L
<1
<1
<1
<1
<1
16
0.50-5.00
0.49-5.00
Appendix IV (b)
Chromium ug/L
0.41
0.68
1.2
3.0
5.2
150
4.88-713.60
0.49-100.00
Cobalt ug/L
0.026
0.063
0.17
0.48
1.1
680
NA
NA
Lead ug/L
0.005
0.018
0.070
0.27
1.0
480
2.5-104.83
2.44 -105.39
Mercury ug/L
NA
NA
NA
NA
NA
NA
0.25-2.00
0.25-2.0
Molybdenum ug/L
0.13
0.32
1.0
3.3
8.0
4700
NA
NA
Selenium ug/L
0.04
0.12
0.34
1.0
3.0
94
2.38-100.00
2.44-100.00
Thallium ug/L
<1
<1
<1
<1
<1
<1
NA
NA
Vanadium ug/L
0.11
0.295
1.4
11
27
190
NA
NA
Aluminum ug/L
0.43
0.98
3.0
4.9
11
1100
NA
NA
Copper mg/L
0.00020
0.00047
0.0010
0.0030
0.0085
2.0
0.025-9.62092
0.025-81.74479
Iron ug/L
0.095
0.81
7.9
93
1500
81000
228.24-125,698.66
50.00-1,100,356.35
Hexavalent Chromium ug/L
NA
NA
NA
NA
NA
NA
NA
NA
Magnesium ug/L
NA
NA
NA
NA
NA
NA
50.00-40,031.32
50.00-137,878.48
Manganese ug/L
0.14
0.85
7.0
84
360
28000
19.51-209.54
15.00-281.71
Nickel ug/L
0.15
0.35
1.1
2.5
4.9
670
NA
NA
Potassium ug/L
NA
NA
NA
NA
NA
NA
NA
NA
Constituents Not
Sodium ug/L
NA
NA
NA
NA
NA
NA
4,500 - 102,484
1-20,000
Identified in the
Strontium ug/L
46
100
270
680
1700
44000
NA
NA
CCR Rule
Zinc mg/L
0.00043
0.0016
0.0048
0.018
0.069
3.3
0.03182-10.00
0.025-10.00
Alkalinity mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Bicarbonate mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Carbonate mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Total Suspended Solids mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Turbidity NTU
NA
NA
NA
NA
NA
NA
NA
NA
Temperature "C
NA
NA
NA
NA
NA
NA
NA
NA
Specific Conductance umhos/cm
NA
NA
NA
NA
NA
NA
NA
NA
Dissolved Oxygen mg/L
NA
NA
NA
NA
NA
NA
NA
NA
Oxidation Reduction Potential mV
NA
NA
NA
NA
NA
NA
NA
NA
Notes:
°C - Degrees Celsius.
CCR - Coal Combustion Residual.
mg/L- milligrams/liter.
DEQ- Department of Environmental Quality.
mV - millivolts.
DHHS - Department of Health and Human Services.
NTU - Nephelometric Turbidity Units.
HI - Hazard Index.
su - Standard units.
NA - Not Available.
ug/L - micrograms/liter.
NC - North Carolina.
umhos/cm - micromhos/centimeter.
USGS - United States Geological Survey.
(a) -The CCR Rule lists these constituents as Constituents for Detection Monitoring (Appendix III).
http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf
(b) -The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(c) - Trace Elements and Radon in Groundwater Across the United States, 1992-2003. USGS, 2011. Scientific Investigations Report 2011-5059,
http://water.usgs.gov/nawqa/trace/pubs/sir20ll-5059i
(d) - North Carolina Public Health - Epidemiology - Well Water & Health - Maps by Contaminant Name
http://epi.publichealth. nc.gov/oee/wellwater/by_contaminant.html
Haley & Aldrich, Inc.
Table 9_2016 -04 -Background Levels Comparison.xlsx APRIL 2016

Page 1 of 1
Table 10
Comparison of Background Threshold Values
Water Supply Well Evaluation
Duke Energy
April 2016
Constituent
Units
Allen
Belews Creek
Buck
Cliffside
Marshall
Mayo
Roxboro
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Regional
BTVs
Facility-
Specific BTVs
Barium
ug/L
103.1
99
126.8
16.98
56.09
87
112.9
36
208.3
890
83.03
132.9
126.8
349
Boron
ug/L
10.12
30
50
37
6
54.02
50
59.7
67.25
29
12.6
65
9
50
Chloride
ug/L
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
130000
Chromium
ug/L
NA
NA
NA
NA
NA
NA
NA
NA
5.253
10.61
NA
NA
NA
NA
Cobalt
ug/L
1
1.913 1
0.6
1.167
1
1 0.395
4.751
4.74
1.33
4.48
1
1.08
3.6
1 14.41
Hexavalent Chromium
ug/L
4.539
34.3
2.2
0.766
2.554
0.761
0.27
1.517
3.304
11
1.646
13.6
0.65
4.401
Iron
ug/L
260.9
2334
610.9
1022
334
257.8
12836
3801
3920
1000
537.6
3780
6862
5368
Lead
ug/L
1.462
3.271
29.57
1.15
2.617
0.167
NA
NA
4.022
0.28
4.078
4.694
16.4
0.11
Manganese
ug/L
NA
NA
NA
NA
66.4
5.799
173.2
134.1
NA
NA
NA
NA
952.1
1220
Nickel
ug/L
7.416
14.8
3
4.838
2.678
1.566
7
13.2
3.681
9
2.512
2.073
380
17.9
Sodium
ug/L
NA
NA
NA
NA
21695
80400
NA
NA
NA
NA
NA
NA
NA
NA
Sulfate
mg/L
NA
NA
NA
NA
33.46
105000
NA
NA
NA
NA
NA
NA
NA
NA
Thallium
ug/L
0.2
0.346
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Vanadium
ug/L
20.27
24.3
3.606
9
16.77
167
6.337
19.77
14.7
23.8
11.22
11.4
7.351
19.26
Zinc
mg/L
NA
NA
NA
NA
0.491
26
NA
NA
NA
NA
NA
NA
NA
NA
Notes:
BTV - Background Threshold Value.
mg/L - milligrams/liter.
NA - Not available/Not applicable.
ug/L- micrograms/liter.
See Appendices for additional BTV information.
Haley & Aldrich, Inc.
Table 10_2016_0417_Summary of BTVs.xlsx April 2016

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Panel (a): Example Box Plot
a Possible Outlier
NOTES
1. BOX PLOT EXPLANATION DIAGRAM ADOPTED FROM
HTTP:HS ITES. GOOGLE.COM/S ITE/DAVI DSSTATI STI CS/HOME/
NOTCHED -BOX -PLOTS.
2. PIPER PLOT ADOPTED FROM CSA REPORT FOR
ALLEN STEAM STATION BY HDR.
Panel (b): Example Piper Plot
Ash Baaln P - ter
Ash smin Walt
® All'RFt' Warb
KIM
s
CATIONS
�Mmna*latrge., a02 oh . Mn
/ANIONS
Upper Whiskers
75th Percentile
aka 3fd Quartile
The "Notch"
55% Confidence Interval of . •.
: Interquartile (IOR)
the Mediani
1557 Pereent of Oatel
Median +1- 1.57 x IQR/n°'.5
25th Percentile
aka tst Quartle
Lower Whiskers
NOTES
1. BOX PLOT EXPLANATION DIAGRAM ADOPTED FROM
HTTP:HS ITES. GOOGLE.COM/S ITE/DAVI DSSTATI STI CS/HOME/
NOTCHED -BOX -PLOTS.
2. PIPER PLOT ADOPTED FROM CSA REPORT FOR
ALLEN STEAM STATION BY HDR.
Panel (b): Example Piper Plot
Ash Baaln P - ter
Ash smin Walt
® All'RFt' Warb
KIM
s
CATIONS
�Mmna*latrge., a02 oh . Mn
/ANIONS