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Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra

TABLE OF CONTENTS SECTION PAGE Executive Summary

1.0 Introduction ..................................................................................................................... 1

2.0 Site Information .............................................................................................................. 5

2.1 Plant Description ........................................................................................................ 5

2.2 Ash Basin Description ............................................................................................... 5

2.3 Regulatory Requirements ......................................................................................... 6

3.0 Receptor Information ..................................................................................................... 8

4.0 Regional Geology and Hydrogeology ...................................................................... 10

5.0 Initial Site Conceptual Model .................................................................................... 14

5.1 Physical Site Characteristics ................................................................................... 14

5.2 Source Characteristics ............................................................................................. 15

5.3 Hydrogeologic Site Characteristics ....................................................................... 17

6.0 Environmental Monitoring ......................................................................................... 21

6.1 Compliance Monitoring Well Groundwater Analytical Results ...................... 21

6.2 Preliminary Statistical Evaluation of Results ....................................................... 21

6.3 Additional Site Data ................................................................................................ 22

7.0 Assessment Work Plan................................................................................................. 24

7.1 Subsurface Exploration ........................................................................................... 25

7.1.1 Ash and Soil Borings ......................................................................................... 26

7.1.1.1 Borings Within The Ash Basin ................................................................ 26

7.1.1.2 Borings Outside Ash Basin ...................................................................... 28

7.1.1.3 Index Property Sampling and Analysis ................................................. 29

7.1.2 Groundwater Monitoring Wells ...................................................................... 30

7.1.2.1 Proposed Wells Upgradient of the Ash Basin ....................................... 32

7.1.2.2 Proposed Monitoring Wells within Ash Basin ..................................... 33

7.1.2.3 Proposed Monitoring Wells Downgradient or Sidegradient of the Ash Basin .................................................................................................... 34

7.1.3 Well Completion and Development ............................................................... 36

7.1.4 Hydrogeologic Evaluation Testing .................................................................. 37

7.2 Ash Pore Water and Groundwater Sampling and Analysis.............................. 38

7.3 Surface Water, Sediment, and Seep Sampling ..................................................... 41

7.3.1 Surface Water Samples ...................................................................................... 41 Page i

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7.3.2 Sediment Samples .............................................................................................. 42

7.3.3 Seep Samples ...................................................................................................... 43

7.4 Field and Sampling Quality Assurance/Quality Control Procedures .............. 43

7.4.1 Field Logbooks ................................................................................................... 43

7.4.2 Field Data Records ............................................................................................. 44

7.4.3 Sample Identification ......................................................................................... 44

7.4.4 Field Equipment Calibration ............................................................................ 44

7.4.5 Sample Custody Requirements ........................................................................ 45

7.4.6 Quality Assurance and Quality Control Samples ......................................... 47

7.4.7 Decontamination Procedures ........................................................................... 48

7.5 Influence of Pumping Wells on Groundwater System ....................................... 48

7.6 Site Hydrogeologic Conceptual Model ................................................................. 49

7.7 Site-Specific Background Concentrations............................................................. 50

7.8 Geologic Mapping/Fracture Trace and Lineament Analysis ............................. 50

7.9 Groundwater Fate and Transport Model ............................................................. 51

7.9.1 MODFLOW/MT3D ............................................................................................ 52

7.9.2 Development of Kd Terms ............................................................................... 53

7.9.3 MODFLOW/MT3D Modeling Process ............................................................ 56

7.9.4 Hydrostratigraphic Layer Development ........................................................ 57

7.9.5 Domain of Conceptual Groundwater Flow Model ....................................... 58

7.9.6 Potential Modeling of Groundwater Impacts to Surface Water ................. 58

8.0 Risk Assessment ............................................................................................................ 60

8.1 Human Health Risk Assessment ........................................................................... 60

8.1.1 Site-Specific Risk-Based Remediation Standards .......................................... 61

8.2 Ecological Risk Assessment .................................................................................... 63

9.0 CSA Report ..................................................................................................................... 66

10.0 Proposed Schedule........................................................................................................ 68

11.0 References ....................................................................................................................... 69

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GAP Revised Dec 2014\Mayo GW Assessment Plan Rev 1.docx

Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra List of Figures

Figure 1 – Site Location Map Figure 2 – Site Layout Map Figure 3 – Geology Map Figure 4 – Water Level Map – July 2014 Figure 5 – Proposed Monitoring Well and Sample Location Map

List of Tables Table 1 – Groundwater Monitoring Requirements Table 2 – Exceedances of 2L Standards Table 3 – Groundwater Analytical Results Table 4 – Seep Analytical Results Table 5 – Environmental Exploration and Sampling Plan Table 6 – Soil, Sediment and Ash Parameters and Analytical Methods Table 7 – Ash Pore Water, Groundwater, Surface Water, and Seep Parameters and Analytical Methods

List of Appendices

Appendix A - NCDENR Letter of August 13, 2014

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EXECUTIVE SUMMARY

Duke Energy Progress, Inc. (Duke Energy), owns and operates the Mayo Steam Electric Plant (Mayo Plant), located near Roxboro, in Person County, North Carolina. The coal ash residue from the coal combustion process has been placed in the plant’s ash basin, which is permitted by the North Carolina Department of Environment and Natural Resources (NCDENR) Division of Water Resources (DWR) under the National Pollution Discharge Elimination System (NPDES), Permit #NC0038377.

Duke Energy has performed voluntary groundwater monitoring around the ash basin from October 2008 until April 2010. The voluntary groundwater monitoring wells were sampled two times each year and the analytical results were submitted to DWR. Groundwater monitoring as required by the NPDES permit began in November 2010. The system of compliance groundwater monitoring wells required for the NPDES permit is sampled three times a year and the analytical results are submitted to the DWR. The compliance groundwater monitoring is performed in addition to the normal NPDES monitoring of the discharge flows from the ash basin. It is Duke Energy’s intention that the assessment will collect additional data to validate and expand the knowledge of the groundwater system at the ash basin. The proposed assessment plan will provide the basis for a data-driven approach to additional actions related to groundwater conditions if required by the results of the assessment and for closure.

In a Notice of Regulatory Requirement (NORR) letter dated August 13, 2014, DWR requested that Duke Energy prepare a Groundwater Assessment Plan to identify the source and cause of contamination, any potential imminent hazards to public health and safety and actions taken to mitigate them, all receptors and complete exposure pathways. In addition, the NORR directed Duke Energy to determine the horizontal and vertical extent of potential soil and groundwater contamination and all significant factors affecting contaminant transport and the geological and hydrogeological features influencing the movement, chemical, and physical character of the contaminants.

This work plan provides procedures for performing the following:

• Implementation of a receptor survey to identify public and private water supply wells (including irrigation wells and unused or abandoned wells), surface water features, and wellhead protection areas (if present) within a 0.5 mile radius of the Mayo Plant compliance boundary;


Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra • Installation of borings within the ash basin and former 1981 landfill permit #73-B

for chemical and geotechnical analysis of residuals and in-place soils;

• Installation of soil borings;

• Installation of monitoring wells;

• Collection and analysis of groundwater and ash pore water samples from existing and newly installed monitoring wells;

• Collection and analysis of surface water, seep, and sediment samples;

• Statistical evaluation of groundwater analytical data;

• Development of a groundwater model to evaluate the long term fate and transport of constituents of concern in groundwater associated with the ash basin; and

• Conduct a screening level human health and ecological risk assessment. This assessment will include the preparation of a conceptual exposure model illustrating potential pathways from the source to possible receptors.

The information obtained through this Work Plan will be utilized to prepare a Comprehensive Site Assessment (CSA) report in accordance with the requirements of the NORR and Coal Ash Management Act (CAMA). During the CSA process if additional investigations are required, NCDENR will be notified.

This Proposed Groundwater Assessment Work Plan, Revision 1 was prepared in response to comments provided to Duke Energy by the NCDENR, dated November 4, 2014, in regards to the Groundwater Assessment Work Plan submitted to NCDENR in September 2014, and subsequent meetings among Duke Energy, SynTerra, and NCDENR. This revised work plan addresses both the general and site-specific comments for the Mayo Plant including:

• Additional assessment wells proposed for specific locations and depths across the site to address horizontal and vertical extent of potential impacts to groundwater.

• Additional background well cluster and relocation of a previously proposed background well cluster.



1.0 INTRODUCTION

Duke Energy Progress, Inc. (Duke Energy), owns and operates the Mayo Steam Electric Plant (Mayo Plant), located near Roxboro, in Person County, North Carolina (Figure 1). The Plant is a single unit, coal-fired electricity-generating facility. Coal ash has historically been managed in the Plant’s on-site ash basin. The discharge from the ash basin is permitted by the North Carolina Department of Environment and Natural Resources (NCDENR) Division of Water Resources (DWR) under the National Pollution Discharge Elimination System (NPDES). Dry ash has been hauled and disposed in the lined dry flyash (DFA) landfill located at the nearby Roxboro Steam Electric Plant (near Semora, North Carolina (NC)). Beginning in November 2014, coal combustion residuals (CCR) from the Plant have been managed in a newly constructed on-site landfill.

Duke Energy has performed voluntary groundwater monitoring around the ash basin from October 2008 until April 2010. The voluntary groundwater monitoring wells were sampled two times each year and the analytical results were submitted to DWR. Groundwater monitoring as required by the NPDES permit began in November 2010. The system of compliance groundwater monitoring wells required for the NPDES permit is sampled three times a year and the analytical results are submitted to the DWR. The compliance groundwater monitoring is performed in addition to the normal NPDES monitoring of the discharge flows from the ash basin.

It is Duke Energy’s intention that the assessment will collect additional data to validate and expand the knowledge of the groundwater system at the ash basin. The proposed assessment plan will provide the basis for a data-driven approach to additional actions related to groundwater conditions if required by the results of the assessment and for closure.

Groundwater monitoring has been performed in accordance with the conditions in the NPDES Permit #NC0038377 beginning in December 2010. A monitoring network of 10 compliance wells is employed. Elevated concentrations appear to be greater than the North Carolina Administrative Code (NCAC) Title 15A Chapter 02L (g) groundwater quality standards (2L Standards) for iron (seven wells, including background wells), manganese (nine wells, including background wells), total dissolved solids (TDS; two wells), and boron (one well, CW-2) have been detected.

The compliance boundary for the Mayo ash basin is defined in accordance with NCAC Title 15A Chapter 02L.0107(a) (T15 A NCAC 02L .0107(a)) as being established at either 500 feet from the waste boundary or at the property boundary, whichever is closest. Monitoring wells CW-1, CW-1D, CW-2, CW-2D, CW-3, CW-4, CW-5, and CW-6 are

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Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra located at or near the compliance boundary. Wells BG-1 and BG-2 are located southwest, upgradient, of the ash basin and are intended to represent background conditions.

In a Notice of Regulatory Requirements (NORR) letter dated August 13, 2014, the DWR of the NCDENR requested that Duke Energy prepare a Groundwater Assessment Plan to conduct a Comprehensive Site Assessment (CSA) in accordance with 15A NCAC 02L .0106(g) to address those groundwater constituents that appear to have elevated values greater than 2L groundwater quality standards at the compliance boundary. A copy of the DWR letter is provided in Appendix A.

The Coal Ash Management Act (CAMA) 2014 – General Assembly of North Carolina Senate Bill 729 Ratified Bill (Session 2013) (SB 729) revised North Carolina General Statute 130A-309.209(a) to require the following:

(a)Groundwater Assessment of Coal Combustion Residuals Surface Impoundments – The owner of a coal combustion residuals surface impoundment shall conduct groundwater monitoring and assessment as provided in this subsection. The requirements for groundwater monitoring and assessment set out in this subsection are in addition to any other groundwater monitoring and assessment requirements applicable to the owners of coal combustion residuals surface impoundments.

(1) No later than December 31, 2014, the owner of a coal combustion residuals surface impoundment shall submit a proposed Groundwater Assessment Plan for the impoundment to the Department for its review and approval. The Groundwater Assessment Plan shall, at a minimum, provide for all of the following:

a. A description of all receptors and significant exposure pathways. b. An assessment of the horizontal and vertical extent of soil and

groundwater contamination for all contaminants confirmed to be present in groundwater in exceedance of groundwater quality standards.

c. A description of all significant factors affecting movement and transport of contaminants.

d. A description of the geological and hydrogeological features influencing the chemical and physical character of the contaminants.

e. A schedule for continued groundwater monitoring. f. Any other information related to groundwater assessment required by the

Department. (2) The Department shall approve the Groundwater Assessment Plan if it determines

that the Plan complies with the requirements of this subsection and will be




sufficient to protect public health, safety, and welfare; the environment; and natural resources.

(3) No later than 10 days from approval of the Groundwater Assessment Plan, the owner shall begin implementation of the Plan.

(4) No later than 180 days from approval of the Groundwater Assessment Plan, the owner shall submit a Groundwater Assessment Report to the Department. The Report shall describe all exceedances of groundwater quality standards associated with the impoundment.

This work plan addresses the requirements of 130A-309.209(a)(1) (a) through (f) and the requirements of the NORR.

On behalf of Duke Energy, SynTerra submitted to NCDENR a proposed Work Plan for the Mayo Plant dated September 2014. Subsequently, NCDENR issued a comment letter dated November 4, 2014 containing both general comments applicable to the Duke Energy ash basin facilities and site-specific comments for the Mayo Plant. In response to these comments, SynTerra has prepared this Proposed Groundwater Assessment Work Plan (Revision 1) on behalf of Duke Energy for performing the groundwater assessment as prescribed in the NORR and NC Senate Bill 729 as ratified August 2014, and to address the NCDENR review of the work plan dated November 4, 2014 and subsequent meetings among Duke Energy, SynTerra, and NCDENR.

The work plan contains a description of the activities proposed to meet the requirements of 15A NCAC 02L .0106(g). This rule requires:

(g) The site assessment conducted pursuant to the requirements of Paragraph (c) of this Rule, shall include: (1) The source and cause of contamination; (2) Any imminent hazards to public health and safety and actions taken

to mitigate them in accordance with Paragraph (f) of this Rule; (3) All receptors and significant exposure pathways; (4) The horizontal and vertical extent of soil and groundwater

contamination and all significant factors affecting contaminant transport; and

(5) Geological and hydrogeological features influencing the movement, chemical, and physical character of the contaminants.

The work proposed in this plan will provide the information sufficient to satisfy the requirements of the CAMA and NORR. However, uncertainties may still exist due to the following factors:



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra • The natural variations and the complex nature of the geological and

hydrogeological characteristics involved with understanding the movement, chemical, and physical character of the contaminants;

• The size of the site;

• The time frame mandated by the CAMA. Site assessments are most effectively performed in a multi-phase approach where data obtained in a particular phase of the investigation can be reviewed and used to refine the subsequent phases of investigation. The mandated 180-day time frame may prevent this approach from being utilized; and

• The 180-day time frame will limit the number of sampling events that can be performed after well installation and prior to report production.

The information obtained through this Work Plan will be utilized to prepare a CSA report in accordance with the requirements of the NORR and the CAMA. In addition to the components listed above, a human health and ecological risk assessment will be conducted. This assessment will include the preparation of a conceptual exposure model illustrating potential pathways from the source to possible receptors. During the CSA process if additional investigations are required, NCDENR will be notified.




2.0 SITE INFORMATION

2.1 Plant Description The Mayo Plant is a coal-fired electricity-generating facility located in Person County, North Carolina, near the city of Roxboro. The location of the plant is shown on Figure 1. The Mayo Plant became fully operational in June 1983.

The plant is located on Boston Road (US Highway 501) north of Roxboro. The northern plant property line extends to the North Carolina/Virginia state line. The overall topography of the Plant generally slopes toward the east (Mayo Reservoir) and northeast (Crutchfield Branch).

2.2 Ash Basin Description The Mayo Plant and ash basin are located west of Mayo Lake. There is a single ash basin present at the site, located northwest of the plant as indicated on Figure 2, which contains ash generated from the plant’s coal combustion. The ash basin is approximately 153 acres in size with an earthen dike and contains approximately 6,900,000 tons of CCR material (Duke Energy, October 31, 2014). The 500-foot compliance boundary encircles the ash basin. According to Duke Energy, ash has not been stored or placed elsewhere on or near the site other than de minimis quantities at unknown locations or in the lined landfill described below.

CCR have historically been managed at the Plant’s on-site ash basin. In 2013, the Mayo Plant converted from a wet to dry bottom ash system. Consequently, 90 percent of currently generated CCR is dry. The only situation in which wet sluicing is conducted is when there is an infrequent shutdown of the dry flyash transport system. This system is currently being upgraded so that all future CCR generation will be dry only. Until recently, dry ash has been hauled and disposed in the lined landfill located at the nearby Roxboro Steam Electric Plant (near Semora, NC). Beginning in November 2014, CCR from the Mayo Plant has been placed in a newly constructed on-site landfill (Permit #73-05). A scrubber unit and lined gypsum settling pond are also located on a small portion of the southeast side of the ash basin (Figure 2).

The Mayo Plant NPDES permit (NC0038377) authorizes two discharges to Mayo Lake. Outfall 001 discharges cooling tower water and circulating water system discharge water. Outfall 002 is comprised of a number of streams including internal outfall 008 (cooling tower blowdown), internal outfall 009 (flue gas desulfurization or FGD blowdown), ash transport water, coal pile runoff, and other sources including water from wastewater treatment processes. A number of stormwater outfalls are also authorized for the Mayo Plant.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra A construction and debris (C&D) landfill is present on the Mayo Plant located to the east of the ash basin (Figure 5). The permitted landfill (Permit No. 73-B) was used to contain debris generated during the construction of the Mayo Plant in the early 1980s. The landfill permit was reopened briefly in the 1990s for a new project; however, the project was cancelled, no additional placement of material occurred in the landfill, and the permit was closed again.

2.3 Regulatory Requirements The NPDES program regulates wastewater discharges to surface waters. The Mayo Plant is permitted to discharge wastewater under NPDES Permit NC0038377, which authorizes discharge from the facility to Mayo Reservoir in accordance with effluent limitations, monitoring requirements, and other conditions set forth in the permit. The ash basins are referred to as “ash ponds” in the Plant’s NPDES permit. In addition to surface water monitoring, the NPDES permit requires groundwater monitoring. Permit Condition A (6) Attachment XX, Version 1.0, dated March 17, 2011, lists the groundwater monitoring wells to be sampled, the parameters and constituents to be measured and analyzed, and the requirements for sampling frequency and results reporting. Attachment XX also provides requirements for well location and well construction. The most recent NPDES permit for the Mayo Plant became effective on November 1, 2009, and was scheduled to expire in March 2012. A permit renewal request has been submitted to NCDENR and is pending.

The compliance boundary for groundwater quality associated with the Mayo Plant ash basin is defined in accordance with Title15A 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. The locations of the compliance monitoring wells, waste boundary, and compliance boundary are shown on Figure 2.

Ten wells comprise the compliance monitoring well network for the Mayo Plant: two wells intended to represent background conditions and eight downgradient wells. The locations for the compliance groundwater monitoring wells were approved by the NCDENR DWR Aquifer Protection Section (APS).

Monitoring wells BG-1 and BG-2 have been used to represent background groundwater quality upgradient (southwest) of the ash basin. The compliance boundary wells on the east side of the ash basin are well cluster CW-1/CW-1D. Monitoring well CW-5 is the compliance boundary well for the west side of the ash basin. Monitoring wells CW-2/CW-2D, CW-3, CW-4, and CW-6 are downgradient compliance boundary wells to the north and northeast of the ash basin.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra The monitoring wells are sampled three times per year in April, July, and November for the parameters listed below (Table 1). The analytical results for the monitoring program are compared to the 2L Standards and the site-specific background concentrations. A summary of the detected concentration ranges for constituents detected at concentrations greater than the 2L Standards through July 2014 is provided in Table 2.

TABLE 1 Groundwater Monitoring Requirements Well

Nomenclature Parameter Description Frequency

Monitoring Wells BG-1, BG-2, CW-1,

CW-1D, CW-2, CW-2D, CW-3, CW-4, CW-5,

CW-6

Aluminum Chloride Mercury TDS

April, July, and

November

Antimony Chromium Nickel Thallium Arsenic Copper Nitrate Water Level Barium Iron pH Zinc Boron Lead Selenium

Cadmium Manganese Sulfate




3.0 RECEPTOR INFORMATION

The August 13, 2014 NORR states:

No later than October 14th, 2014 as authorized pursuant to 15A NCAC 02L .0106(g), the DWR is requesting that Duke perform a receptor survey at each of the subject facilities and submitted to the DWR. The receptor survey is required by 15A NCAC 02L .0106(g) and shall include identification of all receptors within a radius of 2,640 feet (one-half mile) from the established compliance boundary identified in the respective National Pollutant Discharge Elimination System (NPDES) permits. Receptors shall include, but shall not be limited to, public and private water supply wells (including irrigation wells and unused or abandoned wells) and surface water features within one-half mile of the facility compliance boundary. For those facilities for which Duke has already submitted a receptor survey, please update your submittals to ensure they meet the requirements stated in this letter and referenced attachments and submit them with the others. If they do not meet these requirements, you must modify and resubmit the plans.

The results of the receptor survey shall be presented on a sufficiently scaled map. The map shall show the coal ash facility location, the facility property boundary, the waste and compliance boundaries, and all monitoring wells listed in the respective NPDES permits. Any identified water supply wells shall be located on the map and shall have the well owner's name and location address listed on a separate table that can be matched to its location on the map.

In accordance with the requirements of the NORR, SynTerra conducted a receptor survey to identify potential receptors including public and private water supply wells, surface water features, and wellhead protection areas (if present) within a 0.5 mile radius of the Mayo Plant compliance boundary. SynTerra presented the results of the receptor survey in two separate reports. The first report submitted in September 2014 (Drinking Water Well and Receptor Survey) included the results of a review of publicly available data from NCDENR Department of Environmental Health, Virginia Department of Environmental Quality, NC OneMap GeoSpatial Portal, DWR Source Water Assessment Program (SWAP) online database, Person County geographic information system (GIS) data, Environmental Data Resources, Inc. (EDR) Records Review, the United States Geological Survey (USGS) National Hydrography Dataset (NHD), as well as a vehicular survey along public roads located within 0.5 mile radius of the compliance boundary.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra The second report submitted in November 2014 (Supplement to Drinking Water Well and Receptor Survey) supplemented the initial report with additional information obtained from questionnaires completed by property owners who own property within the 0.5 mile radius of the compliance boundary. The report included a scaled map showing the ash basin location, the facility property boundary, the waste and compliance boundaries, all monitoring wells listed in the NPDES permit, and the approximate location of identified water supply wells. A table presented available information about identified wells including the owner's name, address of well location with parcel number, construction and usage data, and the approximate distance from the compliance boundary.

During groundwater assessment, it is anticipated that additional information will become available regarding potential receptors. SynTerra will update the receptor information as necessary, in accordance with the CSA receptor survey requirements. If necessary, an updated receptor survey will be submitted with the CSA report.




4.0 REGIONAL GEOLOGY AND HYDROGEOLOGY

North Carolina is divided into distinct regions by portions of three physiographic provinces: the Atlantic Coastal Plain, Piedmont, and Blue Ridge (Fenneman, 1938). Geographically, the Mayo Plant is situated in the eastern Piedmont region of north-central North Carolina. The Piedmont is characterized by well-rounded hills and rolling ridges cut by small streams and drainages. Stream valley to ridge relief in most areas ranges from 75 to 200 feet. Along the Coastal Plain boundary, the Piedmont rises from an elevation of 300 feet above mean sea level (msl), to the base of the Blue Ridge Mountains at an elevation of 1,500 feet (LeGrand, 2004). Elevations in the area of Mayo Plant range between 570 feet above mean sea level (msl) near the Plant entrance along Boston Road to 360 feet msl in the Crutchfield Branch stream area on the north side of the Plant.

Geologically, the Plant is located at the contact between two regional zones of metamorphosed intrusive rocks: the Carolina Slate Belt (now referred to as Carolina Terrane) on the east and the Charlotte Belt (or Charlotte Terrane) to the west (Figure 3). The majority of the Mayo Plant, including the largest portion of the ash basin and Mayo Lake are situated in the Carolina Terrane (Dicken, et. al., 2007). The characteristics and genesis of the rocks within these regional metamorphic belts have been the subject of intense study to describe the geology in tectonic, structural, and/or litho-stratigraphic terms (Hibbard, et. al., 2002).

Rocks of Charlotte Terrane are characterized by strongly foliated felsic mica gneiss and schist and metamorphosed intrusive rocks. Carolina Terrane rocks in the vicinity of the Plant are typically felsic meta-volcanics and meta-argillites. This is consistent with the description of the geologic nature of the area according to the Geologic Map of North Carolina (1985). The Geologic Map of North Carolina describes the felsic meta-volcanic rock as metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate volcanic rock, meta-argillite and meta-mudstone. The felsic mica gneiss of the Charlotte Terrane is described as being interlayered with biotite and hornblende schist. These general observations are consistent with site-specific observations from well logs for the Mayo Plant, which document the bedrock of the northwestern portion of the compliance boundary as intermediate meta-volcanic rock and the bedrock of the remainder of the site as felsic meta-volcanics or meta-argillites.

The upper portion of the underlying rocks of the region, except where exposed in road cuts, stream channels, and steep hillsides, are covered with unconsolidated material known as regolith. The regolith includes residual soil and saprolite zones and, where



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra present, alluvium. Saprolite is typically composed of clay and coarser granular material and reflects the texture and structure of the rock from which it was formed as a result of in-situ chemical weathering. The degree of weathering decreases with depth and partially weathered rock (PWR) is commonly present near the top of the bedrock surface.

The groundwater system in the Piedmont Province, in most cases, is comprised of two interconnected layers, or mediums: (1) residual soil/saprolite and weathered fractured rock (regolith) overlying (2) fractured crystalline bedrock (Heath, 1980; Harned and Daniel, 1992). As discussed above, bedrock in the vicinity of the Mayo Plant is strongly foliated and compositionally layered and is not strongly massive/crystalline.

The regolith layer is a thoroughly weathered and structureless residual soil that occurs near the ground surface with the degree of weathering decreasing with depth. The residual soil grades into saprolite, typically 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, saprolite, and weathered/fractured rock (transition zone) is a hydrogeologic unit that covers and crosses various types of rock (LeGrand, 1988). This layer serves as the principal storage reservoir and provides an intergranular medium through which the recharge and discharge of water from the underlying fractured rock occurs. Within the fractured crystalline bedrock layer, the fractures control both the hydraulic conductivity and storage capacity of the rock mass. A transition zone at the base of the regolith is present in many areas of the Piedmont. The zone consists of partially weathered/fractured bedrock and lesser amounts of saprolite that grades into competent bedrock and has been described as “being the most permeable part of the system, even slightly more permeable than the soil zone” (Harned and Daniel, 1992). The zone thins and thickens within short distances and its boundaries may be difficult to distinguish. Where present, the zone may serve as a conduit of rapid flow and transport of contaminated groundwater (Harned and Daniel, 1992).

Direct observations at the Mayo Plant confirm the presence of saprolite, developed above the bedrock, which is generally 10 to 30 feet thick. The saprolite extends from the ground surface (soil zones) downward, transitioning through a zone comprised of unconsolidated silt and sand, downward through a transition zone of partially weathered rock in a silt/sand matrix, down to the contact with competent bedrock.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra LeGrand’s (1988; 1989) conceptual model of the groundwater setting in the Piedmont incorporates the above two-medium system into an entity that is useful for the description of groundwater conditions. That entity is the surface drainage basin that contains a perennial stream (LeGrand, 1988). Each basin is similar to adjacent basins and the conditions are generally repetitive from basin to basin. Within a basin, movement of groundwater is generally restricted to the area extending from the drainage divides to a perennial stream (Slope-Aquifer System; LeGrand, 1988; 1989). 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 undulations represent natural groundwater divides within a slope-aquifer system and may limit the area of influence of wells or contaminant plumes located within their boundaries. The concave topographic areas between the topographic divides may be considered as flow compartments that are open-ended down slope. Therefore, in most cases in the Piedmont, the groundwater system is a two-medium system (LeGrand, 1988) restricted to the local drainage basin. Groundwater within the area exists under unconfined, also known as water table, conditions within the saprolite, PWR/transition zone, and in the fractures and joints of the underlying bedrock. The water table and bedrock aquifers are often interconnected. Typically, the residual soil/saprolite is partially saturated and the water table fluctuates within it. The saprolite and PWR/transition zone acts as a reservoir for water supply to the fractures and joints in the underlying bedrock. The near-surface fractured rocks can form extensive aquifers. The character of such aquifers results from the combined effects of the rock type, fracture system, topography, and weathering. Topography exerts an influence on both weathering and the opening of fractures, while the weathering of the bedrock modifies both transmissive and storage characteristics. Groundwater flow paths in the Piedmont are almost invariably restricted to the zone underlying the topographic slope extending from a topographic divide to an adjacent stream. Under natural conditions, the general direction of groundwater flow can be approximated from the surface topography (LeGrand, 2004). As such, shallow groundwater generally flows from local recharge zones in topographically high areas, such as ridges, toward groundwater discharge zones, such as stream valleys. Ridge and topographic high areas serve as groundwater recharge zones. Groundwater flow patterns in recharge areas tend to develop a somewhat radial pattern from the center of the recharge area outward toward the discharge areas and are expected to mimic surface topography. The general direction of groundwater flow at the site appears to follow this regional flow model as shown on Figure 4. The closest surface water discharge for the area downgradient of the ash basin is presumed to be Crutchfield



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra Branch, a small perennial stream that originates near the base of the ash basin dam and flows north into Virginia. The nature of groundwater flow beneath the eastern portion of the plant and relative to the position of the large Mayo Lake, located east of the Mayo Plant, is not well understood and will be evaluated in the course of the assessment. Groundwater recharge in the Piedmont is derived entirely from infiltration of local precipitation. Groundwater recharge occurs in areas of higher topography (i.e., hilltops) and groundwater discharge occurs in lowland areas bordering surface water bodies, wetlands, and floodplains (LeGrand, 2004). Average annual precipitation in the Piedmont ranges from 42-46 inches. Mean annual recharge in the Piedmont ranges from 4.0 to 9.7 inches per year (Daniel, 2001).




5.0 INITIAL SITE CONCEPTUAL MODEL

Information provided in this section forms the basis for the initial conceptual site model (ICSM). The ICSM has been developed based upon regional and site-specific data (e.g. site observations, topography, boring logs, well construction records, etc.). The regional geologic and hydrogeologic framework is discussed in Section 4.0. Existing information from routine compliance monitoring and voluntary monitoring is summarized in Section 6.0. The ICSM has been developed to identify data gaps and to optimize assessment data collection. The ICSM will continue to be developed and refined as discussed in Section 7.0.

The ICSM has been developed to identify data gaps and to optimize assessment data collection presented in Section 7.0. The ICSM will be refined as needed as additional site-specific information is obtained during the site assessment process.

The ICSM serves as the basis for understanding the hydrogeologic characteristics of the site, as well as the characteristics of the ash sources, and will serve as the basis for the Site Conceptual Model (SCM) discussed in Section 7.6.

In general, the ICSM identified the need for the following additional information concerning the site and ash:

• Delineation of the extent of possible soil and groundwater contamination;

• Additional information concerning the direction and velocity of groundwater flow;

• Information on the constituents and concentrations found in the site ash;

• Properties of site materials influencing fate and transport of constituents found in ash; and

• Information on possible impacts to seeps and surface water from the constituents found in the ash.

The assessment work plan has been developed to collect and evaluate this information.

5.1 Physical Site Characteristics The Mayo Plant and ash basin are active and are located west of Mayo Lake. The single ash basin present at the site is located northwest of the plant and contains ash generated from the plant’s coal combustion. The ash basin is approximately 153 acres in size with an earthen dike and contains approximately 6,900,000 tons of CCR material (Duke Energy, October 31, 2014). The 500-foot compliance boundary encircles the ash basin.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra According to Duke Energy, ash has not been stored or placed elsewhere on or near the site other than de minimis quantities at unknown locations or in the lined landfill described below.

CCR have historically been managed at the Plant’s on-site ash basin. In 2013, the Mayo Plant converted from a wet to dry bottom ash system. Consequently, 90 percent of currently generated CCR is dry. The only situation in which wet sluicing is conducting is when there is an infrequent shutdown of the dry flyash transport system. This system is currently being upgraded so that all future CCR generation will be dry only. Until recently, dry ash has been hauled and disposed in the lined landfill located at the nearby Roxboro Steam Electric Plant (near Semora, NC). Beginning in November 2014, CCR from the Mayo Plant is placed in a newly constructed on-site landfill.

The Mayo Plant NPDES permit (NC0038377) authorizes two discharges to Mayo Lake. Outfall 001 discharges cooling tower water and circulating system water. Outfall 002 includes a number of waste streams: internal outfall 008 (cooling tower blowdown), internal outfall 009 (FGD blowdown), ash transport water, coal pile runoff, and other sources including water from wastewater treatment processes. A number of stormwater outfalls are also authorized for the Mayo Plant.

5.2 Source Characteristics Ash in the basin consists of fly ash and bottom ash produced from the combustion of coal. The physical and chemical properties of coal ash are determined by reactions that occur during the combustion of the coal and subsequent cooling of the flue gas. In general, coal is dried, pulverized, and conveyed to the burner area of a boiler for combustion. Material that forms larger particles of ash and falls to the bottom of the boiler is referred to as bottom ash. Smaller particles of ash, fly ash, are carried upward in the flue gas and are captured by an air pollution control device. Approximately 70 percent to 80 percent of the ash produced during coal combustion is fly ash. (EPRI, 1993). Typically 65 percent to 90 percent of fly ash has particle sizes that are less than 0.010 millimeter (mm) in diameter. Bottom ash particle diameters can vary from approximately 38 mm to 0.05 mm in diameter.

The chemical composition of coal ash is determined based on many factors including the source of the coal, the type of boiler where the combustion occurs (the thermodynamics of the boiler), and air pollution control technologies employed. The major elemental composition of fly ash (approximately 90 percent by weight) is generally composed of mineral oxides of silicon, aluminum, iron, and calcium. Minor constituents such as magnesium, potassium, titanium and sulfur comprise approximately 8 percent of the mineral component, while trace constituents such as



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra arsenic, cadmium, lead, mercury, and selenium make up less than approximately 1 percent of the total composition (EPRI, 2009). Other trace constituents in coal ash (fly ash and bottom ash) consist of antimony, barium, beryllium, boron, chromium, copper, lead, mercury, molybdenum, nickel, selenium, strontium, thallium, vanadium, and zinc (EPRI, 2009).

In addition to these constituents, coal ash leachate can contain chloride, fluoride, sulfate, and sulfide. In the United States Environmental Protection Agency’s (US EPA) Proposed Rules Disposal of Coal Combustion Residuals From Electric Utilities, in Federal Register /Vol. 75, No. 118 / Monday, June 21, 2010, the US EPA proposed that the following constituents be used as indicators of groundwater contamination in the detection monitoring program for coal combustion residual landfills and surface impoundments: boron, chloride, conductivity, fluoride, pH, sulfate, sulfide, and TDS. In selecting the parameters for detection monitoring, US EPA selected constituents that are present in coal combustion residual, and would rapidly move through the subsurface and provide an early detection as to whether contaminants were migrating from the landfill or ash basin.

In the Report to Congress Wastes from the Combustion of Fossil Fuels (US EPA, 1998), US EPA presented waste characterization data for ash wastes in impoundments and in landfills. The constituents listed were: arsenic, barium, beryllium, boron, cadmium, chromium, cobalt, copper, lead, manganese, nickel, selenium, silver, thallium, strontium, vanadium, and zinc. In this report, the US EPA reviewed radionuclide concentrations in coal and ash and ultimately, eliminated radionuclides from further consideration due to the low risks associated with the radionuclides.

The geochemical factors controlling the reactions associated with leaching of ash and the movement and transport of the constituents leached from ash is complex. The mechanisms that affect movement and transport vary by constituent, but, in general, are mineral equilibrium, solubility, and adsorption onto inorganic soil particles. Due to the complexity associated with understanding or identifying the specific mechanism controlling these processes, it is believed that the effect of these processes are best considered by determination of site-specific, soil-water distribution coefficient, Kd, values as described in Section 7.9.2.

The oxidation-reductions and precipitation-dissolution reactions that occur in a complex environment such as an ash basin are poorly understood. In addition to the variability that might be seen in the mineralogical composition of the ash, based on different coal types, different age of ash in the basin, etc., it would be anticipated that the chemical environment of the ash basin would vary over time and over distance and



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra depth, increasing the difficulty of making specific predictions related to concentrations of specific constituents.

Due to the complex nature of the geochemical environment and process in the ash basin, SynTerra believes that the most useful representation of the potential impacts to groundwater will be obtained from the sampling and analyses of ash in the basin, seep samples from around the basins, pore-water samples collected from piezometers within the ash basins (near the base of the ash basin), and groundwater samples collected from monitoring wells as proposed in Section 7.0 of this work plan.

Understanding the factors controlling the mobility, retention, and transport of the constituents that may leach from ash are also complex due to the nature of the geochemical environment of the ash basin combined with the geochemical processes occurring in the soils beneath the ash basin and along the groundwater flow paths. The mobility, retention, and transport of the constituents will vary by constituent. As these processes are complex and are highly dependent on the mineral composition of the soils, it may not be possible to determine with absolute certainty the specific mechanisms that control the mobility and retention of the constituents; however, the effect of these processes will be represented by the determination of the site-specific soil-water distribution coefficient, Kd, values as described in Section 7.9.2. As described in that section, samples will be collected to develop Kd terms for the various hydrostratigraphic units encountered at the site. These Kd terms will be used in the groundwater modeling to predict concentrations of constituents at the compliance boundary. In addition, physical material properties related to aquifer geochemistry and fate and transport modeling will be collected as discussed in Section 7.0 to support the Kd information. 5.3 Hydrogeologic Site Characteristics As previously described in Section 4.0, the Mayo Plant is situated in the eastern Piedmont region of north-central North Carolina. The Piedmont is characterized by well-rounded hills and rolling ridges cut by small streams and drainages. Elevations in the area of Mayo Plant range between 570 feet above msl near the Plant entrance along Boston Road to 360 feet msl in the Crutchfield Branch stream area on the north side of the Plant.

Geologically, the Plant is located at the contact between two regional zones of metamorphosed intrusive rocks: the Carolina Slate Belt (now referred to as Carolina Terrane) on the east and the Charlotte Belt (or Charlotte Terrane) to the west (Figure 3). The majority of the Mayo Plant, including the largest portion of the ash basin and Mayo Lake are situated in the Carolina Terrane (Dicken, et. al., 2007). The characteristics and



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra genesis of the rocks within these regional metamorphic belts have been the subject of intense study to describe the geology in tectonic, structural, and/or litho-stratigraphic terms (Hibbard, et. al., 2002).

Based on a review of soil boring and monitoring well installation logs (voluntary and compliance wells) provided by Duke Energy, subsurface stratigraphy consists of the following material types: topsoil, residual soil, saprolite, partially weathered/fractured rock (PWR), and bedrock. Although not encountered by existing site borings, other material types expected at the Mayo Plant include fill, ash, and alluvium. In general, residual soil, saprolite, PWR, and bedrock were encountered on most areas of the site. Bedrock was encountered across the site ranging in depth below ground surface from 12 to 27 feet. The general stratigraphic units, in sequence from the ground surface down to boring termination, are defined as follows: • Fill – Although not directly encountered in existing soil borings at Mayo Plant, fill

material would be expected to consist of re-worked silts and clays that were borrowed from one area of the site and re-distributed to other areas. Fill was used in the construction of dikes and presumably as cover for the landfill (73-B).

• Ash – Although not directly encountered in existing soil borings at Mayo Plant, CCR consists of fly ash and bottom ash produced from the combustion of coal.

• Alluvium – Although not directly encountered in existing soil borings at Mayo Plant, alluvium is unconsolidated soil and sediment that has been eroded and re-deposited by streams and rivers. Alluvium is expected to be present where streams likely existed and flowed toward the major rivers and streams prior to construction of the ash basin.

• Residual Soil– The soil that develops in-place and generally consists of light gray, orange, dry, fine sandy and clayey silt. This unit tends to be thin (generally less than eight feet thick and commonly less) across the site. The residual soil horizon grades into saprolite at depth.

• Saprolite – Saprolite develops by the in-place chemical weathering of igneous and metamorphic rocks. Saprolite is characterized by the preservation of structures that were present in the unweathered parent bedrock.

• Partially Weathered Rock (PWR) – PWR occurs between the saprolite and bedrock and contains saprolite and rock remnants in a clayey matrix. In boring logs from previous site work, little distinction is made between saprolite and PWR. This is likely due to the nature of the underlying rocks. The saprolite extends from the ground surface (soil zones) downward, transitioning through a zone comprised of unconsolidated silt and sand, downward through a transition zone of PWR in a




silt/sand matrix, down to the contact with competent bedrock. These changes in material type are gradational and oftentimes indistinguishable owing to the strongly foliated and compositionally layered nature of the rock.

• Bedrock – Bedrock was encountered in borings completed around the plant area. Depth to top of bedrock ranged from approximately 12 feet to 27 feet below ground surface. Bedrock was described as green-brown, micaceous, meta-argillite or metavolcanic rocks. Fractures and fracture zones were noted in some borings.

Groundwater within the area exists under unconfined, also known as water table, conditions within the saprolite zone and in the fractures and joints of the underlying bedrock. The water table and bedrock aquifers are interconnected. The soil and saprolite act as a reservoir for water supply to the fractures and joints in the underlying bedrock. Shallow groundwater generally flows from local recharge zones in topographically high areas, such as ridges, toward groundwater discharge zones, such as stream valleys. Ridge and topographic high areas serve as groundwater recharge zones. Groundwater flow patterns in recharge areas tend to develop a somewhat radial pattern from the center of the recharge area outward toward the discharge areas and are expected to mimic surface topography. The closest surface water discharge for the plant and ash basin is to the north-northeast at Crutchfield Branch and, for the eastern portions of the property, to the east and Mayo Lake. Due to the paucity of detailed geologic observations and data across the site area, a geologic cross-section has not been developed. Data and observations made as part of the proposed assessment work will be incorporated into geologic cross-sections, as indicated on Figure 5, and included in future reports.

Analysis of groundwater level measurements and corresponding elevations collected over several years of monitoring by SynTerra from the compliance monitoring well network indicate that groundwater flows from upland areas (southwestern portion of the property) towards the northeast and Crutchfield Branch. The approximate groundwater gradient for July 2014 data was 135 feet (vertical change) over 5,500 feet (horizontal distance) or 24.5 feet/1,000 feet as measured from upgradient background well BG-2 to downgradient well CW-2. Groundwater elevation data collected from the two well clusters indicate the vertical gradient tends to be downward or neutral between the transition zone and upper bedrock. The most recent groundwater potentiometric surface map based on data collected in July 2014 is included as Figure 4.

No hydraulic conductivity data is readily available for Mayo Plant groundwater. Hydraulic conductivity measurements will be made as part of the proposed assessment and included in the CSA report.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra Information obtained as part of this CSA will support the development of the CSM and boundary conditions to be used in groundwater modeling of the plant, as discussed in Section 7.0.




6.0 ENVIRONMENTAL MONITORING

6.1 Compliance Monitoring Well Groundwater Analytical Results July 2014 was the twelfth compliance monitoring event conducted in accordance with the NPDES Permit. The routine analytical data indicates that iron, manganese, TDS and pH tend to have concentrations greater than 2L Standards. Iron tends to be detected greater than the 2L Standard in background wells BG-1 and BG-2 and compliance boundary wells CW-5 and CW-6. Manganese tends to be detected greater than the 2L Standard in background well BG-2 and in compliance boundary wells CW-2, CW-2D, CW-5, and CW-6. TDS tends to be similar to or greater than the 2L Standard in compliance boundary well CW-6. In general, the groundwater pH tends to be slightly less than or within the 2L Standard range. The concentration ranges for the constituents with detections greater than the 2L Standards are provided in Table 2 and a summary of historical groundwater results is provided in Table 3.

Antimony, barium, boron, cadmium, chromium, lead, and thallium have each been detected in at least one compliance boundary well at concentrations greater than the 2L Standard. However, these constituents have not been detected at elevated concentration with regularity and are believed to be related to naturally occurring conditions, sample turbidity, or represent data outliers.

6.2 Preliminary Statistical Evaluation of Results As a preliminary evaluation tool, statistical analysis was conducted on the groundwater analytical data collected between December 2010 and July 2014. The statistical analysis was conducted in accordance with US EPA, Statistical Training Course for Ground Water Monitoring Data Analysis, EPA530-R-93-003, 1992 and US EPA’s Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities; Unified Guidance US EPA 530/R-09-007, March 2009.

An inter-well prediction interval statistical analysis was utilized to evaluate the groundwater data. The inter-well prediction interval statistical evaluation involves comparing background well data to the results for the most recent sample date from compliance boundary wells. Monitoring wells BG-1 and BG-2 have historically been used as upgradient background wells. Monitoring wells CW-1, CW-1D, CW-2, CW-2D, CW-3, CW-4, CW-5, and CW-6 are considered downgradient compliance boundary wells. Statistical analysis was performed on the inorganic constituents with detectable concentrations for the July 2014 routine sampling event.

The statistical analysis indicated statistically significant increases (SSIs) over background concentrations for the following:




• CW-1 nitrate (however, the concentration is consistently much less than the 2L Standard);

• CW-2 sulfate (however, the concentration is consistently less than the 2L Standard);

• CW-2D sulfate (however, the concentration is consistently less than the 2L Standard);

• CW-3 chloride and sulfate (concentrations for both constituents are consistently much less than the 2L Standard);

• CW-4 sulfate (however, the concentration is consistently much less than the 2L Standard); and

• CW-6 chloride (which is consistently less than the 2L Standard), manganese (which is consistently greater than the 2L Standard), and sulfate (which is consistently less than the 2L Standard).

It is noteworthy that the current data for CW-5 indicates no SSIs over background concentrations. Based upon topography and available water levels, CW-5 appears to be located upgradient or sidegradient of the influence of the ash basin.

A more robust statistical analysis will be completed as part of the CSA using data from additional background wells. It is understood that the designation of “background” wells is subject to periodic review based upon increased understanding of site chemistry and groundwater flow direction. In the event that a well is determined to not represent background conditions, it will no longer be used as such. At least four sampling events will be required for background well data to be used for statistical analysis. In the interim, the new background well data will be pooled with other existing background well data representative of site conditions for statistical analysis. The identification and use of background wells for statistical analysis will be approved by DWR. Site-specific background determinations will be made by the DWR Director.

6.3 Additional Site Data Duke Energy has performed limited voluntary groundwater monitoring at several locations at the Mayo Plant as well as a surface water and seep evaluation. No data on the geochemical nature of ash generated at the Mayo Plant is readily available. The newly operational landfill began receiving CCR on November 7, 2014; therefore, no leachate data is available. A summary of the results of additional site data is provided below.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra 2014 Seep and Surface Water Sampling

SynTerra conducted a surface water and seep evaluation in 2014. SynTerra performed a site reconnaissance in late winter 2014 to identify potential seeps followed by collection of flow measurements and water quality samples at select locations. SynTerra collected seep and surface water samples from nine locations around the ash basin in August and November 2014. The data are summarized in Table 4. The results were presented in the Seep Monitoring Report -August and November 2014, (SynTerra, December 2014). Seep and surface water locations are indicated on Figure 5.

Analytical data provided by Duke Energy from the split sampling conducted with NCDENR from the March sampling event and analytical data from the August 2014 seep evaluations are included in Table 4. The analytical data collected by NCDENR from the March sampling event has not been provided to Duke Energy, and is not included in Table 4.

Voluntary Groundwater Monitoring Data

Four monitoring wells were voluntarily installed in 2008 by Duke Energy for the purpose of groundwater monitoring. Voluntary well MW-1 has subsequently been renamed “BG-1” and is used as a background well for the scheduled NPDES-related groundwater monitoring conducted three times each year. Voluntary wells MW-2 and MW-3 are located downgradient/downslope of the ash basin dam. Voluntary well MW-4 is located in a sidegradient position just east of the ash basin. The wells were sampled once in 2008, twice in 2009, and once in 2010. The voluntary groundwater data are included in Table 3. The four wells remain in place at the Mayo Plant and appear to be in such a condition that they could be used to collect representative groundwater samples as part of this groundwater assessment work.




7.0 ASSESSMENT WORK PLAN

The scope of work discussed in this plan is designed to meet the requirements of 15A NCAC 02L .0106(g). Solid and aqueous media sampling will be performed to fill data gaps associated with the source and vertical and horizontal extent, in soil and groundwater, for the constituents that have exceeded the 2L Standards. Data will also be collected to obtain a better understanding of the heterogeneity of groundwater flow zones by assessing the fate and transport mechanisms, such as the physical properties of the ash and soil. From this information, a groundwater fate and transport model will be created and the risk assessment performed. Based on readily available national, regional, local, and site-specific background information, and dependent upon accessibility, SynTerra anticipates collecting the following additional samples as part of the subsurface exploration plan:

• Ash and soil samples from borings within and beneath the ash basin to assess source conditions,

• Soil samples from borings located outside the ash basin boundary to assess background and downgradient conditions,

• Groundwater and ash pore water from monitoring wells to assess the source area and the horizontal and vertical extent of COPCs; and

• Surface water, seep, and sediment samples from select locations to support the risk assessment.

In addition, hydrogeologic evaluation testing will be conducted during and following monitoring well installation activities as described in Section 7.1.3. Existing environmental quality data from compliance monitoring wells, voluntary monitoring wells, and soil borings will be used to supplement data obtained from this assessment work.

A summary of the proposed exploration plan, including estimated sample quantities and estimated depths of soil borings and monitoring wells is presented in Table 5. The proposed sampling locations are shown on Figure 5. Samples collected will be analyzed for the constituents listed in Tables 6 and 7. Analytical method reporting limits will be at or below 15A NCAC 2L standards for groundwater or 15A NCAC 2B standards for Class WS-V surface water.

If it is determined that additional investigations are required during the review of existing data or data developed from this assessment, Duke Energy will notify the NCDENR regional office prior to initiating additional investigations.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra 7.1 Subsurface Exploration Characterization of subsurface materials will be conducted through the completion of soil borings and borings performed for installation of monitoring wells as shown on Figure 5. Installation details for soil borings and monitoring wells, as well as estimated sample quantities and depths, are described below and presented in Table 5.

Soil borings and monitoring wells will be installed using rotary-sonic drilling (or similar methods) to provide continuous cores through ash and into the underlying native soil and/or rock. Cores will be described/logged, photographed, and maintained.

Rotary-sonic (sonic) drilling is a drilling method that improves drilling production, placement of well materials and minimizes formation and borehole disturbance. Sonic drilling relies on high frequency vibrations that are applied to the drill rod, casing, or sampling devices relieving the skin friction on the outer walls of the steel tubing. This effect helps to free up the formation out a couple of millimeters thus reducing the side-wall friction. Using a slow rotation rate, there is less smearing and compaction of the borehole wall than occurs with augers or direct push methods. Sonic drilling thus allows for rapid penetration of the borehole, increased daily production, better sample recovery, and it allows the water bearing zones to stay open during well installation. A key benefit of sonic drilling is that high quality continuous cores through unconsolidated and consolidated material are obtained. The process of advancing a steel casing during drilling minimizes the possibly of pulling material down into or below confining units. Well construction materials (the screen, sand filter pack and bentonite seal) are installed within the steel drill casing as it is withdrawn. Placement of the sand pack within the clean, stable casing (annulus) provides for a complete sand pack with less likelihood for turbidity challenges from sand pack bridges. Sonic is preferable over hollow stem auger drilling when monitoring wells are to be installed substantially below the water table due to the drill casing providing a stable borehole during the placement of well materials and the sand pack. For these reasons, as well as to minimize groundwater sample turbidity, it is anticipated that the wells will be installed using sonic drilling methodology. It is anticipated that the borings for material sample collection only may be conducted using direct push technology (DPT).

Water from the potable water source to be used during drilling activities will be sampled and analyzed for the groundwater parameter list (Table 7). The data will be reviewed to determine if concentrations of target analytes are elevated and may pose a potential for cross-contamination, false positive detections, etc.

For clustered monitoring wells, the bedrock monitoring well boring will be utilized for characterization of subsurface materials and sample collection for laboratory analysis



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra and therefore will be drilled first. All subsurface borings will be logged in the field as described below.

At the conclusion of well installation activities, well construction details including casing depth, total well depth, and well screen length, slot size, and placement within specific hydrostratigraphic units will be presented in tabular form for inclusion into the final CSA Report. Well completion records will be submitted to NCDENR within 30 days of completion of field activities.

7.1.1 Ash and Soil Borings Characterization of ash and underlying soil will be accomplished through the completion and sampling of borings advanced at four locations within the ash basin. Six soil borings will be completed outside of the ash basin to provide additional soil quality data. Analytical results from the soil boring samples will also be used to establish input parameters for the computer model.

Field data collected during boring advancement in the ash basin will be used to evaluate:

• the presence or absence of ash,

• areal extent and depth/thickness of ash, and

• groundwater flow and transport characteristics, if groundwater is encountered.

Borings will be logged and ash/soil samples will be photographed, described, and visually classified in the field for origin, consistency/relative density, color, and soil type in accordance with the Unified Soil Classification System (ASTM D2487/D2488). Soil boring samples will be assigned with an “SB” and a sample interval in parenthesis at the end of the sample location description (i.e., MW-12SB (0-2)).

Following collection of the soil samples, the borings will be converted to monitoring wells. Monitoring wells will be constructed as discussed below.

7.1.1.1 Borings Within The Ash Basin Borings are proposed within the ash basin to characterize source COPCs, determine the thickness of ash present in the basin, and to determine the current residual saturation of the ash. Four borings will be installed in the ash basin at the locations shown on Figure 5. The borings and monitoring wells will be installed using sonic drilling (or similar methods), to provide




continuous soil cores through ash and into the underlying native residual soil. Borings are not anticipated in areas with free standing water or where the ash stability presents access safety concerns. Drilling will be extended to approximately 20 feet below the bottom of the ash to allow for characterization of the underlying native soil.

At the request of NCDENR, two of the four proposed borings will be advanced to at least 50 feet into bedrock. It is anticipated that locations AB-2 and AB-4 will be the borings that extend to 50 feet into bedrock. Borings will be advanced through outer surface casing set to the top of the bedrock. At these locations, the boreholes will be grouted using the “tremie method” to the targeted depth (to the bottom elevation of the monitoring well).

Borings associated with the proposed monitoring wells in the ash basin will designated as AB-MW-1 to AB-MW-4. To characterize the geochemical ash composition, the vertical extent of potential constituents of primary concern (COPCs) in soil, and evaluate risk, solid phase samples will be collected for laboratory analysis from the following intervals in each ash basin boring:

• Shallow Ash – approximately 3-5 feet bgs

• Deeper Ash – approximately 2 feet above the ash/soil interface

• Upper Soil – approximately 2 feet below the ash/soil interface

• Deeper Soil – approximately 8-10 feet below the ash/soil interface

• Within the saturated upper transition zone material (if not already included in the two sample intervals above)

• From a primary, open, stained fracture within fresh bedrock, if existent (bedrock core locations only)

One or more of the above listed sampling intervals may be combined if field conditions indicate they are in close proximity to each other (i.e.one sample will be obtained that will be applicable to more than one interval).

If ash is observed to be greater than 30 feet thick, a third ash sample will be collected from the approximate mid-point depth between the shallow and deeper samples. The ash samples will be used to evaluate




geochemical variations in ash located in the ash basin. The soil samples will be used to delineate the vertical extent of potential soil impacts beneath the ash basin.

Ash and soil samples will be analyzed for total inorganic constituents and geotechnical parameters as presented in Table 6. Select ash and soil samples will be analyzed for leachable inorganic constituents using the Synthetic Precipitation Leaching Procedure (SPLP) to evaluate the potential for leaching of constituents from ash into underlying soil.

Following collection of the soil samples, the borings will be converted to monitoring wells as discussed below. Due to safety concerns, borings will not be completed where free-standing water is present within the ash basin or the structural integrity of the ash creates an unsafe situation for drilling activities.

A summary of the proposed boring details is provided in Table 5. The depths at which the samples are collected will be noted on sample IDs. Following collection of the soil samples, if the borings will not be converted to monitoring wells, the borings will be abandoned by filling with a bentonite-grout mixture.

7.1.1.2 Borings Outside Ash Basin Six borings will be located in areas outside the ash basin to provide characterization of native soil conditions. As previously described, preliminary mapping has indicated that a geologic contact bisects a portion of the plant property with differing rock types. Proposed borings SB-1 through SB-4 will provide background soil geochemical data for areas of the plant presumed to be underlain by different rock types. Proposed borings SB-5 and SB-6 will investigate geochemical conditions in subsurface soils around the 1981 landfill (73-B).

Solid phase samples will be collected for laboratory analysis from the following intervals in each boring:

• approximately 0-2 feet bgs for (risk assessment purposes)

• approximately 2-3 feet above the water table

• approximately 2-3 feet below the water table




• within the saturated upper transition zone material (if not already included in the two sample intervals above)

• from a primary, open, stained fracture within fresh bedrock, if existent (bedrock core locations only)

One or more of the above listed sampling intervals may be combined if field conditions indicate they are in close proximity to each other (i.e.one sample will be obtained that will be applicable to more than one interval).

7.1.1.3 Index Property Sampling and Analysis Physical properties of ash and soil will be tested in the laboratory to provide data for use in groundwater modeling. Samples will be collected at selected locations, with the number of samples collected from the material types as follows:

• Ash - 4 samples (AB-1 through AB-4)

• Soil/Saprolite - 4 samples (SB-1, SB-3, SB-4, SB-5)

• Soil/Saprolite directly above refusal - 4 samples (SB-1, SB-3, SB-4, SB-5)

These select samples will be tested for:

• Natural Moisture Content Determination, in accordance with ASTM D-2216

• Grain size with hydrometer determination, in accordance with ASTM Standard D-422

The depth intervals of the selected samples will be determined in the field by the Lead Geologist/Engineer. A summary of the boring details is provided in Table 5.

In addition, thin-walled undisturbed tubes (“Shelby” Tubes) in ash and soil/saprolite will be advanced and collected at the locations specified by the Lead Geologist/Engineer in the field. The Shelby Tubes will be transported to a soil testing laboratory and each tube will be tested for the following:




• Natural Moisture Content Determination, in accordance with ASTM D-2216

• Grain size with hydrometer determination, in accordance with ASTM Standard D-422

• Hydraulic Conductivity Determination, in accordance with ASTM Standard D-5084

• Specific Gravity of Soils, in accordance with ASTM Standard D-854

Approximately ten soil core samples will also be selected from representative material at the site for column tests to be performed in triplicate. Batch Kd tests, if performed, will be executed in triplicate as well. This is discussed in more detail in Section 7.9.

The results of the laboratory soil and ash property determination will be used to determine properties such as porosity, transmissivity, and specific storativity. The results from these tests will be used in the groundwater fate and transport modeling. The specific borings where these samples are collected from will be determined based on field conditions, with consideration given to their location relative to use in the groundwater model.

7.1.2 Groundwater Monitoring Wells Additional groundwater monitoring wells will be installed to provide aquifer and geochemistry data to supplement information obtained from the 13 existing monitoring wells. Additional wells will be used to monitor conditions within the aquifer horizontally and vertically. Data obtained from the existing and newly installed monitoring wells will be used for the fate and transport modeling of the site and to support the risk assessment.

Monitoring wells will be constructed by North Carolina-licensed well drillers in accordance with 15A NCAC 02C (Well Construction Standards). Drilling equipment will be decontaminated prior to use at each location using a high pressure steam cleaner.

Monitoring wells will be constructed of 2-inch ID, National Sanitation Foundation (NSF) grade polyvinyl chloride (PVC) (ASTM 2012a,b) schedule 40 flush-joint threaded casing and 0.010-inch machine-slotted pre-packed screens.




The existing compliance monitoring wells at the site generally produce groundwater samples with turbidities of less than 10 nephelometric turbidity units (NTU). Therefore, the assessment well design will be similar with improvements in the drilling method and pre-packed screens. To improve on well installation, the assessment wells will be installed using sonic drilling and the well construction will include pre-packed screens, plus additional sand in the annular space, to minimize the turbidity of samples. The sonic drilling method disturbs the formation much less than traditional hollow stem or rotary drilling. The slow rotation rate and vibration allows for the minimum impact on the formation resulting in better water quality and flow. As previously discussed, the placement of the sand pack within the sonic casing also improves the overall quality and uniformity of the sand pack. One way this is evident is that the amount of time required for development of a sonic well tends to be less than half the time associated with other drilling methods. Also with sonic drilling there is very little smearing effect to the borehole wall allowing quicker aquifer stabilization.

Where monitoring of different hydrogeologic zones or depth intervals is appropriate, monitoring wells will be installed as well clusters; single wells located within approximately 10 feet of another well designed to monitor a different depth interval. Well designations for the new wells will be consistent with other Duke Energy sites located within the Piedmont physiographic province.

Monitoring wells will be installed within the ash basin at the base of the ash. These locations will be designated with an “AB” at the beginning of the location name (i.e., ABMW-1). Wells installed beneath an ash basin will be named with the appropriate designation discussed below (i.e., ABMW-1S, ABMW-1D, or ABMW-1BR).

Saprolite wells will be installed with the top of the well screen approximately five feet below the water table. Wells installed at this depth interval will be designated with an “S” at the end of the well name (i.e., MW-15S).

If observation of cores during drilling at a monitoring well cluster indicates the presence of a transition zone of PWR between saprolite and competent bedrock of sufficient thickness for monitoring, and/or if discreet flow zones (i.e., “upper” and “lower” zones) are observed within the saprolite, then additional wells will be installed to monitor each discreet flow zone. Wells installed in this depth




interval will be designated with a “D” at the end of the well name (i.e., MW-15D).

Bedrock wells will be installed into the upper portion of the underlying shallow bedrock to an approximate depth, based on specific conditions, of at least 10 feet below the saprolite/bedrock transition zone. This will provide information on the vertical distribution of aquifer characteristics between the zones (chemistry and aquifer parameters) as well was determining the magnitude of vertical hydraulic gradients. Wells installed at this depth interval will be designated with a “BR” at the end of the well name (i.e., MW-15BR). For planning purposes, well clusters only consist of two wells; a single saprolite well and a bedrock well. If a PWR zone or discreet flow zone in lower portions of the saprolite is observed in the field, an additional deeper PWR “D” well will be installed. If bedrock fractures are not encountered or do not yield sufficient water for monitoring within 50 feet of the bedrock surface at a drilling location, bedrock wells will not be installed at that location.

Packer testing will be performed on select fractures observed in the rock cores. See Section 7.1.4 for details regarding packer test implementation.

The locations of the proposed wells are shown on Figure 5. A summary of the details of the proposed and existing wells is provided in Table 5.

7.1.2.1 Proposed Wells Upgradient of the Ash Basin Eight additional wells in four separate locations will be installed in the presumed upgradient direction of the ash basin to further evaluate water quality in different hydrogeologic settings a sufficient distance from the ash basin to avoid possible effects of groundwater mounding. These updgradient wells are intended to possibly be used in the future as background wells for statistical comparison once evaluated and agreed upon by NCDENR. As discussed in Section 6.0, it is understood that the designation of “background” well is subject to periodic review based upon increased understanding of site chemistry and groundwater flow direction.

The proposed wells are located in areas presumed to be underlain by two different rock types (Figure 3), which may yield groundwater with different geochemical signatures.

• Proposed well cluster MW-10S/MW-10BR will be installed east of the power generating facility and over 2,000 feet from the ash basin




in a presumed upgradient position. There is a paucity of groundwater wells and potentiometric data for this area of the Plant, so hydrogeological data from this proposed well cluster will provide information to understanding groundwater flow and groundwater geochemistry in this area.

• Proposed well clusters MW-11S/MW-11BR and MW-12S/MW-12BR will be installed southwest of both the power generating facility and the ash basin (several thousand feet away). There is a paucity of groundwater wells and potentiometric data for this area of the Plant, so hydrogeological data from this proposed well cluster will provide information to understanding groundwater flow. In addition, these well clusters will likely serve as background wells with respect to groundwater geochemistry due their upgradient and distant location relative to the plant and the ash basin.

• Proposed well cluster MW-13S/ MW-13BR will be installed on the west side of US Hwy 501 west of the ash basin. This location appears to be upgradient of the ash basin; however, a cursory look at the topography of the area indicates the potential for a fracture lineament – manifested as linear valleys – in this area. These wells will provide information to understanding groundwater flow and groundwater geochemistry in this area.

The location for each of these wells is shown on Figure 5. A summary of proposed boring and well construction details is provided in Table 5.

7.1.2.2 Proposed Monitoring Wells within Ash Basin Additional monitoring wells will be installed as clusters at the proposed boring locations within the ash basin to collect ash pore water samples from within the ash and groundwater samples beneath the ash, to measure pore water and groundwater elevations, and residual saturation within the basins to gain a better understanding of the groundwater quality and flow conditions within and beneath the ash basins. The borings and monitoring wells are targeted to be placed at either the deepest portion of the basin or at a location that provides spatial variation across the basin. The data will be used for source area modeling.

At each cluster within the ash basin, a monitoring well will be installed with the base of the screen set near the base of the ash. A monitoring well will also be installed within the aquifer below the basin. Monitoring wells




installed within an ash basin will be designated with an “AB” at the beginning of the location name (i.e., ABMW-1). Wells installed beneath an ash basin will be named with the appropriate designation discussed above (i.e., ABMW-1S, ABMW-1D, or ABMW-1BR).

7.1.2.3 Proposed Monitoring Wells Downgradient or Sidegradient of the Ash Basin

Fifteen additional wells in eight separate locations will be installed in the presumed downgradient or sidegradient direction of the ash basin to further evaluate water quality.

• Proposed well cluster MW-14S/MW-14BR will be installed northwest of the ash basin at a distance of about 500 feet in a presumed sidegradient or upgradient position. Hydrogeological data from this proposed well cluster will provide information to understanding groundwater flow and groundwater geochemistry in this area.

• Proposed well MW-5BR will be installed adjacent to existing compliance well CW-5 for the purpose of assessing vertical extent of potential impacts to groundwater from the ash basin in this area. CW-5 is screened from 36 to 41 feet bgs, so CW-5BR will be extended deeper into bedrock and completed in a deeper fracture zone.

• Proposed well MW-3BR will be installed adjacent to existing compliance well CW-3 for the purpose of assessing vertical extent of potential impacts to groundwater from the ash basin in this area. CW-3 is screened from 17 to 32 feet bgs in PWR, so CW-3BR will be extended into and completed in bedrock.

• Proposed well cluster MW-15S/MW-15BR will be installed north of the ash basin, at the property line, at a distance of about 1,500 feet in a presumed downgradient position relative to the ash basin. Hydrogeological data from this proposed well cluster will provide information on groundwater flow and geochemistry in this area.

• Proposed well cluster MW-16S/MW-16BR will be installed north of the ash basin at a distance of about 1,200 feet in a presumed downgradient position relative to the ash basin. Hydrogeological data from this proposed well cluster will provide information on




groundwater flow and geochemistry in this area. This well cluster is proposed to be installed near/along Crutchfield Branch. If groundwater is encountered in the alluvium of Crutchfield Branch, a shallow well may also be installed.

Proposed well clusters MW-15 and MW-16 are located on off-site property not owned by Duke Energy and will require access permission for well installation and monitoring. Duke Energy will contact the property owner to obtain access to the property. Duke Energy will request liaison assistance from DENR if Duke Energy is unable to obtain access to a specific property where sampling is deemed necessary. The liaison request will include available property owner contact information and details of prior discussions with the property owner regarding access to the property for site assessment purposes. An Application for Permit to Construct a Monitoring Well or Recovery Well System (GW-22MR, Rev. 8/13) will be submitted to the Raleigh Regional Office prior to installation of off-site monitoring wells.

• Proposed well MW-6BR will be installed adjacent to existing compliance well CW-6 for the purpose of assessing vertical extent of potential impacts to groundwater from the ash basin in this area. CW-6 is a bedrock well screened in a fracture encountered at 76 feet bgs, so CW-6BR will be extended deeper into bedrock and completed in a deeper fracture zone.

• Proposed well clusters MW-7S/MW-7BR, MW-8S/MW-8BR, and MW-9S/MW-9BR will be installed east of the ash basin in a presumed sidegradient or upgradient position. There is a paucity of groundwater wells and potentiometric data for this area of the Plant. Hydrogeological data from this proposed well cluster will provide information on groundwater flow and geochemistry in this area.

At the request of NCDENR, a number of the proposed monitoring well borings will be advanced to at least 50 feet into bedrock. It is anticipated that locations MW-8BR, MW-10BR, MW-11BR, MW-13BR, and MW-15BR will be the well borings that extend to 50 feet.




7.1.3 Well Completion and Development

Well Completion The shallowest wells will be installed with screen intervals 10 feet in length. Deeper wells will be installed with screen intervals five feet in length. Where well clusters are proposed, bedrock wells will be installed first. Although groundwater within the saprolite, PWR, and shallow bedrock appears to be interconnected, as discussed in Section 5.0, bedrock wells will be installed as double-cased wells as an additional measure to prevent COPCs within overlying material from migrating along the annular space of the borehole and into bedrock. To accomplish this, an outer casing will be installed using sonic drilling equipment with a 10-inch core barrel just into the top of competent bedrock which will be determined based on observation of continuous cores recovered during drilling. A permanent six-inch diameter schedule 40 PVC outer casing will be installed and grouted in-place. After the grout has had sufficient time to set (approximately 24 hours), drilling will advance through the casing using a smaller diameter drilling core barrel and into bedrock to the depth of the first water-bearing zone (determined based on observation of continuous cores) at least 10 feet below the depth of the surface casing.

Each well will be constructed in accordance with 15A NCAC 02C (Well Construction Standards) and consist of 2-inch diameter NSF schedule 40 PVC flush-joint threaded casings and pre-packed screens appropriately sized based on soil conditions identified during previous assessment activities. The annular space between the borehole wall/inner casing and pre-packed well screens for each of the wells will be filled with clean, well-rounded, washed high 20/40 mesh silica sand determined by the field geologist. The sand pack will be placed to approximately two feet above the top of the pre-packed screen and then an approximate two-foot pelletized bentonite seal will be placed above the filter pack. The remainder of the annular space will be filled with a neat cement grout from the top of the upper bentonite seal to near ground surface.

Monitoring wells will be completed with either steel above ground protective casings with locking caps or steel flush-mount manholes with locking expansion caps, and well tags. The protective covers will be secured and completed in a concrete collar and a minimum two-foot square concrete pad.

Well Development Following installation, the monitoring wells will be developed in order to remove drill fluids, clay, silt, sand, and other fines which may have been




introduced into the formation or sand pack during drilling and well installation, and to establish communication of the well with the aquifer. Well development will be performed using a portable submersible pump, which will be repeatedly moved up and down the well screen interval until the water obtained is relatively clear. Development will be continued by sustained pumping until monitoring parameters (e.g., conductivity, pH, temperature) are generally stabilized; estimated quantities of drilling fluids, if used, are removed; and, turbidity decreases to acceptable levels (10 NTUs). The wells will be developed as installed (but no sooner than 24 hours after installation to allow for grout cure time). The ongoing well development information will be used to make adjustments as needed to the well construction design to minimize turbidity and possible other unforeseen factors.

If a well cannot be developed to produce low turbidity groundwater samples, NCDENR will be notified and supplied with the well completion and development measures that have been employed to make a determination if the turbidity is an artifact of the geologic materials in which the well is screened.

Following development, sounding the bottom of the well with a water level meter should indicate a “hard” (sediment-free) bottom. Development records will be prepared under the direction of the Project Scientist/Engineer and will include development method(s), water volume removed, and field measurements of temperature, pH, conductivity, and turbidity.

7.1.4 Hydrogeologic Evaluation Testing In order to better characterize hydrogeologic conditions at the site, falling and constant head tests, and slug tests will be performed as described below. Data obtained from these tests will be used in groundwater modeling. In addition, historical soil boring data at the site will be utilized as appropriate to better characterize hydrogeologic conditions and will be used for groundwater modeling.

Packer Tests Packer tests using a double packer system will be performed in bedrock well borings at locations based on site-specific conditions, with one packer test in each rock core well boring. Packer tests will utilize a double packer system and the interval (five feet or 10 feet based on field conditions) to be tested will be based on observation of the rock core and will be selected by the Lead Geologist/Engineer. The U.S. Bureau of Reclamation test method and calculation




procedures as described in Chapter 17 of their Engineering Geology Field Manual (2nd Edition, 2001) will be used.

Slug Tests After the wells have been developed, hydraulic conductivity tests (rising head slug tests) will be conducted on each of the new wells. The slug tests will be performed in accordance with ASTM D4044-96 Standard Test Method (Field Procedure) for Instantaneous Change in Head (Slug) Tests for Determining Hydraulic Properties of Aquifers and NCDENR Performance and Analysis of Aquifer Slug Test and Pumping Test Policy, dated May 31, 2007.

Prior to performing each slug test, the static water level will be determined and recorded and a Solinst Model 3001 Levelogger® Edge electronic pressure transducer/data logger, or equivalent, will be placed in the well at a depth of approximately six-inches above the bottom of the well. The Levelogger® will be connected to a field laptop and programmed with the well identification, approximate elevation of the well, date, and time.

The slug tests will be conducted by lowering a PVC “slug” into the well casing. The water level within the well is then allowed to equilibrate to a static level. After equilibrium, the slug is rapidly withdrawn from the well, thereby decreasing the water level in the well instantaneously. During the recovery of the well, the water level is measured and recorded electronically using the pressure transducer/data logger. Two separate slug tests will be conducted for each well.

The slug tests will be performed for no less than ten minutes, or until such time as the water level in the test well recovers 95 percent of its original pre-test level, whichever occurs first. Slug tests will be terminated after two hours even if the 95 percent pre-test level is not achieved.

The data obtained during the slug tests will be reduced and analyzed using AQTESOLV™ for Windows, version 4.5, software to determine the hydraulic conductivity of the soils in the vicinity of wells.

7.2 Ash Pore Water and Groundwater Sampling and Analysis New and existing wells will be sampled using low-flow sampling techniques in accordance with US EPA Region 1 Low Stress (low flow) Purging and Sampling Procedure for the Collection of Groundwater Samples from Monitoring Wells (revised January 19, 2010) and Groundwater Monitoring Program Sampling, Analysis and Reporting Plan, Mayo Steam Electric Plant (SynTerra, October 2014). Each new well will be sampled after well



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra development, and at the completion of drilling activities (two sampling events) for inclusion in CSA reports. Voluntary wells MW-2, MW-3, and MW-4 will also be sampled twice.

The new monitoring wells will provide water quality data downgradient or sidegradient from the ash basins waste boundary for use in groundwater modeling (i.e., to evaluate the horizontal and vertical extent of potentially impacted groundwater outside the ash basin waste boundary). Background wells BG-1 and BG-2 and potential background wells MW-11S/BR and MW-12S/BR will be used to provide information on background water quality. The background well locations were selected to provide additional physical separation from possible influence of the ash basin on groundwater. These wells will also be useful in the statistical analysis to determine the site-specific background water quality concentrations (SSBCs).

Subsequent to the two new well sampling events, quarterly sampling of new background wells will be performed to develop a background data set. A site-wide groundwater monitoring schedule will be developed following review of initial data sets collected during the groundwater assessment.

The purposes of the proposed monitoring wells are as follows:

• ABMW-series Wells – The ABMW-series well locations were selected to provide pore water quality data from the base of the ash basin at the deepest point in the basin, based on boring log information.

• MW-series Wells – The MW-series well locations were selected to provide water quality data downgradient, sidegradient, or upgradient from the ash basin waste boundary for use in groundwater modeling (i.e., to evaluate the horizontal and vertical extent of potentially impacted groundwater outside the ash basin waste boundary).

At the Mayo Plant, a low-flow purging technique has been selected as the most appropriate technique to minimize sample turbidity. Groundwater and ash pore water samples will be collected from the monitoring wells to provide water quality data within, beneath, upgradient, downgradient and sidegradient of the ash basins. During low-flow purging and sampling, groundwater is pumped into a flow-through chamber at flow rates that minimize or stabilize water level drawdown within the well. At the Mayo Plant, low-flow sampling is conducted using a peristaltic pump with new tubing. The intake for the tubing is lowered to the mid-point of the screened interval. A multi-parameter water quality monitoring instrument is used to measure field indicator



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra parameters within the flow-through chamber during purging. Measurements include pH, specific conductance, and temperature.

Indicator parameters are measured over time (usually at 3-5 minute intervals). When parameters have stabilized within ±0.2 pH units and ±10 percent for temperature and specific conductivity over three consecutive readings, representative groundwater has been achieved for sampling. Turbidity is not a required stabilization parameter; however, turbidity levels of 10 NTU or less are targeted. Purging will be discontinued and groundwater samples will be obtained if turbidity levels of 10 NTU or less are not obtained after one hour of continuous purging. If the turbidity for a well increases over time, the well may be re-developed to restore conditions.

Ash pore water and groundwater samples will be analyzed by a North Carolina certified laboratory for the parameters listed in Table 7. Total and dissolved metals analysis will be conducted. A summary of the proposed groundwater samples is included in Table 5.

During groundwater sampling activities, water level measurements will be made at the existing site monitoring wells, observation wells, and piezometers, along with the new wells. The data will be used to generate potentiometric maps for each separate hydrogeologic zone (i.e., saprolite, transition zone, and bedrock) as well as to determine the degree of residual saturation beneath the ash basin. The water levels used for preparation of flow maps will be collected during a single 24-hour period.

Groundwater samples will be analyzed by a North Carolina certified laboratory for the constituents included in Table 7. Select constituents will be analyzed for total and dissolved concentrations.

In 2014, the Electric Power Research Institute published the results of a critical review that presented the current state-of-knowledge concerning radioactive elements in coal combustion products (CCPs) and the potential radiological impacts associated with management and disposal. The review found:

Despite the enrichment of radionuclides from coal to ash, this critical review did not locate any published studies that suggested typical CCPs posed any significant radiological risks above background in the disposal scenarios considered, and when used in concrete products. These conclusions are consistent with previous assessments. The USGS (1997) concluded that “Radioactive elements in coal and fly ash should not be sources of alarm. The vast majority of coal and the majority of fly ash are not significantly enriched in radioactive elements, or in associated radioactivity, compared to common soils or rocks.” A year later, the U.S. EPA (1998) concluded that the risks of




exposure to radionuclide emissions from electric utilities are “substantially lower than the risks due to exposure to background radiation.”

To confirm these general findings, Duke Energy proposes to analyze potentially worst-case groundwater samples collected from ash basin areas for radium-266 and radium-228 (Ra226 and Ra228). Existing voluntary well MW-3, immediately downgradient of the ash basin dam, is proposed for radium analysis, with NCDENR concurrence. In addition, new potential background wells MW-12S and MW-12BR are proposed for radium analysis.

Groundwater sample results will be compared to Class GA Standards as found in 15A NCAC 02L .0202 Groundwater Quality Standards, last amended on April 1, 2013.

In addition to total analytes, speciation of inorganics will be conducted for select sample locations to characterize the aqueous chemistry and geochemistry in locations and depths of concern. Inorganic speciation of iron (Fe(II), Fe(III)) and manganese (Mn(II), Mn(IV)) will be conducted at the following locations. Representative samples of ash pore water within the basin, groundwater below the basin, from a potential background location, and from a downgradient location will be collected. Laboratory analyses will be performed in accordance with the methods provided in Table 7.

7.3 Surface Water, Sediment, and Seep Sampling Duke Energy recently collected samples from surface water and seeps identified around the ash basin (SynTerra, December 2014). A summary of the analytical results are included in Table 4 and the sample locations are shown on Figure 5. The results of that work will be supplemented by the collection of surface water, seep, and sediment samples as part of this CSA.

7.3.1 Surface Water Samples To provide additional information on groundwater to surface water pathways and to support the human health and ecological risk assessment discussed in Section 8.0, five water samples will be collected. Three of the samples (S-03, SW-CB1, and SW-CB2) will be collected from Crutchfield Branch on the plant property and after leaving the plant property flowing north into Virginia. Two of the samples (SW-REF1 and S-06) will be collected from an unnamed stream south of the power plant that eventually flows toward Mayo Lake, if sufficient flow is present. The SW-REF1 location may represent upstream conditions. Locations S-03 and S-06 have previously been sampled and may provide information regarding variability in flow and water quality over time. The water samples will be analyzed for the parameters listed in Table 7. This data will be




used to infer preferential pathways and migration from groundwater to surface water.

Location SW-CB2 is on off-site property not owned by Duke Energy and will require access permission for sampling. Duke Energy will contact the property owner to obtain access to the property. Duke Energy will request liaison assistance from DENR if Duke Energy is unable to obtain access to a specific property where sampling is deemed necessary. The liaison request will include available property owner contact information and details of prior discussions with the property owner regarding access to the property for site assessment purposes.

Within Ash Basin At each location, two water samples will be collected – one sample close to the surface (i.e., 0 to 1 foot from surface) and one sample at a depth just above the ash surface (i.e., 1 foot to 2 feet above the ash to avoid suspending the ash within the sample). Prior to sampling, the depth to ash will be measured by slowly lowering a measuring stick or tape until the ash surface is encountered, being careful to avoid suspending the ash. The depth to ash will be noted, and a sample thief (or similar device) will be slowly lowered to the desired depth to collect the sample. The sample thief and sample will be retrieved and the sample will be transferred to the appropriate sample containers provided by the laboratory. In areas where the water body is less than 5 feet deep, one water sample will be collected from the location at a depth just above the ash surface. Ash basin surface water samples will be analyzed for the same constituents as groundwater samples (Table 7). Select constituents will be analyzed for total and dissolved concentrations.

Samples were recently collected (2014) from the open water within the ash basin. The pore water within the ash basins likely represents the highest concentrations of COPCs for source area modeling. Therefore, additional open water samples are not anticipated as part of this assessment. However, if it is decided in the future that additional sampling is necessary, samples will be collected using the procedure described below.

7.3.2 Sediment Samples Sediment samples will be collected from the bed surface at each of the water sample locations discussed above (Figure 5) to evaluate sediment quality and provide data to be used in the risk assessment. The S-06 location will be considered an upstream reference sediment sample. The sediment samples will




be analyzed for total inorganics, using the same constituents list proposed for the soil and ash samples and pH, cation exchange capacity, particle size distribution, percent solids, percent organic matter, and redox potential.

7.3.3 Seep Samples Samples from previously identified and sampled seep locations will be collected, if sufficient flow is present. The collection of flow data and water samples from the previously sampled seep locations will provide information regarding variability in flow and water quality over time. The water samples will be analyzed for the parameters listed in Table 7.

Analytical results for surface water samples collected from outside the ash basin will be compared to 15A NCAC 2B .0200 Classifications and Water Quality Standards Applicable to Surface Waters and Wetlands of North Carolina (2B Standards, WS-V).

7.4 Field and Sampling Quality Assurance/Quality Control Procedures

Documentation of field activities will be completed using a combination of logbooks, field data records (FDRs), sample tracking systems, and sample custody records. Site and field logbooks are completed to provide a general record of activities and events that occur during each field task. FDRs have been designated for each exploration and sample collection task, to provide a complete record of data obtained during the activity.

7.4.1 Field Logbooks The field logbooks provide a daily hand written account of field activities. Logbooks are hardcover books that are permanently bound. All entries are made in indelible ink, and corrections are made with a single line with the author initials and date. Each page of the logbook will be dated and initialed by the person completing the log. Partially completed pages will have a line drawn through the unused portion at the end of each day with the author’s initials. The following information is generally entered into the field logbooks:

• The date and time of each entry. The daily log generally begins with the Pre-Job Safety Brief;

• A summary of important tasks or subtasks completed during the day;

• A description of field tests completed in association with the daily task;




• A description of samples collected including documentation of any quality control samples that were prepared (rinse blanks, duplicates, matrix spike, split samples, etc.);

• Documentation of equipment maintenance and calibration activities;

• Documentation of equipment decontamination activities; and,

• Descriptions of deviations from the work plan.

7.4.2 Field Data Records Sample FDRs contain sample collection and/or exploration details. A FDR is completed each time a field sample is collected. The goal of the FDR is to document exploration and sample collection methods, materials, dates and times, and sample locations and identifiers. Field measurements and observations associated with a given exploration or sample collection task are recorded on the FDRs. FDRs are maintained throughout the field program in files that become a permanent record of field program activities.

7.4.3 Sample Identification In order to ensure that each number for every field sample collected is unique, samples will be identified by the sample location and depth interval, if applicable (e.g., MW-1S (5-6’)). Samples will be numbered in accordance with the proposed sample IDs shown on Figure 5.

7.4.4 Field Equipment Calibration Field sampling equipment (e.g., water quality meter) will be properly maintained and calibrated prior to and during continued use to assure that measurements are accurate within the limitations of the equipment. Personnel will follow the manufacturers’ instructions to determine if the instruments are functioning within their established operation ranges. The calibration data will be recorded on a FDR.

To be acceptable, a field test must be bracketed between acceptable calibration results.

• The first check may be an initial calibration, but the second check must be a continuing verification check.

• Each field instrument must be calibrated prior to use.

• Verify the calibration at no more than 24-hour intervals during use and at the end of the use if the instrument will not be used the next day or time periods greater than 24 hours.




• Initial calibration and verification checks must meet the acceptance criteria listed in the table below.

• If an initial calibration or verification check fails to meet the acceptance criteria, immediately recalibrate the instrument or remove it from service.

• If a calibration check fails to meet the acceptance criteria and it is not possible to reanalyze the samples, the following actions must be taken:

- Report results between the last acceptable calibration check and the failed calibration check as estimated (qualified with a “J”);

- Include a narrative of the problem; and

- Shorten the time period between verification checks or repair/replace the instrument.

• If historically generated data demonstrate that a specific instrument remains stable for extended periods of time, the interval between initial calibration and calibration checks may be increased.

- Acceptable field data must be bracketed by acceptable checks. Data that are not bracketed by acceptable checks must be qualified.

- Base the selected time interval on the shortest interval that the instrument maintains stability.

- If an extended time interval is used and the instrument consistently fails to meet the final calibration check, then the instrument may require maintenance to repair the problem or the time period is too long and must be shortened.

• For continuous monitoring equipment, acceptable field data must be bracketed by acceptable checks or the data must be qualified.

Sampling or field measurement instrument determined to be malfunctioning will be repaired or will be replaced with a new piece of equipment.

7.4.5 Sample Custody Requirements A program of sample custody will be followed during sample handling activities in both field and laboratory operations. This program is designed to assure that each sample is accounted for at all times. The appropriate sampling and laboratory personnel will complete sample FDRs, chain-of-custody records, and laboratory receipt sheets.




The primary objective of sample custody procedures is to obtain an accurate written record that can trace the handling of all samples during the sample collection process, through analysis, until final disposition.

Field Sample Custody Sample custody for samples collected during each sampling event will be maintained by the personnel collecting the samples. Each sampler is responsible for documenting each sample transfer, maintaining sample custody until the samples are shipped off-site, and sample shipment. The sample custody protocol followed by the sampling personnel involves:

• Documenting procedures and amounts of reagents or supplies (e.g., filters) which become an integral part of the sample from sample preparation and preservation;

• Recording sample locations, sample bottle identification, and specific sample acquisition measures on appropriate forms;

• Using sample labels to document all information necessary for effective sample tracking; and,

• Completing sample FDR forms to establish sample custody in the field before sample shipment.

Prepared labels are normally developed for each sample prior to sample collection. At a minimum, each label will contain:

• Sample location and depth (if applicable);

• Date and time collected;

• Sampler identification; and,

• Analyses requested and applicable preservative.

A manually-prepared chain-of-custody record will be initiated at the time of sample collection. The chain-of-custody record documents:

• Sample handling procedures including sample location, sample number and number of containers corresponding to each sample number;

• The requested analysis and applicable preservative;

• The dates and times of sample collection;




• The names of the sampler(s) and the person shipping the samples (if applicable);

• The date and time that samples were delivered for shipping (if applicable);

• Shipping information (e.g., FedEx Air Bill); and,

• The names of those responsible for receiving the samples at the laboratory.

• Chain-of-custody records will be prepared by the individual field samplers.

Sample Container Packing Sample containers will be packed in plastic coolers for shipment or pick up by the laboratory. Bottles will be packed tightly to reduce movement of bottles during transport. Ice will be placed in the cooler along with the chain-of-custody record in a separate, resealable, air tight, plastic bag. A temperature blank provided by the laboratory will also be placed in each cooler prior to shipment if required for the type of samples collected and analyses requested.

7.4.6 Quality Assurance and Quality Control Samples The following Quality Assurance/Quality Control (QA/QC) samples will be collected during the proposed field activities:

• Equipment rinse blanks (one per day)

• Field Duplicates (one per 20 samples per sample medium)

Equipment rinse blanks will be collected from non-dedicated equipment used between wells and from drilling equipment between soil samples. The field equipment is cleaned following documented cleaning procedures. An aliquot of the final control rinse water is passed over the cleaned equipment directly into a sample container and submitted for analysis. The equipment rinse blanks enable evaluation of bias (systematic errors) that could occur due to decontamination.

A field duplicate is a replicate sample prepared at the sampling locations from equal portions of all sample aliquots combined to make the sample. Both the field duplicate and the sample are collected at the same time, in the same container type, preserved in the same way, and analyzed by the same laboratory as a measure of sampling and analytical precision.




Field QA/QC samples will be analyzed for the same constituents as proposed for the soil and groundwater samples, as identified on Tables 6 and 7, respectively.

7.4.7 Decontamination Procedures Proper decontamination of sampling equipment is essential to minimize the possibility of cross contamination of samples. Previously used sampling equipment will be decontaminated before sampling and between the collection of each sample. New, disposable sampling equipment will be used for sampling activities where possible.

Decontamination of Field Sampling Equipment Field sampling equipment will be decontaminated between sample locations using potable water and phosphate- and borax-free detergent solution and a brush, if necessary, to remove particulate matter and surface films. Equipment will then be rinsed thoroughly with tap water to remove detergent solution prior to use at the next sample location.

Decontamination of Drilling Equipment Decontamination of drilling equipment (drill rods, cutting heads, etc.) will be completed at each well or boring location following completion of the well or boring. The decontamination procedures area as follows;

• After completion of well or boring a hot water pressure cleaner will be used to decontaminate tooling as it is extracted from the bore hole.

• The decontamination water will be collected in the drill through tubs that are in place under the deck during drilling activities. There is a seal installed between the tub and land surface to ensure decontamination water does not migrate back down the bore hole before the last tool joint is removed.

• Recovered water is then pumped from the tub into drums, other IDW containers, or directly onto the ground, away from the drilling location.

• The tooling is then loaded directly back on support equipment ready for the next location.

7.5 Influence of Pumping Wells on Groundwater System Based on the results of the receptor survey (SynTerra, November 2014), approximately 21 potential water supply wells may be located within a 0.5 mile radius of the compliance boundary. The wells are believed to be located greater than 0.25 miles from the ash basin and in topographically upgradient positions. It is anticipated that due to the distance from the ash basin and likely limited withdrawal rates, the use of the off-



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra site wells should not substantially affect the groundwater flow system near the ash basin. The anticipated new well clusters near the southern side of the property and near the northwest corner of the property will be used to confirm this assumption.

There are three inactive water supply wells on the Mayo Plant property (DEP 1, DEP2, and DEP3; Figure 5). These wells were drilled in the early 1980s to supply water to the plant during construction and early start-up operations. The wells have been out of service for a number of years; therefore, they are not currently influencing groundwater flow. An evaluation of each of the wells will be conducted during site assessment activities. Any pumps and piping will be removed, the depth of the well and the static water level will be measured, and a downhole camera will be used to video-log the entire well to obtain well-specific data. Based on the results of the well evaluation, a decision will be made, in consultation with the NCDENR Raleigh Regional Office, as to whether well samples from the wells would provide useful information.

7.6 Site Hydrogeologic Conceptual Model The ICSM for the Mayo Plant has been developed using data discussed in Section 2.0 through 6.0 above and was used to develop the Assessment Work Plan. The ICSM has provided sufficient detail to be able to understand the flow dynamics at the Mayo Plant and to identify potential data gaps, such as areas where monitoring wells need to be installed and additional soil and groundwater analytical needs. Sections 7.1 through 7.5 were prepared to address these data gaps.

The data obtained during the proposed assessment will be supplemented by available reports and data on site geotechnical, geologic, and hydrologic conditions to develop the hydrogeologic Site Conceptual Model (SCM). The SCM is a conceptual interpretation of the processes and characteristics of a site with respect to the groundwater flow and other hydrologic processes at the site.

The NCDENR document, “Hydrogeologic Investigation and Reporting Policy Memorandum,” dated May 31, 2007, will be used as general guidance. In general, components of the SCM will consist of developing and describing the following aspects of the site: geologic/soil framework, hydrologic framework, and the hydraulic properties of site materials. More specifically the SCM will describe how these aspects of the site affect the groundwater flow and fate and transport of the CCR constituents at the site. In addition, the SCM will:

• describe the site and regional geology,

• present longitudinal and transverse cross-sections showing the hydrostratigraphic layers,




• develop the hydrostratigraphic layer properties required for the groundwater model,

• present groundwater contour maps showing the potentiometric surfaces of the three hydrostratigraphic layers, and

• present information on horizontal and vertical groundwater gradients.

Additionally, iso-concentration maps, block diagrams, channel networks, and other illustrations may be created to illustrate the SCM. Figure 5 shows the proposed locations for geologic cross sections anticipated for the SCM.

The SCM will serve as the basis for developing the groundwater flow, and fate and transport models.

The historic site groundwater elevations and ash basin water elevations will be used to develop an historic estimated seasonal high groundwater contour map for the site.

7.7 Site-Specific Background Concentrations Statistical analysis will be performed using methods outlined in the Resource Conservation and Recovery Act (RCRA) Unified Guidance (US EPA, 2009, US EPA 530/R-09-007) to develop site-specific background concentrations (SSBCs). The SSBCs will be determined to assess whether or not exceedances can be attributed to naturally occurring background concentrations or attributed to potential contamination.

As discussed in Section 6.1, boron, iron, manganese, TDS, and pH tend to have concentrations greater than 2L Standards in Mayo Plant groundwater as indicated in at least one monitored compliance well. Antimony, barium, cadmium, chromium, lead, and thallium have each been detected in at least one background or compliance boundary well at concentrations greater than the 2L Standard. However, these constituents have not been detected at elevated concentration with regularity and may be related to sample turbidity or represent data outliers.

The relationship between exceedances and turbidity will also be explored to determine whether or not there is a possible correlation due to naturally occurring conditions and/or well construction. Alternative background boring locations will be proposed to NCDENR if the background wells shown on Figure 5 are found to not represent background conditions.

7.8 Geologic Mapping/Fracture Trace and Lineament Analysis As indicated in Sections 4 and 5, the geologic character in the region of the Mayo Plant is complex and variable both from a petrologic and a structural perspective. Closer-



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra scale geologic mapping and fracture trace/lineament analysis is proposed to provide a more detailed understanding of the geologic and geochemical nature of the soil and groundwater and the occurrence and movement of groundwater in the area.

Geologic Mapping Field confirmation of the currently mapped rock types and geologic units will be accomplished through careful observation and examination of materials encountered during boring and well drilling activities. Readily accessible rock outcrops along stream beds or local road cuts may also be examined to provide additional confirmation of the geologic setting. Fracture Trace and Lineament Analysis Structural features in consolidated bedrock are often visible on remote sensing data as lineaments, traceable linear surface features which differ distinctly from the patterns of adjacent features and presumably reflect subsurface conditions. These features may be topographic (linear ridges and valleys), drainage (straight stream segments), or anomalous vegetative/soil features that may indicate vertical zones of fracture concentration. Fracture trace and lineament data will be examined to more accurately identify potential subsurface rock structures that influence recharge, migration, and discharge of groundwater. Final selected well locations may be slightly modified based on fracture analysis results. 7.9 Groundwater Fate and Transport Model Data from existing and new monitoring wells will be used to develop a groundwater fate and transport model of the system. A 3-dimensional groundwater fate and transport model will be developed for the ash basin site. The objective of the model process will be to:

• predict concentrations of the COPCs at the facility’s compliance boundary or other locations of interest over time,

• estimate the groundwater flow and loading to surface water discharge areas, and

• support the development of the CSA report and the groundwater corrective action plan, if required.

The model and model report will be developed in general accordance with the guidelines found in the memorandum Groundwater Modeling Policy, NCDENR DWQ, May 31, 2007 (NCDENR modeling guidelines).

The groundwater model will be developed from the site hydrogeologic SCM, from existing wells and boring information provided by Duke Energy, and information



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra developed from the site investigation. The SCM is a conceptual interpretation of the processes and characteristics of a site with respect to the groundwater flow and other hydrologic processes at the site. Development of the ICSM is discussed in Section 5.0 and the SCM discussed in Section 7.6.

Due to the hydrogeologic complexities at the site, SynTerra believes that a 3-dimensional groundwater model would be more appropriate than performing 2-dimensional modeling. The modeling process, the development of the model hydrostratigraphic layers, the model extent (or domain), and the proposed model boundary conditions are presented below.

7.9.1 MODFLOW/MT3D The groundwater modeling will be performed under the direction of Dr. Ron Falta, Jr., Professor, Department of Environmental Engineering and Earth Sciences, Clemson University. Groundwater flow and constituent fate and transport will be modeled using MODFLOW and MT3DMS via the GMS v. 10 MODFLOW III Software Package.

Duke Energy, SynTerra, and Dr. Falta considered the appropriateness of using MODFLOW and MT3D as compared to the use of MODFLOW coupled with a geochemical reaction code such as PH REdox EQuilibrium (PHREEQC). The decision to use MODFLOW and MT3D was based on the intensive data requirements of PHREEQC, the complexity of developing an appropriate geochemical model given the heterogeneous nature of Piedmont geology, and the general acceptance of MODLFOW and MT3D. However, batch simulations of PHREEQC may be used to perform sensitivity analyses of the proposed sorption constants used with MODFLOW/MT3D, as described below, if geochemistry varies significantly across the site.

Additional factors that were considered in the decision to use MT3D as compared to a reaction based code utilizing geochemical modeling were as follows:

1. Modeling the complete geochemical fate and transport of trace, minor, or major constituents would require simultaneous modeling of the following in addition to groundwater flow:

• All major, minor, and trace constituents (in their respective species forms) in aqueous, equilibrium (solid), and complexed phases




• Solution pH, oxidation/reduction potential, alkalinity, dissolved oxygen, and temperature

• Reactions including oxidation/reduction, complexation, precipitation/dissolution, and ion exchange

2. Transient versus steady-state reaction kinetics may need to be considered. In general, equilibrium phases for trace constituents cannot be identified by mineralogical analysis. In this case, speciation geochemical modeling is required to identify postulated solid phases by their respective saturation indices.

3. If geochemical conditions across the site are not widely variable, an approach that considers each modeled COPC as a single species in the dissolved and complexed, or sorbed, phases is justified. The ratio of these two phases is prescribed by the sorption coefficient Kd which has dimensions of volume (L3) per unit mass (M). The variation in geochemical conditions can be considered, if needed, by examining pH, oxidation/reduction potential, alkalinity, and dissolved oxygen, perhaps combined with geochemical modeling, to justify the Kd approach utilized by MT3DMS. Geochemical modeling using PHREEQC (Parkhurst et al. 2013) running in the batch mode can be used to indicate the extent to which a COPC is subject to solubility constraints, a variable Kd, or other processes.

The groundwater model will be developed in general accordance with the guidelines found in the Groundwater Modeling Policy, NCDENR DWQ, May 31, 2007.

7.9.2 Development of Kd Terms It is critical to determine the ability of the site soils to attenuate, adsorb, or through other processes, reduce the concentrations of constituents of potential concern that may impact groundwater. To determine the capacity of the site soils to attenuate a constituent, the site specific soil adsorption coefficients, Kd terms, will be developed by University of North Carolina Charlotte (UNCC) utilizing soil samples collected during the site investigation. The soil-water distribution coefficient, Kd, is defined as the ratio of the adsorbed mass of a constituent to its concentration in solution and is used to quantify the equilibrium relationship between chemical constituents in the dissolved phase and adsorbed phase.




Experiments to quantify sorption can be conducted using batch or column procedures (Daniels and Das, 2014). A batch sorption procedure generally consists of combining soil samples and solutions across a range of soil-to-solution ratios, followed by shaking until chemical equilibrium is achieved. Initial and final concentrations of chemicals in the solution determine the adsorbed amount of chemical, and provide data for developing plots of adsorbed versus dissolved chemical and the resultant partition coefficient Kd with units of volume per unit mass. If the plot, or isotherm, is linear, the single-valued coefficient Kd is considered linear as well. Depending on the chemical constituent and soil characteristics, non-linear isotherms may also result (EPRI 2004).

The column sorption procedure consists of passing a solution of known chemical concentration through a cylindrical column packed with the soil sample. Batch and column methods for estimating sorption were considered in development of the Kd terms. UNCC recommends an adaption of the column method (Daniels and Das, 2014) to develop Kd estimates that are more conservative and representative of in-situ conditions, especially with regards to soil- to-liquid ratios.

Soil samples with measured dry density and maximum particle size will be placed in lab-scale columns configured to operate in the upflow mode. A solution with measured concentrations of the COPCs will be pumped through each column, effluent samples will be collected at regular intervals over time. When constituent breakthroughs are verified, a “clean” solution (no COPCs) will be pumped through the columns and effluent samples will be collected as well. Samples will be analyzed by inductively coupled plasma-mass spectroscopy (ICP-MS) and ion chromatography (IC) in the Civil & Environmental Engineering laboratories at EPIC building, UNC Charlotte. COPCs measured in the column effluent as a function of cumulative pore volumes displaced will be analyzed using CXTFIT (Tang et al. 2010) to select the appropriate model and associated parameters of the sorption coefficient Kd, either linear, Freundlich, or Langmuir. This allows use of a nonlinear coefficient in the event that a linear one is not suitable for the modeled input concentration range.

It is noted that some COPCs may have indeterminate Kd values by the column method due to solubility constraints and background conditions. In this case, batch sorption tests will be conducted in accordance US EPA Technical Resource Document EPA/530/SW-87/006-F, Batch-type Procedures for Estimating Soil Adsorption of Chemicals. COPC-specific solutions will be used to prepare a




range of soil-to-solution ratios. After mixing, supernatant samples will be drawn and analyzed as described above. Plots of sorbed versus dissolved COPC mass will be used to develop Kd values.

When applied in the fate and transport modeling performed by MT3D, these Kd values will determine the extent to which COPC transport in groundwater flow is attenuated by sorption. In effect, simulated COPC concentrations will be reduced, as will their rate of movement in advecting groundwater.

At a minimum, ten soil core samples will be selected from representative material at the site for column tests to be performed in triplicate. Batch Kd tests, if performed, will be executed in triplicate as well.

The ten anticipated Kd sample locations have been chosen to represent spatial variation across the Plant. Specifically, the following Kd test media and locations are anticipated:

• Ash: AB-1 and AB-4

• Saprolite: SB-1, SB-3, SB-4, and MW-8

• PWR: MW-3BR, MW-5BR, MW-9, and MW-12

These Kd terms will apply to the selected soil core samples and background geochemistry of the test solution, including pH and oxidation-reduction potential. In order to make these results transferable to other soils and geochemical conditions at the site where Kd terms have not been derived, UNCC recommends that the core samples with derived Kds and 20 to 25 additional core samples be analyzed for hydrous ferrous oxides (HFO) content, which is considered to the primary determinant of COPC sorption capacity of soils at the site. In the groundwater modeling study, the correlation between derived Kds and HFO content can be used to estimate Kd at other site locations where HFO and background water geochemistry, especially pH and oxidation-reduction potential, are known. If significant differences in water geochemistry are observed, geochemical modeling can be used to refine the Kd estimate. UNCC recommends that core samples for Kd and HFO tests be taken from locations that are in the path of groundwater flowing from the ash impoundments.

Determination of which COPCs will have Kd developed will be determined after review of the analyses on the site total ash and SPLP concentrations, pore water data, and review of the site groundwater analyses results. SynTerra anticipates that the constituents which have exceeded 2L standards at the site will be




specifically evaluated. The COPCs selected will be considered simultaneously in each test.

7.9.3 MODFLOW/MT3D Modeling Process The MODFLOW groundwater model will be developed using the hydrostratigraphic layer geometry and properties of the site described in the following section. After the geometry and properties of the model layers are input, the model will be calibrated to existing water levels observed in the monitoring wells and in the ash basin. Infiltration into the areas outside of the ash basin will be estimated based on available information. Infiltration within the basin area will be estimated based on available water balance information and pond elevation data.

The MT3D portion of the model will utilize the Kd terms and the input concentrations of constituents found in the ash. The leaching characteristics of ash are complex and are expected to vary with time and as changes occur in the geochemical environment of the ash basin. Due to factors such as the quantity of a particular constituent found in ash, and to other factors such as the mineral complex, solubility, and geochemical conditions, the rate of leaching and the leached concentrations of constituents will vary with time and with respect to each other.

Since the ash within a basin has been placed over a number of years, the analytical results from an ash sample is unlikely to represent the concentrations that are present in the hydrologic pathway between the ash basin and a particular groundwater monitoring well or other downgradient location.

As a result of these factors and due to the time period involved in groundwater flow, concentrations after closure may vary over time and peak concentrations may not yet have arrived at compliance wells. Therefore, the selection of the initial concentrations and the predictions of the concentrations for constituents with respect to time will be developed with consideration of the following:

• Site specific analytical results from leach tests (SPLP) and from total digestion of ash samples taken at varying locations and depths within the ash basin,

• Analytical results from groundwater monitoring wells or surface water/seep sample locations outside of the ash basin,

• Analytical results from monitoring wells installed in the ash basin pore-water (screened in ash),




• Published or other data on sequential leaching tests performed on similar ash.

The information above will be used with constituent concentrations measured at the compliance boundary to calibrate the fate and transport model and to develop a representation of the concentration with respect to time for a particular constituent. The starting time of the model will correspond to the date that the ash basin was placed in service. The resulting model, which will be consistent with the calibration targets mentioned above, can then be used to predict concentrations over space and time. It is noted that SPLP and total digestion results from ash samples will be considered as an upper bound of the total CPOCs available for leaching.

The model calibration process will consist of varying hydraulic conductivity and retardation within and between hydrostratigraphic units in a manner that is consistent with measured values of hydraulic conductivity, sorption terms, groundwater levels, and COPC concentrations.

A sensitivity analysis will be performed for the fate and transport analyses.

The model report will contain the information required by Section II of the NCDENR modeling guidelines, as applicable.

7.9.4 Hydrostratigraphic Layer Development The 3-dimensional configuration of the groundwater model hydrostratigraphic layers will be developed from information obtained during the site investigation process and from the CSM. The thickness and extent for the various layers will be represented by a 3-dimensional surface model for each hydrostratigraphic layer.

The boring data from the site investigation and from existing boring data, as available and provided by Duke Energy, will be entered into the GMS program. The program, along with site specific and regional knowledge of Piedmont hydrogeology will be used to interpret and develop the layer thickness and extent across areas of the site where boring data is not available. The material layers will be categorized based on properties such as visual soil identification and previous data from the site. The material properties required for the model such as total porosity, effective porosity, hydraulic conductivity, and specific storage will be developed from the data obtained in the site investigation and from previously collected data for the site.




To further define heterogeneities, a 2-D scatter point set will be used to define specified hydraulic values within vertical and/or horizontal zones. Specified hydraulic values will be given set ranges that reflect field conditions from core measurements, slug tests, and pump tests (if available).

7.9.5 Domain of Conceptual Groundwater Flow Model The Mayo Plant ash basin model domain encompasses areas where groundwater flow will be simulated to estimate the impacts of the ash basin. By necessity, the conceptual model domain extends beyond the ash basin limits to physical or artificial hydraulic boundaries such that groundwater flow through the area is accurately simulated. Physical hydraulic boundary types may include specified head, head dependent flux, no-flow, and recharge at ground surface or water surface. Artificial boundaries, which are developed based on information from the site investigation, may include the specified head and no-flow types.

Model sources and sinks such as drains, springs, rivers, lakes, and pumping wells will be based on the CSM. As discussed in Section 5.0, Crutchfield Branch and Mayo Lake likely function as groundwater discharge areas and will be used as model boundaries to the north and east. Artificial head boundaries will be established west and south of the basin based on apparent flow conditions. The model layers will consist, at a minimum, of residual soil (if saturated), saprolite, PWR, and bedrock. If site conditions are encountered that warrant changes to the proposed extent of model, NCDENR will be notified.

7.9.6 Potential Modeling of Groundwater Impacts to Surface Water

If the groundwater modeling predicts exceedances of the 2L Standards at or beyond the compliance boundary where the plume containing the exceedances would intercept surface waters, the groundwater model results will be coupled with modeling of surface waters to predict contaminant concentrations in the surface waters.

Model output from the fate and transport modeling (i.e. groundwater volume flux and concentrations of constituents with exceedances of the 2L Standards) will be used as input for surface water modeling in the adjacent water bodies (i.e., streams or reservoirs). The level of surface water modeling will be determined based on the potential for water quality impacts in the adjacent water body. That is, if the available mixing and dilution of the groundwater plume in the water body is sufficient enough that surface water quality standards are expected to be attained within a short distance a simple modeling




approach will be used. If potential water quality impacts are expected to be greater or the water body type requires a more complex analysis, then a more detailed modeling approach will be used. A brief description of the proposed simple and detailed modeling approaches is presented below.

• Simple Modeling Approach – This approach will include the effects of upstream flow on dilution of the groundwater plume within allowable mixing zone limitations along with analytical solutions to the lateral spreading and mixing of the groundwater plume in the adjacent water body. This approach will be similar to that presented in EPA’s Technical Support Document for Water Quality based Toxics Control (EPA/505/2-90-001) for ambient induced mixing that considers lateral dispersion coefficient, upstream flow and shear velocity. The results from this analysis will provide constituent concentrations as a function of the spatial distance from the groundwater input to the adjacent water body.

• Detailed Modeling Approach – This approach will involve the use of water quality modeling that is capable of representing multi-dimensional analysis of the groundwater plume mixing and dilution in the adjacent water body. This method involves segmenting the water body into model segments (lateral, longitudinal and/or vertical) for calculating the resulting constituent concentrations spatially in the water body either in a steady-state or time-variable mode. The potential water quality models that could be used for this approach include: QUAL2K; CE-QUAL-W2; EFDC/WASP; ECOMSED/RCA; or other applicable models.

In either approach, the model output from the groundwater model will be coupled with the surface water model to determine the resulting constituent concentrations in the adjacent water body spatially from the point of input. These surface water modeling results can be used for comparison to applicable surface water quality standards to complete determine compliance.

The development of the model inputs would require additional data for flow and chemical characterization of the surface water that would potentially be impacted. The specific type of data required (i.e. flow, chemical characterization, etc.) and the locations where this data would be collected would depend on the surface water body and the modeling approach selected. If modeling groundwater impacts to surface water is required, SynTerra and Duke Energy will consult with the DWR regional office to present those specific data requirements and modeling approach.




8.0 RISK ASSESSMENT

To support the groundwater assessment and inform corrective action decisions based on current and future land use, potential risks to human health and the environment will be assessed in accordance with applicable federal and state guidance. Initially, screening level human health and ecological risk assessments will be conducted that include development of conceptual exposure models (CEM) to serve as the foundation for evaluating potential risks to human and ecological receptors at the site. Consistent with standard risk assessment practice for developing conceptual models, separate CEMs will be developed for the human health and ecological risk evaluations.

The purpose of the CEM is to identify potentially complete exposure pathways to environmental media associated with the site and to specify the types of exposure scenarios relevant to include in the risk analysis. The first step in constructing a CEM is to characterize the site and surrounding area. Source areas and potential transport mechanisms are then identified, followed by identification of potential receptors and routes of exposure. Potential exposure pathways are determined to be complete when they contain the following elements: 1) a constituent source, 2) a mechanism of constituent release and transport from the source area to an environmental medium, 3) a feasible route of potential exposure at the point of contact (e.g., ingestion, dermal contact, inhalation). A complete exposure pathway is one in which a constituent can be traced or can be expected to travel from the source to a receptor (US EPA, 1997). Completed exposure pathways identified in the CEM are then evaluated in the risk assessment. Incomplete pathways are characterized by some gaps in the links between site sources and exposure. Based on this lack of potential exposure, incomplete pathways are not included in the estimation or characterization of potential risks, since no exposure can occur via these pathways.

Preliminary COPCs for inclusion in the screening level risk assessment will be identified based on the evaluations performed at the site. Both screening level risk assessments will compare maximum constituent concentrations to appropriate risk-based screening values as a preliminary step in evaluating potential risks to receptors. Based on results of the screening level risk assessments, a refinement of COPCs will be conducted and more definitive risk characterization will be performed as part of the corrective action process if needed.

8.1 Human Health Risk Assessment As noted above, the first steps of the human health risk assessment will include the preparation of a CEM, illustrating potential exposure pathways from the source area to possible receptors. The information gathered in the CEM will be used in conjunction



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra with analytical data collected as part of the CSA. Although groundwater appears to be the primary exposure pathway for human receptors, a screening level evaluation will be performed to determine if other potential exposure routes exist.

The human health risk assessment for the site will include an initial comparison of constituent concentrations in various media to risk-based screening levels. The data will be screened against the following criteria:

• Soil analytical results collected from the 0 to 2 foot depth interval will be compared to US EPA residential and industrial soil Regional Screening Levels (RSLs) (US EPA, November 2014 or latest update);

• Groundwater results will be compared to NCDENR Title 15A, Subchapter 2L Standards (NCDENR, 2006);

• Surface water analytical results will be compared to North Carolina surface water standards (Subchapter 2B) and US EPA national recommended water quality criteria (NCDENR, 2007; US EPA, 2006).

• The surface water classification as it pertains to drinking water supply, aquatic life, high/exceptional quality designations and other requirements for other activities (e.g., landfill permits, NPDES wastewater discharges) shall be noted;

• Sediment results will be compared to US EPA residential soil RSLs (US EPA, November 2014 or latest update); and

• Sediment, soil and groundwater data will also be compared to available local, regional and national background sediment, soil and ground water data, as available.

The results of this comparison will be presented in a table, along with recommendations for further evaluation.

8.1.1 Site-Specific Risk-Based Remediation Standards If deemed necessary, based on the results of the initial comparison to standards, site-and media-specific risk-based remediation standards will be calculated in accordance with the Eligibility Requirements and Procedures for Risk-Based Remediation of Industrial Sites Pursuant to N.C.G.S. 130A-310.65 to 310.77, North Carolina Department of Environment and Natural Resources, Division of Waste Management, 29 July 2011. In accordance with this guidance document, it is anticipated that these calculations will include an evaluation of the following, based on site-specific activities and conditions:




• Remediation methods and technologies resulting in emissions of air pollutants are to comply with applicable air quality standards adopted by the Environmental Management Commission (Commission).

• Site-specific remediation standards for surface waters are to be the water quality standards adopted by the Commission.

• The current and probable future use of groundwater shall be identified and protected. Site-specific sources of contaminants and potential receptors are to be identified, protected, controlled, or eliminated whether on or off the site of the contaminant source.

• Natural environmental conditions affecting the fate and transport of contaminants (e.g., natural attenuation) shall be determined by appropriate scientific methods.

• Permits for facilities subject to the programs or requirements of G.S. 130A-310.67(a) shall include conditions to avoid exceedances of applicable groundwater standards pursuant to Article 21 of Chapter 143 of the General Statutes; permitted facilities shall be designed to avoid exceedances of the North Carolina ground or surface water standards.

• Soil shall be remediated to levels that no longer constitute a continuing source of groundwater contamination in excess of the site-specific groundwater remediation standards approved for the site.

• The potential for human inhalation of contaminants from the outdoor air and other site-specific indoor air exposure pathways shall be considered, if applicable.

• The site-specific remediation standard shall protect against human exposure to contamination through the consumption of contaminated fish or wildlife and through the ingestion of contaminants in surface water or groundwater supplies.

• For known or suspected carcinogens, site-specific remediation standards shall be established at levels not to exceed an excess lifetime cancer risk of one in a million. The site-specific remediation standard may depart from this level based on the criteria set out in 40 Code of Federal Regulations § 300.430(e)(9) (July 1, 2003). The cumulative excess lifetime cancer risk to an exposed individual shall not be greater than one in 10,000 based on the sum of carcinogenic risk posed by each contaminant present.

• For systemic toxicants (non-carcinogens), site-specific remediation standards shall be set at levels to which the human population, including




sensitive subgroups, may be exposed without any adverse health effect during a lifetime or part of a lifetime. Site-specific remediation standards for systemic toxicants shall incorporate an adequate margin of safety and shall take into account cases where two or more systemic toxicants affect the same organ or organ system.

The site-specific remediation standards for each medium shall be adequate to avoid foreseeable adverse effects to other media or the environment that are inconsistent with the state’s risk-based approach.

8.2 Ecological Risk Assessment The screening level ecological risk assessment (SLERA) for the site will include a description of the ecological setting and development of the ecological CEM specific to the ecological communities and receptors that may be exposed to COPCs. This scope is equivalent to Step 1: preliminary problem formulation and ecological effects evaluation (US EPA, 1997). The objective of the SLERA is to evaluate the likelihood that adverse ecological effects may result from exposure to environmental stressors associated with conditions at the site.

The screening level evaluation will include compilation of a list of potential ecological receptors (e.g., plants, benthic invertebrates, fish, mammals, birds, etc.). Additionally, an evaluation of sensitive ecological populations will be performed. Preliminary information on listed rare animal species at or near the site will be compiled from the North Carolina Natural Heritage Program database and U.S. Fish and Wildlife county list to evaluate the potential for presence of rare or endangered animal and plant species. Existing ecological studies publically available for the site will be reviewed and incorporated as appropriate to support the SLERA.

Appropriate state and federal natural resource agencies will be contacted to determine the potential presence (or lack thereof) of sensitive species or their critical habitat at the time the SLERA is performed. If sensitive species or critical habitats are present or potentially present, a survey of the appropriate area will be performed. If sensitive species are utilizing the site, an evaluation of the potential for adverse effects due to site-related constituents in groundwater will be developed and presented to the appropriate agencies.

The SLERA will include, as the basis for the CEM, a description of the known fate and transport mechanisms for site-related constituents and potentially complete pathways from assumed source to receptor. An ecological checklist will be completed for the site as required by Guidelines for Performing Screening Level Ecological Risk Assessment within North Carolina (NCDENR, 2003).



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra Following completion of Step 1, the screening level exposure estimate and risk calculations (Step 2), will be performed in accordance with the Guidelines for Performing Screening Level Ecological Risk Assessment within North Carolina (NCDENR, 2003). Step 2 estimates the level of a constituent a plant or animal is exposed to at the site and compares the maximum constituent concentrations to Ecological Screening Values (ESVs).

Maximum detected concentrations or the maximum detection limit for non-detected constituents of potential concern (those metals or other chemicals present in site media that may result in risk to ecological receptors) will be compared to applicable ecological screening values intended to be protective of ecological receptors (including those sensitive species and communities noted above, where available) to derive a hazard quotient (HQ). An HQ greater than 1 indicates potential ecological impacts cannot be ruled out.

Ecological screening values will be taken from the following and other appropriate sources:

• US EPA Ecological Soil Screening Levels (ESV);

• US EPA Region 4 Recommended Ecological Screening Values; and

• US EPA National Recommended Water Quality Criteria and North Carolina Standards.

North Carolina’s SLERA guidance (NCDENR, 2003) requires that constituents be identified as a Step 2 COPC as follows:

• Category 1 - Contaminants whose maximum detection exceeding the media-specific ESV included in the COPC tables.

• Category 2 - Contaminants that generated a laboratory sample quantitation limit that exceeds the US EPA Region IV media-specific ESV for that contaminant.

• Category 3 – Contaminants that have no US EPA Region IV media-specific ESV but were detected above the laboratory sample quantitation limit.

• Category 4 – Contaminants that were not detected above the laboratory sample quantitation limit and have no US EPA Region IV media-specific ESV.

• Category 5 – Contaminants with a sample quantitation limit or maximum detection exceeds the North Carolina Surface Water Quality Standards.



Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra Exceedances of the ESVs indicate the potential need for further evaluation of ecological risks at the site. The frequency, magnitude, pattern and basis of any exceedances will be considered as part of the refinement of COPCs.

The risk assessment process identifies a Scientific-Management Decision Point (SMDP) to evaluate whether the potential for adverse ecological effects are absent and no further assessment is needed or if further assessment should be performed to evaluate the potential for ecological effects. If additional evaluation of potential ecological effects is required, a baseline ecological risk and/or habitat assessment will be developed.




9.0 CSA REPORT

The CSA report will be developed in the format required by the NORR, which include the following components:

• Executive Summary

• Site History and Source Characterization

• Receptor Information

• Regional Geology and Hydrogeology

• Site Geology and Hydrogeology

• Soil Sampling Results

• Groundwater Sampling Results

• Hydrogeological Investigation

• Groundwater Modeling results

• Risk Assessment

• Discussion

• Conclusions and Recommendations

• Figures

• Tables

• Appendices

The CSA report may provide the results of one iterative assessment phase.

The CSA will be prepared to include the items contained in the Guidelines for Comprehensive Site Assessment (guidelines), included as attachment to the NORR, as applicable. SynTerra will provide the applicable figures, tables, and appendices as listed in the guidelines. For summary statistics tables, “average” value(s) will be avoided unless the constituent(s) at the location in question is (are) normally distributed, in which case a mean and standard deviation will be used. For non-normal data, the median value will be used and maximum values will be noted, as appropriate.

As part of CSA deliverables, at a minimum the following tables, graphs, and maps will be provided:




• Box (whisker) plots for locations sampled on four or more events showing the quartiles of the data along with minimum and maximum. Plots will be aligned with multiple locations on one chart. Similar charts will be provided for each COPC,

• Stacked time-series plots will be provided for select COPC. Multiple wells/locations will be stacked using the same x-axis to discern seasonal trends. Turbidity, dissolved oxygen, ORP, or other constituents will be shown on the plots where appropriate to demonstrate influence.

• Piper and/or stiff diagrams showing selected monitoring wells and surface water/seep locations as separate symbols.

• Correlation charts where applicable.

• Orthophoto potentiometric maps for shallow, deep and bedrock wells.

• Orthophoto potentiometric difference maps showing the difference in vertical heads between selected flow zones.

• Orthophoto iso-concentration maps for selected COPCs and flow zones.

• Orthophoto map showing the relationship between groundwater and surface water samples for selected COPCs.

• Geologic cross sections that include the relative position of the bottom of the ash basins and the water table.

• Photographs of cores from each boring location.

• Others as appropriate.




10.0 PROPOSED SCHEDULE

Duke Energy will submit the CSA Report within 180 days of NCDENR approval of this Work Plan. The anticipated schedule for implementation of field work, evaluation of data, and preparation of the Work Plan is presented in the table below.

Activity Start Date Duration to Complete

Field Exploration Program 10 days following Work Plan approval 75 days

Receive Laboratory Data 14 days following end of Exploration Program 15 days

Evaluate Lab/Field Data, Develop CSM 5 days following receipt of Lab Data 30 days

Prepare and Submit CSA 10 days following Work Plan approval 170 days

Project Assumptions Include:

• Data from no more than one iterative assessment step will be included in the CSA report. Iterative assessment data may be provided in supplemental reports, if required;

• Data will not reflect all seasonal or extreme hydrologic conditions; and

• During the CSA process if additional investigations are required, NCDENR will be notified immediately with a description of the proposed work and a timeline for completion.




11.0 REFERENCES

ASTM D422 - 63(2007), Standard Test Method for Particle-Size Analysis of Soils.

ASTM D854-14, Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer.

ASTM, D1785-12, Standard Specification for Poly(Vinyl Chloride), (PVC) Plastic Pipe, Schedules 40, 80, and 120.

ASTM, D2216-10, Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass.

ASTM, D2487-11, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System).

ASTM, D2488-09a, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure).

ASTM, D4044-96, Standard Test Method (Field Procedure) for Instantaneous Change in Head (Slug) Tests for Determining Hydraulic Properties of Aquifers.

ASTM D5084 – 10, Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter.

Daniel, C.C., III, 2001, Estimating ground-water recharge in the North Carolina Piedmont for land use planning [abs.], in 2001 Abstracts with Programs, 50th Annual Meeting, Southeastern Section, April 5-6, 2001: Raleigh, N.C., The Geological Society of America, v. 33, no. 2, p. A-80.

Daniels, John L. and Das, Gautam P. 2014. Practical Leachability and Sorption Considerations for Ash Management, Geo-Congress 2014 Technical Papers: Geo-characterization and Modeling for Sustainability. Wentworth Institute of technology, Boston, MA.

Dicken, Connie L., Suzanne W. Nicholson, John D. Horton, Michael P. Foose, and Julia A.L. Mueller, December 2007, Preliminary integrated geologic map databases for the United States – Alabama, Florida, Georgia, Mississippi, North Carolina, and South Carolina, Version 1.1: United States Geological Survey, USGS Open File Report 2005-1323, < http://pubs.usgs.gov/of/2005/1323>.



http://pubs.usgs.gov/of/2005/1323

Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra Duke Energy, October 31, 2014 (update), Duke Energy Coal Plants and Ash Management,

http://www.duke-energy.com/pdfs/duke-energy-ash-metrics.pdf.

EPRI, August 1993. Fly Ash Exposure in Coal-Fired Power Plants. Electric Power Research Institute - EPRI TR-102576. Radian Corporation - Sacramento, California.

EPRI 2004 Electric Power Research Institute, Chemical Attenuation Coefficients for Arsenic Species Using Soil Samples Collected from Selected Power Plant Sites: Laboratory Studies, Product ID:1005505, December 2004.

EPRI, September 2009. Coal Ash: Characteristics, Management and Environmental Issues. Electric Power Research Institute, Palo Alto, California.

Fenneman, Nevin Melancthon, 1938. Physiography of eastern United States, McGraw-Hill. 1938.

Harned, D. A. and Daniel, C. C., III, 1992, The transition zone between bedrock and regolith: Conduit for contamination?, p. 336-348, in Daniel, C. C., III, White, R. K., and Stone, P. A., eds., Groundwater in the Piedmont: Proceedings of a Conference on Ground Water in the Piedmont of the Eastern United States, October 16-18, 1989, Clemson University, 693p.

Heath, R.C., 1980. Basic elements of groundwater hydrology with reference to conditions in North Carolina. United States Geological Survey Open-File Report 80-44, 86 p.

Hibbard, James P., Edward F. Stoddard, Donald T. Secor, and Allen J. Dennis, 2002, The Carolina Zone: overview of Neoproterozoic to Early Paleozoic peri-Gondwanan terranes along the eastern Flank of the southern Appalachians: Earth Science Reviews, v. 57.

LeGrand, H.E., 1988. Region 21. Piedmont and Blue Ridge, in Hydrogeology: The Geology of North America, v. 0-2, ed. W.B. Black, J.S. Rosenshein, and P.R. Seaber, 201-207. Geological Society of America, Boulder, CO.

LeGrand, H.E., 1989. A conceptual model of ground water settings in the Piedmont region, in Ground Water in the Piedmont, ed. C.C. Daniel III, R. K. White, and P.A. Stone, 693. Proceedings of a Conference on Ground Water in the Piedmont of the Eastern United States, Clemson University, Clemson, South Carolina.

LeGrand, Harry E., 2004. A Master Conceptual Model for Hydrogeological Site Characterization in the Piedmont and Mountain Region of North Carolina, A Guidance Manual, North Carolina Department of Environment and Natural Resources Division of Water Quality, Groundwater Section.



http://www.duke-energy.com/pdfs/duke-energy-ash-metrics.pdf

Proposed Groundwater Assessment Work Plan Revision 1: December 2014 Mayo Steam Electric Plant SynTerra North Carolina Geological Survey, 1985, Geologic map of North Carolina: North Carolina

Geological Survey, General Geologic Map, scale 1:500000.

NCDENR, October 2003. Guidelines for performing screening level ecological risk assessments within the North Carolina Division of Waste Management.

NCDENR, May 31, 2007, Groundwater Modeling Policy.

NCDENR, May 31, 2007, Hydrogeologic Investigation and Reporting Policy.

NCDENR, May 31, 2007, Performance and Analysis of Aquifer Slug Tests and Pumping Test Policy.

NCDENR, Division of Water Resources, November 4, 2014, Duke Energy Progress, LLC, Mayo Steam Electric Plant, NPDES Permit No. NC0003425 – Person County, Review of Groundwater Assessment Work Plan.

Parkhurst, D.L., and Appelo, C.A.J., 2013, Description of input and examples for PHREEQC version 3—A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Techniques and Methods, book 6, chap. A43, 497 p.

SynTerra, September 2014, Drinking Water Well and Receptor Survey for Mayo Steam Electric Plant (Duke Energy Progress, Inc.), Roxboro, NC. SynTerra Corporation, Greenville, South Carolina.

SynTerra, Groundwater Assessment Work Plan for Mayo Steam Electric Plant, 10600 Boston Road, Roxboro, NC, NPDES Permit# NC0038377, September 2014.

SynTerra, October 2014. Groundwater Monitoring Program Sampling, Analysis and Reporting Plan, Mayo Steam Electric Plant.

SynTerra, December 2014, Seep Monitoring Report – August and November 2014 for Mayo Steam Electric Plant (Duke Energy Progress, Inc.), Roxboro, NC. SynTerra Corporation, Greenville, South Carolina.

SynTerra, November 2014, Supplement to Drinking Water Well and Receptor Survey for Mayo Steam Electric Plant (Duke Energy Progress, Inc.), Roxboro, NC. SynTerra Corporation, Greenville, South Carolina.

Tang, G., Mayes, M. A., Parker, J. C., & Jardine, P. M. (2010). CXTFIT/Excel–A modular adaptable code for parameter estimation, sensitivity analysis and uncertainty




analysis for laboratory or field tracer experiments. Computers & Geosciences, 36(9), 1200-1209.

US Bureau of Reclamation, 2001. Engineering Geology Field Manual, 2nd Edition, Volume 2, US Department of the Interior.

US EPA, 1992. Statistical Training Course for Ground Water Monitoring Data Analysis, EPA530-R-93-003.

US EPA, 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments.

US EPA, 1998. Report to Congress Wastes from the Combustion of Fossil Fuels, Volume 2 Methods, Findings, and Recommendations.

US EPA, January 2006. National Recommended Water Quality Criteria: 2006.

US EPA, March 2009. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities; Unified Guidance US EPA 530/R-09-007.

US EPA, January 19, 2010. Low Stress (low flow) Purging and Sampling Procedure for the Collection of Groundwater Samples from Monitoring Wells. US EPA Region 1. EQASOP-GW-001.

US EPA, June 21, 2010. 40 CFR Parts 257, 261, 264 et al. Hazardous and Solid Waste Management System; Identification and Listing of Special Wastes; Disposal of Coal Combustion Residuals From Electric Utilities; Disposal of Coal Combustion Residuals From Electric Utilities; Proposed Rule, in Federal Register /Vol. 75, No. 118 .

US EPA, November 2014 (last update). USEPA Regional Screening Levels (RSLs), available at http://www.epa.gov/region9/superfund/prg/.



http://www.epa.gov/region9/superfund/prg/

FIGURES

PROJECT MANAGER:LAYOUT:

DRAWN BY:K. WEBB

DATE:J. CHASTAIN

FIG 1 (SITE LOCATION MAP)

2014-12-22

FIGURE 1

SITE LOCATION MAP

MAYO STEAM ELECTRIC PLANT

10600 BOSTON RD

ROXBORO, NORTH CAROLINA

CLUSTER SPRINGS, VA QUADRANGLE

2000GRAPHIC SCALE

1000

IN FEET

10000CONTOUR INTERVAL:MAP DATE:

10ft1987

148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA

PHONE 864-421-9999www.synterracorp.com

SOURCE:

USGS TOPOGRAPHIC MAP OBTAINED FROM THE NRCS GEOSPATIAL DATA

GATEWAY AT http://datagateway.nrcs.usda.gov/

MAYO LAKE POWER PLANTPERSON COUNTY

RALEIGH

WILMINGTON

GREENVILLE

GREENSBORO

CHARLOTTEFAYETTEVILLE

PROPERTY BOUNDARY

500' COMPLIANCE

BOUNDARY

WASTE

BOUNDARY

12/24/2014 1:44 PM P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Figures\DE MAYO FIG 1 (USGS SITE LOCATION).dwg

600 0 600 1200GRAPHIC SCALE

IN FEET

FIG 2 (SITE LAYOUT MAP)

2014-12-22J. WYLIES. ARLEDGE

PROJECT MANAGER:LAYOUT NAME:

DRAWN BY:CHECKED BY:

K. WEBB

DATE:DATE:

FIGURE 2

SITE LAYOUT MAP

www.synterracorp.com

148 River Street, Suite 220Greenville, South Carolina 29601

864-421-9999

LEGEND

2014-12-22

500 ft COMPLIANCE BOUNDARY

DUKE ENERGY PROGRESS MAYO PLANT

WASTE BOUNDARY


10600 BOSTON RD


BACKGROUND MONITORING WELL (SURVEYED)

DOWNGRADIENT MONITORING WELL (SURVEYED)

CW-1

BG-1

SOURCES:

1. 2010 AERIAL PHOTOGRAPH OF PERSON COUNTY,

NORTH CAROLINA OBTAINED FROM THE NRCS

GEOSPATIAL DATA GATEWAY AT

http://datagateway.nrcs.usda.gov/

2. 2012 AERIAL PHOTOGRAPH OF HALIFAX COUNTY,

VIRGINIA WAS OBTAINED FROM NRCS GEOSPATIAL

DATA GATEWAY AT http://datagateway.nrcs.usda.gov/

3. 2014 AERIAL PHOTOGRAPH WAS OBTAINED FROM WSP

FLOWN ON APRIL 17, 2014.

4. DRAWING HAS BEEN SET WITH A PROJECTION OF

NORTH CAROLINA STATE PLANE COORDINATE SYSTEM

FIPS 3200 (NAD 83).

NORTH CAROLINA-VIRGINIA STATE LINE

(APPROXIMATE)

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12/24/2014 1:40 PM P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Figures\DE MAYO FIG 3 (GEOLOGY MAP).dwg

148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.com


DRAWN BY:K. WEBB

DATE:J. CHASTAIN

FIG 3 (GEOLOGY MAP)

2014-12-22

FIGURE 3

GEOLOGY MAP

DUKE ENERGY PROGRESS


10600 BOSTON RD


DISCLAIMER

The information on this map was derived from digital databases at the NC Department of Transportation Website. Care was

taken in the creation of this map. SYNTERRA cannot accept any responsibility for errors, omissions, or positional accuracy.

There are no warranties, expressed or implied, including the warranty of merchantability or fitness for a particular purpose,

accompanying this product. However, notification of any errors will be appreciated.

CZbg

LEGEND - UNIT NAME

CZg METAMORPHOSED GRANITIC ROCK ( EASTERN SLATE BELT)

CZfg FELSIC MICA GNEISS (CHARLOTTE AND MILTON BELTS)

PzZg METAMORPHOSED GABBRO AND DIORITE (EASTERN SLATE BELT)

BIOTITE GNEISS AND SCHIST (INNER PIEDMONT)

GEOLOGY SOURCE NOTE:

GEOLOGY SHAPEFILES OBTAINED FROM THE USGS Preliminary integrated geologic map databases for the United

States - Alabama, Florida, Georgia, Mississippi, North Carolina, and South Carolina, DATED 2007 AT

http://pubs.usgs.gov/of/2005/1323/

CZfv FELSIC METAVOLCANIC ROCK (EASTERN SLATE BELT)

CZv METAVOLCANIC ROCK (CHARLOTTE AND MILTON BELTS)

CZve METAVOLCANIC-EPICLASTIC ROCK ( EASTERN SLATE BELT)

CW-1

CW-6CW-5

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BG-2

CW-4CW-3

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10600 BOSTON RD

PERSON COUNTY

NEAR ROXBORO, NC

1500 0 1500 3000GRAPHIC SCALE

IN FEET

500 ft COMPLIANCE BOUNDARYDUKE ENERGY PROGRESS MAYO PLANT

WASTE BOUNDARYCW-3 COMPLIANCE MONITORING WELL

LEGEND

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Figures\DE MAYO FIG 4 (JULY 2014 WL MAP).dwg12/24/2014 1:39 PM

FIGURE 4

WATER LEVEL MAP - JULY 2014


MAYO LAKE POWER PLANT

10600 BOSTON RD


BOST

ON R

OAD

MAYO RESERVIOR

LAKE MAYO RD

FORMER US HW

Y 501

148 RIVER STREET, SUITE 220GREENVILLE, SOUTH CAROLINA 29601PHONE 864-421-9999www.synterracorp.com


DRAWN BY:K. WEBB

DATE:J. CHASTAIN

FIG 4 (WATER LEVEL MAP)

12/24/14

ASH POND WASTE BOUNDARY1981 LANDFILL PERMIT NO. 73-B

PROPERTY LINE (APPROXIMATE)COMPLIANCE BOUNDARY

SOURCES:

1. 2010 AERIAL PHOTOGRAPH WAS OBTAINED FROM THE NRCS GEOSPATIAL DATA GATEWAY AThttp://datagateway.nrcs.usda.gov/

2. WELL SURVEY INFORMATION, PROPERTY LINE, LANDFILL LIMITS AND BOUNDARIES ARE FROM ARCGIS FILESPROVIDED BY S&ME AND PROGRESS ENERGY.

3. WATER LEVEL MEASUREMENTS TAKEN BY SYNTERRA ON JULY 16, 17 & 18, 2014.

LEGEND

COMPLIANCE MONITORING WELLWATER LEVEL IN FEET (msl.)BACKGROUND COMPLIANCE WELL LOCATIONWATER LEVEL IN FEET (msl.)

BG-1507.99

CW-1471.48

WATER LEVEL CONTOUR IN FEET (msl.)

FORMER US HW

Y 501

BG-1507.99

BG-2509.46

CW-1D471.25

CW-1471.48

CW-2374.41

CW-2D374.43

CW-3420.80

CW-4428.88

CW-5500.28

CW-6449.14

ACTIVE ASH POND

POWER PLANT

1981 LANDFILLPERMIT NO. 73-B

RT HESTER RD

500

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460

440 400

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490505

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FIG 5 (PROP MW AND SAMP LOC MAP)

2014-12-152014-12-15J. WYLIE

J. CHASTAIN

PROJECT MANAGER:LAYOUT NAME:

DRAWN BY:CHECKED BY:

KATHY WEBB

DATE:DATE:

12/2

4/20

14 1

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PMP:

\Duk

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.dw

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1000GRAPHIC SCALE

(IN FEET)

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www.synterracorp.com

148 River Street, Suite 220Greenville, South Carolina 29601

864-421-9999


10600 BOSTON RD


FIGURE 5

PROPOSED MONITORING WELL AND

SAMPLE LOCATION MAP

SOURCES:

1. 2010 AERIAL PHOTOGRAPH OF PERSON COUNTY,

NORTH CAROLINA WAS OBTAINED FROM NRCS



2. 2012 AERIAL PHOTOGRAPH OF HALIFAX COUNTY,

VIRGINIA WAS OBTAINED FROM NRCS GEOSPATIAL

DATA GATEWAY AT http://datagateway.nrcs.usda.gov/

3. 2014 AERIAL PHOTOGRAPH WAS OBTAINED FROM WSP

FLOWN ON APRIL 17, 2014.

4. DRAWING HAS BEEN SET WITH A PROJECTION OF

NORTH CAROLINA STATE PLANE COORDINATE SYSTEM

FIPS 3200 (NAD 83).

5. WELL SURVEY INFORMATION, PROPERTY LINE,

LANDFILL LIMITS AND BOUNDARIES ARE FROM ARCGIS

FILES PROVIDED BY S&ME AND PROGRESS ENERGY.

6. PARCEL BOUNDARIES WERE OBTAINED FROM PERSON

COUNTY (NC) GIS DATA AT http://gis.personcounty.net

7. 10ft CONTOUR INTERVALS FROM NCDOT LiDAR DATED

2007

https://connect.ncdot.gov/resources/gis/pages/cont-elev_v2.aspx

8. VIRGINIA 10ft CONTOUR INTERVALS FROM USGS

TOPOGRAPHIC MAP OBTAINED FROM THE NRCS



NOTE:

1. CONTOUR LINES ARE USED FOR REPRESENTATIVE

PURPOSES ONLY AND ARE NOT TO BE USED FOR

DESIGN OR CONSTRUCTION PURPOSES.

BG-1

BG-2

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WELL - NOT IN SERVICE (APPROXIMATE)

DEP 1

EDR 1EDR REPORTED SUPPLY WELL (APPROXIMATE)

NORTH CAROLINA-VIRGINIA STATE LINE (APPROXIMATE)

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T

H

E

S

T

E

R

R

D

R

A

IL

R

O

A

D

R

A

I

L

R

O

A

D

R

A

I

L

R

O

A

D

R

A

I

L

R

O

A

D

R

A

I

L

R

O

A

D

H

U

E

L

L

M

A

T

T

H

E

W

S

H

W

Y

(

U

S

H

W

Y

5

0

1

)

PERSON COUNTY

HALIFAX COUNTY

1

9

8

1

L

A

N

D

F

I

L

L

P

E

R

M

I

T

N

O

.

7

3

-

B

ACTIVE ASH BASIN

POWER PLANT

B

O

S

TO

N

R

D

(U

S

H

W

Y

501)

R

A

I

L

R

O

A

D

W

O

O

D

Y

L

O

O

P

CRUTCHFIELD

BRANCH

MAYO LAKE

MAYO CREEK

F

O

R

M

E

R

U

S

H

W

Y

5

0

1

RAW WATER INTAKE

STRUCTURE

CW-2

CRUTCHFIELD

BRANCH

MAYO CREEK

S-08

S-02B

S-07

S-05

NPDES OUTFALL 002

NPDES OUTFALL 001

SW-CB2

SW-CB1

S-06

SW-REF1

500 ft COMPLIANCE BOUNDARY


LEGEND

WASTE BOUNDARY

BACKGROUND MONITORING WELL (SURVEYED)

COMPLIANCE MONITORING WELL (SURVEYED)MW-5

BG-1

GENERALIZED GROUNDWATER FLOW

DIRECTION

• SUPPORTED BY GROUNDWATER ELEVATION DATA

POINTS OR TOPOGRAPHIC DATA

ABMW-1

ABMW-1S

PROPOSED GEOLOGIC CROSS SECTION

PARCEL LINES

PROPOSED SOIL BORING AND MONITORING

WELL LOCATION

SEEP LOCATION

NPDESOUTFALL 001 NPDES OUTFALL

SW-CB1

PROPOSED SURFACE WATER AND

SEDIMENT LOCATION

FLOW DIRECTION

MONITORING WELL (APPROXIMATE)

PIEZOMETER (APPROXIMATE)

PROPOSED ASH BORING, PORE WATER, AND

GROUNDWATER MONITORING WELL LOCATION

PZ-3

PROPOSED SOIL BORING LOCATIONSB-2

PZ-1

PZ-1A

PZ-2A

PZ-2

PZ-3A

PZ-3

PZ-4A

PZ-4

MW-3

MW-2

MW-4

TABLES

TABLE 2

EXCEEDANCES OF 2L STANDARDS


DUKE ENERGY PROGRESS, INC., ROXBORO, NORTH CAROLINA

PARAMETER ANTIMONY BARIUM BORON CADMIUM CHROMIUM IRON LEAD MANGANESE THALLIUM TDS pH

2L STANDARD (eff. 4/1/2013)

0.001 0.7 0.7 0.002 0.01 0.3 0.015 0.05 0.0002 500 6.5 - 8.5

Units (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) SU

BG-1 Background 0.00013 - 0.0042 0.09 - 1.04 <2L <2L 0.0047 - 0.0401 0.261 - 65.7 0.0023 - 0.0331 0.0089 - 2.27 <0.0001 - 0.00035 <2L 5.2 - 7.0

BG-2 Background <2L <2L <2L <2L 0.0059 - 0.0102 0.152 - 2.66 <2L 0.027 - 0.248 <2L <2L 6.3 - 6.6

CW-1 CB <2L <2L <2L 0.000082 - .00219 <2L <2L <2L 0.007 - 0.104 <2L <2L 5.6 - 6.7

CW-1D CB <2L <2L <2L <2L <0.005 - 0.011 <2L <2L 0.005 - 0.422 <2L <2L <2L

CW-2 CB <2L <2L 0.351 - 0.785 <2L <2L <2L <2L 0.0114 - 0.535 <2L <2L 5.0 - 6.1

CW-2D CB <2L <2L <2L <2L <2L 0.048 - 0.522 <2L 0.0335 - 0.270 <2L <2L 6.1 - 6.8

CW-3 CB <2L <2L <2L <2L <2L 0.021 - 0.908 <2L 0.0121 - 0.481 <2L 421 - 520 6.3 - 6.7

CW-4 CB <2L <2L <2L <2L <2L 0.028 - 0.784 <2L <2L <2L <2L 5.8 - 6.4

CW-5 CB <2L <2L <2L <2L <2L 0.0989 - 1.08 <2L 0.387 - 0.706 <0.0001 - 0.000361 <2L 6.4 - 7.0

CW-6 CB <2L <2L <2L <2L <2L 1.22 - 1.87 <2L 1.09 - 1.44 <2L 417 - 550 6.5 - 7.1

Notes: Prepared by: RBI Checked by: MCM

CB - Compliance Boundary

< 2L - Constituent has not been detected above the 2L Standard or beyond range for pH

Shown concentration ranges only include concentrations detected above the laboratory's reporting limit.

Well

ID

Well Location

Relative to

Compliance

Boundary

Concentration Range

Page 1 of 1

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Table 2 Summary of

Concentration Ranges Greater than 2L Mayo

TABLE 3

GROUNDWATER ANALYTICAL RESULTS



Depth to

WaterpH Temp.

Specific

ConductanceDO ORP Turbidity Eh Aluminum Antimony Arsenic Barium Beryllium BOD Boron COD Cadmium Chloride Chromium Cobalt Copper Fluoride Iron Lead Manganese Mercury Molybdenum

ft SU Deg C µS/cm mg/l mV NTUs mV mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l

NE 6.5 - 8.5 NE NE NE NE NE NE NA 0.001 0.01 0.7 0.004 NE 0.7 NE 0.002 250 0.01 0.001 1 2 0.3 0.015 0.05 0.001 NE

200.7 200.8 200.8 200.7 NA NA 200.7 NA 200.8 300 200.8 200.8 200.7 300 200.7 200.8 200.8 245.1 200.8

Well Type Sample Date

Background 10/31/2008 35.99 5.7 16 141 NM NM NM NM NA 0.00013 0.0014 1.04 NA NA 0.006 NA 0.0011 17 0.0369 NA 0.104 NA 65.7 0.0331 2.27 <0.0001 NA

Background 6/4/2009 34.44 7.0 18 161 NM NM NM NM NA 0.0025 <0.001 0.155 NA NA <0.2 NA <0.001 18 0.0047 NA 0.0192 NA 2.1 0.0129 0.131 <0.0002 NA

Background 10/21/2009 36.55 5.3 16 102 NM NM NM NM NA 0.0042 <0.001 0.175 NA NA <0.2 NA <0.001 15 0.0157 NA 0.497 NA 4.61 0.0023 0.166 <0.0002 NA

Background 4/22/2010 33.59 5.6 15 107 NM NM NM NM NA <0.01 <10 0.12 NA NA <0.05 NA <0.002 14 0.0082 NA 0.018 NA 20 0.0012 0.039 0.00016 NA

Background 12/6/2010 36.64 5.9 16 186 NM NM 10.0 NM 0.77 <0.0005 <0.005 0.105 NA NA <0.05 NA 0.00012 15 0.0153 NA 0.0311 NA 1.08 <0.005 0.0263 <0.0002 NA

Background 4/20/2011 35.36 5.5 20 158 1.16 50.2 22.7 255.2 0.456 <0.0005 <0.005 0.0991 NA NA <0.05 NA 0.00015 14.1 0.0061 NA 0.0117 NA 0.702 <0.005 0.0266 <0.0002 NA

Background 7/11/2011 35.57 5.5 24 163 0.99 -71.2 24.2 133.8 0.584 <0.0005 <0.005 0.101 b NA NA <0.05 NA 0.00023 13.8 b 0.0401 NA <0.005 NA 1.04 <0.005 0.0296 <0.0002 NA

Background 11/3/2011 37.18 5.5 18 165 1.27 -103.0 3.84 102.0 0.216 <0.0005 <0.005 0.0954 NA NA <0.05 NA 0.0002 13.1 0.0079 NA <0.005 NA 0.261 <0.005 0.0089 <0.0002 NA



Background 11/5/2012 37.45 5.4 17 166 0.89 177.7 9.45 382.7 0.465 <0.0005 <0.005 0.101 NA NA <0.05 NA 0.000089 13.4 <0.005 NA <0.005 NA 0.526 <0.005 0.0556 <0.0002 NA

Background 4/10/2013 35.25 5.2 17 165 0.79 213.1 9.05 418.1 0.202 <0.001 <0.001 0.097 NA NA <0.05 NA <0.001 13 0.007 NA <0.005 NA 0.323 <0.001 0.015 <0.00005 NA

Background 7/9/2013 34.17 5.4 19 160 1.02 151.7 8.95 356.7 0.383 <0.001 <0.001 0.097 NA NA <0.05 NA <0.001 13 <0.005 NA <0.005 NA 0.488 <0.001 0.048 <0.00005 NA




Background 12/2/2010 35.57 6.6 19 576 NM NM 13.0 NM 1.7 <0.0005 <0.005 0.0818 NA NA <0.05 NA <0.00008 43.5 0.0067 NA 0.014 NA 2.66 <0.005 0.198 <0.0002 NA

Background 4/20/2011 33.35 6.3 21 623 1.26 6.8 12.1 211.8 0.298 <0.0005 <0.005 0.0613 NA NA <0.05 NA <0.00008 35.4 <0.005 NA <0.005 NA 0.439 <0.005 0.0714 <0.0002 NA

Background 7/11/2011 35.45 6.3 26 706 0.32 -77.2 9.20 127.8 0.298 <0.0005 <0.005 0.0648 b NA NA <0.05 NA <0.00008 32.6 b 0.0102 NA <0.005 NA 0.559 <0.005 0.0642 <0.0002 NA

Background 11/3/2011 35.90 6.3 17 671 0.67 -98.3 5.63 106.7 0.18 <0.0005 <0.005 0.0677 NA NA <0.05 NA <0.00008 32.9 0.0075 NA <0.005 NA 0.312 <0.005 0.0367 <0.0002 NA

Background 4/4/2012 35.71 6.3 21 647 0.34 -92.5 5.55 112.5 <0.1 <0.0005 <0.005 0.0615 NA NA <0.05 NA <0.00008 32.6 <0.005 NA <0.005 NA 0.152 <0.005 0.027 <0.0002 NA

Background 7/9/2012 35.94 6.3 20 652 0.51 -77.6 9.47 127.4 0.262 <0.0005 <0.005 0.0534 NA NA <0.05 NA <0.00008 35.3 0.0059 NA <0.005 NA 0.46 <0.005 0.0549 <0.0002 NA

Background 11/5/2012 36.20 6.3 17 640 0.51 89.5 9.02 294.5 0.506 <0.0005 <0.005 0.0602 NA NA <0.05 NA <0.00008 33.3 0.006 NA <0.005 NA 0.759 <0.005 0.0437 <0.0002 NA

Background 4/10/2013 35.33 6.3 18 725 0.17 -17.0 8.50 188.0 0.226 <0.001 <0.001 0.066 NA NA <0.05 NA <0.001 28 <0.005 NA <0.005 NA 0.646 <0.001 0.111 0.00018 NA

Background 7/9/2013 34.66 6.4 19 695 0.31 -120.4 8.08 84.6 0.412 <0.001 <0.001 0.069 NA NA <0.05 NA <0.001 30 <0.005 NA <0.005 NA 1.13 <0.001 0.248 0.00011 NA

Background 11/13/2013 34.40 6.4 17 658 0.10 18.0 9.50 223.0 0.384 <0.001 <0.001 0.062 NA NA <0.05 NA <0.001 29 <0.005 NA <0.005 NA 0.841 <0.001 0.177 0.00011 NA



Compliance 12/6/2010 19.84 6.7 16 236 NM NM 8.40 NM <0.1 <0.0005 <0.005 0.006 NA NA <0.05 NA 0.000082 13.4 <0.005 NA <0.005 NA <0.05 <0.005 0.104 <0.0002 NA

Compliance 4/20/2011 18.05 5.9 18 170 4.15 -0.6 4.02 204.4 <0.1 <0.0005 <0.005 0.0053 NA NA <0.05 NA 0.00025 17.5 <0.005 NA <0.005 NA 0.0746 <0.005 0.0387 <0.0002 NA

Compliance 7/12/2011 18.73 5.9 24 178 5.20 -54.9 4.49 150.1 0.183 <0.0005 <0.005 <0.005 NA NA <0.05 NA 0.00026 16.7 b <0.005 NA <0.005 NA 0.126 <0.005 0.0379 <0.0002 NA

Compliance 11/4/2011 19.02 6.0 16 180 3.91 -93.0 2.76 112.0 0.149 <0.0005 <0.005 <0.005 NA NA <0.05 NA 0.00029 17.1 <0.005 NA <0.005 NA 0.143 <0.005 0.0299 <0.0002 NA

Compliance 4/5/2012 18.37 6.2 16 171 5.01 -54.7 3.77 150.3 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA 0.0002 18.6 <0.005 NA <0.005 NA <0.05 <0.005 0.0195 <0.0002 NA

Compliance 7/9/2012 19.16 5.8 22 174 4.08 -63.3 0.95 141.7 0.154 <0.0005 <0.005 <0.005 NA NA <0.05 NA 0.00025 18.5 <0.005 NA <0.005 NA 0.142 <0.005 0.0192 <0.0002 NA

Compliance 11/6/2012 19.09 5.9 13 177 4.34 193.2 0.97 398.2 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA 0.00055 17.9 <0.005 NA <0.005 NA 0.0616 <0.005 0.0147 <0.0002 NA

Compliance 4/10/2013 18.41 5.7 19 174 3.80 NM 2.72 NM 0.027 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 16 <0.005 NA <0.005 NA 0.013 <0.001 0.009 <0.00005 NA

Compliance 7/9/2013 18.06 5.6 21 169 2.83 -21.5 2.05 183.5 0.02 <0.001 <0.001 <0.005 NA NA <0.05 NA 0.00219 17 <0.005 NA <0.005 NA 0.021 <0.001 0.008 <0.00005 NA

Compliance 11/13/2013 18.88 5.9 14 175 3.10 159.0 1.50 364.0 0.049 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 17 <0.005 NA <0.005 NA 0.033 <0.001 0.009 <0.00005 NA

Compliance 4/1/2014 18.16 5.8 17 171 4.90 238.0 1.40 443.0 0.217 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 17 <0.005 NA <0.005 NA 0.173 <0.001 0.013 <0.00005 NA

Compliance 7/16/2014 18.40 5.6 19 168 3.58 225.6 1.72 430.6 0.039 b <0.001 <0.001 0.013 NA NA <0.05 NA <0.001 18 <0.005 NA <0.005 NA 0.028 <0.001 0.007 <0.00005 NA

Compliance 12/2/2010 18.64 7.5 17 390 NM NM 9.30 NM 0.244 <0.0005 <0.005 0.0111 NA NA <0.05 NA <0.00008 8.5 0.011 NA 0.0085 NA 0.207 <0.005 0.422 <0.0002 NA

Compliance 4/20/2011 19.39 7.0 17 335 1.43 -33.6 1.08 171.4 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 8.5 <0.005 NA <0.005 NA 0.0791 <0.005 0.0259 <0.0002 NA

Compliance 7/12/2011 20.01 6.9 23 347 1.18 -86.6 1.42 118.4 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 8.6 b <0.005 NA <0.005 NA <0.05 <0.005 0.0092 <0.0002 NA

Compliance 11/4/2011 20.22 6.9 15 333 6.61 -97.1 5.03 107.9 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 8.4 <0.005 NA <0.005 NA <0.05 <0.005 0.0463 <0.0002 NA

Compliance 4/5/2012 19.70 7.0 16 333 2.03 -74.2 3.55 130.8 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 9 <0.005 NA 0.0054 NA 0.0515 <0.005 0.0137 <0.0002 NA

Compliance 7/9/2012 20.36 6.8 22 348 1.02 -61.5 4.77 143.5 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 8.5 <0.005 NA <0.005 NA 0.0689 <0.005 0.019 <0.0002 NA

Compliance 11/6/2012 20.31 7.0 13 384 1.07 149.1 2.15 354.1 <0.1 <0.0005 <0.005 <0.005 NA NA <0.05 NA <0.00008 9.7 <0.005 NA <0.005 NA <0.05 <0.005 0.0526 <0.0002 NA

Compliance 4/10/2013 19.75 6.8 20 365 1.27 NM 2.55 NM 0.029 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 8.9 <0.005 NA <0.005 NA <.01 <0.001 0.005 <0.00005 NA

Compliance 7/9/2013 19.43 6.9 22 353 0.58 -611.3 3.15 -406.3 0.018 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 8.6 <0.005 NA <0.005 NA 0.015 <0.001 0.006 <0.00005 NA

Compliance 11/13/2013 20.10 7.0 13 335 0.70 139.0 2.10 344.0 0.055 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 7.8 <0.005 NA <0.005 NA 0.025 <0.001 <0.005 <0.00005 NA

Compliance 4/1/2014 19.50 6.9 19 360 1.60 238.0 1.50 443.0 0.014 <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 9.6 <0.005 NA <0.005 NA 0.013 <0.001 <0.005 <0.00005 NA

Compliance 7/16/2014 19.71 6.9 19 340 0.66 161.1 1.06 366.1 0.019 b <0.001 <0.001 <0.005 NA NA <0.05 NA <0.001 8.8 <0.005 NA <0.005 NA 0.014 <0.001 <0.005 <0.00005 NA

Constituent Concentrations

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1D

CW-1D

CW-1D

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1D

BG-2

BG-2

BG-1

BG-1

BG-1

Field Measurements

BG-1

BG-1

BG-2

BG-2

BG-2

Analytical Parameter

Analytical Method

Units

Sample ID

BG-1

BG-1

BG-1

BG-1

BG-1

15 NCAC .02L .0202(g) Groundwater Quality Standard

BG-2

BG-1

BG-1

BG-1

BG-1

BG-1

BG-1

BG-2

BG-2

BG-2

BG-2

BG-2

BG-2

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Tables 3 and 4 Groundwater and Seep Data Tables 1 of 6

TABLE 3




Depth to

WaterpH Temp.

Specific




200.7 200.8 200.8 200.7 NA NA 200.7 NA 200.8 300 200.8 200.8 200.7 300 200.7 200.8 200.8 245.1 200.8

Well Type Sample Date Constituent ConcentrationsField Measurements


Analytical Method

Units

Sample ID


Compliance 12/1/2010 13.86 6.1 10 213 NM NM 10.5 NM 0.186 <0.0005 <0.005 0.0753 NA NA 0.401 NA <0.00008 23 <0.005 NA <0.005 NA 0.233 <0.005 0.0378 <0.0002 NA

Compliance 4/20/2011 13.20 5.3 14 177 1.65 -33.1 1.97 171.9 <0.1 <0.0005 <0.005 0.0683 NA NA 0.351 NA <0.00008 19.4 <0.005 NA <0.005 NA <0.05 <0.005 0.0114 <0.0002 NA

Compliance 7/11/2011 14.77 5.3 19 221 1.05 -72.4 3.07 132.6 <0.1 <0.0005 <0.005 0.0712 b NA NA 0.478 NA <0.00008 26.3 b <0.005 NA <0.005 NA <0.05 <0.005 0.0361 <0.0002 NA

Compliance 11/3/2011 14.13 5.5 15 257 0.92 -70.5 0.82 134.5 <0.1 <0.0005 <0.005 0.0987 NA NA 0.451 NA <0.00008 35 <0.005 NA <0.005 NA <0.05 <0.005 0.0308 <0.0002 NA

Compliance 4/5/2012 13.61 5.6 13 243 1.19 -39.6 1.02 165.4 <0.1 <0.0005 <0.005 0.105 NA NA 0.459 NA <0.00008 42.2 <0.005 NA <0.005 NA <0.05 <0.005 0.107 <0.0002 NA

Compliance 7/10/2012 15.05 5.3 18 303 0.74 -65.8 1.30 139.2 <0.1 <0.0005 <0.005 0.0952 NA NA 0.59 NA 0.00012 53.1 <0.005 NA <0.005 NA <0.05 <0.005 0.184 <0.0002 NA

Compliance 11/5/2012 14.58 5.5 15 346 1.20 219.8 0.21 424.8 <0.1 <0.0005 <0.005 0.138 NA NA 0.665 NA 0.000086 69.5 <0.005 NA <0.005 NA <0.05 <0.005 0.186 <0.0002 NA

Compliance 4/10/2013 12.75 5.3 16 269 2.53 201.8 0.59 406.8 0.025 <0.001 <0.001 0.115 NA NA 0.522 NA <0.001 42 <0.005 NA <0.005 NA <.01 <0.001 0.14 <0.00005 NA

Compliance 7/9/2013 13.62 5.2 21 300 0.91 103.8 3.21 308.8 0.045 <0.001 <0.001 0.124 NA NA 0.696 NA <0.001 54 <0.005 NA <0.005 NA 0.051 <0.001 0.36 0.00009 NA

Compliance 11/13/2013 14.40 5.3 12 367 1.70 234.0 6.80 439.0 0.077 <0.001 <0.001 0.157 NA NA 0.785 NA <0.001 73 <0.005 NA <0.005 NA 0.077 <0.001 0.535 <0.00005 NA


Compliance 7/16/2014 14.59 5.0 16 291 1.40 298.1 1.37 503.1 0.05 b <0.001 <0.001 0.116 NA NA 0.7 NA <0.001 54 <0.005 NA <0.005 NA 0.044 <0.001 0.26 <0.00005 NA

Compliance 12/2/2010 14.39 6.7 13 300 NM NM 20.0 NM 0.687 <0.0005 <0.005 0.0342 NA NA 0.233 NA 0.00012 15.6 <0.005 NA 0.0088 NA 0.37 <0.005 0.102 <0.0002 NA

Compliance 4/20/2011 13.60 6.5 17 419 4.19 -34.6 13.6 170.4 0.376 <0.0005 <0.005 0.0334 NA NA 0.202 NA 0.00012 14 <0.005 NA <0.005 NA 0.227 <0.005 0.156 <0.0002 NA

Compliance 7/12/2011 15.26 6.7 19 427 1.31 -139.3 23.8 65.7 1.42 <0.0005 <0.005 0.0323 b NA NA 0.121 NA 0.0002 13.9 b <0.005 NA <0.005 NA 0.522 <0.005 0.254 <0.0002 NA

Compliance 11/3/2011 14.68 6.5 14 365 0.85 -71.4 16.7 133.6 0.481 <0.0005 <0.005 0.0316 NA NA 0.13 NA 0.000092 13.9 <0.005 NA <0.005 NA 0.286 <0.005 0.25 <0.0002 NA

Compliance 4/5/2012 14.14 6.5 14 329 2.53 -50.6 17.4 154.4 0.467 <0.0005 <0.005 0.0274 NA NA 0.14 NA <0.00008 18 <0.005 NA <0.005 NA 0.347 <0.005 0.27 <0.0002 NA

Compliance 7/10/2012 15.61 6.5 20 381 1.20 -54.1 15.2 150.9 0.692 <0.0005 <0.005 0.024 NA NA 0.187 NA 9.30E-05 20 <0.005 NA <0.005 NA 0.392 <0.005 0.231 <0.0002 NA

Compliance 11/5/2012 15.08 6.7 14 328 3.09 155.8 4.51 360.8 0.137 <0.0005 <0.005 0.0373 NA NA 0.26 NA <0.00008 25.8 <0.005 NA <0.005 NA 0.0795 <0.005 0.0335 <0.0002 NA






Compliance 12/2/2010 16.09 6.7 14 761 NM NM 9.90 NM 1.38 <0.0005 <0.005 0.0479 NA NA <0.05 NA <0.00008 155 <0.005 NA <0.005 NA 0.908 <0.005 0.481 <0.0002 NA

Compliance 4/21/2011 15.24 6.4 14 738 2.10 -76.5 5.73 128.5 0.139 <0.0005 <0.005 0.0277 NA NA <0.05 NA <0.00008 137 <0.005 NA <0.005 NA 0.128 <0.005 0.305 <0.0002 NA

Compliance 7/12/2011 15.53 6.4 22 765 0.71 -117.9 4.32 87.1 <0.1 <0.0005 <0.005 0.0245 b NA NA <0.05 NA <0.00008 137 <0.005 NA <0.005 NA 0.0997 <0.005 0.201 <0.0002 NA

Compliance 11/4/2011 16.73 6.4 15 703 0.88 -84.7 2.37 120.3 <0.1 <0.0005 <0.005 0.0206 NA NA <0.05 NA <0.00008 140 <0.005 NA <0.005 NA 0.0985 <0.005 0.0369 <0.0002 NA



Compliance 11/5/2012 17.88 6.5 14 699 1.07 76.8 1.27 281.8 <0.1 <0.0005 <0.005 0.0174 NA NA <0.05 NA <0.00008 149 <0.005 NA <0.005 NA <0.05 <0.005 0.0121 <0.0002 NA

Compliance 4/10/2013 17.49 6.4 19 763 2.56 NM 2.65 NM 0.083 <0.001 <0.001 0.026 NA NA <0.05 NA <0.001 130 <0.005 NA <0.005 NA 0.057 <0.001 0.153 <0.00005 NA

Compliance 7/9/2013 16.42 6.3 20 735 1.28 -629.1 4.88 -424.1 0.102 <0.001 <0.001 0.021 NA NA <0.05 NA <0.001 130 <0.005 NA <0.005 NA 0.095 <0.001 0.061 <0.00005 NA

Compliance 11/14/2013 18.28 6.4 13 696 0.80 357.0 9.60 562.0 0.29 <0.001 <0.001 0.019 NA NA <0.05 NA <0.001 120 <0.005 NA <0.005 NA 0.3 <0.001 0.017 <0.00005 NA



Compliance 12/2/2010 22.53 6.4 13 195 NA NA 21.0 NM 2.11 <0.0005 <0.005 0.0296 NA NA <0.05 NA <0.00008 9 <0.005 NA <0.005 NA 0.784 <0.005 0.0161 <0.0002 NA

Compliance 4/21/2011 22.30 6.0 14 175 1.80 -75.8 5.57 129.2 0.558 <0.0005 <0.005 0.0209 NA NA <0.05 NA <0.00008 7.8 <0.005 NA <0.005 NA 0.254 <0.005 0.0097 <0.0002 NA

Compliance 7/12/2011 22.85 6.0 21 172 2.93 -78.0 2.88 127.0 <0.1 <0.0005 <0.005 0.0196 b NA NA <0.05 NA <0.00008 7.7 b <0.005 NA <0.005 NA 0.0524 <0.005 0.0063 <0.0002 NA




Compliance 11/6/2012 24.28 6.2 13 202 2.06 124.7 4.76 329.7 0.161 <0.0005 <0.005 0.021 NA NA <0.05 NA <0.00008 7.7 <0.005 NA <0.005 NA 0.0976 <0.005 0.0351 <0.0002 NA

Compliance 4/10/2013 22.80 6.0 18 205 0.99 NM 2.52 NM 0.04 <0.001 <0.001 0.018 NA NA <0.05 NA <0.001 7.1 <0.005 NA <0.005 NA 0.028 <0.001 0.012 <0.00005 NA

Compliance 7/9/2013 22.74 5.9 22 175 2.18 -220.1 8.13 -15.1 0.235 <0.001 <0.001 0.021 NA NA <0.05 NA <0.001 6.3 <0.005 NA <0.005 NA 0.127 <0.001 0.013 <0.00005 NA


Compliance 4/1/2014 22.35 6.1 15 195 1.60 239.0 2.30 444.0 9.20E-02 <0.001 <0.001 0.02 NA NA <0.05 NA <0.001 6.6 <0.005 NA <0.005 NA 0.074 <0.001 0.013 <0.00005 NA


Compliance 12/6/2010 10.69 7.0 12 397 NM NM 5.80 NM 0.184 <0.0005 <0.005 0.0553 NA NA <0.05 NA 0.00012 37.2 <0.005 NA <0.005 NA 0.293 <0.005 0.609 <0.0002 NA

CW-4

CW-4

CW-4

CW-5

CW-4

CW-4

CW-4

CW-4

CW-4

CW-4

CW-3

CW-3

CW-4

CW-4

CW-4

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2


TABLE 3




Depth to

WaterpH Temp.

Specific




200.7 200.8 200.8 200.7 NA NA 200.7 NA 200.8 300 200.8 200.8 200.7 300 200.7 200.8 200.8 245.1 200.8

Well Type Sample Date Constituent ConcentrationsField Measurements


Analytical Method

Units

Sample ID


Compliance 4/21/2011 5.83 6.6 14 383 0.29 -84.0 6.23 121.0 <0.1 <0.0005 <0.005 0.0492 NA NA <0.05 NA <0.00008 36.7 <0.005 NA <0.005 NA 0.343 <0.005 0.583 <0.0002 NA

Compliance 7/12/2011 9.61 6.6 22 377 2.55 -95.4 0.45 109.6 <0.1 <0.0005 <0.005 0.0541 b NA NA <0.05 NA <0.00008 32.8 b <0.005 NA <0.005 NA 0.485 <0.005 0.629 <0.0002 NA


Compliance 4/5/2012 7.02 6.5 15 365 2.70 -83.4 3.13 121.6 <0.1 <0.0005 <0.005 0.0445 NA NA <0.05 NA 0.0001 34.2 <0.005 NA <0.005 NA 0.0989 <0.005 0.387 <0.0002 NA


Compliance 11/6/2012 12.83 6.6 14 373 1.16 6.6 0.69 211.6 <0.1 <0.0005 <0.005 0.0526 NA NA <0.05 NA <0.00008 34.2 <0.005 NA <0.005 NA 0.588 <0.005 0.557 <0.0002 NA

Compliance 4/10/2013 6.22 6.6 19 393 2.12 NM 5.54 NM 0.03 <0.001 <0.001 0.047 NA NA <0.05 NA <0.001 29 <0.005 NA <0.005 NA 0.274 <0.001 0.549 <0.00005 NA

Compliance 7/9/2013 6.96 6.4 25 375 0.59 -534.8 1.68 -329.8 0.029 <0.001 <0.001 0.05 NA NA <0.05 NA <0.001 30 <0.005 NA <0.005 NA 0.589 <0.001 0.595 <0.00005 NA



Compliance 7/17/2014 9.32 6.5 17 395 0.41 21.2 8.63 226.2 0.027 b <0.001 <0.001 0.057 NA NA <0.05 NA <0.001 35 <0.005 NA <0.005 NA 1.08 <0.001 0.672 <0.00005 NA

Compliance 12/1/2010 14.33 7.1 14 778 NM NM 10.9 NM 0.188 <0.0005 <0.005 0.0341 NA NA <0.05 NA <0.00008 90.3 0.0071 NA 0.0056 NA 1.22 <0.005 1.09 <0.0002 NA


Compliance 7/12/2011 13.78 6.6 18 794 0.63 -125.9 6.53 79.1 0.145 <0.0005 <0.005 0.0354 b NA NA <0.05 NA <0.00008 94.6 <0.005 NA <0.005 NA 1.33 <0.005 1.16 <0.0002 NA









Compliance 7/16/2014 13.69 6.6 16 827 0.49 -17.7 5.22 187.3 0.018 b <0.001 <0.001 0.041 NA NA <0.05 NA <0.001 90 <0.005 NA <0.005 NA 1.39 <0.001 1.35 <0.00005 NA

Voluntary 10/31/2008 35.99 5.7 60.44 141 NA NA NA NA NA 0.00013 0.0014 1.04 0.0009 <2 0.006 35 0.0011 17 0.0369 NA 0.104 <0.5 65.7 0.0331 2.27 <0.0001 NA

Voluntary 6/4/2009 34.44 7.0 64.40 161 NA NA NA NA NA 0.0025 0.001 0.155 <0.001 10 <0.2 78 <0.001 18 0.0047 NA 0.0192 <0.5 2.1 0.0129 0.131 <0.0002 NA

Voluntary 10/21/2009 36.55 5.3 59.9 102 NA NA NA NA NA 0.0042 0.001 0.175 <0.001 <2 <0.2 21 <0.001 15 0.0157 NA 0.497 <0.25 4.61 0.0023 0.166 <0.0002 NA

Voluntary 4/22/2010 33.59 5.6 58.28 107 NA NA NA NA NA 0.01 0.01 0.12 <0.004 <2 <0.05 <10 <0.002 14 0.0082 NA 0.018 <0.1 2 0.012 0.039 0.00016 NA

Voluntary 10/31/2008 26.91 6.8 60.8 223 NA NA NA NA NA <0.000017 0.00028 0.0392 <0.000051 <2 0.003 16 0.000037 16 0.00069 NA 0.0016 <0.5 0.0981 0.00033 0.201 0.0002 NA

Voluntary 6/4/2009 25.74 6.0 64.4 287 NA NA NA NA NA <0.002 <0.001 0.0456 <0.001 <2 <0.2 <10 <0.001 17 <0.002 NA 0.0021 <0.5 <0.1 <0.001 0.293 <0.0002 NA

Voluntary 10/21/2009 27.28 6.1 63.14 206 NA NA NA NA NA 0.0023 <0.001 0.0396 <0.001 <2 <0.2 <10 <0.001 11 0.0035 NA <0.002 <0.25 0.105 <0.001 0.259 <0.0002 NA

Voluntary 4/21/2010 25.08 6.3 59.18 189 NA NA NA NA NA <0.01 <0.01 0.031 <0.004 <2 <0.05 <10 <0.002 13 <0.005 NA <0.005 0.21 <0.1 0.011 0.073 0.00023 NA

Voluntary 10/31/2008 6.75 6.0 60.98 224 NA NA NA NA NA <0.000017 0.0004 0.0589 <0.000051 <2 0.565 11 0.000092 14 0.00086 NA 0.00093 <0.5 0.0672 0.00022 0.475 0.00011 NA

Voluntary 6/4/2009 6.71 4.3 59.72 273 NA NA NA NA NA <0.002 <0.001 0.0507 <0.001 <2 0.599 11 <0.001 16 <0.002 NA <0.002 <0.5 <0.1 <0.001 0.505 <0.0002 NA

Voluntary 10/21/2009 6.71 6.4 60.44 220 NA NA NA NA NA 0.002 <0.001 0.0469 <0.001 <2 0.672 <10 <0.001 14 0.0043 NA <0.002 <0.25 <0.1 <0.001 0.547 <0.0002 NA

Voluntary 4/21/2010 6.58 5.9 53.42 160 NA NA NA NA NA <0.01 <0.01 0.044 <0.004 <2 0.59 <10 <0.002 13 <0.005 NA <0.005 0.12 <0.1 <0.01 0.39 <0.0001 NA

Voluntary 10/31/2008 35.4 6.7 62.1 252 NA NA NA NA NA 0.00013 0.0003 0.0634 <0.000051 <2 0.0059 14 0.00022 8.7 0.0028 NA 0.007 <0.5 1.07 0.0029 0.331 <0.0001 NA

Voluntary 6/4/2009 32.21 4.9 66.20 454 NA NA NA NA NA <0.002 <0.001 0.0404 <0.001 <2 <0.2 30 <0.001 <10 0.0065 NA 0.0063 <0.5 1.6 0.007 1.06 <0.0002 NA

Voluntary 10/21/2009 35.42 6.2 65.66 304 NA NA NA NA NA <0.002 <0.001 0.0167 <0.001 <2 <0.2 <10 <0.001 7.7 0.0074 NA 0.184 0.29 0.611 0.0024 0.294 <0.0002 NA

Voluntary 4/22/2010 27.42 6.8 57.38 202 NA NA NA NA NA <0.01 <0.01 <0.025 <0.004 <2 <0.05 <10 <0.002 5.6 <0.005 NA 0.007 0.18 0.32 <0.01 0.12 <0.0001 NA

Notes: Prepared By: RBI/BER Checked By: JAW

1. Analytical parameter abbreviations:

Temp. = Temperature

DO = Dissolved oxygen

ORP = Oxidation reduction potential

TDS = Total dissolved solids

TSS = Total suspended solids

TOC = Total organic carbon

2. Units:

˚C = Degrees Celcius

SU = Standard Units

mV = millivolts

µS/cm = microsiemens per centimeter

NTU = Nephelometric Turbidity Unit

mg/L = milligrams per liter

3. NE = Not established

4. NA = Not available

5. NM = Not measured

6 b = Data flagged due to detection in field blank

7.

8.

* Sample data provided by Duke. Temperature data was reported in degrees F.

Analytical results with "<" preceding the result indicates that the parameter

was not detected at a concentration which attains or exceeds the laboratory

reporting limit.

Highlighted values indicate values that exceed the 15 NCAC .02L .0202(g)

Standard

MW-3*

MW-4*

MW-4*

MW-4*

MW-4*

MW-2*

MW-2*

MW-2*

MW-3*

MW-3*

MW-3*

MW-1*

MW-1*

MW-1*

MW-1*

MW-2*

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-5

CW-5

CW-5

CW-6

CW-6

CW-6

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5


TABLE 3





Background 10/31/2008

Background 6/4/2009







Background 4/4/2012

Background 7/9/2012



Background 7/9/2013


Background 4/1/2014






Background 4/4/2012

Background 7/9/2012



Background 7/9/2013


Background 4/1/2014


Compliance 12/6/2010




Compliance 4/5/2012

Compliance 7/9/2012



Compliance 7/9/2013


Compliance 4/1/2014






Compliance 4/5/2012

Compliance 7/9/2012



Compliance 7/9/2013


Compliance 4/1/2014


CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1D

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1D

CW-1D

CW-1D

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1

CW-1D

BG-2

BG-2

BG-1

BG-1

BG-1

BG-1

BG-1

BG-2

BG-2

BG-2


Analytical Method

Units

Sample ID

BG-1

BG-1

BG-1

BG-1

BG-1


BG-2

BG-1

BG-1

BG-1

BG-1

BG-1

BG-1

BG-2

BG-2

BG-2

BG-2

BG-2

BG-2

Nickel Nitrate Nitrite Selenium Silver Strontium Sulfate TDS Thallium TOC TOX Vanadium Zinc

mg/l mg/l mg/l mg/l mg/L mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l

0.1 10 NE 0.02 0.02 NE 250 500 0.0002 NE NE 0.0003 1

200.7 300.0 NA 200.8 NA NA 300 SM2540C 200.8 NA NA NA 200.7

0.0233 <0.25 NA 0.0024 NA NA <25 189 0.00035 NA NA NA 0.229

4.90E-03 <0.05 NA <0.005 NA NA <25 167 <0.001 NA NA NA 0.0693

9.30E-03 0.58 NA <0.005 NA NA <5 146 <0.001 NA NA NA 0.133

<0.04 0.24 NA <0.01 NA NA <1 17 <0.05 NA NA NA <0.02

0.0149 0.36 NA <0.01 NA NA <5 126 <0.0001 NA NA NA 0.071

0.0077 0.35 NA <0.01 NA NA <5 135 <0.0001 NA NA NA 0.0456

0.0404 b 0.44 NA <0.01 NA NA <5 117 b <0.0001 NA NA NA 0.0146

0.0062 0.41 NA <0.01 NA NA <5 106 <0.0001 NA NA NA <0.01

<0.005 0.36 NA <0.01 NA NA <5 107 <0.0001 NA NA NA <0.01

0.0094 0.39 NA <0.01 NA NA 2 128 <0.0001 NA NA NA <0.01

<0.005 0.42 NA <0.01 NA NA <2 123 <0.0001 NA NA NA 0.0116

<0.005 0.4 NA <0.001 NA NA 0.44 130 <0.0002 NA NA NA 0.007

<0.005 0.46 NA <0.001 NA NA 0.52 130 <0.0002 NA NA NA 0.012

<0.005 0.48 NA <0.001 NA NA 0.51 130 <0.0002 NA NA NA 0.03

<0.005 0.5 NA <0.001 NA NA 0.4 140 <0.0002 NA NA NA 0.029

<0.005 0.52 NA <0.001 NA NA 0.46 140 <0.0002 NA NA NA 0.016

<0.005 <0.1 NA <0.01 NA NA 8.5 349 <0.0001 NA NA NA 0.0309

<0.005 <0.1 NA <0.01 NA NA 8.3 382 <0.0001 NA NA NA 0.0187

0.0094 b <0.2 NA <0.01 NA NA 7.2 b 367 b <0.0001 NA NA NA <0.01

0.0052 <0.2 NA <0.01 NA NA 6.9 341 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 7.5 412 <0.0001 NA NA NA <0.01

<0.005 <0.02 NA <0.01 NA NA 7.7 382 <0.0001 NA NA NA <0.01

<0.005 <0.02 NA <0.01 NA NA 8.3 389 <0.0001 NA NA NA <0.01

<0.005 0.03 NA <0.001 NA NA 5.4 430 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 5.2 430 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 5.2 360 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 4.8 450 <0.0002 NA NA NA 0.008

<0.005 <0.023 NA <0.001 NA NA 4.9 400 <0.0002 NA NA NA 0.005

<0.005 0.82 NA <0.01 NA NA <5 147 <0.0001 NA NA NA <0.01

<0.005 1.5 NA <0.01 NA NA 8.4 130 <0.0001 NA NA NA 0.0126

<0.005 1.5 NA <0.01 NA NA 8.2 b 142 b <0.0001 NA NA NA <0.01

<0.005 1.6 NA <0.01 NA NA 8.3 163 <0.0001 NA NA NA <0.01

<0.005 1.6 NA <0.01 NA NA 9 121 <0.0001 NA NA NA 0.0185

<0.005 1.4 NA <0.01 NA NA 9.4 132 <0.0001 NA NA NA 0.0122

<0.005 1.5 NA <0.01 NA NA 10.2 123 <0.0001 NA NA NA 0.019

<0.005 1.4 NA <0.001 NA NA 8.8 140 <0.0002 NA NA NA 0.012

<0.005 1.5 NA <0.001 NA NA 8.9 140 <0.0002 NA NA NA 0.018

<0.005 1.4 NA <0.001 NA NA 8.6 140 <0.0002 NA NA NA 0.011

<0.005 1.5 NA <0.001 NA NA 9.8 150 <0.0002 NA NA NA 0.011

<0.005 1.4 NA <0.001 NA NA 8.9 140 <0.0002 NA NA NA 0.01

0.0065 <0.1 NA <0.01 NA NA 5.1 218 <0.0001 NA NA NA 0.0163

<0.005 0.26 NA <0.01 NA NA <5 192 <0.0001 NA NA NA 0.0138

<0.005 0.25 NA <0.01 NA NA <5 198 b <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA <5 <25 <0.0001 NA NA NA <0.01

<0.005 0.28 NA <0.01 NA NA <5 192 <0.0001 NA NA NA <0.01

<0.005 0.24 NA <0.01 NA NA 4.1 202 <0.0001 NA NA NA <0.01

<0.005 0.18 b NA <0.01 NA NA 4.9 203 <0.0001 NA NA NA <0.01

<0.005 0.33 NA <0.001 NA NA 4.2 220 <0.0002 NA NA NA <0.005

<0.005 0.4 NA <0.001 NA NA 4.4 220 <0.0002 NA NA NA <0.005

<0.005 0.25 NA <0.001 NA NA 2.7 200 <0.0002 NA NA NA <0.005

<0.005 0.4 NA <0.001 NA NA 4.7 220 <0.0002 NA NA NA <0.005

<0.005 0.33 NA <0.001 NA NA 3.5 210 <0.0002 NA NA NA <0.005



TABLE 3






Analytical Method

Units

Sample ID






Compliance 4/5/2012




Compliance 7/9/2013


Compliance 4/1/2014






Compliance 4/5/2012




Compliance 7/9/2013


Compliance 4/1/2014






Compliance 4/4/2012

Compliance 7/9/2012



Compliance 7/9/2013


Compliance 4/1/2014






Compliance 4/4/2012




Compliance 7/9/2013


Compliance 4/1/2014



CW-4

CW-4

CW-4

CW-5

CW-4

CW-4

CW-4

CW-4

CW-4

CW-4

CW-3

CW-3

CW-4

CW-4

CW-4

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-3

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2D

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2

CW-2



0.1 10 NE 0.02 0.02 NE 250 500 0.0002 NE NE 0.0003 1



<0.005 <0.1 NA <0.01 NA NA 41.8 129 <0.0001 NA NA NA <0.01

<0.005 <0.1 NA <0.01 NA NA 39.6 118 <0.0001 NA NA NA 0.0143

<0.005 <0.2 NA <0.01 NA NA 39.4 b 132 b <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 38.8 139 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 37.2 140 <0.0001 NA NA NA <0.01

<0.005 0.023 NA <0.01 NA NA 43.2 186 <0.0001 NA NA NA <0.01

<0.005 0.038 b NA <0.01 NA NA 39 199 <0.0001 NA NA NA <0.01

<0.005 <0.023 NA <0.001 NA NA 40 150 <0.0002 NA NA NA 0.008

<0.005 0.03 NA <0.001 NA NA 42 190 <0.0002 NA NA NA 0.011

<0.005 0.19 NA <0.001 NA NA 37 220 <0.0002 NA NA NA 0.008

<0.005 <0.023 NA <0.001 NA NA 38 150 <0.0002 NA NA NA 0.008

<0.005 0.03 NA <0.001 NA NA 39 210 <0.0002 NA NA NA 0.006

<0.005 <0.1 NA <0.01 NA NA 50.2 205 <0.0001 NA NA NA 0.042

<0.005 <0.1 NA <0.01 NA NA 52.6 208 <0.0001 NA NA NA 0.0283

<0.005 <0.2 NA <0.01 NA NA 52.1 207 b <0.0001 NA NA NA 0.015

<0.005 <0.2 NA <0.01 NA NA 50 197 <0.0001 NA NA NA 0.0153

<0.005 <0.2 NA <0.01 NA NA 47.5 221 <0.0001 NA NA NA 0.0155

<0.005 0.026 NA <0.01 NA NA 53.1 260 <0.0001 NA NA NA 0.0127

<0.005 0.032 b NA <0.01 NA NA 51.4 274 <0.0001 NA NA NA <0.01

<0.005 0.05 NA <0.001 NA NA 46 210 <0.0002 NA NA NA 0.012

<0.005 <0.023 NA <0.001 NA NA 49 260 <0.0002 NA NA NA 0.011

<0.005 0.03 NA <0.001 NA NA 53 260 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 46 230 <0.0002 NA NA NA 0.026

<0.005 <0.023 NA <0.001 NA NA 48 250 <0.0002 NA NA NA 0.014

<0.005 <0.1 NA <0.01 NA NA 15 438 <0.0001 NA NA NA <0.01

<0.005 0.12 NA <0.01 NA NA 12.9 463 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 12.9 b 474 <0.0001 NA NA NA <0.01

<0.005 0.2 NA <0.01 NA NA 13 421 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 14.6 456 <0.0001 NA NA NA <0.01

<0.005 0.25 NA <0.01 NA NA 14.1 487 <0.0001 NA NA NA <0.01

<0.005 0.27 NA <0.01 NA NA 14 447 <0.0001 NA NA NA <0.01

<0.005 0.31 NA <0.001 NA NA 15 520 <0.0002 NA NA NA <0.005

<0.005 0.27 NA <0.001 NA NA 16 510 <0.0002 NA NA NA 0.007

<0.005 0.28 NA <0.001 NA NA 14 460 <0.0002 NA NA NA <0.005

<0.005 0.27 NA <0.001 NA NA 15 470 <0.0002 NA NA NA <0.005

<0.005 0.3 NA <0.001 NA NA 15 470 <0.0002 NA NA NA <0.005

<0.005 0.14 NA <0.01 NA NA 11.6 150 <0.0001 NA NA NA <0.01

<0.005 0.16 NA <0.01 NA NA 8.5 140 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 10.6 b 207 b <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 10.7 154 <0.0001 NA NA NA <0.01

<0.005 0.21 NA <0.01 NA NA 10.9 124 <0.0001 NA NA NA <0.01

<0.005 0.23 NA <0.01 NA NA 12.7 149 <0.0001 NA NA NA <0.01

<0.005 0.22 b NA <0.01 NA NA 12.8 137 <0.0001 NA NA NA <0.01

<0.005 0.22 NA <0.001 NA NA 11 160 <0.0002 NA NA NA 0.008

<0.005 0.21 NA <0.001 NA NA 15 150 <0.0002 NA NA NA 0.006

<0.005 0.17 NA <0.001 NA NA 16 160 <0.0002 NA NA NA <0.005

<0.005 0.18 NA <0.001 NA NA 15 160 <0.0002 NA NA NA <0.005

<0.005 0.14 NA <0.001 NA NA 19 150 <0.0002 NA NA NA <0.005

<0.005 <0.1 NA <0.01 NA NA <5 243 <0.0001 NA NA NA <0.01


TABLE 3






Analytical Method

Units

Sample ID





Compliance 4/5/2012




Compliance 7/9/2013


Compliance 4/1/2014






Compliance 4/5/2012




Compliance 7/9/2013


Compliance 4/1/2014


Voluntary 10/31/2008

Voluntary 6/4/2009


Voluntary 4/22/2010


Voluntary 6/4/2009


Voluntary 4/21/2010


Voluntary 6/4/2009


Voluntary 4/21/2010


Voluntary 6/4/2009


Voluntary 4/22/2010

Notes:


Temp. = Temperature





TOC = Total organic carbon

2. Units:


SU = Standard Units

mV = millivolts


NTU = Nephelometric Turbidity Unit





6 b = Data flagged due to detection in field blank

7.

8.

* Sample data provided by Duke. Temperature data was reported in degrees F.

Analytical results with "<" preceding the result indicates that the parameter

was not detected at a concentration which attains or exceeds the laboratory

reporting limit.

Highlighted values indicate values that exceed the 15 NCAC .02L .0202(g)

Standard

MW-3*

MW-4*

MW-4*

MW-4*

MW-4*

MW-2*

MW-2*

MW-2*

MW-3*

MW-3*

MW-3*

MW-1*

MW-1*

MW-1*

MW-1*

MW-2*

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-6

CW-5

CW-5

CW-5

CW-6

CW-6

CW-6

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5

CW-5



0.1 10 NE 0.02 0.02 NE 250 500 0.0002 NE NE 0.0003 1



<0.005 <0.1 NA <0.01 NA NA <5 242 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA <5 253 b <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA <5 <25 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 5.5 230 <0.0001 NA NA NA <0.01

<0.005 <0.02 NA <0.01 NA NA 6.2 250 <0.0001 NA NA NA <0.01

<0.005 0.15 b NA <0.01 NA NA 6.4 241 <0.0001 NA NA NA <0.01

<0.005 <0.023 NA <0.001 NA NA 5.3 250 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 5.6 240 0.000361 NA NA NA 0.006

<0.005 <0.023 NA <0.001 NA NA 5.1 250 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 5.7 280 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 5.5 270 <0.0002 NA NA NA <0.005

<0.005 <0.1 NA <0.01 NA NA 40.1 445 <0.0001 NA NA NA 0.0141

<0.005 <0.1 NA <0.01 NA NA 37.8 481 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 38.9 b 417 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 39.2 464 <0.0001 NA NA NA <0.01

<0.005 <0.2 NA <0.01 NA NA 37.8 486 <0.0001 NA NA NA <0.01

<0.005 1.3 NA <0.01 NA NA 39.8 524 <0.0001 NA NA NA <0.01

<0.005 <0.02 NA <0.01 NA NA 41.1 528 <0.0001 NA NA NA <0.01

<0.005 <0.023 NA <0.001 NA NA 39 550 <0.0002 NA NA NA <0.005

<0.005 0.07 NA <0.001 NA NA 40 550 <0.0002 NA NA NA 0.007

<0.005 <0.023 NA <0.001 NA NA 36 520 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 39 550 <0.0002 NA NA NA <0.005

<0.005 <0.023 NA <0.001 NA NA 39 550 <0.0002 NA NA NA <0.005

0.0233 <0.25 <0.25 0.0024 0.00035 NA <25 189 0.00035 <5 <0.03 NA 0.229

0.0049 <0.05 <0.05 <0.005 <0.001 NA <25 167 <0.001 10.1 <0.03 NA 0.0693

0.0093 0.58 <0.25 <0.005 <0.001 NA <5 146 <0.001 1.06 <0.03 NA 0.133

<0.04 0.24 <0.02 <0.01 <0.005 NA <1 17 <0.05 1.7 0.00742 NA <1.05

0.0037 <0.25 <0.25 0.0009 <0.000011 NA 18 186 0.000012 <5 <0.03 NA 0.0041

0.0031 <0.05 <0.05 <0.005 <0.001 NA <25 251 <0.001 2.6 <0.03 NA 0.0131

0.0026 0.057 <0.25 <0.005 <0.001 NA 17 200 <0.001 1.47 <0.03 NA 0.0088

<0.04 0.26 <0.02 <0.01 <0.005 NA 20 180 <0.05 2.1 0.0213 NA <1.05

0.0034 <0.25 <0.25 0.0016 <0.000011 NA 21 135 <0.000011 <5 <0.03 NA 0.0054

0.0023 <0.05 <0.05 <0.005 <0.001 NA <25 183 <0.001 1.76 0.0388 NA 0.0104

0.0035 0.043 <0.25 <0.005 <0.001 NA 25 172 <0.001 1.32 0.0316 NA 0.0092

<0.04 0.095 <0.02 <0.01 <0.005 NA 23 140 <0.05 1.8 0.0291 NA <0.02

0.0044 0.84 <0.25 0.0009 0.000016 NA 30 203 0.000039 1.38 <0.03 NA 0.0133

0.0046 <0.05 <0.05 <0.005 <0.001 NA 26 308 <0.001 2.42 <0.03 NA 0.0417

0.0026 1.4 <0.25 <0.005 <0.001 NA 28 200 <0.001 <1 <0.03 NA 0.0395

<0.04 0.73 <0.02 0.15 <0.005 NA 27 130 <0.05 5.1 0.00424 NA <0.02

Prepared By: RBI/BER Checked By: JAW


TABLE 4

SEEP ANALYTICAL RESULTS



pH Temp.Specific

ConductanceDO ORP Flow Turbidity Aluminum Antimony Arsenic Barium Boron Cadmium Calcium Chloride Chromium COD Copper Fluoride Hardness Iron Lead Magnesium Manganese

SU °C µS/cm mg/l mV MGD NTUs mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l (CaCO3) mg/l mg/l mg/l mg/l

200.7 200.8 200.8 200.7 200.7 200.8 200.7 300 200.8 HACH 8000 200.8 300 200.7 200.7 200.8 200.7 200.7

LocationSample Collection

Date

Stormwater Outfall 004 8/27/2014 7.6 21 481 5.10 129 0.00106 2.42 0.044 <0.001 <0.001 0.061 0.12 <0.001 30.4 6.6 0.00205 <20 0.0012 0.51 132 0.044 <0.001 13.7 <0.005

Stormwater Outfall 005 8/27/2014 6.9 22 327 3.98 122 0.05261 7.05 0.189 <0.001 <0.001 0.047 1.25 <0.001 29 56 <0.001 <20 0.00197 0.22 115 0.291 <0.001 10.4 0.039

West Toe Drain 8/27/2014 6.2 19 447 1.80 -16.1 0.0041 1.21 0.02 <0.001 0.00264 0.126 1.51 <0.001 23.2 58 <0.001 <20 <0.001 0.15 90 13.4 <0.001 7.8 2.78

East Toe Drain 8/27/2014 5.7 17 477 3.02 44.2 0.00362 1.87 0.009 <0.001 <0.001 0.165 1.67 <0.001 31.9 95 <0.001 <20 <0.001 <0.1 139 4.08 <0.001 14.5 2.37

East Toe Drain 8/27/2014 5.7 17 477 3.02 44.2 0.00362 1.87 0.008 <0.001 <0.001 0.161 1.63 <0.001 31.4 95 <0.001 <20 <0.001 <0.1 137 3.97 <0.001 14.1 2.32

Crutchfield Branch 8/27/2014 6.4 19 396 5.07 55.8 0.02456 3.25 0.066 <0.001 <0.001 0.067 1.34 <0.001 29.6 66 <0.001 <20 <0.001 0.14 120 0.485 <0.001 11.3 1.07

Downstream of West Toe Drain 8/27/2014 6.3 25 405 4.01 -31.1 NM 12.4 0.124 <0.001 0.00197 0.144 1.28 <0.001 22.2 52 <0.001 <20 <0.001 0.16 86.9 11.4 <0.001 7.65 3.18

Ash Basin 8/27/2014 8.4 27 514 4.33 109 0 1.81 0.021 <0.001 0.00303 0.073 2.13 <0.001 48.6 94 <0.001 <20 0.00156 0.3 187 0.028 <0.001 15.9 0.02

Tributary to Mayo Lake 8/27/2014 7.2 21 193 6.70 100 0.01102 5.44 0.06 <0.001 <0.001 0.024 <0.05 <0.001 15.3 11 <0.001 <20 <0.001 0.18 59.1 0.383 <0.001 5.08 0.115

NE of East Toe Drain 11/12/2014 6.5 15 540 NM NM 0.000724 21.2 0.214 <0.001 <0.001 0.118 1.67 <0.001 36.1 110 <0.001 <20 <0.001 0.11 187 2.83 <0.001 23.5 3.23

Outfall 002 3/12/2014 NA NA NA NA NA NA NA 0.11 0.00102 0.00411 0.114 8.79 <0.001 NA 320 0.00217 NA <0.005 <1 652 0.097 <0.001 NA 0.429

Outfall 004 3/12/2014 NA NA NA NA NA NA NA 0.284 <0.001 <0.001 0.041 0.079 <0.001 NA 8 0.00263 NA <0.005 <1 101 0.179 <0.001 NA <0.005

Outfall 005 3/12/2014 NA NA NA NA NA NA NA 2.22 0.0016 0.00244 0.101 2.37 0.00109 NA 120 0.00629 NA 0.01 <1 329 2.52 0.00409 NS 0.161

Ash Pond West Weir Toe Drain 3/12/2014 NA NA NA NA NA NA NA 0.023 <0.001 0.00223 0.123 1.45 <0.001 NA 50 <0.005 NS <0.005 <1 87.8 13.6 <0.001 NS 2.88

Ash Pond East Weir Toe Drain 3/12/2014 NA NA NA NA NA NA NA 0.008 <0.001 <0.001 0.157 1.57 <0.001 NA 88 <0.005 NA <0.005 <1 140 4.43 <0.001 NA 2.57

Crutchfield Branch 3/12/2014 NA NA NA NA NA NA NA 0.346 <0.001 <0.001 0.056 0.776 <0.001 NA 40 <0.005 NA <0.005 <1 83.4 0.948 <0.001 NA 0.758

Ash Pond West Drainage Ditch 3/12/2014 NA NA NA NA NA NA NA 0.119 <0.001 0.00236 0.129 1.02 <0.001 NA 29 <0.005 NA <0.005 <1 82.1 17.4 <0.001 NA 2.81

Lake Intake 3/12/2014 NA NA NA NA NA NA NA 0.047 <0.001 <0.001 0.052 1.52 <0.001 NA 66 <0.005 NA <0.005 <1 127 0.069 <0.001 NA 0.039

Notes:


Temp. = Temperature



COD = Chemical oxygen demand



2. Units:


SU = Standard Units


MGD = millions of gallons per day


CaCO3 = calcium carbonate




6.

* Samples collected by SynTerra at locations as described (SynTerra, October 2014).

** Split sample data analyzed by Duke Lab of NCDENR identified locations.

S-05*

Outfall 005*

S-01*

S-02*

S-03*

S-04*

Outfall 004*

Field MeasurementsConstituent Concentrations

2014007461**

Analytical results with "<" preceding the result indicate that the parameter was not

detected at a concentration which attains or exceeds the laboratory reporting limit.

2014007448**

2014007449**

2014007457**

2014007458**

2014007459**

2014007460**

2014007447**

S-02 Dup.*


Units

Analytical Method

Sample ID

S-06*

S-08*

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Tables 3 and 4 Groundwater and Seep Data Tables Page 1 of 2

TABLE 4

SEEP ANALYTICAL RESULTS



LocationSample Collection

Date

Stormwater Outfall 004 8/27/2014

Stormwater Outfall 005 8/27/2014

West Toe Drain 8/27/2014

East Toe Drain 8/27/2014

East Toe Drain 8/27/2014

Crutchfield Branch 8/27/2014

Downstream of West Toe Drain 8/27/2014

Ash Basin 8/27/2014

Tributary to Mayo Lake 8/27/2014

NE of East Toe Drain 11/12/2014

Outfall 002 3/12/2014

Outfall 004 3/12/2014

Outfall 005 3/12/2014

Ash Pond West Weir Toe Drain 3/12/2014

Ash Pond East Weir Toe Drain 3/12/2014

Crutchfield Branch 3/12/2014

Ash Pond West Drainage Ditch 3/12/2014

Lake Intake 3/12/2014

Notes:


Temp. = Temperature



COD = Chemical oxygen demand



2. Units:


SU = Standard Units


MGD = millions of gallons per day


CaCO3 = calcium carbonate




6.

* Samples collected by SynTerra at locations as described (SynTerra, October 2014).

** Split sample data analyzed by Duke Lab of NCDENR identified locations.

S-05*

Outfall 005*

S-01*

S-02*

S-03*

S-04*

Outfall 004*

2014007461**

Analytical results with "<" preceding the result indicate that the parameter was not

detected at a concentration which attains or exceeds the laboratory reporting limit.

2014007448**

2014007449**

2014007457**

2014007458**

2014007459**

2014007460**

2014007447**

S-02 Dup.*


Units

Analytical Method

Sample ID

S-06*

S-08*

Mercury Molybdenum NickelOil &

GreaseSelenium Sulfate Thallium TDS TSS Zinc

mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l

245.1 200.8 200.8 1664B 200.8 300 200.8 SM2540C SM2540D 200.7

<0.00005 0.0138 <0.001 <5 0.00258 99 <0.0002 310 <5 0.013

<0.00005 0.00533 <0.001 <5 0.00208 36 <0.0002 230 7 0.111

<0.00005 <0.001 0.0012 <5 <0.001 46 <0.0002 270 7 <0.005

<0.00005 <0.001 0.00241 <5 <0.001 47 <0.0002 330 <5 0.014

<0.00005 <0.001 0.00204 <5 <0.001 47 <0.0002 330 <5 0.013

<0.00005 <0.001 <0.001 <5 <0.001 36 <0.0002 250 <5 <0.005

<0.00005 <0.001 0.00137 <5 <0.001 41 <0.0002 250 22 0.005

<0.00005 0.014 <0.001 <5 <0.001 61 <0.0002 380 <5 <0.005

<0.00005 <0.001 <0.001 <5 <0.001 6 <0.0002 140 5 <0.005

<0.00005 <0.001 0.00125 <5 <0.001 59 <0.0002 320 7 0.005

NA 0.0257 0.00266 NA 0.00192 140 0.00078 NA 864 0.00829

NA 0.00971 <0.001 NA 0.00145 91 <0.0002 NA 247 0.0144

NS 0.0136 0.00576 NS 0.0116 150 0.00034 NS 499 0.819

NS <0.001 <0.005 NS <0.001 41 <0.0002 NS 259 <0.005

NA <0.001 <0.005 NA <0.001 47 <0.0002 NA 236 0.013

NA <0.001 <0.005 NA <0.001 30 <0.0002 NA 160 0.006

NA <0.001 <0.005 NA <0.001 28 <0.0002 NA 148 0.005

NA 0.0052 <0.005 NA <0.001 33 <0.0002 NA 192 <0.005


P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Tables 3 and 4 Groundwater and Seep Data Tables Page 2 of 2

TABLE 5

ENVIRONMENTAL EXPLORATION AND SAMPLING PLAN



Exploration Area

Boring IDs QuantityEstimated Depth

(ft bgs)Well IDs Quantity

Estimated Well

Depth

(ft bgs)

Screen Length

(ft)Well IDs Quantity

Estimated Well

Depth

(ft bgs)

Screen

Length (ft)Well IDs Quantity

Estimated Well

Depth

(ft bgs)

Screen

Length (ft)Well IDs Quantity

Estimated Well

Depth

(ft bgs)

Screen

Length (ft)

Ash Basin

AB-1

AB-2

AB-3

AB-4

4

30

80

30

80

ABMW-1

ABMW-2

ABMW-3

ABMW-4

4

30

30

30

30

5

ABMW-1S

ABMW-2S

ABMW-3S

ABMW-4S

5

40

40

40

40

10 N/A 0 N/A N/A N/A 0 N/A N/A

Background/

1981 Landfill

(#73-B)

SB-1

SB-2

SB-3

SB-4

SB-5

SB-6

6

100

100

100

100

100

100

N/A 0 N/A N/A N/A 0 N/A N/A N/A 0 N/A N/A N/A 0 N/A N/A

Upgradient/

Beyond Waste

Boundary

MW-10SB

MW-11SB

MW-12SB

MW-13SB

4

100

100

100

100

N/A 0 N/A N/A

MW-10S

MW-11S

MW-12S

MW-13S

4

50

50

50

50

10

No wells planned,

but will be installed

if a transition zone

is present.

Example well name

is

MW-10D

TBD TBD 5

MW-10BR

MW-11BR

MW-12BR

MW-13BR

4

100

100

100

100

5

Downgradient

/Sidegradient

MW-3SB

MW-5SB

MW-6SB

MW-7SB

MW-8SB

MW-9SB

MW-14SB

MW-15SB

MW-16SB

9

100

100

100

100

100

100

100

100

100

N/A 0 N/A N/A

MW-7S

MW-8S

MW-9S

MW-14S

MW-15S

MW-16S

6

50

50

50

50

50

50

10

No wells planned,

but will be installed

if a transition zone

is present.

Example well name

is

MW-16D

TBD TBD 5

MW-3BR

MW-5BR

MW-6BR

MW-7BR

MW-8BR

MW-9BR

MW-14BR

MW-15BR

MW-16BR

9

100

100

100

100

100

100

100

100

100

5

Exploration Area

Sample IDsQuantity of

Locations

Quantity of

SamplesSample IDs

Quantity of

Locations

Quantity of

SamplesSample IDs

Quantity of

Locations

Quantity of

SamplesWell IDs

Quantity of

Locations

Quantity of

Samples

Ash Basin N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Background/

1981 LandfillN/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Upgradient/

Beyond Waste

Boundary

S-7 1 1 S-6, SW-REF1 2 2 S-6, SW-REF1 2 2BG-1, BG-2, DEP1,

DEP2, DEP35 7

Downgradient/

Sidegradient

S-1, S-2,

S-4, S-84 4

S-3, SW-CB1,

SW-CB23 3

S-3, SW-CB1,

SW-CB23 3

CW-1, CW-1D, CW-2,

CW-2D, CW-3, CW-4,

CW-5, CW-6, MW-2,

MW-3, MW-4

11 22

Notes:

1. Estimated boring and well depths based on data available at the time of work plan preparation and subject to change based on site-specific conditions in the field.

2. Laboratory analyses of soil, ash, groundwater, ash pore water, and surface water samples will be performed in accordance with the constituents and methods identified in Tables 6 and 7.

3. Additionally, soils will be tested in the laboratory to determine grain size (with hydrometer), specific gravity, and permeability.

4. During drilling operations, downhole testing will be conducted to determine in-situ soil properties such as horizontal and vertical hydraulic conductivity.

5. Actual number of field and laboratory tests will be determined in field by Field Engineer or Geologist in accordance with project specifications.

6. Existing ash basin dam piezometers will be utilized for water level measurements only (PZ1/1A, PZ2/2A, PZ3/3A, and PZ4/4A).

Bedrock Monitoring Wells

("BR" Series)

For Groundwater Sampling

(Double Cased)

Transition zone (PWR) Monitoring Wells

("D" Series)


(Single Cased)

Seeps

Ash Basin Monitoring Wells

("AB" Series)

For Ash Pore Water Sampling

(Single Cased)

Existing Monitoring Wells and Piezometers (see

note #6)

Saprolite Monitoring Wells

("S" Series)


(Single Cased)

Soil Borings

SedimentSurface Water

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Table 5 Exploration and Sampling Plan MAYO

TABLE 6

SOIL, SEDIMENT, AND ASH PARAMETERS AND ANALYTICAL METHODS



INORGANIC COMPOUNDS UNITS METHOD

Aluminum mg/kg EPA 6010C

Antimony mg/kg EPA 6020A

Arsenic mg/kg EPA 6020A

Barium mg/kg EPA 6010C

Beryllium mg/kg EPA 6020A

Boron mg/kg EPA 6010C

Cadmium mg/kg EPA 6020A

Calcium mg/kg EPA 6010C

Chloride mg/kg EPA 9056A

Chromium mg/kg EPA 6010C

Cobalt mg/kg EPA 6020A

Copper mg/kg EPA 6010C

Iron mg/kg EPA 6010C

Lead mg/kg EPA 6020A

Magnesium mg/kg EPA 6010C

Manganese mg/kg EPA 6010C

Mercury mg/kg EPA Method 7470A/7471B

Molybdenum mg/kg EPA 6010C

Nickel mg/kg EPA 6010C

Nitrate as Nitrogen mg/kg EPA 9056A

pH SU EPA 9045D

Potassium mg/kg EPA 6010C

Selenium mg/kg EPA 6020A

Sodium mg/kg EPA 6010C

Strontium mg/kg EPA 6010C

Sulfate mg/kg EPA 9056A

Thallium (low level) (SPLP Extract only) mg/kg EPA 6020A

Vanadium mg/kg EPA 6020A

Zinc mg/kg EPA 6010C

Sediment Specific Samples

Cation exchange capacity meg/100g EPA 9081

Particle size distribution %

Percent solids %

Percent organic matter % EPA/600/R-02/069

Redox potential mV Faulkner et al. 1898

Notes:

1. Soil samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA

Method 9045, as noted above.

2. Ash samples to be analyzed for Total Inorganics using USEPA Methods 6010/6020 and pH using USEPA

Method 9045; select ash and soil samples will also be analyzed for leaching potential using SPLP Extraction

Method 1312 in conjunction with USEPA Methods 6010/6020.

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec

2014\Tables\Table 6 Soil and Ash Parameters.xlsx

TABLE 7

ASH PORE WATER, GROUNDWATER, SURFACE WATER, AND SEEP PARAMETERS

AND ANALYTICAL METHODS



PARAMETER RL UNITS METHOD

pH NA SU Field Water Quality MeterSpecific Conductance NA µS/cm Field Water Quality MeterTemperature NA ºC Field Water Quality MeterDissolved Oxygen NA mg/L Field Water Quality MeterOxidation Reduction Potential NA mV Field Water Quality MeterTurbidity NA NTU Field Water Quality MeterFerrous Iron NA mg/L Field Test Kit

Aluminum 0.005 mg/L EPA 200.7 or 6010CAntimony 0.001 mg/L EPA 200.8 or 6020AArsenic 0.001 mg/L EPA 200.8 or 6020ABarium 0.005 mg/L EPA 200.7 or 6010CBeryllium 0.001 mg/L EPA 200.8 or 6020ABoron 0.05 mg/L EPA 200.7 or 6010CCadmium 0.001 mg/L EPA 200.8 or 6020AChromium 0.001 mg/L EPA 200.7 or 6010CCobalt 0.001 mg/L EPA 200.8 or 6020ACopper 0.005 mg/L EPA 200.7 or 6010CIron 0.01 mg/L EPA 200.7 or 6010CLead 0.001 mg/L EPA 200.8 or 6020AManganese 0.005 mg/L EPA 200.7 or 6010CMercury (low level) 0.000012 mg/L EPA 245.7 or 1631Molybdenum 0.005 mg/L EPA 200.7 or 6010CNickel 0.005 mg/L EPA 200.7 or 6010CSelenium 0.001 mg/L EPA 200.8 or 6020AStrontium 0.005 mg/L EPA 200.7 or 6010CThallium (low level) 0.0002 mg/L EPA 200.8 or 6020AVanadium (low level) 0.0003 mg/L EPA 200.8 or 6020AZinc 0.005 mg/L EPA 200.7 or 6010C

Total Combined Radium 5 pCi/L EPA 903.0

Alkalinity (as CaCO3) 20 mg/L SM 2320BBicarbonate 20 mg/L SM 2320Calcium 0.01 mg/L EPA 200.7Carbonate 20 mg/L SM 2320Chloride 0.1 mg/L EPA 300.0 or 9056AMagnesium 0.005 mg/L EPA 200.7Methane 0.1 mg/L RSK 175Nitrate as Nitrogen 0.023 mg-N/L EPA 300.0 or 9056APotassium 0.1 mg/L EPA 200.7Sodium 0.05 mg/L EPA 200.7Sulfate 0.1 mg/L EPA 300.0 or 9056ASulfide 0.05 mg/L SM4500S-DTotal Dissolved Solids 25 mg/L SM 2540CTotal Organic Carbon 0.1 mg/L SM 5310Total Suspended Solids 2 mg/L SM 2450D

Iron Speciation Vendor Specific mg/L IC-ICP-CRC-MS

Manganese Speciation Vendor Specific mg/L IC-ICP-CRC-MS

Notes:

INORGANICS

FIELD PARAMETERS

NA indicates not applicable.

ADDITIONAL CONSTITUENTS

1. Select constituents will be analyzed for total and dissolved concentrations.2. RL is the laboratory analytical method reporting limit.

ANIONS/CATIONS

RADIONUCLIDES

P:\Duke Energy Progress.1026\ALL NC SITES\DENR Letter Deliverables\GW Assessment Plans\Mayo\Mayo GAP Revised Dec 2014\Tables\Table

7 Groundwater_Surface Water_Seep Parameters

APPENDIX A

NCDENR LETTER OF AUGUST 13, 2014

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