2016-0418_Duke_App_F_Mayo_F

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www.haleyaldrich.com
EVALUATION OF WATER SUPPLY WELLS IN THE VICINITY OF DUKE
ENERGY COAL ASH BASINS IN NORTH CAROLINA
APPENDIX F - MAYO STEAM ELECTRIC PLANT
by Haley & Aldrich, Inc.
Boston, Massachusetts
for Duke Energy
File No. 43239
April 2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Table of Contents
Page
List of Tables
List of Figures iii
List of Attachments iv
List of Acronyms v
F. Mayo 1
F.1 INTRODUCTION
F.1.1
Facility Location and Description
F.1.1.1 Facility Setting
F.1.1.2 Past and Present Operations
F.1.1.3 Facility Geological/Hydrogeological Setting
F.1.2
Current CAMA Status
F.1.2.1 Receptor Survey, September 2014, updated November 2014
F.1.2.2 Comprehensive Site Assessment, Round 1 Sampling Event, March —
September 2015
F.1.2.3 Round 2 Sampling Event, October 2015
F.1.2.4 Corrective Action Plan — Part 1, 1 December 2015
F.1.2.5 Round 3 (December 2015) and Round 4 (January 2016) Groundwater
Sampling
F.1.2.6 Corrective Action Plan — Part 2, February 2016
F.1.3
Investigation Results
F.1.4
Selected Remedial Alternative and Recommended Interim Activities
F.1.5
Risk Classification Process
F.1.6
Purpose and Objectives
F.2 WATER SUPPLY WELL DATA EVALUATION
F.2.1
Data Sources
F.2.2
Screening Levels
F.2.3
Results
F.3 STATISTICAL EVALUATION OF BACKGROUND
F.3.1 Initial Data Evaluation
F.3.1.1 Regional Background Water Supply Well Data
F.3.1.2 Facility Background Monitoring Well Data
F.3.2 Raw Data Evaluation
F.3.2.1 Regional Background Water Supply Well Data
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F.3.2.2 Facility Background Monitoring Well Data
F.3.3 Testing of Statistical Assumptions
F.3.3.1 Regional Background Water Supply Well Data
F.3.3.2 Facility Background Monitoring Well Data
F.3.4 BTV Estimates
F.3.5 Comparison of Water Supply Well Data to the Regional and Facility -Specific
BTVs
F.4 GROUNDWATER FLOW EVALUATION
F.4.1 Introduction
F.4.2 Site Geology
F.4.3 Site Hydrogeology
F.4.3.1 Site Conceptual Model
F.4.3.2 Groundwater Flow Direction
F.4.3.3 Groundwater Seepage Velocities
F.4.3.4 Constituents Associated with CCR
F.4.3.5 Extent of Boron Exceedances in Groundwater
F.4.3.6 Bedrock and Depth of Water Supply Wells
F.4.3.7 Groundwater Mounding
F.4.3.8 Summary
F.4.4 Site Groundwater Model Development and Results
F.4.5 Summary and Conclusions
F.5 GROUNDWATER CHARACTERISTICS EVALUATION
F.5.1
Evaluation Approach
F.5.2
CCR -Related Constituents Screening for Signature Development
F.5.3
Data Analysis Methods
F.5.3.1 Data Sources
F.5.3.2 Data Aggregation
F.5.3.3 Box Plot
F.5.3.4 Correlation Plot
F.5.3.5 Piper Plot
F.5.4
Evaluation Results
F.5.4.1 Box Plot Comparison
F.5.4.2 Correlation Plot Evaluation
F.5.4.3 Piper Plot
F.5.5
Conclusions
F.6 SUMMARY
F.7 REFERENCES
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Appendix F — Mayo
List of Tables
Title
Table No.
Title
F2-1
Comparison of NCDEQ Water Supply Well Data to 2L Screening Levels
F2-2
Comparison of NCDEQ Water Supply Well Data to MCL Screening Levels
F2-3
Comparison of NCDEQ Water Supply Well Data to DHHS Screening Levels
F2-4
Comparison of NCDEQ Water Supply Well Data to RSL Screening Levels
F2-5
Comparison of Duke Energy Background Well Data to 2L Screening Levels
F2-6
Comparison of Duke Energy Background Well Data to MCL Screening Levels
F2-7
Comparison of Duke Energy Background Well Data to DHHS Screening Levels
F2-8
Comparison of Duke Energy Background Well Data to RSL Screening Levels
F2-9
Do Not Drink Letter Summary
F3-1
Duke Energy Background Water Supply Well Data
F3-2
Facility Specific Background Data for Bedrock and Deep Monitoring Wells
F3-3
Background Data Statistical Evaluation
F3-4
Comparison of NCDEQ Water Supply Well Sampling Data to Background
Threshold Values
F3-5
Comparison of NCDEQ Water Supply Well Sampling Data to Facility Specific
Background Threshold Values
F5-1
Coal Ash Indicator Concentrations Observed in the Water Supply Wells of Low
Oxygen
List of Figures
Figure No.
Title
F1-1
Location Map
F1-2
Key Features
F1-3
Location of Water Supply Wells and Facility Groundwater Conditions
F3-1
Facility Background Wells
F4-1
Site Conceptual Model — Plan View
F4-2
Conceptual Cross -Section A -A'
F4-3
Water Supply Well Capture Zones
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Appendix F — Mayo
F5-1
Pourbaix Diagrams for Manganese with Measured Eh and pH from Site
Monitoring Wells
F5-2
Example Box Plot and Piper Plot
F5-3
Box Plot Comparison for Major Coal Ash Constituents
F5-4
Box Plot Comparison for Barium and Cobalt
F5-5
Box Plot Comparison for Dissolved Oxygen, Iron, and Manganese
F5-6
Bedrock Groundwater Wells and Direction of Groundwater Flow
F5-7
Correlation Plot for Boron and Dissolved Oxygen
F5-8
Sampled Water Supply Wells
F5-9
Piper Plot Evaluation - Ash Basin Porewater and Facility Downgradient Bedrock
Wells
F5-10
Piper Plot Evaluation - Water Supply Wells and Facility Bedrock Wells
F5-11
Piper Plot Evaluation - Water Supply, Facility Bedrock, and Ash Basin Porewater
Wells
List of Attachments
Attachment Title
F-1 Histograms and Probability Plots for Selected Constituents
F-2 Results of Statistical Computations
F-3 Method Computation Details
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Appendix F — Mayo
List of Acronyms
213 Standards North Carolina Surface Water Quality Standards as specified in T15 NCAC 026.0211
and.0216
2L Standards North Carolina Groundwater Quality Standards as specified in Title 15A NCAC.0202L
amsl Above mean sea level
BR Bedrock
BTV Background Threshold Value
CAMA North Carolina Coal Ash Management Act of 2014
CAP Corrective Action Plan
CC Confidence Coefficient
CFR Code of Federal Regulations
CCR Coal Combustion Residuals
CSA Comprehensive Site Assessment
D Deep
EPRI Electric Power Research Institute
GOF Goodness -Of -Fit
HSL Health Screening Levels
IID Independent, Identically Distributed
IMAC Interim Maximum Allowable Concentrations
IQR Interquartile Range
KM Kaplan -Meier
µg/L Micrograms per Liter
MCL Maximum Contaminant Level
MDL Method Detection Limit
MNA Monitored Natural Attenuation
NCAC North Carolina Administrative Code
NCDEQ North Carolina Department of Environmental Quality
ND Non -Detect
NPDES National Pollutant Discharge Elimination System
NCDHHS North Carolina Department of Health and Human Services
PPBC Proposed Provisional Background Concentration
ROS Robust Regression on Order Statistics
RSL Risk -Based Screening Level
S Shallow
SCM Site Conceptual Model
SMCL Secondary Maximum Contaminant Level
TDS Total Dissolved Solids
TZ Transition Zone
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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Appendix F — Mayo
F. Mayo
The contents of this document supplements previous work completed by Duke Energy to meet the
requirements of the North Carolina Coal Ash Management Act of 2014 (CAMA) for the Mayo Steam
Electric Plant (Mayo Plant or site), a coal-fired generating station. The purpose of this document is to
provide the North Carolina Department of Environmental Quality (NCDEQ) with the additional
information it needs to develop a final risk classification for the Mayo ash basin under the CAMA
requirements. A technical weight of evidence approach has been used to evaluate the available data for
the Mayo site, and the evaluation demonstrates that groundwater utilized by local water supply wells
near the Mayo coal ash impoundment is not impacted by coal ash sources. These results support the
NCDEQ's Low classification for the Mayo Plant under the CAMA.
F.1 INTRODUCTION
The first section of this document provides a description of the facility location, setting, past and present
operations, a summary of activities conducted to meet the CAMA requirements, a summary of the on-
site and background data evaluation findings and recommendations of the following reports:
• Comprehensive Site Assessment (CSA; SynTerra Corporation, Inc. [Synterra], 2015a);
• Corrective Action Plan Part 1 (CAP -1; SynTerra, 2015b);
• Corrective Action Plan Part 2 (CAP -2; SynTerra, 2016); and
A review of the risk classification process and the status of that process are also provided.
This report 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.
F.1.1 Facility Location and Description
Duke Energy owns and operates the Mayo Plant which is located in Person County near the city of
Roxboro, North Carolina (Figure F1-1).
F.1.1.1 Facility Setting
The Mayo Plant became fully operational in June 1983. The Mayo Plant occupies 460 acres of land and
is located next to Mayo Lake or Mayo Reservoir as shown on Figure F1-2. Forested areas encircle the
southeast portion of the property to the southwest, south, east, and northwest. Mayo Lake borders the
entire eastern portion of this part of the site (Figure F1-2). A portion of the northern Plant property line
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Appendix F — Mayo
extends to the North Carolina/Virginia state line. The site is roughly bisected by Highway 501. The
majority of the site, including the power plant, the ash basin, and the majority of operational features, is
located east of Highway 501 and extends to the eastern shore of Mayo Lake. The property is bounded
to the north by the North Carolina/Virginia state line. Mayo Lake Road runs west to east from the
intersection with Highway 501 to NC County Road 1504. The portion of the site located west of Highway
501 contains the recently operational ash monofill and a haul road that connects the monofill with the
operational portion of the Mayo Plant. A railroad spur bisects the western portion of the property. RT
Hester Road also cuts across the northeastern portion of the western property.
Per the North Carolina Administrative Code (15A NCAC 02L.0102), "Compliance Boundary' means a
boundary around a disposal system at and beyond which groundwater quality standards may not be
exceeded, and only applies to facilities that have received a permit issued under the authority of North
Carolina General Statute (G.S.) 143-215.1 or G.S. 130A. The ash basin compliance boundary is defined in
accordance with 15A NCAC 02L.0107(a) as being established at either 500 feet from the waste boundary
or at the property boundary, whichever is closer to the waste.
Properties located within a 0.5 -mile radius of the Mayo Plant compliance boundary are all contained
within the site with the exception of the undeveloped parcel located due north of the northern plant
boundary along Mayo Lake Road. Properties adjacent to Mayo Plant are located in Person County,
North Carolina and Halifax County, Virginia. Undeveloped land occurs on the site west of Highway 501
with the exception of the recently completed monofill. The closest residences to the east of the site are
along the easternmost shore of Mayo Lake. Undeveloped land borders the Mayo Plant to the north.
Several residences are located just outside the Plant boundaries to the south and northwest (North
Carolina and Virginia).
The Mayo Plant's compliance boundary encircles the ash basin and the groundwater monitoring well
network, except on the northeastern edge of the site where the compliance boundary is co -located with
the boundary of the site. There are 22 private water supply wells and three former water supply wells
identified within a 0.5 -mile radius of the ash basin compliance boundary (Figure F1-3). There are three
inactive water supply wells on the site (informally designated as DEP-1, DEP-2, and DEP-3); it is
noteworthy that the wells have been out of service for a number of years, even decades; therefore, they
are not currently influencing groundwater flow.
F.1.1.2 Past and Present Operations
The Mayo Plant began coal-fired power production in 1983. There is a single ash basin present at the
site, located northwest of the Plant, that contains ash generated from historic coal combustion. No
other areas of coal ash, other than possible de minimis quantities, are known to exist at the site.
The ash basin is situated to the northwest of the railroad line, and the power plant and majority of
supporting operational features (e.g., coal pile, cooling towers, administrative buildings, substation, etc.)
are situated southeast of the railroad line. Forested areas encircle the southeast portion of the property
to the southwest, south, east, and northwest. Mayo Lake borders the entire eastern portion of this part
of the site (Figure F1-2).
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Appendix F — Mayo
The majority of sluiced ash was discharged to the basin on the northwest side of the railroad line. An
obvious "ash delta" is noted in historical photographs where active sluicing occurred. Historical
photographs dated 2008 also indicate that the site appears almost identical to the present day with
mostly wooded areas surrounding the ash basin and power plant areas. The ash basin is approximately
half open water and half ash.
The Mayo Plant ash basin, operating under National Pollutant Discharge Elimination System (NPDES)
Permit NC0038377, is impounded by an earthen embankment system approximately 2,300 feet long,
with a dam height of 110 feet, and a crest height elevation of 479.8 feet above mean sea level (amsl).
The basin area is approximately 144 acres and contains approximately 6,900,000 tons of coal
combustion residual (CCR) material.
F.1.1.3 Facility Geological/Hydrogeologica/ Setting
The Mayo Plant is located in the geologic region known as the Piedmont Province which stretches from
New Jersey to central Alabama. The widest portion of the Piedmont is located in North Carolina. The
overall topography of the Plant generally slopes toward the east (Mayo Lake or Mayo Reservoir) and
northeast (Crutchfield Branch). The topographically highest portion of the site is along the Plant
entrance road just off of Highway 501. In general, the topography slopes away from the entrance road
and the power plant area towards Mayo Lake. The power plant area is situated at an approximate
elevation of 520 feet amsl and Mayo Lake is at an elevation of about 435 feet amsl, a vertical difference
(relief) of 85 feet. One small stream traverses the southern end of this portion of the site flowing from
west to east, originating south of the coal pile, and eventually flowing into Mayo Lake.
Based on the site investigation, the groundwater system in the natural materials (alluvium, soil,
soil/weathered bedrock, and bedrock) at the Mayo Plant is a fractured bedrock system and is an
unconfined, connected system of flow layers. The Mayo Plant groundwater system is divided into three
layers referred to in this report as the shallow (S), deep transition zone (D or TZ), and bedrock (BR) flow
layers to distinguish the flow layers within the connected aquifer system.
The nature of the Mayo Plant ash basin and the former stream valley of Crutchfield Branch in which the
basin was constructed is the primary influence on groundwater flow and constituent transport. The
basin acts as a bowl -like feature towards which groundwater flows from all directions except north.
Groundwater flows from the ash basin into the small valley formed by Crutchfield Branch, which flows
north.
More detail on the site hydrogeology is provided in Section F.4.
F.1.2 Current CAMA Status
The CAMA is primarily administered by the NCDEQ. The CAMA requires the NCDEQ to, as soon as
practicable, but no later than 31 December 2015, prioritize for the purpose of closure and remediation
CCR surface impoundments, including active and retired sites, based on these sites' risks to public
health, safety, and welfare, the environment, and natural resources.
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Appendix F — Mayo
To this end, CAMA includes the following requirements for coal -fueled facilities that manage coal ash or
CCR, the material that results from the combustion of coal for the creation of electric energy:
• An assessment of groundwater at CCR surface impoundments; and
• Corrective action for the restoration of groundwater quality at CCR surface impoundments.
Duke Energy owns and operates, or has operated, 14 coal -fueled electric generating facilities in the state
of North Carolina. Per the CAMA, the investigation reporting milestones for each facility include the
following:
• Groundwater Assessment Work Plan;
• Groundwater Assessment Report, referred to as a Comprehensive Site Assessment (CSA); and
Corrective Action Plan (CAP), Note: As agreed with NCDEQ, the CAP reports were prepared in
two parts: CAP -1 and CAP -2.
Duke Energy has submitted the Groundwater Assessment Work Plans, CSAs, and CAP reports as required
by the CAMA schedule. The CSA reports were submitted for all facilities by 2 September 2015. The CAP -
1 reports were submitted for all facilities by 8 December 2015. CAP -2 reports were submitted by
7 March 2016. The CAP -2 reports include a site-specific human health and ecological risk assessment
that will be used to inform the remedial decision making for each facility.
The CAMA also requires a survey of drinking water supply wells and replacement of water supplies if
NCDEQ determines a well is contaminated by CCR -derived constituents. NCDEQ has yet to make such a
determination under the CAMA. Duke Energy provided the NCDEQ with an evaluation of the NCDEQ-
sampled water supply well (private well) data in December 2015 (Haley & Aldrich, 2015). This report
serves to augment the evaluations provided in the December 2015 report.
A brief summary of the objectives and approach for the Receptor Survey, CSA, CAP -1, CAP -2, and
multiple sampling events is provided below:
F.1.2.1 Receptor Survey, September 2014, updated November 2014
The receptor survey was conducted by Duke Energy for the purpose of identifying drinking water wells
within a 0.5 -mile (2,640 -foot) radius of the Mayo Plant ash basin compliance boundary. Supplemental
receptor survey information was obtained from responses to water supply well survey questionnaires
mailed to property owners within the required distance requesting information on the presence of
water supply wells, well details, and well usage. There were 22 private water supply wells and three
former water supply wells on the Mayo Plant property identified 0.5 miles within the compliance
boundary. Additionally, one NCDEP-registered public water supply well is located at the Bethel Hill
Baptist Church, approximately 0.5 miles south (upgradient) of the Site. NCDEQ has reported analytical
data for three private wells in the vicinity of the Mayo Plant. Figure F1-3 shows the water supply wells
within this 0.5 -mile radius.
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Appendix F — Mayo
F.1.2.2 Comprehensive Site Assessment, Round 1 Sampling Event, March — September 2015
The purpose of the Mayo Plant CSA was to collect information necessary to characterize the extent of
impacts resulting from historical production and storage of coal ash, evaluate the chemical and physical
characteristics of CCR constituents, investigate the geology and hydrogeology of the site including
factors relating to contaminant transport, and examine risk to potential receptors and exposure
pathways.
The following assessment activities were performed as part of the CSA:
• Installation of 29 groundwater monitoring wells and 11 soil borings to facilitate collection and
analysis of chemical, physical, and hydrogeological parameters of subsurface materials
encountered within and beyond the waste and compliance boundary.
• Collection of groundwater sampled from 23 groundwater monitoring wells.
• Collection of seep, surface water, and sediment samples.
• Evaluation of laboratory analytical data to support the development of the site conceptual
model (SCM).
• Completion of a screening -level human health and ecological risk assessment.
F.1.2.3 Round 2 Sampling Event, October 2015
A second round of groundwater, seep, and surface water samples were collected during the Round 2
event. The locations and methods were modeled after the first data collection event conducted for the
CSA (SynTerra, 2015a). Samples were analyzed for total and dissolved CCR constituents.
F.1.2.4 Corrective Action Plan — Part 1, 1 December 2015
The purpose of the CAP -1 report was to summarize CSA findings, evaluate background conditions by
calculating Proposed Provisional Background Concentrations (PPBCs) for soil and groundwater, evaluate
exceedances per sample medium with regard to PPBCs, refine the SCM, and present the results of the
groundwater flow and contaminant fate and transport model, and the groundwater to surface water
interaction model.
The Mayo Plant CAP -1 (SynTerra, 2015b) presented PPBCs for groundwater, and soil. The PPBCs and
other applicable regulatory standards were compared to the current site data from each of these media
to determine the CCR constituents to be addressed in a potential corrective action to be proposed in
CAP -2. This evaluation is updated in the subsequent CAP -2 report (SynTerra, 2016), as additional data
was collected and evaluated against regulatory standards for each medium.
Groundwater modeling of the fate and transport of CCR constituents identified to exceed standards was
conducted to inform the corrective action plan. Three modeling scenarios were completed to assess the
impact of potential corrective actions as follows: existing conditions; the effect of capping the CCR
source areas to reduce rainfall infiltration; and the effect of excavating CCR materials. All three
scenarios were modeled over a 100 -year timeframe.
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F.1.2.5 Round 3 (December 2015) and Round 4 (January 2016) Groundwater Sampling
In response to an NCDEQ request, Duke Energy collected two rounds of groundwater samples from
background wells. Facility background wells within the compliance boundary were identified and based
on the SCM during preparation of the CSA Work Plan (SynTerra, 2014). Groundwater sample collection
and analysis were conducted using procedures described in the CSA Report.
See Section F.3 for a statistical evaluation of background concentrations.
F.1.2.6 Corrective Action Plan — Part 2, February 2016
The purpose of the CAP -2 report is to provide the following:
• A description of exceedances of groundwater quality standards, surface water quality standards,
and sample results greater than the Interim Maximum Allowable Concentrations (IMAC) and
North Carolina Department of Health and Human Services (NCDHHS) health screening levels
(HSL);
• Present Round 3 of the groundwater sampling results;
• A refined SCM;
• Refined groundwater flow and fate and transport model results;
• Refined groundwater to surface water model results;
• Site geochemical model results;
• Findings of the human health and ecological risk assessment;
• Evaluation of methods for achieving groundwater quality restoration;
• Conceptual plan(s) for recommended proposed corrective action(s);
• A schedule for implementation of the proposed corrective action(s); and
• A plan for monitoring and reporting of the effectiveness of the proposed corrective action(s).
Groundwater data collected during the four sampling rounds were compared to the following standards:
• North Carolina Groundwater Quality Standards as specified in Title 15A NCAC.0202L
(21- Standards);
• I MAC;
• U.S. Environmental Protection Agency (USEPA) National Recommended Water Quality Criteria;
• North Carolina Surface Water Quality Standards as specified in T15 NCAC 0213.0211 and.0216
(amended effective January 2015) (26 Standards); and/or
• Site-specific PPBCs for groundwater at the Mayo Plant.
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Appendix F — Mayo
Data gap wells were installed at the site in January 2016 including:
Monitoring well ABMW-02BRL located in the ash basin to assess vertical extent in bedrock
groundwater; and
• Piezometer MW-17BR located on the west side of the Plant railroad to provide a key
hydrogeologic data point for water level and flow direction between groundwater flow regimes
to the north and east.
In addition, a surface water sample was collected from the small tributary to Crutchfield Branch that
originates east of the 1981 landfill.
F.1.3 Investigation Results
Based on the CSA, CAP -1, and CAP -2 results, general observations regarding the spatial distribution of
constituents in groundwater at the Mayo Plant are depicted in Figure F1-3 and are described as follows:
• Impacts from CCR -constituents in groundwater are spatially limited to areas beneath the ash
basin and within the ash basin compliance boundary.
• Groundwater impacts are present in the shallow soil/alluvium and deep soil/weathered bedrock
flow layers at the site.
• Surface water impacts were identified in the Crutchfield Creek.
• Constituents exceeding groundwater standards were higher beneath the ash basin, and
downgradient and north of the ash basin and dry ash landfill. The area where boron and total
dissolved solids exceed the 2L standard is identified on Figure F1-3.
• Groundwater flows north-northeast from the ash basin into the small valley formed by
Crutchfield Branch.
Constituents identified to exceed the applicable state and federal regulatory standards are listed by
location below:
• Surficial aquifer: boron, cobalt, iron, manganese, vanadium, and zinc.
• Bedrock and transition zone aquifer: aluminum, antimony, barium, chromium, cobalt, iron, lead,
manganese, molybdenum, vanadium, and zinc.
• Ash basin water: aluminum, boron, chromium, cobalt, iron, lead, manganese, vanadium, and
zinc.
• Crutchfield Branch and south creek area: aluminum, cobalt, iron, manganese, and zinc.
Boron exceeded its 2L Standards beneath and downgradient of the ash basin and is considered to be
detection monitoring constituents in Code of Federal Regulations Title 40 (40 CFR) Section 257
Appendix III of USEPA's Hazardous and Solid Waste Management System; Disposal of Coal Combustion
Residuals from Electric Utilities CCR Rule (USEPA, 2015a). The USEPA detection monitoring constituents
are potential indicators of groundwater contamination from CCR as these constituents are associated
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with CCR and move with groundwater flow unlike other constituents whose movement is impeded by
chemical or physical interactions with soil and weathered rock.
F.1.4 Selected Remedial Alternative and Recommended Interim Activities
The recommended remedial alternative selected for the Mayo Plant is the combination of two
remediation technologies: 1) capping the ash basin, and 2) monitored natural attenuation (MNA).
Groundwater modeling showed that the construction of an engineered cap to reduce infiltration would
also reduce the movement of groundwater from the ash basin.
MNA is deemed most appropriate on the basis of: environmental protection; closure design that can
include engineering controls to minimize the amount of ash in contact with groundwater; modeling
simulations that indicate basin closure (capping) will result in the retreat of constituent plume and a
reduction in constituent concentrations downgradient of the ash basin; technical effectiveness and
simplicity; and sustainability. A MNA program including collection and evaluation of groundwater data
would be implemented until remedial objectives are reached.
Additional groundwater monitoring well installation and a Tier III MNA evaluation (USEPA, 2007) was
recommended for implementation in 2016. The final closure option may be modified based on the final
risk classification proposed by the NCDEQ.
F.1.5 Risk Classification Process
Duke is required by the CAMA to close the Mayo Plant ash basin system no later than 1 August 2029 or
as otherwise dictated by the NCDEQ risk ranking classification. On 31 January 2016, NCDEQ released
draft proposed risk classifications for Duke Energy's coal ash impoundments in North Carolina (NCDEQ,
2016). The proposed risk classification for the Mayo Plant ash basin was Low. Risk classifications were
based upon potential risk to public health and the environment. A public meeting was held by NCDEQ
regarding the proposed risk classification for the Mayo Plant ash basin. NCDEQ will release the final risk
classifications after review of public comments.
According to the NCDEQ document "Coal Combustion Residual Impoundment Risk
Classifications, January 2016" (NCDEQ 2016), the ash basin at the Mayo Plant is ranked "Low." The
following are the classification factors for the Mayo Plant as provided in the NCDEQ document:
Groundwater Kev Factor:
• Based on the information received to date, there appears to be no downgradient receptors
located 1,500 feet downgradient of the impoundment compliance boundary.
Based on the data provided in CSA Report and results of the groundwater modeling results
presented in the CAP Report, the number of down -gradient receptors (well users) 1,500 feet
from the compliance boundary that are potentially or currently known to be exposed to
impacted groundwater from source(s) or migration pathways related to the CCR
impoundments:
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— Ash Pond. LOW RISK. There are no reported supply wells within 1,500 feet
downgradient of the impoundment compliance boundary.
• Exceedance of 2L Standard or IMAC at or Beyond the Established CCR Impoundment
Compliance Boundary:
- Ash Pond. HIGH RISK. Monitoring well CW -02 has detections of Boron greater than
the 2L Standard or IMAC. CW -02 appears to be at a location near the compliance
boundary but it is unclear if this well is located exactly at the compliance boundary
or just inside the boundary. CW -03 has detections of vanadium greater than the
IMAC. MW -16S has a detection of cobalt greater than the IMAC.
• Population Served by Water Supply Wells Within 1,500 feet Up -Gradient or Side -Gradient of
the Established CCR Impoundment Compliance Boundary:
- Ash Pond. LOW/INTERMEDIATE RISK. Four water supply wells appear to be located
within 1,500 feet of the compliance boundary. With the assumption of 2.5 users per
well, there would be approximately 10 users.
• Population Served by Water Supply Wells within 1,500 feet Downgradient of the Established
CCR Impoundment Compliance Boundary:
- Ash Pond. LOW RISK. Based on information in the CSA Report and groundwater
modeling presented in the CAP Report, there are no water supply wells that are
located in the overall downgradient groundwater flow direction of the impoundment
compliance boundary.
• Proximity of 2L Standard or IMAC Exceedances Beyond the Established CCR Impoundment
Compliance Boundary with Respect to Water Supply Wells:
- Ash Pond. HIGH RISK. MW-14BR has detections of vanadium, iron, manganese, and
cobalt greater than the 2L Standards or IMAC. MW-14BR is expected to be in a
downgradient or side -gradient location in regards to the impoundment. This
monitoring well appears to be less than 500 feet from residential well DW -4 (Duke
water supply well survey), although some degree of uncertainty exists for the
horizontal distance given the water supply well survey map is a separate figure from
the master site figure (2-1). The DW -4 location has two other water supply wells
(DW -3 and DW -5) located on adjacent properties. One well is location to the north
of DW -4 and one well to the south. These wells would be covered by the horizontal
distance of 500 to 1,500 feet for this category.
Groundwater Emanating from the Impoundment that Exceeds 2L Standard or IMAC and that
Discharges into a Surface Water Body:
- Ash Pond -Groundwater Risk Ranking. HIGH RISK. Identified seeps S -02B and S-08
which appear to discharge into Crutchfield Branch have detected concentrations (but
not limited to) of boron and cobalt greater than the 2L Standards or IMAC. S-08 also
has detections of vanadium greater than the IMAC. Engineered toe drains 5-01 and
5-02 have detected concentrations of boron (but not limited to) greater than the
2L Standard. The seeps appear to discharge into Crutchfield Branch.
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• Data Gaps and Uncertainty Related to Transport of Contaminants to Potential Receptors:
Ash Pond, INTERMEDIATE RISK. The extent of potential contaminants in the area
near the water supply well cluster on the northwest side of the facility may require
additional vertical extent and possibly horizontal extent definition. CW -04 and CW -
05 are either on or very near the compliance boundary. MW-05BR is located beyond
the compliance boundary at a more close location to the water supply well cluster.
The following monitoring wells have detections (but not limited to) greater the 2L
Standards or IMAC as listed: CW -5 (iron and manganese), MW-05BR (iron and
manganese), and MW-14BR (cobalt, iron, manganese, and vanadium). The extent of
potential contaminants in the area on the south side of the facility nearest the water
well cluster in that area may require additional vertical and horizontal extent
definition. Monitoring well pair MW -12S and MW -12D have detections of cobalt,
manganese, and vanadium greater than the 2L Standards or IMAC. The intent of
MW -12S and MW -12D was as a background well set for naturally occurring
groundwater geochemistry in a generally upgradient (in relation to the
impoundment) location. Also, boron was detected in well CW -02 at 804 micrograms
per liter (µg/L), which is at a location approximately 80 feet from the compliance
boundary in the upgradient direction. The result implies a 2L Standard violation may
be present at the compliance boundary for boron.
F.1.6 Purpose and Objectives
The purpose of this document is to provide additional detailed evaluation of the Mayo Plant -related
data to clarify the subjects noted in the NCDEQ risk classification comments (see previous section).
More specifically, this appendix is written to provide a technical evaluation showing where water supply
wells in the vicinity of the Mayo Plant may be affected by CCR constituents and provide a better
understanding of those metals and other constituents that are found both in ash basin water and are
naturally occurring and present in water supply wells.
This document is divided into four sections:
• Section F.2 provides an evaluation of the water supply well data with respect to regulatory
standards and health -risk-based screening levels.
• Section F.3 presents additional statistical evaluation of the water supply well data and
background data to provide a more detailed and critical evaluation of constituents that may be
present either due to the influence of nearby ash basins or are naturally occurring and
commonly found in groundwater not affected by Mayo Plant operations.
• Section F.4 provides the hydrogeologic findings of additional groundwater modeling and an
additional evaluation of groundwater flow patterns in the vicinity of the Mayo Plant with
respect to the locations of the water supply wells.
• Section F.5 provides an evaluation of the geochemical fingerprint of pore water and
groundwater at the ash basin and related coal ash facilities compared to the geochemical
fingerprint of water supply wells and regional background wells. This comparison provides a
statistical evaluation of constituent data for specific data sets: ash basin pore water, facility
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groundwater, facility background groundwater, water supply wells, and regional background
groundwater, and identifies where these fingerprints are the same, similar, or significantly
different. An interpretation of the data is provided together with specific conclusions regarding
areas that show the potential presence of CCR constituents within and outside of the
compliance boundary for the Mayo Plant.
Section F.6 provides a summary of conclusions and a discussion of their potential impact on the
risk classification for this site.
F.2 WATER SUPPLY WELL DATA EVALUATION
The purpose of this section is to evaluate data for water supply wells in the vicinity of Mayo with respect
to applicable screening levels.
F.2.1 Data Sources
As noted above, 1 public water supply well and 22 private water supply wells are in use and located
within a 0.5 -mile radius of the Mayo Plant ash basin compliance boundary (Figure F1-3). This section
presents an evaluation of the water supply well data from the following two sources:
• A total of 3 samples collected by the NCDEQ from 3 wells within a 0.5 -mile radius of the Mayo
ash basin compliance boundary; and
• A total of 14 samples collected by Duke Energy from background water supply wells located
within a 2- to 10 -mile radius from the Mayo site boundary.
Where there were multiple results for a single well in the NCDEQ-sampled local water supply well
dataset, a representative value was identified to be used in the evaluation, which is defined as the
maximum of the detected values if the analytical results are not detected values. If the analytical results
are all not detected, the lowest reporting limit is defined as the representative value.
F.2.2 Screening Levels
Analytical data from the NCDEQ water supply wells and the background water supply wells were
compared to the following state and federal drinking water levels:
• North Carolina Statute 15A NCAC 02L.0202 (2L Standard) groundwater standards (NCAC, 2013),
note IMACs are included when referring to 2L Standards in this report;
• Federal Safe Drinking Water Act maximum contaminant levels (MCLS) and secondary drinking
water standards (SMCLs) (USEPA, 2012);
• NCDHHS screening levels (NCDHHS, 2015); and
• USEPA Risk -Based Screening Levels (RSLs) (USEPA, 2015b).
As discussed in the main report, the IMAC value used by NCDEQ and the NCDHHS screening level for
vanadium has been changed, but to date the new screening level has not been released. Similarly, the
NCDHHS screening level for hexavalent chromium has been changed, but to date the new screening
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level has not been released. Thus, these screening tables use the publicly available values for these two
constituents.
F.2.3 Results
Tables F2-1 through F2-4 present the comparison of the data for the NCDEQ-sampled water supply wells
located within a 0.5 -mile radius of the Mayo ash basin compliance boundary to 2L standards, USEPA
MCLS, NCDHHS screening levels, and USEPA RSLs, respectively.
Tables F2-5 through F2-8 present the comparison of the Duke Energy data for the background water
supply wells to 2L standards, USEPA MCLS, NCDHHS screening levels, and USEPA RSLs, respectively.
The concentration of boron and the other potential coal ash indicators (discussed in Section 3 of the
main report) were low and not above screening levels in the water supply wells sampled by NCDEQ.
Boron was not detected in the NCDEQ sampled water supply wells; boron was detected in 1 of the
14 Duke Energy background wells. Lead was below the drinking water standard in 2 of the 3 NCDEQ-
sampled water supply wells. pH was below the drinking water standard range in 1 of the 3 NCDEQ-
sampled water supply wells. This result is not unexpected, based on a study published by the United
States Geological Survey (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.
None of the NCDEQ-sampled water supply well results were above Federal primary drinking water
standards (MCLS), with the exception of the pH results and lead result noted above. Two aluminum and
iron results were above the SMCL, as was one of the results for manganese; however, the SMCLs are
based on aesthetics, and all results but one result for manganese are below the USEPA risk-based RSLs.
A "Do Not Drink" letter was issued by NCDHHS for one water supply well at Mayo Steam Station (see
Table F2-9). The letter was issued for vanadium, iron, lead, and sodium, though the vanadium value was
based on the now -outdated screening level, and "Do Not Drink" warnings have been lifted for
vanadium.
A detailed statistical evaluation of background and comparison to the water supply well data is provided
in the next section.
F.3 STATISTICAL EVALUATION OF BACKGROUND
The purpose of the background evaluation is to develop a site-specific or facility -specific descriptor of
background for constituents of interest, i.e., a background threshold value (BTV). If a sample result is
below the BTV, there is reasonable confidence that the constituent concentration is consistent with
background. However, a sample result above a BTV does not mean that it is not consistent with
background, only which statistically it cannot be determined based on the available background dataset.
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Appendix F — Mayo
Two datasets are available to describe background groundwater conditions in the vicinity of Mayo:
• The Duke Energy background water supply well dataset; and
• The Mayo facility background monitoring wells.
The Duke Energy background water supply well dataset is referred to here as regional background, and
the Mayo background monitoring well dataset is referred to as facility -specific background.
Eight constituents were selected for the background evaluation studies at Mayo. 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 presented in Section F.S. The
BTV values were estimated for the eight constituents at Mayo 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.
The statistical methodology and the conclusions for the background evaluation are presented in the
following sections.
F.3.1 Initial Data Evaluation
The initial statistical evaluation was performed to check the homogeneity of variance assumption for
multiple groups of wells included in the Mayo facility -specific background monitoring well dataset,
before combining each into a single dataset. In this step, data from discrete data sources for each
background dataset were tested for statistical variations using Levine's test. The test examines if the
differences in sample variances occur because of random sampling. 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.
F.3.1.1 Regional Background Water Supply Well Data
The regional background dataset for Mayo was provided by Duke Energy. As there is just one regional
background dataset, a test for homogeneity is not required. Table F3-1 presents the regional
background water supply well dataset for Mayo.
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F.3.1.2 Facility Background Monitoring Well Data
Water supply wells in this region of North Carolina are predominantly bedrock wells. Section F.4
discusses this in more detail.
Background wells sampled at Mayo for the CSA included BG -01, BG -02, MW-10BR, MW-11BR, MW-
13BR, MW -12D, MW-14BR, MW -12S, and MW-16BR. The initial facility specific background evaluation
for Mayo was performed on three background deep (transition zone) wells and five background bedrock
monitoring wells (BG -01, BG -02, MW-10BR, MW-11BR, MW-13BR, MW -12D, MW-14BR, and MW-16BR)
(see Figure F3-1). Background wells screened in the shallow formation were excluded from the analysis
to limit the data used to the same flow layer that the off-site water supply wells draw from. The facility -
specific background monitoring well data that are used in the background data evaluation for Mayo are
presented in Table F3-2. The sample size for both vanadium and hexavalent chromium consists of less
than or equal to five samples per well. The results of the statistical computations indicated that there
are no significant differences between monitoring well data for vanadium and hexavalent chromium.
Although decisions based upon statistics computed using discrete data sets of small sizes (e.g., < 8) are
generally not used to make decisions, based on facility -specific knowledge developed during the
detailed environmental investigations and the limited statistical evaluation, the data from facility -
specific background monitoring wells presented in Table F3-2 and Figure F3-1 were combined for the
facility BTV estimates. The results of the Levine's test are presented in Attachment F-1.
F.3.2 Raw Data Evaluation
In the raw data evaluation for Mayo, the descriptive statistics for eight constituents for both the regional
and facility -specific datasets were computed and tabulated in Table F3-3. The most common descriptive
statistics included the following: Frequency of Detection (Column 3), Percent Non -Detects (ND)
(Column 4), Range of Non -Detects (Column 5), Mean (Column 6), Variance (Column 7), Standard
Deviation (Column 8), Coefficient of Variation (Column 9), 50th percentile (Column 10), 95th Percentile
(Column 11), and Maximum Detects (Column 12). Critical information such as the requirement for a
certain minimum number of samples and percent NDs were evaluated during this step. Ideally, 8-10
background measurements would be available, and preferably more, to perform meaningful statistical
tests.
In cases where there is a small fraction of non -detects in a dataset (10-15% or less) censored at a single
reporting limit, simple substitution methods were utilized by substituting each non -detect with an
imputed value of the method detection limit (MDL). In complicated situations such as the presence of
multiple MDLs intermingled with difference non -detect levels or when the proportion of non -detects
was larger, strategies such as Kaplan -Meier (KM) and Robust Regression on Order Statistics (ROS) were
utilized.
Visual plots such as histograms and probability plots were plotted to examine the data closely and
visually determine if there were extreme outliers in the dataset. If extreme outliers were visually
identified, then outlier tests (Dixon's and Rosner's) were performed to confirm if there are outliers at a
5% significance level. The decision to include or exclude outliers in statistical computations was decided
by the project team based on constituent and facility -specific knowledge. If the presence of an outlier
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was confirmed, and if there was enough evidence to remove the outlier, then the outlier was removed
from further statistical analysis. The results of the outlier tests, Outlier Presence (Column 13) and Outlier
Removal (Column 14), for eight constituents for both regional and facility -specific datasets are
presented in Table F3-3. Attachment F-1 presents the histograms, probability plots and outlier tests for
the eight constituents.
F. 3.2.1 Regional Background Water Supply Well Data
The descriptive statistics indicated the presence of a high percentage of non -detects (NDs) for boron,
cobalt, and nickel; boron had 1 detect, cobalt had no detects, and nickel had 3 detects out of 14 total
samples. Due to the presence of a high percentage of NDs in the dataset, the outlier test statistics were
computed using the detected data alone. As presented in Table F3-3 (Columns 13 -14), an analysis using
visual plots and the Dixon's Outlier Test indicated the presence of outliers in the data set. However,
outliers are inevitable in most environmental data and the decisions to exclude them are made based on
existing knowledge about the facility and groundwater conditions. In this instance, based on existing
knowledge, that these are data from background locations not adjacent to the facility, no outliers were
removed from the regional water supply dataset.
F.3.2.2 Facility Background Monitoring Well Data
The descriptive statistics performed on facility -specific background data indicated that greater than
40 percent of samples had NDs for boron, cobalt, hexavalent chromium, lead, and nickel. Boron had
1 detect and lead had 5 detects out of 68 samples; cobalt had 5 detects out of 39 samples; hexavalent
chromium had 13 detects out of 24 samples; and nickel had 16 detects out of 32 samples. Statistical
computations indicated the presence of outliers in the dataset, specifically with regard to monitoring
well BG -01. Sampling results from BG -01 for the October 2008 event showed significant concentration
variation from the remaining sample results for this well and, therefore, the October 2008 results for
this well were removed from further analysis and descriptive statistics were recalculated.
F.3.3 Testing of Statistical Assumptions
After performing the initial statistical evaluation and addressing outliers as discussed in the previous
section, two critical statistical assumptions were tested for IID measurements and normality. In general,
the background groundwater data for both the regional and facility -specific datasets were assumed to
have IID measurements for statistical analysis because the design and implementation of a monitoring
program typically results in IID measurements. The groundwater samples are not statistically
independent when analyzed as aliquots or splits from a single physical sample. Therefore, split sample
data were treated as described in Section F.2.1, such that a single value for each constituent was used in
the statistical evaluations.
To test for normality, the data was first analyzed visually by generating histograms and probability plots.
This was followed by an evaluation using GOF tests. The GOF statistics were generated using USEPA
ProUCL software (USEPA, 2013), which tests for normal, lognormal and gamma distributions to establish
the appropriate distribution. If the GOF test statistics suggested the data to follow normal, lognormal or
gamma distributions, parametric methods were utilized to estimate BTV values. If the normality
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assumption was not met the data was considered to be distribution free, and non -parametric statistical
methods were 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). In general, it has been
observed that the use of a gamma distribution tends to yield reliable and stable values. The
distributions determined by GOF tests (Column 15) for eight constituents for both regional and facility -
specific datasets are presented in Table F3-3. Attachment F-2 presents the GOF tests statistics.
F. 3.3.1 Regional Background Water Supply Well Data
The test statistics revealed that most of the constituents follow parametric distribution except boron
and cobalt; hence, parametric methods were used to compute BTVs for all constituents except boron
and cobalt. No further evaluation was performed on boron and cobalt due to the presence of <_ 1
detect.
F.3.3.2 Facility Background Monitoring Well Data
The test statistics revealed that most of the constituents follow a parametric distribution except boron
and hexavalent chromium; hence, parametric methods were used to compute BTVs for all constituents
except boron and hexavalent chromium. Non -parametric test methods were used to compute the BTV
for hexavalent chromium. No further evaluation was performed on boron due to the presence of only 1
detect.
F.3.4 BTV Estimates
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 dataset used to estimate BTVs represents an
unimpacted, single statistical population that is free from outliers. However, since outliers are
inevitable in most environmental data (high percentage 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 BTVs for the constituents
were estimated using ProUCL (USEPA, 2013) by using one of the following methods.
• Parametric or non -parametric 95 %Upper Prediction Limits (UPL95)
• Parametric or non -parametric Upper Tolerance Limits (UTL95-95) with 95% confidence and 95%
coverage
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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]).
Prediction interval tells about the distribution of values, not the uncertainty in determining the
population mean. A UPL95 represents that statistical concentration, such that an independently -
collected new/future observation from the population will exhibit a concentration less than or equal to
the UPL95 with a CC of 0.95.
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% of the observations (current and future)
from the target population will be less than or equal to the UTL95-95 with a CC of 0.95. Stated
differently, the 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 on-site 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 UCL and
UTL 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.
Table F3-3 presents the estimated BTV values (Column 16) and applicable methods (Column 17) used in
estimating the upper threshold values. Attachment F-3 presents the proUCL output of the BTVs
computations.
F.3.5 Comparison of Water Supply Well Data to the Regional and Facility -Specific BTVs
The data for the water supply wells located within a 0.5 -mile radius from the ash basin compliance
boundary were compared to the regional background BTVs and facility -specific BTVs presented in
Table F3-3. Comparison to the regional background BTVs are presented in Table F3-4, and comparison
to the facility -specific background BTVs are presented in Table F3-5.
There are three NCDEQ-sampled water supply results. BTVs were derived for eight constituents. Two of
the constituents, boron and cobalt, were not detected in the water supply wells. The results for the
remaining six constituents were below the regional BTVs with the exception of two results for iron and
one result for lead, and were below the facility -specific BTVs with the exception of one result for lead.
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Appendix F — Mayo
F.4 GROUNDWATER FLOW EVALUATION
[The evaluation in Section F.4, including figures and tables, was provided by SynTerra Corporation.]
F.4.1 Introduction
The objective of this section is to expand upon the groundwater flow and water quality data that were
presented in the CSA report (SynTerra, 2015a) for the Mayo Plant to demonstrate that ash impacted
groundwater associated with the ash basin system has not migrated toward or intercepted water supply
wells located upgradient and side gradient of the ash basin system.
The CSA was conducted to comply with the CAMA. Field work for the CSA was implemented in
accordance with the NCDEQ-approved Groundwater Assessment Plan (Work Plan; SynTerra, 2014)
which included an evaluation of groundwater quality and flow characteristics from 13 existing
monitoring wells and the installation of 29 additional monitoring wells. The new wells were installed at
specific locations and depths to delineate potential impacts to groundwater from the ash basin. Eight of
the newly installed/existing monitoring wells are clearly located in upgradient locations relative to the
ash basin to characterize background conditions. Ten additional site wells can be considered to be
outside of any potential impact from the ash basin because they are located in separate
topographic/geologic flow regimes. To date, four groundwater CSA sampling events have been
conducted. Water level measurements are collected during each sampling event to evaluate the
groundwater flow direction. Prior to the CSA, routine groundwater monitoring was conducted three
times each year since 2010, with groundwater levels and flow direction determined for each event. The
information consistently indicates the groundwater flow direction is from upland areas northwest, west,
southwest, south, and southeast of the Plant toward the ash basin, as would be expected by the local
topography.
Groundwater flow within a distinct slope -aquifer system is directly influenced by the underlying geologic
framework of the site. The geologic nature underlying the site is described in Section F.4.2. The
regional groundwater system and the hydrogeological SCM are presented in Section F.4.3.1, and the
location of water supply wells in the vicinity of the facility and hydrogeology of the site is presented in
Section F.4.3.2. Detailed data have been used to evaluate groundwater flow direction, horizontal and
vertical gradients, and the velocity of groundwater flow as described in Section F.4.3. The data were
used to support the development of a groundwater flow model, which resulted in an understanding of
current and potential future groundwater conditions. The model incorporated the effects of pumping
from nearby water supply wells. The groundwater modeling results are discussed in Section F.4.4.
F.4.2 Site Geology
The Mayo site is located in the Piedmont Province of North Carolina. The geology observed during the
installation of the monitoring wells is defined as:
• Alluvium — Alluvium is unconsolidated sediment that has been eroded and redeposited by
streams. Very thin alluvium was observed on the north side of the ash basin along Crutchfield
Branch (MW -03 and MW -16S). Alluvium would be anticipated to be present in the vicinity of
current and former stream channels.
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• Residuum (Regolith -Residual Soils) — Residuum is the shallow soil that has developed over time
from the in-place weathering of the parent bedrock. Residuum was observed to very thin (less
than 10 feet thick) but mostly nonexistent at the site. Where present, the residuum does not
contain groundwater.
• Saprolite/Weathered Rock (Regolith) — Saprolite is a soil -like material that developed by the
in-place weathering of parent bedrock but still exhibits the original relic rock structure (texture
and layering) from the parent rock. Saprolite, where present beneath the Mayo Plant, was
observed at depths ranging from a few feet to 66 feet below ground surface (MW -12).
Groundwater was rarely encountered in the saprolite beneath the Mayo Plant.
• Partially Weathered/Fractured Rock — This material consists of partially weathered and/or highly
fractured bedrock below the saprolite and above competent bedrock. The partially
weathered/fractured rock layer is also referred to as the 'transition zone' (TZ). The thickness of
the TZ ranged from about 8 feet to 20 feet. At Mayo, the presence of groundwater in the TZ is
not consistent across the site area.
• Bedrock — Bedrock is hard, competent rock that is unweathered to slightly weathered and
mostly unfractured. The dominant rock types observed at Mayo were metamorphic granitoid
gneiss and mica gneiss with less frequent mica schist and phyllite. Metavolcanics were also
noted. In general, metamorphic grade increases to the southwest and west of the Plant.
Within the ash basin, ash was generally found to be comprised of fine -to -medium sand -sized particles
with abundant silt and clay size particles. The thickness of the ash observed during drilling activities
ranged from 13 to 66 feet below ground surface. Additional information on the geologic nature of the
Mayo Plant subsurface is provided in the CSA, Section 6.1 (SynTerra, 2015a).
F.4.3 Site Hydrogeology
F. 4.3.1 Site Conceptual Model
An SCM was developed during preparation of the CSA Work Plan to inform decisions regarding the field
exploration (i.e., monitoring well locations, screened intervals, target depths, etc.). The SCM was based
largely on the LeGrand (1988, 1989) conceptual model of the groundwater setting in the Piedmont and
incorporated Harned and Daniel's (1992) two -medium system, the overburden and competent bedrock.
The generalized conceptual model defines a slope -aquifer system in which a drainage basin is contained
within one or more adjacent topographic divides - located along ridge tops which serve as the upper
hydraulic boundaries - and a stream, river, or lake that serves as the lower hydraulic boundary (LeGrand,
1988).
Each basin is similar to adjacent basins with hydrogeologic conditions being generally repetitive from
basin to basin within each ridgeline toward an adjacent surface water feature. Within a drainage basin,
movement of groundwater is generally restricted to the area extending from the topographic ridges to
perennial streams (LeGrand, 1988; 1989; 2004). Rarely does groundwater move beneath a perennial
stream to another more distant stream or across drainage divides (LeGrand, 1989). The crests of the
water table underneath topographic drainage divides represent natural groundwater divides within the
slope -aquifer system and control the direction of groundwater flow within each drainage basin. The
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Appendix F — Mayo
concave topographic areas between the topographic divides may be considered as flow compartments
that are open-ended in the down slope direction. As a result, natural groundwater flow paths in the
Piedmont are confined to the area underlying the topographic slope extending from a topographic ridge
or drainage divide to an adjacent stream or water feature, with the water feature serving as the
groundwater discharge location (or surface expression of groundwater). Under natural conditions, the
general direction of groundwater flow can be approximated from the surface topography (LeGrand,
2004).
The two -medium system consists of two interconnected layers, or mediums: (1) residual soil/saprolite
and weathered fractured rock (regolith), overlying (2) fractured crystalline bedrock (Heath, 1980; Heath,
1984; Harried and Daniel, 1992). The residual soil grades into saprolite, a coarser grained material that
retains the structure of the parent bedrock. Beneath the saprolite, partially weathered/fractured
bedrock occurs with depth until competent bedrock is encountered. This mantle of residual soil and
saprolite (regolith) is a hydrogeologic unit that covers and crosses various types of rock (LeGrand, 1988).
These layers serve as the principal groundwater storage reservoir and provide an intergranular medium
through which the recharge and discharge of water from the underlying fractured rock occurs (Daniel
and Harned, 1998). Within the fractured crystalline bedrock layer, the fractures control both the
hydraulic conductivity and storage capacity of the bedrock. A transition zone at the base of the regolith
is present in many areas of the Piedmont. Harried and Daniel (1992) described the zone as "being the
most permeable part of the system, even slightly more permeable than the soil zone." Additional
details of the SCM are presented in Sections 5.2 and 6.4 of the CSA report (SynTerra, 2015a) and
Section 3.0 of the Mayo CAP -1 (SynTerra, 2015b).
Based on the results of the CSA, the groundwater system in the in-situ materials (alluvium, soil,
soil/saprolite, and bedrock) and overlying ash at Mayo is consistent with the slope-aquifer/regolith-
fractured rock groundwater model and is an unconfined, connected aquifer system.
The hydrostratigraphic layers (layers of material that have different hydraulic parameters) at the site
consist of in-situ units (alluvium, residuum [regolith -residual soil], saprolite/weathered rock [regolith],
partially weathered rock/transition one, and competent bedrock), and anthropogenic units, ash, as
described in Section F.4.2. These units are used in the groundwater model of the site and are discussed
in Section F.4.4. Additional information concerning the development of the hydrostratigraphic layers is
presented in Section 11.0 of the CSA (SynTerra, 2015a).
F.4.3.2 Groundwater Flow Direction
The Mayo groundwater system is divided into three flow layers referred to as the shallow (S), deep (D or
TZ), and bedrock (BR) flow layers to distinguish the layers within the connected, unconfined aquifer
system. Monitoring wells have been installed with screens placed in each of these flow layers.
Groundwater elevations measured in monitoring wells surrounding the ash basin area show that
groundwater flow, in all three flow zones, is from higher elevations to lower elevations along the
northern side of the ash basin and Crutchfield Branch. Higher topographic areas serve as groundwater
recharge zones, and Crutchfield Branch and its associated stream valley serve as a groundwater
discharge zone. Groundwater flow direction is consistent with the slope -aquifer system (described
above) and show that groundwater flow is away from off-site water supply wells and toward the ash
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Appendix F — Mayo
basin and Crutchfield Branch. East of the ash basin, there is a groundwater divide that separates the
Crutchfield Branch flow regime from the Mayo Lake flow regime.
The vertical gradients are near equilibrium across the site indicating that there is no distinct horizontal
confining layer beneath the Mayo Plant. The horizontal gradients, hydraulic conductivity, and
groundwater flow velocities indicate that most of the groundwater transport occurs through the
transition zone and shallow bedrock, as most of the regolith encountered is largely unsaturated.
The hydrologic and hydrogeologic characteristics of the ash basin environment are the primary influence
on groundwater flow and constituent transport. The basin acts as a bowl -like feature towards which
groundwater flows from all directions except north. The former stream valley in which the ash basin
was constructed represents a distinct slope -aquifer system in which flow of groundwater into the ash
basin (former stream valley) and out of the ash basin is restricted to the local flow regime and is
separate from adjacent slope -aquifer units. Flow downgradient and downstream of the ash basin is
funneled into the small valley formed by Crutchfield Branch. There are no substantive differences in
water level among wells completed in the different flow zones (shallow/surficial, transition zone,
bedrock), and lateral groundwater movement predominates over vertical movement.
The location of water supply wells and groundwater flow direction are shown on Figures F4-1 and F4-2
based upon water level measurements collected during the CSA (SynTerra, 2015a). The groundwater
flow direction is consistent with the slope -aquifer system and shows that groundwater flow is away
from off-site water supply wells and toward the ash basin and Crutchfield Branch.
F.4.3.3 Groundwater Seepage Velocities
Groundwater seepage velocities were estimated for the flow zones beneath the site. The seepage
velocity is calculated using the average horizontal hydraulic conductivity values from field slug tests,
average effective porosity from laboratory testing or from technical literature, and measured horizontal
hydraulic gradients between well pairs. For the surficial zone, groundwater seepage velocities ranged
1.73 to 4.80 feet/year. Velocities across the site in the transition zone ranged from 4.99 to
8.23 feet/year. Velocity in bedrock ranged from 0.11 to 1.35 feet/year. The large variation in estimated
velocities in bedrock is reflective of the nature of groundwater flow and fracture geometry within
crystalline bedrock.
Additional details on the field testing and laboratory testing for estimating hydrogeologic parameters
are presented in Section 11.0 of the CSA (SynTerra, 2015a).
F.4.3.4 Constituents Associated with CCR
Certain constituents present in coal ash can serve as indicators of a release from a coal ash management
area to groundwater; these have been used by USEPA to design the groundwater monitoring program
under recent regulation.
On 17 April 2015, the USEPA published its final rule "Disposal of Coal Combustion Residuals from Electric
Utilities" (Final CCR Rule) to regulate the disposal of CCR as solid waste under subtitle D of the Resource
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Conservation and Recovery Act (USEPA, 2015a). The USEPA defined a phased approach to groundwater
monitoring. The first phase is detection monitoring where groundwater is monitored to detect the
presence of specific constituents that are considered to be indicators of a release from a coal ash
management area (e.g., metals) and other monitoring parameters (e.g., pH, total dissolved solids [TDS]).
These data are used to determine if there has been a release from a coal ash management area.
Detection monitoring is performed for the following list of "indicator" constituents identified in
Appendix III of the CCR Rule:
• Boron;
• Calcium;
• Chloride;
• Fluoride (this constituent was not analyzed for in the CSA);
• pH;
• Sulfate; and
• TDS.
In selecting the constituents for detection monitoring, USEPA chose constituents that are present in CCR
and that are more soluble and move through the soil column and with groundwater without
retardation, relative to other constituents. Thus, groundwater monitoring for these constituents allows
for an evaluation of whether constituents are migrating from a CCR unit. Coal ash constituents dissolve
in groundwater with no measurable increase in density as compared to other constituents that would
tend to "sink" in the aquifer, such as dense non -aqueous phase liquids or saltwater. Thus, releases from
coal ash management areas tend to remain in the shallower groundwater flow layers.
F.4.3.5 Extent of Boron Exceedances in Groundwater
Groundwater at Mayo was monitored for a wide range of constituents as required by the CAMA and
reported in the CSA (SynTerra, 2015a). Boron may be one of the more common indicators for
evaluation of groundwater for releases from coal ash management areas due to boron concentrations in
CCR leachate being usually higher than in typical groundwater. Boron also tends to be highly mobile in
groundwater. For these reasons, boron is often used as an indicator constituent for CCR leachate
(Electric Power Research Institute [EPRI), 2005). Boron exceedances of the 2L Standards reported in
groundwater during 2015 are shown on Figure F1-3 to illustrate where this leading indicator associated
with CCR is located across the site. Boron was selected since it is prevalent in CCR and is very
infrequently detected in site background groundwater wells. As shown, the boron exceedances of the
2L Standard in groundwater are located beneath the ash basin and extend to near the property
boundary on the north side of the site. Boron has typically not been detected in groundwater beyond
the site property boundary, confirming the groundwater flow direction is not toward the supply wells
located upgradient to the northwest of the ash basin and upgradient to the south of the ash basin.
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Appendix F — Mayo
F.4.3.6 Bedrock and Depth of Water Supply Wells
Monitoring wells installed during the CSA investigation were located and screened at depths to
characterize potential vertical and horizontal extent of impacts from the ash basin. Monitoring wells
were installed to assess groundwater in each of the three flow layers: shallow, transition zone, and
deep (bedrock) where saturated conditions were observed. These monitoring wells are located in areas
of suspected impacts, in presumed background areas, and in areas between the ash basin and off-site
water supply wells. Water supply wells constructed in the Piedmont Province are typically drilled to
greater depths than monitoring wells. Bedrock monitoring wells installed in upgradient locations
between the ash basin and the water supply wells have confirmed that impacted groundwater in
shallow bedrock is not flowing towards the water supply wells.
Based on a survey of properties located near the Plant, up to 22 private water supply wells may be
located within or in close proximity to the 0.5 -half mile survey area. Little information is available
regarding well characteristics including surface casing depths, well depths, pump placement, and flow
rates. Typically in the Piedmont, private water supply wells are assumed to be open boreholes 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).
Duke Energy mailed water supply well questionnaires to surrounding well owners during the Receptor
Survey in 2015; however, few questionnaires were returned with well construction information. It is our
understanding that the NCDEQ requested that their third -party samplers record well construction
information (if available) during sampling of the supply wells, but Duke Energy has not been provided
with that data. Limited survey information from around the Mayo Plant indicates that the depths of
wells range from around 60 feet (likely completed in the transition zone or shallow bedrock) to around
300 feet. In the absence of well -specific construction data, published literature (Daniel, 1989) was
consulted to yield an average depth of water supply wells (for domestic, commercial -industrial, public
water) as 154 feet from the ground surface with 100 feet in bedrock. Water supply wells are generally
cased though the regolith (soil/saprolite), with additional boring performed as needed into bedrock to
produce the desired well yield.
No public supply wells were located based on the receptor survey of the Plant area conducted during
the CSA, with the exception of a water supply well located at Bethel Hill Baptist Church located
approximately 0.5 miles south (upgradient) of the site. The pumping rate for the public water supply
well is unknown. For additional information regarding water supply wells, see CSA Section 4.0.
F.4.3.7 Groundwater Mounding
Groundwater mounding refers to the extent to which ash basins, or any other impoundment, may raise
or variably influence the natural groundwater levels causing flow to leave the basin radially against the
prevailing slope -aquifer gradient. Topographical and monitoring well groundwater data can be used
establish the extent to which localized hydraulic mounding may emanate from an ash basin and if this
may affect the local groundwater flow direction. A review of topographic and monitoring well
groundwater data at Mayo indicate potential mounding is contained within the groundwater flow
system beneath the ash basin.
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F.4.3.8 Summary
The hydrogeologic SCM presented in the CSA (SynTerra, 2015a) and refined in the CAP -2 (SynTerra,
2016) describes the hydrologic and hydrogeologic characteristics of the ash basin environment as the
primary influence on groundwater flow and constituent transport. Figure F4-2 depicts the SCM and the
geology creating the different flow regimes beneath Mayo Plant. The basin acts as a bowl -like feature
towards which groundwater flows from all directions except north. The former stream valley in which
the ash basin was constructed represents a distinct slope -aquifer system in which flow of groundwater
into the ash basin (former stream valley) and out of the ash basin is restricted to the local flow regime
and is separate from adjacent slope -aquifer units. Flow downgradient and downstream of the ash basin
is funneled into the small valley formed by Crutchfield Branch. Water supply wells are located in the
opposite direction of groundwater flow, upgradient of the ash basin to the northwest and south.
Groundwater flows away from the water supply wells. No water supply wells have been identified
downgradient of the ash basin.
F.4.4 Site Groundwater Model Development and Results
Three-dimensional groundwater flow and constituent transport models were developed to predict the
groundwater flow and constituent transport that will occur as a result of possible corrective actions at
the site. The models have three main components: a geologic model, a groundwater flow model, and a
contaminant transport model. The geologic model was based on well log information and other known
surface and geologic data for the site. The model has dimensions of approximately 3 miles by 3 miles
and consists of six units: Ash, Saprolite, Transition Zone, Upper Bedrock, Middle Bedrock, and Lower
Bedrock. The flow model was constrained by known hydrologic features such as lakes, rivers, streams,
swamps, and ditches. The flow model specifically considered the potential effects of local water table
mounding from the ash basins due to enhanced infiltration from the basins.
The initial conceptual flow model was calibrated by adjusting the hydraulic conductivities of the
hydrostratigraphic layers and zones to best match the observed hydraulic heads in monitoring wells at
the site. This refined the models and the predicted hydraulic heads were under 10 percent of the
measured data. A major part of the development process was evaluating alternative conceptual models
that considered various heterogeneities including fracture zones and both high and low hydraulic
conductivity zones. These refinements to the flow model continued until the model accuracy could not
be further improved at the site.
A primary concern of the modeling effort was possible impacts to supply wells from the ash basin. The
calibrated groundwater flow and transport model was used to assess possible impacts by considering
pumping from supply wells within the model domain of the site. Two modeling approaches were used.
The first approach included pumping wells in the calibrated flow and transport models to assess the
degree to which the wells were impacted by boron and other constituents of interest that may have
originated at the ash basin. No impact to supply wells above 2L standards were seen in the model
simulations for the Mayo site.
The flow and transport model for the Mayo site was built in a step -wise manner. The first step was to
build a three-dimensional model of the site hydrostratigraphy based on field data and observations. The
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Appendix F — Mayo
next step was determination of the model domain and construction of the numerical grid. The
numerical grid was then populated with flow parameters which were adjusted during the steady-state
flow model calibration process. Once the flow model was calibrated, the flow parameters were used to
develop a transient model to replicate historical flow patterns at the site. The historical flow model was
then used to provide the time -dependent flow field for the constituent transport simulations. For
calibration purposes, the steady state flow model incorporated 47 water level measurements
from June 2015 (SynTerra, 2015b).
Certain constituents were selected during the modeling process and were based mainly on ash pore
water concentrations that were significantly higher than background concentrations and if there was a
distinct plume of the constituent extending downgradient from the ash basin. Site-specific constituents
selected for the modeling process were boron and arsenic for the 2015 transport simulations.
Manganese was added later as a modeled constituent. Boron was chosen as a main tracer for the ash
basin for three main reasons: (1) boron is always present in coal ash; (2) there is typically a low
background of boron concentrations; and (3) boron is the most mobile constituent.
Predictive groundwater modeling demonstrates that constituents remain within the vicinity of the plant
boundary through time, downgradient of the site. Further, modeling predictions indicate that the boron
plume and the manganese plumes will retreat over time after ash basin closure. Attenuation
mechanisms will reduce constituent concentrations over time.
A second assessment approach was a numerical capture zone analysis which is similar to the first
approach, but instead of using the constituent transport model to predict concentrations, a computer
program called MODPATH was used with the calibrated flow model. MODPATH is a widely used United
States Geological Survey (USGS) program that is designed to interface with the MODFLOW flow model
that was used. MODPATH is a "particle tracking' model that traces the groundwater flow lines from any
desired starting position. MODPATH can also do "reverse tracking' to identify where water originates in
the flow model. MODPATH is a standard part of the modeling platform that was used to construct the
flow and transport models.
MODPATH can be used with the reverse tracking feature to trace the groundwater flowlines around
each well to see where the water that is pumped from the well originates. This well-known procedure is
called a well capture zone analysis, because it identifies the zone from which all of the water entering
the well is captured. The capture zone analysis was performed for the Mayo site. Although pumping
rates for the individual supply wells near the site were not available, an assumption equal to the average
U.S. household water use rate of 400 gallons per day (USEPA, 2008) was used. It was assumed that all of
the wells in the model domain were pumping continuously unless they were known to be inactive.
A numerical capture zone analysis for the Mayo site was conducted to evaluate potential impact to
upgradient water supply pumping wells. The analysis for nearby water supply wells indicates that well
capture zones projected into the indefinite future are limited to the immediate vicinity of the well head
and do not extend toward the ash basin and the impoundment as demonstrated in Figure F4-3. Further,
none of the particle tracks originating in the ash basin or the impoundment moved into the well capture
zones.
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Appendix F — Mayo
F.4.5 Summary and Conclusions
Major findings from the evaluation of groundwater flow at the Mayo site are as follows:
• The groundwater system at Mayo is consistent with LeGrand's slope -aquifer system that
describes groundwater flow conditions in the Piedmont as confined to the area underlying the
topographic slope extending from a drainage divide to an adjacent stream or water feature,
with the water feature serving as the groundwater discharge location.
The groundwater system at Mayo is also consistent with the conceptual model of groundwater
within an unconfined, two -medium system (regolith consisting of soil and saprolite overlying
bedrock) separated by a transition zone of higher hydraulic conductivity (permeability) within a
slope -aquifer system. Three primary flow layers (as defined by the regolith, the transition zone
and bedrock) are present in the unconfined groundwater system at the site; shallow (S - water
table), deep (D or TZ), and bedrock (BR).
Site-specific water level measurements confirm that groundwater flow is to the north and
northeast into the Crutchfield Branch stream valley and away from water supply wells located
northwest and south of the ash basin. These observations and data confirm groundwater flow
model predictions.
The hydrogeologic characteristics of the ash basin environment serve as the primary influence
on groundwater flow. The basin acts as a bowl -like feature towards which groundwater flows
from all directions except north. The former stream valley in which the ash basin was
constructed represents a distinct slope -aquifer system in which flow of groundwater into the
ash basin (former stream valley) and out of the ash basin is restricted to the local flow regime
and is separate from adjacent slope -aquifer units. Flow downgradient and downstream of the
ash basin is funneled into the small valley formed by Crutchfield Branch.
Water supply wells in the area are located completely opposite the direction of groundwater
flow upgradient of the ash basin to the northwest and south. No water supply wells have been
identified downgradient of the ash basin.
The water supply well capture zone analysis, as delineated by reverse particle tracking, shows
that the water supply wells are supplied with water from precipitation recharge to the regolith
(soil/saprolite) surrounding the pumping well(s) and the capture zones do not intersect or
originate in the coal ash sources. This analysis considered the potential combined effects of
adjacent pumping wells. Site-specific water level measurements and groundwater modeling
confirm that the combined pumping effect of the water supply wells is not affecting the overall
site groundwater flow direction.
• Based on this evidence, groundwater utilized by water supply wells near the Mayo Plant is not
impacted by the Mayo Plant ash basin.
F.5 GROUNDWATER CHARACTERISTICS EVALUATION
The results from the local water supply well testing conducted by the NCDEQ in the vicinity of the Mayo
facility indicated that some constituents were present at concentrations above state and/or federal
standards and/or screening levels. As noted previously, these constituents are naturally occurring, and
few can be associated with releases from coal ash basins. Thus, it is critical to understand the naturally
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Appendix F — Mayo
occurring background conditions, the groundwater conditions in the tested local water supply wells, and
the conditions in groundwater at the facility where CCR -impacts have been demonstrated. A detailed
statistical evaluation of background groundwater data compared to the local water supply well data was
presented in Section F.3. As indicated in Section F.4.3, the local water supply wells are generally cased
through the regolith (soil/saprolite) and obtain water through the bedrock fractures that convey stored
groundwater in the regolith. Based on the groundwater transport modeling results in Section F.4.4, the
source of groundwater for the local water supply wells is not from the ash basin, and supplied by
recharge falling on areas not impacted by coal ash. In this section, the chemistry of the groundwater at
the facility in both CCR -impacted areas and areas not impacted by a CCR release is compared to the
chemistry of the local water supply wells. The similarity or discrepancy in the chemistry of groundwater
among various facility monitoring well groups and the local water supply wells is expected to provide
additional insights on the extent of CCR impacted groundwater.
The objective of the evaluation is to understand, from the groundwater chemistry perspective, whether
the CCR -impacted groundwater at the facility has resulted in the water quality exceedances found in the
local water supply wells.
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.
Based on the results of this evaluation, there is no relationship between the CCR -impacted groundwater
and the water quality exceedances reported in the local water supply wells, indicating that the
exceedances are due to natural sources of constituents in supply well groundwater.
More details regarding the evaluation approach, data analysis methods, results, and conclusions are
presented below.
F.5.1 Evaluation Approach
A multiple -lines -of -evidence approach, as summarized below, was used to facilitate the development of
chemical signatures of the CCR impacted groundwater.
The approach consists of the following key components:
Screen the geochemical and transport behaviors of typical CCR -related constituents to establish
candidate constituents for further evaluation.
• Assess the presence and magnitude or range in concentration of candidate constituents in the
groundwater beneath the site as a result of a release from the ash basin by comparing the
concentration magnitude of these constituents in the four major well groups below:
— Ash basin porewater monitoring wells;
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— 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 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. These designations were
determined by referencing bedrock groundwater flow directions discussed in the CAP -2
(SynTerra, 2016), which are consistent with the bedrock groundwater flow model created by
SynTerra and presented in Section F.S.
• Identify useful reduction -oxidation (redox) 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.
• 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 (SynTerra, 2015a,
2015b, 2016) and summarized in Section F.4, 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.
F.5.2 CCR -Related Constituents Screening for Signature Development
The first step for determining 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. Based on the chemical properties of CCR
related constituents and the site-specific geochemical evaluation (SynTerra, 2016), typical
cations (e.g., sodium and calcium) and anions (e.g., chloride and sulfate), boron, manganese
(under the reducing conditions), and cobalt can meet this requirement.
• 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.
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Based on these criteria and a review of the chemical data in the CSA report (SynTerra, 2015a), the
following constituents are considered to be the candidates for signature development:
Boron, calcium, sulfate, chloride, and TDS: Based on the understanding of the behavior of
constituents that can be released from coal ash into groundwater, USEPA has identified those
constituents that are considered to be indicators of a potential release from coal ash. These
constituents belong to the CCR Rule Appendix III constituents (USEPA, 2015a). Of these, boron
and sulfate are the most common constituents used to evaluate the potential for an ash
management area impact in groundwater, as will be shown in the evaluation presented below.
• Barium and cobalt: These two trace metals are less sensitive to the redox conditions and are
not readily sorbed to mineral surfaces (Table F5-1), and can be associated with CCR impacts to
groundwater (USEPA, 2015a). These two trace metals are also selected as candidate
constituents. Total barium and cobalt concentrations were used in this evaluation.
• Dissolved oxveen. dissolved iron. and dissolved manvanese: Groundwater in the ash basin area
generally contains very low concentrations of dissolved oxygen, but high concentrations of
dissolved iron and manganese (SynTerra, 2015a). The site-specific geochemical analysis
indicates that the redox state of groundwater in the ash basin area is generally manganese
reducing (Figure F5-1) (SynTerra, 2016). It is noted that, because groundwater samples
collected from the regional background wells and local water supply wells only analyzed for
total iron, total iron concentrations were used to conservatively represent the iron
concentrations in these groundwater samples. Because the concentrations of dissolved iron and
manganese are sensitive to the presence of dissolved oxygen, including the iron and manganese
data used in this evaluation will help identify and compare the redox conditions of the different
well groups.
F.5.3 Data Analysis Methods
F.5.3.1 Data Sources
The groundwater analytical data used in this evaluation are from the following sources:
• Facility groundwater monitoring well data;
• Local water supply well data from NCDEQ; and
• Duke Energy background water supply well data.
F.5.3.2 Data Aggregation
The general rules for data aggregation are described here. When multiple sampling events occur for a
well, the following rules were used to find a representative concentration value for the box plot and
correlation plot evaluations:
• For boron, calcium, chloride, sulfate, TDS, barium, and cobalt, the representative value is
defined as the maximum of the detected values if the analytical results are not all NDs. If the
analytical results are all NDs, the lowest reporting limit is defined as the representative value.
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Using the maximum concentrations will help not underestimate the CCR impacts to the local
water supply wells and facility monitoring wells.
• For dissolved oxygen, total and dissolved iron, and total and dissolved manganese, the average
concentration is used as the representative value for the general conditions observed in a well.
• For piper plots, the average concentration is used as the representative values for the general
conditions observed in a well.
• The reporting limits are used to represent the ND results.
F.5.3.3 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). Figure F5-2
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.
This analysis includes both detected and non-detected values.
F.5.3.4 Correlation Plot
The constituents found to be a signature indicator of the 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
one constituent on the x-axis and the concentrations of the other constituent on the y-axis. The
clustering patterns or trends illustrate correlations among data groups.
F.5.3.5 Piper Plot
Piper plots have been frequently used to assess the relative abundance of general cations (sodium,
potassium, magnesium, and 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 the CCR -impacted groundwater may show a different clustering pattern than
the background groundwater or the groundwater that has not been impacted by CCR.
In the CSA report, the piper plots were used to evaluate the water chemistry between the porewater in
the ash basin and groundwater in other groups of facility monitoring wells. An example figure is shown
in Figure F5-2, which compares the general water chemistry among the porewater in the ash basin and
groundwater in the bedrock wells. 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 MW-10BR shows about 38 percent of
the total cation charges from sodium and potassium, approximately 35 percent from calcium, and about
27 percent from magnesium. In the anion subplot, the same data point of MW-10BR shows about
40 percent of the total anion charges from sulfate, approximately 15 percent from chloride, and
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Appendix F — Mayo
45 percent from carbonate (CO32-)plus bicarbonate (HCO3-). In the diamond subplot, the same data
point shows about 55 percent of the total anion charges from chloride and sulfate, and approximately
60 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).
F.5.4 Evaluation Results
F. 5.4.1 Box Plot Comparison
The box plot comparison of boron, calcium, chloride, sulfate, and TDS concentrations among various
well groups is shown in Figure F5-3. Boron showed the most significant concentration difference
between the results of the ash basin porewater wells and the local water supply wells: boron was found
to be present at significantly higher concentrations in ash basin porewater compared to regional
background groundwater and local water supply wells. Calcium and TDS show only slightly elevated
concentrations in the ash basin porewater compared to other on-site locations and compared to the
local water supply wells, whereas chloride and sulfate demonstrate little to no change in concentrations.
It is noted that the boron concentrations for the local water supply wells and regional background wells
were all below 50 micrograms per liter (µg/L), as a result of that boron were not detected in several
local water supply wells and regional background wells at the reporting limit of 50 µg/L.
The box plot comparison of barium and cobalt is provided in Figure F5-4. The barium concentration
difference between the ash basin porewater and the groundwater in local water supply wells is
pronounced, but not as significant as boron. The concentration difference for cobalt is not significant.
Because boron and barium are very mobile, subject to little sorption onto mineral surfaces, and not
susceptible to degradation or transformation, and because they show the most elevated concentrations
(relative to the concentrations found in the local water supply wells), they are thus considered to be
effective signature constituents.
The box plot comparison of dissolved oxygen, iron, and manganese is shown in Figure F5-5. The trend of
dissolved oxygen concentrations shows that the groundwater in the local water supply wells is generally
more oxygenic than in the ash basin porewater. The observed low oxygen concentrations in the ash
basin porewater are consistent with the understanding that coal ash leachate is a chemically reduced
solution (USEPA, 1980). The depletion of dissolved oxygen in the leachate is attributed to the
occurrence of sulfite or other oxidation processes when oxygenic water contacts with coal ash (USEPA,
1980). It should be noted that Duke Energy regional background wells were not analyzed for dissolved
oxygen or iron.
It is noted that dissolved oxygen occurs in groundwater through recharge by precipitation and air within
the unsaturated zone. Dissolved oxygen remains in groundwater until it is used by bacteria, organic
material, or reduced minerals (Cunningham and Daniel, 2001). High dissolved oxygen concentrations in
groundwater may indicate relatively rapid groundwater recharge (Cunningham and Daniel, 2001). The
range of the dissolved oxygen concentrations observed in the local water supply wells is consistent with
the range of dissolved oxygen concentrations found in the similar geologic environment (i.e., fractured
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Appendix F — Mayo
crystalline rocks mantled with weathered regolith in the Piedmont Physiographic Province) by the USGS
(Brief, 1997).
There is some uncertainty associated with the dissolved oxygen concentrations observed in local water
supply wells and regional background wells. These concentration values may be less accurate because
the sampling protocol for these wells is not known and the dissolved oxygen measurements may be
affected by the interference from well and plumbing configurations that admit air to the sample water
(Donnahue and Kibler, 2007). Although the dissolved oxygen concentrations may be overestimated in
some cases, the trend of dissolved oxygen data collected from water supply wells have been used for
other studies to help understand the general geochemical conditions (Winograd and Robertson, 1982;
Cunningham and Daniel, 2001; Donnahue and Kibler, 2007).
The iron and manganese concentration trends are not as clear as that of dissolved oxygen; however, the
median concentrations are reduced compared to those of the porewater in the ash basin. Based on the
site-specific geochemical evaluation, the site groundwater is quite variable and some areas are enriched
in reduced iron and manganese, which is consistent with the lower oxygen contents in groundwater in
those areas. The results are consistent with the iron and manganese geochemical behavior in that they
tend to form precipitates under oxygenic conditions, and are removed from the groundwater.
It is noted that high concentrations of iron and manganese are a common water quality issue within the
Piedmont Physiographic Province (Daniel and Dahlen, 2002). The mineral composition of the regolith
and bedrock has a strong influence on groundwater quality, as it is extremely susceptible for chemical
weather, which greatly impacts the dissolved constituents in groundwater (Daniel and Dahlen, 2002).
Due to the variability of the reducing conditions in the groundwater at the site, the lack of dissolved
oxygen in the ash basin porewater cannot serve as a very unique signature. Typically, if the
groundwater obtained by a local water supply or facility monitoring well is primarily from the ash basin,
it is expected that the dissolved oxygen concentration would be low, because there is no effective mass
transfer process to increase the dissolved oxygen concentration during groundwater transport in the
deep overburden and bedrock units. However, due to the natural variability in the reducing conditions
in the vicinity of the site, a low dissolved oxygen concentration may not confirm that the source water
for that well has been impacted by CCR -related constituents. In contrast, elevated iron and manganese
concentrations may not directly imply that the well was impacted by the ash basin, as elevated
concentrations may be due to natural processes. While the lack of dissolved oxygen may not be an
indicator of CCR impact, the presence of dissolved oxygen may serve as an indicator of lack of CCR
impact, as discussed below.
F.5.4.2 Correlation Plot Evaluation
Boron and dissolved oxygen were identified to be the most useful signature constituents to assess the
extent of the CCR -impacted groundwater, within the context of the discussion above. The spatial
patterns of boron and dissolved oxygen concentrations were evaluated for the ash basin monitoring,
facility bedrock, and local water supply wells through a correlation plot. Duke Energy regional
background wells were not analyzed for dissolved oxygen; therefore, those wells are not included in the
correlation plots.
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In this correlation plot evaluation, the boron and dissolved oxygen concentration pairs are grouped as
follows:
• Ash basin porewater wells;
• Local water supply wells; and
• Facility bedrock wells (Figure F5-6), which are further divided into three subgroups:
— Subgroup 1 (Downgradient): The bedrock wells are located beneath or hydraulically
downgradient of the ash basin or ash landfill, or groundwater flowing through these
wells is likely originated from the ash basin. CCR -impacted groundwater is more likely
to impact these wells based on the groundwater flow field in the deep overburden and
bedrock units (SynTerra, 2016). Wells ABMW-02BR, ABMW-04BR, MW-03BR, and MW-
16BR belong to this subgroup.
— Subgroup 2 (Side Gradient): The wells are located cross gradient of the ash basin or
groundwater flowing through these wells is not likely to subsequently flow beneath the
footprint of the ash basin. These wells are not expected to be greatly influenced by the
ash basin groundwater. Wells MW0713R, MW-08BR, and MW-09BR belong to this group.
— Subgroup 3 (Upgradient): Groundwater flowing through the bedrock wells in this
subgroup is expected to flow beneath the ash basin later. Wells MW -1013R, MW -116R,
MW-13BR, MW-14BR, and MW-05BR are in this well group.
The data obtained from the facility bedrock wells may help identify the potential groundwater chemistry
characteristics of a CCR -impacted bedrock well and help illustrate the spatial pattern of CCR -impacted
facility bedrock wells, which may be used to help assess the potential impacts to the local water supply
wells. It should be noted that the subgroups formed above is to facilitate the evaluation presented
below. The final well group assignment will be based on the evaluation results, as shown in Figure F5-6.
The correlation plot is shown in Figure F5-7. Panel (a) shows the correlation plot for the ash basin
porewater wells and the facility downgradient bedrock wells. These results are distinguished by
elevated boron concentrations and relatively low dissolved oxygen concentrations for ash basin
porewater wells, and downgradient facility bedrock wells containing low to non -detect boron results
with relatively low dissolved oxygen concentrations. Panel (b) shows the data from the facility side
gradient and upgradient bedrock wells in addition to the data in Panel (a). These added wells are
distinguished by relatively low to non -detect boron concentrations and dissolved oxygen concentrations
that are similar to and slightly higher than the ash basin porewater wells in Panel (a). Panel (c) shows
the overlay of the data from the local water supply wells on the data in Panel (b). These added wells are
distinguished by very low to non -detect levels of boron (5 µg/L), and a range of dissolved oxygen
concentrations. The Panel (c) plot shows that the data are clustered in three distinct areas: Area 1
contains the data from the ash porewater wells; Area 2 contains the data from the local water supply
wells; and Area 3 contains the data from the facility bedrock wells, as well as one local water supply well
(MY5).
The ash basin porewater data pairs tend to generally cluster together in Area 1 with a significantly
different boron signature in comparison to the facility bedrock monitoring wells or local water supply
wells. Area 2 contains the data clustering pattern of two local water supply wells, specifically those
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wells that contain higher levels of dissolved oxygen. Area 3 is defined by the data clustering pattern of
all facility bedrock wells and local water supply well MY5, which displays a lower dissolved oxygen
concentration. The correlation plot result shows that the low oxygen and elevated boron
concentrations serve as an effective signature pair to help identify the CCR -impacted groundwater. The
two local water supply wells with significantly more dissolved oxygen demonstrates that these two local
water supply wells do not obtain groundwater primarily from the ash basin because no effective mass
transfer mechanism can replenish oxygen during the groundwater transport from the ash basin to a
local water supply well. The exponentially lower boron concentration in facility bedrock wells and local
water supply wells also serves as an effective signature to demonstrate a lack of CCR -impacted
groundwater in these wells.
The groundwater data for local water supply well MY5 exhibits low dissolved oxygen concentrations
(lower than 4,000 µg/L). The boron concentration in the well is less than 50 µg/L, suggesting that it is
not likely to be affected by CCR -impacted groundwater. To further ascertain that there is no CCR impact
to this well, the barium concentration in this well was used for further evaluation. Table F5-1 shows the
comparison between the observed boron and barium concentrations in this well and the site-specific
facility BTVs for these constituents. The results show that the boron and barium concentrations
observed in these wells are below the BTVs derived in Section F.3. The sulfate concentration
(5,700 µg/L) in MY5 is comparable with that of the other local water supply well MY7 (2,700 µg/L) and
within the 501h percentile of the sulfate concentrations (13,000 µg/L) in groundwater in the Piedmont
Province (Brief, 1997). Therefore, the sulfate concentration in MY5 is considered to be within the
normal background conditions. The location of this local water supply wells is shown in Figure F5-8.
Note that MY5 is located in the same area but slightly further away from the ash compliance boundary
that the other two NCDEQ-sampled water supply wells.
Based on Figure F5-7, CCR -impacted groundwater does not appear to be found in the facility bedrock
wells that are within or downgradient of the ash basin footprint. The groundwater in the facility
upgradient and side gradient bedrock wells typically display a constituent signature similar to
downgradient facility bedrock wells implying that these wells are not being supplied by CCR -impacted
groundwater. The correlation plots and the conceptual groundwater flow directions consistently
support the conceptual groundwater transport process that the background groundwater of high and/or
low dissolved oxygen and low boron concentrations is located in the bedrock units beneath the site, and
that flow through or beneath the ash basin is not causing the groundwater to become enriched with
boron.
Note that this correlation plot evaluation uses groundwater concentration data under the influence of
historic pumping of the local water supply wells. The lack of elevated concentrations of CCR -related
signatures and the distinct discrepancy between the data patterns on the correlation plots indicate that
the pumping of the local water supply wells does not capture the ash basin porewater.
F.5.4.3 Piper Plot
Two piper plots were created to evaluate the relative abundance patterns of major ions in the ash basin
porewater and in the facility downgradient bedrock wells. The results are shown in Figure F5-9.
Panel (a) shows the data for the ash basin porewater wells; the cation subplot shows that calcium is the
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Appendix F — Mayo
dominant cation in the porewater, the diamond subplot shows that the relative abundance of calcium
and magnesium in the porewater are larger than 70 percent, and the anion subplot shows that the
relative abundance of chloride is generally less than 20 percent.
Panel (b) shows the data for both the ash basin porewater wells and the facility downgradient bedrock
wells. The data of the facility downgradient bedrock wells are clustered with those of the ash basin
porewater wells in the anion subplot, but show only a loose correlation to the ash basin porewater wells
in the cation and diamond subplots. The results of this piper plot show the variability of bedrock
groundwater quality within and under the ash basin footprint.
It is noted that piper plots are intended to represent aqueous analytical results when the sample is at
equilibrium. According to electrochemical charge balance calculations completed in the CSA, only
6.4 percent of the collected samples were within the expected range (less than 10 percent charge
balance error) (SynTerra, 2015a). The majority of samples collected were found to be anion deficient,
which could result from multiple natural and human causes. These occurrences can include, but are not
limited to, reworking of surficial soils and saprolite, calcite precipitants not taken into account during
laboratory analysis (Fritz, 1994), and the effects of hydroxyl radicals (OH-) within the sample, which has
no analytical method to be evaluated (SynTerra, 2015a). Due to this charge imbalance, data
represented on these piper plots may not be precise and should only be used as a general guide for the
relative abundance patterns within well groups.
The piper plots for the local water supply, upgradient, and side gradient bedrock wells are provided in
Figure F5-10. Panel (a) of Figure F5-10 shows the data for the local water supply wells. Since regional
background wells were not analyzed for multiple constituents, those wells are not plotted in the
following piper plots. As can be seen, these well data display limited clustering patterns, with a distinct
outlier in the anion and diamond subplots (MY3, see the data in blue circles). This indicates that they
have different major ion characteristics or the sample collection technique may have affected the
sample. The grouping for these wells is slightly distinct from the ash basin related wells in Figure F5-9.
Panel (b) of Figure F5-10 shows the data for two subgroups of the facility bedrock wells (upgradient and
side gradient) on top of the data of the local water supply wells in Panel (a) of Figure F5-10. When
viewed this way, it is clear that two of the local water supply wells are within the variability of the
upgradient and side gradient bedrock wells; however, the few number of water supply wells sampled
and the loose clustering pattern of these wells makes determining the characteristics of these well
groups difficult.
Figure F5-11 shows a side-by-side comparison of the ash basin related well data in Panel (a), and the
local water supply well related data in Panel (b). The apparent difference in groundwater characteristics
between the CCR -impacted wells and the local water supply wells is shown in their diamond subplots.
The area defined by the blue dotted line in Panel (b) encloses almost all the local water supply well data,
but excludes most data in Panel (a).
The data for the downgradient facility bedrock wells are generally within the variability of the ash basin
porewater well data. These piper plot results are consistent with the results of the correlation plots;
both show a wide range of results between the facility bedrock wells and the CCR -impacted ash basin
porewater wells. In the piper plots, the local water supply well and the upgradient and side gradient
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Appendix F — Mayo
well data show a recognizably different cluster pattern in comparison with the data of the ash basin
porewater wells, indicating that the source water for the supply wells likely is not CCR -impacted
groundwater.
F.5.5 Conclusions
Based on this evaluation, the following key conclusions can be drawn:
Boron concentrations in the ash basin groundwater are considerably higher than the maximum
plausible boron concentration found in the local water supply wells. Because boron exhibits
little sorption to mineral surfaces and is not expected to precipitate or be degraded under the
site geochemical conditions, it is considered to be the most effective signature constituent
among the coal ash related constituents for evaluating the groundwater impacts from the ash
basin.
Boron concentrations were not detected in the local water supply wells and barium and sulfate
concentrations are both within the range of the facility background wells; therefore, the local
water supply wells are considered to not be affected by CCR impacted groundwater.
• Redox conditions in the ash basin porewater are generally anoxic, with the characteristics of low
dissolved oxygen concentrations, and high iron and manganese concentrations. The redox
conditions found in the local water supply wells are generally significantly more oxygenic. The
lack of dissolved oxygen is considered to be a useful signature of CCR -impacted groundwater.
This demonstrates that two of the local water supply wells do not obtain groundwater primarily
from the ash basin because no effective mass transfer mechanism can replenish oxygen during
the groundwater transport from the ash basin to these local water supply wells. However, due
to the variability in natural redox conditions beneath the site, low dissolved oxygen
concentrations in bedrock well may not imply that the supply water at the well is being sourced
by CCR -impacted groundwater.
• There are no definitive CCR -impacted facility bedrock wells identified using the correlation and
piper plots. The local water supply wells are generally upgradient or side gradient of the ash
basin.
• The correlation and piper plots show recognizably different clustering patterns for 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 evaluation uses groundwater concentration data under the influence of historic pumping of
the local water supply wells. The lack of elevated concentrations of CCR -related signatures and
the distinct discrepancy between the data patterns on the correlation plot and piper plot
indicate that the pumping of the local water supply wells does not capture CCR -impacted
groundwater.
• This evaluation has provided additional lines of evidence, using (1) the presence of CCR
signature constituents, and (2) general major ion chemistry, to support the groundwater flow
and transport results presented in Section FAA
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It is concluded that there is no connection between the CCR -impacted groundwater and the
water quality exceedances found in the local water supply wells.
F.6 SUMMARY
This document presents the results of supplemental technical evaluations in four important assessment
areas to determine whether or not the water supply wells located within a 1,500 -foot radius of the
Mayo Plant ash basin compliance boundary could be impacted by CCR releases from the ash basin. The
evaluations in this document are based on the currently available data, which includes: generally one
sampling round from the water supply wells (note some wells had one or more re -analyses), three to
four sampling rounds from the ash basin wells, and multiple years of compliance well sampling. The
conclusion from the detailed weight of evidence demonstrates that water supply wells in the vicinity of
the Mayo Plant are not impacted by CCR releases from the ash basin.
The evaluation of the private and public water supply well data collected by NCDEQ and the detailed
statistical analysis of regional background groundwater data indicate that constituent concentrations in
the water supply wells are generally consistent with background. Boron was not detected in private
water supply wells located proximate to the Mayo Plant and the other potential coal ash indicators were
low and not above screening levels in the water supply wells sampled by NCDEQ. None of the NCDEQ-
sampled water supply well results were above Federal primary drinking water standards (MCLs), with
the exception of the pH results and a single lead result. The water supply well results are consistent
with regional background. The pH results are consistent with literature on the pH of groundwater in
North Carolina (Briel, 1997; Chapman, et al., 2013).
The comprehensive evaluation of groundwater flow with respect to local water supply wells
demonstrates that groundwater flow is to the north toward Crutchfield Branch from the topographic
divides south, east, and west of the ash basin system away from where the water supply wells are
located. The water supply well capture zone analysis indicates that groundwater utilized by water
supply wells is not impacted by the coal ash sources. Coal ash constituents do not measurably increase
the density of groundwater or have a separate liquid phase in groundwater as compared to other dense
liquids that would "sink" in the aquifer, like saltwater. Thus, releases from coal ash management areas
tend to remain in the shallower groundwater flow layers.
This conclusion is confirmed by the detailed characterization of groundwater chemistry including
evaluation of CCR indicators, redox conditions, and correlation evaluations. The results of the chemical
correlation analyses indicate that, based on the different constituent clustering patterns from the ash
basin porewater wells and the water supply wells, the source water for the water supply wells is not
CCR -impacted groundwater.
Based on this combined weight of evidence, groundwater utilized by water supply wells near the coal
ash impoundments is not impacted by the coal ash sources.
These results provide further support for the NCDEQ Low classification for the Mayo Steam Electric Plant
under the CAMA.
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F.7 REFERENCES
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23. SynTerra. 2015a. Comprehensive Site Assessment Report, Duke Energy Mayo Steam Electric
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33. Winograd, I.J. and Robertson, F.N. 1982. Deep oxygenated ground water: anomaly or common
occurrence? Science, 216(4551), pp.1227-1230.
34. 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 40 %UICH

Table F2-1
Comparison of NCDEQ Water Supply Well Data to 2L Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Page 1 of 3
15A NCAC 02L.0202
d(a):
Groundwater Standard (a)
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
NS
20
0.2
Federal MCL/SMCL(b):
(' denotes secondary standard)
NS
NS
*250
6.5-8.5
*250
"500
6
30
2000
4
5
100
NS
15
2
NS
50
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1 L
18
20
0.2
RSL 2015(d):
4000
NS
NS
NS
NS
NS
7.8
0.052
3800
25
9.2
22000
6
15
5.7
100
100
0.2
Appendix III
App
endix IV
Boron
Calcium
Chloride
pH
Sulfate
Total
Dissolved
Solids
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Lead
Mercury
Molybdenum
Selenium
Thallium
Plant Well Owner ID
u L
u L
m L
su
m L
m L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
Mao MY3
<5
28000
40
6.42
66
293
<0.5
<0.5
78
<0.2
<0.08
0.6
<0.5
24
<0.2
<0.5
1.3
<0.1
Mayo MYS
<5
84800
39.7
7.08
5.7
349
<5
<5
54.5
<2
<0.08
<50
<5
2.7
<0.2
<5
<5
<1
Mao MY7
<5
7490
5.5
6.07
2.7
88
<0.5
<0.5
30
<0.2
<0.08
0.86
<0.5
1.8
<0.2
3.8
<0.5
<0.1
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 2L April 2016

Table F2-1
Comparison of NCDEQ Water Supply Well Data to 2L Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
ISA NCAC 02L.0202
Groundwater Standard (a):
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1
NS
NS
NS
NS
Federal MCL/SMCL (b):
(* denotes secondary standard)
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5
NS
NS
NS
NS
DHHS Screening Level (c):
0.3
3500
1
2500
0.07
NS
200
100
NS
20000
2100
1
NS
NS
NS
NS
RSL 2015(d):
86
20000
0.8
14000
44(e)
NS
430
390
NS
NS
12000
6
NS
NS
NS
NS
Constituents Not Identified in the CCR
Rule
Total
Vanadium
Aluminum
Copper
Iron
Hexavalent
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
Alkalinity
Bicarbonate
Carbonate
Suspended
Chromium
Solids
Plant Well Owner ID
u L
u L
m L
u L
u L
u L
u L
u L
u L
u L
u L
m L
m L
m L
m L
m L
Mao MY3
3.03
3480
0.132
1750
0.13
3600
25
1.2
1600
37000
450
0.0311
28.5
28.5
< 1
13.4
Mayo MYS
< 10
430
0.0419
953
< 0.03
4830
517
<5
8350
22500
621
< 0.05
189
189
<5
11
Mao MY7
2.5
< 10
0.0678
< 50
0.63
2410
0.78
1.5
1400
9660
106
0.0364
37
37
<5
< 2.5
Page 2 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 2L April 2016

Table F2-1
Comparison of NCDEQ Water Supply Well Data to 2L Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Page 3 of 3
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 2L April 2016
15A NCAC 02L.0202
Groundwater
Standard (a):
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
(* denotes secondary standard)
NS
NS
NS
NS
N5
DHHS Screening Level (c):
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Oxidation
Specific
Dissolved
Turbidity
Temperature
Conductance
Oxygen
Reduction
Potential
Plant
Well Owner ID
NTU
°C
umhos cm
m L
my
Mao
MY3
30
18
399
9.24
259.3
Mayo
MY5
1.5
15.7
571.9
1.8
241.6
Mao
MY7
<1
18
85.1
7.07
281.4
Page 3 of 3
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 2L April 2016

Comparison of NCDEQ Water Supply Well Data to Screening Levels
Mayo Steam Station
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
A - Denotes [MAC value.
* - Denotes SMCL value.
°C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL - Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA - Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL- Practical Quantitation Limit (h).
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.
Data Qualifiers
B Detected in method blank (MB).
1 Estimated result between PQL and MDL.
12 Spike recovery outside quality assurance limits @ 135%.
Zb Sample was clear but contained sand -like particles.
Zc Well depth was 635 feet per well tag.
18 Temperature of the sample was exceeded during storage.
BH Method Blank (MB) greater than one half of the Reporting Level (RL), but the sample concentrations are greater than 10x the MB.
** Alkalinity = carbonate + bicarbonate.
S1 Matrix spike and / or matrix spike duplicate sample recovery was not within control limits due to matrix interference. Laboratory Control Sample (LCS) was within control limits.
Z Sample was re -digested and re -analyzed with similar sample and spike results.
M1 Matrix spike recovery exceeded QC limits. Batch accepted based on laboratory control sample (LCS) recovery.
D6 The relative percent difference (RPD) between the sample and sample duplicate exceeded laboratory control limits.
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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://portal.ncdenr.org/c/document_library/get_file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tapwater. HI = 1.
http://www.epa.gov/risk/risk-based-screening-ta ble-generic-tables
(e) - 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.
(f) - 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
(g) -The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is above the sreening level.
Reporting limit is above the screening level.
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 4/9/2016

Table F2-2
Comparison of NCDEQ Water Supply Well Data to MCL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Groundwater
15A"water NCAC 021
.nd.r 020
Standard a:
700
NS
250
6.S-8.5
250
500
1
30
700
4
2
30
1
15
1
NS
20
0.2
Federal MCL/SMCL(b(:
" denotes secondary standard
NS
NS
`250
6.5-8.5
'250
•500
6
10
2000
4
5
100
NS
15
2
NS
50
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1 L
18
20
0.2
RSL 201S (d):
4000
NS
NS
NS
NS
NS
7.8
0.052
3800
25
9.2
22000
6
35
5.7
100
100
0.2
Appendix III f
Appendix IV
Boron
Calcium
Chloride
pH
Sulfate
Total
Dissolved
Solids
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Lead
Mercury
Molybdenum
Selenium
Thallium
Plant
Well Owner ID
u L
u L
m L
su
m L
m L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
Mao
MY3
<S
28000
40
6.42
66
293
<0.5
<0.5
78
<0.2
<0.08
0.6
<O.5
24
c0.2
<O.S
1.3
<0.1
Mayo
MYS
<5
84800
39.7
7.08
5.7
349
<5
<5
54.5
<2
<0.08
<50
<5
2.7
<0.2
<5
<5
<1
Mao
MY7
<5
7490
5.5
6.07
2.7
88
<0.5
<O.S
30
<0.2
<0.08
0.86
<O.5
1.8
c0.2
3.8
<0.5
<0.1
Page 1 of 2
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx MCL April 2016

Table F2-2
Comparison of NCDEQ Water Supply Well Data to MCL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Page 2 of 2
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx MCL April 2016
15A NCAC 02r 02020.3
Groundwater
Standard a:
NS
1
300
NS
NS
50
100
NS
NS
NS
1
NS
NS
NS
NS
NS
NS
NS
NS
NS
Federal MCL/SMCL(b):
* denotes secondary standard
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5
NS
NS
NS
NS
NS
NS
NS
NS
NS
DHHS Screening Level (c):
0.3
3500
1
2500
0.07
NS
200
100
NS
20000
2100
1
NS
NS
NS
NS
NS
NS
NS
NS
NS
RSL 201S (d):
86
20000
0.8
14000
44(e)
NS
430
390
NS
NS
12000
6
NS
NS
NS
NS
NS
NS
NS
NS
NS
Constituents
Not Identified
in the CCR Rule
Total
Oxidation
Hexavalent
Dissolved
Vanadium
Aluminum
Copper
Iron
Chromium
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
Alkalinity
Bicarbonate
Carbonate
Suspended
Solids
Turbidity
Temperature
CoSpecific nductance
Oxygen
Reduction
Potential
Plant
Well Owner ID
u L
u L
m L
u L
u L
u L
u L
u L
u L
u L
u L
m L
m L
m L
m L
m L
NTU
'C
umhos cm
m L
mV
Mao
MY3
3.03
3480
0.132
1750
0.13
3600
25
1.2
1600
37000
450
0.0311
28.5
28.5
<1
13.4
30
18
399
9.24
259.3
Mayo
MY5
<10
430
0.0419
953
<0.03
4830
517
<5
8350
22500
621
<0.05
189
189
<5
11
1.5
15.7
571.9
1.8
241.6
Mao
MY7
2.5
<10
0.0678
<50
0.63
2410
0.78
1.5
1 1400
9660
106
0.0364
37
37
<5
<2.5
<1
18
85.1
7.07
281.4
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx MCL April 2016

Comparison of NCDEQ Water Supply Well Data to Screening Levels
Mayo Steam Station
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
A - Denotes [MAC value.
* - Denotes SMCL value.
°C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL - Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA - Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL- Practical Quantitation Limit (h).
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.
Data Qualifiers
B Detected in method blank (MB).
1 Estimated result between PQL and MDL.
12 Spike recovery outside quality assurance limits @ 135%.
Zb Sample was clear but contained sand -like particles.
Zc Well depth was 635 feet per well tag.
18 Temperature of the sample was exceeded during storage.
BH Method Blank (MB) greater than one half of the Reporting Level (RL), but the sample concentrations are greater than 10x the MB.
** Alkalinity = carbonate + bicarbonate.
S1 Matrix spike and / or matrix spike duplicate sample recovery was not within control limits due to matrix interference. Laboratory Control Sample (LCS) was within control limits.
Z Sample was re -digested and re -analyzed with similar sample and spike results.
M1 Matrix spike recovery exceeded QC limits. Batch accepted based on laboratory control sample (LCS) recovery.
D6 The relative percent difference (RPD) between the sample and sample duplicate exceeded laboratory control limits.
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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://portal.ncdenr.org/c/document_library/get_file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tapwater. HI = 1.
http://www.epa.gov/risk/risk-based-screening-ta ble-generic-tables
(e) - 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.
(f) - 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
(g) -The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is above the sreen ing level.
_Reporting limit is above the screening level.
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 4/9/2016

Table F2-3
Comparison of NCDEQ Water Supply Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Page 1 of 3
15A NCAC 02L.0202
d(a):
Groundwater Standard (a)
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
NS
20
0.2
Federal MCL/SMCL(b):
(' denotes secondary standard)
NS
NS
*250
6.5-8.5
*250
"500
6
10
2000
4
5
100
NS
15
2
NS
50
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
30
1
15
1 L
18
20
0.2
RSL 2015(d):
4000
NS
NS
NS
NS
NS
7.8
0.052
3800
25
9.2
22000
6
15
5.7
100
100
0.2
Appendix III
App
endix IV
Boron
Calcium
Chloride
pH
Sulfate
Total
Dissolved
Solids
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Lead
Mercury
Molybdenum
Selenium
Thallium
Plant Well Owner ID
u L
u L
m L
su
m L
m L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
Mao MY3
<5
28000
40
6.42
66
293
<0.5
<0.5
78
<0.2
<0.08
0.6
<0.5
24
<0.2
<0.5
1.3
<0.1
Mayo MYS
<5
84800
39.7
7.08
5.7
349
<5
<5
54.5
<2
<0.08
<50
<5
2.7
<0.2
<5
<5
<1
Mao MY7
<5
7490
5.5
6.07
2.7
88
<0.5
<0.5
30
<0.2
<0.08
0.86
<0.5
1.8
<0.2
3.8
<0.5
<0.1
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx DHHS April 2016

Table F2-3
Comparison of NCDEQ Water Supply Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
15A NCAC 02L.0202
Groundwater Standard (a):
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1
NS
NS
NS
NS
Federal MCL/SMCL (b):
(• denotes secondary standard)
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5
NS
NS
NS
NS
DHHS Screening Level (c):
0.3
3500
1
2500
0.07
NS
200
100
NS
20000
2100
1
NS
NS
NS
NS
RSL 2015(d):
86
20000
0.8
14000
44(e)
NS
430
390
NS
NS
12000
6
NS
NS
NS
NS
Constituents Not Identified in the CCR
Rule
Total
Vanadium
Aluminum
Copper
Iron
Hexavalent
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
Alkalinity
Bicarbonate
Carbonate
Suspended
Chromium
Solids
Plant Well Owner ID
u L
u L
m L
u L
u L
u L
u L
u L
u L
u L
u L
m L
m L
m L
m L
m L
Mao MY3
3.03
3480
0.132
1750
0.13
3600
25
1.2
1600
37000
450
0.0311
28.5
28.5
< 1
13.4
Mayo MYS
< 10
430
0.0419
953
< 0.03
4830
517
<5
8350
22500
621
< 0.05
189
189
<5
11
Mao MY7
2.5
< 10
0.0678
< 50
0.63
2410
0.78
1.5
1400
9660
106
0.0364
37
37
<5
< 2.5
Page 2 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx DHHS April 2016

Table F2-3
Comparison of NCDEQ Water Supply Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
15A NCAC 02L .020
Groundwater Standard (a):
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
(• denotes secondary standard)
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Oxidation
Specific
Dissolved
Turbidity
Temperature
Conductance
Oxygen
Reduction
Potential
Plant Well Owner ID
NTU
°C
umhos cm
m L
my
Mao MY3
30
18
399
9.24
259.3
Mayo MYS
1.5
15.7
571.9
1.8
241.6
Mao MY7
< 1
18
85.1
7.07
281.4
10
Page 3 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx DHHS April 2016

11
Comparison of NCDEQ Water Supply Well Data to Screening Levels
Mayo Steam Station
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
A - Denotes [MAC value.
* - Denotes SMCL value.
°C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL - Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA - Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL- Practical Quantitation Limit (h).
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.
Data Qualifiers
B Detected in method blank (MB).
1 Estimated result between PQL and MDL.
12 Spike recovery outside quality assurance limits @ 135%.
Zb Sample was clear but contained sand -like particles.
Zc Well depth was 635 feet per well tag.
18 Temperature of the sample was exceeded during storage.
BH Method Blank (MB) greater than one half of the Reporting Level (RL), but the sample concentrations are greater than 10x the MB.
** Alkalinity = carbonate + bicarbonate.
S1 Matrix spike and / or matrix spike duplicate sample recovery was not within control limits due to matrix interference. Laboratory Control Sample (LCS) was within control limits.
Z Sample was re -digested and re -analyzed with similar sample and spike results.
M1 Matrix spike recovery exceeded QC limits. Batch accepted based on laboratory control sample (LCS) recovery.
D6 The relative percent difference (RPD) between the sample and sample duplicate exceeded laboratory control limits.
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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://portal.ncdenr.org/c/document_library/get_file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tapwater. HI = 1.
http://www.epa.gov/risk/risk-based-screening-ta ble-generic-tables
(e) - 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.
(f) - 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
(g) -The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is above the sreening level.
6.Reporti ng limit is above the screening level.
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 4/9/2016

Table F2-4
Comparison of NCDEQ Water Supply Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
15A NCAC 02L.0202
d(a):
Groundwater Standard (a)
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
NS
20
0.2
Federal M L(b):
(' denotes secondary standard)
NS
NS
*250
6.5-8.5
*250
*500
6
10
2000
4
5
100
NS
15
2
NS
50
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1 L
18
20
0.2
RSL 2015(d):
4000
NS
NS
NS
NS
NS
7.8
0.052
3800
25
9.2
22000
6
15
5.7
100
100
0.2
Append x III f
Appendix IV
Boron
Calcium
Chloride
pH
Sulfate
Total
Dissolved
Solids
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Lead
Mercury
Molybdenum
Selenium
Thallium
Plant Well Owner ID
u L
u L
m L
su
m L
m L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
u L
Mao MY3
<5
28000
40
6.42
66
293
<0.5
<0.5
78
<0.2
<0.08
0.6
<0.5
24
<0.2
<0.5
1.3
<0.1
Mayo MY5
<5
84800
39.7
7.08
5.7
349
<5
<5
54.5
<2
<0.08
<50
<5
2.7
<0.2
<5
<5
<1
Mao MY7
<5
7490
5.5
6.07
2.7
88
<0.5
<0.5
30
<0.2
<0.08
0.86
<0.5
1.8
<0.2
3.8
<0.5
<0.1
12
Page 1 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx RSL April 2016

Table F2-4
Comparison of NCDEQ Water Supply Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
15A NCAC 02L.0202
Groundwater Standard (a):
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1
NS
NS
NS
NS
Federal MCL/SMCL (b):
(* denotes secondary standard)
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5
NS
NS
NS
NS
DHHS Screening Level (c):
0.3
3500
1
2500
0.07
NS
200
100
NS
20000
2100
1
NS
NS
NS
NS
RSL 2015(d):
86
20000
0.8
14000
44(e)
NS
430
390
NS
NS
12000
6
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Total
Vanadium
Aluminum
Copper
Iron
Hexavalent
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
Alkalinity
Carbonate
Suspended
Chromium
Solids
Plant Well Owner ID
u L
u L
m L
u L
u L
u L
u L
u L
u L
u L
u L
m L
m Lm
kcarbonate
L
m L
Mao MY3
3.03
3480
0.132
1750
0.13
3600
25
1.2
1600
37000
450
0.0311
28.5
< 1
13.4
Mayo MY5
< 10
430
0.0419
953
< 0.03
4830
517
<5
8350
22500
621
< 0.05
189
<5
11
Mao MY7
2.5
< 10
0.0678
< 50
0.63
2410
0.78
1.5
1400
9660
106
0.0364
37
<5
< 2.5
13
Page 2 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx RSL April 2016

Table F2-4
Comparison of NCDEQ Water Supply Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
15A NCAC 02L .020
Groundwater Standard (a):
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
(• denotes secondary standard)
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
RSL 201S (d):
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Oxidation
Specific
Dissolved
Turbidity
Temperature
Conductance
Oxygen
Reduction
Potential
Plant Well Owner ID
NTU
°C
umhos cm
m L
my
Mao MY3
30
18
399
9.24
259.3
Mayo MY5
1.5
15.7
571.9
1.8
241.6
Mao MY7
< 1
18
85.1
7.07
281.4
14
Page 3 of 3
Haley & Aldrich, Inc.
Tables F2-142-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx RSL April 2016

15
Comparison of NCDEQ Water Supply Well Data to Screening Levels
Mayo Steam Station
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
A - Denotes [MAC value.
* - Denotes SMCL value.
°C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL - Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA - Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL- Practical Quantitation Limit (h).
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.
Data Qualifiers
B Detected in method blank (MB).
1 Estimated result between PQL and MDL.
12 Spike recovery outside quality assurance limits @ 135%.
Zb Sample was clear but contained sand -like particles.
Zc Well depth was 635 feet per well tag.
18 Temperature of the sample was exceeded during storage.
BH Method Blank (MB) greater than one half of the Reporting Level (RL), but the sample concentrations are greater than 10x the MB.
** Alkalinity = carbonate + bicarbonate.
S1 Matrix spike and / or matrix spike duplicate sample recovery was not within control limits due to matrix interference. Laboratory Control Sample (LCS) was within control limits.
Z Sample was re -digested and re -analyzed with similar sample and spike results.
M1 Matrix spike recovery exceeded QC limits. Batch accepted based on laboratory control sample (LCS) recovery.
D6 The relative percent difference (RPD) between the sample and sample duplicate exceeded laboratory control limits.
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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://portal.ncdenr.org/c/document_library/get_file?p_I_id=1169848&folderld=24814087&name=DLFE-112704.pdf
(d) - USEPA Risk Based Screening Levels (November 2015). Values for tapwater. HI = 1.
http://www.epa.gov/risk/risk-based-screening-ta ble-generic-tables
(e) - 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.
(f) - 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
(g) -The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is a Bove the sreeni ng level.
Reporting limit is above the screeni ng level.
Haley & Aldrich, Inc.
Tables F2 -1-F2-4 NCDEQ Data Water Supply Well Screen_2016-04.xlsx 4/9/2016

16
Table F2-5 Page 1 of 3
Comparison of Duke Energy Background Well Data to 21. Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016
15A NCAC 02L.0202
Groundwater Standard a:
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
*250
6.5-8.5
*250
*500
6
10
2,000
4
5
100
NS
15
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
11.
RSL 2015 (d):
4,000
NS
NS
NS
NS
NS
7.8
0.052
3,800
25
9.2
22,000
6
15
5.7
Appendix III (f)
Appendix IV (g)
Station
Well ID
Boron
ug/L
Calcium
ug/L
Chloride
mg/L
pH
SI Units
Sulfate
mg/L
Total
Dissolved
Solids
mg/L
Antimony
Arsenic
Barium
Beryllium
Cadmium Chromium
Cobalt
Lead
Mercury
ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
<50
22700
<1
<1
6
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY2
<50
83600
1.05
<1
<5
<1
<1
<5
<1
6.37
<0.05
Mayo
DBKG-MY3
<5
8300
1.1
<0.S
23.7
<0.2
<0.08
1.7
<0.S
0.24
<0.2
Mayo
DBKG-MY4
<5
36800
1.1
<0.5
33.6
<0.2
<0.08
<0.S
<0.S
<0.1
<0.2
Mayo
DBKG-MYS
12.6
89100
1
<0.S
8.3
<0.2
<0.08
<0.S
<0.S
0.36
<0.2
Mayo
DBKG-MY6
<50
24700
<1
<1
9
<1
<1
<5
<1
2.61
<0.05
Mayo
DBKG-MY7
<50
23700
1.04
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY8
<50
2380
1.12
<1
19
<1
<1
<5
<1
2.16
<0.05
Mayo
DBKG-MY9
<50
27600
<1
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY10
<50
12400
<1
<1
108
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY11
<5
1780
1.1
<0.S
20
<0.2
<0.08
<0.S
<0.S
1.5
<0.2
Mayo
DBKG-MY12
<50
12300
<1
<1
71
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY13
<5
2180
0.96
<0.S
11.6
<0.2
<0.08
<0.S
<0.S
0.7
<0.2
Mayo
DBKG-MY14
<5
19100
1
<0.S
1.S
<0.2
<0.08
2.6
<0.S
0.65
<0.2
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016

17
Table F2-5 Page 2 of 3
Comparison of Duke Energy Background Well Data to 21. Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016
15A NCAC OZL.0202
Groundwater Staandad(a):
Standard a:
NS
20
0.2
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1,000
Federal MCL/SMCL (b):
* denotes secondary standard
NS
50
2
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5000
DHHS Screening Level (c):
18
20
0.2
0.3
3,500
1
2,500
0.07
NS
200
100
NS
20,000
2,100
1,000
RSL 2015 (d):
100
100
0.2
86
20,000
0.8
14,000
44 (e)
NS
430
390
NS
NS
12,000
6,000
Appendix IV (g)
Constituents
Not Identified in the CCR
Rule
Station
Well ID
Molybdenum Selenium
ug/L ug/L
Thallium
ug/L
Vanadium
Aluminum
Copper
Iron
Hexavalent
Chromium
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
1.12
<1
<0.2
0.409
44
'0.005
118
3420
18
<5
3050
8990
76
<5
Mayo
DBKG-MY2
< 1
< 1
< 0.2
2.25
< 5
0.035
< 10
0.19
31800
< S
< S
288
42000
201
1380
Mayo
DBKG-MY3
1.5
<0.5
<0.1
1.6
<10
0.0031
<50
1.1
2760
12.8
2.6
2940
7160
81.2
5.6
Mayo
DBKG-MY4
0.6
< 0.5
< 0.1
< 1
< 10
< 0.001
1090
< 0.03
7330
211
< 0.5
4880
10600
181
6.2
Mayo
DBKG-MY5
0.8
< 0.5
< 0.1
< 1
< 10
0.0022
78.8
< 0.6
12300
47.6
< 0.5
3660
26300
268
5.4
Mayo
DBKG-MY6
< 1
< 1
< 0.2
0.318
6
0.082
< 10
0.079
11600
< S
< S
1550
13900
231
69
Mayo
DBKG-MY7
< 1
< 1
< 0.2
0.467
< 5
< 0.005
< 10
0.41
2790
5
< 5
369
9180
107
227
Mayo
DBKG-MY8
<1
<1
<0.2
<0.3
<5
0.018
18
1.5
758
<S
<S
665
9680
17
225
Mayo
DBKG-MY9
< 1
< 1
< 0.2
< 0.3
< 5
< 0.005
91
< 0.03
3990
9
< 5
1730
10100
107
157
Mayo
DBKG-MY10
<1
<1
<0.2
14.4
116
0.019
132
0.94
5610
36
<5
17SO
13200
163
39
Mayo
DBKG-MY11
'0.5
< 0.5
< 0.1
< 1
< 10
0.0262
< 50
< 0.6
627
11.S
< 0.5
578
9260
11.1
37.8
Mayo
DBKG-MY12
< 1
< 1
< 0.2
19.6
6
0.025
< 10
1.2
6120
< S
< S
1230
20300
141
18
Mayo
DBKG-MY13
< 0.5
< 0.5
< 0.1<
1
< 10
0.0214
132
< 0.6
634
76.8
0.63
1420
10300
20.7
133
Mayo
DBKG-MY14
<0.5
<0.5
<0.1
<1
35.6
0.0223
74
1.6
7410
19
1.6
201
8970
55.1
61.5
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016

18
Table F2-5 Page 3 of 3
Comparison of Duke Energy Background Well Data to 21. Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016
15A NCAC 02L.0202
Groundwater Standard a:
NS
NS
NS
NS
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
NS
NS
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Station
Well ID
Alkalinity
Bicarbonate
Carbonate
Total
Suspended
Solids
mg/L
Turbidity
Temperature
Specific
Conductance
Dissolved
Oxygen
Oxidation
Reduction
Potential
Mayo
DBKG-MY1
Mayo
DBKG-MY2
Mayo
DBKG-MY3
Mayo
DBKG-MY4
Mayo
DBKG-MY5
Mayo
DBKG-MY6
Mayo
DBKG-MY7
Mayo
DBKG-MY8
Mayo
DBKG-MY9
Mayo
DBKG-MY10
Mayo
DBKG-MY11
Mayo
DBKG-MY12
Mayo
DBKG-MY13
Mayo
DBKG-MY14
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx 2L April 2016

Comparison of Duke Energy Background Well Data to Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
^ - Denotes IMAC value.
* - Denotes SMCL value.
'C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL- Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA- Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL - Practical Quantitation Limit (h).
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.
Data Qualifiers
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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/dwstandards20l2.pdf.
(c) - 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
(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) - Alternative screening level calculated for hexavalent chromium using RSL calculator (http:Hepa-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.
(f) - 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
(g) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is above the sreening level.
_Reporting limit is above the screening level.
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx
19
Page 1 of 1
4/10/2016

20
Table F2-6 Page 1 of 3
Comparison of Duke Energy Background Well Data to MCL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016
15A NCAC 02L.0202
Groundwater Standard a
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
Federal MCL/SMCL (b):
' denotes secondary standard
NS
NS
`250
6.5-8.5
"250
`500
6
10
2000
4
5
100
NS
15
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1L
RSL 2015 (d):
4,000
NS
NS
NS
NS
NS
7.8
0.052
3,800
25
9.2
22,000
6
15
5.7
Appendix III (f)
Appendix IV (g)
Station
Well ID
Boron
ug/L
Calcium
ug/L
Chloride
mg/L
pH
SI Units
Sulfate
mg/L
Total
Dissolved
Solids
mg/L
Antimony
Arsenic
Barium
Beryllium
Cadmium Chromium
Cobalt
Lead
Mercury
ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
<50
22700
<1
<1
6
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY2
<50
83600
1.05
<1
<5
<1
<1
<5
<1
6.37
<0.05
Mayo
DBKG-MY3
<5
8300
1.1
<0.S
23.7
<0.2
<0.08
1.7
<0.S
0.24
<0.2
Mayo
DBKG-MY4
<5
36800
1.1
<0.5
33.6
<0.2
<0.08
<0.S
<0.S
<0.1
<0.2
Mayo
DBKG-MYS
12.6
89100
1
<0.S
8.3
<0.2
<0.08
<0.S
<0.S
0.36
<0.2
Mayo
DBKG-MY6
<50
24700
<1
<1
9
<1
<1
<5
<1
2.61
<0.05
Mayo
DBKG-MY7
<50
23700
1.04
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY8
<50
2380
1.12
<1
19
<1
<1
<5
<1
2.16
<0.05
Mayo
DBKG-MY9
<50
27600
<1
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY10
<50
12400
<1
<1
108
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY11
<5
1780
1.1
<0.S
20
<0.2
<0.08
<0.S
<0.S
1.5
<0.2
Mayo
DBKG-MY12
<50
12300
<1
<1
71
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY13
<5
2180
0.96
<0.S
11.6
<0.2
<0.08
<0.S
<0.S
0.7
<0.2
Mayo
DBKG-MY14
<5
19100
1
<0.S
1.S
<0.2
<0.08
2.6
<0.S
0.65
<0.2
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016

21
Table F2-6 Page 2 of 3
Comparison of Duke Energy Background Well Data to MCL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016
15A NCAC OZL.0202
Groundwater Staandad(a):
Standard a
NS
20
0.2
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1,000
Federal MCL/SMCL (b):
* denotes secondary standard
NS
50
2
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5000
DHHS Screening Level (c):
18
20
0.2
0.3
3,500
1
2,500
0.07
NS
200
100
NS
20,000
2,100
1,000
RSL 2015 (d):
100
100
0.2
86
20,000
0.8
14,000
44 (e)
NS
430
390
NS
NS
12,000
6,000
Appendix IV (g)
Constituents
Not Identified in the CCR
Rule
Station
Well ID
Molybdenum Selenium
ug/L ug/L
Thallium
ug/L
Vanadium
Aluminum
Copper
Iron
Hexavalent
Chromium
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
1.12
<1
<0.2
0.409
44
'0.005
118
3420
18
<5
3050
8990
76
<5
Mayo
DBKG-MY2
< 1
< 1
< 0.2
2.25
< 5
0.035
< 10
0.19
31800
< 5
< 5
288
42000
201
1380
Mayo
DBKG-MY3
1.5
<0.5
<0.1
1.6
<10
0.0031
<50
1.1
2760
12.8
2.6
2940
7160
81.2
5.6
Mayo
DBKG-MY4
0.6
< 0.5
< 0.1
< 1
< 10
< 0.001
1090
< 0.03
7330
211
< 0.5
4880
10600
181
6.2
Mayo
DBKG-MY5
0.8
< 0.5
< 0.1
< 1
< 10
0.0022
78.8
< 0.6
12300
47.6
< 0.5
3660
26300
268
5.4
Mayo
DBKG-MY6
< 1
< 1
< 0.2
0.318
6
0.082
< 10
0.079
11600
< 5
< 5
1550
13900
231
69
Mayo
DBKG-MY7
< 1
< 1
< 0.2
0.467
< 5
< 0.005
< 10
0.41
2790
5
< 5
369
9180
107
227
Mayo
DBKG-MY8
<1
<1
<0.2
<0.3
<5
0.018
18
1.5
758
<5
<5
665
9680
17
225
Mayo
DBKG-MY9
< 1
< 1
< 0.2
< 0.3
< 5
< 0.005
91
< 0.03
3990
9
< 5
1730
10100
107
157
Mayo
DBKG-MY10
<1
<1
<0.2
14.4
116
0.019
132
0.94
5610
36
<5
1750
13200
163
39
Mayo
DBKG-MY11
'0.5
< 0.5
< 0.1
< 1
< 10
0.0262
< 50
< 0.6
627
11.5
< 0.5
578
9260
11.1
37.8
Mayo
DBKG-MY12
< 1
< 10.2
19.6
6
0.025
< 10
1.2
6120
< 5
< 5
1230
20300
141
18
Mayo
DBKG-MY13
< 0.5
< 0.50.1
< 1
< 10
0.0214
132
< 0.6
634
76.8
0.63
1420
10300
20.7
133
Mayo
DBKG-MY14
<0.5
<0.SEP
0.1
<1
35.6
0.0223
74
1.6
7410
19
1.6
201
8970
55.1
61.5
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016

22
Table F2-6 Page 3 of 3
Comparison of Duke Energy Background Well Data to MCL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016
15A NCAC 02L.0202
Groundwater Standard a
NS
NS
NS
NS
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
NS
NS
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Station
Well ID
Alkalinity
Bicarbonate
Carbonate
Total
Suspended
Solids
mg/L
Turbidity
Temperature
Specific
Conductance
Dissolved
Oxygen
Oxidation
Reduction
Potential
Mayo
DBKG-MY1
Mayo
DBKG-MY2
Mayo
DBKG-MY3
Mayo
DBKG-MY4
Mayo
DBKG-MY5
Mayo
DBKG-MY6
Mayo
DBKG-MY7
Mayo
DBKG-MY8
Mayo
DBKG-MY9
Mayo
DBKG-MY10
Mayo
DBKG-MY11
Mayo
DBKG-MY12
Mayo
DBKG-MY13
Mayo
DBKG-MY14
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx MCL April 2016

Comparison of Duke Energy Background Well Data to Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
^ - Denotes IMAC value.
* - Denotes SMCL value.
'C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL- Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA- Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL - Practical Quantitation Limit (h).
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.
Data Qualifiers
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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/dwstandards20l2.pdf.
(c) - 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
(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) - Alternative screening level calculated for hexavalent chromium using RSL calculator (http:Hepa-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.
(f) - 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
(g) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value is above the sreening level.
_ Reporting limit i s a bove the screening level.
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx
23
Page 1 of 1
4/10/2016

24
Table F2-7 Page 1 of 3
Comparison of Duke Energy Background Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016
15A NCAC 02L.0202
Groundwater Standard a
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
*250
6.5-8.5
*250
*500
6
10
2,000
4
5
100
NS
15
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1L
RSL 2015 (d):
4,000
NS
NS
NS
NS
NS
7.8
0.052
3,800
25
9.2
22,000
6
15
5.7
Appendix III (f)
Appendix IV (g)
Station
Well ID
Boron
ug/L
Calcium
ug/L
Chloride
mg/L
pH
SI Units
Sulfate
mg/L
Total
Dissolved
Solids
mg/L
Antimony
Arsenic
Barium
Beryllium
Cadmium Chromium
Cobalt
Lead
Mercury
ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
<50
22700
<1
<1
6
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY2
<50
83600
1.05
<1
<5
<1
<1
<5
<1
6.37
<0.05
Mayo
DBKG-MY3
<5
8300
1.1
<0.5
23.7
<0.2
<0.08
1.7
<0.5
0.24
<0.2
Mayo
DBKG-MY4
<5
36800
1.1
<0.5
33.6
<0.2
<0.08
<0.5
<0.5
<0.1
<0.2
Mayo
DBKG-MY5
12.6
89100
1
<0.5
8.3
<0.2
<0.08
<0.5
<0.5
0.36
<0.2
Mayo
DBKG-MY6
<50
24700
<1
<1
9
<1
<1
<5
<1
2.61
<0.05
Mayo
DBKG-MY7
<50
23700
1.04
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY8
<50
2380
1.12
<1
19
<1
<1
<5
<1
2.16
<0.05
Mayo
DBKG-MY9
<50
27600
<1
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY10
<50
12400
<1
<1
108
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY11
<5
1780
1.1
<0.5
20
<0.2
<0.08
<0.5
<0.5
1.5
<0.2
Mayo
DBKG-MY12
<50
12300
<1
<1
71
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY13
<5
2180
0.96
<0.5
11.6
<0.2
<0.08
<0.5
<0.5
0.7
<0.2
Mayo
DBKG-MY14
<5
19100
1
<0.5
1.5
<0.2
<0.08
2.6
<0.5
0.65
<0.2
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016

25
Table F2-7 Page 2 of 3
Comparison of Duke Energy Background Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016
15A NCAC OZL.0202
Groundwater Staandad(a):
Standard a
NS
20
0.2
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1,000
Federal MCL/SMCL (b):
* denotes secondary standard
NS
50
2
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*S000
DHHS Screening Level (c):
18
20
0.2
0.3
3,500
1
2,500
0.07
NS
200
100
NS
20,000
2,100
1,000
RSL 2015 (d):
100
100
0.2
86
20,000
0.8
14,000
44 (e)
NS
430
390
NS
NS
12,000
6,000
Appendix IV (g)
Constituents
Not Identified in the CCR
Rule
Station
Well ID
Molybdenum Selenium
ug/L ug/L
Thallium
ug/L
Vanadium
Aluminum
Copper
Iron
Hexavalent
Chromium
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
1.12
<1
<0.2
0.409
44
'0.005
118
3420
18
<5
3050
8990
76
<5
Mayo
DBKG-MY2
< 1
< 1
< 0.2
2.25
< 5
0.035
< 10
0.19
31800
< S
< S
288
42000
201
1380
Mayo
DBKG-MY3
1.5
<0.5
<0.1
1.6
<10
0.0031
<50
1.1
2760
12.8
2.6
2940
7160
81.2
5.6
Mayo
DBKG-MY4
0.6
< 0.5
< 0.1
< 1
< 10
< 0.001
1090
< 0.03
7330
1 211
< 0.5
4880 1
10600
181 1
6.2
Mayo
DBKG-MY5
0.8
<0.5
<0.1
<1
<10
0.0022
78.8
<0.6
12300
47.6
<0.5
3660
26300
268
5.4
Mayo
DBKG-MY6
< 1
< 1
< 0.2
0.318
6
0.082
< 10
0.079
11600
< S
< S
1550
13900
231
69
Mayo
DBKG-MY7
< 1
< 1
< 0.2
0.467
< 5
< 0.005
< 10
0.41
2790
5
< 5
369
9180
107
227
Mayo
DBKG-MY8
<1
<1
<0.2
<0.3
<5
0.018
18
1.5
758
<S
<S
665
9680
17
225
Mayo
DBKG-MY9
< 1
< 1
< 0.2
< 0.3
< 5
< 0.005
91
< 0.03
3990
9
< 5
1730
10100
107
157
Mayo
DBKG-MY10
<1
<1
<0.2
14.4
116
0.019
132
0.94
5610
36
<S
17SO
13200
163
39
Mayo
DBKG-MY11
'0.5
< 0.5
< 0.1
< 1
< 10
0.0262
< 50
< 0.6
627
11.S
< 0.5
578
9260
11.1
37.8
Mayo
DBKG-MY12
< 1
< 1
< 0.2
19.6
6
0.025
< 10
1.2
6120
< S
< S
1230
20300
141
18
Mayo
DBKG-MY13
< 0.5
< 0.5
< 0.1
< 1
< 10
0.0214
132
< 0.6
634
76.8
0.63
1420
10300
20.7
133
Mayo
DBKG-MY14
<0.5
<0.5
<0.1
<1
35.6
0.0223
74
1.6
7410
19 1
1.6
201
8970
55.1
61.5
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016

26
Table F2-7 Page 3 of 3
Comparison of Duke Energy Background Well Data to DHHS Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016
15A NCAC 02L.0202
Groundwater Standard a
NS
NS
NS
NS
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
NS
NS
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Station
Well ID
Alkalinity
Bicarbonate
Carbonate
Total
Suspended
Solids
mg/L
Turbidity
Temperature
Specific
Conductance
Dissolved
Oxygen
Oxidation
Reduction
Potential
Mayo
DBKG-MY1
Mayo
DBKG-MY2
Mayo
DBKG-MY3
Mayo
DBKG-MY4
Mayo
DBKG-MY5
Mayo
DBKG-MY6
Mayo
DBKG-MY7
Mayo
DBKG-MY8
Mayo
DBKG-MY9
Mayo
DBKG-MY10
Mayo
DBKG-MY11
Mayo
DBKG-MY12
Mayo
DBKG-MY13
Mayo
DBKG-MY14
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx DHHS April 2016

Comparison of Duke Energy Background Well Data to Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
^ - Denotes IMAC value.
* - Denotes SMCL value.
'C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL- Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA- Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL - Practical Quantitation Limit (h).
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.
Data Qualifiers
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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/dwstandards20l2.pdf.
(c) - 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
(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) - Alternative screening level calculated for hexavalent chromium using RSL calculator (http:Hepa-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.
(f) - 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
(g) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
Detected value isatrovethasmening level.
_ Reporting limit is above the screening level.
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx
27
Page 1 of 1
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28
Table F2-8 Page 1 of 3
Comparison of Duke Energy Background Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016
15A NCAC 02L.0202
Groundwater Standard a
700
NS
250
6.5-8.5
250
500
1
10
700
4
2
10
1
15
1
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
*250
6.5-8.5
*250
*500
6
10
2,000
4
5
100
NS
15
2
DHHS Screening Level (c):
700
NS
250
NS
250
NS
1
10
700
4
2
10
1
15
1L
RSL 2015 (d):
4,000
NS
NS
NS
NS
NS
7.8
0.052
3,800
25
9.2
22,000
6
15
5.7
Appendix III (f)
Appendix IV (g)
Station
Well ID
Boron
ug/L
Calcium
ug/L
Chloride
mg/L
pH
SI Units
Sulfate
mg/L
Total
Dissolved
Solids
mg/L
Antimony
Arsenic
Barium
Beryllium
Cadmium Chromium
Cobalt
Lead
Mercury
ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
<50
22700
<1
<1
6
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY2
<50
83600
1.05
<1
<5
<1
<1
<5
<1
6.37
<0.05
Mayo
DBKG-MY3
<5
8300
1.1
<0.5
23.7
<0.2
<0.08
1.7
<0.5
0.24
<0.2
Mayo
DBKG-MY4
<5
36800
1.1
<0.5
33.6
<0.2
<0.08
<0.5
<0.5
<0.1
<0.2
Mayo
DBKG-MY5
12.6
89100
1
<0.5
8.3
<0.2
<0.08
<0.5
<0.5
0.36
<0.2
Mayo
DBKG-MY6
<50
24700
<1
<1
9
<1
<1
<5
<1
2.61
<0.05
Mayo
DBKG-MY7
<50
23700
1.04
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY8
<50
2380
1.12
<1
19
<1
<1
<5
<1
2.16
<0.05
Mayo
DBKG-MY9
<50
27600
<1
<1
<5
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY10
<50
12400
<1
<1
108
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY11
<5
1780
1.1
<0.5
20
<0.2
<0.08
<0.5
<0.5
1.5
<0.2
Mayo
DBKG-MY12
<50
12300
<1
<1
71
<1
<1
<5
<1
<1
<0.05
Mayo
DBKG-MY13
<5
2180
0.96
<0.5
11.6
<0.2
<0.08
<0.5
<0.5
0.7
<0.2
Mayo
DBKG-MY14
<5
19100
1
<0.5
1.5
<0.2
<0.08
2.6
<0.5
0.65
<0.2
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016

29
Table F2-8 Page 2 of 3
Comparison of Duke Energy Background Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016
ISA NCAC 02L.0202
Groundwater Standard a:
NS
20
0.2
0.3
NS
1
300
NS
NS
50
100
NS
NS
NS
1,000
Federal MCL/SMCL (b):
• denotes secondary standardl
NS
50
2
NS
*50 to 200
1.3
*300
NS
NS
*50
NS
NS
NS
NS
*5000
DHHS Screening Level (c):
18
20
0.2
0.3
3,500
1
2,500
0.07
NS
200
100
NS
20,000
2,100
1,000
RSL 2015 (d):
100
100
0.2
86
20,000
0.8
14,000
44 (e)
NS
430
390
NS
NS
12,000
6,000
Appendix IV (g)
Constituents Not Identified in the CCR
Rule
Station
Well ID
Molybdenum Selenium
y
ug/L ug/L
Thallium
ug/L
Vanadium
Aluminum
Co
Copper
Iron
Hexavalent
Chromium
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Zinc
ug/L ug/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L
ug/L
Mayo
DBKG-MY1
1.12
<1
<0.2
0.409
44
<0.005
118
3420
18
<5
3050
8990
76
<5
Mayo
DBKG-MY2
< 1
< 1
< 0.2
2.25
< 5
0.035
< 10
0.19
31800
< 5
< 5
288
42000
201
1380
Mayo
DBKG-MY3
1.5
<0.5
<0.1
1.6
<10
0.0031
<50
1.1
2760
12.8
2.6
2940
7160
81.2
5.6
Mayo
DBKG-MY4
0.6
< 0.5
< 0.1
< 1
< 10
< 0.001
1090
< 0.03
7330
211
< 0.5
4880
10600
181
6.2
Mayo
DBKG-MY5
0.8
<0.5
<0.1
<1
<10
0.0022
78.8
<0.6
12300
47.6
<0.5
3660
26300
268
5.4
Mayo
DBKG-MY6
< 1
< 1
< 0.2
0.318
6
0.082
< 10
0.079
11600
< 5
< 5
1550
13900
231
69
Mayo
DBKG-MY7
< 1
< 1
< 0.2
0.467
< 5
< 0.005
< 10
0.41
2790
5
< 5
369
9180
107
227
Mayo
DBKG-MY8
< 1
< 1
< 0.2
< 0.3
< 5
0.018
18
1.5
758
< 5
< 5
665
9680
17
225
Mayo
DBKG-MY9
<1
<1
<0.2
<0.3
<5
<0.005
91
<0.03
3990
9
<5
1730
10100
107
157
Mayo
DBKG-MY10
<1
<1
<0.2
14.4
116
0.019
132
0.94
5610
36
<5
1750
13200
163
39
Mayo
DBKG-MY11
<0.5
<0.5
<0.1
<1
<10
0.0262
<50
<0.6
627
11.5
<0.5
578
9260
11.1
37.8
Mayo
DBKG-MY12
< 1
< 1
< 0.2
19.6
6
0.025
< 10
1.2
6120
< 5
< 5
1230
20300
141
18
Mayo
DBKG-MY13
<0.5
<0.5
<0.1
<1<10
0.0214
132
<0.6
634
76.8
0.63
1420
10300
20.7
133
Mayo
DBKG-MY14
<0.5
<0.5
<0.1
<1
35.6
0.0223
74
1.6
7410
19
1.6
201
8970
55.1
61.5
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016

30
Table F2-8 Page 3 of 3
Comparison of Duke Energy Background Well Data to RSL Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016
15A NCAC 02L.0202
Groundwater Standard a
NS
NS
NS
NS
NS
NS
NS
NS
NS
Federal MCL/SMCL (b):
* denotes secondary standard
NS
NS
NS
NS
NS
NS
NS
NS
NS
DHHS Screening Level (c):
NS
NS
NS
NS
NS
NS
NS
NS
NS
RSL 2015(d):
NS
NS
NS
NS
NS
NS
NS
NS
NS
Constituents Not Identified in the CCR Rule
Station
Well ID
Alkalinity
Bicarbonate
Carbonate
Total
Suspended
Solids
mg/L
Turbidity
Temperature
Specific
Conductance
Dissolved
Oxygen
Oxidation
Reduction
Potential
Mayo
DBKG-MY1
Mayo
DBKG-MY2
Mayo
DBKG-MY3
Mayo
DBKG-MY4
Mayo
DBKG-MY5
Mayo
DBKG-MY6
Mayo
DBKG-MY7
Mayo
DBKG-MY8
Mayo
DBKG-MY9
Mayo
DBKG-MY10
Mayo
DBKG-MY11
Mayo
DBKG-MY12
Mayo
DBKG-MY13
Mayo
DBKG-MY14
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx RSL April 2016

Comparison of Duke Energy Background Well Data to Screening Levels
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
^ - Denotes IMAC value.
* - Denotes SMCL value.
'C - Degrees Celsius.
Blank data cells indicate no data available.
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.
MDL- Method Detection Limit.
mg/L - milligrams/liter.
mV - millivolts.
NA- Not available.
NS - No Standard Available.
NTU - Nephelometric Turbidity Units.
PQL - Practical Quantitation Limit (h).
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.
Data Qualifiers
< Measurement limited by threshold (cannot detect measureable amount below this number). Actual detectable amount below threshold is unknown.
(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/dwstandards20l2.pdf.
(c) - 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
(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) - Alternative screening level calculated for hexavalent chromium using RSL calculator (http:Hepa-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.
(f) - 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
(g) - The CCR Rule lists these constituents as Constituents for Assessment Monitoring (Appendix IV).
(h) - Each analytical procedure has a PQL, which is defined as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to
five times the calculated MDL for the analytical procedure, and represents a practical and routinely achievable reporting limit with a relatively good certainty that any reported value is reliable.
""value is above the sreening level.
Reporting limit isabovethe screening level.
Haley & Aldrich, Inc.
Tables F2 -5-F2-8 Duke Bkg Well Screen_2016-04.xlsx
31
Page 1 of 1
4/10/2016

Page 1 of 1
32
Table F2-9
Do Not Drink Letter Summary
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Constituents Listed in Part 1 of Letter
Hex
Facility
Well ID
Vanadium Chromium Chloride Chromium Cobalt Iron Lead Manganese Sodium Strontium Sulfate Thallium Zinc
Mayo
MY -3
X X X X
Total number of Constituent Letters
1 0 0 0 0 1 1 0 1 0 0 0 0
Total Number of "Do Not Drink" Letters
(Excluding Hexavalent Chromium and
1
Vanadium)
Total Number of "Do Not Drink" Letters
(Including Hexavalent Chromium and
1
Vanadium)
Total Number of "Do Not Drink" Letters
0
for Hexavalent Chromium
Total Number of "Do Not Drink" Letters
1
for Vanadium
Haley & Aldrich, Inc.
Table F2-9 Do Not Drink Summary.xlsx April 2016

33
Table F3-1 Page 1 of 2
Duke Energy Background Water Supply Well Data
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
<- Not detected, value is the reporting limit.
°C - Degrees Celsius.
mg/L - milligrams/liter.
"i -
millivolts.
NTU - Nephelometric Turbidity Units.
su - standard units.
ug/L - micrograms/liter.
umhos/cm micromhos/centimeter.
Haley & Aldrich, Inc.
Table F3-1 Duke Energy Background Well Data_2016-04.xlsx April 2016

34
Table F3-1 Page 2 of 2
Duke Energy Background Water Supply Well Data
Maya Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
==MwM====MMMMM
=mom
Notes:
<- Not detected, value is the reporting limit.
°C - Degrees Celsius.
mg/L - milligrams/liter.
my - millivolts.
NTU - Nephelometric Turbidity Units.
su-standard units.
ug/L- micrograms/liter.
umhos/cm micromhos/centimeter.
Haley & Aldrich, Inc.
Table F3-1 Duke Energy Background Well Data_2016-04.xlsx April 2016

35
Page 1 of 2
Table F3-2
Facility Specific Background Data for Bedrock and Deep Monitoring Wells
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Well ID
Sample ID
Date Sampled
Barium
(ug/L)
Boron
(ug/L)
Cobalt
(ug/L)
Hexavalent Chromium
(ug/L)
Iron
(ug/L)
Lead
(ug/L)
Nckel, Dissolved Vanadium
(ug/L) (ug/L)
BG -01
BG -01-20081031
31 -Oct -08
1040
6
65700
33.1
BG -01
BG -01-20090604
04 -Jun -09
155
< 200
2100
12.9
BG -01
BG -01-20091021
21 -Oct -09
175
< 200
4610
2.3
BG -01
BG -01-20100422
22 -Apr -10
120
< 50
2000
12
BG -01
BG -01-20101206
06 -Dec -10
105
< 50
1080
< 5
BG -01
BG -01-20110420
20 -Apr -11
99.1
< 50
702
< 5
BG -01
BG -01-20110711
11 -Jul -11
101
<50
1040
<5
BG -01
BG -01-20111103
03 -Nov -11
95.4
< 50
261
< 5
BG -01
BG -01-20120404
04 -Apr -12
93
< 50
388
< 5
BG -01
BG -01-20120709
09 -Jul -12
101
<50
640
<5
BG -01
BG -01-20121105
05 -Nov -12
101
< 50
526
< 5
BG -01
BG -01-20130410
10 -Apr -13
97
< 50
323
< 1
BG -01
BG -01-20130709
09 -Jul -13
97
< 50
488
< 1
BG -01
BG -01-20131113
13 -Nov -13
95
< 50
412
< 1
BG -01
BG -01-20140401
01 -Apr -14
90
< 50
290
< 1
BG -01
BG -01-20140718
18 -Jul -14
93
< 50
325
< 1
BG -01
BG -01-20141112
12 -Nov -14
95
< 50
466
< 1
BG -01
BG -01-20150413
13 -Apr -15
90
< 50
< 1
409
< 1
BG -01
BG -01-20150707
07 -Jul -15
97
< 50
< 1
557
< 1
4.94
BG -01
BG -01-20150910
10 -Sep -15
91
< 50
< 1
300
< 1
1.46 3.93
BG -01
BG -01-20151103
03 -Nov -15
90
< 50
< 1
45
< 1
3.4
BG -01
BG -01-20151205
05 -Dec -15
94
< 50
< 0.5
0.31
350
0.13
< 2.5 4.2
BG -01
BG -01-20160108
08 -Jan -16
87
< 50
< 1
0.2
272
< 1
1.28 3.94
BG -02
BG -02 DUP-20150413
13 -Apr -15
55
< 50
< 1
546
< 1
BG -02
BG -02-20101202
02 -Dec -10
81.8
< 50
2660
< 5
BG -02
BG -02-20110420
20 -Apr -11
61.3
< 50
439
< 5
BG -02
BG -02-20110711
11 -Jul -11
64.8
<50
559
<5
BG -02
BG -02-20111103
03 -Nov -11
67.7
< SD
312
< 5
BG -02
BG -02-20120404
04 -Apr -12
61.5
< 50
152
< 5
BG -02
BG -02-20120709
09 -Jul -12
53.4
<50
460
<5
BG -02
BG -02-20121105
05 -Nov -12
60.2
< 50
759
< 5
BG -02
BG -02-20130410
10 -Apr -13
66
< 50
646
< 1
BG -02
BG -02-20130709
09 -Jul -13
69
<50
1130
<1
BG -02
BG -02-20131113
13 -Nov -13
62
< 50
841
< 1
BG -02
BG -02-20140401
01 -Apr -14
71
< 50
943
< 1
BG -02
BG -02-20140718
18 -Jul -14
65
<50
1010
<1
BG -02
BG -02-20141112
12 -Nov -14
61
< 50
647
< 1
BG -02
BG -02-20150413
13 -Apr -15
54
< 50
-<1
435
< 1
Haley & Aldrich, Inc.
Table F3.2—Facility Bkg Data.xisx April 2016

36
Page 2 of 2
Table F3-2
Facility Specific Background Data for Bedrock and Deep Monitoring Wells
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Well ID
Sample ID
Date Sampled
Barium
(ug/L)
Boron
(ug/L)
Cobalt
(ug/L)
Hexavalent Chromium
(ug/L)
Iron
(ug/L)
Lead
(ug/L)
Nckel, Dissolved
(ug/L)
Vanadium
(ug/L)
BG -02
BG -02-20150707
07 -Jul -15
54
< 50
< 1
< 2.09999997168779E-02
467
< 1
5.88
BG -02
BG -02-20150911
11 -Sep -15
50
< 50
< 1
244
< 1
1.48
4
BG -02
BG -02-20151103
03 -Nov -15
51
< SO
< 1
513
< 1
6.63
BG -02
BG -02-20151209
09 -Dec -15
60
< 50
< 0.5
< 0.03
450
< 0.1
0.96
5.8
BG -02
BG -02-20160108
08 -Jan -16
58
< 50
< 1
< 0.03
471
< 1
< 1
4.2
M W-10BR
M W-IOBR-20150317
17 -Mar -15
27
< 50
< 1
883
< 1
1.91
1.66
MW-1OBR
MW-10BR-20150911
11 -Sep -1S
5
< SO
< 1
37
< 1
2.13
1.73
MW-1OBR
M W-10BR-20151203
03 -Dec -15
< 5
< 50
< 1
< 0.03
193
< 1
1.93
1.5
M W-10BR
M W-10BR-20160107
07 -Jan -16
< 5
< 50
< 1
< 0.03
33
< 1
1.88
1.68
MW-11BR
MW-11BR-20150625
25 -Jun -15
44
<50
<1
115
<1
<1
2.69
MW-11BR
MW-11BR-20150911
11 -Sep -15
32
<50
<1
153
<1
<1
9.15
MW-11BR
MW-11BR-20151203
03 -Dec -15
22
< 50
< 1
13.6
304
< 1
< 1
12.1
MW-11BR
MW-11BR-20160107
07 -Jan -16
24
< 50
< 1
12.2
98
< 1
< 1
12.7
MW -12D
MW -12D DUP-20151202
02 -Dec -15
20
< 50
< 1
0.64
393
< 1
1.65
0.768
MW -12D
MW -12D-20150624
24 -Jun -15
26
<50
1.37
326
<1
1.82
0.719
MW -12D
MW -12D-20150625
25 -Jun -15
0.334
MW -12D
MW -12D-20150910
10 -Sep -15
20
<50
<1
0.357
277
<1
1.38
0.637
MW -12D
MW -12D-20151202
02 -Dec -15
21
< 50
< 1
0.55
504
< 1
1.8
1.01
MW -12D
MW -12D-20151204
04 -Dec -15
20
<50
0.51
0.64
280
<0.1
2.1
<1
MW -12D
MW -12D-20160107
07 -Jan -16
22
<50
< 1
0.52
968
< 1
1.18
1.65
MW-13BR
MW-13BR-20150623
23 -Jun -15
40
<50
1.19
0.005
1130
<1
<1
0.381
MW-13BR
MW-13BR-20150908
08 -Sep -15
51
<50
<1
2400
<1
<1
0.465
M W-13BR
M W-13BR-20151202
02 -Dec -15
45
< 50
< 1
< 0.03
2490
< 1
< 1
0.429
MW-13BR
MW-13BR-20160107
07 -Jan -16
42
<50
<1
<0.03
2550
<1
1.3
<0.3
MW-14BR
MW-14BR-20150312
12 -Mar -15
30
<50
1.41
907
<1
<1
1.29
MW-14BR
MW-14BR-20150909
09 -Sep -15
42
65
1.09
2730
<1
<1
0.469
M W-14BR
M W-14BR-20151202
02 -Dec -15
22
< 50
< 1
< 0.03
396
< 1
1.03
1.82
MW-14BR
MW-14BR-20160107
07 -Jan -16
17
<50
<1
<0.03
98
<1
<1
2.45
MW-16BR
MW-16BR-20150623
23 -Jun -15
11
<50
< 1
0.017
80
< 1
< 1
2.79
MW-16BR
MW-16BR-20150909
09 -Sep -15
7
< 50
< 1
0.013
22
< 1
< 1
2
MW-16BR
MW-16BR-20151204
I 04 -Dec -15
6.2
< 50
< 0.5
< 0.03
58
0.1
< 0.5
1.2
M W-16BR
MW-16BR-20160107
I 07 -Jan -16
9
< 50
< 1
< 0.03
126
< 1
< 1
1.06
Notes:
<- Not Detected, value is the reporting limit.
ug/L- Microgram per liter.
Haley & Aldrich, Inc.
Table F3.2 -Facility Bkg Data.xisx April 2016

37
Page 1 of 1
Table F3-3
Background Data Statistical Evaluation
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
1 1
2
3
1 4
5
6 1
7
8
9
10
11
12
13
14
15
16
17
Regional Background Evaluation
Frequency of
Detection
Percent
Non-
Detects
Range of Non
-Detects
KM Mean
KM
Variance
KM Standard
Deviation
KM
Coefficient of
Variation
50th
Percentile
(Q2)
95th
Percentile
Maximum
Detect
Outlier
Presence*
Outlier
Removed
Distribution
BTV
Method
Barium
ug/L
66 /
Variable
Units
Frequency of
Detection
Percent
Non-
Detects
Range
of Non -Detects
KM Mean
KM
Variance
KM Standard
Deviation
KM
Coefficient of
Variation
50th
Percentile
(Q2)
95th
Percentile
Maximum
Detect
Outlier
Presence"
Outlier
Removed
Distribution
BTV
Method
Barium
ug/L
11
/
14
21%
5
5
22.59
881.7
29.69
1.315
10.3
83.95
108
Yes
No
Gamma
83.03
95%Approx. Gamma UPL WH and KM
Boron
ug/L
1
/
14
93%
5
50
6.267
8.022
2.832
0.452
50
5o
12.6
N/A
No
N/A
12.6
Maximum Detect
Cobalt
ug/L
0
/
14
100%
0.5
1
N/A
N/A
N/A
N/A
1
1
N/A
N/A
No
N/A
1
Maximum RL
Hexavalent Chromium
ug/L
8
/
13
38%
0.03
0.6
0.526 1
0.342
0.585
1.113
0.6
1.535
1.6
No
No
Normal
1.646
95% KM UPL
Iron
ug/L
8
/
14
43%
10
50
128.4
73371
270.9
2.11
62
467.3
1090
Yes
No
Lognormal
1 537.6
195% KIM UPL
Lead
ug/L
8
/
14
43%
0.1
1
1.196
2.608
1.615
1.351
1
3.926
6.37
Yes
No
Gamma
4.078
95% Approx. Gamma UPL WH and KM
Nickel
ug/L
3
/
14
79%
0.5
5
1.055
0.631
0.795
0.753
S
5
2.6
No
No
Normal
2.512
95%KM UPL
Vanadium
ug/L
7
/
14
50%
0.3
1
2.96
34.13
5.842
1.974
1
16.22
19.6
Yes
No I
Gamma
1 11.22
95%Approx. Gamma UPL WH and KM
Facility Specific Background
Evaluation
Variable
Units
Frequency of
Detection
Percent
Non-
Detects
Range of Non
-Detects
KM Mean
KM
Variance
KM Standard
Deviation
KM
Coefficient of
Variation
50th
Percentile
(Q2)
95th
Percentile
Maximum
Detect
Outlier
Presence*
Outlier
Removed
Distribution
BTV
Method
Barium
ug/L
66 /
68
3%
5
5
60.34
1327
36.43
0.604
60.1
103.6
175
Yes
Yes
Normal
132.9
95%UTL
Boron
ug/L
1 /
68
99%
50
200
50.23
3.357
1.832
0.0365
50
5o
65
N/A
No
N/A
65
Maximum Detect
Cobalt
ug/L
5 /
39
87%
0.5
1
0.581
0.0553
0.235
0.405
1
1.208
1.41
No
No
Normal
1.08
95% KIM UTL
Hexavalent Chromium
ug/L
13 /
24
46%
0.021
0.03
1.23 1
12.47
3.531
2.871
0.03
10.47
13.6
Yes
No
Distribution free
13.6
Maximum Detect (95% UTL)
Iron
ug/L
68 /
68
0%
N/A
N/A
717.9
677432
823.1
1.146
455
2529
4610
Yes
Yes
Lognormal
3780
95% UTL
Lead
ug/L
5 /
68
93%
0.1
5
0.511
4.413
2.101
4.108
1
5
12.9
Yes
Yes
Normal
4.694
95%KM UTL
Nickel
ug/L
16 /
32
50%
0.5
2.5
1.162
0.28
0.529
0.456
1.015
2.114
2.13
No
No
Normal
2.073
195% KIM UPL
Vanadium
ug/L
34 /
36
6%
1 0.3
1
3.058
9.304
3.05
0.997
1.775 1
9.888
12.7
Yes
No I
Gamma 1
11.4
95%Approx. Gamma UTL WH and KM
Notes:
*-Tested at 5% significance level. ug/L- Microgram per liter.
BTV - Background Threshold Value. UPLs - Upper Prediction Limits.
KM - Kaplan -Meier Method. UTLs - Upper Tolerance Limits.
NA - Not Available. Var - Variance.
RL - Reporting Limit. WH -Wilson Hilferty Transformation.
BTV values and statistics were calculated using ProUCL v. 5.0.00
Haley & Aldrich, Inc.
Table F3-3_Backgr d Eval.atm May..%IS% April 2016

38
Page 1 of 1
Table F3-4
Comparison of NCDEQ Water Supply Well Sampling Data to Regional Background Threshold Values
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Constituents
Units
Frequency of
Detection (a)
Range of Detected
Concentrations
Mean
Detect
10th
Percentile
25th
Percentile
50th
Percentile
75th
Percentile
90th
Percentile
Regional
Background Threshold
Value (BTV) (b)
Number of Samples
Above Regional BTV
Barium
ug/L
3 / 3
30 - 78
S4.17
34.9
42.25
S4.S
66.25
73.3
83.03
0
Boron
ug/L
0/ 3
NA - NA
NA
5
5
5
5
5
12.6
0
Cobalt
ug/L
0 / 3
NA - NA
NA
0.5
0.5
0.5
2.75
4.1
1
0
Hexavalent Chromium
ug/L
2 / 3
0.13 - 0.63
0.38
0.05
0.08
0.13
0.38
0.53
1.646
0
Iron
ug/L
2 / 3
953 - 1,750
1352
230.6
501.5
953
1352
1591
537.6
2
Lead
ug/L
3 / 3
1.8 - 24
9.5
1.98
2.25
2.7
13.35
19.74
4.078
1
Nickel
ug/L
2 / 3
1.2 - 1.5
1.35
1.26
1.35
1.5
3.25
4.3
2.512
0
Vanadium
I ug/L
1 2 / 3
1 2.5 - 3.03
1 2.765
1 2.606
1 2.765
1 3.03
1 6.515
1 8.606
1 11.22
1 0
Notes:
BTV - Background Threshold Value.
DEQ- Department of Environmental Quality.
NA - Not Applicable.
NC - North Carolina.
ug/L - micrograms/liter.
(a) - Frequency of Detection: number of detects / total number of results.
(b) - BTV values shown on Table F3-3.
Haley & Aldrich, Inc.
Table F3-4 NCDEQ Water Supply Well Data Compared to Regional BTVs.xlsx April 2016

39
Page 1 of 1
Table F3-5
Comparison of NCDEQ Water Supply Well Sampling Data to Facility Specific Background Threshold Values
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Constituents
Units
Frequency of
Detection (a)
Range of Detected
Concentrations
Mean
Detect
10th
Percentile
25th
Percentile
50th
Percentile
75th
Percentile
90th
Percentile
Facility Specific
Background Threshold
Value (BTV) (b)
Number of Samples
Above Facility
Specific BTV
Barium
ug/L
3 / 3
30 - 78
54.17
34.9
42.25
54.5
66.25
73.3
132.9
0
Boron
ug/L
0/ 3
NA - NA
NA
5
5
5
5
5
65
0
Cobalt
ug/L
0 / 3
NA - NA
NA
0.5
0.5
0.5
2.75
4.1
1.08
0
Hexavalent Chromium
ug/L
2 / 3
0.13 - 0.63
0.38
0.05
0.08
0.13
0.38
0.53
13.6
0
Iron
ug/L
2 / 3
953 - 1,750
1352
230.6
501.5
953
1352
1591
3780
0
Lead
ug/L
3 / 3
1.8 - 24
9.5
1.98
2.25
2.7
13.35
19.74
4.694
1
Nickel
ug/L
2 / 3
1.2 - 1.5
1.35
1.26
1.35
1.5
3.25
4.3
2.073
0
Vanadium
ug/L
2 / 3
2.5 - 3.03
2.765
2.606
2.765
3.03
6.515
8.606
11.4
0
Notes:
BTV - Background Threshold Value.
DEQ- Department of Environmental Quality.
NA - Not Applicable.
NC - North Carolina.
ug/L - micrograms/liter.
(a) - Frequency of Detection: number of detects / total number of results.
(b) - BTV values shown on Table F3-3.
Haley & Aldrich, Inc.
Table F3-5 NCDEQ Water Supply Well Data Compared to Facility Specific BTVs.xlsx April 2016

Table F5-1
Coal Ash Indicator Concentrations Observed in the Water Supply Wells of Low Oxygen
Mayo Steam Electric Plant
Water Supply Well Evaluation
Duke Energy
April 2016
Notes:
BTV - Background Threshold Value.
µg/l_ - Micrograms per liter.
a) The water supply well contains dissolved oxygen less than 4,000 microgram per liter (µg/L)
b) Boron value is a non -detect (ND) concentration with a laboratory reporting limit of 50µg/L.
c) BTV = background threshold value in the unit of µg/l_ determined from the facility background well data.
Haley & Aldrich, Inc.
Table F5-1.xlsx
Page 1 of 1
April 2016
40
Dissolved
Boron (ug/ )
Barium BTV
Water Supply Well (a)
Oxygen
Boron BTV(c)
Barium 1µg/L)
(b)
(c)
(Vg/L)
MY5
1800
<50
65
54.5 132.9
Notes:
BTV - Background Threshold Value.
µg/l_ - Micrograms per liter.
a) The water supply well contains dissolved oxygen less than 4,000 microgram per liter (µg/L)
b) Boron value is a non -detect (ND) concentration with a laboratory reporting limit of 50µg/L.
c) BTV = background threshold value in the unit of µg/l_ determined from the facility background well data.
Haley & Aldrich, Inc.
Table F5-1.xlsx
Page 1 of 1
April 2016
40

VIRGINIA
L i, I I III i
--------' --- MAYO
I --------- II• ROXBORO, NC
BELEWS CREEK R MORA, NC
O
BELEWS CREEK, NC
• I •
L u,
L II
BUCK
I + + I MARSHALL SALISBURY, NC
I, dl TERELL, NC
� =li Dile
I I •,• III•
CLIFFSIDE
MOORESBORO,NC ALLEN
BELMONT, NC
+ •ai ill
IIIIIII li 3' ff
SOUTH
CAROLINA
,III •i E
NORTH
CAROLINA

RT
HFSrFR
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HALIFAX CO r _
i�
MAYO PLANT 11
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1981 �
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l
A
j MAYO LAKE
1 =�
\ r`
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A
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/ PERSON CO
Nan bAN
\�
MAYO PLANT 11
MONOFILL ' J
in
o
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` 15 NOTES
J
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j MAYO LAKE
1 z
ti
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ulky

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I �MW-12D
o I
y `
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0 )
/ BMW.14BR
L -
HALIFAX CO
-PERSON CO /
LEGEND
�MW-16BR
� � r
f 5 NOTES
1981 �
DFI
J
l
A
�MW-10BR r �f�
MAYO LAKE
1 =�
\ r`
~r----

,ay v •
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r.
r - • `'
L
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1
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e
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d _ _
oo
o
FIGURE F4-1
low
1' -. _ . O O -� _r • • .�[ e } of w e d^
., r

A
A'
(WEST)
(EAST)
DUKE ENERGY
MAYO STEAM ELECTRIC PLANT PROPERTY
COMPLIANCE BOUNDARY
MW-14BR PROFILE BASED ON HISTORIC
> WATER LEVEL USGS TOPOGRAPHIC MAP
o = IS 503.88 ms/.
N cn m
WASTE BOUNDARY
MW-09BR PROFILE BASED ON HISTORIC
FMWAWliERLEVEL 1981 -► WATER LEVEL USGS TOPOGRAPHIC MAP
w
LANDFILL
94.54 ms/.
IS 468.82mS1.
m
r
r, M zrLn
m
r
J
co V t, a ry>
REGOLITH �
�
Q
��L r
^- • r
�
ACTIVE ASH BASIN
�
..r ,. ..
_
TD484'msl. -- - ____________________________________TOP
OF DAM 488'msl._ -- -
-- WE=480'msl------------------
_
REGO�ITH�
� _
. _
\
TD 466' msI. - ASH --
`
TD 465' msl.
TO ±455' msL 446' msl.
TD ?
MAYO LAKE
`
\ TOP OF DAM 444' msl_
TD ? GENERALIZED GROUNDWgTER
GENERALIZED GROUNDWATER
TD 435' mSI.=*11
REGOLITH
WE=433' msl
FLOW DIRECTION
FLOW DIRECTION
`\�
La
FORMER UNNAMEDA
ASH /
ERA
w 1011 O/RECT/pN OUNpIIATER
o_o
'� _
w
Ifo INTERMITTENT CREEK
0
FORMER CHANNEL OF
3 0
>
ZI>
CRUTCH FIELD CREEK
o BEDROCK o o
PROFILE BASED ON HISTORIC
AREA OF BORON CONCENTRATIONS
;
;
USGS TOPOGRAPHIC MAP
IN GROUNDWATER ABOVE 2L
PROFILE BASED ON HISTORIC
BEDROCK
USGS TOPOGRAPHIC MAP
FORMER CHANNEL
OF MAYO CREEK
BEDROCK
?
BEDROCK
LEGEND
GENERALIZED WATER TABLE
MY3
NCDWR WATER SUPPLY WELL OWNER ID
DW -3
NCDWR WATER SUPPLY WELL ID
MW-17BR MONITORING WELL
TD 233' msl. TOTAL DEPTH ELEVATION OF WELL
VERTICAL EXAGGERATION 5X
FIGURE F4-2
CONCEPTUAL CROSS-SECTION A -A'
MAYO STEAM ELECTRIC PLANT
SOURCE INFORMATION:
148 RIVER STREET, SUITE 220
GREENVILLE, SOUTH CAROLINA 29601
EXISTING GROUND SURFACE BASED ON A DRAWING PROVIDED BY THE WSP GROUP, TITLED "MAYO PLANT FINAL", DATED MAY 19, 2015.
PHONE [phone]
www.synterracorp.com
10660 BOSTON RD
HISTORIC GROUND SURFACE BASED ON THE 7-1/2' USGS TOPOGRAPHIC MAP FOR CLUSTER SPRINGS, VA DATED 1968.
Y JOHN CHAS FAIN ue DATe .4/05/2016
MONITORING WELL DATA WAS OBTAINED FROM THE COMPREHENSIVE SITE ASSESSMENT REPORT PREPAREED BY SYNTERRA, DATED SEPTEMBER 2, 2015.
ROXBORO, NORTH CAROLINA
PRIVATE WATER SUPPLY WELL INFORMATION WAS OBTAINED FROM A LIST PROVIDED BY DUKE ENERGY PROGRESS
S nTer�
PDRAWN ROJECT RY
LAYOUT: SEFCTION A -A'
MONITORING WELL WATER LEVELS WERE COLLECTED BY SYNTERRA ON DECEMBER 15, 2015.
04/17/2016 8:24 PM P:\Duke Energy Progress.1026\14. corporate
Support\02. Management Reports\Mayo\5ECTlONS\DWG\DE MAYO CROSS-SECTIONS.dwg

Figure F4-3: The supply well capture zones are represented in this figure by the yellow particle tracks.
The blue arrows show the overall directions of groundwater flow. In general, the shape of a given
capture zone is a function of recharge, hydraulic conductivity, flow rate, and hydraulic gradient. For
Mayo, the primary influence on the shape of the capture zone is the hydraulic gradient. When the
prevailing hydraulic gradient is small and relatively flat, the capture zone approaches a circular
configuration. As the hydraulic gradient increases, the shape becomes elongated in a locally upgradient
direction. As can be seen from this figure, the recharge areas supplying water to the private water wells
are away from the direction of the ash basin due to topographic ridge lines that separate the recharge
areas.

0
3
w
1
.5
0
—.5
Todorokite
Mn
Hausm annite
dachrosit
Ala bandite
m (O js
M OH),(a
Mn(OH
25°C
0 2 4 6 8 10 12 14
pH
NOTE
DIAGRAMS ADOPTED FROM APPENDIX E OF THE CAP -2
REPORT FOR THE MAYO STEAM ELECTRIC PLANT BY SYNTERRA.

Panel (a): Example Box Plot
a Possible Outlier
L1161l*�
1. BOX PLOT EXPLANATION DIAGRAM ADOPTED FROM
HTTP:HS ITES. GOOGLE.COM/S ITE/DAVI DSSTATISTICS/HOME/
NOTCHED -BOX -PLOTS.
2. PIPER PLOT ADOPTED FROM CSA REPORT FOR MAYO
STEAM ELECTRIC PLANT BY SYNTERRA.
do.– Ca
Panel (b): Example Piper Plot
n —
a '1
d MW-10BR
20%
o� a Ci o
b �C�
a °'Q A MW-10BR
— CI --0
Upper Whiskers
75th Percentile
aka 3fd Quartile
The "Notch"
55% Confidence Interval of . •.
: Interquartile (IOR)
the Median
iia 1557 Pereent of Dahl
Median +1- 1.57 x IQR/na.5 , `
25th Percentile
.........
aka tst Quartle
Lower Whiskers
L1161l*�
1. BOX PLOT EXPLANATION DIAGRAM ADOPTED FROM
HTTP:HS ITES. GOOGLE.COM/S ITE/DAVI DSSTATISTICS/HOME/
NOTCHED -BOX -PLOTS.
2. PIPER PLOT ADOPTED FROM CSA REPORT FOR MAYO
STEAM ELECTRIC PLANT BY SYNTERRA.
do.– Ca
Panel (b): Example Piper Plot
n —
a '1
d MW-10BR
20%
o� a Ci o
b �C�
a °'Q A MW-10BR
— CI --0

AI—AHTHnR (RANTRnWFN—nFFIfF PHX
10000000.0
MAYO
Boron
Calcium
Chloride
Sulfate
Total Dissolved Solids -
10000o0_0
100000.0
T
10000.0 —
J
.. ... ....
3
O
�� 1000.0
C
. ... ... .. ... . . ... .. .. .. . ... .. ... ...
V
C
V
100.0.
--
............ ........... ....:....... .......................
.......... r ........... ....... ... ........
0.1
AB FM RBG WSW
AB
FM
RBG
WSW
AB
FM RBG
WSW
AB
FM RBG WSW
AB FM RBG WSW
NOTE
1 ACRONYMS: GASH
MAYO STEAM ELECTRIC PLANT
m`WATER SUPPLY WELL EVALUATION
UICH
BASIN POREWATER WELL
FM = OTHER FACILITY MONITORNG WELL
DUKE ENERGY
RBG = REGIONAL BACKGROUND WELL
WSW = WATER SUPPLY WELL
2. NO REGIONAL BACKGROUND DATA FOR CHLORIDE,
BOX PLOT COMPARISON FOR
SULFATE, AND TOTAL DISSOLVED SOLIDS.
MAJOR COAL
ASH CONSTITUENTS
3. ALL DUKE ENERGY FACILITY MONITORING WELLS WERE
NON -DETECT FOR BORON.
APRIL 2016
FIGURE F5-3

10000.0
MAYO
Barium Cobalt
1000.0
J 100.0
m x
Z
0
is
V
C
O
C] 10.0
1-U
wv
0.1
AB FM RBG WSW AB FM RBG WSW
NOTE
ACRONYMS:
AB =ASH BASIN POREWATER WELL
FM = OTHER FACILITY MONITORNG WELL
RBG = REGIONAL BACKGROUND WELL
WSW = WATER SUPPLY WELL

100000.0
Dissolved Oxygen
1nano .0
10.0
1.0
0.1
AB
i
MAYO
Iron
DISSOLVED
DISSOLVED TOTAL
TOTAL
Manganese
DISSOLVED
DISSOLVED
T
TOTAL
TOTAL
FM RBG WSW AB FM RBG WSW AB FM RBG WSW
NOTES
1. ACRONYMS:
AB = ASH BASIN POREWATER WELL
FM = OTHER FACILITY MONITORNG WELL
RBG = REGIONAL BACKGROUND WELL
WSW = WATER SUPPLY WELL
2. NO REGIONAL BACKGROUND DATA FOR DISSOLVED
OXYGEN.

Rr
*& r'4
Rp
HALIFAX CO _
s I � � PERSON CO
MW-03BR
MW-14BR�
zS
MW-13BR
A(
ASH
AB
\\\
�AB
MAYO PLANT 11
MONOFILL f J
BR�0
z
�MW-11
_ - J
J '
0
0
0
N 'N
�MW-16BR
`SET^tD-
MW-08BR
MW-07BR®
®mw-09L
�J
l
�\A
MW-10BR
J � ` � MAYO LAKE
MAYO STEAM r
ELECTRIC PLANT Z
ti
\ r`
~r----
LEGEND
I ---
NOTES -NOTES
FN Tal
ITA
ulky

10000
,)AW
7.000
6,000
5,000
4•WO '
a
3,000
7,490
1,001)
0
1
Panel (c)
NOTES
1. ONLY WELLS SAMPLED FOR BOTH BORON AND DISSOLVED OXYGEN
ARE PLOTTED.
2. AREA 1 IS DEFINED BY THE DATA CLUSTERING PATTERN OF THE ASH BASIN
POREWATER; AREA 2 IS DEFINED BY THE DATA CLUSTERING PATTERN OF THE
WATER SUPPLY WELLS; AREA 3 IS DEFINDED BY THE DATA CLUSTERING
PATTERN OF ALL FACILITY BEDROCK WELLS AND WATER SUPPLY WELL MY -5.
10
Panel (b)
a Ash Basln Well
*Facility Bedrock Well (0owngradient)
O Facility Bedrock Well (Side Gradient)
•Facility Bedrock Well (li pgraclent)
A A
A
30 X00 1.000 10000
BarenConcalpatlora (la/Ly
A Ash Basin Well
O F acility Bedock Well (Oowngradlent)
*Facility Bedrock Well (Side (oradient)
*Facility Bedrock Well (llpgradenlj
♦ Water Supply Well
1w
Bao" Cooe"Iri[Ian (up/L)
r________..,,—..s
Area 1 A
i AA
L----___�....�.,..�
1,000 10,000
Panel (a)
1$006?
10.000
A Ash Basin Well
9'040 -
•Facility Bedrock W!0 (Dow"gradie"lj
9,000 -
8,000
-
$,000
7,000
-
7,000
6.000
"5,000
5.000
a.0r10
a.,0lW -
3,000
3.000
25 2.000
3 2,000 -
3,000 -
■ ,
1,000
• A A
i
10 100 1,000 10000
1
Baro" C4nc*tMftlon (u'/L)
10000
,)AW
7.000
6,000
5,000
4•WO '
a
3,000
7,490
1,001)
0
1
Panel (c)
NOTES
1. ONLY WELLS SAMPLED FOR BOTH BORON AND DISSOLVED OXYGEN
ARE PLOTTED.
2. AREA 1 IS DEFINED BY THE DATA CLUSTERING PATTERN OF THE ASH BASIN
POREWATER; AREA 2 IS DEFINED BY THE DATA CLUSTERING PATTERN OF THE
WATER SUPPLY WELLS; AREA 3 IS DEFINDED BY THE DATA CLUSTERING
PATTERN OF ALL FACILITY BEDROCK WELLS AND WATER SUPPLY WELL MY -5.
10
Panel (b)
a Ash Basln Well
*Facility Bedrock Well (0owngradient)
O Facility Bedrock Well (Side Gradient)
•Facility Bedrock Well (li pgraclent)
A A
A
30 X00 1.000 10000
BarenConcalpatlora (la/Ly
A Ash Basin Well
O F acility Bedock Well (Oowngradlent)
*Facility Bedrock Well (Side (oradient)
*Facility Bedrock Well (llpgradenlj
♦ Water Supply Well
1w
Bao" Cooe"Iri[Ian (up/L)
r________..,,—..s
Area 1 A
i AA
L----___�....�.,..�
1,000 10,000

0
LEGEND
WATER SUPPLY WELL, SAMPLED BY NCDEQ
® WATER SUPPLY WELL, NOT SAMPLED
0'
O' -4*— APPARENT DIRECTION OF GROUNDWATER FLOW
— — — DUKE ENERGY PROPERTY BOUNDARY
ASH BASIN WASTE BOUNDARY
MYS �
O HALIFAX CO_ _
PERSON—MI
Rry�ST�R L \�
Rp
Y
u
E \\
u \\ \ \
i
L
n
Y \\u
� MAYO PLANT
11
MONOFILL J
S
Of
O
0
m°
1�� \
I
�O
ra
o
u ❑
J
0 j
i
LANDFILL/STRUCTURAL FILL BOUNDARY
F ---
i COUNTY BOUNDARY
NOTES
1. ASH BASIN WASTE BOUNDARIES, ASH STORAGE AREA
BOUNDARIES, AND WATER SUPPLY WELL LOCATIONS ARE
APPROXIMATE.
2. THE COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO
THE DEFINITION FOUND IN 15A NCAC 02L.01 07(a).
3. AERIAL IMAGERY SOURCE: NC ONEMAP
4. DUKE ENERGY PROPERTY BOUNDARY WAS PROVIDED BY DUKE
ENERGY REAL ESTATE VIA HDR AND SYNTERRA.
5. ALL OTHER MAP DATA WAS PROVIDED BY HDR AND SYNTERRA.
0 800 1,600
SCALE IN FEET
ASH BASIN COMPLIANCE BOUNDARY
y
\
ASH BASIN COMPLIANCE BOUNDARY COINCIDENT
— — —
WITH DUKE ENERGY PROPERTY BOUNDARY
0.5 -MILE OFFSET FROM ASH BASIN COMPLIANCE
(')
_
BOUNDARY
i
LANDFILL/STRUCTURAL FILL BOUNDARY
F ---
i COUNTY BOUNDARY
NOTES
1. ASH BASIN WASTE BOUNDARIES, ASH STORAGE AREA
BOUNDARIES, AND WATER SUPPLY WELL LOCATIONS ARE
APPROXIMATE.
2. THE COMPLIANCE BOUNDARY IS ESTABLISHED ACCORDING TO
THE DEFINITION FOUND IN 15A NCAC 02L.01 07(a).
3. AERIAL IMAGERY SOURCE: NC ONEMAP
4. DUKE ENERGY PROPERTY BOUNDARY WAS PROVIDED BY DUKE
ENERGY REAL ESTATE VIA HDR AND SYNTERRA.
5. ALL OTHER MAP DATA WAS PROVIDED BY HDR AND SYNTERRA.
0 800 1,600
SCALE IN FEET

(a) Ash Basin Porewater Wells Only
EXPLANATION 100
A Ash Basin Well
X u w�
\ / X\ /
AV / `\ \ /
/\ x /\
0 A / ` / \ \ i \ � `` 0
\/ „ \/
100 0 i \\ `� i \\ 0 100
x
100 – – `� '– –\ / '– V-' – –
(b) Ash Basin Porewater and Downgradient Facility Bedrock Wells
100
EXPLANATION
A Ash Basin Well
Facility Bedrock Well(Downgradient)
\ /
L n d,x
/`\
V
aP
too o ; \ /"\ /�\ 0 100
0 100 100 0 0-
100
-100 0 0 100 100
Ca" CI -
CATIONS ANIONS
`♦ I ,A\
---y ---2 / v ---y ---
k
Ca"
CATIONS CATIONS
0
loo ♦� ♦� `'
100 100 0
0 100
Cl -
ANIONS

(a) Water Supply Wells
(b) Water Supply Wells and Up- and Side Gradient Facility Bedrock Wells
EXPLANATION 100 EXPLANATION 100
• Water Supply Well • Water Supply Well
■ Facility Bedrock Well (Upgradient)
❑ Facility Bedrock Well (Side Gradient)
\ / O L� \ / O
AMY -5
too 0 ; • ,A\ /\ 0 100 100 0; • ,A\ /� 0 100
\, \/ A \/
\/ v
^\ L� \\ i `\ i /^\
-- ------� — —— s --- --- 2 / \ --- --- s
--- f ----y---- ---y-- - -------I'-----v---- - -v y
___�` ___Y•__ ___ 100 ___ ___Y___ ___ ___100
_■�_7/Y•__
0 100 100 0 0 100 100
100 0 0 100 100 0 0 100
Cal' CI Ca" Cl -
CATIONS ANIONS CATIONS ANIONS
NOTE
BLUE CIRCLES SHOW THE DATA THAT APPARENTLY DEVIATE
FROM THE GENERAL DATA CLUSTERING PATTERN.

(a) Ash Basin Porewater and Downgradient Facility Bedrock Wells
(b) Water Supply Wells and Up- and Side -Gradient Facility Bedrock Wells
EXPLANATION 100 EXPLANATION 100
♦ Ash Basin Well • Water Supply Well
A Facility Bedrock Well (Downgradient) ■ Facility Bedrock Well (Upgradient)
❑ Facility Bedrock Well (Side Gradient)
&
x ,v d,x x ,v w�
ry
0 A /// v , tv 0 0 / ■ v i v //�� 0
loo 0 , ,n\ /� 0 loo 100 0 , ,A\ /\ 0 100
/ e
\/ v
^\ L� \\ i \\ i /^`
---y — ——/ \ ---_V — ——
s ---y ---
s
\ , \ / �r< L \, \ / \ , \ / ter• L \ , �,
Y____�___ 100 ___�____Y____{r___ ___ Y -___ 100 ___�____Y____�___
AA
0 100 100 0 0 100 100
loo 0 0 100 100 0 0 100
Cal' Cl -Ca" Cl -
CATIONS ANIONS CATIONS ANIONS
NOTE
BLUE DIAMOND DEFINES THE GENERAL DATA CLUSTERING
PATTERN OF THE WATER SUPPLY WELLS AND FACILTIY
UPGRADIENT AND SIDE GRADIENT WELLS.
0

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
ATTACHMENT F-1
Histograms and Probability Plots for Selected Constituents
APRIL 2016 1 U'CH

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part -1: Mayo Regional Background Water Supply Well
Data Test for Equal Variances
APRIL 2016 2 %UICH

MAYO FACILITY BACKGROUND MONITORING WELL DATA
Test for Equal Variances: Chromium (VI) - ug/L - T versus sys_loc_code
Method
Null hypothesis All variances are equal
Alternative hypothesis At least one variance is different
Significance level a = 0.05
95% Bonferroni Confidence Intervals for Standard Deviations
sys loc code N StDev CI
BG -01 2 0.077782 (
BG -02 3 0.005196 (0.0000011, 194.807)
MW-10BR 2 0.000000
MW-11BR 2 0.989949
MW -12D 6 0.134033 (0.0464738, 0.690)
MW-13BR 3 0.014434 (0.0000032, 541.130)
MW-14BR 2 0.000000 ( *, *)
MW-16BR 4 0.008813 (0.0018438, 0.124)
Individual confidence level = 99.1667%
Tests
Method
Multiple comparisons
Levene
Test
Statistic P -Value
- 0.000
62.26 0.000
* NOTE * The graphical summary cannot be displayed because the multiple comparison
intervals
cannot be calculated.
Test for Equal Variances: Vanadium - ug/L - T versus sys_loc-code
Method
Null hypothesis All variances are equal
Alternative hypothesis At least one variance is different
Significance level a = 0.05
95% Bonferroni Confidence Intervals for Standard Deviations
sys_loc_code N StDev CI
BG -01 5 0.56091 (0.098810, 7.027)
BG -02 5 1.14622 (0.381949, 7.591)
MW-10BR 4 0.09946 (0.005684, 5.501)
MW-11BR 4 4.58389 (0.301279, 220.421)
MW -12D 6 0.36861 (0.052222, 4.780)
MW-13BR 4 0.07135 (0.005715, 2.815)
MW-14BR 4 0.83900 (0.069451, 32.033)
MW-16BR 4 0.80043 (0.079911, 25.339)
Individual confidence level = 99.375%

Tests
Method
Multiple comparisons
Levene
Test
Statistic P -Value
— 0.000
3.60 0.007
Test for Equal Variances: Vanadium - ug/L - T vs sys_loc_code
Multiple comparison intervals for the standard deviation, a = 0.05
BG -01 H Multiple Comparisons
P -Value 0.000
BG -02 l.--1 Levene's Test
P -Value 0.007
0
10 20
30 40
If intervals do not overlap, the corresponding stdevs are significantly different.
MW-10BR
H
N
O
V
I
MW-11BR
O
-I
MW -12D
H
LA
V
MW-13BR
H
MW-14BR
H—�
MW-16BR
I—I
0
10 20
30 40
If intervals do not overlap, the corresponding stdevs are significantly different.

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part 2: Histograms and Probability Plots for Background Regional Background
Water Supply Well Data and Facility Background Monitoring Well Data
APRIL 2016 3 %UICH

T
c
ar
7
W
LL
Histogram of Background Constituents- Mayo (Regional)
Barium (ug/y Boron(u L) Cobalt (u y
8 8
5.0
4 4-
2.5
0.0 0 0
0 20 40 60 80 100 10 ZO 30 40 s0 0.5 0.6 0.7 0.8 0.9 1.0
_ Hexava lent Chromium(ug/L) Iron u L Lead(ug/L)
4-
2-
2.5 2 2.5
0 0- 0. )
0.0 0.4 0.8 12 1.6 0 200 400 600 800 1000 0 1 2 3 4 5 6
Nickel (ug/L) Vanadium u
8 O
4 5
0 0
1 2 3 4 5 0 5 10 15 20
Probability Plot of of Background Constituents- Mayo
Normal - 95% CI (Regional)
Bariumu Boron u 99 Cobak u
90 90 90
So 50 so -
10.
o 30 10 . 10-
1 1
-100 0 100 0 60 120 0.0 0.8 L6
99
C
09
a
L �
WwA OF
19'.4lAdo I wA
to
i ww
o u s
99 Nickel u yy Vanadium u
90 ' 90
50- W
10 10
LS 3.0 -1000
0.0
1000 -5
.
1 1
0 5 10 -20 0 20
Histogram of Background Constituents- Mayo (Facility)
Barium - ug/L - T Bor0-ug/L - T Cobalt - u L -T
40 3
50
20 LS
25
0 0 ,
O If PQO 9r0 '•v0 40 ob N;P
T Chromium 1 -u L -T Iron - u L-7 Lead - u L -T
� zo
� 10 zs
LL
0 0
13,,yp P,00 ya1> b,.p O 5 7 � '10 � ,60
vanadium - ug/L - T
16
10
8
s
0 0
Probability Plot of Background Constituents- Mayo
Normal - 95% CI (Facility)
99.9 99.9 LZ L -x
T 99 L -
99 • 99
90 90 r - ��' 90
50 So 50 ^vw .ams
10
10 10
1 1
o.l 0.1
o soo iaao o loo zao os l.o Ls .oma
99 X(VI) 9.9 99.--
• 902 Cy90SD10101
o.l oa
-SO 0 30 40000 D 40000 0 20 40
99 99 .
•
90 90
So So
10 10 i nvw .nom
1-_- 1 •
0 1 2 -8 0 8
PRIVLEGED &CONFIDENTIAL —ATTORNEY-CLIENT COMMUNICATION —ATTORNEY
WORK PRODUCT — DO NOT DISTRIBUTE WITHOUT APPROVAL OF COUNSEL

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part 3: Mayo Regional Background Water Supply Well
Data Outlier Test Statistics
APRIL 2016 4 %UICH

Attachment F-1: Mayo Regional Background Water Supply Well Data Outlier Test Statistics
Outlier Tests for Selected Uncensored Variables
User Selected Options
Date/Time of Computation 4/6/2016 12:19:08 PM
From File WorkSheet.xls
Full Precision OFF
Dixon's Outlier Test for Barium (ug/L)
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 108 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.722
For 10% significance level, 108 is an outlier.
For 5% significance level, 108 is an outlier.
For 1 % significance level, 108 is an outlier.
2. Observation Value 1.5 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.109
For 10% significance level, 1.5 is not an outlier.
For 5% significance level, 1.5 is not an outlier.
For 1 % significance level, 1.5 is not an outlier.
Dixon's Outlier Test for Hexavalent Chromium (ug/L)
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 1.6 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.255
For 10% significance level, 1.6 is not an outlier.
For 5% significance level, 1.6 is not an outlier.
For 1 % significance level, 1.6 is not an outlier.
2. Observation Value 0 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.025
For 10% significance level, 0 is not an outlier.
For 5% significance level, 0 is not an outlier.
Haley & Aldrich, Inc.
Outlier test stats_regional.xlsx
Page 1 of 3
4/9/2016

Attachment F-1: Mayo Regional Background Water Supply Well Data Outlier Test Statistics
For 1 % significance level, 0 is not an outlier.
Dixon's Outlier Test for Iron (ug/L)
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 1090 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.887
For 10% significance level, 1090 is an outlier.
For 5% significance level, 1090 is an outlier.
For 1% significance level, 1090 is an outlier.
2. Observation Value 10 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.000
For 10% significance level, 10 is not an outlier.
For 5% significance level, 10 is not an outlier.
For 1 % significance level, 10 is not an outlier.
Dixon's Outlier Test for Lead (ug/L)
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 6.37 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.700
For 10% significance level, 6.37 is an outlier.
For 5% significance level, 6.37 is an outlier.
For 1 % significance level, 6.37 is an outlier.
2. Observation Value 0.1 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.126
For 10% significance level, 0.1 is not an outlier.
For 5% significance level, 0.1 is not an outlier.
For 1 % significance level, 0.1 is not an outlier.
Dixon's Outlier Test for Nickel (ug/L)
Haley & Aldrich, Inc.
Outlier test stats_regional.xlsx
Page 2 of 3
4/9/2016

Attachment F-1: Mayo Regional Background Water Supply Well Data Outlier Test Statistics
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 5 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.000
For 10% significance level, 5 is not an outlier.
For 5% significance level, 5 is not an outlier.
For 1 % significance level, 5 is not an outlier.
2. Observation Value 0.5 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.000
For 10% significance level, 0.5 is not an outlier.
For 5% significance level, 0.5 is not an outlier.
For 1 % significance level, 0.5 is not an outlier.
Dixon's Outlier Test for Vanadium (ug/L)
Number of Observations = 14
10% critical value: 0.492
5% critical value: 0.546
1 % critical value: 0.641
1. Observation Value 19.6 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.900
For 10% significance level, 19.6 is an outlier.
For 5% significance level, 19.6 is an outlier.
For 1 % significance level, 19.6 is an outlier.
2. Observation Value 0.3 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.009
For 10% significance level, 0.3 is not an outlier.
For 5% significance level, 0.3 is not an outlier.
For 1 % significance level, 0.3 is not an outlier.
Haley & Aldrich, Inc.
Outlier test stats_regional.xlsx
Page 3 of 3
4/9/2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part 4: Mayo Facility Background Monitoring Well Data Outlier Test Statistics
APRIL 2016 5 %UICH

Attachment F-1: Mayo Facility Background Monitoring Well Data Outlier Test Statistics
Outlier Tests for Selected Uncensored Variables
User Selected Options
Date/Time of Computation 4/6/2016 4:00:47 PM
From File WorkSheet a.xls
Full Precision OFF
Rosner's Outlier Test for Barium - ug/L - T
Mean 74.54
Standard Deviation 123.4
Number of data 69
Number of suspected outliers 1
Potential Obs. Test Critical Critical
# Mean sd outlier Number value value (5%) value (1%)
1 74.54 122.5 1040 1 7.879 3.254 3.614
For 5% Significance Level, there is 1 Potential Outlier
Potential outliers is: 1040
For 1 % Significance Level, there is 1 Potential Outlier
Potential outliers is: 1040
Rosner's Outlier Test for Cobalt - ug/L - T
Mean 0.976
Standard Deviation 0.186
Number of data 39
Number of suspected outliers 1
Potential Obs.
# Mean sd outlier Number
1 0.976 0.184 0.5 5
For 5% Significance Level, there is no Potential Outlier
For 1% Significance Level, there is no Potential Outlier
Dixon's Outlier Test for Chromium (VI) - ug/L - T
Number of Observations = 24
10% critical value: 0.367
5% critical value: 0.413
1 % critical value: 0.497
1. Observation Value 13.6 is a Potential Outlier (Upper Tail)?
Test Statistic: 0.954
For 10% significance level, 13.6 is an outlier.
Haley & Aldrich, Inc.
Outlier test stats_Facility.xlsx
Test Critical Critical
value value (5%) value (1%)
2.591 3.03 3.37
Page 1 of 3
4/9/2016

Attachment F-1: Mayo Facility Background Monitoring Well Data Outlier Test Statistics
For 5% significance level, 13.6 is an outlier.
For 1% significance level, 13.6 is an outlier.
2. Observation Value 0.005 is a Potential Outlier (Lower Tail)?
Test Statistic: 0.019
For 10% significance level, 0.005 is not an outlier.
For 5% significance level, 0.005 is not an outlier.
For 1 % significance level, 0.005 is not an outlier.
Rosner's Outlier Test for Iron - ug/L - T
Mean 1660
Standard Deviation 7865
Number of data 69
Number of suspected outliers 1
Potential Obs. Test Critical Critical
# Mean sd outlier Number value value (5%) value (1%)
1 1660 7808 65700 1 8.202 3.254 3.614
For 5% Significance Level, there is 1 Potential Outlier
Potential outliers is: 65700
For 1 % Significance Level, there is 1 Potential Outlier
Potential outliers is: 65700
Rosner's Outlier Test for Lead - ug/L - T
Mean 2.576
Standard Deviation 4.457
Number of data 69
Number of suspected outliers 1
Potential Obs. Test Critical Critical
# Mean sd outlier Number value value (5%) value (1%)
1 2.576 4.424 33.1 1 6.899 3.254 3.614
For 5% Significance Level, there is 1 Potential Outlier
Potential outliers is: 33.1
For 1% Significance Level, there is 1 Potential Outlier
Potential outliers is: 33.1
Rosner's Outlier Test for Nickel - ug/L - D
Mean 1.322
Standard Deviation 0.464
Number of data 32
Haley & Aldrich, Inc.
Outlier test stats_Facility.xlsx
Page 2 of 3
4/9/2016

Attachment F-1: Mayo Facility Background Monitoring Well Data Outlier Test Statistics
Number of suspected outliers 1
Potential Obs. Test Critical Critical
# Mean sd outlier Number value value (5%) value (1%)
1 1.322 0.457 2.5 2 2.581 2.94 3.27
For 5% Significance Level, there is no Potential Outlier
For 1% Significance Level, there is no Potential Outlier
Rosner's Outlier Test for Vanadium - ug/L - T
Mean 3.071
Standard Deviation 3.083
Number of data 36
Number of suspected outliers 1
Potential Obs. Test Critical Critical
# Mean sd outlier Number value value (5%) value (1%)
1 3.071 3.04 12.7 18 3.167 2.99 3.33
For 5% Significance Level, there is 1 Potential Outlier
Potential outliers is: 12.7
For 1 % Significance Level, there is no Potential Outlier
Haley & Aldrich, Inc.
Outlier test stats_Facility.xlsx
Page 3 of 3
4/9/2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
ATTACHMENT F-2
Results of Statistical Computations
APRIL 2016 6 %UICH

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part -1: Mayo Regional Background Water Supply Well Data GOF Statistics
APRIL 2016 7 %UICH

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Goodness -of -Fit Test Statistics for Data Sets with Non -Detects
User Selected Options
Date/Time of Computation 4/6/2016 12:25:04 PM
From File WorkSheet.xls
Full Precision OFF
Confidence Coefficient 0.95
Barium (ug/L)
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2Normal ROS
Correlation Coefficient R 0.863 0.823 0.832 0.843
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Num Obs
Num Miss
Num Valid
Detects
NDs
% NDs
Raw Statistics
14
0
14
11
3
21.43%
Data Not Normal
Number
Minimum
Maximum
Mean
Median
SD
Statistics (Non -Detects Only)
3
5
5
5
5
0
Statistics (Detects Only)
11
1.5
108
28.34
19
32.63
Statistics (All: NDs treated as DL value)
14
1.5
108
23.34
10.3
30.29
Statistics (All: NDs treated as DL/2 value)
14
1.5
108
22.8
10.3
30.66
Statistics (Normal ROS Imputed Data)
14
-38.75
108
16.87
10.3
36.93
Statistics (Gamma ROS Imputed Data)
14
0.01
108
22.27
10.3
31.06
Statistics (Lognormal ROS Imputed Data)
14
0.941
108
22.66
10.3
30.76
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
Statistics (Detects Only)
1.013
0.797
27.97
2.775
1.187
0.428
Statistics (NDs = DL)
0.932
0.78
25.04
2.525
1.153
0.457
Statistics (NDs = DL/2)
0.792
0.67
28.77
2.377
1.308
0.55
Statistics (Gamma ROS Estimates)
0.352
0.324
63.28
Statistics (Lognormal ROS Estimates)
2.291
1.434
0.626
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2Normal ROS
Correlation Coefficient R 0.863 0.823 0.832 0.843
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.754
0.85
Data Not Normal
0.284
0.267
Data Not Normal
0.691
0.874
Data Not Normal
0.281
0.237
Data Not Normal
0.703
0.874
Data Not Normal
0.274
0.237
Data Not Normal
0.903
0.874
Data Appear Normal
0.212
0.237
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/2aamma RO:
Correlation Coefficient R 0.983 0.975 0.982 0.99
Anderson -Darling (Detects Only)
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Test value Crit. (0.05) Conclusion with Alpha(0.05)
0.304 0.751
Page 1 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Kolmogorov-Smirnov (Detects Only)
0.162
0.262
Detected Data Appear Gamma Distributed
Anderson -Darling (NDs = DL)
0.575
0.763
Data Appear Lognormal
Kolmogorov-Smirnov (NDs = DL)
0.167
0.236
Data Appear Gamma Distributed
Anderson -Darling (NDs = DL/2)
0.432
0.769
Data Appear Lognormal
Kolmogorov-Smirnov (NDs = DL/2)
0.136
0.237
Data Appear Gamma Distributed
Anderson -Darling (Gamma ROS Estimates)
0.589
0.822
Data Appear Lognormal
Kolmogorov-Smirnov (Gamma ROS Est.)
0.192
0.246
Data Appear Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.984 0.983 0.985 0.991
Hexavalent Chromium (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 1 13 8 5 38.46%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.976
0.85
Data Appear Lognormal
Lilliefors (Detects Only)
0.113
0.267
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.968
0.874
Data Appear Lognormal
Lilliefors (NDs = DL)
0.142
0.237
Data Appear Lognormal
Shapiro -Wilk (NDs = DL/2)
0.959
0.874
Data Appear Lognormal
Lilliefors (NDs = DL/2)
0.154
0.237
Data Appear Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.971
0.874
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.104
0.237
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are not recommended.
0.01
Hexavalent Chromium (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 1 13 8 5 38.46%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number
Minimum
Maximum
Mean
Median
SD
5
0.03
0.6
0.372
0.6
0.312
8
0.079
1.6
0.877
1.02
0.585
13
0.03
1.6
0.683
0.6
0.546
13
0.015
1.6
0.611
0.3
0.575
13
-0.776
1.6
0.44
0.347
0.772
13
0.01
1.6
0.583
0.37
0.598
13
0.0332
1.6
0.58
0.239
0.596
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
1.5
1.021
0.585
-0.5
1.097
-2.195
0.99
0.813
0.69
-0.965
1.405
-1.456
0.802
0.668
0.762
-1.232
1.59
-1.291
0.591
0.506
0.986
-1.269
1.387
-1.093
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.97 0.971 0.938 0.988
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 2 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.916
0.818
Data Appear Normal
Lilliefors (Detects Only)
0.168
0.313
Data Appear Normal
Shapiro -Wilk (NDs = DL)
0.921
0.866
Data Appear Normal
Lilliefors (NDs = DL)
0.176
0.246
Data Appear Normal
Shapiro -Wilk (NDs = DL/2)
0.859
0.866
Data Not Normal
Lilliefors (NDs = DL/2)
0.252
0.246
Data Not Normal
Shapiro -Wilk (Normal ROS Estimates)
0.952
0.866
Data Appear Normal
Lilliefors (Normal ROS Estimates)
0.131
0.246
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO;
Correlation Coefficient R 0.886 0.932 0.927 0.906
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value Crit. (0.05)
0.511
0.728
0.265
0.299
0.514
0.758
0.201
0.243
0.415
0.768
0.167
0.245
0.499
0.783
0.179
0.248
Conclusion with Alpha(0.05)
Detected Data Appear Gamma Distributed
Data Appear Gamma Distributed
Data Appear Gamma Distributed
Data Appear Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.925 0.929 0.939 0.965
Iron (ug/L)
Conclusion with Alpha(0.05)
Data Appear Lognormal
Data Appear Lognormal
Data Not Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Test value
Crit. (0.05)
Shapiro -Wilk (Detects Only)
0.846
0.818
Lilliefors (Detects Only)
0.28
0.313
Shapiro -Wilk (NDs = DL)
0.847
0.866
Lilliefors (NDs = DL)
0.242
0.246
Shapiro -Wilk (NDs = DL/2)
0.868
0.866
Lilliefors (NDs = DL/2)
0.199
0.246
Shapiro -Wilk (Lognormal ROS Estimates)
0.908
0.866
Lilliefors (Lognormal ROS Estimates)
0.193
0.246
Note: Substitution methods such as DL or DU2 are not recommended.
Iron (ug/L)
Conclusion with Alpha(0.05)
Data Appear Lognormal
Data Appear Lognormal
Data Not Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Data Appear Lognormal
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 3 of 9
4/9/2016
Num Obs
Num Miss
Num Valid
Detects
NDs
% NDs
Raw Statistics
14
0
14
8
6
42.86%
Number
Minimum
Maximum
Mean
Median
SD
Statistics (Non -Detects Only)
6
10
50
23.33
10
20.66
Statistics (Detects Only)
8
18
1090
216.7
104.5
354.8
Statistics (All: NDs treated as DL value)
14
10
1090
133.8
62
279
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 3 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Statistics (All: NDs treated as DL/2 value)
14
5
1090
128.8
49.5
280.9
Statistics (Normal ROS Imputed Data)
14
-768
1090
-86.09
46
460.1
Statistics (Gamma ROS Imputed Data)
14
0.01
1090
123.8
46
283.2
Statistics (Lognormal ROS Imputed Data)
14
2.331
1090
127.4
46
281.5
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
Statistics (Detects Only)
0.866
0.625
250.3
4.7
1.128
0.24
Statistics (NDs = DL)
0.619
0.534
216.3
3.903
1.366
0.35
Statistics (NDs = DL/2)
0.506
0.445
254.6
3.606
1.635
0.453
Statistics (Gamma ROS Estimates)
0.182
0.19
681
Statistics (Lognormal ROS Estimates)
3.515
1.7
0.484
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.699 0.641 0.646 0.651
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.521
0.818
Data Not Normal
0.469
0.313
Data Not Normal
0.442
0.874
Data Not Normal
0.431
0.237
Data Not Normal
0.447
0.874
Data Not Normal
0.424
0.237
Data Not Normal
0.88
0.874
Data Appear Normal
0.246
0.237
Data Not Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/2aamma RO'
Correlation Coefficient R 0.892 0.869 0.887 0.943
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
1.065
0.741
0.396
0.303
Data Not Gamma Distributed
1.054
0.783
0.267
0.24
Data Not Gamma Distributed
0.884
0.793
0.241
0.242
Detected Data appear Approximate Gamma Distri
1.221
0.896
0.285
0.254
Data Not Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.906 0.944 0.954 0.972
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only) 0.862 0.818 Data Appear Lognormal
Lilliefors (Detects Only) 0.311 0.313 Data Appear Lognormal
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 4 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Shapiro -Wilk (NDs = DL)
0.889
0.874
Data Appear Lognormal
Lilliefors (NDs = DL)
0.165
0.237
Data Appear Lognormal
Shapiro -Wilk (NDs = DL/2)
0.902
0.874
Data Appear Lognormal
Lilliefors (NDs = DL/2)
0.175
0.237
Data Appear Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.946
0.874
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.179
0.237
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
6.37
Lead (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 0 14 8 6 42.86%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number
Minimum
Maximum
Mean
Median
SD
6
0.1
1
0.85
1
0.367
8
0.24
6.37
1.824
1.1
2.028
14
0.1
6.37
1.406
1
1.587
14
0.05
6.37
1.224
0.5
1.657
14
-2.456
6.37
0.821
0.656
2.115
14
0.01
6.37
1.144
0.533
1.714
14
0.0746
6.37
1.191
0.59
1.68
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
1.123
0.785
1.624
0.0938
1.097
11.7
1.247
1.027
1.128
-0.111
1.024
-9.235
0.951
0.795
1.287
-0.408
1.162
-2.848
0.443
0.396
2.582
-0.536
1.241
-2.314
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.874 0.808 0.783 0.889
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.777
0.818
Data Not Normal
0.224
0.313
Data Appear Normal
0.679
0.874
Data Not Normal
0.315
0.237
Data Not Normal
0.636
0.874
Data Not Normal
0.338
0.237
Data Not Normal
0.907
0.874
Data Appear Normal
0.166
0.237
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO:
Correlation Coefficient R 0.984 0.942 0.952 0.99
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 5 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Anderson -Darling (Detects Only)
0.272
0.734
Data Appear Lognormal
Kolmogorov-Smirnov (Detects Only)
0.206
0.301
Detected Data Appear Gamma Distributed
Anderson -Darling (NDs = DL)
0.499
0.755
Data Appear Lognormal
Kolmogorov-Smirnov (NDs = DL)
0.235
0.234
Detected Data appear Approximate Gamma Distri
Anderson -Darling (NDs = DL/2)
0.86
0.762
Data Appear Lognormal
Kolmogorov-Smirnov (NDs = DL/2)
0.27
0.236
Data Not Gamma Distributed
Anderson -Darling (Gamma ROS Estimates)
0.431
0.804
Data Appear Lognormal
Kolmogorov-Smirnov (Gamma ROS Est.)
0.189
0.243
Data Appear Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.99 0.97 0.953 0.994
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.973
0.818
Data Appear Lognormal
Lilliefors (Detects Only)
0.159
0.313
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.956
0.874
Data Appear Lognormal
Lilliefors (NDs = DL)
0.186
0.237
Data Appear Lognormal
Shapiro -Wilk (NDs = DL/2)
0.929
0.874
Data Appear Lognormal
Lilliefors (NDs = DL/2)
0.197
0.237
Data Appear Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.985
0.874
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.113
0.237
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
Nickel (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 0 14 3 11 78.57%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number Minimum Maximum Mean Median SD
11 0.5 5 3.773 5 2.102
3 0.63 2.6 1.61 1.6 0.985
14 0.5 5 3.309 5 2.097
14 0.25 2.6 1.827 2.5 1.006
14 -2.945 2.801 -0.0719 -0.0719 1.883
14 0.01 2.838 0.765 0.182 1.016
14 0.0548 3.206 0.862 0.43 1.004
K hat K Star Theta hat Log Mean Log Stdv Log CV
N/A N/A N/A N/A N/A N/A
1.547 1.263 2.139 0.84 1.024 1.219
1.775 1.442 1.029 0.295 0.985 3.334
0.348 0.321 2.198
-0.87 1.336 -1.535
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 1 0.856 0.834 0.731
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 6 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
1
0.767
Data Appear Normal
0.176
0.512
Data Appear Normal
0.705
0.874
Data Not Normal
0.361
0.237
Data Not Normal
0.676
0.874
Data Not Normal
0.391
0.237
Data Not Normal
0.959
0.874
Data Appear Normal
0.0984
0.237
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/2aamma RO:
Correlation Coefficient R N/A 0.721 0.682 0.926
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.984 0.855 0.816 0.988
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
Anderson -Darling (Detects Only)
N/A
N/A
Kolmogorov-Smirnov (Detects Only)
N/A
N/A
Anderson -Darling (NDs = DL)
1.93
0.75
Data Not Lognormal
Kolmogorov-Smirnov (NDs = DL)
0.363
0.233
Data Not Gamma Distributed
Anderson -Darling (NDs = DL/2)
2.385
0.748
Data Not Lognormal
Kolmogorov-Smirnov (NDs = DL/2)
0.397
0.232
Data Not Gamma Distributed
Anderson -Darling (Gamma ROS Estimates)
1.337
0.823
Data Appear Lognormal
Kolmogorov-Smirnov (Gamma ROS Est.)
0.329
0.246
Data Not Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.984 0.855 0.816 0.988
Vanadium (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 0 14 7 7 50.00%
Number Minimum Maximum Mean Median SD
Statistics (Non -Detects Only) 7 0.3 1 0.8 1 0.342
Statistics (Detects Only) 7 0.318 19.6 5.578 1.6 7.978
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 7 of 9
4/9/2016
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
N/A
N/A
Lilliefors (Detects Only)
N/A
N/A
Shapiro -Wilk (NDs = DL)
0.706
0.874
Data Not Lognormal
Lilliefors (NDs = DL)
0.345
0.237
Data Not Lognormal
Shapiro -Wilk (NDs = DL/2)
0.65
0.874
Data Not Lognormal
Lilliefors (NDs = DL/2)
0.379
0.237
Data Not Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.957
0.874
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.116
0.237
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are not recommended.
Vanadium (ug/L)
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 14 0 14 7 7 50.00%
Number Minimum Maximum Mean Median SD
Statistics (Non -Detects Only) 7 0.3 1 0.8 1 0.342
Statistics (Detects Only) 7 0.318 19.6 5.578 1.6 7.978
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 7 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Statistics (All: NDs treated as DL value)
14
0.3
19.6
3.189
1
5.964
Statistics (All: NDs treated as DL/2 value)
14
0.15
19.6
2.989
0.5
6.05
Statistics (Normal ROS Imputed Data)
14
-13.81
19.6
-0.632
0.364
9.273
Statistics (Gamma ROS Imputed Data)
14
0.01
19.6
2.823
0.364
6.128
Statistics (Lognormal ROS Imputed Data)
14
0.0161
19.6
2.884
0.37
6.101
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
Statistics (Detects Only)
0.553
0.412
10.08
0.589
1.689
2.867
Statistics (NDs = DL)
0.596
0.516
5.348
0.122
1.308
10.68
Statistics (NDs = DL/2)
0.484
0.428
6.175
-0.224
1.479
-6.599
Statistics (Gamma ROS Estimates)
0.255
0.248
11.08
Statistics (Lognormal ROS Estimates)
-0.923
2.161
-2.342
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.849 0.714 0.706 0.762
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.714
0.803
Data Not Normal
0.376
0.335
Data Not Normal
0.524
0.874
Data Not Normal
0.42
0.237
Data Not Normal
0.514
0.874
Data Not Normal
0.406
0.237
Data Not Normal
0.914
0.874
Data Appear Normal
0.235
0.237
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO:
Correlation Coefficient R 0.953 0.927 0.936 0.958
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.616
0.748
0.26
0.326
Detected Data Appear Gamma Distributed
1.793
0.785
0.329
0.24
Data Not Gamma Distributed
2.049
0.796
0.389
0.242
Data Not Gamma Distributed
1.093
0.854
0.244
0.25
Detected Data appear Approximate Gamma Distri
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.948 0.914 0.902 0.983
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only) 0.875 0.803 Data Appear Lognormal
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Page 8 of 9
4/9/2016

Attachment F-2: Mayo Regional Background Water Supply Well Data GOF Statistics
Lilliefors (Detects Only)
0.217
0.335
Shapiro -Wilk (NDs = DL)
0.832
0.874
Lilliefors (NDs = DL)
0.252
0.237
Shapiro -Wilk (NDs = DL/2)
0.813
0.874
Lilliefors (NDs = DL/2)
0.339
0.237
Shapiro -Wilk (Lognormal ROS Estimates)
0.957
0.874
Lilliefors (Lognormal ROS Estimates)
0.114
0.237
Note: Substitution methods such as DL or DL/2 are
not recommended.
Haley & Aldrich, Inc.
GOF test stats_regional.xlsx
Data Appear Lognormal
Data Not Lognormal
Data Not Lognormal
Data Not Lognormal
Data Not Lognormal
Data Appear Lognormal
Data Appear Lognormal
Page 9 of 9
4/9/2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part -2: Mayo Facility Background Monitoring Well Data GOF Statistics
APRIL 2016 8 %UICH

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Goodness -of -Fit Test Statistics for Data Sets with Non -Detects
User Selected Options
Num Obs
Date/Time of Computation
4/6/2016 4:04:44 PM
From File
WorkSheet a.xls
Full Precision
OFF
Confidence Coefficient
0.95
Barium - ug/L - T
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.974 0.974 0.976 0.977
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Lilliefors (Detects Only)
Num Obs
Num Miss
Num Valid
Detects
NDs
% NDs
Raw Statistics
72
4
68
66
2
2.94%
0.107
Number
Minimum
Maximum
Mean
Median
SD
Statistics (Non -Detects Only)
2
5
5
5
5
0
Statistics (Detects Only)
66
5
175
62.02
60.6
35.93
Statistics (All: NDs treated as DL value)
68
5
175
60.34
60.1
36.7
Statistics (All: NDs treated as DL/2 value)
68
2.5
175
60.27
60.1
36.82
Statistics (Normal ROS Imputed Data)
68
-32.02
175
59.41
60.1
38.49
Statistics (Gamma ROS Imputed Data)
68
5
175
60.5
60.1
36.47
Statistics (Lognormal ROS Imputed Data)
68
5
175
60.43
60.1
36.58
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
Statistics (Detects Only)
2.315
2.22
26.79
3.896
0.782
0.201
Statistics (NDs = DL)
1.995
1.917
30.25
3.829
0.863
0.225
Statistics (NDs = DL/2)
1.872
1.799
32.2
3.809
0.922
0.242
Statistics (Gamma ROS Estimates)
2.132
2.047
28.38
Statistics (Lognormal ROS Estimates)
3.842
0.832
0.216
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.974 0.974 0.976 0.977
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Lilliefors (Detects Only)
0.1
0.109
Data Appear Normal
Lilliefors (NDs = DL)
0.0993
0.107
Data Appear Normal
Lilliefors (NDs = DL/2)
0.0991
0.107
Data Appear Normal
Lilliefors (Normal ROS Estimates)
0.0954
0.107
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO:
Correlation Coefficient R 0.967 0.963 0.96 0.966
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
1.303
0.761
0.115
0.111
Data Not Gamma Distributed
1.517
0.763
0.126
0.109
Data Not Gamma Distributed
1.569
0.765
Page 1 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Kolmogorov-Smirnov (NDs = DL/2) 0.133 0.11 Data Not Gamma Distributed
Anderson -Darling (Gamma ROS Estimates) 1.371 0.763
Kolmogorov-Smirnov (Gamma ROS Est.) 0.118 0.109 Data Not Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.949 0.941 0.93 0.948
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Lilliefors (Detects Only)
0.16
0.109
Data Not Lognormal
Lilliefors (NDs = DL)
0.171
0.107
Data Not Lognormal
Lilliefors (NDs = DL/2)
0.177
0.107
Data Not Lognormal
Lilliefors (Lognormal ROS Estimates)
0.166
0.107
Data Not Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
39
Cobalt - ug/L - T
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 72 33 39 5 34 87.18%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number
Minimum
Maximum
Mean
Median
SD
34
0.5
1
0.956
1
0.144
5
0.51
1.41
1.114
1.19
0.362
39
0.5
1.41
0.976
1
0.186
39
0.25
1.41
0.559
0.5
0.254
39
-1.461
1.41
-0.0106
-0.0101
0.704
39
0.01
1.41
0.307
0.121
0.406
39
0.0582
1.41
0.403
0.297
0.345
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
8.649
3.593
0.129
0.049
0.417
8.508
22
20.33
0.0444
-0.047
0.233
-4.954
7.247
6.706
0.0772
-0.651
0.356
-0.547
0.467
0.448
0.657
-1.214
0.791
-0.651
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2Normal ROS
Correlation Coefficient R 0.916 0.761 0.702 0.979
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.845
0.762
Data Appear Normal
0.274
0.396
Data Appear Normal
0.6
0.939
Data Not Normal
0.448
0.142
Data Not Normal
0.511
0.939
Data Not Normal
0.475
0.142
Data Not Normal
0.984
0.939
Data Appear Normal
Page 2 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Lilliefors (Normal ROS Estimates) 0.0437 0.142 Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO;
Correlation Coefficient R 0.851 0.748 0.767 0.964
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.609
0.679
0.335
0.32
0.358
Detected Data Appear Gamma Distributed
8.857
0.747
Data Not Lognormal
0.471
0.141
Data Not Gamma Distributed
8.727
0.75
0.598
0.445
0.142
Data Not Gamma Distributed
2.445
0.82
Data Not Lognormal
0.277
0.15
Data Not Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.869 0.726 0.76 0.996
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.768
0.762
Data Appear Lognormal
Lilliefors (Detects Only)
0.335
0.396
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.542
0.939
Data Not Lognormal
Lilliefors (NDs = DL)
0.477
0.142
Data Not Lognormal
Shapiro -Wilk (NDs = DL/2)
0.598
0.939
Data Not Lognormal
Lilliefors (NDs = DL/2)
0.422
0.142
Data Not Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.981
0.939
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.0525
0.142
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
0.015
Chromium (VI) - ug/L - T
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 72 48 24 13 11 45.83%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Number
Minimum
Maximum
Mean
Median
SD
11
0.021
0.03
0.0292
0.03
0.00271
13
0.005
13.6
2.26
0.357
4.736
24
0.005
13.6
1.238
0.03
3.604
24
0.005
13.6
1.231
0.015
3.607
24
-5.963
13.6
0.224
0.015
4.298
24
0.005
13.6
1.229
0.0115
3.607
24
6.1985E-4
13.6
1.235
0.0444
3.606
K hat
Statistics (Detects Only) 0.335
Statistics (NDs = DL) 0.28
K Star Theta hat Log Mean Log Stdv Log CV
0.309 6.742 -1.204 2.33 -1.935
0.273 4.416 -2.274 2.062 -0.906
Page 3 of 9
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Statistics (NDs = DL/2) 0.253 0.249 4.863 -2.592
Statistics (Gamma ROS Estimates) 0.241 0.238 5.106
Statistics (Lognormal ROS Estimates) -2.735
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.7 0.591 0.592 0.621
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
2.283 -0.881
2.581 -0.944
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.5
0.866
Data Not Normal
0.48
0.246
Data Not Normal
0.365
0.916
Data Not Normal
0.483
0.181
Data Not Normal
0.366
0.916
Data Not Normal
0.482
0.181
Data Not Normal
0.695
0.916
Data Not Normal
0.378
0.181
Data Not Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma ROc
Correlation Coefficient R 0.913 0.893 0.898 0.901
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
1.163
0.823
0.219
0.349
0.255
Data Not Gamma Distributed
3.286
0.861
Data Not Lognormal
0.31
0.194
Data Not Gamma Distributed
3.322
0.873
0.802
0.32
0.195
Data Not Gamma Distributed
3.257
0.879
Data Not Lognormal
0.305
0.196
Data Not Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.951 0.923 0.898 0.982
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.904
0.866
Data Appear Lognormal
Lilliefors (Detects Only)
0.219
0.246
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.851
0.916
Data Not Lognormal
Lilliefors (NDs = DL)
0.308
0.181
Data Not Lognormal
Shapiro -Wilk (NDs = DL/2)
0.802
0.916
Data Not Lognormal
Lilliefors (NDs = DL/2)
0.325
0.181
Data Not Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.96
0.916
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.115
0.181
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Page 4 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Lead - ug/L - T
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.902 0.755 0.631 0.501
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
Num Obs
Num Miss
Num Valid
Detects
NDs
% NDs
Raw Statistics
72
4
68
5
63
92.65%
0.107
Number
Minimum
Maximum
Mean
Median
SD
Statistics (Non -Detects Only)
63
0.1
5
1.86
1
1.699
Statistics (Detects Only)
5
0.1
12.9
5.486
2.3
6.427
Statistics (All: NDs treated as DL value)
68
0.1
12.9
2.127
1
2.459
Statistics (All: NDs treated as DL/2 value)
68
0.05
12.9
1.265
0.5
2.138
Statistics (Normal ROS Imputed Data)
68
-17.62
12.9
-4.066
-4.031
6.167
Statistics (Gamma ROS Imputed Data)
68
0.01
12.9
0.722
0.01
2.252
Statistics (Lognormal ROS Imputed Data)
68
9.0233E-5
12.9
0.524
0.0259
2.125
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
Statistics (Detects Only)
0.461
0.318
11.9
0.306
2.367
7.723
Statistics (NDs = DL)
1.207
1.163
1.763
0.286
0.979
3.42
Statistics (NDs = DL/2)
0.979
0.945
1.293
-0.356
0.997
-2.799
Statistics (Gamma ROS Estimates)
0.232
0.232
3.112
Statistics (Lognormal ROS Estimates)
-3.67
2.549
-0.695
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.902 0.755 0.631 0.501
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.782
0.762
Data Appear Normal
Lilliefors (Detects Only)
0.29
0.396
Data Appear Normal
Shapiro -Wilk (NDs = DL)
N/A
N/A
Lilliefors (NDs = DL)
0.427
0.107
Data Not Normal
Shapiro -Wilk (NDs = DL/2)
N/A
N/A
0.111
Lilliefors (NDs = DL/2)
0.39
0.107
Data Not Normal
Shapiro -Wilk (Normal ROS Estimates)
N/A
N/A
Lilliefors (Normal ROS Estimates)
0.0319
0.107
Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO;
Correlation Coefficient R 0.836 0.9 0.828 0.943
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.479
0.716
0.26
0.373
Detected Data Appear Gamma Distributed
10.21
0.776
0.411
0.111
Data Not Gamma Distributed
10.33
0.781
0.419
0.111
Data Not Gamma Distributed
14.67
0.899
0.46
0.119
Data Not Gamma Distributed
Page 5 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.932 0.852 0.854 0.998
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.834
0.762
Data Appear Lognormal
Lilliefors (Detects Only)
0.239
0.396
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
N/A
N/A
0.403
Lilliefors (NDs = DL)
0.365
0.107
Data Not Lognormal
Shapiro -Wilk (NDs = DL/2)
N/A
N/A
0.5
Lilliefors (NDs = DL/2)
0.382
0.107
Data Not Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
N/A
N/A
1.056
Lilliefors (Lognormal ROS Estimates)
0.0301
0.107
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
1.067
Nickel - ug/L - D
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 72 40 32 16 16 50.00%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Statistics (Detects Only)
Statistics (NDs = DL)
Statistics (NDs = DL/2)
Statistics (Gamma ROS Estimates)
Statistics (Lognormal ROS Estimates)
Number
Minimum
Maximum
Mean
Median
SD
16
0.5
2.5
1.063
1
0.403
16
0.96
2.13
1.581
1.565
0.373
32
0.5
2.5
1.322
1.015
0.464
32
0.25
2.13
1.056
0.995
0.609
32
-0.0272
2.13
1.125
1.067
0.581
32
0.277
2.13
1.181
1.095
0.515
32
0.535
2.13
1.223
1.097
0.465
K hat
K Star
Theta hat
Log Mean
Log Stdv
Log CV
18.03
14.69
0.0877
0.43
0.249
0.58
8.947
8.129
0.148
0.222
0.342
1.542
2.948
2.692
0.358
-0.125
0.624
-5.008
4.833
4.4
0.244
0.131
0.383
2.918
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2 Normal ROS
Correlation Coefficient R 0.983 0.922 0.927 0.983
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.949
0.887
Data Appear Normal
0.159
0.222
Data Appear Normal
0.854
0.93
Data Not Normal
0.266
0.157
Data Not Normal
0.84
0.93
Data Not Normal
0.288
0.157
Data Not Normal
Page 6 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Shapiro -Wilk (Normal ROS Estimates) 0.97 0.93 Data Appear Normal
Lilliefors (Normal ROS Estimates) 0.096 0.157 Data Appear Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/2aamma ROc
Correlation Coefficient R 0.97 0.952 0.935 0.977
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.366
0.737
0.174
0.177
0.215
Detected Data Appear Gamma Distributed
2.084
0.747
Data Not Lognormal
0.258
0.156
Data Not Gamma Distributed
2.294
0.753
0.839
0.294
0.157
Data Not Gamma Distributed
0.229
0.748
Data Not Lognormal
0.0923
0.156
Data Appear Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.976 0.929 0.923 0.989
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.939
0.887
Data Appear Lognormal
Lilliefors (Detects Only)
0.174
0.222
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.873
0.93
Data Not Lognormal
Lilliefors (NDs = DL)
0.244
0.157
Data Not Lognormal
Shapiro -Wilk (NDs = DL/2)
0.839
0.93
Data Not Lognormal
Lilliefors (NDs = DL/2)
0.287
0.157
Data Not Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.963
0.93
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.102
0.157
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
1.775
Vanadium - ug/L - T
Num Obs Num Miss Num Valid Detects NDs % NDs
Raw Statistics 72 36 36 34 2 5.56%
Statistics (Non -Detects Only)
Statistics (Detects Only)
Statistics (All: NDs treated as DL value)
Statistics (All: NDs treated as DL/2 value)
Statistics (Normal ROS Imputed Data)
Statistics (Gamma ROS Imputed Data)
Statistics (Lognormal ROS Imputed Data)
Number
Minimum
Maximum
Mean
Median
SD
2
0.3
1
0.65
0.65
0.495
34
0.381
12.7
3.214
1.91
3.114
36
0.3
12.7
3.071
1.775
3.083
36
0.15
12.7
3.053
1.775
3.098
36
-3.965
12.7
2.904
1.775
3.312
36
0.01
12.7
3.036
1.775
3.114
36
0.18
12.7
3.055
1.775
3.096
K hat K Star Theta hat Log Mean Log Stdv Log CV
Statistics (Detects Only) 1.323 1.226 2.43 0.744 0.963 1.294
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Page 7 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Statistics (NDs = DL) 1.244 1.159 2.468 0.669 0.997 1.489
Statistics (NDs = DL/2) 1.168 1.09 2.613 0.631 1.058 1.678
Statistics (Gamma ROS Estimates) 0.883 0.828 3.438
Statistics (Lognormal ROS Estimates) 0.638 1.043 1.636
Normal GOF Test Results
No NDs NDs = DL NDs = DL/2Normal ROS
Correlation Coefficient R 0.891 0.886 0.889 0.891
Shapiro -Wilk (Detects Only)
Lilliefors (Detects Only)
Shapiro -Wilk (NDs = DL)
Lilliefors (NDs = DL)
Shapiro -Wilk (NDs = DL/2)
Lilliefors (NDs = DL/2)
Shapiro -Wilk (Normal ROS Estimates)
Lilliefors (Normal ROS Estimates)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.794
0.933
Data Not Normal
0.182
0.152
Data Not Normal
0.785
0.935
Data Not Normal
0.191
0.148
Data Not Normal
0.79
0.935
Data Not Normal
0.189
0.148
Data Not Normal
0.873
0.935
Data Not Normal
0.168
0.148
Data Not Normal
Gamma GOF Test Results
No NDs NDs = DL NDs = DL/23amma RO:
Correlation Coefficient R 0.985 0.986 0.987 0.988
Anderson -Darling (Detects Only)
Kolmogorov-Smirnov (Detects Only)
Anderson -Darling (NDs = DL)
Kolmogorov-Smirnov (NDs = DL)
Anderson -Darling (NDs = DL/2)
Kolmogorov-Smirnov (NDs = DL/2)
Anderson -Darling (Gamma ROS Estimates)
Kolmogorov-Smirnov (Gamma ROS Est.)
Test value
Crit. (0.05)
Conclusion with Alpha(0.05)
0.402
0.769
0.0946
0.115
0.154
Detected Data Appear Gamma Distributed
0.43
0.771
Data Appear Lognormal
0.117
0.15
Data Appear Gamma Distributed
0.346
0.773
0.978
0.104
0.151
Data Appear Gamma Distributed
0.35
0.782
Data Appear Lognormal
0.0869
0.152
Data Appear Gamma Distributed
Lognormal GOF Test Results
No NDs NDs = DL NDs = DL/2 Log ROS
Correlation Coefficient R 0.992 0.993 0.992 0.993
Test value Crit. (0.05) Conclusion with Alpha(0.05)
Shapiro -Wilk (Detects Only)
0.968
0.933
Data Appear Lognormal
Lilliefors (Detects Only)
0.0946
0.152
Data Appear Lognormal
Shapiro -Wilk (NDs = DL)
0.971
0.935
Data Appear Lognormal
Lilliefors (NDs = DL)
0.0919
0.148
Data Appear Lognormal
Shapiro -Wilk (NDs = DL/2)
0.978
0.935
Data Appear Lognormal
Lilliefors (NDs = DL/2)
0.0905
0.148
Data Appear Lognormal
Shapiro -Wilk (Lognormal ROS Estimates)
0.978
0.935
Data Appear Lognormal
Lilliefors (Lognormal ROS Estimates)
0.0915
0.148
Data Appear Lognormal
Note: Substitution methods such as DL or DU2 are
not recommended.
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Page 8 of 9
4/9/2016

Attachment F-2: Mayo Facility Background Monitoring Well Data GOF Statistics
Goodness -of -Fit Test Statistics for Uncensored Full Data Sets without Non -Detects
User Selected Options
Date/Time of Computation 4/6/2016 4:04:19 PM
From File WorkSheet a.xls
Full Precision OFF
Confidence Coefficient 0.95
Iron - ug/L - T
Raw Statistics
0.83
Number of Valid Observations
68
Number of Missing Observations
4
Number of Distinct Observations
66
Minimum
22
Maximum
4610
Mean of Raw Data
717.9
Standard Deviation of Raw Data
823.1
Khat
1.093
Theta hat
657.1
Kstar
1.054
Theta star
681
Mean of Log Transformed Data
6.053
Standard Deviation of Log Transformed Data
1.097
Normal GOF Test Results
Correlation Coefficient R
0.83
Approximate Shapiro Wilk Test Statistic
0.706
Approximate Shapiro Wilk P Value
0
Lilliefors Test Statistic
0.24
Lilliefors Critical (0.05) Value
0.107
Data not Normal at (0.05) Significance Level
Gamma GOF Test Results
Correlation Coefficient R 0.968
A -D Test Statistic 1.212
A -D Critical (0.05) Value 0.778
K -S Test Statistic 0.131
K -S Critical(0.05) Value 0.111
Data not Gamma Distributed at (0.05) Significance Level
Lognormal GOF Test Results
Correlation Coefficient R
0.983
Approximate Shapiro Wilk Test Statistic
0.961
Approximate Shapiro Wilk P Value
0.0915
Lilliefors Test Statistic
0.122
Lilliefors Critical (0.05) Value
0.107
Data appear Approximate—Lognormal at (0.05) Significance Level
Haley & Aldrich, Inc.
GOF after removing outliers test stats_Facility.xlsx
Page 9 of 9
4/9/2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
ATTACHMENT F-3
Method Computation Details
APRIL 2016 9 %UICH

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part -1: Mayo Regional Background Water Supply Well Data BTVs Statistics
APRIL 2016 10 %UICH

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
User Selected Options
Date/Time of Computation
From File
Full Precision
Confidence Coefficient
Coverage
Different or Future K Observations
Number of Bootstrap Operations
Barium (ug/L)
Background Statistics for Data Sets with Non -Detects
4/6/2016 12:25:30 PM
WorkSheet.xls
OFF
95%
95%
1
2000
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614
Page 1 of 6
Number of Missing Observations
General Statistics
Total Number of Observations
14
Number of Distinct Observations
12
Number of Detects
11
Number of Distinct Detects
11
Minimum Detect
1.5
Maximum Detect
108
Variance Detected
1065
Mean Detected
28.34
Mean of Detected Logged Data
2.775
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614
Page 1 of 6
Number of Missing Observations
0
Number of Non -Detects
3
Number of Distinct Non -Detects
1
Minimum Non -Detect
5
Maximum Non -Detect
5
Percent Non -Detects
21.43%
SD Detected
32.63
SD of Detected Logged Data
1.187
d2max (for USL) 2.372
Gamma GOF Tests on Detected Observations Only
A -D Test Statistic 0.304 Anderson -Darling GOF Test
5% A -D Critical Value 0.751 Detected data appear Gamma Distributed at 5% Significance
Level
K -S Test Statistic 0.162 Kolmogrov-Smirnoff GOF
5% K -S Critical Value 0.262 Detected data appear Gamma Distributed at 5% Significance
Level
Detected data appear Gamma Distributed at 5% Significance Level
Gamma Statistics on Detected Data Only
k hat (MLE) 1.013 k star (bias corrected MLE)
0.797
Theta hat (MLE) 27.97 Theta star (bias corrected MLE)
35.54
nu hat (MLE) 22.28 nu star (bias corrected)
17.54
MLE Mean (bias corrected) 28.34
MLE Sd (bias corrected) 31.73 95% Percentile of Chisquare (2k)
5.179
Gamma ROS Statistics using Imputed Non -Detects
GROS may not be used when data set has > 50% NDs with many tied observations at multiple DLs
GROS may not be used when kstar of detected data is small such as < 0.1
For such situations, GROS method tends to yield inflated values of UCLs and BTVs
For gamma distributed detected data, BTVs and UCLs may be computed using gamma distribution on KM estimates
Minimum 0.01 Mean
22.27
Maximum 108 Median
10.3
SD 31.06 CV
1.395
k hat (MLE) 0.352 k star (bias corrected MLE)
0.324
Theta hat (MILE) 63.28 Theta star (bias corrected MLE)
68.71
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx
4/9/2016

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
0.579
nu hat (KM)
Page 2 of 6
nu hat (MLE) 9.852 nu star (bias corrected)
9.074
MLE Mean (bias corrected) 22.27 MLE Sd (bias corrected)
39.11
95% Percentile of Chisquare (2k) 2.892 90% Percentile
65.02
95% Percentile 99.33 99% Percentile
187.7
The following statistics are computed using Gamma ROS Statistics on Imputed Data
135.1
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
1.924
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 197.6 284.1 95% Approx. Gamma UPL 106
131.7
95% Gamma USL 165.1 227.3
General Statistics
The following statistics are computed using gamma distribution and KM estimates
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
k hat (KM)
0.579
nu hat (KM)
16.2
WH
HW
WH
HW
95% Approx. Gamma UTL with 95% Coverage 141.6
161.8
95% Approx. Gamma UPL 83.03
87.71
95% Gamma USL 121.2
135.1
95% KM USL
1.924
Hexavalent Chromium (ug/L)
Mean
0.611
General Statistics
0.575
95% UTL95% Coverage
Total Number of Observations
13
Number of Missing Observations
1
Number of Distinct Observations
10
1.557
Number of Detects
8
Number of Non -Detects
5
Number of Distinct Detects
8
Number of Distinct Non -Detects
2
Minimum Detect
0.079
Minimum Non -Detect
0.03
Maximum Detect
1.6
Maximum Non -Detect
0.6
Variance Detected
0.342
Percent Non -Detects
38.46%
Mean Detected
0.877
SD Detected
0.585
Mean of Detected Logged Data
-0.5
SD of Detected Logged Data
1.097
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.671 d2max (for USL) 2.331
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.916 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.818 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.168 Lilliefors GOF Test
5% Lilliefors Critical Value 0.313 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
0.579
SD
0.577
95% UTL95% Coverage
2.12
95% KM UPL (t)
1.646
90% KM Percentile (z)
1.318
95% KM Percentile (z)
1.528
99% KM Percentile (z)
1.921
95% KM USL
1.924
DL/2 Substitution Background Statistics Assuming Normal Distribution
Mean
0.611
SD
0.575
95% UTL95% Coverage
2.147
95% UPL (t)
1.674
90% Percentile (z)
1.348
95% Percentile (z)
1.557
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx 4/9/2016

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
Iron (ug/L)
Lead (ug/L)
99% Percentile (z) 1.949
DL/2 is not a recommended method. DL/2 provided for comparisons and historical reasons
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614
Page 3 of 6
95% USL 1.951
Number of Missing Observations 0
Number of Non -Detects
General Statistics
Total Number of Observations
14
Number of Distinct Observations
9
Number of Detects
8
Number of Distinct Detects
7
Minimum Detect
18
Maximum Detect
1090
Variance Detected
125915
Mean Detected
216.7
Mean of Detected Logged Data
4.7
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614
Page 3 of 6
95% USL 1.951
Number of Missing Observations 0
Number of Non -Detects
6
Number of Distinct Non -Detects
2
Minimum Non -Detect
10
Maximum Non -Detect
50
Percent Non -Detects
42.86%
SD Detected
354.8
SD of Detected Logged Data
1.128
d2max (for USL) 2.372
Lognormal GOF Test on Detected Observations Only
Shapiro Wilk Test Statistic
0.862 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value
0.818 Detected Data appear Lognormal at 5% Significance Level
Lilliefors Test Statistic
0.311 Lilliefors GOF Test
5% Lilliefors Critical Value
0.313 Detected Data appear Lognormal at 5% Significance Level
Detected Data appear
Lognormal at 5% Significance Level
Background Lognormal ROS Statistics Assuming Lognormal Distribution Using Imputed Non -Detects
Mean in Original Scale
127.4
Mean in Log Scale
3.515
SD in Original Scale
281.5
SD in Log Scale
1.7
95% UTL95% Coverage
2860
95% BCA UTL95% Coverage
1090
95% Bootstrap (%) UTL95% Coverage
1090
95% UPL (t)
758.4
90% Percentile (z)
297
95% Percentile (z)
550.7
99% Percentile (z)
1754
95% USL
1894
Statistics using KM estimates on Logged Data and Assuming Lognormal Distribution
KM Mean of Logged Data
3.69 95% KM UTL (Lognormal)95% Coverage
1626
KM SD of Logged Data
1.417
95% KM UPL (Lognormal)
537.6
95% KM Percentile Lognormal (z)
411.7
95% KM USL (Lognormal)
1153
Background DL/2 Statistics Assuming Lognormal Distribution
Mean in Original Scale
128.8
Mean in Log Scale
3.606
SD in Original Scale
280.9
SD in Log Scale
1.635
95% UTL95% Coverage
2640
95% UPL (t)
736.6
90% Percentile (z)
299
95% Percentile (z)
541.5
99% Percentile (z)
1650
95% USL
1776
DL/2 is not a Recommended Method. DL/2 provided for comparisons and historical reasons.
General Statistics
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx 4/9/2016

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
Total Number of Observations
14
Number of Distinct Observations
10
Number of Detects
8
Number of Distinct Detects
8
Minimum Detect
0.24
Maximum Detect
6.37
Variance Detected
4.114
Mean Detected
1.824
Mean of Detected Logged Data
0.0938
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614
Page 4 of 6
Number of Missing Observations 0
Number of Non -Detects
6
Number of Distinct Non -Detects
2
Minimum Non -Detect
0.1
Maximum Non -Detect
1
Percent Non -Detects
42.86%
SD Detected
2.028
SD of Detected Logged Data
1.097
d2max (for USL) 2.372
Gamma GOF Tests on Detected Observations Only
A -D Test Statistic 0.272 Anderson -Darling GOF Test
5% A -D Critical Value 0.734 Detected data appear Gamma Distributed at 5% Significance Level
K -S Test Statistic 0.206 Kolmogrov-Smirnoff GOF
5% K -S Critical Value 0.301 Detected data appear Gamma Distributed at 5% Significance Level
Detected data appear Gamma Distributed at 5% Significance Level
Gamma Statistics on Detected Data Only
k hat (MLE) 1.123 k star (bias corrected MLE)
0.785
Theta hat (MLE) 1.624 Theta star (bias corrected MLE)
2.322
nu hat (MLE) 17.97 nu star (bias corrected)
12.57
MLE Mean (bias corrected) 1.824
MLE Sd (bias corrected) 2.058 95% Percentile of Chisquare (2k)
5.129
Gamma ROS Statistics using Imputed Non -Detects
GROS may not be used when data set has > 50% NDs with many tied observations at multiple DLs
GROS may not be used when kstar of detected data is small such as < 0.1
For such situations, GROS method tends to yield inflated values of UCLs and BTVs
For gamma distributed detected data, BTVs and UCLs may be computed using gamma distribution on KM estimates
Minimum 0.01 Mean
1.144
Maximum 6.37 Median
0.533
SD 1.714 CV
1.499
k hat (MLE) 0.443 k star (bias corrected MLE)
0.396
Theta hat (MLE) 2.582 Theta star (bias corrected MLE)
2.891
nu hat (MLE) 12.4 nu star (bias corrected)
11.08
MLE Mean (bias corrected) 1.144 MLE Sd (bias corrected)
1.818
95% Percentile of Chisquare (2k) 3.3 90% Percentile
3.237
95% Percentile 4.77 99% Percentile
8.63
The following statistics are computed using Gamma ROS Statistics on Imputed Data
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 9.525 12.37 95% Approx. Gamma UPL 5.167
5.939
95% Gamma USL 7.981 9.991
The following statistics are computed using gamma distribution and KM estimates
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
k hat (KM) 0.548 nu hat (KM) 15.35
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx 4/9/2016

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
1.055
SD
0.795
95% UTL95% Coverage
3.132
Page 5 of 6
WH
HW
WH
HW
95% Approx. Gamma UTL with 95% Coverage 6.748
7.378
95% Approx. Gamma UPL 4.078
4.188
95% Gamma USL 5.823
6.241
Nickel (ug/L)
1.827
SD
1.006
95% UTL95% Coverage
General Statistics
95% UPL (t)
3.672
Total Number of Observations
14
Number of Missing Observations
0
Number of Distinct Observations
5
95% USL
4.214
Number of Detects
3
Number of Non -Detects
11
Number of Distinct Detects
3
Number of Distinct Non -Detects
2
Minimum Detect
0.63
Minimum Non -Detect
0.5
Maximum Detect
2.6
Maximum Non -Detect
5
Variance Detected
0.97
Percent Non -Detects
78.57%
Mean Detected
1.61
SD Detected
0.985
Mean of Detected Logged Data
0.321
SD of Detected Logged Data
0.72
Warning: Data set has only 3 Detected Values.
This is not enough to compute meaningful or reliable statistics and estimates.
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614 d2max (for USL) 2.372
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 1 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.767 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.176 Lilliefors GOF Test
5% Lilliefors Critical Value 0.512 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
1.055
SD
0.795
95% UTL95% Coverage
3.132
95% KM UPL (t)
2.512
90% KM Percentile (z)
2.073
95% KM Percentile (z)
2.362
99% KM Percentile (z)
2.904
95% KM USL
2.94
DU2 Substitution Background Statistics Assuming Normal Distribution
Mean
1.827
SD
1.006
95% UTL95% Coverage
4.458
95% UPL (t)
3.672
90% Percentile (z)
3.117
95% Percentile (z)
3.482
99% Percentile (z)
4.168
95% USL
4.214
DU2 is not a recommended method. DU2 provided for comparisons and historical reasons
Vanadium (ug/L)
General Statistics
Total Number of Observations 14
Number of Distinct Observations 9
Number of Detects 7
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx
Number of Missing Observations 0
Number of Non -Detects 7
4/9/2016

Attachment F-3: Mayo Regional Background Water Supply Well Data BTVs Statistics
Page 6 of 6
Number of Distinct Detects
7
Number of Distinct Non -Detects
2
Minimum Detect
0.318
Minimum Non -Detect
0.3
Maximum Detect
19.6
Maximum Non -Detect
1
Variance Detected
63.64
Percent Non -Detects
50%
Mean Detected
5.578
SD Detected
7.978
Mean of Detected Logged Data
0.589
SD of Detected Logged Data
1.689
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.614 d2max (for USL) 2.372
Gamma GOF Tests on Detected Observations Only
A -D Test Statistic 0.616 Anderson -Darling GOF Test
5% A -D Critical Value 0.748 Detected data appear Gamma Distributed at 5% Significance
Level
K -S Test Statistic 0.26 Kolmogrov-Smirnoff GOF
5% K -S Critical Value 0.326 Detected data appear Gamma Distributed at 5% Significance Level
Detected data appear Gamma Distributed at 5% Significance Level
Gamma Statistics on Detected Data Only
k hat (MLE) 0.553 k star (bias corrected MLE)
0.412
Theta hat (MLE) 10.08 Theta star (bias corrected MLE)
13.55
nu hat (MLE) 7.749 nu star (bias corrected)
5.761
MLE Mean (bias corrected) 5.578
MLE Sd (bias corrected) 8.695 95% Percentile of Chisquare (2k)
3.386
Gamma ROS Statistics using Imputed Non -Detects
GROS may not be used when data set has > 50% NDs with many tied observations at multiple DLs
GROS may not be used when kstar of detected data is small such as < 0.1
For such situations, GROS method tends to yield inflated values of UCLs and BTVs
For gamma distributed detected data, BTVs and UCLs may be computed using gamma distribution on KM estimates
Minimum 0.01 Mean
2.823
Maximum 19.6 Median
0.364
SD 6.128 CV
2.171
k hat (MLE) 0.255 k star (bias corrected MLE)
0.248
Theta hat (MILE) 11.08 Theta star (bias corrected MLE)
11.39
nu hat (MLE) 7.136 nu star (bias corrected)
6.94
MLE Mean (bias corrected) 2.823 MLE Sd (bias corrected)
5.671
95% Percentile of Chisquare (2k) 2.406 90% Percentile
8.48
95% Percentile 13.7 99% Percentile
27.62
The following statistics are computed using Gamma ROS Statistics on Imputed Data
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 26.6 32.79 95% Approx. Gamma UPL 12.91
13.68
95% Gamma USL 21.64 25.5
The following statistics are computed using gamma distribution and KM estimates
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
k hat (KM) 0.257 nu hat (KM)
7.187
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 20.69 21.77 95% Approx. Gamma UPL 11.22
10.87
95% Gamma USL 17.33 17.77
Haley & Aldrich, Inc.
BTV test stats_regional.xlsx
4/9/2016

Evaluation of Water Supply Wells
in the Vicinity of Duke Energy Coal Ash Basins
Appendix F — Mayo
Part -2: Mayo Facility Background Monitoring Well Data BTVs Statistics
APRIL 2016 11 U'CH

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Background Statistics for Data Sets with Non -Detects
User Selected Options
General Statistics
Date/Time of Computation
4/6/2016 4:09:36 PM
From File
WorkSheet a.xls
Full Precision
OFF
Confidence Coefficient
95%
Coverage
95%
Different or Future K Observations
1
Number of Bootstrap Operations
2000
Barium - ug/L - T
Cobalt - ug/L - T
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 1.991
Page 1 of 6
Number of Missing Observations 4
Number of Non -Detects
General Statistics
Total Number of Observations
68
Number of Distinct Observations
51
Number of Detects
66
Number of Distinct Detects
51
Minimum Detect
5
Maximum Detect
175
Variance Detected
1291
Mean Detected
62.02
Mean of Detected Logged Data
3.896
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 1.991
Page 1 of 6
Number of Missing Observations 4
Number of Non -Detects
2
Number of Distinct Non -Detects
1
Minimum Non -Detect
5
Maximum Non -Detect
5
Percent Non -Detects
2.941%
SD Detected
35.93
SD of Detected Logged Data
0.782
d2max (for USL) 3.073
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.944 Normal GOF Test on Detected Observations Only
5% Shapiro Wilk P Value 0.0089 Data Not Normal at 5% Significance Level
Lilliefors Test Statistic 0.1 Lilliefors GOF Test
5% Lilliefors Critical Value 0.109 Detected Data appear Normal at 5% Significance Level
Detected Data appear Approximate Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
60.34
SD
36.43
95% UTL95% Coverage
132.9
95% KM UPL (t)
121.6
90% KM Percentile (z)
107
95% KM Percentile (z)
120.3
99% KM Percentile (z)
145.1
95% KM USL
172.3
DL/2 Substitution Background Statistics Assuming Normal Distribution
Mean
60.27
SD
36.82
95% UTL95% Coverage
133.6
95% UPL (t)
122.1
90% Percentile (z)
107.5
95% Percentile (z)
120.8
99% Percentile (z)
145.9
95% USL
173.4
DL/2 is not a recommended method. DL/2 provided for comparisons and historical reasons
General Statistics
Total Number of Observations 39 Number of Missing Observations 33
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Chromium (VI) - ug/L - T
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.124 d2max (for USL) 2.857
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.845 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.762 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.274 Lilliefors GOF Test
5% Lilliefors Critical Value 0.396 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
0.581
SD
Page 2 of 6
Number of Distinct Observations
7
95% KM UPL (t)
0.982
Number of Detects
5
Number of Non -Detects
34
Number of Distinct Detects
5
Number of Distinct Non -Detects
2
Minimum Detect
0.51
Minimum Non -Detect
0.5
Maximum Detect
1.41
Maximum Non -Detect
1
Variance Detected
0.131
Percent Non -Detects
87.18%
Mean Detected
1.114
SD Detected
0.362
Mean of Detected Logged Data
0.049
SD of Detected Logged Data
0.417
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.124 d2max (for USL) 2.857
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.845 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.762 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.274 Lilliefors GOF Test
5% Lilliefors Critical Value 0.396 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
0.581
SD
0.235
95% UTL95% Coverage
1.08
95% KM UPL (t)
0.982
90% KM Percentile (z)
0.882
95% KM Percentile (z)
0.967
99% KM Percentile (z)
1.128
95% KM USL
1.252
DU2 Substitution Background Statistics Assuming Normal Distribution
12
Number of Distinct Non -Detects
Mean
0.559
SD
0.254
95% UTL95% Coverage
1.1
95% UPL (t)
0.994
90% Percentile (z)
0.885
95% Percentile (z)
0.978
99% Percentile (z)
1.151
95% USL
1.286
DU2 is not a recommended method. DU2 provided for comparisons and historical reasons
Mean of Detected Logged Data
Nonparametric Distribution Free Background Statistics
Data appear to follow a Discernible Distribution at 5% Significance Level
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016
General Statistics
Total Number of Observations
24
Number of Missing Observations
48
Number of Distinct Observations
14
Number of Detects
13
Number of Non -Detects
11
Number of Distinct Detects
12
Number of Distinct Non -Detects
2
Minimum Detect
0.005
Minimum Non -Detect
0.021
Maximum Detect
13.6
Maximum Non -Detect
0.03
Variance Detected
22.43
Percent Non -Detects
45.83%
Mean Detected
2.26
SD Detected
4.736
Mean of Detected Logged Data
-1.204
SD of Detected Logged Data
2.33
Critical Values for
Background Threshold Values (BTVs)
Tolerance Factor K (For UTL)
2.309
d2max (for USL)
2.644
Nonparametric Distribution Free Background Statistics
Data appear to follow a Discernible Distribution at 5% Significance Level
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Iron - ug/L - T
General Statistics
Lead - ug/L - T
Page 3 of 6
Nonparametric Upper Limits for BTVs(no distinction made between detects and nondetects)
Order of Statistic, r 24 95% UTL with95% Coverage 13.6
Approximate f 1.263 Confidence Coefficient (CC) achieved by UTL 0.708
95% UPL 13.25 95% USL 13.6
95% KM Chebyshev UPL 16.94
Note: The use of USL to estimate a BTV is recommended only when the data set represents a background
data set free of outliers and consists of observations collected from clean unimpacted locations.
The use of USL tends to provide a balance between false positives and false negatives provided the data
represents a background data set and when many onsite observations need to be compared with the BTV.
Total Number of Observations 68
Minimum
22
Second Largest
2730
Maximum
4610
Mean
717.9
Coefficient of Variation
1.146
Mean of logged Data
6.053
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 1.991
Number of Distinct Observations 66
Number of Missing Observations 4
First Quartile
279.3
Median
455
Third Quartile
851.5
SD
823.1
Skewness
2.52
SD of logged Data
1.097
d2max (for USL) 3.073
Lognormal GOF Test
Shapiro Wilk Test Statistic 0.961 Shapiro Wilk Lognormal GOF Test
5% Shapiro Wilk P Value 0.0915 Data appear Lognormal at 5% Significance Level
Lilliefors Test Statistic 0.122 Lilliefors Lognormal GOF Test
5% Lilliefors Critical Value 0.107 Data Not Lognormal at 5% Significance Level
Data appear Approximate Lognormal at 5% Significance Level
Background Statistics assuming Lognormal Distribution
95% UTL with 95% Coverage 3780
95% UPL (t) 2688
95% USL 12391
Total Number of Observations
Number of Distinct Observations
Number of Detects
Number of Distinct Detects
Minimum Detect
Maximum Detect
Variance Detected
Mean Detected
90% Percentile (z) 1736
95% Percentile (z) 2586
99% Percentile (z) 5461
General Statistics
68
Number of Missing Observations
4
7
5
Number of Non -Detects
63
5
Number of Distinct Non -Detects
3
0.1
Minimum Non -Detect
0.1
12.9
Maximum Non -Detect
5
41.31
Percent Non -Detects
92.65%
5.486
SD Detected
6.427
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Nickel - ug/L - D
Page 4 of 6
Mean of Detected Logged Data 0.306 SD of Detected Logged Data 2.367
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 1.991 d2max (for USL) 3.073
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.782 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.762 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.29 Lilliefors GOF Test
5% Lilliefors Critical Value 0.396 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean
0.511
SD
2.101
95% UTL95% Coverage
4.694
95% KM UPL (t)
4.041
90% KM Percentile (z)
3.204
95% KM Percentile (z)
3.967
99% KM Percentile (z)
5.399
95% KM USL
6.968
DU2 Substitution Background Statistics Assuming Normal Distribution
1.581
Mean of Detected Logged Data
Mean
1.265
SD
2.138
95% UTL95% Coverage
5.521
95% UPL (t)
4.857
90% Percentile (z)
4.005
95% Percentile (z)
4.781
99% Percentile (z)
6.238
95% USL
7.835
DU2 is not a recommended method. DU2 provided for comparisons and historical reasons
Number of Missing Observations 40
Number of Non -Detects
Number of Distinct Non -Detects
Minimum Non -Detect
Maximum Non -Detect
Percent Non -Detects
SD Detected
SD of Detected Logged Data
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.186 d2max (for USL)
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.949 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.887 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.159 Lilliefors GOF Test
5% Lilliefors Critical Value 0.222 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean 1.162
16
3
0.5
2.5
50%
0.373
0.249
2.773
SD 0.529
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016
General Statistics
Total Number of Observations
32
Number of Distinct Observations
19
Number of Detects
16
Number of Distinct Detects
16
Minimum Detect
0.96
Maximum Detect
2.13
Variance Detected
0.139
Mean Detected
1.581
Mean of Detected Logged Data
0.43
Number of Missing Observations 40
Number of Non -Detects
Number of Distinct Non -Detects
Minimum Non -Detect
Maximum Non -Detect
Percent Non -Detects
SD Detected
SD of Detected Logged Data
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.186 d2max (for USL)
Normal GOF Test on Detects Only
Shapiro Wilk Test Statistic 0.949 Shapiro Wilk GOF Test
5% Shapiro Wilk Critical Value 0.887 Detected Data appear Normal at 5% Significance Level
Lilliefors Test Statistic 0.159 Lilliefors GOF Test
5% Lilliefors Critical Value 0.222 Detected Data appear Normal at 5% Significance Level
Detected Data appear Normal at 5% Significance Level
Kaplan Meier (KM) Background Statistics Assuming Normal Distribution
Mean 1.162
16
3
0.5
2.5
50%
0.373
0.249
2.773
SD 0.529
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Vanadium - ug/L - T
Page 5 of 6
95% UTL95% Coverage 2.319 95% KM UPL (t) 2.073
90% KM Percentile (z) 1.84 95% KM Percentile (z) 2.032
99% KM Percentile (z) 2.393 95% KM USL 2.629
DU2 Substitution Background Statistics Assuming Normal Distribution
Mean 1.056 SD 0.609
95% UTL95% Coverage 2.388 95% UPL (t) 2.105
90% Percentile (z) 1.837 95% Percentile (z) 2.058
99% Percentile (z) 2.473 95% USL 2.745
DU2 is not a recommended method. DU2 provided for comparisons and historical reasons
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.148 d2max (for USL) 2.824
Gamma GOF Tests on Detected Observations Only
General Statistics
0.402 Anderson -Darling GOF Test
5% A -D Critical Value
Total Number of Observations
36
Number of Missing Observations
36
Number of Distinct Observations
35
Gamma Statistics on Detected Data Only
k hat (MLE)
Number of Detects
34
Number of Non -Detects
2
Number of Distinct Detects
33
Number of Distinct Non -Detects
2
Minimum Detect
0.381
Minimum Non -Detect
0.3
Maximum Detect
12.7
Maximum Non -Detect
1
Variance Detected
9.698
Percent Non -Detects
5.556%
Mean Detected
3.214
SD Detected
3.114
Mean of Detected Logged Data
0.744
SD of Detected Logged Data
0.963
Critical Values for Background Threshold Values (BTVs)
Tolerance Factor K (For UTL) 2.148 d2max (for USL) 2.824
Gamma GOF Tests on Detected Observations Only
A -D Test Statistic
0.402 Anderson -Darling GOF Test
5% A -D Critical Value
0.769 Detected data appear Gamma Distributed at 5% Significance Level
K -S Test Statistic
0.115 Kolmogrov-Smirnoff GOF
5% K -S Critical Value
0.154 Detected data appear Gamma Distributed at 5% Significance Level
Detected data appear Gamma Distributed at 5% Significance Level
Gamma Statistics on Detected Data Only
k hat (MLE)
1.323 k star (bias corrected MLE) 1.226
Theta hat (MLE)
2.43 Theta star (bias corrected MLE) 2.622
nu hat (MLE)
89.94 nu star (bias corrected) 83.34
MLE Mean (bias corrected)
3.214
MLE Sd (bias corrected)
2.903 95% Percentile of Chisquare (2k) 6.839
Gamma ROS Statistics using Imputed Non -Detects
GROS may not be used when data set has > 50% NDs with many tied observations at multiple DLs
GROS may not be used when kstar of detected data is small such as < 0.1
For such situations, GROS method tends to yield inflated values of UCLs and BTVs
For gamma distributed detected data, BTVs and UCLs may be computed using gamma distribution on KM estimates
Minimum 0.01 Mean 3.036
Maximum 12.7 Median 1.775
SD 3.114 CV 1.026
k hat (MLE) 0.883 k star (bias corrected MLE) 0.828
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016

Attachment F-3: Mayo Facility Background Monitoring Well Data BTVs Statistics
Page 6 of 6
Theta hat (MLE) 3.438 Theta star (bias corrected MLE)
3.667
nu hat (MLE) 63.58 nu star (bias corrected)
59.61
MLE Mean (bias corrected) 3.036 MLE Sd (bias corrected)
3.336
95% Percentile of Chisquare (2k) 5.306 90% Percentile
7.321
95% Percentile 9.727 99% Percentile
15.39
The following statistics are computed using Gamma ROS Statistics on Imputed Data
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 12.91 14.77 95% Approx. Gamma UPL 9.673
10.58
95% Gamma USL 19.25 23.56
The following statistics are computed using gamma distribution and KM estimates
Upper Limits using Wilson Hilferty (WH) and Hawkins Wixley (HW) Methods
k hat (KM) 1.005 nu hat (KM)
72.37
WH HW WH
HW
95% Approx. Gamma UTL with 95% Coverage 11.4 12.1 95% Approx. Gamma UPL 8.749
9.023
95% Gamma USL 16.5 18.36
Haley & Aldrich, Inc.
BTV after removing outliers test stats_Facility.xlsx 4/9/2016